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

Supporting Information

Regional Board 2 - San Francisco Bay Region

Water Body Name:	Pacific Ocean at Muir Beach
Water Body ID:	CAC2013001320070321192155
Water Body Type:	Coastal & Bay Shoreline


DECISION ID	148597	Region 2
Pacific Ocean at Muir Beach

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; due to restoration activities
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 section 4.3 a single line of evidence is necessary to assess listing status. Seven lines of evidence are available in the administrative record to assess this pollutant. Twenty-five of four hundred eighty-six samples exceed the enterococcus geometric mean objective. In 2009, a coastal restoration project was undertaken by the National Park Service (NPS) to restore the ecological functions of the Creek, freshwater wetlands, intermittent tidal lagoon, and dunes over a 46-acre site at the mouth of this iconic Bay Area watershed (National Park Service 2013). Additionally, NPS has relocated the Creek away from the hills with residential development and its associated septic systems. The effect of this relocation has been to increase the upland buffer between the hillside septic systems and the Creek by an average of several hundred feet. The increased buffer is likely to have reduced, and will continue to reduce, any potential discharges from the septic systems to the Creek. A new 225-linear foot pedestrian bridge, with a visitor gathering area, also now spans the creek and its floodplain, providing access to the Muir Beach while protecting these habitats and the plants and animals that live there. The bridge significantly reduces human and horse access to the Creek and Lagoon, and decreases the potential for bacteria discharges from these sources to reach the Creek and, ultimately, Muir Beach. About 500 linear feet of the Coastal Trail was also realigned in 2010 to allow a weedy, eroded ravine and hillside that drain into the Creek to be fully restored. This restoration effort is likely to have resulted in better filtration of bacteria discharges in stormwater runoff and, therefore, improved water quality at Muir Beach. Lastly, the project permanently reconfigured and relocated the visitor parking lot away from the main creek channel and its floodplain and replaced the previous parking lot porta-potties with new vault toilets that are more secure and further away from the creek bank. These changes will result in a decrease in any bacteria contribution from the parking lot and restroom facilities to the Creek and Beach. 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 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. Twenty-five of four hundred eighty-six samples exceed the enterococcus geometric mean objective and this does not exceed the allowable frequency listed in Table 4.2 of the Listing Policy. 4. Pursuant to section 3.11 of the Listing Policy, no additional data and information are available indicating that standards are not met.

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

State Board Review of Regional Board Conclusion and Recommendation:

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

Line of Evidence (LOE) for Decision ID 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

300543

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

SSM

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 Pacific Ocean at Muir Beach to determine beneficial use support and the results are as follows: 1 of the 8 samples exceeded the water quality threshold for Coliform, Fecal. The water quality threshold is based on a Single Sample Maximum (SSM) value that is calculated daily. This data is for an AB411 beach. This LOE specifically corresponds with dry weather samples and only includes samples collected between April 1 and October 31 of each year.

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 in ocean waters applies a single sample maximum of fecal coliform, not to exceed 400 per 100 mL. (Ocean Plan 2019)

Objective/Criterion Reference:

SWRCB. 2005. Water Quality Control Plan, Ocean Waters of California (Ocean Plan). California Environmental Protection Agency, State Water Resources Control Board. February 2, 2019

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): MUIR BEACH - CENTRAL (MUIR BEACH - CENTRAL-Muir Beach, Marin).

Temporal Representation:

The samples were collected between the days of 2015-09-08 and 2015-10-27 .

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 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

300245

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

SSM

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 Pacific Ocean at Muir Beach to determine beneficial use support and the results are as follows: 0 of the 8 samples exceeded the water quality threshold for Coliform, Fecal. The water quality threshold is based on a Single Sample Maximum (SSM) value that is calculated daily. This data is for an AB411 beach. This LOE specifically corresponds with dry weather samples and only includes samples collected between April 1 and October 31 of each year.

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 in ocean waters applies a single sample maximum of fecal coliform, not to exceed 400 per 100 mL. (Ocean Plan 2019)

Objective/Criterion Reference:

SWRCB. 2005. Water Quality Control Plan, Ocean Waters of California (Ocean Plan). California Environmental Protection Agency, State Water Resources Control Board. February 2, 2019

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): MUIR BEACH - NORTH (MUIR BEACH - NORTH-Muir Beach, Marin).

