North Bay’s Cold War Bunker, an engineering feat
Political tensions ran high in the 1950s. Aggravations between the USSR and the United States stirred frightening visions of Cold War hostilities turning into the heat of nuclear battle. If this happened, Canada would be midway under soaring atomic bombs.
Governments devised an ingenious strategy. An underground bunker would keep a protected eye on the skies and allow quick response by North American Air Defence Agreement (NORAD) to incoming air threats with the American Semi-Automatic Ground Environment (SAGE) system.
Among locations scattered around the continent, CFB North Bay encompassed all the requirements that a large-scale military project needed, plus an unusual advantage. An enormous, subterranean layer of granite that could be transformed into a rock-solid bunker. The task took planning, imagination, and a lot of muscle.
The North Bay bunker entrance was excavated wide enough for two vehicles, ca 1960. Civil Defence Musuem, Photo #66.
“The bunker is one of the greatest achievements of the Royal Canadian Air Force (RCAF) Construction Engineering Branch, which coordinated the work of several private firms,” stated Canada’s Historic Places. “The complex possesses certain unique qualities that speak to the will for survival and state of mind associated to the Cold War.” The drawings called for several sections, the Power Cavern and Control Building, the Main Installation, and capacity for utilities and reservoir.
Chiselling entrances into a low hill in early 1959, two tunnels on a ten-percent grade were drafted for the complex. Military and civilian personnel entered the bunker from the military base via the North Tunnel, sized at 3.65m x 3.96m, and just over 2 kms in length. The South Tunnel was 4.87m x 5.18m and almost 1 km length, with its exit pointing toward Trout Lake. Sixty stories deep, the facility’s caverns were blasted out of the rock. Due to the complexities of granite excavation, a massive five-drill rig was designed for the bunker job. As well, a new method of smooth wall blasting was used.
Developed in Sweden, “the smooth wall line technique is composed around the final excavation line underground where the holes are lightly loaded to reduce the amount of overbreak,” said R.Q. Eades and Kyle Perry in “Understanding the connection between blasting and highwall stability” January 2019. “The smooth wall technique also involves more perimeter drill holes when compared to conventional underground methods.”
Diagram of North Bay underground bunker, with entrances and personnel spaces. Ca 1950. Civil Defence Museum. Photo #67.
Workers excavated over 680,000 tonnes of granite through the brawn of nearly 700 tonnes of explosives. (One cubic metre of granite weighs a hefty 2.96 tonnes.) “Speeding along at 33 feet per day, with 24 hour/6 days a week excavation work, the excavation began before the exact plans for the building had been completed so that the target completion date could be met,” described UGS50, A Virtual Exhibit of North Bay’s Underground Complex. The excavated granite was used to augment the city’s Lake Nipissing waterfront.
The two large caverns were 13.7 m wide and 16.46 m high, sufficient for buildings almost 10 m wide and three storeys tall. “The extra clearance around the building allows for ducts, cabling, piping, and space for inspection and rock wall scaling,” according to Jim Williamson on the Communication and Electronics Museum.
Assembled without frills, the buildings contained offices, large computer room, kitchen, bathrooms, control centre for maintenance, and command post, in case hostilities erupted. There was also a barber shop, medical office, gym, and meeting rooms, and spacious enough to house 400 people for several weeks if needed.
Planning for geological disasters such as earthquakes or nuclear shock, the buildings were constructed on specifically-designed piers. The pilings were robust enough to tolerate a bone crushing four-megaton nuclear explosion, a blast more destructive than the bomb dropped on Hiroshima in WWII.
Located between the large caverns, a clean water reservoir of over 757,000 L was prepared for human consumption. A second reservoir of almost 19 million L, said Williamson, “was stored for cooling and air conditioning in the event that water from Trout Lake was unavailable.”
The subterranean complex “used civilian hydroelectricity but had two banks of batteries to provide electricity in case of power failure,” noted Innovation, Science and Economic Development Canada. The batteries “were backed up by generators that could run on diesel or natural gas.”
Military personnel on duty at North Bay NORAD bunker. Civil Defence Museum. Photo #65.
Electricity was essential to operate and cool the energy-gulping, enormous SAGE computer, a first-generation machine using heat-producing vacuum tubes. The computer provided “high speed detection of aircraft, assistance in their rapid identification, and, when required, aiding quick Ground Controlled interception of unknown, suspicious and hostile aircraft,” said Bruce Ricketts of Civil Defence Museum and Archives. SAGE was associated with the Bomarc nuclear-armed surface-to-air defense missiles.
The tab for the four-year-long bunker construction came to $51 million, with Canada paying one-third, and the United States covering the balance. In early 2005, the Control Building and Power Cavern were designated together as a Classified Federal Heritage Building.
Known locally as The Hole, the NORAD site underwent several transformations before closing operations in 2006. Visit the Civil Defence Museum for more fascinating information about the Cold War.
This article first appeared in Ontario Construction News in March 2020. (C) Susanna McLeod