Draft California 2020 Integrated Report (303(d) List/305(b) Report)

Fact Sheet: Final Recommended Aquatic Life Ambient Water Quality Criteria for Diazinon

Evaluation Guideline:

Diazinon is toxic to birds and aquatic life; especially invertebrates. The one-hour average concentration of diazinon should not exceed 0.17 µg/L more than once every three years on the average (acute criterion) and the four-day average concentration of diazinon should not exceed 0.17 µg/L more than once every three years on the average (chronic criterion). (U.S. EPA, 2006).

Guideline Reference:

Spatial Representation:

Samples were collected from the middle Trabuco Creek at Oso Parkway. Lat/Long: 33.5850/-117.6358.

Temporal Representation:

Samples were taken on various dates starting March 25, 1999 to February 23, 2000.

Environmental Conditions:

QAPP Information:

Data submitted to the DPR¿s Surface Water Database is subject to the document ¿Requirements for Inclusion of Monitoring Data in DPR¿s Surface Water Database.¿

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105538, Diazinon	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216545

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

None of the 18 samples exceed the continuous concentration for Diazinon criteria of 0.1 ug/L.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in the water column, sediments or biota at concentration(s) that adversely affect beneficial uses.

Objective/Criterion Reference:

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

Evaluation Guideline:

The freshwater chronic value for diazinon is 0.1 ug/L, expressed as a continuous concentration (Finlayson, 2004).

Guideline Reference:

Spatial Representation:

Samples were collected at 4 monitoring sites (TC-DO, TCOLO2, TC-AP and SMC00206).

Temporal Representation:

Samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

Data were submitted with the County of Orange Stormwater Program Quality Assurance Management Plan (QAMP) dated January 2010. However, data were collected prior to the development of this QAMP, therefore the quality of these data are unknown

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 105538, Diazinon	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216562

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

None of the 18 samples exceed the CADPH Notification Level for Diazinon criteria.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in the water column, sediments or biota at concentration(s) that adversely affect beneficial uses.

Objective/Criterion Reference:

Drinking Water Notification and Response Levels: An Overview

Evaluation Guideline:

The California Department of Public Health (CDPH) Notification Level for Diazinon is 1.2 ug/L.

Guideline Reference:

Spatial Representation:

Samples were collected at 4 monitoring sites (TC-DO, TCOLO2, TC-AP and SMC00206).

Temporal Representation:

Samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	105544	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Malathion
Final Listing Decision:	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
Reason for Delisting:	Flaws in original listing
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 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. Zero of the 18 samples exceeded the water quality threshold for the WARM beneficial use, and zero of the 18 samples exceeded the water quality threshold for the MUN beneficial use. 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. Zero of 18 samples exceeded the water quality threshold for the WARM beneficial use, zero of the 18 samples exceeded the water quality threshold for the MUN beneficial use, 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 the original basis for listing was flawed, and the water body was split into upper and lower reaches for assessment purposes.

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 105544, Malathion	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216609

Pollutant:

Malathion

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

Zero of 18 samples exceed the maximum (Instantaneous) concentration for Malathion in freshwater of 100 ng/L.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in the water column, sediments or biota at concentration(s) that adversely affect beneficial uses.

Objective/Criterion Reference:

Quality Criteria for Water. USEPA Office of Water and Hazardous Materials. Washington, D.C

Evaluation Guideline:

The maximum (Instantaneous) concentration for Malathion in freshwater is 100 ng/L.

Guideline Reference:

Spatial Representation:

Samples were collected at 4 montoring sites (TC-DO, TCOLO2, TC-AP and SMC00206).

Temporal Representation:

Samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105544, Malathion	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216563

Pollutant:

Malathion

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

None the 18 samples exceed the CDPH notification level for Malathion criteria of 160.0 ug/L.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in the water column, sediments or biota at concentration(s) that adversely affect beneficial uses.

Objective/Criterion Reference:

2006 edition of the drinking water standards and health advisories. EPA 822-R-03-013

Evaluation Guideline:

The California Department of Public Health (CDPH) notification level criteria for malathion in freshwater is 160.0 ug/L.

Guideline Reference:

Spatial Representation:

Samples were collected at 4 monitoring sites (TC-DO, TCOLO2, TC-AP and SMC00206).

Temporal Representation:

Samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	105536	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Benthic Community Effects
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:	2025
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Benthic Community Effects is being considered for delisting from the CWA Section 303(d) list under sections 4.9 and 4.1 of the Listing Policy. Based on the readily available data and information, the weight of evidence does not provide sufficient justification for removing Benthic Community Effects in this water segment 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. Pursuant to section 4.9 of the Listing Policy, the water exhibits significant degradation in biological populations and/or communities as compared to reference site(s) using the California Stream Condition Index. 16 of 20 benthic-macroinvertebrate samples from the 2020 Cycle exceed the California Stream Condition Index (CSCI) impairment threshold. One sample is a same-day replicate. These data indicate that the waterbody remains impaired for Benthic Community Effects. Note that CSCI scores between Arroyo Golf Club and Beebe meet the threshold, suggesting this segment is not impaired. 4. Pursuant to section 4.9 of the Listing Policy, the water segment has associated pollutant(s) samples that exceed water quality objectives. 5. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are being 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 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134346

Pollutant:

Diazinon

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

Data Reference:

Department of Pesticide Regulation (DPR), 2003. Surface Water Database, April 2003. Accessed July 8, 2007

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Fact Sheet: Final Recommended Aquatic Life Ambient Water Quality Criteria for Diazinon

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from the middle Trabuco Creek at Oso Parkway. Lat/Long: 33.5850/-117.6358.

Temporal Representation:

Samples were taken on various dates starting March 25, 1999 to February 23, 2000.

Environmental Conditions:

QAPP Information:

Data submitted to the DPR¿s Surface Water Database is subject to the document ¿Requirements for Inclusion of Monitoring Data in DPR¿s Surface Water Database.¿

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216567

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:

TOXICITY TESTING

Data Used to Assess Water Quality:

Three of the four samples collected show significant toxicity levels (SL) for Ceriodaphnia dubia young/female (#) and Selenastrum capricornutum (total cell count) (SWAMP, 2007).