Temporal Representation:

The samples were collected between the days of 2015-09-08 and 2015-10-27 .

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 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

300283

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

GeoMean

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 Pacific Ocean at Muir Beach to determine beneficial use support and the results are as follows: 0 of the 4 samples exceeded the water quality threshold for Coliform, Fecal. The water quality threshold is based on a 30-Day rolling geomean. This data is for an AB411 beach. This LOE specifically corresponds with dry weather samples and only includes samples collected between April 1 and October 31 of each year.

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 in ocean waters applies a 30 day geometric mean of fecal coliform based on the five most recent samples at each site, not to exceed 200 per 100 mL. (Ocean Plan 2019)

Objective/Criterion Reference:

SWRCB. 2005. Water Quality Control Plan, Ocean Waters of California (Ocean Plan). California Environmental Protection Agency, State Water Resources Control Board. February 2, 2019

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): MUIR BEACH - NORTH (MUIR BEACH - NORTH-Muir Beach, Marin).

Temporal Representation:

The samples were collected between the days of 2015-09-08 and 2015-10-27 .

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 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

300281

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

SSM

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Data Reference:

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

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bacteria water quality objective to protect the REC-1 beneficial use in ocean waters applies a single sample maximum of fecal coliform, not to exceed 400 per 100 mL. (Ocean Plan 2019)

Objective/Criterion Reference:

SWRCB. 2005. Water Quality Control Plan, Ocean Waters of California (Ocean Plan). California Environmental Protection Agency, State Water Resources Control Board. February 2, 2019

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): MUIR BEACH - SOUTH (MUIR BEACH - SOUTH-Muir Beach, Marin).

Temporal Representation:

The samples were collected between the days of 2015-09-08 and 2015-10-27 .

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 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

300263

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

GeoMean

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Data Reference:

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

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

SWRCB. 2005. Water Quality Control Plan, Ocean Waters of California (Ocean Plan). California Environmental Protection Agency, State Water Resources Control Board. February 2, 2019

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): MUIR BEACH - SOUTH (MUIR BEACH - SOUTH-Muir Beach, Marin).

Temporal Representation:

The samples were collected between the days of 2015-09-08 and 2015-10-27 .

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 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

300262

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

GeoMean

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Data Reference:

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

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

SWRCB. 2005. Water Quality Control Plan, Ocean Waters of California (Ocean Plan). California Environmental Protection Agency, State Water Resources Control Board. February 2, 2019

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): MUIR BEACH - CENTRAL (MUIR BEACH - CENTRAL-Muir Beach, Marin).

Temporal Representation:

The samples were collected between the days of 2015-09-08 and 2015-10-27 .

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 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

300022

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 Pacific Ocean at Muir Beach to determine beneficial use support and the results are as follows: 9 of the 73 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 in ocean waters, 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. (Ocean Plan 2019)

Objective/Criterion Reference:

SWRCB. 2005. Water Quality Control Plan, Ocean Waters of California (Ocean Plan). California Environmental Protection Agency, State Water Resources Control Board. February 2, 2019

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): MUIR BEACH - NORTH (MUIR BEACH - NORTH-Muir Beach, Marin).

Temporal Representation:

The samples were collected between the days of 2010-09-08 and 2020-10-15 .

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 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

300180

Pollutant:

Enterococcus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

GeoMean

Beneficial Use:

Water Contact Recreation

Number of Samples:

158

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed BeachWatch_Marin County data for Pacific Ocean at Muir Beach to determine beneficial use support and the results are as follows: 6 of the 158 samples exceeded the geomean water quality threshold for Enterococcus. This is a six week rolling geomean that is calculated weekly.

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 in ocean waters applies a six-week rolling geomean to enterococcus, not to exceed 30 cfu/100mL. (Ocean Plan 2019)

Objective/Criterion Reference:

SWRCB. 2005. Water Quality Control Plan, Ocean Waters of California (Ocean Plan). California Environmental Protection Agency, State Water Resources Control Board. February 2, 2019

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): MUIR BEACH - CENTRAL (MUIR BEACH - CENTRAL-Muir Beach, Marin).

