the contamination even further. The building materials from the Luminuous Processes building were eventually turned into landfill. The U.S. Environmental Protection Agency began removing contaminated material in 1986. The work continues. Areas still affected by radiation Sixteen areas of Ottawa are still radioactive. The United States Department of Health and Human Services released a study, outlining areas where contamination by radium-226 (Ra-226), as well as emissions of radon-222 (Rn-222), are at or above normal levels. These areas include homes, public areas, schools, and even a car sales lot that is housed directly over the old Radium Dial Company site. A score of 28.5/100 or higher qualifies an area for the Superfund National Priority List, and Ottawa's hazardous ranking score is 50/100. The radium in Ottawa's water supply occurs naturally in water from deep wells across northern Illinois. A reverse osmosis water treatment plant removes the radium so the city's tap water complies with federal regulations. Notable people See also Fisher–Nash–Griggs House Knuessl Building Marquette Academy Andrew J. O'Conor III House Ottawa Commercial Historic District Ottawa East Side Historic District Ottawa Station (Rock Island Line) Ottawa Township High School Starved Rock Jeremiah Strawn House Summit View Cemetery References External links Reddick Public Library Ottawa Visitors Center, Ottawa, Illinois 1853 establishments in Illinois Cities in Illinois Cities in LaSalle County, Illinois County seats in Illinois Ottawa, IL Micropolitan Statistical Area Populated places established in 1853 Populated places on the Underground Railroad