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10 January 1997 <br /> AGE-NC Project No 95-0143 <br />' Page 2 of 3 <br />' Pacheco, California (MAI), and were analyzed for total petroleum hydrocarbons quantified as <br /> gasoline(TPH-g),and for volatile aromatic compounds(benzene,toluene, ethylbenzene and xylenes <br /> BTE&X)with methyl-tertiary-butyl-ether(MTBE) in accordance with EPA methods 5030 and 602, <br />' respectively <br />' 3.0. FINDINGS <br /> 3 1 RELATIVE GROUND WATER ELEVATION AND GRADIENT <br /> The relative elevation of ground water in each well was calculated by subtracting the depth to water <br /> from the surveyed casing elevation (Table 1) Ground water elevation decreased an average of 0 47 <br /> feet between August and November 1996 The approximate gradient was calculated to be 0 0054 ft/ft <br /> north of the site, corresponding to gradients measured at the Madison site However, a shallower <br /> gradient of 0 0010 ft/ft was measured on the southern corner of the subject property The flow <br /> direction was generally toward the north to northeast Relative ground water elevation contours for <br /> the November 1996 monitoring event are illustrated as Figures 3 <br /> 3 2 ANALYTICAL RESULTS OF WATER SAMPLES <br /> TPH-g was detected at concentrations of 200,000 parts per billion(ppb, reported as m,crograms per <br /> liter), 5,100 ppb, 14,000 ppb and 15,000 ppb, in samples from MW-3, MW-6, MW-7 and MW-9, <br /> respectively, during the November 1996 monitoring BTE&X were detected in the same wells at <br /> concentrations as high as 50,000 ppb (toluene, MW-3) Xylenes were also detected in the sample <br /> collected from MW-16 at a concentration of 1 1 ppb Petroleum hydrocarbons were not detected in <br /> the samples collected from MW-10, MW-14, MW-15 or MW-17 MTBE was not detected in any <br /> samples collected during the November 1996 monitoring event Free product was not encountered <br /> at the site Analytical results are summarized on Table 2 The laboratory report (MAI Laboratory I <br /> ID Nos 71047 - 71055) and chain-of-custody forms are included in Appendix B <br /> 4 0. CONCLUSIONS & RECOMMENDATIONS <br /> 41 CONCLUSIONS <br /> Based upon data collected from the site, AGE has the following conclusions <br /> • Petroleum hydrocarbons were not detected in wells MW-10, MW-14, MW-15 and MW-17, <br />. and only traces of xylenes were detected in MW-16, thereby defining the maximum <br />