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28 February 1997 <br /> AGE-NC Project No 96-0173 <br /> Page 2 of 4 _ <br /> 2 2 GROUND WATER SAMPLING <br /> Monitoring wells MW-1 through MW-4 were allowed to recover for a minimum of one hour prior <br /> to sample collection Ground water samples were collected utilizing new, disposable polyethylene <br /> bailers and new nylon rope Sufficient sample was collected from each well to fill three 40-m1 EPA- <br /> approved VOA vials containing 0 5 nil 1 S% hydrochloric acid as a preservative for the sample, and <br /> a one-liter amber bottle Care was taken to ensure that visible air bubbles were not present in the vials <br /> after filling and capping Ground water sample containers were labeled with the well designation, <br /> date, time, and sampler's initials <br /> 23 LABORATORY ANALYSIS OF GROUND WATER SAMPLES <br />' After collection, each sample was logged on a chain-of-custody form laced in a chilled container <br /> p Sg y , P <br /> and transported to Castle Analytical Laboratories (CAI.), a California State-certified laboratory for <br /> analysis of total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g & TPH-d), volatile <br /> aromatics (benzene, toluene, ethylbenzene and xyleneq BTE&X) and methyl-tertiai-y butyl ether <br /> (MTBE)in accordance with EPA methods 8015M and 8020 <br /> 3 0. FINDINGS <br /> 3 1 RELATIVE GROUND WATER ELEVATION AND GRADIENT <br /> The depths to ground water in wells MW-1 through MW-4 ranged between 35 49 and 36 18 feet <br /> below the tops of the well casings Between August and December 1996, ground water elevation <br /> increased an average of l 00 feet The tops of the screened intervals in wells MW-1 through MW-4 <br /> are between 5 49 and 6 18 feet above the ground water surface <br /> The relative ground water surface elevation as measured on 02 December 1996 is depicted in Figure <br /> 3 Due to the low ground water gradient, the gradient and flow direction was calculated by solving <br /> for the maximum gradient and direction as three-point problems using MW-1, MW-2 and MW-3 for <br /> one set and MW-1 MW-3 and MW-4 for the second set The results were averaged to determine the <br /> flow direction and gradient <br /> tIn August 1996, the gradient was calculated to be 0 002 ft/ft or approximately I2 feet per mile, <br /> directed N 600E In December 1996, the gradient was calculated to be 0 002 ft/ft, directed N 67°E <br /> Between August and December 1996, ground water flow direction beneath the site rotated <br /> approximately 7° towards the east <br />