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SER vvwwsecoccom INTERNAINCORPORATED RanchIONAL 3017 o oiIC ore Road,Suite 100 S E C O R ordova,CA 95670 916-861-0400 rEI 916-861-0430 rnx March 11, 2003 Mr. Robert J. Cochran Chevron Environmental Management Company 6001 Bollinger Canyon Road, Room L4068 P.O. Box 6004 San Ramon, California 95843 RE: Work Plan for Site Assessment Chevron Service Station 20-0764 4747 North West Lane Stockton, California SECOR Project No.: 77CH.99999.03 Dear Mr. Cochran: SECOR International Incorporated (SECOR), on behalf of Chevron Environmental Management Company (Chevron), has prepared this work plan for site assessment at the above-referenced site (Figure 1). This work plan has been prepared to evaluate potential hydrocarbon impact to soil and groundwater beneath the subject sites associated with the underground storage tanks (USTs), associated product lines, and dispensers. The proposed work is being performed at the request of Chevron for the purpose of due diligence, and is not being carried out to meet the requirements of any regulatory agency. This work plan includes a brief discussion of the site background, proposed scope of work, and schedule. Field and laboratory procedures are presented as Attachment 1. SITE BACKGROUND The site is an active Chevron branded service station located in a commercial area of Stockton, California. The current station facilities include two dispenser islands and a mini-mart under a common canopy, three gasoline underground storage tanks (USTs), and a carwash (Figure 2). On October 15 and 16, 2001, three soil borings were drilled at the. Soil samples were collected for lagging and chemical analysis. Total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, and xylenes (BTEX), and methyl tertiary-butyl ether(MtBE)were not detected above laboratory detection limits in any soil sample. The soil borings were completed as groundwater monitoring wells MW-1 through MW-3. Groundwater was collected and submitted for chemical analysis on November 13, 2001. TPHg, BTEX, and MtBE were not detected above concentrations of regulatory concern in any of the three monitoring wells during the groundwater monitoring event. On January 9 through 15, 2002, six cone penetration test and direct-push soil borings were advanced. Groundwater samples were collected from each boring and submitted for chemical analysis. TPHg, BTEX, and MtBE were not detected in any groundwater sample collected. On January 16, 2002, slug tests were performed in wells MW-1, MW-2, and MW-3. Hydraulic conductivity ranged from 1.3 x 10-3 to 9.8 x 10 centimeters per second (cm/sec) with a calculated I:\Chevron\200764\Reports\200764 Work Plan for Site Assessment 2003.doc