| Water Body Name: | Arroyo Seco (Sonoma County) |
| Water Body ID: | CAR2064002020210519034958 |
| Water Body Type: | River & Stream |
DECISION ID |
144635 |
Region 2 |
Arroyo Seco (Sonoma County) |
||
| Pollutant: | Oxygen, Dissolved |
| 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: | |
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| LOE ID: | 285751 | ||||
| Pollutant: | Oxygen, Dissolved | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | Total | ||||
| Beneficial Use: | Warm Freshwater Habitat | ||||
| Number of Samples: | 3 | ||||
| Number of Exceedances: | 0 | ||||
| Data and Information Type: | PHYSICAL/CHEMICAL MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed Clean Streams in S. SoCo Pathogen Source Detection data for Arroyo Seco (Sonoma County) to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Oxygen, Dissolved. | ||||
| Data Reference: | Field, Habitat, WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 2. | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | Dissolved oxygen objectives for waters designated as warm water habitat shall be of a 5.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.) | ||||
| Objective/Criterion Reference: | Water Quality Control Plan (Basin Plan) San Francisco Bay Basin (Region 2) | ||||
| Evaluation Guideline: | |||||
| Guideline Reference: | |||||
| Spatial Representation: | The samples were collected at 1 monitoring site: 206SCH00905 (Arroyo Seco at Schell Creek). | ||||
| Temporal Representation: | The samples were collected between the dates of 2019-02-06 and 2019-02-19 | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Sonoma County Permit and Resource Management Department. 2019. Clean Streams in Southern Sonoma County (CS3C). | ||||
| QAPP Information Reference(s): | Clean Streams in Southern Sonoma County (CS3C) | ||||
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| LOE ID: | 285863 | ||||
| Pollutant: | Oxygen, Dissolved | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | Total | ||||
| Beneficial Use: | Cold Freshwater Habitat | ||||
| Number of Samples: | 3 | ||||
| Number of Exceedances: | 0 | ||||
| Data and Information Type: | PHYSICAL/CHEMICAL MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed Clean Streams in S. SoCo Pathogen Source Detection data for Arroyo Seco (Sonoma County) to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Oxygen, Dissolved. | ||||
| Data Reference: | Field, Habitat, WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 2. | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | Dissolved oxygen objectives for waters designated as cold water habitat shall be of a 7.0 mg/l minimum. (Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives.) | ||||
| Objective/Criterion Reference: | Water Quality Control Plan (Basin Plan) San Francisco Bay Basin (Region 2) | ||||
| Evaluation Guideline: | |||||
| Guideline Reference: | |||||
| Spatial Representation: | The samples were collected at 1 monitoring site: 206SCH00905 (Arroyo Seco at Schell Creek). | ||||
| Temporal Representation: | The samples were collected between the dates of 2019-02-06 and 2019-02-19 | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Sonoma County Permit and Resource Management Department. 2019. Clean Streams in Southern Sonoma County (CS3C). | ||||
| QAPP Information Reference(s): | Clean Streams in Southern Sonoma County (CS3C) | ||||
DECISION ID |
144637 |
Region 2 |
Arroyo Seco (Sonoma County) |
||
| Pollutant: | Temperature, water |
| 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: | |
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| LOE ID: | 288579 | ||||
| Pollutant: | Temperature, water | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | Not Recorded | ||||
| Beneficial Use: | Cold Freshwater Habitat | ||||
| Number of Samples: | 3 | ||||
| Number of Exceedances: | 0 | ||||
| Data and Information Type: | PHYSICAL/CHEMICAL MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed Clean Streams in S. SoCo Pathogen Source Detection data for Arroyo Seco (Sonoma County) to determine beneficial use support and results are as follows: 0 of 3 samples exceeded the water quality threshold for Temperature. | ||||
| Data Reference: | Field, Habitat, WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 2. | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: “- The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. - The temperature of any cold or warm freshwater habitat shall not be increased by more than 5°F (2.8°C) above natural receiving water temperature.” | ||||
| Objective/Criterion Reference: | Water Quality Control Plan (Basin Plan) San Francisco Bay Basin (Region 2) | ||||
