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21 March 2006 AGE-NC Project No 97-0290 ' Page 7 of 15 ' 47 feet bsg (Figure 3) Petroleum hydrocarbon-Impacted soli in the vadose zone appeared to be centered near wells VW-1, ' MW2, SW 1,and SW2 Impacted soil at the site had an estimated diameter of 160 feet and appeared to extend downward to a depth of 60 bsg The greatest volume of Impacted soil was present between P3 and SWI at depths of 15 feet to 25 feet and 35 feet to 45 feet bsg,soil with declining hydrocarbon ' concentrations was present from 45 feet and 60 feet bsg An in-situ method of remediation was recommended to be most effective at the site The pilot test performed at the site Indicated that soil vapor extraction described In this CAP would be effective to remediate the site Based upon limited regulatory acceptance of bio-remediation, in-situ air sparging/soll vapor extraction and "pump and treat"were cost-effective methods to remediate the site Remediation of impacted ground water in the"core"area was conducted concurrently with soil remediation through the installation of IAS at the site concurrently with the proposed SVE system to prevent re- contamination of remediated soil 61 CORRECTIVE ACTION - SOIL AND GROUND WATER In Februaryand March 2000 thirteen soil borings were advanced at the site the borings were g � g completed as remediation wells VW-2 through VW-7 and SW-3 through SW-9 Soil samples were collected from vapor extraction well pilot borings VW2 through VW7, with the exception of VW3 (VW3 was not sampled), and soil samples were collected from air sparge well pilot borings SW3 I through SW9 A total of 27 soil samples were analyzed for TPH-g, TPH-d, and BTEX compounds TPH-g was detected In 26 of the 27 soil samples analyzed from borings VW2 through VW7 and SW3 through SW9 at concentrations as high as 7,400 mg/kg(SW7-45) TPH-d was detected in 22 of the 27 soil samples analyzed from the borings, with the exception of VW6, at concentrations as high as 2,300 mg/kg(SW7-45) BTEX compounds were detected in all the borings at concentrations as high as 29 mg/kg, 180 mg/kg, 110 mg/kg and 690 mg/kg,respectively(SW7-45) Methyl tertiary- butyl ether(MTBE)was not detected in any of the soil samples collected from borings VW2 through VW7 or SW3 through SW9 Analytical results of soil samples are summarized on Table 1 In early 2000, borings VW2 through VW7 were completed as vapor extraction wells using 2-Inch diameter PVC casing with a 0 020-inch slotted screen VW2 was drilled at a 15 degree angle from vertical and was completed to a total depth of 52 feet bsg with two I0-foot screen intervals VW3 was drilled at 25 degrees from vertical to a total depth of 55 feet bsg with a 10-, 12-, and 16-foot screen interval VW4 and VW5 were drilled to a total depth of approximately 50 feet bsg with three 10-foot screen intervals VW6 and VW7 were drilled to depths of 55 feet and 50 feet bsg, Irespectively VW6 was completed with one 15-foot and one 10-foot screen interval and VW7 was completed with two 10-foot screen Intervals Borings SW3 through SW9 were completed as air Advanced GeoEnvironmental,Inc I