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Down the Drain?

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Photograph by Alan Schein, CORBIS 

The Chicago River, which once flowed east and emptied into Lake Michigan, now flows west into the Des Plaines River via the Chicago Sanitary and Ship Canal and empties into the Mississippi River.

The Wayfaring Waters of the Windy City

By Cassandra Marie Profita

The city of Chicago has gone a long way to preserve the sanctity of its freshwater reservoir. More than a century of urban ingenuity has gone into transport and treatment of the city's wastewater, and the job still isn't done.

Chicago's eight million people draw 2.4 billion gallons (9.1 billion liters) of fresh water from Lake Michigan every day, none of which will ever return to the Great Lakes. Instead, the water will wind its way through a descending network of tunnels, canals and riverbeds that draw the water away from Lake Michigan and eventually into the Mississippi River, in keeping with a treatment system that began in the nineteenth century.

However, there's a flaw in this system that might explain why Chicago had to close down its public beaches on several occasions this summer.  A heavy rainstorm can cause the city's undersized sewer system to overflow and contaminate the water on the lakefront. The logic behind a system that allows this to happen is wrapped up in the city's long history of water management.

The seeds of the city's water treatment system were sown shortly after the Chicago Fire of 1871. Much of the rebuilding took place along the Chicago River. All the new industries, including the stockyards, dumped their waste into the river, which at that time flowed directly into Lake Michigan.

Major sanitation problems might have developed in 1885 when heavy rainfall flooded parts of the city. Fortunately—at the convergence of the Illinois & Michigan Canal and the south and west forks of the South Branch—the current was strong enough to carry the raw sewage away from the city and Lake Michigan, curtailing a marked rise in contamination and disease. It could have been worse. Such close calls led to the creation of the Metropolitan Sanitary District of Greater Chicago, founded in 1889 to stop polluted water from contaminating the city's drinking water. A plan was made to construct channels and canals to reverse the flow of the rivers away from the lake.

Work on the canal system began in 1892. Thirty years later, 56 miles (90 kilometers) of canals were sending Chicago River water into the Des Plaines and Calumet Rivers instead of into Lake Michigan. To prevent Chicago's diversion of water from lowering the level of Lake Michigan, locks were installed on the waterfront to control the outflow.

After World War II, Chicago's population grew. More people used more water and produced more waste. More pastures were converted to concrete, which increased the amount of storm-water runoff. Chicago's sewer system was designed to hold two billion gallons (eight billion liters) of wastewater per day, but a single rainstorm in the 1950s could produce five billion gallons (19 billion liters) of runoff. To prevent flooding, the river locks were opened into Lake Michigan, allowing contaminated water onto the beaches. By the early 1970s, Chicago's beaches had to be closed to the public about 25 percent of the time.

With the aid of federal money provided by the 1972 Clean Water Act, Chicago developed the Tunnel and Reservoir Plan (TARP) which would build large underground tunnels and reservoirs to catch storm water runoff so it could be treated and returned to the waterways. Thirty-two miles (52 kilometers) of the tunnel system, known as the "Deep Tunnel," were completed by 1985. TARP is still 15 years from completion. When the project is through, there will be four tunnels and three large reservoirs aimed at keeping the shores of Lake Michigan—as well as the banks of the Illinois, Des Plaines and Mississippi Rivers—free from contamination.

As the last line of defense against water contamination, the project should plug the leak in the city's wastewater treatment system and extend Chicago's age-old pursuit of clean fresh water into the future.

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