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Marc Pilon

The Cornwall Canal at Lock 21 Canal (Eastward) & the Long Sault Rapids

To most people, The Long Sault Parkway is synonymous with camping, beaches, watersports, wildlife photography, and many other outdoor activities. Mention the Long Sault Parkway to a SCUBA Diver and the immediate response is “Lock 21”. A dive site like none other in the world (to my knowledge…), and unbelievably complicated to describe to anyone who falls into the “most people” category. The exception would be the townspeople who witnessed the Great Lakes Freighters, the Canalers, Tugboats & Barges “locking through” the Cornwall Canal system on a daily schedule (except once the river was frozen) up until the planned inundation of 1958. They witnessed what Lock 21 looked like and had a clear concept of its operation, they understood the magnitude of the labor and engineering involved in the building of these canals and locks. They had first- hand experience of how the system used the higher down flowing water to fill a hand built basin (270’ long x 45’ wide x 14’ deep) equipped with a pair of doors at each end to lock in a floating ship, then drain the contents through a series of stone tunnels and gates to lower the vessel to downstream river level, thus allowing the vessel to continue on its way. This sequence of events was necessary to move cargo and passengers safely bypassing the mighty Long Sault Rapids as well as negotiating the land height difference as you move farther inland from sea level.

   Ontario boasts 2 similar and operational canal-lock systems built in the same era and both are listed as UNESCO World Heritage Sites today. The Rideau Canal Waterway (202 km long) connects Lake Ontario from Kingston to the Ottawa River in Ottawa, and the Trent-Severn Waterway (386 km long) connects another part of Lake Ontario from Trenton to Georgian Bay at Port Severn. Although designed for smaller ships, both waterway systems work and operate the same as the Cornwall Canal System did and are a “must see” destination if traveling anywhere near them.

   Lock 21 at MacDonell Island hosts hundreds of Divers weekly in peak season, most have dove this site repeatedly and without boredom. The current can be strong and visibility can be low but divers are constantly parked or camping at its shoreline ready for the next chance to dive this site. Note that this is considered an Advanced dive.

   The Cornwall Canal was conceived around 1830 as the St. Lawrence River was dangerously difficult to navigate due to some of its fast flowing rapids, numerous islands and some shallow depths. Construction on this epic project started in 1834 but was plagued with budget constraints, hence the 18km (11 miles) canal was system was not completed until 1843. Accounts of this project are scarce but a British artist named W.H. Bartlett (1809-1854) who in his relatively short life managed to travel the world and illustrate countless landscapes & cityscapes. His finely detailed works are widely regarded as historical time pieces, as in our case his print titled “Long Sault Rapids, on the St. Laurence” in 1840.


This painting depicting the ongoing dig of the canal and the rapids is viewed looking south from what is present day MacDonell Island. Note the severity of the rapids at that time and the height from his perspective.


By zooming into the bottom left section, his other focus were the work crews excavating the original Cornwall Canal with teams of livestock drawn carts.


This forever altered the river patterns by essentially widening it, therefore softening the flow and intensity of the rapids. Before the completion of the canal, it was already considered inadequate as vessels had already increased in size and depth. Between 1876 & 1904 the Cornwall Canal underwent several enlargements to stay modern, until the St. Lawrence Seaway and Power Project in the 1950s rendered it obsolete and was inundated to the water level we have today thus erasing any tangible signs of its existence.


This photo taken in the 1950’s, ironically from the same angle that W.H. Bartlett rendered his illustration 140 years earlier.


Present day photo taken from the same vantage point. The inundation added approximately 40ft of water to the river system. Note the Long Sault Control Dam (located on the American side) in the middle of the photo, essentially connecting 2 islands, Long Sault island and Barnhart Island.

   There was a unique phenomenon that took place between the 4th April and 11th of December 1957, when the Long Sault Rapids area was temporarily dammed and drained (east of Cofferdam- E, directly in front of MacDonell Island). The flow was diverted south around Long Sault Island in order to finalize work on the Long Sault Control Dam. With the river bottom exposed, one could now understand why the rapids were so ferocious. Enormous truck sized boulders were randomly strewn about, flat bedrock plates 100 ft long were now exposing earthquake-like fault lines, then a dropped layer of bedrock 5-10’ below repeated several times giving the illusion of a giant set of stairs. A 20ft x 2ft thick flat rock, illogically propped up on boulder was nicknamed Table Rock, as the public was allowed to roam and explore this moonscape-like riverbed. There are natural bored holes through plate rock several feet thick and some up to 3 feet in diameter, tricking your brain to question if they were actually done mechanically. 


