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CALIFORNIA REGIONr,4,JATER QUALITY CONTROL BOARD Cal/EPA CENTRAL VALLEY REGION e 3443 Routier Road, Suite A �`i„ r'„�rC l c/Al. 7/1IL %j Sacramento, CA 95827-3098 Phone(916)255-3000 r FAX(916)255-3015 Pete Wilson Governor 18 July 1997 Mr. Nathan Esformes Triple E Produce P.O. Box 239 Tracy, CA 95378 REPORT ON GROUNDWATER EXTRACTION EFFECTIVENESS, TRIPLE E PRODUCE, TRACY, SAN JOAQ UIN CO UNTY I have reviewed the 13 May 1997 report entitled Report on Ground Water Extraction Effectiveness submitted by Condor Earth Technologies (CET) for Triple E Produce (Triple E) in Tracy. The report evaluates the effectiveness of groundwater extraction at the Triple E facility to contain the chloroform plume. The report also satisfies the requirement of Provision 7 in Waste Discharge Requirements Order No. 96-118 issued to Triple E Produce on 6 May 1996. CET concludes in the report that although the extraction system has not reversed the groundwater flow direction in the area of MW-7 the chloroform plume is stable or decreasing in concentration and that the elevated chloroform in the domestic well identified as 42B is abnormal and unusual. Triple E proposes to increase the pumping rate from XW-1 as much as possible to attempt to overcome other influences on the gradient near MW-7 and to assess the occurrence of chloroform in 42B by resampling this well and investigating the water system for sources of chloroform. The comments below address Triple E's conclusions and proposals. Chloroform Trends The chloroform plume does appear to be stable or decreasing in concentration for the depth intervals of Triple E's monitoring wells. However, this may not be true for chloroform at depths below that being monitored by Triple E's monitoring wells. The elevated concentrations of chloroform in 42B indicate that higher concentrations of chloroform may be present at depths below that being monitored by Triple E's monitoring wells. Chloroform in 42B Triple E states that the chloroform concentrations in the domestic well identified as 42B appear to be abnormal and unusual based on the differing results obtained from two different laboratories (62/60 µg/1 and 42 µg/1) and comparison to chloroform concentrations in nearby well MW-7 (22 µg/1). The elevated chloroform concentrations in 42B may be the result of a slight downward trend of chloroform in groundwater from the source area. Figure 5 of the report shows this is likely and since 42B is screened at a slightly lower interval than MW-7 it would not be abnormal for chloroform concentrations to be higher —� in 42B than in MW-7. Recycled Paper Our mission is to preserve and enhance the quality of California's water resources,and ensure their proper allocation and efficient use for the benefit ofpresent and future generations.