Draft California 2024 Integrated Report (303(d) List/305(b) Report)

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 150428, Ammonia	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253556

Pollutant:

Nitrogen, ammonia (Total Ammonia)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 0 of the 21 samples exceeded the water quality threshold for Ammonia as N. Although a total of 22 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013 document.

Objective/Criterion Reference:

Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628437).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-02 to 2018-07-10

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 150428, Ammonia	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

2166

Pollutant:

Ammonia

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

QAPP Information:

QA Info Missing

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 150428, Ammonia	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

257135

Pollutant:

Nitrogen, ammonia (Total Ammonia)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 45 samples exceeded the water quality threshold for Ammonia as N.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137276	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Diazinon
Final Listing Decision:	Delist from 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)(2018)
Revision Status	Revised
Reason for Delisting:	Applicable WQS attained; reason for recovery unspecified
TMDL Name:	Calleguas Creek Toxicity (2)
TMDL Project Code:	355
Date TMDL Approved by USEPA:	03/14/2006
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 4.1 and 4.6 of the Listing Policy. Eight lines of evidence are available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is insufficient justification for removing this water segment-pollutant combination from the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 2, 0 of 2, 1 of 24, 1 of 3, 0 of 43 and 0 of 43 samples exceeded the criteria and 0 of 1 sample exceeded the guideline and this does not exceed the allowable frequency listed in Table 4.1 of the Listing Policy. 4. Pursuant to SECTION 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be removed from the section 303(d) list because applicable water quality standards for the pollutant are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137276, Diazinon	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254406

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Diazinon. Although a total of 11 samples were collected, 11 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The freshwater chronic value for diazinon is 0.10 ug/L (4 day average)(Finlayson, 2004).

Guideline Reference:

Water quality for diazinon. Memorandum to J. Karkoski, Central Valley RWQCB. Rancho Cordova, CA: Pesticide Investigation Unit, CA Department of Fish and Game

Guideline Reference:

Water quality criteria for diazinon and chlorpyrifos. Administrative Report 00-3. Rancho Cordova, CA: Pesticide Investigations Unit, Office of Spills and Response. CA Department of Fish and Game (with minor corrections to significant figures as described in Beaulaurier et al., 2005).

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137276, Diazinon	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254432

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 11 samples exceeded the water quality threshold for Diazinon.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA drinking water health advisory for diazinon rounded to one significant figure is 1 µg/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137276, Diazinon	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260108

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Diazinon.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The freshwater chronic value for diazinon is 0.10 ug/L (4 day average)(Finlayson, 2004).

Guideline Reference:

Water quality for diazinon. Memorandum to J. Karkoski, Central Valley RWQCB. Rancho Cordova, CA: Pesticide Investigation Unit, CA Department of Fish and Game

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137276, Diazinon	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260051

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Diazinon.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA drinking water health advisory for diazinon rounded to one significant figure is 1 µg/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137276, Diazinon	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254434

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 1 of the 3 samples exceeded the water quality threshold for Diazinon. Although a total of 13 samples were collected, 10 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The freshwater chronic value for diazinon is 0.10 ug/L (4 day average)(Finlayson, 2004).

Guideline Reference:

Water quality for diazinon. Memorandum to J. Karkoski, Central Valley RWQCB. Rancho Cordova, CA: Pesticide Investigation Unit, CA Department of Fish and Game

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628437).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2019-06-30

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137276, Diazinon	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260145

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Diazinon.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA drinking water health advisory for diazinon rounded to one significant figure is 1 µg/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137276, Diazinon	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260125

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Diazinon.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The freshwater chronic value for diazinon is 0.10 ug/L (4 day average)(Finlayson, 2004).

Guideline Reference:

Water quality for diazinon. Memorandum to J. Karkoski, Central Valley RWQCB. Rancho Cordova, CA: Pesticide Investigation Unit, CA Department of Fish and Game

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137276, Diazinon	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254586

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 1 of 13 samples exceeded the water quality threshold for Diazinon.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA drinking water health advisory for diazinon rounded to one significant figure is 1 µg/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2019-06-30

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137276, Diazinon	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

2171

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Not Specified

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a listing decision made by USEPA for 2006.

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

QAPP Information:

QA Info Missing

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137276, Diazinon	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83376

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

One sample was collected to evaluate sediment toxicity. The sample exhibited significant toxicity. The toxicity test included survival of Hyalella azteca. One sample can have multiple toxicity test results but will be counted only once.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in, human, plant, animal, or aquatic life. Region 4 Basin Plan.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Toxicity is defined as a statistically significant effect in the sample exposure compared to the control using EPA-recommended hypothesis testing. For SWAMP data exceedances are counted with the significant effect code SL. SL is defined as the result being significant compared to the negative control based on a statistical test, less than stated the alpha level, AND less than the evaluation threshold.

Guideline Reference:

Methods for Measuring the Toxicity and Bioaccumulation of Sediment-associated Contaminants with Freshwater Invertebrates, Second Edition. U.S. Environmental Protection Agency Office of Research and Development, Duluth, MI , U.S. Environmental Protection Agency Office of Water, Washington, DC EPA-600/R-99/064

Spatial Representation:

The sample was collected at station 408SUP059.

Temporal Representation:

The sample was collected in January 2007.

Environmental Conditions:

QAPP Information:

All data was collected following the Standard Operating Procedures and Data Quality Objectives outlined in the SWAMP QAMP, (Puckett, 2002). QA data are included in submission.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137276, Diazinon	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83368

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP data for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) to determine beneficial use support and results are as follows: 0 of 1 samples exceed the criterion for Diazinon.

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan for the Los Angeles Region (LARWQCB 2004): All waters shall be maintained free of toxic substances in concentrations which are toxic to, or which produce detrimental physiological responses in, human, plant, animal, or aquatic life.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

There is no diazinon evaluation guideline specific to "sediment, interstitial water" (pore water). The following evaluation guideline was used to evaluate an exceedance in water quality standards: the freshwater chronic value for diazinon is 0.1 ug/L, expressed as a continuous concentration (Finlayson, 2004).

Guideline Reference:

Water quality for diazinon. Memorandum to J. Karkoski, Central Valley RWQCB. Rancho Cordova, CA: Pesticide Investigation Unit, CA Department of Fish and Game

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)


DECISION ID	137292	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Organophosphate Pesticides
Final Listing Decision:	Delist from 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)(2018)
Revision Status	Revised
Reason for Delisting:	Applicable WQS attained; reason for recovery unspecified
TMDL Name:	Calleguas Creek Toxicity (2)
TMDL Project Code:	355
Date TMDL Approved by USEPA:	03/14/2006
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the CWA section 303(d) List under section 4.1 of the Listing Policy. Under this section a single line of evidence is necessary to assess listing status. Three lines of evidence are available in the administrative record to assess this pollutant. Line of evidence 2169 is a placeholder for a decision to list made prior to 2006, and will not be considered for assessment. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for removing this water segment-pollutant combination from the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 2, 1 of 27 and 1 of 43 samples exceeded the criteria and this does not exceed the allowable frequency listed in Table 4.1 of the Listing Policy. 4. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be removed from the section 303(d) list because applicable water quality standards for the pollutant are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137292, Organophosphate Pesticides	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

264231

Pollutant:

Organophosphate Pesticides

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Organophosphorus Pesticides.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for the protection of aquatic life from the additive effects of the organophosphate pesticides chlorpyrifos and diazinon is one toxic unit equivalent. A toxic unit equivalent is equal to the sum of chlorpyrifos and diazinon from a single sample, each having their reported concentration divided their respective evaluation guideline prior to being summed. If this results in a value greater than one, the sample is considered to be in exceedance of the water quality standard. (Bailey et al., 1997).

Guideline Reference:

Joint acute toxicity of Diazinon and Chlorpyrifos to Ceriodaphnia dubia.

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137292, Organophosphate Pesticides	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

264285

Pollutant:

Organophosphate Pesticides

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 1 of 43 samples exceeded the water quality threshold for Organophosphorus Pesticides.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Joint acute toxicity of Diazinon and Chlorpyrifos to Ceriodaphnia dubia.

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137292, Organophosphate Pesticides	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255572

Pollutant:

Organophosphate Pesticides

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Joint acute toxicity of Diazinon and Chlorpyrifos to Ceriodaphnia dubia.

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2019-06-30

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137292, Organophosphate Pesticides	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255508

Pollutant:

Organophosphate Pesticides

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 14 samples exceeded the water quality threshold for Organophosphorus Pesticides.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Joint acute toxicity of Diazinon and Chlorpyrifos to Ceriodaphnia dubia.

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2018-12-31

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137292, Organophosphate Pesticides	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

2169

Pollutant:

Organophosphate Pesticides

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.

Data Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

QAPP Information:

QA Info Missing

QAPP Information Reference(s):


DECISION ID	137263	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Boron
Final Listing Decision:	Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)(2018)
Revision Status	Revised
Sources:	Atmospheric Deposition \| Domestic Use of Ground Water \| Groundwater Loadings \| Irrigated Crop Production \| Major Municipal Point Source-dry weather discharge \| Surface Runoff
TMDL Name:	Calleguas Creek Boron/Sulfate/TDS (4)
TMDL Project Code:	357
Date TMDL Approved by USEPA:	12/02/2008
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal on the section 303(d) list under sections 2.2 and 4.1 of the Listing Policy. Under section 4.1 of the Policy, a minimum of one line of evidence is needed to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the section 303(d) list. There is sufficient justification to place it in the Being Addressed portion of the 303(d) list because a TMDL has been completed and adopted by the Los Angeles RWQCB and approved by USEPA, and is expected to result in attainment of the standard. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 57 of 132 samples exceeded the site specific objective and these exceed the allowable frequency listed in Table 4.1of the Listing Policy. 4. The TMDL for Boron, Chloride, Sulfate, and TDS (Salts) in the Calleguas Creek Watershed was approved by USEPA on 12/2/2008. 5. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137263, Boron	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

28019

Pollutant:

Boron

LOE Subgroup:

Narrative Description Data

Matrix:

Not Specified

Fraction:

None

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

A TMDL has been approved for this water segment-pollutant combination. The Calleguas Creek Watershed Salts TMDL was adopted by the Los Angeles RWQCB on October 04, 2007 and subsequently approved by USEPA. The TMDL was integrated into the Basin Plan as Attachment A of Regional Board Resolution No. 2007-016.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

QAPP Information:

QA information unavailable.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137263, Boron	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

4056

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Unspecified

Objective/Criterion Reference:

Evaluation Guideline:

Unspecified

Guideline Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Spatial Representation:

Unspecified

Temporal Representation:

Unspecified

Environmental Conditions:

Unspecified

QAPP Information:

Unspecified

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137263, Boron	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

243855

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed data from the Simi Valley Wastewater Quality Control Plan to determine beneficial use support. The results are as follows: 54 out of 66 samples exceed the criterion for Boron.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region list a site specific objective for Boron in the Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) of 1 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station RSW-001 (34.282, -118.8129), located in Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list).

Temporal Representation:

The water samples were taken between 5/5/2015 - 10/6/2020, per the monitoring requirements listed in the Simi Valley Wastewater Quality Control Plan NPDES Permit monitoring and reporting program.

Environmental Conditions:

QAPP Information:

The work was performed in accordance with the Simi Valley Wastewater Quality Control Plan NDPES Permit quality assurance provisions for water quality monitoring.

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137263, Boron	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

243866

Pollutant:

Boron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed data from the Simi Valley Wastewater Quality Control Plan to determine beneficial use support. The results are as follows: 3 out of 66 samples exceed the criterion for Boron.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region list a site specific objective for Boron in the Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) of 1 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station RSW-002 (34.28169, -118.8135), located in Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list).

Temporal Representation:

The water samples were taken between 5/5/2015 - 10/6/2020, per the monitoring requirements listed in the Simi Valley Wastewater Quality Control Plan NPDES Permit monitoring and reporting program.

Environmental Conditions:

QAPP Information:

The work was performed in accordance with the Simi Valley Wastewater Quality Control Plan NDPES Permit quality assurance provisions for water quality monitoring.

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137266	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Chloride
Final Listing Decision:	Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)(2018)
Revision Status	Revised
Sources:	Atmospheric Deposition \| Domestic Use of Ground Water \| Groundwater Loadings \| Irrigated Crop Production \| Major Municipal Point Source-dry weather discharge \| Surface Runoff
TMDL Name:	Calleguas Creek Boron/Sulfate/TDS (4)
TMDL Project Code:	357
Date TMDL Approved by USEPA:	12/02/2008
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal on the CWA section 303(d) List under sections 2.2 and section 4.2 of the Listing Policy. Under section 4.2 of the Policy, a minimum of one line of evidence is needed to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. LOEs 4057 and 28020 are placeholders for decisions not held in the assessment database. They will not be used for assessment because there are other data sufficient to determine beneficial use support. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. There is sufficient justification to place it in the Being Addressed portion of the CWA 303(d) List because a TMDL has been completed and approved by RWQCB and USEPA, and is expected to result in attainment of the standard. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 108 of 132 samples exceeded the objective and these exceed the allowable frequency listed in Table 4.2 of the Listing Policy. 4. The TMDL for Salts in the Calleguas Creek Watershed was approved by USEPA on 12/2/2008. 5. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137266, Chloride	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

4057

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Non-Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Unspecified

Objective/Criterion Reference:

Evaluation Guideline:

Unspecified

Guideline Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Spatial Representation:

Unspecified

Temporal Representation:

Unspecified

Environmental Conditions:

Unspecified

QAPP Information:

Unspecified

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137266, Chloride	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

28020

Pollutant:

Chloride

LOE Subgroup:

Narrative Description Data

Matrix:

Not Specified

Fraction:

None

Beneficial Use:

Non-Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

QAPP Information:

QA information unavailable.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137266, Chloride	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

243862

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed data from the Simi Valley Wastewater Quality Control Plan to determine beneficial use support. The results are as follows: 55 out of 66 samples exceed the criterion for Chloride.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region list a site specific objective for Chloride in the Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) of 150 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station RSW-001 (34.282, -118.8129), located in Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list).

Temporal Representation:

The water samples were taken between 5/5/2015 - 10/6/2020, per the monitoring requirements listed in the Simi Valley Wastewater Quality Control Plan NPDES Permit monitoring and reporting program.

Environmental Conditions:

QAPP Information:

The work was performed in accordance with the Simi Valley Wastewater Quality Control Plan NDPES Permit quality assurance provisions for water quality monitoring.

