Since the operation of the skier subway at what is now Park City Mountain shut down in the late 1960s, the Thaynes mine shaft has deteriorated, creating a cavern that could potentially destabilize the overall building and headframe at its surface.
In 2021 the local nonprofit Friends of Ski Mountain Mining History began devising a plan to stabilize the structure.
The following year the group agreed to collaborate with the Utah Division of Oil, Gas and Mining to close the mine’s shaft, in order to proceed with a larger restoration project. The state agency is charged with closing thousands of mines across the state.
They initially planned to “plug” the shaft in the summer of 2023, but had to delay due to the historic snowmelt from the prior winter.
“There were virtual waterfalls of water entering the shaft because of all that snow melt moving through the ground,” Friends of Ski Mountain Mining History Project Manager Brian Buck said.
That’s Brian Buck, project manager with Friends of Ski Mountain Mining History. Buck said the water levels didn’t make for the right conditions.
That’s because water doesn’t pair well with polyurethane foam, the primary material used to plug the mine’s shaft.
State crews, with the help of two Kamas construction firms, went to Thaynes Canyon Sept. 10 to begin the stabilization.
“This polyurethane foam is strong stuff,” Buck said. “It’s used in construction for a variety of things. And so what we’re doing is we’re filling the bottom 30 feet of that cavern with solid blocks of polyurethane foam that are being created right there at the work site.”
The foam, known as “PUF” for short, is created by mixing two liquid components that expand to form a light, but strong, solid. Once the blocks of foam are installed in the cavern, they are glued together with liquid “PUF” to produce a permeable plug allowing water to continue to seasonally flow into the shaft.
A layer of concrete and more solid foam is being placed above the permeable layer at the upper part of the cavern to protect it.
Buck expressed gratitude for state officials prioritizing the Park City project.
“They’ve just been great at supporting our overall program,” Buck said. “Because… we can’t do anything to stabilize the buildings if the shaft hasn’t been stabilized, and so it’s critical that we get this work done.”
The work paves the way for the nonprofit to move forward with an over $1 million restoration of the Thaynes Mine. Next year Friends of Ski Mountain Mining History plans to begin guided tours of the historic structure, along with the nearby Silver King Coalition Mine.
