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• 09 August 2000 AGE-NC Project No. 95-0106 + Page 6of10 chain of custody to McCampbell Analytical, Inc. (MAI), a California Department of Health Services (DHS)-certified analytical laboratory for analysis. The samples ivere analyzed for: • Total petroleum hydrocarbons quantified as gasoline (TPH-g) in accordance with EPA'' Method 8015-Modified, . • Volatile aromatic compounds, specifically benzene, toluene; ethylbenzene, and total xylenes ' (BTEX)with methyl tertiary butyl ether(MTBE) in accordance with EPA Method 8020, and • Oxygenated fuel,additives: MTBE, tertiary butyl alcohol (TBA), di-isopropyl ether(DIPS); , ethyl tertiary butyl ether(ETBE) and tertiary amyl methyl ether(TAME) in accordance with EPA Method 8260-Modified. 4.0. FINDINGS '. Ground water elevation and flow direction were calculated from field data; hydrocarbon-impact to ground water was inferred from laboratory analysis of the groundwater samples. ' 4.1.. GROUND WATER ELEVATION AND FLOW DIRECTION The average relative ground,water elevation increased an average of.1.44 feet since the November_ 1999. monitoring,event and the"average'flow direction was,northward, varying from northeastward ' to northwestward. The average ground water flow direction in the area enclosed by monitoring wells MW3, MW4, and MW6 was toward the northeast at a gradient of approximately 0.006 ft/ft, and the flow direction was toward the north-northwest in the area bounded by MW 1, MWS, and MW4 at a gradient of approximately 0.005 ft/ft. Ground water elevation data isp.resented in Table 1• the contoured ground water elevation'data is shown on Figure'4. Ground water elevation in MW4 has ' been unusually high for reasons not currently understood; ' 4.2. LABORATORY RESULTS OF GROUNDWATER SAMPLES _ Petroleum hydrocarbons were detected in the ground water samples collected from monitoring wells' " ' MW-I and BMW-4; MW-1 .is located slightly cross and down-gradient. from the former UST ' excavation and MW-4 is located further north in the-generally down-gradient direction. TPH-g was detected at concentrations of 880 micrograms per liter(,ug/l) and 1,400,yg/l, respectively,in samples ' from the two wells.-Benzene was detected at 150 4g/1 and 57 µg/1 in samples from MW-1 and MW-4, respectively. Other-volatile aromatic compounds were detected at concentrations.of 54 4gll. ' Advanced CeoEnvironmental,Inc.