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

From the Basin Plan, all waters shall be free of toxic substances that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life (RWQCB, 2007).

Objective/Criterion Reference:

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

Evaluation Guideline:

According to SWAMP, waters are considered toxic when samples show significant toxicity levels (SWAMP code SL) when compared to a negative control. Significant toxicity is determined when statistical tests result in an alpha of less than 5% and percent control values less than the evaluation threshold.

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (901SJATC5).

Temporal Representation:

Water samples were collected from 10/29/2002 through 5/12/2003.

Environmental Conditions:

QAPP Information:

Quality control for this study was conducted in accordance with the California's Surface Water Ambient Monitoring Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216568

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

One of the three samples collected show significant toxicity levels (SL) to Hyalella azteca growth (weight) according to results from the Surface Ambient Monitoring Program results (SWAMP, 2007).

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

From the Basin Plan, all waters shall be free of toxic substances that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life (RWQCB, 2007).

Objective/Criterion Reference:

California Stream Condition Index Scores for the 2020 Integrated Report

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (901SJATC5).

Temporal Representation:

Sediment samples were collected from 10/29/2002 through 5/12/2003.

Environmental Conditions:

QAPP Information:

Quality control for this study was conducted in accordance with the California's Surface Water Ambient Monitoring Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

218248

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 901TC__DO to determine beneficial use support and the results are as follows: 6 of 6 samples exceeded the threshold. CSCI scores were from 0.3659 to 0.7729 .

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in, human, plant or animal, or aquatic life. Compliance with this objective will be determined by use of indicator organisms, analysis of species diversity, population density, growth anomalies, bioassays of appropriate duration, or other appropriate methods as specified by the Regional Board. Region 9 Basin Plan.

Objective/Criterion Reference:

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

Evaluation Guideline:

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

Guideline Reference:

Spatial Representation:

Samples were collected from station 901TC__DO

Temporal Representation:

Samples were collected from 5/16/2011 to 6/22/2017.

Environmental Conditions:

QAPP Information:

The data was collected under a permit required receiving waters monitoring and reporting program

QAPP Information Reference(s):

Quality Assurance Project Plan for Southern California Regional Watershed Monitoring Program Bioassessment, Version 1.0, and Freshwater Bioassessment from Weston Solutions.

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

218246

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for SMC00963 to determine beneficial use support and the results are as follows: 0 of 1 samples exceeded the threshold. CSCI scores were from 0.87168743 to 0.87168743 .

Data Reference:

California Stream Condition Index Scores for the 2020 Integrated Report

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from station SMC00963

Temporal Representation:

Samples were collected from 7/9/2014 to 7/9/2014.

Environmental Conditions:

QAPP Information:

The data was collected under a permit required receiving waters monitoring and reporting program

QAPP Information Reference(s):

Quality Assurance Project Plan for Southern California Regional Watershed Monitoring Program Bioassessment, Version 1.0, and Freshwater Bioassessment from Weston Solutions.

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

218247

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for SMC01934 to determine beneficial use support and the results are as follows: 1 of 1 samples exceeded the threshold. CSCI scores were from 0.56827563 to 0.56827563 .

Data Reference:

California Stream Condition Index Scores for the 2020 Integrated Report

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from station SMC01934

Temporal Representation:

Samples were collected from 6/15/2012 to 6/15/2012.

Environmental Conditions:

QAPP Information:

The data was collected under a permit required receiving waters monitoring and reporting program

QAPP Information Reference(s):

Quality Assurance Project Plan for Southern California Regional Watershed Monitoring Program Bioassessment, Version 1.0, and Freshwater Bioassessment from Weston Solutions.

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

218245

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 901M14138 to determine beneficial use support and the results are as follows: 0 of 1 samples exceeded the threshold. CSCI scores were from 0.8086 to 0.8086 .

Data Reference:

California Stream Condition Index Scores for the 2020 Integrated Report

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from station 901M14138

Temporal Representation:

Samples were collected from 6/20/2017 to 6/20/2017.

Environmental Conditions:

QAPP Information:

The data was collected under a permit required receiving waters monitoring and reporting program

QAPP Information Reference(s):

Quality Assurance Project Plan for Southern California Regional Watershed Monitoring Program Bioassessment, Version 1.0, and Freshwater Bioassessment from Weston Solutions.

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

218243

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 901ATCDOS to determine beneficial use support and the results are as follows: 2 of 2 samples exceeded the threshold. CSCI scores were from 0.3539 to 0.6391 .

Data Reference:

California Stream Condition Index Scores for the 2020 Integrated Report

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from station 901ATCDOS

Temporal Representation:

Samples were collected from 4/29/2014 to 6/22/2017.

Environmental Conditions:

QAPP Information:

The data was collected under a permit required receiving waters monitoring and reporting program

QAPP Information Reference(s):

Quality Assurance Project Plan for Southern California Regional Watershed Monitoring Program Bioassessment, Version 1.0, and Freshwater Bioassessment from Weston Solutions.

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

218244

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 901M14118 to determine beneficial use support and the results are as follows: 0 of 1 samples exceeded the threshold. CSCI scores were from 0.9602 to 0.9602 .

Data Reference:

California Stream Condition Index Scores for the 2020 Integrated Report

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from station 901M14118

Temporal Representation:

Samples were collected from 4/30/2015 to 4/30/2015.

Environmental Conditions:

QAPP Information:

The data was collected under a permit required receiving waters monitoring and reporting program

QAPP Information Reference(s):

Quality Assurance Project Plan for Southern California Regional Watershed Monitoring Program Bioassessment, Version 1.0, and Freshwater Bioassessment from Weston Solutions.

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

218249

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 901S00206 to determine beneficial use support and the results are as follows: 4 of 5 samples exceeded the threshold. CSCI scores were from 0.64645778 to 0.886 .

