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r 26 September 1996 AGE-NC Protect No 95-0130 ' Page 2 of 4 ' was taken to ensure that visible air 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 1 23 LABORATORY ANALYSIS OF GROUND WATER SAMPLES Each ground water sample was logged on a chain-of-custody form, P laced in a chilled container and transported to Castle Analytical Laboratories (CAL), a California state-certified laboratory for analysis of hazardous materials Each sample was analyzed for total petroleum hydrocarbons quantified as gasoline (TPH-g), volatile aromatics (benzene, toluene, ethyl benzene and xylene BTE&X), and methyl-tertiary butyl ether (M TBE) in accordance with EPA methods 5030 and 602, ' respectivety The laboratory report (CAL Laboratory No 815) and chain-of-custody forms arc presented in Appendix B 3 0. FINDINGS 3 1 RELATIVE GROUND WATER ELEVATION AND GRADIENT The relative elevation of ground water in each well was calculated by subtracting the ground water depth from the surveyed relative casing elevation (Table 1 - Ground Water Elevations) Gi ound water depths at the site ranged from 50 20 to 51 10 feet Ground water at the site rose an average Iof 0 23 feet between April 1996 and July 1996 Ground water is approximately 4 to 10 feet above the tops of the screen intervals of monitoring wells MW-1 through MW-4, and is approximately 0 4 feet below the top of the screen interval of MW-5 Ground water flow direction was generally tov�ard the south at an approximate gradient of 0 006 ft/ft, or 3 2 feet per mile (Figure 3 -Relative G ound Water Elevations Map) 3 2 LABORATORY RESULTS OF GROUND WATER SAMPLES TPH-g was detected in ground water samples from wells MW-3 and MW-5 at concentrations of 740 yg/l (microgram per Mer or parts per billion ppb) and 12,000 ppb, respectively The highest concentration of benzene at 1,600 ppb was detected in the sample from MW-5 Two additional samples from MW-2 and MW-3 were found to contain benzene at concentrations of 1 4, and 190 ppb, respectively The concentrations of the other aromatic compounds ranged up to 760 ppb Similar to the distribution of benzene, the sample from MW-5 contained the highest