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The TPHg was selected based on experience at other sites,benzene'was based on the U. S. Environmental Protection Agency (EPA) Region IX's industrial PRG and for groundwater the regulatory limits established for drinking water. j a } These goals are considered conservative in that the risk asse Isment'calculated the risk for all exposure pathways to be below the EPA acceptable criteria for both carcinogenic and noncarcinogenic chemicals (URS, 1999). These goals may not be achievable due to site conditions and will be revisited as remediation progresses. P 3.3 Selected Remedial Alternative l The 1996 pilot test (Geocon, 1996) applied a vacuum of 12,500 pascals (Pa) (50 inches of water [in. WC]) to well VW-1 and resulted in a flow rate from VW-1 of 102 standard cubic meters per hour (sm3/hr) (60 standard cubic ft per minute [scfm]). An influence of up to 719 Pa(2.85 in. WC) was observed in well VM-1 located 6.1 m(20 ft) away An influence of up to 650 Pa(2.6 in. WC) was observed in well VM-2, located 12.2 m(40 ft) away. Based on these measurements, a radius of influence (ROI) of 24.4 m (80 ft)�was postulated. The SVE wells will be located to influence the soil containing petroleum hydroa bons'and benzene and to capture the injected air from air sparging. Figure 7 shows the proposed locations of the vapor extraction r-� wells (VEW-I and VEW-2). Each well will be screened froin 4.6 in (15 ft) to 14 m (46 ft) bgs to encompass the soil containing petroleum hydrocarbons. The well 'screens will end above the water table to prevent groundwater being drawn into the well and covering the well screen. Based on IT's experience, the typical ROI for an air sparge well is,7.6 m (25 ft) based on experience. Therefore, four air sparge wells (ASW-1 through ASW-4) are proposed and shown on Figure 7. '1 .9 I1. f 'f S cOP•Nl acDIIIM21PAJIVJIIM1329942sb.das 3-2 (0102 ) f