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DECISION ID |
10793 |
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| Pollutant: |
Nitrate |
| 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 |
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| Weight of Evidence: |
This pollutant is being considered for listing under section 3.1 of the Listing Policy. Under section 3.1, water segments shall be evaluated to determine whether the weight of evidence demonstrates that a water quality standard is not attained. One line of evidence is available in the administrative record to assess this water body.
Based on the readily available data for this water body, 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.
This conclusion is based on the staff findings that:
1. The data used satisfy the data quality requirements of section 6.1.4 of the Policy.
2. The data used satisfy the data quantity requirements of section 6.1.5 of the Policy.
3. None of three available concentrations exceeded the water quality guideline and this does not exceed the allowable frequency using 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. |
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| RWQCB Board Decision / Staff Recommendation: |
After review of the available data and information, Water Board staff concludes that there is insufficient information to demonstrate that this water body is not meeting applicable water quality standards to support the cold freshwater habitat beneficial use. Therefore, the water body-pollutant combination should not be placed on the section 303(d) list. |
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| SWRCB Board Decision / Staff Recommendation: |
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| USEPA Decision: |
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| LOE ID: |
23466 |
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| Pollutant: |
Nitrate |
| LOE Subgroup: |
Pollutant-Water |
| Matrix: |
Water |
| Fraction: |
Dissolved |
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| Beneficial Use: |
Cold Freshwater Habitat |
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| Number of Samples: |
3 |
| Number of Exceedances: |
0 |
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| Data and Information Type: |
PHYSICAL/CHEMICAL MONITORING |
| Data Used to Assess Water Quality: |
Water quality assessment in Morses Gulch Creek was conducted by SWAMP in 2005-2006. Nitrate concentrations (NO3-N) were analyzed three times and ranged from 0.19 to 0.23mg/L. The measured nitrate levels did not exceed the guideline threshold indicative of conditions leading to excessive algal growth, however, no data on algae or macrophytes are available to ensure compliance with the water quality objective. |
| Data Reference: |
Data collected by the Surface Water Ambient Monitoring Program, San Francisco Bay Regional Water Quality Control Board. Years 4 and 5 Assessment |
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| 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. |
| Objective/Criterion Reference: |
San Francisco Bay Basin (Region 2) Water Quality Control Plan (Basin Plan) |
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| Evaluation Guideline: |
Total nitrogen levels greater than 0.5 mg/L can result in large masses of nuisance algae unless other factors limit algae growth (Bowie et al. 1985; Biggs 2000). Since nitrate is one component of total nitrogen in water, nitrate levels should also be less than 0.5 mg/L. |
| Guideline Reference: |
Eutrophication of streams and rivers: dissolved nutrient-chlorophyll relationships for benthic algae. J. N. Am. Benthol. Soc. 19:17-31 |
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Rates, Constant, and Kinetics Formulations in Surface Water Quality Modeling, 2nd Edition. EPA/600/3-85/040. USEPA Environmental Research Laboratory, Athens, GA |
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| Spatial Representation: |
Nitrate was sampled at one monitoring location in the lower reach of Morses Gulch Creek in the close proximity to Bolinas Lagoon. |
| Temporal Representation: |
Water samples were collected for nitrate analyses during spring (April 2005), summer dry season (June 2005) and winter wet season (February 2006). |
| Environmental Conditions: |
Morses Gulch is a small intermittent creek draining to Bolinas Lagoon in West Marin County. |
| QAPP Information: |
All samples were collected and analyzed using procedures comparable with the SWAMP Quality Assurance Management Plan (SWRCB, 2002). |
| QAPP Information Reference(s): |
Quality Assurance Management Plan for the State of California's Surface Water Ambient Monitoring Program. Sacramento, CA. State Water Resources Control Board. SWAMP. December 2002 (1st version)
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