Chicago wasn’t always a towering city with skyscrapers. How did it become the bombing city of today? What environmental changes happened during the development of Chicago? How did Chicago soil go from flourishing to now contaminated with lead?
Belive it or not, Chicago was once a swampy, muddy wetland. According to geologists, a giant prehistoric lake (Lake Chicago) used to sit on what is now Chicago. This lake gathered dead leaves and animals over time (as all lake do), whos remains sat on the bottom of the lake. This accumulation of dead material turned into a large abundance of organic matter. As time went on, and more and more organic matter gathered on the bottom of the lake, the lake dried up leaving behind some mucky soil.
The movement of this water exposed a layer of soil that was hidden under Lake Chicago, exposing marshy lowlands. Chicago, and the greater Cook County region, was a huge marshy wetland!
According to researchers, development has caused around 80% of these wetlands have been lost. Most being drained or turned into small lakes across Chicago. (I’ll talk more about this in a later article, soon to come!).
Chicago was once a big mushy blob of wetland habitats formed from a giant prehistoric lake that came for the melting of the glaciers. But what does this mean for development?
According to the Encyclopedia of Chicago, “Most of Chicago was built on the lakebed soils, which were too wet for the construction of a city, so the land surface was raised by repeated filling. The deep canals dug for navigation, along with the sewers, helped to rid the city of water as more soil was covered.” Because of the mucky soils of Chicago, developers had to come up with innovative ways to build the city. Draining and filling the soils were some of the first options.
Chicagoans later discovered that far under the layers of mucky soil is dolomite, hard bedrock that is used to anchors Chicago’s skyscrapers using cement. This was helpful when Chicago decided to stat building taller.
Believe it or not, but the 1871 Chicago Fire greatly shaped the soil of Chicago. The fire destroyed three and half square miles of the heart of the city leaving lots a debris. A lot of the debris was either left or used to fill in mucky areas in Chicago so development may happen more easily.
For example, present day Grant Park was built upon debris from the Chicago fire. Chicagoans wanted to stabilize the shoreline and they needed a place to put the debris from the fire so it was a win-win for them. They ended up adding a layer of soil on top of the trash and using it as a large public park.
Lead, as most people know, is dangerous for human development. In industrial times, lead wasn’t regulated but was used widely used in paints, piping, gasoline, and other sources and has left residue in Chicago’s soils.
According to the EPA, soil lead levels under 400 ppm are considered safe but precautions still should be taken. This means that areas in red, on the map shown above, are where concentrations of lead are the most dangerous.
According to research, gardening in lead contaminated soil is said to be safe, but safe regulations should be in place. The lead will not absorb much through the roots of plants, but dirt on the veggies that aren’t washed off can be dangerous. Cation must still be taken.
The overall biology of Chicago’s soils has changed dramatically due to our development. An area of wetlands become industrialized, stripping away the natural environment and completely altering and contaminating the soil. But what can we do now?
As residents, we can be open to the idea of introducing wetlands or marshes into our communities. After all, if Chicago was once mostly a large wetland, shouldn’t scientists be restoring our natural areas to wetlands to bring back the flora and fauna that once was here before development?
More importantly, we can look deeper into the soil health in our own backyards and see how we can help restore it with methods such as plant plants, using compost, etc..
Chicago Wetlands Shrank by 40% During the 20th Century
http://www.encyclopedia.chicagohistory.org/pages/1164.html
https://news.wttw.com/2021/10/08/grant-park-chicago-s-front-yard-rose-trash-great-fire
https://www.epa.gov/sites/default/files/2015-08/documents/plv-gardening-fs-2013-en.pdfhttps://extension.illinois.edu/global/chicago-safe-soils-initiative
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