ARCHIVED REPORTS_XR0009516 - Laserfiche WebLink

Home Browse Search

' 2.3 Contaminated Soil Removal Over excavation of contaminated soil in the vicinity of the former UST was conducted in ' December 1994. Approximately 108 cubic yards of contaminated soil was removed from the vicinity of the former UST and disposed of off site. ' 2.4 Additional Soil and Groundwater Investigation Eleven (11) soil probe holes were advanced during November 1995 and January 1996 in the ' vicinity of, and down-gradient from, the former UST. Soil and groundwater samples were collected to define the lateral extent of soil and groundwater contamination. Results of this investigation are presented in the Wm. J. Hunter and Associates report entitled Interim Report ' Covering Results of Soil and Groundwater Investigation (1996). Soil probe locations are shown in Plate III of the Interim Report (1996). Analytical results from the soil samples collected during this investigation indicated that TPH-g and BTEX were not detected (ND) ' above the laboratory detection limit in ten of the eleven soil probe holes (A-1, A-2, A-5, 82, B- 3, B-4, C-2, D-1, D-2, and D-3). However, soil probe A-4 located northeast of the former UST near the east side of the property contained low levels of TPH-g and BTEX at concentrations of 57, 0.116, 0.594, 1.20, and 3.54 ppm, respectively. Analytical results of the grab groundwater sample collected at 15 feet bgs from the easternmost boring 0-2 contained 59, 3.0, 24, 3.6 ppb of BTEX and 5.1 ppb TPH-g, however, these constituents were all ND in the grab groundwater sample collected at 24 feet bgs. ' In May 1996, a fourth groundwater monitoring well (MW-4) was installed down-gradient of the site (see Figure 2). The well was installed to a depth of approximately 25 feet, and screened ' from approximately 5 to 25 feet bgs. Due to rising groundwater levels, monitoring well MW-2 was no longer screened across the top of the water table and in September 1999, a fifth groundwater monitoring well (MW-5) was installed seven feet west of MW-2 to address this ' problem. MW-5 was installed to approximately 21 feet bgs and screened from approximately 5 to 20 feet bgs. ' 2.5 Groundwater Monitoring Program Groundwater monitoring at the site began in March 1994 and continued through 1999 on a ' quarterly basis, originally with three monitoring wells MW-1 through MW-3. Monitoring well MW-4 was added to groundwater monitoring program in 1996 and MW-5 in 1999. Since 2000, groundwater has been monitored on an annual basis. ' Analytical results of groundwater samples from MW-2 declined from 96,000 parts per billion (ppb) TPH-g in March 1994, to 4010 ppb in December 1997, to ND in May 2002. BTEX ' components also have declined in MW-2. Benzene trended from 400ppb in 1994 to ND at the present. Analytical results of the groundwater sample from MW-5 (screened from 5 feet bgs to 25 feet bgs) were 2,500 ppb TPH-g and 60 ppb benzene in September 1999, but have since fallen considerably to ND in May 2002. The historical summary of groundwater sample results is presented in Table 2.. Current.TPH-g, BTEX, and oxygenate concentration levels . are discussed in the following section (Section 3.0). 1 ' 3 JJW GEOSCIENCES Inc.