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I ' 25 February 2005 AGE-NC Project No 95-0104 ' Page 3 of 10 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) 2.0. SITE CONCEPTUAL MODEL ' Based on the data collected to date from the monitoring wells on-site, AGE has developed a site conceptual model(SCM)for the migration and distribution of the l,2-DCA dissolved In the ground water at the site (Figures 3 through 6) The soil profile beneath the site Is generally composed of sandy silt and silty sand with lenses of fine- grained sand and silt (Figures 3, 4 and 5) Based on ten years of quarterly monitoring, the depth to ' ground water has ranged between approximately 52 27 feet and 82 58 feet bsg(Table 1) at the site, and has consistently had a northeast flow direction, with the exception of the past two quarterly monitoring events In June 2003 and September 2004(Figure 7)the ground water flow direction has ' been toward the north,with an average September 2004 depth to water of 77 feet bsg Ground water occurs in a generally sandy silt unit interbedded with fine to medium sands that dominate the llthology of the site Thereatest concentrations of hydrocarbon-impacted soil has been encountered at vapor well VW-I g Figures 8 and 9 depict general lrthology 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 migrated vertically to 50 or 55 feet bsg, intercepted a high water table level and ' dissolved Into the ground water 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 308 gallons of gasoline In the Impacted soil at the site Assuming that VW-1 Is within the source area, an effective radius of fifteen-feet was used to estimate the volume of Impacted soil An average concentration of 14,000 mg/kg was used to calculate the total volume of remaining hydrocarbons from 15 to 30 feet bsg, while 1 1 mg/kg was used to calculate the total volume from 30 to 45 feet bsg Petroleum hydrocarbon-Impacted soil volume assumptions and ' calculations are also Included In Appendix A Hydrocarbon Impacted-soil was vertically defined In the source area,by soil samples collected from ' soil boring V W 1 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 those soil samples Indicated that there Is no 1,2-DCA Impacted soil beneath the site (Table 2) Total petroleum hydrocarbons as gasoline and diesel (TPH-g and TPH-d), benzene, toluene, ' Advanced GeoEnvironmental,Inc