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1 - • Hydrological Unit 2(HU2)extends from 45 to approximately 75 feet bsg,11U2 is composed • of sand, with minor layers of silt and cemented sand The interval is characterized by low ' pore pressure • Hydrological Unit 3 (HU3) extends from 75 to 113 feet bsg, and is dominantly composed of ' silt, clay and stiff, fine-grained intervals Unit 3 is charactenzed by a fluctuating range of pore pressures, varying from low to medium low • Hydrological Unit 4 (HU4) extends from 113 feet bsg to 117 feet bsg, and is composed of ' sand The interval 2s characterized by low pore pressures • Hydrological Unit 5 (HU5)extends from 117 feet bsg to total depth, and is composed of silt ' The interval is characterized by increasing pore pressures, from medium low at approximately 117 feet bsg to high at total depth of 147 feet ' Cross sections A-A' and B-B' depicted general lithology beneath the site The hydrological units are depicted in cross sectional views A-A' and B-B' I HYDROCARBON IMPACTED SOIL AND CONTAMINANT MIGRATION ' The mayor source of soil contamination was the former gasoline UST located at the western edge of the main office building 1• A release of petroleum hydrocarbons occurred from the former gasoline UST Hydrocarbons were detected at concentrations as high as 5,800 mg/kg Available data is suggestive of ' discharge at the western edge former gasoline UST area • Once released to the subsurface, the contaminants migrated to a vertical depth of approximately 40 feet bsg(MW-6),at which point the contaminants migrating locally down to a depth of 85 feet bsg(CPT1-85) The contaminants migrated east and northeast from the former UST area, under the building at the site, to a then vertical depth of approximately I 40 feet bsg,where the variation concentration in soil samples suggest a smear zone between 35 feet and 40 feet bsg Low concentrations of impacted soil was only detected at greater than 30 feet bsg in downgradient monitoring well pilot boring samples • The highest impact to soil in the upper vadose zone is present at boring MW-6 The highest impact to soil near the water table and below the water table to a depth of 85 feet bsg occurs inthe area of bonng MW-6 and CPT1 Soil samples collected from the a depth of 30 feet bsg had concentrations of TPH-g (4,100 mg/kg), benzene (17 mg/kg) and EDB/1,2-DCA (460 mg/kg/410 mg/kg), which represents the core of the impacted soil • TPH-g were detected in ground water samples collected from wells on the site, at concentrations as high as 150,000 µg/1 from the ground water extraction well in the former UST excavation TPH-g-impacted shallow ground water has been defined,with only minor concentration detected in well MW-3, north of the former UST IAdvanced GeoEnnronmental,Inc