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137266, Chloride	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

243867

Pollutant:

Chloride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed data from the Simi Valley Wastewater Quality Control Plan to determine beneficial use support. The results are as follows: 53 out of 66 samples exceed the criterion for Chloride.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region list a site specific objective for Chloride in the Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) of 150 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station RSW-002 (34.28169, -118.8135), located in Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list).

Temporal Representation:

The water samples were taken between 5/5/2015 - 10/6/2020, per the monitoring requirements listed in the Simi Valley Wastewater Quality Control Plan NPDES Permit monitoring and reporting program.

Environmental Conditions:

QAPP Information:

The work was performed in accordance with the Simi Valley Wastewater Quality Control Plan NDPES Permit quality assurance provisions for water quality monitoring.

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137270	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Chlorpyrifos
Final Listing Decision:	Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Name:	Calleguas Creek Toxicity (2)
TMDL Project Code:	355
Date TMDL Approved by USEPA:	03/14/2006
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal on the CWA section 303(d) List under sections 2.2 and sections 4.1 and 4.6 of the Listing Policy. Under section 4.1 of the Policy, a minimum of one line of evidence is needed to assess listing status. Eight lines of evidence are available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. There is sufficient justification to place it in the Being Addressed portion of the CWA 303(d) List because a TMDL has been completed and approved by RWQCB and USEPA, and is expected to result in attainment of the standard. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 9 of 43 samples exceeded the criteria for Chlorpyrifos in water and these exceed the allowable frequency listed in Table 4.1 of the Listing Policy. 4. The TMDL for Toxicity in Calleguas Creek was approved by USEPA on 3/14/2006. 5. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137270, Chlorpyrifos	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

258679

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Chlorpyrifos.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA drinking water health advisory for lifetime exposure to chlorpyrifos is 2 µg/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137270, Chlorpyrifos	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253815

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 1 of the 4 samples exceeded the water quality threshold for Chlorpyrifos. Although a total of 14 samples were collected, 10 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The freshwater criterion continuous concentration to protect aquatic organisms is 0.015 ug/L (Siepmann and Finlayson 2000, with minor corrections to significant figures as described in Beaulaurier et al., 2005).

Guideline Reference:

Water quality criteria for diazinon and chlorpyrifos. Administrative Report 00-3. Rancho Cordova, CA: Pesticide Investigations Unit, Office of Spills and Response. CA Department of Fish and Game

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628438).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2018-12-31

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137270, Chlorpyrifos	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253816

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Chlorpyrifos. Although a total of 11 samples were collected, 11 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Water quality criteria for diazinon and chlorpyrifos. Administrative Report 00-3. Rancho Cordova, CA: Pesticide Investigations Unit, Office of Spills and Response. CA Department of Fish and Game

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137270, Chlorpyrifos	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

258273

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 2 of 2 samples exceeded the water quality threshold for Chlorpyrifos.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Water quality criteria for diazinon and chlorpyrifos. Administrative Report 00-3. Rancho Cordova, CA: Pesticide Investigations Unit, Office of Spills and Response. CA Department of Fish and Game

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137270, Chlorpyrifos	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

258274

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Chlorpyrifos.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA drinking water health advisory for lifetime exposure to chlorpyrifos is 2 µg/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137270, Chlorpyrifos	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

2170

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a listing decision made by USEPA for 2006.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

QAPP Information:

QA Info Missing

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137270, Chlorpyrifos	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253874

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA drinking water health advisory for lifetime exposure to chlorpyrifos is 2 µg/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2018-12-31

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137270, Chlorpyrifos	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

258697

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 9 of 43 samples exceeded the water quality threshold for Chlorpyrifos.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Water quality criteria for diazinon and chlorpyrifos. Administrative Report 00-3. Rancho Cordova, CA: Pesticide Investigations Unit, Office of Spills and Response. CA Department of Fish and Game

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

Statewide Project Urban Pyrethroid Status Monitoring

Line of Evidence (LOE) for Decision ID 137270, Chlorpyrifos	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83437

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

One sample result was not used in the assessment because the laboratory method detection limit was above the guideline and the result was non-detect, therefore the results could not be quantified with the level of certainty required by the Listing Policy.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

There is no chlorpyrifos evaluation guideline specific to "sediment, interstitial water" (pore water). The following evaluation guideline was used to evaluate an exceedance in water quality standards: the freshwater criterion continuous concentration to protect aquatic organisms is 0.015 ug/L (Siepmann and Finlayson 2000, with minor corrections to significant figures as described in Beaulaurier et al., 2005).

Guideline Reference:

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 137270, Chlorpyrifos	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83376

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The sample was collected at station 408SUP059.

Temporal Representation:

The sample was collected in January 2007.

Environmental Conditions:

QAPP Information:

All data was collected following the Standard Operating Procedures and Data Quality Objectives outlined in the SWAMP QAMP, (Puckett, 2002). QA data are included in submission.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137270, Chlorpyrifos	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253877

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA drinking water health advisory for lifetime exposure to chlorpyrifos is 2 µg/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137299	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Sulfates
Final Listing Decision:	Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)(2018)
Revision Status	Revised
Sources:	Atmospheric Deposition \| Domestic Use of Ground Water \| Groundwater Loadings \| Irrigated Crop Production \| Major Municipal Point Source-dry weather discharge \| Surface Runoff
TMDL Name:	Calleguas Creek Boron/Sulfate/TDS (4)
TMDL Project Code:	357
Date TMDL Approved by USEPA:	12/02/2008
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal on the CWA section 303(d) List under sections 2.2 and section 4.2 of the Listing Policy. Under section 4.2 of the Policy, a minimum of one line of evidence is needed to assess listing status. 1 line of evidence is available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. There is sufficient justification to place it in the Being Addressed portion of the CWA 303(d) List because a TMDL has been completed and approved by RWQCB and USEPA, and is expected to result in attainment of the standard. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 131 of 132 samples exceeded the objective and these exceed the allowable frequency listed in Table 4.2of the Listing Policy. 4. The TMDL for Salts in the Calleguas Creek Watershed was approved by USEPA on 12/2/2008. 5. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	This is a decision previously approved by the State Water Resources Control Board and the USEPA. No new data were assessed by the Regional Board for the current. The decision has not changed.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 137299, Sulfates	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

243875

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed data from the Simi Valley Wastewater Quality Control Plan to determine beneficial use support. The results are as follows: 65 out of 66 samples exceed the criterion for Sulfate.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region list a site specific objective for Sulfate in the Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) of 250 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station RSW-002 (34.28169, -118.8135), located in Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list).

Temporal Representation:

The water samples were taken between 5/5/2015 - 10/6/2020, per the monitoring requirements listed in the Simi Valley Wastewater Quality Control Plan NPDES Permit monitoring and reporting program.

Environmental Conditions:

QAPP Information:

The work was performed in accordance with the Simi Valley Wastewater Quality Control Plan NDPES Permit quality assurance provisions for water quality monitoring.

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137299, Sulfates	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

243864

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed data from the Simi Valley Wastewater Quality Control Plan to determine beneficial use support. The results are as follows: 66 out of 66 samples exceed the criterion for Sulfate.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region list a site specific objective for Sulfate in the Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) of 250 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station RSW-001 (34.282, -118.8129), located in Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list).

Temporal Representation:

The water samples were taken between 5/5/2015 - 10/6/2020, per the monitoring requirements listed in the Simi Valley Wastewater Quality Control Plan NPDES Permit monitoring and reporting program.

Environmental Conditions:

QAPP Information:

The work was performed in accordance with the Simi Valley Wastewater Quality Control Plan NDPES Permit quality assurance provisions for water quality monitoring.

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137299, Sulfates	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

4058

Pollutant:

Sulfates

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Unspecified

Objective/Criterion Reference:

Evaluation Guideline:

Unspecified

Guideline Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Spatial Representation:

Unspecified

Temporal Representation:

Unspecified

Environmental Conditions:

Unspecified

QAPP Information:

Unspecified

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137299, Sulfates	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

28021

Pollutant:

Sulfates

LOE Subgroup:

Narrative Description Data

Matrix:

Not Specified

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

QAPP Information:

QA information unavailable.

QAPP Information Reference(s):


DECISION ID	137301	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Total Dissolved Solids
Final Listing Decision:	Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)(2018)
Revision Status	Revised
Sources:	Atmospheric Deposition \| Domestic Use of Ground Water \| Groundwater Loadings \| Irrigated Crop Production \| Major Municipal Point Source-dry weather discharge \| Surface Runoff
TMDL Name:	Calleguas Creek Boron/Sulfate/TDS (4)
TMDL Project Code:	357
Date TMDL Approved by USEPA:	12/02/2008
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal on the CWA section 303(d) List under sections 2.2 and section 4.2 of the Listing Policy. Under section 4.2 of the Policy, a minimum of one line of evidence is needed to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. LOEs 4059 and 28022 are placeholders for an older decision not kept in the assessment database. They will not be used for assessment because there are sufficient other data. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. There is sufficient justification to place it in the Being Addressed portion of the CWA 303(d) List because a TMDL has been completed and approved by RWQCB and USEPA, and is expected to result in attainment of the standard. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 130 of 132 samples exceeded the objective and these exceed the allowable frequency listed in Table 4.2 of the Listing Policy. 4. The TMDL for Salts in the Calleguas Creek Watershed was approved by USEPA on 12/2/2008. 5. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137301, Total Dissolved Solids	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

4059

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Unspecified

Objective/Criterion Reference:

Evaluation Guideline:

Unspecified

Guideline Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Spatial Representation:

Unspecified

Temporal Representation:

Unspecified

Environmental Conditions:

Unspecified

QAPP Information:

Unspecified

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137301, Total Dissolved Solids	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

243865

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region list a site specific objective for Total Dissolved Solids in the Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) of 850 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station RSW-001 (34.282, -118.8129), located in Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list).

Temporal Representation:

The water samples were taken between 5/5/2015 - 10/6/2020, per the monitoring requirements listed in the Simi Valley Wastewater Quality Control Plan NPDES Permit monitoring and reporting program.

Environmental Conditions:

QAPP Information:

The work was performed in accordance with the Simi Valley Wastewater Quality Control Plan NDPES Permit quality assurance provisions for water quality monitoring.

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137301, Total Dissolved Solids	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

243876

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station RSW-002 (34.28169, -118.8135), located in Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list).

Temporal Representation:

The water samples were taken between 5/5/2015 - 10/6/2020, per the monitoring requirements listed in the Simi Valley Wastewater Quality Control Plan NPDES Permit monitoring and reporting program.

Environmental Conditions:

QAPP Information:

The work was performed in accordance with the Simi Valley Wastewater Quality Control Plan NDPES Permit quality assurance provisions for water quality monitoring.

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137301, Total Dissolved Solids	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

28022

Pollutant:

Total Dissolved Solids

LOE Subgroup:

Narrative Description Data

Matrix:

Not Specified

Fraction:

None

Beneficial Use:

Agricultural Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Data Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

QAPP Information:

QA information unavailable.

QAPP Information Reference(s):


DECISION ID	137304	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Toxicity
Final Listing Decision:	Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (being addressed with USEPA approved TMDL)(2018)
Revision Status	Revised
Sources:	See TMDL documentation
TMDL Name:	Calleguas Creek Toxicity (2)
TMDL Project Code:	355
Date TMDL Approved by USEPA:	03/14/2006
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under sections 2.2 and 4.1 of the Listing Policy. Under section 4.1 a single line of evidence are necessary to assess listing status. Three lines of evidence are available in the administrative record to assess this pollutant. Line of evidence 2172 is a placeholder for a decision to list made prior to 2006. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against removing this water segment-pollutant combination from the CWA section 303(d) List. There is sufficient justification to place it in the Being Addressed portion of the CWA 303(d) List because a TMDL has been completed and approved by RWQCB and USEPA, and is expected to result in attainment of the standard. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 4 samples exceeded the criteria and 1 of 1 sample exceeded the guideline and this sample size is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. A minimum of 28 samples is needed to determine if a beneficial use is fully supported using table 4.1. 4. The TMDL for Toxicity in the Calleguas Creek Watershed was approved by USEPA on 3/14/2006. 4. Pursuant to SECTION 4.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137304, Toxicity	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

244569

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

0 of the 4 samples collected by Ventura Countywide Stormwater Quality Mgmt Program for Calleguas Creek Reach 7 (Arroyo Simi) exhibited toxicity. A sample may have multiple toxicity test results, but will only be counted once. A sample is defined as being collected on the same day and the same location. The following organisms and parameters were utilized for the toxicity tests: Ceriodaphnia dubia for Survival, Ceriodaphnia dubia for Young/female.

Data Reference:

Field, Toxicity, WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in, human, plant, animal, or aquatic life.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The sample is toxic when the response of the organisms exposed to the sample is significantly different (worse) than the response of the organisms exposed to the laboratory control based on statistical hypothesis testing. An exceedance is counted when the significant effect code is “Significant; Less Similarity,” which means that the sample result is significantly different than the control result, and the percent effect is greater than the evaluation threshold. The default evaluation threshold is 20% unless otherwise stated.

Guideline Reference:

Short-term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater Organisms. Fourth Edition. Office of Water, U.S. Environmental Protection Agency. Washington, D.C. EPA-821-R-02-013

Spatial Representation:

The samples were collected at monitoring site: MO-SIM ( MO-SIM ).

Temporal Representation:

The samples were collected between the dates of 2016-10-28 and 2019-11-27.

Environmental Conditions:

QAPP Information:

Ventura County . 2006. Ventura Countywide Stormwater Monitoring Program DATA QUALITY EVALUATION STANDARD OPERATING PROCEDURES (SOPs), And Stormwater Program: Water Quality Monitoring Standard Operating Procedures 2009 - 2014..

QAPP Information Reference(s):

Ventura Countywide Stormwater Monitoring Program DATA QUALITY EVALUATION STANDARD OPERATING PROCEDURES (SOPs), And Stormwater Program: Water Quality Monitoring Standard Operating Procedures 2009 - 2014.

Line of Evidence (LOE) for Decision ID 137304, Toxicity	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83376

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The sample was collected at station 408SUP059.

Temporal Representation:

The sample was collected in January 2007.

