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

Line of Evidence (LOE) for Decision ID 137436, Diazinon	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2231

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:

Data for Various Pollutants in Ventura County, 2006-2009.

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 137436, Diazinon	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

96166

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:

Two samples exceeded the water quality evaluation guideline criteria.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Region 4 Basin Plan objective is "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 2005 US EPA Aquatic life Ambient Water Quality Criteria for one-hour average concentration is 0.01 ug/L.

Guideline Reference:

Aquatic Life Ambient Water Quality Criteria for Diazinon

Spatial Representation:

Twenty-one samples were collected at Calleguas Creek at University Drive, North Fork Arroyo Conejo (tributary to Conejo Creek)at sampling location Thousand Oaks-1.

Temporal Representation:

Water samples were collected in 2006 (one sample), in 2007 (6 samples), in 2008 (6 samples), in 2009 (6 samples) and in 2010 (two samples).

Environmental Conditions:

There was no special environmental condition reported.

QAPP Information:

Samples were collected and analyzed in accordance to Ventrua County Agricultural Irrigated Land Group (VCAILG) Quality Assurance Project Plan (QAPP) dated Augus 3, 2006.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137436, Diazinon	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

260053

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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	137437	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Dieldrin
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 Historic Pesticides (5)
TMDL Project Code:	358
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. Two lines of evidence are available in the administrative record to assess this pollutant. Dieldrin was not listed on the 303(d) list for this water body due to impairment, but due to being included in a TMDL . The USEPA final decision for the 2006 303(d) list added this listing to the being addressed by USEPA approved TMDL portion of the 303(d) List because the Calleguas Creek OC Pesticides & PCBs TMDL was approved by USEPA on 03/14/2006. LOE 2228 is a placeholder for this decision and will not be considered. 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 and 0 of 36 samples exceeded the criteria for dieldrin in water 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 137437, Dieldrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

260557

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:

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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):

Line of Evidence (LOE) for Decision ID 137437, Dieldrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2228

Pollutant:

Dieldrin

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:

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 137437, Dieldrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

260537

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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	137441	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Malathion
Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	List on 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
Expected TMDL Completion Date:	2029
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 section 4.1 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 2 and 8 of 57 samples exceed the guideline and this exceeds the allowable frequency listed in Table 4.1 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 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 137441, Malathion	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

262848

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137441, Malathion	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

262934

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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):

Data for Various Pollutants in Ventura County, 2006-2009.

Line of Evidence (LOE) for Decision ID 137441, Malathion	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

96167

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:

Eight of the 21 samples exceeded the water quality evaluation guideline criteria.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Los Angeles Region Basin Plan states "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 Aquatic Life Protection Recommended Criteria for Maximum (Instantaneous) is 0.1 ug/L (U.S. Environmental Protection Agency, Quality Criteria for Water (1976) [The Red Book]. http://www.epa.gov/waterscience/criteria/redbook.pdf.)

Guideline Reference:

Spatial Representation:

Twenty-one samples were collected at Calleguas Creek at University Drive, North Fork Arroyo Conejo (tributary to Conejo Creek)at sampling location Thousand Oaks-1.

Temporal Representation:

Water samples were collected in 2006 (one sample), in 2007 (6 samples), in 2008 (6 samples), in 2009 (6 samples) and in 2010 (two samples).

Environmental Conditions:

There was no special environmental condition reported.

QAPP Information:

Samples were collected and analyzed in accordance to Ventrua County Agricultural Irrigated Land Group (VCAILG) Quality Assurance Project Plan (QAPP) dated Augus 3, 2006.

