Madison County, Illinois: drinking water report. Madison County in southwestern Illinois has about 264,000 residents in communities including Edwardsville,…
Madison County in southwestern Illinois has about 264,000 residents in communities including Edwardsville, Alton, and Granite City. Water comes from the Mississippi River and the American Bottoms aquifer, with Illinois American Water serving the largest share of the population. The county sits across the river from St. Louis and includes some of the heaviest industrial activity in the Metro East.
Granite City's steel industry and the Wood River oil refinery complex left industrial contamination across the American Bottoms floodplain. According to Illinois EPA's 2024 site assessment database, the county has over 50 properties with confirmed soil or groundwater contamination from petroleum, heavy metals, and chlorinated solvents. The American Bottoms aquifer, which sits in the Mississippi River floodplain, is vulnerable to contamination from these surface sources.
The St. Louis Lambert International Airport across the river and Scott Air Force Base in neighboring St. Clair County both contribute PFAS to the regional environment. Illinois EPA's 2024 investigation found PFAS at 12 ppt in monitoring wells in the southern part of Madison County, likely influenced by Scott AFB's documented AFFF contamination.
Madison County's industrial legacy is concentrated in the American Bottoms communities along the river. If you are on a private well in the floodplain, testing for VOCs and metals is important given the density of contamination sites.
Check your water for data at your location. For the industrial mix found in this area, reverse osmosis provides the broadest household protection. Our water filter guide covers systems suited to industrial-area water. Pull your detailed report for local data, and visit our Illinois page for statewide context.