Where excavations extend below the water table, it is necessary to prevent the excavation from being flooded by water seeping out of the ground into the excavation. In some cases this can be accomplished by pumping from shallow ditches around the bottom of the excavation. Where excavations are deep or the soils are highly permeable, it is necessary to intercept the water with deep wells or vacuum wellpoints before it seeps into the excavation.
A sump pump removing seeping water from an excavation in jointed rock, in Washington, DC.
A system of deep wells at the top of the excavation and three lines of well points on the berms were used to dewater the 50-foot deep excavation for Port Allen Lock in Louisiana.
Equipotential lines for Port Allen Lock with the dewatering system.
An aerial view of Port Allen Lock.