Coffer; Temporary dam
A temporary watertight enclosure built for specialized construction below water level.
Construction in water is a difficult and dangerous job that requires a dry working surface. Cofferdams are one type of temporary structure designed to keep water and/or soil from the execution of construction at a site, so that the permanent facility/structure can be constructed in water (Anderson 2001). A cofferdam should have waterproof walls more than 1 m higher than the maximum water level to ensure that water does not enter the opposite side. Cofferdam design and construction involve the consideration of the structure, local soil and water conditions, often construction offshore, and the possibility of severe weather during construction. The hydrostatic force of the water and the dynamic force due to currents and waves must be considered in the design.