Tech Area II Historic District
Sandia’s Technical Area II was designed and constructed in 1948 specifically for the assembly of the non-nuclear components of nuclear weapons. Between 1948 and 1952, Tech Area II was the primary assembly site for America’s nuclear weapons.
Both the architecture and location of the early buildings in the district reflect their original purpose. The site was located away from the main area of Sandia’s operations (Tech Area I) and the buildings within Tech Area II were separated from one another, both decisions reflecting that weapons assembly would involve handling thousands of pounds of high explosives at a time.
The architectural firm of W. C. Kruger and Associates designed the initial set of five buildings for Tech Area II. Kruger was a noted New Mexico architect whose credits included serving as the State Architect (1936-1937); creating the Los Alamos master plan of 1947; the Governor’s Manion in Santa Fe in 1955; the University of New Mexico Medical school Basic Sciences Building in 1965; and St. Joseph’s Hospital for the Sisters of Charity, Albuquerque in 1965.
The buildings opened for occupancy September 7, 1948. By the time they opened, the Atomic Energy Commission already had plans in place to move weapons assembly activities elsewhere in the burgeoning nuclear weapons complex. By 1952, assembly activities were well underway at the Burlington, Iowa, assembly plant and the Pantex, Texas site also was coming online.
Weapons Assembly and Sandia
Among other changes, when Los Alamos reorganized in July 1945, it gathered up the ordnance engineering and assembly functions into a group called Z Division. Z Division was responsible for the design, testing, and production (whether through internal assembly or procurement) of all non-nuclear components of nuclear weapons. The assembly assignment included assembling weapons for testing (e.g., the Operation Crossroads nuclear tests in the summer of 1946) and, as more weapons were designed and produced, assembling weapons for the stockpile.
Most of the nuclear weapons in the early Cold War were implosion designs, based on the Manhattan Project’s Fat Man. This was a central core of nuclear material surrounded by a sphere of high explosives. Detonation of the high explosive squeezed the central core, compressing it to a supercritical mass. Introduction of neutrons to the core initiated the nuclear chain reaction.
These early weapons were assembled and stored without their central core and were known as sub-assemblies or mechanical assemblies. Were a weapon to be used, it had to be partially disassembled, the nuclear core inserted, and the weapon reassembled. Sealed-pit weapons—weapons with their nuclear components installed during assembly—did not enter the stockpile until 1957.
The Site Layout
Tech Area II was a diamond-shaped piece of land of approximately 45 acres located about ½-mile south of Sandia’s Tech Area I on what is now Kirtland Air Force Base near Albuquerque, New Mexico.
It was surrounded by a 10-foot high chain link fence, with one guard tower (Building 909) standing outside the gate at the western point of the diamond and a guard house (Building 900) just inside the gate providing security.
The primary buildings in the original design were Building 901 (housing the change, break, and laundry rooms) and Buildings 904 and 907 (the assembly facilities). Building 901 was just east of the area’s entrance. To the southeast and northeast of Building 901, Buildings 904 and 907 were aligned along the north-south center line of the area, approximately 1,100 feet apart.
Buildings 903 and 908, the mechanical rooms for Buildings 904 and 907, respectively, also date from the initial 1948 construction, as does Building 902 (the standby power generator).
Elements of the Historic District: Guard Tower
The guard tower (Building 909) was built outside of the western point of the diamond-shaped parcel that formed Tech Area II. A guard house (Building 900) was also constructed at the entrance to the site and is visible at the foot of the tower.
The guard tower was of a common military design of the period. It stood on four metal posts with metal cross braces in four sections rising to a wood and metal platform holding a wood and metal observation room with windows on all four sides and a flat roof. The deck was surrounded by a low wall with multiple generations of lighting attached to it. Metal stairs with metal handrails rise around the outside of the post-and-cross brace to a hatch in the platform deck.
An original light fixture remained attached to the bracing beneath the tower platform. A metal arm extends the reflector out toward the edge of the tower.
When the site was photographed in 1998, the tower had not been used in decades and was showing wear. The windows on the observation room were collapsing and its door had been removed. The coping on the roof’s edge was missing in places and it was leaking.
Elements of the Historic District: Assembly Facilities
The assembly buildings (Buildings 904 and 907) were designed to house the linear movement of items through the assembly process. Components and sub-assemblies entered the building at the low (one-story) end and moved along as they were assembled into weapons, finally reaching the high-bay at the opposite end of the building. From there they exited the building and were sent to storage.
Buildings 904 and 907 were mirrors of one another. The high bays where the completed sub-assemblies were packaged for shipping were at the north end of Building 907 and the south end of Building 904, placing the two largest concentrations of high explosive in the area as far as possible from one another. Twenty-five feet from each building’s north and south ends was a 17-foot tall blast wall of 12-inch thick concrete with an earth berm on the side away from the building. Beyond the wall and berm on each building’s high bay end was the mechanical room supporting that building with a plenum extending up and over the barricade to provide utilities to the building.
