WORK PLANS - Laserfiche WebLink

Home Browse Search

Groundwater Well Installation Work Plan Sharpe Army Depot Lathrop, California Wells will be set at the following depths: • Two extraction wells (EWC6 and EWC7) will be set in the C Zone at approximately 127 ft bgs (Figure 9) • Two extraction wells (EWC8 and EWC9) will be set in the C Zone at approximately 135 ft bgs (Figure 10). • One extraction well (EWCC7) will be set in the C Zone at approximately 155 ft bgs (Figure 11). • Two monitoring wells (MW549C and MW550C) will be set in the C Zone at approximately 110 ft bgs (Figure 12). • One monitoring well (MW551B)will be set in the B Zone at approximately 85 ft bgs (Figure 12). • One monitoring well (MW551C) will be set in the C Zone at approximately 140 ft bgs (Figure 12). • One monitoring well (MW552C) will be set in the C Zone at approximately 135 ft bgs (Figure 12). The borehole diameter will be 16-inch nominal for extraction wells and 8-inch nominal for all monitoring wells.Well installation will be completed under the Project Geologist's supervision,who is responsible for borehole logging,well installation, and development activities. General procedures for borehole drilling and logging include the following: • The well location will be verified and determined to be safe from underground utilities and aboveground hazards during construction operations. • Drilling equipment will be staged at each location to avoid disturbing the normal flow of traffic to the extent practicable, using safety delineators and signs as needed. Support equipment will be set up in a centrally-located staging area at the Ahtna office trailer or the Central Area Groundwater Treatment Plant. • 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 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 to determine the lithology in the proposed screen interval. Final well depths and screen intervals will be determined by the supervising Project Geologist and the Project Manager based on lithologic conditions. 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 drilling equipment and tools will be cleaned and decontaminated before mobilizing to the next well location. Equipment will be maintained in a clean condition throughout well installation activities, including: • Clearing the caked drill cuttings, soil, or other materials using a brush • Steam-cleaning using a hot water high-pressure washer • Rinsing with potable water before being used downhole and between boreholes Decontaminated equipment will be kept off the ground by storing it on clean metal racks (not wooden pallets) or wrapped in plastic. Ahtna Environmental,Inc. 9