Oregon — The U.S. Army Corps of Engineers (USACE) Portland District has extended the public comment period by 15 days and scheduled an additional in-person information session in Stayton for its draft Supplemental Environmental Impact Statement (SEIS) examining potential changes to Willamette Valley dam operations.
The new deadline to submit written comments is Jan. 13, 2026. The SEIS builds on a six-year study completed in April 2025 and responds to new legal and regulatory requirements that emerged shortly before that study concluded.
Among the updates addressed in the SEIS is a new Biological Opinion (BiOp) issued by the National Marine Fisheries Service. The BiOp calls for a deeper fall drawdown at Detroit Reservoir to support endangered fish species. USACE officials say the drawdown is not expected to occur until late fall or early winter 2026, and the SEIS evaluates potential impacts to water quality, recreation, and nearby communities.
The document also examines compliance with the Water Resources Development Act (WRDA) of 2024, which directs USACE to study an additional alternative that would remove hydropower as an authorized purpose at some Willamette Valley dams.
“The feedback will help guide our decisions, while we keep our forward momentum to complete this study,” said Liz Oliver, project manager for the supplemental study. She said the extension allows more time for meaningful public participation following the holidays.
The SEIS analyzes potential environmental, operational, and community impacts associated with these changes across the Willamette Valley System, which includes 13 federally operated dams providing flood risk management, irrigation and municipal water supply, hydropower, recreation, and fish and wildlife benefits. USACE estimates the system prevents approximately $900 million in flood damages annually.
An open-house style public meeting will be held Dec. 16, 2025, at 6 p.m. at 400 W. Virginia St. in Stayton. USACE biologists and technical staff will be available to answer questions and explain the alternatives under review. A recording of a previous public information session is also available online.
Written comments may be submitted by email to willamette.eis@usace.army.mil, by mail to U.S. Army Corps of Engineers, Attn: CENWP-PME-E / Willamette SEIS, P.O. Box 2946, Portland, OR 97208-2946, or delivered in person at the Stayton meeting. The draft SEIS and additional information are available on the USACE Portland District website.
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