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Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer .
In addition to resource abundance, deep-sea mining benefits from high-grade deposits and lower operational costs compared to terrestrial mining due to reduced overburden removal. Optimizations such as reduced trench depth can cut mining time by 26% and increase deposit value by 53%. [138]
Excavation is done using a special clamshell-shaped digger or a hydromill trench cutter, suspended from a crane. The excavator digs down to design depth (or bedrock) for the first wall segment. The excavator is then lifted and moved along the trench guide walls to continue the trench with successive cuts as needed.
Overdrafting has socio-economic impacts due to cost inequities that increase as the water table drops. As the water table drops, deeper wells are required to reach water in the aquifer. This not only requires deepening of already existing wells, but also digging new wells. [22] Both processes are expensive.
Excavation may be classified by type of material: [1]: 13.1 Topsoil excavation; Earth excavation; Rock excavation; Muck excavation – this usually contains excess water and unsuitable soil; Unclassified excavation – this is any combination of material types; Excavation may be classified by the purpose: [1]: 13.1, 13.2
The risk of cave-in increases from surcharge load, which is any weight placed outside the trench near its edge. These loads include the spoil pile (soil excavated from the trench) or heavy equipment. These add extra stress to the walls of the trench. Inability to escape the trench because of steep and unstable walls, which may be difficult to ...
Tunnel Construction. Tunnels are dug in types of materials varying from soft clay to hard rock. The method of tunnel construction depends on such factors as the ground conditions, the ground water conditions, the length and diameter of the tunnel drive, the depth of the tunnel, the logistics of supporting the tunnel excavation, the final use and shape of the tunnel and appropriate risk management.
A grab dredge. Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing dams, dikes, and other controls for streams and shorelines; and recovering valuable mineral deposits or marine life having commercial value.