Despite a new $1 billion flood-control reservoir more than 20 times bigger than Soldier Field, rain and melting snow swamped the largest section of the Deep Tunnel project in less than a day last month, according to records obtained by the Tribune.
Starting on Feb. 20, more than 2 inches of rain flushed a torrent of sewage mixed with runoff from rooftops, streets and parking lots into stormwater tunnels stretching from Wilmette to Westchester, rapidly filling the McCook Reservoir built to hold wastewater until it can be treated.
After the 5.1 billion-gallon system swelled to capacity, leftovers from the storm surge began backing up in basements and pouring out of overflow pipes into the Chicago River and other area streams during the next two days.
Nearly 4 billion gallons of raw sewage, debris and runoff gushed into the waterways, most of it from a pair of pumping stations that convey waste from homes and factories on the North and South sides to the district’s treatment plants, according to a summary compiled by the Metropolitan Water Reclamation District at the Tribune’s request.
Another government agency, the Chicago Department of Water Management, fielded 510 reports of basement flooding during and after the storm, and recorded 240 cases of standing water on city streets.
Officials at the water reclamation district said the Deep Tunnel worked as planned. By diverting 3.5 billion gallons into the McCook Reservoir and holding another 1.6 billion gallons in the stormwater tunnels, the system limited flooding and other damage in Chicago and suburban Cook County, said David St. Pierre, the district’s executive director.
Yet the February storm also highlighted the shortcomings of a system billed as an engineering marvel and model for flood-prone communities throughout the nation.
Frank Pajak, director of the Central Stickney Sanitary District in the southwest suburb, said his constituents were repeatedly assured that one of the nation’s most expensive public works projects would solve their chronic flooding problems.
“I’ve been hearing about Deep Tunnel forever,” said Pajak, who posted a complaint on the district’s Facebook page about the system’s performance during the storm. “I was at the ribbon-cutting (for the reservoir), and it looked great. So why am I still getting calls about people standing in ankle-deep sewage in their basement?”
While the reservoir will be able to hold 10 billion gallons after a nearby quarry is mined out by 2029, officials at the water reclamation district were alarmed by the rate of sewage and runoff rushing into the section that opened in December. If the storm had dumped a little more rain on the area, St. Pierre acknowledged, even the larger reservoir would have been filled within a day.
But without the reservoir, St. Pierre said, the district likely would have been forced to release sewage and runoff into Lake Michigan — the outlet of last resort when streets and basements are flooded.
“Before McCook came online, we would start seeing (sewage overflows) almost as soon as it started raining,” St. Pierre said. “This time the system held on for 20 hours, which makes me fairly optimistic that what we saw last month will be relatively rare.”
With the bulk of the project completed, even some of the project’s most ardent backers say the city and county need to start focusing more intensely on neighborhood-focused improvements that allow runoff to soak into the ground before it reaches local sewers.
Yet state legislative leaders in Springfield have blocked measures that would authorize the water reclamation district to spend taxpayer funds on the smaller-scale initiatives, which can help prevent sewage from backing up into basements and take pressure off the larger system of sewers and stormwater tunnels.
Meanwhile, staff turnover at the city has slowed progress on a pilot project in the low-lying Chatham neighborhood on the South Side, where the nonprofit Center for Neighborhood Technology has drafted plans to direct downspouts away from homes, seal foundation cracks and install rain gardens and other landscaping improvements to absorb runoff.
“They are good at what they do,” Scott Bernstein, the center’s co-founder, said of the Deep Tunnel’s operators. “But we are seeing more intense storms like what happened in February, and it’s clear we still aren’t ready to deal with all of that rain.”
St. Pierre agrees. “We are not going to be able to solve this with pipes alone,” he said. “Once again, this storm shows why you shouldn’t build a large city in a swamp.”
The problem starts with sewers in Chicago and older suburbs that combine runoff with waste from homes and factories. When it rains, the combined sewers quickly fill up and begin spilling the waste through dozens of overflow pipes into local streams.
A Tribune analysis last year found that sewage and runoff flowed into the Chicago River and connected waterways about once every six days during 2016, and even more frequently during the May-to-October recreation season.
Lake Michigan has been hit more frequently since 2008 than it was during the previous quarter-century, district records show.
The Deep Tunnel is supposed to sharply reduce, if not completely eliminate, those problems. Technically known as the Tunnel and Reservoir Plan, the project has been in the works since the mid-1970s and became the metropolitan area’s official response to the federal Clean Water Act.
Two separate, smaller sections of the project, serving the Calumet region and communities near O'Hare International Airport, have essentially put an end to raw sewage and runoff pouring into local waterways during and after rainstorms. But there are lingering questions about whether the larger system can handle quick, powerful storms hitting the region more frequently as the climate changes.
The Calumet and O’Hare systems collect runoff from 102 square miles combined. By contrast, the McCook Reservoir's service area is more than double that amount: 252 square miles, stretching from Wilmette south and west across a vast swath of Chicago and including western suburbs along the Des Plaines River.
Hawthorne, M. (2018) Chicago Tribune