Environmental Conditions:

QAPP Information:

All data was collected following the Standard Operating Procedures and Data Quality Objectives outlined in the SWAMP QAMP, (Puckett, 2002). QA data are included in submission.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137304, Toxicity	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

2172

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a listing decision made by USEPA for 2006.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

QAPP Information:

QA Info Missing

QAPP Information Reference(s):


DECISION ID	137311	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Acrolein
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137311, Acrolein	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253399

Pollutant:

Acrolein

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Acrolein.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The acrolein criterion for the protection of human health from the consumption of water and organisms is 320 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Water Quality Standards 2000. Establishment of numeric criteria for priority toxic pollutants for the State of California: Rules and regulations. Federal Register Vol. 65, No. 97. Washington, D.C.: Environmental Protection Agency

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2020-02-04 and 2020-02-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137311, Acrolein	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253353

Pollutant:

Acrolein

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA recommended acrolein criterion for the protection of aquatic life in freshwater is 3 ug/L ( 4-day average).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2020-02-04 and 2020-02-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137312	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Aldrin
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 0, 0 of 2, 0 of 0 and 0 of 43 samples exceeded the guideline and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137312, Aldrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256352

Pollutant:

Aldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Aldrin.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The aldrin criterion maximum concentration (expressed as a 1-day average) to protect aquatic life in freshwater is 1.5 ug/L. The criterion of 3 ug/L provided in the California Toxics Rule is an instantaneous maximum concentration and was divided by 2 in order to better represent a criterion maximum concentration (CMC) value as specified in footnote (g) of Table (b)(1) of the California Toxics Rule (2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137312, Aldrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256367

Pollutant:

Aldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Aldrin. Although a total of 43 samples were collected, 43 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The aldrin criterion for the protection of human health from the consumption of water and organisms is 0.00013 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137312, Aldrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256366

Pollutant:

Aldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Aldrin. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The aldrin criterion for the protection of human health from the consumption of water and organisms is 0.00013 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137312, Aldrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256365

Pollutant:

Aldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Aldrin.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137258	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Antimony
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137258, Antimony	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253540

Pollutant:

Antimony

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Antimony.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for antimony is 0.006 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2019-08-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137258, Antimony	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253324

Pollutant:

Antimony

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA Quality Criteria for Water (Gold Book) states that for antimony toxicity to algae occurs at 610 ug/l. (USEPA, 1986)

Guideline Reference:

Quality Criteria for Water 1986. United States Environmental Protection Agency. Office of Water. Regulations and Standards. Washington D.C. EPA 440/5-86-001.

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-08-04 and 2015-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137258, Antimony	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253584

Pollutant:

Antimony

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for antimony is 0.006 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-08-04 and 2015-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137258, Antimony	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253301

Pollutant:

Antimony

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA Quality Criteria for Water (Gold Book) states that for antimony toxicity to algae occurs at 610 ug/l. (USEPA, 1986)

Guideline Reference:

Quality Criteria for Water 1986. United States Environmental Protection Agency. Office of Water. Regulations and Standards. Washington D.C. EPA 440/5-86-001.

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2019-08-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137259	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Arsenic
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 23 and 0 of 23 samples exceeded the criteria and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137259, Arsenic	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253568

Pollutant:

Arsenic

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for arsenic is 10 ug/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137259, Arsenic	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253523

Pollutant:

Arsenic

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 12 samples exceeded the water quality threshold for Arsenic.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for arsenic is 10 ug/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137259, Arsenic	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253588

Pollutant:

Arsenic

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved arsenic criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 150 ug/L. The conversion factor used to convert the total fraction criterion for arsenic to dissolved fraction criterion is 1. Therefore all data was considered to be representative of the dissolved fraction. (California Toxics Rule, 2000)

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137259, Arsenic	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253590

Pollutant:

Arsenic

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137260	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Atrazine
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137260, Atrazine	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

257346

Pollutant:

Atrazine

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Atrazine.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for atrazine is 1 ug/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2010-12-19

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137260, Atrazine	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

257342

Pollutant:

Atrazine

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Atrazine.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for Atrazine is the USEPA Aquatic Life Benchmark of < 1 ug/L for a nonvascular plant (acute). The benchmark was derived from a 'less-than' value (for example, <1,500) and may underestimate toxicity.

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2010-12-19

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137261	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Barium
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 22 samples exceeded the criteria and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137261, Barium	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253673

Pollutant:

Barium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for barium is 1 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137261, Barium	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253672

Pollutant:

Barium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 10 samples exceeded the water quality threshold for Barium.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for barium is 1 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-08-04 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	151138	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Benthic Community Effects
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Benthic Community Effects are being considered for placement on the CWA section 303(d) List under sections 3.9 of the Listing Policy. Under section 3.9, additional lines of evidence (LOEs) associating the Benthic Community Effects decision with a water or sediment concentration of pollutants other than benthic-macroinvertebrate bioassessment or habitat assessment LOEs are necessary to place a water body on the 303(d) List for Benthic Community Effects. Four line(s) of evidence evaluating benthic-macroinvertebrate bioassessment data is/are available in the administrative record to assess this indicator. Three of four benthic-macroinvertebrate samples exceed the California Stream Condition Index (CSCI) impairment threshold. A minimum of two benthic-macroinvertebrate samples are needed to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing Benthic Community Effects in this waterbody segment on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Three of four benthic-macroinvertebrate bioassessment samples had CSCI scores below 0.79. The available information is insufficient to determine whether the waterbody/pollutant combination should be placed on the 303(d) List of impaired waters at this time. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 151138, Benthic Community Effects	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

305423

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 408CAL012 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.599924343 to 0.599924343.

Data Reference:

California Stream Condition Index (CSCI) Scores for the 2024 Integrated Report for Region 4.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that are lethal to or that produce significant alterations in population or community ecology or receiving water biota. In addition, the health and life history characteristics of aquatic organisms in waters affected by controllable water quality factors shall not differ significantly from those for the same waters in areas unaffected by controllable water quality factors.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Stream Condition Index (CSCI) is a biological scoring tool that helps aquatic resource managers translate complex data about benthic macroinvertebrates found living in a stream into an overall measure of stream health. The CSCI score is calculated by comparing the expected condition with actual (observed) results (Rehn, A.C. et al., 2015). CSCI scores range from 0 (highly degraded) to greater than 1 (equivalent to reference). CSCI scoring of biological condition are as follows (per the scientific paper supporting the development of the CSCI scoring tool): greater than or equal to 0.92 = likely intact condition, 0.91 to 0.80 = possibly altered condition, 0.79 to 0.63 = likely altered condition, less than or equal to 0.62 = very likely altered condition. Sites with scores below 0.79 are considered to have exceeded the water quality objective for the aquatic life beneficial use.

Guideline Reference:

Bioassessment in complex environments: designing an index for consistent meaning in different settings

Spatial Representation:

Samples were collected from station 408CAL012.

Temporal Representation:

Samples were collected from 10/30/2001 to 10/30/2001.

Environmental Conditions:

QAPP Information:

Data were collected using Surface Water Ambient Monitoring Program protocols

QAPP Information Reference(s):

This is a placeholder reference for data that was collected after QAPP requirements were developed, but exempt from the requirements.

Line of Evidence (LOE) for Decision ID 151138, Benthic Community Effects	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

305401

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 408BH5Cxx to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.608216145 to 0.608216145.

Data Reference:

California Stream Condition Index (CSCI) Scores for the 2024 Integrated Report for Region 4.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Bioassessment in complex environments: designing an index for consistent meaning in different settings

Spatial Representation:

Samples were collected from station 408BH5Cxx.

Temporal Representation:

Samples were collected from 6/18/2010 to 6/18/2010.

Environmental Conditions:

QAPP Information:

Data were collected using Surface Water Ambient Monitoring Program protocols

QAPP Information Reference(s):

This is a placeholder reference for data that was collected after QAPP requirements were developed, but exempt from the requirements.

Line of Evidence (LOE) for Decision ID 151138, Benthic Community Effects	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

305399

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 408BH5Axx to determine beneficial use support and the results are as follows: 0 of 1 samples exceeded the threshold. CSCI scores were from 0.846616924 to 0.846616924.

Data Reference:

California Stream Condition Index (CSCI) Scores for the 2024 Integrated Report for Region 4.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Bioassessment in complex environments: designing an index for consistent meaning in different settings

Spatial Representation:

Samples were collected from station 408BH5Axx.

Temporal Representation:

Samples were collected from 6/18/2010 to 6/18/2010.

Environmental Conditions:

QAPP Information:

Data were collected using Surface Water Ambient Monitoring Program protocols

QAPP Information Reference(s):

This is a placeholder reference for data that was collected after QAPP requirements were developed, but exempt from the requirements.

Line of Evidence (LOE) for Decision ID 151138, Benthic Community Effects	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

305400

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 408BH5Bxx to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.73113276 to 0.73113276.

Data Reference:

California Stream Condition Index (CSCI) Scores for the 2024 Integrated Report for Region 4.

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Bioassessment in complex environments: designing an index for consistent meaning in different settings

Spatial Representation:

Samples were collected from station 408BH5Bxx.

Temporal Representation:

Samples were collected from 6/18/2010 to 6/18/2010.

Environmental Conditions:

QAPP Information:

Data were collected using Surface Water Ambient Monitoring Program protocols

QAPP Information Reference(s):

This is a placeholder reference for data that was collected after QAPP requirements were developed, but exempt from the requirements.


DECISION ID	137264	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Bromoform
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 25 samples exceeded the CRITERIA and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137264, Bromoform	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253826

Pollutant:

Bromoform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bromoform criterion for the protection of human health from the consumption of water and organisms is 4.3 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137264, Bromoform	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253805

Pollutant:

Bromoform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bromoform criterion for the protection of human health from the consumption of water and organisms is 4.3 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2020-03-31

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137267	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Chlorine
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 70 samples exceeded the criterion and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137267, Chlorine	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253645

Pollutant:

Chlorine

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 0 of the 35 samples exceeded the water quality threshold for Chlorine, Total Residual. Although a total of 66 samples were collected, 31 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: Chlorine residual shall not be present in surface water any concentration that causes impairment of beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA recommended chlorine criterion for the protection of aquatic ife in freshwater is 11 ug/L (4-day average).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628438).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-05-05 to 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137267, Chlorine	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253647

Pollutant:

Chlorine

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: Chlorine residual shall not be present in surface water any concentration that causes impairment of beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA recommended chlorine criterion for the protection of aquatic ife in freshwater is 11 ug/L (4-day average).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628437).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-05-05 to 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137269	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Chloroform
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 45 samples exceeded the criteria and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137269, Chloroform	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253737

Pollutant:

Chloroform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 13 samples exceeded the water quality threshold for Chloroform.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: All waters shall be maintained free of toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in, human, plant, animal, or aquatic life.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA National Recommended Water Quality Criterion for chloroform for the protection of human health from consumption of water and organisms is 60 ug/L.

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2019-12-31

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137269, Chloroform	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253763

Pollutant:

Chloroform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA National Recommended Water Quality Criterion for chloroform for the protection of human health from consumption of water and organisms is 60 ug/L.

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2020-09-30

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137271	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Chromium, hexavalent
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137271, Chromium, hexavalent	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253987

Pollutant:

Chromium, hexavalent

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 4 samples exceeded the water quality threshold for Chromium VI.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved chromium (VI) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 11 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2018-02-06 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137271, Chromium, hexavalent	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254129

Pollutant:

Chromium, hexavalent

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Chromium VI.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved chromium (VI) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 11 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2019-08-06 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137272	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Chromium, trivalent
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137272, Chromium, trivalent	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254198

Pollutant:

Chromium, trivalent

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 7 samples exceeded the water quality threshold for Chromium III.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for total chromium is 0.05 mg/L (Title 22 of the California Code of Regulations).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2016-02-02 and 2020-05-05

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137272, Chromium, trivalent	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254101

Pollutant:

Chromium, trivalent

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for total chromium is 0.05 mg/L (Title 22 of the California Code of Regulations).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2016-02-02 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137272, Chromium, trivalent	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254243

Pollutant:

Chromium, trivalent

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved chromium (III) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 180 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2016-02-02 and 2020-05-05

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137272, Chromium, trivalent	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254173

Pollutant:

Chromium, trivalent

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2016-02-02 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137274	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Cyanide
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. 2 lines of evidence are available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 64 and 1 of 64 samples exceeded the criteria and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137274, Cyanide	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254161

Pollutant:

Cyanide

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 1 of 33 samples exceeded the water quality threshold for Cyanide.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The cyanide criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 5.2 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-10-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137274, Cyanide	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254115

Pollutant:

Cyanide

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 31 samples exceeded the water quality threshold for Cyanide.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for cyanide is 0.15 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2017-11-07

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137274, Cyanide	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254068

Pollutant:

Cyanide

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for cyanide is 0.15 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-10-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137274, Cyanide	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254160

Pollutant:

Cyanide

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The cyanide criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 5.2 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2017-11-07

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137278	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Dichloromethane
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137278, Dichloromethane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255210

Pollutant:

Dichloromethane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dichloromethane (methylene chloride) criterion for the protection of human health from the consumption of water and organisms is 4.7 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2016-08-02 and 2016-08-02

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137278, Dichloromethane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255193

Pollutant:

Dichloromethane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dichloromethane (methylene chloride) criterion for the protection of human health from the consumption of water and organisms is 4.7 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2016-08-02 and 2016-08-02

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137279	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Dieldrin
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.6 of the Listing Policy. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. Seven lines of evidence are available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for not placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 0, 0 of 2, 1 of 1, 0 of 23, 0 of 0 and of 43 samples exceeded the criteria and 0 of 1 samples exceeded the guideline and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. There is not an associated sediment toxicity data as required by Section 3.6 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137279, Dieldrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254641

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Dieldrin. Although a total of 11 samples were collected, 11 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dieldrin criterion for the protection of human health from the consumption of water and organisms is 0.00014 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137279, Dieldrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260366

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Dieldrin.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dieldrin criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.056 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137279, Dieldrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260408

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Dieldrin.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dieldrin criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.056 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137279, Dieldrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260485

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Dieldrin. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dieldrin criterion for the protection of human health from the consumption of water and organisms is 0.00014 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

Statewide Project Urban Pyrethroid Status Monitoring

Line of Evidence (LOE) for Decision ID 137279, Dieldrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83372

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

In freshwater sediments the probable effect concentration (predictive of sediment toxicity for sediment-dwelling organisms) for dieldrin is 61.8 ug/Kg dry weight (MacDonald et al. 2000).

