OEC Tank 4 is constructed of reinforced concrete, with a flexible, food-grade liner.  The tank has a sloping bottom, which aids in allowing dirt and detritus to move towards the tank drain. 

Unlike all of our other large tanks, OEC Tank 4 has a solid concrete top which acts as both a top for the tank and a floor for the deck above. The goal of this design is to allow researchers to set up a sealed gas layer above the body of water in the tank. Researchers can then study the movement of gases and other substances between the water and the atmosphere. 

The tank has three access hatches in the top, which allow access into the tank by specially trained Aquatron staff members. A smaller, fourth hatch is located close to a wall on the top deck. This hatch is designed with a sacrificial metal plate, which allows instruments to be located inside the tank while keeping the tank sealed.

The tank has a volume of 400 m3 and is 18 .6 m (61’) long, 6.7 m (22’) wide and 3.2 m (10’6”) deep.