Water may leak through the underground flow of water or through the piling sheet of the cofferdam. The following measures can be adopted to prevent leakages in cofferdam.
1. Water entering the dewatered area through fissures or cracks in the rocks can be stopped by grouting the fissures by cement grout.
2. Clay or mixture of clay and sand can be dumped in form of beams both on inside and outside faces of the cofferdam.
3. In case of single-walled cofferdams, sheeting should be connected through V-shaped notches and filled with clay puddle.
4. Cracks or fine joints or nail holes in the sheet piles should be closed using bitumen or cement mortar.
5. If a lot of leakages is taking place and no measures stated above have been to control it, the water face of the cofferdam may be completely covered with canvass coated with tar or tarpaulin.
6. In case of double-walled cofferdams leakage is generally because of insufficient compaction of the filling material. In this case, measures to control seepage through filling material should be adopted.
7. Another method may be a box filled with the mixture of ashes and sawdust held near the leaking joints. Leaking water carries these contents into the joints and thus helps check the leakage to some extent.
8. Sufficient grease applied at interlocks of sheet piles also helps check leakage of water.