I have been looking for a while and its a hard project.
We were working on:
Whalon Lake, crappy viz and horrible access.
Lemont awesome Viz, great location and access....SHALLOW as all hell - this one was a heartbreaker when we dove it.
Joliet---Owners want nothing to do with it
Plainfield---We have access do dive anytime we want, but not open to the public and never will be
Got a couple more I am looking into, but its hard....I have talked with ALOT of quarry owners and they have no interest. Damn Lawyers and liability!
So Jim, if you want to do this....here are some things you could look for
Old water tower a city isn't using
Old Nuclear tower...now that would be fun, except for the third eye
A big bomb that we can just blow up and make a quarry, I can find the land
Old water treatment plant with all the underwater connections and pools it could be really fun
Find a bank or a prison, and flood it...hopefully the walls are thick enough
Find a 20 story building---flood it and hope it doesn't fall apart after 2 floors of water