News Release

Preserving Our Manhattan Project Historic Sites

Date: May 21, 2020
Contact: Jonathan Creel, [e-mail]

LOS ALAMOS, N.M. - (May 21, 2020) - Los Alamos National Laboratory (LANL), the Department of Energy National Nuclear Security Administration’s Los Alamos Field Office (NA-LA), and the National Park Service (NPS) work together to preserve and share the nationally significant historic sites, stories, and legacies associated with the Manhattan Project. Ensuring that historic sites associated with the Manhattan Project remain intact to tell the story of this world changing event is a crucial component of this collaborative effort. 

In Los Alamos, many sites constructed during the Manhattan Project were not designed to withstand the test of time. Researchers and military personnel hurriedly built structures for specific purposes in the race to win World War II. Since the end of the war, 75 years ago, some of these sites sat unused—exposed to the harsh Northern New Mexico environment. 

“Concrete has proven to be especially susceptible to the dozens of freeze-thaw cycles that often take place on a winter day in Los Alamos,” said Jeremy Brunette from LANL’s Historic Building Surveillance and Maintenance Program.  

The Manhattan Project National Historical Park team has identified several sites that need attention, and they work continuously to maintain, restore, and protect these Manhattan Project sites. Most recently, two sites, the Concrete Bowl and Gun Site, underwent preservation work. These sites share different stories from the early years of the Laboratory. 

During the Manhattan Project, uranium and plutonium were so rare and costly that scientists carefully conserved every gram. By the end of 1945, it cost an estimated $390 million to create the plutonium for the Manhattan Project—that is around $5.6 billion in today’s money! During the Trinity Test, Project Y scientists planned to carry out a test with half the world’s plutonium, so tensions were understandably high. If the Trinity Test did not succeed, scientists needed a way to recover the precious plutonium rather than losing it on a failed test. 

Manhattan Project researchers discussed several possible recovery approaches; no approach was too far-fetched because of the scarcity of the material. One idea was the “water recovery method.” For this method, researchers constructed a concrete bowl 200 feet in diameter and built a water tank on a tower in the center. In this water tank, they would place a bomb mock-up. The water from the explosion would fall into this concrete reservoir and allow researchers to filter out the bits of nuclear material. Scientists realized this method was not feasible on a full-scale nuclear test and moved on to other potential recovery methods. 

The Concrete Bowl remains in place—an example of the wartime Laboratory’s practice of simultaneously testing different solutions to solve complex problems. In the 75 years since the bowl’s construction, weeds and trees moved in and the local fauna discovered it as a reliable watering hole on the arid Pajarito Plateau.  
“One of the pleasures of working at the Concrete Bowl is the amount of wildlife in the area. We saw elk, deer, and coyotes every day,” Brunette said.  

Brunette also described that “in the concrete bowl, the steel reinforcing mesh was placed too close to the surface, exposing it to the elements and allowing it to carry moisture and rust into the concrete.” 

Before any work began, the Lab’s Environmental Protection and Compliance Division ensured there was no contamination remaining from these early tests at the site. LANL’s Historic Buildings team then worked with Vital Consulting Group from Albuquerque on the removal of damaging vegetation to preserve this historic site for the Manhattan Project National Historical Park. Vital Consulting Group also graded the soil away from the bowl to lessen the accumulation of water inside the bowl.  

While the deer and elk may need to find a new watering hole, these efforts will preserve this historic site for years to come.  

Manhattan Project researchers also developed the Gun Site, known in 1943 as Anchor Ranch Proving Ground, to design and test nuclear weapon prototypes. From nearly the beginning of Project Y, Robert Oppenheimer and Manhattan Project physicists believed they could make a “gun-type” atomic bomb. But, they had to perfect the mechanism that could cause a sustained chain-reaction in fissionable material. At this site, scientists, engineers, and ordinance experts conducted experiments on the inner workings of this design. The name Gun Site refers to this site’s role in the development of the uranium weapon, Little Boy.  

Because researchers fired numerous “gun-assembly” tests at this site using special gun barrels made by the U.S. Navy, they needed bunkers for protection during high-explosives tests. Manhattan Project engineers constructed the buildings in a natural drainage, placing the tests above the bunkers and lessening the hazards of these experiments. These concrete and earthen bunkers also had a periscope that scientists used when observing the tests. 

Today, the preservation mission for this site comes back to a familiar issue—concrete. Brunette explains why Manhattan Project concrete presents the greatest preservation challenge. “We find that much of the Manhattan Project era concrete was mixed using large, smooth river rock aggregate that would not be suitable for modern construction.” 

The buildings at Gun Site underwent extensive concrete repairs in 2012, including the reconstruction of the concrete parapet wall and a concrete cap to drain water from the top. However, that concrete cap failed and allowed further degradation to the historic site. LANL and Vital Consulting Group worked to remove the crumbling concrete from the 2012 project. With this work completed, the Manhattan Project team will move forward with additional preservation efforts at Gun Site. 

These sites tell the story of Los Alamos National Laboratory’s history of solving difficult scientific and technological challenges, as well as the story of a collective effort to achieve a common goal. The Manhattan Project was an immense project that created new fields of science and helped shape the world we live in today.  

The NPS, NNSA, and LANL work together to protect these sites for future generations. In the spirit of its namesake, care for the Manhattan Project National Historical Park comes from numerous divisions and groups across the Laboratory. The historical park team is not finished; they have already begun preservation work in another important Manhattan Project historic location, V-Site.  

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Formally established in November 2015 via a Memorandum of Agreement between the Department of Energy and the National Park Service to preserve portions of three World War II sites where the United States developed the first atomic weapons, the Park marks the history of the people, science, events, and controversy associated with the creation of the atomic bomb in the top-secret effort known as the Manhattan Project. Under the agreement, the NPS and DOE jointly manage and administer the park.