PORTLAND, Ore. – The U.S. Army Corps of Engineers (Corps) will again delay spill operations for temperature control to allow the City of Salem time to implement and train personnel on new equipment and treatment options designed to better test and prevent toxins from entering Salem’s water treatment facility.
The Corps will now begin the spill operations on June 21 to meet water temperature requirements for threatened salmon and winter steelhead.
This is the third delay request the Corps has received. Normally, spill operations at Detroit Dam would have commenced on June 1. However, the delays have been necessary to let the City of Salem institute additional monitoring capabilities arising from the detection of cyanobacteria in the city’s drinking water.
“We are grateful to Marion County and the Corps for their proactive measures in helping us protect Salem’s drinking water source, the Detroit Reservoir. These efforts have been ongoing and pre-date Salem’s drinking water advisory for vulnerable populations,’ said Steve Powers, City of Salem City Manager. “Since the initial detection of cyanobacteria, we continue to collaborate daily and share data regarding water samples and results.”
The reason for spill operations is to change water temperature in the river downstream to create optimal spawning and rearing conditions for threatened spring Chinook and winter steelhead. Spill operations do not increase the amount of water that is regularly released from Detroit Dam on a daily basis.
Populations of threatened Upper Willamette River spring Chinook and winter steelhead rely on the North Santiam River basin for their spawning and rearing habitat. Since 2007, a combination of spill and normal releases of water for hydropower generation from Detroit Dam has been used to approximate natural pre-dam North Santiam River temperatures. At full conservation pool, opening a spillway gate at Detroit Dam releases warmer water from a depth of approximately 20 feet below the surface of the lake. Cooler water from more than 150 feet below the surface of the reservoir is released when water passes through the hydropower turbines, allowing the production of electricity.
In spilling and generating hydropower at Detroit Dam on a daily basis, warm and cold water mixes in the small pool between Detroit and Big Cliff dams, and is continuously released from Big Cliff Dam to sustain North Santiam River flows at a target temperature.
The Corps has developed a monitoring plan during the spill operations and will provide test results with Marion County, and the cities of Salem and Stayton. Additionally, the Corps has provided water retention times in the Big Cliff reservoir, travel time to the City of Salem treatment facility intake, and daily operational release schedules.
Detroit Dam works together with Big Cliff Dam to provide flood risk management. Detroit’s other authorized purposes also include hydropower, water quality, water supply, fish and wildlife, navigation, and recreation.
The U.S. Army Corps of Engineers Portland District operates a system of 13 dams and reservoirs in the Willamette River Basin to help protect lives and reduce property damage from floods. The District also works to increase awareness of flood risks and empower the public to take individual actions to reduce their risk.