CANNON BEACH The goal: evacuate downtown Cannon Beach before a tsunami hits.
The problem: The existing bridge across Ecola Creek will collapse, stranding students at Cannon Beach Elementary School and those at the Cannon Beach Conference Center who need to reach the higher north end of town across the creek.
The solution: a stationary pedestrian bridge made of concrete or a floating bridge made of wood.
And therein lies the conflict.
The citys emergency preparedness committee supports a 12-foot wide concrete pedestrian bridge across the creek in addition to the current bridge. The cost could range between $1.6 million to $3 million, depending on the bridges alignment.
The committee is working with a proposal from OBEC Consulting Engineers of Eugene, that suggests two bridge alignments. Although the proposal, requested by Public Works Director Mark See, was submitted to the committee in February, it wasnt until this month that some members of the City Council learned about it.
Meanwhile, Mayor Mike Morgan began talking to architect and former mayor Jay Raskin about a wooden stationary pedestrian bridge or a floating bridge that would cost between $300,000 and $600,000.
Discussion over the two concepts already has become heated, especially now that the city has an opportunity to seek a grant from the Oregon Department of Transportation to do a geological study of the creek bank. The grant application is due this month.
I think its great that the city got OBEC involved and came up with a proposal for a fixed bridge, Morgan said at a City Council meeting earlier this month. But a fixed bridge will cost $1.5 million to $3 million.
The option Jay is proposing is to have a flexible bridge that will withstand an earthquake and allow the evacuation of children and the conference center and then be destroyed by a tsunami.
I think both approaches have merit, but it would be hard to pass a bond measure for a $3 million bridge, where $300,000 to $500,000 is more doable, Morgan said.
If the city were to spend $3 million on a bridge that is wide enough for pedestrians and possibly an emergency vehicle, Morgan added, it might as well replace the existing two-lane bridge.
State geologists have said that the wooden pilings under the existing Ecola Creek Bridge wouldnt withstand either an earthquake or a tsunami. The wooden bridge that spanned the creek during the 1964 tsunami collapsed when a house and other debris hit it. It took several months before that bridge was replaced with the bridge that is there now.
Bill Brehm, chairman of the emergency preparation committee, asked the Council how anyone would know if the wooden bridge proposed by Raskin would withstand an earthquake. He noted that quite a bit of work has already gone into studying a proposed concrete bridge.
The (ODOT) grant application ought to go in for the OBEC bridge, Brehm told the Council.
The OBEC proposal suggests a 12-foot-wide deck that would carry the load of an emergency vehicle and withstand a 1,000-year interval Cascadia earthquake and a higher level tsunami wave.
According to the preliminary design, the bridge would be constructed of precast slab spans and anchored to concrete-filled steel pipe pilings.
The bridges cost would depend on its location. One option would have the 650-foot-long bridge aligned with an extension of Spruce Street north to Fifth Street west of Cannon Beach Elementary School.
A second option would have the bridge alignment parallel to and downstream from the existing bridge. It would begin at the northeast corner of the school and end directly west of the Fir Street-Fifth Street intersection to the north. The bridge would be 250 to 300 feet long but would have less tsunami resistance than the first option. Some private land also might need to be purchased for the bridges right-of-way.
We're trying to solve the problem of when the existing bridge collapses and we have 20 minutes to get people out of town, Raskin said.