Friday, April 20, 2012

West-half draw span repairs will close Hood Canal Bridge nightly

By guest blogger Joe Irwin

Taking a look at the west-end of the Hood Canal Bridge
For the State Route 104 Hood Canal Bridge, wind, waves and tide changes are just part of the daily grind.

But after 30 years this grind is wearing out more than its welcome, it’s also taking a toll on key components on the bridge’s west-half draw span pontoon.

Depressions are forming in the 1.5-inch thick steel plates that run the length of the draw span, making it increasingly difficult to open the west half of the bridge. The steel plates protect the pontoon’s concrete from 4-foot wide rollers which guide the floating bridge’s 900-foot-long draw span as it opens and closes.

The west span is in the closed position a vast majority of time, allowing traffic to flow across the bridge between Kitsap and Jefferson counties. But the cars and trucks on the roadway aren’t the only things moving during these extended periods.

As the floating bridge shifts due to tidal changes and other conditions on the canal, the rollers and the plates constantly rub together. They’re both steel, mind you, but even the toughest materials bend to the whims of Mother Nature and Father Time.

The steel plates are doing their job and preserving the concrete pontoon, but now they’re worn down and the west draw span isn’t moving the way it should. The depressions are creating a situation not unlike starting a car and driving it out of a rut. It’ll go, but takes a little more gas to get rolling.

In the draw span’s case, crews must ramp up the rpms on huge engines to get it moving. While this works as a short-term solution, the engines are not designed to run at these higher levels for long. Instead of risking burning out this expensive equipment, our crews are taking aim at a relatively low-cost solution.

Maintenance crews will grind and weld the 32 depressed areas in the steel plates.

To complete the weather-dependent work, crews must open the west-half draw span, closing the bridge to drivers for a minimum of four nights, beginning Monday, May 7. Closures are scheduled from 8:45 to 10:45 p.m., 11 p.m. to 1 a.m., and 1:15 to 3:45 a.m., which will allow traffic to flush through from both sides and help drivers avoid the only other viable travel alternative to and from the Olympic Peninsula during the nighttime hours – a 130-mile detour down US 101.

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