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21 February 1997 <br /> AGE-NC Project No 95-0130 <br /> Page 2 of 4 <br /> disposable polyethylene bailers and new nylon rope Sufficient ground water sample was collected <br /> from each well to fill three 40-m1 EPA vials containing 0 5 m] 18% hydrochloric acid as a preservative <br /> for the samples Care was taken to ensure that visible air bubbles were not present in the VOAs after <br /> I filling and capping Ground water sample containers were labeled with the well designation, date, <br /> time, and sampler's initials <br /> 23 LABORATORY ANALYSIS OF GROUND WATER SAMPLES <br /> Each ground water sample was logged on a chain-o#-custody form, placed in a chilled container and <br /> transported to a California state-certified laboratory for analysis of total petroleum hydrocarbons <br /> quantified as gasoline (TPH-g), and volatile aromatics (benzene, toluene, ethyl benzene and xylene <br /> BTE&X) with methyl-tertiary butyl ether (MTBE) in accordance with EPA methods 5030 and 602, <br /> respectively The laboratory report(Castle Analytical Laboratories Reference No 98 1) and chain-of- <br /> custody forms are presented in Appendix B <br /> 3 0. FINDINGS <br /> 3 1 RELATIVE GROUND WATER ELEVATION AND GRADIENT <br /> Depths to ground water at the site ranged from 48 99 to 50 02 feet below surface grade (bsg) <br /> Ground water elevation at the site increased an average of 1 54 feet between October 1996 and <br /> January 1997 Ground water is approximately 5 03 to 11 01 feet above the tops of the screen intervals <br /> of monitoring wells MW-I through MW-4, and apps oximately 0 70 feet below the top of the screen <br /> interval of MW-5 <br /> In October 1996, the gradient was calculated at 0 006 ft/ft (approximately 31 7 feet per mile) with <br /> a ground water flow direction generally S 20°E In January 1997, the gradient was calculated at <br /> 0 008 ft/ft (approximately 44 feet per mile) with a ground water flow direction generally S 25°E <br /> (Figure 3 - Relative Ground Water Elevationy Map) Between October 1996 and January 1997, <br /> ground water flow direction beneath the site rotated approximately 5' eastward <br /> I <br /> 3 2 LABORATORY RESULTS OF GROUND WATER SAMPLES <br /> TPH-g was detected in ground water samples from wells MW-2, MW-3, MW-5 and VW-1C at <br /> concentrations ranging between 94 and 200,000 µg/1 (microgram per liter or parts per billion ppb) <br /> Benzene was detected in ground water samples from wells MW-2, MW-3, MW-5, and VW-IC at <br /> concentrations ranging between 12 ug/I and 47,000 gg/l The other volatile aromatic compounds <br />