What is a Cofferdam?

By definition, a cofferdam is a temporary watertight enclosure used to pump out water and expose the bed of a body of water. [1] Diverting the water from the construction site allows construction workers to build structures on dry land.

According to research, the first recorded use of a cofferdam can be traced back to 539 BC when King Cyrus of Persia used it to temporarily divert water from the Euphrates River, aiding the capture of Babylon. In 102 AD, the Romans used wood pilings as a cofferdam to build Trajan’s Bridge across the Danube River. [2] The Industrial Revolution further transformed the construction of cofferdams. The development of steam-powered machinery and improved materials such as steel and concrete allowed for the construction of larger and more durable cofferdams.

Today, cofferdams are commonly used in the construction industry. One of the most popular techniques for underwater construction is using cofferdams.

There are various types of cofferdams depending on the depth, soil conditions, water level fluctuation and types of materials used. [3]

Cofferdams can be classified into the following types:

• Earthen Cofferdams
• Rock-Filled Cofferdams
• Braced Cofferdams
• Cellular Cofferdams
• Single-Walled Cofferdams
• Double-Walled Cofferdams

A caisson and a cofferdam are both engineering structures used in construction projects to create a dry work environment, particularly in marine projects such as bridges and piers. While they both serve a similar purpose, there are key differences between the two in terms of their design, construction, and application.

Firstly, a caisson is a watertight structure that is used in the construction of foundations in areas with difficult soil conditions. It is typically cylindrical or rectangular in shape and is constructed onshore before being lowered into place using cranes or other heavy equipment. Caissons are often prefabricated and require careful planning to ensure a proper fit and alignment with the construction site. Once in place, they are usually filled with concrete to provide stability and support for the structure being built.

On the other hand, a cofferdam is a temporary structure built to enclose an area and allow for dewatering. Unlike caissons, cofferdams are built in situ, meaning they are constructed at the construction site using sheet piles, steel plates, or other materials to form a watertight barrier.

Another key difference between caissons and cofferdams is their application. Caissons are primarily used in deep water and are typically employed in the construction of offshore structures such as oil platforms and bridge piers. Caissons are designed to withstand high water pressure and are often used in conjunction with other foundation techniques such as pile driving. On the other hand, cofferdams are usually used in shallower water and are more commonly employed for smaller-scale construction projects.