Lincoln Air Force Base Bunker Complex

A part of the Korean War Cold War escalation, Lincoln Air Force Base was chosen as a Strategic Air Command bomber base. The air base was initially marked for re-activation with one medium bomb wing in 1952 (45 bombers). The first bunkers built during 1954 and are noticeable as inner-ring from aerial imagery. When a second bomb was announced to occupy the field further construction commenced and the second ring was built in 1956.

Primarily, the heavily guarded site held free-fall nuclear bombs for the B-47 bombers of the base. However it remains the policy of the U.S. Air Force not to officially announce what bombs were deployed at bases. Various sources point to Mark-6 nuclear bombs being deployed on Lincoln bombers (reported after an infamous crash in England during a training exercise). The Mark-6 was a direct descendant of the Mark-3, the bomb that devastated Nagasaki. The Mark-6 had a variable yield of 8 to 160 kilotons (or 8 to 160 thousand tons of TNT equivalents).

Other bombs deduced to have possibly been deployed aboard Lincoln bombers include the Mark-15, a thermonuclear bomb with a 1 to 3 megaton yield (1 to 3 million tons of TNT equivalent), the B-43, a more modern thermonuclear bomb with similar yield and finally the B-41 bomb. The B-41 was the most powerful nuclear weapon ever deployed by U.S. forces with a yield of 25 megatons. It only was able to carried by either the B-47 or the current B-52 and due to Lincoln being one of the last combat-ready B-47 bases in the United States (1964 and 1965), it is quite possible this bomb was carried by Lincoln bombers.

Along with the nuclear free-fall bombs, the W-38 missile warhead definitely served at Lincoln. It was the main armament of the Atlas-F Intercontinental Ballistic Missile, America’s first ICBM. The warhead had a yield of 3.75 megatons.

In addition to nuclear bombs, various small arms munitions were stored at the complex, particularly the 20mm cannon shells utilized by the B-47’s tail-gun turret. Smaller hand-held munitions were stored here as well.

The bunkers themselves are constructed of highly reinforced concrete construction. The purpose of the shielding was to prevent large scale destruction with the possibility of one of the bombs exploding. Except when being prepared for flight, the nuclear core of the bombs were always stored separately from the bombs themselves. This meant that the actual possibility of explosion came from the high-explosive “lenses” in the bombs meant to start the fission criticality, it would not have produced a nuclear explosion.

The complex lied under the jurisdiction of the 34th Air Depot Squadron (later 34th Munitions Maintenance Squadron). Security was strictly handled by the 818th Air Police (Later Combat Defense) Squadron. SAC’s nuclear weapons policy mandated a “two-man” rule, meaning that no single person was to be allowed near a nuclear weapon at any time.

The last nuclear weapons were removed in mid 1965. The complex remained under U.S. Air Force property management presumably until 1972 with the transfer of all Air Park property to the Lincoln Airport Authority. It remains in LAA hands today, closed to the general public.
A 1954 "inner-ring" bunker, these were larger than the 1956 bunkers perhaps in correlation to the decreasing size of nuclear weapons during the period. 
A 1956 style smaller bunker. Heavily reinforced with thick concrete and covered by earth, these were constructed to dampen potential internal explosions.

Now demolished building 2774 once located on the northeast edge of the bunker complex.

Demolished building 2770, a small warehouse on the east edge of the complex and listed only as "general shops" in the 1966 database. 

Listed as "Pyrotechnics", seems to be an old lock-up for possibly small arms and explosives?