A cofferdam (also coffer dam) is a temporary enclosure in or around a body of water that is constructed to allow dewatering, diversion or damming of an enclosed area. The primary purpose of a cofferdam is to create a dry environment for a project to proceed. They were first used in 1736. Today's cofferdams are typically conventional embankment dams of both earth- and rock-fill, although concrete or some sheet piling also may be used.
There is a company headquartered in Michigan - Dam-It Dams, Inc. - whose cofferdams use on-site water to fill dual inner tubes that cause the dam's chambers to slowly and evenly inflate, forming a strong, stable cylindrical tube. As the inner tubes continue to fill and the water pressure builds, the dam unrolls in a controlled manner to create the cofferdam.
There are as many water-control applications for cofferdams as there are types of cofferdams. Dam-It Dams' patented, portable, water-filled Cofferdams offer effective and cost-efficient solutions for these major types of situations that are called the 3-Ds of water control:
Dewatering: unwatering and water control are common terms used to describe the removal or drainage of ground or surface water, typically on a construction site. Dewatering is often required before subsurface excavation for such things as foundations, shoring, cellar space and repairs to existing water structures.
Diversion: is the temporary (or sometimes permanent) re-routing of water. It may be required to initiate a project and/or allow a project to proceed.
Damming: is the process of creating a barrier that holds back water. The barrier may be needed to maintain water table levels, collect water for storage and prevent water from crossing established/safety threshholds.