Data Reference:

California Stream Condition Index Scores for the 2020 Integrated Report

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from station 901S00206

Temporal Representation:

Samples were collected from 6/5/2014 to 6/22/2017.

Environmental Conditions:

QAPP Information:

The data was collected under a permit required receiving waters monitoring and reporting program

QAPP Information Reference(s):

Quality Assurance Project Plan for Southern California Regional Watershed Monitoring Program Bioassessment, Version 1.0, and Freshwater Bioassessment from Weston Solutions.

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

218250

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Water Board staff assessed data for 901TCSMP1 to determine beneficial use support and the results are as follows: 3 of 3 samples exceeded the threshold. CSCI scores were from 0.5306 to 0.7348 .

Data Reference:

California Stream Condition Index Scores for the 2020 Integrated Report

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from station 901TCSMP1

Temporal Representation:

Samples were collected from 5/25/2010 to 5/5/2010.

Environmental Conditions:

QAPP Information:

Data collected following SWAMP QA protocols.

QAPP Information Reference(s):

Quality Assurance Program Plans, Quality Assurance Project Plans, and Standard Operating Procedures for the SWAMP program

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134410

Pollutant:

Benthic-Macroinvertebrate Bioassessments

LOE Subgroup:

Population/Community Degradation

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Benthic macroinvertebrate surveys

Data Used to Assess Water Quality:

Fifteen samples were collected at five stations in lower Arroyo Trabuco downstream from the USFS boundary. Thirteen samples had CSCI scores below the 0.79 threshold, and are therefore exceeding the water quality objective for the aquatic life beneficial use.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

RWB9 Stormwater Monitoring Council CY 2009

Region 9 CSCI Scores & Water Body Information

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at stations TC-DO, 901PS0057, TC-AP, SMC00206

Temporal Representation:

The samples were collected from 2006 to 2009.

Environmental Conditions:

QAPP Information:

Data collected following SWAMP QA protocols for the County of Orange NPDES MS4 Copermittees Receiving Waters Monitoring and Reporting Program, and for the SWAMP Statewide Perennial Streams Assessment 2008, and Southern California Regional Watershed Monitoring Program Bioassessment Quality Assurance Project Plan.

QAPP Information Reference(s):

RWB9 Stormwater Monitoring Council CY 2009

QAPP Information Reference(s):

QAPP Information Reference(s):

Quality Assurance Project Plan for the Orange County Stormwater Program.

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134360

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

zero of two samples exceeded the water quality objective for mercury.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

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

Objective/Criterion Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

Evaluation Guideline:

National Recommended Water Quality Criteria Continuous Concentrations (4-day average concentrations) for freshwater aquatic organisms exposure to elemental mercury is 0.77 ug/L.

Guideline Reference:

Spatial Representation:

Samples were collected from Arroyo Trabuco Creek at Del Obispo (TCOL02) and at SMC00206.

Temporal Representation:

Samples were collected from September 2006 through May of 2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216549

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

Twenty-one samples were collected to test for toxicity. Six of the 21 samples exhibited statistically and biologically significant toxicity. The toxicity tests that exhibited significant toxicity included Mysid biomass and survival, Ceriodaphnia reproduction, and Selenastrum growth.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

From the Basin Plan, all waters shall be free of toxic substances that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life (RWQCB, 2007).

Objective/Criterion Reference:

Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, Fifth Edition. EPA-821-R-02-012

Evaluation Guideline:

Toxicity is defined as a statistically significant effect in the sample exposure compared to the control using EPA-recommended hypothesis testing. The t-test is used to determine if there is a statistically significant decrease in organism response in the sample as compared to the control. Additionally, the biological significance of the sample is evaluated by determining whether the sample response is lower than the evaluation threshold.

Guideline Reference:

Guideline Reference:

Spatial Representation:

The samples were collected at 3 sites (TC-AP, TC-DO and TCOL02).

Temporal Representation:

The samples were collected from 6/28/2006 through 11/18/2009.

Environmental Conditions:

QAPP Information:

The data collected under the Quality Assurance Management Plan for The Orange County Stormwater Program. The SWAMP measurement quality objectives were followed for toxicity data. The performance of toxicity bioassays and evaluation of reference toxicants were performed using USEPA and Standard Methods.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105536, Benthic Community Effects	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134344

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

All nine flow-weighted event mean concentrations exceeded the water quality objective according to results in the the Orange County Stormwater Program annual progress reports. Samples were collected from December 2002 to March 2006.

Data Reference:

Orange County Stormwater Program. 2004-2007. Unified Annual Progress Reports, Program Effectiveness Assessment (San Diego Region)

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Orange County Stormwater Program. 2004-2007. Unified Annual Progress Reports, Program Effectiveness Assessment (San Diego Region)

Spatial Representation:

Samples were collected at the mass loading station TCOL02 at Del Obispo Street at 33.4975°, 117.6657°.

Temporal Representation:

Samples were collected from December 2002 to March 2006.

Environmental Conditions:

Samples were collected during storm events.

QAPP Information:

Quality control for the bacteria analysis portion of this study was conducted in accordance with the County of Orange Quality Assessment/Quality Control documents for their stormwater monitoring program.

QAPP Information Reference(s):


DECISION ID	105534	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Toxicity
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)(2018)
Revision Status	Revised
Sources:	A Source Unknown
Expected TMDL Completion Date:	2019
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the CWA section 303(d) List under sections 4.1 and 4.6 of the Listing Policy. Under sections 4.1 and 4.6, at least one line of evidence is necessary to assess listing status. Seven lines of evidence are available in the administrative record to assess this pollutant. Nine of 30 water samples exhibited toxicity (sufficient sample size to determine beneficial use rating), and one of three sediment samples exhibited toxicity (insufficient sample size to determine beneficial use rating). 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. 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. Nine of 30 water samples exhibited toxicity, and this sample size is sufficient to determine beneficial use support, with the power and confidence 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 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 105534, Toxicity	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216549

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

From the Basin Plan, all waters shall be free of toxic substances that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life (RWQCB, 2007).