Guideline Reference:

Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Environmental Contamination and Toxicology. 39: 20-31

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 137279, Dieldrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254545

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dieldrin criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.056 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137279, Dieldrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254621

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality threshold for Dieldrin. Although a total of 12 samples were collected, 11 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dieldrin criterion for the protection of human health from the consumption of water and organisms is 0.00014 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628438).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2019-06-30

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137279, Dieldrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254595

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dieldrin criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.056 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2019-06-30

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137279, Dieldrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260570

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Dieldrin. Although a total of 43 samples were collected, 43 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dieldrin criterion for the protection of human health from the consumption of water and organisms is 0.00014 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137280	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Endosulfan sulfate
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 2, 0 of 2, 0 of 1, 0 of 1, 0 of 43 and 0 of 43 samples exceeded the CRITERIA and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137280, Endosulfan sulfate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260822

Pollutant:

Endosulfan sulfate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Endosulfan Sulfate.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA National Recommended Water Quality Criteria toxicity threshold for endosulfan sulfate for freshwater aquatic life protection is 0.056 ug/l (24 hour average)

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137280, Endosulfan sulfate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260797

Pollutant:

Endosulfan sulfate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Endosulfan Sulfate.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan sulfate criterion for the protection of human health from the consumption of water and organisms is 110 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137280, Endosulfan sulfate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260820

Pollutant:

Endosulfan sulfate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Endosulfan Sulfate.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan sulfate criterion for the protection of human health from the consumption of water and organisms is 110 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137280, Endosulfan sulfate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254657

Pollutant:

Endosulfan sulfate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA National Recommended Water Quality Criteria toxicity threshold for endosulfan sulfate for freshwater aquatic life protection is 0.056 ug/l (24 hour average)

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2018-05-01 and 2018-05-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137280, Endosulfan sulfate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254679

Pollutant:

Endosulfan sulfate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan sulfate criterion for the protection of human health from the consumption of water and organisms is 110 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2018-05-01 and 2018-05-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137280, Endosulfan sulfate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260931

Pollutant:

Endosulfan sulfate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Endosulfan Sulfate.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA National Recommended Water Quality Criteria toxicity threshold for endosulfan sulfate for freshwater aquatic life protection is 0.056 ug/l (24 hour average)

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

Statewide Project Urban Pyrethroid Status Monitoring


DECISION ID	137281	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Endrin
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under sections 3.1 and 3.6 of the Listing Policy. Under section 3.1, at least one line of evidence is necessary to assess listing status, and under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants in sediment. Pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. 2 lines of evidence are available in the administrative record to assess this pollutant in water. 0 of 2 samples exceeded the criteria 0 of 2 samples exceeded the criteria 0 of 43 samples exceeded the criteria 0 of 43 samples exceeded the criteria 2 lines of evidence are available in the administrative record to assess this pollutant in sediment. 0 of 1 sample exceeded the GUIDELINE. 1 of 1 sample exhibited sediment toxicity. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 2, 0 of 2, 0 of 43 and 0 of 43 samples exceed the criteria and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 0 of 1 sample exceeded the GUIDELINE and this sample size is insufficient to determine beneficial use support, with the power and confidence of the Listing Policy. There is not an associated sediment toxicity data as required by Section 3.6 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137281, Endrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83376

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The sample was collected at station 408SUP059.

Temporal Representation:

The sample was collected in January 2007.

Environmental Conditions:

QAPP Information:

All data was collected following the Standard Operating Procedures and Data Quality Objectives outlined in the SWAMP QAMP, (Puckett, 2002). QA data are included in submission.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137281, Endrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

261306

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Endrin.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endrin criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.036 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137281, Endrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

261039

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Endrin.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endrin criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.036 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137281, Endrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

261281

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Endrin.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endrin criterion to protect human health from the consumption of water and organisms is 0.76 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

Statewide Project Urban Pyrethroid Status Monitoring

Line of Evidence (LOE) for Decision ID 137281, Endrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83373

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

In freshwater sediments the probable effect concentration (predictive of sediment toxicity for sediment-dwelling organisms) for endrin is 207 ug/Kg dry weight (MacDonald et al. 2000).

Guideline Reference:

Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Environmental Contamination and Toxicology. 39: 20-31

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 137281, Endrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

261041

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Endrin.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endrin criterion to protect human health from the consumption of water and organisms is 0.76 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137282	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Endrin aldehyde
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 2, 0 of 1, and 0 of 43 samples exceeded the CRITERIA and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137282, Endrin aldehyde	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

261214

Pollutant:

Endrin aldehyde

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Endrin Aldehyde.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endrin aldehyde criterion to protect human health from the consumption of water and organisms is 0.76 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137282, Endrin aldehyde	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254874

Pollutant:

Endrin aldehyde

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endrin aldehyde criterion to protect human health from the consumption of water and organisms is 0.76 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2019-05-07 and 2019-05-07

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137282, Endrin aldehyde	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

261148

Pollutant:

Endrin aldehyde

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Endrin Aldehyde.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endrin aldehyde criterion to protect human health from the consumption of water and organisms is 0.76 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137283	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Fluoride
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 35 samples exceeded the criteria and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137283, Fluoride	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254937

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 17 samples exceeded the water quality threshold for Fluoride.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for fluoride is 2 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137283, Fluoride	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254979

Pollutant:

Fluoride

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 18 samples exceeded the water quality threshold for Fluoride.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for fluoride is 2 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137314	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Hexachlorocyclohexane (HCH), alpha
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137314, Hexachlorocyclohexane (HCH), alpha	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

262126

Pollutant:

Hexachlorocyclohexane (HCH), alpha

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for HCH, alpha-. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The alpha-HCH (alpha-BHC) criterion for the protection of human health from consumption of water and organisms is 0.0039 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137314, Hexachlorocyclohexane (HCH), alpha	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

262127

Pollutant:

Hexachlorocyclohexane (HCH), alpha

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for HCH, alpha-. Although a total of 43 samples were collected, 43 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The alpha-HCH (alpha-BHC) criterion for the protection of human health from consumption of water and organisms is 0.0039 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137313	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Hexachlorocyclohexane (HCH), beta
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 2 and 0 of 43 samples exceeded the CRITERIA and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137313, Hexachlorocyclohexane (HCH), beta	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

262193

Pollutant:

Hexachlorocyclohexane (HCH), beta

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for HCH, beta-.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The beta-HCH (beta-BHC) criterion for the protection of human health from consumption of water and organisms is 0.014 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137313, Hexachlorocyclohexane (HCH), beta	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

262171

Pollutant:

Hexachlorocyclohexane (HCH), beta

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for HCH, beta-.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The beta-HCH (beta-BHC) criterion for the protection of human health from consumption of water and organisms is 0.014 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137285	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Lead
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137285, Lead	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255022

Pollutant:

Lead

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved lead criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 2.5 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2017-02-07 and 2020-02-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137285, Lead	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254977

Pollutant:

Lead

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for lead is 15 ug/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2017-02-07 and 2017-02-07

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137285, Lead	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255137

Pollutant:

Lead

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for lead is 15 ug/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2017-02-07 and 2020-02-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137285, Lead	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255019

Pollutant:

Lead

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2017-02-07 and 2017-02-07

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137286	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Lindane/gamma Hexachlorocyclohexane (gamma-HCH)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 and 3.6 of the Listing Policy. Under section 3.1 a single line of evidence are necessary to assess listing status. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. 5 lines of evidence are available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is insufficient justification for placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 2, 0 of 2, 0 of 43 and 0 of 43 sample exceeded the criteria and 0 of 1 sample exceeded the guideline and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137286, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

262067

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for HCH, gamma-.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The gamma-BHC (Lindane, gamma-HCH) criterion maximum concentration to protect aquatic life in freshwater is 0.95 ug/L. (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137286, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

262071

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for HCH, gamma-.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The gamma-BHC (Lindane, gamma-HCH) criterion for the protection of human health from the consumption of water and organisms is 0.019 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137286, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

261991

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for HCH, gamma-.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The gamma-BHC (Lindane, gamma-HCH) criterion for the protection of human health from the consumption of water and organisms is 0.019 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

Statewide Project Urban Pyrethroid Status Monitoring

Line of Evidence (LOE) for Decision ID 137286, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83389

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

In freshwater sediments the probable effect concentration (predictive of sediment toxicity for sediment-dwelling organisms) for Lindane (gamma-HCH) is 4.99 ug/Kg dry weight (MacDonald et al. 2000).

Guideline Reference:

Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Environmental Contamination and Toxicology. 39: 20-31

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 137286, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

262157

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for HCH, gamma-.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The gamma-BHC (Lindane, gamma-HCH) criterion maximum concentration to protect aquatic life in freshwater is 0.95 ug/L. (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137287	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Malathion
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 2, 0 of 2, 0 of 43 and 2 of 43 samples exceeded the CRITERIA and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137287, Malathion	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

262915

Pollutant:

Malathion

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 2 of 43 samples exceeded the water quality threshold for Malathion.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Aquatic life should not be affected unacceptably if the 4-day average concentration of malathion does not exceed 0.028 ug/L (UC Davis Aquatic Life Criteria).

Guideline Reference:

Aquatic life water quality criteria derived via the UC Davis method: l. Organophosphate insecticides. Reviews of Environmental Contamination and Toxicology 216:1-48.

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137287, Malathion	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

262874

Pollutant:

Malathion

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Malathion.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Aquatic life should not be affected unacceptably if the 4-day average concentration of malathion does not exceed 0.028 ug/L (UC Davis Aquatic Life Criteria).

Guideline Reference:

Aquatic life water quality criteria derived via the UC Davis method: l. Organophosphate insecticides. Reviews of Environmental Contamination and Toxicology 216:1-48.

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137287, Malathion	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

263066

Pollutant:

Malathion

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Malathion.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA drinking water health advisory for lifetime exposure to malathion is 500 ug/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137287, Malathion	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

262856

Pollutant:

Malathion

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Malathion.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA drinking water health advisory for lifetime exposure to malathion is 500 ug/L.

Guideline Reference:

2018 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.


DECISION ID	149482	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Mercury
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 149482, Mercury	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255184

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Mercury. Although a total of 31 samples were collected, 31 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The mercury criterion for the protection of human health from the consumption of water and organisms is 0.050 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-05-05 to 2017-11-07

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149482, Mercury	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255055

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Mercury. Although a total of 31 samples were collected, 31 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

National Recommended Water Quality Criteria Continuous Concentration (4-day average concentrations) for freshwater aquatic organisms exposure to total mercury is 0.77 ug/L.

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-05-05 to 2017-11-07

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149482, Mercury	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255167

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Mercury. Although a total of 31 samples were collected, 31 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The mercury criterion for the protection of human health from the consumption of water and organisms is 0.050 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-05-05 to 2017-11-07

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149482, Mercury	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255231

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Mercury. Although a total of 31 samples were collected, 31 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

National Recommended Water Quality Criteria Continuous Concentration (4-day average concentrations) for freshwater aquatic organisms exposure to total mercury is 0.77 ug/L.

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-05-05 to 2017-11-07

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137291	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	N-Nitrosodimethylamine
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137291, N-Nitrosodimethylamine	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255483

Pollutant:

N-Nitrosodimethylamine

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for Nitrosodimethylamine, N-.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The N-nitroso-di-methylamine criterion for the protection of human health from the consumption of water and organisms is 0.00069 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2019-08-06 and 2019-08-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137288	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Naphthalene
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137288, Naphthalene	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255081

Pollutant:

Naphthalene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA recommended naphthalene criterion for the protection of freshwater aquatic life is 620 ug/l. (EPA 440/5-80-059)

Guideline Reference:

Ambient Water Quality Criteria for Naphthalene

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2019-11-05 and 2019-11-05

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137288, Naphthalene	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255088

Pollutant:

Naphthalene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Drinking water notification levels are published by the Division of Drinking Water and are for chemicals for which there is no drinking water MCL. If a notification level is exceeded, local government notification is required and customer notification is recommended. The notification level for naphthalene is 0.017 mg/L.

Guideline Reference:

Drinking Water Notification and Response Levels: An Overview

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2019-11-05 and 2019-11-05

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137289	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Nickel
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 108 and 0 of 108 samples exceeded the criteria and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137289, Nickel	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255298

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 53 samples exceeded the water quality threshold for Nickel.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved nickel criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 52 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137289, Nickel	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255047

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 55 samples exceeded the water quality threshold for Nickel.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The maximum contaminant level of nickel in public water systems shall be 0.1 mg/L (California Code of Regulations, Title 22, Division 4, Chapter 15, Sections 64431).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137289, Nickel	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255367

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The maximum contaminant level of nickel in public water systems shall be 0.1 mg/L (California Code of Regulations, Title 22, Division 4, Chapter 15, Sections 64431).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137289, Nickel	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255325

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	149483	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Nitrogen, Nitrate
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 9 of 184 and 9 of 184 samples exceeded the OBJECTIVE and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 149483, Nitrogen, Nitrate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

302461

Pollutant:

Nitrogen, Nitrate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 8 of 45 samples exceeded the water quality threshold for Nitrate as N.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region (page 3-34) states that: Waters shall not exceed 10 mg/L as nitrate-nitrogen (NO3-N).

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 149483, Nitrogen, Nitrate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255048

Pollutant:

Nitrogen, Nitrate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 1 of 56 samples exceeded the water quality threshold for Nitrate as N.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for nitrate (as N) 10 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149483, Nitrogen, Nitrate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

263805

Pollutant:

Nitrogen, Nitrate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 8 of 45 samples exceeded the water quality threshold for Nitrate as N.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for nitrate (as N) 10 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 149483, Nitrogen, Nitrate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255049

Pollutant:

Nitrogen, Nitrate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 56 samples exceeded the water quality threshold for Nitrate as N.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for nitrate (as N) 10 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149483, Nitrogen, Nitrate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

302606

Pollutant:

Nitrogen, Nitrate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region (page 3-34) states that: Waters shall not exceed 10 mg/L as nitrate-nitrogen (NO3-N).

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149483, Nitrogen, Nitrate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

302560

Pollutant:

Nitrogen, Nitrate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region (page 3-34) states that: Waters shall not exceed 10 mg/L as nitrate-nitrogen (NO3-N).

