The 3.35 mi double-track Portland Streetcar Loop extension project is bringing the modern streetcar system to the eastern side of the city of Portland, Oregon, for the first time. Testing of the system and work on the contractor’s punch list is currently under way. Courtesy of Portland Streetcar
Punch list work is under way on the Portland Streetcar Loop extension project, which brings a modern streetcar system to the eastern side of the city of Portland for the first time.
May 15, 2012—The 3.35 mi double-track Portland Streetcar Loop extension project, on which ground was broken in 2009 and major construction was recently completed, is bringing the modern streetcar system to the eastern side of the city of Portland, Oregon, for the first time. The system—which operates using electricity provided by overhead cables—crosses a historic bascule bridge located over the Willamette River at one end of its route and a new flyover constructed over existing Union Pacific railroad lines at the other.
The majority of the streetcar extension will operate at grade along four-lane-wide, one-way roads, according to Steve Wood, the project manager for Stacy and Witbeck, Inc., the construction manager and general contractor for the project. The new extension includes 28 new stops; when combined with the city’s existing streetcar line, the system is expected to carry 3.5 million riders annually, according to information contained on the Portland Streetcar, Inc., website.
The extension crosses the 100-year-old Broadway Bridge, the largest Rall-type wheel bascule bridge in existence, according to Mark Dorn, P.E., the design project manager for URS Corporation, the primary design consultant for the streetcar extension. The double-leaf bascule bridge opens when each of the two leaves tilts upward on a hinge, halves of the movable operates by opening on either side, like a hinge—similar to a typical draw bridge—but then the two leaves withdraw from one another, rolling out of the way, Dorn explains. The bridge opens on demand, which occurs approximately 20 times a month.
Since the streetcars run on overhead electrical wires, the fact that the lines had to cross a bridge that opens created a particularly tricky situation for the designers to resolve. “Imagine, if you will, a plug in your wall, [and] that has to plug in and disconnect every time,” says Carl Dances, the systems manager for Stacy and Witbeck, Inc. “We had the same [situation] on the overhead conductor rail.”
The resulting electrical system the designers developed for the bascule span contains eight movable sections of rigid aluminum conductor rails, according to Dances. Each section is balanced on an axle and driven by a small electric motor so that it can rotate upright, and thus out of the way, as the bridge opens. When the bridge is lowered, the overhead rails rotate back down and lock into place with a mechanism that completes the circuit so that the streetcars can once again cross the bridge. “It’s fully automated and it’s programmed to self-adjust if it ever gets out of adjustment,” Dances explains.
An additional complication in adapting the bascule bridge for streetcars was the condition that Multnomah County placed upon its approval to allow streetcars on the historic bridge: No additional weight could be introduced on the crossing. The designers came up with solutions to “strip weight from the lift spans wherever we could, in order to offset the weight for the new rails and conductor rail,” Dorn says. The team accomplished this by replacing existing sidewalks, railings, and other sections of the bridge with lighter-weight materials. Additionally, they had to replace the locking mechanisms that held the two leaves of the bridge together. “And then [the lift spans] had to be rebalanced because the weight was distributed differently,” Dorn notes.
Workers add the track on which the streetcars will operate to the
deck of the historic bascule bridge. No additional weight could be
introduced on the bridge so the designers replaced some existing
elements with lighter-weight versions to offset the weight of the
new rails and the overhead conductor rail. Courtesy of Portland
At the southern terminus of the streetcar extension, the system had to cross existing railroad tracks—while respecting the height restrictions imposed by local power lines—before it reached its termination point at the Oregon Museum of Science and Industry. A flyover was built for the streetcars, but as Dorn explains, “it was like threading a needle.”
The relevant electrical code, National Fire Protection Agency (NFPA) 70: National Electrical Code, required a 14 ft clearance between the transmission wire and the streetcars’ overhead contact system wire, Dorn explains. “If we didn’t achieve that, we would have had to relocate three major circuits serving all of downtown Portland,” he says.
Modeling the transmission lines at their maximum sag point—occurring at 200 degrees Farenheit—Dorn notes that “we had to pull out all stops to achieve the clearances, including lowering the overhead contact system wire to its minimum clearance above the rails, developing a new method of rail-fixation to the bridge, and optimizing the position of the [flyover] structure as it crosses under the transmission power lines.
“We made the 14-foot clearance by a mere 4 inches,” Dorn says.
The cost of the streetcar extension project is anticipated to total $148.27 million, according to the project website; the federal government is providing approximately $75 million, while the remainder is coming from a variety of city, regional, and state funding sources.
The streetcar expansion project comes close to creating a fixed-rail inner-city circulator loop in Portland. The full circulator loop will be created with the completion of a new transit bridge—which will only be accessed by pedestrians, bikes, buses, streetcars, and light-rail—in September 2015. The completion of that bridge will link the terminus of the current extension to the southern tip of the existing streetcar line, which was completed in 2001, according to Kay Dannen, the community relations manager for Portland Streetcar, Inc. David Evans and Associates, Inc., completed the structural design work for the bascule bridge and the railroad flyover.
The operation of the new streetcar extension system is slated to begin at 10 AM on Saturday, September 22, 2012, at the Oregon Museum of Science and Industry Plaza, according to Dannen. While major construction work on the system was formally completed five weeks ago, testing of the system and work on the contractor’s punch list is currently underway.