Draft California 2026 Integrated Report (303(d) List/305(b) Report)

Supporting Information

Regional Board 1 - North Coast Region

Water Body Name:	Clam Beach (near Mad River mouth)
Water Body ID:	CAC1091001120110712113517
Water Body Type:	Coastal & Bay Shoreline


DECISION ID	161502	Region 1
Clam Beach (near Mad River mouth)

Pollutant:	Indicator Bacteria
Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)(2018)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	The State Water Board’s Water Quality Control Plan for Inland Surface Waters, Enclosed Bays, and Estuaries of California (the “ISWEBE Plan”) was adopted on August 7, 2018, and contains bacteria water quality objectives applicable to the REC-1 beneficial use. This has resulted in a change from assessing fecal coliform to assessing E. coli in fresh water and Enterococcus in saline water. Fecal coliform and freshwater enterococcus lines of evidence used in previous REC-1 beneficial use indicator bacteria decisions in the North Coast Region are not included in the 2026 Integrated Report assessment. The pollutant will again be considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. 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. Lacking constant inputs, indicator bacteria do not persist in the environment for a long period and effects are of relatively short duration. As a result, the historic levels of E. coli 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. Historic lines of evidence for data collected prior to October 21, 2012 (i.e., data collected more than 10 years from the 2026 data solicitation cutoff date) were evaluated pursuant to these considerations and, when more recent data were available, the pre-October 21, 2012, data 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. This pollutant is being considered for placement on the CWA section 303(d) List under section 3.2 of the Listing Policy. Under this section a single line of evidence is necessary to assess listing status. Five lines of evidence are available in the administrative record to assess this pollutant. Geometric means are used to assess the data for the REC-1 beneficial use. Where geometric means are not available, statistical threshold values are used. Geometric means are available for Clam Beach Near Mad River Mouth and will be used for the assessment. *DO NOT LIST REC-1 BENEFICIAL USE* For Enterococcus, 2 of 59 geometric means exceed the objective for the REC-1 beneficial use, and this does not exceed the allowable frequency in Table 3.2 of the Listing Policy. For Fecal Coliform, 0 of 1 single sample maximum exceeds the objective for the REC-1 beneficial use, and this is insufficient data to apply Table 3.2 of the Listing Policy. *DO NOT DELIST SHELL BENEFICIAL USE* For Total Coliform, 1 of 7 weekly medians exceed the objective for the SHELL beneficial use, and this exceeds the allowable frequency in Table 4.2 of the Listing Policy. For Total Coliform, 6 of 7 monthly percents exceed the objective for the SHELL beneficial use, and this exceeds the allowable frequency in Table 4.2 of the Listing Policy. 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. For the SHELL beneficial use total coliform SSM, 6 of 7 SSMs exceed the objective and this exceeds the allowable frequency listed in Table 3.2 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. This listing applies to the entire water body.

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

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 161502, Indicator Bacteria	Region 1
Clam Beach (near Mad River mouth)

LOE ID:

353483

Pollutant:

Enterococcus

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_Humboldt County data for Clam Beach (near Mad River mouth) to determine beneficial use support and the results are as follows: 1 of the 29 samples exceeded the geomean water quality standard for Enterococcus. This is a six week rolling geomean that is calculated weekly.

Data Reference:

Humboldt County Beachwatch data reformatted to match CEDEN fields.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bacteria water quality objective to protect the REC-1 beneficial for all ocean waters , is a six-week rolling GM of Enterococci not to exceed 30 cfu/100mL (calculated weekly).

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:

Samples were collected at North Mad River Mouth.

Temporal Representation:

Data was assessed for samples collected within 10 years of the close of data solicitation for the 2026 Integrated Report (October 21, 2012 to October 21, 2022).

Environmental Conditions:

QAPP Information:

Data exempt from QAPP requirement. Draft QAPP for Humboldt County Beachwatch data used instead. Represents data collection procedure prior to development of a formal QAPP.

QAPP Information Reference(s):

Draft QAPP for Humboldt County Beachwatch data. Represents data collection procedure prior to development of a formal QAPP.