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149483, Nitrogen, Nitrate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

302451

Pollutant:

Nitrogen, Nitrate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region (page 3-34) states that: Waters shall not exceed 10 mg/L as nitrate-nitrogen (NO3-N).

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_MADER (Arroyo Simi At MaderaAvenue).

Temporal Representation:

The samples were collected between the dates of 2010-11-10 and 2015-05-05

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 149483, Nitrogen, Nitrate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

263848

Pollutant:

Nitrogen, Nitrate

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for nitrate (as N) 10 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 07_MADER (Arroyo Simi At MaderaAvenue).

Temporal Representation:

The samples were collected between the dates of 2010-11-10 and 2015-05-05

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.


DECISION ID	149484	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Nitrogen, Nitrite
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 183 samples exceeded the OBJECTIVE and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 149484, Nitrogen, Nitrite	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

264412

Pollutant:

Nitrogen, Nitrite

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for nitrite (as N) is 1.0 mg/L (Title 22 of the California Code of Regulations).

Guideline Reference:

Maximum Contaminant Levels for organic and inorganic chemicals. CCR Title 22

Spatial Representation:

The samples were collected at 1 monitoring site: 07_MADER (Arroyo Simi At MaderaAvenue).

Temporal Representation:

The samples were collected between the dates of 2010-11-10 and 2015-05-05

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 149484, Nitrogen, Nitrite	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255050

Pollutant:

Nitrogen, Nitrite

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for nitrite (as N) is 1.0 mg/L (Title 22 of the California Code of Regulations).

Guideline Reference:

Maximum Contaminant Levels for organic and inorganic chemicals. CCR Title 22

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149484, Nitrogen, Nitrite	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

264373

Pollutant:

Nitrogen, Nitrite

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 45 samples exceeded the water quality threshold for Nitrite as N.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for nitrite (as N) is 1.0 mg/L (Title 22 of the California Code of Regulations).

Guideline Reference:

Maximum Contaminant Levels for organic and inorganic chemicals. CCR Title 22

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 149484, Nitrogen, Nitrite	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255068

Pollutant:

Nitrogen, Nitrite

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for nitrite (as N) is 1.0 mg/L (Title 22 of the California Code of Regulations).

Guideline Reference:

Maximum Contaminant Levels for organic and inorganic chemicals. CCR Title 22

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	151860	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Oxygen, Dissolved
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 132 samples exceeded the objective and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 151860, Oxygen, Dissolved	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

308078

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 66 samples exceeded the water quality threshold for Oxygen, Dissolved.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region (page 3-39) states that: The dissolved oxygen content of all surface waters designated as WARM shall not be depressed below 5 mg/L as a result of waste discharges.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 151860, Oxygen, Dissolved	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

308079

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137296	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	PCBs (Polychlorinated biphenyls)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137296, PCBs (Polychlorinated biphenyls)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

264442

Pollutant:

PCBs (Polychlorinated biphenyls)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for PCBs (Polychlorinated biphenyls). Although a total of 37 samples were collected, 37 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The PCB, total aroclors criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.014 ug/L. This value corresponds to the sum of aroclors 1242, 1254, 1221, 1232, 1248, 1260, and 1016 (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-11-09 to 2017-05-09

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137296, PCBs (Polychlorinated biphenyls)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255554

Pollutant:

PCBs (Polychlorinated biphenyls)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 0 of the 1 samples exceeded the water quality threshold for PCBs (Polychlorinated biphenyls). Although a total of 12 samples were collected, 11 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628438).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2018-06-30

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137296, PCBs (Polychlorinated biphenyls)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255680

Pollutant:

PCBs (Polychlorinated biphenyls)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for PCBs (Polychlorinated biphenyls). Although a total of 11 samples were collected, 11 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137296, PCBs (Polychlorinated biphenyls)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

264494

Pollutant:

PCBs (Polychlorinated biphenyls)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for PCBs (Polychlorinated biphenyls). Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137296, PCBs (Polychlorinated biphenyls)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255600

Pollutant:

PCBs (Polychlorinated biphenyls)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The PCB criterion for the protection of human health from consumption of water and organisms is 0.00017 ug/L and is equal to the maximum of the sum of aroclors or congeners (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2017-02-07 and 2017-02-07

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137296, PCBs (Polychlorinated biphenyls)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255599

Pollutant:

PCBs (Polychlorinated biphenyls)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2017-02-07 and 2017-02-07

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137295	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Phenol
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137295, Phenol	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255564

Pollutant:

Phenol

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The phenol criterion for the protection of human health from the consumption of water and organisms is 21,000 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2019-11-05 and 2019-11-05

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137310	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Prometryn
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137310, Prometryn	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

265464

Pollutant:

Prometryn

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Prometryn.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The USEPA expected safe lifetime exposure limit in drinking water for prometryn, calculated using the IRIS Reference Dose, is 28 ug/L. This was calculated assuming 70 kg body weight, 2 liters/day water consumption, 20% relative source contribution from drinking water, and 0.004 mg/kg/day as the reference dose.

Guideline Reference:

IRIS Reference Summary (Various Pollutants)

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2010-12-19

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137310, Prometryn	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

265447

Pollutant:

Prometryn

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Prometryn.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

UC Davis Aquatic Life Criteria: Aquatic life should not be affected unacceptably if the four-day average concentration of Prometryn does not exceed 0.562 ug/L (Bower, et al. 2017).

Guideline Reference:

Water Quality Criteria Report for Prometryn Phase III: Application of the pesticide water quality criteria methodology. Department of Environmental Toxicology. University of California, Davis.

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2010-12-19

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137298	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Simazine
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Insufficient information is available to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. Beneficial use support will be reassessed in a future cycle, if more data are available.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 137298, Simazine	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

266523

Pollutant:

Simazine

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Simazine.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for simazine incorporated is 4 ug/L (Basin Plan).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2010-12-19

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137298, Simazine	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

266585

Pollutant:

Simazine

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Simazine.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for simazine is the USEPA Aquatic Life Benchmark of 6 ug/L for a nonvascular plant (acute).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2010-12-19

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.


DECISION ID	151898	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Surfactants (MBAS)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. None of the 91 samples exceeded the objective and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 151898, Surfactants (MBAS)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

307974

Pollutant:

Surfactants (MBAS)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 44 samples exceeded the water quality threshold for MBAS.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region (page 3-33) states that: Waters shall not have MBAS concentrations greater than 0.5 mg/L in waters designated MUN.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-11-05

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 151898, Surfactants (MBAS)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

307975

Pollutant:

Surfactants (MBAS)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 47 samples exceeded the water quality threshold for MBAS.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region (page 3-33) states that: Waters shall not have MBAS concentrations greater than 0.5 mg/L in waters designated MUN.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-08-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137300	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Temperature, water
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 132 samples exceeded the OBJECTIVE and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137300, Temperature, water	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256030

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region (page 3-45) states that: For waters designated WARM, water temperature shall not be altered by more than 5 °F above the natural temperature. At no time shall these WARM-designated waters be raised above 80 °F as a result of waste discharges.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137300, Temperature, water	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255962

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137302	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Total Trihalomethane (TTHM)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 45 samples exceeded the criterion and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137302, Total Trihalomethane (TTHM)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256062

Pollutant:

Total Trihalomethane (TTHM)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for total trihalomethanes is 80 ug/L (Title 22 of the California Code of Regulations).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2020-09-30

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137302, Total Trihalomethane (TTHM)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256063

Pollutant:

Total Trihalomethane (TTHM)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for total trihalomethanes is 80 ug/L (Title 22 of the California Code of Regulations).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2019-12-31

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137305	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Turbidity
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 14 of 132 and 5 of 132 samples exceeded the objective and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137305, Turbidity	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256234

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 2 of 66 samples exceeded the water quality threshold for Turbidity.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: Waters shall be free of changes in turbidity that cause nuisance or adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Turbidities of 40 NTU or greater can cause a reduced foraging efficiency and a shift in prey selection in piscivorous fish (largemouth bass) due to interference with their ability to find prey (Shoup, D.E. and Wahl D.H., 2009).

Guideline Reference:

The Effects of Turbidity on Prey Selection by Piscivorous Largemouth Bass

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137305, Turbidity	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256218

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 6 of 66 samples exceeded the water quality threshold for Turbidity.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: Waters shall be free of changes in turbidity that cause nuisance or adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Secondary Maximum Contaminant Level for turbidity is 5 NTU (California Code of Regulations, Title 22). Calculation of a numeric objective for other beneficial uses requires comparison with upstream or other background data which may not be available as part of the data used for water quality assessment.

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137305, Turbidity	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256251

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 8 of 66 samples exceeded the water quality threshold for Turbidity.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: Waters shall be free of changes in turbidity that cause nuisance or adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137305, Turbidity	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256215

Pollutant:

Turbidity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 3 of 66 samples exceeded the water quality threshold for Turbidity.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: Waters shall be free of changes in turbidity that cause nuisance or adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

The Effects of Turbidity on Prey Selection by Piscivorous Largemouth Bass

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137306	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Zinc
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 22 and 0 of 22 samples exceeded the criteria and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137306, Zinc	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256204

Pollutant:

Zinc

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Secondary Maximum Contaminant Level for zinc is 5.0 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2019-08-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137306, Zinc	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256273

Pollutant:

Zinc

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved zinc criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 120 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137306, Zinc	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256109

Pollutant:

Zinc

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2019-08-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137306, Zinc	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256271

Pollutant:

Zinc

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Secondary Maximum Contaminant Level for zinc is 5.0 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137275	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	alpha-Endosulfan (Endosulfan 1)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 2, 0 of 2, 0 of 2, 0 of 2., 0 of 43 and 0 of 43 samples exceeded the CRITERIA and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137275, alpha-Endosulfan (Endosulfan 1)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260648

Pollutant:

alpha-Endosulfan (Endosulfan 1)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Endosulfan I.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan I (alpha-endosulfan) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.056 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137275, alpha-Endosulfan (Endosulfan 1)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260649

Pollutant:

alpha-Endosulfan (Endosulfan 1)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Endosulfan I.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan I (alpha-endosulfan) criterion for the protection human health from the consumption of water and organisms is 110 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137275, alpha-Endosulfan (Endosulfan 1)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260763

Pollutant:

alpha-Endosulfan (Endosulfan 1)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Endosulfan I.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan I (alpha-endosulfan) criterion for the protection human health from the consumption of water and organisms is 110 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137275, alpha-Endosulfan (Endosulfan 1)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

261004

Pollutant:

alpha-Endosulfan (Endosulfan 1)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Endosulfan I.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan I (alpha-endosulfan) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.056 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137275, alpha-Endosulfan (Endosulfan 1)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254573

Pollutant:

alpha-Endosulfan (Endosulfan 1)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan I (alpha-endosulfan) criterion for the protection human health from the consumption of water and organisms is 110 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2018-05-01 and 2018-05-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137275, alpha-Endosulfan (Endosulfan 1)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254550

Pollutant:

alpha-Endosulfan (Endosulfan 1)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan I (alpha-endosulfan) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.056 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2018-05-01 and 2018-05-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137275, alpha-Endosulfan (Endosulfan 1)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254673

Pollutant:

alpha-Endosulfan (Endosulfan 1)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan I (alpha-endosulfan) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.056 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2019-11-05 and 2019-11-05

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137275, alpha-Endosulfan (Endosulfan 1)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254625

Pollutant:

alpha-Endosulfan (Endosulfan 1)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan I (alpha-endosulfan) criterion for the protection human health from the consumption of water and organisms is 110 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2019-11-05 and 2019-11-05

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137293	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	beta-Endosulfan (Endosulfan 2)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List in the Water Quality Limited Segments category. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 2, 0 of 2, 0 of 43 and 0 of 43 samples exceeded the CRITERIA and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137293, beta-Endosulfan (Endosulfan 2)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260703

Pollutant:

beta-Endosulfan (Endosulfan 2)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Endosulfan II.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan II (beta-endosulfan) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.056 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137293, beta-Endosulfan (Endosulfan 2)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260660

Pollutant:

beta-Endosulfan (Endosulfan 2)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Endosulfan II.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan II (beta-endosulfan) criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.056 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137293, beta-Endosulfan (Endosulfan 2)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260862

Pollutant:

beta-Endosulfan (Endosulfan 2)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Endosulfan II.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan II (beta-endosulfan) criterion to protect human health from the consumption of water and organisms is 110 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137293, beta-Endosulfan (Endosulfan 2)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260924

Pollutant:

beta-Endosulfan (Endosulfan 2)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 43 samples exceeded the water quality threshold for Endosulfan II.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The endosulfan II (beta-endosulfan) criterion to protect human health from the consumption of water and organisms is 110 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137294	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	pH
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 132 and 0 of 132 samples exceed the objective and this exceeds the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because applicable water quality standards are not being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137294, pH	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255666

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, Los Angeles Basin: the pH for inland surface waters, bays, or estuaries shall not be depressed below 6.5 or raised above 8.5 as a result of waste discharges.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137294, pH	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255402

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, Los Angeles Basin: the pH for inland surface waters, bays, or estuaries shall not be depressed below 6.5 or raised above 8.5 as a result of waste discharges.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137294, pH	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255475

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, Los Angeles Basin: the pH for inland surface waters, bays, or estuaries shall not be depressed below 6.5 or raised above 8.5 as a result of waste discharges.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137294, pH	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255526

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, Los Angeles Basin: the pH for inland surface waters, bays, or estuaries shall not be depressed below 6.5 or raised above 8.5 as a result of waste discharges.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137308	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Bifenthrin
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
Expected TMDL Completion Date:	2037
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under sections 3.1 and 3.6 of the Listing Policy. Under section 3.1, one line of evidence is necessary to assess listing status. Under Section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants in sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. 3 lines of evidence are available in the administrative record to assess this pollutant. 12 of 12 samples exceeded the criteria. 1 of 1 samples exceeded the criteria. 1 of 1 samples exceeded the guideline. Based on the readily available data and information, the weight of evidence indicates that there is INSUFFICIENT justification FOR placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 12 of 12 and 1 of 1 samples exceeded the criteria and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 1 of 1 sample exceeded the sediment guideline and this is insufficient to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy. A minimum of 16 samples is needed to determine if a beneficial use is fully supported using Table 3.1. There is not an associated sediment toxicity data as required by Section 3.6 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137308, Bifenthrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83432

Pollutant:

Bifenthrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for bifenthrin is the median lethal concentration (LC50) of 0.43 ug/g and is normalized by the percentage of organic carbon in the sediment sample. The LC50 0.43 ug/g is the geometric mean of LC50 values for bifenthrin from Amweg et al. (2005) and Amweg and Weston (2007).

