SITE HISTORY - Laserfiche WebLink

Home Browse Search

22 October 2009 AGE-NC Project No. 000697 Page 7 of 10 results of soil samples collected from the site are summarized in Table 1. To date,a total of 45 soil samples(including those from the UST removal activities)were submitted for laboratory analysis of petroleum hydrocarbons at depths ranging between 4 and 58 feet bsg. Initially,two soil samples(R1 and U1)were collected at 4 feet bsg beneath the leaded and unleaded gasoline USTs. Based on the laboratory results,TPH-g was reported from R1 at a concentration of 570 mg/kg,toluene was reported at a concentration of 84 mg/kg,and total xylenes were reported at a concentration of 250 mg/kg. Based on soil samples collected during advancement of soil borings, TPH-g was reported in six samples at concentrations as high as 550 mg/kg(MW6-10).TPH-d was reported in two samples at concentrations as high as 750 mg/kg (MW6-10). Benzene was reported in two samples at concentrations as high as 1.1 mg/kg (MW6-10). Toluene and ethylbenzene were detected in five samples at concentrations as high as 8.4 mg/kg toluene and 7.6 mg/kg ethylbenzene (MW6-10), respectively; xylenes were detected in eight samples at concentrations as high as 32.5 mg/kg (MW6-10). TAME and 1,2-DCA were reported in one sample at concentrations as high as 0.020 mg/kg(B6-5). Petroleum hydrocarbon-impacted soil extends from the former leaded UST towards the east encompassing an area 40 feet by 45 feet (Figure 2). The vertical extent of TPH-g impacted soil extends to a depth of 15 feet bsg across most of the site;in the area of well MW-6,TPH-g impacted soil extends to a depth of 20 feet bsg(MW6-20).Additionally,xylenes were detected to a maximum depth of 28 feet bsg in MW-6.Benzene was not detected below 10 feet bsg in any ofthe soil samples analyzed. Utilizing Figures 5,6 and 7,the mass of TPH-g in soil can be determined by splitting the soil plume into three elliptical contoured zones.Based on analytical results for soil samples collected at the site to date,AGE estimates 57.16 pounds(lbs),or 9.15 gallons total petroleum hydrocarbons appear to remain in soil at the site.The assumptions for the calculation of hydrocarbon mass remaining in soil is presented in Appendix G. 6.0. ASSESSMENT OF HYDROCARBON-IMPACTED GROUND WATER Between November 2004 and October 2008, approximately seventeen 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 have detected TPH-g and BTEX from monitoring well MW-3 at concentrations as high as 3,300µg/1 and 490µg/1(benzene),respectively(November 2005 Advaneed GeoEnvironn"tnl,Int.