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amec- ' , <br /> February 15, 2011 <br /> Project 0141430000.00008 <br /> Mr. Dean Hubbard <br /> Regional Water Quality Control Board <br /> Central Valley Region <br /> 1685 E Street <br /> Fresno, California 93706 <br /> Subject: Work Plan Addendum <br /> TAOC 6th Street Tracy Rail Yard <br /> Tracy, California <br /> Dear Mr. Hubbard: <br /> AMEC Geomatrix, Inc. (AMEC), prepared this letter on behalf of Chevron Environmental <br /> Management Company (CEMC) to propose additional investigation activities at the Tidewater <br /> Associated Oil Company (TAOC) 6th Street Tracy Rail Yard site (Figure 1) located in Tracy, <br /> California. AMEC prepared this work plan addendum in response to the Central Valley Regional <br /> Water Quality Control Board's (Water Board's) letter dated December 7, 2010, which provided <br /> comments on the July 30, 2010, Soil and Groundwater Investigation Report(Investigation <br /> Report). In their letter, Water Board staff requested additional soil and groundwater sampling in <br /> the vicinity of two previous sample locations, TRY-1 and TRY-29 (Figure 2). These comments, <br /> and the responses presented herein, were discussed with you in a January 20, 2010, telephone <br /> conversation. <br /> Water Board staff requests are presented below in italics. The response to Water Board <br /> comments and the proposed additional work follows. <br /> VICINITY OF TRY-1 <br /> Water Board Comment: <br /> Additional characterization is needed in the vicinity of OU-2 boring TRY-1 to determine if the <br /> TPHc(total petroleum hydrocarbons quantified as crude oil]detected in soil (12,000 mg/kg <br /> [milligrams per kilogram]) at six feet bgs[below ground surface]is associated with the <br /> historical pipelines or is related to the former railroad maintenance facility. The lateral and <br /> vertical extent of crude oil affected soil/groundwater needs to be determined. Fuel fingerprint <br /> evaluation of TPH affected soil should be considered to determine the nature and source of <br /> petroleum product present. <br /> Response <br /> Source Determination/Fingerprinting <br /> Based on a Southern Pacific Railroad Company valuation map dated 1951 and revised in 1958, <br /> the former Old Valley Pipeline (OVP) carried Bunker C fuel to a large aboveground storage tank <br /> (AST) at the rail yard in the vicinity of TRY-1. Therefore, it is possible that the impacts identified <br /> AMEC Geomatrix, Inc. AMEC Geomatrix <br /> 2101 Webster Street, 12th Floor <br /> Oakland,California <br /> USA 94612-3066 <br /> Tel (510)663-4100 <br /> Fax (510)663-4141 <br /> www.amecgeomatrixinc.com <br />