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t. .. 02 November 2001 AGE-NC Project No. 98-0440 ' Page 2 of 4. ' ' 2.2• COLLECTION OF GROUND WATER SAMPLES Water samples were collected -from each purged well .using new disposable plastic bailers Additionally,water samples were collected from domestic well DW5157 after'tFie well purge valve r F was opened and water was allowed to run for more thazl 15-Ininutes, allowing the pump to turn.on. Each water sample was transferred into one I-liter amber bottle without sample preservative'"and into ' three•40-m1 VOA vials containing 0.5 ml 18% hydrochloric acid as a sample preservative. After' collection, the samples were properly labeled, placed in a chilled,container and transported under chain-of-custody to McCampbell Analytical,Inc.(MAI),a California Department of Health Services. ' (DHS)-certified analytical laboratory in Pacheco, California. Each sample was analyzed for: • Total petroleum hydrocarbons quantified as'gasoline gasoline anal•. diesel(TPH-g and TPH-d,, respectively) by EPA Methods 8015M/5030I3550; 'Volatile aromatic compounds'- benzene, toluene, ethyl benzene and xylene (BTEX) with methyl-tertiary butyl ether(MTBE) by EPA Method 8020. ' 3.0. FINDINGS Ground:water elevation, flow direction, and gradient were determined from field dais collected on 13 September 2001; the contaminant impact;to ground water was- assessed ;by the laboratory analytical data. ' 3.L., GROUND WATER GRADIENT AND FLOW DIRECTION The elevation of ground water in each well was calculated by subtracting the depth to ground water from-the surveyed well casing elevations.(Table.1). Depths'to ground water ranged from 10.54 feet to 11.92 feet below the,well -ng tops.; Ground water elevations at the site.ranged from,28.51 feet above,mean sea level.(MSL) in,well MW6 to 29.92 feet above MSL in well MW L Ground water elevations at.the site increased an average of 1.65 feet betwee'n.the June 2001'and September 2001 sampling events. Ground water levels were within the screened intervals of all the monitoring wells on-site: : The'grdund water flow direction was inferredrusing:ground water elevation data. The ground water_ at the' site on 13 September 2001 was inferred to have been flowing to the north-northeast under an. average hydraulic gradient of 0:009 feet/feet.Figure 4 illustrates the ground water elevation contours. Advanced GeoEpvironnnentai,Iric.