In 2000. Mason City, Iowa, began planning an upgrade of its water treatment system in order to meet the regulations established by the U.S. Environmental Protection Agency's Final Radionuclide Rule. Until the new standard became effective on Dec. 8, 2003, the city's treatment for drinking water had consisted of aeration, chlorination, and fluoridation. In order to lower the concentration of radium in their raw water to meet the levels set by the new regulation, Mason City replaced this system as part of an $18 million water project.