SITE INFORMATION AND CORRESPONDENCE 1995-2004

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James L. Tjosvold, P.E. September 24, 1996 Page 2 Please note that a figure showing the assumed ND line for Zone B was included as an attachment in our August 7, 1996 responses to DTSC's July 9, 1996 comments on the Phase IV Report. We have also included a sentence in attached Section 5.0 recommending that as new information regarding the extent of groundwater contamination in Zone B becomes available, the FS will be revised to include this information. Comment: 2. The Agency's comments concerning lack of recommendation's to address contamination detected in Area II has not been addressed in your letter response. Instead the issue is deferred for discussion in our meeting on August 8, 1996. DTSC understands the Phase IV workplan goals did not specifically include characterization of "additional"potential contaminant sources, nevertheless the overall investigation goals do. As stated and approved in the Remedial Investigation Report dated 8193, the objectives of the RI/FS/RAP are to: *Determine the nature and occurrence of hazardous substances... *Identify existing and potential migration pathways... *Determine the magnitude and probability of actual or potential harm... *Identify and evaluate appropriate response measures... Area If contamination was discovered during the phase IVworkplan implementation activities, therefore, it would be appropriate to address the need for additional investigation work in the Phase IV report. The determination on data needs would be based on the overall investigation goals listed above. Response: 2. We have discussed and identified additional data needs for Area II during our August 8, 1996 and September 12, 1996 meetings. At a site visit with DTSC and RWQCB representatives on September 23, 1996, we determined where it may be feasible to install soil borings (given that Area II is an active substation). We will submit a workplan detailing our plans for soil borings in Area II to investigate the nature and occurrence of contamination discovered during the Phase IV groundwater investigation. However, to address your comment, we have included a statement in the attached Section 5.0 recommending that we investigate possible soil contamination in Area H. In addition, we acknowledge comment#3, which was included in the September 6, 1996 letter for our clarification and does not require a response for finalizing the Phase IV Groundwater Investigation Report.