Dive photo of 12” bore hole, 70’ depth, Long Sault Rapids area, taken by Jason Xenakis

 

This geological anomaly was apparently caused by the retreating glaciers and remnants of the Champlain Sea which encompassed the valleys of the St. Lawrence and Ottawa Rivers as well as the Lake Champlain region some 13,000 years ago. Of course, the water flow of the rapids played a great deal in shaping this prehistoric look as this dramatic riverbed is not found anywhere else in the nearby area.


Diving this area

   We’ll use the Lock 21 site area as an Entry Point but not part of our actual dive as it should be done on its own. Drifting East along the north wall is a nice change of pace and scenery, venturing into the canal bottom will give you a maximum depth of 55 feet/16.8 meters. A 30-minute drift will take you halfway down MacDonell Island to a relatively easy Exit Point where the Old King’s Highway #2 pavement peaks in and out of the shoreline. You’ll find a flat grassy “day use area” of the Long Sault Parkway and a short walk back to the Lock 21 entry point, or choose to park a return vehicle there. Opting to do a 1-hour drift dive on the north wall will take you to the easternmost end of the MacDonell Island know as Long Sault Rapids Point, where the pavement of Old Hwy #2 once again goes in to the river. Note that this is not a boat launch area. Along the wall you may find cut off telephone posts sticking up from its upper bank then a collection of larger boulders as the shoreline is much steeper and offers no exit point till the end of the island. A guide rope is in place signaling the end of the island and leads you up to the paved road making it an easy exit point. Take note not to miss the exit rope as the current picks up in that area and you will find yourself surface swimming back from Royal Baker Island… “been there, done that” (a few times), don’t miss the rope!


Topographical Chart pre-flooding, green outline is present day land, yellow circles are where Old Hwy #2 pavement goes in/out of the river, 2 blue lines indicate guide/exit ropes signaling end of the dive, red arrow lines show the drift dive along the north and south canal wall, other red lines indicate possible routes for DPV/Scooter dives.

   For a more advanced dive and dramatic landscape, let’s cross over to the south wall of the canal (aka the Towpath) and into the old riverbed of the Long Sault Rapids, again from the Lock 21 entry point. Drifting eastward down the wall will reveal piles of irregularly cut boulders used to bolster and prevent erosion the canal wall. Depending on your trajectory, you may find the river bottom getting shallower as you cross over the mound that once was “Cofferdam E”, the man-made earthen dam created to divert and drain the water from the Long Sault Rapids for 8 months. From here on, the 70-80’ river bottom becomes increasingly more scenic but combines with a heavy current. Do not get distracted from where you need to be and keep it slow. Stay on or close to the canal wall, you may venture into the riverbed as long as you’re always mindful to keep canal wall to your left. After 40-45 minutes you may consider crossing the canal onto the north wall and work your way to the exit leading to the Old Hwy #2 pavement at the eastern point of MacDonell Island. Should you encounter the rope on the south wall from the old riverbed, follow it up the wall to the edge where you will then cross the canal and find the north wall exit rope to make your way out. Note that you don’t want to miss the south wall guide rope. Better yet, cross over the canal BEFORE you even encounter this rope. Again, this is an advanced dive, so familiarize yourself with landmarks, attempt shorter dives to gauge your time & distance, or better yet if you could buddy up with someone who has experience with this dive.

   For our Scooter/DPV divers, this area is an open playground for you as you have your choice of entry and exit points. If you choose to enter anywhere east of the grassy “day use area” of the island, make sure to head upstream for a bit to prevent a long surface scooter back to the car. You have the option to cross the river heading more to the south until you hit the shallows of our American neighbor’s island, Long Sault Island (yes, you have skipped over the international border line to an uninhabited U.S. Island, do not get stranded or set foot there). Take note that this waterway is a busy pleasure boat corridor in the summer, always have a DSMB (safety sausage) with you.

Enjoy

Written by Marc Pilon and experienced with Andrew Emard, Jason Xenakis, and Sam Hamed.


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