The leak was confirmed in November 2022 but revealed this week.
Minnesota agencies announced this week they are monitoring the cleanup of about 400,000 gallons of radioactive water that leaked from a nuclear generating plant near Minneapolis this past fall.
The leak at the Xcel Energy plant in Monticello was not revealed to the public until now because it "poses no health and safety risk to the local community or the environment," according to the Minneapolis-based utility company.
"We have taken comprehensive measures to address this situation on-site at the plant," Chris Clark, president of Xcel Energy-Minnesota, North Dakota and South Dakota, said in a statement Thursday. "While this leak does not pose a risk to the public or the environment, we take this very seriously and are working to safely address the situation."
The leak was detected by routine groundwater monitoring systems and confirmed on Nov. 22, 2022, according to Xcel Energy, which said it notified the state and the U.S. Nuclear Regulatory Commission that day.
The Minnesota Pollution Control Agency, the Minnesota Department of Health and the Minnesota Department of Natural Resources are monitoring the cleanup at the plant, which located is along the Mississippi River, about 40 miles northwest of Minneapolis.
"The leak has been stopped and has not reached the Mississippi River or contaminated drinking water sources," the Minnesota Pollution Control Agency said in a statement Thursday. "There is no evidence at this time to indicate a risk to any drinking water wells in the vicinity of the plant."
Xcel Energy said the leaked water contains levels of tritium -- a byproduct of the production of electricity by nuclear power plants that emits low levels of radiation -- that are below Nuclear Regulatory Commission safety thresholds. The company said it has been pumping, storing and processing the water for reuse and has so far recovered about 25% of the tritium released.
Ongoing monitoring from more than two dozen wells has determined the leaked water is "fully contained on-site" and has not been detected in any local drinking water, Xcel Energy said.
"We continue to gather and treat all potentially affected water while regularly monitoring nearby groundwater sources," Clark said. "We will continue to partner with local groundwater specialists, and we remain in close cooperation with state and federal regulators and our local community throughout the remediation effort."
State agencies are also reviewing data, including the well-sampling results, while monitoring the cleanup, the Minnesota Pollution Control Agency said.
"Our top priority is protecting residents and the environment," Kirk Koudelka, Minnesota Pollution Control Agency's assistant commissioner for land and strategic initiatives, said in a statement. "We are working to ensure this cleanup is concluded as thoroughly as possible with minimal or no risk to drinking water supplies."
The leak occurred in a water pipe that runs between two buildings. Water is being diverted to an in-plant water treatment system to prevent water from leaving the plant until a permanent solution can be installed this spring, Xcel Energy said. An inspection found no other leaks, according to the company, which added it will examine the pipe that leaked "to better understand why this happened."
When tritium-contaminated water leaks occur, they are usually contained to the power plant property or "involve such low offsite levels of tritium that they do not affect public health and safety," the Nuclear Regulatory Commission said.