Marion County, OR. — Marion County has submitted two additional comment letters urging the U.S. Army Corps of Engineers to revise its Draft Supplemental Environmental Impact Statement (SEIS) for the Willamette Valley System, citing significant deficiencies in the analysis of water quality, infrastructure impacts, and fish mortality associated with deep drawdowns at Detroit Lake.
In letters submitted January 13, the County argued that the SEIS fails to fully assess or mitigate foreseeable environmental consequences of draining Detroit Lake below normal operating levels. One letter focuses on risks to municipal drinking-water systems—particularly slow-sand filtration facilities used by Salem and Stayton—warning that fine sediment released during a deep drawdown could cause irreversible damage and potentially halt potable water production for entire cities.
A second letter highlights fish mortality risks that the SEIS acknowledges but does not adequately prevent. Marion County cited the 2023 drawdown at Green Peter Reservoir, where more than one million kokanee salmon died due to barotrauma caused by rapid pressure changes as fish passed through the dam during low water levels…