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i 27 September 1996 AGE-NC Project No 95-0104 Page 2 of 4 2 2 GROUND WATER SAMPLING Monitoring wells MW-1 through MW-4 were allowed to recover for a minimum of one hour prior to sample collection Ground water samples were collected utilizing disposable polyethylene bailers and new nylon rope Sufficient sample was collected from each well to fill three 40-m1 EPA vials containing hydrochloric acid as a preservative for the samples Care was taken to ensure that visible an-bubbles were not present in the VOAs after filling and capping Ground water sample containers were labeled with the well designation, date, time, and sampler's initials I2 3 LABORATORY ANALYSIS OF GROUND WATER SAMPLES IAfter collection, each sample was logged on a chain-of-custody form, placed in a chilled container and transported to Alpha Analytical Laboratories (AAL), a California state-certified laboratory for analysis of hazardous materials Each sample was analyzed for total petroleum hydrocarbons (TPH- g), volatile aromatics (benzene, toluene, ethylbenzene and xylenes BTE&X), methyl-tertiary butyl ether (MTBE) and halogenated volatile organic compounds (HVOCs) in accordance with EPA methods 5030, 602, 5030/602 and 601, respectively 3 0. FINDINGS 31 RELATIVE GROUND WA rER ELEVATION AND GRADIENT The relative ground water surface elevation as measured on 08 August 1996 is depicted in Figure 3 The ground water depths in wells MW-1 through MW-4 ranged between 70 10 and 70 65 feet below the tops of the well casings Between April and August 1996, ground water elevation decreased an average of 6 22 feet The tops of the screened intervals in wells MW-2, MW-3 and MW-4 are between nine and ten feet below the ground water surface In August 1996, the gradient was calculated to be 0 010 ft/ft or approximately 53 feet per mile g g PP Y directed S 70°E Between April and August 1996, ground water flow direction beneath the site rotated approximately 48' from northeast to southeast 3 2 ANALYTICAL RESULTS OF GROUND WATER SAMPLES During the August 1996 sampling, TPH-g and toluene were detected in the sample collected from 1\4W-1 at concentrations of 360 and 0 59 parts per billion (ppb, reported as nucrograms per liter), respectively Other target petroleum hydrocarbons were not detected in samples collected during the August 1996 sampling Analytical results of TPH-g and BTE&X in ground water are summarized in