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ENV. <br /> AMERICA �� <br /> L� <br /> 244 California Street, Suite 500 C I�P ME <br /> rn <br /> San Francisco, CA 94111 11 <br /> (415)989-9933 <br /> Fax(415)989-9934 NOV <br /> 2 2 2004 <br /> W <br /> W .envamencaxonl 4 <br /> ENVIRONMENT HEALTH <br /> November 17, 2004 PERMIT/SERVICES <br /> Mr. Duane White <br /> Department of Toxic Substances Control <br /> 8800 Cal Center Drive <br /> Sacramento, California 95826-3200 <br /> RE: Proposed Revised Groundwater Monitoring Program <br /> Former Manufactured Gas Plant Site <br /> Stockton, California <br /> Dear Mr. White: <br /> ENV America Incorporated (ENV America) has prepared this letter on behalf of Pacific Gas <br /> and Electric Company (PG&E) for the former manufactured gas plant (MGP) site (Site) <br /> located in Stockton, California. This letter has been prepared based on a draft letter <br /> transmitted by the California Department of Toxic Substances Control (DTSC) to PG&E on <br /> September 30, 2004, and a follow-up conference call on October 19, 2004, between <br /> DTSC, PG&E, and ENV America representatives regarding a proposed revised <br /> groundwater monitoring program for the site. <br /> Based on the discussion, the parties agreed to revise the Groundwater Monitoring <br /> Decision Tree and the groundwater monitoring program for the site. These revisions are <br /> described in the following sections. <br /> REVISED GROUNDWATER MONITORING DECISION TREE <br /> The Groundwater Monitoring Decision Tree (Decision Tree) was developed in 2000 as part <br /> of the remediation operation and maintenance program for the site. The site has been <br /> capped and quarterly groundwater monitoring data have been collected since then. These <br /> data indicate that site conditions are stable and natural attenuation of the constituents of <br /> concern (COCs) in groundwater is occurring. The quarterly groundwater-monitoring <br /> frequency is no longer warranted based on the data collected from the site to date. As <br /> such, the monitoring frequency in the Decision Tree is reduced, as shown on Figure 1. <br /> REVISED GROUNDWATER MONITORING PROGRAM <br /> Analytical data collected from each monitoring well will be evaluated using the revised <br /> Decision Tree. The revised groundwater monitoring program, in general, is summarized in <br /> the following table: <br />