Permafrost Tunnel Undergoing Expansion
In the early 1960’s, engineers dug a tunnel into permafrost roughly 16 miles north of Fairbanks. They were testing underground excavation methods. The US Bureau of Mines also used part of the original tunnel to test mining techniques in permafrost. On March 15th, personnel with the Army Corps of Engineer’s Cold Climate Research and Engineering laboratory, or CRREL, wrapped up a months’ worth of digging as part of a project to build a new tunnel that will eventually join the older one.
Roughly 50 feet underground, an enormous yellow excavator fitted with a special digging apparatus turns from left to right slowly, scraping at a wall of light brown frozen earth. Kevin Bjela mans the excavator. He’s a Research Civil Engineer with the CRREL. He studies at the impact of permafrost on engineering projects in places like Fairbanks. He’s doing some of that research as he digs. “Every time we do a cycle, we then survey the face, look for bones, look at paleosols and see if we need to take any samples for carbon dating and so we don’t want to go too fast,” he explains. “We never want to go too fast. It would be great to get the project done, but at the the same time we want to do science too.”
This particular project will eventually connect to an older tunnel, which has been used for research for five decades. “There’s a lot of great research that was done in the old tunnel and we wanted to expand upon that,” says Bjela. “Not that everything has been done in the old tunnel, but having a whole new exposure and expanding to it can expand the story. Really what we see in the walls here is a lot of climate records.”
Those climate records look like thick dark stripes in the tunnel walls. These are old soil layers that indicate when the climate was warmer and wetter, anywhere between seven and 30,000 years ago. They can explain what might happen as climate changes in the future. Bjela says the new tunnel will also be used as a geophysical test bed. “So, we actually know where all the ice is on a three dimensional scale and when we apply geophysics to it, we’ll be able to apply different geophysical techniques that are looking forground ice.” he says. “So, there’s a couple different reasons, but in the end we’ll have a whole overarching group of people in here from paleo-scientists, geologists, microbiologists, researchers even extraterrestrial. We have had NASA projects in the old tunnel.”
But to connect the old tunnel, with this newer one, Bjela and his colleagues will have to dig about a thousand feet into a hillside. And they have to find a way to do it without melting any permafrost. “It is challenging,” he admits. “The original tunnel was built with all equipment that was electrically powered, so there was very little heat generation. We’re obviously dealing with this diesel powered excavator that does have a lot of heat generation, so in addition to getting the diesel fumes out for the operator, we need to keep the temperature down and so we are having to blow in copious amounts of cold air and the colder the better.”
The crew can only dig in the winter, and because it’s so slow going, they only dig about 100 feet per year. The project could take up to a decade. Funding for the project isn’t available on a regular basis, which also slows progress. “This is internally funded through CRREL,” explains Bjela. “We didn’t take any congressional appropriation for this. It’s driven from internally that we see that there’s a great benefit to expanding the facility.”
In addition to expanding the tunnel, CRREL has laid the foundation and purchased logs to build a new visitor center. It will replace a small trailer that currently houses the office for the permafrost tunnel. The Army Corps is looking to improve an education and outreach program associated with the tunnel and ongoing research at the site.