Historically, cities dumped untreated wastewater into the nearest body of water. “Dilution as the solution to pollution” was once the mantra of wastewater engineers, but in an era of increasing urban densities and unpredictable weather patterns, that approach no longer flies.
“Because of climate change, we’re having more and more really intense rainstorms which our old infrastructure is unable to handle,” says Mariyana Spyropoulos, president of the board of commissioners of the Metropolitan Water Reclamation District of Chicago (MWRD), the 125-year old public agency charged with managing both stormwater and wastewater throughout the Chicago region.
Under Spyropoulos’ leadership, MWRD unleashed a flurry of initiatives to better accommodate the deluges that seem to be the new norm and to deliver cleaner effluent to area waterways. Challenges are everywhere—flooded streets and basements have become commonplace in recent decades and the EPA has levied fines against the city for failing to comply with Clean Water Act standards. An all-hands-on-deck campaign has been mounted to attack the problem from every angle, ranging from multi-billion dollar infrastructure upgrades, to green technology development, to educational outreach. More than 5 million residents spread across 125 communities populate MWRD’s jurisdiction, so fixing the wastewater woes of Chicagoland is “not easy, to put it mildly,” Spyropoulos says. “There’s not a magic bullet to solve all the problems.”
Cleaning Up from History
The dilution-as-the-solution approach has been problematic for Chicago longer than it has for other cities of a comparable size, largely as a consequence of geography. Most cities siphon water from the nearest river upstream of the urbanized area, where it is relatively clean and then discharge their effluent just downstream of city limits so dilution can do its work before the water arrives at the next municipal intake in the watershed. When Chicago was settled, the local river—known simply as the Chicago River—was more of a swampy backwater at the bottom end of Lake Michigan than it was a clear, flowing river. The obvious choice was to draw drinking water from the lake. Unfortunately, all that water made its way back to the lake in the form of raw sewage, via the slow, meandering Chicago River, creating a cesspool. “As you can imagine, this caused numerous problems—like cholera and dysentery,” Spyropoulos says.
Chicago’s hygiene issues in the late 1800s propelled the state legislature to create the Chicago Sanitary District, the organization now known as MWRD. Its first major success went down in history as one of the great engineering feats of the day—in 1900, the direction of the Chicago River was reversed to flow away from the lake and into the Illinois River, which in turn flows into the Mississippi River and into the Gulf of Mexico.
Preparing for Another Century of Growth
The Chicago Sanitary and Ship Canal was a historic stepping stone for the city, allowing it to industrialize and rapidly expand in the early 20th century without fear of drowning in its own waste. Chicago’s explosive urban growth in the past century eventually surpassed the capacity of canal to handle the city’s waste and stormwater, leading to the recent water quality issues and prompting city leaders to explore options for how another century of growth could be accommodated.
The first solution is part of a bold package that rivals the reversal of the Chicago River in its impressive engineering: the $4 billion Tunnel and Reservoir Plan (TARP). Known popularly as the Deep Tunnel project, after its most notable feature—a 30-foot diameter tunnel that runs beneath city streets at a depth of about 300 feet—TARP is scaled to epic proportions. The tunnel is fed by a network of 109 miles of smaller tunnels, absorbing stormwater like a sieve beneath the city any time there’s rain. Not a moment too soon, either, as climate researchers predict that the frequency of storms dumping 2.5 inches or more of rainwater on the city in a 24-hour period will more than double by the end of the century.
Since joining the MWRD Board of Commissioners in 2009, Spyropoulos has helped execute the reservoir portion of the TARP plan, which is where the water collected by the tunnel system deposits during storms.
“When you have these heavy rain events, that water has to go somewhere,” she says.
The first of three planned reservoirs, the 350 million-gallon Gloria Alitto Majewski Reservoir on the north side of the city, was completed several years ago, but the MWRD cut the ribbon on its much bigger cousin south of the city on September 1, 2015. The Deep Tunnel now outlets at the Thornton Quarry, dubbed the “Grand Canyon of Chicago’s southern suburbs.” The quarry, once the source of much of the aggregate that built Chicago, now is refashioned as a 7.9 billion-gallon reservoir that prevents flooding for an area inhabited by about 500,000 people in 14 Chicago area communities. “The Thornton Quarry is expected to mitigate about $40 million worth of flooding damage per year,” Spyropoulos says.
Of course, Chicago’s stormwater system is tied into its sewage system, a common design known as a combined sewer overflow (CSO), which means the new tunnel system and reservoirs are filled with both rain water and wastewater after big storms. They are designed to hold the water temporarily until the city’s seven wastewater treatment plants can process the excess volume. The second prong of MWRD’s current strategy, then, is to improve their ability to treat all of that water before it is released back into the Chicago Sanitary and Ship Canal. The EPA has mandated that Chicago bring its effluent up to a “swimmable” level. Currently, some waterways in the area are considered unfit for any form of human contact.
“We’re not encouraging people to get their swimsuits ready yet, but that’s the direction that were going in,” Spyropoulos says. Two facilities have been targeted so far for improvements. The O’Brien plant north of the city will be outfitted with an expensive, but highly effective UV treatment system, while the Calumet plant south of the city will employ a chlorination/dechlorination method.
The Thornton Quarry reservoir is nothing compared to TARP’s grand finale—the 10 billion-gallon McCook Reservoir, currently under construction west of the city. “Green infrastructure will be needed to compliment the infrastructure that we have in place,” Spyropoulos says. The problem is that the TARP plan was based on historic rainfall patterns, which are rapidly changing.
“More tunnels are not necessarily going to be enough to deal with flooding, especially with climate change,” she says. “So although we have these reservoirs at the tail end, we have to somehow reduce the flow that’s going in.”
It’s impossible to stop the rain, so the challenge becomes reducing the water volume coming into the front end of the system. That’s where green infrastructure comes in, the third prong of MWRD’s efforts. The idea of green infrastructure is simply to hold the water above ground for as long as possible after it rains and then let it slowly trickle into the sewer system. Vegetated roofs, bio-swales, and rain barrels are but a few of the tools being proposed. Each acts a bit like a sponge, absorbing water when precipitation is plentiful and releasing it when it is not. Unlike the massive, centralized infrastructure projects that were recently completed, green infrastructure solutions are designed to be spread through the city in thousands of tiny projects that add up to one big sponge. For example, MWRD has entered into a partnership with community-based organizations throughout the region to distribute 15,000 rain barrels to homeowners.
“If you’re going to use a rain barrel as a method of reducing floodwater, you can’t just do it one here and there, you need a lot of them,” Spyropoulos says.
Another green infrastructure project involves collaboration between MWRD and the Chicago Public School System. Asphalt schoolyards are being repaved with permeable concrete, which allows the water to soak slowly into the soil rather than run into a storm drain. Just as importantly, the new schoolyards are being outfitted with new playground equipment designed for interactive learning opportunities.
“These are areas where teachers can take the kids out to learn about green infrastructure,” Spyropoulos says. “By getting the kids involved they already understand from a young age what that’s all about and how useful it can be.”
Known as the Space to Grow Program, the initiative launched with three pilot schools in 2014 and soon will expand to at least 30 more sites. The project is also geared toward combating childhood obesity by making the playgrounds more appealing for physical activity.
“If you have people using the playgrounds in the way that they’re supposed to be used, you can also reduce crime,” Spyropoulos says. “So we think that it’s hitting a lot of different fronts in a positive way. And it reduces flooding, which is huge.”