Guideline Reference:

Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California, USA. Environmental Toxicology and Chemistry, 24:966-972, with erratum 24:No. 5

Guideline Reference:

Whole-sediment toxicity identification evaluation tools for pyrethroid insecticides: I. piperonyl butoxide addition. Environ. Toxicol. Chem. 26:2389-2396.

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 137308, Bifenthrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

258042

Pollutant:

Bifenthrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 12 of the 12 samples exceeded the water quality threshold for Bifenthrin. Although a total of 42 samples were collected, 30 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The chronic criterion for bifenthrin is 0.1 ng/L (expressed as a 4-day average). If the freely dissolved concentrations of bifenthrin were reported or could be calculated then these values were used for this assessment. In the absence of freely dissolved concentrations, total concentrations were used.

Guideline Reference:

Water Quality Criteria Report for Bifenthrin

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

Statewide Project Urban Pyrethroid Status Monitoring

Line of Evidence (LOE) for Decision ID 137308, Bifenthrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83376

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The sample was collected at station 408SUP059.

Temporal Representation:

The sample was collected in January 2007.

Environmental Conditions:

QAPP Information:

All data was collected following the Standard Operating Procedures and Data Quality Objectives outlined in the SWAMP QAMP, (Puckett, 2002). QA data are included in submission.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137308, Bifenthrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

258064

Pollutant:

Bifenthrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality threshold for Bifenthrin. Although a total of 2 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Water Quality Criteria Report for Bifenthrin

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137262	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Bis(2ethylhexyl)phthalate (DEHP)
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
Expected TMDL Completion Date:	2037
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 6 of 7 samples exceed the criterion and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137262, Bis(2ethylhexyl)phthalate (DEHP)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253752

Pollutant:

Bis(2ethylhexyl)phthalate (DEHP)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 3 of the 4 samples exceeded the water quality threshold for Bis(2-ethylhexyl)phthalate. Although a total of 11 samples were collected, 7 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bis(2-ethylhexyl)phthalate criterion for the protection of human health from the consumption of water and organisms is 1.8 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628438).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2018-06-30

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137262, Bis(2ethylhexyl)phthalate (DEHP)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253753

Pollutant:

Bis(2ethylhexyl)phthalate (DEHP)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 3 of the 3 samples exceeded the water quality threshold for Bis(2-ethylhexyl)phthalate. Although a total of 9 samples were collected, 6 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bis(2-ethylhexyl)phthalate criterion for the protection of human health from the consumption of water and organisms is 1.8 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628437).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137268	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Chlorodibromomethane
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
Expected TMDL Completion Date:	2037
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 9 of 18 samples exceed the criteria and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137268, Chlorodibromomethane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254610

Pollutant:

Chlorodibromomethane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 9 of the 18 samples exceeded the water quality threshold for Dibromochloromethane. Although a total of 19 samples were collected, 1 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The chlorodibromomethane criterion for the protection of human health from the consumption of water and organisms is 0.41 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628438).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-09-30 to 2020-09-30

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137268, Chlorodibromomethane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254615

Pollutant:

Chlorodibromomethane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Dibromochloromethane. Although a total of 11 samples were collected, 11 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The chlorodibromomethane criterion for the protection of human health from the consumption of water and organisms is 0.41 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137315	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Cyfluthrin
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
Expected TMDL Completion Date:	2037
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under sections 3.1 and 3.6 of the Listing Policy. Under section 3.1 at least one line of evidence is necessary to assess listing status for pollutants in water. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants in sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. Three lines of evidence are available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 7 of 7 samples exceeded the criteria and this exceeds the allowable frequency of Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137315, Cyfluthrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83438

Pollutant:

Cyfluthrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for cyfluthrin is the median lethal concentration (LC50) of 1.1 ug/g and is normalized by the percentage of organic carbon in the sediment sample. The LC50 1.1 ug/g is the geometric mean of LC50 values for cyfluthrin from Amweg et al. (2005).

Guideline Reference:

Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California, USA. Environmental Toxicology and Chemistry, 24:966-972, with erratum 24:No. 5

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 137315, Cyfluthrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

259281

Pollutant:

Cyfluthrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 7 of the 7 samples exceeded the water quality threshold for Cyfluthrin. Although a total of 42 samples were collected, 35 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The chronic criterion for cyfluthrin is 0.2 ng/L (expressed as a 4-day average). If the freely dissolved concentrations of cyfluthrin were reported or could be calculated then these values were used for this assessment. In the absence of freely dissolved concentrations, total concentrations were used.

Guideline Reference:

Water Quality Criteria Report for Cyfluthrin

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137315, Cyfluthrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

259271

Pollutant:

Cyfluthrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Cyfluthrin. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Water Quality Criteria Report for Cyfluthrin

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

Statewide Project Urban Pyrethroid Status Monitoring


DECISION ID	137309	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Cypermethrin
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
Expected TMDL Completion Date:	2037
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under sections 3.1 and 3.6 of the Listing Policy. Under section 3.1 one line of evidence is necessary to assess listing status. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants in sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. 3 lines of evidence are available in the administrative record to assess this pollutant. 0 of 0 samples exceeds the criteria. 8 of 8 samples exceeds the criteria. 0 of 0 samples exceeds the guideline. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 0 and 8 of 8 samples exceed the criteria and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 0 of 0 samples exceeded the guideline and this sample size is insufficient to determine beneficial use support, with the power and confidence of the Listing Policy. There is not an associated sediment toxicity data as required by Section 3.6 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137309, Cypermethrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83445

Pollutant:

Cypermethrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

One of one sample result was non-detect. It was not used in the assessment because after the laboratory method detection limit value was organic carbon normalized the result was above the guideline, therefore the result could not be quantified with the level of certainty required by the Listing Policy.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for cypermethrin is the median lethal concentration (LC50) of 0.3 ug/g and is normalized by the percentage of organic carbon in the sediment sample. The LC50 0.3 ug/g is the geometric mean of LC50 values for cypermethrin from Maund et al. (2002).

Guideline Reference:

Partitioning, bioavailability, and toxicity of the pyrethroid insecticide cypermethrin in sediments. Environmental Toxicology and Chemistry 21:9-15

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 137309, Cypermethrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

259388

Pollutant:

Cypermethrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Cypermethrin. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The chronic criterion for cypermethrin is 0.3 ng/L (expressed as a 4-day average). If the freely dissolved concentrations of cypermethrin were reported or could be calculated then these values were used for this assessment. In the absence of freely dissolved concentrations, total concentrations were used.

Guideline Reference:

Water Quality Criteria Report for Cypermethrin

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137309, Cypermethrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

259262

Pollutant:

Cypermethrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 8 of the 8 samples exceeded the water quality threshold for Cypermethrin. Although a total of 42 samples were collected, 34 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Water Quality Criteria Report for Cypermethrin

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

Statewide Project Urban Pyrethroid Status Monitoring

Line of Evidence (LOE) for Decision ID 137309, Cypermethrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83376

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The sample was collected at station 408SUP059.

Temporal Representation:

The sample was collected in January 2007.

Environmental Conditions:

QAPP Information:

All data was collected following the Standard Operating Procedures and Data Quality Objectives outlined in the SWAMP QAMP, (Puckett, 2002). QA data are included in submission.

QAPP Information Reference(s):


DECISION ID	137316	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Deltamethrin
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
Expected TMDL Completion Date:	2037
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under sections 3.1 and 3.6 of the Listing Policy. Under section 3.1, at least one line of evidence is necessary to assess listing status for pollutants in water. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants in sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. Three lines of evidence are available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. Three of 3 sample exceeded the criteria for pollutants in water and this exceeds the frequency allowable by Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137316, Deltamethrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83367

Pollutant:

Deltamethrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for deltamethrin is the median lethal concentration (LC50) of 0.79 ug/g and is normalized by the percentage of organic carbon in the sediment sample. The LC50 0.79 ug/g is the geometric mean of LC50 values for deltamethrin from Amweg et al. (2005).

Guideline Reference:

Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California, USA. Environmental Toxicology and Chemistry, 24:966-972, with erratum 24:No. 5

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 137316, Deltamethrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

259843

Pollutant:

Deltamethrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Deltamethrin. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for deltamethrin is the USEPA Aquatic Life Benchmark of 0.000026 ug/L for an invertebrate (chronic).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137316, Deltamethrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

260289

Pollutant:

Deltamethrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 3 of the 3 samples exceeded the water quality threshold for Deltamethrin. Although a total of 42 samples were collected, 39 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for deltamethrin is the USEPA Aquatic Life Benchmark of 0.000026 ug/L for an invertebrate (chronic).

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137277	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Dichlorobromomethane
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
Expected TMDL Completion Date:	2037
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 28 of 42 samples exceed the criterion and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137277, Dichlorobromomethane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253779

Pollutant:

Dichlorobromomethane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 28 of 29 samples exceeded the water quality threshold for Bromodichloromethane.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dichlorobromomethane criterion for the protection of human health from the consumption of water and organisms is 0.56 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2020-09-30

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137277, Dichlorobromomethane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253801

Pollutant:

Dichlorobromomethane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dichlorobromomethane criterion for the protection of human health from the consumption of water and organisms is 0.56 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-06-30 and 2019-12-31

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137284	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Iron
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
Expected TMDL Completion Date:	2037
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 2 of 20 and 2 of 20 samples exceed the criteria and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137284, Iron	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254825

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 1 of 10 samples exceeded the water quality threshold for Iron.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

National Recommended Water Quality Criteria Continuous Concentrations are intended protect freshwater aquatic organisms from chronic exposures and are expressed as 4-day average concentrations. The evaluation guideline for Iron is 1,000 ug/L.

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137284, Iron	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254804

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Secondary Maximum Contaminant Level for iron is 0.3 mg/L (Title 22 California Code of Regulations).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137284, Iron	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254910

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Secondary Maximum Contaminant Level for iron is 0.3 mg/L (Title 22 California Code of Regulations).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137284, Iron	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254803

Pollutant:

Iron

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-02-03 and 2020-08-04

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137317	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Permethrin
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
Expected TMDL Completion Date:	2037
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 0, 0 of 1 and 2 of 2 samples exceed the CRITERIA and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137317, Permethrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83390

Pollutant:

Permethrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for permethrin is the median lethal concentration (LC50) of 8.9 ug/g and is normalized by the percentage of organic carbon in the sediment sample. The LC50 8.9 ug/g is the geometric mean of LC50 values for permethrin from Amweg et al. (2005).

Guideline Reference:

Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California, USA. Environmental Toxicology and Chemistry, 24:966-972, with erratum 24:No. 5

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 137317, Permethrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

264717

Pollutant:

Permethrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 2 of the 2 samples exceeded the water quality threshold for Permethrin. Although a total of 42 samples were collected, 40 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The chronic criterion for permethrin is 1 ng/L (expressed as a 4-day average). If the freely dissolved concentrations of permethrin were reported or could be calculated then these values were used for this assessment. In the absence of freely dissolved concentrations, total concentrations were used.

Guideline Reference:

Water Quality Criteria Report for Permethrin

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137317, Permethrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

265001

Pollutant:

Permethrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Permethrin. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Water Quality Criteria Report for Permethrin

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137307	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Pyrethroids
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
Expected TMDL Completion Date:	2037
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 1 of 1 and 14 of 14 samples exceed the GUIDELINE and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137307, Pyrethroids	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

265489

Pollutant:

Pyrethroids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 14 of 14 samples exceeded the water quality threshold for Pyrethroids.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The summed ratios of the pyrethroid pesticides bifenthrin, cyfluthrin, cypermethrin, esfenvalerate, lambda-cyhalothrin, permethrin and their respective chronic concentration goals are not to exceed 1. If the freely dissolved concentrations of these pesticides were reported or could be calculated then these values were used for this assessment. In the absence of freely dissolved concentrations, total concentrations were used.

Guideline Reference:

Amendment to the Water Quality Control Plan for the Sacramento River and San Joaquin River Basins for the Control of Pyrethroid Pesticide Discharges

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2011-03-20 and 2018-03-21

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137307, Pyrethroids	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

265437

Pollutant:

Pyrethroids

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality threshold for Pyrethroids. Although a total of 43 samples were collected, 42 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Amendment to the Water Quality Control Plan for the Sacramento River and San Joaquin River Basins for the Control of Pyrethroid Pesticide Discharges

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.


DECISION ID	149481	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Specific Conductivity
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown \| No Source Analysis Available
Expected TMDL Completion Date:	2037
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 132 of 132 samples exceed the OBJECTIVE and this exceeds the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 149481, Specific Conductivity	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255834

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 66 of 66 samples exceeded the water quality threshold for SpecificConductivity.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Secondary Maximum Contaminant Level recommended level for specific conductance is 900 uS/cm (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149481, Specific Conductivity	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255833

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Secondary Maximum Contaminant Level recommended level for specific conductance is 900 uS/cm (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2020-10-06

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137265	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Chlordane
Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Name:	Calleguas Creek PCBs (7)
TMDL Project Code:	360
Date TMDL Approved by USEPA:	03/24/2006
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under sections 3.1 and 3.6 of the Listing Policy. Under section 3.1 of the Policy, a minimum of one line of evidence is needed to assess listing status. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. Seven lines of evidence are available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 4 of 4, 4 of 4, 2 of 2 and 2 of 2 sample exceeded the criteria and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137265, Chlordane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

267510

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 2 of the 2 samples exceeded the water quality threshold for Total Chlordane. Although a total of 43 samples were collected, 41 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The chlordane criterion for the protection of human health from the consumption of water and organisms is 0.00057 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

Statewide Project Urban Pyrethroid Status Monitoring

Line of Evidence (LOE) for Decision ID 137265, Chlordane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83433

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

In freshwater sediments the probable effect concentration (predictive of sediment toxicity for sediment-dwelling organisms) for chlordane is 17.6 ug/Kg dry weight (MacDonald et al. 2000).

