Silo Access Portal

Although it was built with steel reinforced concrete walls more than a foot (30 cm) thick, the access portal was regarded as soft. If a nuclear bomb exploded nearby it is likely the structure would have collapsed. The access portal was approximately 16 ft (5 m) square and about 35 ft (10 m) deep. Major components of the portal included the outer stairwell and stairwell cover (usually left open); the outer portal door and phone; the entrapment area, telephone and closed-circuit TV camera; the stairway; the elevator; and a blast door with its associated phone. Also located within the access portal was an exhaust fan with its vent hood on the "roof" of the portal and a sump pump located at the bottom of the elevator shaft.

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