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

Supporting Information

Regional Board 1 - North Coast Region

Water Body Name:	Eureka Plain HU, Humboldt Bay
Water Body ID:	CAB1100000020020108173626
Water Body Type:	Bay & Harbor


DECISION ID	157037	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	PCBs (Polychlorinated biphenyls)
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:	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. Six lines of evidence are available in the administrative record to assess pollutant. Two of two samples exceed the objective for the shellfish fraction of tissue. 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. Two of two samples exceed the ojective for the shellfish fraction of tissue 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. This listing applies to the entire waterbody. This listing applies to the entire waterbody.

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:	This listing applies to the entire waterbody.

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 157037, PCBs (Polychlorinated biphenyls)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

23467

Pollutant:

PCBs (Polychlorinated biphenyls)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

It is unknown if any of the 13 PCB samples collected in Humboldt Bay exceed the evaluation guideline. All of the samples were non-detect, but the detection limits are unknown. Samples were collected by the Wiyot Tribe and data are summarized by the Tribe (Wiyot 2007).

Data Reference:

Wiyot Tribe Water Quality Monitoring Program. Data for multiple parameters in McNultly Slough, Humboldt Bay Entrance, Indian Island, Mad River Slough, and Reservation Wetland, December 2004 to December 2006

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Per the Federal Register, Vol. 64, No. 216, pp. 61181 to 61196: The human health criterion for PCBs is 0.00017 ug/l for the protection of human health from consumption of aquatic organisms.

Guideline Reference:

Water Quality Standards; Establishment of Numeric Criteria for Priority Toxic Pollutants; States' Compliance - Revision of Polychlorinated Biphenyls (PCBs) Criteria. Federal Register. Volume 64, No. 216, pp. 61181 - 61196

Spatial Representation:

The data were collected from 4 sites in Humboldt Bay as follows: (1) Humboldt Bay Entrance just northeast of the east edge of the north jetty; (2) Indian Island just off one of the old pilings between the old industrial site on the Tribe's land and the middle channel of north Humboldt Bay; (3) Mad River Slough at the Samoa Boulevard Bridge over the Slough; and (4) the Reservation Wetland at the northeast corner of the Table Bluff Reservation. At the Reservation Wetland site, samples from December 2004 to February 2006 were collected from surface wetland waters. Starting in March 2006, two shallow-water monitoring wells were installed in the wetland and serve as the sample collection sites.

Temporal Representation:

Three samples were collected in March, July and November of 2006 for five of the areas sampled (Indian Island, Mad River Slough, & Bay Entrance, Wetland sites 1 & 2). The main Reservation wetland was sampled one time in May 2005.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Samples were collected according to Wiyot Tribe¿s ¿Draft Quality Assurance Program Plan (QAPP) for Water Quality Assessment and Monitoring¿ (McKernan et al. 2004). Specific detection limits are not specified.

QAPP Information Reference(s):

Draft Quality Assurance Program Plan (QAPP) for Water Quality Assessment and Monitoring. Table Bluff Reservation - Wiyot Tribe. Tribal Environmental Department. Prepared by Yurok Tribe Environmental Program. September 2004

Line of Evidence (LOE) for Decision ID 157037, PCBs (Polychlorinated biphenyls)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

31735

Pollutant:

PCBs (Polychlorinated biphenyls)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Shellfish

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Shellfish surveys

Data Used to Assess Water Quality:

Both samples exceeded the guideline. Non-detect results were reported as zero (no method detection limits were provided) and were not included in the assessment. Data were reported on a dry weight basis and were converted to a wet weight basis by multiplying the dry-weight concentration by a factor of 1 minus the percentage of moisture content expressed as a decimal.

Data Reference:

State Mussel Watch Program Data 1977-2000; Winter 2007-Winter 2009. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, North Coast Region (NCRWQCB 2011): 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:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for polychlorinated biphenyls in shellfish tissue is 3.9 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 21 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. (Brodberg, R.K., and G.A. Pollock, 1999; Klasing, S., and R. Brodberg, 2008)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Samples are collected by hand from three sub-locations for each site. The composite samples were collected from site EUSB at Eureka Samoa Bridge, and another from HMBJ at Eureka Humboldt Bay Jetty.

Temporal Representation:

Samples were collected from Humboldt Bay as follows: EUSB on 1/23/2009 and from HMBJ on 1/22/2009.

Environmental Conditions:

QAPP Information:

Samples were collected as part of the State Water Board's Mussel Watch Program which is a part of the National Oceanic Administration's (NOAAs) National Status and Trends (NS&T). Mussels are shipped to NOAAs contract labs for analysis of trace constituent

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 157037, PCBs (Polychlorinated biphenyls)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322728

Pollutant:

PCBs (Polychlorinated biphenyls)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 4 samples exceeded the water quality threshold for PCBs (Polychlorinated biphenyls). Monitors collected 6 composites: 1 composite of California Halibut composed of 2 fish, 1 composite of Leopard shark composed of 3 fish, 1 composite of Leopard shark composed of 10 fish, 1 composite of White Surfperch composed of 7 fish, and 2 composites of White Surfperch composed of 8 fish each. Because 2 or more composites were collected within the same averaging period, these composites resulted in 4 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

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. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum total PCB Arochlor concentration of 500 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Data for this line of evidence were collected between 2010-08-30 and 2019-09-18. When composited fish were collected over multiple days, the first day of fish collection was used as the sample date in the LOE, both for LOE writing, and for averaging period purposes.

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157037, PCBs (Polychlorinated biphenyls)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

3669

Pollutant:

PCBs (Polychlorinated biphenyls)

LOE Subgroup:

Pollutant-Sediment

Matrix:

Not Specified

Fraction:

None

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

This LOE is a placeholder to support a 303(d) listing decision made prior to 2006.

Data Reference:

Placeholder reference pre-2006 303(d)

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Unknown

Temporal Representation:

Unknown

Environmental Conditions:

Unknown

QAPP Information:

Unknown

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 157037, PCBs (Polychlorinated biphenyls)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322734

Pollutant:

PCBs (Polychlorinated biphenyls)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157037, PCBs (Polychlorinated biphenyls)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322731

Pollutant:

PCBs (Polychlorinated biphenyls)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for polychlorinated biphenyls in fish tissue is 2.6 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	157039	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Aldrin
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 157039, Aldrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322387

Pollutant:

Aldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Aldrin. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Aldrin concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Data for this line of evidence were collected between 2010-08-30 and 2010-08-30. When composited fish were collected over multiple days, the first day of fish collection was used as the sample date in the LOE, both for LOE writing, and for averaging period purposes.

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157039, Aldrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121348

Pollutant:

Aldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Aldrin. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157039, Aldrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121172

Pollutant:

Aldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157039, Aldrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121389

Pollutant:

Aldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157039, Aldrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322385

Pollutant:

Aldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	161407	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Ammonia
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 161407, Ammonia	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

327928

Pollutant:

Nitrogen, ammonia (Total Ammonia)

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:

Water Board staff assessed EPA National Aquatic Resources Survey (NARS) data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and results are as follows: 0 of 1 samples exceeded the water quality threshold for Ammonia as N.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The Total Ammonia criterion continuous concentration (expressed as a 30-day average) to protect aquatic life in freshwater is Temperature and pH dependent, and was calculated according to the formula listed in the Aquatic Life Ambient Water Quality Criteria for AmmoniaNAFreshwater 2013 document.

Objective/Criterion Reference:

Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10232 (NCA_CA-10232).

Temporal Representation:

The samples were collected between the dates of 2015-08-20 and 2015-08-20

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 161407, Ammonia	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

327923

Pollutant:

Nitrogen, ammonia (Total Ammonia)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

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 (North Coast Regional Water Quality Control Board).

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The USEPA Health Advisory for lifetime exposure to Ammonia as a drinking water level is a concentration of 30 mg/L

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10285 (NCA_CA-10285).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 161407, Ammonia	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

327910

Pollutant:

Nitrogen, ammonia (Total Ammonia)

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10216 (NCA_CA-10216).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 161407, Ammonia	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

327922

Pollutant:

Nitrogen, ammonia (Total Ammonia)

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10214 (NCA_CA-10214).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 161407, Ammonia	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

327918

Pollutant:

Nitrogen, ammonia (Total Ammonia)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

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 (North Coast Regional Water Quality Control Board).

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The USEPA Health Advisory for lifetime exposure to Ammonia as a drinking water level is a concentration of 30 mg/L

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10214 (NCA_CA-10214).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 161407, Ammonia	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

327924

Pollutant:

Nitrogen, ammonia (Total Ammonia)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

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 (North Coast Regional Water Quality Control Board).

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The USEPA Health Advisory for lifetime exposure to Ammonia as a drinking water level is a concentration of 30 mg/L

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10216 (NCA_CA-10216).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 161407, Ammonia	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

327933

Pollutant:

Nitrogen, ammonia (Total Ammonia)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

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 (North Coast Regional Water Quality Control Board).

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The USEPA Health Advisory for lifetime exposure to Ammonia as a drinking water level is a concentration of 30 mg/L

Guideline Reference:

2012 Edition of the Drinking Water Standards and Health Advisories

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10232 (NCA_CA-10232).

Temporal Representation:

The samples were collected between the dates of 2015-08-20 and 2015-08-20

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 161407, Ammonia	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

327903

Pollutant:

Nitrogen, ammonia (Total Ammonia)

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater 2013

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10285 (NCA_CA-10285).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	157028	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Chlordane
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 157028, Chlordane	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

31738

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Shellfish

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Shellfish surveys

Data Used to Assess Water Quality:

Data were reported on a dry weight basis and were converted to a wet weight basis by multiplying the dry-weight concentration by a factor of 1 minus the percentage of moisture content expressed as a decimal. Chlordane result was calculated by summing the results for chlordane isomers: cis- and trans-nonachlor, alpha- and gamma-chlordane, and oxychlordane. Non-detect results were reported as zero (no method detection limits were provided) and were not included in the summation for a sample in the assessment.

Data Reference:

State Mussel Watch Program Data 1977-2000; Winter 2007-Winter 2009. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for total chlordane in shellfish tissue is 6.0 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 21 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. (Brodberg, R.K., and G.A. Pollock, 1999; Klasing, S., and R. Brodberg, 2008)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Samples are collected by hand from three sub-locations for each site. The composite samples were collected from site EUSB at Eureka Samoa Bridge, and another from HMBJ at Eureka Humboldt Bay Jetty.

Temporal Representation:

Samples were collected from Humboldt Bay as follows: EUSB on 1/23/2009 and from HMBJ on 1/22/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 157028, Chlordane	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121259

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Total Chlordanes. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum total Chlordane concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157028, Chlordane	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121377

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Total Chlordanes. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for total chlordane in fish tissue is 3.9 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157028, Chlordane	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121170

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Total Chlordanes. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157028, Chlordane	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121148

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Total Chlordanes. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157028, Chlordane	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322414

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Chlordane. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157028, Chlordane	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322404

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Chlordane. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157028, Chlordane	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322408

Pollutant:

Chlordane

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Chlordane. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	158397	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Chlorophyll-a
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 158397, Chlorophyll-a	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

328234

Pollutant:

Chlorophyll-a

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Waters shall not contain biostimulatory substances in concentrations that promote aquatic growths to the extent that such growths cause nuisance or adversely affect beneficial uses. (Basin Plan, 2018)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

North Carolina Administrative code (NCAC), Title 15ANAEnvironmental and Natural Resources, Subchapter 2B-Surface water and wetland standards, Rule 0211-Fresh surface water quality standards for class C waters (Class C is defined as freshwaters protected for secondary recreation, fishing, aquatic life including propagation and survival, and wildlife).Section 3(a) of Rule 0211 applies to all fresh surface waters and states that chlorophyll a is not to exceed 40 ug/L.

Guideline Reference:

North Carolina standards, criteria, or toxic concentrations. Adopted per title 15A North Carolina Administrative Code subchapter 2B - Surface water and wetland standards

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10216 (NCA_CA-10216).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 158397, Chlorophyll-a	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

328229

Pollutant:

Chlorophyll-a

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

North Carolina standards, criteria, or toxic concentrations. Adopted per title 15A North Carolina Administrative Code subchapter 2B - Surface water and wetland standards

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10214 (NCA_CA-10214).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 158397, Chlorophyll-a	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

328231

Pollutant:

Chlorophyll-a

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

North Carolina standards, criteria, or toxic concentrations. Adopted per title 15A North Carolina Administrative Code subchapter 2B - Surface water and wetland standards

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10232 (NCA_CA-10232).

Temporal Representation:

The samples were collected between the dates of 2015-08-20 and 2015-08-20

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 158397, Chlorophyll-a	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

328202

Pollutant:

Chlorophyll-a

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

North Carolina standards, criteria, or toxic concentrations. Adopted per title 15A North Carolina Administrative Code subchapter 2B - Surface water and wetland standards

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10285 (NCA_CA-10285).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	161311	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	DDT (Dichlorodiphenyltrichloroethane)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 161311, DDT (Dichlorodiphenyltrichloroethane)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322761

Pollutant:

Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD). Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for total DDT in fish tissue is 15 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 161311, DDT (Dichlorodiphenyltrichloroethane)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322769

Pollutant:

Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD). Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum total DDT concentration of 1000 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 161311, DDT (Dichlorodiphenyltrichloroethane)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322775

Pollutant:

Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD). Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 161311, DDT (Dichlorodiphenyltrichloroethane)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

31730

Pollutant:

DDT (Dichlorodiphenyltrichloroethane)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Shellfish

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Shellfish surveys

Data Used to Assess Water Quality:

Both samples did not exceed the guideline. Non-detect results were reported as zero (no method detection limits were provided) and were not included in the assessment. Data were reported on a dry weight basis and were converted to a wet weight basis by multiplying the dry-weight concentration by a factor of 1 minus the percentage of moisture content expressed as a decimal. The total DDTs were calculated as the sum of 4,4- and 2,4- isomers of DDT, DDE, and DDD).

