Here’s more information about the cable work that’s occurring beneath the Hood Canal Bridge. Won’t make the long waits while the bridge is closed any easier, yet does provide under-the-water view. Bridge scheduled to be closed through Oct. 2nd.
Reprinted from the Kitsap Sun Updated Sept 27, 2015
NORTH KITSAP — A state contractor is replacing mammoth anchor cables that keep the Hood Canal floating bridge from floating away.
Forty-eight cables keep the 1.5-mile-long bridge in place. They’re 3 inches in diameter and 4,000 feet long in the middle of the canal, where the water is 380 feet deep. There, they travel 2,000 feet to the anchor, loop through it and return to the pontoon.
Under a $7.3 million contact, Manson Construction is changing out 21 of 24 cables securing the bridge’s west side. They’re 31 years old, installed after the west end sank during a Feb. 13, 1979, windstorm. New cables and anchors were added as part of the east-half bridge replacement from 2003 to 2009.
The cables are made of galvanized steel strands banded together and coated with an anti-corrosion film. Anchors are 46-foot-across, three-story-tall concrete tubs filled with rocks, said state Department of Transportation field engineer Amy Amos during a site visit Thursday.
Cables are inspected every two years for broken strands and general condition, the top 50 feet by swimmers, the depths by remotely operated vehicles.
Each cable takes workers three to five days to change. Since the project began July 5, Manson has replaced 14 of them.
Cables are replaced one at a time, but tension must be released equally on the one across from it so the pull on the bridge remains balanced. The anchor has an opening, like the eye of a needle. The new and old cables are connected and the old cable is pulled out, threading in the new one. Nobody even gets wet.
“The goal is you don’t ever have to go down there,” Amos said.
The task is nowhere near as easy as that sounds. The cables are heavy, tides strong and bridge openings for boats intermittent.
Those were among factors that stuck the draw span open for six hours on Sept. 9. Workers were replacing the cable just west of where the draw span splits in opposite directions. During the project, only the east side is being opened for boats, which is required within an hour of a request. After the vessel passed through, the draw span was closed, but it wouldn’t line up. With the end cables loose, an especially strong tide shoved it 14 feet out of alignment. The contractor’s small tugboat tried to nudge it back into place but didn’t have enough power. Larger tugs were brought in from Seattle to finally do it.
Of the six cables remaining, two are on the draw span but aren’t expected to be a problem.
“We shouldn’t have much movement on the draw span for the remaining cables,” DOT project engineer Michele Britton said.
The Department of Transportation can deny boats passage between 3 and 6:15 p.m. during the summer because of the effect on vehicle traffic. The agency has suspended that policy in exchange for requesting that boats request openings during slack tides.
“People may not be aware that the Hood Canal bridge is the only floating bridge in the world in a saltwater environment subject to tidal swings of up to 12 feet,” Britton said. “The huge tides in Hood Canal make bridge construction challenging, requiring a lot of energy and expertise.”