Lake Oswego City Council approves repairs to North Shore Bridge
The city of Lake Oswego finally decided on plans to replace the retaining walls on the North Shore Bridge after its closure this past July.
During the Dec. 21 meeting, councilors approved the replacement of the northwest and northeast retaining walls to improve the structural stability of the bridge. The project is estimated to cost between $1 million and $1.25 million.
Over the summer, the city engineering staff found structural issues in the nearby retaining wall of the bridge, which prompted its closure.
The retaining wall, which supports the approaching roadway to the bridge, was separating from the wall, and the city found cracks and movement in the wall during an inspection of the bridge.
In October, Lake Oswego entered two contracts with a design team and contractor — which will work together simultaneously — totaling about $116,000.
"The project team considered several alternatives for this retaining wall, including leaving it as existing, a localized spot repair and full replacement," read the city's staff report. "To supplement the visual inspections performed, an area of the roadway was excavated to determine geotechnical properties. Those findings were used when performing the slope stability analysis of the existing wall configuration."
Stefan Broadus, assistant city engineer, said the slope stability factor of safety came in at a score of 1.1 — a score of 1 shows that the structure will fail when it reaches the design load and can't support an additional load — compared to the minimum factor of safety, which is 1.5.
"Obviously, we are deficient there," said Broadus, adding that a spot repair wasn't feasible.
Broadus presented three design options, and the council decided not to have a public engagement process with the designs.
"I think speed is of the essence," said Councilor John Wendland.
Councilor Rachel Verdick added that there aren't many options in terms of aesthetic and she didn't see a need for community engagement on this project, though she expressed her appreciation of that process.
Staff plans to explore further details and costs of each design.
Council President Daniel Nguyen asked if the bridge, which is fairly narrow, could be replaced to improve accessibility and safety for pedestrian crossing.
Broadus said widening the bridge to provide a more prototypical sidewalk would likely be 10 times the cost of what is currently being proposed.
While funds were not budgeted for the replacement project, resources from the American Rescue Plan Act are eligible to be used.
While Broadus noted concerns with availability of material and labor, he estimated that construction on the bridge would likely be complete in May 2022.
For more information, visit the city's website.
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