Data Reference:

State Mussel Watch Program Data 1977-2000; Winter 2007-Winter 2009. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Per the Basin Plan (NCRWQCB 2011): No individual pesticide or combination of pesticides shall be present in concentrations that adversely affect beneficial uses. There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life.

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for total DDT in shellfish tissue is 23 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 21 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. (Brodberg, R.K., and G.A. Pollock, 1999; Klasing, S., and R. Brodberg, 2008)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Samples are collected by hand from three sub-locations for each site. The composite samples were collected from site EUSB at Eureka Samoa Bridge, and another from HMBJ at Eureka Humboldt Bay Jetty.

Temporal Representation:

Samples were collected from Humboldt Bay as follows: EUSB on 1/23/2009 and from HMBJ on 1/22/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	157029	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Dieldrin
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 157029, Dieldrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322425

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 0 samples exceeded the water quality threshold for Dieldrin. Monitors collected 1 composite of Leopard shark composed of 3 fish. Because no averaging period applies, this composite represents 1 independent sample. This sample was not used in the assessment because the laboratory data reporting limit was above the objective and therefore the result could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for dieldrin in fish tissue is 0.32 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157029, Dieldrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121256

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Dieldrin. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Dieldrin concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157029, Dieldrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121499

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Waterboard staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: Zero of Zero samples exceeded the water quality standard for Dieldrin. Although data was collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite), all 1 sample(s) had to be thrown out due to quantitation issues.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157029, Dieldrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121088

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Dieldrin. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157029, Dieldrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322427

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 1 sample exceeded the water quality threshold for Dieldrin. Monitors collected 1 composite of Leopard shark composed of 3 fish. Because no averaging period applies, this composite represents 1 independent sample.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157029, Dieldrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

31731

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Shellfish

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Shellfish surveys

Data Used to Assess Water Quality:

None of the two samples did exceed the guideline. Non-detect results were reported as zero (no method detection limits were provided) and were not included in the assessment. Data were reported on a dry weight basis and were converted to a wet weight basis by multiplying the dry-weight concentration by a factor of 1 minus the percentage of moisture content expressed as a decimal.

Data Reference:

State Mussel Watch Program Data 1977-2000; Winter 2007-Winter 2009. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for dieldrin in shellfish tissue is 0.49 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 21 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. (Brodberg, R.K., and G.A. Pollock, 1999; Klasing, S., and R. Brodberg, 2008)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Samples are collected by hand from three sub-locations for each site. The composite samples were collected from site EUSB at Eureka Samoa Bridge, and another from HMBJ at Eureka Humboldt Bay Jetty.

Temporal Representation:

Samples were collected from Humboldt Bay as follows: EUSB on 1/23/2009 and from HMBJ on 1/22/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 157029, Dieldrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322438

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157029, Dieldrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121153

Pollutant:

Dieldrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Dieldrin. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

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


DECISION ID	157030	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Endosulfan
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 157030, Endosulfan	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121183

Pollutant:

Endosulfan

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Endosulfan. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Endosulfan, Total concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157030, Endosulfan	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322462

Pollutant:

Endosulfan

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 1 sample exceeded the water quality threshold for Endosulfan. Monitors collected 1 composite of Leopard shark composed of 3 fish. Because no averaging period applies, this composite represents 1 independent sample.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for endosulfan (l and ll) in fish tissue is 13,000 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008; USEPA, 2000)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Guidance for Assessing Chemical Contaminant Data for Use In Fish Advisories Volume 1: Fish Sampling and Analysis

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157030, Endosulfan	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322450

Pollutant:

Endosulfan

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 1 sample exceeded the water quality threshold for Endosulfan. Monitors collected 1 composite of Leopard shark composed of 3 fish. Because no averaging period applies, this composite represents 1 independent sample.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157030, Endosulfan	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121460

Pollutant:

Endosulfan

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Endosulfan. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157030, Endosulfan	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121440

Pollutant:

Endosulfan

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Endosulfan. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Guidance for Assessing Chemical Contaminant Data for Use In Fish Advisories Volume 1: Fish Sampling and Analysis

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157030, Endosulfan	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121246

Pollutant:

Endosulfan

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Endosulfan. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157030, Endosulfan	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322456

Pollutant:

Endosulfan

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 1 sample exceeded the water quality threshold for Endosulfan. Monitors collected 1 composite of Leopard shark composed of 3 fish. Because no averaging period applies, this composite represents 1 independent sample.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	157031	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Endrin
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 157031, Endrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322483

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Endrin. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for endrin in fish tissue is 660 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008; USEPA, 2000)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Guidance for Assessing Chemical Contaminant Data for Use In Fish Advisories Volume 1: Fish Sampling and Analysis

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157031, Endrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322488

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Endrin. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Endrin concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157031, Endrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121032

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Endrin. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157031, Endrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121358

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Endrin. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157031, Endrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121101

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Endrin. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Guidance for Assessing Chemical Contaminant Data for Use In Fish Advisories Volume 1: Fish Sampling and Analysis

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157031, Endrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121468

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Endrin. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157031, Endrin	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322487

Pollutant:

Endrin

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Endrin. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	157032	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Heptachlor
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 157032, Heptachlor	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121277

Pollutant:

Heptachlor

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Heptachlor. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Heptachlor concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157032, Heptachlor	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322530

Pollutant:

Heptachlor

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Heptachlor. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157032, Heptachlor	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121276

Pollutant:

Heptachlor

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Heptachlor. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157032, Heptachlor	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121469

Pollutant:

Heptachlor

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Heptachlor. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157032, Heptachlor	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322536

Pollutant:

Heptachlor

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Heptachlor. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	157033	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Heptachlor epoxide
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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:

Line of Evidence (LOE) for Decision ID 157033, Heptachlor epoxide	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

31736

Pollutant:

Heptachlor epoxide

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Shellfish

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Shellfish surveys

Data Used to Assess Water Quality:

The one sample did not exceed the guideline. Non-detect results were reported as zero (no method detection limits were provided) and were not included in the assessment. Data were reported on a dry weight basis and were converted to a wet weight basis by multiplying the dry-weight concentration by a factor of 1 minus the percentage of moisture content expressed as a decimal.

Data Reference:

State Mussel Watch Program Data 1977-2000; Winter 2007-Winter 2009. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for heptachlor epoxide in shellfish tissue is 1.4 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 21 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. (Brodberg, R.K., and G.A. Pollock, 1999; Klasing, S., and R. Brodberg, 2008; OEHHA, 1999)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Samples are collected by hand from three sub-locations for each site. The composite samples were collected from site EUSB at Eureka Samoa Bridge, and another from HMBJ at Eureka Humboldt Bay Jetty.

Temporal Representation:

Samples were collected from Humboldt Bay as follows: EUSB on 1/23/2009 and from HMBJ on 1/22/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 157033, Heptachlor epoxide	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322544

Pollutant:

Heptachlor epoxide

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 0 samples exceeded the water quality threshold for Heptachlor Epoxide. Monitors collected 1 composite of California Halibut composed of 2 fish. Because no averaging period applies, this composite represents 1 independent sample. This sample was not used in the assessment because the laboratory data reporting limit was above the objective and therefore the result could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for heptachlor epoxide in fish tissue is 0.93 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008; OEHHA, 1999)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Public Health Goal for Heptachlor and Heptachlor Epoxide in Drinking Water

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157033, Heptachlor epoxide	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322560

Pollutant:

Heptachlor epoxide

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 1 sample exceeded the water quality threshold for Heptachlor Epoxide. Monitors collected 1 composite of California Halibut composed of 2 fish. Because no averaging period applies, this composite represents 1 independent sample.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Heptachlor Epoxide concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157033, Heptachlor epoxide	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322540

Pollutant:

Heptachlor epoxide

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 1 sample exceeded the water quality threshold for Heptachlor Epoxide. Monitors collected 1 composite of California Halibut composed of 2 fish. Because no averaging period applies, this composite represents 1 independent sample.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	157034	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Hexachlorobenzene/ HCB
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 157034, Hexachlorobenzene/ HCB	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322570

Pollutant:

Hexachlorobenzene/ HCB

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Hexachlorobenzene. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for hexachlorobenzene in fish tissue is 2.8 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008; OEHHA, 2005)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Air Toxics Hotspots Program Risk Assessment Guidelines. Part ll Technical Support Document for Describing Available Cancer Potency Values.

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157034, Hexachlorobenzene/ HCB	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121360

Pollutant:

Hexachlorobenzene/ HCB

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Hexachlorobenzene. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Air Toxics Hotspots Program Risk Assessment Guidelines. Part ll Technical Support Document for Describing Available Cancer Potency Values.

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

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


DECISION ID	157035	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Lindane/gamma Hexachlorocyclohexane (gamma-HCH)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 157035, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322495

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for HCH, gamma-. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for lindane in fish tissue is 4.6 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008; OEHHA, 2005)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Air Toxics Hotspots Program Risk Assessment Guidelines. Part ll Technical Support Document for Describing Available Cancer Potency Values.

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157035, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322506

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for HCH, gamma-. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

National Academy of Science guidelines (NAS 1972) establish a maximum Lindane concentration of 100 ug/Kg (wet weight) in tissue samples for protection of aquatic life from bioaccumulation of toxic substances.

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157035, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322516

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for HCH, gamma-. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157035, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121325

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for HCH, gamma-. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157035, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121290

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for HCH, gamma-. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157035, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121462

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for HCH, gamma-. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Air Toxics Hotspots Program Risk Assessment Guidelines. Part ll Technical Support Document for Describing Available Cancer Potency Values.

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157035, Lindane/gamma Hexachlorocyclohexane (gamma-HCH)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121168

Pollutant:

Lindane/gamma Hexachlorocyclohexane (gamma-HCH)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for HCH, gamma-. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

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


DECISION ID	71311	Region 1
Eureka Plain HU, Humboldt Bay

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

Regional Board Conclusion:	This pollutant is being considered for placement on the section 303(d) list under section 3.5 of the Listing Policy. Under section 3.5 a single line of evidence is necessary to assess listing status. Four lines of evidence are available in the administrative record to assess mercury concentrations in fish fillets. LOEs 133302, 132947, 133038 and 9108 present the average of the trophic level 3 tissue samples collected at a single site. For LOEs 133302, 132947, 133038 one of one sample exceeds the objective for the COMM, MAR and WILD beneficial uses. LOE 9108 states zero out of six samples exceeded the guideline for the CUL beneficial use. LOE 133965 states zero out of 82 samples exceeded the guideline for the SHELL beneficial use.This sample size is insufficient to determine with the power and confidence of the Listing Policy if standards are being met, as a minimum of either (1) 16 samples, or (2) greater than or equal 2 exceedances of the evaluation guideline with less than 16 samples is needed for application of Table 3.1. 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 section 303(d) list in the Water Quality Limited Segments category (i.e., sufficient justification to not 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 one samples exceeded the objective for the COMM, MAR and WILD beneficial uses, zero of six samples exceeded the guideline for the CUL beneficial use, and zero of 82 samples exceeded the guideline for the SHELL beneficial use. The sample sizes are insufficient to determine if standards are being met. A minimum of either three composite fish tissue samples per assessed beneficial use are needed to determine attainment, or one exceeding composite tissue sample aggregated from eight or more individual fish per assessed beneficial use is needed to fully determine the final use support rating in accordance with the mercury objectives following section 3.11 of the Listing Policy. Additionally, non-attainment may be determined by two exceedances from a minimum of two years for a beneficial use thus exceeding 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. 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 71311, Mercury	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

9108

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Total

Beneficial Use:

Cultural/Traditional Rights

Number of Samples:

Number of Exceedances:

Data and Information Type:

BIOLOGICAL MONITORING

Data Used to Assess Water Quality:

None of the 6 Humboldt Bay fish tissue samples analyzed for mercury exceed the evaluation guideline. The mercury values ranged from 0.036 ppm to 0.045 ppm. These samples were collected by the California State Mussel Watch Program. Data are summaried in the "California State Mussel Watch Ten Year Data Summary 1977-1987" (SWRCB 1988).

Data Reference:

California State Mussel Watch Ten Year Data Summary 1977-1987. Water Quality Monitoring Report No. 87-3. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Per the Basin Plan (NCRWQCB 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. Compliance with this objective will be determined by use of indicator organisms, analyses of species diversity, population density, growth anomalies, bioassays of appropriate duration, or other appropriate methods as specified by the Regional Water Board.

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Per the "General Protocol for Sport Fishing Sampling and Analysis" (Gassel & Broberg 2005): The screening value for mercury concentrations that pose a potential public health concern is 0.08 ppm wet weight. This is a conservative screening value based upon a woman of childbearing age who consumes 12 meals a month.

Guideline Reference:

General Protocol for Sport Fish Sampling and Analysis. Pesticide and Environmental Toxicology Branch. Office of Environmental Health Hazard Assessment. California Environmental Protection Agency. December 2005

Spatial Representation:

The samples were collected from 6 sites in Humboldt Bay. These sites are as follows: (1) at Mad River Slough, (2) at Arcata Ruin, (3) at Samoa Bridge West, (4) at Woodley Island, (5) at Eureka STP, and (6) at Eureka.

Temporal Representation:

The samples were collected during 1 site visit on February 15, 1984.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Samples were collected according to the protocols provided by the CA State Mussel Watch Program (California State Mussel Watch 1988, Appendix A).

QAPP Information Reference(s):

California State Mussel Watch Ten Year Data Summary 1977-1987. Water Quality Monitoring Report No. 87-3. State Water Resources Control Board

Line of Evidence (LOE) for Decision ID 71311, Mercury	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

133965

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Shellfish

Beneficial Use:

Shellfish Harvesting

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Zero of 82 samples exceed the guideline for mercury. The mercury values rang from 0.003 ppm to 0.084 ppm. These samples were collected by the California State Mussel Watch Program.