| Evaluation Guideline: | Per Effects of Temperature, Dissolved Oxygen/Total Dissolved Gas, Ammonia, and pH on Salmonids (Carter 2008, Moyle 1976, and USEPA 1977), the lethal temperature evaluation guideline for both the steelhead adult migration and holding and the steelhead juvenile growth and rearing life stages is 24°C. | ||||
| Guideline Reference: | Temperature criteria for freshwater fish: protocol and procedures. Ecological Research Series. EPA-600/3-77-061 (NTIS PB270032). Prepared by W.A. Brungs and B.R. Jones. U.S. Environmental Protection Agency, Washington, D.C | ||||
| Guideline Reference: | Inland Fishes of California | ||||
| 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: | The samples were collected at 1 monitoring site: 206SCH00905 (Arroyo Seco at Schell Creek). | ||||
| Temporal Representation: | The samples were collected between the dates of 2019-02-06 and 2019-02-19 | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Sonoma County Permit and Resource Management Department. 2019. Clean Streams in Southern Sonoma County (CS3C). | ||||
| QAPP Information Reference(s): | Clean Streams in Southern Sonoma County (CS3C) | ||||
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| LOE ID: | 298620 | ||||
| Pollutant: | Temperature, water | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | Not Recorded | ||||
| Beneficial Use: | Fish Migration | ||||
| Number of Samples: | 2 | ||||
| Number of Exceedances: | 0 | ||||
| Data and Information Type: | PHYSICAL/CHEMICAL MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed Clean Streams in S. SoCo Pathogen Source Detection data for Arroyo Seco (Sonoma County) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for Temperature. | ||||
| Data Reference: | Field, Habitat, WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 2. | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | Temperature objectives for surface waters are specified in the San Francisco Bay Regional Water Quality Control Plan. The following temperature objectives apply to surface waters: The natural receiving water temperature of inland surface waters shall not be altered unless it can be demonstrated to the satisfaction of the Regional Board that such alteration in temperature does not adversely affect beneficial uses. The temperature of any cold or warm freshwater habitat shall not be increased by more than 5 degrees F (2.8 degrees C) above natural receiving water temperature. | ||||
| Objective/Criterion Reference: | Water Quality Control Plan (Basin Plan) San Francisco Bay Basin (Region 2) | ||||
| Evaluation Guideline: | Scientific literature reviewed by the Washington Department of Ecology and U.S. EPA indicates that stream temperatures higher than 21C are associated with avoidance behavior and migration blockages in steelhead trout. | ||||
| Guideline Reference: | EPA Region 10 Guidance for Pacific Northwest State and Tribal Temperature Water Quality Standards. EPA 910-B-03-002. Region 10 Office of Water, Seattle, WA | ||||
| Guideline Reference: | U.S. Environmental Protection Agency (USEPA). 2001. Issue Paper 1: Salmonid Behavior and Water Temperature Prepared as Part of EPA Region 10 Temperature Water Quality Criteria Guidance Development Project. Region 10, Seattle, WA. EPA-910-D-01-001 May 2001. | ||||
| Guideline Reference: | Washington State Department of Ecology (WDOE). 2002. Evaluating Standards for Protecting Aquatic Life in Washington’s Surface Water Quality Standards: Temperature Criteria. Draft Discussion Paper and Literature Summary. Publication Number 00-10-070. | ||||
| Guideline Reference: | Beschta RL, Bilby RE, Brown GW, Holtby LB, Hofstra TD. 1987. Stream temperature and aquatic habitat: Fisheries and forestry interactions. In: Salo EO, Cundy TW, eds. Streamside management: forestry and fishery interactions. College of Forest Resources, University of Washington, Seattle. Contribution No. 57. Proceedings of a Symposium held at University of Washington, February 12-14, 1986, pp. 191-231. | ||||
| Spatial Representation: | The samples were collected at 1 monitoring site: 206SCH00905 (Arroyo Seco at Schell Creek). | ||||
| Temporal Representation: | The samples were collected between the dates of 2019-02-13 and 2019-02-19 | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Sonoma County Permit and Resource Management Department. 2019. Clean Streams in Southern Sonoma County (CS3C). | ||||
| QAPP Information Reference(s): | Clean Streams in Southern Sonoma County (CS3C) | ||||
DECISION ID |
144636 |
Region 2 |
Arroyo Seco (Sonoma County) |
||
| Pollutant: | pH |
| 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: | |
