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4coc CALIFORNIA REGIONomp-WATER QUALITY CONTROL BOARD Cal/EPA CENTRAL VALLE'r`REGION 3443 Routier Road, Suite A - Sacramento,CA 95827-3003 Phone(916)255-3000 -, FAX(916)255-3015 J q Pete Wilson,Governor 16 March 1998 Mr.Nathan Esformes Triple E Produce P.O. Box 239 Tracy, CA 95378 EVALUATION OF CHLOROFORM IN GROUNDWATER AND EFFECTIVENESS OF EXTRACTION SYSTEM, TRIPLEEPRODUCE, TRACY, SAN JOAQUIN COUNTY I have reviewed the 5 November 1997 Evaluation of Chloroform in Groundwater and Effectiveness of Extraction and the 15 January 1998 Fourth Quarter 1997 Groundwater Monitoring Report submitted by Condor Earth Technologies for the Triple E Produce facility in Tracy. The reports evaluate the effectiveness of the groundwater extraction at the Triple E facility and conclude that the center of the chloroform plume is stable or decreasing in concentration,but at the perimeter of the plume there has been little change in chloroform concentration. However, chloroform concentrations in two domestic wells west(well 42B) and northwest (well 21B) of the most downgradient monitoring well (MW-7) show a significant rise in concentration since 1991. Chloroform in well 42B has risen from 2.2 µg/1 in 1991 to as high as 62 µg/1 in 1997. Well 21B, which is more distance from MW-7 than well 42B,has less of a rise in chloroform, from 1.8 µg/1 to 11 gg/1 during this same period. The monitoring report also notes a rise in the chloroform concentration in the upgradient well MW-1 that may be due to effluent water percolating to groundwater from the aeration pond. The effectiveness report states that reversal of the groundwater flow from the region of well MW-7 to the extraction system wells will not occur until the year 2000. This implies that containment of the plume surrounding wells 42B and 21B also will not occur until the year 2000 or later. Although the extraction system is shrinking the area of high chloroform concentration near the Triple E facility,the rise in concentration at the downgradient perimeter is not acceptable. The groundwater extraction system must be modified so as to contain the northernmost perimeter of the chloroform plume. The chloroform concentration at monitoring well MW-1 has increased significantly since the extraction system began in April 1996, probably due to percolation from the aeration pond. The chloroform concentration at MW-1 increased from 1.7 µg/l in December 1995 to 160 µg/1 in December 1997. The quarterly monitoring report states that the pond is a possible source since no other upgradient source of chloroform is known. An investigation is needed to determine the source of the increase in chloroform in the upgradient well MW-1. 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 of present and future generations.