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4 <br /> f{ STATE OF CALIFORNIA- Environmental Protels Agency • PETE WILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD <br /> CENTRAL VALLEY REGION <br /> 3443 Routier Road, Suite A L 111 i`.;L HEA,1_r11 <br /> Sacramento, CA 95827-3098 <br /> I'F. <br /> PHONE: (916) 255-3000 _ <br /> DOD FAX: (916) 255-3052 Q^J. OCT <br /> 20 PM 2: 10 <br /> 15 October 1993 1 f' G <br /> Mr. Able Haines <br /> Environmental Protection Office <br /> Bldg. S-108, Sharpe Site <br /> Defense Distribution Region West <br /> P.O. Box 960001 <br /> Stockton, CA 95296-0710 <br /> GROUNDWATER TREATMENT PILOT PLANT SYSTEM START-UP, PROVE-OUT AND <br /> EVALUATION REPORTS, DEFENSE DISTRIBUTION REGION WEST (DDRW), TRACY, SAN <br /> JOAQUIN COUNTY <br /> We have reviewed the above referenced documents received in the first half of 1993. Although the <br /> documents have been finalized, we expect our comments to be considered or addressed in future <br /> system evaluation reports. Overall the documents were well prepared and illustrate that the full <br /> scale operation of the Interim Remedial Measures (IRM) air stripper plant is performing consistently <br /> within the Waste Discharge Requirements (WDRs) adopted for this system. Our comments are <br /> presented in the enclosed memorandum. <br /> In the Three Month Evaluation Report No. 1, pesticides chlordane and dieldrin were detected in the <br /> treatment plant influent and effluent. Potential pesticide contamination will be evaluated in the <br /> Comprehensive Site-wide Remedial Investigation/Feasibility Study (RI/FS). The Comprehensive <br /> Site-wide RI/FS will evaluate background concentrations in both soil and groundwater. The effluent <br /> treatment standard for dieldrin, established as part of the Operable Unit No. 1 (OU-1) Record of <br /> Decision (ROD), will be reevaluated if the background dieldrin concentration in the receiving <br /> aquifer is greater than the current effluent standard, and if the dieldrin contamination is not caused <br /> by DDRW, Tracy. However, should it be determined that a dieldrin groundwater plume exists for <br /> which the Tracy Depot is responsible, appropriate action will be necessary. This may include <br /> installation of additional extraction wells and/or monitoring wells and utilizing wellhead treatment <br /> technology for selected extraction wells. <br /> Other issues requiring updates in status include the renewal of the modification of the IRM WDRs <br /> for discharge into to the stormwater pond. The current modification granted 29 March 1993 allows <br /> DDRW, Tracy to discharge into the stormwater and evaporation-percolation ponds 1 and 2 from <br /> April through October 1993. The ponds also must be operated to provide sufficient capacity for <br /> their intended use as stormwater and waste water effluent ponds. To extend the modification of the <br /> IRM WDRs, DDRW, Tracy must submit a request for an extension in writing along with <br /> information on the performance of the ponds ability to maintain adequate capacity for their intended <br /> use over the last six months. DDRW, Tracy must demonstrate that the ponds past performance will <br /> be adequate to maintain two feet of freeboard during the upcoming rainy season. In addition, <br />