Editing St. Lawrence Seaway (section)

== Lock, channel dimensions, and additional statistical data ==
The size of vessels that can traverse the seaway is limited by the size of the [[Lock (water navigation)|locks]]. Those on the St. Lawrence and the Welland Canal are {{convert|766|ft|1|abbr=on}} long, {{convert|80|ft|1|abbr=on}} wide, and {{convert|30|ft|2|abbr=on}} deep. The maximum allowed vessel size is slightly smaller: {{convert|740|ft|1|abbr=on}} long, {{convert|78|ft|1|abbr=on}} wide, and {{convert|26.5|ft|1|abbr=on}} deep. After the opening of the seaway, many vessels designed for use on the Great Lakes were built to the maximum size permissible by the locks, known informally as Seawaymax or Seaway-Max. Large vessels of the [[lake freighter]] fleet are built on the lakes and cannot travel downstream beyond the Welland Canal. On the remaining Great Lakes, these ships are constrained only by the largest lock on the [[Great Lakes Waterway]], the Poe Lock at the [[Soo Locks]] (at Sault Ste. Marie), which is {{convert|1200|ft|1|abbr=on}} long, {{convert|110|ft|1|abbr=on}} wide, and {{convert|32|ft|1|abbr=on}} deep.

A vessel's [[draft (hull)|draft]] is another obstacle to its passage on the seaway, particularly in connecting waterways such as the St. Lawrence River. The depth in the seaway's channels is {{convert|41|ft|1|abbr=on}} (Panamax depth) downstream of [[Quebec City]], {{convert|35|ft|1|abbr=on}} between Quebec City and [[Deschaillons-sur-Saint-Laurent, Quebec|Deschaillons]], {{convert|37|ft|1|abbr=on}} to Montreal, and {{convert|27|ft|1|abbr=on}} upstream of Montreal. Channel depths and limited lock sizes mean that only 10% of current oceangoing ships, which have been built much larger than in the 1950s, can traverse the entire seaway. Proposals to expand the seaway, dating from as early as the 1960s, have been rejected since the late 20th century as too costly. In addition, researchers, policy makers, and the public are much more aware of the environmental issues that have accompanied seaway development and are reluctant to open the Great Lakes to more invasions of damaging species, as well as associated issues along the canals and river. Questions have been raised as to whether such infrastructure costs could ever be recovered. Lower water levels in the Great Lakes have also posed problems for some vessels in recent years, and pose greater issues to communities, industries, and agriculture in the region.

While the seaway is (as of 2010) mostly used for shipping [[bulk cargo]], the possibility of its use for large-scale [[Containerization|container shipping]] is under consideration as well. If the expansion project were to go ahead, [[feeder ship]]s would take containers from the port of [[Oswego, New York|Oswego]] on Lake Ontario in upstate [[New York (state)|New York]] to [[Melford International Terminal]] in [[Nova Scotia]] for transfer to larger oceangoing ships.<ref>{{cite news|url=http://www.syracuse.com/news/index.ssf?/base/news-13/122469336925650.xml&coll=1 |first=John |last=Doherty |title=Oswego Considered For Major Container Port: Plan calls for $3M facility to create first Great Lakes site handling global container shipments |archive-url=https://web.archive.org/web/20090623124034/http://www.syracuse.com/news/index.ssf?%2Fbase%2Fnews-13%2F122469336925650.xml&coll=1 |archive-date=June 23, 2009 |url-status=dead |newspaper=[[The Post-Standard]] |date=October 22, 2008}}</ref>

A website hosts measurements of wind, water, levels and water temperatures.<ref>{{cite web |url=http://www.greatlakes-seaway.com/R2/jsp/R2.jsp?language=E&loc=EV00.jsp |title=Great Lakes St. Lawrence Seaway System |website=Greatlakes-seaway.com |access-date=November 25, 2016 |archive-date=November 4, 2016 |archive-url=https://web.archive.org/web/20161104081907/http://greatlakes-seaway.com/R2/jsp/R2.jsp?language=E&loc=EV00.jsp |url-status=dead }}</ref> A real-time interactive map of seaway locks, vessels, and ports is available at.<ref>{{cite web |url=http://www.greatlakes-seaway.com/en/navigating/map/index.html |title=Seaway System |website=Greatlakes-seaway.com |access-date=November 25, 2016 |archive-date=June 12, 2010 |archive-url=https://web.archive.org/web/20100612101610/http://www.greatlakes-seaway.com/en/navigating/map/index.html |url-status=dead }}</ref> The United States' [[National Oceanic and Atmospheric Administration]]-funded [[Great Lakes Water Level Dashboard]] compiles statistics on water depth at various points along the seaway.<ref>{{cite web|url=https://www.glerl.noaa.gov/data/wlevels/dashboard/ |website=noaa.gov |title=Great Lakes Water Level Dashboard |access-date=January 26, 2025}}</ref>