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WASTE DISCHARGE REQUIREMENTS ORDER NO.R5-2002-0213 • 12 <br /> U.S. DEPARTMENT OF DEFENSE <br /> DEFENSE LOGISTICS AGENCY <br /> DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN <br /> SHARPE GROUNDWATER REMEDIATION SYSTEM <br /> SAN JOAQUIN COUNTY <br /> beneficial use of the SSJID Canal is deemed inappropriate, and is removed through the basin <br /> planning process, receiving water and/or alternative final effluent limits would be established <br /> based upon the results of the DilutionlMixing Zone Study to ensure protection of the MUN <br /> beneficial use in French Camp Slough. <br /> c. 'End-of-Pipe' Compliance with new MCL <br /> Without additional information or study, the Discharger can ensure compliance with water <br /> quality standards by meeting the new USEPA primary MCL of 10 gg/L (ppb) at the point of <br /> effluent discharge to SSJID Canal. The compliance date for water purveyors to meet the new <br /> MCL is 23 January 2006. This Order includes a final monthly average effluent limitation for <br /> arsenic of 10 gg/L (ppb) consistent with the new USEPA primary MCL and effective 23 <br /> January 2006. <br /> Considering these options, this Order provides a time schedule for completion of a <br /> Dilution/Mixing Zone Study for arsenic. This study shall be completed prior to the new USEPA <br /> MCL compliance date for water purveyors and effective date of the final monthly average <br /> effluent limitation for arsenic of 23 January 2006. The Discharger may concurrently pursue a <br /> Basin Plan Amendment de-designating the MUN beneficial use of the SSJID Canal, however the <br /> Dilution/Mixing Zone Study must still be completed to ensure the protection of French Camp <br /> Slough. Upon completion of the Study, this Order may be reopened and alternative final effluent <br /> limitations considered. If the Study is not completed, this Order includes a final monthly average <br /> effluent limitation for arsenic of 10 µg/L (ppb) consistent with the new USEPA primary MCL <br /> and effective 23 January 2006. <br /> This Order retains the 40 µg/L(ppb) monthly median effluent limitation and daily maximum <br /> effluent limitation of 50 µg/L (ppb) for arsenic from the previous Order as interim limitations <br /> until the study required by this Order is completed. Previous Order No. 95-258 included a <br /> receiving water limitation for arsenic of 10 gg/L (ppb) in French Camp Slough based upon the <br /> water quality objectives for trace elements in the Delta, as provided in Table III-1 of the Basin <br /> Plan. Footnote a of Table III-1 provides in part that "Metal objectives in this table are dissolved <br /> concentrations." Since domestic and municipal supply is a beneficial use of French Camp <br /> Slough,this Order includes a 10 gg/L (ppb)receiving water limitation and monitoring <br /> requirement for total recoverable arsenic in French Camp Slough for protection of the municipal <br /> and domestic supply beneficial use of French Camp Slough. <br /> 22. Previous Order No. 95-258 included a monthly median effluent limitation for hexavalent <br /> chromium of 11µg/L(ppb). The basis for this limitation as described in the Order was that the <br /> limitation was consistent with other NPDES permits issued in the area, and was technically <br /> achievable. The air stripping GWTPs utilized by the Discharger are not designed for removal of <br /> hexavalent chromium. As summarized in Attachment C, results of effluent monitoring of the <br /> three GWTPs indicates the maximum effluent concentrations (MECs) of hexavalent chromium <br /> in the final effluent were less than 10 gg/L(ppb). The data indicate final effluent does not have <br /> the reasonable potential to exceed the minimum CTR/NTR aquatic life CCC water quality <br />