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. 18 August 2004 AGE-NC Project No ,98-0534 ' Page 2 of 4 ' 2 2 COLLECTION AND ANALYSIS OF GROUND WATER SAMPLES After depth to ground water was re-measured to ensure that a minimum of 80% well-volume ' recharge had been achieved, a water sample was collected from each well using the dedicated, disposable plastic bailer Immediately upon retrieval, samples were transferred into a 1-liter amber bottle and three 40-m1 EPA-approved volatile organic analysis(VOA)vials containing 0 5 ml 18% ` ' hydrochlonc acid as a sample preservative The samples were logged on a chain of custody form, then stored in a chilled container under ice The samples were later transported under chain of custodyto Cal Tech Environmental Laboratories(CTEL),a State of California Department of Health ' Services (DHS)-certified analytical laboratory, for analysis The samples were analyzed for • Total'petroleum hydrocarbons quantified as gasoline (TPH-g) and diesel (TPH-d) in faccordance with EPA Method 8015 Modified, • Benzene, toluene, ethylbenzene and total xylenes (BTEX) and methyl tertiary-butyl ether ' (MTBE) in accordance with EPA Method 8260B, and • Oxygenated compounds - di-isopropyl ether (DIPE), ethyl tertiary-butyl ether (ETRE), MTBE, tertiary-amyl methyl ether (TAME), tertiary butanol (TBA), 1,2-dibromoethane lie (EDB) and 1,2-dichloroethane (1,2-DCA) in accordance with EPA Method 8260B, I3.0. FINDINGS Ground water elevation, flow direction and gradient were determined from field data collected on 16 July 2004, the contaminant impact to ground water was assessed from the laboratory data 3 1 GROUND WATER ELEVATION AND GRADIENT The relative elevation of ground water in each well was calculated by subtracting the depth to ground u water from the relative casing elevation(Table 1) The depth to ground water on 16 July 2004 ranged between 1129 to 12 49 feet below the tops of the well casings, relative ground water elevations ranged between 6 00 feet (MW-5)to 7 31 feet(MW-4)below mean sea level (MSL) Presently the water table is at the top of the screened interval of the wells. The potentzometric surface was.inferred to be relatively flat in the area of the former UST area, trending towards a steeper 1vest-onented trough at the northern portion of the site, in the area I of well MW-4 (Figure 3) The gradient ranged from 0 005 ft/ft at the former UST area to between x 0 02 ft/ft and 0 03 fUft along the walls of the trough ly Advanced GeoEnvironmental,Inc I