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South St. Paul is seeking financial help to build a water treatment plant to deal with high levels of radium, a naturally occurring carcinogen, in one of the city's wells.

Water from the well with high radium — Well 3 — has been diluted and used only on a limited basis since 2019 when the city discovered its levels were about one and a half times what the Environmental Protection Agency and the Minnesota Department of Health allow, said Pat Dunn, South St. Paul public works director.

"Obviously, anytime there are contaminants in water it's a concern," said Sue Polka, South St. Paul city engineer. "It's one of our better producing wells."

The solution, city officials say, is a water treatment plant, which the suburb does not have. It could cost $8.6 million to $10.1 million, and the city is seeking state bonding money and maybe federal funds to help pay for it.

A water treatment plant could remove manganese and iron as well as radium, Polka said. (Manganese and iron primarily are aesthetic concerns.)

Karla Peterson, supervisor for the Minnesota Department of Health's community public water supply unit, said radium is "in our deepest aquifers."

It can be found in wells in the upper Midwest and throughout eastern and southeastern Minnesota, mostly in city wells that use the Mount Simon-Hinckley aquifer, Peterson said, though South St. Paul uses two other aquifers.

"It's primarily a municipal water concern [rather than a private well concern]," she said.

South St. Paul, which has eight wells, studied whether blending the contaminated water with water from other city wells would dilute the radium to safe levels.

The blending method works, officials found. But Dunn said the Department of Health allows the city to use only a certain volume of blended water each year — an amount that doesn't meet demand.

In Minnesota, cities that have had to address radium in their wells include Lakeville, Red Wing and Winona, Peterson said.

Winona and Lakeville use existing water-treatment plants to remove radium while Red Wing built a plant to address it, she said.

Many Minnesotans have home water softeners, which not only remove calcium, or hardness, but radium as well.

"That really minimizes the population … that's potentially affected," she said.

Drinking water with radium in it for short periods is "a minimal health risk" but drinking it at concentrations above 5.4 picocuries per liter over a long time increases a person's cancer risk, she said. South St. Paul's Well 3 is at 8.4 picocuries per liter.

"With radium, it acts a lot like calcium where it resides in your bones and accumulates over time," she said.

South St. Paul has asked for nearly $6 million in state bonding that would go toward a larger $12 million utility rehabilitation project that includes the water treatment plant, said City Administrator Joel Hanson.

The request was not part of Gov. Tim Walz's recently unveiled bonding proposal.

City officials also may try to secure funding from the federal infrastructure bill but are uncertain on "how that program is going to work," Hanson said.

He said not using Well 3 puts more pressure on the two other primary wells for the city.

"We need that well to be in service," Hanson said.