There are several Oxidation ditch layouts. They're usually a racetrack of sewage with a big aerator mixer on one end. Sometimes the sides are straight walls and sometimes they're sloped. If the walls are straight, they're typically too long to use anything but a cantilever wall design. For the curved end portions, they're a little tricky. They don't truly develop hoop stresses, since they're not closed. So you're best off designing them like cantilevers, too. I like to put an expansion joint between the curved portion and the straight one.
If you have a big aerating mixer, they have their own challenges. Vibration limits are set by the manufacturer. This requires an abnormally stiff and large structure. If this structure covers the whole curved area, it is likely to develop chemical damage due to exposure to hydrogen sulfide. So coat the bottom of it.
As far as a reference, you're not going to find one. Your best reference is someone who's done one before.
JedClampett, Thanks for the info. I figured the long walls would have to be designed like a cantilever design. I wasn't sure about the hoop stresses on the circular portion since like you said they aren't really closed. We are just in the preliminary stages right now and the oxidation ditch hasn't been sized yet. Thanks again for your input.