QAPP Information Reference(s):


DECISION ID	137433	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Chlordane
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 Historic Pesticides (5)
TMDL Project Code:	358
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 4.1 of the Listing Policy. Under 4.1 of the Policy, a minimum of one line of evidence is needed to assess listing status. 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 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 of the Policy. 2. The data used satisfies the data quantity requirements of section 6of the Policy. 3. 0 of 0, 0 of 0 and 0 of 0 sample exceeded the criteria 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 28 samples are required for delisting. 4. The Calleguas Creek Historic Pesticides was approved by USEPA on 03/14/2006. 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 not be removed from the section 303(d) list because there was a previous listing and there are not enough data to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137433, Chlordane	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

267526

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) 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 36 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 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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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):

Line of Evidence (LOE) for Decision ID 137433, Chlordane	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2227

Pollutant:

Chlordane

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:

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 137433, Chlordane	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

267506

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) 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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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):


DECISION ID	137434	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

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 section 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 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 2, 0 of 0 and 8 of 57 samples exceeded the criteria and these exceed the allowable frequency listed in Table 4.1 of the Listing Policy. 4. The Calleguas Creek Toxicity TMDL 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 137434, Chlorpyrifos	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2230

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:

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:

Data for Various Pollutants in Ventura County, 2006-2009.

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 137434, Chlorpyrifos	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

96165

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:

Eight samples exceeded the water quality evaluation guideline criteria.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Region 4 Basin Plan objective is "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:

Freshwater Aquatic Life Protection Recommended Continuous Concentration(4-day Average)Criteria is 0.014 ug/L.

Guideline Reference:

Spatial Representation:

Twenty-one samples were collected at Calleguas Creek at University Drive, North Fork Arroyo Conejo (tributary to Conejo Creek)at sampling location Thousand Oaks-1.

Temporal Representation:

Water samples were collected in 2006 (one sample), in 2007 (6 samples), in 2008 (6 samples), in 2009 (6 samples) and in 2010 (two samples).

Environmental Conditions:

There was no special environmental condition reported.

QAPP Information:

Samples were collected and analyzed in accordance to Ventrua County Agricultural Irrigated Land Group (VCAILG) Quality Assurance Project Plan (QAPP) dated Augus 3, 2006.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137434, Chlorpyrifos	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

258476

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:

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 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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137434, Chlorpyrifos	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

258268

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:

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 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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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	137445	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	PCBs (Polychlorinated biphenyls)
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:	See TMDL documentation
TMDL Name:	Calleguas Creek PCBs (7)
TMDL Project Code:	360
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 SECTION of the Listing Policy. Under SECTION of the Policy, a minimum of one line of evidence is needed to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. PCBs have not been specifically listed on the 303(d) list for this water body. The USEPA final decision for the 2006 303(d) list added this listing to the being addressed by USEPA approved TMDL portion of the 303(d) List because the Calleguas Creek OC Pesticides & PCBs TMDL was approved by USEPA on 03/14/2006. Line of evidence 2209 represents this decision and will not be considered for assessment. 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. 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 0 and 0 of 0 samples exceeded the criteria 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. 4. The TMDL for PCBs 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 there was a previous listing and there are not enough data to determine beneficial use support for this waterbody-pollutant combination with the statistical power and confidence required by the Listing Policy.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 137445, PCBs (Polychlorinated biphenyls)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

264534

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) 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 30 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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 4.

Line of Evidence (LOE) for Decision ID 137445, PCBs (Polychlorinated biphenyls)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

264657

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) 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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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):

Line of Evidence (LOE) for Decision ID 137445, PCBs (Polychlorinated biphenyls)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2229

Pollutant:

PCBs (Polychlorinated biphenyls)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

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 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):


DECISION ID	137452	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

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 2 and 0 of 36 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 137452, Aldrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

256360

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:

Data Reference:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137452, Aldrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

256348

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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):

Data for various pollutants in Calleguas Creek Reach 10, Jan. 2005-Jun. 2010


DECISION ID	153883	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Aluminum
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:	During the 2024 cycle, the 1988 National Recommended Water Quality Criteria used to assess aluminum data was replaced with U.S. EPA’s 2018 Final Recommended Aquatic Life Criteria for Aluminum in Freshwater. 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 36 samples exceeded the criteria listed in the evaluation guideline in water and this does not exceed the allowable frequency listed in Table 3.1 of the Listing Policy for warm freshwater habitat. 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 153883, Aluminum	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

315100

Pollutant:

Aluminum

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 Receiving Waters Monitoring-Quarterly data for Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) to determine beneficial use support and results are as follows: 0 of 18 samples exceeded the water quality threshold for Aluminum.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Water Quality Control Plan for the Los Angeles Region states that: Surface waters shall not contain concentrations of chemical constituents in amounts that adversely affect any designated beneficial use.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

The aluminum criterion for the protection of aquatic life, is pH, total hardness, and dissolved organic carbon (DOC) dependent. When total hardness or DOC data were not available, default values based on the level III ecoregions developed by U.S EPA were substituted (EPA, 2018). When pH data were not available, the median pH value for the ecoregion, a pH value from a comparable waterbody, or a pH value from a local study in the same waterbody was used as a comparable surrogate.

