Experts from Manhattan Project National Historical Park join the fun at Los Alamos ScienceFest Discovery Day July 16

July 14, 2022

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S-Site complex in 1946.

Sequestered on the property of Los Alamos National Laboratory sit a group of historically significant structures critical to the development of the very first atomic weapons, which were used to help end World War II in 1945. These sites, along with others at Oak Ridge, Tennessee and Hanford, Washington, are preserved as part of the Manhattan Project National Historical Park. However, like the Trinity Site at White Sands Missile Range, the park is open for tours twice a year in April and October.

This week, science history enthusiasts can learn more about the history of the Manhattan Project from the historical preservationists who are making the park happen, at Los Alamos ScienceFest Discovery Day. Event booths provide free, hands-on activities and engaging exhibits for all ages on July 16, from 10 a.m. to 3 p.m. at Ashley Pond in downtown Los Alamos. Discovery Day is part of Los Alamos ScienceFest, which runs July 12-17.

A peek into recent park activities, S-Site restoration project

When the Manhattan Project came to Los Alamos in 1943, its leaders developed a main high-explosives area away from the primary technical area near an old sawmill site, where a large pile of sawdust remained from former lumber operations. Thus, this location received its name, the “S-Site,” or “Sawmill Site.” Several of S-Site’s original structures are a part of the park.

Construction teams hurriedly erected buildings across S-Site. An immense complex of buildings, roads, a steam plant, storage magazines and protective structures spread across the mesas at the southwestern edge of the wartime laboratory.

Today, this landscape is vastly different. One of the few remaining Manhattan Project structures is a one-story, single-room, high-explosives storage building, known as a “magazine,” comprised of a reinforced-concrete floor and walls with a wooden roof. A protective earthen berm encircles the magazine. If an accidental explosion had occurred during the Manhattan Project, the magazine’s wooden roof would have directed the force upward rather than outward, lessening the chance of one accidental explosion igniting more explosions across the site.

The Laboratory’s cultural resources team created a rehabilitation plan to save this structure with a focus on site longevity. According to historic buildings specialist J.T. Stark, maintaining the wood plank decking was a high priority since the original wartime construction crew used it to form the concrete walls. The remnants of the magazine’s original concrete are still visible on the ceiling. The team made sure this part of the structure was protected from weather hazards. The roof above the wood planking was not original and nearing the end of its functional lifespan, so the team replaced it.

The structure’s wooden wing walls also needed reconstruction, as they were rotting and falling apart. Laboratory carpenters reconstructed them based on the original dimensions and design plans from the Manhattan Project.

The wood plank decking inside the magazine is original—it was constructed during the Manhattan Project.

Collaboration key to preservation efforts

During the Manhattan Project, developers were not concerned with the longevity of these buildings and did not cover them with shingles at all. The exterior of most structures was essentially bare drywall. Asbestos shingles were later added. “When conducting our research on these Manhattan Project structures, we found that most were covered with a green colored, triple-sealed gypsum board,” said historic buildings subject-matter expert Jeremy Brunette. Needing to protect the gypsum board from the weather while eliminating the asbestos hazard, the team covered the gypsum board with modern wooden shingles. They also recreated the visual accuracy of the building by painting the exterior the same green used during the war years.

Although the building has been safely rehabilitated, the maintenance work will continue to ensure future generations are able to see this piece of history as it appeared in the past. The project’s success was the result of extensive collaboration among Lab’s many craft specialists, insulators, carpenters, painters, operators, laborers, sheet metal workers and roofers.

The Manhattan Project Historical Park will next be open for guided tours on October 15. Registration begins in August. Sign up here.