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31 July 2002 <br /> AGE=NC Project No. 98-0520 <br /> ' Page 2 of 4 <br /> container and transported under chain-of-custody to Cal Tech Environmental Laboratories(CTEL), <br /> ' a California Department of Health Services(DHS)-certified analytical laboratory, for analysis. The <br /> samples were analyzed for: _ <br /> Total petroleum hydrocarbons, quantified ,as gasoline (TPH-g) in accordance with EPA <br /> Method 5030/8015M; <br /> • Benzcne,toluene,ethyl benzene and kylene(BTEX)and methyl tertiary-butyl ether(MTBE) <br /> in accordance with EPA Method 8021; and. <br /> ' Fuel oxygenates,including terti ary butano I(TBA),di-isopropyl ether(DIPE),ethyl tert-butyl <br /> ether (ETBE), tert-amyl methyl ether (TAME), and MTBE, with 1,2-dichloroethane <br /> (1,2-DCA) and 1,2-dibromoethane (EDB) in accordance with EPA Method 8260B. <br /> ' 30. FINDINGS <br /> Ground water elevation and flow direction were determined from field data. Hydrocarbon-impact <br /> to ground water was inferred from laboratory analysis of the ground water samples. <br /> ' .3.1. GROUND WATER ELEVATION AND GRADIENT <br /> The elevation of ground water in each well was calculated by subtracting the depth to ground water . <br /> ' from the surveyed casing elevations (Table 1). Depths to ground water ranged from 21.07 feet to <br /> 22.21 feet below the tops of the well casings. Ground water elevations at the site ranged from <br /> 14.78 feet (MW-6) t6,15.02 feet (MW-10) above mean sea level. <br /> ground water flow direction was determined using The gr g ground water elevation data from water table <br /> wells MW-1 through MW-5 and MW-7 through MW-10; elevation data from well MW-6 was not <br /> ' utilized because well-MW-6 was a deep-screen well. The ground water table underlying the site <br /> formed a trough-like depression, with the base of the trough plunging north-northwest under an <br /> average gradient of 0.001 ft/ft. The western limb of the trough flows northeast; the eastern limb's <br /> ' flow direction is northwest. At such a low gradient,small measurement variations can greatly affect <br /> the calculated flow direction.Figure 3 illustrates the contoured ground water elevations as measured <br /> on 18 June 2002. <br /> 1 Advanced CeoEnvironmental,Inc. <br />