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"ATE OF CALIFORNIA-Environmental Protection Agency PETE WILSON,Governor <br /> "CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD l <br /> CENTRAL VALLEY REGION <br /> 3443 Routier Road,Suite A , <br /> Sacramento, CA 95827-3098 <br /> PHONE'(916)255-3000 <br /> FAX (916)255-3015 <br /> 6 April 1995 <br /> Mr. Fernando Amador <br /> Department of Toxics Substances Control <br /> 10151 Croydon Way, Suite 3 <br /> Sacramento, CA 95827-2106 <br /> COMMENTS ON THE PHASE III TECHNICAL MEMORANDUM, PG&E STOCKTON <br /> FORMER MANUFACTURED GAS PLANT, SAN JOAQUIN COUNTY <br /> I have reviewed the 14 March 1995 Phase III Technical Memorandum for PG&E's former manufactured <br /> gas plant in Stockton. My comments are presented below. <br /> I. Section 2.4.1, Nearby Site Investigations. <br /> The memo described two sites northwest of the facility which have ongoing investigations. PG&E <br /> should obtain more detailed information regarding the investigation/remediation at these sites to <br /> determine if they are contributing to PG&E's contamination. These sites also should be shown on a <br /> site map to demonstrate their position relative to PG&E. <br /> 2. Section 3.2.1, Drilling and Well Installation <br /> The memo stated that the Phase III investigation revealed similar geology encountered during the <br /> Remedial Investigation/Feasibility Study (RDFS). The cross-sections presented in the RI/FS should <br /> be revised to include geologic information (particularly Zone C) obtained during the Phase III <br /> investigation. The revised cross-sections should be included in the memo. <br /> 3. Section 3.2.3, Ground Water Elevation Measurements <br /> The memo stated that the ground water flow direction in Zone A has varied from southeast to east <br /> and that of Zone B from northeast to east. The memo also stated that the gradient observed in Zone <br /> C is not consistent with the regional gradient to the northeast, therefore, the three new Zone C wells <br /> are upgradient of the site. <br /> As agreed at our 28 February 1995 meeting, PG&E will measure monthly water elevations for six <br /> months to establish ground water flow directions and gradients at the site. Six months may not be <br /> adequate to consider the effects of seasonal changes and a longer ground water elevation monitoring <br /> program may be needed. <br />