Periodically, I happen to fly into or out of Chicago, and, for various reasons, I often use Chicago's secondary airport, Midway Airport, located on the South Side of Chicago.
If conditions are just right, it's not uncommon that our flight path takes us along an easily-visible east-west trunk route in Chicago's far south suburbs, a stretch of Interstate Highway that is, simultaneously, I-80 and I-294, and which also connects I-90, I-94, I-57, I-65, I-355, and probably more freeways that have been built since I lived in Chicago.
Anyway, right in the middle of that part in the world, in between the cities of Harvey and Homewood, sits a Gigantic Hole In The Ground, with a 10-lane super-highway running right through the middle of it, which always fascinates me when I fly over it. (Yes, this is the sort of thing that fascinates me.)
I recently came across a nice article about what this hole in the ground is all about, and it spurred me on to chase some more links: Tunnel Vision
The history of Chicago can be told as a series of escapes from wastewater, each more ingenious than the last. Before the Civil War, entire city blocks were lifted on hydraulic jacks to allow for better drainage, and the first tunnel to bring in potable water from the middle of Lake Michigan was completed in 1867. In 1900, engineers reversed the flow of the Chicago River to protect the city’s drinking water, shifting its fetid contents from the Great Lakes to the Mississippi, enraging the city of St. Louis (which sued, and lost) and, years later, making Chicago the single-largest contributor to the “dead zone” in the Gulf of Mexico. In 1955, the American Society of Civil Engineers declared the river reversal one of the seven engineering wonders of the United States, alongside such better-known undertakings as the Hoover Dam, the Empire State Building, and the Panama Canal.
By the mid-20th century, the metropolis was once again plagued by persistent flooding problems. In 1978, Illinois Republican Sen. Charles Percy, looking back at decades’ worth of damage, declared Chicago the site of “the worst urban flooding known to any major city in America”—structural damage in neighborhoods, plus sewage in the river and the lake to the tune of 200 million solid pounds each year.
I moved to Chicago in 1981, but I didn't really know any of this. Yes, they told us the stories about reversing the river, and how the city had terrible water quality problems, and I knew about dying the river green for St. Patrick's Day ("to cover up the sewage", the wags said).
But I don't remember hearing anything about the Deep Tunnel project, which is a bit odd, as it's the sort of thing that I would have remembered.
Meanwhile, the project went on.
And on, and on, and on.
Renamed the TARP, or Tunnel and Reservoir Plan, the project finally started to come operational about a dozen years ago.
Although the tunnel itself is enormous, what really makes the project work is the Thornton Composite Reservoir, which can hold ...
... brace yourself ...
8 BILLION GALLONS OF RAW SEWAGE!
The tunnel took a long time to drill (excuse me, to "bore"), but the reservoir was no simple project, either:
the north lobe of the Thornton Quarry was converted into a reservoir with the capacity to retain nearly 8 billion gallons of CSO prior to treatment.
It sounds nicer if you say CSO, rather than "combined sewer overflow," doesn't it?
You can see a great picture of the Thornton Reservoir partially full in this article, which has lots of other detail: Chicago's Deep Tunnel Project Holds 17.5 Billion Gallons of Sewage Underground
You may say that all of this could have been avoided if the city was not designed on a combined sewer system, but the problem is, that was the best thing engineers knew how to do in that day. You might be surprised when studying the past of waste engineering that modern day practices really weren't developed but in the last 50 or so years. Many places around the world have combined sewer systems, mostly stemming from successive waste management developments. As cities transitioned from open channel sewage systems, many places simply covered the channels with metal plates or concrete arches, creating 'closed channel' systems. For a long time, no engineers saw the need to manage and treat wastewater or stormwater, as the effects of maltreatment were largely unknown.
Well, those effects are known now, and we're finally starting to deal with the mess properly.
And even if sewage systems aren't really your thing, it's nifty to know those little details; for example, that you can schedule yourself a tour of a bit of the Chicago City Limits which is located 365 feet underground: This Is The Deepest Depth A Human Can Go In Chicago City Limits
How low can you go within Chicago city limits?
About 365 feet below ground, according to Kevin Fitzpatrick, managing civil engineer for the Metropolitan Water Reclamation District of Greater Chicago.
That's where the floor of the Calumet TARP Pumping Station pump rooms rest far below Chicago's Riverdale neighborhood at 400 E. 130th St.
It's the lowest inhabitable point in Chicago.
The pumping station is part of the Calumet Water Reclamation Plant, which is a component of a massive system in Chicago and the suburbs designed to protect water quality in Lake Michigan and the Chicago Area Waterway System and to manage stormwater.
And you can try to wrap your head around its size and complexity by contemplating strange metaphors, such as those shared by the Slate article:
“I’ve been hearing about Deep Tunnel forever,” Frank Pajak, director of the Central Stickney Sanitary District, told the Tribune after that February 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?”
One retort from the MWRD: If you think this is bad, imagine what shape we’d be in without all these tunnels. Small storms no longer contaminate the river, and the capacity of the system is still increasing—McCook will nearly triple in size by 2029. That being said, on account of an EPA funding dispute in the 1970s, the final system will be smaller than its designers envisioned. The congested network of neighborhood sewers in Chicago and its suburbs—local roads leading to the Deep Tunnel highway—also remain an unresolved issue. In many storms, says Aaron Koch, who served as chief resilience officer for the city and now works as the Chicago director of the Trust for Public Land, the Deep Tunnel is helpless to empty undersized sewers battling against supersize storms and sprawl. “What the Deep Tunnel system represents is a bathtub, and if you don’t have big enough straws to get to the bathtub, it doesn’t matter how big your bathtub is.”
It’s a cautionary tale for a time when climate change has the nation’s planners, scientists, and engineers contemplating enormous endeavors like storm surge barriers or more radical, long-term geoengineering schemes. It’s also a reminder that any project that spans six decades from commencement to completion will be finished in a different world than the one in which it was conceived.
So, the next time you find yourself flying into or out of Midway Airport in Chicago, you can look out the window over the immense South Side of Chicago, and see if you can see that enormous quarry with the freeway right down the middle of it, and now you can understand just what exactly it is being used for, nowadays.