Recent groundwater testing revealed that a chemical from the former Twin Cities Army Ammunition Plant in Arden Hills is present in the Prairie du Chien aquifer.
One city in particular, New Brighton, faces the highest risk. However, city and Ramsey County officials said Friday that 1,4-dioxane (also referred to as dioxane) levels are low in New Brighton's drinking water and don't pose a health risk.
Exposure to dioxane causes irritation of the eyes, nose, throat and lungs in humans, according to the U.S. Environmental Protection Agency. Dioxane can be found in the industrial solvent Trichloroethylene (TCE).
Since 1988, the Army has been paying for a special filtration system to ensure New Brighton's water supply is free from TCE and safe to drink. A plume of groundwater was contaminated with the chemical from the old Army ammunition plant.
New Brighton city manager Dean Lotter said the city tests for dioxane on a monthly basis. In February, it found between 2.9 parts per billion to 5.5 parts per billion in wells that pump from the Prairie du Chien aquifer.
"We've turned off all the wells that have tested positive for dioxane," he said, "and we've turned up the wells that have tested to be free of dioxane."
Dioxane is on a list of emerging contaminants departments of health across the country are watching out for.
Minnesota set its acceptable dioxane levels at a conservative 1 part per billion, while other states like New York go as high as 50, Lotter said.
New Brighton provides water to Fridley. The city closed its connection between the two communities to make sure contamination doesn't spread.
New Brighton is taking short-term actions to address the contamination. It's pumping from a deeper aquifer, the Mount Simon-Hinckley, but a major treatment plant is necessary to reach low Minnesota standards in the long run.
"Once we have that constructed we will then be able to take the dioxane out of the water," Lotter said. "But it takes a while to study it, then you have to design it, you have to engineer it, you have to bid, it you have to build it, and then you have to test it once it's built."
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