The U.S. Army Corps of Engineers has released the first environmental impact statement since 1980 for its Willamette Valley system of 13 dams. The final EIS analyzes several alternatives and selects the preferred alternative the Corps says will be best for spring Chinook and winter steelhead listed under the Endangered Species Act. The Corps expects to release its Record of Decision in May.
However, the FEIS is just the first step in a two-step process. The Corps now must complete a study required by the 2024 Water Resources Development Act to analyze an alternative that ceases hydropower operations at the eight Willamette Valley dams where the Corps currently generates electricity.
The second step, according to the Corps, will be a supplemental EIS that will include the new hydropower analysis, as well as the effects of a deeper drawdown for fish passage of Detroit Dam’s reservoir on the North Fork of the Santiam River.
“The completion of this EIS is a significant milestone that deserves celebration, but there is more to do,” said Col. Dale Caswell, Jr., Portland District commander. “Over the next year, we will have another opportunity to listen to the public and work with our partners to finalize how we will operate these dams for future generations.”
The deep drawdown in the Detroit reservoir is a requirement of NOAA Fisheries’ 2024 biological opinion (released Dec. 26, 2024) and the dams’ impacts on salmon, steelhead, resident fish and wildlife. Upper Willamette River wild spring Chinook salmon and Upper Willamette River wild winter steelhead are listed as threatened under the federal Endangered Species Act.
However, the Corps will not perform the deep drawdown this year, but instead will analyze the effects of the drawdown and include that in the SEIS in early 2026.
“Until we complete the supplemental EIS, we will carry out water quality and downstream fish passage operations like we have done over the past few years,” the Corps said at its FEIS webpage (https://www.nwp.usace.army.mil/WVS-EIS/). “We do not anticipate a deep reservoir drawdown at Detroit Dam until fall of 2026.”
The federal agency said it is working with NOAA Fisheries to develop the timing and duration of the deep fall drawdown at Detroit Dam and considering potential impacts to communities and water quality. It will ask for public comment on the drawdown as a part of the supplemental EIS process.
Since it completed the last EIS in 1980, the Corps said it has “made many changes to help endangered fish, made improvements to the dams, and optimized operations for fish passage and improved water quality. Until now, we reviewed these changes one dam at a time—not as a complete system. We also have new information about how our operations effect the environment.”
The FEIS examines different alternatives in how the Corps could adjust its operations and how these changes would affect people and the environment. In its list of alternatives and its preferred alternative analyzed in the FEIS, the Corps said it has only considered those that allow it to continue all its Congressionally authorized purposes, including flood risk management, water supply, water quality, fish and wildlife protection, recreation and hydropower generation.
The Corps said the primary purpose of the Willamette Valley dams is flood risk management.
“It has prevented an average of $1.08 billion in damages annually,” the Corps said in a news release this week. “Water managers must keep reservoir elevations low to maintain storage space, capture rainfall and minimize flooding potential through spring. This must be balanced with what seem to be conflicting purposes: refilling the reservoirs before summer for irrigation, hydropower generation, water quality improvement and recreation.”
The Corps’ preferred alternative includes both structural and operational measures that, taken as a whole, prove to be best for the ESA-listed threatened spring Chinook and winter steelhead, according to FEIS. The preferred alternative, which is alterative 5, rates high for viable salmonid population metrics, as well as passage efficiency for juveniles at the dams and their survival through the dams.
The preferred alternative includes:
Floating Screen Structure and Temperature Control Tower at Detroit
Adult fish facility at Green Peter Dam
Spring and fall draw down to Diversion Tunnel at Cougar Dam
Floating Surface Collector at Lookout Point
Pacific lamprey passage and infrastructure
Integrated Habitat and temperature flow regime
In more detail by river, alternative 5 measures include:
North Santiam (Detroit and Big Cliff dams)
•Detroit spring/summer spill for downstream fish passage and water temperature management
•Detroit falls lower regulating outlet (RO) for downstream water temperature management
•Detroit winter upper RO for downstream fish passage
•Big Cliff spread spill to reduce TDG
South Santiam River (Green Peter and Foster dams)
•Green Peter spring spill for downstream fish passage
•Green Peter fall deep drawdown for downstream fish passage through ROs
•Foster spring delayed refill and spill for downstream fish passage
•Foster fall spill for downstream fish passage
McKenzie River (Cougar Dam)
•Fall drawdown for downstream fish passage through ROs
•Spring delayed refill for downstream fish passage through ROs
Middle Fork Willamette River (Lookout Point, Dexter and Fall Creek dams)
•Hills Creek winter night-time RO prioritization for fish passage
•Lookout Point/Dexter spring/summer spill for downstream fish passage and water temperature management
•Lookout Point fall deep drawdown for downstream fish passage through ROs
•Fall Creek extended winter deep drawdown for downstream fish passage
•Fall Creek spring delayed refill for downstream fish
The Willamette River is 180 miles long and drains 11,487 square miles or nearly 12 percent of the state of Oregon. It meets the Columbia River at Portland. Today, over 70 percent of Oregonians live in the Willamette River basin.
