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respective recommendation fields in this decision. <br />Note: All lines of evidence (LOEs) previously made by the Regional Boards have <br />been revised where necessary in accordance with USEPA's final decision. <br />Regional Board Decision Regional Water Board Decision Recommendation (prior to State Water Board <br />Recommendation: approval): <br />This pollutant is being considered for placement on the section 303(d) list under <br />section 3.3 of the Listing Policy. <br />One line of evidence is available in the administrative record to assess this <br />pollutant. Thirty of 64 samples exceeded the EPA's single sample value of 236. <br />While the frequency of measurements above this single sample value would <br />warrant listing pursuant to the Listing Policy (Table 3.2), listing on the bases of <br />these data is not appropriate at this time, based on the following: <br />(1). The samples were collected on a monthly basis, insufficient samples were <br />collected to derive geomeans. EPA has made clear in relevant guidance and <br />regulation on EPA's bacteria criteria (e.g., Section IV B 3 of 40 CFR Part 131 <br />(Water Quality Standards for Coastal and Great Lakes Recreation Waters, Final <br />Rule) that the geometric mean is the more relevant value for ensuring that <br />appropriate actions are taken to protect and improve water quality because it is a <br />more reliable measure, being subject to less random variation and more directly <br />linked to the underlying studies on which the 1986 bacteria criteria were based. <br />EPA has consistently stated that the single sample standard is best used in making <br />beach notifications and closure decisions. <br />(2). The single sample value of 236 employed for comparative purposes is <br />inappropriate since it is based on inappropriate assumptions regarding data <br />variability and the intensity of recreational use at the sites (there are not designated <br />beach areas). <br />The value of 236 is derived based on the assumptions that (1) the log standard <br />deviation of measured E. coli concentrations is 0.4 (essentially a default value that <br />is assumed in the absence of adequate data/analysis), and (2) that the 75th <br />percentile value should be selected to protect designated beach areas. EPA <br />recommends that this percentile value be used for designated beach areas where a <br />higher level of confidence is needed to assure that the geomean is being met. (As <br />described in detail by EPA, single sample maximum values are statistical <br />constructs designed to provide the assurance that geomean objectives are met. <br />Greater confidence is needed where recreational use, and the threat of exposure, <br />is highest; where there is limited recreational use, lower confidence is needed that <br />the geomean is achieved.) <br />However, the waters at issue here are not designated beach areas and receive <br />little recreational use. Further, data variability is higher than the default value of 0.4. <br />As a result, the applicable single sample value for comparative assessment <br />purposes is not 236, but a higher value (which should be determined through a <br />standards setting process, the Stormwater Quality Standards Task Force is <br />engaged in this effort right now. Based on the readily available data and <br />information, the weight of evidence indicates that there is sufficient justification <br />against placing this water segment -pollutant combination on the section 303(d) list <br />in the Water Quality Limited Segments category. <br />This conclusion is based on the staff findings that: <br />1. The data used satisfies the data quality requirements of section 6.1.4 of the <br />Policy. <br />2. The data used satisfies the data quantity requirements of section 6.1.5 of the <br />