Objective/Criterion Reference:

Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, Fifth Edition. EPA-821-R-02-012

Evaluation Guideline:

Guideline Reference:

Guideline Reference:

Spatial Representation:

The samples were collected at 3 sites (TC-AP, TC-DO and TCOL02).

Temporal Representation:

The samples were collected from 6/28/2006 through 11/18/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105534, Toxicity	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216568

Pollutant:

Toxicity

LOE Subgroup:

Toxicity

Matrix:

Sediment

Fraction:

Not Recorded

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

TOXICITY TESTING

Data Used to Assess Water Quality:

One of the three samples collected show significant toxicity levels (SL) to Hyalella azteca growth (weight) according to results from the Surface Ambient Monitoring Program results (SWAMP, 2007).

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

From the Basin Plan, all waters shall be free of toxic substances that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life (RWQCB, 2007).

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (901SJATC5).

Temporal Representation:

Sediment samples were collected from 10/29/2002 through 5/12/2003.

Environmental Conditions:

QAPP Information:

Quality control for this study was conducted in accordance with the California's Surface Water Ambient Monitoring Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105534, Toxicity	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216567

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:

TOXICITY TESTING

Data Used to Assess Water Quality:

Three of the four samples collected show significant toxicity levels (SL) for Ceriodaphnia dubia young/female (#) and Selenastrum capricornutum (total cell count) (SWAMP, 2007).

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

From the Basin Plan, all waters shall be free of toxic substances that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life (RWQCB, 2007).

Objective/Criterion Reference:

Orange County Stormwater Program. 2004-2007. Unified Annual Progress Reports, Program Effectiveness Assessment (San Diego Region)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site (901SJATC5).

Temporal Representation:

Water samples were collected from 10/29/2002 through 5/12/2003.

Environmental Conditions:

QAPP Information:

Quality control for this study was conducted in accordance with the California's Surface Water Ambient Monitoring Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105534, Toxicity	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134343

Pollutant:

Toxicity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Ambient toxicity testing (chronic)

Data Used to Assess Water Quality:

From the four samples, there was no observed acute or chronic toxicity to Hyalella azteca, Selenastrum Algae Growth or Ceriodaphnia dubia. Toxicity data reviewed came from the Orange County Water Annual Progess Report from 2002 to 2006. Samples were collected from December 2002 through May 2005.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be sustain free from toxic substances in concentrations that are toxic to, or that produce harmful physiological responses in human, plant, animal, or aquatic life.
Samples were found to exhibit toxicity when the No Observed Effect Concentration (NOEC) or median lethal concentration (LC50) for any given species was estimated to be less than 100% of the test sample concentration.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Orange County Stormwater Program. 2004-2007. Unified Annual Progress Reports, Program Effectiveness Assessment (San Diego Region)

Spatial Representation:

Samples were collected at two locations in Trabuco Creek. Samples were collected at the end of Avery Parkway (TC-AP) and at Del Obispo Rd (TC-DO).

Temporal Representation:

Samples were collected from December 2002 to May 2005.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	105542	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Arsenic
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. Two lines of evidence are available in the administrative record to assess this pollutant. Zero of the 48 samples exceed the water quality threshold. 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. Zero of the 48 samples exceed the water quality threshold, 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:	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 105542, Arsenic	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216606

Pollutant:

Arsenic

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the 11 samples exceeded the water quality objective for arsenic.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

All waters shall be maintained free of toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life. Inland surface waters, enclosed bays, and estuaries shall not contain toxic pollutants in excess of the numerical objectives applicable to California specified in 40 CFR 131.36 (section 131.36 revised at 57 FR 60848, December 22, 1992).

Objective/Criterion 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

Evaluation Guideline:

California Toxics Rule (CTR) lists criterion continuous concentrations (4-day average) to protect aquatic life in freshwater. The CTR for arsenic is 150 ug/L.

Guideline Reference:

Spatial Representation:

Samples were collected from 4 monitoring sites (TC-AP, TC-DO, TCL02 and SMC00206).

Temporal Representation:

Samples were collected from 11/6/2007 through 5/18/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105560	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Cadmium
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. Two lines of evidence are available in the administrative record to assess this pollutant. Zero of the 18 samples exceed the water quality threshold for the WARM beneficial use, and zero of the 18 samples exceeds the water quality threshold for the MUN beneficial use. 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. Zero of the 18 samples exceed the water quality threshold for the WARM beneficial use, and zero of the 18 samples exceeds the water quality threshold for the MUN beneficial use, 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:	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 105560, Cadmium	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216555

Pollutant:

Cadmium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Zero of the 18 samples exceeded the hardness adjusted water quality objective for cadmium.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion 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

Evaluation Guideline:

California Toxics Rule (CTR) lists criterion continuous concentrations (4-day average) to protect aquatic life in freshwater. The dissolved criterion in freshwater is hardness dependent for each sample and varies based on the ambient hardness during sampling. Section (b)(1) in CTR contains the hardness dependent formula for the metals criterion.

Guideline Reference:

Spatial Representation:

Samples were collected at 4 monitoring sites (TC-AP, TC-DO, TCOL02 and SMC00206).

Temporal Representation:

Samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105560, Cadmium	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216553

Pollutant:

Cadmium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Zero of the 18 samples exceeded the water quality objective for cadmium.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Public Health Goal for Cadmium in Drinking Water

Evaluation Guideline:

Total cadmium levels should not exceed the California Department of Public Health Primary MCL of 5 ug/L.

Guideline Reference:

Guideline Reference:

MCLs for Regulated Drinking Water Contaminants, California Department of Public Health.

Spatial Representation:

Samples were collected from 4 monitoring sites (TC-AP, TC-DO, TCOL02 and SMC00206).

