When structures are constructed near the shoreline, there is a good chance that part of the new structure foundation will need to be submerged underwater. Since humans cannot build underwater, water needs to be temporarily redirected to expose the ground and ensure a dry area for the construction. Removing water from an area can be achieved through the construction of a coffer dam.

What Is a Coffer Dam?

A coffer dam is a structure built within a body of water that prevents water from flowing into the area. The water within the enclosure is pumped out, leaving a patch of dry ground for construction. Usually, very long steel sheets are driven into the waterbed to a depth greater than the hydrostatic pressure of the water on the outside of the enclosure, ensuring that the water does not flood back after pumping the water to the outside of the enclosure.

How Does a Coffer Dam work?

To understand how a coffer dam works, we need to explain three common types of coffer dams used according to the purpose they need to achieve.

Braced and Cellular

Braced coffer dams are formed by joining individual sheet piles driven into the water bed. The braced sheet piles form a box-like structure around the building site. The water is pumped out, and construction can start.

Cellular coffer dams offer a watertight barrier created by steel pile sheets filled with sand and clay for stability. They usually follow a circular pattern and are often joined by smaller arcs.


Water-inflated coffer dams are a more modern type of coffer dam that is kinder to nature by minimizing the disruption to the water bed and the topsoil around the building site. According to the World Wildlife Organization, the last 150 years of continuous construction have robbed the planet of half its topsoil, which is why this type of coffer dam is so important. The water-inflated dam consists of plastic sheeting sleeves that are placed on the shoreline. The water is pumped into the plastic sleeves, filling the internal tubes and unrolling the structure. The structure can easily be guided into place as the water fills the tubes. The water inside the coffer dam is then pumped out to one side, leaving a dry working area. Once the project is completed, the water is pumped out of the internal tubes, and the whole structure can be packed up to be used again at a different site.

When you are in need of a coffer dam for your project, reach out and we will help you choose the best method to suit your needs.