Tuesday, August 4, 2020
Aug. 4, 2020

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Clark Asks: Why not replace I-5 Bridge trunnion while traffic’s light?

Officials say they need replacement parts, more time before northbound span can close

By , Columbian staff reporter
Published:
4 Photos
The Interstate 5 Bridge.
The Interstate 5 Bridge. (The Columbian files) Photo Gallery

With people hunkered down at home because of COVID-19, wouldn’t now be a good time to replace the Interstate 5 Bridge’s cracked trunnion?

That idea, suggested by a Columbian reader through our Clark Asks feature, makes lots of sense from a traffic standpoint.

The Oregon Department of Transportation confirmed that bridge traffic has declined since large sectors of the community — schools, businesses, stores, theaters, gyms, bars and restaurants not offering takeout, drive-through or delivery service — closed to limit the virus’s spread.

That said, ODOT is sticking with the Sept. 12-20 schedule to close the northbound span and replace portions of the drawbridge’s lifting mechanism.

The needed custom parts are being fabricated in Alabama and aren’t expected to arrive here until August.

ODOT says it also needs more time to coordinate with the U.S. Coast Guard, shipping companies, along with state, county, city and transit agencies, plus businesses, truck drivers and commuters.

“River levels are not as low right now as they will be in September,” said Kimberly Dinwiddie, a spokeswoman for ODOT in the Portland area. “Lower river levels allows most vessels to travel under the Interstate Bridge without a bridge lift.”

The closure is to replace two trunnions, which are axles, 20 inches in diameter, that help raise and lower the bridge’s lift span. The work also will replace sheaves, or wheels about 12 feet in diameter, sheave covers and cables.

In 1999, a crack was found in the east trunnion on the northbound bridge’s south tower, just two years after the span was shut down to replace the north tower’s two trunnions.

During this year’s repair, the northbound span will be closed to vehicles, pedestrians and bicyclists and all vehicular traffic will be switched to the three-lane southbound span. As was the case with the 1997 closure, a movable “zipper” barrier will create two travel lanes to accommodate rush-hour traffic into Portland in the morning and two lanes for the afternoon commute to Clark County.

The zipper barrier is not available on short notice. Other work needs to be done on both ends of the southbound span so the barrier can be moved twice a day, at 2 a.m. and again at noon.

“We don’t use the zipper barrier really anywhere else,” Dinwiddie said. “It is something special to this trunnion project.”

Dinwiddie said community outreach has been underway for two years, but officials want to make sure everyone has adequate time to plan ahead.

“We realize that we are living in a time of disruption,” she said. “And we want to ensure we don’t add to that now by closing a major section of the interstate system.”

ODOT is taking advantage of decreased traffic to do work where it can, she said. As of Friday, it did not have numbers for how much traffic is down on the I-5 Bridge.

“We are working with our engineering folks in Salem to do a comparison of what they were to what they are now,” Dinwiddie said.

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