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in its December 10, 1992 letter, that the existing monitoring wells at the Site must be maintained and <br /> monitored annually <br /> In early 1994 the RWQCB issued revised UST closure requirements as "Tri-Regional Staff <br /> Recommendations for Preliminary Investigation and Evaluation of Underground Tank Site, Appendix <br /> B - Requests for Closure" (RWQCB, March 1, 1994) It is understood that the PHS-EHD adheres <br /> to these standards As a result of these new closure standards, UST sites may now be closed with <br /> no further action, or closed with conditions, such as groundwater monitoring From discussions with <br /> both PHS-EHD and the RWQCB, it was understood that conditional closure for this site may be <br /> obtained if information supporting the mass of hydrocarbon removed, modeling of hydrocarbon fate <br /> and transport, and the risks associated with hydrocarbon migration could be supplied Following <br /> those discussions, Dames & Moore prepared a Draft Amended Closure Request (Dames & Moore, <br /> August 1994) following the RWQCB Guidance Document <br /> Comments on the Draft Amended Closure Request were submitted by the PHS-EHD on <br /> _ August 29, 1994 These comments included a request that the report also address the technical and <br /> economic feasibility of reducing the amount of contamination to background levels based upon the <br /> highest recorded water elevation at the site which is 35 feet below ground surface The PHS-EHD <br /> also requested additional soil sampling to assess any changes in subsurface conditions since <br /> completion of the remedial actions in 1990, and construction of a monitoring well in close proximity <br /> and downgradient of the former waste oil tank A work plan addressing additional soil sampling and <br /> an additional monitoring well has been prepared as a companion document (Dames & Moore, <br /> November 1994) <br /> i <br /> SAC127 10 3 <br /> DAMES &MOORE <br />