October 9, 2022
On a business trip to Peterborough in July I had a few minutes to stop and watch the operation of Lock 21 on the Trent-Severn Waterway. The waterway is 386 kilometres long and was first travelled by a European in 1615 when Jacques Cartier explored the region using long standing indigenous routes.
The canal was originally surveyed as a military route with the first lock being built in 1833 as part of a commercial venture. Three more locks were under construction in 1837 when the Rebellion broke out. It was determined that the canal would have too many locks to be used for rapid troop movements and so the three locks were completed, and progress was suspended. With the canal incomplete and no outlet to a major lake it was connected to other travel routes by toll roads, plank roads and eventually by railways. The image below shows the side view of the lift lock in Peterborough,
It was restarted in the late 1880s by the government of Sir John A. Macdonald, but little progress was made, and it was generally used as a political tool to get votes from the communities along the route. In the late 1890s it was undertaken with a new commitment, and it reached Peterborough and Lake Simcoe in 1904. The First World War slowed progress again and it didn’t reach Trenton until 1918 and Georgian Bay in 1920. By this time the ships had grown too big for the canal system and railways were carrying most of the commercial traffic. It became a pleasure route and eventually would be declared a National Historic Site of Canada and be used as a linear park. The image below shows the lift lock with the left hand side elevated and the right side being loaded for the next lift.
When it was completed in 1904 it was the highest hydraulic boat lift in the world and the largest concrete structure in the world. The vertical lift was 65 feet (20 metres) while most conventional locks had a lift of 7 feet (2.3 metres). The system consists of two identical caissons that sit at the level of the river at their lowest point. They each sit on a 7.5 metre diameter ram. In the picture below the lift is half completed and the two caissons can be seen beside each other.
When the lift reaches the top, it stops 12 inches below the water level in the upper reach. The gate is opened and water flows in to equalize with the level of the river in the upper reach. This causes the upper caisson to increase in weight so that it is 1844 short tons compared to the lower one which has 1700 tons of water in it. When the system is ready to reverse the valve between the two rams is opened and the extra weight in the upper caisson pushed the ram of the lower caisson up until the positions are reversed. The system requires no external power as the weight of the water is enough to operate the system.
Just below the lock is a swing bridge that allows the Canadian Pacific Railway to cross the river. When not in use by the railway it is moved out of the way of boat traffic on the river.
The Peterborough Lift lock was declared a National Historical Site in 1979.
Google Maps Link: Peterborough Lift Lock
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