Buildings 904 and 907 housed the weapon assembly activities. Subsystems and components assembled or purchased elsewhere entered the buildings at their lower ends and moved through a series of assembly bays until they reached the high bay at the building’s opposite end.
Elements of Historic District: Change Building
Building 901, located just east of the gate into Tech Area II, housed the change, break, and laundry room for the weapon assembly workforce. Workers stopped at the building on their way in to work and changed into their work clothes. They then rode a small bus out to Building 904 or 907. During breaks, they returned to 901 to eat and relax. At the end of their shift, they stopped in 901 to shower and change. Work clothes remained in the building and were laundered there before being returned to service. The goal was to keep explosives dust and residue from leaving the area.
The amount of high explosive handled in the assembly area was a key concern in the architectural design of its facilities. The front (west) exterior wall of Building 901 extended in wings to the north and south and along the top of the building to provide a retaining wall for the earth covering the building. This provided blast protection should there be a detonation in one of the two assembly buildings in the area.
Explosion-Proof Features
The original floor plans of Buildings 904 and 907 indicate how the assembly process worked. They also reflect the risks of handling high explosives. Note the narrower rooms with no openings between the larger assembly rooms. These were rubble-filled rooms meant to buffer and collapse onto the rooms next door in the case of an explosion.
The west walls of the narrower, rubble-filled buffer rooms were apparent in the buildings’ north-south corridors. The concrete west walls extended approximately 10 inches into the corridor.
In the years since weapon assembly ended in Tech Area II, modifications to the buildings included opening up one of the rubble-filled buffer rooms in Building 904 to use for storage. The wall between this room and the assembly room next door is 2 feet thick. The interior walls of the buffer room lean outward as they go up, a design meant to encourage the collapse on the neighboring assembly rooms in the case of an explosion.
The original fixtures in the buildings were “explosion-proof,” meaning spark-resistant. Telephones were heavy, sealed Western Electric units that prevented sparks from escaping the casing; light figures were similarly heavy-duty, with thick glass reducing the chance of sparking and metal cages protecting them from breakage.
Metal storage igloo with front wall extending to serve as a retaining wall for the earth blast berm that covers the structure. The storage igloos were standard military designs, meeting specifications for explosives storage.
Evolution of Tech Area II
Weapon assembly continued in the area after 1952, but the major responsibility for assembling nuclear weapons shifted to other sites in the Atomic Energy Commission’s integrated contractor complex. Eventually, Sandia’s assembly responsibilities ended, and the Lab moved explosives research activities into Tech Area II. Additional buildings were added to meet different design and testing requirements.
A variety of different structures were added to the area after its initial construction, including storage igloos for explosives and other materials. Multiple storage igloos of different sizes extended along the northwest perimeter and a few along the southwest perimeter of the area by 1998.
In 1957, an explosive devices development laboratory was added to the area. Building 922 was specifically built as a research area for explosive components. It had a firing pad in the back and portholes to observe and record tests. In the early 1980s, a gas gun was added to the facility in support of research on explosive detonation and shock-induced chemistry of explosives. The building also contained a laser spectroscopy lab with diagnostic equipment.
An explosive chemical laboratory (Building 940) was built in 1965. The building included a large work and control room in the front and seven vaulted test rooms with frangible walls to blow out away from the area in the back. The building housed a remote control facility for the precision machining of explosive components and materials, as well as big ovens for aging components. Notably, the building witnessed the development of the semiconductor bridge, which could ignite explosions 1,000 times faster than any previous igniter.
In addition to increasing the number of facilities in Tech Area, Sandia also modified the existing structures. Building 907 was converted to explosives testing, with test pads added to the exterior of the east side.
Tests were controlled from Building 907’s interior, with heavy glass and steel ports allowing observation and data capture.
End of Life
By the 1990s, the aged facilities were difficult and expensive to maintain. Most were no longer in use. The small amounts of explosives Sandia used in the research and testing of high-explosive components did not require the thick walls and large spaces of Buildings 904 and 907. The other buildings used for research in the area proved challenging to modify and adapt to new research and testing needs. A new, modern, and more efficient facility was proposed, built, and occupied in 1995.
Historic District
In consultation with the New Mexico State Historic Preservation Officer (SHPO), the U.S. Department of Energy/Kirtland Area Office (DOE/KAO) determined that the old Tech Area II was a historic district. This determination was based on Tech Area II’s original role as the primary assembly site for U.S. nuclear weapons for the period 1948-1952 and for its role in the research and development of explosive components for nuclear weapons for the 1954-1989 period. These activities fall under the established Sandia National Laboratories Cold War themes of weapons assembly and weapon design.
In 1998, the Tech Area II facilities were slated for demolition and were documented, per agreement among the NM SHPO, DOE/KAO, and the Advisory Council on Historic Preservation. In succeeding years, the facilities were decontaminated and torn down.