CHICAGO SANITARY AND SHIP CANAL, in the United States, is an engineering development of special importance to the city of Chicago and surrounding districts. It was first opened in 1900 and the cost of construction with improvements has been about $70,000,000. Before the construction of the canal Chicago discharged sewerage into Lake Michigan, which was also the source of the water-supply. Such serious contamination re sulted that ultimately the extension of water intake pipes for a distance of 8 m. out into Lake Michigan failed to avoid dangerous pollution.
A few miles west of the city, a low limestone ridge marks the division of the watersheds leading to the Des Plaines and Chicago rivers. The Des Plaines, to the west of the ridge, flows south west to the Illinois river and thence to the Mississippi river. The Chicago river, to the east of the ridge, normally drains into Lake Michigan. A canal channel was dug through the ridge by which the Chicago was connected with the Des Plaines river and at the same time the flow in the Chicago river was reversed from east to west. The refuse of the city is collected in great central city mains and turned into the canal and carried down to the Gulf of Mexico. The canal is 34 m. long, 26o ft. wide and 22 ft. in depth. In 1920 more than 9,00o cu.ft. per second was being drawn from Lake Michigan to carry away the sewerage of Chicago and be cause of the tremendous growth of the city still greater require ments were anticipated. Another phase of the project, in 1928 undeveloped, was the creation of an all-water route between the Great Lakes and the Gulf of Mexico.