SITE INFORMATION AND CORRESPONDENCE_1993-2003

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WASTE DISCHARGE REQUIREMENTS ORDER NO.RS-2002-0213 • 15 U.S. DEPARTMENT OF DEFENSE DEFENSE LOGISTICS AGENCY DEFENSE DISTRIBUTION DEPOT SAN JOAQUIN SHARPE GROUNDWATER REMEDIATION SYSTEM SAN JOAQUIN COUNTY Following the establishment of the interim limit, the mass of mercury discharged shall not exceed the interim mercury mass limit twelve months on a running average. In calculating for compliance, the Discharger shall count all non-detect measures at one-half of the detection level and apply the monthly average flow from the sampled discharge. If compliance with the effluent limit is not attained due to the non-detect contribution, the Discharger will be directed to improve and implement available analytical capabilities and compliance will be evaluated with consideration of the detection limits. For each calendar month, the Discharger shall calculate twelve-month mass loadings. For monthly measures, monthly loadings shall be calculated using the average monthly flow and the average of all mercury analyses conducted that month. The Discharger shall submit a cumulative total of mass loadings for the previous twelve months with each self-monitoring report. Compliance will be determined based on the previous 12-month moving averages over the previous twelve months of monitoring. Until sufficient data are collected to establish a performance based interim effluent mass limitation, this Order shall include a preliminary mercury mass limitation (annual limitation) using the concentration and average flow limitations of the previous Order (0.000012 mg/L (ppm) x 8.3�x 1.152 mgd x 365 =0.042 lbs/yr). Upon completion of the Interim Mercury Mass Limitation Study required by this Order, this Order shall be reopened and an interim performance based mercury mass effluent limitation established. Final effluent limitations may include: a waste load allocation derived from the TMDL, or a site-specific water quality objective. The economic effect of the provisions of this permit on the discharger is nominal. When established, the interim mercury effluent limits require the discharger to simply maintain current plant performance. 25. Results of effluent monitoring of the three GWTPs indicates the MECs of total selenium in the final effluent are typically less than the analytical reporting limit of 5 µg/L (ppb). Selenium was detected in the final effluent of the North Balloon GWTP on two ocassions, 2 May 2000 (llµg/L (ppb)), and 5 June 2001 (6.0 µg/L (ppb)). As shown in Attachment C, 40 CFR 131.38 includes a CCC criterion for selenium expressed in the total recoverable form. While other criteria for selenium were promulgated for specific waters in California in the NTR, it is the 5 µg/L (ppb) chronic criterion shown in Attachment C which applies to additional waters of the United States in the State of California pursuant to 40 CFR 131.38(c). Since the preservation and enhancement of fish, wildlife, and other aquatic resources and habitats is an existing beneficial use of the SSJID Canal, this criterion applies to the SKID Canal. The GWTPs operate independently, and the final discharge is a made up of the co-mingled GWTP effluents. While the MEC from the North Balloon GWTP did exceed the selenium criterion, it is unlamown if the final effluent concentration would exceed the criterion after mixing with the other GWTP effluent flows. This Order requires the Discharger to collect additional effluent and receiving water data for selenium, and may be re-opened if the data indicate concentrations of selenium are or may be discharged at a level which will cause or have the reasonable potential to cause or contribute to an in-stream excursion above the selenium criterion.