In the news:
I-5 bridge over Columbia could last ‘indefinitely,’ inspector says
With diligent maintenance, an Oregon state inspector says, the existing Interstate 5 bridge between Washington and Oregon could last indefinitely.
The Associated Press
PORTLAND — Absent a big earthquake or a catastrophic encounter with a too-tall truck or ship, the Interstate 5 bridge that now spans the Columbia River could stand almost indefinitely, an Oregon state inspector says.
It may need to.
If plans to replace the bridge don’t advance by mid-March, Oregon Gov. John Kitzhaber has promised to pull the plug on it — after more than 10 years and $190 million spent.
The project is in trouble. The Washington Legislature decided last year not to participate, and that has raised concern in the Oregon Legislature, particularly in the Senate, about an Oregon-only project projected to cost $2.8 billion.
A new bridge project could take a decade to get going.
In the meantime, Oregon’s state bridge engineer, Bruce Johnson, said the current bridge will need repairs and, in 15 to 20 years, a $75 million paint job.
“If you’re willing to do those kinds of fixes and you have a robust inspection system like we have, you could almost say the bridge will last indefinitely,” Johnson told The Oregonian.
The Interstate 5 bridge linking Portland and Vancouver, Wash., is actually two spans.
The first opened in 1917 and replaced a ferry. It now carries northbound traffic.
Its twin opened in 1958; it carries southbound traffic.
Marc Gross, a former Army engineer, heads the full-time bridge crew of 10. Supporting the crew costs more than $1 million a year, split equally between Oregon and Washington. Routine subcontracted repairs and maintenance are budgeted for an additional $1 million annually.
“Vibration is our biggest enemy,” Gross said. He hires a full-time electrician to keep connections tight and maintain the system.
Friction is a close second.
Each year, the crew lubricates six miles of drawbridge cables by hand, applying about 3,200 pounds of grease. An additional 4,000 or 5,000 pounds of grease is applied to lubricate gears, bearings and other parts.
Then there are starlings, which flock in at night to roost or nest, with the expected consequences in droppings. Gross mounted orchard cannons along the bridge fired at irregular intervals, but suspended the firing this year.
“It’s taken me probably nine years of doing it,” he said. “I’ve depleted about 40,000 to 60,000 starlings down to under 1,000.”
Johnson said that if the bridge were to see conditions that would qualify it as structurally deficient, repairs could be made. Among those are cracking of the steel floor system and corrosion of steel truss members and connections.
“The major issues that might make repair and rehabilitation of the bridges infeasible would be a major earthquake or a major impact from an overheight vehicle or a ship,” Johnson said.