Guideline Reference:

Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Environmental Contamination and Toxicology. 39: 20-31

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 137265, Chlordane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255842

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 3 of the 3 samples exceeded the water quality threshold for Total Chlordane. Although a total of 11 samples were collected, 8 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The chlordane criterion for the protection of human health from the consumption of water and organisms is 0.00057 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628437).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137265, Chlordane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

267796

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Total Chlordane. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The chlordane criterion for the protection of human health from the consumption of water and organisms is 0.00057 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137265, Chlordane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

267817

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 2 of the 2 samples exceeded the water quality threshold for Total Chlordane. Although a total of 43 samples were collected, 41 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The chlordane criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.0043 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137265, Chlordane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255841

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality threshold for Total Chlordane. Although a total of 9 samples were collected, 8 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The chlordane criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.0043 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628438).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137265, Chlordane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255892

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 3 of the 3 samples exceeded the water quality threshold for Total Chlordane. Although a total of 11 samples were collected, 8 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The chlordane criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.0043 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628437).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137265, Chlordane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

267403

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Total Chlordane. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The chlordane criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.0043 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137265, Chlordane	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255866

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality threshold for Total Chlordane. Although a total of 9 samples were collected, 8 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The chlordane criterion for the protection of human health from the consumption of water and organisms is 0.00057 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628438).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137273	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Copper
Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
TMDL Name:	Calleguas Creek Metals (6)
TMDL Project Code:	359
Date TMDL Approved by USEPA:	03/14/2006
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 14 of 107 samples exceed the criteria and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137273, Copper	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254288

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The copper criterion for the protection of human health from the consumption of water and organisms is 1,300 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137273, Copper	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254181

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 0 of 52 samples exceeded the water quality threshold for Copper.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The copper criterion for the protection of human health from the consumption of water and organisms is 1,300 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137273, Copper	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254199

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 2 of 55 samples exceeded the water quality threshold for Copper.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The dissolved copper criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is hardness dependent. The criterion when calculated using a default hardness of 100 mg/L is 9 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137273, Copper	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254247

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 12 of 52 samples exceeded the water quality threshold for Copper.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	149485	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	DDD (Dichlorodiphenyldichloroethane)
Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Name:	Calleguas Creek PCBs (7)
TMDL Project Code:	360
Date TMDL Approved by USEPA:	03/24/2006
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 0, 0 of 0 and 8 of 8 samples exceed the criteria and 0 of 1 sample exceeds the guideline and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 149485, DDD (Dichlorodiphenyldichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

259691

Pollutant:

DDD (Dichlorodiphenyldichloroethane)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 8 of the 8 samples exceeded the water quality threshold for DDD(p,p'). Although a total of 43 samples were collected, 35 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The 4,4'-DDD criterion for the protection of human health from the consumption of water and organisms is 0.00083 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 149485, DDD (Dichlorodiphenyldichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

259674

Pollutant:

DDD (Dichlorodiphenyldichloroethane)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for DDD(p,p'). Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The 4,4'-DDD criterion for the protection of human health from the consumption of water and organisms is 0.00083 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 149485, DDD (Dichlorodiphenyldichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

253977

Pollutant:

DDD (Dichlorodiphenyldichloroethane)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for DDD(p,p'). Although a total of 11 samples were collected, 11 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The 4,4'-DDD criterion for the protection of human health from the consumption of water and organisms is 0.00083 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149485, DDD (Dichlorodiphenyldichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254297

Pollutant:

DDD (Dichlorodiphenyldichloroethane)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for DDD(p,p'). Although a total of 11 samples were collected, 11 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The 4,4'-DDD criterion for the protection of human health from the consumption of water and organisms is 0.00083 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149485, DDD (Dichlorodiphenyldichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83451

Pollutant:

DDD (Dichlorodiphenyldichloroethane)

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

In freshwater sediments the probable effect concentration (predictive of sediment toxicity for sediment-dwelling organisms) for sum of DDD is 28.0 ug/Kg dry weight (MacDonald et al. 2000).

Guideline Reference:

Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Environmental Contamination and Toxicology. 39: 20-31

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)


DECISION ID	149486	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	DDE (Dichlorodiphenyldichloroethylene)
Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Name:	Calleguas Creek PCBs (7)
TMDL Project Code:	360
Date TMDL Approved by USEPA:	03/24/2006
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 0, 2 of 2 and 17 of 17 samples exceed the criteria and 0 of 1 sample exceeds the guideline and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 149486, DDE (Dichlorodiphenyldichloroethylene)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254002

Pollutant:

DDE (Dichlorodiphenyldichloroethylene)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for DDE(p,p'). Although a total of 11 samples were collected, 11 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The 4,4'-DDE [DDE(p,p')] criterion to protect human health from the consumption of water and organisms is 0.00059 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149486, DDE (Dichlorodiphenyldichloroethylene)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

259728

Pollutant:

DDE (Dichlorodiphenyldichloroethylene)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 17 of the 17 samples exceeded the water quality threshold for DDE(p,p'). Although a total of 43 samples were collected, 26 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The 4,4'-DDE [DDE(p,p')] criterion to protect human health from the consumption of water and organisms is 0.00059 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 149486, DDE (Dichlorodiphenyldichloroethylene)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

259508

Pollutant:

DDE (Dichlorodiphenyldichloroethylene)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 2 of 2 samples exceeded the water quality threshold for DDE(p,p').

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The 4,4'-DDE [DDE(p,p')] criterion to protect human health from the consumption of water and organisms is 0.00059 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

The samples were collected between the dates of 2010-12-19 and 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

Statewide Project Urban Pyrethroid Status Monitoring

Line of Evidence (LOE) for Decision ID 149486, DDE (Dichlorodiphenyldichloroethylene)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83452

Pollutant:

DDE (Dichlorodiphenyldichloroethylene)

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

In freshwater sediments the probable effect concentration (predictive of sediment toxicity for sediment-dwelling organisms) for sum of DDE is 31.3 ug/Kg dry weight (MacDonald et al. 2000).

Guideline Reference:

Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Environmental Contamination and Toxicology. 39: 20-31

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 149486, DDE (Dichlorodiphenyldichloroethylene)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254001

Pollutant:

DDE (Dichlorodiphenyldichloroethylene)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for DDE(p,p'). Although a total of 11 samples were collected, 11 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The 4,4'-DDE [DDE(p,p')] criterion to protect human health from the consumption of water and organisms is 0.00059 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	149487	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	DDT (Dichlorodiphenyltrichloroethane)
Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Name:	Calleguas Creek PCBs (7)
TMDL Project Code:	360
Date TMDL Approved by USEPA:	03/24/2006
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 0, 0 of 0, 0 of 0, 0 of 0, 7 of 7 and 7 of 7 samples exceed the criteria and 0 of 1 and 0 of 1 sample exceed the guideline and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 149487, DDT (Dichlorodiphenyltrichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

259815

Pollutant:

DDT (Dichlorodiphenyltrichloroethane)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for DDT(p,p'). Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The DDT(4,4') criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.001 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 149487, DDT (Dichlorodiphenyltrichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

259814

Pollutant:

DDT (Dichlorodiphenyltrichloroethane)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for DDT(p,p'). Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The DDT(4,4') criterion for the protection of human health from the consumption of water and organisms is 0.00059 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

Statewide Project Urban Pyrethroid Status Monitoring

Line of Evidence (LOE) for Decision ID 149487, DDT (Dichlorodiphenyltrichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83453

Pollutant:

DDT (Dichlorodiphenyltrichloroethane)

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

In freshwater sediments the probable effect concentration (predictive of sediment toxicity for sediment-dwelling organisms) for sum of DDT is 62.9 ug/Kg dry weight (MacDonald et al. 2000).

Guideline Reference:

Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Environmental Contamination and Toxicology. 39: 20-31

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 149487, DDT (Dichlorodiphenyltrichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254093

Pollutant:

DDT (Dichlorodiphenyltrichloroethane)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for DDT(p,p'). Although a total of 9 samples were collected, 9 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The DDT(4,4') criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.001 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149487, DDT (Dichlorodiphenyltrichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

259853

Pollutant:

DDT (Dichlorodiphenyltrichloroethane)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 7 of the 7 samples exceeded the water quality threshold for DDT(p,p'). Although a total of 43 samples were collected, 36 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The DDT(4,4') criterion for the protection of human health from the consumption of water and organisms is 0.00059 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 149487, DDT (Dichlorodiphenyltrichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254120

Pollutant:

DDT (Dichlorodiphenyltrichloroethane)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for DDT(p,p'). Although a total of 11 samples were collected, 11 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The DDT(4,4') criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.001 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149487, DDT (Dichlorodiphenyltrichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254144

Pollutant:

DDT (Dichlorodiphenyltrichloroethane)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for DDT(p,p'). Although a total of 11 samples were collected, 11 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The DDT(4,4') criterion for the protection of human health from the consumption of water and organisms is 0.00059 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149487, DDT (Dichlorodiphenyltrichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

254190

Pollutant:

DDT (Dichlorodiphenyltrichloroethane)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for DDT(p,p'). Although a total of 9 samples were collected, 9 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The DDT(4,4') criterion for the protection of human health from the consumption of water and organisms is 0.00059 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

Data for this waterbody were collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 149487, DDT (Dichlorodiphenyltrichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83375

Pollutant:

Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

In freshwater sediments the probable effect concentration (predictive of sediment toxicity for sediment-dwelling organisms) for total DDTs is 572 ug/Kg dry weight (MacDonald et al. 2000).

Guideline Reference:

Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Environmental Contamination and Toxicology. 39: 20-31

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)

Line of Evidence (LOE) for Decision ID 149487, DDT (Dichlorodiphenyltrichloroethane)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

259872

Pollutant:

DDT (Dichlorodiphenyltrichloroethane)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 7 of the 7 samples exceeded the water quality threshold for DDT(p,p'). Although a total of 43 samples were collected, 36 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The DDT(4,4') criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.001 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137290	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Nitrate/Nitrite (Nitrite + Nitrate as N)
Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
TMDL Name:	Calleguas Creek Nitrogen (1)
TMDL Project Code:	228
Date TMDL Approved by USEPA:	07/16/2003
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 5 of 32 samples exceed the objective and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137290, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

243874

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed data from the Simi Valley Wastewater Quality Control Plan to determine beneficial use support. The results are as follows: 1 out of 56 samples exceed the criterion for Nitrate + Nitrite as N.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region list a site specific objective for Nitrate + Nitrite as N in the Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) of 10 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station RSW-002 (34.28169, -118.8135), located in Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list).

Temporal Representation:

The water samples were taken between 5/5/2015 - 12/3/2019, per the monitoring requirements listed in the Simi Valley Wastewater Quality Control Plan NPDES Permit monitoring and reporting program.

Environmental Conditions:

QAPP Information:

The work was performed in accordance with the Simi Valley Wastewater Quality Control Plan NDPES Permit quality assurance provisions for water quality monitoring.

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137290, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

243863

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed data from the Simi Valley Wastewater Quality Control Plan to determine beneficial use support. The results are as follows: 0 out of 55 samples exceed the criterion for Nitrate + Nitrite as N.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station RSW-001 (34.282, -118.8129), located in Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list).

Temporal Representation:

The water samples were taken between 5/5/2015 - 12/3/2019, per the monitoring requirements listed in the Simi Valley Wastewater Quality Control Plan NPDES Permit monitoring and reporting program.

Environmental Conditions:

QAPP Information:

The work was performed in accordance with the Simi Valley Wastewater Quality Control Plan NDPES Permit quality assurance provisions for water quality monitoring.

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137290, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

244087

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed data from the Calleguas Creek TMDL Work Plan Monitoring to determine beneficial use support. The results are as follows: zero out of 11 samples exceed the criterion for Nitrate/Nitrite (Nitrite + Nitrate as N).

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region lists a site specific objective for Nitrate/Nitrite (Nitrite + Nitrate as N) in Calleguas Creek Reach 7 of 10 mg/L

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station 07_MADER (34.2778, -118.796), located in Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list).

Temporal Representation:

Water samples were taken from 5/11/2011 to 5/15/2018 as part of the Calleguas Creek TMDL Work Plan Monitoring.

Environmental Conditions:

QAPP Information:

The work was performed in accordance with the quality control and quality assurance provisions of the Calleguas Creek TMDL Work Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137290, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

244086

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed data from the Calleguas Creek TMDL Work Plan Monitoring to determine beneficial use support. The results are as follows: five out of 22 samples exceed the criterion for Nitrate/Nitrite (Nitrite + Nitrate as N).

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region lists a site specific objective for Nitrate/Nitrite (Nitrite + Nitrate as N) in Calleguas Creek Reach 7 of 10 mg/L

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station 07_HITCH (34.2717, -118.923), located in Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list).

Temporal Representation:

Water samples were taken from 5/11/2011 to 5/15/2018 as part of the Calleguas Creek TMDL Work Plan Monitoring.

Environmental Conditions:

QAPP Information:

The work was performed in accordance with the quality control and quality assurance provisions of the Calleguas Creek TMDL Work Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.


DECISION ID	137297	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Selenium
Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	Major Municipal Point Source-dry and/or wet weather discharge \| Other Urban Runoff \| See TMDL documentation
TMDL Name:	Calleguas Creek Metals (6)
TMDL Project Code:	359
Date TMDL Approved by USEPA:	03/26/2007
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 of the Policy, a minimum of one line of evidence is needed to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there sufficient evidence to place it in the Being Addressed portion of the CWA 303(d) List because a TMDL has been completed and approved by RWQCB and USEPA, and is expected to result in attainment of the standard. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 112 and 87 of 112 samples exceeded the criteria and these exceed the allowable frequency listed in Table 3.1 of the Listing Policy. 4. The TMDL for Metals and Selenium in Calleguas Creek, its Tributaries and Mugu Lagoon was approved by USEPA on 3/26/2007. 5. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137297, Selenium	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255805

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 35 of 56 samples exceeded the water quality threshold for Selenium.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The selenium criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 5 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137297, Selenium	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255609

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and results are as follows: 52 of 56 samples exceeded the water quality threshold for Selenium.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The selenium criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 5 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137297, Selenium	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255613

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for selenium is 0.05 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628437 (RSW-001).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137297, Selenium	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255806

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The California Maximum Contaminant Level for selenium is 0.05 mg/L (California Code of Regulations, Title 22).

Guideline Reference:

California MCLs - Title 17 and Title 22 documents for 2019 - California Regulations Related to Drinking Water

Spatial Representation:

The samples were collected at 1 monitoring site: 628438 (RSW-002).

