I honestly do not fish for catfish often. I'll give you my thought process if I was forced to attack the Chatty gravel pits.
You've got it in your head that there's some kind of magic depth. You're missing the "hidden factors" that are food availability, oxygen availability, and cover. All fish require these three things to survive and it is your job to study aerial photographs, bathymetric maps, and spend time on the water in order to find the spots that have these three requirements.
Let's start with what catfish eat in the Chatfield ponds. They eat primarily live and dead crawfish, perch, shiners, and mollusks. All of these food items live primarily in the shallower parts of the lake. This is even more true at night when zooplankton make their daily migration to the surface to feed on photoplankton. Baitfish and crawfish follow the zoops and the big fish follow the little fish.
So you're going to be looking for large, shallow, productive flats mostly free of weeds. What makes these places even better is the presence of brush piles, rocks, hollow logs, pipes, tires, or anywhere else where the catfish can find overhead cover. At night catfish do not hang out under cover, but the more cover there is the more catfish there will be. There are plenty of these areas in the larger of the two pits, and that's where I'd start fishing.