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' Historical Conceptual Model Background & Site <br /> . g <br />' AGE-NC Prod ect No O 1-0827 <br /> Page 2 of 9 <br />' UST43 was a 500 gallon diesel UST These two USTs serviced the western dispenser on the fuel <br /> Island Contamination was reportedly evident on the southern excavation wall However, the only <br /> sample with reported hydrocarbons was collected at the dispenser Island (P1) Sample P-1 had <br />' reported detections of total petroleum hydrocarbons as gasoline (TPH-g), TPH-diesel (TPH-d) <br /> toluene, ethylbenzene and xylenes at concentrations of 1,600 mg/kg, 4,900 mg/kg, 0 33 mg/kg, <br />' 4 9 mg/kg and 56 mg/kg, respectively <br />' 22 SITE ASSESSMENT MILESTONES <br /> In December 1988 the assessment of the petroleum hydrocarbons release from the USTs began with <br />' the Installation of soil borings B1 through B3, completed as ground water monitoring wells MW-1 <br /> through MW-3 Soil samples from boring B 1 contained TPH-g at a maximum concentration of <br /> 350 mg/kg(B 1-25) Benzene,toluene, ethylbenzene and xylenes(BTEX)were detected in the same <br /> I sample at concentration of 4 7 mg/kg,21 mg/kg, 18 mg/kg and 110 mg/kg,respectively Monitoring <br /> well MW-1 was installed at the western edge of the former UST cluster area, well MW-2 was <br /> installed 100 feet east of well MW-1,and well MW-3 was installed 90 feet south of well MW-1 and <br /> 10 <br /> the former UST excavation The wells were first sampled on 12 December 1988 <br /> In May 1990,five additional soil borings,B4 though B8 were established on the site Boring B8 was <br />' completed as monitoring well MW-4,at a location 140 feet north of well MW-I and the former UST <br /> excavation <br />' In August and September 1992,five additional soil borings,B9 though B 13,were established on the <br /> site Boring B 13 was completed as remediation well RW-1,at a location 20 feet north of well MW-1 <br /> and the former UST excavation Boring B12 was completed as groundwater observation well PZ-1 <br />' between well RW-1 and the former UST excavation Additionally, boring B9 was completed as <br /> vapor well VW-1, boring B 10 was completed as vapor well VW-2 and boring B 11 was completed <br /> as dual-screened vapor well VW-2 During September 1992, a set of ground water and soil vapor <br />' extraction.(SVE)remediation feasibility pilot studies were conducted on the site One ground water <br /> extraction(GWE) pilot test was conducted at well RW-1 and one SVE pilot test was conducted on <br />' wells VW-2 and VW-3 <br /> In September 1993, four additional soil borings, boring B14 thought B17 were established on the <br />' site Boring B 14 was completed as monitoring well MW-5 at a location 100 feet west of well MW-1 <br /> and the former UST excavation Boring B15 was established inside the truck bay of the building, <br /> north of the former UST excavation Boring B 16 was completed as vapor well VW-4 and boring B 17 <br />' was completed as dual-screened vapor well VW-5 During January 1994,a second SVE remediation <br /> feasibility pilot study was conducted on the site, on wells VW-1 and VW-5 During October 1994, <br /> • a third SVE remediation feasibility pilot study was conducted on well VW-1 Based on the pilot <br /> Advanced GeoEnwronmenta[,Inc <br />