| Water Body Name: | North Slough (Napa County) |
| Water Body ID: | CAR2065008020110829151118 |
| Water Body Type: | River & Stream |
DECISION ID |
98507 |
Region 2 |
North Slough (Napa County) |
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| 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 | 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 of evidence is necessary to assess listing status.
One line of evidence is available in the administrative record to assess this pollutant. Zero of six 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. Zero of six samples exceed the guideline 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. |
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| LOE ID: | 92326 | ||||
| Pollutant: | Mercury | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | Total | ||||
| Beneficial Use: | Estuarine Habitat | ||||
| Number of Samples: | 6 | ||||
| Number of Exceedances: | 0 | ||||
| Data and Information Type: | Non-fixed station physical/chemical (conventional + toxicants) | ||||
| Data Used to Assess Water Quality: | None of the six samples exceeded the CTR. | ||||
| Data Reference: | NPDES receiving water data for bacteria and metals in San Francisco Bay, Jan. 2005-Sep. 2009 | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | All waters shall be maintained free of toxic substances that are lethal to or that produce other detrimental responses in aquatic organisms. | ||||
| Objective/Criterion Reference: | Water Quality Control Plan (Basin Plan) San Francisco Bay Basin (Region 2) | ||||
| Evaluation Guideline: | National Recommended Water Quality Criterion Continuous Concentrations (4-day average concentrations) for saltwater aquatic organisms exposure to elemental mercury is 0.94 ug/L. | ||||
| Guideline Reference: | National Recommended Water Quality Criteria. United States Environmental Protection Agency. Office of Water. Office of Science and Technology | ||||
| Spatial Representation: | Samples were taken from one sample locations in the receiving water of an adjacent American Canyon waste-water treatment plant. Samples taken within one-week were averaged. | ||||
| Temporal Representation: | Samples were collected monthly from January of 2005 through June of 2005. | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Samples were collected for NPDES ORDER No. R2-2010-0054. | ||||
| QAPP Information Reference(s): | |||||