OVERWHELMED BY RAIN?: The weather instability as a result of climate change, such as extreme downpours, may eclipse the ability of cities like Chicago to cope, even with new infrastructure investments. Image: flickr/Isaac Singleton Photography
CHICAGO -- This largest of American lakefront cities has long relied on feats of engineering to keep its sewage away from Lake Michigan, its primary freshwater resource and recreational crown jewel.
In 1900, the Sanitary District of Chicago reversed the Chicago River's flow, sending wastewater from homes, businesses and streets west toward the Illinois and Mississippi rivers rather than continue to foul the city's waterfront along what today is Lakeshore Drive.
As Chicago grew over the next 110 years, so did its sewers -- morphing from a rudimentary straight-pipe sewage system into something far more complex, if only moderately cleaner. The conduit for the new plumbing system was the Chicago Sanitary and Ship Canal, which linked the Chicago and Calumet rivers to the Mississippi, which provided a trench for Chicago's wastewater to flow downstream.
Today's sewer network, built and maintained by the Metropolitan Water Reclamation District of Greater Chicago, is a behemoth among urban wastewater collection systems. Girded by more than 109 miles of deep underground pipe, Chicago's massive "Tunnel and Reservoir Plan" (TARP) ranks among the nation's largest public works projects, both in term of scale and cost, estimated at $3.58 billion.
But questions remain as to whether -- having installed all this -- Chicago can keep up with the increasingly stringent demands of Mother Nature, especially as climate change ushers in greater weather instability marked by repeated record precipitation events.
The heaviest rain in Chicago history, a 6.86-inch deluge on July 23, 2011, put its so-called Deep Tunnel system to its toughest test yet. It flunked, and sewer managers were forced to relieve flooding by opening outfalls to the Chicago River and Lake Michigan, allowing tens of millions of gallons of filthy, bacteria-laden stormwater to pour into local waterways, including along the swimming beaches that line Lakeshore Drive.
The 2011 storm was only slightly larger than two previous record rainfalls -- on July 23 and 24, 2010, and Sept. 13, 2008. Those storms, too, produced severe flooding that overtopped highways and streets, filled underground parking garages and basements, and triggered similar spoutings of untreated sewage into the lake and river.
Dubbed "City of the Big Shoulders" in 1916 by its most famous poet, Carl Sandburg, Chicago had never seen anything like these. Experts say the rising frequency and intensity of rain events has changed many Chicagoans' assumptions about what climatologists call the "100-year storm," or the rain event that has a 1 percent chance of occurring in any given year. And for many more, climate change became more a reality than a theory.
"Certainly, it has put our residents in a new frame of mind," said David St. Pierre, executive director of the Metropolitan Water Reclamation District (MWRD), which he joined in June 2011 after two decades managing wastewater systems in Atlanta and St. Louis.
Tunnels working as designed
Since last year's floods, St. Pierre said, he has attended numerous public meetings to field Chicagoans' complaints about chronic flooding and offer reassurance that the district's multibillion-dollar TARP system is working as designed. The problem, he tells residents, is that the region's first-line sewers are overwhelmed by the high volume of stormwater rushing off streets, sidewalks and parking lots.
That surging wastewater is unable to move quickly enough into interceptor sewers that feed water to the 2.3-billion-gallon-capacity Deep Tunnel system, where it can be routed to treatment plants before discharge into the Sanitary and Ship Canal. The result is that stormwater rises in low-lying areas and backs up into homes and buildings across the region, creating an environmental and public health hazard.