Quote:
Originally Posted by MayDay
Operative words - these days. Historically for Cleveland, that was an issue because if you wanted to build anything substantial, you have about 200-250 feet (60-70M) of glacial till
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Wow, that's some deep bedrock. As a fellow great lakes city, Chicago is in a very similar boat to Cleveland with LOTS of glacial till (various soggy clays and sands) before you get down to our dolemite bedrock.
But in Chicago's case, bedrock is typically about 100' below grade, going down as deep as nearly 200' in some spots. I believe that the Hancock Center still holds the record for the deepest rock caissons ever sunk in the city at ~190' deep.
Still, even with its terrible soils for skyscraper bearing, Chicago was the second city on the planet to ever erect supertall skyscrapers. Chicago actually pioneered most of what we know today as drilled shaft foundations, or "caissons" as they're called in the Chicago construction industry.
Unlike Manhattan, Chicago wasn't gifted with solid rock to build upon just below the surface, but as the old adage goes,
"where there's a will, there's a way."