The Navy said it has completed construction of an $84.8 million drive-in submarine magnetic silencing facility at Pearl Harbor.

The Navy awarded a contract to Honolulu-based Watts-Healy Tibbitts to replace the original submarine "deperming" piers and structures at Pearl Harbor with an improved facility modeled after one at King’s Bay Naval Submarine Base, Ga.

During normal ship operations, ships and submarines develop a magnetic signature, which can be detected by mines, ships or aircraft. Removing the magnetism requires wrapping a submarine with electrical cables and using high current to reset its magnetic signature.

The Navy said submarines are depermed about once a year.

In January 2009 the contractor began dredging operations for the new pier location and approach area at Beckoning Point so the new facility would be able to accommodate larger Virginia-class submarines, the Navy said.

Three new Virginia-class submarines are based at Pearl Harbor, and more will be assigned to Hawaii in the future.

One hundred seventy-three piles fabricated on Guam with a nonmagnetic, coral-based concrete aggregate were shipped to Hawaii and installed over a nine-month period, the Navy said.

An access pier and a set of 700-foot-long parallel piers also were built.

In October workers installed 18 trusses that straddle the parallel piers. The trusses will hold high-voltage cables that run above and perpendicular to the hull of the submarine, the Navy said. The cabling also will extend underwater.

The Navy said Watts-Healy Tibbitts was awarded an additional $3.5 million contract to install the cables for the superstructure. Work began Jan. 10 and is expected to continue through the year.

Naval Facilities Engineering Command Hawaii said it expects to deliver the submarine silencing facility in early 2012.

Further tests will follow, with the facility expected to be fully functional in 2013, the command said.