The Peterborough Lift Lock is not a bridge, however this impressive structure that has two structures that physically raise and lower to move boats through a change in elevation on the Trent-Severn Waterway has a number of features similar to and of interest to bridge enthusiasts. The lock structures that raise and lower utilize a riveted pony truss design to bear the load of the water they contain. Also of interest to bridge enthusiasts, the structure also includes a concrete arch span over Hunter Street. Finally, the truss-like lift locks themselves were built by a bridge builder, the Dominion Bridge Company. A local contractor, Corry and Laverdure of Peterborough built the concrete substructure.
The Trent-Severn Waterway has another lift lock, although it is smaller, slightly newer, and more heavily altered from its original design. It is the Kirkfield Lift Lock. Visit that page to see photos of interpretive signage that explain in detail how both lift locks work. Note also that the Kirkfield Lift Lock has riveted, trussed towers beside the lift locks instead of the unreinforced concrete towers found here at Peterborough.
This is the highest hydraulic lift lock in the world and for this reason it is a National Historic Site of Canada. It is also noteworthy for its substantial use of concrete in its construction. Although reinforced concrete was becoming common (yet still in a somewhat experimental stage) when this lift lock was built, this lift lock uses unreinforced concrete. It was when built the largest unreinforced concrete structure in the world. It uses compressed Portland cement and is reported to be the largest and tallest structure to use a compressed form of Portland cement.
Gord Young, Editor for Lakefield Heritage Research provided the following detailed discussion which explains why the Kirkfield Lift Lock has the trussed steel towers instead of concrete, and the significance of the Portland Cement that was used in the Peterborough Lift Lock.
The Peterborough Lift Lock is the largest and tallest compressed Portland cement structure in the world. We know this, because test walls created at the Lakefield Portland Cement Company's former property have the highest density Portland cement recorded. Kirkfield Lift Lock on the other hand had to substitute a steel cage using the same shape as that at Peterborough, only because Rogers and later, Grant who replaced Rogers, could not get adequate "on-time" deliveries of the Lakefield Portland Cement Company. Something was wrong with the materials coming out of a Portland cement plant that was created near Kirkfield to try to alleviate the problem. Nothing worked for Grant. He threw up his hands and built the steel-caging instead. The design for Peterborough and Kirkfield was based on the Peavey-Haglin grain elevator in St. Paul MN. Only two things changed from the grain elevator to the lift locks. The concrete forms were squared, and, the Portland cement was compressed after being poured. Haglin's grain elevator was a simple Portland pour. Both lift locks and the grain elevator used the same principle of pour a form and then jack-up the form when the lower-half was nearly set. Rogers had a certain amount of Portland cement poured into the form, then had it tamped until it was nearly dry, poured more, tamped, poured more, tamped, then when full, began jacking up the form. Now that the outer slathing-parging has peeled off, you can see the ridges of the pouring forms.
Information and Findings From Canada's Historic Places
Description of Historic Place
The Peterborough Lift Lock National Historic Site of Canada is located on the Otonabee River section of the Trent Canal in the City of Peterborough, Ontario. It is a large concrete structure along the Trent-Severn Waterway designed to lift boats 19.8 metres. The lock operates on a balance system, whereby water is let into the upper chamber, a connecting valve is opened and the heavier chamber automatically descends, forcing up the lower chamber to start a new cycle. The lift lock continues to function as part of the Trent-Severn Waterway National Historic Site of Canada under the management of Parks Canada. Official recognition refers to the lift lock, including the immediate upper and lower canal cuts, embankments and underground works associated with the function of the lock at the time of designation.
The Peterborough Lift Lock was designated a National Historic Site of Canada because:
- it is the highest hydraulic lift lock in the world.
The heritage value of this site resides in its surviving physical attributes, and the fact that it was, and remains, an engineering achievement of national and international renown. When completed in 1904, it was the highest hydraulic lift lock ever built, with a vertical lift of nearly 20 metres (65 feet) and was reputed to be the largest unreinforced concrete structure in the world. Its engineering features include the immediate upper and lower canal cuts and the embankments, which are integral components of the lock design and operation.
Source: Historic Sites and Monuments Board of Canada, Minutes, May 1979; The Trent-Severn Waterway Commemorative Integrity Statement, 2000.
The key elements that contribute to the heritage character of this site include:
Heritage Designation and Type: National Historic Site of Canada
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