Could the Highway 101 bridge collapse?

The city's emergency preparedness committee fears that this bridge on U.S. Highway 101, just south of the north entrance of Cannon Beach, may not withstand “the big one” — a 9.0 Cascadia Subduction Zone earthquake — unless it is seismically upgraded.

The seismic stability of two essential bridges in Cannon Beach's north end have ended up on the emergency preparedness committee's list of concerns.

After a 9.0 Cascadia Subduction Zone event, the bridge just south of Cannon Beach's north entrance on U.S. Highway 101 may no longer qualify as a “bridge,” to put it mildly, and its collapse will effectively cut off Cannon Beach from other cities along that stretch of highway.

“If we have a level-nine earthquake, we're going to be a bunch of islands of survivors that don't have highway mobility access,” Public Works Director Dan Grassick said. “If you can swim, you'd probably be OK ... But then what are you going to do?”

The smaller Fir Street bridge that crosses Ecola Creek may not withstand an earthquake, either. Once it fails, Cannon Beach may have thousands of people in the downtown core — residents and visitors — who will need to head toward higher ground quickly but won't be able to without taking the long way toward Sunset Boulevard about a mile away.

If the Fir Street bridge does somehow manage to survive “the big one,” it will likely get taken out by the tsunami 15 or so minutes later — lifted off its foundations and carried upstream by the surge, as it did during the 1964 tsunami when a house ran into the former bridge, Grassick said.

“Neither one is designed to survive much shaking. They're both wood piling bridges,” he said. “If you have that volume of people there, and the evacuation route over Ecola Creek is not available, they've got a long ways to go, and the potential for loss of life is pretty high.”

Last year, the emergency preparedness committee persuaded city officials to put $100,000 from the general fund into a reserve fund that eventually will pay for a replacement bridge on Fir Street; nothing more was added to the reserve this year.

The highway 101 bridge, however, is a matter for the Oregon Department of Transportation. Typically, the department will do seismic upgrades on a bridge when that bridge comes up for maintenance.

The state transportation department's current position on Cannon Beach's bridge is clear: “The bridge is not in need of repair at this time, and with the limited resources we have for maintaining bridges, we will not be working on it until such time as it's in need of repair or replacement,” said Larry McKinley, Area 1 manager for the transportation department.

He added that the bridge, built in 1952, is functioning “very well” in terms of handling highway traffic.

“In this region, that's not a high-priority replacement bridge,” Grassick said. “Compared to other bridges — that have major problems — this one's in pretty good shape.”

With so many other bridges along Oregon's highways in need of repair — so many would-be capital projects competing for the transportation department's attention and funding — the Cannon Beach bridge will probably not become an agenda item for a long time, unless something unforeseen goes really wrong with it.

But because the transportation department keeps a close watch on all of its bridges, including the 142 along highway 101, the odds of a sudden structural failure of the Cannon Beach bridge is rather low, Grassick said.

“It's not likely that something out of the ordinary — that they didn't know was already happening — is going to come up,” he said, adding that the transportation department's philosophy is: “If you can catch something before it fails, you can extend the life of the structure substantially.”

The emergency preparedness committee recently opened up a conversation with McKinley about the need to reinforce Cannon Beach's bridge.

Led by Bob Mushen and Doug Wood, the committee “is going to explore what means we have” to get Cannon Beach's bridge on the transportation department's maintenance schedule sooner rather than later,”said committee member Karolyn Adamson.

One strategy may be to find money in the city's budget to spend on the project.

“If the city had a couple million to throw at it, that means the transportation department wouldn't have to spend as much,” Grassick said. This would allow the transportation department's funds to go further on Cannon Beach's bridge project than it would on other bridge projects, all else being equal.

Another strategy would be to put political clout behind it.

“You would need somebody like (State Sen.) Betsy Johnson to say, 'This is a No. 1 priority for this reason,'” he said.

As things stand, though, Grassick estimates that the bridge is “a good 10 years away” from seeing any funds from Transportation department for maintenance and seismic upgrades.

But it's not for nothing that the emergency preparedness committee has gotten the project underway. By bringing it to the transportation department's attention, the committee can get at least a preliminary idea of the cost involved and what a new bridge design could look like, Grassick said.

'If we have a level-nine earthquake, we're going to be a bunch of islands of survivors that don't have highway mobility access'

Dan Grassick

public works director


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