BELOIT - A City of Beloit water supply well has been off line since October due to amounts of radium in the well that exceeded the maximum contaminate level approved by the U.S. Environmental Protection Agency (EPA), according to a notice sent to residents.
Water samples sent by the city to the Wisconsin Department of Natural Resources (WDNR) as part of quarterly testing were flagged for containing radium levels that are a violation of state and federal safe drinking water standards, according to a notice sent to an effected resident and obtained by the Beloit Daily News.
According to the city, the detection was based on an annual average, November 2018 through September 2019, which resulted in a detection above maximum contaminant levels.
Beloit Strategic Communications Director Sarah Millard said the city was not notified of the radium in the well until the last quarterly test from Sept. 18. Radium is a naturally-occurring radioactive element contained in rock formations, of which two forms of radium can most likely be transferred from the rock into Wisconsin drinking water.
According to the EPA, the established maximum level for radium in public water supply is five picocuries per liter (pCI/L). The curie is a standard measurement for the intensity of radioactivity contained in a sample of radioactive material and a picocurie is one trillionth of a curie.
The elevated test results occurred in one of the city's eight wells, and water service is not expected to be interrupted due to the well closure, Millard said.
"We could have continued to operate the well, but we took it off line right away to be proactive," Millard said.
The city was not required by WDNR to shut down the well exceeding the combined radium levels and the well could have remained in service, according to a Nov. 6 City of Beloit Public Works notice published on the city's website.
On Nov. 12 a notice was sent by Illinois American Water, the company that services South Beloit residents and buys water from the City of Beloit, informing customers of the issue.
According to the National Academy of Sciences, long-term exposure to elevated levels of radium in drinking water may result in an increased risk of cancer. When ingested into the body from drinking water, radium can accumulate in the bones. Radium naturally occurs in some of Wisconsin's groundwater over time after dissolving out of rock and into the water supply.
According to the city notice, the water resources division for Beloit does not plan to return the well to service until mitigation efforts are put in place. The WDNR and Wisconsin Public Service Commission will review and approve the mitigation plan before the city can proceed forward, according to the notice.
Those mitigation efforts could include blending the high radium water with water from sources containing lower levels of radium to dilute the radium; find an alternative water supply or construct a new well into a low-radium aquifer; soften or apply another effective radium removal treatment technique to the city's water supply, the notice said.