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Groundwater Well Installation Work Plan Sharpe Army Depot Lathrop, California Ahtna Environmental, Inc. 7 • A hand auger will be used to advance the borehole from 0 to 5 ft bgs to check that underground utilities are not present at each borehole location. • During drilling, soil cuttings collected from the shaker will be classified in general accordance with ASTM D2488-17, Standard Practice for Description and Identification of Soils (Visual-Manual) Procedures (ASTM, 2017). • Discrete soil samples will be collected according to Section 3.2.7. Drilling equipment will be decontaminated at the driller’s work yard via steam-cleaning and rinsing with potable water before entering the site. Downhole materials will be wrapped in plastic to remain clean. Drilling equipment brought to the site will be in operable condition and free of leaks in the hydraulic, lubrication, fuel, and other fluid systems. Downhole equipment and tools will be cleaned and decontaminated before remobilizing the rig to the next well location and will be maintained in a clean condition throughout well installation activities. Downhole drilling equipment will be: • Cleaned of caked drill cuttings, soil, or other materials using a brush • Steam-cleaned using a hot water high-pressure washer • Rinsed with potable water before being used downhole and between boreholes Decontaminated equipment will be kept off the ground by storing on clean metal racks (not wooden pallets) or wrapped in plastic. 3.2.1 Well Construction Well construction activities and materials will conform to the sections below. Special consideration and care will be taken during construction to ensure that the casing and screen are joined correctly, and in a manner that does not place excess pressure or stress on each joint. Well construction diagrams for the extraction wells and monitoring wells are presented in Figures 13-15. The drilling subcontractor will have a State of California C-57 license, and a copy of the certificate will be kept onsite. Each well boring will be advanced to its total depth using a truck-mounted mud rotary drill rig. Downhole equipment, tools, and well materials will be free of solvents, oils, grease, paint, and dirt before installation. If the supervising Project Geologist determines that the well screen or casing is not clean, steam-cleaning of the drill bit and rods, well screen and casing, or other equipment and tools will be performed before installation. Well Casing Blank well casing for extraction wells will be flushed-threaded 8-inch diameter, Schedule 80 polyvinyl chloride (PVC). Blank well casing for monitoring wells will be flushed-threaded 4-inch diameter, Schedule 40 PVC. Sections of casing will be received from the supplier in polyethylene protective wrappers with sealed ends to limit exposure to potential contaminants. The casing will not be removed from the wrapping until installation. After the borehole has been drilled to the proposed total depth, the well screen and casing will be lowered into the center of the borehole. The well screen and casing will be plumb and centered in the hole by use of centralizers placed at the top and bottom of the screened interval, as described below.