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' 07 February 1999 <br /> AGE-NC Project No 95-0135- <br /> Page <br /> 5-0135Page 2 of 4 <br /> i <br /> F <br />' chain,of custody,to Precision Enviro-Tech (PET) of Stockton, a State of California Department of <br /> Health 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 /> I _ Method 8015 Modified, <br /> Volatile aromatics benzene, toluene, ethyl benzene and total xylene (BTEX), oxygenating <br /> compounds including methyl tertiary-butyl ether (MTBE), tertiary-butyl alcohol (TBA), dt- <br /> isopropyl ether (DIPE), ethyl tertiary-butyl ether (ETBE) and tertiary-amyl methyl ether <br />' (TAME) in accordance with EPA Method 8260 Modified <br /> I r <br /> 3.0. FINDINGS <br /> Ground water flow direction and gradient were inferred from field data, petroleum hydrocarbon <br /> rimpact on ground water was quantified by the results of laboratory analysis <br /> 3 1 GROUND WATER ELEVATION AND GRADIENT <br /> During the December 1999 monitoring event,depths to ground water in wells MW-1 through MW-3 <br /> were measured between 24 88 and 26 33 feet below the tops of well casings, ground water elevations <br /> were calculated to be between 12 96 feet and 14 11 feet below mean sea level Ground water <br /> elevation at the site decreased an average 0 73 feet between the September 1999 and December 1999 <br /> ground water monitoring events During the December 1999 monitoring event the ground water <br /> underlying the site flowed to the southeast under a gradient of 0 005 ft/ft The ground water'elevation <br /> data for MW-1B through MW-313 during the December 1999 ground water monitoring event is <br /> depicted In Figure,3 <br /> Due to the low gradient at the site, slight variations in ground water measurements or changes of <br /> recharge/discharge of the local ground water could greatly modify ground water flow direction <br /> 32 LABORATORY RESULTS OF GROUND WATER SAMPLES <br /> TPH-g concentrations decreased'in five of the six wells and BTEX concentrations also generally <br /> decreased in the wells Benzene was detected in all water samples from well MW-1A/B and MW- <br /> 2A/B <br /> Advanced GeoEnvironmental,Inc <br /> , <br />