| Water Body Name: | Santiago Creek, Reach 1 |
| Water Body ID: | CAR8011100019991014153910 |
| Water Body Type: | River & Stream |
DECISION ID |
77117 |
Region 8 |
Santiago Creek, Reach 1 |
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| Pollutant: | Indicator Bacteria |
| 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: | No new data were assessed this cycle. The decision has not changed, and is as follows:
This pollutant is being considered for placement on the section 303(d) list under section 3.3of the Listing Policy. Under section 3.3 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. Three of 21 samples exceeded the EPA's single sample value of 236. While the frequency of measurements above this single sample value would warrant listing pursuant to the Listing Policy (Table 3.2), listing on the bases of these data is not appropriate at this time, based on the following: (1). The samples were collected on a monthly basis; insufficient samples were collected to derive geomeans. EPA has made clear in relevant guidance and regulation on EPA¿s bacteria criteria (e.g., Section IV B 3 of 40 CFR Part 131 (Water Quality Standards for Coastal and Great Lakes Recreation Waters; Final Rule) that the geometric mean is the more relevant value for ensuring that appropriate actions are taken to protect and improve water quality because it is a more reliable measure, being subject to less random variation and more directly linked to the underlying studies on which the 1986 bacteria criteria were based. EPA has consistently stated that the single sample standard is best used in making beach notifications and closure decisions. (2). The single sample value of 236 employed for comparative purposes is inappropriate since it is based on inappropriate assumptions regarding data variability and the intensity of recreational use at the sites (there are not designated beach areas). The value of 236 is derived based on the assumptions that (1) the log standard deviation of measured E. coli concentrations is 0.4 (essentially a default value that is assumed in the absence of adequate data/analysis), and (2) that the 75th percentile value should be selected to protect designated beach areas. EPA recommends that this percentile value be used for designated beach areas where a higher level of confidence is needed to assure that the geomean is being met. (As described in detail by EPA, single sample maximum values are statistical constructs designed to provide the assurance that geomean objectives are met. Greater confidence is needed where recreational use, and the threat of exposure, is highest; where there is limited recreational use, lower confidence is needed that the geomean is achieved.) However, the waters at issue here are not designated beach areas and receive little recreational use. Further, data variability is higher than the default value of 0.4. As a result, the applicable single sample value for comparative assessment purposes is not 236, but a higher value (which should be determined through a standards setting process; the Stormwater Quality Standards Task Force is engaged in this effort right now.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 section 303(d) list in the Water Quality Limited Segments category. 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. Three of 21 samples exceeded the Ocean Plan's single sample standard and this standard is not appropriate on which to base listing decisions. The geometric mean standard is the appropriate standard on which to base listing decisions. The data available consists of monthly samples and geometric means can not be calculated. 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: | This is a decision previously approved by the State Water Resources Control Board and the USEPA. No new data were assessed by the Regional Board for the current. The decision has not changed. |
| 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: | 21552 | ||||
| Pollutant: | Escherichia coli (E. coli) | ||||
| LOE Subgroup: | Pollutant-Water | ||||
| Matrix: | Water | ||||
| Fraction: | None | ||||
| Beneficial Use: | Water Contact Recreation | ||||
| Number of Samples: | 21 | ||||
| Number of Exceedances: | 3 | ||||
| Data and Information Type: | PATHOGEN MONITORING | ||||
| Data Used to Assess Water Quality: | Of the 21 single samples collected, only three exceeded EPA's Recommended single sample criteria. | ||||
| Data Reference: | Orange County Coast Keeper Coastal Watersheds Project | ||||
| SWAMP Data: | Non-SWAMP | ||||
| Water Quality Objective/Criterion: | USEPA Recommended Ambient Water Quality Criteria for Bacteria -1986: E. coli: log mean less than 126 organisms/100 mL based on five or more samples per 30¿day period, and single sample shall not exceed 235 organisms/100mL. | ||||
| Objective/Criterion Reference: | Ambient Water Quality Criteria for Bacteria - 1986. EPA440/5-84-002 | ||||
| Evaluation Guideline: | |||||
| Guideline Reference: | |||||
| Spatial Representation: | The samples were collected at Santiago Oaks Park. This site is located at the entrance of the Santiago Oaks Park, north of the road in the creek bed, just below the concrete step. | ||||
| Temporal Representation: | The samples were collected monthly starting on December 13, 2002 through June 15, 2004. | ||||
| Environmental Conditions: | Staff is not aware of any special conditions that might effect interpretation of the data. | ||||
| QAPP Information: | The data's quality is deemed appropriate because it was obtained under the auspices of a QAPP approved by the Regional Board. | ||||
| QAPP Information Reference(s): | |||||