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r <br /> ENV. <br /> A M F H ! C A <br /> 244 California Street, Suite 500 <br /> San Francisco, CA 94111 <br /> (415)989.9933 <br /> Fax(415)989.9934 <br /> www envamenca.com <br /> April 29, 2005 <br /> Mr. Duane White <br /> Department of Toxic Substances Control <br /> 8800 Cal Center Drive <br /> Sacramento, California 95826-3200 <br /> RE: Response to DTSC Comments <br /> Work Plan to Address Groundwater Conditions in the Vicinity of MW-26R <br /> Former Manufactured Gas Plant <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. <br /> ENV America prepared and submitted the Work Plan to Address Groundwater Conditions <br /> in the Vicinity of MW-26R and to Decommission Eight Monitoring Wells (Work Plan) for the <br /> Site to the Department of Toxic Substances Control (DTSC) in February 2005. DTSC <br /> provided comments on the Work Plan in a letter to PG&E dated April 1, 2005. These <br /> comments were discussed during a conference call on April 20, 2005, among PG&E, <br /> DTSC, and ENV America representatives. The DTSC indicated during the conference call <br /> that it would be appropriate for PG&E to submit a letter addressing DTSC comments, <br /> rather than submitting a revised Work Plan as requested in the DTSC letter. <br /> Based on the discussions, PG&E and ENV America's responses to the DTSC comments <br /> are presented below. <br /> 1. DTSC comments: In the Work Plan, MW-27 was proposed to be installed using the <br /> hollow-stem auger (HSA) method which is the same method that was used to install the <br /> other B zone wells at the site. The DTSC recommended the mud-rotary or air-rotary <br /> casing hammer method which would prevent the formation of a conduit between the A <br /> zone and B zone and between flow zones within the B zone. In an April 25, 2005, email <br /> to PG&E, the DTSC stated that if PG&E uses the HSA method to install the B zone <br /> well, PG&E should collect a grab groundwater sample in the A zone to document that <br /> shallow groundwater at the location of MW-27 is not affected by the former MGP. <br />