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.
“The Corps’ own fisheries biologists have already documented the catastrophic consequences of deep drawdowns,” the County wrote. “The SEIS must fully account for these impacts before any similar action is taken at Detroit Lake.”
County officials also noted that the Draft SEIS does not evaluate how large-scale fish mortality could affect species protected under the Endangered Species Act that rely on those fish as part of their diet, including the gray wolf—an omission the County said is inconsistent with required federal environmental review.
“The loss of over a million kokanee salmon at Green Peter wasn’t theoretical,” said Commissioner Colm Willis, Chair of Marion County. “It was real, it was catastrophic, and it was preventable.
“Detroit Lake should not be the next site for a preventable kokanee massacre,” Willis added. “The Corps should revise its plans to ensure our communities and environment are protected.”
The Army Corps is currently accepting public comment on the Draft SEIS as part of its review of operations for the Willamette Valley System, including proposed reservoir drawdown strategies intended to address dam safety and fish passage concerns.
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The deep draw of Green Peter was a total and utter ecological FAILURE! IT killes more than a million Kokanee, destyroyed a once great recreational fishery to accomplich what exactly, WHAT? A hypithesis that it would create easier passage of chinook smolts through the dam and downstream. Same thing happened wioth Lookout Point Res abovew eugene. Hundreds of thousands of fish washed through that dam, trout, kokanee, walleye, suckers, whitefish,, drained down so low that neareby property wells went dry. Now there is abundant walleye and bass downdtream from Dexter Res, predating on salnon and steelhead smolts. All because some mid-guided group out of portlandia found a symopathetic court and sued the COO. Now they try and do the same with Detroit, a once famed destination Kokanee fishery. Oohh not to mention the increase in fees for fishing licenses as well, FOR WHAT!!!!!!! Less opportunity. Screw them!