The discovery of trace levels of a new contaminant in New Brighton's drinking water has prompted the city to draw its water from deeper wells while the Army determines how to fix the problem.

Chemicals used at the former Twin Cities Army Ammunition Plant (TCAAP) in Arden Hills are the probable source of the contaminant, officials said Friday.

City Manager Dean Lotter stressed that the amount of the chemical — 1,4-dioxane — found in the city's wells is so minute that residents would need to drink two liters a day for 70 years to have a heightened health risk. Still, he said, "We take any risk seriously and have developed an interim solution, as well as a long-term solution."

The Minnesota Department of Health began testing for the chemical last fall, Lotter said, and notified the city of its presence in February. Testing conducted by health officials found dioxane levels ranging from 2.9 parts per billion to 5.5 parts per billion. There are no enforceable state or federal regulations regarding dioxane in drinking water, Lotter said. But state officials have set an advisory limit of 1 part per billion.

Lotter said standards in other states, such as New York, allow for higher concentrations of the chemical.

In a letter sent to New Brighton residents Friday, Lotter said "the city has already taken steps to remove the risk by using wells in a deeper aquifer that have been confirmed to be dioxane-free. The city will continue to use these dioxane-free wells until a proven treatment technology, funded by the Army, is in place to remove dioxane from wells where it has been detected."

There will be no cost to New Brighton residents, he said.

The Army will include dioxane cleanup as part of its ongoing agreement to pay New Brighton's costs for operating its water treatment facility for the next 30 years. As part of that January agreement, the federal government will pay at least $59.4 million over that time.

Ramsey County officials said the presumed source of the contamination is not on the 427-acre Rice Creek Commons site, which the county is working to develop, but is located within the part of TCAAP that houses the Arden Hills Army Training Site.

"Public health and safety are of the utmost importance to Ramsey County, and we stand with the City of New Brighton and nearby local governments as they implement both immediate and permanent solutions to protect public health and the environment," Ramsey County Deputy Manager Heather Worthington said in a statement.

"Ramsey County is working closely with the MPCA and the U.S. Environmental Protection Agency to test for 1,4-dioxane in the soil at Rice Creek Commons. We do not expect to find the compound in the soil in amounts exceeding the MPCA's threshold because the compound does not readily persist in soil."

If dioxane is found on the county's property, she said, it would be cleaned up to meet residential standards.

New Brighton will present information about dioxane at a May 2 open house at the city's community center. Representatives of the Minnesota Department of Health, the Minnesota Pollution Control Agency and the Army will attend. The city also is posting information about the chemical on its website: www.ci.new-brighton.mn.us.