Thule Air Base is the U.S. Armed Forces’ northernmost installation, located 750 miles north of the Arctic Circle, in Greenland. Thule’s arctic environment offers some of the most spectacular scenery found anywhere in the world, including majestic icebergs in North Star Bay, the massive polar ice cap, and Wolstenholme Fjord – the only place on earth where three active glaciers join together. It’s also home to the northernmost deep-water port in the world.
Recently, Jacobs Engineering Group selected ZEBRA Environmental to participate in two subsurface investigation projects at Thule. The first project required conventional soil and ground water sampling for the Air Force Center for Engineering and the Environment (AFCEE) near a jet fuel storage facility. A second investigation involved collecting permafrost data for the Cold Regions Research and Engineering Lab (CRREL), which was directed by CRREL’s Kevin Bjella. The field team collected soil cores, used air rotary to install thermistors to depths of up to 15 feet below ground surface, and installed a geothermal loop using the air-rotary technique to 50 feet below ground service.
ZEBRA made plans to airlift all equipment and supplies from McGuire Air Force Base in New Jersey (near ZEBRA’s branch office in Atlantic Highlands, N.J.) to Thule a few weeks before the project start date. Due to mission-critical shipments, a last-minute call informed project planners that space on the cargo planes was no longer available. All equipment needed to be shipped, and everything needed to be in a sealed container in Norfolk, Va., in only two weeks. With all of ZEBRA’s 66 series and 77 series rigs scheduled for the next three weeks to five weeks, the firm had no rig readily available for the last-minute change.
“That’s when we turned to our friends at Geoprobe,” says Paul Fleischmann, president of ZEBRA Environmental. “A lot of people at Geoprobe made it possible to get a rig to Norfolk by the deadline. We purchased a brand-new 7720DT, Geoprobe rig number 34 for us, and sent it on its maiden voyage to Greenland.”
After a seven-week sail on an ocean-going barge, the rig joined the field team at Thule, and was ready for the three weeks of investigating a jet fuel storage facility, installing thermal sensors associated with the permafrost study, and installing the geothermal loop. The crew performed both conventional direct-push soil sampling and air-rotary drilling to 50 feet below grade at the base.
According to ZEBRA’s Sam Migliaccio, “The biggest challenge, and the one that presented the proverbial ‘steepest learning curve,’ was preventing the permafrost from melting during the air-rotary process. Our solution was to case off the upper part of the hole with a 4-inch piece of steel scrap to keep the holes open. It was simple, yet effective.”
Permafrost is soil at or below the freezing point of water for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but frequently it occurs and may be in amounts exceeding the potential hydraulic saturation of the ground material. Most permafrost is located in high latitudes (i.e. land in close proximity to the North and South Poles), but alpine permafrost may exist at high altitudes at much lower latitudes.
Another challenge was finding a compressor at the site for the air-rotary work. “It’s not like there were hardware stores or tool rental centers at the air base,” comments ZEBRA’s Shawn Tibbetts. “The terrain was rugged and the days were long. Greenland has 22 hours of daylight during that time of year. We were very thankful for the help of the local support contractors in Greenland. They helped make the project a success.”
After the project was completed, the rig and crew flew home in first-class style on a DC-8 in cargo configuration.
ZEBRA Environmental, established in 1992, is a specialized environmental contracting company dedicated to providing high-quality subsurface sampling, installation, injection and data collection services to engineering and consulting firms.