The Secret $4BN Tunnel Network Under Chicago

walk around the streets of Chicago and you'll see giant skyscrapers Wrigley Field and lots of deep dish pizza restaurants but deep beneath all this the city is hiding something more 90 meters below your feet you'll find a secret underground tunnel Network that sprawls 175 kilometers beneath the metropolis and surrounding area it's one of the largest civil engineering projects in the world construction's been underway since the 1970s and it's a key tool in the fight against climate change so what is this secret Labyrinth concealed beneath one of America's largest cities why does it exist and how exactly was it built without anyone noticing we're heading underground to find out now our built environment and the process of constructing it accounts for around 40 percent of all Global greenhouse gas emissions so while many of us might not realize it if we really want to tackle climate change it's kind of essential that we build and use our buildings cities and Transport Systems in a much more sustainable way uh Bill world is critical in combating the effects of climate change too some of those effects are now inevitable as global temperatures are predicted to rise by 1.5 degrees Celsius regardless of the many actions being taken construction can help build a more sustainable world and protect us from the impacts of our changing climate and America's windy city is just one place deploying defenses let's rewind a bit throughout the late 19th and 20th Century Chicago was rapidly expanding but as its population swelled infrastructure began having a hard time catching up Chicago was built on top of a literal swamp and as such its geography was very flat and low lying and that created severe drainage problems following storms mud-filled streets and pools of standing water would form all over the city eventually authorities decided to construct a comprehensive sewer system but digging an underground system would have been too expensive so Chicago just raised the whole city out of the mud by a couple of meters added above ground sewer pipes and filled the gaps in with dirt but as one problem was being solved another was being created all those newly laid sewers flowed directly into waterways waterways that eventually flowed into Lake Michigan the source of the city's drinking water that caused a lot of disease among residents so officials began looking for yet another fix and if you thought raising the city off the ground wasn't ambitious enough already then wait till you hear this plan the Chicago River was reverse engineered instead of flowing into the lake it was redirected into the Mississippi River changing the direction of a river works like this first a series of locks were constructed along with a brand new 45 kilometer Canal that sloped downhill pumping stations then directed water through the canal as it deepened towards the Des Plaines and Mississippi rivers thus creating a reversal effect to this day the river still runs backwards but as the population continued to swell the sewer system that had once saved the city began getting overwhelmed by the 1960s sewers were overflowing more than 100 days each year flooding became more common and Chicago once again found itself trying to solve a giant problem so the Water Reclamation District teamed up with some other local entities and put a bold new plan into action enter the cleverly named tunnel and Reservoir plan also known as the deep tunnel system it's that 175 kilometer underground tunnel Network set to feature no fewer than three reservoirs that goes right through the heart of downtown Chicago it's meant to help manage the Overflow and pollution issue any extra runoff water from storms could now be redirected through the new tunnels and stored in the reservoirs before being treated and eventually released construction began way back in 1975 with phase one the tunnels themselves now these weren't your average sized tunnels back then four distinct systems stretched up to 10 meters in diameter and under 100 meters of solid Bedrock it was to say we're going to make the contractor use a tunnel boring machine to create these tunnels and rack even though at the time more traditional Drilling and Blasting techniques may have been a little bit cheaper and more reliable they thought well the machine is probably not going to cause as much damage to the rock as blasting wood so they were getting you know maybe 50 feet of uh tunnel constructed in a day back when they started and then by you know within 10 15 years they're up to 150 feet 200 feet per day by the time this whole network was finally finished in 2006 they could manage nearly 9 billion liters of water that's around 2.3 billion gallons it also helped reduce pollution by nearly 85 percent [Music] and while the Deep tiles construction wasn't originally built in response to climate change it now finds itself as a critical tool in combating the effects of it according to the latest National Climate assessments an increase in heavy rain and storms in the midwest could lead to flooding which may destroy property and contaminate drinking water that's why phase two of the project is becoming increasingly urgent it consists of three massive reservoirs that allow the system to handle even more water two of them are already complete you know we have these wheel Gates that isolate the tunnels from the reservoirs they operate only when when the reservoir goes to completion or if somebody's working there will have to close it and isolate it in addition and there's a grout curtain that surrounds the reservoir and this is really to kind of seal the reservoir almost like a bathtub it's almost like cocking all the holes in the rack so what we're doing is we're we're drilling down a hole almost 500 feet it's a it's about a three inch diameter hole and we're pumping it with with this grout material under pressure and that seeps through cracks sealing it and they put these holes every five feet around the three mile perimeter of the reservoir so now when it rains in Chicago water first flows into the local combined sewers these were originally directed into the rivers but now that water is intercepted by the newer sewers then overflow shoots 70 to 90 meters down a drop shaft into tunnels deep underground here water is pushed into the reservoirs where it's stored until the Reclamation plants have enough capacity to clean it that process normally occurs during dry weather or during moderate rainfall once the water is cleaned at the plants it's steadily released into the river when all three reservoirs are complete in 2029 the entire system will be able to hold over 64 billion liters of water that'll continue to ease flooding and pollution after big storms and even though construction Works still have a few more years to go Chicago is already seeing the benefits of its secret tunnel Network less contamination has enabled more species to return to the waterways since the 1970s the number has skyrocketed from 10 to nearly 80 different kinds of fish waterfront property construction is also booming something that's been good for Chicago's economy the city even built a brand new Riverwalk with restaurants and bars that's become a popular walking spot now 64 billion liters may sound like a lot of water and it certainly is but during big storms the system can and will hit capacity when that happens it'll revert to the original process of redirecting the combined overflow into the waterways that can cause polluted water to flood streets and basements and further effects of climate change could of course make that a much more regular occurrence we have a very good model of our of our entire sewer Network and tunnel system that we use to sort of simulate what-if scenarios and we look at potential expansion of the tunnel and Reservoir plan you know but really right now we're looking at using a lot of green infrastructure it's trying to simulate Nature by having water kind of stay where it lands by infiltrating it into the ground sending it through bios whales or rain Gardens or things like that and really that the idea is to keep it out of the sewer itself if it doesn't make it to the Sewer then it's not going to make it to the Waterway or is not going to back up into somebody's basement for more than a century Chicago has continued to build its way out of problem after problem with some of the biggest engineering projects in the world but unlike before preparing for the impacts of climate change is a moving Target it's an event we can see happening across the world with a future we have no president for and we'll need to prepare our cities for its in a variety of ways foreign the tunnel and Reservoir plan is just one of them and it's a project that many other urban areas could learn from as we fight the impacts of a changing climate together construction is Central in ensuring a sustainable future for us all while we may all see and feel increasingly common storms like these Chicago's way of dealing with them is much more tucked away it shows once again the remarkable power that construction has to shape change and save our world even if you can't see it happening you can learn more about Chicago's deep tunnels and the other topics on our Channel over on the world's best construction podcasts available now wherever you get your podcasts and as always if you enjoyed this video and you want to get more from the definitive video channel for construction make sure you're subscribe to the p1m [Music]

Channel: The B1M

Views: 1,131,148

Keywords: B1M, TheB1M, Construction, architecture, engineering, The B1M, Fred Mills, building, chicago, tunnel, infrastructure, climate change, flood, chicago river, illinois, TARP, tunnel and reservoir plan, chicago river reversal, sewer, rain, engineer, civil engineering, travel, windy city, skyscrapers, US infrastructure, climate, flooding, lake Michigan

Id: 2klS1diYMWU

Length: 10min 47sec (647 seconds)

Published: Wed Feb 01 2023