A new bridge for the ‘Big One’

The Fir Street Bridge is expected to fail during an earthquake or tsunami.

CANNON BEACH — Trying to ensure residents and visitors survive the “Big One” that could strike at any time, the Cannon Beach City Council voted Tuesday night to pursue a Connect Oregon VI grant for a new pedestrian bridge over Ecola Creek.

The city’s evacuation plan directs pedestrians south because of the likelihood of a bridge collapse over the creek. Public Works Director Dan Grassick said the Fir Street Bridge is “woefully inadequate” when it comes to seismic and resulting tsunami activity. From downtown, where many shop, the trip south to high ground is a longer route that could waste precious time.

“The creek is a physical barrier that will cause a lot of deaths if you don’t have some way to cross it,” Grassick said. “Scores of people will lose their lives trying to escape the tsunami.”

The Emergency Preparedness Committee developed options and asked permission to seek the grant in the amount of $1.8 million. If awarded under Connect Oregon’s multimodal transportation funding program, the city will have to provide a 30 percent match.

Officials set aside $100,000 from the roads repair and replacement fund in 2013 to build a new bridge.

If Cannon Beach receives the grant, Grassick suggested the city use OBEC Engineering Consultants to build upon its 2011 bridge study and help select the specific design and location. The Emergency Preparedness Committee closely examined locations near Fir Street and NeCus’ Park.

Grassick said the pedestrian bridge would have to be no less than 30 feet away from the traffic bridge, 10 feet wide to accommodate the mass of people who would cross it and would likely be built with 100-feet-deep piling filled with concrete to withstand sand liquefaction.

Mayor Sam Steidel and Councilor George Vetter asked about replacing or retrofitting the current bridge.

Grassick said the pedestrian bridge is more realistic cost-wise. A traffic bridge would cost between $5 and $6 million, and there isn’t as much assistance available for its type.

A new pedestrian bridge would have a 95 percent chance of surviving a quake, he added.

In 1964, a 9.2 magnitude earthquake in Alaska caused a tsunami that wiped out the Fir Street Bridge. Nine were killed in Alaska during the quake, but no deaths were reported in Oregon, according to the West Coast and Alaska Tsunami Warning Center.

A distant tsunami typically provides hours of warning. In the case of a local tsunami off the Oregon coast, the public would have about 20 minutes to evacuate.

According to an Oregon State University study, there is a 40 percent chance for a major Cascadia Subduction Zone earthquake off the Oregon coast in the next 50 years. It is estimated that at least 1,080 people would head toward the Fir Street Bridge on a typical summer day in the case of an earthquake.

“Our No. 1 priority is to save lives,” Emergency Preparedness Committee Chair Karolyn Adamson wrote in a letter to the council. “I believe this proposal will do that.”

The council voted 4-1 to seek the Connect Oregon grant. Steidel was the lone no.

Grant applications are due Nov. 20 and will be awarded next year.

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