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Detour bridge could speed Sellwood Bridge replacement, save $10 million

by:  In this illustration provided by Multnomah County, the current Sellwood Bridge over-water span has been moved north by about 40 feet, attached to new temporary ramps, and the space it currently occupies is now cleared for removal of the old ramps and construction of the new bridge.

With a full table of participants, the Sellwood Bridge Community Advisory Committee re-started its meetings on Monday, April 4th, at SMILE Station, under the direction of facilitator Alex Cousins from JLA Public Involvement.

Multnomah County's spokesman for the project, Mike Pullen, told THE BEE that the group was now meeting to consider smaller design elements. 'The big decisions have already been made. These choices are about the 'look and feel' of the bridge, such as pedestrian amenities, lighting, and community gateway treatments.' But there was a bigger item on the agenda to introduce to the committee.

As the volunteer CAC members continued to feast on pizza that evening, Multnomah County Commissioner Deborah Kafoury was on hand to welcome the group.

'On behalf of the County Commissioners, I thank the CAC members for returning and signing up for another tour-of-duty. What impressed me the most about this entire process is the involvement from the community; we've had an unprecedented level of support from both from the CAC, and the community at large.'

Saying she's looking forward to meeting with the committee throughout the next phase, Kafoury added, 'We still have a funding gap, and we're keeping our fingers crossed that on May 17, the vote in Clackamas County goes our way, so we don't have an even wider funding gap.'

The meeting moved briskly along, as Multnomah County's Ian Cannon reviewed the decisions made so far on the project - concepts that have all been covered in detail in THE BEE.

Mike Pullen introduced CAC members, and the 17 folks in the audience, to a new construction idea that reportedly has the potential both to reduce the cost to rebuild the Sellwood Bridge, and to dramatically cut down the time to do it by as much as 25%. 'Our consultant team says potential benefits include increased safety for bridge users and construction workers, and improved bridge design.'

Called a 'shoo fly' option, it involves building new piers in the Willamette River 40 feet north of the current bridge alignment, and then carefully sliding the main span of the existing Sellwood Bridge deck northward on rails, using a hydraulic jacking system. The old bridge could thus serve as a temporary bypass bridge for the entire construction project, which could cut a year off the construction time, says Pullen.

'There are currently two proposals for how to do the 'shoo fly' option; one of them provides greater cost savings, but has potentially more impact to neighbors,' explained Pullen.

'The part of the bridge deck they'd move [the main span over the river] is in relatively good condition,' Pullen pointed out. 'Once in place, traffic would be routed over this section, while contractors remove the old piers, and begin to build the new bridge in a single, shorter construction phase.'

A 'shoo fly' bridge detour, Pullen said, in addition to cutting construction time, would reduce material, labor and equipment costs as much as $10 million, would result in a better-looking new bridge (since it would not have to be constructed in two halves as originally planned), and would more safely separate construction work from highway traffic.

'Because the entire new bridge can be built in a single phase,' Pullen explained, 'it would have two larger and more robust arches, instead of four [built two at a time], with two for each half of the bridge, as in the current design.'

Shoo fly construction would also decrease the environmental impact of the construction project, because it requires fewer temporary work bridges and in-water and riparian work.

Using a 'shoo fly' detour isn't a new concept, Pullen revealed. The primary building contractor hired by the County for the project, Slayden Construction, previously used this technique in rebuilding the Elkton Bridge near Eugene. [See video of this project on YouTube: www.youtube.com/watch?v=QkBM-S9cfyU ] It was their previous experience with this option that led them to suggest it to the county for the Sellwood Bridge project. 'They suggested it. If we can save money and time, the public should hear about the newly introduced ideas.'

The downside is that a shoo fly connection section would be built over part of the Riverpark Condominiums, although it would not require demolition of any units there. 'The occupants of one unit would need to relocate for a short period of time during construction of the 'shoo fly'; the temporary alignment might lead to an increase in traffic noise there.'

As the county rolls the idea out to neighbors represented by the SMILE neighborhood association and the Sellwood-Westmoreland Business Alliance (SWBA), it is soliciting feedback from neighbors and businesspeople. 'The business district has asked we don't close the bridge during the Christmas shopping season or their annual Passport Weekend event - a request we can honor.'

Shifting the existing bridge to a 'shoo fly' detour just north of the present bridge position shouldn't close bridge traffic for more than four days, Pullen pointed out, and the county is committed to trying to limit total bridge closures during the entire bridge construction project to a total of no more than 30 days, either way.

The Multnomah County Board of Commissioners would need to approve an agreement for use of additional property needed to build the 'shoo fly', Pullen added, and the Board is expected to make the decision whether or not to pursue this new option by September. 'The Board is expected to consider the issue this spring. The County board and regulatory agencies need to approve the 'shoo fly' before it could be built. If the shoo fly is approved, construction would likely begin this December,' said Pullen, with the in-river construction of the piers for the temporary bridge.

Meantime, Multnomah County is soliciting comments regarding this new bridge-building option. Attend the next CAC meeting on May 9, at 5:30 p.m. at SMILE Station, on the southeast corner of S.E. 13th and Tenino in Sellwood - or go online and comment at: www.sellwoodbridge.org (click the 'Contact Us' tab).