Data Reference:

State Mussel Watch Program Data 1977-2000: trace elements by wet weight. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The USEPA 304(a) recommended water quality criterion for concentrations of methylmercury in shellfish tissue (wet weight) is 0.20 ppm. (Brodberg, R.K., and G.A. Pollock, 1999; USEPA, 2001)

Guideline Reference:

Water Quality Criterion for the Protection of Human Health: Methylmercury. Final. United States Environmental Protection Agency Office of Science and Technology Office of Water. EPA-823-R-01-001. January 2001

Guideline Reference:

Prevalence of Selected Target Chemical Contaminants in Sport Fish From Two California Lakes: Public health designed screening study. Sacramento, CA: Office of Environmental Health Hazard Assessment

Spatial Representation:

Samples were collected from the following Mussel Watch collection sites (station name/station number):
Arcata Dock (100.5)
Samoa Bridge/West (101)
Humboldt Bay/Halberson Shoreline (101.8)
Samoa Bridge/East (102)
Woodley Island (102.5)
Humboldt Bay/J Street (102.6)
Humboldt Bay/H Street (102.7)
Humboldt Bay/C Street (102.8)
Eureka Channel (103)
Humboldt Bay/14th Street Drain (103.1)
Louisiana Pacific Dock (103.2)
Humboldt Bay/E Street (103.3)
Humboldt Del Norte Pier (103.4)
Humboldt Bay/Clark Slough (103.5)
Simpson Dock (103.6)
Eda Dock (103.7)
Eureka STP/Outfall (104)
Eureka STP/Control (104.5)
Humboldt Bay/Entrance (105)
Fields Landing (106)

Temporal Representation:

Samples were collected from 1978 to 1999.

Environmental Conditions:

QAPP Information:

Samples were collected according to the protocols provided by the CA State Mussel Watch Program (California State Mussel Watch 1988, Appendix A). Data for Humboldt Bay was previously assessed without a QAPP. Data reassessed without a QAPP for consistency.

QAPP Information Reference(s):

This is a placeholder reference for data that was collected after QAPP requirements were developed, but exempt from the requirements.

Line of Evidence (LOE) for Decision ID 71311, Mercury	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

133038

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Wildlife Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the water quality standard for Mercury. This LOE contains data only for trophic level 3 fish. The concentration of Mercury in fish collected within the same calendar year, for the same trophic level were averaged into a single sample for comparison with the objective. A total of 3 fish were aggregated into 1 annual averages, which consisted of 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite). Of these annual averages, 1 average(s), (Year(s): 2010) exceeded the objective.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The Statewide Sport Fish Water Quality Objective for the protection of Wildlife Habitat comes from the Statewide Water Quality Control Plan for Inland Surface Waters, Enclosed Bays, and Estuaries of California, and is 0.2 mg/Kg wet weight skinless fillet samples of trophic level 3, or trophic level 4 fish (whichever is highest in the water body) over a one year averaging period. If trophic level 3 fish are used in the assessment then the Prey Fish Water Quality Objective must also be used to determine that the Sport Fish Objective is being met. Trophic levels of applicable fish are defined in, but not limited to those in Attachment C of the Final Regulatory Language document (Appendix A) of State Water Resources Control Board Resolution No. 2017-0027.

Guideline 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

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31. When composited fish were collected over multiple days, the first day of fish collection was used as the sample date in the LOE, both for LOE writing, and for averaging period purposes.

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 71311, Mercury	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

132947

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The Statewide Sport Fish Water Quality Objective for the protection of Marine Habitat comes from the Statewide Water Quality Control Plan for Inland Surface Waters, Enclosed Bays, and Estuaries of California, and is 0.2 mg/Kg wet weight skinless fillet samples of trophic level 3, or trophic level 4 fish (whichever is highest in the water body) over a one year averaging period. If trophic level 3 fish are used in the assessment then the Prey Fish Water Quality Objective must also be used to determine that the Sport Fish Objective is being met. Trophic levels of applicable fish are defined in, but not limited to those in Attachment C of the Final Regulatory Language document (Appendix A) of State Water Resources Control Board Resolution No. 2017-0027.

Guideline 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

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 71311, Mercury	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

133302

Pollutant:

Mercury

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The Statewide Sport Fish Water Quality Objective for the protection of the Commercial and Sport Fishing beneficial comes from the Statewide Water Quality Control Plan for Inland Surface Waters, Enclosed Bays, and Estuaries of California, and is 0.2 mg/Kg wet weight skinless fillet samples of trophic level 3, or trophic level 4 fish (whichever is highest in the water body) over a one year averaging period. Trophic levels of applicable fish are defined in, but not limited to those in Attachment C of the Final Regulatory Language document (Appendix A) of State Water Resources Control Board Resolution No. 2017-0027.

Guideline 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

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

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


DECISION ID	161481	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Microcystins
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 161481, Microcystins	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

328558

Pollutant:

Microcystins

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Waters shall not contain toxic substances in concentrations that are toxic to, or that produce detrimental physiological responses in human, plant, animal, or aquatic life, as specified in subsection 3.3.16 of the 2018 Water Quality Control Plan for the North Coast Region (Basin Plan).

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The California Cyanobacteria and Harmful Algal Bloom (CCHAB) Network established 6 ug/L of microcystins as the water concentration protective of swimmers and other contact recreational users including water-skiing/jet-skiing, fishing, boating, sail boarding, and canoeing.

Guideline Reference:

Appendix to the CCHAB preliminary changes to the statewide voluntary guidance on cyanoHABs in recreational waters, January 2016. Appendix A. Description of cyanotoxin triggers in recreational waters.

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10285 (NCA_CA-10285).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 161481, Microcystins	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

328556

Pollutant:

Microcystins

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

USEPA 10-day microcystin health advisory for bottle-fed infants and young children of pre-school age is 0.3 ug/L.

Guideline Reference:

Drinking Water Health Advisory for the Cyanobacterial Microcystin Toxins

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10285 (NCA_CA-10285).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 161481, Microcystins	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

328554

Pollutant:

Microcystins

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Not Recorded

Beneficial Use:

Wildlife Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

California Office of Environmental Health Hazard Assessment (OEHHA) established 2 ug/L of microcystins as the subchronic water concentration for dog intake/ingestion (Office of Environmental Health Hazard Assessment Public Health Action Level for microcystin and Human Recreational Uses (May 2012)). OEHHA Action Level for subchronic water intake, dog.

Guideline Reference:

Toxicological Summary and Suggested Action Levels to Reduce Potential Adverse Health Effects of Six Cyanotoxins

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10285 (NCA_CA-10285).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	157036	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Mirex
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 157036, Mirex	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121359

Pollutant:

Mirex

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Waterboard staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: Zero of Zero samples exceeded the water quality standard for Mirex. Although data was collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite), all 1 sample(s) had to be thrown out due to quantitation issues.

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for mirex in fish tissue is 0.28 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day. This constituent is a carcinogen therefore the risk level is set to one in a million. A cooking reduction factor of 1 is applied for skin-off fillets. (Klasing, S., and R. Brodberg, 2008; OEHHA, 1992)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Expedited Cancer Potency Values and Proposed Regulatory Levels for Certain Proposition 65 Carcinogens.

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 157036, Mirex	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322696

Pollutant:

Mirex

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 0 samples exceeded the water quality threshold for Mirex. Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples. These samples were not used in the assessment because the laboratory data reporting limits were above the objectives and therefore the results could not be quantified with the level of certainty required by the Listing Policy Section 6.1.5.5.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Guideline Reference:

Expedited Cancer Potency Values and Proposed Regulatory Levels for Certain Proposition 65 Carcinogens.

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	158398	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Nitrate/Nitrite (Nitrite + Nitrate as N)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 158398, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

328671

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The California Maximum Contaminant Level for nitrate + nitrite (as N) that is incorporated by reference in the Water Quality Control Plan, North Coast Basin is 10.0 mg/L (Water Quality Control Plan, North Coast Basin).

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10216 (NCA_CA-10216).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 158398, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

328645

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10285 (NCA_CA-10285).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 158398, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

328656

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10214 (NCA_CA-10214).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 158398, Nitrate/Nitrite (Nitrite + Nitrate as N)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

328662

Pollutant:

Nitrate/Nitrite (Nitrite + Nitrate as N)

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10232 (NCA_CA-10232).

Temporal Representation:

The samples were collected between the dates of 2015-08-20 and 2015-08-20

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	155019	Region 1
Eureka Plain HU, Humboldt Bay

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. Six lines of evidence are available in the administrative record to assess this pollutant. Fourteen of the 107 samples exceed the guideline. For the MAR beneficial use, 11 of 103 samples exceed the guideline. For the COLD beneficial use, 3 of 4 samples exceed the guideline. 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. For the MAR beneficial use, 11 of 103 samples exceed the guideline. For the COLD beneficial use, 3 of 4 samples exceed the guideline. Neither exceeds 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:

Line of Evidence (LOE) for Decision ID 155019, Oxygen, Dissolved	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318911

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Fish Spawning

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed dissolved oxygen data for EPA National Aquatic Resources Survey (NARS) and determined that 1 of 1 sample is less than the April-November minimum of 6.0 mg/L and 0 of 0 samples are less than the December-May minimum of 9.0 mg/L, so that 1 of 1 sample exceeds the water quality objective.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, North Coast Basin, Chapter III, General Objectives for all Inland Surface Waters, Enclosed Bays and Estuaries states: Dissolved oxygen concentrations shall conform to those limits listed in Section 3.3.5. Section 3.3.5 lists dissolved oxygen concentration limits for COLD beneficial use waters to be a daily minimum of 6.0 mg/L and a 7-day moving minimum average of 8.0 mg/L and dissolved oxygen concentration limits for SPWN beneficial use waters to be a daily minimum of 9.0 mg/L and a 7-day moving average of 11.0 mg/L.

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

This sample was collected at sampling station name: NCA_CA-10214; station code: NARS_WQX-NCA_CA-10214.

Temporal Representation:

This sample was collected on 8/19/2015.

Environmental Conditions:

QAPP Information:

QAPP for EPA National Aquatic Resources Survey (NARS)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 155019, Oxygen, Dissolved	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

101404

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

The following process is utilized to interpret the narrative temperature objective in the Basin Plan for impairment assessments. Step 1: Determine if temperatures reflect natural conditions. If Yes, then the water body is not considered impaired, if No, then go to Step 2. Step 2: Determine if temperatures adversely affect beneficial uses. If Yes, then the water body is considered impaired, if No , then go to Step 3. Step 3: Determine if temperatures are increased by 5 degrees F. If Yes, then water body is impaired, if No, then water body is not impaired.

Data Reference:

Presentation: Interpreting Temperature Standards in the North Coast Region. North Coast Regional Water Quality Control Board.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, North Coast Region (NCRWQCB 2018): Dissolved oxygen (DO) concentrations shall conform to the numeric objectives expressed in section 3.3.5.

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

EVIDENCE OF ALTERATION OF NATURAL RECEIVING WATER TEMPERATURES (NON-NATURAL TEMPS): The water temperatures of the Eureka Plain HU, Humboldt Bay do not reflect natural conditions as environmental factors that influence water temperature have been anthropogenically altered due to ranching (California Society for Ecological Restoration 2015) road-related activities, forestry practices and causing channel aggradation and pool infilling leading to changes in riparian shade cover, increased solar heating. EVIDENCE OF SALMONID PRESENCE & LIFE CYCLE USE: Steelhead, Chinook and Coho are present in Humboldt Bay (California Department of Fish and Game 2005, Moyle et al., 2008, NOAA 2014). Rearing occurs year round and spawning/incubation/emergence occurs from December through March (California Department of Fish and Game 2005, Moyle et al., 2008, NOAA 2014). Non-core rearing is supported throughout Humboldt Bay.

Guideline Reference:

Final Recovery Plan for the Southern Oregon/Northern California Coast Evolutionarily Significant Unit of Coho Salmon (Onchorhynchus kisutch)

Guideline Reference:

Salmon Creek Estuary Restoration and Monitoring Results

Guideline Reference:

Humboldt Bay Watershed Salmon and Steelhead Conservation Plan

Guideline Reference:

Salmon, Steelhead, and Trout in California: Status of an Emblematic Fauna

Spatial Representation:

Information pertains to the Eureka Plain HU, Humboldt Bay

Temporal Representation:

Data are reflective of current conditions in this water body.

Environmental Conditions:

QAPP Information:

Information is considered to be of adequate quality for the Integrated Report process.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 155019, Oxygen, Dissolved	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

23451

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Dissolved

Beneficial Use:

Marine Habitat

Aquatic Life Use:

Cold Freshwater Habitat | Wildlife Habitat

Number of Samples:

103

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Eleven of the 103 monthly dissolved oxygen (DO) averages (by individual monitoring locations) exceed the objective. In other words, they were below the 6.0 mg/l minimum objective. The majority of these (10 of 11) occurred at the Reservation Wetland site. The average of the 11 exceedances is 3.9 mg/l. There were no exceedances of the 50th percentile or 90th percentile objectives. The lower 50th percentile (of average monthly DO) for all data in Humboldt Bay was 7.71 mg/l. The lower 90th percentile (of average monthly DO) for all data in Humboldt Bay was 6.96 mg/l. Samples were collected by the Wiyot Tribe and data are summarized by the Tribe (Wiyot 2007).

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Per the Basin Plan (NCRWQCB 2007): The minimum dissolved oxygen objective is 6.0 mg/l. The 90% lower limit dissolved oxygen objective is 6.0 mg/l. The 50% lower limit dissolved oxygen objective is 7.0 mg/l. The 90% and 50% lower limits represent the 90/50 percentile values for a calendar year. 90% or 50% or more of the values must be greater than or equal to the lower limit.

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

At Humboldt Bay Entrance, DO samples were collected every two weeks from December 2004 to December 2006 during the last hour of the incoming tide. The sonde was deployed for approximately 15 minutes, with a 3 - 5 minute equilibration period and an 8 - 10 minute sampling period with 4 second intervals. The average of the daily data was used.

