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.,-- 4191-E Power Inn Road,Sacramento,CA 95026 _ (916)452-2901 <br /> app/iBd Ge�Syst�ms •Fremont •Costa Mesa •Sacramento <br /> October 7, 1987 <br /> 1007CNIC <br /> AGS Job No. 87031.-2 <br /> Mr. C. D. Nichols <br /> Li.S.A. petroleum Corporation <br /> p. o. Box 1.834 <br /> Santa Monica, California 90406 <br /> Subject: Report No. 87031-2 regarding installation of two <br /> ground-water monitoring wells at U.S.A. Station No. <br /> 110, 2132 East Mariposa Road, Stockton, California. <br /> Mr. Nichols: <br /> We have enclosed four copies of our report regarding drilling of <br /> two soil borings and installation of two ground-water monitoring <br /> wells at the above-referenced site. The report summarizes the <br /> work performed and presents the results of chemical analyses of <br /> soil and ground-water samples. our recommendations for the <br /> mitigation of soil contamination and ground water at the site are <br /> also included. <br /> Floating gasoline product, appruximately 2.1 feet thick, was <br /> detected in the previvasly installed monitoring well S-1. Soil <br /> samples collected during the drilling of the soil borings showed <br /> only very slight subjective evidence of soil. contamination below <br /> a depth of 30 feet in boring B-1 and immediately above the <br /> ground-water surface in B-1 and B-2• Ground-water <br /> and samples <br /> no showed <br /> concentrations of dissolved volatile hydrocarbons <br /> oatin <br /> product in the newly installed monitoring wells 14W-1 and Mw-2. <br /> Benzene concentrations in both wells exceed action levels for <br /> drinking water recommended by the California Department of Health <br /> Services, while toluene, ethylbenzene, and xylenes are present in <br /> amounts lower than action levels. We conclude that floating <br /> product and contamination of the soil exists in the immediate <br /> vicinity of the tank cavity, and that dissolved hydrocarbon <br /> constituents have permeated to the locations of the newly <br /> installed monitoring wells. <br /> o <br />