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A S S O C I A T E S I N C MW-3 located 87 feet away No response was observed in wells MW-1 and VW-4, located just 6 to 7 feet from the extraction well, indicating that preferential pathways for airflow in the subsurface exist Influent VOC vapor concentrations monitored with a flame ionization detector were initially measured at 6,500 parts per million Lack of oxygen in the airstream prevented additional measurements Laboratory results of the vapor samples indicated that volatile hydrocarbons were detected in the influent samples Approximately 0 2 pounds of TPHg was 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 4.1.3 Conclusions The radius of influence of vapor extraction during vapor extraction testing vaned from less that 6 feet to greater than 40 feet Some response was observed up to 87 feet from the vapor extraction well Petroleum hydrocarbons were removed at an average rate of 3 pounds per day 4_2 Well Abandonment—February 17 1999 During the vapor extraction/air sparge pilot test conducted in November 1998, ATC observed that the grout seal surrounding well VW-2s was cracked and was allowing air to flow the length of the well casing on the outside Well VW-2s was nested with deeper well VW-2d At the direction of PHS/EHD, ATC abandoned vapor well VW-2s using extreme caution in order to preserve the integrity of well VW-2d and to reestablish an air tight system at the site so the air sparge pilot test could be completed On February 17, 1999, ATC supervised the abandonment of vapor well VW-2s by V&W Drilling (C57 license 720904) 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 tremie pipe When V&W attempted to lower the trenue pipe into the well, they encountered an unknown obstruction at 9 feet below ground surface (bgs) and were not able to lower the tremie pipe past this depth ATC discussed the situation with Mr Jeff Wong of PHS/EHD and it was decided to use a direct push drill ng to attempt to remove the obstruction The ng was use to advance drill rods to 30 feet bgs ' Approximately 50 gallons of grout was pumped into the well but only the bottom portion of the well was filled The depth to bottom of well VW-2d was then measured at 41 feet bgs, indicating the deeper seal was withholding the grout An additional 20 gallons of grout was pumped into the shallow well which brought it to the top of the casing On February 18, 1999, ATC purged groundwater from vapor well VW-2d to verify the integrity of the well A groundwater sample was collected and measured for pH in the field The pH reading was normal at 7 0 indicating that the grout used to abandon well VW-2s did not enter the deeper well Copies of field notes are contained in Appendix C W 162574 011pdot-fs report dor. 5