As it looks for ways to help reintroduce
anadromous fish upstream of Willamette Valley dams, the U.S. Army Corps of
Engineers is considering adding a $100 to $200 million water temperature
control tower in the Detroit Reservoir.
A tower would aid downstream juvenile passage
with attractor flows in the reservoir and it would help control discharge water
temperatures downstream of Detroit Dam and Big Cliff Dam, the Corps’
re-regulation dam downstream, and beyond into the Santiam River system.
The idea ran into stiff opposition at local
Corps open houses, however, when the agency explained that to build the 300
foot tall tower it may have to drain the reservoir for up to two years, a
prospect that local merchants and water users in Salem and Stayton, Oregon said
would be economically devastating, according to news reports. The Corps
recently said the project could impact thousands of Willamette Valley
“In the long-term, this project has a lot of
positives, from a healthier environment for fish to better operation of the
dam,” Marion County commissioner Kevin Cameron was quoted saying in a Salem
Statesman Journal article. “But there is a huge risk in the short-term.”
The Corps has not made the decision to build
the water temperature control tower, but it is considering it as an option as
part of a National Environmental Policy Act review. It just completed the
initial public scoping process Jan. 23, the first step in the NEPA process. The
construction project is addressing a reasonable and prudent alternative
recommended by the 2008 Biological Opinions for the Willamette Valley, the
The final product in the NEPA process will be an environmental
impact statement for the project. The Corps expects to complete a draft EIS,
along with alternatives, by the Fall of 2018.
If it decides to move ahead with building the
tower, construction wouldn’t begin until 2021.
The project, like many of its fish-related
projects in the Willamette Valley, is part of a broader effort to reduce the
effects of Corps-operated dams on winter steelhead and spring chinook salmon,
the Corps said. Both species are listed as threatened under the federal
Endangered Species Act.
The Corps operates and maintains 13
multipurpose dams and reservoirs (including Detroit Dam and Lake) in the
Willamette River Basin in Oregon, collectively referred to as the Willamette
Valley Project (see http://www.nwp.usace.army.mil/Locations/Willamette-Valley/).
But the issues at Detroit Dam aren’t new, the
Corps said. It’s just gained momentum due to the public comment process in
November and December, and ending Jan. 6.
“We want to find a solution together,” said
Kelly Janes, Portland District environmental resource specialist, who
spearheaded outreach to stakeholders across the valley. “Input from the
community is critical. For this process alone, we’ve received substantial
information that will really guide our construction process and our
environmental analysis of potential impacts.”
The tower at Detroit Dam would actually be the
second such tower built by the Corps and the third in Oregon. One is at Cougar
Dam in the Willamette River system and the other is at the Pelton Round Butte
Complex of dams on the Deschutes River in Central Oregon and is the target of a
two-year old court case.
The Corps began operating its first Willamette
Valley water temperature control tower in 2010 at Cougar Dam on the South Fork
of the McKenzie River, a dam that was built in the 1960s.
Biologists estimated that habitat upstream of
the dam supported as many as 4,000 adult spring chinook prior to the dam being
built. However, water released from the dam was cooler than pre-dam river
temperatures in the spring and summer and warmer in the fall and winter, which
is one reason fewer chinook returned to the river and juveniles emerged from
gravel redds earlier, the Corps said.
“Wild adult spring Chinook salmon began
returning to the South Fork McKenzie River almost as soon as the temperature
control tower came on line,” the Corps said on its website (http://www.nwp.usace.army.mil/willamette/cougar/temperature/). “Returns to the new adult fish collection facility downriver of
the dam since it opened in 2010 have ranged between 250 and 525. We expect
similar returns in the future until a long-term solution is implemented to help
improve survival of juvenile salmon attempting to pass the dam on their way
downstream from their spawning grounds to the ocean.”
The third temperature control tower was built
at the Pelton Round Butte Complex of Dams by its owners Portland General
Electric and the Confederated Tribes of the Warm Springs Reservation in 2009,
and it was built for similar reasons as the tower at the Corps’ Cougar Dam.
Like the Corps in its efforts to reintroduce
salmon and steelhead upstream of its Willamette basin dams, PGE and the Tribes
also began a reintroduction program in 2010. The mixing tower serves as a
surface attractor to help juvenile salmon and steelhead that rear upstream find
their way downstream to the dam where they are trapped, marked and transported
below the dams. The tower is an integral part of the utility’s reintroduction
Called a selective water withdrawal facility,
the tower reaches nearly 270 feet below Lake Billy Chinook’s surface.
“This structure needs to be connected to the
original intake structure to supply water for power generation while attracting
fish and withdrawing water from the upper 40 feet of the reservoir,” Steve
Corson, spokesperson for PGE, said.
The components of the structure are a floating
surface collection structure (SWT), which screens surface water to exclude fish
from powerhouse flow while directing juveniles to the transfer facility, a
vertical flow conduit (VFC), a bottom structure (SWB), an access bridge (ABR)
and the fish transfer facility (FTF). The SWB directs water from the SWT/VFC to
the original powerhouse intake and also provides for direct water withdrawal
from the bottom of the reservoir into the original power tunnel, Corson
During operation, powerhouse flows are drawn
from the surface structure or mixed with water from the bottom of the
reservoir, depending on fish passage or water quality requirements.
PGE did not drain the reservoir to install the
SSW, but instead built the majority on the water on barges next to the dam. The
SWB was floated into place and anchored to bedrock at the reservoir bottom, 270
Construction was not without its problems. A
portion of the VGC failed when the structure was initially deployed, Corson
said. However, the problem was corrected and the SWW was deployed with a delay
of seven months.
The Deschutes River Alliance says that PGE’s
tower is likely the cause of water quality violations in the Deschutes River
downstream of the dams and has sued the utility in U.S. District Court of
Oregon over those alleged violations of the Clean Water Act. DRA filed its original
petition Aug. 12, 2016. The case is still working its way through court.
--CBB, December 8, 2017, “Corps Seeking Public
Input On Detroit Dam Fish Passage, Temperature Control Scoping Process,” http://www.cbbulletin.com/439923.aspx
-- CBB, June 16, 2017, “Willamette BiOp For
Fish: Four Subbasins Focus Of Corps’ Salmon Reintroduction Programs Above Dams”