Oregon’s busiest two-lane crossing has opened after four years of planning and construction that included building a new bridge and moving an old one for use as a detour.

The Sellwood Bridge, a $227 million project in Portland, opened a new 2,000-ft-long span over the Willamette River this month, replacing a 1925-built bridge that was moved during the project for use as a detour.

A joint venture of Slayden Constructors and Sundt Construction, the Multnomah County project designed by T.Y. Lin International gives us an open-spandrel steel deck arch structure with two vehicle lanes in each direction on the west end, narrowing to one lane in each direction on the east end. The bridge also has two six-ft-wide bike lanes and two 12-ft-wide sidewalks.

The only crossing spanning the Willamette River for 12 miles, the original Sellwood Bridge will now get removed.

“Aside from the project’s massive scope and complexity, the biggest challenge for us was figuring out the best way to replace this vital travel artery with as little disruption to the community as possible,” says Chad Yount, Sundt project manager. The project was allowed to close the bridge to traffic for 30 days. And with eight months remaining in the five-year contract, the bridge has closed only 20 days.

Slayden-Sundt broke ground on the project in December 2011. A key factor in reducing disruption to the community was to construct the new bridge in the footprint of the existing structure without shutting down traffic flow. Rather than rebuilding the bridge in sections and shifting traffic back and forth between structures and newly completed segments, the team created a shoofly bridge.

The approach involved lifting the old bridge deck and truss with hydraulic jacks and moving it to one side, then placing it on a set of temporary piers and connecting it to temporary approach spans so that traffic could continue to use it while the new bridge was constructed. The 1,100-ft-long steel bridge truss was moved in a single 12-hour operation and became one of the longest bridge sections ever moved.

Now Portland-area commuters have a wider—and much newer—way to cross the Willamette.

Follow Tim Newcomb on Twitter at @tdnewcomb.