Caribou Air Force Station
Caribou Air Force Station was the first of five, United States Air Force, Air Material Command (AMC) installations that were constructed during the period of 1951 – 1953. Each of the five installations was built specifically to provide operational storage of the nuclear stockpile, and to provide a specified number of weapons to their adjacent Strategic Air Command (SAC) bases. The first four installations were built and occupied by 1953. The fifth installation, although completed in 1953, would not be utilized until 1955. The first installation, code named “Site Easy” was originally known as the “North River Depot”. It was constructed between 1951-1952, and operations began in 1952. Funds were provided in 1951 to the Armed Forces Special Weapons Project (AFSWP), for the planning and construction of an ordnance storage site in the vicinity of a new Strategic Air Command Base. The AFSWP was directed to utilize the services of the Corps of Engineers, Department of Army, for planning and construction, and was made responsible for monitoring such work, and for operational security measures during these phases. The original directive to the AFSWP stipulated that upon completion of construction the installation would be turned over to Headquarters, Air Material Command for operational responsibilities.
Caribou Air Force Station
In addition to the special type igloos that were constructed in 1954, four additional storage igloos were built. These were known as Type VI storage structures. They looked something like the standard or special type igloo because they too were made of reinforced concrete, and were earth covered. These small igloos measured only 26 feet-5 inches in width, and 15 feet-4 inches in length. Although these structures were built like igloos on the outside, they were more like Vaults on the inside. Each of the type VI igloos contained two separate rooms. The first or outer room measured 12 feet in width by 12 feet in length. The height of the room measured 12 feet-5 inches. This room contained a variety of electrical and mechanical equipment. A 16-inch by 16-inch air intake duct was located at the top center of the structure’s front facade, located above the outer doorway. This duct system had a capability of introducing 1100 cfm of outside air into the structure. This same duct system also contained two throwaway type fiberglass filters complete with filter gauges, and two electric duct heaters that were thermostatically controlled. The outer room also contained a wall mounted electric unit (space) heater to heat the room to a comfortable working environment. Of the 1100 cfm of air which was brought into the structure and heated, 600 cfm was used to heat the outer room, and 500 cfm was ducted into the inner room (vault). This was accomplished through another 16 inch by 16-inch duct that branched off of the original air intake duct, and was connected to a vent near the top of the wall. Within this wall was a door to the inner room (vault). An exhaust fan was installed in the ceiling of the outer room, which was rated as being able to expel 1100 cfm of air. This was ducted out of the top of the structure into a duct designed to handle 600 cfm. This duct was connected to a rounded 16-inch, 14 gauge, galvanized steel exhaust pipe. The pipe (exhaust stack) towered twelve feet high above the storage igloo. Both the intake and exhaust ducts had 16-inch by 16-inch positive seal type dampers that were normally closed and only opened when the fans and damper motors were energized. This effect caused a constant positive pressure in the outer room, which prevented air from entering or escaping without the fans and damper motors running.