GENERAL INFORMATION: 503-823-7404
1120 SW Fifth Ave, Suite 600, Portland, OR 97204
The Willamette River Crossing (WRX) project will construct a seismically hardened transmission main under the Willamette River, providing a reliable source of water to wholesale and retail customers on the west side of the river after a significant seismic event. The new pipeline under the Willamette River will be large enough to provide the average daily need to Westside customers.
The Water Bureau anticipates beginning construction on a new seismically hardened crossing of the Willamette River beginning in 2018. The project will consist of a new tunneled 42” inch steel river crossing, approximately 1,500 feet long and 80 feet below the river bed.
Seismically hardened means the water main is restrained so it is
less likely to move and break during a significant earthquake.
Transmission mains that cross the Willamette River are a critical part of providing water to Portland’s wholesale and retail customers on the west side of the river. The water system currently has six (6) active transmission mains that cross the Willamette River; the oldest river crossing is more than 110 years old and the youngest is over 30. They are made up of steel, ductile iron, or concrete. The water mains lay along the river bottom, or are attached to a bridge. None of the existing crossings are seismically hardened, which means the water mains are not restrained so they may move and break in the event of a significant seismic event.
The greatest seismic hazard to existing Willamette River crossings is a Cascadia Subduction Zone earthquake (CSZ, 9.0M). Current science indicates that there is about a 15 percent chance that a CSZ earthquake will occur in the next 50 years. There is a 16-55 percent chance that three (3) central city crossings will fail due to liquefaction and that the others may be damaged or break due to falling debris during a CSZ earthquake. With the central city crossings not functioning, the remaining crossings could not supply demand due to limited capacity and inadequate connectivity to the city center and the west hills. It is estimated that 11 percent of Water Bureau Westside customers could be out of water for up to six months.
Besides addressing possible earthquake failure, the City needs to have the ability to take one of the central crossings out of service for repair work. Repairs could take several months, making redundancy-or backup- for the central Portland area necessary during construction. Because of this, at least three central crossings are necessary. The Ross Island Bridge and Clay Street crossings are anticipated to be removed or replaced within the next 25 years.