A cofferdam is a structure that retains water and soil that allows the enclosed area to be pumped out and excavated dry. Cofferdams are typically dismantled after permanent works are completed.
Use of Cofferdam :-
Cofferdams are commonly used for construction of bridge piers and other support structures built within water.
Types Of Cofferdams :-
(a) Earthen cofferdam
(b) Rock-fill cofferdam
(c) Single-walled cofferdam
(d) Double-walled cofferdam
(e) Crib cofferdam
(f) Cellular cofferdam (Circular or diaphragm type)
For more detail information about above types of Cofferdam :-