Rubber Bridge


Portland has spent months debating which new bridge to build. DMA’s winning entry spans the Willamette River with a cable stay design.
Courtesy TriMet

Portland, Oregon, sometimes called the Bridge City, is known for its many gorgeous crossings. But it has been more than 30 years since a new span has been built across the Willamette River near downtown. That will soon change, however. With the planning of the Portland-Milwaukee Light Rail Project, which will connect the city center to northern Clackamas County, the city has invested in the exploration of concepts that could herald another masterpiece. What has erupted since is a debate over the final design for the 780-foot span.

Led by the Tri-County Metropolitan Transportation District of Oregon (TriMet), the proposed bridge will carry light rail, buses, pedestrians, bicyclists, and possibly a future streetcar while providing green zones at each end. The initial concept, put forth during the research phase, was designed by bridge architect Miguel Rosales’ firm Rosales + Partners.

TriMet initially favored Rosales + Partners "Wave" design, but it was deemed too expensive.
Courtesy Rosales + Partners

Entitled “Wave,” the proposal featured a hybrid structure comprising both suspension and cable stay systems that create an undulating profile. This system, said Rosales, softens the angular geometry of a typical cable stay bridge by decreasing the height of its towers. It also pays tribute to one of Portland’s most stunning spans, the St. Johns Bridge, he added.

But on May 28, the Willamette River Bridge Advisory Committee (WRBAC) deemed the Wave too costly. The committee voted instead for a cable stay bridge designed by Donald MacDonald Architects (DMA) of San Francisco that is estimated to cost $110 million. The Wave had an estimated cost of $134 million.

The choice sparked public discussion about the city’s dismissal of aesthetic grandeur in favor of the bottom line. In a letter to TriMet and DMA dated June 10, the WRBAC stated, “The committee would like to acknowledge that a few of its members continue to support the original hybrid version.” The debate was also highlighted in the story “Soaring or boring?” in The Oregonian on June 16.

DMA’s proposal won out on cost, but some have called it uninspiring.
Courtesy TriMet

Meanwhile DMA has been working to better satisfy design expectations, despite the focus on budget. On July 24, the firm presented design options for a refined cable stay bridge that has slightly inward canting towers, cantilevered bike and pedestrian paths, and an emphasis on a lightness of structure. Further design development is expected to continue well into next year.

In the meantime, TriMet Project Director Robert Barnard defended the transit department’s decision by pointing out that Portland’s identity can be found in “an understated aesthetic.” “Our goal is to deliver a bridge that embodies the Portland aesthetic and is functional and affordable,” he said.

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