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C111ARWATER G R 0 L' P I N C 7 4 3 Groundwater Extraction and Treatment System Proposed recovery well RW-2 should be constructed similarly to RW-1 RW-2 should be installed in a 10-inch diameter borehole advanced by a truck-mounted drill rig equipped with hollow-stem augers The well should be constructed with 4- inch diameter PVC well materials, with 0 020-inch slotted well screen extending from 10 to 30 feet below grade and blank PVC riser extending to the surface A clean filter pack should be placed from the bottom of the well to approximately 12 feet below grade and sealed with a hydrated bentonite layer covered with neat cement Proposed well construction details of RW-2 are shown on Figure 17 Following installation, RW-2 should be developed by a combination of surging and bailing to remove sediment from the well and increase its hydraulic conductivity to the formation Controllerless, total fluids, top filling, pneumatic pumps capable of at least 7 gpm at a depth 25 feet should be installed in RW-1 and RW-2 The pumps should be the top filling type in order to extract any SPH that may enter the recovery wells The bottom of the pumps should be placed approximately 2 feet off the bottom of the well such that the inlet of the pump is at a depth of approximately 25 feet below grade The downhole supply air, elimination air, and elimination water lines can either be flexible tubing equipped with "quick connect' type fittings supplied by the manufacturer or hard plumbed with appropriately sized PVC If plumbed downhole with flexible tubing, appropriate fittings should be used so that flexible tubes can be coupled with PVC in the above ground well vault space The wellhead should be fitted with a 4-inch diameter PVC tee fitting so one opening can be used ' for groundwater extraction and the other for soil vapor extraction The groundwater equipment supply and discharge lines should pass through a compression fitting on the PVC tee to ensure an airtight fitting for concurrent soil ' vapor extraction Existing well boxes should be replaced with larger well vaults, approximately 2 feet by 2 feet, in order to accommodate above ground remedial equipment A schematic diagram for dual-phase wellheads is shown on Figure 18 The pneumatic pumps should receive air from an electric powered air compressor ' capable of satisfying air flow and pressure needs of the pumps This will include moisture and oil filters at the supply end of the air compressor The air compressor should also be able to use 230-volt 1-phase, 200 ampere power or 115-volt power, ' which can be obtained by a drop from nearby power pole The air should be supplied to the pumps via a 1-inch diameter PVC line placed in the system utility trench Ball valves should be located in the air supply lines in the remedial compound in order to turn individual pumps on and off ' D-107,PAR/RAP 23 February 21, 1996