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It’s going to be a long-haul project for Multnomah County.

Replacing or retrofitting the venerable Burnside Bridge in Portland is among the most important tasks the county is likely to face over the next decade. On Thursday, a policy group across the Willamette River in the event of a severe earthquake met with consultants to discuss the future of the 92-year-old bridge.

鈥淭he design criteria is going to be one of the most robust set of criteria for a bridge in the United States,鈥� said Steve Drahota, an engineering consultant with Omaha, Nebraska-based HDR. 鈥淚t’s meant to serve as a lifeline, as the singular bridge that remains open after a magnitude 8 or 9 earthquake.鈥�

A range of options was presented to the group, which consists of state, local and federal elected officials from around the region, as well as representatives of public agencies. Nine potential solutions, all but two involving full bridge replacement, have risen to the top of the list for consideration. These options come from two categories 鈥� enhanced seismic retrofit and replacement 鈥� initially presented by consultants. Others since discarded include a no-build option, a full seismic retrofit of the current bridge or enhancement of another bridge altogether.

Six screening criteria were used, said Jeff Heilman, an planning consultant with Parametrix. These were: seismic resiliency, non-motorized transportation needs, connectivity, equity, impact to the built environment and financial stewardship. The top scoring concepts were then recommended to advance to the next project phase.

鈥淲e looked at total scores and said, 鈥極K, how do we land on a reasonable range to carry to the EIS (environmental impact statement)?鈥� he said. 鈥淲e want this document to be clear and understandable.鈥�

Actual construction is probably eight to 10 years out, but potential options identified so far are likely to have a similar cost. They range from roughly $590 million for an enhanced seismic retrofit and widening of the current bridge to just shy of $750 million for a solution featuring mode-separate structures for motor vehicles and bicycles and pedestrians.

鈥淥ptions evaluation is where we are now,鈥� said Heather Catron, an HDR vice president and its director of federal transportation.

The current work is part of an ongoing feasibility study set to wrap up in September that will help identify preferred options for making the bridge earthquake-ready.

One option that didn’t make the initial cut was the proposal for a vehicular tunnel under the Willamette River that would have had to be constructed roughly 100 feet under the riverbed because of existing pipes.

鈥淭hat has the highest economic displacement,鈥� Heilman said. 鈥淭he portals at the east end and the portals at the west end are huge, and we end up with 120 businesses displaced. There’s a major impact to build a tunnel, especially because it’s flat on both ends.鈥�

Another idea that won’t be moving forward is the concept of a 120-foot-tall fixed bridge that would extend the bridgeheads much farther west and east of the current structure. Project costs for this configuration would run up to an estimated $900 million.

鈥淥ne of the key problems with the 120s is the impact that they have to the built environment that’s out there,鈥� Heilman said. 鈥淢any of them, you’re taking a bridge that currently ends about (Southwest) Second (Avenue) on the west side and you’re raising it up and taking it out to Seventh or Eighth, out to the Park Blocks.鈥�

For comparison, he added, the Marquam Bridge, in the South Waterfront District, stands 130 feet in height.

Projected costs for all of the proposed projects include National Environmental Policy Act compliance, right-of-way acquisition, design and construction. These costs are escalated to the year of construction between 2026 and 2028.

The county will perform additional community outreach this summer, with public open houses set for June and July. Following that, the county board of commissioners will need to approve a final range of alternatives, purpose and need, likely later in the fall.

Then consultants will be able to forge ahead in work with county, state and federal officials to develop a draft environmental impact statement. That process could take up to two years to complete.

Sources of funding have not yet been identified, but a sizable federal component would likely be required to make the project feasible. One option is to toll the bridge in a fashion similar to what is being considered for interstates 5 and 205 in the metro area.

鈥淲e haven’t talked about tolling yet,鈥� Commissioner Jessica Vega Pederson said. 鈥淚 think as we move into this there will be a larger conversation about how to fund the design and construction phase; we haven’t had that chat yet.鈥