SITE INFORMATION AND CORRESPONDENCE

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• Site-Wide Comprehensive ROD -9- 1 May 1997 DDRW Tracy 12. Section 9.2.1: This section states, in part, that "a cost-benefit analysis was appropriate to determine whether it was more cost-effective to directly address contamination in soils, or to allow the CoCs to be flushed from the vadose zone and captured by the OU-1 system." The text implies that such criteria was used as part of the basis for no further action determinations and selecting remedies. We believe that no such criteria was used in making these decisions. DDRW Tracy should review whether or not this criteria was used. If this criteria was used, the rationale should be described in the basis for no further action decisions and the comparative analysis of alternatives. Because this approach may not comply with state ARARs, re-evaluation of some no further action sites/groundwater CoCs and selected remedies may be necessary. 13. Section 9.3.6 (Dieldrin in OU-1 Groundwater): This section states, in part, "the remedy will also meet ARARs by reducing dieldrin, monuron, and diuron concentrations to below numerical beneficial use limits . . ." As a result, the rationale for no further action to address monuron and diuron in ground water is inadequate and inappropriate. Remedial action for these constituents is being conducted; therefore, the ROD should acknowledge and describe this action and include ground water cleanup levels for monuron and diuron. Furthermore, based on data presented in the RDFS Report which show the areal extent of these contaminants is within areas of ground water to be addressed as part of the OU-1 remedy and extraction wells to be used to address dieldrin contamination, it appears to be technically and economically feasible to cleanup these contaminants to background ground water conditions. 14. Section 10.0 (Statutory Determinations): The ARARs discussed in this section are not complete (see general comment 43). The word "potential" when referring to ARARs should be deleted. In addition, in cases where "institutional controls" is identified as the selected remedial alternative, statements are made that the selected remedy will comply with all Federal and state ARARs, but no ARARs are identified. We recall that these remedial alternatives were selected based on a number of ARARs which should be identified. The ROD should further describe how the best "balance of tradeoffs," among the alternatives were evaluated with respect to the CERCLA evaluation criteria, and how compliance with ARARs will be achieved. 15. Section 10.1: This sub-section specifies that two additional sites are recommended for no further action based on acceptable risk and prohibitive costs for any remedial alternative and that no statutory requirements are included for these sites. However, it is not clear what sites are referred to in this text. These sites should be clearly identified in the ROD, including the rationale for making the no further action determinations. Site-specific Comments 1. Group A Sites (SWA'IU 1/Area 2, Area 1 Building 237, & Area 3): Figure 9-2 for SWMU 1/Area 2 includes a notation which states that " This area of PCE contamination will not be treated with SVE since the contaminant is shallow . . . " All contaminants must be cleaned up to meet their respective cleanup levels, including in this case, the narrative cleanup standard (also see general comments 47 & 8). The text does not discuss this approach which is not justified. This notation should be deleted. The site characterization for Area 1 Building 237 should state that TCE, in addition to PCE, have contaminated soil, and that this site is a source area for both these constituents. TCE has been