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Pacific Gas and Electric Company Environmental Services <br /> P.O.Box 7,640 _-I hr L HE AL T11 <br /> San Francisco, Gk9m��U(_ <br /> 415/973`7000 <br /> November 5, 1996 Di�rA gy11 157-92g 2 3 <br /> James L. Tjosvold, P.E. <br /> Chief, Site Mitigation Branch <br /> California Department of Toxic Substances Control <br /> r 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: Quarterly Summary Report(Third Quarter. 1996) <br /> Pacific Gas and Electric Company (PG&E) submits this third quarter(1996) summary report <br /> for the Stockton Former Manufactured Gas Plant Site (site) in accordance with Provision 3.7 <br /> of the above-referenced order. This report summarizes technical activities conducted by <br /> PG&E in compliance with the order from July 1, 1996 to September 30, 1996 and activities <br /> planned for the next quarter. <br /> I. Activities Performed During Previous Ouarter: <br /> On May 22, 1996, a meeting between PG&E, the Department of Toxic Substances Control <br /> (DTSC) and the Central Valley Regional Water Quality Control Board (RWQCB)was <br /> conducted to discuss remedial objectives and goals for groundwater;the conceptual model of <br /> how constituents have migrated to groundwater; modeling results for evaluating current <br /> conditions and how long it takes for constituents of potential concern to migrate to <br /> groundwater; and treatability results for in-situ soil stabilization. The conceptual model was <br /> agreed on and further sensitivity analysis work was discussed with respect to the VLEACH <br /> model. The treatability study indicated mixed results for stabilization of the source area soils. <br /> At the meeting, it was recommended that the soil and groundwater feasibility studies be <br /> combined into one Feasibility Study(FS) and that a range of groundwater goals and points of <br /> compliance be used to evaluate the technologies in the combined FS. This understanding was <br /> set forth in a June 6, 1996 letter submitted to DTSC by PG&E. In a July 2, 1996 letter, <br /> DTSC clarified that background or non-detect groundwater quality (where economically and <br /> technically feasible) is the starting point for evaluating alternatives in the FS. <br /> The"Phase IV Groundwater Investigation Draft Report" describing the installation of six new <br /> groundwater monitoring wells at the site was submitted for DTSC and RWQCB review on <br /> June 11, 1996. On June 24, 1996, a conference call was conducted to review the results of <br />