Would you say that: wherever there are more than one conduit, there is a ductbank? Or would there be a situation where this is not the case? Would you have conduits grouped together and not in a casing?
Yes, there are situations where 2 or more conduits (2in gray PVC) run parallel and are what is called "Direct Buried". This means they are not inside a Duct Bank. Why? it costs less to direct bury conduit than put it inside a duct bank.