How do you keep Colorado hikers from falling 300 feet down a mine shaft? Foam.

Since 1980, the Colorado division of mining and the Forest Service have gated and plugged more than 13,000 inactive mines, often using expanding foam

Jason Blevins
The Colorado Sun
Brady Kutscher unloads the equipment off his horse, Dale, while working with the Forest Service to plug a shaft at the Fourth of July Mine, Aug. 30, 2022, in the Indian Peaks Wilderness.
Hugh Carey/The Colorado Sun

ARAPAHO PASS — The bent and broken tent frame draped with an old tarp is wedged about 10 feet down the mine shaft.

“That will work,” says Brady Kutscher, clipping his harness into a rope wrapped around old machinery at the entrance shaft to the Fourth of July Mine. He leans over the hole and shakes a bag about the size of a carry-on. Inside the bag, chemicals mix with resin, creating an exothermic reaction. Soon the bag is spewing foam into the shaft. 

The Forest Service and the Colorado Division of Reclamation Mining and Safety do not like that mine shaft. They guess it falls about 300 feet down to the mile-long horizontal tunnel below — or adit — of the long-abandoned Fourth of July Mine in the Indian Peaks Wilderness. 

Polyurethane foam hardens in the main shaft. One hundred and fifty bags of PUF was needed to fill the shaft from the tarps resting several feet below the surface.
Hugh Carey/The Colorado Sun

After pouring the bags of the quick-hardening foam everyone calls “PUF” into the mine shaft — enough to fill about 50 cubic feet — and covering that foam with a layer of old mining debris, no hiker or animal can fall into the shaft. 

The whole project is all about keeping people from falling into the old mine. (And then trying to sue the Forest Service or state for not properly closing the mines.) It’s part of a mine-shuttering public-safety mission that began in the 1980s and has seen the state and Forest Service close about 13,000 abandoned shafts and tunnels. 


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