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M.wGERS EEK.NERg�nSi,CTeMS <br /> I <br /> Results from MW-10, a blind duplicate of MW-2A, indicated acceptable laboratory repeatability <br />' of greater than 80% for all constituents tested The equipment decontamination blank (MW-11) <br /> indicated that the equipment was sufficiently decontaminated <br />' 5.0 SUMMARY AND RECOMMENDATIONS <br />' The following is a summary of the facts developed by the SJCHSA building Phase III soil and <br /> groundwater investigation: <br /> • Three of the four soil samples analyzed from MW-2A, which was drilled near the <br />' former location of the large tank excavation, contained petroleum constituents. <br /> Petroleum constituents increased with depth from 30 feet to 45 feet bgs. <br />' • Groundwater flow in the vicinity of the former tank excavation is along a <br /> northeast to southwest trending trough at a gradient of approximately 3.6 x 10'3 <br /> feet per foot <br />' • Petroleum product in the form of beads and sheen were encountered in soil and <br /> groundwater during the drilling and sampling of MW-2A <br />' • Low concentrations of TPH-g and benzene were detected in MW-$,approximately <br /> 300 feet northeast and downgradient of the site <br /> Based on the above summary of facts, WESTON recommends <br />' • Quarterly monitoring be continued at the site for another year, after which the <br /> quarterly data can be used to re-evaluate the site <br />' • Two to three additional borings be drilled to the south of MW-2A to evaluate the <br /> southernly extent of impact to the soil One of the borings should be converted <br /> to a monitoring well to evaluate petroleum constituents in groundwater upgradient <br />' of the former tank excavation <br /> LTROJEci MANJOQ1IUAPHASE M 8 29 Aupst 1995 <br />