Temporal Representation:

The samples were collected from 9/26/06 through 5/18/09.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105562	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Chlorpyrifos
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. Three lines of evidence are available in the administrative record to assess this pollutant. Zero of the 50 samples exceed the water quality threshold for the WARM/COLD beneficial use. 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. Zero of 50 samples exceeded the threshold, 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:	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 105562, Chlorpyrifos	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134390

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

None of 33 samples exceed the continuous concentration for Chlorpyrifos criteria of 14.0 ng/L, however for two samples the reporting limit was greater than the evaluation guideline, therefore these data are not of sufficient resolution to determine if water quality standards are being achieved.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in the water column, sediments or biota at concentration(s) that adversely affect beneficial uses.

Objective/Criterion 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

Evaluation Guideline:

The Criteria Continuous Concentration (four day average) for chlorpyrifos in freshwater is 14.0 ng/L. Ref12

Guideline Reference:

Spatial Representation:

Nineteen samples were collected at Segunda Deshecha Creek, sites: SD-AP and SDCM02

Temporal Representation:

Samples were collected from 2006 through 2009.

Environmental Conditions:

According to the County of Orange Stormwater Program Quality Assurance Management Plan (QAMP) dated January 2010, samples were collected during the dry season and storm events.

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105562, Chlorpyrifos	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216558

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

None of 18 samples exceed the USEPA Health Advisory 2011 ed., criteria for chlorpyrifos.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in the water column, sediments or biota at concentration(s) that adversely affect beneficial uses.

Objective/Criterion Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Evaluation Guideline:

USEPA Health Advisory 2011 ed., criteria for chlorpyrifos in freshwater is 2.0 ug/L (represents a life-time risk).

Guideline Reference:

Spatial Representation:

Samples were collected at 4 monitoring sites (TC-DO, TCOLO2, TC-AP and SMC00206).

Temporal Representation:

Samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105562, Chlorpyrifos	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216559

Pollutant:

Chlorpyrifos

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

None of 17 samples exceed the continuous concentration for Chlorpyrifos criteria of 14.0 ng/L, however for six samples the reporting limit was greater than the evaluation guideline, therefore these data are not of sufficient resolution to determine if water quality standards are being achieved.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

No individual pesticide or combination of pesticides shall be present in the water column, sediments or biota at concentration(s) that adversely affect beneficial uses.

Objective/Criterion 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

Evaluation Guideline:

The Criteria Continuous Concentration (four day average) for chlorpyrifos in freshwater is 14.0 ng/L. Ref12

Guideline Reference:

Spatial Representation:

Samples were collected at 4 monitoring sites (TC-DO, TCOLO2, TC-AP and SMC00206).

Temporal Representation:

Samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	105564	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Chromium
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. Two lines of evidence are available in the administrative record to assess this pollutant. Zero of 18 samples exceed the water quality threshold for the WARM beneficial use, and zero of 18 samples exceed the water quality threshold for the MUN beneficial use. 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. Zero of 18 samples exceed the water quality threshold for the WARM beneficial use, zero of 18 samples exceed the water quality threshold for the MUN beneficial use, 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:	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 105564, Chromium	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216543

Pollutant:

Chromium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the 18 samples exceeded the water quality objective for chromium.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Maximum Contaminant Levels for organic and inorganic chemicals. CCR Title 22

Evaluation Guideline:

The CDPH Primary MCL for chromium is 50 ug/L.

Guideline Reference:

Spatial Representation:

Samples were collected from 4 monitoring sites (TC-AP, TC-DO, TCOL02 and SMC00206).

Temporal Representation:

The samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105564, Chromium	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216541

Pollutant:

Chromium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the 18 samples exceeded the hardness adjusted water quality objective for chromium.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion 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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from 4 monitoring sites (TC-AP, TC-DO, TCOL02 and SMC00206).

Temporal Representation:

Samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105566	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Copper
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. One line of evidence is available in the administrative record to assess this pollutant. Zero of the 18 samples exceed the water quality threshold. 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. Zero of the 18 samples exceed the water quality threshold, 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:	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 105566, Copper	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216571

Pollutant:

Copper

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the 18 samples collected for dissolved copper exceeded the hardness adjusted water quality objective for copper.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion 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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from 4 monitoring sites (TC-AP, TC-DO, TCOL02 and SMC00206).

Temporal Representation:

Samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105570	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Lead
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:	Pollution

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.1 of the Listing Policy. Under section 3.1 a single line of evidence is necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. Zero of the 18 samples exceed the water quality threshold. 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. Zero of the 18 samples exceed the water quality threshold, 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:	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 105570, Lead	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216574

Pollutant:

Lead

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

Zero of 18 samples exceeded the hardness adjusted water quality objective for lead.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion 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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from 4 monitoring sites (TC-AP, TC-DO, TCOL02 and SMC00206).

Temporal Representation:

Samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105547	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Nickel
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. One line of evidence is available in the administrative record to assess this pollutant. Zero of 18 samples exceed the water quality threshold. 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. Zero of 18 samples exceed the water quality threshold, 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:	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 105547, Nickel	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216608

Pollutant:

Nickel

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the 18 samples exceeded the hardness adjusted water quality objective for nickel.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion 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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from 4 monitoring sites (TC-AP, TC-DO, TCOL02 and SMC00206).

Temporal Representation:

Samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105549	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Oxygen, Dissolved
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 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Two lines of evidence are available in the administrative record to assess this pollutant. One of 18 samples exceed the objective. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification against placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. One of 18 samples exceed the objective, and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	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 105549, Oxygen, Dissolved	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216578

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Zero of the 17 samples exceeded the objective.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Dissolved oxygen levels shall not be less than 5.0 mg/l in inland surface waters with designated MAR or WARM beneficial uses or less than 6.0 mg/l in waters with designated COLD beneficial uses. The annual mean dissolved oxygen concentration shall not be less than 7 mg/l more than 10% of the time

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from 3 monitoring sites (TC-AP, TC-DO and TCOL02).

Temporal Representation:

Samples were collected from 9/6/2006 through 4/29/2009.

