Laserfiche WebLink
Pacific Gas and Electric, Company Environmental Services _„7 T r1 <br /> P.O.Box 7640 1 -r I„_1 @ <br /> San Francisco,CA 94120 <br /> 415/973-7000 <br /> Direct Dial 415/973- rc. ,+•r , r <br /> March 13, 1996 <br /> Telecopy 415/973-9201 3' �� 4 <br /> James L. Tjosvold,P.E. <br /> Chief, Site Mitigation Branch <br /> California Environmental Protection Agency <br /> Department of Toxic Substances Control <br /> 10151 Croydon Way, Suite 3 <br /> Sacramento, CA 95827 <br /> Attention: Mr. Fernando Amador <br /> Dear Mr. Tjosvold: <br /> Re: Docket#HSA 90/91-08 - Stockton Former Manufactured Gas Plant Site <br /> Subject: Report Evaluating Potential Groundwater Impacts <br /> from Residues in Soil and Revised Project Schedule <br /> Attached for your review and comment are two copies of Pacific Gas and Electric <br /> Company's (PG&E's) report"Evaluation of Potential Groundwater Impacts from <br /> Residues in Soil" for the Stockton Former Manufactured Gas Plant Site. Also attached <br /> for your review and approval is a revised project schedule for PG&E's Stockton Former <br /> Manufactured Gas Plant Site. <br /> The attached report summarizes work conducted in response to the Department of Toxic <br /> Substances Control (DTSC) and the Central Valley Regional Water Quality Control <br /> Board (RWQCB) comments on the draft Soil Operable Unit Feasibility Study (OUFS), <br /> which was submitted to DTSC and the RWQCB on November 8, 1995. Written <br /> comments from DTSC and the RWQCB, dated December 26, 1995, indicated that <br /> additional criteria need to be developed for defining source areas which were <br /> recommended for remedial action in the draft soil OUFS. In particular,PG&E was <br /> requested to define criteria to establish soil clean-up levels that would be protective of <br /> groundwater using site specific and resource specific information. Criteria are to be <br /> supported using the RWQCB's Designated Level Methodology or its equivalent. <br /> Rather than develop specific criteria for establishing soil clean-up levels, this report utilizes <br /> EPA's VLEACH model, chemical specific travel times, and diesel residual soil <br /> concentrations to demonstrate quantitatively that the recommended action in the draft soil <br /> OUFS (remediation of four potential soil source areas) is protective of groundwater. The <br /> report demonstrates that, after treatment of the four potential soil source areas identified <br />