ARCHIVED REPORTS XR0000697 - Laserfiche WebLink

Home Browse Search

31 August 2005 ' AGE-NC Project No 96-0232 Page 16 of 30 a subsurface petroleum hydrocarbon investigation Laboratory analysis of eighty-two soil samples from the subsurface investigation detected MTBE in 19 samples, TPH-g, TPH-d, BTEX and TBA were only detected in one sample (P31-10) During the March-April 1995 UST removals, an additional seventeen soil samples were collected from the tank pit sidewalls, beneath the tank pit floor and beneath product piping, TPH-g, BTEX were detected beneath one product piping sample (L3B), and xylene was detected beneath a second product piping sample (L2B) Based on analytical results of soil samples,the greatest MTBE-impacted soil was encountered near the south-southwest sections of the site (UST pit area) at soil borings P1-35 feet bsg(0 14 mg/kg), P20-20 feet bsg (0 35 mg/kg) and P22-15 feet bsg (0 63 mg/kg), significant MTBE-impacted soil was also encountered near the southeast corner of the fuel dispenser area at P31-10 feet bsg (0 54 mg/kg) and the northeast corner of the fuel dispenser area at P34-10 feet bsg (0 72 mg/kg) Soil boring locations are depicted in Figure 2 TPH-g and TPH-d-impacted soil were detected near the southeast corner of the fuel dispenser area from P31-10 feet at concentrations of 3 2 and 2 2 mg/kg, respectively, TPH-g-impacted soil was detected from product piping removal soil sample L3B at a concentration of 1 5 mg/kg, TPH-d- impacted soil was detected near the northern edge of the property boundary from P41-30 at a concentration of 1 7 mg/kg BTEX compounds were detected near the southeast cornier of the fuel dispenser area from P31-10 and from product piping removal soil sample L3B at concentrations as high as 0 26 mg/kg, total xylenes were detected from product piping removal soil sample L2B at a concentration of 0 028 mg/kg TBA was detected in soil samples collected near the southeast and northeast corners of the fuel dispenser areas from P31-10 feet and P34-10 feet at concentrations of 0 071 and 0 120 mg/kg, respectively The vertical extent of MTBE-impacted soil has been modeled to extend to maximum depths of 40 feet bsg (Figures 10 through 12) The lateral extent of petroleum impacted soil is mapped as an elongated, elbow-shaped plume that extends towards the north and southwest(Figure 13) 3 1 VADOSE ZONE MTBE-IMPACT Based on depth to ground water measured between May 1991 to March 2005,water level during this period typically ranged between 7 and 15 feet bsg Therefore, soil samples collected from 7 feet bsg or less could be considered as representative of vadose zone conditions Vadose zone petroleum- impacted soil was only encountered beneath product piping removal sample L3B (51/z feet bsg) at Advanced GeoEnvironmental,Inc