Guideline Reference:

Final Aquatic Life Ambient Water Quality Criteria for Aluminum. EPA-822-R-18-001. Washington, D.C.: Office of Water, USEPA.

Spatial Representation:

The samples were collected at 1 monitoring site: R2 (NA).

Temporal Representation:

The samples were collected between the dates of 2006-11-08 and 2011-02-09

Environmental Conditions:

QAPP Information:

Data was previously assessed without a QAPP. Data reassessed without a QAPP for consistency.

QAPP Information Reference(s):

This is a placeholder for previously assessed data that does not have quality assurance information but would require it under newly developed policies. These LOEs were previously assessed and approved at the Regional, State and Federal level in past cycles. The LOEs needed to be moved and/or reassessed but required this reference code for movement within the decision making database.

Line of Evidence (LOE) for Decision ID 153883, Aluminum	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

315099

Pollutant:

Aluminum

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:

Data for various pollutants in Calleguas Creek Reach 10, Jan. 2005-Jun. 2010

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:

Final Aquatic Life Ambient Water Quality Criteria for Aluminum. EPA-822-R-18-001. Washington, D.C.: Office of Water, USEPA.

Spatial Representation:

The samples were collected at 1 monitoring site: R1 (NA).

Temporal Representation:

The samples were collected between the dates of 2006-11-08 and 2011-02-09

Environmental Conditions:

QAPP Information:

Data was previously assessed without a QAPP. Data reassessed without a QAPP for consistency.

QAPP Information Reference(s):


DECISION ID	137432	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

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 137432, Atrazine	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

257387

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:

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 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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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	137454	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Deltamethrin
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 137454, Deltamethrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

260118

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) 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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137454, Deltamethrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

260253

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality threshold for Deltamethrin. Although a total of 36 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:

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 (10_GATE).

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.


DECISION ID	137438	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

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 and 0 of 36 samples exceeded the Ocriteria 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 137438, Endosulfan sulfate	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

261223

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137438, Endosulfan sulfate	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

261203

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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	137439	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

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 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 36, 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 137439, Endrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

261082

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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):

Data for various pollutants in Calleguas Creek Reach 10, Jan. 2005-Jun. 2010

Line of Evidence (LOE) for Decision ID 137439, Endrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

94026

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

108

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

None of the 108 samples exceeded the water quality objective for Endrin is 2.0 ug/L.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Los Angeles Region Basin Plan objective is "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:

California Toxic Rule criteria fresh aquatic life protection continuous concentration (4-day average)is 0.036 ug/L.

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

108 water samples were collected from Reach 1 and Reach 2 of Calleguas Creek Reach 10 (Conejo Creek, Hill Canyon)-was part of formerly Conejo Crk Reaches 2 & 3, and lower Conejo Crk/Arroyo Conejo N Fk on 1998 303d list).

Temporal Representation:

Samples were collected eight times in 2006 (fall & winter), twenty-four times in 2007 (winter, spring, summer, and fall), twenty-one times in 2008 (winter, spring, summer, and fall), twenty-four times in 2009(winter, spring, summer, and fall), twenty-four times in 2010, and six times in 2011 (winter, spring, summer, and fall).

Environmental Conditions:

There was no special environmental conditions reported.

