Elevated radium levels found in Inver Grove Heights water supply

Inver Grove Heights is taking steps to address elevated levels of radium — a carcinogen — that were recently discovered in the city's water supply.

On Jan. 30, the city learned its water had radium levels above the state's allowable levels. The "maximum contaminant level" is 5.4 picoCuries per liter; a picoCurie is a measurement of radioactivity. The city's water tested at 6.0 picoCuries per liter in October 2022, according to the Minnesota Department of Health.

"That test tipped us over the threshold," said Kris Wilson, Inver Grove Heights' city administrator.

On Tuesday, city officials held a community meeting about the radium levels. Several dozen residents attended. The city also sent a notice to the 7,800 households with city water.

"Radium is naturally occurring," Wilson said. "We've always had radium in the groundwater."

Wilson said officials don't believe there's actually more radium in the city's water lately. Instead, aging filters at the water treatment plant are likely not as effective at removing it.

While the heightened levels have residents concerned, the city's water is safe to drink and the situation isn't an emergency. That message was shared at Tuesday's meeting, she said.

Brian Connolly, the city's public works director, said the city has short and long-term plans to address the issue. The city hired a chemist within a week of notification of the high radium levels. The chemist assessed the city's water system and recommended ways to modify the chemical treatment process to address the radium.

To remove it, the city puts chemicals in the water that bind with the radium to form a solid. That solid is then filtered out.

The city now does in-house tests daily to ensure the chemicals are working, he said.

The Department of Health's latest radium test will be available at the end of March, Connolly said. The state is testing the water quarterly now and it will take at least two more tests to bring the city into compliance.

Long term, the city will replace the sand water filters at its water treatment plant, Connolly said. Work will begin late in 2023, with completion planned for spring of 2024.

Karla Peterson, the Department of Health supervisor for the community water supply unit, said radium can be found across one-third of Minnesota and throughout the upper Midwest in the deepest aquifers.

A person must drink water with elevated radium levels consistently over a long period for there to be a cancer risk, she said.

Water systems are tested for radium either every year or every three years, depending on the system's quality, she said.

Between 3 and 6 water systems in Minnesota typically have radium violations each year, she said.

"Most systems can solve it pretty quickly" through short-term fixes at the treatment plant, she said.

Peterson said she's "feeling pretty positive" that Inver Grove Heights' latest water sample will test below allowable radium levels when it comes back later this month.