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5.0 CONCLUSIONS/RECOMMENDATIONS SBased on field observations and analytical data from the Site,we present the following conclusions regarding petroleum hydrocarbon impact to soil and groundwater in the vicinity of Ithe former USTs • The maximum depth of petroleum hydrocarbon-impacted soil is approximately 95 feet bgs • Some lateral migration of petroleum hydrocarbons occurred within a sandy unit between approximately 30 feet and 45 feet bgs Analytical data for soil samples from B-2, MW-1, and MW-2 suggest that hydrocarbons attenuate to non-detectable concentrations in the sandy unit within 25 feet south of B-2, and within 55 feet west of B-2 • The lateral extent of hydrocarbon migration to the north and east in the sandy unit has not been established,but is likely consistent with migration in other directions • Petroleum hydrocarbons have unpacted groundwater beneath the Site Based on analytical results, the highest hydrocarbon concentrations were encountered in MW-2, with 27,000 ,ug/L TPHg and 4,800,ug/L Benzene The northwest boundary of the plume of impacted groundwater is in the vicinity of monitoring well MW-3 The west, east, and ! south margins of the plume have not been defined • Petroleum hydrocarbons have not been detected in the domestic well at the Site • Groundwater elevation data for the Site indicates that groundwater flow is toward the domestic well BSK recommends that additional monitoring wells be installed to define the west, south, and east margins of the plume of impacted groundwater BSK further recommends that a_agjLyVor extraction (SVE) pilot study be conducted at the Site to assess the feasibility of implementing interimremediation by SVE Recommended well locations are shown on Figure 4 as MW-5,MW-6, MW-7, and VEW-1 The well identified as VEW-1 should be completed as a vapor extraction well, for use during the pilot study and potentially for Site remediation The existing monitoring wells would serve as observation wells for the SVE pilot study Monitoring of the domestic well and monitoring wells and should continue The domestic well should be sampled monthly and the monitoring wells should be monitored quarterly ! Groundwater samples should continue to be analyzed for TPHg and BTEX using EPA Method 8015/8020 (Modified) and for fuel oxygenates using EPA Method 8260 r 6.0 LIMITATIONS ' This report has been prepared for the exclusive use of Mr Raymond Greer Unauthorized use of or reliance on the information contained in this report by others, unless given the express written consent by BSK & Associates, is prohibited The conclusions presented in this report are professional opinions based on the indicated data described in this report This report has been prepared in accordance with generally accepted methodologies and standards of professional Intenm Report-07400178-May 1999 6