The 55-acre former municipal solid waste landfill located at 4100 West Frontage Road, Hillside, Illinois, commonly known as the Congress Landfill or the Hillside Landfill is owned by Congress Development Company and has been operated by Allied Waste Transportation, Inc. since 2007. During the history of the landfill, odor complaints have been common. In 2005, there was a significant increase in the frequency and strength of odors impacting residents surrounding the landfill and a resulting increase in odor complaints to the Illinois Environmental Protection Agency. In 2006, landfill gas was found to be migrating offsite potentially causing hazardous conditions in nearby buildings. The Illinois EPA and the Illinois Attorney General’s Office took action at that time forcing the landfill to address problems that were immediately dangerous offsite, including requiring monitors in basements for the detection of landfill gas. Since 2006, there have been continuing odors, high landfill gas readings and other incidents including a leachate release in 2009, although actions taken by the landfill to address these issues have greatly reduced the strength and frequency of these issues.