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The Sellwood Bridge was constructed in 1925 to replace the Spokane Street Ferry,
which shuttled passengers across the Willamette River between Sellwood and West
Portland. The bridge was designed by Gustav Lindenthal,
a noted bridge engineer
of the time, and--like the Ross Island and Burnside bridges--was built with funds
from a $4.5 million local bond measure.
In response to public outcry at budget overruns on the Burnside Bridge, the Sellwood
Bridge design was scaled back to minimize cost. With a construction cost of just
$541,000, the scaled-down design resulted in a number of limitations. The bridge
is extremely narrow: two lanes, no shoulders or median, and one 4-foot-wide sidewalk.
The Sellwood Bridge is the only four-span continuous truss highway bridge in Oregon
and possibly in the nation. (A continuous truss requires fewer parts and is cheaper
to construct than other bridge types.) It was also Portland’s first “fixed span”
bridge across the Willamette (meaning it was high enough to avoid the need to “open”
for river traffic). It was Portland’s first Willamette bridge without trolley tracks.
Because it was not designed for the additional weight of streetcars, the structure
itself is not as substantial as the city’s other river crossings.
In addition to these design limitations, the bridge also has topographical challenges.
The west end of the bridge was constructed on fill material and is located in an
area that is geologically unstable. The hillside above the bridge is slowly sliding
toward the river, exerting pressure on the west end of the bridge. In fact, in the late 1950s,
the hillside actually slid several feet toward the bridge. As a result, a section
of the bridge had to be removed and foundations were reinforced. The west end interchange
with Highway 43 was completely re-built in 1980. Since then, ground movement has
caused the west end approach girders to crack. The bridge is also not designed to
withstand a significant earthquake.
In May 1999, Metro's Joint Policy Advisory Committee on Transportation made final recommendations
for the South Willamette River Crossing Study area, which included the Sellwood Bridge. The study
identified needed improvements for cars, transit, bikes, and pedestrian traffic crossing the river.
The study examined several options for the Sellwood bridge, including:
- Keeping the Sellwood Bridge in its current configuration
- Upgrading it to meet current seismic, vehicular, bike, and pedestrian standards
- Closing the bridge to auto traffic, but leaving it open only for bikes and pedestrians
- Replacing the Bridge with a two- or four-lane facility
- Making modifications to the Ross Island Bridge in an effort to reduce bottlenecks at the west end of that bridge and to increase the Ross Island Bridge to three lanes each way
- A new crossing in Clackamas County
- Increasing transit services and other programs that would reduce travel demand on the Sellwood Bridge
The study recommended the following:
- Preserve existing Sellwood Bridge or replace it as a 2-lane bridge with better service
for bike and pedestrian travel
- Consider improvements to the Ross Island and I-205 bridges in a different study
- Increase motor vehicle capacity on regional facilities, such as McLoughlin and Highway 224
- Mitigate traffic on Tacoma Street, Highway 99E in Milwaukie, and on A Avenue and Highway 43 in Lake Oswego
- Increase transit services and improve bicycle and pedestrian facilities in the corridor
- Bring more jobs to Clackamas County
Multnomah County continues to take steps to prolong the safe use of the bridge until
a long-term solution can be found. In June 2004 after the discovery of the cracks
in both the east and west concrete approaches, cracks were restrained with steel
clamps and the weight limit for vehicles traveling across the bridge was reduced
from 32 tons to 10 tons. This limit has caused the diversion of 94 daily TriMet
bus trips (a loaded bus weighs about 19 tons), which formerly crossed the bridge.
A 2005 engineering study recommended short-term safety improvements for the bridge;
Cracks in the girders and columns will be injected with epoxy in 2007. The county
is also inspecting the Sellwood Bridge every 3 months to monitor the cracks and
slope to ensure the bridge is safe to use.
Existing Bridge Deficiencies
- Buses and trucks are restricted from using the bridge
- Narrow lanes
- Narrow sidewalk
- No shoulders
- No bike facilities and poor connections to trail system
- Bridge not designed to withstand earthquakes
- Tight turns at west end
- Unstable slope at west end
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