A bulk material transport apparatus which includes a containment structure on a wheeled frame which is formed of perimeter wall members about a bulk material containment area, further includes at least one modular hopper unit mountable at a bottom side of the containment area for discharging contents of the bulk material containment area therethrough. The modular hopper units can be readily interchanged with other hopper units which are different in gate opening size, gate opening height, gate opening orientation, and/or other characteristics relative to one another. One optional modular hopper unit is a side discharge unit which is reversible for discharging to a selected one of two laterally opposed sides of the transport apparatus.