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r <br /> I i , <br /> d � <br /> 06 July 1999 <br /> AGE-NC Project No 95-0135 <br /> Page 2`6f 4 " <br /> r Services'(DHS)-certified laboratory, for analytical analysis The samples were analyzed for <br /> • Total petroleum hydrocarbons quantified as gasoline (TPH-g) in accordance with EPA <br /> Method 8015 Modified, M <br /> I Volatile aromatics benzene, toluene, ethyl benzene and total xylene (BTEX) in accordance- ` <br /> with EPA Method 8020 and <br /> I Volatile organic compounds (VOCs) and fuel oxygenates including methyl tertiary-butyl <br /> ether(MTBE), tertiary-butyl alcohol (TBA), di-Isopropyl ether (DIPE), ethyl tertiary-butyl <br /> ether(ETBE)and tertiary-amyl methyl ether(TAME) in accordance with EPA Methods EPA <br /> IMethod 8260 and 8260 Modified <br /> I , 3.0. FINDINGS <br /> Ground water flow direction and gradient were inferred from field data, petroleum hydrocarbon <br /> impact on ground water was determined by the results of laboratory analysis <br /> V1 <br /> 3 1 GROUNTDh WATER ELEVATION AND GRADIENT <br /> On 18 December 1997, the� casing elevat1on'of each new well was surveyed relative to the elevation Y of the City of Stockton Bench Mark number 28 (BM#28- 12 IT) The ground water elevation In`each <br /> well was calculated by subtracting the depth to ground water from the surveyed casing elevation _ <br /> (Table 1) <br /> Ground water was inferred to be,flowing toward the north at a calculated gradient of 0 006 on 20 <br /> rNovember I998 The contoured groundwater elevation data from the site Is illustrated in Figure 3 <br /> 3 2 LABORATORY RESULTS OF GROUND WATER SAMPLES <br /> TPH-g concentrations dedreased in five of the'six wells and BTEX concentrations also showed a <br /> decrease in the wells, except for the concentration of ethyl benzene In well MW-lA Benzene was. <br /> detected in all 'vvater'samples from well MW-IA/B and MW-2A/B <br /> The hlgliest concentrations of hydrocarbons were detected In well MW-1 located near the western , <br /> edge of the property, north of the former dispenser at the site `Benzene was detected in the water <br /> sample from'well,MW-I A at 3,200 micrograms per Ilter (µg/l) <br /> Adtianced GeoEn\ironmental,Inc <br />