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IDecember 1998., <br /> f . <br /> "AGE-NC Project No: 95-0106 <br /> 2 of 4 <br /> Page <br /> . ' <br /> '.*in of custody to McGam , � _ _ , • ;. , . .• i ., r :.. - , i <br /> pbell Analytical;Inc. (MAI),a California Department of Health Sery ce ' <br /> (DHS)-certified analytical laboratory for'analysis. The samples were analyzed for:. <br /> Total petroleum hydrocarbons quantified..as'gasoline (TPH-g) in accordance with EPA H �, <br /> Method 8015- <br /> modified, <br /> ' Volatile organic compounds (VOCs); specifically benzene, toluene, ethylbenzene, and total r <br /> xylenes(BTEX) in accordance with EPA Method 8020, and <br /> •' ;;`Oxygenated fuel'additives: methyl tertiary butyl ether(MTBE),tertiary butyl alcohol(TBA), <br />' di=isopropyl ether(RIPE), ethyl tertiary Nutyl'ether(ETBE) and tertiary amyl methyl ether <br /> (TAIVIE)' n'accordance with,EP.A method 8260 and 8260m. ' <br /> 3.0, FINDINGS ; <br /> The.ground water elevation has declined slightly since,the,last monitoring event and:the flow <br /> ' direction has shifted slightly toward the'north-northwest at a low,gradient.-The distribution 'and <br /> concentrations of detected petroleum hydrocarbons were similar to previous results. +. <br /> I; I. ; ,GROUND WATER'ELEVATION AND FLOW DIRECTION <br /> The average,ground water elevation•was 3 3.7 1feet, a decline."of approximately 0.66,feet since the <br /> I; last moiiitohhg'event."The'ground water was inferred to'be flowing north=northwest,at.a gradient o£' <br /> approximately 0.004:feetlfoot,,.or 22 feet per iriile.'Figure'3 show's the contoured relative ground <br /> i-water elevations. , ` <br /> Ii ~'3.2:: ­LABORATORY'RESULTS OF GROUND WATER SAMPLES . <br /> Petroleum hydrocarbons were detected in the ground water.samples collected'fro>ri monitoring'well <br /> located down-gradient.(north)'.of the-former UST excavation. TPH-g'was detected.'at a.,. <br /> 3` concentration 6f,'2,3 00µg/1..BTEX compounds were'detecied at concentrations of 110µg/l benzene; <br /> 26ug/1'tol'uene,,'f120 1.cg/l ethylbenzeie,and'150µg/1 xylenes. These concentrations are the same or <br /> slightly reduced from'the concentrations detected"during the May.1998 ground water moivtoring <br /> event. ,In addition; 0.64 ,ug/1 toluene and 1.2' 'g total xylenes were detected in the'ground water <br /> sample collected froin the,lower MW-6;.and 2.8'Azg/l benzene and 0.54-µg/l toluene were'detected <br /> in the sample from-MW-1, an increase from the undetectable'concentrations encountered during the <br /> previous"sampling event. , <br /> 4, Advanced.GeoEnvironinental,Ia'a <br />