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� l II� j 26 April 2011 AGE-NC Project No. 95-0104 Page 8 of 12 { On 14 July 2000, one confirmational soil probe boring (P-1) was advanced at the site to assess the effectiveness of SVE remediation effort at the site. TPH-d was detected in four of the soil samples collected from probe boring P-1 at concentrations as high as 410 mg/kg (P1-25). TPH-d was not detected in soil samples collected from depths of 35 and 40 feet bsg however, the 45-foot soil sample contained TPH-d 'at a concentration of 1.8 mg/kg. TPH-g and BTEX compounds were not detected in any of the `soil samples analyzed. The only soil samples collected from the site that have been analyzed for 1,2-DCA were collected from probe boring P-1 in July 2000.Analysis of the post remediation soil samples indicated that there is no 1 ,2-DCA impacted soil beneath the site (Table 2). 5.0. ASSESSMENT OF HYDROCARBON-IMPACTED SOIL AND GROUNDWATER SOIL IMPACT I Between 1988 and 2000, two soil borings (B-1 and P-1), fourteen ground water monitoring E € wells (MW-1 through MW-14) and one soil vapor extraction well (VW-1)were installed at the site to investigate the extent of hydrocarbon-impacted soil and ground water in the vicinity of the former UST and down-gradient of the former UST area. a The greatest concentrations of hydrocarbon-impacted soil has:been encountered at vapor well VW-1. Figures 4 through 6 depict general lithology'and selected soil sample results beneath the site in cross sectional view. The UST appears to have been the release point, once discharged into the subsurface the contamination �igrated vertically to 50 or 55 feet bsg, intercepted a high water table level and dissolved into the groundwater.The dissolved hydrocarbons and fuel additive 1,2-DCA migrated east-northeast as depicted in Figure 6. A volume-mass calculation using the data collected during investigation of the former UST area, yields approximately 1,287 pounds or 206 gallons of gasoline in the impacted soil at the site prior to SVE remediation. The lateral extent of impacted soil, prior to SVE remediation is depicted in Figure 2. An average concentration of 8,050 mg/kg (Tank Bottom @1T and VW1-25) was used to calculate the total vol 1 me of initial hydrocarbons from 15 to 30 feet bsg, while 3.4 mg/kg (MW 1-45)was used to calculate the total volume from 15 to 45 feet bsg. Current residual mass has not been calculated, based on the lack of petroleum detections for gasoline. Petroleum hydrocarbon-impacted soil volume calculations (pre-remediation) are included in Appendix D. k �r AGE estimated that operation of the SVE system removed approximately 158.92 gallons of gasoline,or approximately 77 percent of petroleum hydrocarbons formerly impacting soil at the site. iP ii Advanced GeoEnvironmental,Inc. 'r 4 k