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CAMS RIA branded service station with two underground gasoline storage tanks, one underground waste oil tank, four dispenser islands, and a station building (Figure 2) Previous Investigations Soil samples were collected during an underground storage tank (UST), product line, and fuel dispenser replacement project in April 1996 Total purgeable petroleum hydrocarbons as gasoline (TPPH) were identified primarily in shallow soils beneath the northern-most dispenser island near Fremont Street at concentrations ranging from 18 ppm to 6,800 ppm at depths between 3 and 5 feet below grade (fbg) Benzene concentrations in this area ranged from none detected to 9 2 ppm An elevated concentration of methyl tertiary butyl ether (MTBE) was detected in a soil sample which was collected from the western portion of the former UST excavation at a depth of 19 fbg The MTBE concentration in this sample was 1,800 ppm TPPH and BTEX concentrations were below or near detection limits in the soil samples collected from the former UST excavation These data are documented in the Enviros, Inc Underground Storage Tank Removal Report dated June 20, 1996 Additional investigation performed during October 1997 included drilling two soil borings (SB-I and SB-2) with Geoprobe equipment to determine the vertical extent of petroleum hydrocarbons and MTBE previously identified during tank removal activities Soil boring SB-1 delineated the vertical extent of the petroleum hydrocarbons and MTBE in the western portion of the former tank complex Soil boring SB-2 was drilled to the depth of 35 5 fbg where drilling refusal was encountered The final soil sample collected at 35 5 fbg contained TPPH at a concentration of 5,700 ppm and did not contain detectable levels of benzene and MTBE These data are documented in Cambria's December 1, 1997 Site Investigation Report During April 1998, one soil boring (SB-3) was drill at the location of boring SB-2, to further delineate the vertical extent of petroleum hydrocarbons and MTBE in soil This boring was drilled with a limited access drilling rig to 55 fbg where drilling refusal was encountered TPPH was detected in a soil sample collected at 50 fbg from this boring Groundwater was encountered in this boring at approximately 52 fbg Since petroleum hydrocarbons were present in soil immediately above groundwater, three groundwater monitoring wells (S-1, S-2, and S-3) were installed at the site (Figure 2) These data are documented in Cambria's June 29, 1998 Site Investigation Report . Wells S-1, S-2, and S-3 have been monitored and sampled quarterly since they were installed Groundwater flow direction has been predominantly to the south and southeast Groundwater 241-0797 3