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1 I 09 April 2002 AGE-NC Project No. 97-0301 Page 2 of 14 2.2. UNDERGROUND STORAGE TANK REMOVAL On 04 September 1998, one 10,000-gallon diesel UST and two 10,000-gallon gasoline USTs and associated fueldispensers and product piping were removed from the site. Laboratory analysis ofsoil samples collected beneath the former UST areas detected total petroleum hydrocarbons quantified as gasoline, diesel and kerosene (TPH-g, TPH-d and TPH-k, respectively) at concentrations up to O 9,000 mg/kg (milligrams per kilogram). Benzene, toluene, ethylbenzene and xylene constituents I- I (BTEX) were detected at concentrations as high as 520 mg/kg; methyl tertiary butyl ether (MTBE) was detected in two stockpiled soil samples at concentrations up to 0.012 mg/kg. Analytical results j of soil samples collected during tank removal activities are summarized in Table 1 . l2 .3 . PREVIOUS SUBSURFACE INVESTIGATION The following is a brief summary of site assessment activities: • June 1999 - Four soil borings (P- 1 through P-4) were advanced to approximately 40 feet l below surface grade (bsg) at the site to assess the lateral and vertical extent of petroleum- impacted soil and ground water. TPH-g and TPH-d were detected in soil samples collected from probe boring P- 1 at concentrations ranging as high as 330 mg/kg; BTEX constituents were detected in soil samples collected from P- 1 and P-4 at concentrations ranging as high as 9. 5 mg/kg. TPH-g and TPH-d were detected in "grab" water samples collected from borings P- 1 , P-2 and P-4 at concentrations as high as 350,000 micrograms per liter (µg/1); Lll BTEX constituents were detected in water samples collected from P- 1 though P-4 at _l concentrations as high as 3 ,300 µg/1. Tert butanol (TBA) and di-isopropyl ether (RIPE) compounds were detected in ground water samples collected from P- 1 , P-2 and P-4 at concentrations as high as 140 µg/1. Analytical results of soil and grab ground water samples - collected during the June 1999 investigation are summarized in Tables 2 and 3 . Results of the June 1999 investigation were reported in Preliminary Investigation and Evaluation Report (PIER), dated 26 July 1999. i •—December-l999—four-ground water-monitoring-wells (MW-1,MW-2, MW-3-and MW-4}-- were W-4}were installed at the site as part of site assessment activities. TPH-g, TPH-d and TPH-k were . J detected in soil samples collected from MW- I at concentrations as high as 7,000 mg/kg; BTEX constituents were detected at concentrations as high as 54 mg/kg. TPH-g was detected i j in the initial ground water sample collected from well MW- 1 at a concentration of 47,000 !; _ I µg/l; TPH-d was detected in water samples collected from wells MW-1 , MW-2 and MW4 at concentrations as high as 3 ,500 µgll; TPH-k was detected in ground water samples collected from wells MW- 1 and MW-4 at concentrations of 12,000 and 62 µg/1, respectively, and BTEX constituents were detected in the initial ground water samples collected from wells MW4 and MW-4 at concentrations as high as 6,400 µg/1. Analytical results of soil and '—'� Advanced GeoEnvironmental, Inc.