QAPP Information:

The NPDES permit No. CA0056294 for City of Thousand Oaks Hill Canyon Wastewater Treatment Plant Order No. R4-2003-0083 (as Revised by Order No. R4-2004-0121) The Monitoring and Reporting program is in Attachment T of this document.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 137439, Endrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

261084

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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	137440	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

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:	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 36 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 137440, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

262237

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:

Data Reference:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137440, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

261904

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:

Data Reference:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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	137442	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Nitrate/Nitrite (Nitrite + Nitrate as N)
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 21 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 137442, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

244088

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Groundwater Recharge

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 21 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 10 of 10 mg/L

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station 10_GATE (34.2178, -118.928), located in Calleguas Creek Reach 10 (Conejo Creek (Hill Canyon)-was part of Conejo Crk Reaches 2 & 3, and lower Conejo Crk/Arroyo Conejo N Fk on 1998 303d list).

Temporal Representation:

Water samples were taken from 11/9/2010 to 5/6/2018 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.


DECISION ID	149455	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

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. 0 of 27 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 149455, Nitrogen, Nitrate	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

302369

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

Temporal Representation:

The samples were collected between the dates of 2010-11-09 and 2015-05-06

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	137443	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Organophosphate Pesticides
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 36 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 137443, Organophosphate Pesticides	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

264377

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:

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 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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137443, Organophosphate Pesticides	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

264322

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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	137451	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

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 137451, Prometryn	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

265463

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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	137446	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

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 137446, Simazine	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

266542

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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	137447	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Toxaphene
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 137447, Toxaphene	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

267727

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) 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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137447, Toxaphene	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

267672

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) 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 36 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:

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 (10_GATE).

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.


DECISION ID	137435	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

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 and 0 of 36 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 137435, alpha-Endosulfan (Endosulfan 1)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

260991

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137435, alpha-Endosulfan (Endosulfan 1)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

260787

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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	137444	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

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 and 0 of 36 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 137444, beta-Endosulfan (Endosulfan 2)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

260732

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137444, beta-Endosulfan (Endosulfan 2)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

260730

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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	137449	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Bifenthrin
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. 0 of 0 and 10 of 10 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 137449, Bifenthrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

257676

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Bifenthrin. 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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137449, Bifenthrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

257675

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) to determine beneficial use support and the results are as follows: 10 of the 10 samples exceeded the water quality threshold for Bifenthrin. Although a total of 36 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:

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 (10_GATE).

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.


DECISION ID	137453	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Cyfluthrin
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. 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. 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 137453, Cyfluthrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

259302

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) to determine beneficial use support and the results are as follows: 8 of the 8 samples exceeded the water quality threshold for Cyfluthrin. Although a total of 36 samples were collected, 28 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 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 (10_GATE).

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 137453, Cyfluthrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

259441

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) 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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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	137450	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Cypermethrin
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. 0 of 0 and 4 of 4 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 137450, Cypermethrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

259509

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) 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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137450, Cypermethrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

259701

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) to determine beneficial use support and the results are as follows: 4 of the 4 samples exceeded the water quality threshold for Cypermethrin. Although a total of 36 samples were collected, 32 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 (10_GATE).

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.


DECISION ID	137455	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Permethrin
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. 0 of 0 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 137455, Permethrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

264716

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) 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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137455, Permethrin	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

264944

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) 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 36 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 Permethrin

Spatial Representation:

The samples were collected at 1 monitoring site (10_GATE).

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.


DECISION ID	137448	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

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. 0 of 0 and 10 of 10 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 137448, Pyrethroids	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

265523

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) to determine beneficial use support, and the results are as follows: 0 of the 0 samples exceeded the evaluation guideline for Pyrethroids. Although a total of 36 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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 137448, Pyrethroids	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

265472

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:

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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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.


DECISION ID	149454	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	DDT (Dichlorodiphenyltrichloroethane)
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 Historic Pesticides (5)
TMDL Project Code:	358
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 and 3 of 3 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 149454, DDT (Dichlorodiphenyltrichloroethane)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

259871

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) 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 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: 10_GATE (Conejo Creek Hill CanyonBelow N Fork).

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 149454, DDT (Dichlorodiphenyltrichloroethane)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

259909

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 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo) to determine beneficial use support and the results are as follows: 3 of the 3 samples exceeded the water quality threshold for DDT(p,p'). Although a total of 36 samples were collected, 33 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 (10_GATE).

