PORTLAND, Ore. — In 2009, dam safety inspectors dangled from ropes to inspect the spillway gates at federal dams throughout Oregon. The team, in their top-to-bottom inspection, determined that the aging spillway gates might malfunction when the water levels were high.
"The original engineers didn’t fully understand the implications of operating the gates at high pools, which we now recognize through testing and evaluation,” said Chris Manley, structural engineer.
After the visual inspections, a dam safety assessment concluded the gates could fail to open or could stick, which was a serious safety risk because that could have effected how Portland District dams released water.
In response, the Corps lowered the reservoir pool elevations to reduce pressure on the gates – meaning the dams couldn't store as much water during flood season.
The Corps also began the work to rehabilitate the spillways, including wire ropes, gearboxes, electrical controls and gate hinges, known as "trunnions," at dams on the Columbia River, Rogue River and Willamette Valley Project.
For Ross Hiner, Dam Safety Program manager, it's an investment in the safety of communities like Eugene, Springfield, Albany and Salem, which are downriver from Corps dams.
"This ... will help ensure flood risk is reduced in the region for decades to come," Hiner said.
In December, the District lifted pool restrictions at Blue River Dam after completing gate rehabilitation there. This improvement is incredibly important to dam operators in the Willamette Valley, according to Dustin Bengtson, deputy Operations Project Manager.
“It builds reliability back into the system,” said Bengtson. “Rehabilitation increases the reliability and diminishes risk in our systems,” he said. “The need to use these gates may be rare but when we have a high water event they have to be absolutely reliable.”
Gate rehabilitation is also complete at Big Cliff, Green Peter, Lookout Point, Dexter and Fall Creek dams. To learn more, visit: www.nwp.usace.army.mil/Missions/Water-Management/Spillway-Gates/.