The Operations Center itself lies along one side of a main tunnel bored almost a mile through the solid granite heart of the mountain. The tunnel is designed to route the worst of a blast’s shock wave out the other end, past the two 25-ton blast doors that mark one wall. The center was designed to withstand up to a 30 megaton blast within 1-nautical-mile (1.9 km).
The underground Combat Operations Center (COC) was originally intended to provide a 70% probability of continuing to function if a five-megaton nuclear weapon detonated three miles (5.6 km) away, but was ultimately built to withstand a multimegaton blast within 1.5 nautical miles (2.8 km; 1.7 mi). It was also designed to be self-sufficient for brief periods, have backup communications and television intercom with related commands, house personnel during an emergency, and protect staff against fallout and biological and chemical warfare.
The main entrance to the complex is about one-third of a mile (540 m) from the North Portal via a tunnel which leads to a pair of 25-ton steel blast doors. Behind them is a steel building complex built within a 4.5 acres (18,000 m2) grid of excavated chambers and tunnels and surrounded by 2,000 feet (600 m) of granite. The main excavation consists of three chambers 45 feet (15 m) wide, 60 feet (20 m) high, and 588 feet (180 m) long, intersected by four chambers 32 feet (10 m) wide, 56 feet (17 m) high and 335 feet (100 m) long. Fifteen buildings, freestanding without contact with the rock walls or roofs and joined by flexible vestibule connections, make up the inner complex. Twelve of these buildings are three stories tall; the others are one and two stories.
The outer shell of the buildings is made of three-eighths-inch (9.5 mm) continuously welded low carbon steel plates which are supported by structural steel frames. Metal walls and tunnels serve to attenuate electromagnetic pulse (EMP). Metal doors at each building entrance serve as fire doors to help contain fire and smoke. Emphasis on the design of the structure is predicated on the effects of nuclear weapons; however, building design also makes it possible for the complex to absorb the shock of earthquakes. During a nuclear explosion, powerful springs that support the complex can absorb much of the energy.
Blast valves, installed in reinforced concrete bulkheads, have been placed in the exhaust and air intake supply, as well as water, fuel, and sewer lines. Sensors at the North and South Portal entrances will detect overpressure waves from a nuclear explosion, causing the valves to close and protect the complex. The buildings in the complex are mounted on 1,319 steel springs, each weighing about 1,000 pounds (450 kg). The springs allow the complex to move 12 inches (30 cm) in any one direction. To make the complex self-sufficient, adequate space in the complex is devoted to support functions. A dining facility, medical facility with dental office, pharmacy and a two-bed ward; two physical fitness centers with exercise equipment and sauna; a small base exchange and barber shop are all located within the complex.
Electricity comes primarily from the city of Colorado Springs, with six 1,750 kilowatt diesel generators for backup.
Water for the complex comes from an underground supply inside Cheyenne Mountain, deposited into four excavated reservoirs with a capacity of 1.5 million US gallons (6,000 m³) of water. Three serve as industrial reservoirs and the remaining one is the complex’s primary domestic water source. They are so large that workers sometimes cross them in rowboats. About 30,000 to 120,000 US gallons (110 to 450 m³) are actually retained at any given time.
Incoming air may be filtered through a system of chemical/biological/radiological/nuclear (CBRN) filters to remove harmful pathogens and/or radioactive and chemical particles. The fresh air intake is mainly from the south portal access which is 17 ½ feet (5.3 m) high and 15 feet (4.6 m) wide and linked to the north portal access which is 22 ½ feet (7 m) high and 29 feet (9 m) wide. The entire tunnel from north to south entry portals is nine-tenths of a mile (1.5 km) long.
The NORAD command center has been modernized several times over the years. The original equipment resembled Mission Control for NASA’s Project Apollo in the 1960s-1970s and used similar Philco-Ford consoles and display systems. The current (2005) version, with ordinary desks and flat-screen displays, looks rather ordinary by comparison and resembles NASA’s current (2000s) mission control.