Temporal Representation:

The samples were collected between the dates of 2015-05-05 and 2019-12-03

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)


DECISION ID	137303	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Toxaphene
Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
TMDL Name:	Calleguas Creek PCBs (7)
TMDL Project Code:	360
Date TMDL Approved by USEPA:	03/24/2006
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 0, 0 of 0, 2 of 2, 2 of 2, 1 of 1 and 1 of 1 samples exceed the CRITERIA and this exceeds the allowable frequency listed in Table 3.1 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137303, Toxaphene	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255742

Pollutant:

Toxaphene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality threshold for Toxaphene. Although a total of 11 samples were collected, 10 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The toxaphene criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.0002 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628438).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137303, Toxaphene	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

256165

Pollutant:

Toxaphene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality threshold for Toxaphene. Although a total of 11 samples were collected, 10 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The toxaphene criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.0002 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628437).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137303, Toxaphene	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

267709

Pollutant:

Toxaphene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Toxaphene. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The toxaphene criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.0002 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137303, Toxaphene	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255739

Pollutant:

Toxaphene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality threshold for Toxaphene. Although a total of 11 samples were collected, 10 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The toxaphene criterion for the protection of human health from the consumption of water and organisms is 0.00073 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628437).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137303, Toxaphene	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

267885

Pollutant:

Toxaphene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Toxaphene. Although a total of 2 samples were collected, 2 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The toxaphene criterion for the protection of human health from the consumption of water and organisms is 0.00073 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: 07_HITCH (Arroyo Simi East Of HitchBoulevard).

Temporal Representation:

Data for this waterbody were collected over the date range 2010-12-19 to 2012-01-23

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137303, Toxaphene	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

267886

Pollutant:

Toxaphene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality threshold for Toxaphene. Although a total of 42 samples were collected, 41 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The toxaphene criterion continuous concentration (expressed as a 4-day average) to protect aquatic life in freshwater is 0.0002 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):

WQ data from the California Integrated Water Quality System (CIWQS) assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137303, Toxaphene	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

255738

Pollutant:

Toxaphene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed eSMR_Simi Valley WQCP data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality threshold for Toxaphene. Although a total of 11 samples were collected, 10 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The toxaphene criterion for the protection of human health from the consumption of water and organisms is 0.00073 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (628438).

Temporal Representation:

Data for this waterbody was collected over the date range 2015-06-30 to 2017-08-01

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2008. Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP).

QAPP Information Reference(s):

Calleguas Creek Watershed Management Plan Quality Assurance Project Plan (QAPP)

Line of Evidence (LOE) for Decision ID 137303, Toxaphene	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

267825

Pollutant:

Toxaphene

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Calleguas Creek TMDL Work Plan Monitoring data for Calleguas Creek Reach 7 (Arroyo Simi) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality threshold for Toxaphene. Although a total of 42 samples were collected, 41 of these samples were not included in the assessment because the laboratory data reporting limit(s) was above the water quality threshold and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The toxaphene criterion for the protection of human health from the consumption of water and organisms is 0.00073 ug/L (California Toxics Rule, 2000).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (07_HITCH).

Temporal Representation:

Data for this waterbody was collected over the date range 2010-11-09 to 2018-05-15

Environmental Conditions:

QAPP Information:

LARRY WALKER ASSOCIATES. 2020. Calleguas Creek Watershed Management Plan.

QAPP Information Reference(s):


DECISION ID	68267	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Indicator Bacteria
Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)(2016)
Revision Status	Original
Sources:	A Source Unknown
Expected TMDL Completion Date:	2019
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the section 303(d) list under section 4.3 of the Listing Policy. Under section 4.3 a single line of evidence is necessary to assess delisting status. Two lines of evidence are available in the administrative record to assess this pollutant. Based on the readily available data and information, the weight of evidence indicates there is sufficient justification against removing this water segment-pollutant combination from the section 303(d) list. This conclusion is based on the staff findings that: 1. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 2. 7 of 10 samples exceeded the Basin Plan water quality objective for indicator bacteria (E. coli), and this exceeds the allowable frequency listed in Table 4.2 of the Listing Policy. 3. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be removed from the section 303(d) list because applicable water quality standards for the pollutant are being exceeded.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 68267, Indicator Bacteria	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

2167

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Twenty-four bacteria samples, 17 samples exceeding. Geomean of 909 exceed 200/100 ml standard (SWRCB, 2003).

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Basin Plan: In waters designated for water contact recreation (REC-1), the fecal coliform concentration shall not exceed a log mean of 200/100 ml (based on a minimum of not less than four samples for any 30-day period), nor shall more than 10 percent of total samples during any 30-day period exceed 400/100 ml.

Objective/Criterion Reference:

Calleguas Creek volunteer water quality monitoring data for 2006 conducted by Ventura Coastkeeper.

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Two sites.

Temporal Representation:

Summer, fall, winter, spring.

Environmental Conditions:

QAPP Information:

Calleguas Creek Characterization Study

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 68267, Indicator Bacteria	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

25234

Pollutant:

Indicator Bacteria

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

Other Agencies/Organizations provided monitoring data

Data Used to Assess Water Quality:

6 out of 10 samples exceeded the Basin Plan single sample water quality objectives for indicator bacteria in fresh water. Water quality samples were taken and analyzed for indicator bacteria by the Ventura Coastkeepers.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Basin Plan bacteria objectives state that to protect water contact recreation in fresh waters individual samples shall not exceed the following limits: fecal coliform density shall not exceed 400/100 ml; and E. coli density shall not exceed 235/100 ml. The bacteria objectives also establish that the geometric means of individual samples shall not exceed the following limits: the fecal coliform density shall not exceed 200/100 ml; and the E. coli density shall not exceed 126/100 ml, as a geometric mean. The bacteria objectives are found in Attachment A of Regional Board Resolution No. 2001-018.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The Ventura Coastkeepers conducted sampling at the monitoring station AS1 located in Arroyo Simi (Calleguas Creek Reach 7) at Madera Road.

Temporal Representation:

Grab samples were taken and analyzed from February 2006 to December of 2006.

Environmental Conditions:

QAPP Information:

Not Available.

QAPP Information Reference(s):


DECISION ID	93796	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Cyhalothrin, Lambda
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.6 of the Listing Policy. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. 2 lines of evidence are available in the administrative record to assess this pollutant. 0 of 1 sample exceeded the GUIDELINE. 1 of 1 sample exhibited sediment toxicity. Based on the readily available data and information, the weight of evidence indicates that there is INSUFFICIENT justification FOR placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 1 sample exceeded the GUIDELINE and this sample size is INSUFFICIENT to determine beneficial use support, with the power and confidence of the Listing Policy. There is not an associated sediment toxicity data as required by Section 3.6 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 93796, Cyhalothrin, Lambda	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83444

Pollutant:

Cyhalothrin, Lambda

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for lambda-cyhalothrin is the median lethal concentration (LC50) of 0.44 ug/g and is normalized by the percentage of organic carbon in the sediment sample. The LC50 0.44 ug/g is the geometric mean of LC50 values for lambda-cyhalothrin from Amweg et al. (2005).

Guideline Reference:

Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California, USA. Environmental Toxicology and Chemistry, 24:966-972, with erratum 24:No. 5

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)


DECISION ID	93851	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Esfenvalerate/Fenvalerate
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.6 of the Listing Policy. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. 2 lines of evidence are available in the administrative record to assess this pollutant. 0 of 1 sample exceeded the GUIDELINE. 1 of 1 sample exhibited sediment toxicity. Based on the readily available data and information, the weight of evidence indicates that there is INSUFFICIENT justification FOR placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 1 sample exceeded the GUIDELINE and this sample size is INSUFFICIENT to determine beneficial use support, with the power and confidence of the Listing Policy. There is not an associated sediment toxicity data as required by Section 3.6 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 93851, Esfenvalerate/Fenvalerate	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83374

Pollutant:

Esfenvalerate/Fenvalerate

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for esfenvalerate/fenvalerate is the median lethal concentration (LC50) of 1.5 ug/g and is normalized by the percentage of organic carbon in the sediment sample. The LC50 1.5 ug/g is the geometric mean of LC50 values for esfenvalerate/fenvalerate from Amweg et al. (2005).

Guideline Reference:

Use and Toxicity of Pyrethroid Pesticides in the Central Valley, California, USA. Environmental Toxicology and Chemistry, 24:966-972, with erratum 24:No. 5

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)


DECISION ID	93904	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Fenpropathrin
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.6 of the Listing Policy. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. 2 lines of evidence are available in the administrative record to assess this pollutant. 0 of 1 sample exceeded the GUIDELINE. 1 of 1 sample exhibited sediment toxicity. Based on the readily available data and information, the weight of evidence indicates that there is INSUFFICIENT justification FOR placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 1 sample exceeded the GUIDELINE and this sample size is INSUFFICIENT to determine beneficial use support, with the power and confidence of the Listing Policy. There is not an associated sediment toxicity data as required by Section 3.6 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 93904, Fenpropathrin	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83379

Pollutant:

Fenpropathrin

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for fenpropathrin is the median lethal concentration (LC50) of 1 ug/g and is normalized by the percentage of organic carbon in the sediment sample. The LC50 1 ug/g is the geometric mean of LC50 values for fenpropathrin from Ding et al. ( 2011).

Guideline Reference:

Toxicity of Sediment-Associated Pesticides to Chironomus dilutus and Hyalella azteca. Arch. Environ. Contam. Toxicol. 61:83¿92.

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)


DECISION ID	93957	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Fipronil
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.6 of the Listing Policy. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. 2 lines of evidence are available in the administrative record to assess this pollutant. 0 of 0 sample exceeded the GUIDELINE. 1 of 1 sample exhibited sediment toxicity. Based on the readily available data and information, the weight of evidence indicates that there is INSUFFICIENT justification FOR placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 0 sample exceeded the GUIDELINE and this sample size is INSUFFICIENT to determine beneficial use support, with the power and confidence of the Listing Policy. There is not an associated sediment toxicity data as required by Section 3.6 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 93957, Fipronil	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83380

Pollutant:

Fipronil

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for fipronil is the median lethal concentration (LC50) of 0.13 ug/g and is normalized by the percentage of organic carbon in the sediment sample (Maul et al. 2008).

Guideline Reference:

Effect of sediment-associated pyrethroids, fipronil, and metabolites on Chironomus tentans growth rate, body mass, condition index, immobilization, and survival. Environ. Toxicol. Chem. 27(12):2582-2590.

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)


DECISION ID	93958	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Fipronil Sulfide
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.6 of the Listing Policy. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. 2 lines of evidence are available in the administrative record to assess this pollutant. 0 of 0 sample exceeded the GUIDELINE. 1 of 1 sample exhibited sediment toxicity. Based on the readily available data and information, the weight of evidence indicates that there is INSUFFICIENT justification FOR placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 0 sample exceeded the GUIDELINE and this sample size is INSUFFICIENT to determine beneficial use support, with the power and confidence of the Listing Policy. There is not an associated sediment toxicity data as required by Section 3.6 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 93958, Fipronil Sulfide	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83383

Pollutant:

Fipronil Sulfide

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for fipronil sulfide is the median lethal concentration (LC50) of 0.16 ug/g and is normalized by the percentage of organic carbon in the sediment sample (Maul et al. 2008).

Guideline Reference:

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)


DECISION ID	93959	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Fipronil Sulfone
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.6 of the Listing Policy. Under section 3.6 at least two lines of evidence are necessary to assess listing status for pollutants sediment, and pollutant concentrations in sediment must be associated with sediment toxicity to justify adding that pollutant to the CWA section 303(d) List. 2 lines of evidence are available in the administrative record to assess this pollutant. 0 of 0 sample exceeded the GUIDELINE. 1 of 1 sample exhibited sediment toxicity. Based on the readily available data and information, the weight of evidence indicates that there is INSUFFICIENT justification FOR placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 0 sample exceeded the GUIDELINE and this sample size is INSUFFICIENT to determine beneficial use support, with the power and confidence of the Listing Policy. There is not an associated sediment toxicity data as required by Section 3.6 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list. The readily available data and information is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 93959, Fipronil Sulfone	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

83384

Pollutant:

Fipronil Sulfone

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Statewide Project Urban Pyrethroid Status Monitoring

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The evaluation guideline for fipronil sulfone is the median lethal concentration (LC50) of 0.12 ug/g and is normalized by the percentage of organic carbon in the sediment sample (Maul et al. 2008).

Guideline Reference:

Spatial Representation:

Data for this line of evidence for Calleguas Creek Reach 7 (was Arroyo Simi Reaches 1 and 2 on 1998 303d list) was collected at 1 monitoring site [ Arroyo Simi @ Tapo Upper station (408SUP059).]

Temporal Representation:

Data was collected on a single day 1/7/2007.

Environmental Conditions:

Staff is not aware of any special conditions that might affect interpretation of the data.

QAPP Information:

SWAMP data collected before September 2008 followed the QAMP (2002).

QAPP Information Reference(s):

Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)


DECISION ID	69775	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

Pollutant:	Sedimentation/Siltation
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (TMDL required list)(2016)
Revision Status	Original
Sources:	A Source Unknown
Expected TMDL Completion Date:	2006
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for listing under section 2.2 of the Listing Policy. Under this section of the Policy, a minimum of one line of evidence is needed to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. A TMDL has been developed and is expected to result in attainment of the standard. The Calleguas Creek Historic Pesticides TMDL was approved by the RWQCB in 2005. Based on the readily available information, the weight of evidence indicates that there is sufficient justification in favor of placing this water segment-pollutant combination in the Water Quality Limited Segments Being Addressed portion of the section 303(d) list. USEPA in its final decision for the 2006 303(d) list, has determined that a TMDL has not been approved by USEPA for this pollutant water body combination. Therefore, this water body pollutant combination is being placed back on the 303(d) list (TMDL required list) pending completion and USEPA approval of a TMDL.

Regional Board Decision Recommendation:	This is a decision previously approved by the State Water Resources Control Board and the USEPA. No new data were assessed by the Regional Board for the current. The decision has not changed.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	After review of this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 69775, Sedimentation/Siltation	Region 4
Calleguas Creek Reach 7 (Arroyo Simi)

LOE ID:

2168

Pollutant:

Sedimentation/Siltation

LOE Subgroup:

Pollutant-Water

Matrix:

Not Specified

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Unspecified--This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.

Data Reference: