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'-? Site Geology and Hydro-geolo�v A boring advanced at the site on December 13 2001, to 100 Petit bias utilizing CPT methods Indicated variable lavers of clavev silt and silty clav with some organic material were encountered from the surface to approximately 18 feet bias Soil from approximately 18 to 33 feet ' bgs generally of consisted of silty sand ana sandy silt Soil from approximately 33 feet to 40 feet bgs consisted of clayey silt and silty clay Soli from approximately 50 feet to 55 feet bgs ' consisted of clav Soil from approximately 55 feet to 57 fee:bgs consisted of very stiff fine- grained material Soil from approximately 57 to 73 feet bgs generally of consisted of silty sand arid sandy silt 3.0 PREVIOUS ENVIRONVIENT_kL, WORK ' In February 1987, SEMCO removed and disposed of one 3,000-gallon unleaded gasoline underground storage tank (UST'), associated piping, and fuel dispenser from the location shown on Figure 2 A soil sample collected from 13 feet below ground surface (bgs) contained elevated ' concentrations of petroleum hydrocarbon contaminants The excavation was subsequently backfilled and resurfaced On July 23, 1997, an ATC geologist supervised the advancement of five soil borings (SBI through SB5) ranging in depth from 6 to 46 feet bgs The soil borings were advanced using a truck mounted Geoprobeg) narrow diameter ng employing direct push technology Petroleum �1 hydrocarbons were detected in soil samples submitted for laboratory analyses Site activities are 1 summarized In ATC's Summary Report for Subsurface Investigation, dated October 20, 1997 ' On September 25, 1998, ATC personnel supervised the advancement of soil boring MWl at the site to a depth of approximately 65 feet bgs to evaluate groundwater for the presence of petroleum hydrocarbons The soil boring was completed as a groundwater monitoring well and on September 28, 1998 the well was developed and sampled Analytical data indicated that soil and groundwater samples contained detectable concentrations of petroleum hydrocarbons Field activities and analytical results are detailed in ATC's Summary Report of 4dditronal Subsurface Investigation, dated January 8, 1999 ' In December 1999, ATC personnel supervised the advancement of soil bonngs MW2, MW3, and MW4 at the site to depths of approximately 65 feet bgs to evaluate groundwater for the presence of petroleum hydrocarbons and to determine the gradient direction and magnitude The borings (f� were completed as momtonng wells Analytical data indicated that soil samples collected from boring MW2 contained detectable concentrations of petroleum hydrocarbons Petroleum ' hydrocarbons were also detected in a groundwater sample collected from well MW2 A groundwater sample collected from MW3 contained very low concentrations of only a few of the requested analytes Petroleum hydrocarbons were not detected in the groundwater sample collected from MW4 Field activities and analytical results are detailed in ATC's Summary Report of 4dditional Subsurface Investigation dated February 24, 2000 z s 5etviromental162577-Diesel Perflreporrsbntenm_rem#2 doc 1