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Groundwater Well Installation Work Plan Sharpe Army Depot Lathrop, California Ahtna Environmental, Inc. 13 3.2.4 Surface Completion Surface completions will be aboveground. For extraction wells, a 16-inch diameter locking steel casing set into a concrete pad (2–4 ft square pad) will be installed around each well casing. The top of the steel casing will be set approximately 3 ft above the ground surface. The concrete pad will be sloped from the edge of steel casing to the edge of the pad and will be smoothed with a trowel to facilitate the flow of surface water away from the well. The well will also be protected by three or more bollards consisting of concrete-filled, 4-inch-diameter steel pipe cast surrounding the installed well. For monitoring wells, a 6-inch diameter locking steel casing set into a concrete pad (2–4 ft square pad) will be installed around each well casing. The top of the steel casing will be set approximately 3 ft above the ground surface. The stickup (steel casing) diameter will be 6 inches. The concrete pad will be sloped from the edge of steel casing to the edge of the pad and will be smoothed with a trowel to facilitate the flow of surface water away from the well. The well will also be protected by three or more bollards consisting of concrete-filled, 4-inch-diameter steel pipe cast surrounding the installed well. In addition, a tag will be attached to every well lid that lists the well depth, screen interval, location coordinates, surface elevation, alphanumeric identification, and monitoring zone designation. 3.2.5 Conveyance Piping Installation and Electrical Hook -up Extraction well EWNC7 will be connected to the existing contaminated-water conveyance piping that runs to the North Balloon GWTP (Figure 8). Electrical and communications conduits will be installed to allow connection of the new wells to the existing electrical power supply and allow for connection to the GWTP control systems. EWNC7 is located approximately 300 ft north of existing well EWNB6, as shown in Figure 8. EWA1R will be located approximately 20 ft southwest of EWA1. The replacement well will be connected to the existing contaminated water conveyance piping that runs to the South Balloon GWTP (Figure 12). Trenching will be required to install the new conveyance piping and electrical and communications conduits, and the displaced soil will be managed as discussed in Section 3.3 (“Waste Management”). The new wells and trenching areas will not be located in soil contaminant areas. Each new well will have a new local control panel installed. The local control panel will follow the standard architecture currently deployed at North Balloon and Central Area well panels, consisting of a local programmable logic controller with standard discrete inputs and outputs and analog inputs to monitor and control the well pump. The programmable logic controller will monitor water level and flow and report the data to the supervisory control and data acquisition system. 3.2.6 Surveying A professional California-licensed land surveyor will survey the newly installed wells and conveyance piping for horizontal and vertical coordinates. Horizontal coordinates will be determined to the closest 0.01 ft and referenced to the State Plane Coordinate System, Zone 3, North American Datum of 1983. Ground surface elevations will be surveyed using the National Geodetic Vertical Datum of 1988 to the closest 0.01 ft. Elevations of the top of well casings will be determined. The measurement point on the casing will be clearly and permanently marked for future water level measurements. Following the