Moving the Sellwood Bridge: Big feat of engineering is about to begin

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PORTLAND, Ore. - Folks who regularly travel the Sellwood Bridge are going to have find a different way to get around for a week.

The bridge, which first opened to traffic in 1925, is getting replaced with a new one and this week crews will be sliding over the existing truss span to create a detour bridge that will be used during construction.

"It's probably one of the longest old bridges that's ever been moved, especially in this unusual way where it moves further from one end to the other," said Mike Pullen with Multnomah County. "We don't know if it's setting a world record."

The bridge will close at 5 a.m. on Thursday, Jan. 17 and is expected to reopen by 7 a.m. on Thursday, Jan. 24. The truss span will be moved in a full-day operation on Saturday, Jan. 19, weather permitting.

• Northern Detour: Hwy 43 to Ross Island Bridge to Hwy 99E
• Southern Detour: Hwy 99E to I-205 (Abernethy Bridge) to Hwy 43
• View map

It's a major operation and the company heading up the project is Omega Morgan, which specializes in large-scale moves and transportation. They say moving the Sellwood Bridge does pose a challenge because the east end needs to be moved 33 feet and the west end 66 feet - so it's not a straight-across move.

"It's not rare to move big parts of bridges, but this is a different way of moving," Pullen added. "It's kind of rare to move an old bridge all in one piece."

"Omega Morgan has moved bridges weighing upwards of eight million pounds, but this one does offer some additional challenges," the company's CEO, John McCalla, said in a news release describing the project.

"This is why we like what we do," chief engineer Ralph DiCaprio added. "There's something different on every project."

This particular method of building a new bridge is called a Shoo Fly. The idea is to shift the existing bridge out of the way so crews can build the new one right next to it.

The benefits are that traffic can continue to flow and construction on the new bridge (slated for a 2015 completion) can be done all at once, instead of in stages. The animation below shows how the method works:

• Omega Morgan bridge move to save up to US$10 million

How can I watch the move?

Contrary to what you might think, you won't actually be able to see the bridge move if you're watching it from the shore or from a boat a safe distance away. The move will be painstakingly slow.

"Its movement won't be detectable in real time - it's that slow," said Pullen.

The best way to see the whole operation is to watch the time lapse video that will be posted on the project website shortly after the move. You can also watch live video online if you want to see the progress at any given time.

However, if you do really want to see it in person, you can go to Sellwood Riverfront Park on the northeast side of the bridge at Southeast Spokane Street and Oaks Park Way. Just keep in mind that the park has very limited space for public parking and you may need to park several blocks away and walk in. Also, Southeast Spokane Street will be closed west of Southeast Oaks Park Way the day of the bridge move.

Boaters who want to watch the operation from the water will need to remain 500 feet away for safety reasons. The river under the bridge will be closed to boats the day of the big move and the sheriff's river patrol will be there to make sure no one gets too close.

What if something goes wrong?

The age of the bridge and the angle at which it needs to be moved does pose a challenge, but Pullen said at no time will the bridge ever be in danger of simply falling into the river.

"The risk isn't that it would be dropped in the river, but that it would be bent or twisted," he said. "We will move it a few inches and measure it and make sure it's not being bent or twisted and then we'll move it some more."

And as far as worker safety, Pullen said every precaution is being taken.

"There will be people on the bridge while it's moving," he said. "We have emergency plans if we need to get someone off that moving bridge."

Why is the bridge being replaced?

Although the bridge was quite innovative when it was first built (it is actually the only bridge of its kind in Oregon), today it is old and outdated. The lanes are narrow, the traffic volume is too much for it (it's the busiest two-lane bridge in Oregon) and it was not designed to withstand earthquakes.

Cracks were discovered in 2004 and temporarily fixed but engineers determined the bridge would eventually need to be replaced. Buses and trucks have not been able to cross the bridge for a while now.

• For more on the need for replacement
• Map showing the configuration of the new bridge (pdf)

Once the new Sellwood Bridge is ready to go, the old one will be demolished and the materials recycled.

If the old bridge has problems, will it be safe as a detour?

According to Pullen, the part of the bridge that has the cracks and has been the issue all along will be removed. The rest of the bridge, which is fine, will be used as the detour.

"The detour bridge is all built to today's construction code versus the code of 1925," Pullen said. "So it's built to a higher standard. And the bridge won't be opened to the public until it's gone through a very extensive inspection."

What's the price tag for the new bridge?

The total cost of the project is $299 million, which consists of funding from the following sources:

• $128.1 million - Multnomah County VRF ($19 per year vehicle registration fee)
• $18 million – Multnomah County VRF (collected)
• $84.5 million - City of Portland (new revenues from the Oregon Jobs and Transportation Act)
• $35 million - State of Oregon (Jobs and Transportation Act) for Highway 43 interchange
• $17.7 million - Federal TIGER grant
• $15.7 million - Previously secured federal funds

How can I keep tabs on the project?

Multnomah County has been providing regular updates on the Sellwood Bridge project, which you can access via RSS feed or by signing up for their mailing list.

• For details