A unique solution to Chicago's water pollution: tunnels and reservoirs

For more than 125 years Chicago has been diverting water from Lake Michigan to serve its domestic/industrial water needs, to dilute the city’s polluted waters, and to enable navigation to Chicago from the Illinois River system.These diversions created a series of controversies with other lake states and seven of these controversies have gone to the U.S. Supreme Court.The city of Chicago has faced serious water pollution problems since the 1870s and made adjustments to use lake waters to move its polluted waters down the Illi-nois River.Heavy rains brought in-city flooding and to relieve the flooding,polluted waters were often released into Lake Michigan, an undesirable act since the lake is the city’s source of water.In the 1960s the city proposed a costly solution, construction of 110 miles of large water storage tunnels under the city.This unique tunnel and reservoir project (TARP) has been built largely with federal funding, and has been found to handle most rainstorms except forinfrequent storms having multi-hour rainfall amounts in the 100-year category.In summary, TARP has been found to be a very valuable system for reducing urban flooding and the spread of pollution into the lake or down the Illinois River. It addresses the hydrology and water quality of a large region.Now the Asian Carp is causing a new controversy affecting the diversion and water treatment.