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2,4 Site Investigations <br /> The site investigations conducted indicate that the petroleum hydrocarbon impact to the <br /> subsurface is probably due to existing steel underground storage tanks. It is Pinnacle's <br /> understanding, based on investigations conducted to date, that 10 monitoring wells, six <br /> on site and four off-site, have been installed, ranging from 20-62 feet bgs, to characterize <br /> the extent of petroleum hydrocarbon impact to the soil and groundwater. <br /> The vertical extent of the petroleum hydrocarbon impact to soil is defined by non- <br /> detectable concentrations in soil borings for MW-8 at 45 feet bgs. The lateral extent of <br /> soil impact is defined by non-detectable concentrations in the soil samples at monitoring <br /> wells MW-1 through MW-3. <br /> The lateral extent of impact to groundwater, to the east and south appears to be defined <br /> by monitoring wells MW-5 and MW-7, respectively, while the impact to the north is <br /> defined by wells MW-1 and MW-2. Highest detected TPHG, BTEX and MTBE <br /> concentrations are found in on-site well S-1, located northwest of the UST complex. The <br /> lateral extent to the west is not defined based on groundwater impacts in MW-8. The <br /> concentration of TPHG, benzene, and MTBE in well MW-8 during the third quarter 1998 <br /> monitoring event was recorded to be 1,900 parts per billion (ppb), 200 ppb, and 2,500 <br /> ppb, respectively. <br /> E5J:1E:1U5A100651REPORTs10065P201.DOC-98Vsg:I Rev.0,1/2G/99 <br /> 20A41-007.001 2-3 <br />