In the market for a span? Mount Si Bridge is for sale

The design is simple and elegant, and the price is right, but when it comes to taking the Mount Si Bridge off King County's hands, there's a catch: Some assembly required.

Built in 1914, it's the only one maintained by the county that's held together by steel pins, rather than bolts or rivets.

It's an Ikea-style deal: The buyer would have to dismantle, move and reassemble the bridge, not to mention pay for the required permits.

In exchange, the recipient would get a "trail bridge for a public golf course, a foot bridge. Maybe somebody has a small train, like in zoos," said Julia Turney, an environmental engineer with county Road Services Division.

At 19 feet wide, it's too narrow for many of the roughly 4,000 vehicles that cross it on an average day.

If it were sold for scrap, the 93-ton bridge could fetch an estimated $10,000, said Jim Markus, engineering manager for the county Road Services Division.

But because the bridge, which crosses the Snoqualmie River near North Bend, is a county landmark with statewide historical significance, the law requires that county officials try to find a new home for the old steel trusses before putting them on the surplus list.

And because county code allows the Road Services Division to negotiate directly with government agencies, "we could come to some agreement with a government agency for no cost," she added.

County officials are aiming to find a government agency to take the bridge off their hands before 2008, when its replacement is completed.

The county has made its bridges available to outside entities on only two other occasions, though elsewhere it's more common, Markus said.

The last time, in 2000, there were no takers for the Novelty Bridge, which crosses the Snoqualmie River and was being replaced.

Piecing the Mount Si Bridge together probably wouldn't be the hardest part of moving it. The bridge's pin-and-eye bolt design was popular in the U.S. from the 1880s to the 1920s because it was relatively easy to transport and could be put together by someone without special skills.

"A lot of railroads used it because they could put it on a flatbed and take it out on site to erect it," Turney said.

Some pins might be so rusty they'd need to be replaced, however, and that would require custom fabrication, Turney said.

In that event, the county could provide the original drawings for the bridge, which was built by the Bellefontaine Bridge and Steel Co. of Ohio.

The bridge has proved it can withstand a move.

Originally, it spanned the White River in Buckley, was called the Buckley Bridge, and had a twin. One of the bridges was relocated to the Mount Si site in 1955, after the state Department of Transportation built the Highway 410 Bridge over the White River.

County officials don't know exactly what happened to the other bridge, but it may have gone to Pierce County, Markus said.

What is now the Mount Si Bridge was moved to the Middle Fork of the Snoqualmie River, a growing area served at the time by a bridge made of wood.

A photo of it in pieces makes it look "like it was Tinker Toys taken apart," Turney said.

That move cost the county $40,000 — not bad, Turney figures, for a structure that has lasted nearly a century and connected two communities.

"The people of King County have really gotten a good bargain with the bridge," she said.

Now, perhaps, the people of other counties, or cities, will step forward to do the same.

Amy Roe: 206-464-3347 or aroe@seattletimes.com