Temporal Representation:

The samples were collected between the days of 2010-09-08 and 2020-10-15 .

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 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

90524

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Water Contact Recreation

Number of Samples:

130

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Zero of the 130 geomeans exceeded the fecal coliform objective.

Data Reference:

Data for Region 2 Beach Watch.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The geometric mean standard for fecal coliform states that the density shall not exceed 200 per 100 mL. Water Quality Control Plan for Ocean Waters 2009.

Objective/Criterion Reference:

California Ocean Plan Water Quality Control Plan Ocean Waters of California 2009

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected at stations Muir Beach - Central, Muir Beach - North, and Muir Beach - South. The results from these stations were averaged because they were located within 200 meters.

Temporal Representation:

Samples were collected approximately once a week from April 2005 to September 2010.

Environmental Conditions:

QAPP Information:

The samples were collected for the Beach Watch program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

90821

Pollutant:

Enterococcus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Water Contact Recreation

Number of Samples:

161

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed BeachWatch data for Pacific Ocean at Muir Beach to determine beneficial use support and results are as follows: 3 of 161 samples exceed the criterion for Enterococci.

Data Reference:

Data for Region 2 Beach Watch.

Data for Region 1 Beach Watch.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

California Ocean Plan (SWRCB 2009) single sample maximum states that enterococcus density shall not exceed 104 per 100 mL.

Objective/Criterion Reference:

California Ocean Plan Water Quality Control Plan Ocean Waters of California 2009

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data for this line of evidence for Pacific Ocean at Muir Beach was collected at 3 monitoring sites [ Muir Beach - Central, Muir Beach - North and Muir Beach - South]

Temporal Representation:

Data was collected over the time period 4/7/2005-8/25/2010.

Environmental Conditions:

These sites are within 200 meters and the results were averaged.

QAPP Information:

The samples were collected for the Beach Watch program.

QAPP Information Reference(s):

Beach Act Monitoring and Notification Program. Application Workplan

QAPP Information Reference(s):

Environmental Health Policy and Procedure No. 00-1. Subject: Ocean Water Sampling Program Procedures. County of Sonoma Department of Health Services

Line of Evidence (LOE) for Decision ID 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

90522

Pollutant:

Enterococcus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Water Contact Recreation

Number of Samples:

130

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

One of the 130 geomeans exceeded the enterococcus objective.

Data Reference:

Data for Region 2 Beach Watch.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The geometric mean standard for enterococcus states that the enterococcus density shall not exceed 35 per 100 mL. Water Quality Control Plan for Ocean Waters 2009.

Objective/Criterion Reference:

California Ocean Plan Water Quality Control Plan Ocean Waters of California 2009

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected at stations Muir Beach - Central, Muir Beach - North, and Muir Beach - South. The results from these stations were averaged because they were located within 200 meters.

Temporal Representation:

Samples were collected approximately once a week from April 2005 to September 2010.

Environmental Conditions:

QAPP Information:

The samples were collected for the Beach Watch program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

90819

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Water Contact Recreation

Number of Samples:

161

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed BeachWatch data for Pacific Ocean at Muir Beach to determine beneficial use support and results are as follows: 1 of 161 samples exceed the criterion for Coliform, Fecal.

Data Reference:

Data for Region 2 Beach Watch.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

California Ocean Plan (SWRCB 2009) single sample maximum states that fecal coliform density shall not exceed 400 per 100ml

Objective/Criterion Reference:

California Ocean Plan Water Quality Control Plan Ocean Waters of California 2009

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Data for this line of evidence for Pacific Ocean at Muir Beach was collected at 3 monitoring sites [ Muir Beach - Central, Muir Beach - North and Muir Beach - South]

Temporal Representation:

Data was collected over the time period 4/7/2005-8/25/2010.

Environmental Conditions:

These sites are within 200 meters and the results were averaged.

QAPP Information:

The samples were collected for the Beach Watch program.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

352

Pollutant:

Indicator Bacteria

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Available data indicate sufficient exceedances of bacterial indicator objectives. There were 12 out of 67 samples exceeding the geomean for total coliform, and 18 out of 67 exceedances of the geomean for enterococci (USEPA, 2007).

