Chuck, I was down there last December right after demolition of the Wrigley factory began, since I wanted to capture the tracks leading to the factory. The concrete wall you're referring to I think was a shield for the tanks that used to be there. I looked on Historic Aerials and it shows some tanks, the remnants are still there (those concrete pads with the semi-circles on them where the tank would sit). As for what they were used for, there's a sign there that's badly rusted but still tells some of the story. You can see it in the middle of the frame of your second photo. When I went, it had fallen, but I picked it up and took a picture. It said "Stop, Chlorine car connector". My guess is that since chlorine gas is quite hazardous, that was there to protect the tank from a vehicle coming from 36th street, while the railcars protected it on the northern side. Here is a frame grab of my video showing the sign.
