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EDMUND G.BROWN JH. <br /> w� •i. GOVERNOR <br /> 1 <br /> MATTHEW RODRIOUEZ <br /> SECRETARY FOR <br /> C A LP O R N I A ENVIRONMENTAL VROTECTION <br /> Water Boards <br /> Central Valley Regional Water Quality Control Board <br /> S301A83S/LIVVd3d <br /> 411V3H 1VLN3wN0HlAN3 <br /> £LOZ 9 9 330 <br /> 18 December 2013 a3/ \I3^38 <br /> Michael N. Oliphant <br /> Chevron Environmental Management Company <br /> 6001 Bollinger Canyon Road <br /> San Ramon, CA 94583 <br /> REVIEW — SOIL VAPOR INVESTIGATION WORKPLAN, TAOC TRACY PUMP STATION, 880 <br /> BEECHNUT AVENUE, TRACY, SAN JOAQUIN COUNTY <br /> Chevron Environmental Management Company (Chevron) submitted the Soil Vapor Investigation <br /> Workplan (Workplan) for the Tidewater Associated Oil Company (TAOC), 880 Beechnut Avenue <br /> project. The Workplan, dated 18 November 2013 was prepared for Chevron by AMEC Environment <br /> & Infrastructure, Inc. (AMEC) and submitted to Central Valley Regional Water Quality Control Board <br /> staff (Staff) for review and comment. <br /> The Workplan proposes three soil borings to collect vapor samples as offsets to locations where <br /> xylenes and naphthalene were reported in soil samples collected from prior borings. Previous site <br /> investigative findings reported low concentrations of naphthalene (0.057 to 2.6 milligrams per <br /> kilogram [mg/kg]) in two soil samples collected from a boring depth of five and ten feet below <br /> ground surface (bgs). Xylene was detected at a concentration of 0.78 mg/kg in a sample obtained <br /> from another boring at a depth of five feet bgs; the proposed borings are located across the <br /> approximate center of the project. <br /> The purpose of the Workplan is to evaluate the extent of the naphthalene and xylenes previously <br /> identified at the project. The soil vapor results would be used to revise a previous Human Health <br /> Risk Assessment (HHRA) in support of a future commercial/industrial use scenario which would <br /> allow construction of buildings/structures on the site. Shallow borings and appropriate soil vapor <br /> sampling and collection equipment will be utilized. <br /> The soil vapor samples will be analyzed by an onsite State-certified mobile laboratory. For each <br /> day of borings and soil vapor sampling, one background ambient air sample will be collected and <br /> submitted to a State-certified laboratory for determination of benzene, toluene, ethylbenzene and <br /> xylenes, and naphthalene. <br /> KARL E. LONGLEY SCD, P.E„CIIAIR ] PAMELA C. CREEDON P.E., BCEE,SHEOUTIvE OrrIGER <br /> 1685 E Street,Fresno.CA 93706 1 www,waterboarcis.ca.gov/centraivalley <br /> .R�RECYCLED PAPER <br />