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23 July 1998 <br /> • AGE-NC Project No 95-0143 <br /> Page 2 of 4 <br /> container,to McCampbell Analytical,Inc (MAI)in Pacheco,California The samples were analyzed <br /> by <br /> IEPA Method 5 03 0/801 5 modified for total petroleum hydrocarbons quantified as gasoline <br /> (TPH-g), <br /> • EPA Method 602 for volatile aromatic compounds (benzene, toluene, ethylbenzene and <br /> xylenes BTE&X), and by <br /> I EPA Method 8260 for volatile organic compounds with oxygenated compounds (methyl <br /> ternary-butyl ether [MTBE], di-Isopropyl ether [DIPS], ethyl tert-butyl ether [ETBE], tert- <br /> amyl methyl ether [TAME] and tert-butanol [TBA]) <br /> 3.0. FINDINGS <br /> I <br /> 3 1 RELATIVE GROUND WATER ELEVATION AND GRADIENT <br /> 1 • 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 increased an average of 2 33 <br /> feet between February and May 1998 Ground water was above the screened interval of all wells at <br /> the site from over one foot above the screened Interval in MW-17 to approximately ten feet above <br /> the screened Interval in MW-3 and MW-9 The approximate hydraulic gradient was calculated to be <br /> 0 004 ft/ft with a northerly flow direction north of the site However, a shallower gradient of 0 00I <br /> ft/ft was measured on the subject property with a northeasterly flow direction Ground water <br /> elevation contours for the May 1998 monitoring event are Illustrated in Figure 3 <br /> 32 ANALYTICAL RESULTS OF WATER SAMPLES <br /> Duringthe <br /> May 1998 monitoring event, TPH-g was detected at concentrations of 180,000 parts per <br /> billion(ppb,reported as micrograms per liter),2,600 ppb, 1,500 ppb and 42,000 ppb in samples from <br /> MW-3, MW-6,MW-7 and MW-9,respectively BTE&X compounds were detected in samples from <br /> the same wells at concentrations as high as 51,000 ppb (toluene In the sample from MW-3) <br /> N-butyl benzene was detected in MW-6 and MW-9 at a concentration of 5 9 ppb and 45 ppb, <br /> respectively, below and at the State of California Action Level (AL) of 45 ppb 1,2-Dichloroethane <br /> (1,2-DCA) was detected in MW-14 at a concentration of 7 7 ppb, above the State of California <br /> Maximum Contaminant Level (MCL) of 0 5 ppb BTE&X were detected by EPA Method 8260 at <br /> concentrations similar to EPA Method 602 Eight additional constituents that do not have established <br /> Advanced GeoEnvironmental,Inc <br /> f <br />