SITE INFORMATION AND CORRESPONDENCE_1993-2003

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WASTE DISCHARGE REQUANTS ORDER NO. R5-2002-0213 • 7 U.S.DEPARTMENT OF DEFENSE DEFENSE LOGISTICS AGENCY DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN SHARPE GROUNDWATER REMEDIATION SYSTEM SAN JOAQUIN COUNTY French Camp Slough. The Basin Plan (Table II-1) designates the Delta as being both a cold and warm freshwater habitat. Therefore, pursuant to the Basin Plan (Table II-1, Footnote(2)), the cold designation applies to French Camp Slough. The cold-water habitat designation necessitates that the in-stream dissolved oxygen concentration be maintained at, or above, 7.0 mg/L (ppm). This approach recognizes that, if the naturally occurring in-stream dissolved oxygen concentration is below 7.0 mg/L(ppm), the Discharger is not required to improve the naturally occurring level. Upon review of the flow conditions, habitat values, existing and potential beneficial uses of the Delta, and the facts described above, the Regional Board fmds that the beneficial uses identified in the Basin Plan for the Delta are applicable to French Camp Slough. 11. The Regional Board also finds that based on the available information and on the Discharger's application, that the SKID Canal, absent the discharge, is at times a seasonal and/or ephemeral waterbody. This seasonal and/or ephemeral nature of the SSJID Canal means that the beneficial uses must be protected, but that no year-round credit for receiving water dilution is available. Although the discharge, at times,maintains the aquatic habitat, constituents may not be discharged tiat may cause harm to aquatic life. At other times, flows within the SSJID Canal help support aquatic life. Both conditions may exist within a short time span, where the SSJID Canal would be dry without the discharge and periods when sufficient background flows provide hydraulic continuity with French Camp Slough and the Delta. The lack of dilution results in more stringent effluent limitations to protect recreational uses and aquatic life . Significant dilution may occur during the irrigation season, and immediately following high rainfall events. The Discharger may conduct flow monitoring of the SSJID Canal to determine the actual flow regime. To the extent seasonal assimilativecapacity is available in the receiving water to accommodate constituents in the effluent which exceed reasonable potential criteria, this permit contains a re-opener to consider final effluent limitations based upon demonstrated assimilative capacity. However, effluent limitations contained in this permit do not account for the receiving waters having assimilative capacity. The Discharger may submit additional receiving water characterization to demonstrate the flow regime and pollutant assimilative capacity and ask the Regional Board to re-open the permit to consider this new information. 12. Areas of the Delta have been identified as a Water Quality Limited Segment under section 303(d) of the CWA. The list of pollutants for which the Delta is impaired appears on a list (the "California 303(d) List"),which was most recently updated in 1998. Pollutants and/or conditions identified on the California 303(d) List as impairing Delta Waterways, to which the SSJID Canal and French Camp Slough are tributary, include mercury, electrical conductivity, low dissolved oxygen, chlorpyrifos, diazinon, DDT, Group A pesticides (aldrin, dieldrin, endrin, heptachlor, heptachlor epoxide, chlordane (total), hexachlorocyclohexane (total), endosulfan (total), and toxaphene), and unknown toxicity.