On Chicagos West Side, the threat of flooding does not begin when water reaches the curb. It begins with a forecast, a darkening sky, and the familiar calculation of what can be lifted from a basement before the sewer backs up again.
A new pilot project beneath two residential streets is intended to give families more time and the neighborhoods aging sewer system more room. The Chicago Department of Water Management and the Metropolitan Water Reclamation District of Greater Chicago are building underground stormwater storage structures beneath Maypole Avenue and LeMoyne Street. Together, the structures will temporarily hold nearly 1.7 million gallons of rainwater during intense storms.
The $12 million project is expected to provide additional flood protection for more than 2,900 homes, businesses, and other buildings in the 28th, 29th, and 37th wards. North Austin, South Austin, West Garfield Park, and Galewood are expected to receive the greatest benefit.
The Maypole Avenue structure, located between Cicero and Lavergne avenues, was completed this spring. Construction is continuing beneath LeMoyne Street between Luna and Lorel avenues, where a series of 12-foot-by-12-foot concrete boxes will form an underground holding tank. Austin Weekly News reported that the LeMoyne portion is scheduled for completion this fall.
The structures are not designed to permanently retain the water. During a heavy storm, they will collect water that might otherwise rush into already strained local sewers. Once the sewer system regains capacity, the stored water will be released gradually and sent for treatment.
It provides additional volume for the sewers to have a little more time to drain, Metropolitan Water Reclamation District engineer Justin Kirk told WTTW News.
That extra time can be the difference between water remaining below the street and sewage entering a familys basement. It also represents a change in scale. Chicagos massive Tunnel and Reservoir Plan, commonly known as the Deep Tunnel, manages billions of gallons across the region, but water must first travel through neighborhood sewer lines to reach it. Many of those local pipes are more than a century old and were built before much of the city was covered by pavement, parking lots, and other surfaces that prevent rain from soaking naturally into the ground.
Following several rounds of severe storms between July 2 and July 4, WTTW reported that the Deep Tunnels reservoirs reached unprecedented levels and were nearly full. Another round of severe weather moved through the Chicago area July 27, producing flooding, damaging winds, and new reminders that the citys drainage system is repeatedly being asked to carry more water, more quickly. The Chicago Sun-Times reported that hundreds of basements flooded during Mondays storms, which also produced four confirmed tornadoes in the region.
The West Side pilot grew out of the damaging July 2023 storms. A city disaster-recovery plan recorded 1,870 flood-related complaints from that event. Cook County was later included in a federal disaster declaration covering severe storms and flooding from June 29 through July 2, 2023.
The damage from those storms was not limited to furniture or boxes stored downstairs. Floodwater can destroy furnaces, electrical systems, appliances, family photographs, and the lower levels of homes that residents use as bedrooms or living space. Renters may lose property even when they have no control over a buildings drainage, while homeowners can face repair costs that exceed their insurance coverage or savings.
City officials have described the underground tanks as one part of a larger response, not a complete solution. Other measures include monitoring sewer flow in real time, disconnecting downspouts from sewer lines, installing devices that slow water entering catch basins, and adding green infrastructure that allows rainfall to soak into the ground.
The location of the tanks also shows why the approach may be difficult to reproduce block by block. Underground Chicago is already crowded with gas lines, water mains, sewer pipes, cables, and other utilities. Department of Water Management Commissioner Randy Conner told WTTW that adding infrastructure in a dense neighborhood can resemble assembling a 1,000-piece puzzle.
Officials plan to evaluate the structures for six to nine months after both are operating. The findings should answer questions that matter beyond the pilot area: how much water the tanks capture during the most intense storms, whether nearby basement backups decline, how quickly the tanks empty, and whether the design can work in other flood-prone neighborhoods.
For West Side residents, success will not be measured by the size of the concrete boxes or the number of gallons listed in a news release. It will be measured during the next hard rain, when families look downstairs and find their basements dry.