Interstate Bridge Repair Slated for this Fall

Portland, Oregon -- Oregon Department of Transportation officials report a $3 million project to repair the Interstate Bridge between Portland and Vancouver will take place this fall. The project to replace a cracked axle-like steel structure, or trunnion, will require complete closure of the northbound bridge for approximately three weeks beginning after Labor Day in September.

"The bridge is not in immediate danger, however, the risks go up the longer repairs are put off," said Region Manager Don Wagner. Because of this risk, according to Wagner, ODOT bridge engineers have determined it is necessary to make repairs this fall in order to ensure the integrity of the bridge and safety of the public.

The decision was made after a series of public meetings to discuss construction impacts and timing with business owners, shippers, residents and emergency services from both sides of the Columbia River.

The 81-year old structure carries an average 119,000 vehicles a day during the month of September. Congestion on and in the vicinity of the bridge is expected to be considerable. Traffic impacts will affect both states' transportation systems for a 20-mile radius as motorists seek alternate routes.

A multi-agency traffic mitigation plan is already underway. ODOT, the Washington Department of Transportation, local jurisdictions, Tri-Met, C-Tran, Amtrak, and others have entered an accord to pool their collective talents and resources for the two-state traffic plan.

"We're looking at the type of impacts that will occur not only to users of the bridge but businesses and commerce that rely on this key link between both states," said ODOT Traffic Manager Bill Ciz. "The magnitude of this (traffic) impact requires no less than the best we can muster," Ciz added.

The trunnion supports a sheave, over which cables run as the bridge is lifted. All three parts are critical because they support the 700-ton concrete counterweight that offsets the weight of the lift span as it rises. Failure could cause the counterweight to fall and go through the bridge deck which could send the north span into the river. Or the counterweight could swing and topple both spans.

A 1987 ultrasound inspection of the bridge indicated a possible crack. The internal location of the part -- enclosed by the drum and bearings -- made the diagnosis difficult. In 1994, newer technology called acoustical emission monitoring made it possible to locate an actively growing crack. The crack grows with every bridge lift.

Transportation officials have tentatively identified May 29, 1997, as the bid letting date with contractor selection by June 30, 1997. A separate contract is required for the fabrication of the new parts. The contract is expected to include incentive clauses to reduce the amount of time the bridge is closed.
 

For More Information Contact:

	Don Owings, owingsd@wsdot.wa.gov 360-905-2032 telephone 360-905-2222 facsimile Washington State Department of Transportation
		Katy Tobie, kathleen.a.tobie@state.or.us 503-731-8281 telephone 503-731-8259 facsimile Oregon Department of Transportation

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