The Byron Nuclear Generating Station is a nuclear power plant located in Ogle County, Illinois, east of the Rock River. The reactor buildings were constructed by Commonwealth Edison and house two Westinghouse Four-Loop pressurized water reactors, Unit 1 and Unit 2, which began operation in September 1985 and August 1987 respectively. The plant is owned and operated by Constellation Energy. The plant provides electricity to northern Illinois and the city of Chicago. In 2005 it generated on average about 2,450 MWe, enough power to supply about 2 million average American homes. The station employs over 600 people, mostly from Ogle and Winnebago counties, and features two prominent cooling towers. The Byron plant has been subject to some controversy with respect to a lawsuit in 1981 with concerns over tritium contamination in groundwater. Tritium contamination at Byron and other Illinois nuclear power plants led the state of Illinois to pass legislation requiring plants to report such contamination to the state within 24 hours. History Construction on Byron Nuclear Generating Station began in 1975, at a 1,782-acre (7.2 km) site, 17 miles (27 km) southwest of Rockford, Illinois, south of the city of Byron in Ogle County. The firm of Sargent & Lundy acted as consulting engineer during construction and Babcock & Wilcox oversaw the completion of the reactor vessels. Before construction was completed on the reactor vessels and facilities, at least three groups joined in a 1981 lawsuit to halt Byron Nuclear Generating Station's completion. The League of Women Voters, DeKalb Area Alliance for Responsible Energy, and others were involved in the lawsuit over the safety of and need for the plant. In 1984 the Atomic Safety and Licensing Board, a division of the U.S. Nuclear Regulatory Commission (NRC), stopped the planned nuclear station at Byron by refusing its owners, then Commonwealth Edison, permission to begin operation. The decision stemmed from concerns about the quality control of independent contractors hired during construction. Ultimately, the board overturned its decision in October 1984 and permission was granted to operate after a re-inspection of over 200,000 items and components within the plant. Byron Station consists of two pressurized water reactors, termed Byron Unit One and Byron Unit Two, and the surrounding grounds and facilities. Byron Unit One received its operating license from the NRC on February 14, 1985 and Unit Two received its license on January 30, 1987. On September 16, 1985, Unit One