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t t <br /> r STATE OF CALIFORNIA <br /> PETE WILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD— <br /> CENTRAL VALLEY REGION <br /> 3443 ROUTIER ROAD, SUITE A <br /> F <br /> SACRAMENTO. CA 95827-3098 � <br /> PHONE'. (916) 361-5600 <br /> FAX (916) 361-5686 <br /> VE <br /> 31 July 1991 RECEI <br /> AUG 2 1991 <br /> ENVIRONMENTAL HEALTH <br /> PERMIT✓$ERVICE� <br /> Mr. Marshall Cloud <br /> DDRW-WB <br /> Defense Distribution Region West, Tracy <br /> Tracy, CA 95376-5000 <br /> OFF-SITE SUPPLY WELLS, DEFENSE DISTRIBUTION REGION WEST (DDRW), TRACY, SAN <br /> JOAQUIN COUNTY <br /> Based on the data submitted in the March 1991 Remedial Investigation/Feasibility <br /> Study (RI/FS) Report for the DDRW, Tracy site, we have become aware that the <br /> volatile organic constituent (VOC) plume migration has been exacerbated by the <br /> pumping of adjacent off-site agricultural supply wells and that some of the off- <br /> site agricultural and domestic wells have been contaminated above State Action <br /> Levels for some VOCs. Therefore, we request that DDRW, Tracy investigate options <br /> and take actions to discontinue the use of the agricultural supply wells and to <br /> replace the water supply for those well owners. In addition, it is imperative <br /> that DDRW, Tracy collect samples for water quality analyses from all supply wells <br /> immediately down gradient and adjacent to the VOC plume, as soon as possible. <br /> In particular, we are quite concerned that Mr. Raspo, an adjacent land owner, has <br /> continued to use his agricultural supply well , AGW-3, which is known to have <br /> concentrations of trichloroethylene (TCE) above the Primary Drinking Water <br /> Standard of 5 micrograms per liter (µg/1 ) . The continued use of deep <br /> agricultural supply wells threatens to cross contaminate a lower aquifer which <br /> is the regional potable water supply. <br /> The last water quality samples of off-site supply wells were collected and <br /> analyzed in 1987. To our knowledge, additional monitoring of these wells has not <br /> been conducted since that time. We believe that the concentrations of VOCs may <br /> have increased since 1987 in the off-site wells due to the migration of the plume <br /> and that the existing monitoring program needs to be expanded to incorporate <br /> these off-site supply wells. <br /> Therefore, by 15 September 1991 we request that DDRW, Tracy inform us as to the <br /> actions taken to discontinue the use and replace the water supply of the <br /> agricultural supply wells and propose a monitoring program for the off-site <br /> supply wells. <br />