ARCHIVED REPORTS_XR0005067 - Laserfiche WebLink

Home Browse Search

.14 December 2001 : . �,j• AGE-NC Project No. 98-0520 Page 2 of 4 • Total petroleum hydrocarbons quantified as gasoline (TPH-g) in 'accordance with EPA ' Method 5030/8015M; • Benzene, toluene, ethyl benzene and xylene (BTEX) and for methyl tertiary'butyl ether (MTBE) - in accordance with EPA Method 8020; and_ • Fuel oxygenates,including tertiary butanol(TBA),di-isopropyl ether(DIPE),ethyl tert-butyl ether (ETBE), tert-amyl methyl ether_.(TAME), and MTBE, with 1,2-dichloroethane (1,2-DCA) in accordance with EPA Method 8260B. 3.0. FINDINGS ' Ground water elevation, and flow direction were derived from field data; hydrocarbon-impact to ground water was quantified by laboratory analysis" of ground water samples. 3.1. GROUND WATER ELEVATION AND GRADIENT ' • The elevation of ground water in each well was calculated by subtracting the depth tot ground water from the surveyed casing elevations (Table 1). Depths to ground water ranged from 22.30 feet to 23.01 feet below the tops of the well casings. Ground water elevations at the site ranged from 14.03 ' .feet (MW-3 and MW-5) to 14.05 feet (MW-1, MW-2 and MW-4) above mean sea level. The ground water flow.direction was determined using ground water elevation data. The ground ' water table underlying the site formed a trough-like depression,with the base of the trough plunging northwest under-an average gradient of 0.0005 ft/ft. The.horthern limb of the trough flows west- southwest; the southern' limb's flow direction is north-northeast. At such a low gradient, small measurement variations can.greatly affect the inferred flow direction. Figure 2 illustrates the contoured ground water elevations as measured on 10 September 2001. 3.2. ANALYTICAL RESULTS OF GROUND WATER SAMPLES TPH-g was detected in all the water samples at concentrations ranging from 230 micrograms per liter (µg/1) in MW-4 to 4,400 µg/1 in MW-5 (Figure 3). ' Various BTEX compounds were detected in all ofthe water samples _ p p analyzed.Benzene was detected in the sample from MW-.5.(2.4 µg/1). Toluene was detected in samples from MW-1,MW-2,MW-3 ' and MW-5;the maximum toluene concentration was found in the sample from MW-5(6.7µg/1).The �. maximum ethylbenzene and xylene concentrations were detected in the sample from MW-5 at ' Advanced GeoEnviron mental,Inc.