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i7CT-07-1996 00 27 EA NORTH SACRAMENTO 1 916 924 7460 P 02/03 FACSIMILE MESSAGE Whe upper, closed part of the well, is maintained under vacuum by an above ground blower Air as drawn to the stripper tray through a fresh air pipe the upper end is open to the atmosphere, and the lower end terminates in the pinhole air stripper tray Soil vapor is also drawn into the UVB well from the vadose zone through the upper well screen The vacuum within the upper part of the U" well also causes a rise in water level within the well The air stripper tray is balanced below the water level within the well and is free-floating to allow for changing water levels Air drawn from the atmosphere through the intake pipe creates an air bubble flow between the pinhole stripper tray and the water surface within the well The air bubbles strip contaminants from the water and then rise to the surface of the water within the well The stripped air is then removed by the blower, along with extracted soil vapor A groundwater circulation cell is created around a LTB well Stripped groundwater, streaming upwards due to the lifting effect of the air bubbles, leaves the well casing through the upper screen section of the LTB well The flow of water leaving the LTB well through the upper screen is counterbalanced by the flow of groundwater Wough the lower screened section of the well, thereby setting up a three-dimensional groundwater circulation cell around the UVB well The radius of the three-dimensional groundwater circulation cell around a LNB well primarily depends on the degree of anisotropy, that is the ratio of the horizontal to vertical hydraulic conductivity within the treated zone The higher the anisotropy, the larger the radius of the three-dimensional groundwater circulation cell around a LTB well UVB technology has the following advantages for groundwater remediation at Exxon RS 7-3942 6 A UVB system would not require a discharge permit, because of concurrent groundwater extraction and injection from the same well A UVB system would not likely pull off-site plumes underneath a remediated site, because of the concurrent extraction and infection from a single UVB well O In addition to the stripping of contanvnantq of concern in the LTB well, enrichment of the recirculated water with air will promote in-situ biodegradation • With fewer moving parts, a UVB system has a higher on-stream time and requires less operation and maintenance than a pump and treat system 0 A UVB system has a low profile ORIGINAI WB,L ❑I'CJLLUW VIh MATE 0 FOLLOW'VIA OVERNIGHT EXPRESS L]FOLLOW VIA MODEM ©NOT FOLLOW BALTIMORE NEWYORK SAN FRANCI=O-LINCULN NEW JERSEY CHGAGO ATLANTA DALLAS CHARLOTTE-WASHINGTON DC-BOSTON SACRAMENTO-SEATTLE ALASKA SAN ANTONIO COLORADO-HONOLULU-DELAWARE