Cianbro builds, floats 5,000-ton dry dock piece to Kittery shipyard

Courtesy / Cianbro Cos. The 5,000-ton entrance structure leaves the Fore River in Portland on Sunday afternoon, bound for Portsmouth Naval Shipyard in Kittery.

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By Staff

Pittsfield-based construction contractor Cianbro Corp. has delivered one of the first major pieces of a new job — after floating the 5,000-ton concrete structure 50 miles down the Maine coast.

The company is working on a $158 million project to modernize a dry dock at Portsmouth Naval Shipyard in Kittery. The contract, awarded in November 2019, calls for Cianbro to build a “superflood basin” and a new portal crane system at the yard’s Dry Dock No. 1.

The upgrades will ensure that the shipyard can efficiently dock the Navy's Los Angeles-class and Virginia-class submarines for maintenance and renovation.

The 3.5-acre superflood basin — similar to a canal lock — will operate as a sort of gateway to the repair facility. When completed, the basin will artificially raise the surrounding water level so that subs can berth without the use of buoyancy assist tanks. The dock’s current buoyancy system is more than 40 years old.

At the company’s facility on Ricker’s Wharf in Portland, Cianbro has been working for the past year and a half on the basin’s concrete entrance structure. On Sunday, the time came to transport the huge structure, which weighs about the same as 50 commercial airliners, by barge to Kittery.

A Cianbro spokesman told Mainebiz the structure left Portland’s Fore River at 5 p.m. and arrived at the shipyard about 8:30 a.m. Monday.

“This is a remarkable feat, and our team has truly risen to the challenge on one of the most technically complex projects our company has tackled,” said Andi Vigue, president and CEO of the Cianbro Cos.

“The Superflood Project is a perfect example of the dedication and commitment of our team working to deliver quality outcomes, safely and on time.”

With the entrance structure now onsite, Cianbro said it now must build cofferdams, shore up the dry dock’s existing granite wall, conduct dredging and rock removal, erect thousands of feet of crane and rail systems, and do much more.

The project is one of the largest ever at Portsmouth Naval Shipyard, which is the oldest — established in 1800 — of four Navy-operated yards.