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ATC SITE SAFETY PLAN <br /> FACILITY BACKGROUND <br /> In April 1987, SEMCO removed and disposed of two 1,000-gallon regular gasoline underground <br /> storage tanks (USTs), associated piping, and fuel dispenser. A soil sample was collected from <br /> the end of each tank at approximately 17 feet below ground surface. Analytical testing indicated <br /> the collected samples contained detectable concentrations of petroleum hydrocarbon constituents. <br /> The excavation was subsequently backfilled to the ground surface. <br /> On July 24, 1997, to investigate the extent of residual soil contamination at the site, a total of six <br /> soil borings were advanced to depths ranging from approximately 16 to 31 feet below ground <br /> surface (bgs). Detectable concentrations of total petroleum hydrocarbons as gasoline (TPHg), <br /> total petroleum hydrocarbons as diesel (TPHd), and benzene, toluene, ethylbenzene, and xylenes <br /> (BTEX) were observed in soil samples collected from the site. The distribution of petroleum <br /> constituents beneath the site has been essentially defined and appears to be limited laterally to the <br /> immediate vicinity of the former tank pit. The highest concentrations were reported between 10 <br /> and 20 feet bgs and generally attenuate rapidly with depth. Only low concentrations of toluene <br /> (0.064 mg/kg) and xylenes (0.012 mg/kg) were detected at approximately 30 feet bgs in one <br /> boring, the maximum depth explored. Attempts were made to further advance the Geoprobe unit <br /> in several of the borings, however probe refusal was encountered at depths ranging from <br /> approximately 16 to 30 feet bgs due to the hardness of the formation. <br /> WORK PLAN <br /> Task One: <br /> ATC will advance one soil boring and collect and analyze an estimated two soil samples <br /> and one groundwater sample from the boring. <br /> PAGE 4 <br />