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| LOE ID: | 287630 | ||||
| Pollutant: | pH | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | None | ||||
| Beneficial Use: | Cold Freshwater Habitat | ||||
| Number of Samples: | 2 | ||||
| Number of Exceedances: | 0 | ||||
| Data and Information Type: | PHYSICAL/CHEMICAL MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed Clean Streams in S. SoCo Pathogen Source Detection data for Arroyo Seco (Sonoma County) to determine beneficial use support and results are as follows: 0 of 2 samples exceeded the water quality threshold for pH. | ||||
| Data Reference: | Field, Habitat, WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 2. | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | Water Quality Control Plan, San Francisco Bay Basin, Chapter III Water Quality Objectives, Section 3.3.9 pH states: The pH shall not be depressed below 6.5 nor raised above 8.5. This encompasses the pH range usually found in waters within the basin. Controllable water quality factors shall not cause changes greater than 0.5 units in normal ambient pH levels. | ||||
| Objective/Criterion Reference: | Water Quality Control Plan (Basin Plan) San Francisco Bay Basin (Region 2) | ||||
| Evaluation Guideline: | |||||
| Guideline Reference: | |||||
| Spatial Representation: | The samples were collected at 1 monitoring site: 206SCH00905 (Arroyo Seco at Schell Creek). | ||||
| Temporal Representation: | The samples were collected between the dates of 2019-02-13 and 2019-02-19 | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Sonoma County Permit and Resource Management Department. 2019. Clean Streams in Southern Sonoma County (CS3C). | ||||
| QAPP Information Reference(s): | Clean Streams in Southern Sonoma County (CS3C) | ||||
DECISION ID |
148538 |
Region 2 |
Arroyo Seco (Sonoma County) |
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| Pollutant: | Indicator Bacteria |
| 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: | See TMDL documentation |
| TMDL Name: | Sonoma Creek Pathogens |
| TMDL Project Code: | 63 |
| Date TMDL Approved by USEPA: | 02/29/2008 |
| 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 3.11 of the Listing Policy. Under this section when all other listing factors do not result in the listing of a water segment but information indicates non-attainment of standards, a water segment shall be evaluated to determine whether the weight of evidence demonstrates that water quality standard is not attained. If the weight of evidence indicates non-attainment, the water segment shall be placed on the CWA section 303(d) List. When making a listing decision based on the situation-specific weight of evidence, the Regional Water Board must justify its recommendation by: • Providing any data or information including current conditions supporting the decision; • Describing in fact sheets how the data or information affords a substantial basis in fact from which the decision can be reasonably inferred; • Demonstrating that the weight of evidence of the data and information indicate that the water quality standard is not attained; and • Demonstrating that the approach used is scientifically defensible and reproducible. Arroyo Seco is a tributary to Sonoma Creek. The Sonoma Creek and its tributaries, including Arroyo Seco, are impaired by indicator bacteria (pathogens) and subject to the Sonoma Creek Pathogen TMDL. The weight of evidence indicates that there is sufficient justification for placing this water segment-pollutant combination on the CWA section 303(d) List, specifically on the being addressed portion of the CWA section 303(d) List because a TMDL has been completed and approved by RWQCB and USEPA, and is expected to result in attainment of the standard. 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. Arroyo Seco is a tributary to Sonoma Creek which is impaired by pathogens. E. coli measured at several Sonoma Creek watershed locations during the development of the Sonoma Creek Pathogen TMDL showed moderate but widespread exceedances of water quality objectives, indicating pathogen impairment of REC-1 and REC-2 beneficial uses throughout the watershed. The sources of pathogens such as onsite wastewater treatment systems, confined animal facilities, grazing lands and municipal runoff exist throughout the Sonoma Creek watershed, including the Arroyo Seco watershed. 