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Page 2 of 3 I indicated that the ground water is semi-confined i nd(under pressure),thus the water in monitoring wells may be higher than the actual w iter level in the aquifer. Boring logs for B-2,B-3 and MW-3 show that the fust incidence; f ground water was at 42-ft to 44-13 below grade with static water level stabilizing at a round 40 feet, indicating that the ground water is under 2 to 4 feet of head at these ocations, The boring logs for MW-1, MW-2,B-2,B-3 and MW-3 all show sand or silt sand present between 45 to 50 feet (logs go only to 50-R depth). The CPT-based crs sections AA' and BV indicate that the 50-60 ft interval consists of sand and sandy/swith some gravelly sand fingers. Thus the saturated thickness to be remediated begins 91i' he end of the silt sequence and transitions into the sand sequence immediately ow it. We believe the saturated thicknessbe regarded as a single unit from about5 feet to about 60 feet for the purpose of designing ozone injection wells. The ozone injection well will target the zone of h ghest ground water concentrations in the source area. The sparge point(the micro-pon us section)will be installed at the bottom of the aquifer thickness to be remediated.t This design will provide proper lateral and vertical dispersion of the released ozone and: ure adequate coverage of the plume, The radius of influence(ROI) is related to injecti' n depth, soil permeability,and interconnected pore channels present in the subo face. For this site the ROI based on injection depth and soil type is estimated at 20 to' 5 feet. Six wells are proposed whose locations are shown on Figure 1. The well netwo k will thoroughly cover the onsite plume over an area approximately 60-ft x 60 ft x, 5 ft(saturated thickness). A typical well construction detail is shown on Figure 2. W asdmate the system will require an injection pressure of 15-25 pounds per square ih and up to 5 cubic feet per minute of ozone per well. If'you have any questions, please call the unders edNe . 1., Sincerely, i t�,�.r..3 M?u7 n Wright Environmental Services,Iec.)24A /y"L R. M,agbool Wit.PE (Enpro Solutions, Inc.) John lynch President CH 4767 Att*cllmeats:Figures 1 and 2, Draft Cross Sections AA" and BB', boring logs from original site investigation ._. ........_.—