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14 ARCADIS BBL A1115 0 2 2007 <br /> Infrastructure, environment, facilities ARCADIS U.S.,Inc. <br /> ENVIRONNI NT HEA 6'9 10470 Old Placerville Road <br /> Suite 110 <br /> Sacramento <br /> Mr. Brian Taylor California 95827 <br /> Tel 916.843.1900 <br /> California Regional Water Quality Control Board— Fax 918.843.1965 <br /> Central Valley Region w .arcadis-us.com <br /> 11020 Sun Center Drive, Suite 200 <br /> Rancho Cordova, California 95670 <br /> INDUSTRIAL <br /> Subject <br /> Tier I Risk Based Corrective Action Evaluation <br /> Chevron Bulk Fuel Terminal 1001621 <br /> 22888 Kasson Road <br /> Banta, California Date. <br /> July 27, 2007 <br /> Dear Mr.Taylor: Contact <br /> David M. Evans <br /> ARCADIS U.S., Inc(ARCADIS BBL, formerly known as Blasland, Bouck and Lee, <br /> Inc.)is pleased to submit this Tier I Risk-Based Corrective Action(RBCA)evaluation Phone: <br /> on behalf of Chevron Environmental Management Company(Chevron).As 916.857.0214 x226 <br /> requested by the California Regional Water Quality Control Board Central Valley <br /> Region (CVR-RWQCB)in a letter dated June 5, 2007, risks and hazards were Email: <br /> estimated due to potential exposures to chemicals of potential concern(COPCs) david.evans@ <br /> identified in groundwater beneath the onsite office building at the Chevron Bulk Fuel arcadis-us.com <br /> Terminal No. 1001621, located at 22888 Kasson Road, Banta, California. The main <br /> purpose of this report is to answer the question,"Could concentrations of chemicals Our ref: <br /> in groundwater pose adverse health effects to occupants of the office building 80045513.00002 <br /> located on the site?" In general, risk and hazard estimates provide an answer to that <br /> question.The results of this evaluation may be used to support a RBCA process for <br /> the site. <br /> This evaluation describes the methods and assumptions used to evaluate potential <br /> vapor intrusion exposures to onsite office workers. Based on the results of this <br /> evaluation, potential health risks for onsite workers exposed to COPC vapors that <br /> could migrate from groundwater beneath the office building are within acceptable <br /> levels.The estimated cumulative risk, 1 x 105,does not exceed the acceptable risk <br /> range from 1 x 105 to 1 x 104 as defined by the California Environmental Protection <br /> Agency(Cal-EPA),the United States Environmental Protection Agency(USEPA), <br /> and other regulatory agencies. In addition, the estimated hazard index, 0.05,does <br /> not exceed the target hazard index of 1.0 as defined by Cal-EPA and the USEPA. <br /> Furthermore, none of the maximum COPC concentrations detected in groundwater <br /> monitoring wells beneath the onsite office building exceed Cal-EPA Environmental <br /> Screening Levels(ESLs)for the evaluation of potential vapor intrusion concerns. <br /> Imagine the result <br /> WON moocd'nmm621ownnoo_re,i RecA Ev Iuaeon doc <br />