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Based on the feasibility test results, air sparging and soil vapor extraction should be eliminated for consideration as a remediation alternative for the site. 9.3 Groundwater "Pump and Treat" Groundwater "pump and treat" is a method in which contaminated groundwater is pumped from a pumping well to the surface and then treated in one of several ways such as air stripping, carbon absorption, ultraviolet (UV) peroxidation, etc. prior to disposal. Historically, "pump and treat" has had limited success in groundwater remediation for several reasons, particularly that hydrocarbons have a high affinity to soil, that soil in the capillary zone often goes untreated, and that it takes long periods of time to remove significant volumes of hydrocarbons when the hydrocarbon concentrations in groundwater are in the parts per billion range. "Pump and treat" is; however, considered an effective method of containing a plume and preventing further migration of contamination downgradient. This is because the water table is drawn down and groundwater surrounding the pumping wells flow toward the pumping well. The pumping test at the site showed a capture zone of 32.3 feet at a sustained pumping rate of 7 gpm. To effectively provide a barrier to prevent off-site migration of hydrocarbons, four to five wells would be required along the western portion of the site. Although this method m a y be possible, approximately 50,000 gallons of water would have to be treated and disposed of each day. Given the cost and requirements of t h e local sewer district to receive this water, this would be a very costly method of remediation. In addition, in the absence of soil remediation, the effectiveness of this method would be in question. For these reasons, "pump and treat" should not he considered as a remediation option for the site. 9.4 In-Site Rioreme.. Lo_n In-situ bioremediation was considered as a remedial option at the site. There are several options to achieve this form of remediation, which involves increasing the amount of dissolved oxygen in the groundwater to enhance naturally occurring aerobic bacterial degradation of petroleum hydrocarbons in-situ. It has been known for some time that naturally occurring bacteria readily degrade (digest) petroleum hydrocarbons into harmless byproducts. Although anaerobic bacteria will degrade 574 West Grant Line Road CAP - January 2002 -18-