Environmental Conditions:

QAPP Information:

NPDES quality assurance.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105549, Oxygen, Dissolved	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134365

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Numeric data generated from 1 sample of Dissolved Oxygen concentrations had 1 exceedences.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

From the Basin Plan: Dissolved oxygen levels shall not be less than 5.0 mg/l in inland surface waters with designated MAR or WARM beneficial uses or less than 6.0 mg/l in waters with designated COLD beneficial uses. The annual mean dissolved oxygen concentrations shall not be less than 7 mg/l more than 10% of the time.

Objective/Criterion Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

One sample was collected from the 901PS0057 station.

Temporal Representation:

One sample was collected in May 2008.

Environmental Conditions:

QAPP Information:

NPDES quality assurance.

QAPP Information Reference(s):


DECISION ID	105553	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Selenium
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:	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 this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 105553, Selenium	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216546

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

One of the 11 samples exceeded the water quality objective for selenium. Samples with non-detect results and reporting limits greater than the water quality threshold were not used.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion 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

Evaluation Guideline:

California Toxics Rule (CTR) lists criterion continuous concentrations (4-day average) to protect aquatic life in freshwater. The CTR for selenium is 5.0 ug/L.

Guideline Reference:

Spatial Representation:

Samples were collected from 4 sampling sites (TC-AP, TC-DO, TCOL02 and SMC00206).

Temporal Representation:

Samples were collected from 11/6/2007 through 5/18/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105555	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Silver
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. One line of evidence is available in the administrative record to assess this pollutant. Zero of 18 samples exceed 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. Zero of 18 samples exceed 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:	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 105555, Silver	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216550

Pollutant:

Silver

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the 18 samples exceeded the hardness adjusted water quality objective for silver.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion 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

Evaluation Guideline:

California Toxics Rule (CTR) lists criterion maximum concentrations for silver to protect aquatic life in freshwater (1-hour average). The dissolved silver criterion in freshwater is hardness dependent for each sample and varies based on the ambient hardness during sampling. Section (b)(1) in CTR contains the hardness dependent formula for the metals criterion. If no hardness data were available, a value of 100 mg/L was used.

Guideline Reference:

Spatial Representation:

Samples were collected from 4 monitoring sites (TC-AP, TC-DO, TCOL02 and SMC00206).

Temporal Representation:

Samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105558	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Zinc
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. One line of evidence is available in the administrative record to assess this pollutant. Zero of 18 samples exceed the water quality threshold. 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. Zero of 18 samples exceed the water quality threshold, 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:	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 105558, Zinc	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216552

Pollutant:

Zinc

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

None of the 18 samples exceeded the hardness adjusted water quality objective for zinc.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion 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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from 4 monitoring sites (TC-AP, TC-DO, TCOL02 and SMC00206).

Temporal Representation:

Samples were collected from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105551	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	pH
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 3.2 of the Listing Policy. Under section 3.2 a single line of evidence is necessary to assess listing status. Three lines of evidence are available in the administrative record to assess this pollutant. Zero of 20 samples exceed the objective. 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. Zero of 20 samples exceed the objective, and this does not exceed the allowable frequency listed in Table 3.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:	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 105551, pH	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

216575

Pollutant:

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:

None of the 18 samples exceeded the water quality threshold for pH.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The pH of all inland surface waters shall not be depressed below 6.5 or raised above 8.5 as a result of waste discharges.

Objective/Criterion Reference:

Data for bacteria in various waterbodies, Feb. 2005-May 2007

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from 4 monitoring sites (SMC00206, TC-AP, TC-DO and TCOL02).

Temporal Representation:

Samples were collected approximately twice a month from 9/26/2006 through 5/18/2009.

Environmental Conditions:

QAPP Information:

NPDES quality assurance.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105551, pH	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134367

Pollutant:

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:

Numeric data generated from 1 sample of pH data had no exceedences.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The pH of all inland surface waters shall not be depressed below 6.5 or raised above 8.5 as a result of waste discharges.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from the Trabuco Creek station.

Temporal Representation:

One sample was collected on 5/5/2007.

Environmental Conditions:

QAPP Information:

NPDES quality assurance.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105551, pH	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134370

Pollutant:

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:

Numeric data generated from 1 sample collected had no exceedences.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

In inland surface waters[,] the pH shall not be depressed below 6.5 nor raised above 8.5.

Objective/Criterion Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from the 901PS0057 station.

Temporal Representation:

One sample was collected in May 2008

Environmental Conditions:

QAPP Information:

SWAMP QAPP

QAPP Information Reference(s):


DECISION ID	105569	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Indicator Bacteria
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	Original
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 4.3 of the Listing Policy. Under this section a single line of evidence is necessary to assess listing status. This water body was split for assessment purposes. In this water body section, no new E. coli data is available in the administrative record to assess this pollutant. Under section 4.3 of the Listing Policy, a minimum of 26 samples is required to delist. 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. 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. No new data were assessed for the current cycle. Under section 4.3 of the Listing Policy, a minimum of 26 samples is required to delist. 4. Pursuant to section 4.11 of the Listing Policy, no additional data and information are available indicating that standards are met. The State Water Board’s Water Quality Control Plan for Inland Surface Waters, Enclosed Bays, and Estuaries of California (the “ISWEBE Plan”) contains two bacteria water quality objectives applicable to the REC-1 beneficial use, which were adopted on August 7, 2018. Because the salinity level of this waterbody is equal to or less than 1 part per thousand 95 percent or more of the time, the E. coli bacteria objective applies Therefore, this waterbody is being considered for placement on or removal from the CWA section 303(d) List under section 3.3 or 4.3 of the Listing Policy, as applicable, using the E. coli objective. In accordance with section 6.1.5.3 of the Listing Policy, data should be representative of the critical timing that the pollutant is expected to impact the waterbody. Indicator bacteria (total coliform, fecal coliform, E. coli, enterococci) populations may fluctuate substantially on a daily, seasonal, or yearly basis. Lacking constant inputs, they do not persist in the environment for a long period and effects are of relatively short duration. As a result, the historic levels of indicator bacteria in the waterbody may be a poor indicator of current risks to human health, particularly when more recent data are available to sufficiently assess the water quality standard. Additionally, water quality conditions in waterbodies may change as a result of management actions that have been implemented to address bacteria. Unrepresentative data may result in incorrectly placing or not placing a water body segment on the list, which could result in the unnecessary expenditure of public resources or missing a human health problem. Historic lines of evidence for data collected prior to 2010 were evaluated pursuant to these considerations and were not used to assess water quality standards attainment because they do not meet the temporal representation requirements of section 6.1.5.3 of the Listing Policy. For E. coli data, Listing Policy sections 3.3 and 4.3 instructs to use the binomial distribution table in sections 3.2 and 4.2, as applicable. To use the binomial table that uses a four percent exceedance frequency, the data must be collected from coastal beaches or inland surface waters from April 1 through October 31 only, and where collected from inland waters from April 1 through October 31 only, bacterial measurements must be indicative of human fecal matter, and there is substantial human contact in the waterbody. No fecal coliform data are used in this assessment because the fecal coliform water quality objective was superseded and is no longer used as the basis of any 303(d) List decision for water contact recreation.

