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A RESNA company `---- <br /> Environmental Solutions <br /> r Through Applied Science, <br /> 3164 Gold Camp Drive, Suite 200 Engineering&Construction <br /> Rancho Cordova, CA 95670 <br /> Phone (916) 852-6690 <br /> FAX (916) 852-6688 <br /> May 6, 1992 <br /> Mr. Bob Boust <br /> Unocal Corporation <br /> P.O. Box 5155 <br /> San Ramon, California 94583 <br /> Subject: Status of Environmental Investigation and Ground-Water Monitoring, First- <br /> Quarter 1992, at and Near Former Unocal Service Station No. 2859, 1665 <br /> Pacific Avenue, Stockton, California. <br /> Mr. Boust: <br /> RESNA Industries (RESNA) is reporting on the status of work conducted during the first <br /> quarter 1992 at the request of Unocal Corporation (Unocal) at the subject site (shown on <br /> Plate 1). Work included drilling five soil borings, installing two ground-water monitoring <br /> wells and three vapor-extraction wells, conducting the quarterly monitoring event and a <br /> vapor-extraction test (VET). The purpose of installing the monitoring wells was to delineate <br /> dissolved hydrocarbons in ground water near the southern boundary of the site and offsite. <br /> The purpose of quarterly sampling was to monitor changes in concentrations of dissolved <br /> gasoline hydrocarbons in the ground water and changes in the ground-water gradient. The <br /> vapor-extraction wells were used to conduct a vapor-extraction test and to evaluate the <br /> feasibility of vapor extraction as a remedial alternative. <br /> BACKGROUND <br /> Five soil borings were drilled at the site in January 1988 as part of an environmental <br /> investigation conducted by J.H. Kleinfelder & Associates (Kleinfelder) of Sacramento, <br /> California. Results of that investigation indicated that hydrocarbons were present in soil <br /> underlying the site (Kleinfelder, March 3, 1988, Report No. 24-2081-01). <br /> In March and April 1988, RESNA (formerly Applied GeoSystems) observed removal of the <br /> underground storage tanks at the site and collected soil samples for laboratory analysis of <br /> hydrocarbons. Results of analyses indicated that hydrocarbons were present in the soil <br /> underlying the tanks (Applied GeoSystems, April 28, 1988, Report No. 38012-1). In June <br /> 1988, we installed ground-water monitoring wells MW-1 through MW-3 (Applied <br /> GeoSystems, July 28, 1988, Report No. 38012-2). Results indicated a further investigation <br /> of ground water downgradient was warranted; therefore, in August 1989, two ground-water <br /> 0327bnou <br /> 38012-9 <br />