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Drinking Water Supply |
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Early settlers first drew water from the Chicago River, but as it became polluted, they turned to the lake shore or shallow wells. The settlers either carried water home in buckets or bought it from peddlers who sold the water from horse-drawn wagons. Chicago's first water system, privately owned, cost $24,000
and began operating in 1842. Lake water was pumped to an elevated wooden tank from which
it flowed by gravity through wooden pipes laid under the streets. This water system soon
became inadequate for the fast growing City so a new water works, municipally owned, was
built and placed into operation in 1854. A new pumping station at Chicago Avenue had a
steam-driven walking-beam type pump known as "Old Sally" and furnished 8 million
gallons of water per day through new cast iron mains. The old Water Tower that stands at Michigan and Chicago Avenue was erected in 1869 and withstood the Chicago Fire of 1871. Originally, it housed a 138 foot high standpipe, 3 feet in diameter, that served to equalize the pressure and minimize the pulsations of the water flowing in the mains. In 1969, the year of its centennial anniversary, the Tower was nationally recognized as the First American Water Landmark, and, in 1972, the Chicago Landmarks Commission designated the Chicago Water Tower and the Chicago Avenue Pumping Station as City landmarks. Today, Chicago's water system supplies an average of more than one billion gallons of water a day to over 5,050,000 people. This system supplies filtered water to an area of 836 square miles for domestic, commercial and industrial use and fire protection. The Chicago metropolitan area is fortunate in being located on one of the world's finest sources of fresh water, Lake Michigan. The water's journey from Lake Michigan begins either at the intake cribs or the shore intakes of the water purification plants. The four active or standby intake cribs are located in the Lake, two miles off shore in water 32 to 35 feet deep. Cribs in service are monitored around the clock, throughout the year. Lake water enters the crib through ports near the bottom of the crib, rises around the outside of the central shaft and flows through upper openings in the central shaft and down the shaft to large supply tunnels located from 75 to 200 feet below the surface of the Lake. These horseshoe and circular shaped water tunnels vary in size from 10 to 20 feet in height and have a concrete liner to reduce friction. In the early days, tunnels were built in clay and were brick-lined; but since 1910, they have been constructed in rock. The water flows by gravity through these tunnels to large pumps at the purification plants. The pumps raise the water to a height of some 20 feet above the Lake level to a point where it flows by gravity through the purification plant. It flows first through the chemical application channels, then through the coagulation and settling basins and finally through into the reservoirs. It takes the water eight hours to pass through the purification plant. In the treatment process, the chemicals applied to the water are: chlorine for sterilization, aluminum sulfate or alum and polymer for coagulation to settle out impurities, lime and caustic soda to prevent corrosion of the distribution mains, activated carbon to remove taste and odors, and fluoride to prevent dental cavities in children's teeth. The safe pure water then flows by gravity from the storage reservoirs through three large underground tunnel systems to twelve pumping stations strategically located throughout the City. Three pumping stations serve the North area of the City: Lake View, Thomas Jefferson and Mayfair Pumping Stations. Four serve the Central area: Chicago Avenue, Cermak, Springfield Avenue and Central Park Avenue and four serve the South and Southwest area: 68th Street, Roseland, Western Avenue and the Southwest Pumping Stations. The Lexington Avenue pumping station provides service to DuPage County. Large pumps at the pumping stations pump the water from the supply tunnels to the distribution mains at 30 to 60 pounds per square inch pressure. The homes, apartment buildings, stores, factories, and fire hydrants in the City and the over 118 suburban communities supplied with water by the City of Chicago receive water through over 4,227 miles of water mains. The water mains leading from the pumping stations are called feeder mains and vary in size from 24 to 60 inches in diameter. They are constructed of ductile iron, prestressed concrete or steel. The feeder mains supply water to the service mains which vary in size from 6 to 16 inches. The service mains carry the water to more than one-half million service connections. A vital need for water in any urban community is in fire fighting. Water in sufficient volume and adequate pressure is available around the clock to the 47,054 fire hydrants located throughout the City. Large volumes of water are used also by commerce and industry. It is an indispensable ingredient, for example, in the packing and food processing industries. About 32 percent of the water pumped by the Chicago Water System goes to suburban communities surrounding Chicago. In most instances, each of these suburbs provides reservoir facilities to store sufficient water for at least one day's supply. Thus we have seen the water moved from Lake Michigan, through the intake cribs by tunnels to the purification plants, through the purification plants, then by tunnels to the pumping stations, and from the pumping stations into the underground network of water mains comprising the distribution system, finally reaching the point of usage by individual consumers, industry, firefighters and suburbia. |
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3/23/95 |
