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WASTE DISCHARGE REQUANTS ORDER NO. RS-2002-0213 • 13 <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 /> criterion for hexavalent chromium of 11 gg/L (ppb). Effluent data summarized in Attachment C <br /> represents new information which was not available at the time of adoption of previous Order <br /> 95-258. Considering these facts, the monthly median effluent limitation for hexavalent <br /> chromium from previous Order No. 95-258 has been removed from this Order(new <br /> information). This Order does require continued effluent and receiving water monitoring for <br /> hexavalent chromium, and may be re-opened if hexavalent chromium is or may be discharged at <br /> a level that will cause or have the reasonable potential to cause or contribute to an in-stream <br /> excursion above the CTR/NTR criteria. <br /> 23. Previous Order No. 95-258 included a weekly average effluent limitation for total lead of 3.2 <br /> gg/L (ppb). Previous Order No. 95-258 indicates this limitation was based upon a receiving <br /> water hardness of 100 mg/L(ppm) as CaCO3, however the final effluent limitation does not <br /> account for changes in the hardness of the receiving water. As noted previously, hardness levels <br /> of the SKID Canal have been reported as low as 28 mg/L (ppm) as CaCO3. As shown in <br /> Attachment C, results of effluent monitoring of the three GWTPs indicates the MECs of total <br /> lead in the final effluent have been less than the analytical reporting limit of 3 µg/L (ppb). For <br /> purposes ofthereasonable potential analysis, and as summarized in Attachment C, the CMC and <br /> CCC aquatic life criteria of 40 CFR 131.38 were adjusted based upon the minimum observed <br /> hardness of the SSJID Canal (28 mg/L(ppm)). The adjusted CMC and CCC are 16.2 µg/L (ppb) <br /> and 0.63 µg/L (ppb) respectively. Considering the Reporting Limits (RLs) utilized by the <br /> Discharger, existing data are not of sufficient quality for comparison with the adjusted CCC <br /> criterion, and a determination of whether reasonable potential exists cannot be made. The data <br /> indicate that final effluent from the three GWTPs does not have the reasonable potential to <br /> exceed the adjusted CMC. <br /> At times, the effluent from the DDJC Sharpe facility may constitute the majority or entire flow <br /> of water in the SSJID Canal. Pursuant to Section 1.3 of the SIP, when the observed maximum <br /> ambient background concentration exceeds a criterion, an effluent limitation is required. Results <br /> of monitoring in French Camp Slough indicate two instances where concentrations of total lead <br /> were detected. On 7 July 1998, and on 13 July 1999, total lead concentrations in French Camp <br /> Slough were reported as 3.0 µg/L (ppb). The hardness of French Camp Slough was also <br /> monitored on 13 July 1999, and was reported as 100 mg/L (ppm) as CaCO3. Considering that at <br /> 100 mg/L hardness as CaCO3 the adjusted CCC criterion for total lead is 3.2 µg/L (ppb)), the <br /> data indicate that the observed maximum background concentration did not exceed the CCC for <br /> total lead. <br /> Based upon the results of effluent and receiving water monitoring, there is insufficient <br /> information to determine whether the discharge from the DDJC-Sharpe facility does or does not <br /> not have the reasonable potential to exceed the adjusted CCC criterion for lead. This Order <br /> requires the Discharger to collect additional effluent and receiving water data for lead of <br /> sufficient quality for comparison with appropriate criteria. This Order may be may be re-opened <br /> if the data indicate concentrations of lead are or may be discharged at a.level which will cause or <br /> have the reasonable potential to cause or contribute to an in-stream excursion above the <br />