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Over half of wastewater treatment plants in Idaho violated Clean Water Act permits in 2022

An aerial view of the wastewater treatment plant in Driggs, Idaho. Two ponds with a grid of agitators in each, with three buildings and a solar power array nearby.
City of Driggs
An aerial view of the city of Driggs' wastewater treatment plant, which opened in 2013. The City is being sued by the EPA over on-going violations of the plant's clean water act discharge permits.

An annual report compiled by the Idaho Conservation League shows that while some facilities have improved from past years, over half of Idaho’s wastewater treatment plants had at least one violation of the Clean Water Act in 2022.

Just 11 facilities were responsible for more than half the 520 violations in Idaho last year. They ranged from excess discharge of phosphorus and nitrogen, or ammonia, to depleted oxygen levels or suspended solids making the water cloudier than it should be.

What wastewater treatment plants release back into Idaho waterways is regulated and permitted by the Environmental Protection Agency or the state Department of Environmental Quality. ICL’s report looks at what those permits allow versus what the 119 wastewater plants sample and report. Permits may vary from one plant to another.

ICL has published the summary each year since 2017.

“That would only be concerning to me if we weren't already aware of those issues,” explained DEQ Surface and Wastewater Division Manager Mary Anne Nelson. DEQ enforces violations of discharge permits.

“Generally speaking, I think our wastewater treatment plants are performing well. There definitely are some that have issues,” Nelson said.

Facilities in Jerome, Kuna, Parma and Nez Perce had more violations or greater excess discharge levels compared to most in the state. Kuna’s “north” treatment plant had high levels of ammonia released into Indian Creek during three months in early 2022. That followed a change in how the waste was being treated.

“They have a membrane bioreactor,” Nelson explained. “We have been working with them on making sure that they operate that correctly. Sometimes when you have new things that come online, you're working out bugs and working out quirks.”

She said that same facility has had additional violations since, but expects current issues to be resolved by the end of this year.

Driggs treatment plant in east Idaho has a long history of violations going back to when it first opened in 2013. Last year, the EPA sued and Nelson said federal regulators are working with that facility.

Driggs had the most individual violations of any wastewater plant in Idaho in 2022.

Jerome’s treatment plant had the highest total discharge volume beyond permitted levels in 2022, most of which came in the first two months of the year. Nelson was unable to share more about issues at that plant due to what she called an on-going investigation by DEQ.

Violations of the Clean Water Act are punishable through court action by fines of up to $51,570 per violation per day. Idaho Conservation League spokeswoman Abby Urbanek said the group doesn’t have any plans to bring legal action against any operators currently, but would be following up to ensure improvements are being made at the most problematic treatment plants.

Nelson said DEQ has multiple levels of enforcement action, from informal to formal.

“If the facility has made us aware of things, [if] they are working with us and accepting the assistance, we're definitely going to be more likely to take those informal enforcement actions,” she said.

Financial penalties, as the biggest hammer, can be especially hard on smaller municipalities and potentially take away from funding which could otherwise be used to fix problems.

Only one facility has been fined for 2022 discharge violations, according to ICL’s summary: Twin Falls. Fines for other violations could still be in the works.

While the report noted significant and/or on-going issues at some wastewater sites, it also commended operators which have reduced violations; Blackfoot, Weiser, Marsing, Firth, Kendrick and Tensed all moved from ICL’s "worst violators" list in 2021 to having few or no violations last year at all.

Overall, 43% of treatment plants in Idaho had no violations last year, and most serving the state’s largest population centers had fewer than a handful each.

Troy Oppie is a reporter and local host of 'All Things Considered' for Boise State Public Radio News.

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