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19 March 1999 <br /> AGE-NC Protect No 97-0312 <br /> Page 2 of 4 <br /> 2 2 COLLECTION OF GROUND WATER SAMPLES <br /> The depth to water was re-measured following purging to assure a minimum of 80% recharge prior <br /> to sampling Water samples were then retrieved from each purged well using new disposable bailers <br /> Each sample was transferred into 40-m1 EPA-approved VOA vials containing 0 5 ml of 18% <br /> hydrochloric acid as a sample preservative and into one 1-liter amber bottle without preservative <br /> The samples were labeled, placed in a chilled container and transported to McCampbell Analytical, <br /> Inc (MAI), a California Department of Health Services (DHS)-certified laboratory in Pacheco, <br /> California The samples were analyzed for <br /> a Total petroleum hydrocarbons quantified as gasoline (TPH-g) and diesel (TPH-d) in <br /> accordance with EPA Methods 5030 and 8015m, <br /> a Volatile aromatic compounds (benzene, toluene, ethylbenzene and xylenes BTE&X) and <br /> methyl tertiary-butyl ether (MTBE) in accordance with EPA Method 60218020, and <br /> a Volatile organic compounds with oxygenated compounds (methyl tertiary-butyl ether <br /> [MTBE], di-isopropyl ether [DIPE], ethyl tert-butyl ether [ETBE], tert-amyl methyl ether <br /> [TAME] and tert-butanol [TBA]) in accordance with EPA Method 8260 modified <br /> i <br /> 3.0. FINDINGS <br /> The casing elevation of each well was previously surveyed relative to a City of Stockton bench mark <br /> Ground water elevations were determined by subtracting the measured depths-to-water from the <br /> casing elevations (Table 1) Ground water flow direction was determined by contouring the water <br /> elevations on a scaled site plan (Figure 3) <br /> 3 1 GROUND WATER ELEVATION AND GRADIENT <br /> Ground water elevation increased an average of 160 feet at the former USTs location and an average <br /> of 195 feet in wells north of the site since the September 1998 monitoring event Ground water flow <br /> direction was inferred to be northeasterly with a gradient of 0 0015 ft/ft The flow direction is similar <br /> to previous monitoring events Figure 3 - Ground Water Elevation depicts the contours for <br /> December 1998 <br /> Static ground water was approximately ten feet above the screened interval in UST-2, UST-3 and <br /> UST-4 and approximately one foot over the screened interval of UST-5 A minimum of 80% <br /> recharge was measured in each well immediately following purging <br /> Adianced GeoEmironmental,Inc <br />