Colorado had a secret Manhattan Project mill that poisoned workers for decades

Durango’s Secret Uranium Mill and the Manhattan Project

In 1943, a secret mill fired up under Smelter Mountain in Durango.

For twenty years, workers there turned raw ore into yellowcake uranium for atomic bombs, first for the Manhattan Project, then for Cold War weapons.

The U.S. Vanadium Corporation ran the plant, processing 800,000 tons of ore from mines across the Colorado Plateau.

Meanwhile, mill workers breathed in radon gas and uranium dust with no masks or proper gear. When the mill shut down in 1963, it left behind over a million cubic yards of radioactive waste.

Today, the Animas River path in Durango tells this hidden story through signs that mark where America’s nuclear age took shape.

U.S. Vanadium Secretly Built a Uranium Mill Under Smelter Mountain

In 1943, U.S. Vanadium Corporation built a uranium mill beneath Smelter Mountain in Durango. This was one of only two secret uranium plants in Colorado for the Manhattan Project.

They picked this spot because it had been a lead smelter since 1882, making the new operation less obvious.

Workers pulled uranium from carnotite ore found across the Colorado Plateau.

They sent the uranium straight to a secret refinery in Grand Junction. General Leslie Groves and his team kept a close watch on everything.

The War Ended and So Did the First Round of Uranium Processing

The Durango mill made uranium sludge until 1946, helping produce about 2.6 million pounds of uranium oxide.

This made up roughly 14 percent of all uranium used in the Manhattan Project. After World War II ended, the mill stopped making uranium.

Workers tore down the green sludge processing plant that same year. The site sat empty for three years while the government figured out what to do next.

Nobody in town knew what had really happened there.

Government Kept Control Through a Clever Ownership Trick

The new U.S. Atomic Energy Commission bought the mill from U.S. Vanadium Corporation in 1948. They quickly rented it back to Vanadium Corporation of America with an option to buy it later.

This setup let the government stay in charge while private companies did the work. The AEC started in 1946 to oversee nuclear energy and weapons production.

This ownership trick became common for uranium mills across the West as Cold War tensions grew.

Uranium Fever Hit Durango as Cold War Tensions Grew

Operations started again in 1949 with Vanadium Corporation of America processing uranium for national defense. The AEC offered cash bonuses and set prices to boost uranium mining and milling across western states.

Durango became a hub for processing uranium ore from the Four Corners region. From 1948 to 1953, Vanadium ran the mill for the AEC under their rental deal.

The need for uranium shot up during these early Cold War years as America built nuclear weapons to counter Soviet threats.

Private Owners Ramped Up Production to Meet Military Demand

Vanadium Corporation of America bought the mill outright on June 30, 1953. The plant processed uranium non-stop for the next decade until March 1963.

During its twenty-year life, workers at the mill processed about 800,000 tons of uranium ore. They turned raw ore into yellowcake, a uranium oxide powder shipped to other places for weapons making.

The mill took in ore from mines across southwestern Colorado, southeastern Utah, northern New Mexico, and Arizona.

Workers Faced Invisible Dangers With No Protection

Men at Durango Mill breathed in radon gas, uranium dust, and radioactive particles daily. They worked without proper masks, air systems, or protective clothing.

Nobody told them about radiation dangers they carried home on their clothes and skin. Mill work exposed them to radium-226, thorium, polonium, and other harmful radioactive materials.

Many got cancer, lung disease, and other radiation-related illnesses years later. The government finally created payment programs for these workers, but only after decades of suffering.

Mountains of Pink Dust Grew Along the Animas River

Milling left behind roughly 1.2 million cubic yards of radioactive waste over twenty years. The tailings dirty about 33 acres while liquid waste spoiled another 20 acres.

Workers piled waste against the mountain slope and along the banks of the Animas River, creating a growing health risk.

Winds often picked up radioactive dust from these piles and blew it across town.

Local people took tailings for free to use in building projects, roads, and home foundations, not knowing they brought radiation into their homes.

The Mill Shut Down But Left Its Toxic Legacy Behind

Vanadium Corporation of America closed and took apart the mill in March 1963. The company moved its uranium work to Shiprock, New Mexico, on the Navajo Reservation.

The empty waste ponds kept leaking toxic radioactive liquids into the Animas River for years. A mountain of pink radioactive dust stayed open, blowing over Durango with every strong wind.

About 122,000 cubic yards of tailings had already spread to properties and building sites throughout Durango.

Congress Finally Recognized the Danger Lurking in Durango

Lawmakers passed the Uranium Mill Tailings Radiation Control Act in 1978 after studies showed these wastes threatened public health.

The law listed 24 uranium mill sites nationwide for cleanup, with Durango ranking fourth worst. EPA and Department of Energy officials set rules and planned cleanup actions.

The Durango Tailings Task Force formed in 1979 to keep locals updated about DOE cleanup plans. Federal Superfund money paid for the massive cleanup job.

Scientists confirmed that radiation levels in some areas of town far topped safe limits.

A Massive Five-Year Cleanup Moved Mountains of Waste

From 1986 to 1991, Department of Energy crews removed mill tailings and dirty soil from the original site.

They also cleaned hundreds of properties where mill tailings had been used as fill or mixed into concrete and mortar.

Workers moved 2.5 million cubic yards of low-level radioactive materials in total. They hauled everything to a disposal facility built in Bodo Canyon, 3.5 miles southwest of Durango.

The cleanup cost over $500 million and was one of the first federal uranium cleanup projects finished in the country.

Visiting Durango, Colorado

You can visit the former uranium mill site where workers processed 800,000 tons of ore for nuclear weapons from 1943 to 1963.

The area is now Durango Off-Leash Dog Park with natural trails, free and open daily.

Park at Schneider Park on 950 Roosa Avenue, then walk through the Highway 160 underpass to reach the site on the Animas River’s west bank.

The Animas Museum at 3065 West 2nd Avenue has exhibits about the uranium processing history.

This article was created with AI assistance and human editing.

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