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Multnomah County Board of Commissioners chairwoman Deborah Kafoury knew what was coming at Thursday’s board briefing on the seismic safety of the county’s bridges in downtown Portland.

鈥淚t’s just a time for us to get scared so we’re afraid to drive across bridges,鈥� she said. 鈥淚’m noticing a trend with these conversations and I don’t like it.鈥�

Sure enough, Ian Cannon, county bridge engineering services manager, and consultant Steve Drahota, vice president of HDR‘s Portland office, warned that the historic Broadway, Burnside, Morrison and Hawthorne bridges all are in danger of failing in a major earthquake. To illustrate this potential scenario, Drahota shared photos of bridges dramatically damaged during earthquakes in California, Japan and Chile.

But the idea wasn’t to frighten county commissioners, he explained. It was to show that past mistakes in bridge design inform engineers on how to make new and existing structures seismically safer.

鈥淭he intent of my presentation is to take the lessons from those other events and what we can learn from those and apply that to our bridges,鈥� he told commissioners. 鈥淭hose catastrophes, we learn from them.鈥�

Drahota, a senior engineer at HDR, has designed more than 30 bridge retrofits in California and written seismic retrofit standards for the Oregon Department of Transportation. He is the technical lead on an update to the Multnomah County Willamette River Bridges Capital Improvement Plan. The looks at the current conditions and maintenance needs of the county’s six crossings over the Willamette River and their risks of sustaining damage in an impending high-magnitude earthquake near the Oregon coastline.

In recent years, county officials have focused on replacing two of the neediest bridges. The Sauvie Island Bridge was rebuilt in 2008 and the new Sellwood Bridge is scheduled to open in fall 2015. The updated capital improvement plan centers on the county’s four other bridges 鈥� the Broadway, Burnside, Morrison and Hawthorne 鈥� and includes seismic evaluations of them. All four are listed on the National Register of Historic Places. The Hawthorne and Broadway bridges are more than 100 years old.

A draft plan scheduled to be released early next year will include cost estimates for seismic retrofits of the county’s oldest bridges, Cannon said.

鈥淭hey were all designed before seismic (risk) was a consideration,鈥� he said. 鈥淭he plan is a blueprint or a road map into the future. The next step is doing a little bit more research to figure out how we’ll get the funding.鈥�

The four downtown bridges share similar seismic vulnerabilities, Drahota said. This includes the potential for the deck to fall from its supports when the soil under it liquefies, columns collapsing, trusses breaking apart and failure of mechanical and electrical components.

鈥淭he era of design takes itself to a place where the details of the vulnerabilities are carried all the way through,鈥� he said.

Much can be done to fix these issues, Drahota said, such as installing seismic braces and performing an extensive overhaul where the columns are replaced.

鈥淥ur past is what we need to correct,鈥� he said. 鈥淭he technology is there to make them more seismic resistant.鈥�

This is where learning from past bridge failures in earthquakes comes in handy, he said. Small details, such as how a bridge column is constructed, can make a huge difference in whether the structure collapses in an earthquake, Drahota said.

鈥淓very little detail has to be thought about to make sure you have a safe structure,鈥� he said. 鈥淲e can make improvements that can save our bridges.鈥�

These improvements won’t be cheap, Drahota said, but he encouraged county commissioners to seek funding for seismic upgrades before a tragedy strikes.

鈥淚t takes courage to go and get a funding package before an earthquake event has happened,鈥� he said.

County commissioner Jules Bailey agreed that it wouldn’t be prudent to wait until after an earthquake to retrofit the bridges.

鈥淲e need to get on this,鈥� he said. 鈥淭here is a lot of work to get done. It’s obviously a critical need and it’s all-hands-on-deck time.鈥