Federal regulators have finished their investigation into tritium leaks at a Will County nuclear power plant. The Nuclear Regulatory Commission issued a mild rebuke to Exelon, the operator of the Braidwood Nuclear Power Station. It found the Braidwood plant leaked the radioactive chemical tritium 22 times over the past nine years.

The agency won’t impose fines, but it has asked Exelon to monitor and document how tritium’s getting off site. The NRC is not responsible for regulating tritium that flowed off company property. That falls to the state of Illinois, which filed suit against the company.

The Illinois Attorney General claims Exelon contaminated state groundwater. Tritium also turned up in one private well, though the contamination level was below federal safety limits. Several homeowners near the Braidwood plant are also suing Exelon. They worry the leaks could damage their property values.