Cofferdams are temporary enclosure structures built within, or in pairs across, a body of water and soil. By pumping the water out of the enclosed area a dry work environment is created so that the actual building activities can proceed. Enclosed coffers are commonly used for construction and repair of oil platforms, bridge piers and other support structures built within or over water. These cofferdams are usually welded steel structures, with components consisting of sheet piles, walings, and cross braces. Such structures are typically dismantled after the work is completed.