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r <br /> Lee Higgins - 2 - 6 January 2011 <br /> Tracy Rail Yard-Offsite West Area <br /> • The vertical extent of affected groundwater remains unknown in the area previously <br /> reporting the highest concentrations of petroleum hydrocarbons detected in <br /> groundwater from borings drilled in Baldwin Court in 2005. Boring TRY-35 with <br /> sampling is proposed near the location of the previous borings. <br /> • A contingent boring location (TRY-36) is proposed near the north end of Rockingham <br /> Court to collect soil samples to evaluate the lateral extent of affected soil in this area. <br /> • Soil samples will be submitted for analysis of total petroleum hydrocarbons as crude oil <br /> (TPHc); benzene, toluene, ethylbenzene, and xylenes (BTEX); and polynuclear <br /> aromatic hydrocarbons (PAHs). Results of analysis for samples from approximate <br /> depths up to 10 feet below ground surface will be considered for use in a future site <br /> human health risk assessment. One affected soil sample will be submitted for fuel <br /> fingerprint evaluation. <br /> • Groundwater samples will be submitted for analysis of TPH as diesel (TPHd), BTEX, <br /> and PAHs. One affected sample will be submitted for fuel fingerprint determination. <br /> Central Valley Regional Water Quality Control Board (Central Valley Water Board) staff has <br /> reviewed the Workplan and we have the following comments: <br /> • Contingent soil boring location TRY-36 should be drilled and samples collected for <br /> evaluating the lateral extent of affected soil and/or groundwater for this part of the site. <br /> • A soil boring should be drilled and groundwater sampled in East 6th Street, <br /> approximately 200 to 250 feet west-northwest of TRY-30 to evaluate the downgradient <br /> extent of impacted groundwater. <br /> Central Valley Water Board staff concurs with the additional soil and groundwater investigation <br /> described in the Workplan provided comments outlined above are addressed. <br /> By 1 June 2011, please submit the soil and groundwater investigation report. <br /> If you have any questions or comments, please contact Dean Hubbard at (559) 445-5179 or <br /> by email at dhubbard(a)-waterboards.ca.gov. <br /> .l <br /> /r <br /> SHELTON R. GRAY C. DEAN HUBBARD <br /> Senior Engineering Geologist Engineering Geologist <br /> P,G. No. 6357 <br /> cc: Michael J. Infurna, San Joaquin County DEH, Stockton <br /> Gary Foote, AMEC Geomatrix, Oakland <br />