The U.S. Army Corps of Engineers, in an effort to improve juvenile salmon survival, announced it will not operate turbines at Detroit Dam between 6 a.m. and 10 a.m. and 6 p.m. and 10 p.m. from Nov. 1, 2020, through Feb. 1, 2021, except in emergencies.
During those times, the Corps will release water exclusively through the upper regulating outlets over the three months when downstream passage rates are high.
"The operation is part of a suite of interim measures that the Corps is planning to implement to benefit Endangered Species Act-listed salmon in the Willamette River Basin" a Nov. 9 news release from the agency said.
During this period, the Corps will work to complete the Willamette Valley System EIS and associated ESA consultation on the Corps' operation and maintenance of the Willamette Valley Project.
The Corps will also install and operate a rotary screw trap below Big Cliff to monitor the new operation, manage Detroit Dam to minimize total dissolved gas below Big Cliff, and release water through spillways at Detroit Dam during the summer when possible.
The modified operations come after U.S. District Judge Marco Hernandez ruled in August in a suit brought by several environmental groups against the Corps and the National Marine Fisheries Service [18-437]. Hernandez said the Corps violated the ESA after missing numerous deadlines in a 2008 BiOp for operating 13 dams in the Willamette Valley Project. Nine of the dams generate electricity, with a total capacity of just over 400 MW.
After the judge's ruling, the environmental groups filed a proposed remedy that included a similar interim operational change to the one the Corps instituted at Detroit Dam, along with about 50 other measures at several other dams.
Their proposed remedy would draw down the reservoir below minimum pool starting Nov. 1, and would use the lower regulating outlet for temperature control. The groups also asked for the turbines to be turned off from 4 p.m. to 8 a.m. daily from Nov. 1 through Feb. 1.
The federal defendants have not yet responded to the proposed remedy, but did object in a Nov. 5 filing to a motion by the State of Oregon to appear as amicus curiae.
"It is apparent from its motion for leave to file an amicus brief that the State intends to act as a de facto adversarial party in the litigation rather than as an amicus," the defendants' opposition brief says.
It said Oregon's requests are beyond the scope of amicus participation.