At Indian Island, DO samples were collected every two weeks from December 2004 to September 2006 during the mid tide. The sonde was deployed for approximately 15 minutes, with a 3 - 5 minute equilibration period and an 8 - 10 minute sampling period with 4 second intervals. The average of the daily data was used. Also at Indian Island, DO samples were collected at 15 minute intervals from January 13, 2006 to March 9, 2006 and from September 22, 2006 to December 22, 2006.

At Mad River Slough, DO samples were collected every two weeks from December 2004 to December 2006 during the outgoing tide. The sonde was deployed for approximately 15 minutes, with a 3 - 5 minute equilibration period and an 8 - 10 minute sampling period with 4 second intervals. The average of the daily data was used.

At the Reservation Wetland, DO samples were collected every two weeks during the wet season from December 2004 to February 2006. DO samples were also collected every two weeks from March 2006 to December 2006. The sonde was deployed for approximately 15 minutes, with a 3 - 5 minute equilibration period and an 8 - 10 minute sampling period with 4 second intervals. The average of the daily data was used.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Samples were collected according to Wiyot Tribe¿s ¿Draft Quality Assurance Program Plan (QAPP) for Water Quality Assessment and Monitoring¿ (McKernan et al. 2004).

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 155019, Oxygen, Dissolved	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318922

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Fish Spawning

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed dissolved oxygen data for EPA National Aquatic Resources Survey (NARS) and determined that 0 of 1 sample is less than the April-November minimum of 6.0 mg/L and 0 of 0 samples are less than the December-May minimum of 9.0 mg/L, so that 0 of 1 sample exceeds the water quality objective.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

This sample was collected at sample station name: NCA_CA-10285; station code: NARS_WQX-NCA_CA-10285.

Temporal Representation:

This sample was collected on 8/19/2015.

Environmental Conditions:

QAPP Information:

QAPP for EPA National Aquatic Resources Survey (NARS)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 155019, Oxygen, Dissolved	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318914

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Fish Spawning

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

This sample was collected at sample station name: NCA_CA-10216; station code: NARS_WQX-NCA_CA-10216.

Temporal Representation:

This sample was collected on 8/19/2015.

Environmental Conditions:

QAPP Information:

QAPP for EPA National Aquatic Resources Survey (NARS)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 155019, Oxygen, Dissolved	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318917

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Fish Spawning

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

This sample was collected at sample station name: NCA_CA-10232; station code: NARS_WQX-NCA_CA-10232.

Temporal Representation:

This sample was collected on 8/20/2015.

Environmental Conditions:

QAPP Information:

QAPP for EPA National Aquatic Resources Survey (NARS)

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	157038	Region 1
Eureka Plain HU, Humboldt Bay

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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 157038, Selenium	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322745

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 4 samples exceeded the water quality threshold for Selenium. Monitors collected 6 composites: 1 composite of California Halibut composed of 2 fish, 1 composite of Leopard shark composed of 3 fish, 1 composite of Leopard shark composed of 10 fish, 1 composite of White Surfperch composed of 7 fish, and 2 composites of White Surfperch composed of 8 fish each. Because 2 or more composites were collected within the same averaging period, these composites resulted in 4 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The OEHHA Fish Contaminant Goal for selenium in fish tissue is 7.4 ppm. This screening level assumes an average body weight of 70 kg and a consumption rate of 32 g/day. A background dietary consumption rate of 0.114 mg/day is applied for this micronutrient. (Klasing, S., and R. Brodberg, 2008)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 157038, Selenium	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121185

Pollutant:

Selenium

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Selenium. Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

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


DECISION ID	163016	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Specific Conductivity
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 163016, Specific Conductivity	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

329144

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed EPA National Aquatic Resources Survey (NARS) data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and results are as follows: 1 of 1 samples exceeded the water quality threshold for SpecificConductivity.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Waters designated for use as domestic or municipal supply (MUN) shall not contain concentrations of chemical constituents in excess of the limits specified in California Code of Regulations, Title 22, Chapter 15, Division 4, Article 4, Section 64435 (Tables 2 and 3), and Section 64444.5 (Table 5), and listed in Table 3-2 of this Plan (Water Quality Control Plan, North Coast Basin).

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Basin Plan's 'Chemical Constituents' objective. The California Secondary MCL for specific conductivity is 900 uS/cm.

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10285 (NCA_CA-10285).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163016, Specific Conductivity	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

329147

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Basin Plan's 'Chemical Constituents' objective. The California Secondary MCL for specific conductivity is 900 uS/cm.

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10216 (NCA_CA-10216).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163016, Specific Conductivity	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

329158

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Basin Plan's 'Chemical Constituents' objective. The California Secondary MCL for specific conductivity is 900 uS/cm.

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10214 (NCA_CA-10214).

Temporal Representation:

The samples were collected between the dates of 2015-08-19 and 2015-08-19

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 163016, Specific Conductivity	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

329151

Pollutant:

Specific Conductivity

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Municipal & Domestic Supply

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

California Maximum Contaminant Levels (MCLs) apply to ambient waters under the Basin Plan's 'Chemical Constituents' objective. The California Secondary MCL for specific conductivity is 900 uS/cm.

Guideline Reference:

California Code of Regulations, Title 22, Division 4, Chapter 15. Domestic Water Quality and Monitoring

Spatial Representation:

The samples were collected at 1 monitoring site: NARS_WQX-NCA_CA-10232 (NCA_CA-10232).

Temporal Representation:

The samples were collected between the dates of 2015-08-20 and 2015-08-20

Environmental Conditions:

QAPP Information:

Generic SWAMP QAPrP

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	155021	Region 1
Eureka Plain HU, Humboldt Bay

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	Revised
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 4.2 of the Listing Policy. Under this section a single line of evidence is necessary to assess listing status. Nine lines of evidence are available in the administrative record to assess this pollutant. Zero of 129 samples exceed the cold freshwater habitat beneficial use objective. 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. Zero of 129 samples exceed the cold freshwater habitat beneficial use objective and this exceeds the allowable frequency listed in Table 4.2 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.

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:

Line of Evidence (LOE) for Decision ID 155021, Temperature, water	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318916

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Fish Spawning

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed temperature data for EPA National Aquatic Resources Survey (NARS) and determined that 0 of 1 sample is greater than the April-November maximum of 24 degrees Celcius and 0 of 0 samples are greater than the December-May maximum of 20 degrees Celcius, so that 0 of 1 sample exceeds the water quality objective.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, North Coast Basin, Chapter III, General Objectives for all Inland Surface Waters, Enclosed Bays and Estuaries states: Natural receiving water temperature of intrastate waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Water 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 degrees Fahrenheit (F) above natural receiving water temperature.

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

According to Carter (2008) the lethal temperature for spawning, incubation, and emergence life stages are 20 degrees C. The lethal temperatures for adult migration and holding, and juvenile migration and rearing is 24 degrees C.

Guideline Reference:

Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids. Implications for California's North Coast TMDLs. California Regional Water Quality Control Board, North Coast Region

Spatial Representation:

This sample was collected at sample station name: NCA_CA-10216; station code: NARS_WQX-NCA_CA-10216.

Temporal Representation:

This sample was collected on 8/19/2015.

Environmental Conditions:

QAPP Information:

QAPP for EPA National Aquatic Resources Survey (NARS)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 155021, Temperature, water	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318913

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Fish Spawning

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

This sample was collected at sampling station name: NCA_CA-10214; station code: NARS_WQX-NCA_CA-10214.

Temporal Representation:

This sample was collected on 8/19/2015.

Environmental Conditions:

QAPP Information:

QAPP for EPA National Aquatic Resources Survey (NARS)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 155021, Temperature, water	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

5548

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

It is unknown if any of the 11,248 temperature samples collected in Humboldt Bay exceed the objective. The samples collected were ambient water samples collected in Humboldt Bay. The bay drains to the ocean every 6 hours or so. There is not sufficient information available to determine the natural receiving water temperature of the marine waters of Humboldt Bay and thus, Regional Water Board staff are unable to evaluate compliance with the objective. Samples were collected by the Wiyot Tribe and data are summarized by the Tribe (Wiyot 2007).

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Per the Thermal Plan (SWRCB 1972): For existing discharges: (1) Elevated temperature waste discharges shall comply with limitations necessary to assure protection of beneficial uses. For new discharges: (1) Elevated temperature waste discharges shall comply with limitations necessary to assure protection of beneficial uses. The maximum temperature of waste discharges shall not exceed the natural temperature of the receiving waters by more than 20°F. (2) Thermal waste discharges having a maximum temperature greater than 4°F above the natural temperature of the receiving water are prohibited. And per the Basin Plan (NCRWQCB 2007): The natural receiving water temperature of intrastate waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Water 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 by more than 5°F above natural receiving water temperature.

Objective/Criterion Reference:

Water Quality Control Plan for Control of Temperature in the Coastal and Interstate Waters and Enclosed Bays and Estuaries of California (Thermal Plan). State Water Resources Control Board

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The temperature data were collected from 4 sites in Humboldt Bay as follows: (1) Humboldt Bay Entrance just northeast of the east edge of the north jetty; (2) Indian Island just off one of the old pilings between the old industrial site on the Tribe's land and the middle channel of north Humboldt Bay; (3) Mad River Slough at the Samoa Boulevard Bridge over the Slough; and (4) the Reservation Wetland at the northeast corner of the Table Bluff Reservation. At the Reservation Wetland site, samples from December 2004 to February 2006 were collected from surface wetland waters. Starting in March 2006, two shallow-water monitoring wells were installed in the wetland and serve as the sample collection sites.

Temporal Representation:

At Humboldt Bay Entrance, temperature samples were collected every two weeks from December 2004 to December 2006 during the last hour of the incoming tide. The sonde was deployed for approximately 15 minutes, with a 3 - 5 minute equilibration period and an 8 - 10 minute sampling period with 4 second intervals. The average of the daily data was used. At Indian Island, temperature samples were collected every two weeks from December 2004 to September 2006 during the mid tide. The sonde was deployed for approximately 15 minutes, with a 3 - 5 minute equilibration period and an 8 - 10 minute sampling period with 4 second intervals. The average of the daily data was used. Also at Indian Island, temperature samples were collected at 15 minute intervals from January 13, 2006 to March 9, 2006 and from September 22, 2006 to December 22, 2006. At Mad River Slough, temperature samples were collected every two weeks from December 2004 to December 2006 during the outgoing tide. The sonde was deployed for approximately 15 minutes, with a 3 - 5 minute equilibration period and an 8 - 10 minute sampling period with 4 second intervals. The average of the daily data was used. At the Reservation Wetland, temperature samples were collected every two weeks during the wet season from December 2004 to February 2006 during the wet season. Temperature samples were also collected every two weeks from March 2006 to December 2006. The sonde was deployed for approximately 15 minutes, with a 3 - 5 minute equilibration period and an 8 - 10 minute sampling period with 4 second intervals. The average of the daily data was used.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Samples were collected according to Wiyot Tribe¿s ¿Draft Quality Assurance Program Plan (QAPP) for Water Quality Assessment and Monitoring¿ (McKernan et al. 2004).

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 155021, Temperature, water	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

101382

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:

Not Specified

Data Used to Assess Water Quality:

Data Reference:

Presentation: Interpreting Temperature Standards in the North Coast Region. North Coast Regional Water Quality Control Board.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, North Coast Region (NCRWQCB 2018): Natural receiving water temperature of intrastate waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Water 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 degrees Fahrenheit (F) above natural receiving water temperature.

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Final Recovery Plan for the Southern Oregon/Northern California Coast Evolutionarily Significant Unit of Coho Salmon (Onchorhynchus kisutch)

Guideline Reference:

Salmon Creek Estuary Restoration and Monitoring Results

Guideline Reference:

Humboldt Bay Watershed Salmon and Steelhead Conservation Plan

Guideline Reference:

Salmon, Steelhead, and Trout in California: Status of an Emblematic Fauna

Spatial Representation:

Information pertains to the Eureka Plain HU, Humboldt Bay

Temporal Representation:

Data are reflective of current conditions in this water body.

Environmental Conditions:

QAPP Information:

Information is considered to be of adequate quality for the Integrated Report process.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 155021, Temperature, water	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318710

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Fish Spawning

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed temperature data for Wiyot Tribe, California (Tribal) and determined that 0 of 27 samples are greater than the April-November maximum of 24 degrees Celcius and 0 of 17 samples are greater than the December-March maximum of 20 degrees Celcius, so that 0 of 44 samples exceed the water quality objective.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

These samples were collected at sampling station name: Bay Entrance; station code: WIYOT_WQX-BE-1.

Temporal Representation:

These samples were collected from 9/9/2010-2/23/2012.

Environmental Conditions:

QAPP Information:

QAPP for Wiyot Tribe, California (Tribal)

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 155021, Temperature, water	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318709

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Fish Spawning

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed temperature data for Wiyot Tribe, California (Tribal) and determined that 0 of 23 samples are greater than the April-November maximum of 24 degrees Celcius and 0 of 21 samples are greater than the December-March maximum of 20 degrees Celcius, so that 0 of 44 samples exceed the water quality objective.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

These samples were collected at sampling station name: Bay Entrance; station code: WIYOT_WQX-BE-1.

Temporal Representation:

These samples were collected from 9/9/2010-2/23/2012.

Environmental Conditions:

QAPP Information:

QAPP for Wiyot Tribe, California (Tribal)

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 155021, Temperature, water	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318861

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Fish Spawning

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed temperature data for Wiyot Tribe, California (Tribal) and determined that 0 of 23 samples are greater than the April-November maximum of 24 degrees Celcius and 0 of 14 samples are greater than the December-March maximum of 20 degrees Celcius, so that 0 of 37 samples exceed the water quality objective.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

These samples were collected at sampling station name: Indian Island; station code: WIYOT_WQX-II-1.

Temporal Representation:

These samples were collected from 9/9/2010-2/9/2012.

