SITE INFORMATION AND CORRESPONDENCE

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RI/FS Report Review -4- 5 July 1991 DDRW, Tracy accomplished in this RI Report. The requirements of the TPCA may readily be incorporated into the RI/FS process through the proposed cleanup work for the industrial waste lagoons and any additional work to be performed as part of a site-wide RI/FS. Any additional work required for the HAR may best be addressed in the work plan for the site-wide RI/FS. Any work needed for the HAR or for the cleanup of the lagoons can be deferred until the site-wide RI/FS is performed. Most of the requirements of the TPCA can probably be handled administratively. The soils work needed in each of the WMUs is not considered to be necessary information to complete the RI for VOC ground water contamination in the northern portion of the site. However, any future soils work should be designed for more than one purpose so that as much information may be collected as possible from one sampling round. Soils work in the WMUs must be conducted so that a remedial alternative may be developed and selected based on the soils analytical data. Future soil sample analyses should be for soluble concentrations of contaminants so that these data may be used to perform an environmental fate analysis, such as the Designated Methodology, to determine the potential threat to water quality posed by the residual waste constituents in the unsaturated zone. From this analysis, soil cleanup levels and potential remedial alternatives may be developed. Existing analytical data for total heavy metals concentrations may be used "^ an environmental fate analysis. Tracy may assume that the constituents are 100 PE;---';.it soluble and back calculate the soluble concentrations from the total concentrations, or Tracy may collect samples and analyze for both total and soluble concentrations and establish a ratio between the concentrations for each constitent of concern. This ratio may then be used to calculate the soluble concentrations using the existing total concentration data base. If the soils work to be performed for each WMU indicates that ground water may have been impacted, then monitor well will need to be installed immediately downgradient of the WMU. If it is determined that monitor wells are needed, then this information should be included as part of the site-wide RI/FS. FEASIBILITY STUDY Overall , the FS Report was well prepared and organized. The FS Report contained a section on applicable or relevant and appropriate requirements (ARARs) . My major concern with this section of the FS is that the TPCA was not considered as an ARAR. The TPCA must be added as an ARAR. In addition, discussions in the FS Report were unclear as to aquifer cleanup goals or remedial response objectives versus performance standards. It needs to be clarified that the aquifer cleanup goal is not the same as performance standards for the discharge of treated ground water. The proposed aquifer cleanup goal is 5 Fig/l , which is the Primary Drinking Water Standard for TCE and PCE. However, it is our position that the aquifer should be cleaned up to background conditions, within engineering and economic feasibility. We will provide Tracy with information on our ARARs under a separate cover letter. The FS proposed nine different ground water cleanup alternatives . Four of these alternatives were selected for a detailed analysis and comparison. These four alternatives were: no action (Alternative 1) , the designed IRM at 340 gallons per minute (gpm) (Alternative 3) , a 500 gpm pump and treat system (Alternative 5) and a 500 gpm pump and treat system with in-situ bioremediation (Alternative 8) . The pump and treat systems consisted of extraction, air stripping and reinjection. The recommended