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California F�;ional Water Qualit3 `�ontrol Board Central Valley Region iFl Peter M.Rooney Sacramento Main Office Ed J. Schnabel Secretaryfor Internet Address: httpJ/www.swrcb.ca.gov/-rwgcb5/home.html Chair Environmental 3443 Routier Road,Suite A,Sacramento,California 95827-3003 n Protection Phone(916)255-3000•FAX(916),25-5-3015 ' 18 August 1998 Mr. Nathan Esformes Triple E Produce P.O. Box 239 Tracy, CA 95378 WORK PLAN FOR EVAL UA TION OF CHLOROFORM INCREASE AT MW-1, FIRST AND SECOND QUARTER 1998 MONITORING REPORTS, SAN JOA QUIN COUNTY I have reviewed the 30 April 1998 Work Plan for Evaluation of Chloroform Increase at MW4, Modification to the Groundwater Extraction and Treatment System, Triple E Produce Facility, and the 15 April 1998 First Quarter 1998 and 13 July 1998 Second Quarter 1998 Monitoring Reports submitted by Condor Earth Technologies (Condor) for Triple E Produce. I have the following comments. The work plan states that Condor believes the source of contamination in well MW-1 is the aeration pond. Condor believes that infiltration from the aeration pond is causing a mound that locally reverses the groundwater gradient causing chloroform contaminated groundwater to flow towards well MW-1. The only method of investigation proposed in the work plan to determine whether the-pond is the source of chloroform contamination is to reduce or cease discharge of groundwater to the aeration pond thereby reducing the size of the groundwater mound. The work plan states that if the concentration of chloroform decreases in well MW-1 following the reduction of groundwater discharge to the pond, it would be definitive evidence that the mounding beneath the pond is the source of chloroform. The proposed groundwater mound investigation is not approved at this time for the following reasons. 1. The work plan does not provide data on the duration or amount of the reduction in discharge to the aeration pond that is needed to reduce the mound to a pre-discharge condition which would allow a comparison with current conditions. Information is needed on how much to reduce the discharge to the aeration pond and how long it would take for the mound to dissipate so that uncontaminated groundwater can be extracted from well MW-1. 2. The work plan does not specify the change in concentration that would be statistically significant to show that the mound is the source. Concentrations of chloroform in well MW-1 before 1995 were less than 14 µg/1. Chloroform concentrations in well MW-1 over the last year have ranged from 71 to 200 µg/1. Thus a large reduction in concentration may be needed to demonstrate the impact of the California Environmental Protection Agency cc3 Recycled Paper