Geology, hydrology, and water quality of the Cambrian and Ordovician systems in northern Illinois
Cambrian and Ordovician strata provide much of the groundwater supplyfor approximately 250 municipalities and 150 industries in the northern halfof Illinois. This report represents the cooperative effort of the IllinoisState Water Survey, Illinois State Geological Survey, and U.S. GeologicalSurvey to provide a current hydrogeologic evaluation of this water resource.