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Former Beacon Station No 12474 June 7,2005 Stockton California Results of Additional Groundwater Assessment . Volatilized vapors, such as benzene and other BTEX compounds, have the potential to migrate from impacted soil or groundwater, enter into the atmosphere and enclosed spaces such as the station building and off-site, residential or commercial buildings and be inhaled by commercial workers or residents The migration of vapors from impacted soils into the atmosphere would mainly be in the area of the eastern dispenser island and be impeded by overlying pavement Concentrations of BTEX compounds in air in the dispenser island area originating from the impacted sot] are likely negligible compared with those originating from fueling operations The vapor exposure pathway from impacted soil to workers in the station building is likely incomplete given the distance to the eastern dispenser island area, approximately 50 feet The vapor exposure pathway from impacted groundwater to workers in the station building and off-site residents is likely incomplete because of the depth to groundwater and the limited lateral extent of groundwater impacted with volatile hydrocarbons Gasoline constituents in subsurface soils have the potential to leach to and be transported by groundwater Down-gradient migration of dissolved hydrocarbons in groundwater is a transport mechanism that has the potential to impact groundwater utilized for potable uses via water wells This exposure pathway does not appear to be complete with respect to known domestic or municipal drinking water wells because of the known extent of groundwater impacts and the intervening distance to the known wells as discussed in the following section Sensitive Receptor Survey In February 2002, Horizon conducted a sensitive receptor survey for the area within a 2000- foot radius of the site The sensitive receptor survey included identification of natural surface water bodies, land usage, schools and churches, and a water well search in the survey area . Mormon Slough trends roughly east-west at the southern edge of the survey area Flow in Mormon Slough is diverted into Stockton Diverting Canal approximately 3 miles east Addtn1GWass=t Project No 1474 15 11 HORIZON ENVIRONMENTAL INC.