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

Supporting Information

Regional Board 2 - San Francisco Bay Region

Water Body Name:	Drakes Estero (at Schooner Bay oyster beds)
Water Body ID:	CAC2012101120110712213842
Water Body Type:	Coastal & Bay Shoreline


DECISION ID	149321	Region 2
Drakes Estero (at Schooner Bay oyster beds)

Pollutant:	Indicator Bacteria
Final Listing Decision:	Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Delist from 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Reason for Delisting:	Applicable WQS attained; according to new assessment method
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 3.2 and 3.3 of the Listing Policy. The number of measured exceedances is less than the minimum number of exceedances needed to place the water segment on the section CWA section 303(d) List for conventional pollutants (Table 3.2 of the Listing Policy). The data used satisfies the data quality requirements (section 6.1.4) and data quantity requirements (section 6.1.5) of the Listing Policy. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met. Based on the readily available data and information, the weight of evidence indicates that this water segment-pollutant combination should not be placed on the CWA section 303(d) List. Refer to the lines of evidence in this fact sheet for the data and information, sample counts and exceedances, quality assurance documentation, beneficial uses, and water quality objectives or numeric evaluation guidelines relied upon for this decision.

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 149321, Indicator Bacteria	Region 2
Drakes Estero (at Schooner Bay oyster beds)

LOE ID:

96987

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:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed BeachWatch data for Drake's Estero to determine beneficial use support and results are as follows: three of the forty-four STVs (calculated monthly) exceeded the objective.

Data Reference:

Beach Watch Data for Six SF Bay Regional Water Quality Control Board Beaches for 2018 Listing Cycle

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The objective is a statistical threshold value (STV) of 110 cfu/100 mL, not to be exceeded more than 10 percent of the time, calculated monthly.

Objective/Criterion Reference:

Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data for this line of evidence for Drakes Estero (at Schooner Bay oyster beds) was collected at 1 monitoring site.

Temporal Representation:

The data were collected approximately April through October in the years 2006-2012.This LOE replaces #90852, which included data collected over the time period 4/4/2006-8/17/2010. This new LOE is based on an analysis of the same data but in comparison to the newly adopted enterococcus objectives to protect contact recreation.

Environmental Conditions:

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

QAPP Information:

The samples were collected for the Beach Watch program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 149321, Indicator Bacteria	Region 2
Drakes Estero (at Schooner Bay oyster beds)

LOE ID:

299596

Pollutant:

Total Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Median

Beneficial Use:

Shellfish Harvesting

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed BeachWatch_Marin County data for Drakes Estero (at Schooner Bay oyster beds) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality threshold for Coliform, Total. The water quality threshold for shellfish is based on the median concentration at each station, and is calculated as a 30-day median.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 2.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.1 Bacteria: Table 3-1 provides a summary of the bacterial water quality objectives and identifies the sources of those objectives. The total coliform objective for shellfish harvesting is a 30-day median less than 70 MPN/100 ML.

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) San Francisco Bay Basin (Region 2)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): DRAKES ESTERO (DRAKES ESTERO-DRAKES ESTERO, Marin).

Temporal Representation:

The samples were collected between the days of 2010-08-31 and 2020-10-14 .

Environmental Conditions:

QAPP Information:

State Board Staff. 2021. QAPP Reference for Beach Watch Program.

QAPP Information Reference(s):

QAPP Reference for Beach Watch Program

Line of Evidence (LOE) for Decision ID 149321, Indicator Bacteria	Region 2
Drakes Estero (at Schooner Bay oyster beds)

LOE ID:

299999

Pollutant:

Enterococcus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

STV

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed BeachWatch_Marin County data for Drakes Estero (at Schooner Bay oyster beds) to determine beneficial use support and the results are as follows: 1 of the 11 samples exceeded the Statistical Threshold Value (STV) water quality threshold for Enterococcus. The STV is based on a 10% exceedance rate that is calculated monthly.

Data Reference:

WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 2.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bacteria water quality objective to protect the REC-1 beneficial use where the salinity is 1 ppth or higher 95 percent or more of the time applies a Statistical Threshold Value to enterococcus of 110 cfu/100 mL, not to be exceeded by more than 10 percent of samples collected within in a calendar month. (ISWEBE 2018)

Objective/Criterion Reference:

Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): DRAKES ESTERO (DRAKES ESTERO-DRAKES ESTERO, Marin).

Temporal Representation:

The samples were collected between the days of 2010-10-26 and 2020-10-14 .

Environmental Conditions:

QAPP Information:

State Board Staff. 2021. QAPP Reference for Beach Watch Program.

QAPP Information Reference(s):

QAPP Reference for Beach Watch Program

Line of Evidence (LOE) for Decision ID 149321, Indicator Bacteria	Region 2
Drakes Estero (at Schooner Bay oyster beds)

LOE ID:

96986

Pollutant:

Enterococcus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Water Contact Recreation

Number of Samples:

106

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed BeachWatch data for Drake's Estero to determine beneficial use support and results are as follows: five of the one hundred six geometric means (calculated weekly) exceeded the objective. We required a minimum of 5 samples to compute each valid geomean, consistent with the objective.

Data Reference:

Beach Watch Data for Six SF Bay Regional Water Quality Control Board Beaches for 2018 Listing Cycle

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The objective is a six-week rolling geometric mean (calculated weekly), not to exceed 30 cfu/100 mL.

Objective/Criterion Reference:

Inland Surface Waters, Enclosed Bays, and Estuaries Plan. Part 1: Trash Provisions; Part 2: Tribal Subsistence Beneficial Uses and Mercury Provisions; Part 3: Bacteria Provisions and Variance Policy

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data for this line of evidence for Drakes Estero (at Schooner Bay oyster beds) was collected at 1 monitoring site.

Temporal Representation:

The data were collected approximately April through October in the years 2006-2010. This LOE replaces #90600, which included data collected from April 2006 to August 2010. This new LOE includes this same data plus data from 2012 but is based on an analysis of all available data in comparison to the newly adopted enterococcus objectives to protect contact recreation.

Environmental Conditions:

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

QAPP Information:

The samples were collected for the Beach Watch program.

QAPP Information Reference(s):