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� T <br /> ENV. <br /> AMERICA <br /> 244 California Street,Suite 500 <br /> San Francisco,CA 94111 g <br /> (415)989-9933 "a N 13 2005 <br /> Fax(415)989-9934 <br /> w .envamenca.com LiuViRONMENT HEALTH <br /> PERl,XT/SERVICES <br /> January 11, 2005 <br /> Mr. Duane White <br /> Department of Toxic Substances Control <br /> 8800 Cal Center Drive <br /> Sacramento, California 95826-3200 <br /> RE: Cost Estimate for Financial Assurance <br /> Long-term Operation and Maintenance <br /> Former Manufactured Gas Plant Site <br /> Stockton, California <br /> Dear Mr. White: <br /> ENV America Incorporated (ENV America) has prepared this cost estimate on behalf of <br /> Pacific Gas and Electric Company (PG&E) for the former manufactured gas plant (MGP) <br /> site (Site) located in Stockton, California. This cost estimate was requested by the <br /> California Department of Toxic Substances Control (DTSC) in a December 21, 2004, letter <br /> to PG&E. The DTSC requested a cost estimate for long-term operation and maintenance <br /> (O&M) for the Site based on the revised groundwater monitoring program described in the <br /> letter. <br /> Cost Estimate <br /> The cost estimate for the long-term O&M at the Site is limited to 30 years (Table 1) as <br /> suggested by the DTSC. The estimate includes: <br /> • Task 1 —Annual Groundwater Monitoring and Reporting <br /> • Task 2 — Biennial Sampling and Evaluation for Natural Attenuation <br /> • Task 3 —Annual Cap/Deed Restrictions Inspection and Reporting <br /> • Task 4 — Cap Maintenance (estimated) <br /> • Task 5 — Five-Year Review <br /> • DTSC Oversight (estimated) <br /> The assumptions for each of these cost elements are described in the following sections. <br /> The detailed cost estimates for the five tasks are shown in Table 2. <br /> Task 1 —Annual Groundwater Monitoring and Reporting <br /> A total of 18 wells will be sampled once per year according to the revised program <br /> approved by DTSC, as summarized in the following table. <br />