Line of Evidence (LOE) for Decision ID 161502, Indicator Bacteria	Region 1
Clam Beach (near Mad River mouth)

LOE ID:

353484

Pollutant:

Enterococcus

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_Humboldt County data for Clam Beach (near Mad River mouth) to determine beneficial use support and the results are as follows: 1 of the 30 samples exceeded the geomean water quality standard for Enterococcus. This is a six week rolling geomean that is calculated weekly.

Data Reference:

WQ from the BeachWatch for the 2026 Integrated Report in Region 1

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:

Samples were collected at North Mad River Mouth.

Temporal Representation:

Data was assessed for samples collected within 10 years of the close of data solicitation for the 2026 Integrated Report (October 21, 2012 to October 21, 2022).

Environmental Conditions:

QAPP Information:

QAPP for BeachWatch

QAPP Information Reference(s):

QAPP Reference for Beach Watch Program

Line of Evidence (LOE) for Decision ID 161502, Indicator Bacteria	Region 1
Clam Beach (near Mad River mouth)

LOE ID:

353435

Pollutant:

Total Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Percent

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_Humboldt County data to determine beneficial use support and the results are as follows: 6 of the 7 samples exceeded the water quality standard for Total Coliform. The water quality standard for shellfish is based on the percent of Total Coliform at each station that exceed 230 per 100 mL, and is calculated on a monthly basis.

Data Reference:

Sonoma County Beachwatch data reformatted to match CEDEN fields.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

California Ocean Plan (SWRCB 2018) states that not more than 10 percent of the samples shall exceed 230 per 100 mL.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): North Mad River Mouth

Temporal Representation:

The samples were assessed for the ten years before the close of data solicitation (2012-10-21 to 2022-10-21).

Environmental Conditions:

QAPP Information:

Data exempt from QAPP requirement. Draft QAPP for Humboldt County Beachwatch data used instead. Represents data collection procedure prior to development of a formal QAPP.

QAPP Information Reference(s):

Draft QAPP for Humboldt County Beachwatch data. Represents data collection procedure prior to development of a formal QAPP.

Line of Evidence (LOE) for Decision ID 161502, Indicator Bacteria	Region 1
Clam Beach (near Mad River mouth)

LOE ID:

353434

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_Humboldt County data to determine beneficial use support and the results are as follows: 1 of the 7 samples exceeded the water quality standard for Total Coliform. The water quality standard for shellfish is based on the median concentration of Total Coliform at each station, and is calculated on a monthly basis.

Data Reference:

Humboldt County Beachwatch data reformatted to match CEDEN fields.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

California Ocean Plan (SWRCB 2018) states that the median concentration of total coliform samples shall not exceed 70 per 100 ml.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): North Mad River Mouth

Temporal Representation:

The samples were assessed for the ten years before the close of data solicitation (2012-10-21 to 2022-10-21).

Environmental Conditions:

QAPP Information:

Data exempt from QAPP requirement. Draft QAPP for Humboldt County Beachwatch data used instead. Represents data collection procedure prior to development of a formal QAPP.

QAPP Information Reference(s):

Draft QAPP for Humboldt County Beachwatch data. Represents data collection procedure prior to development of a formal QAPP.

Line of Evidence (LOE) for Decision ID 161502, Indicator Bacteria	Region 1
Clam Beach (near Mad River mouth)

LOE ID:

133674

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:

PATHOGEN MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed Beachwatch_Humboldt County data for Clam Beach (near Mad River mouth) to determine beneficial use support and the results are as follows: 0 of the 1 samples exceeded the water quality standard for Coliform, Fecal. The water quality standard is based on a Single Sample Maximum (SSM) value that is calculated daily.

Data Reference:

Humboldt County Beachwatch data reformatted to match CEDEN fields.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

California Ocean Plan (SWRCB 2018) states that the Single Sample Maximum concentration of Fecal Coliform shall not exceed 400 per 100 ml.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site(s), station(s): North Mad River Mouth

Temporal Representation:

The samples were collected between the days of 2015-09-15 and 2015-09-15 .

Environmental Conditions:

QAPP Information:

Data exempt from QAPP requirement. Draft QAPP for Humboldt County Beachwatch data used instead. Represents data collection procedure prior to development of a formal QAPP.

QAPP Information Reference(s):

Draft QAPP for Humboldt County Beachwatch data. Represents data collection procedure prior to development of a formal QAPP.