2. The Sonoma Creek implementation plan states “The overall intent of this implementation plan is to restore and protect beneficial uses of Sonoma Creek and its tributaries by reducing pathogen loadings. Potential pathogen sources in the watershed include: septic systems, sanitary sewer system failures, municipal runoff, livestock grazing, and dairies.” The TMDL implementation actions (e.g., the Conditional Waiver Program from Grazing Operations and the NPDES general stormwater permit), were written to include the entire Sonoma Creek watershed. As such, the Sonoma Creek Pathogen TMDL already applies to the Arroyo Seco subwatershed. Sources of pathogens exist in the Arroyo Secco subwatershed and contribute to exceedances of E.coli objectives for water contact recreation. 3. The most severe and consistent exceedances of the E.coli objectives were observed in downstream Sonoma Creek and in the Nathanson/Schell Creek subwatershed. Exceedance frequency of E.coli geomean increased 10 percent during the post-TMDL wet season sampling. The water quality data are insufficient to determine that water quality have been improved and water quality objectives are met in the Sonoma Creek watershed in general and in Arroyo Seco subwatershed in particular. Therefore, based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for placing this water segment-pollutant combination on the being addressed portion of the CWA section 303(d) List because a TMDL has been completed and approved by RWQCB and USEPA, and is expected to result in attainment of the standard. 4. This process is scientifically defensible and reproducible. The Arroyo Seco subwatershed was part of the Sonoma Creek Pathogen TMDL assessment. The TMDL assessment included a rigorous technical review, the public participation process, and approval by U.S. EPA. Additionally, the data analysis for the TMDL made use of the E. coli objectives that were in place at the time of TMDL development. Although these objectives have been subsequently updated, exceedances of the older objectives would also constitute exceedances of the revised (lower) objectives. |
| 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: | Therefore, based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for placing this water segment-pollutant combination on the being addressed portion of the CWA section 303(d) List because a TMDL has been completed and approved by RWQCB and USEPA, and is expected to result in attainment of the standard. 4. This process is scientifically defensible and reproducible. The Arroyo Seco subwatershed was part of the Sonoma Creek Pathogen TMDL assessment. The TMDL assessment included a rigorous technical review, the public participation process, and approval by U.S. EPA. Additionally, the data analysis for the TMDL made use of the E. coli objectives that were in place at the time of TMDL development. Although these objectives have been subsequently updated, exceedances of the older objectives would also constitute exceedances of the revised (lower) objectives. |
| State Board Decision Recommendation: | |
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| LOE ID: | 300130 | ||||
| Pollutant: | Escherichia coli (E. coli) | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | STV | ||||
| Beneficial Use: | Water Contact Recreation | ||||
| Number of Samples: | 1 | ||||
| Number of Exceedances: | 1 | ||||
| Data and Information Type: | PATHOGEN MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed Clean Streams in S. SoCo Pathogen Source Detection data for Arroyo Seco (Sonoma County) to determine beneficial use support and the results are as follows: 1 of the 1 samples exceeded the Statistical Threshold Value (STV) water quality threshold for E. coli. The STV is based on a 10% exceedance rate that is calculated monthly. | ||||
| Data Reference: | Field, Habitat, WQ data from the California Environmental Data Exchange Network assembled for the 2024 Integrated Report in Region 2. | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | The bacteria water quality objective to protect the REC-1 beneficial use where the salinity is less than 1 parts per thousand 95 percent or more of the time applies a statistical threshold value to E. coli of 320 cfu/100 mL, not to be exceeded by more than 10 percent of samples within a calendar month (ISWEBE 2018). | ||||
| Objective/Criterion 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 | ||||
| Evaluation Guideline: | |||||
| Guideline Reference: | |||||
| Spatial Representation: | The samples were collected at 1 monitoring site(s), station(s): 206SCH00905 (Arroyo Seco at Schell Creek). | ||||
| Temporal Representation: | The samples were collected between the days of 2019-02-06 and 2019-02-19 . | ||||
| Environmental Conditions: | |||||
| QAPP Information: | Sonoma County Permit and Resource Management Department. 2019. Clean Streams in Southern Sonoma County (CS3C). | ||||
| QAPP Information Reference(s): | Clean Streams in Southern Sonoma County (CS3C) | ||||