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Pacific Gas and Electric, Company Environmental Services <br /> P.O.Box 7640 <br /> San Francisco,CA 94120 — <br /> 415/973-7000 <br /> Direct Dial 415/973 i IR;&) 7f; �� �1: 3� <br /> Telecopy 415/973-9201 <br /> January 22, 1997 <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 /> Subject: Docket#HSA 90/91-08 - Stockton Former Manufactured Gas Plant Site: <br /> Submittal of Revised Proiect Schedule <br /> Enclosed for your approval is a revised project schedule which updates the schedule <br /> previously submitted to you on August 21, 1996. This schedule has been revised to allow <br /> incorporation of the results of the soil and groundwater investigation conducted <br /> in <br /> December, 1996 into the VLEACH model and into the Feasibility Study(FS). Three <br /> additional meetings have been added. One meeting will be to go over the results of the <br /> VLEACH model, which is being revised to include new polygons generated from the soil <br /> data obtained in December, 1996. We also hope to obtain agreement then on all the input <br /> parameters to be used when running the VLEACH model. A meeting has been added to <br /> go over the groundwater mixing cell model (used in conjunction with the VLEACH model <br /> to estimate groundwater concentrations from soil concentrations) and agree on its input <br /> parameters. And a meeting to discuss soil source area volumes and to discuss <br /> groundwater and soil remedies has been added to facilitate in preparation of the FS. Time <br /> is also allowed for incorporating use of the VLEACH and mixing cell models into the FS <br /> process. These models will be used to help evaluate the effectiveness of the remedial <br /> strategies proposed in the FS with respect to the three groundwater goals and the two <br /> points of compliance proposed in the FS. <br /> Prior to our next conference call to discuss the results of the December, 1996 field <br /> investigation, we plan to submit the soil analytical results (including the results of the DI <br /> WET analyses) and revised figures showing the location of each soil boring and its <br /> respective total PNA, carcinogenic PNA, TPH-gasoline and TPH-diesel concentrations <br /> with depth. <br />