Jan 28, 2019

SWS City Report: Chicago

The Windy City takes big leaps to manage storm water

The Windy City takes big leaps to manage storm water


The SWS City Report is a year-long project, where SWS and a small committee of industry professionals collaborate to assign grades to the storm water infrastructure in some of the nation’s largest cities. Modeled after the American Society of Civil Engineer’s annual Infrastructure Report Card, the SWS City Report specifically examines storm water infrastructure on a city level. Keeping certain criteria in mind—the condition of the infrastructure, how it will meet future needs, its resilience, how it meets capacity requirements, and its level of innovation—the committee assigns a letter grade, which is followed by a brief, high-level overview of the city’s storm water infrastructure. The project will examine one major city in each region of the U.S.: Chicago, Los Angeles, New York, Phoenix and Houston. It starts with the Windy City. 

Chicago has a rich history. It is home to beloved sports teams, delicious pizza and contentious politics. It also was built on a swamp. 

Because of Chicago’s location, water and wastewater management always has been a challenge. It implemented combined sewers in the 19th century at the height of technology. This eventually led to the reversal of the flow of the Chicago River and the city’s first wastewater treatment plants. Historically, it seems the city has encountered problem after problem with water management, but it always finds a solution. Even today, as the problems get larger, so do the solutions. 

Urban Flooding

Many Chicago residents have tales of basements filled nearly to the ceiling with sewage, said Andrew Billing, lead stormwater reviewer for Mackie Consultants LLC, consultant to the city of Chicago Department of Buildings. Combined sewer overflows (CSOs) have flooded city structures after major—and minor—weather events for years. Unfortunately, there was no simple solution. With approximately 4,000 miles of sewers in the city, separating the combined sewers is not a viable option, according to Billing. In the 1970s, the Metropolitan Water Reclamation District of Greater Chicago (MWRD)—the governing body responsible for wastewater and storm water management in Cook County, Ill., separate from the city of Chicago—formulated the Tunnel and Reservoir Plan (TARP).

TARP includes a deep tunnel system with arteries throughout Chicago. After major weather events, 109 miles of tunnels channel CSOs to three flood reservoirs, which hold the storm water and sewage mixture until treatment plants can process and release the water. The newest addition to TARP is stage one of the McCook Reservoir. It came online in 2017, and can hold 3.5 billion gal of water. In 2018 alone, it captured 27.2 billion gal, according to MWRD. Stage two will come online in 2029 and will provide an additional 6.5 billion gal of storage.

Without a doubt, TARP is a massive undertaking, with positive results. Since McCook came online, CSOs have been reduced, and the tunnel system is working as expected. However, there is speculation that the storage capacity is not enough. The system originally was planned nearly 50 years ago, and with an increase in extreme weather events, engineers may not have accurately predicted the storage capacity necessary to mitigate CSOs. When stage two comes online in the next decade, MWRD will have a better idea of how it will match up against climate change.

TARP is not Chicago’s only massive tunnel. One of its newest is the Albany Park Stormwater Diversion Tunnel in the northside neighborhood of Albany Park. It alleviates rampant flooding in this neighborhood by diverting storm water from the river to this underground tunnel. It diverts the water directly to the North Shore Channel. While this tunnel alleviates flooding by acting as an underground river, it does not offer any treatment benefits like the TARP system. Nevertheless, projects like the Albany Park tunnel and TARP demonstrate that the city and its partners are willing to allocate resources to help improve urban flooding.  

Green Infrastructure 

Chicago’s congested and highly developed urban environment means most new storm water infrastructure either is built underneath the city or scattered on top of it. Like many major cities, Chicago is using green infrastructure as a cost-effective and efficient way to manage storm water. Both the city and MWRD have formal plans in place to utilize green infrastructure.  

According to the U.S. Green Building Council (USGBC), Chicago was ranked as the nation’s greenest city in August 2018 for the second year in a row; nearly 70% of its space is green certified. In addition, Chicago received LEED for Cities Platinum certification in 2018—the highest level of certification from the USGBC. 

