Temporary repairs were being made today on two spillway gates at Big Cliff Dam on the North Santiam River, about four miles downstream from Detroit Reservoir.
Two of the dam's three spillway gates experienced mechanical problems last week, said Scott Clemens, a spokesman for the U.S. Army Corps of Engineers in Portland. Usually, this would not be a problem, but the dam's generator is out of service for maintenance and water could not be released through the powerhouse. That left gate three as the only way to pass water through the dam.
A rod that connects the gates with cables that lift and lower them failed on gates one and two, Clemens said. The dam was inspected in 2006 and the structure and the gates were determined to be sound. Clemens said the connecting rod is "always submerged and could not be inspected at that time."
Today, short term repairs were being made on gate one and gate three was inspected to make sure it will continue to function properly. Normally, the Corps raises and lowers the spillway gates several times a day to regulate water released from Detroit Dam.
Water flow in the North Santiam River was disrupted and the water temperature increased for four days last week, said Amy Echols, another Corps spokesperson.
"There was a combination of water coming off the top of the reservoir that is warmer, plus lower water flow, plus last week's extremely hot weather," Echols said. "For a while, the water temperature got to about 68 degrees and we would like it to be in the 50s. We were able to mitigate that by running water from the power house, which is very cold, and mixing it in Big Cliff reservoir. That helped balance the temperature."
There was some Oregon chub mortality in river channels near Stayton, Echols said.
"With the current water temperature, we don't anticipate any impacts on fish, although there may be some displacement of rearing juvenile fish," Echols said.
The Big Cliff boat ramp has been closed and the public is advised to be cautious due to the river water level fluctuating as much as 18 inches during the repair cycle.
Big Cliff Dam was completed in 1954 and has one generator that produces 18 megawatts of hydropower.