The Corps’ Willamette Valley System consists of 13 reservoirs, encompass 11 multiple purposes with 2 re-regulating dams and 8 hydropower dams. The dams were built between 1939 and 1969 and the last EIS was in 1980. Most of the dams are “high head” dams, over 250 feet tall and as a result, the Project blocks about 70 percent of Chinook and 33 percent of steelhead historic habitat in the upper Willamette basin while also modifying downstream habitat, the DEIS says.
The WVS also includes 5 fish hatcheries, a Willamette bank protection program and 100 miles of revetments (bank support and changes). The WVS provides approximately $1 billion in annual flood risk benefits, 26 million in hydropower revenue, and 5.4 million in recreation benefits, the EIS says.
More information about WRDA 2024 is here: https://www.usace.army.mil/Missions/Civil-Works/Project-Planning/Legislative-Links/wrda_2024/
NOAA Fisheries 2024 BiOp is here: https://www.fisheries.noaa.gov/s3/2024-12/WCRO-2023-00324-PERM-BiOp-WillametteValleySystem-20241226.pdf
For background, see:
— CBB, March 23, 2023, Comments On Corps’ Draft EIS for 13 Willamette Valley Dams Question Whether Plan Avoids Jeopardy For ESA-Listed Salmonids, https://columbiabasinbulletin.org/comments-on-corps-draft-eis-for-13-willamette-valley-dams-question-whether-plan-avoids-jeopardy-for-esa-listed-salmonids/
— CBB, March 9, 2023, SCIENCE PANEL GIVES THUMBS-UP ON FISH RESPONSE MODELS CORPS USED TO DEVELOP DRAFT WILLAMETTE RIVER BASIN EIS, https://cbbulletin.com/science-panel-gives-thumbs-up-on-fish-response-models-corps-used-to-develop-draft-willamette-river-basin-eis/
— CBB, December 2, 2022, CORPS RELEASES DRAFT EIS FOR 13 WILLAMETTE BASIN DAMS INTENDED TO AID ESA-LISTED SALMON, STEELHEAD; DRAWDOWNS, STRUCTURAL CHANGES, LESS POWER, https://cbbulletin.com/corps-releases-draft-eis-for-13-willamette-basin-dams-intended-to-aid-esa-listed-salmon-steelhead-drawdowns-structural-changes-less-power/
— CBB, February 24, 2022, CORPS DETAILS TO COUNCIL NUMEROUS MEASURES TAKEN AT WILLAMETTE PROJECTS TO AVOID JEOPARDIZING LISTED SALMON, STEELHEAD, HTTPS://CBBULLETIN.COM/CORPS-DETAILS-TO-COUNCIL-NUMEROUS-MEASURES-TAKEN-AT-WILLAMETTE-PROJECTS-TO-AVOID-JEOPARDIZING-LISTED-SALMON-STEELHEAD/
— CBB, September 2, 2021, JUDGE ISSUES FINAL ORDER FOR OPERATIONS AT CORPS’ WILLAMETTE VALLEY DAMS TO AID ESA SALMON, STEELHEAD; DEEP DRAWDOWNS, SPILL, HTTPS://CBBULLETIN.COM/JUDGE-ISSUE-FINAL-ORDER-FOR-OPERATIONS-AT-CORPS-WILLAMETTE-VALLEY-DAMS-TO-AID-ESA-SALMON-STEELHEAD-DEEP-DRAWDOWNS-SPILL/
— See CBB, July 15, 2021, “Federal Judge Orders Corps To Take Immediate Action To Protect ESA-Listed Willamette Valley Wild Spring Chinook, Steelhead; ‘No Patience For Further Delay,’” https://cbbulletin.com/federal-judge-orders-corps-to-take-immediate-action-to-protect-esa-listed-willamette-valley-wild-spring-chinook-steelhead-no-patience-for-further-delay/