Green infrastructure prevents storm water from hitting sewers to avoid CSOs. With more than 640 green roofs covering nearly 6 million sq ft, Billing said Chicago is the world leader for green roofs. Its Sustainable Development Policy incentivizes adding green roofs to developments through a point system. In addition, MWRD developed a Green Infrastructure Plan as part of its Consent Decree with the U.S. EPA. This agreement requires the MWRD, in collaboration with local stakeholders, to implement green infrastructure projects to increase the acceptance  of green infrastructure and reduce CSOs, localized flooding and storm water impacts. These policies hold both the community and the governing bodies accountable for storm water management. 

The city also promotes a Green Alley Program, advocating the use of permeable pavement to infiltrate rainwater into the ground, rather than directing it to the sewer. Across the city, permeable pavement has been implemented on approximately 300 projects, and bioinfiltration systems have been implemented on approximately 600 projects.  

In addition, MWRD collaborated on the Space to Grow program, which is a partnership with the Chicago Department of Water Management and Chicago Public Schools that converts impervious, unused surfaces—like parking lots—into outdoor play and learning spaces that capture and retain storm water runoff. The program prioritizes areas that have documented flooding issues or lack green play spaces for kids, said Joseph Kratzer, managing civil engineer of the storm water management section, engineering department, for MWRD. 

“Anytime you can use green infrastructure to take a load off the combined sewer system, you’re also helping alleviate not only CSOs, but ... [also] backups in the schools that are selected,” he said.


Like any metropolis, Chicago still has room for improvement. 

“There has not been as much work done on storm water management as we would like to see,” said Margaret Frisbie, executive director of Friends of the Chicago River, a local organization dedicated to the health of the Chicago River. 

Most storm water professionals in Chicago would agree that Chicago’s ultimate storm water goal is to eliminate CSOs. But it has not quite made it yet, and the health of the Chicago River is indicative of the frequency of CSOs. The river now features kayakers and fishers, but is not swimmable; wildlife has improved, but it could still welcome more species. 

“If we can imagine the Chicago River system as a blue-green corridor of public open space with natural river banks that are hospitable to wildlife in clean water that’s healthy for aquatic life and for people too ... that’s the real vision,” Frisbie said. 

TARP and green infrastructure are reducing CSOs, but have not eliminated them. Frisbie calls for a more comprehensive, holistic plan that is less reactionary with storm water projects. Billing suggests even stricter requirements to limit storm water pollution. Ultimately, there appears to be a consensus that the storm water work in Chicago is not finished, yet. 

“We need to be looking, thinking outside the box a little bit from our traditional toolbox and trying to identify the most kind of practical and cost-effective means for addressing storm water management,” Kratzer said. 

Chicago is not a singular entity. The river carries storm water pollution from the county and surrounding counties, and anything Chicago contributes also flows down to the gulf. Chicago’s infrastructure is aging, and new infrastructure struggles to keep up with the storms it sees. But for such a metropolis, it is very green, and has an impressive tunnel system that most cities cannot match. 

“Chicago’s either been at the head of it or keeping up with the with the best of the best innovation in the world,” Billing said.


The committee members, who will remain anonymous, shared some of their reasonings for assigning Chicago’s storm water infrastructure grade.

  • “I love the green roofs and the Green Alleys Program, but since they are spending billions on new tunnels and new pipes to rush the storm water and wastewater away faster, I am not sure that they have fully understood the root cause of their problem and how to solve it.” – Member 1
  • “While Chicago has a great LEED score, storm water is only–at a maximum–four points into that score ... In my opinion, the LEED scoring does not put enough weight on drainage or storm water.” – Member 2
  • “I see the fact that they are taking action, expanding capacity and simultaneously working on runoff reduction as positives, and lack of focus on water quality and treatment, concerns about capacity, and not being particularly innovative as negatives.” – Member 3

About the author

Lauren Baltas is managing editor of SWS. Baltas can be reached at [email protected] or 847.391.1019.