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�1un 6 1996 4 16PM [EU TE"�IIULuG [Es No 2616 P 6/31 95-WP 103 05 + through the lower screen and is moved up in the treatment well to the stepping zone by the action of the pump as well as the air lift effect The water is snipped of VOCs, and is returned to the groundwater flow regime through the upper screen The artificial groundwater circulation cell established by the UVB system is superimposed over the natural groundwater flow surface, and results to a three-dimensional flow regime around the LTVB well Treatment Well Construction Prior to installation of the UVB treatment well, a pilot soil boring was installed using the dual-tube percussion drill rig to a depth of 118 5 ft bgss to collect soil samples and obtain litholognc information The pilot boring was partially sealed with beatomte upon completion The WB treatment well was then drilled at the location of the pilot boring to a total depth of 87 5 feet using a 26 inch bucket-auger drill rig Figure 2 shows the construction details of the UVB treatment well. The well is 16 inches m diameter and consists of tvvo screened sections separated by blank mild steel casing The lower (influent) screen section is comprised of 12 ft of steel bridge-slot casing, while the upper (effluent) screen section is comprised of three feet of bridge-slot casing with an additional 12 ft of double-cased stainless steel screen which is filled with 318-inch Teflon beads Within the annulus of the borehole, three 2,mch PVC monitoring wells with stainless steel screens were installed. One well (WI) is screened at approximately the same interval as the influent portion of the treatment well, to allow collection of groundwater samples specific to the influent portion of the treatment cell The two remaining monitoring wells within the annulus (W2 and W3) are both screened . between 40-55 feet bgs_ These wells were installed to allow collection of groundwater samples specific to the effluent portion of the treatment well- Wells W2 and W3 were installed at the same depths and at 180° from each other Treatment Well Internal Components Virtually all of the down-hole components of the UVB treatment well including the double-wall stepper reactor, pinhole (diffuser) plate, internal ceatrahzers, and piping are made of high density polyethylene (HDPE), with the exception of the upper 40 feet of the 3-inch diameter fresh air intake pipe„ which is made of aluminum The use of HDPE minar 1the number of metal pieces that would corrode while being submerged in groundwater over attended periods of time The pump used in the UVB treatment well is a Grundfos KP 300 MI submersible pump equipped with a 15 mm orifice flow restrictor to provide a cons=ent upward flow within the well The calculated pump rate is approximately 22 gpm The entire set of UVB down-hole components (except for the packer) is free-floating and can adjust to fluctuations in groundwater elevations Aboveground Treatment System Components Figure 3 shows the layout of the aboveground UVB system installed at Site 31. The entire system is enclosed by a chain-sink fence equipped with a locking gate The blower is located adjacent to the UVB well-head and the suction side of this blower is connected to the 16-inch well casing via a 4-inch HDPE pipe to create a vacuum in the casing The blower is mounted on a moisture knockout drum. No accumulation of liquid has occurred during the study Four-inch diameter PVC pipe is used to connect • the discharge side of the blower to two 1800-1b vapor phase carbon canisters_ Four sampling/monitoring ports (Vi through V4) are installed within the aboveground airstream piping network (Figure 3) 4