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PARSONS <br /> 2121 N.California Blvd.,Suite 500•Walnut Creek,CA 94596.(925)941-3700.Fax(925)979-9781 <br /> www.parsons.com <br /> February 5, 2010 <br /> Mr. Robert Aragon <br /> Department of Toxic Substances Control <br /> Northern California - Coastal Cleanup Operations Branch <br /> 700 Heinz Avenue, Suite 200 <br /> Berkeley, CA 94710-2721 <br /> RE: ITEMIZED RESPONSES TO DTSC'S <br /> COMMENTS OF JANUARY 26, 2010 <br /> Subject: Draft Final Remedial Investigation Report for the Former Tracy MGP Site, <br /> Tracy, CA dated June 19, 2009 <br /> Former Tracy MGP Site <br /> 502 E. Grant Line Road <br /> Tracy, California 95376 <br /> Dear Mr. Aragon: <br /> On behalf of the Pacific Gas and Electric Company (PG&E), Parsons has prepared this <br /> letter as a response to the Geological Services Unit of the Department of Toxic <br /> Substances Control (DTSC) itemized comments submitted to PG&E on January 26, <br /> 2010 regarding the subject document. It is anticipated that if these responses are <br /> acceptable to DTSC, and with DTSC's approval, the RI Report will be finalized and <br /> submitted in hardcopy and electronic format. <br /> DTSC Comment No. 1 <br /> The data in the report may be sufficient to move to the Feasibility Study and Risk <br /> Assessment; however, I have a concern about the potential for tetraethyl lead to be <br /> present in soil gas. There is a California Human Health Screening Level for tetraethyl <br /> lead (in soil gas) of 0.206 micrograms per cubic meter for residential use. According to <br /> the second paragraph on page 2 of the Draft Final RI, the gasoline underground storage <br /> tank (UST) that was located at the northwestern area of the site was installed in the early <br /> 1960's. The third paragraph on page 2 indicates that the UST was removed in October <br /> 1987. As such, gasoline stored in this UST probably contained tetraethyl lead. Here is <br /> the link to the CHHSLs document. Table 2 contains the soil gas CHHSLs: <br /> http://www.calepa.ca.gov/brownfields/documents/2005/CHHSLsGuide.pdf <br /> Response to DTSC Comment No. 1: Comment Noted. During the course of the soil <br /> and soil gas investigation at the Site, we did not request tetra-ethyl lead analyses. A <br />