The Cofferdam’s Third Cell Completed!
What is a cell?
Each cell forms a part of the cofferdam that will hold water back from the construction site while the new dam is being built. The cofferdam will be 10.6 metres (34.8 feet) in thickness, and is comprised of seven cells in total that are connected, running the width of the existing channel above the dam. Each cell, in general, takes two weeks to construct.
To construct a cell, vertical sheet piling is embedded into till (glacial sediment). Sheets are installed on three sides with the fourth side being the previous cell. When the steel perimeter is complete, the contractor excavates the silt and mud out of the cell until the till is reached. The till forms the base and rock and gravel are used to fill in the rest of the cell.
A large crane is used to complete this work. As each cell is completed, the crane moves onto it to complete the next cell.