Environmental Conditions:

QAPP Information:

QAPP for Wiyot Tribe, California (Tribal)

QAPP Information Reference(s):

Data collected by a California Tribe QAPP Approved by U.S. EPA QAPP Reference

Line of Evidence (LOE) for Decision ID 155021, Temperature, water	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318919

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Fish Spawning

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

This sample was collected at sample station name: NCA_CA-10232; station code: NARS_WQX-NCA_CA-10232.

Temporal Representation:

This sample was collected on 8/20/2015.

Environmental Conditions:

QAPP Information:

QAPP for EPA National Aquatic Resources Survey (NARS)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 155021, Temperature, water	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318924

Pollutant:

Temperature, water

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Cold Freshwater Habitat

Aquatic Life Use:

Fish Spawning

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

This sample was collected at sample station name: NCA_CA-10285; station code: NARS_WQX-NCA_CA-10285.

Temporal Representation:

This sample was collected on 8/19/2015.

Environmental Conditions:

QAPP Information:

QAPP for EPA National Aquatic Resources Survey (NARS)

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	166029	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)
Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
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 the available data and information, SWRCB staff concludes that the water body-pollutant combination should not be placed on the section 303(d) list because it cannot be determined if applicable water quality standards are not being exceeded.

Line of Evidence (LOE) for Decision ID 166029, Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121335

Pollutant:

Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD). Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 166029, Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322769

Pollutant:

Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD). Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 166029, Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121399

Pollutant:

Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD). Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 166029, Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121261

Pollutant:

Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD). Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

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 166029, Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322775

Pollutant:

Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD). Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 166029, Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

322761

Pollutant:

Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows: 0 of 2 samples exceeded the water quality threshold for Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD). Monitors collected 2 composites: 1 composite of California Halibut composed of 2 fish and 1 composite of Leopard shark composed of 3 fish. Because no composites were collected within the same averaging period, these composites represent 2 independent samples.

Data Reference:

Habitat, Tissue from the Surface Water Ambient Monitoring Program for the 2026 Integrated Report in Region 1

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Data were collected from 1 station(s). Station Code(s): 11064HUMB (Humboldt Bay).

Temporal Representation:

Environmental Conditions:

QAPP Information:

QAPP for Surface Water Ambient Monitoring Program (SWAMP)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 166029, Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

121500

Pollutant:

Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Cold Freshwater Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Water Board staff assessed SWAMP Sportfish Coastal Zones data for Eureka Plain HU, Humboldt Bay to determine beneficial use support and the results are as follows 0 of the 1 samples exceeded the water quality standard for Total DDT (sum of 4,4'- and 2,4'- isomers of DDT, DDE, and DDD). Data were collected for 1 fish species (1 composite(s) of Bat Ray each composed of 3 fish per composite).

Data Reference:

Water Quality Assessment Data for the 2018 solicitation cycle submitted through CEDEN for SWAMP Sportfish Coastal Zones .

SWAMP Data:

SWAMP

Water Quality Objective/Criterion:

There shall be no bioaccumulation of pesticide concentrations found in bottom sediments or aquatic life. (Water Quality Control Plan for the North Coast Region)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

National Academy of Sciences. Water Quality Criteria 1972. EPA-R3-73-033. Washington, D.C.: U.S. Environmental Protection Agency

Spatial Representation:

Data was collected from 1 station(s) with the station code(s): 11064HUMB.

Temporal Representation:

Data for this line of evidence were collected between 2010-08-31 and 2010-08-31

Environmental Conditions:

QAPP Information:

Quality Assurance Program Plan and Standard Operating Procedures for SWAMP program

QAPP Information Reference(s):

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


DECISION ID	155020	Region 1
Eureka Plain HU, Humboldt Bay

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. COLD Beneficial Use: Four lines of evidence are available in the administrative record to assess this pollutant. One of the four samples exceed the Objective. MAR Beneficial Use: One line of evidence is available in the administrative record to assess this pollutant. Fifty-one of 330 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 four samples for COLD and 51 of 330 samples for MAR exceeded 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:	This region was not assessed this cycle. All decisions have been carried over from the previous cycle and remain the same.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 155020, pH	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

23470

Pollutant:

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Marine Habitat

Number of Samples:

330

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Over 13,300 pH samples were collected from Humboldt Bay from the continous data recorders & grab samples. Daily averages were calculated for each monitoring location. Of the daily averages, 51 of the 330 pH values exceed the objective (they were below the minimum objective of 7.0). All of these exceedances were collected at the Reservation¿s wetland sites. These exceedances ranged from 5.7 to 6.97, and averaged 6.5. It is possible, but unknown, if these wetlands are somewhat acidic due to naturally high levels of dissolved organic carbon. None of the pH measurements (or daily pH averages) exceeded the high pH objective of 8.5. Samples were collected by the Wiyot Tribe and data are summarized by the Tribe (Wiyot 2007).

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Per the Basin Plan (NCRWQCB 2007, p. 3-8.00): The maximum pH objective is 8.5. The minimum pH objective is 7.0. Changes in normal ambient pH levels shall not exceed 0.2 units in waters with designated marine (MAR) beneficial uses.

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

At Humboldt Bay Entrance, pH samples were collected every two weeks from December 2004 to December 2006 during the last hour of the incoming tide. The sonde was deployed for approximately 15 minutes, with a 3 - 5 minute equilibration period and an 8 - 10 minute sampling period with 4 second intervals. The average of the daily data was used.

At Indian Island, pH samples were collected every two weeks from December 2004 to September 2006 during the mid tide. The sonde was deployed for approximately 15 minutes, with a 3 - 5 minute equilibration period and an 8 - 10 minute sampling period with 4 second intervals. The average of the daily data was used. Also at Indian Island, pH samples were collected at 15 minute intervals from January 13, 2006 to March 9, 2006 and from September 22, 2006 to December 22, 2006.

At Mad River Slough, pH samples were collected every two weeks from December 2004 to December 2006 during the outgoing tide. The sonde was deployed for approximately 15 minutes, with a 3 - 5 minute equilibration period and an 8 - 10 minute sampling period with 4 second intervals. The average of the daily data was used.

At the Reservation Wetland, pH samples were collected every two weeks during the wet season from December 2004 to February 2006 during the wet season. pH samples were also collected every two weeks from March 2006 to December 2006. The sonde was deployed for approximately 15 minutes, with a 3 - 5 minute equilibration period and an 8 - 10 minute sampling period with 4 second intervals. The average of the daily data was used.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Samples were collected according to Wiyot Tribe¿s ¿Draft Quality Assurance Program Plan (QAPP) for Water Quality Assessment and Monitoring¿ (McKernan et al. 2004).

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 155020, pH	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318923

Pollutant:

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:

Water Board staff assessed pH data for EPA National Aquatic Resources Survey (NARS) and determined that background level for the lower limit is undetermined and 0 of 1 sample is greater than pH 8.5, so that 0 of 1 sample exceeds the water quality objective.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Water Quality Control Plan, North Coast Basin, Chapter III, General Objectives for all Inland Surface Waters, Enclosed Bays and Estuaries states the following: The pH shall conform to the values listed in Table 3-1 which states that the water quality objective for pH shall not be depressed below natural background levels or raised above 8.5.

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

This sample was collected at sample station name: NCA_CA-10285; station code: NARS_WQX-NCA_CA-10285.

Temporal Representation:

This sample was collected on 8/19/2015.

Environmental Conditions:

QAPP Information:

QAPP for EPA National Aquatic Resources Survey (NARS)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 155020, pH	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318912

Pollutant:

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

This sample was collected at sampling station name: NCA_CA-10214; station code: NARS_WQX-NCA_CA-10214.

Temporal Representation:

This sample was collected on 8/19/2015.

Environmental Conditions:

QAPP Information:

QAPP for EPA National Aquatic Resources Survey (NARS)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 155020, pH	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318915

Pollutant:

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:

Water Board staff assessed pH data for EPA National Aquatic Resources Survey (NARS) and determined that background level for the lower limit is undetermined and 1 of 1 sample is greater than pH 8.5, so that 1 of 1 sample exceeds the water quality objective.

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

This sample was collected at sample station name: NCA_CA-10216; station code: NARS_WQX-NCA_CA-10216.

Temporal Representation:

This sample was collected on 8/19/2015.

Environmental Conditions:

QAPP Information:

QAPP for EPA National Aquatic Resources Survey (NARS)

QAPP Information Reference(s):

Generic SWAMP QAPrP

Line of Evidence (LOE) for Decision ID 155020, pH	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

318918

Pollutant:

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:

Data Reference:

WQX from the NWQMP for the 2026 Integrated Report in Region 1

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

This sample was collected at sample station name: NCA_CA-10232; station code: NARS_WQX-NCA_CA-10232.

Temporal Representation:

This sample was collected on 8/20/2015.

Environmental Conditions:

QAPP Information:

QAPP for EPA National Aquatic Resources Survey (NARS)

QAPP Information Reference(s):

Generic SWAMP QAPrP


DECISION ID	70917	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Dioxin Toxic Equivalents
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	Do Not Delist from 303(d) list (TMDL required list)(2016)
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Regional Board Conclusion: The pollutant was placed on the section 303(d) list in a previous assessment cycle under the pollutant name Dioxin Toxic Equivalents. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: (A) Dioxin toxic equivalents in Humboldt Bay are being considered for removal from the Section 303(d) List under Sections 4.5 and 4.6 of the Listing Policy. Nine lines of evidence are available in the administrative record to access this pollutant. These lines of evidence are discussed in detail below: (1) One of the lines of evidence (LOE 26439) is based on data compiled and assessed by the State Water Resources Control Board during the 2006 listing cycle and shows 14 out of 29 exceedances of the evaluation guideline used to interpret the water quality objective. Two lines of evidence (LOEs 21366 and 26044) are based on data assessed by the North Coast Regional Water Board during the current 2008 listing cycle and show 11 out of 41 exceedences of the evaluation guideline. Combined, there are 25 out of 70 exceedences of the evaluation guideline. The evaluation guideline is the dioxin toxic equivalent screening value for fish and shellfish tissue of 0.3 ng/kg by wet weight, which was developed by the Office of Environmental Health Hazard Assessment (Brodberg and Pollock 1999). The 0.3 ng/kg screening value is based on a low mean consumption value of fish of 21 g/day. (2) Four lines of evidence (LOEs 21425, 21430, 21383, and 21427) analyze sediment data from Humboldt Bay in relation to the Marine Habitat Beneficial Use. These lines of evidence show that the Marine Habitat Beneficial Use is protected due to 9 out of 117 exceedances of the Canadian Sediment Quality Guideline used to interpret the toxicity water quality objective, which are within the number of exceedances acceptable for a waterbody to be delisted per Table 4.1 of the Listing Policy. (3) The two remaining lines of evidence (LOEs 7810 and 21365) include data that are insufficient to make a decision regarding the dioxin impairment of Humboldt Bay. For LOE 7810, data could not be evaluated against the evaluation guideline as the data were presented in dry weight without a conversion factor, instead of wet weight. For LOE 21365, data quality was poor as information did not include sampling and analysis methods and quality assurance and control documents. (B) Based on readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of continuing to place this water segment-pollutant combination on the Section 303(d) List in the Water Limited Segments category (i.e., sufficient justification to not delist). 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 in all but one line of evidence (LOE 21365). (2) The data used satisfies the data quantity requirements of Section 6.1.5 of the Policy. (3) Combined, 25 out of 70 fish or shellfish tissue samples exceed the 0.3 ng/kg OEHHA screening value used to interpret the toxicity water quality objective for the protection of the Commercial and Sport Fishing Beneficial Use, 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. This listing applies to the entire waterbody.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 70917, Dioxin Toxic Equivalents	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21382

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Not Recorded

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Nine of the 45 sediment TCDD equivalent samples (dry weight) collected in Humboldt Bay exceeded the evaluation guideline. The TCDD equivalent values range from <0.0002 ng/kg to 4.8 ng/kg. Samples were collected by the Soil/Water/Air Protection Enterprise (SWAPE), and data are summarized in the SWAPE attachment to Humboldt Baykeeper's letter of February 28, 2007 (Humboldt Baykeeper 2007).

Data Reference:

Letter from Michelle D. Smith of Humboldt Baykeeper to Bruce Gwynne of the North Coast Regional Water Quality Control Board dated February 28, 2007, regarding Data Solicitation, 2008 Clean Water Act 303(d) List of Impaired Waters

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Per the Canadian Sediment Quality Guidelines for the Protection of Aquatic Life (CCME 2001): The Interim Sediment Quality Guideline for polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans is 0.85 ng/kg (dry weight) expressed on a toxic equivalent unit basis using toxic equivalent factors for fish.

Guideline Reference:

Canadian Sediment Quality Guidelines for the Protection of Aquatic Life: Polychlorinated dioxins and furans (PCDD/Fs). In: Canadian Environmental Quality Guidelines, 1999, Canadian Council of Ministers of the Environment, Winnipeg. Excerpt from Publication No. 1299; ISBN1-896997-34-1

Spatial Representation:

Samples were collected at 3 sites in Humboldt Bay, as follows: 2 sites in the mud flats of Humboldt Bay (S-8 & S-9), and 1 site in Hookton Slough (S-10).

Temporal Representation:

Samples collected April 18, 2006.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Quality control was conducted in accordance with the Soil/Water/Air Protection Enterprise's "Sampling and Analysis Plan" (Humboldt Baykeeper 2006).

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 70917, Dioxin Toxic Equivalents	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21366

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Shellfish surveys

Data Used to Assess Water Quality:

Eleven of the 25 shellfish tissue TCDD equivalent samples (wet weight) collected in Humboldt Bay exceed the evaluation guideline. The TCDD equivalent values range from 0.1 ng/kg to 4.3 ng/kg. Samples were collected by EnviroNet and ENVIRON on behalf of Sierra Pacific Industries, Arcata Division Sawmill in commercially grown oysters and mussels from Humboldt Bay. Data are summarized by EnviroNet and ENVIRON (2003).

