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21'December 2000 , <br /> AGE-NC Project No. 99-0657 <br /> Pdge:2 of 4 <br /> 1 Analytical; Inc. (MAI), a California Department of Health.Services .(DHS)-certified 'analytical= <br /> F� laboratory in Pacheco, California. Each sample was analyzed f' <br /> p y ar. <br /> Total petroleum hydrocarbons- quantified as gasoline and diesel (TPH-g and TPH-d, <br /> respectively) by EPA Methods 8015M1503,0/3550; <br /> Volatile:aromatic compounds: benzene, toluene, ethyl benzene and xylene (BTEX) with , <br /> methyl-tertiary, butyl ether (MTBE) by EPA Method 8020; ; <br /> FINDINGS <br /> Groundwater elevation,,flow direction, and gradient were determined from field data collected on <br /> i OS December, 2000; the contaminant impact to groundwater was assessed from the-,laboratory <br /> rr analytical data: - <br /> 3.1`. .-GROUND WATER GRADIENT AND FLOW DIRECTION <br /> �4 <br /> The'elevation of ground water in each wellwas calculated by subtracting the depth to ground water <br /> from the surveyed well casing elevations (Table'1). <br /> Depths to ground water ranged from 11.97.feet to 12.58 feet,below the well casing tops.Ground <br /> ` i water elevations at the site ranged from 27.83 feet above mean sea level (MSL) in well MW-3:to <br />_1 k' 28.49 feet above MSL in well,MW-1'.' <br /> !� The ground water flaw direction was calculated'using groundwater elevation'data.`The groundwater ' <br /> =" at,the. site was inferred to have been flowing to the-.north-northv est` e <br /> g y,With an average hydraulic ' <br /> •. <br /> gradient of 0.007,feet/feet. Figure'3.illustrates the ground:water elevation`contours. <br /> 3.2. GROUND WATER ANALYTICAL RESULTS = ' <br /> TPH-g was,detected in the water samples collected fromhmonitoring wells MW!-1,, MW-2;.MW=3 " <br /> - and MW-6 at c6ncentrations of 74'micrograms•per;liter(,ug/l);2,800',ug/l, 2,100µg/l.and.,41 Q.ug/1, ` <br /> respectively. TPH-d was detected in the water samples collected from monitoring wells MW-2, <br /> MW-5 and MW-6 at concentrations as high as 630 Ecg/1'in MW=S, ' <br /> Benzene,was detected in ground water samples collected from all'the wells'with the exception-of <br /> MW-6, at concentrations ashigh'as 340µg/1 in well.N4W-2. , remaining BTEX compounds were <br /> Advanced GeoEnvironmental,Inc.,.: ' <br />