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I ' 19 September 2002 i AGE-NC Project No 98-0534 Page 2 of 4 a 2 2 COLLECTION AND ANALYSIS OF GROUND WATER SAMPLES I After the depth to ground water was measured to ensure that a minimum of 80% well-volume recharge had been achieved, a water sample was collected from each well using a dedicated and disposable plastic bailer Immediately upon retrieval, samples were transferred into one-liter amber bottles and three 40-m1 EPA-approved volatile organic analysis(VOA)vials containing 0 5 ml 18% hydrochloric acid as a sample preservative The samples were logged on a chain-of-custody form and stored in a chilled container under ice The samples were later transported under chain-of-custody to McCampbell Analytical Inc (MAI),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 r accordance with EPA Method 8015 Modified, ■ • Benzene, toluene, ethylbenzene and total xylenes (BTEX) and methyl tertiary-butyl ether (MTBE) in accordance with EPA Method 8020, and • The oxygenated compounds di-isopropyl ether (DIPE), ethyl tertiary-butyl ether (ETBE), MTBE,tertiary-amyl methyl ether(TAME),tertiary butanol(TBA),ethanol,methanol, 1,2- dibromoethane (EDB) and 1,2-dichloroethane(1,2-DCA) in accordance with EPA Method 8260-Modified 3.0. FINDINGS Ground water elevation, flow direction and gradient were determined from field data collected on 14 June 2002, 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 water from the relative casing elevation (Table 1) The average depth to ground water on 14 June 2002 was 10 feet below the tops of the well casings, presently the water table is at the top of the screened interval of the wells The water table was inferred to be relatively flat in the area of the former UST area,but was inferred to form a depression at the northern portion of the site, in the area of well MW-4, the gradient ranged from essentially flat at the former UST area to 0 05 ft/ft at the northern edge of the site (Figure 3) 9 Advanced GeoEnvi ron mental,Inc