Repairs to one of Foster Dam’s spillway gates are complete, and the U.S. Army Corps of Engineers reopened Foster Dam Road Thursday after the contractor on the project finished removing a crane and equipment from the dam.
“Our final inspection is complete,” said Mark Dasso, the Corps’ project manager for the gate repair. “We thank the local community for their patience during this repair project.”
A 110-ton crane pulled the stop logs, allowing the dam to resume its “normal flood damage reduction mission,”Dasso said.
Use of the repaired spillway gate, gate one at the north end of the dam, restores flood damage reduction benefits and will allow the Corps to resume normal storage and release of water through the spring. The Corps also is resuming hydropower generation, as reservoir levels can now be held high enough to flow through the two-generator powerhouse capable of producing 20 megawatts of electricity.
Work on the gate began in early November after inspections during the summer revealed that each of the four spillway gates had sustained damage. The Corps is preparing plans and working to secure funding to repair the remaining gates later this year. These future repairs will not require lowering the reservoir.
This was an example of the Corps’ inspection system working, said Col. Steve Miles, Portland District commander. The Corps’ rigorous inspection schedule enabled it to detect and fix the problem prior to it becoming a catastrophe.
“It gets the focus back to its purpose, flood damage reduction,” Miles said.
The Corps will mainly rely on gate one “if we get into a situation with a great deal of water,” said Scott Annus, resident engineer with the Portland District construction office. Although unlikely, if the Corps needs to use a second gate to release water, gate four also can be used. The Corps will avoid using gates two and three if it can because they are in the most critical state of disrepair.
The timing of repairs to gates two through four depends on when funding becomes available, Annus said. The proposed federal stimulus package could help.
“We’ve submitted this as part of the president’s budget,” Miles said. The district’s goal is to complete the repairs immediately when it has the funding.
The repairs involved replacing the upper steel structural members running between the gate’s “hinges” and the gate itself. The Corps replaced bushings in the hinge with greaseless bearings.
Uneven movement of the bearings and the stresses from opening the gates are two of the probable causes of the damage to the gates, according to Corps officials. The bearings were damaged, and the structural members were deformed.
The Corps built the dam in 1968, and the technology is 40 to 50 years old, Miles said. The technology has improved since then, and officials are hoping they will extend the life of the gates by more than 50 years.
This problem isn’t unique to Foster Dam, Miles said. Elsewhere, Corps officials are finding slight levels of deformation in gate structures as it conducts inspections on its dams, he said.
“At this point, we do anticipate we’re going to have to do similar repairs (elsewhere).”
The U.S. Army Corps of Engineers operates 13 dam and reservoir projects in the Willamette River drainage system. Each dam contributes to a water resource management system that provides flood damage reduction, power generation, irrigation, water quality improvement, fish and wildlife habitat, recreation and navigation on the Willamette River and many of its tributaries. Since their completion, the dams have cumulatively prevented over $20 billion in flood damages to the Willamette Valley. For more information, visit http://www.nwp.usace.army.mil/op/v/home.asp.
Much of the Portland District infrastructure is 60 to 70 years old, he said. Bonneville Dam is 80 years old. Like a car or house, infrastructure requires maintenance and repair and should be anticipated.
“The aspect of anticipation is to be able to have a good system of inspections,” he said. “Our inspection program worked.”
Sometimes, people can take the effect of these dams for granted, he said. Because they work, it’s difficult to see how important they are.
“You could argue we as a nation just don’t respect our infrastructure,” Miles said. “This is a small investment in our infrastructure, but to someone who lives along here, this is probably the number one concern.”
The primary purpose of the dams is flood damage reduction, Miles said, and “what we saw in this last storm is how critical these dams are in the valley.”