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�.r42'.: EuM�nc'Ci 6licwn Jx, <br /> C A L F/O"x a � .YIATHEn'fic UxlOUE[ <br /> Water Boards <br /> vxonc nix. <br /> Central Valley Regional Water Quality Control Board <br /> TO: Shelton R. Gray <br /> Senior Engineering Geologl}t <br /> FROM: C. Dean Hubbard 'f <br /> Engineering Geologist . r <br /> P. G. No. 6351 <br /> DATE: 26 September 2012 <br /> SUBJECT: REVIEW— HUMAN HEALTH AND ECOLOGICAL SCREENING EVALUATION, <br /> TRACY RAIL YARD — OFFSITE, WEST AREA, TRACY, SAN JOAQUIN <br /> COUNTY <br /> Chevron Environmental Management Company (Chevron) submitted a Human Health and Ecological <br /> Screening Evaluation report (Report; Screening Evaluation) for the Tidewater Associated Oil Company <br /> (TAOC) Tracy Rail Yard (TRY) Offsite-West project (Site). TAOC is a Chevron predecessor company. <br /> The Report, dated 10 July 2012, was prepared for Chevron by AMEC Environment & Infrastructure <br /> (AMSC). The Site is east of Tracy Boulevard and south of 6th Street, in central Tracy. The City of <br /> Tracy Boyd Service Center lies between Tracy Boulevard and the project Site. I have reviewed the <br /> Report and related 2005— 2010 documents ino r project files and my comments are provided below. <br /> �` <br /> The Site is adjacent to and west of the TAOC TRY 6th Street Rail Yard project, which is also being <br /> investigated for Chevron by AMSC, and consists of a residential neighborhood of single family homes. <br /> The former Union Pacific Railroad (UPRR) right-of-way (ROW) is along the north-northeast side of the <br /> Site. Vacant land is present beyond the UPRR ROW further northwest-northeast. The historical <br /> TAOC crude oil pipelines extended from east to west through the approximate center of the Site. <br /> Based on the findings, Central Valley Regional Water Quality Control Board (Central Valley Water <br /> Board) staff concurred in a 26 March 2012 letter to Chevron, that crude oil affected soil and <br /> groundwater had been delineated. Since it was established that adequate data had been collected, a <br /> Screening Evaluation could be prepared. <br /> Site soil and groundwater has been affected by total petroleum hydrocarbons as crude oil (TPHc), low <br /> concentrations of certain polynuclear aromatic hydrocarbon (PAH) compounds, and benzene, toluene, <br /> ethylbenzene, and xylenes (BTEX; volatile organic carbon [VOCs] compounds). A previous fuel <br /> fingerprint evaluation determined that the petroleum hydrocarbons present are consistent with <br /> weathered San Joaquin Valley crude oil. <br /> According to AMEC's Screening Evaluation: <br /> • Chemicals of potential concern (COPCs) are analytes detected in at least one soil sample <br /> between depths of 0 and 10 feet below ground surface (bgs). Concentrations of BTEX <br /> and/or certain PAHs are considered Site COPCs and were evaluated quantitatively for the <br /> Screening Evaluation. Any chemical detected in at least one sample from within the 0 to 10 <br /> feet bgs interval was considered a COPC for the human health risk evaluation of the <br /> KAFi_ C —ONGLE" Sc D, F.E.. o,jmr j PAMELA C. Ci RGCOON r.E,. 13GEE. ExrOWFVv: oFFICEF, <br /> 1685 F Sheet,Fresno CA 93706 www wlrorho.lo&en LJovfcen;rawalley <br />