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I <br />,CvvATC <br /> A S S O C I A T E S I N C <br /> were detected in the influent samples Approximately 0 16 pounds of TPHg was removed during <br />' the pilot test Laboratory results of the effluent vapor sample indicated a destruction efficiency of <br /> over 98 percent for all constituents analyzed <br /> 1 On June 30 1999 ATC performed a short-term air sparge test The purpose of the test was to <br /> PP rP <br /> 1 determine if the lack of airflow during the previous pilot test was due to subsurface stratigraphy <br /> and/or equipment size Well MW-1 was used as the air injection point Prior to the test, a grab <br /> 1 groundwater sample was collected from well MW-1 Two air compressors capable of producing <br /> flows up to 10 cfin were connected in series and used to pressurize the well casing to 10 psi <br /> 1 Airflow was initiated at a flowrate of 2 cfin and gradually increased to 4 cfin Helium was then <br /> injected at a flowrate of 2 cfm in addition to the air for a total flowrate of 6 cfin After 80 minutes <br /> 1 of operation, helium was detected in well VW-5d but no helium was detected in well VW-4, <br /> seven feet away It was determined that the injected air and helium were channeling through the r �( <br /> subsurface to well VW-5d At the direction of PHS/EHD, the air sparge test was terminated to <br /> prevent the migration of the plume to the north Results and field readmgs from the short-term air <br /> 1 sparge test performed on June 30, 1999 are summarized in Table 7 <br /> 1 Laboratory results of the groundwater samples collected from MW-1 before and after the test <br /> 1 indicated that petroleum hydrocarbons increased during the test An injection rate of 4 cfin was <br /> attainable using two small air compressors Positive pressure was observed approximately 20 feet <br />' away from the injection point, with the highest measurements in well VW-5d Helium was also <br /> detected in this well at 18% <br /> 4.0 SUMMARY OF SOIL AND GROUNDWATER CONDITIONS <br /> 1 4!I Extent of Hydrocarbon-Impacted Soil <br /> The lateral extent of gasoline hydrocarbons in soil is delineated by bonngs B-6 and B-7 to the west, <br />' boring B-5 to the south, boring B4 to the east, and boring B-15 to the north The highest <br /> concentrations of residual gasoline hydrocarbons appear to be north and west of tank T3, from <br /> approximately 15 feet bsg to the top of the groundwater surface at the time of the investigation(42 feet <br />' W 162574 011CAP report doc 7 <br />