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" Pacific Gas and Electric Campany Environmental Services "s " <br /> P.O.Box 7640 <br /> San Francisco,CA 94120 <br /> 415/973-7000 S E P 2 1��2 <br /> Direct Dial 415/973- <br /> September 22, 1992 Telecopy415/973-9201 ENVIRONMENTAL HEALTH <br /> ff"Mifig <br /> Mr. Val F. Siebal <br /> California Environmental Protection Agency <br /> Department of Toxic Substances Control <br /> ' 10151 Croydon Way <br /> r Sacramento, CA 95827 <br /> G? <br /> Attention: Mr. Fernando Amador <br /> Dear Mr. Siebal : <br /> Re: Docket #HSA 90/91-08 - Stockton Manufactured Gas Plant Site <br /> Subject: Completion of IRM on Hazelton Avenue <br /> (Revision of July 28, 1992 Letter) <br /> On January 15, 1992, PG&E submitted the "Interim Remedial Measure Report <br /> of Findings and Recommendations - PG&E Stockton Former MGP Site" which <br /> provided the results of surface soil sampling on the Hazelton Avenue <br /> strip and evaluated remedial actions. The soil sampling results <br /> indicated elevated levels of PNAs (greater than background) occurred in <br /> the area tested. Subsequent surface soil testing reported February 6, <br /> 1992 further defined the extent of PNAs in surface soils. <br /> The January 15 document provided evaluation of nine alternatives ranging <br /> from no action, fencing, capping or sealing, to excavation and disposal . <br /> The alternatives were evaluated based on effectiveness in mitigating <br /> potential exposure, implementability, and relative cost. Based on this <br /> evaluation, PG&E recommended that a cement cap be placed over the <br /> embankment soils. The Department approved the cement cap as an Interim <br /> Remedial Measure (IRM) by letter of February 14, 1992. <br /> PG&E has completed construction of the Portland cement cap located on <br /> the northern embankment of Hazelton Avenue south of the former gas plant <br /> site and Station A Substation. The attached figure shows the extent of <br /> the cement cap constructed. A summary of the construction activities <br /> follows. Work was conducted by PG&E health and safety certified <br /> engineering and construction personnel and permitted by the City of <br /> Stockton. Construction was completed on schedule, beginning April 28 <br /> and ending June 1, 1992. Traffic and dust control were maintained <br /> throughout the project. All construction was consistent with the pre- <br /> construction specifications and design, with one revision to Detail <br /> Section 3 as shown in the attached figure. <br /> Prior to construction, existing concrete riprap and vegetation was <br /> removed from the embankment. The slope was graded to a flat uniform <br /> slope with drainage as specified in the plan. Approximately 560 cubic <br /> yards of cement conforming to Caltrans Class B was placed in wood forms <br />