CHICAGO (AP) — Illinois is framed and bisected by water, including the mighty Mississippi and a 60-mile slice of Lake Michigan shoreline that is a gateway to the biggest source of fresh water on the planet. Yet the problems that strain drinking water systems in other parts of the U.S. also threaten Illinois. A 2011 estimate by the U.S. Environmental Protection Agency calculated that Illinois would need a staggering $18.9 billion over 20 years to ensure the system can continue to provide safe drinking water. The vast majority of that is for replacement of pipes that distribute water, which are around a century old in many parts of the state. Illinois receives the fourth largest allotment of federal aid for drinking water infrastructure. It totaled $667 million from 2011 to 2015.