SITE INFORMATION AND CORRESPONDENCE

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Site-Wide Comprehensive ROD -5- 1 May 1997 DDRW Tracy of construction, based on DLA funding available during the period the excavations are being conducted. The record shows that we have emphasized the need for a one-time removal action to meet final cleanup levels at these sites to be cost-effective and eliminate the probable need for future actions to complete site characterization and remobilization to be excavate further to meet final cleanup levels (see all previous RWQCB comment letters on the EE/CA documents and state letter dated 31.March 1997). As we have discussed, the ground water table is relatively shallow, approximately 18 feet bgs, and a number of the CoCs are present in soils at depth at these sites; therefore, the additional excavation necessary to meet final cleanup levels is critical to protecting water quality and may be limited. In order to meet cleanup levels in the ROD and be cost-effective, the excavation of contaminated soils should be implemented as a final remedial action. Final cleanup is achieved when concentrations of CoCs present in soils remaining above the water table are shown to be at or below final cleanup levels, as set forth in the ROD. The ROD should clarify that confirmation sampling will be conducted as part of the remedial action in accordance with an approved sampling and analysis plan (also see specific comments SWMUs 2, 3, & 33). Furthermore, these SWMUs have been identified as main source areas of ground water contamination at DDRW Tracy and remedial action is necessary to protect water quality. Soil cleanup levels must be achieved in order to meet groundwater cleanup levels. The assumption that the CoC soil (soil source area) concentrations were equal to final cleanup levels at SWMUs 2, 3 and 33 (e.g., see RI/FS Report Sections 12.3.4.1.0.3 & 12.3.4.2.0.4) was used as part of the basis for determining the need for groundwater remedial action and the cleanup levels. In addition, DDRW Tracy proposes to continue using the lagoons for percolating wastewater discharged from the wastewater treatment plant. Regional Board Order No. 96-122 regulates this discharge. Therefore, the ROD should state that if final soil cleanup levels are not met at these sites, DDRW Tracy will re-evaluate the remaining threat to groundwater and the ability to meet groundwater cleanup levels. 10. Correlate Soil Source Areas With Ground Water Plumes: The ROD does not clearly correlate soil source areas and ground water contamination identified at DDRW Tracy. The ROD should identify the soil source area(s) related to the areas where concentrations have been detected above ground water cleanup levels. Maps of contaminant plumes which show soil source areas for VOCs and pesticides should be included. 11. No Substance In Declaration For The ROD: This part of the ROD should present a concise summary of the selected remedies, basis for selecting these remedies, and statutory determinations. The site location should be modified to include the description presented in Section 1.2 of the OU-1 ROD. The declaration should state that the ROD presents the selected remedial actions for all soil sites (identified as a SWMU or soil source area) and for the OU-1 ground water plume and refer to map(s) which shows their location at DDRW Tracy. Plume maps which illustrate associated source area sites should be used (see General comment #10 ). The text should also clarify how the underground storage tanks (USTs) were addressed outside CERCLA. All references to LUFT Guidelines should be replaced by Tri-Regional Guidelines. The USTs which were addressed as part of SWMUs should be so specified. Major components of each selected remedy should be presented in bullet fashion. Additional language should summarize the