One could understandably assert it is not an everyday occurrence to climb over a pile of radioactive waste and live to tell about it, none the worse for wear.

One would be wrong.

The Weldon Spring, Mo., Nuclear Waste Adventure Trail and Museum, officially known as the Weldon Spring Site and Interpretive Center, offers just such an opportunity.

Visitors can clamber to the top of a burial mound of sorts. Underneath lie the remains of the buildings, industrial equipment and the radioactive byproducts of the former plants known as the Weldon Spring Ordnance Works and Weldon Spring Uranium Feed Material Plant.

The manufacturing complex — originally 17,232 acres and including several wastewater treatment plants, seven discharge lagoons and more than 1,000 buildings — was built to produce explosives during World War II. Output was prolific, yielding 700 million pounds of TNT from November 1941 through January 1944.

The stairway leading up to the summit of the Weldon Spring nuclear disposal cell. The mound, under which the remains of 44 buildings, equipment and a stockpile of radioactive material is buried, rises 75 feet above the surrounding prairie. The highest accessible point in St. Charles County, Mo., it yields a view into five contiguous counties, and the Gateway Arch in St. Louis 35 miles to the east can be seen on a clear day. (Kbh3rd/Wikimedia Commons)

The Weldon Spring Chemical Plant, the second complex on the site, processed uranium during the Cold War. The first works, the nation’s largest producer of explosives, operated during World War II and produced 700 million pounds of TNT. (Public Domain via Wikimedia Commons)

Workers remove soil from one of the drainage areas near the Weldon Spring site as part of the government’s decontamination project. The decision was made to bury the contaminated remains of a uranium processing plant onsite rather than risk shipping the material to Utah or Washington state. (Public Domain via Wikimedia Commons)

Hard-packed clay was excavated to construct the permanent disposal facility for the Weldon Spring chemical works site. The clay provided the foundation and cover for the 1.48 million cubic yards of radioactive waste buried in the cell, which is designed to keep the material entombed without leakage for 1,000 years. (Public Domain via Wikimedia Commons)

The timeline of the property chronicles the contamination, decontamination and remediation of the land for public purposes. Highlights include:

• April 1945, the Ordnance Review Board, an agency of the U.S. Army, declared the site surplus property and was slated for disposal to private and public entities.
• October 1946, the first decontamination eff orts were undertaken. The process was deficient, however, and several workers died from improperly decontaminated equipment.
• January 1947 through December 1949, the majority of the site was parceled out to the Missouri Department of Conservation, University of Missouri and St. Charles County Public Schools.
• June 1957 through December 1966, a contractor for the Atomic Energy Commission operated a feed materials plant, including processing uranium ore, known as yellow cake.
• January 1967, the Army proposed production of Agent Orange at the plant, but scuttled those plans in February 1969 when military demand for the defoliant waned.
• August 1975, the Army determined in a preliminary assessment of environmental conditions that the existing chemical plant could not be released for unrestricted use without decontaminating the land and buildings.
• 1984, the Army repaired several of the buildings and conducted some decontamination.
• June 1991, building dismantlement began and structural material, machinery and debris were placed in secure storage.
• December 1992, the Environmental Protection Agency and Department of Energy decided to dispose of all radioactive material by burying it onsite. The alternative, transporting 1.3 million cubic yards of contaminated material to Utah or Washington state, was rejected as unduly risky.
• April 1997, construction began on the disposal cell, with the first placement of waste commencing March 1998.
• June 2001, the last of the 1.48 million cubic yards of contaminated materials were deposited into the cell.
• October 2001, the “last rock” of the cell’s cap was placed, completing construction of the cell.
• Spring 2002, approximately 150 acres of soil surrounding the disposal cell were prepared for the planting of more than 80 species of prairie grasses and native forbs.
• August 2002, the Weldon Spring Interpretive Center was opened in the building formerly housing the checkpoint for decontaminating site workers.
• May 2004, the 8-acre Native Plant Educational Garden was established in front of the interpretive center. The garden includes perennials, shrubs and trees, along with walking paths, benches and informational markers.

The continually monitored disposal cell is designed to last 1,000 years without leakage of its radioactive contents.

It is founded on a base liner with leachate collection and removal systems. The cell contents are surrounded by compacted clay soil and the cover system includes multiple layers of clay, liners, gravel drains, sand filters and a mixture of cobblestones.

The mound rises 75 feet above the surrounding countryside and marks the highest accessible point in St. Charles County, Mo. On a clear day from atop the structure one can see the Gateway Arch in St. Louis, 35 miles to the east.

A concrete stairway leads to the summit, which is bedecked with benches and monuments detailing the history and specifications of the site.

The area also bustles with prairie wildlife, including butterflies, songbirds, hawks, deer and coyote.

The tourist attraction welcomed 786 curiosity seekers in its first year of operation. Over the last decade the interpretive center has logged an average of more than 23,500 visitors a year.

Three towns were displaced by the construction of the ordnance works and the federal government conscripted a portion of nearby Weldon Spring, population 5,443, which is now separated from the attraction by I64.

So, is the site safe for visitors? Decidedly so, according to a fact sheet posted on www.lm.doe.gov/weldon.

The fact sheet, “Fundamentals of Radiation,” reports the average radiation exposure in the United States as 620 millirems per year, half each from natural and manmade sources.

A recent detailed survey of the Weldon Spring disposal cell stairs and monument area, gravel road surrounding the cell, paths leading to the cell and picnic benches outside the interpretive center revealed radiation levels at or below the baseline figure of 5 millirems, an exposure level roughly equal to that of a round trip cross-country flight on a commercial airliner or half that of a chest X-ray.

The site and museum are operated by the Office of Legacy Management, a component of the Department of Energy. Admission is free.

For more information, visit www.lm.doe.gove or call (636) 300-2601. To contact the town of Weldon Spring, visit www.weldonspring.org or call (636) 441-2110.