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�4$�--'Zx'� CLEARWATER G R O U P Hnvirunmenlaf Services Periodically throughout the GWE/SVE testing, pressure was measured in surrounding wells MW-1, MW-513, MW-6, and MW-7 Throughout testing, the vacuum in MW-513, the nearest well to DPW-1, was measured between 0 02 and 0 10 in w c , the highest vacuum being measured during 30 in w c of SVE Vacuum was only slightly noticeable in MW-6 during SVE, which was only measured as high as 0 02 in w c No vacuum was detected in MW-1 and MW-7 throughout the GWE/SVE testing Table 5 summarizes the observed vacuums in surrounding wells during SVE step testing 3p'� c 1 �l��vuisi Induced vacuum at observation points MW-5B and MW-6 throughout the test suggest that extraction from DPW-1 with an applied vacuum of 40 in w c results in an effective remedial radius of influence of 6 to 8 feet (Table 3a) The closest observation well, MW-5B located only 10 feet from DPW-1, displayed a vacuum between 0 02 to 0 1 in w c An effective remedial radius of influence for SVE is generally accepted as greater than 0 1 in w c of induced ' vacuum at an observation point Radius of influence data suggest that SVE extraction wells spaced at intervals of 12 to 16 feet would be required to cover the aerial extent of sorbed-phase contarrunation(12,000 square feet),however, that would necessitate an unmanageable number (i a approximately 60) of SVE vertical extraction wells for full ' scale remediation of sorbed-phase hydrocarbons Horizontal wells or trenches are other possible options for SVE 1 Contaminant recovery rates for SVE alone are likely to be relatively modest, based on low air flow rates and relatively low extractable contaminant concentrations in the air stream Air samples collected during the GWE/SVE ' test are summarized in Table 2 In the four soil samples collected during SVE on March 13, 2002, TPHg ranged from 35 to 77 mg/m3 and benzene ranged from 0 41 to 0 94 mg/rni Thus, TPHg recovery rates from one vertical extraction well would be —0 022 lbs/day, assuming an air flow rate of 5 cfm and air TPHg concentration of 50 ' mg/m3 Since a large number wells would be required to remediate the entire sorbed-phase contaminant plume, recovery rates for the entire plume would be sufficient, but impractical Other methods of SVE, such as horizontal ' wells and trenches,could be more practical solutions to sorbed-phase contarrunation at the site ' GWE/SVE/AS Test Results—March 14,2002 GWE/SVE/AS testing started with GWE to drawdown water level in DPW-1 to approximately 25 feet bgs followed by SVE in DPW-1 at a vacuum of 10 in w c AS began shortly after starting SVE at a pressure of 30 psi, in order to push down the water in AS-1, so air can pass through the well screen into the formation Once air cleared the screen in AS-1, the running sparge pressure was between 9 and 15 psi At this pressure, the sparge compressor operated at an air flow of 17 cfm While the applied air flow rate in AS-1 was held at 17 cfm, the vacuum pressure in DPW-1 was increased in steps at approximately 10, 20, 30, and 40 in w c over two hours GWE in DPW-1 continued throughout the testing at a pumping rate generally between 2 5 and 2 75 gpm Data from combined GWE/SVE/AS ' testing is included in Table 6 ZB178C Feas Test Report 7 May 9, 2002