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Test Results <br /> 16 1 <br /> The SVE pilot test has indicated that the maximum sustainable vacuum extraction pressure is <br /> approximately 110 in we for vadose wells screened close to the saturated zone Vacuum rates <br /> higher than 110 in we will begin to suction the groundwater below the well upwards, and <br /> ultimately flood the extraction well This reaction effectively limits the maximum vacuum for <br /> design Extraction well design should consider the maximum elevation of groundwater at the <br /> Site to avoid accelerating the flooding process. <br /> With the system operating at near the maximum sustainable vacuum extraction rates, observation <br /> wells reached a stable vacuum response within 140 minutes of extraction. No substantial <br /> fluctuation was observed in the wells over the remainder of the test period. The average vacuum <br /> measured at each observation well during the maximum sustainable vacuum extraction rate was <br />' Observation Well Vacuum Distance from Extraction <br /> (inches of water) Well (feet) <br /> MW-1 002 77 <br /> MW-2 008 55 <br /> MW-3 Screen Flooded 16 <br />' MW-4 02 29 <br /> MW-5 0.07 47 <br /> The attached figure shows the location of these observation wells Observed vacuum in each <br /> well versus distance from the VE well are plotted on the attached graph Based on conservative <br /> tinterpretation of the data, a radius-of-influence of 20 feet is recommended for design purposes <br /> to allow for full coverage of the impacted area, with a safety margin for potential decreases in <br /> system performance over time. <br /> PID readings collected during the test ranged consistently between 418 parts per million volume <br />' (ppmv) and 518 ppmv Two duplicate tedlar bag vapor samples were collected after 5 hours and <br /> 20 minutes of testing The tedlar bag vapor sample analytical data sheets and chain-of-custody <br /> records are included in this Appendix Both samples had detectable concentrations of BTEX and <br />' TPH-G Benzene concentrations ranged from 12 to 21 ppm volume/volume (v/v), and TPH-G <br /> concentrations ranged from 2,100 ppm to 3,700 ppm v/v These laboratory data indicate that <br /> the PID readings were approximately seven times lower than values reported by the laboratory <br />' analyses due to the decreased sensitivity of the field instrument <br /> Mass removal rates can be calculated based on the average vapor extraction rate and the <br />' laboratory analytical data Since gasoline is comprised with many different chemical <br /> compounds, the removal rate can not be calculated for gasoline, only for representative single <br /> compounds, such as hexane Assuming that the maximum bag sample concentration of 3,700 <br /> ppmv/v consisted entirely of hexane, and the average flow rate was 24 cfm, the following <br /> calculations can be made. <br />' i 110Ica3 2 <br /> I <br />