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Californi,*egional Water Quality Cool Board <br /> Central Valley Region <br /> �- <br /> Karl E. Longley,ScD,PE, Chair <br /> Linda S.Adams Arnold <br /> Secretaryfor Fresno Branch Office Schwarzenegger <br /> Environmental 1685 E Street,Fresno,California 93706 Governor <br /> Protection (559)445-5116•Fax(559)445-5910 <br /> http://www.waterboards.ca.gov/ceiitralval ley <br /> 12 June 2007 <br /> M. Scott Mansholt <br /> Chevron Environmental Management Company <br /> 6001 Bollinger Canyon Road <br /> Room K2066 <br /> San Ramon, CA 94583-2324 <br /> REVIEW-HUMAN HEALTH RISK ASSESSMENT, FORMER TIDEWATER ASSOCIATED OIL <br /> COMPANY, TRACY PUMP STATION, 880 BEECHNUT, TRACY, SAN JOAQUIN COUNTY <br /> Regional Water Board staff has reviewed - Responses to the January 16, 2007 Comments <br /> Regarding the Human Health Risk Assessment (HHRH) for the Former Tidewater Associated <br /> Oil Company (TAOC) Tracy Pump Station, 880 Beechnut, Tracy, San Joaquin County, dated <br /> 30 April 2007, prepared for Chevron and the Union Pacific Railroad (UPRR) by Geomatrix <br /> Consultants, Inc. (Geomatrix). The document was submitted in response to our 16 January <br /> 2007 letter to Chevron/UPRR requesting additional information and clarification to comments <br /> (dated 13 October 2006) submitted by the Office of Environmental Health Hazard Assessment <br /> (OEHHA). The OEHHA toxicologists written comments addressed various topics presented in <br /> the 30 June 2005 HHRA document prepared by Geomatrix for Chevron and UPRR. <br /> In response to OEHHA's 13 October 2006 review of the HHRA document, Regional Water <br /> Board staff requested additional information/clarification for certain items addressed by the <br /> toxicologist. Additionally, Geomatrix included clarification for other topics discussed in <br /> OEHHA's review. <br /> OEHHA's and/or the Regional Water Board staff's January 2007 review comments to the <br /> HHRA are italicized below and Geomatrix's comments/clarification follow each OEHHA/Water <br /> Board reference. Regional Water Board's comments to Geomatrix's recent letter follow their <br /> comments. <br /> Based on a review of the Geomatrix responses to requested clarification of certain topics <br /> outlined by OEHHA, the following items were addressed: <br /> 1. Regional Water Board comment. <br /> Chevron/UPRR's consultant may collect soil-gas samples for analyses if necessary or use the <br /> NAPL version of the Johnson & Ettinger model-based spread sheet to evaluate/determine the <br /> potential exposure to inhalation of indoor/ambient air vapors originating from groundwater as <br /> suggested by OEHHA. <br /> California Environmental Protection Agency <br /> 4'p�Recycled Paper <br />