Data Reference:

Evaluation of the Results of Dioxin and Other Chemical Testing of Commercial Oyster Beds in Humboldt Bay, California From June and October 2002. Prepared by EnviroNet and ENVIRON for Sierra Pacific Industries

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Per the Office of Environmental Health Hazard Assessment (Brodberg and Pollack 1999): The dioxin toxic equivalent screening value for fish and shellfish tissue is 0.3 ng/kg by wet weight. It is appropriate for the 2,3,7,8-tetracholorodibenzodioxin (TCDD) toxic equivalent concentration (TEQ) for mammals to be compared against this screening value. The TCDD equivalent is the sum of the concentrations of chlorinated dibenzodioxins (2,3,7,8-CDDs) and chlorinated dibenzofurans (2,3,7,8-CDFs) multiplied by their respective toxicity factors.

Guideline Reference:

Prevalence of Selected Target Chemical Contaminants in Sport Fish From Two California Lakes: Public health designed screening study. Sacramento, CA: Office of Environmental Health Hazard Assessment

Spatial Representation:

Samples were collected from 10 sites in Humboldt Bay as follows: (1) at Coast Seafood, Inc., East Bay Bed 6-2; (2) at Coast Seafood, Inc., East Bay Bed 1-2; (3) at North Bay Shellfish Company Bed; (4) at North Bay Shellfish Company wet storage oyster; (5) at Coast Seafoods, Inc., Mad River Bed 7-1; (6) at Coast Seafoods, Inc., Mad River Bed 7-2; (7) at Coast Seafoods, Inc. Sand Island North Bed; (8) at Coast Seafoods, Inc., Sand Island North Bed 1-2; (9) at Coast Seafoods, Inc., Bird Island North Bed; and (10) at at Coast Seafoods, Inc., Bird Island South Bed.

Temporal Representation:

Data was collected June 21 and October 21, 2002.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storm events, etc.) that may have impacted these data.

QAPP Information:

Sampling and testing methods are described by EnvironNet and ENVIRON (2003). The TEQs were calculated using World Health Organization mammalian toxic equivalent factors from 1998. Non-detect data were represented using one half the congener-specific detection limit or estimated maximum possible concentrations reported by the laboratory.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 70917, Dioxin Toxic Equivalents	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21427

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Not Recorded

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Chemical monitoring of sediments

Data Used to Assess Water Quality:

None of the 6 sediment TCDD equivalent samples (dry weight) collected in Humboldt Bay exceeded the evaluation guideline. The TCDD equivalent values range from 0.01 ng/kg to 0.17 ng/kg. Samples were collected by Toxscan Inc. and Kinnetic Laboratories Inc. Data are summarized in the "Chemical Analysis, Toxicity Evaluation and Bioaccumulation Exposure of Sediments from Humboldt Bay: Baseline Survey II, Fiscal Year 1994" (Toxscan and Kinnetic 1994).

Data Reference:

Chemical Analysis, Toxicity Evaluation and Bioaccumulation Exposure of Sediments from Humboldt Bay: Baseline Survey II, Fiscal Year 1994. Final Report. Prepared for U.S. Army Engineering District San Francisco Corps of Engineers. November 1994

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Composite samples were collected at 3 sites in Humboldt Bay, as follows: (1) at Eureka Upper Channel, (2) at Samoa Turning Basin, and (3) at Fields Landing Lower Channel and Turning Basin.

Temporal Representation:

Samples were collected April 1 and 2, 1994.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Quality control was conducted as specified in Toxscan Inc. and Kinnetic Laboratories Inc. (1994).

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 70917, Dioxin Toxic Equivalents	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21425

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Not Recorded

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Chemical monitoring of sediments

Data Used to Assess Water Quality:

None of the 6 sediment TCDD equivalent samples (dry weight) collected in Humboldt Bay exceeded the evaluation guideline. The TCDD equivalent values range from 0.01 ng/kg to 0.12 ng/kg. Samples were collected by Toxscan Inc. and Kinnetic Laboratories Inc. Data are summarized in the "Chemical Analysis, Toxicity Evaluation and Bioaccumulation Testing of Sediments from Humboldt Bay: Baseline Survey 1, Fiscal Year 1993" (Toxscan and Kinnetic 1994).

Data Reference:

Chemical Analysis, Toxicity Evaluation and Bioaccumulation Testing of Sediment from Humboldt Bay: Baseline Survey I, Fiscal Year 1993. Final Report. Prepared for US. Army Engineering District San Francisco Corps of Engineers. Final Revision September 1994

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Composite samples were collected at 3 sites in Humboldt Bay, as follows: (1) at Eureka Upper Channel, (2) at Samoa Turning Basin, and (3) at Fields Landing Lower Channel and Turning Basin.

Temporal Representation:

Samples were collected October 30 to November 1, 1992.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Quality control was conducted as specified in Toxscan Inc. and Kinnetic Laboratories Inc. (1994).

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 70917, Dioxin Toxic Equivalents	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

26044

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fish tissue analysis

Data Used to Assess Water Quality:

None of the 16 fish tissue TCDD equivalent samples (wet weight) collected in Mad River Slough exceed the evaluation guideline. The TCDD equivalent values range from 0.03 ng/kg to 0.29 ng/kg. Samples were collected by Geomatrix on behalf of Sierra Pacific Industries, Arcata Division Sawmill as fish fillets. Data are summarized by Geomatrix (2006).

Data Reference:

Revised Supplement to Scoping Ecological and Off-site Human Health Risk Assessment. Sierra Pacific Industries. Arcata Divsion Sawmill. Arcata, CA. Project No. 9329.000, Task 20

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Prevalence of Selected Target Chemical Contaminants in Sport Fish From Two California Lakes: Public health designed screening study. Sacramento, CA: Office of Environmental Health Hazard Assessment

Spatial Representation:

Samples were collected from 15 sites in the Mad River Slough, which drains to Humboldt Bay.

Temporal Representation:

Data was collected between March 16, 2005 and May 10, 2005.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storm events, etc.) that may have impacted these data.

QAPP Information:

Sampling and testing methods are described by Geomatrix (2006). The TEQs were calculated using World Health Organization mammalian toxic equivalent factors (2003), but were updated to the WHO 2005 values by Regional Water Board Staff.

QAPP Information Reference(s):

Revised Supplement to Scoping Ecological and Off-site Human Health Risk Assessment. Sierra Pacific Industries. Arcata Divsion Sawmill. Arcata, CA. Project No. 9329.000, Task 20

Line of Evidence (LOE) for Decision ID 70917, Dioxin Toxic Equivalents	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

26439

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Dissolved

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

This line of evidence (LOE) is a revision of LOE number 1 that was originally prepared by the State Water Resources Control Board for the 2006 303(d) List. The revision is necessary in order to state the proper evaluation guideline of 0.3 ng/kg instead of 3 ng/kg, and in order to provide references to the data used in the 2006 assessment.

As analyzed by the State Water Board, 14 out of 29 samples exceed the evaluation guideline. Crab, mussel, oyster, and sculpin samples were taken in the North and South Bays from 3/24/02 to 10/25/02. Data was originally cited as coming from Smith (2006). Available data can be found in the spreadsheet prepared by the State Water Resources Control Board (SWRCB 2006).

Data Reference:

Data for Dioxins and Furans in Humboldt Bay, March to October 2002. Compiled by the State Water Resources Control Board.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Prevalence of Selected Target Chemical Contaminants in Sport Fish From Two California Lakes: Public health designed screening study. Sacramento, CA: Office of Environmental Health Hazard Assessment

Spatial Representation:

Two sample locations (Lappe S2) in the southern section of the Bay, south of the mouth, and 12 samples in the northern section of Humboldt Bay. Some samples taken in close proximity were averaged (pursuant to Section 6.1.5.2 of the Policy).

Temporal Representation:

Samples were taken from 3/24/02 to 10/25/02.

Environmental Conditions:

QAPP Information:

Sierra Pacific Industries Humboldt Bay.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 70917, Dioxin Toxic Equivalents	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21430

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Not Recorded

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Chemical monitoring of sediments

Data Used to Assess Water Quality:

None of the 60 sediment TCDD equivalent samples (dry weight) collected in Humboldt Bay exceeded the evaluation guideline. The TCDD equivalent values range from 0.001 ng/kg to 0.75 ng/kg. Samples were collected by Toxscan Inc. and Kinnetic Laboratories Inc. Data are summarized in the "Chemical Analysis, Toxicity Evaluation and Bioaccumulation Exposure of Sediments from Humboldt Bay: Baseline Survey III, Fiscal Year 1995" (Toxscan and Kinnetic 1996).

Data Reference:

Chemical Analysis, Toxicity Evaluation and Bioaccumulation Exposure of Sediments from Humboldt Bay: Baseline Survey III, Fiscal Year 1995. Final Report. Prepared for: U.S. Army Engineering District San Francisco Corps of Engineers. February 1996

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Composite samples were collected at 4 sites in Humboldt Bay, as follows: (1) at Eureka Upper Channel, (2) at Samoa Turning Basin, (3) at Fields Landing Lower Channel and Turning Basin, and (4) at Eureka Upper Channel Extension.

Temporal Representation:

Samples were collected April 1 to 4, 1995.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Quality control was conducted as specified in Toxscan Inc. and Kinnetic Laboratories Inc. (1996). Although it is not specified if dioxin data is reported in dry or wet weight, EPA Method 8290 dictates reporting as dry weight, and it is thus assumed that all dioxin data are in dry weight.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 70917, Dioxin Toxic Equivalents	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21365

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Shellfish surveys

Data Used to Assess Water Quality:

None of the 34 shellfish tissue TCDD equivalent samples (wet weight) collected in Humboldt Bay exceed the evaluation guideline. The TCDD equivalent values range from 0 to 0.170 ng/kg. Samples were collected by the California Department of Health Services and data are summarized in their letter of March 3, 2006 (DHS 2006).

Data Reference:

Letter from Michael F. Hernandez of the California Department of Health Services, Food and Drug Branch to Mary Middleton of Pacific Shellfish Institute dated March 3, 2006. State of California Health and Human Services Agency, Department of Health Services

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Prevalence of Selected Target Chemical Contaminants in Sport Fish From Two California Lakes: Public health designed screening study. Sacramento, CA: Office of Environmental Health Hazard Assessment

Spatial Representation:

Samples were collected from 7 sites in the northern portion of Humboldt Bay, above Indian Island.

Temporal Representation:

Data was collected April 15-18, 2002.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storm events, etc.) that may have impacted these data.

QAPP Information:

The quality assurance and quality control measures used to collect the samples is unknown. Data were presented as TEQs for "dioxins in molluscan shellfish" and it is unknown which specific dioxin and/or furan congeners were present and used to calculate the TEQ.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 70917, Dioxin Toxic Equivalents	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

7810

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Shellfish surveys

Data Used to Assess Water Quality:

It is unknown if any of the 4 TCDD equivalent samples collected in Humboldt Bay exceed the evaluation guideline as data were presented as dry weight and the evaluation guideline is in wet weight. Since no conversion factor for calculating dry to wet weight was given in the data, the data could not be evaluated against the evaluation guideline. TCDD equivalent values range from 0.11 to 10.9 pg/g. TCDD equivalent values were analyzed from the tissue of the Bay Mussel (Mytilus edulus), a species endemic to Humboldt Bay. Samples were collected by Regional Water Board staff and data are summarized in a preliminary report (Rodriguez 1989).

Data Reference:

Preliminary Report on Mussel Collections and Analyzes for Dioxins and Furans along the North Coast from the Mouth of San Francisco Bay to Crescent City. California Regional Water Quality Control Board, North Coast Region

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Prevalence of Selected Target Chemical Contaminants in Sport Fish From Two California Lakes: Public health designed screening study. Sacramento, CA: Office of Environmental Health Hazard Assessment

Spatial Representation:

Samples were collected from 4 sites in Humboldt Bay as follows: (1) Mad River Slough Oyster Bed #1; (2) Bird Island West Side; (3) inside the North Jetty at the interface between the dolos and rock; and (4) in the Eureka Channel, Samoa Bridge pier, southeast side.

Temporal Representation:

One sample was collected from each site on June 5, 6, or 7, 1989.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storm events, etc.) that may have impacted these data.

QAPP Information:

The procedures used to collect and analyze the data are summarized by Rodriguez (1989). No project specific quality control spikes or duplicates were collected due to funding constraints.

QAPP Information Reference(s):


DECISION ID	169592	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Dioxin compounds (including 2,3,7,8-TCDD)
Final Listing Decision:	List on 303(d) list (TMDL required list)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	A Source Unknown
TMDL Priority:	Low
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Regional Board Conclusion: The pollutant was placed on the section 303(d) list in a previous assessment cycle under the pollutant name Dioxin Toxic Equivalents. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: (A) Dioxin toxic equivalents in Humboldt Bay are being considered for removal from the Section 303(d) List under Sections 4.5 and 4.6 of the Listing Policy. Nine lines of evidence are available in the administrative record to access this pollutant. These lines of evidence are discussed in detail below: (1) One of the lines of evidence (LOE 26439) is based on data compiled and assessed by the State Water Resources Control Board during the 2006 listing cycle and shows 14 out of 29 exceedances of the evaluation guideline used to interpret the water quality objective. Two lines of evidence (LOEs 21366 and 26044) are based on data assessed by the North Coast Regional Water Board during the current 2008 listing cycle and show 11 out of 41 exceedences of the evaluation guideline. Combined, there are 25 out of 70 exceedences of the evaluation guideline. The evaluation guideline is the dioxin toxic equivalent screening value for fish and shellfish tissue of 0.3 ng/kg by wet weight, which was developed by the Office of Environmental Health Hazard Assessment (Brodberg and Pollock 1999). The 0.3 ng/kg screening value is based on a low mean consumption value of fish of 21 g/day. (2) Four lines of evidence (LOEs 21425, 21430, 21383, and 21427) analyze sediment data from Humboldt Bay in relation to the Marine Habitat Beneficial Use. These lines of evidence show that the Marine Habitat Beneficial Use is protected due to 9 out of 117 exceedances of the Canadian Sediment Quality Guideline used to interpret the toxicity water quality objective, which are within the number of exceedances acceptable for a waterbody to be delisted per Table 4.1 of the Listing Policy. (3) The two remaining lines of evidence (LOEs 7810 and 21365) include data that are insufficient to make a decision regarding the dioxin impairment of Humboldt Bay. For LOE 7810, data could not be evaluated against the evaluation guideline as the data were presented in dry weight without a conversion factor, instead of wet weight. For LOE 21365, data quality was poor as information did not include sampling and analysis methods and quality assurance and control documents. (B) Based on readily available data and information, the weight of evidence indicates that there is sufficient justification in favor of continuing to place this water segment-pollutant combination on the Section 303(d) List in the Water Limited Segments category (i.e., sufficient justification to not delist). 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 in all but one line of evidence (LOE 21365). (2) The data used satisfies the data quantity requirements of Section 6.1.5 of the Policy. (3) Combined, 25 out of 70 fish or shellfish tissue samples exceed the 0.3 ng/kg OEHHA screening value used to interpret the toxicity water quality objective for the protection of the Commercial and Sport Fishing Beneficial Use, 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. This listing applies to the entire waterbody.

