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' 07 November 2005 • AGE-NC Project No 04-1239 ' Page 2 of 4 ' 2 2 COLLECTION AND ANALYSIS OF GROUND WATER SAMPLES Ground water samples were collected from each well using the Waterra inertia pump and dedicated ' tubing after allowing the wells to achieve a minimum 80%recovery of the pre-purge water volume Each water sample was transferred into three laboratory-supplied,40-milliliter(ml)volatile organic analysis (VOA) vials containing 0 5 ml 18% hydrochloric acid solution as a sample preservative ' After collection, the samples were properly labeled, placed in a chilled container, and transported under chain of custody to Cal Tech Environmental Laboratories (CTEL), a State of California Department of Health Services(DHS)-certified analytical laboratory in Paramount, California The ' samples were analyzed for • Total petroleum hydrocarbons quantified as gasoline(TPH-g) in accordance with EPA ' Method 8015M, and • Benzene,toluene,ethylbenzene,and total xylenes(BTEX)and fuel additives methyl tertiary- butyl ether(MTBE),tertiary-butyl alcohol(TBA), di-isopropyl ether(DIPE), ethyl tertiary- butyl ether(ETBE),tertiary-amyl methyl ether(TAME), 1,2-dibromoethane(EDB),and 1,2- dichloroethane (1,2-DCA) in accordance with EPA Method 8260B I � I3.0. FINDINGS Ground water elevation and flow direction were inferred from field data, hydrocarbon impact to ground water was quantified by laboratory analysis of the ground water samples ' 3 1 GROUND WATER GRADIENT AND FLOW DIRECTION At the time of the September 2005 sampling event, depths to ground water ranged from 19 54 feet ' (MW-9) to 20 57 feet (MW-10) below the tops of the well casings Groundwater elevation at the site ranged from 9 42 feet(MW-9)to 9 87 feet(MW-10)below mean sea level(MSL,Table 1), and averaged approximately 9 60 feet below MSL, indicating a decrease in average ground "water elevation of 1 47 feet since the last monitoring event in April 2005 During this monitoring event, the ground water level in well MW-9 was 0 46 feet above the top of the well screen However, during the purge cycle, the depth to water was reduced to a level within the well screen, thus Irecharging the well with water from the screen area exposed to the surrounding sediments and water- bearing layers IGround water at the site was inferred to be flowing toward the west-southwest under a hydraulic gradient of approximately 0 02 foot/foot (ft/ft) Figure 3 illustrates the contoured ground water A*arrced Gcu nvrronmcaW,Inc I