A few years ago New York proposed tough new standards for ballast water treatment aboard west bound ships that sail through the locks at Massena. They are looking to eliminate the risk of foreign species traveling to inland waterways, for instance the lamprey eel.
Ships with lighter loads require ballast water for efficiency and control. These lighter loads cause a ship to ride higher in the water, possibly with sections of propeller and rudder out of the water.
Stricter ballast water standards require that the present Seaway-max ships that travel upstream of Montreal, exchange their water at the Port of Valleyfield. The Seaway-max days may be numbered as the new generation of Panamax 2 ship carries 4x the number of shipping containers, eating up 1/3 the fuel , with the same numbers of crew. With this size comes a deeper draft, and river accessibility for 300 kilometres east of Montreal. After opposition to the huge dredging operation rose , the Panamax -2’s will have to operate on part load between Quebec City and Montreal. The offloading will then affect the number of containers river ships will be needed to carry.
As new river ships are designed and built options can be builtin to minimize or even eliminate the need for ballast. There is new maritime technology that can adjust the height of the propulsion and steering systems relative to the water surface. The azipod mechanism combines the swivel steering of an outboard boat motor, with an electrically powered propeller. Even with a light load , the propeller will ride at a depth of several meters and be efficient and under directional control.
Essentially , we are looking to be ballast free , denying access of foreign species up our river systems.
University of Michigan : Ballast free ship design.