Alberta Historic Resources Foundation (Judy Larmour)
Exploring concession contract models for public transport in
Another new wave of grain elevator design and construction was on the horizon, although this wave would virtually end the wooden grain elevator reign as we know it! And these new styles of concrete elevators would replace the BSB elevators as well – the construction cost was a huge part of the decision, but as well the loading of grain hopper cars was substantially different. For example on a typical BSB elevator a grain hopper car could be loaded around 30 minutes, while as a high-output elevator could load the hopper car in 6-7 minutes. Additionally, the rail car siding capacity at these elevators came into play as well. Several of the BSB terminals were located on branchlines that had smaller siding capacity (usually 25 cars or less), unlike the newer high-output elevators that have 50 or more car capacity on their sidings. Some of the newer elevators include a ‘loop track’ which enables the railways to bring the cars onto the property and unhook the engine and then go again, and the elevator would load the cars and then call the railway back to pick them up when they were done. These types of tracks could easily hold an entire train (up to 135 cars) without the need to break them up into smaller units!
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Back home, Alberta Wheat Pool approved a BSB 2000 terminal for Boyle, AB in 1984 that would become operational in 1986. Around this time, a different type of concrete elevator construction was experimented for a country grain elevator, slip-form construction. Slip-forming is a construction method in which quick-setting concrete is poured continuously in a moving form allowing for cast-in-place (no joints or seams). Inside and outside forms create the cavity of the wall, and inside this cavity, reinforcing steel is tied together vertically and horizontally to reinforce the concrete wall. The form is then connected to jack rods with hydraulic jacks, which automatically move the form vertically in minute increments as the concrete is being poured. The rate of “jacking” is in direct relation to the rate at which the concrete cures sufficiently to advance the forms. Typically, the forms are raised 20 to 24 feet per 24 hours. Once pouring begins, it continues around the clock until the top of the structure is reached, allowing for a monolithic poured concrete structure. Actually, the method has been in place at the turn-of-the-century, with many grain terminals at the ports were built in the same concept. It fell out of favor for awhile, but gained resurgence in the mid to late 1980s. Alberta Wheat Pool’s first slip-form elevator would be located at Grande Prairie, AB in 1989.