Prospects for Larger Vessels on the St. Lawrence Seaway

Great Lakes Trader
ATB tug Joyce L. VanEnkevort and barge Great Lakes Trader (Pete Markham / CC BY 2.0)

Published Apr 25, 2023 10:35 PM by Harry Valentine

The only feasible way by which to sail higher capacity vessels along the St. Lawrence Seaway would be to extend the interior length of each of the navigation locks between Montreal and Lake Erie. There is proven tug-barge technology sailing on the Upper Great Lakes today which could sail between Lake Erie and Montreal if the navigation locks were to be lengthened.


Some 20 years ago, discussions revolved around modifying the navigation channels and navigation locks along the St. Lawrence Seaway to transit the earlier generation of Panamax ships built to 105-ft beam and 1,000-ft length. Environmentalists responded by vehemently opposing proposals to deepen the navigation channel to transit the wider and deeper draft vessels between Montreal and the Upper Great Lakes. As well, the cost of widening and deepening the navigation locks was prohibitive. The combination of environmental opposition and high cost of reconstruction resulted in the proposal having been abandoned.

Events that occurred over the years that follow that abandonment now invite discussion about lengthening the navigation locks along the St. Lawrence Seaway, to transit extended length vessels. Proven tug-barge technology that sails on the Upper Great Lakes is built to the same beam as Seaway-max size ships and includes vessels such as ERIE TRADER with a barge built to the maximum Seaway width of 78-ft by 740-ft length.

Tug-barge technology increases payload capacity by transferring the volumetric space required by the engine and fuel tanks into the tug. These vessels are well proven sailing the Upper Great Lakes, including during storms that produce ocean size waves on Lake Superior. While present tugs are powered by diesel fuel, future extend tug length tugs could operate on any of a variety of low-carbon and carbon-free propulsion systems that include battery power. Converting a tug-barge to carbon-free operation retains full payload capacity in the barge in terms of both weight and volume.

Extended length tugs could carry any of a variety of green power options, like grid-scale batteries, insulated tanks of liquefied air, thermal storage tanks or tanks of hydrogen. Concerns about carbon emissions provide opportunity to explore possible future operation where extended length tugs push and navigate Seaway-max size barges on the Upper Great Lakes, and also to evaluate structural stresses at the articulation coupling. There is scope for computer-based structural analysis software to explore possible extending barge length to increase payload capacity and provide background information to determine the possible future interior length of Seaway navigation locks.

Environmental Impact

Future extended length tug-barges would include the identical draft, identical beam and identical bow profile as existing Seaway-max ships and produce the identical bow wave while sailing at the same speed as shorter Seaway-max ships. The environmental impact of the extended length vessel would therefore be negligible compared to wider vessels that sail at deeper draft. The presence of power dams near several Seaway navigation locks provides opportunity to recharge grid-scale size of batteries on battery-electric tugs during scheduled delays encountered when future extended-length tug-barges transit through each of several Seaway navigation locks.

The Seaway’s three-month annual closure would allow for winter time construction to lengthen Seaway navigation locks. During the closure, locks would be drained of water. Such a change would initially allow diesel-powered and later carbon-free tug-barges to sail between the Upper Great Lakes and Lake Ontario and eventually to the Lower St. Lawrence River. The barges would mainly carry agricultural dry bulk that would undergo ship-to-ship transfer to ocean-going vessels at locations downstream of Montreal. There may be scope for tug-barges to carry containers from Montreal or Halifax to any of Hamilton, Cleveland or Duluth.


The railway system has for decades been the main competitor to the St. Lawrence Seaway insofar as providing a link between coastal Atlantic cities and inland cities. Rail traffic volumes have grown while the long-distance intercity railway network has barely changed over several decades. A large proportion of main railway lines across the United States now operate near peak capacity, with the combination of head-end and mid-train groups of locomotives working extended length freight trains. There is much reserve capacity available along the inland waterway system, allowing for future operation of larger and more frequent vessels.

Expanding the intercity railway network in the United States and even in heavily populated areas of Eastern Canada may no longer be an option. It may actually be less costly to increase the length of navigation locks along both the St. Lawrence Seaway and American inland waterway system to transit extended length tug barges. Such a change on the American inland waterway system would result in barge tows of 3 by 8-arrangement of 24-barges to transit navigation locks instead of tows of 15-barges. Seaway locks could be lengthened to transit extended length tug-barges.

Transportation Costs

During 2010, a study undertaken by University of Michigan revealed that a tug-barge carrying 100-containers along America’s inland waterway was cost competitive against railway transportation. Waterway transportation proved more cost competitive as numbers of containers increased. A ship of under 500-feet length carrying containers between Antwerp, Belgium and Cleveland USA proved cost competitive against a mega-size container ship sailing across the North Atlantic to Newark followed by railway transportation to Cleveland. Future railway transportation costs will increase as future demand for container and bulk transportation increases as future main-line railway transportation capacity increases only slightly.

Extended-length tug-barges operating along the inland waterway system and the Seaway would incur lower transportation cost per ton when carrying bulk freight as well as lower transportation cost per container when carrying containers. The combination of changing future weather patterns along with improved future agricultural advances could increase future crop yields and increase the volume of future bulk freight on the inland waterway system. Extended length tug-barges would be capable of carrying future increased export crop yields, at competitive transportation costs. The prospect of lower transportation costs could transfer more freight on to the St. Lawrence Seaway.


There was a time many years ago when government officials considered modifying the St. Lawrence Seaway to transit wider and deeper-draft vessels, except the environmental opposition scuttled such plans. At the present day, proven extended-length vessel technology sails regularly on the Upper Great Lakes and could sail through to Montreal after extending the interior length of Seaway locks. The absence of wildlife habitat and aquatic spawning immediately upstream and downstream of each lock minimizes environmental opposition to lengthening each of the locks.

Top image: ATB tug Joyce L. VanEnkevort and barge Great Lakes Trader (Pete Markham / CC BY 2.0)

The opinions expressed herein are the author's and not necessarily those of The Maritime Executive.