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

Supporting Information

Regional Board 2 - San Francisco Bay Region

Water Body Name:	Hill Slough
Water Body ID:	CAR2072300020050602210728
Water Body Type:	River & Stream


DECISION ID	68186	Region 2
Hill Slough

Pollutant:	Mercury
Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	Do Not List on 303(d) list (TMDL required list)(2016)
Revision Status	Revised
Sources:	Historic Land Management Activities
TMDL Name:	Suisun Marsh Dissolved Oxygen and Mercury TMDL
TMDL Project Code:	553
Date TMDL Approved by USEPA:	12/31/2018
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Hill Slough is part of the Suisun Marsh system. As such, the impairments for Suisun Marsh are applicable to sloughs within the marsh. Further, the TMDL for Suisun Marsh will resolve the impairments for sloughs within the Suisun Marsh system. Accordingly, the mercury impairment in Hill Slough will be addressed and resolved by the Suisun Marsh TMDL for dissolved oxygen approved by USEPA on 12/31/2018.

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:	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 68186, Mercury	Region 2
Hill Slough

LOE ID:

1829

Pollutant:

Mercury

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:

Fish tissue analysis

Data Used to Assess Water Quality:

Two samples were collected on the same day at the same location (hence they are considered one sample). Thus, 1 out of 1 sample exceeded. Two filet individual samples of striped bass were collected in 1997 (TSMP, 2002).

Data Reference:

Placeholder reference 2006 303(d)

SWAMP Data:

Non-SWAMP

Water Quality Objective/Criterion:

San Francisco Bay RWQCB Basin Plan: Many pollutants can accumulate on particles, in sediment, or bioaccumulate in fish and other aquatic organisms. Controllable water quality factors shall not cause a detrimental increase in concentrations of toxic substances found in bottom sediments or aquatic life. Effects on aquatic organisms, wildlife, and human health will be considered.

Objective/Criterion Reference:

Placeholder reference 2006 303(d)

Evaluation Guideline:

OEHHA Screening Value 0.3 ug/g (Brodberg and Pollock, 1999).

Guideline Reference:

Placeholder reference 2006 303(d)

Spatial Representation:

One station located upstream of McCoy Ditch near Suisun City.

Temporal Representation:

Samples were collected 2/27/97.

Environmental Conditions:

QAPP Information:

Environmental Chemistry Quality Assurance and Data Report for the Toxic Substances Monitoring Program,1996 to 2000. Department of Fish and Game.

QAPP Information Reference(s):


DECISION ID	100852	Region 2
Hill Slough

Pollutant:	Oxygen, Dissolved
Final Listing Decision:	List on 303(d) list (being addressed by USEPA approved TMDL)
Last Listing Cycle's Final Listing Decision:	New Decision
Revision Status	Revised
Sources:	Historic Land Management Activities
TMDL Name:	Suisun Marsh Dissolved Oxygen and Mercury TMDL
TMDL Project Code:	553
Date TMDL Approved by USEPA:	12/31/2018
Impairment from Pollutant or Pollution:	Pollutant

Regional Board Conclusion:	Hill Slough is part of the Suisun Marsh system. As such, the impairments for Suisun Marsh are applicable to sloughs within the marsh. Further, the TMDL for Suisun Marsh will resolve the impairments for sloughs within the Suisun Marsh system. Accordingly, the dissolved oxygen impairment in Hill Slough will be addressed and resolved by the Suisun Marsh TMDL for dissolved oxygen approved by USEPA on 12/31/2018. We should note that the impairment for Suisun Marsh was originally for organic enrichment/low dissolved oxygen. While this original pollutant description is the most accurate, the impairment for this slough is given as low dissolved oxygen.

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:	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 100852, Oxygen, Dissolved	Region 2
Hill Slough

LOE ID:

125376

Pollutant:

Oxygen, Dissolved

LOE Subgroup:

Pollutant-Water

Matrix:

Water

Fraction:

None

Beneficial Use:

Estuarine Habitat

Number of Samples:

Number of Exceedances:

Data and Information Type:

Not Specified

Data Used to Assess Water Quality:

This is a placeholder LOE to allow Hill Slough dissolved oxygen impairment to be associated with the TMDL for Suisun Marsh

Data Reference:

Staff Report for Proposed Basin Plan Amendment - Establish Water Quality Objectives and a Total Maximum Daily Load for Dissolved Oxygen in Suisun Marsh and add Suisun Marsh to the SF Bay Mercury TMDL

SWAMP Data:

Water Quality Objective/Criterion:

This is a placeholder LOE to allow Hill Slough dissolved oxygen impairment to be associated with the TMDL for Suisun Marsh. This placeholder LOE will fulfill database requirements to create a listing for Hill Slough. This slough listing will subsequently be associated with the TMDL for Suisun Marsh - which aims to resolve the mercury and low DO/organic enrichment impairments. Hill Slough is part of the Suisun Marsh system so resolution of the Suisun Marsh impairments will resolve those in Hill Slough as well.

Objective/Criterion Reference:

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

Evaluation Guideline:

Guideline Reference:

Spatial Representation:

Temporal Representation:

Environmental Conditions:

QAPP Information:

This is a placeholder LOE to allow Hill Slough dissolved oxygen impairment to be associated with the TMDL for Suisun Marsh.

QAPP Information Reference(s):