PORTLAND, Ore. -- The U.S. Army Corps of Engineers (USACE) Portland District is seeking public input on a draft study that considers changes to how the agency operates its Willamette Valley dams.
This study – referred to as a Supplemental Environmental Impact Statement (SEIS) –builds upon a six-year study completed in April 2025 and addresses new requirements regarding endangered fish and hydropower production that emerged shortly before the six-year study was finalized.
The SEIS will analyze the potential impacts of these changes on the environment, local communities, and dam operations.
The comment period is part of a federal process that provides opportunities for public participation in decision-making processes that may significantly affect the environment. During the comment period, USACE will hold information sessions to explain the draft SEIS.
“Public input is the cornerstone of success when we’re working with projects that impact our communities,” said Liz Oliver, the project manager for the supplemental study. “Comments will help us better understand how the proposed changes in the SEIS may affect communities, the environment, and reservoir users.”
The draft supplemental study specifically addresses:
-
A new environmental review for protected species, called a Biological Opinion , from the National Marine Fisheries Service. The Biological Opinion requires a deeper fall drawdown at Detroit Reservoir to support endangered fish passing through the dam. This drawdown is not expected to occur until fall 2026, and the SEIS will evaluate its potential effects on water quality and local communities.
"We're moving quickly to complete this study and ensure we're meeting our obligations, while also considering potential impacts to communities," said Col. Dale Caswell, commander of the Portland District, USACE. "We encourage everyone to participate in the public comment period and help us make informed decisions about the future management of the Willamette Valley dams."
The public comment period runs for 45 days, from Nov. 14 to Dec. 29. A link to the draft SEIS will be posted on the webpage www.nwp.usace.army.mil/WVS-EIS/ Nov. 14.
USACE will host public information sessions to provide information and answer questions about the draft SEIS. These sessions are an opportunity to learn more about the study and share your input:
Virtual Information Sessions
📅Nov. 19, 2025
⏰ Noon
🔗 Meeting Link
Meeting ID: 993 148 805 804
Passcode: md3qN7xc
☎️ Dial in by phone
+1 601-262-2433
Conference ID: 849 999 963
📅 Nov. 19, 2025
⏰ 5:30 p.m.
🔗 Meeting Link
Meeting ID: 993 353 552 564
Passcode: mH9Yy3n2
☎️ Dial in by phone
+1 601-262-2433
Conference ID: 870 696 779#
In-Person Meetings
Dec. 6, 2025
⏰ 10 a.m. - noon
🏢 Detroit City Council Chambers
345 Santiam Ave
Detroit, OR 97342
📅 Dec. 10, 2025
⏰ Noon – 2 p.m.
🏢 Broadway Commons
1300 Broadway St. NE, Room 307
Salem, Oregon 97301
📅 Dec. 10, 2025
⏰ 5:30 – 7:30 p.m.
🏢 Broadway Commons
1300 Broadway St. NE, Room 307
Salem, Oregon 97301
Comments on the draft SEIS must be submitted in written form: USACE will accept comments via email or mail.
Email: willamette.eis@usace.army.mil
Mail: U.S. Army Corps of Engineers
Attn: CENWP-PME-E / Willamette SEIS
P.O. Box 2946
Portland, OR 97208-2946
For more information, visit www.nwp.usace.army.mil/WVS-EIS/.
Background:
USACE operates and maintains 13 dams in the Willamette River Basin. These dams provide flood risk management, water for irrigation and communities, recreation opportunities, in addition to supporting fish and wildlife. Managing these dams is a complex task that requires balancing a variety of needs and interests. The Willamette Valley System saves the region an estimated $900 million annually by preventing flood damages.