[ardecila]

^
https://www.structuremag.org/wp-cont...ht-Dec-071.pdf

http://www.thorntontomasetti.com/wp-...7_Overview.pdf

Also there is this fun image... yes, that is the outside face of the CTA tunnel. Basically an interstitial space between the foundation wall of Block 37 and the Blue Line tunnel. CTA would have needed to bust through both sets of walls to connect tracks into Block 37.