WORK PLANS - Laserfiche WebLink

Home Browse Search

. A � 19 November 2009 AGE-NC Project No. 02-0950 Page 9 of 13 Based on soil data collected during the investigation, the lateral and vertical extent of petroleum impacted soil prior to soil corrective action(i.e. excavation)is depicted in cross sectional and plan views(Figures 6 through 8).From Figures 6 through 8, the lateral extent of petroleum hydrocarbon- impacted soil appeared to extend from the core area of the plume(i.e. soil boring B2)approximately 33 feet towards the southwest, approximately 13 feet towards the north, approximately 19 feet towards the west and approximately 9 feet towards the east. The vertical extent of petroleum impacted soil appears to extend to approximately 36 feet bsg (B2 and MW-2 at 35 feet). Utilizing Figures 6 through 8, the mass of total petroleum hydrocarbons (TPH) in soil prior to corrective action can be determined by separating the soil plume into four contoured areas of 10,000 mg/kg, 1,000 mg/kg, 100 mg/kg and 1 mg/kg(i.e. non detect). The volume of each contoured zone was estimated utilizing the AutoCADTM computer program to determine the area between each contoured zone (Figure 8), and then multiplying the area by the height of the contoured zone as modeled from cross-sections D-D' and E-E' (Figures 6 and 7). AutoCADTM has a specific function to calculate the area of a selected object, such as each area between the above referenced TPH isoconcentration intervals. Based on the above results, AGE estimates that 4,292 pounds (lbs), or 687 gallons of total petroleum hydrocarbon was present in soil at the site prior to corrective action. The assumptions for the calculations of hydrocarbon mass in soil prior to corrective action is presented in Appendix H . Utilizing Figures 10 and 11, the mass of TPH remaining in soil can be depicted in cross sectional views D-D' and E-E' by removing the volume of impacted soil associated with the July 2007 excavation. Based on the above assumption that 3,287 pounds of TPH were removed from the site (section 4.0.) as a result of excavation activities, then AGE calculates that a mass of 1,005 pounds of TPH remains beneath the site. 6.0. ASSESSMENT OF HYDROCARBON-IMPACTED GROUND WATER Between October 20003 and May 2009, twenty-three (23) ground water monitoring events were performed at the site to monitor dissolved petroleum hydrocarbon concentrations in ground water and to characterize ground water flow direction and gradient on the site. Laboratory analysis of ground water samples historically detected TPH-g, TPH-d and BTEX from monitoring wells MW-2 and MW-7. Additionally, TAME was sporadically detected from wells MW-2 and MW-7,while 1,2-DCA was sporadically detected only from well MW-2. Ground water analytical data is summarized in Table 6. Based on laboratory analysis of ground water monitoring well samples, dissolved petroleum hydrocarbon compounds were generally not detected from ground water samples collected from Advanced GcoEnvironmental,Inc.