Data Reference:

Placeholder reference 2006 303(d)

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Title 17 C.C.R. Section 7958 states: Based on a single sample, the density of bacteria in water from each sampling station at a public beach or public water contact sports area shall not exceed:
(A) 1,000 total coliform bacteria per 100 milliliters, if the ratio of fecal/total coliform bacteria exceeds 0.1; or
(B) 10,000 total coliform bacteria per 100 milliliters; or
(C) 400 fecal coliform bacteria per 100 milliliters; or
(D) 104 enterococcus bacteria per 100 milliliters.

Based on the mean of the logarithms of the results of at least five weekly samples during any 30-day sampling period, the density of bacteria in water from any sampling station at a public beach or public water contact sports area, shall not exceed:
(A) 1,000 total coliform bacteria per 100 milliliters; or
(B) 200 fecal coliform bacteria per 100 milliliters; or
(C) 35 enterococcus bacteria per 100 milliliters. (DHS, 1999)

Objective/Criterion Reference:

Placeholder reference 2006 303(d)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Station ID# MC200

Temporal Representation:

04/03/2003-10/25/2005

Environmental Conditions:

QAPP Information:

Data record: summers 2003-2005, Marin County Health Dept.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

300177

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 Pacific Ocean at Muir Beach to determine beneficial use support and the results are as follows: 7 of the 68 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:

Objective/Criterion Reference:

SWRCB. 2005. Water Quality Control Plan, Ocean Waters of California (Ocean Plan). California Environmental Protection Agency, State Water Resources Control Board. February 2, 2019

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): MUIR BEACH - CENTRAL (MUIR BEACH - CENTRAL-Muir Beach, Marin).

Temporal Representation:

The samples were collected between the days of 2010-09-08 and 2020-10-15 .

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 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

299554

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 Pacific Ocean at Muir Beach to determine beneficial use support and the results are as follows: 7 of the 66 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:

Objective/Criterion Reference:

SWRCB. 2005. Water Quality Control Plan, Ocean Waters of California (Ocean Plan). California Environmental Protection Agency, State Water Resources Control Board. February 2, 2019

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): MUIR BEACH - SOUTH (MUIR BEACH - SOUTH-Muir Beach, Marin).

Temporal Representation:

The samples were collected between the days of 2010-09-29 and 2020-10-15 .

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 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

300153

Pollutant:

Enterococcus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

GeoMean

Beneficial Use:

Water Contact Recreation

Number of Samples:

158

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Data Reference:

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

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bacteria water quality objective to protect the REC-1 beneficial in ocean waters applies a six-week rolling geomean to enterococcus, not to exceed 30 cfu/100mL. (Ocean Plan 2019)

Objective/Criterion Reference:

SWRCB. 2005. Water Quality Control Plan, Ocean Waters of California (Ocean Plan). California Environmental Protection Agency, State Water Resources Control Board. February 2, 2019

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): MUIR BEACH - SOUTH (MUIR BEACH - SOUTH-Muir Beach, Marin).

Temporal Representation:

The samples were collected between the days of 2010-09-29 and 2020-10-15 .

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 148597, Indicator Bacteria	Region 2
Pacific Ocean at Muir Beach

LOE ID:

299977

Pollutant:

Enterococcus

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

GeoMean

Beneficial Use:

Water Contact Recreation

Number of Samples:

170

Number of Exceedances:

Data and Information Type:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed BeachWatch_Marin County data for Pacific Ocean at Muir Beach to determine beneficial use support and the results are as follows: 13 of the 170 samples exceeded the geomean water quality threshold for Enterococcus. This is a six week rolling geomean that is calculated weekly.

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 in ocean waters applies a six-week rolling geomean to enterococcus, not to exceed 30 cfu/100mL. (Ocean Plan 2019)

Objective/Criterion Reference:

SWRCB. 2005. Water Quality Control Plan, Ocean Waters of California (Ocean Plan). California Environmental Protection Agency, State Water Resources Control Board. February 2, 2019

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): MUIR BEACH - NORTH (MUIR BEACH - NORTH-Muir Beach, Marin).

Temporal Representation:

The samples were collected between the days of 2010-09-08 and 2020-10-15 .

Environmental Conditions:

QAPP Information:

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

QAPP Information Reference(s):

QAPP Reference for Beach Watch Program