Ice Pier - Seawater Construction

Seawater Construction

The ice piers deployed at McMurdo Station have grown in sophistication and size since the ice fender prototype. A contemporary pier is approximately 800 feet (244 m) long by 300 feet (90 m) wide and 22 feet (6.7 m) thick. Fleet operations personnel make the floating pier during the winter. They build upon naturally occurring frozen seawater in McMurdo Sound after the pack ice reaches approximately 0.6 m (2 ft) in thickness.

Subsequently, workers construct a snow berm to a depth of several feet along the perimeter of the soon-to-be ice pier. High-volume pumps then flood the pack ice with seawater to a depth of about 10 cm (4 in). The seawater typically freezes solid within 24 hours. Personnel repeat the flooding until they achieve a thickness of 1.5 m (5 ft).

Next a reinforcement mat of approximately 2,100 m (6,900 ft) of 1” (25mm) steel cable is secured to 2” (50mm) steel pipe embedded in the ice pier. The pier overall requires approximately 6,300 m (21,000 ft) of steel cable for construction, according to National Science Foundation permit documentation.

Workers repeat the entire process three more times until the ice pier is approximately 6.7 m (22 ft) thick. Wooden utility poles drilled about four deep into the final ice pier support electrical and telephone service to the pier. Moreover, during the final construction phase, personnel mount shorter poles in the ice edge to serve as bollards to secure the pier to the shore at McMurdo. A 15–20 cm (6–8 in) layer of volcanic gravel tops off the pier to provide a non-slip surface and to insulate the ice from the summer sun.

Experience has shown that ice piers have a lifespan of three to five years. Factors such as stress cracking and erosion shorten the duration. In addition, storm surges, wave action, contact with vessels, and the warm water discharge from ships contribute to degradation of the pier’s seaward edge.