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	73712	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Excess Algal Growth
Final Listing Decision:	Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Delist from 303(d) list (TMDL required list)(2016)
Revision Status	Original
Reason for Delisting:	Flaws in original listing
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 of the Listing Policy. Under this section of the Policy, a minimum of one line of evidence is needed to assess listing status. The original line of evidence supporting the listing does not identify a pollutant but rather, a condition caused by a pollutant(s) (algal growth). A TMDL was approved by RWQCB on October, 2002 and subsequently approved by USEPA on June, 2003 and this TMDL is expected to address this water body condition. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of removing these listing from the 303(d) Water Quality Limited Segment list because the segment pollutant combinations is not a pollutant.

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 73712, Excess Algal Growth	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2217

Pollutant:

Excess Algal Growth

LOE Subgroup:

Narrative Description Data

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:

A TMDL for this water segment-pollutant combination was approved by the RWQCB in October 2002. The TMDL has an approved implementation plan. USEPA approved the TMDL on June 20, 2003. This TMDL will address this water body condition.

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 Info Missing

QAPP Information Reference(s):


DECISION ID	76243	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Endosulfan (tissue)
Final Listing Decision:	Delist from 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	Delist from 303(d) list (being addressed by USEPA approved TMDL)(2016)
Revision Status	Original
Reason for Delisting:	Applicable WQS attained; reason for recovery unspecified
TMDL Name:	Calleguas Creek Historic Pesticides (5)
TMDL Project Code:	358
Date TMDL Approved by USEPA:	03/24/2006
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. Four lines of evidence are available in the administrative record to assess this pollutant. One placeholder decision exceeded the objective. Zero of zero samples exceeded the objective. Zero of 108 samples exceeded the objective. Zero of 108 samples exceeded the objective. 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. One placeholder decision exceeded the objective, zero of zero, zero of 108, and zero of 108 samples exceeded the objective 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:	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 76243, Endosulfan (tissue)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2223

Pollutant:

Endosulfan

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:

Data for various pollutants in Calleguas Creek Reach 10, Jan. 2005-Jun. 2010

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 76243, Endosulfan (tissue)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

94025

Pollutant:

Endosulfan

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

108

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

None of the 108 samples exceeded the water quality objective for Endosulfan I is 0.056 ug/L.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Los Angeles Region Basin Plan states "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 California Toxic Rule criteria fresh aquatic life protection continuous concentration (4-day average)is 0.056 ug/L. THE CRITERIA FOR ENDOSULFAN I WAS USED.

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

Temporal Representation:

Environmental Conditions:

There was no special environmental conditions reported.

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 76243, Endosulfan (tissue)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

94024

Pollutant:

Endosulfan

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

108

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

None of the 108 samples exceeded the water quality objective for Endosulfan II is 0.056 ug/L.

Data Reference:

Data for various pollutants in Calleguas Creek Reach 10, Jan. 2005-Jun. 2010

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Los Angeles Region Basin Plan states "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 California Toxic Rule criteria fresh aquatic life protection continuous concentration (4-day average)is 0.056 ug/L. THE CRITERIA FOR ENDOSULFAN II WAS USED.

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

108 water samples were collected fromCalleguas Creek Reach 10 (Conejo Creek, Hill Canyon)-was part of formerly Conejo Crk Reaches 2 & 3, and lower Conejo Crk/Arroyo Conejo N Fk on 1998 303d list).

Temporal Representation:

Environmental Conditions:

There was no special environmental conditions reported.

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 76243, Endosulfan (tissue)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

30135

Pollutant:

Endosulfan (tissue)

LOE Subgroup:

Narrative Description Data

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:

A TMDL has been approved for this water segment-pollutant combination. The Calleguas Creek OC Pesticides and PCBs TMDL was adopted by the Los Angeles RWQCB on July 07, 2005 and subsequently approved by USEPA on March 24, 2006. The TMDL was integrated into the Basin Plan as Attachment A of Regional Board Resolution No. 2006-010.

