ARCHIVED REPORTS XR0006868 - Laserfiche WebLink

Home Browse Search

' 2 BACKGROUND ' The following background information presents EMCON Associates' understanding of the site history based upon information supplied to ' EMCON Associates by Teichert. 2.1 Removal of Tanks C-14 North, C-14 South, and WO-4 } Three underground storage tanks (C-14 North, C-14 South, and WO-4) were removed from the site in October 1986. The former tank locations, capacities, and contents are presented on Drawing 1 . To subsequently h characterize the lateral and vertical extent of soil and ground-water impact, ' !I soil borings were drilled and ground-water monitoring wells were installed. Borings B-1 through B-16 were drilled and sampled in December 1986 and January 1987 (see Figure 2). Borings B-10, B-12, and B-13 were con- w verted to monitoring wells MW-1 through MW-3, respectively. The soil and ground-water analytical results from these site characterization activities are presented in Table 1. In September 1987 overexcavation of the impacted soil near the former P � P tank complex was completed. Wells MW-1 and MW-2 were destroyed ' during removal of this soil. Confirmation soil samples were collected from the bottom and sidewalls of the excavation. Confirmation soil sample ana- lytical results are presented in Table 2. The total petroleum hydrocarbons as gasoline (TPHG) and benzene concentrations detected in these sam- ples are shown on Figures 2 and 3, respectively. TPHG was detected at a ' concentration of 338 milligrams per kilogram (mg/kg) at a depth of 32 feet at the north-central side of the excavation where the pump island was located (see Figure 2). TPHG was also detected at a concentration of ' 2 mg/kg in the sample from the bottom (38 feet) center of the tank excava- tion (see Figure 2). TPHG was not detected in samples collected from the ' other areas of the excavation. Benzene was only detected in one of the confirmation soil samples collected during the overexcavation. Benzene was detected in the sample from the bottom center of the tank excavation ' at a concentration of 0.037 mg/kg. As shown in Figure 2, following the September 1987 overexcavation activ- ities, TPHG was left in place below 30 feet at three locations. At these pjfV92V920201 a 2 Rev. 0 June 1, 1992 MCon sssociotas