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b 1 ATE OF CALIFORNIA-Environmental Prote. _ >gency PETE WILSON, Govemor CALIF, .cGIONAL WATER QUALITY CONTROL BOARD CENTRAL VALLEY REGION - gl��N�A1 y£ lam— 3443 Routier Road,Suite A q ,�P L��r/ Sacramento,CA 95827-3098 96�C'T`� R ��/O / $ PHONE:(916)255-3000 / N�'�, /C ikim F FAX:(916)255-3015 C, 30 September 1996 Mr. Nathan Esformes Triple E Produce P.O. Box 239 Tracy, CA 95378 DOMESTIC WELL SURVEY NORTH OF MW-7, TRIPLE E PRODUCE FACILITY, TRACY, SAN JOAQUIN COUNTY I have reviewed the 11 June 1996 letter from Tom Guido regarding the Board's request that Triple E Produce (Triple E) sample domestic wells north of MW-7. We do not agree that the extraction system will demonstrate that monitoring well MW-7 is the northernmost point of chloroform contamination. Only sampling of ground water north of MW-7 will confirm the extent of the chloroform plume. The Board appreciates the resources Triple E has expended to investigate the extent of chloroform in ground water and to remediate the plume. However, the data suggest that it is likely the domestic wells downgradient of MW-7 have been impacted by chloroform originating from the Triple E facility. We are obligated under Proposition 65 to inform residents who may be exposed to concentrations of chloroform exceeding 10 µg/l. Although the highest chloroform detected in domestic wells north of MW-7 during the last domestic well survey conducted by Triple E in February 1991 was 4.1 µg/1, the increases of chloroform in MW-7 from 8.7 µg/1 when it was first sampled in October 1992 to 43 µg/1 in December 1994 indicate the chloroform plume has migrated to the northwest towards the residential area north of Fair Oaks Road. As I discussed with Mr. Michael Campos on 19 September 1996, we have prepared an estimate of the Board costs to sample six domestic wells north of MW-7. The total cost would be approximately $1,500.