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	68657	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

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:	2027
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	303(d) listing decisions made prior to 2006 were not held in an assessment database and are not available in the administrative record. Even though fecal coliform is no longer the applicable indicator bacteria for fresh waters in the Los Angeles Region, studies show (Noble et al., 2003) that 80 to 90% of fecal coliform are E coli in the Los Angeles Region, and therefore the fecal coliform data used to list this waterbody is a reasonable stand in for E coli until E coli data is available. This conservative approach will limit the potential for delisting this waterbody which data has shown to be impaired for fecal indicating bacteria.

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 68657, Indicator Bacteria	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2219

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, 11 samples exceeding the 400/100 ml standard. Geomean of 431 exceeds 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:

Data for various pollutants in Calleguas Creek Reach 10, Jan. 2005-Jun. 2010

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):


DECISION ID	69944	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Toxaphene (tissue & sediment)
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)(2016)
Revision Status	Original
Sources:	Nonpoint Source
TMDL Name:	Calleguas Creek Historic Pesticides (5)
TMDL Project Code:	358
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 4.1 of the Listing Policy. Under 4.1 of the Policy, a minimum of one line of evidence is needed to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. One placeholder decision for a CWA section 303(d) Listing made in a previous assessment cycle exceed the criteria. Zero of zero samples exceed the criteria. 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. One placeholder decision and zero of zero samples exceeded the criteria and these exceed the allowable frequency listed in Table 4.1 of the Listing Policy. 4. The Calleguas Creek Historic Pesticides TMDL was approved by USEPA on 03/14/2006. 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 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 69944, Toxaphene (tissue & sediment)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

94030

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:

Since the criteria is smaller than the reporting limit and method detection limit, none of samples can be counted.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Los Angeles Region Basin Plan objective is "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:

Criteria Continuous Concentration (4-day Average) is 0.0002 ug/L.

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

Temporal Representation:

Environmental Conditions:

There was no special environmental conditions reported.

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 69944, Toxaphene (tissue & sediment)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2224

Pollutant:

Toxaphene (tissue & sediment)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

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:

Data for various pollutants in Calleguas Creek Reach 10, Jan. 2005-Jun. 2010

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	94829	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Heptachlor
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 3.1 of the Listing Policy. Under section 3.1 a single line of evidence are necessary to assess listing status. 1 line of evidence is available in the administrative record to assess this pollutant. 0 of 0 sample exceeded the CRITERIA. 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 CRITERIA 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 16 samples is needed to determine if a beneficial use is fully supported using table 3.1. 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 94829, Heptachlor	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

94027

Pollutant:

Heptachlor

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:

Since the criteria is smaller than the reporting limit and method detection limit, none of samples can be counted.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Los Angeles Region Basin Plan objective is "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:

California Toxic Rule criteria fresh aquatic life protection continuous concentration (4-day average) is 0.038 ug/L.

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

Temporal Representation:

Environmental Conditions:

There was no special environmental conditions reported.

QAPP Information:

QAPP Information Reference(s):


DECISION ID	94731	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Methoxychlor
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 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. 1 line of evidence is available in the administrative record to assess this pollutant. 0 of 108 samples exceeded the CRITERIA. 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 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. 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 94731, Methoxychlor	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

94028

Pollutant:

Methoxychlor

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

108

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

None of the 108 samples exceeded the water quality objective for Methoxychlor is 0.03 ug/L.

Data Reference:

Data for various pollutants in Calleguas Creek Reach 10, Jan. 2005-Jun. 2010

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Los Angeles Region Basin Plan states "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 Nationally Recommended Criteria for fresh aquatic life protection continuous concentration (4-day average)is 0.03 ug/L.

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

There was no special environmental conditions reported.

QAPP Information:

QAPP Information Reference(s):


DECISION ID	100407	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Pentachlorophenol (PCP)
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 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. 1 line of evidence is available in the administrative record to assess this pollutant. 0 of 108 samples exceeded the CRITERIA. 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 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. 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 100407, Pentachlorophenol (PCP)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

94029

Pollutant:

Pentachlorophenol (PCP)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

108

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

None of the 108 samples exceeded the Water Quality Objective.

