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y ' STATE OF CALIFORNIA-Environmental ProteAkAgency PETE WILSON Governor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD CENTRAL VALLEY REGION 3443 Routier Road, Suite A Vppeas a Sacramento, CA 95827-3098 �.�` ' PHONE: (916) 255-3000 DOD FAX: (916) 255-3052 APR 12 1993 ENVIRONMENTAL HEALTH 8 April 1993 PERMIT/SERVICES Mr. Abel Haines Environmental Protection Office Bldg. S-108, Sharpe Site Defense Distribution Region West P. 0. Box 960001 Stockton, CA 95296-0710 WELL MONITORING PROGRAM, DEFENSE DISTRIBUTION REGION WEST (DDRW), TRACY, SAN JOAQUIN COUNTY We have reviewed the Final Engineering Report for the Well Monitoring Program for DDRW, Tracy submitted on 1 February 1993. The Final Report contained responses to our comments on the Draft version of the Report and contained proposals (Table 6-6) for the ongoing well monitoring program. The responses to our comments on the Draft of this Report have been adequately addressed. We are pleased that concentration versus time graphs and stiff diagrams were prepared. We believe that graphics such as these serve as a valuable tool in the interpretation of the hydrogeologic system. The evaluation of these data should be incorporated into the interpretation of the data collected as part of the site-wide remedial investigation (RI) . We approve of the finalization of this Report. We have also reviewed the 31 March 1993 Montgomery Waston letter to the Corps of Engineers regarding the April Quarterly Monitoring Program. We are concerned that some of the proposals for monitoring in this letter, as well as some of the proposals in Table 6-6 of the Final Engineering Report, are unnecessary. In our 11 September 1992 review of the Draft Report, and again in our 26 March 1993 letter, we stated that except for some of the monitor wells, we believe that the continued monitoring for heavy metals, pesticides and total petroleum hydrocarbons (TPH) is excessive and should not be conducted. For those wells where these constituents were consistently not detected in the first four quarters, monitoring of these consitituents should be discontinued. In particular, we do not concur with the proposal for biannual monitoring for these constituents (Table 6-6) , and monitoring for dissolved and total metals in all of the monitor wells, as we believe that this would be a waste of available funds. We believe that when the site-wide RI is completed and additional monitor wells are installed immediately down gradient of potential source areas, existing monitor wells and the newly installed wells should be sampled and analyzed for a minimum of two quarters. This comprehensive evaluation of all monitoring points should decisively determine whether or not heavy metal , pesticide or TPH ground water contamination, associated with a particular source area, has occurred.