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

Supporting Information

Regional Board 4 - Los Angeles Region

Water Body Name:	Westlake Creek
Water Body ID:	CAR4042500020111229150307
Water Body Type:	River & Stream


DECISION ID	96517	Region 4
Westlake Creek

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)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence are necessary to assess listing status. 1 line of evidence is available in the administrative record to assess this pollutant. 0 of 118 samples exceeded the OBJECTIVE. Based on the readily available data and information, the weight of evidence indicates that there is insufficient justification for placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 118 samples exceeded the OBJECTIVE and this sample size is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. A minimum of 26 samples is needed to determine if a beneficial use is fully supported using table 3.2. 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 96517, Oxygen, Dissolved	Region 4
Westlake Creek

LOE ID:

90077

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Warm Freshwater Habitat

Number of Samples:

118

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Numeric data generated from 118 minimums of Dissolved Oxygen concentrations had no exceedences.

Data Reference:

Data for Metals, Nuisance, Nutrients, Other Inorganics, and Salinity in Various Region 4 Water Bodies, 2006-2010.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Dissolved Oxygen Water Quality Objective of all surface waters designated as Warm Fresh Water Aquatic Habitat shall not be depressed below 5 mg/l.

Objective/Criterion Reference:

Water Quality Control Plan Los Angeles Region R4 Basin Plan

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected from the MCW-15b station.

Temporal Representation:

Samples were collected approximately once a week from March 2008 to June 2010.

Environmental Conditions:

QAPP Information:

NPDES quality assurance

QAPP Information Reference(s):


DECISION ID	96577	Region 4
Westlake Creek

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)(2016)
Revision Status	Original
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under section 3.2 a single line of evidence are necessary to assess listing status. 1 line of evidence is available in the administrative record to assess this pollutant. 0 of 115 samples exceeded the OBJECTIVE. Based on the readily available data and information, the weight of evidence indicates that there is insufficient justification for placing this water segment-pollutant combination on the CWA section 303(d) List. This conclusion is based on the staff findings that: 1. The data used satisfies the data quality requirements of section 6.1.4 of the Policy. 2. The data used satisfies the data quantity requirements of section 6.1.5 of the Policy. 3. 0 of 115 samples exceeded the OBJECTIVE and this sample size is insufficient to determine, with the power and confidence of the Listing Policy, the applicable beneficial use support rating. A minimum of 26 samples is needed to determine if a beneficial use is fully supported using table 3.2. 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 96577, pH	Region 4
Westlake Creek