Data Reference:

Data for various pollutants in Calleguas Creek Reach 10, Jan. 2005-Jun. 2010

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Los Angeles Region Basin Plan objective is "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 California Toxics Rule Criteria Continuous Concentration (4-day Average) for Aquatic Life for Pentachlorophenol (PCP) is 15 ug/L (at pH= 7.8) as expressed as a function of pH

Guideline Reference:

Code of Federal Regulations 40 part 131.38 Establishment of numeric criteria for priority toxic pollutants for the State of California. 7/1/2011 Edition

Spatial Representation:

36 water samples were collected from Reach 1 and Reach 2 of Calleguas Creek Reach 10 (Conejo Creek, Hill Canyon)-was part of formerly Conejo Crk Reaches 2 & 3, and lower Conejo Crk/Arroyo Conejo N Fk on 1998 303d list).

Temporal Representation:

Samples were collected eight times in 2006 (fall & winter), twenty-four times in 2007 (winter, spring, summer, and fall), twenty-one times in 2008(winter, spring, summer, and fall), twenty-four times in 2009(winter, spring, summer, and fall), twenty-four times in 2010, and six times in 2011 (winter, spring, summer, and fall).

Environmental Conditions:

There was no special environmental conditions reported.

QAPP Information:

QAPP Information Reference(s):


DECISION ID	76966	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Trash
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:	2021
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the section 303(d) list under section 3.7 of the Listing Policy. Under section 3.7 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 for placing this water segment-pollutant combination on the 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. Seven of 11 samples exceeded the narrative objectives for trash listed in the Basin Plan, and evaluated using numeric targets derived in Los Angeles River Trash TMDL 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 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 76966, Trash	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

30189

Pollutant:

Trash

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Aquatic Life Use:

Wildlife Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Seven of 11 samples exceeded the numeric target of zero trash.

Data Reference:

Calleguas Creek Watershed Monitoring Report prepared by Wishtoyo Foundation, Ventura Coastkeeper, 2006

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

From the Los Angeles RWQCB Basin Plan: Waters shall not contain floating materials, including solids, liquids, foams, and scum, in concentrations that cause nuisance or adversely affect beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Narrative objective evaluated using numeric target of zero trash in Los Angeles River Trash TMDL and other regional trash TMDLs.

Guideline Reference:

Spatial Representation:

One monitoring station in Calleguas Creek, Reach 10 (CJ2).

Temporal Representation:

11 observations and trash counts were taken every month from February to December of 2006.

Environmental Conditions:

QAPP Information:

Data was collected in compliance with the sampling and monitoring procedures detailed in Wishtoyo Foundation Volunteer Monitoring Quality Assurance Project Plan.

QAPP Information Reference(s):

Wishtoyo Foundation Volunteer Monitoring Quality Assurance Project Plan


DECISION ID	69681	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Ammonia
Final Listing Decision:	List on 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)(2016)
Revision Status	Original
Sources:	Nonpoint Source \| Point Source
TMDL Name:	Calleguas Creek Nitrogen (1)
TMDL Project Code:	228
Date TMDL Approved by USEPA:	06/20/2003
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 approved by USEPA and an approved implementation plan is expected to result in attainment of the standard. The Calleguas Creek Nitrogen TMDL was approved by USEPA in June 20, 2003. 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.

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 69681, Ammonia	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2226

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:

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	72430	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	ChemA (tissue)
Final Listing Decision:	List on 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)(2016)
Revision Status	Original
Sources:	Agriculture-storm runoff
TMDL Name:	Calleguas Creek Historic Pesticides (5)
TMDL Project Code:	358
Date TMDL Approved by USEPA:	03/24/2006
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 of the Listing Policy. Under 2.2 of the Policy, a minimum of one line of evidence is needed 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 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.

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 72430, ChemA (tissue)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2221

Pollutant:

ChemA (tissue)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

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):

Line of Evidence (LOE) for Decision ID 72430, ChemA (tissue)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

30134

Pollutant:

ChemA (tissue)

LOE Subgroup:

Narrative Description Data

Matrix:

Not Specified

Fraction:

None

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

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	72395	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Chloride
Final Listing Decision:	List on 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)(2016)
Revision Status	Original
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 Chloride (3)
TMDL Project Code:	356
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 of the Listing Policy. Under 2.2 of the Policy, a minimum of one line of evidence is needed 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 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.

