Three south metro cities are making expensive changes to deal with elevated radium in their water supply after receiving notice that their levels are above what the state and federal government allow.

In South St. Paul, Savage and Inver Grove Heights, city officials are using different strategies to reduce levels of the naturally occurring carcinogen, from building a new water treatment plant to buying more water from a neighboring city.

"We tend to find [radium] in the deepest and oldest aquifers in Minnesota," said Karla Peterson, supervisor of the Minnesota Department of Health's (MDH) community public water supply unit, adding that those include the Mount Simon and Jordan aquifers.

In Minnesota, radium can be found in bedrock as far northeast as Hinckley and as far southwest as Carver County, she said, and in the water supply of some cities along the Wisconsin border, like Winona. The "maximum contaminant level" is 5.4 picoCuries (pCi) per liter and water above that level requires treatment; a picoCurie is a measure of radioactivity. According to the Department of Health, everyone is exposed to radiation in daily life. But a person has a higher risk of getting cancer if they drink water with radium in it every day for many years.

Peterson said when the U.S. Environmental Protection Agency initially set allowable radium levels in 2000, most cities with violations were identifying radium in their water supply for the first time.

"As time has gone on ... aging infrastructure has been the primary reason for exceedances," she said, adding that filters and other equipment needs replacement every 20 years or so.

Between 2020 and 2023, about 10 public water systems per year in Minnesota have received violations for too-high radium levels, according to Department of Health data. Almost all are in small cities outside the metro. Rural cities have different challenges — both financial and managerial — to comply with state requirements than a metro-area city may have, Peterson said.

Inver Grove Heights and Savage were the only metro cities to see violations since 2020. Elevated radium levels were also found in the water system at Skyline Village, a manufactured home community in Inver Grove Heights, in 2021, 2022 and 2023.

Brian Connolly, Inver Grove Heights' public works director, said Skyline Village plans to eventually hook up to city water. Molly Boyle, RHP Properties spokesperson, confirmed those plans.

South St. Paul

South St. Paul received a violation notice that its Well 3 had high radium levels in 2019 and began blending that water with water from other wells to reduce levels. In November 2023, the city began building an $8.5 million water treatment plant — they didn't have one previously — using a low-interest loan from the state's Drinking Water Revolving Fund.

"The only way to really address it long term is by building a plant that can specifically address radium and other contaminants," said Nick Guilliams, South St. Paul's city engineer.

The new plant will also treat water for other chemicals, like manganese and iron.


Savage got notice this year that two 2023 tests showed higher-than-allowed radium levels in one of its two water treatment plants. The city typically buys about 60% to 85% of its water from Burnsville and gets the rest from a total of eight wells, said Seng Thongvanh, the city engineer and utilities director.

Since the violation, the city has purchased all of its water from Burnsville, Thongvanh said.

"The city's committed to providing that safe, plentiful drinking water," he said, adding that Savage has multiple water sources.

Savage is waiting for the most recent radium tests — done both by the state and an independent lab hired by the city — to come back. If levels are still high at the treatment plant, the city could speed up the timeline for rehabilitating the plant, which had been scheduled for 2027. Thongvanh said the city also has other short-term strategies to improve water quality.

Inver Grove Heights

Inver Grove Heights received notice that its radium levels were high in 2023 and has since been using more water from its wells that don't have high radium.

The city also performed some "minor chemical adjustments" to pull out more radium and get the water under the required threshold, Connolly said. Long term, Inver Grove Heights will replace filters and make other upgrades to its treatment plant, which is more than 25 years old.

The project is currently out for bid and updates will likely cost just over $5 million; the City Council hasn't finalized its approval yet but the city will probably take out a low-interest loan from the state and use some American Rescue Plan Act money.

Testing questions

Savage and Inver Grove Heights officials said they had questions about the state's radium testing, including why the state's tests showed higher radium levels than those conducted by the outside labs each city paid to do testing.

"The response I got back from MDH was there's just variation in those results," Thongvanh said. "We had to just accept it, I guess, in terms of what it is."

Connolly said Inver Grove Heights' tests have shown lower radium levels, and the state hasn't been able to explain the discrepancy. The two most recent MDH tests done through a third-party lab were closer to the city's results, adding to the confusion.

MDH "has been pretty tight-lipped about it," he said, adding that the city has "struggled working with them over the past year."

Peterson said that cities often ask questions about the state's testing, and the agency has developed a new fact sheet to better explain things.

Different testing methods equal different results, she said, and radioactivity is a difficult thing to measure. While testing for other contaminants has an "allowable variability" of 10%, for radium it's much higher, at 30%.

"There's very likely going to be a difference but it's an allowable difference," she said.

Peterson recommends cities do "baseline, side-by-side monitoring" instead of comparing tests from different labs.

The state never issues a violation based on one test result with high radium, instead averaging out four consecutive quarterly tests to determine if levels are elevated, she said.