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STATE OF CALIFORNIA • • <br /> PETE WILSON Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— <br /> CENTRAL VALLEY REGION r --- <br /> 3443 ROUTIER ROAD. SUITE A <br /> SACRAMENTO. CA 95827-3098 <br /> PHONE: (916) 361 5600 v�e gay 4 s 4ei <br /> FAX (916) 3 61 5 686 <br /> SEP 1 ) 1992 <br /> €NVIRONMENTAL f IEALTW <br /> 11 September 1992 <br /> PERM IT/SERVICE6 <br /> Mr. Abel Haines <br /> Environmental Protection Office <br /> Bldg. 231, Tracy Location <br /> Defense Distribution Region West <br /> P. 0. Box 960001 <br /> Stockton, CA 95296-0250 <br /> DRAFT ENGINEERING REPORT FOR THE WELL MONITORING PROGRAM, DEFENSE DISTRIBUTION <br /> REGION WEST (DDRW), TRACY, SAN JOAQUIN COUNTY <br /> We have reviewed the Draft Engineering Report for the Well Monitoring Program <br /> for DDRW, Tracy submitted on 13 July 1992. The Draft Report summarizes the <br /> results of the first four consecutive and comprehensive ground water <br /> monitoring quarters conducted in May, August and November 1991 and February <br /> 1992. In general , we find that the report is relatively comprehensive and <br /> contains the basic elements, such as plume maps, summary tables and monitoring <br /> recommendations, that should be included in an annual monitoring report. <br /> However, we have three major concerns with the Draft Report. These concerns <br /> are summarized below and are discussed in more detail , along with other <br /> specific comments, in the enclosed memorandum. <br /> 1 . Data from wells screened above the upper horizon have not been included in <br /> the evaluation of the upper horizon. We believe that the failure to <br /> include these wells has underestimated the extent of the trichloroethylene <br /> (TICE) and tetrachloroethylene (PCE) plumes and may ultimately lead to <br /> inappropriate remedial actions for both soils and ground water. <br /> 2. Recommendations for on-going monitoring for pesticides, metals and <br /> hydrocarbons appears to be excessive. The first four consecutive quarters <br /> of data generally revealed only sporadic, slightly elevated concentrations <br /> of varying contaminants that frequently could not be confirmed. We <br /> believe that on-going monitoring for pesticides, metals and hydrocarbons <br /> should be deferred until the completion of the site-wide Remedial <br /> Investigation (RI) for all waste management units (WMUs) and underground <br /> storage tanks (USTs) . <br /> 3. Background has not been clearly established for metals and minerals. We <br /> believe that additional work is needed to determine background <br /> concentrations for these potential pollutants. In addition, two of the <br /> off-site "background" wells, selected for the Operable Unit No. 1 (OU-1) <br />