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at Valley Motors, it is likely that the analyses would be more extensive and costly than those encountered during normal quarterly groundwater monitoring events. Perhaps the biggest limitation of in-well air stripping at this site may be that the pumping rate may be lower,relative to what might be achieved by groundwater extraction, resulting in a reduced radius of influence,of the pumping wells. If so,the remedial effort might appear effective at first,but subsequent monitoring could show that the areal extent of the cleanup was limited and contaminant levels could rise again toward their previous values. Another disadvantage of this method is the increased utility(electrical)costs to operate the compressor and vapor extraction blower. Those costs would not be incurred in the pump and treat method. The need to collect and analyze vapor concentration and dissolved oxygen data and vacuum readings in nearby monitoring wells adds an additional layer of complication to the in-well stripping method. Due to the lower water sampling frequency with this method,vapor and DO samples(or at least field measurements of their concentrations) may be the most readily available data regarding the efficacy of the method, and analyzing this information and incorporating it into reports would increase the reporting time and cost over that of groundwater extraction. PILOT TESTS Due to the potential limitations of both methods and the difficulty of developing firm cost estimates without all necessary data, it will be important to conduct a pilot test of the chosen method to size the system and confirm that it will be as effective as estimated. Brief descriptions of the proposed tests are given below. In order to conduct a pilot test,it will first be necessary to install a treatment well. However,as presently envisioned,either method would require at least two treatment wells, so it would be more cost effective to install both wells in one mobilization rather than in two separate mobilizations, especially since the location and construction of the wells would be the same for either method. Figure 1 shows the proposed locations of the wells, and Figure 2 shows their construction. Based on the available information about the subsurface hydrogeology,it appears reasonable to assume that each well could attain a minimum radius of influence(Rol)of at least 30 feet. This assumption is based on the fact that during the August 2007 air sparging pilot test that was conducted in VM-1, a definite increase in air pressure was observed in VM-2(30 feet east of VM-1)and slight increases in pressure were noted in VM-3 and VM-4(95 feet southeast and 50 feet east of VM-1,respectively). Hence,two circles depicting radii of 30 feet and 40 feet are drawn around each well in Figure 1. With a 30-foot Rol,well VM-9 would encircle the two most impacted wells (VM-2 and VM-1) and would reach out almost to VM-4 and VM-7. With the larger Rol,both of these wells would also be within the influence of VM-9.VM-10 would address the southeastern 4