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Working To Restore Nature <br /> 3164 Gold Camp Drive <br /> Rancho Cordova, CA 95670 <br /> Phone (916) 852-6690 <br /> Fax (916)852-6688 <br /> • <br /> July 30, 1992 <br /> Mr Bob Boust <br /> •' Unocal Corporation <br /> P O Box 5155 <br /> San Ramon, California 94583 <br /> Subject Ground-Water Monitoring, Second Quarter 1992, at Former Unocal Service <br /> Station No 2859, 1665 Pacific Avenue, Stockton, California <br /> Mr Boust <br /> This report summarizes the results of the second quarter 1992 ground-water monitoring that <br />•! RESNA Industries (RESNA) conducted at the request of Unocal Corporation (Unocal) at <br /> the subject site (Plate 1) The purpose of quarterly sampling is to monitor changes in <br /> concentrations of dissolved gasoline hydrocarbons in the ground water and changes in the <br /> ground-water gradient Work for this monitoring phase included subjectively analyzing <br /> ground water in monitoring wells MW-4, MW-5, MW-6, and MW-7 and collecting and <br /> analyzing ground-water samples for dissolved hydrocarbon constituents We did not collect <br /> water samples from wells MW-1 through MW-3 or measure depths to water because these <br /> wells were dry The locations of the monitoring wells are shown on Plate 2 <br /> BACKGROUND <br /> w Five soil borings were drilled at the site in January 1988 by J H Kleinfelder & Associates <br /> (Kleinfelder) of Sacramento, California Hydrocarbons were detected in soil underlying the <br /> site (Kleinfelder, March 3, 1988, Report No 24-2081-01) RESNA (formerly Applied <br /> GeoSystems) conducted an environmental investigation in conjunction with underground- <br /> storage tank removal in March and April 1988. Residual gasoline hydrocarbons were <br /> • present in the soil underlying the tank pit (Applied GeoSystems, April 28, 1988, Report No. <br /> 38012-1) In June 1988, we installed ground-water monitoring wells MW-1 through MW-3 <br /> (Applied GeoSystems, July 28, 1988, Report No 38012-2) Dissolved hydrocarbons were <br /> detected in ground water samples collected from those wells In August 1989, two ground- <br /> water wells were installed offsite to delineate dissolved hydrocarbons (Applied GeoSystems, <br />• December 12, 1990, Report No 38012-5) <br /> 0528bbou <br /> 38012-9 <br />• <br />