| Water Body Name: | Drakes Estero (at Schooner Bay oyster beds) |
| Water Body ID: | CAC2012101120110712213842 |
| Water Body Type: | Coastal & Bay Shoreline |
DECISION ID |
97327 |
Region 2 |
Drakes Estero (at Schooner Bay oyster beds) |
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| Pollutant: | Indicator Bacteria |
| Final Listing Decision: | Delist from 303(d) list (TMDL required list) |
| Last Listing Cycle's Final Listing Decision: | List on 303(d) list (TMDL required list)(2016) |
| Revision Status | Revised |
| Reason for Delisting: | Applicable WQS attained; due to change in WQS |
| Impairment from Pollutant or Pollution: | Pollution |
| 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.
Two lines of evidence are available in the administrative record to assess this pollutant. All available enterococcus data (2006 through 2012) were evaluated for this assessment. Five of one hundred six samples exceeded the geometric mean objective. Consistent with the contact recreation water quality objective provided in the Inland Surface Waters Enclosed Bays and Estuaries Plan, only the geomean was used to determine use attainment because there were enough samples to calculate the geomean. This waterbody was originally listed based on exceedance of a total coliform objective from SF Bay Basin Plan. This total coliform objective no longer exists so we reassessed all available enterococcus data. Based on the readily available data and information, the weight of evidence indicates that there is sufficient justification for 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. Five of one hundred six samples exceeded the geometric mean objective and this does not exceed the allowable frequency listed in Table 4.2 of the Listing Policy (exceedance frequency appropriately adjusted for April through October sampling). 4. Pursuant to section 4.11 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 be removed from the section 303(d) list because applicable water quality standards for the pollutant are not being exceeded. |
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| LOE ID: | 96986 | ||||
| Pollutant: | Enterococcus | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | None | ||||
| Beneficial Use: | Water Contact Recreation | ||||
| Number of Samples: | 106 | ||||
| Number of Exceedances: | 5 | ||||
| Data and Information Type: | PATHOGEN MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed BeachWatch data for Drake's Estero to determine beneficial use support and results are as follows: five of the one hundred six geometric means (calculated weekly) exceeded the objective. We required a minimum of 5 samples to compute each valid geomean, consistent with the objective. | ||||
| Data Reference: | Beach Watch Data for Six SF Bay Regional Water Quality Control Board Beaches for 2018 Listing Cycle | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | The objective is a six-week rolling geometric mean (calculated weekly), not to exceed 30 cfu/100 mL. | ||||
| 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: | Data for this line of evidence for Drakes Estero (at Schooner Bay oyster beds) was collected at 1 monitoring site. | ||||
| Temporal Representation: | The data were collected approximately April through October in the years 2006-2010. This LOE replaces #90600, which included data collected from April 2006 to August 2010. This new LOE includes this same data plus data from 2012 but is based on an analysis of all available data in comparison to the newly adopted enterococcus objectives to protect contact recreation. | ||||
| Environmental Conditions: | Staff is not aware of any special conditions that might affect interpretation of the data. | ||||
| QAPP Information: | The samples were collected for the Beach Watch program. | ||||
| QAPP Information Reference(s): | |||||
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| LOE ID: | 96987 | ||||
| Pollutant: | Enterococcus | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | None | ||||
| Beneficial Use: | Water Contact Recreation | ||||
| Number of Samples: | 44 | ||||
| Number of Exceedances: | 3 | ||||
| Data and Information Type: | PATHOGEN MONITORING | ||||
| Data Used to Assess Water Quality: | Water Board staff assessed BeachWatch data for Drake's Estero to determine beneficial use support and results are as follows: three of the forty-four STVs (calculated monthly) exceeded the objective. | ||||
| Data Reference: | Beach Watch Data for Six SF Bay Regional Water Quality Control Board Beaches for 2018 Listing Cycle | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | The objective is a statistical threshold value (STV) of 110 cfu/100 mL, not to be exceeded more than 10 percent of the time, calculated monthly. | ||||
| 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: | Data for this line of evidence for Drakes Estero (at Schooner Bay oyster beds) was collected at 1 monitoring site. | ||||
| Temporal Representation: | The data were collected approximately April through October in the years 2006-2012.This LOE replaces #90852, which included data collected over the time period 4/4/2006-8/17/2010. This new LOE is based on an analysis of the same data but in comparison to the newly adopted enterococcus objectives to protect contact recreation. | ||||
| Environmental Conditions: | Staff is not aware of any special conditions that might affect interpretation of the data. | ||||
| QAPP Information: | The samples were collected for the Beach Watch program. | ||||
| QAPP Information Reference(s): | |||||