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tGERAGHTY E' MILLER, INC <br /> samples collected from the zone of system influence (vadose zone) indicate that the majority of <br /> the petroleum hydrocarbons are located within the zone of seasonal groundwater fluctuation <br /> VADOSE ZONEXAPILLARY FRINGE <br /> ' SVE and excavation were options considered for source removal in the vadose zone. The <br /> reduction of the vadose-zone source will improve the quality of the groundwater by reducing <br /> ' the dissolution of petroleum hydrocarbons to groundwater SVE has the advantages of <br /> enhancing bioactivity, minimizing the impact to station operation, and lower cost, which <br /> together led to its selection as an interim remedial measure rather than the excavation and <br /> ' disposal of all impacted soil <br /> ' The SVE system installation was completed m February 1997 and is documented in <br /> Geraghty & Miller's CAP dated May 29, 1997 Operation and maintenance costs for SVE <br /> ' using the catalytic oxidation unit are approximately $2,000 per month Operation and <br /> maintenance of a bioventmg system using the installed vapor-extraction wells can be performed <br /> t for approximately $800 per month Bioventmg consists of extracting air from some wells and <br /> injecting air into others to establish new flow patterns through the subsurface to oxygenate the <br /> vadose zone Effective enhancement of biological activity in the vadose zone can be more cost- <br /> effectively performed by bioventmg <br /> ' It is anticipated that SVFJbioventing will continue for approximately one year The total <br /> cost of operation will vary significantly, depending on how long the catalytic oxidation system <br /> is operated prior to the onset of bioventing <br /> CAPILLARY FRINGE/GROUNDWATER <br /> ' Groundwater can either be remediated throughP the use of airs argmg to enhance bioactivity <br /> ' or contained through the use of groundwater extraction. An air-sparging system was installed <br /> in February 1997 as an interim remedial measure to enhance the bioremediation of hydro- <br /> carbons. Groundwater extraction is ineffective for hydrocarbon mass removal of the dissolved <br /> ' petroleum hydrocarbons in groundwater and has poor cost-effectiveness due to the cost of <br /> long-term operation and maintenance <br /> 1 <br /> The installation of the air-sparging system is documented in Geraghty & Miller's CAP <br /> ' dated May 29, 1997 The air-sparging system has operated approximately 3,000 hours since <br /> startup in April 1997,injecting air into the remediation wells at a rate of approximately 15 cubic <br /> ' <br /> Project No RC0309 010 <br />