SITE INFORMATION AND CORRESPONDENCE 1995-2004

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James L. Tjosvold, P.E. August 7, 1996 Page 2 conclusions made must be adequately supported by conclusive data clearly presented in the Report. Recommendations made in Section 5.0 must include proposals for addressing data gaps and fulfilling goals. As discussed in your Report, during the Phase IV fteldwork, soil and groundwater contamination has been detected in Area II. The Report states that previously existing off-site industries may be contributing sources, but does not provide adequate data to support this conclusion. The Report also fails to provide recommendations to collect any additional information to properly define and address the newly discovered contamination in Area II. Response: 2. As discussed in our June 24, 1996 conference call meeting and as implied in Section 4.0, PG&E believes that the only data gap relates to groundwater concentrations in Zone B, specifically beneath Area II. As discussed during the conference call and as outlined in Section 5.0,the recommendations regarding groundwater concentrations in Zone B are to assume a non-detect line for total PNAs in Zone B for the purpose of preparing the Feasibility Study (FS). This assumed nondetect line is shown in the attached figure as being the perimeter of PG&E Areas I and II. During preparation of the feasibility study the assumed ND limit can be varied to estimate its affect on remedial action alternatives. Groundwater concentrations will continue to be monitored in Zone A, B, and C wells while the final FS is being prepared. Due to overhead and underground utilities, data collection and potential remedial alternatives in Area II are very limited. However,both your July 9, 1996 letter and your July 2, 1996 letter on our proposed feasibility study approach suggest that you believe more data is needed. Therefore,PG&E is looking forward to our August 8, 1996 meeting to discuss our next steps; whether to collect more soil and groundwater data(which will be limited given the obstacles present in Area II) at this time or whether to wait until completion of the FS to determine what, if any, investigation is necessary in Area II. As discussed in more detail on page 4 of these comments,PG&E is informing DTSC to the fact that other historic petroleum-related sites existed in the vicinity of the site. Due to similar groundwater concentrations in wells located upgradient and crossgradient of the site and little to no site investigation activities outside of the PG&E site, it is not possible to make a conclusion in this report about the other potential contributing sources in the area. Comment: 3. Section 5.0 includes a recommendation to "implement a soil remedy alternative recommended in the final FS and described in the RAP"consisting of treatment of four source areas within Area I to minimize migration of contaminants to groundwater. DTSC has not approved, much less received, a final FS or RAP. It appears a bit premature for PG&E to be proposing implementation of a final soil remedy without first completing the final Feasibility Study.