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6. CONCLUSIONS Based on the analytical results for soil samples collected from confirmatory soil borings SB4- ' SB7 drilled within the former UST basin to quantify the success of the remedial efforts, and soil boring SB3 drilled to assess the presence of hydrocarbons in the southeast corner of the property, the SVE system, which removed 1,551 pounds of hydrocarbons, successfully remediated the ' vadose soil at the site Of the 20 soil samples collected during this field effort, oxygenates and benzene were not detected at or above reported detection limits with the exception of 3 81 mg/kg benzene in sample SBS at 36 feet hgs TPH-g was detected in three of the 20 samples collected, ' at concentrations ranging from 0 501 to 14,300 mg/kg in SB5-SB7 As presented in Figure 4a, the numerous soil samples collected for analysis from the confirmation soil bonngs, as well as ' samples collected before remedial efforts, allows this detection of 14,300 mg/kg TPH-g in saturated sample SB5-36 to be defined as limited in extent Benzene was not detected in the any of the grab groundwater samples collected from these five confirmation soil borings Of the oxygenates, MTBE was detected in three of the five samples at concentrations ranging from 4 89 to 19 6 gg/L TPH-g was detected in one of the five grab groundwater samples (SB7W), at 3,930 gg/L During the 30 July 2000 groundwater sampling event, BTEX and TPH-g were not detected above reported detection limits during this event MTBE was detected in wells MW6 and VEW2 at 6 and 21 µg/L, respectively As presented in Table 1, samples from well MW6 have been analyzed for MTBE during 15 quarterly events since 1996, and MTBE has only been detected one other time, at 12 gg/L Based on this, as well as the historical data, the plume has stabilized A nsked-based corrective action (RBCA) analysis was performed to assess the risks associated ' with no further action at the site Historical soil and groundwater data were used along the conservative assumptions of a Tier I RBCA analysis The results of the RBCA analysis are that (1) petroleum hydrocarbon and MTBE concentrations in soils and groundwater detected ' following remediation efforts at the site do not pose a significant risk to daily site occupants under commercial./industrial land use or existing residential receptors at offsite locations, (2) petroleum hydrocarbon and MTBE concentrations in soils detected following remediation efforts at the site do not pose a significant nsk to future construction workers at the site, and that (3) prior to initiation of construction work, an appropriate health and safety plan should be developed to ensure construction worker health and safety Based on the historical and existing concentrations in soil and groundwater, the successful remediation of potential onsite sources, and the results of the RBCA analysis, ETIC recommends ' no further action and requests site closure h Ticjrns%701771Maa rMVr�CILnureI 10O4U137utex[d0c 19