Laserfiche WebLink
16 December 2005 ` <br /> , AGE-NC Project No 98-04b5 ' <br /> Page 4 of 6 <br /> iTPH_g' ( and TPH-d, respectively) at concentrations'up to 300 mg/kg (milligrams per kilogram <br /> Volatile aromatic compounds benzene, toluene, ethylbenzene, and xylenes (BTEX) were detected r <br /> ' at concentrations up to 0 29 m <br /> „pr g/kg,methyl tertiary-butyl ether(MTBE)was detected in soil samples <br /> 'at concentrations up to 0 54 mg/kg <br /> Soil impact at the former UST release area does not appear to extend significantly beyond the tank <br /> , <br /> pit After removal of the overburden and tanks, samples collected from the side walls were non- <br /> detect for TPH-g and TPH-d with the exception of sample TK-1 S MTBE was detected at very low <br /> MTBE were all less than 1 0 mg/kg <br /> concentrations m samples D-1, D-2, TK1-S, TK1-N, TK2-S and TK2-N The concentrations of <br /> ' <br /> Between July 2000 and July 2005, twenty-one ' <br /> 1 the site to monitor dissolved petroleum hydrocarbon bon con entrat onmonitorinos ents inegroundewater and at <br /> o - <br /> characterize groundwater flow direction and gradient on the site Sine initiation of the groundwater <br /> monitoring program, ground water elevations have ranged from approximately 5 to 10 feet below <br /> mean sea level and the ground water flow has been consistently towards the north to northwest at <br /> low hydraulic gradients TPH-g and/or MTBE have been detected in water samples collected from <br />' wells`M W-1 through MW-4 at concentrations as high as 1,100 µg/1 TPH-g and 1,200 µg/1 MTBE <br /> The MTBE concentrations have declined suddenly at the site since initiation of ground water <br /> extraction at the Sanchez Property site (northwest and dowtz_gradient) during the first quarter of <br /> 2005 <br /> At the present time the hydrocarbon Impacted ground water is laterally and vertically defined in all <br /> directions, ground water is defined to the north by monitoring well MW-2, in the south by boring <br /> to'the west by borings B-2 and B-3, to the east by monitoring well MW-4 and boring B-4 <br /> Figure 4 depicts the lateral extent of MTBE-Impact to ground water <br /> Based on AGE's interpretation of the available data, the release(s) of petroleum hydrocarbons <br /> occurred at the former UST area during the removal activities performed in 1999 The only ground <br /> I water samples collected with TPH and BTEX were"grab"mix matrix water samples from the LIST <br /> I excavations No significant concentrations of,TPH or BTEX were detected at monitoring wells <br /> within or down from the former JUST area,and only MTBE was detected from round w <br /> monitoring events at the`site g water <br /> Once released to the subsurface, the contaminants migrated directly Into sand maters <br /> backfill) to a vertical depth of approximatelyeetY al (UST <br /> encountered saturated sandy soil and began to migrate a laterally whichat Po <br /> donet the contaminants <br /> to be <br /> significant adsorbed contamination beyond the tank pit The lateral migration f d ssoly d <br /> contaminates was dominantly towards the north, in the direction of ground water flow <br /> r Advanced GeoEnvironmental,Inc <br />