The city of Salem is asking a federal judge to postpone the U.S. Army Corps of Engineers’ plan to lower water levels in the Detroit Reservoir, which city officials said will harm its ability to provide safe, clean drinking water to residents.

The lawsuit filed Wednesday, July 8, in the Eugene U.S. District Court argues that the U.S. Army Corps of Engineers must complete a federally mandated report analyzing the impacts from prior drawdowns before proceeding with the Detroit drawdown.

The drawdown, planned for the fall, aims to make it easier for salmon to move through the North Santiam River. It would bring the water level to the lowest since the Detroit Dam was built 70 years ago.

City leaders said the planned drawdown will increase the turbidity — the amount of sediment — in the North Santiam River and temporarily overwhelm the sand filtration system that handles the city’s drinking water.

The lawsuit also claimed that the Army Corps disregarded the city’s concerns over the drawdown’s likely impacts, missed a deadline mandated by Congress to submit its report analyzing the impacts of past drawdowns, and that the proposed drawdown would likely raise turbidity to levels that violate Oregon law.

Detroit Dam and the reservoir are part of the Willamette Valley System, a network of dams and reservoirs owned and operated by the Army Corps, the city said in its complaint. The city of Salem operates the area’s main drinking water treatment facility on Geren Island, which supplies drinking water to about 220,000 people.

“Our drinking water is safe, clean and plentiful, but the corps’ plan raises critical concerns about the long-term reliability of our water supply,” Salem City Manager Krishna Namburi said a statement Wednesday. “Our actions today will help safeguard our water source now while allowing the system to support future population and economic growth.”

A biological opinion issued by the National Marine Fisheries Service in December 2024 found that the corps needs to lower the lake to support steelhead and salmon fish populations in the North Santiam River, the primary source of Salem’s drinking water.

According to the city’s complaint, the Army Corps failed for years to facilitate fish passage, and was ordered by a federal judge in 2021 to come up with a plan.

The corps then proposed the deep drawdown of the reservoir as a solution.

The city said in its complaint that the increase in sediment as a result of the drawdown “will cause irreparable harm to the city of Salem’s drinking water treatment system, which relies on slow sand filtration and is designed to treat raw water with very low turbidity levels.”

The city said a stretch of high turbidity in the river would ultimately cause “complete failure and shutdown of the filtration system, resulting in the inability to produce any safe drinking water.”

The city’s complaint said the Army Corps did not submit a report to Congress analyzing the impacts of increased turbidity in prior drawdowns and detailing lessons learned, which was due by Jan. 4, 2026.

The city argued that the drawdown should be postponed until its comments and concerns are considered.

The lawsuit also claimed that because turbidity levels in past drawdowns exceeded limits set by the state of Oregon, fall’s drawdown is likely to violate state law. City leaders said it should be postponed until the corps proposes a drawdown which would yield lower turbidity levels.

In its complaint, the city asked a federal judge to halt the drawdown until the federal agency complies with the laws “to ensure the protection of the city of Salem’s water supply and consequently the health, safety and welfare of the community depending on it.”

The lawsuit comes after more than a year of back and forth between the city and the Army Corps on how to minimize impacts to Salem’s water system.

The lawsuit said the Army Corps failed to consider the city’s input.

“(Salem’s) comments identified specific turbidity risks that will impact thousands of people, as well as the operational safeguards necessary to protect the city’s drinking water treatment system for a reliable delivery of safe drinking water to the region,” the lawsuit said.

Late last year, the corps said it planned to do a more gradual drawdown of the reservoir over several years to reduce the downstream impact on communities that rely on the North Santiam River for drinking water.

In March, the agency announced the drawdown would take less time than previously expected and that the lake would be at a lower level for two weeks near the end of this year, reducing the amount of time the city of Salem would need to rely on backup drinking water resources should the drawdown disrupt the system.

Those resources include groundwater wells on Geren Island, an aquifer storage and recovery facility in south Salem, and the ability to tap into the city of Keizer’s water supply.

“The city anticipates these sources will meet the expected water demand during the initial drawdown and recovery period planned by the corps for this fall,” a city statement on Wednesday said.

The lawsuit also demanded the federal government invest in a solution to help facilitate young salmon migration and to establish a threshold that would stop or pause the drawdown should sediment reach levels capable of overwhelming the city’s filtration system.

According to the release, the city and the Army Corps have corresponded for more than a year about measures designed to keep the city’s drinking water intact. The city had pushed for safeguards to be set that would trigger a pause or a stop to the drawdown should the city’s sand filtration fans be overwhelmed by a sudden increase in sediment.

The Marion County Board of Commissioners voiced their support for the city’s lawsuit in a Wednesday statement.

Marion County sued the corps over the drawdown, in May, arguing the agency is required to complete a report on past drawdown efforts and how those affected other communities. The county demanded the drawdown pause until the report is done.

The county said both lawsuits hit on similar points seeking to protect the community’s drinking water by asking a federal court to pause the drawdown efforts until the mandated turbidity study is done.

“We welcome the city of Salem joining the county in fighting to protect the drinking water of our communities. Clean, reliable drinking water should never be thoughtlessly put at risk anywhere in the county,” the commissioners’ joint statement said.

This story was originally published by Salem Reporter, a news outlet that focuses exclusively on reporting about the Salem area. The Salem Reporter provides clear and compelling coverage of local government, insights into the people who hold power in the Salem community and daily news about everything from community events to students making a difference.