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REVISED WORK PLAN AND EVALUATION OF ALTERNATIVES FOR CONTAINMENT OF THE CHLOROFORM PLUME IN GROUNDWATER TRIPLE E PRODUCE FACILITY,TRACY, CA 1. introduction This work plan has been prepared by Condor Earth 'Technologies, Inc. on behalf of Triple E Produce in response to a request by the California Regional Water Quality Control Board (Regional Board) as stated in a letter to Triple E dated 18 April, 1995, and as modified at a meeting on July 7 attended by Ms. Polly Lowry and Ms. Wendy Cohen. The area in the vicinity of the 'Triple E site, located at 8690 West Linne Road, Tracy, California, has been undergoing remediation for chloroform presence in groundwater. This document contains an introductory summary of previous work at the site, followed by a presentation of alternatives for containing the plume, a description of the selected alternative, a schedule of activities, and a progress report on bioremediation activities at the site. The location Of the site is illustrated in Figure 1. 2. Review of previous work 2.1 Aquifer Characteristics and Pump ']Lest Results Groundwater occurs at approximately 65 feet below ground surface (bgs) across the site. Chloroform has been reported in groundwater samples from monitoring wells in an aquifer composed of sands, silty sands and gravels. The sediment package extends below the deepest well, MW-4B drilled through the heart of the plume to 137 feet bgs and screened below 117 feet. No chloroform has been detected in MW-4B. The impacted monitoring wells are screened between 60-91 feet bgs. There are 8 monitoring wells at the site as shown on the site map of Figure 2. A pump test of monitoring well MW-4A was conducted in the summer of 1992 and described in a report titled Grouncitrater Remediation Plait Triple E Produce, D-acy, California (Weston) dated November 20, 1992. 'ihe pump test estimated hydraulic conductivity in the aquifer based on recovery in well MW-4A. Test data were obtained after 46,000 gallons had been removed during a 48-hour aquifer test consisting of a 47-hour drawdown phase and a one-hour recovery phase. The average of five solution-approaches to the data was 0.003 ft/min. (4.32 ft/day), which is within the range of expected values for the type of sediment, silty sand, sand and gravel, reported on logs of MWAA in the screened interval. Similar materials were noted at other wells in the aquifer. Computer modeling of the aquifer, presented in the same report, showed that extraction of 15-20 gpm from MW-4A alone, or MW-4A and MW-6 would create a cone of depression reaching 750-800 feet downgradient towards MW-7. Pumping from MW-4A and/or MW-6, based on the computer simulation would contain the plume by reversing the groundwater }low to the northwest of these wells. t, I CONDOR