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 cycle. The decision has not changed.

State Board Review of Regional Board Conclusion and Recommendation:	The State Water Board’s Water Quality Control Plan for Inland Surface Waters, Enclosed Bays, and Estuaries of California (the “ISWEBE Plan”) contains two bacteria water quality objectives applicable to the REC-1 beneficial use, which were adopted on August 7, 2018. Because the salinity level of this waterbody is equal to or less than 1 part per thousand 95 percent or more of the time, the E. coli bacteria objective applies Therefore, this waterbody is being considered for placement on or removal from the CWA section 303(d) List under section 3.3 or 4.3 of the Listing Policy, as applicable, using the E. coli objective. In accordance with section 6.1.5.3 of the Listing Policy, data should be representative of the critical timing that the pollutant is expected to impact the waterbody. Indicator bacteria (total coliform, fecal coliform, E. coli, enterococci) populations may fluctuate substantially on a daily, seasonal, or yearly basis. Lacking constant inputs, they do not persist in the environment for a long period and effects are of relatively short duration. As a result, the historic levels of indicator bacteria in the waterbody may be a poor indicator of current risks to human health, particularly when more recent data are available to sufficiently assess the water quality standard. Additionally, water quality conditions in waterbodies may change as a result of management actions that have been implemented to address bacteria. Unrepresentative data may result in incorrectly placing or not placing a water body segment on the list, which could result in the unnecessary expenditure of public resources or missing a human health problem. Historic lines of evidence for data collected prior to 2010 were evaluated pursuant to these considerations and were not used to assess water quality standards attainment because they do not meet the temporal representation requirements of section 6.1.5.3 of the Listing Policy. For E. coli data, Listing Policy sections 3.3 and 4.3 instructs to use the binomial distribution table in sections 3.2 and 4.2, as applicable. To use the binomial table that uses a four percent exceedance frequency, the data must be collected from coastal beaches or inland surface waters from April 1 through October 31 only, and where collected from inland waters from April 1 through October 31 only, bacterial measurements must be indicative of human fecal matter, and there is substantial human contact in the waterbody. No fecal coliform data are used in this assessment because the fecal coliform water quality objective was superseded and is no longer used as the basis of any 303(d) List decision for water contact recreation.

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 105569, Indicator Bacteria	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134402

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

The one geomean exceeded the fecal coliform objective.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The geometric mean fecal coliform concentration shall not exceed more than 200/100ml. Water Quality Control Plan for the San Diego Basin.

Objective/Criterion Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected from site TCOL02, Trabuco Creek at Del Obispo.

Temporal Representation:

The samples were collected from April 2007 to November 2008.

Environmental Conditions:

QAPP Information:

The samples were collected and analyzed under the Quality Assurance Management Plan for The Orange County Stormwater Program. Mass Emissions Monitoring Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105569, Indicator Bacteria	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134399

Pollutant:

Enterococcus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Eleven of the eleven samples exceeded the enterococcus objective.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The single sample enterococcus concentration shall not exceed more than 61/100ml. Region 9 Basin Plan. Ambient Water Quality Control Criteria USEPA.

Objective/Criterion Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected from site TCOL02, Trabuco Creek at Del Obispo.

Temporal Representation:

The samples were collected from April 2007 to November 2008.

Environmental Conditions:

QAPP Information:

The samples were collected and analyzed under the Quality Assurance Management Plan for The Orange County Stormwater Program. Mass Emissions Monitoring Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105569, Indicator Bacteria	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134400

Pollutant:

Enterococcus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

The one geomean exceeded the enterococcus objective.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The geomeric mean enterococcus concentration shall not exceed more than 33/100ml. Water Quality Control Plan for the San Diego Basin.

Objective/Criterion Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected from site TCOL02, Trabuco Creek at Del Obispo.

Temporal Representation:

The samples were collected from April 2007 to November 2008.

Environmental Conditions:

QAPP Information:

The samples were collected and analyzed under the Quality Assurance Management Plan for The Orange County Stormwater Program. Mass Emissions Monitoring Program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 105569, Indicator Bacteria	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134401

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Eight of the eleven samples exceeded the fecal coliform objective.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The single sample fecal coliform concentration shall not exceed more than 400/100ml. Region 9 Basin Plan.

Objective/Criterion Reference:

Orange County Stormwater Program. 2004-2007. Unified Annual Progress Reports, Program Effectiveness Assessment (San Diego Region)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected from site TCOL02, Trabuco Creek at Del Obispo.

Temporal Representation:

The samples were collected from April 2007 to November 2008.

Environmental Conditions:

QAPP Information:

The samples were collected and analyzed under the Quality Assurance Management Plan for The Orange County Stormwater Program. Mass Emissions Monitoring Program.

