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In permafrost valleys, artesian wells often penetrate highly pressurized aquifers beneath confining subpermafrost. These wells must be quickly brought under control at installation, and heated through their operational life to prevent them from freezing in winter. However, water breakthrough of the permafrost barrier around the casing results in loss of control of the well. Seepage icing impacts to property and infrastructure can be catastrophic, and the costs to regain well control and mitigate damages high. Methods to regain control of artesian wells in permafrost are few and risky. A new method, cryogenic freezeback, was successfully used to mitigate an uncontrolled artesian well in a permafrost valley north of Fairbanks, Alaska. This paper documents the freezeback method, seepage and thermal analyses, and well abandonment and retrofit. Thermal monitoring results are presented to demonstrate the long-term effectiveness of the method.

Timely bioremediation of petroleum-contaminated soils in the Arctic is possible with innovative engineering and environmental manipulation to enhance microbial activity beyond the natural effective season. Key parameters in extending the period of beneficial microbial activity in Arctic biopiles are temperature and substrate availability. A multidisciplinary team of engineers, microbiologists and electricians has designed and installed a thermally enhanced biopile at a diesel-contaminated gravel pad in Prudhoe Bay, AK. The combination of bioventing with active warming, fertilization and power cycling is working toward timely remediation at this site. Primary components for success are the (1) thermal insulation system (TIS) design, (2) microbiological monitoring plan, and (3) power optimization. (Alternate power sources are considered for use at this and future remote bioremediation sites.) This paper discusses the TIS design and extension of the effective treatment season, fertilization and the results of a treatability study that compared simple fertilization with application of commercially available bioproducts under simulated site conditions, and adjusting power utilization to prevent permafrost thaw. Through an integrated approach to bioremediation, we are treating diesel-contaminated soils at an Arctic site.

Bioremediation of petroleum-contaminated soils in cold regions is hampered by low temperatures, frozen soils, and short summers. Extreme environmental conditions limit remedial efforts to a few technologies. Bioventing and combined air-sparging and soil vapor extraction have shown promise in subarctic regions. Expensive thermal desorption or encapsulation of organically contaminated soil is practiced in arctic Alaska and Canada, in lieu of successful bioremediation. Thermal insulation systems have recently been developed for innovative bioremediation efforts in cold regions. Commercially available insulation, electrical heating elements, and construction materials have been uniquely packaged to enhance bioremediation at two petroleum-contaminated sites in Alaska. Thermally enhanced bioventing successfully remediated hydrocarbon contamination in the vadose zone at a subarctic site within two years. Preliminary results from an oxygenated and fertilized biopile, actively warmed and covered with a thermal insulation system, show promise at an arctic site. A guide for thermal insulation system design for bioremediation application in cold regions is developed.