Nearly 60 feet below ground, the temperature inside the Permafrost Tunnel Research Facility near Fairbanks is about 28 °F. The goal of the facility is to keep the ice in the permafrost frozen so biologists, paleontologists and engineers can examine the different ice formations layered in the earth.

The permafrost tunnel is the only one of its kind in the world. Operated by the Army Corps of Engineers as part of the Cold Regions Research and Engineering Laboratory, a second phase of the tunnel is now underway. When it’s complete, it will connect with the old tunnel.

"We'll be able to confirm the studies that have been done in the other tunnel, we'll be able to expand upon those, we'll have more of a 3D view of this whole area, and we'll be able to map the ice more intricately," said Kevin Bjella, a research civil engineer with the Army Corps of Engineers.

For engineers, keeping the permafrost frozen across Alaska is one of the many challenges of building in a cold climate. The heat from roadways, buildings and homes can melt the ice in permafrost, turning it into unstable ground.

"Some frozen layers are stable,” said Daniel White, director of the Institute of Northern Engineering at the University of Alaska Fairbanks. “But if it's not stable and you thaw it, it becomes unstable and you lose the value of the infrastructure."

Shifting homes and buildings are common in cold climates like Fairbanks. One of the most extreme examples of the problem is Ruth Macchione's log cabin, overlooking Goldstream Valley. Her husband built the home in 1957. Macchione said the cabin was level for years, but then it gradually started to settle into the ground until it became too dangerous for her to live in.

"It was just settling, like a ship listing. I used to tell the kids 'it's like a ship listing to the northeast,'" said Macchione.

She now lives next door. The original cabin sits just feet away, now part of her view of Goldstream Valley.

"It'll just have to behave itself and stay put," she said.