QAPP Information Reference(s):


DECISION ID	105537	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Nitrogen
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	Original
Sources:	A Source Unknown
Expected TMDL Completion Date:	2019
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for removal from the 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. One line of evidence is available in the administrative record to assess pollutant. Eight of the nine samples exceed the water quality threshold. 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. 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. Eight of nine samples exceeded the threshold and this exceeds 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 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 105537, Nitrogen	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134345

Pollutant:

Total Nitrogen as N

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

Eight of nine flow-weighted event mean concentrations exceeded the water quality objective according to results in the Orange County Stormwater Program annual progress reports. Samples were collected nine times from December 2002 to March 2006.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water bodies shall not contain biostimulatory substances in concentrations that promote aquatic growth to the extent that such growths cause nuisance or adversely affect beneficial uses (RWQCB, 2007).
The Water Quality Control Plan for the San Diego Basin (9) states: ¿A desired goal in order to prevent plant nuisance in streams and other flowing waters appears to be 0.1 mg/L total P. These values are not to be exceeded more than 10% of the time unless studies of the specific water body in question clearly show that water quality objective changes are permissible and changes are approved by the Regional Board. Analogous threshold values have not been set for nitrogen compounds; however, natural ratios of nitrogen to phosphorus are to be determined by surveillance and monitoring and upheld. If data are lacking, a ratio of N:P = 10:1, on a weight to weight basis shall be used.¿ Since the goal for total phosphorus is 0.1 mg/L, then according to the ratio provided, the goal for total nitrogen is 1 mg/L.

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Orange County Stormwater Program. 2004-2007. Unified Annual Progress Reports, Program Effectiveness Assessment (San Diego Region)

Spatial Representation:

Samples were collected at the mass loading station at Del Obispo Street at 33.4975°, 117.6657°. Station identification number is TCOL02.

Temporal Representation:

Samples were collected during two to four storm events a year from December 2002 to March 2006.

Environmental Conditions:

Samples were collected during wet weather.

QAPP Information:

QAPP Information Reference(s):


DECISION ID	105535	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Phosphorus
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	Original
Sources:	A Source Unknown \| Natural Sources \| Urban Runoff/Storm Sewers
Expected TMDL Completion Date:	2019
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. One line of evidence are available in the administrative record to assess pollutant. Nine of the 9 samples exceed the threshold. 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. 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. Nine of 9 samples exceeded the threshold, and this exceeds 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 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 105535, Phosphorus	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134344

Pollutant:

Phosphorus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical monitoring (conventional pollutants only)

Data Used to Assess Water Quality:

Data Reference:

Orange County Stormwater Program. 2004-2007. Unified Annual Progress Reports, Program Effectiveness Assessment (San Diego Region)

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Orange County Stormwater Program. 2004-2007. Unified Annual Progress Reports, Program Effectiveness Assessment (San Diego Region)

Spatial Representation:

Samples were collected at the mass loading station TCOL02 at Del Obispo Street at 33.4975°, 117.6657°.

Temporal Representation:

Samples were collected from December 2002 to March 2006.

Environmental Conditions:

Samples were collected during storm events.

QAPP Information:

QAPP Information Reference(s):


DECISION ID	105541	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Ammonia (Unionized)
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	Original
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 this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 105541, Ammonia (Unionized)	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134353

Pollutant:

Ammonia (Unionized)

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:

0 of 1 samples exceed the water objective for un-ionized ammonia (NH3) at 0.025 mg/l (as N). Un-ionized ammonia (as N) was calculated from Total Ammonia (as N) from monthly samples reported in the data. The calculated un-ionized ammonia (as N) values was then established and compared to the un-ionized Ammonia (as N) at 0.025 mg/L in the RB9 Basin Plan. The data are reported as underneath the quantitation limit. These quantitation values are less than or equal to the water quality standard, the value will be considered as meeting the water quality standard, objective, criterion, or evaluation guideline.

Data Reference:

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, San Diego Region (SDRWQCB 2007): All waters shall be maintained free of toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life. The discharge of wastes shall not cause concentrations of un-ionized ammonia (NH3) to exceed 0.025 mg/l (as N) in inland surface waters, enclosed bays and estuaries and coastal lagoons.

Objective/Criterion Reference:

Surface Water Ambient Monitoring Program Quality Assurance Program Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected at 901PS0057 (Arroyo Trabuco 57).

Temporal Representation:

Samples collected on 5/14/2008.

Environmental Conditions:

QAPP Information:

SWAMP QAPP (2008) was followed.

QAPP Information Reference(s):


DECISION ID	105546	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Mercury
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	Original
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 this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 105546, Mercury	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134360

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fixed station physical/chemical (conventional plus toxic pollutants)

Data Used to Assess Water Quality:

zero of two samples exceeded the water quality objective for mercury.

Data Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

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

Objective/Criterion Reference:

Data for Various Waterbodies in Region 8 and Region 9, 2006-2009.

Evaluation Guideline:

National Recommended Water Quality Criteria Continuous Concentrations (4-day average concentrations) for freshwater aquatic organisms exposure to elemental mercury is 0.77 ug/L.

Guideline Reference:

Spatial Representation:

Samples were collected from Arroyo Trabuco Creek at Del Obispo (TCOL02) and at SMC00206.

Temporal Representation:

Samples were collected from September 2006 through May of 2009.

Environmental Conditions:

QAPP Information:

Samples were collected and analyzed in accordance with the signed and certified, Quality Assurance Management Plan for the Orange County Stormwater Program.

QAPP Information Reference(s):


DECISION ID	105557	Region 9
Arroyo Trabuco Creek, Lower

Pollutant:	Temperature, water
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	Original
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 this Regional Board decision, SWRCB staff recommend the decision be approved by the State Board.

Line of Evidence (LOE) for Decision ID 105557, Temperature, water	Region 9
Arroyo Trabuco Creek, Lower

LOE ID:

134376

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

One of 17 samples exceeded the objective.

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The natural receiving water temperature of intrastate waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. At no time or place shall the temperature of any COLD water be increased more than 5°F above the natural receiving water temperature.

Objective/Criterion Reference: