Friday, October 22, 2021

Progress on a New Burnside Bridge


Tied Arch Version (Multnomah County)

Even though funding sources and a specific budget are not yet known, designers of the proposed new Burnside Bridge are looking at ways to cut costs.

 So far, the likeliest cost-savers are slimming the bridge width from five vehicular traffic lanes to four, and narrowing pedestrian/bicycle lanes from 20 feet widths to 15.5 feet on both sides.

That said, a couple major decisions appear to have been reached in designing a bridge to replace the earthquake-vulnerable existing bridge, which is nearly 100 years old.   The west end running to and from the Skidmore-Old Town National Historic District is to be supported by long girders, extending to the mid-river bascules that allow the bridge to open for river traffic.  This design has minimal visual impact as motorists and others travel westward into Old Town.

 Bridge planners also have decided that bascules – which allow the bridge to open and close using counterweights below the roadway – are the preferred system handling river traffic.  The bascule system would be similar to how the bridge operates today, but would be entirely new mechanically.

The new bridge could be Portland's only bridge capable of handling major traffic after a high-intensity earthquake.  That is the primary reason for scrapping the current bridge. 

 The final major planning decision for the new bridge is how to handle the “long span” from the bascules to the east end of the bridge at Martin Luther King Jr. Boulevard, crossing the I-5 freeway and Union Pacific Railway tracks.  It is squishy soil under the Willamette River’s east bank that renders the current bridge violently broken in case of a major earthquake.  The soft soils extend as much as 200 feet below the surface.

 Two options being studied for the eastern portion included a tied arch structure, akin to the big arch of the Fremont Bridge, and a cable-stayed option akin to the structure of Tillicum Crossing.  The option chosen could have a large impact on the final budget, but the appearance of the structure itself would be a landmark – for better or worse – in the center of Portland for many decades to come. 

Cable-stayed Version (Multnomah County)

 It is reasonable to guess that the ultimate choice could pit aesthetics against costs.  A final recommendation is expected next February, with the rest of 2022 being devoted to the final design.  Megan Neill, engineering services manager for Multnomah County, said a funding strategy has yet to be defined. 

 She said a federal infrastructure plan proposed by President Biden is likely to be one component, but she added, “We’ve always known we have to fund additional funds.”  As a start, county motorists are already paying bridge fees when renewing their vehicle licenses.

 CLARIFICATION: Last week’s screed about Portland’s proposed overhaul of rules for adding or removing historic landmarks and landmark districts missed a key point that could be a benefit to preservation advocates.  The proposed rules streamline the process and reduce costs for seeking landmark status for individual sites, and recommendations to the City Council would be made by the Portland Historic Landmarks Commission.

However, the Planning and Sustainability Commission would be the body involved in recommending additions or changes to historic districts.  Given the makeup of the current commission, is it’s laughable to think they would propose anything but reductions to the city’s landmark districts.

 ---Fred Leeson

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  1. The cable stay version, purely for aesthetics, would be my recommendation. The two towers nicely off-quote the twin towers of the convention center, helping reinforce the idea as an eastside visual cue. (Perhaps one tower represents Albina, the other for East Portland?) The arch span by contrast feels like it diminishes the Fremont.

  2. I agree with your assessment. The tied arch interferes too much with views of East Portland. The cable-stay version is much more airy and delicate.