Regional Board Decision Recommendation:	After review of the available data and information, RWQCB staff concludes that the water body-pollutant combination should be placed on the section 303(d) list because applicable water quality standards are exceeded and a pollutant contributes to or causes the problem.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 169592, Dioxin compounds (including 2,3,7,8-TCDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21366

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Shellfish surveys

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Prevalence of Selected Target Chemical Contaminants in Sport Fish From Two California Lakes: Public health designed screening study. Sacramento, CA: Office of Environmental Health Hazard Assessment

Spatial Representation:

Temporal Representation:

Data was collected June 21 and October 21, 2002.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storm events, etc.) that may have impacted these data.

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 169592, Dioxin compounds (including 2,3,7,8-TCDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21425

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Not Recorded

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Chemical monitoring of sediments

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Composite samples were collected at 3 sites in Humboldt Bay, as follows: (1) at Eureka Upper Channel, (2) at Samoa Turning Basin, and (3) at Fields Landing Lower Channel and Turning Basin.

Temporal Representation:

Samples were collected October 30 to November 1, 1992.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Quality control was conducted as specified in Toxscan Inc. and Kinnetic Laboratories Inc. (1994).

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 169592, Dioxin compounds (including 2,3,7,8-TCDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

26044

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Fish fillet

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Fish tissue analysis

Data Used to Assess Water Quality:

Data Reference:

Revised Supplement to Scoping Ecological and Off-site Human Health Risk Assessment. Sierra Pacific Industries. Arcata Divsion Sawmill. Arcata, CA. Project No. 9329.000, Task 20

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Prevalence of Selected Target Chemical Contaminants in Sport Fish From Two California Lakes: Public health designed screening study. Sacramento, CA: Office of Environmental Health Hazard Assessment

Spatial Representation:

Samples were collected from 15 sites in the Mad River Slough, which drains to Humboldt Bay.

Temporal Representation:

Data was collected between March 16, 2005 and May 10, 2005.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storm events, etc.) that may have impacted these data.

QAPP Information:

QAPP Information Reference(s):

Revised Supplement to Scoping Ecological and Off-site Human Health Risk Assessment. Sierra Pacific Industries. Arcata Divsion Sawmill. Arcata, CA. Project No. 9329.000, Task 20

Line of Evidence (LOE) for Decision ID 169592, Dioxin compounds (including 2,3,7,8-TCDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21427

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Not Recorded

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Chemical monitoring of sediments

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Composite samples were collected at 3 sites in Humboldt Bay, as follows: (1) at Eureka Upper Channel, (2) at Samoa Turning Basin, and (3) at Fields Landing Lower Channel and Turning Basin.

Temporal Representation:

Samples were collected April 1 and 2, 1994.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Quality control was conducted as specified in Toxscan Inc. and Kinnetic Laboratories Inc. (1994).

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 169592, Dioxin compounds (including 2,3,7,8-TCDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

26439

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Dissolved

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Data Reference:

Data for Dioxins and Furans in Humboldt Bay, March to October 2002. Compiled by the State Water Resources Control Board.

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Prevalence of Selected Target Chemical Contaminants in Sport Fish From Two California Lakes: Public health designed screening study. Sacramento, CA: Office of Environmental Health Hazard Assessment

Spatial Representation:

Temporal Representation:

Samples were taken from 3/24/02 to 10/25/02.

Environmental Conditions:

QAPP Information:

Sierra Pacific Industries Humboldt Bay.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 169592, Dioxin compounds (including 2,3,7,8-TCDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21430

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Not Recorded

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Chemical monitoring of sediments

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Samples were collected April 1 to 4, 1995.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 169592, Dioxin compounds (including 2,3,7,8-TCDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21365

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Shellfish surveys

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Prevalence of Selected Target Chemical Contaminants in Sport Fish From Two California Lakes: Public health designed screening study. Sacramento, CA: Office of Environmental Health Hazard Assessment

Spatial Representation:

Samples were collected from 7 sites in the northern portion of Humboldt Bay, above Indian Island.

Temporal Representation:

Data was collected April 15-18, 2002.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storm events, etc.) that may have impacted these data.

QAPP Information:

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 169592, Dioxin compounds (including 2,3,7,8-TCDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Dissolved

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

Fourteen out of 29 samples exceeded the screening value. Crab, mussel, oyster and sculpin samples were taken in the North and South Bays from 3/24/02 to 10/25/02 (Smith, 2006).

Data Reference:

Placeholder reference 2006 303(d)

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

North Coast RWQCB Basin Plan: 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:

Placeholder reference 2006 303(d)

Evaluation Guideline:

OEHHA Screening Value 3 ng/kg.

Guideline Reference:

Placeholder reference 2006 303(d)

Spatial Representation:

Two sample location (Lappe S2) in the southern section of the bay, south of the mouth and 12 samples in the northern section of Humboldt Bay. Some samples taken in close proximity were averaged (pursuant to Section 6.1.5.2 of the Policy).

Temporal Representation:

Samples were taken from 3/24/02 to 10/25/02.

Environmental Conditions:

QAPP Information:

Sierra Pacific Industries Humboldt Bay.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 169592, Dioxin compounds (including 2,3,7,8-TCDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21382

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Sediment

Matrix:

Sediment

Fraction:

Not Recorded

Beneficial Use:

Marine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Samples were collected at 3 sites in Humboldt Bay, as follows: 2 sites in the mud flats of Humboldt Bay (S-8 & S-9), and 1 site in Hookton Slough (S-10).

Temporal Representation:

Samples collected April 18, 2006.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Quality control was conducted in accordance with the Soil/Water/Air Protection Enterprise's "Sampling and Analysis Plan" (Humboldt Baykeeper 2006).

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 169592, Dioxin compounds (including 2,3,7,8-TCDD)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

7810

Pollutant:

Dioxin Toxic Equivalents

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Not Recorded

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Shellfish surveys

Data Used to Assess Water Quality:

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Prevalence of Selected Target Chemical Contaminants in Sport Fish From Two California Lakes: Public health designed screening study. Sacramento, CA: Office of Environmental Health Hazard Assessment

Spatial Representation:

Temporal Representation:

One sample was collected from each site on June 5, 6, or 7, 1989.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storm events, etc.) that may have impacted these data.

QAPP Information:

The procedures used to collect and analyze the data are summarized by Rodriguez (1989). No project specific quality control spikes or duplicates were collected due to funding constraints.

QAPP Information Reference(s):


DECISION ID	75456	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	2,3,5,6-Tetrachlorophenol
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:	Regional Board Conclusion: The pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: Regional Water Board conclusion: This pollutant was considered for placement on the section 303(d) List in a previous Integrated Report cycle. No new information was reviewed for this current Integrated Report cycle. Therefore, the previous conclusion remains unchanged, and is as follows: Tetrachlorophenol in Humboldt Bay is being considered for placement on the 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. It is unknown whether any of the 4 Humboldt Bay fish tissue samples analyzed for tetrachlorophenol exceed the objective, as there is no suitable evaluation guideline relating potential public health concerns from ingesting fish tissue containing tetrachlorophenol. Samples ranged from 2.75 ppb to 6.00 ppb. Based on the readily available data and information, the weight of evidence indicates that there is insufficient information available to determine if it is appropriate to place this water segment-pollutant combination on the Section 303(d) list in the Water Quality Limited Segments category.

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:

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 75456, 2,3,5,6-Tetrachlorophenol	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21443

Pollutant:

2,3,5,6-Tetrachlorophenol

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

None

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

BIOLOGICAL MONITORING

Data Used to Assess Water Quality:

It is unknown whether any of the 4 Humboldt Bay fish tissue samples analyzed for tetrachlorophenol exceed the objective, as there is no suitable evaluation guideline relating potential public health concerns from ingesting fish tissue containing tetrachlorophenol. Samples ranged from 2.75 ppb to 6.00 ppb. These samples were collected by the California State Mussel Watch Program. Data are summarized in the "California State Mussel Watch Ten Year Data Summary 1977-1987" (SWRCB 1988).

Data Reference:

California State Mussel Watch Ten Year Data Summary 1977-1987. Water Quality Monitoring Report No. 87-3. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected from 4 sites in Humboldt Bay. These sites are as follows: (1) at Mad River Slough, (2) at Arcata Ruin, (3) at Samoa Bridge West, and (4) at Woodley Island.

Temporal Representation:

Samples were collected on February 15, 1984.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Samples were collected according to the protocols provided by the CA State Mussel Watch Program (California State Mussel Watch 1988, Appendix A).

QAPP Information Reference(s):

California State Mussel Watch Ten Year Data Summary 1977-1987. Water Quality Monitoring Report No. 87-3. State Water Resources Control Board


DECISION ID	78094	Region 1
Eureka Plain HU, Humboldt Bay

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)(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 3.1 of the Listing Policy. Under section 3.1 a single line(s) of evidence are necessary to assess listing status. One line of evidence is available in the administrative record to assess this pollutant. None of the 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. None of the 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 16 samples is needed to determine if a beneficial use is fully supported using table 3.1. 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. 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 78094, Arsenic	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

31778

Pollutant:

Arsenic

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Shellfish

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Shellfish surveys

Data Used to Assess Water Quality:

One of one sample exceeded the evaluation guideline. Data were reported on a dry weight basis and were converted to a wet weight basis by multiplying the dry-weight concentration by a factor of 1 minus the percentage of moisture content expressed as a decimal. Ten percent of the total arsenic result was used to estimate of the amount of inorganic arsenic in the sample; this number was screened against the guideline. Two composite samples were collected from Humboldt Bay within one week, and thus, the average of the two composite samples was calculated, per USEPA 2001, resulting in a sample value of 0.0105 ppm.

Data Reference:

State Mussel Watch Program Data 1977-2000; Winter 2007-Winter 2009. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for arsenic in shellfish tissue is 0.0052 ppm. This screening level assumes an average body weight of 70 kg and a consumption rate of 21 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. (Brodberg, R.K., and G.A. Pollock, 1999; Klasing, S., and R. Brodberg, 2008; OEHHA, 2004)

Guideline Reference:

Guidance for Assessing Chemical Contaminant Data for Use In Fish Advisories Volume 1: Fish Sampling and Analysis

Spatial Representation:

Samples were collected in Humboldt Bay at: (EUSB) - Eureka Samoa Bridge and another from (HMBJ) - Eureka Humboldt Bay Jetty. One composite was made from fish at each of the two locations within Humboldt Bay.

Temporal Representation:

Samples were collected from Humboldt Bay as follows: EUSB on January 23, 2009 and from HMBJ on January 22, 2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	70996	Region 1
Eureka Plain HU, Humboldt Bay

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

Regional Board Conclusion:	Regional Board Conclusion: The pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: This pollutant is being considered for placement on the 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 to assess protection of the commercial and sport fishing (COMM) 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 section 303(d) list in the Water Quality Limited Segments category (i.e., sufficient justification to not 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) The data in LOE 31885 evaluating the COMM beneficial use were all detect not quantifiable (DNQ) and the data reporting limit and method detection limit were above the evaluation guideline. Thus, per the Listing Policy the data were not used in this assessment. Therefore, there are no data available to assess against protection of the MUN beneficial use. (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:	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:

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 70996, Cadmium	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

9109

Pollutant:

Cadmium

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

None

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

BIOLOGICAL MONITORING

Data Used to Assess Water Quality:

None of the 80 Humboldt Bay fish tissue samples analyzed exceeded the screening value for cadmium. These samples were collected by the California State Mussel Watch Program. Data are summarized in the "California State Mussel Watch Data Summary 1977-1997" (SWRCB 1988).

Data Reference:

California State Mussel Watch Ten Year Data Summary 1977-1987. Water Quality Monitoring Report No. 87-3. State Water Resources Control Board

State Mussel Watch Program Data 1977-2000: trace elements by wet weight. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Office of Environmental Health Hazard Assessment (OEHHA) Screening Value of 3 mg/kg to protect human health when consuming fish (OEHHA, 1999).

Guideline Reference:

Prevalence of Selected Target Chemical Contaminants in Sport Fish From Two California Lakes: Public health designed screening study. Sacramento, CA: Office of Environmental Health Hazard Assessment

Spatial Representation:

The samples were collected from 16 sites in Humboldt Bay. These sites are as follows: (1) at Mad River Slough, (2) at Arcata Ruin, (3) at Samoa Bridge West, (4) Samoa Bridge East, (5) at Woodley Island, (6) at Eureka STP, (6) at Eureka STP Outfall, (7) Eureka STP Control, (8) C Street, (9) J Street, (10) H Street, (11) Eureka Channel, (12) Louisiana Pacific Dock, (13) EDA Dock, (14) Fields Landing, (15) E Street and, (16) Halberson Shore

Temporal Representation:

The samples were collected from 1980 to 1997.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Samples were collected according to the protocols provided by the CA State Mussel Watch Program (California State Mussel Watch 1988, Appendix A).

QAPP Information Reference(s):

California State Mussel Watch Ten Year Data Summary 1977-1987. Water Quality Monitoring Report No. 87-3. State Water Resources Control Board


DECISION ID	71676	Region 1
Eureka Plain HU, Humboldt Bay

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

Regional Board Conclusion:	Regional Board Conclusion: The pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: Regional Water Board conclusion: This pollutant was considered for placement on the section 303(d) List in a previous Integrated Report cycle. No new information was reviewed for this current Integrated Report cycle. Therefore, the previous conclusion remains unchanged, and is as follows: Chromium in Humboldt Bay is being considered for placement on the 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. It is unknown whether any of the 6 Humboldt Bay fish tissue samples analyzed for chromium exceed the objective, as there is no suitable evaluation guideline relating potential public health concerns from ingesting fish tissue containing cadmium. Chromium values ranged from 0.6 ppm to 0.88 ppm. Based on the readily available data and information, the weight of evidence indicates that there is insufficient information available to determine if it is appropriate to place this water segment-pollutant combination on the Section 303(d) list in the Water Quality Limited Segments category.

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 71676, Chromium	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

9110

Pollutant:

Chromium (total)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Total

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

BIOLOGICAL MONITORING

Data Used to Assess Water Quality:

It is unknown whether any of the 6 Humboldt Bay fish tissue samples analyzed for chromium exceed the objective, as there is no suitable evaluation guideline relating potential public health concerns from ingesting fish tissue containing chromium. Chromium values ranged from 0.73 ppm to 1.87 ppm. These samples were collected by the California State Mussel Watch Program. Data are summaried in the "California State Mussel Watch Ten Year Data Summary 1977-1987" (SWRCB 1988).

Data Reference:

California State Mussel Watch Ten Year Data Summary 1977-1987. Water Quality Monitoring Report No. 87-3. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

The samples were collected during 1 site visit on February 15, 1984.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Samples were collected according to the protocols provided by the CA State Mussel Watch Program (California State Mussel Watch 1988, Appendix A).

QAPP Information Reference(s):

California State Mussel Watch Ten Year Data Summary 1977-1987. Water Quality Monitoring Report No. 87-3. State Water Resources Control Board


DECISION ID	170541	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Indicator Bacteria
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:	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 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 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. No data has been collected from on or after October 21, 2012 and so the existing decision will carry-over. Beneficial use support will be reassessed in a future cycle, if more data are available.

Regional Board Decision Recommendation:	This region was not assessed this cycle. All decisions have been carried over from the previous cycle and remain the same.

State Board Review of Regional Board Conclusion and Recommendation:

State Board Decision Recommendation:

Line of Evidence (LOE) for Decision ID 170541, Indicator Bacteria	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

31815

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Shellfish Harvesting

Number of Samples:

1555

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

Twenty of the 1555 samples sollected in Humboldt Bay exceeded the 43MPN/100ml objective.

Data Reference:

Data for bacteria in Humboldt Bay, Jan. 2004-Aug. 2010

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Per the Basin Plan (NCRWQCB 2011): At all areas where shellfish may be harvested for human consumption (SHELL), the fecal coliform concentration throughout the water column shall not exceed 43MPN/100ml for a 5-tube decimal dilution test or 49MPN/100ml when a three-tube decimal dilution test is used.

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected from fourteen sites in Humboldt Bay. Those sites were WQ # 20, 21, 22, 24, 26, 28, 31, 33, 34, 43, 45, 51, 52, and 53.

Temporal Representation:

The samples were collected once a month from 2000 to 2010.

Environmental Conditions:

QAPP Information:

The samples were collected under the Management Plan For Commercial Shellfishing In Humboldt Bay, California. California Department of Public Health.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170541, Indicator Bacteria	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

23463

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total Dissolved

Beneficial Use:

Shellfish Harvesting

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

None of the 16 fecal coliform samples collected in Humboldt Bay exceed the 43 MPN / 100 ml objective. Samples range from non detect (with a detection limit of less than 2 MPN / 100 ml) to 23 MPN / 100 ml. Samples were collected by the Wiyot Tribe and data are summarized by the Tribe (Wiyot 2007).

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Per the Basin Plan (NCRWQCB 2007): The bacteriological quality of waters of the North Coast Region shall not be degraded beyond natural background levels. In no case shall coliform concentrations in waters of the North Coast Region exceed the following: In waters designated for contact recreation (REC-1), the median fecal coliform concentration based on a minimum of not less than five samples for any 30-day period shall not exceed 50 MPN* / 100 ml, nor shall more than 10% of total samples during any 30-day period exceed 400 MPN / 100 ml. At all areas where shellfish may be harvested for human consumption (SHELL), the fecal coliform concentration throughout the water column shall not exceed 43 MPN / 100 ml for a 5-tube decimal dilution test or 49 MPN / 100 ml when a three-tube decimal dilution is used. *Note: MPN is the most probable number of coliform units.

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Samples were collected according to Wiyot Tribe¿s ¿Draft Quality Assurance Program Plan (QAPP) for Water Quality Assessment and Monitoring¿ (McKernan et al. 2004).

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170541, Indicator Bacteria	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

33296

Pollutant:

Fecal Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Water Contact Recreation

Number of Samples:

1555

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

The samples were collected from fourteen sites in Humboldt Bay. One of the 1556 samples exceeded the evaluation guideline. The sample value exceeding the evaluation guideline was 500 MPN.

Data Reference:

Data for bacteria in Humboldt Bay, Jan. 2004-Aug. 2010

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

The bacteriological quality of waters of the North Coast Region shall not be degraded beyond natural background levels. In no case shall coliform concentrations in waters of the North Coast Region exceed the following: In waters designated for contact recreation (REC-1), the median fecal coliform concentration based on a minimum of not less than 5 samples for any 30-day period shall not exceed 50 MPN/ 100 ml, nor shall more than 10% of total samples during any 30-day period exceed 400 MPN / 100 ml. Water Quality Control Plan, North Coast Region (NCRWQCB 2011)

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

Beach posting is recommended when single sample fecal coliform levels exceed 400 MPN / 100 ml. Draft Guidance for Fresh Water Beaches" (DHS 2011).

Guideline Reference:

Draft Guidance for Fresh Water Beaches. Last Update: May 8, 2006. Initial Draft: November 1997. California Department of Public Health.

Spatial Representation:

The samples were collected from fourteen sites in Humboldt Bay. Those sites were WQ # 20, 21, 22, 24, 26, 28, 31, 33, 34, 43, 45, 51, 52, and 53.

Temporal Representation:

The samples were collected once a month from 2000 to 2010.

Environmental Conditions:

QAPP Information:

The samples were collected under the Management Plan For Commercial Shellfishing In Humboldt Bay, California. California Department of Public Health.

QAPP Information Reference(s):

Line of Evidence (LOE) for Decision ID 170541, Indicator Bacteria	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

24852

Pollutant:

Total Coliform

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

Total

Beneficial Use:

Water Contact Recreation

Number of Samples:

Number of Exceedances:

Data and Information Type:

PHYSICAL/CHEMICAL MONITORING

Data Used to Assess Water Quality:

None of the 16 total coliform samples collected in Humboldt Bay exceed the 10,000 MPN / 100 ml objective. Samples range from less than 2 to more than 1,600 MPN / 100 ml. Samples were collected by the Wiyot Tribe and data are summarized by the Tribe (Wiyot 2007).

Data Reference:

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Per the "Draft Guidance for Fresh Water Beaches" (DHS 2006): Beach posting is recommended when single sample total coliform levels exceed 10,000 MPN / 100 ml.

Guideline Reference:

Draft Guidance for Fresh Water Beaches. Last Update: May 8, 2006. Initial Draft: November 1997. California Department of Public Health.

Spatial Representation:

Temporal Representation:

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Samples were collected according to Wiyot Tribe¿s ¿Draft Quality Assurance Program Plan (QAPP) for Water Quality Assessment and Monitoring¿ (McKernan et al. 2004).

QAPP Information Reference(s):


DECISION ID	79098	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	PAHs (Polycyclic Aromatic Hydrocarbons)
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:	Regional Board Conclusion: The pollutant was considered for placement on the section 303(d) list in a previous assessment cycle. No new information was reviewed for this current assessment cycle. Therefore, the previous conclusion remains unchanged, and is as follows: This pollutant is being considered for placement on the 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 to assess protection of the commercial and sport fishing (COMM) 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 section 303(d) list in the Water Quality Limited Segments category (i.e., sufficient justification to not 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 two samples exceed the evaluation guideline, and this sample size is insufficient to determine with the power and confidence of the Listing Policy if standards are not met, as a minimum of either (A) 16 samples, or (B) greater than or equal 2 exceedances of the objective with less than 16 samples is needed for application of Table 3.1. (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:	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:

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 79098, PAHs (Polycyclic Aromatic Hydrocarbons)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

31737

Pollutant:

PAHs (Polycyclic Aromatic Hydrocarbons)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

Shellfish

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

Shellfish surveys

Data Used to Assess Water Quality:

One sample result of 2.53 ppb did exceed the guideline. Non-detect results were reported as zero (no method detection limits were provided) and were not included in the assessment. Data were reported on a dry weight basis and were converted to a wet weight basis by multiplying the dry-weight concentration by a factor of 1 minus the percentage of moisture content expressed as a decimal. The total PAHs were calculated as the potency equivalency concentration or the sum of the toxic equivalency factors multiplied by the concentrations of: Acenaphthene, Acenaphthylene, Anthracene, Benz[a]anthracene, Benzo[a]pyrene, Benzo[b]fluoranthene, Benzo[g,h,i]perylene, Benzo[k]fluoranthene, Dibenzo[a,h]anthracene, Chrysene, Fluoranthene, Fluorene, Indeno[1,2,3-c,d]pyrene, Phenanthrene, and Pyrene.

Data Reference:

State Mussel Watch Program Data 1977-2000; Winter 2007-Winter 2009. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) for the North Coast Region

Evaluation Guideline:

The modified OEHHA Fish Contaminant Goal for polycyclic aromatic hydrocarbons in shellfish tissue is 1.1 ppb. This screening level assumes an average body weight of 70 kg and a consumption rate of 21 g/day for a 30 year exposure over a 70-year lifetime. This constituent is a carcinogen therefore the risk level is set to one in a million. (Brodberg, R.K., and G.A. Pollock, 1999; Klasing, S., and R. Brodberg, 2008; USEPA, 2000)

Guideline Reference:

Development of Fish Contaminant Goals and Advisory Tissue Levels for Common Contaminants in California Sport Fish: Chlordane, DDTs, Dieldrin, Methylmercury, PCBs, Selenium, and Toxaphene

Spatial Representation:

Samples are collected by hand from three sub-locations for each site. The composite samples were collected from site EUSB at Eureka Samoa Bridge, and another from HMBJ at Eureka Humboldt Bay Jetty.

Temporal Representation:

Samples were collected from Humboldt Bay as follows: EUSB on 1/23/2009 and from HMBJ on 1/22/2009.

Environmental Conditions:

QAPP Information:

QAPP Information Reference(s):


DECISION ID	70912	Region 1
Eureka Plain HU, Humboldt Bay

Pollutant:	Pentachlorophenol (PCP)
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:	Regional Water Board conclusion: This pollutant was considered for placement on the section 303(d) List in a previous Integrated Report cycle. No new information was reviewed for this current Integrated Report cycle. Therefore, the previous conclusion remains unchanged, and is as follows: Pentachlorophenol in Humboldt Bay is being considered for placement on the 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. It is unknown whether any of the 4 Humboldt Bay fish tissue samples analyzed for pentachlorophenol exceed the objective, as there is no suitable evaluation guideline relating potential public health concerns from ingesting fish tissue containing pentachlorophenol. Samples ranged from 20.52 ppb to 153.6 ppb. Based on the readily available data and information, the weight of evidence indicates that there is insufficient information available to determine if it is appropriate to place this water segment-pollutant combination on the Section 303(d) list in the Water Quality Limited Segments category.

Regional Board Decision Recommendation:	This region was not assessed this cycle. All decisions have been carried over from the previous cycle and remain the same.

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 70912, Pentachlorophenol (PCP)	Region 1
Eureka Plain HU, Humboldt Bay

LOE ID:

21422

Pollutant:

Pentachlorophenol (PCP)

LOE Subgroup:

Pollutant-Tissue

Matrix:

Tissue

Fraction:

None

Beneficial Use:

Commercial or recreational collection of fish, shellfish, or organisms

Number of Samples:

Number of Exceedances:

Data and Information Type:

BIOLOGICAL MONITORING

Data Used to Assess Water Quality:

It is unknown whether any of the 4 Humboldt Bay fish tissue samples analyzed for pentachlorophenol exceed the objective, as there is no suitable evaluation guideline relating potential public health concerns from ingesting fish tissue containing pentachlorophenol. Samples ranged from 20.52 ppb to 153.6 ppb. These samples were collected by the California State Mussel Watch Program. Data are summarized in the "California State Mussel Watch Ten Year Data Summary 1977-1987" (SWRCB 1988).

Data Reference:

California State Mussel Watch Ten Year Data Summary 1977-1987. Water Quality Monitoring Report No. 87-3. State Water Resources Control Board

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

Objective/Criterion Reference:

Water Quality Control Plan (Basin Plan) - North Coast Region (Region 1)

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

The samples were collected from 4 sites in Humboldt Bay. These sites are as follows: (1) at Mad River Slough, (2) at Arcata Ruin, (3) at Samoa Bridge West, and (4) at Woodley Island.

Temporal Representation:

The samples were collected during 1 site visit on February 15, 1984.

Environmental Conditions:

There are no known environmental conditions (e.g., seasonality, land use practices, fire events, storms, etc.) that are related to these data.

QAPP Information:

Samples were collected according to the protocols provided by the CA State Mussel Watch Program (California State Mussel Watch 1988, Appendix A).

QAPP Information Reference(s):

California State Mussel Watch Ten Year Data Summary 1977-1987. Water Quality Monitoring Report No. 87-3. State Water Resources Control Board