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ATTACHMENT 6: ' SUMMARY OF VACUUM-INFLUENCE TESTS The SVE system began operation on September 10, 1997 Elevated groundwater levels had ' previously prevented operMon of the installed remediation system Initial hydrocarbon concentrations in the system influent were measured by an explosimeter at between 100 parts per million by volume (ppmv) and 250 ppmv These concentrations of hydro- carbons indicate that long-term operation of the catalytic oxidation system may not be required to abate hydrocarbon vapors removed from the subsurface Effective enhancement of biological activity in the vadose zone can be more cost-effectively performed by bioventmg ' Geraghty & Miller performed two field tests to determine the influence of the SVE system on September 26, 1997 Two extraction wells, GM-1 and VW-1, were utilized to determine influence in nearby monitoring and extraction wells A vacuum was applied to each well independently, and surrounding monitoring and remediation wells were monitored for vacuum influence Vacuum influence data varied sigruf1cantly during the tests, as shown in Table 6-1 During the first test, a vacuum was applied to Well GM-1 for approximately 40 minutes Vacuum m fluence was measured in MW-5, GM-2, GM-3, GM-4, and MW-1 until measurements stabilized A vacuum influence was observed at every monitoring point, including MW-1, nearly 90 feet from the point of ' applied vacuum During the second test, a vacuum was applied to Well VW-1 for approximately 1 hour and 20 minutes A vacuum was observed in Wells MW-1, GM-4, and GM-5, however, no ' vacuum was observed in MW-5 ' These data indicate that the zone of capture of the SVE system is larger than the spacing of the remechation wells, but influence is not uniform throughout the site These data are not conducive to the calculation of an average effective radius of influence over the site System influence will increase as groundwater levels continue to decline, allowing a higher vacuum to be applied to extraction wells and a larger subsurface volume to be exposed to air flow 16 r GM-RICHMOND DATA CHEVRON CHEV N Z WBENJAM CORR-ACr Arrch6&c GERAGHTY& MILLER,INC LOP