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v A S S O C I A T E S I N C 17 feet from the extraction well CNo response was observed-in wells MW-1-and VW-64, located just 6 to 7 feet from the extraction well This may have been due to preferential pathways present in the subsurface or because the wells are screened approximately 8 to 13 feet below the current water table Vacuums of up to 0 5 inches of water were observed in well MW-3 located 87 feet away which is screened approximately 3 feet below the water table Laboratory results of the ' vapor samples indicated that volatile hydrocarbons were detected in the influent samples Approximately 0 2 pounds of total petroleum hydrocarbons as gasoline (TPHg) were removed during the pilot test Laboratory results of the effluent vapor sample indicated a destruction ' efficiency of approximately 70 percent for benzene and over 98 percent for all other constituents analyzed On November 24, 1998, a short-term air sparge test was initiated by ATC using vapor well VW- 5d as the air injection point Upon startup of the test, an air leak was observed in nearby vapor well VW-2s from an apparent crack in the well seal The test was terminated and provisions were ' made to abandon well VW-2s ' On February 17, 1999, ATC supervised the abandonment of vapor well VW-2s It was proposed in the workplan to pressure grout the well with neat cement from the bottom of the casing to the surface using a treinie pipe but an unknown obstruction was encountered at 9 feet bsg and it was not possible to lower the tremie pipe past this depth A direct push drill ng was used to attempt y to remove the obstruction The ng was used to advance drill rods to 30 feet bsg and approximately 70 gallons of grout was pumped into the well ' On April 22, 1999, ATC performed a short-term air sparge test Well MW-1 was used as the air injection point An air compressor capable of producing flows up to 10 cfm was used to ' pressurize the well casing to 10 pounds per square inch (psi) ATC attempted to initialize airflow but the airflow reading was zero The pressure in the well was incrementally increased to 100 psi, the maximum pressure the compressor could produce Helium tanks were also used to increase ' the pressure in the well but the airflow reading remained zero Helium is used as a tracer in groundwater to aid in the determination of an effective radius of influence for air sparging Helium measurements were taken from adjacent well VW-4, seven feet away, but no helium was ' detected It was uncertain whether the lack of airflow was a result of compressor size or the subsurface stratigraphy The air sparge test was terminated During the subsequent vapor extraction test, a helium reading was taken from well VW-5s Helium was measured at 20% at a ' distance of 17 feet from the sparge well ' Following the air sparge test, a vapor extraction test was performed using vapor well VW-1 as the vapor extraction point Vapors were extracted for approximately 2 hours using an IC engine equipped with a 5-hp blower and a moisture knockout chamber Two influent vapor samples and ' one effluent vapor sample were collected during the test Results and field readings from the short-term vapor extraction and air sparge tests performed on April 22, 1999 are summarized in Tables 5 and 6 W 162574 011C"report doe 4