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 72395, Chloride	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

4069

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 72395, Chloride	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

28035

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:

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):


DECISION ID	71546	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	DDT (tissue)
Final Listing Decision:	List on 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)(2016)
Revision Status	Original
Sources:	Nonpoint Source
TMDL Name:	Calleguas Creek Historic Pesticides (5)
TMDL Project Code:	358
Date TMDL Approved by USEPA:	03/14/2006
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 approved by USEPA and an approved implementation plan is expected to result in attainment of the standard. The Calleguas Creek Historic Pesticides TMDL was approved by the RWQCB in 2005 and subsequently approved by USEPA. 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.

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 71546, DDT (tissue)	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2222

Pollutant:

DDT (tissue)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

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:

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	68707	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Nitrogen, Nitrite
Final Listing Decision:	List on 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)(2016)
Revision Status	Original
Sources:	Nonpoint Source \| Point Source
TMDL Name:	Calleguas Creek Nitrogen (1)
TMDL Project Code:	228
Date TMDL Approved by USEPA:	06/20/2003
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for delisting under sections 4.1 of the Listing Policy. Under section 4.1 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 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. 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. Five of 42 water samples exceeded the water quality objective. However, a TMDL is in place to address this pollutant in this water body. The Calleguas Creek Nitrogen TMDL was approved by USEPA on The TMDL has an approved implementation plan. USEPA approved the TMDL on June 20, 2003. 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:	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 68707, Nitrogen, Nitrite	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2220

Pollutant:

Nitrogen, Nitrite

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Groundwater Recharge

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Forty-two water samples, 5 samples exceeding (SWRCB, 2003).

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Basin Plan: Waters shall not exceed 10 mg/L nitrogen as nitrate-nitrogen plus nitrite-nitrogen (NO2-N), 45 mg/L as nitrate (NO3), 10 mg/L as nitrate-nitrogen (NO3-N), or 1 mg/L nitrite-nitrogen (NO2-N) or as otherwise designated in [another part of the Basin Plan].

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One site.

Temporal Representation:

Summer, fall, winter spring.

Environmental Conditions:

Data 2-5 years old, data measured at site, data measured during all seasons.

QAPP Information:

NPDES Program and Calleguas Creek Ambient Water Quality Monitoring Program

QAPP Information Reference(s):


DECISION ID	76412	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Sulfates
Final Listing Decision:	List on 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)(2016)
Revision Status	Original
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 of the Listing Policy. Under 2.2 of the Policy, a minimum of one line of evidence is needed 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 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.

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 76412, Sulfates	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

4070

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 listing decision made by USEPA for 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:

Unspecified

Temporal Representation:

Unspecified

Environmental Conditions:

Unspecified

QAPP Information:

Unspecified

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 76412, Sulfates	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

28036

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	70554	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Total Dissolved Solids
Final Listing Decision:	List on 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)(2016)
Revision Status	Original
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 of the Listing Policy. Under 2.2 of the Policy, a minimum of one line of evidence is needed 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 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.

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 70554, Total Dissolved Solids	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

4071

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:

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 70554, Total Dissolved Solids	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

28037

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:

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	69136	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

Pollutant:	Toxicity
Final Listing Decision:	List on 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)(2016)
Revision Status	Original
Sources:	Nonpoint Source \| Point Source
TMDL Name:	Calleguas Creek Toxicity (2)
TMDL Project Code:	355
Date TMDL Approved by USEPA:	03/14/2010
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 approved by USEPA and an approved implementation plan is expected to result in attainment of the standard. The Calleguas Creek Toxicity TMDL was approved by the RWQCB in July of 2005 and subsequently approved by USEPA. 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.

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 69136, Toxicity	Region 4
Calleguas Creek Reach 10 (Aroyo Conejo: Conejo Creek to North Fork Arroyo Conejo)

LOE ID:

2225

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 303(d) listing decision made prior to 2006.

Data Reference: