A Homeowner’s Guide to Permafrost in the Northwest Territories Keep Your House on Solid Ground Publication, contents and images copyright, 2015 Environment Division Department of Environment and Natural Resources Government of the Northwest Territories PO Box 1320, 7th Floor, Scotia Center, 5102 Franklin Ave, Yellowknife, NT, X1A 2L9, (867) 873-7854 www.nwtclimatechange.ca Printed in Canada Content provided by CS Environmental Design & Illustration provided by Soaring Tortoise Creative Yellowknife, NWT A Homeowner’s Guide to Permafrost in the Northwest Territories Acknowledgements The Government of the Northwest Territories Should Department of Environment and Natural Resources would like to acknowledge the contributions of colleagues within other departments of the GNWT, the Geological I Be Survey of Canada and the Government of Nunavut Environment Department; all of whom contributed time and resources to Concerned the creation of this guide. About Permafrost is common and exists under many houses in the NWT Permafrost? This Guide is not a legal document nor is The Guide is intended to provide it intended to be a complete manual on homeowners with general information dealing with problems caused by permafrost on permafrost, the damage permafrost to your home. The Government of the thaw can cause to a house and areas Northwest Territories does not assume any where maintenance or risk prevention is responsibility or liability with respect to advisable. It is not meant as a replacement any damage or loss arising from the use or for site-specific geotechnical investigations interpretation of this Guide. It is provided by by engineering and / or geoscience the Department of Environment and Natural professionals. Resources as a courtesy only. With federal support through Natural Resources Canada’s Regional Adaptation Collaborative Program. 1 3 7 12 21 Permafrost House My and Permafrost Permafrost? Ice-Rich on House My Is Permafrost on Living Checklist Foundation Should I Be Concerned About Permafrost? 5 Permafrost Permafrost is ground that is frozen for two or more years. That ground can be rock, gravel, sand, clay, silt or a mix of these. Ground that contains a great deal of frozen water, or ice causes the most problems for engineers and homeowners. When ice-rich permafrost thaws, the ice melts to water, creating spaces in the soil that lead to ground settlement and building problems. This Guide contains information on permafrost as it is used in designing a house. It can also help you determine if your home is built on permafrost, the risks related to thawing and tips on how to properly maintain your house Ice-rich permafrost from a core sample photo by Mike Palmer and foundation to reduce permafrost thaw. There is also information on other northern Northern engineers and architects have long foundation issues such as rotting piles and developed innovative techniques to deal with the shifting of heating oil tanks. challenges of building on permafrost. However, climate change is causing rapid changes to Keeping your house and foundation in good the permafrost that was once thought would repair is one way to avoid the risks caused by be around for generations. Homeowners in the the thawing of permafrost. Every community NWT are starting to realize that their houses and every house faces different permafrost rely on potentially unstable permafrost that may related challenges. Determining what is lie under their home. Cracking walls and doors happening to the ground your house sits on is that won’t close are early indications of bigger the best way to figure out your level of risk and problems that may lie ahead. how to deal with it. 1 Air temperatures and permafrost distribution by latitude (°N) in the NWT Latitude (°N) N Credit: Modified from Wolfe,S 1998 Tuktoyaktuk Inuvik Norman Wells Yellowknife Hay River -10.2°C -8.8°C -5.5°C -4.6°C -2.9°C 70° Treeline 65° 60° Beaufort Sea 0 Permafrost Great 200 Slave Mackenzie Lake 400 River Depth (m) Depth 600 800 Continuous Extensive Sporadic permafrost discontinuous discontinuous permafrost permafrost N Latitude (°N) S Tuktoyaktuk Inuvik Norman Wells Yellowknife Hay River Permafrost-10.2°C is found throughout the-8.8°C Northwest -5.5°CIce-rich permafrost,-4.6°C the type that -2.9°Ccan be most Territories but tends to be more common harmful to houses when it thaws, is generally found further north.70° PermafrostTreeline also tends to be in river65° valleys, low-lying peaty ground and soil60° thickerBeaufort and colder in the northern regions. For pockets in bedrock areas. Ice-rich areas are found example,Sea the0 area around Tuktoyaktuk has in isolated patches throughout the Northwest cold, continuous permafrost,Permafrost often hundreds Territories but are most commonGreat in the Northern 200 Slave of metres thick. Hay River has sporadicMackenzie Islands, Beaufort Delta area and along the patches400 of relatively warm and shallow Mackenzie Valley. Mean annualLake air temperatures permafrost. Areas between these communities River are often a good indicator of the presence have discontinuous permafrost which can vary of permafrost. The average air temperatures Depth (m) Depth 600 from patchy to widespread. from 1971-2000 are shown for some NWT 800 communities in the figure above. Continuous Extensive Sporadic permafrost discontinuous discontinuous permafrost permafrost 2 How can Permafrost Frost-Heave Many houses in the NWT use the strength of The upward movement of the ground surface permafrost to keep their foundation solid. caused by the formation of ice in the soil. When permafrost thaws, the house may no longer have a solid base to hold it up. This Thaw Settlement can lead to uneven floors, cracks in walls The downward movement of the ground due to and, eventually, serious structural problems. ice melting in the soil. Many factors affect permafrost stability. Piles It is important homeowners understand how Wooden or steel building supports drilled into their actions affect permafrost. The good the permafrost are called piles. They are less news is you can reduce permafrost thaw susceptible to settling, but are subject to and, even re-grow permafrost. creeping (moving down) or frost-jacking (moving up) as permafrost warms. Surface Foundation Permafrost These adjustable foundations that sit on a gravel pad or concrete footings are more Ground that remains frozen for at least affected by thaw settlement and frost-heave two years. than piles. Examples include pad and wedge, space frames or screw jacks (see page 11). Active Layer The top layer of ground that is subject to Organic Layer annual thawing and freezing. When the active The top layer of dark soil or peat. A thick layer gets deeper, it can thaw the ice-rich organic layer insulates the permafrost in the permafrost below and cause thaw settlement. summer. Disturbing the organic layer usually results in rapid permafrost thaw. Ice-Rich Permafrost Permafrost containing excess ice. Ice-rich Gravel Pad permafrost can form thick layers of ice The gravel pad is designed to insulate the (lenses) in clay or silty soils, which can melt permafrost and allow water to move through and cause thaw settlement. the pad and away from the house. 3 Impact My House 10 9 8 7 3 4 Permafrost In the Summer It is natural for the top layer of soil to in causing permafrost thaw, as groundwater thaw in the summer. When this active layer transfers heat more easily than dry ground. gets deeper every year, it is considered Wind evaporates moisture under your house, permafrost thaw. which helps keep the ground dry and prevents permafrost thaw. Four main factors affect how much permafrost thaws in the summer under your house: temperature, sun, water and wind. The Tip: Think of the space under your house. warmer it gets under your house, the more Can you reduce the negative factors of permafrost will thaw. The sun also warms water, sun and temperature while helping the ground and thaws permafrost, but your the positive factor of wind? foundation is usually shaded from the sun’s full effects. Water may be the greatest factor temperature sun water wind 5 Permafrost In the Summer In the Winter Winter is the season when permafrost keeps the cold from reaching into the ground rebuilds. The cold temperatures and low and prevents permafrost from re-growing. Wind snowfall in NWT winters provide good moves the snow around and deposits it in conditions for refreezing the ground that protected areas while exposing windswept areas. thawed the previous summer. There are three main factors that affect how Tip: Winter winds should be allowed to much the permafrost will rebuild under your blow under your house to remove snow house in the winter. They are temperature, build-up. This exposes the ground to snow and wind. Cold temperatures must very cold temperatures that re-build the reach deep into the ground to recharge the permafrost every year. permafrost but, snow acts like a blanket. It temperature snow wind Skirting 6 Is My House on Ice-Rich Permafrost? Inuvialuit communities typically have This is a good question that may not very cold (-5°C to -8°C) permafrost. While this have an easy answer. The following clues permafrost is in less danger of thawing, it does and information on the next four pages contain a lot of ice, which could cause major may help! problems for homeowners. Gwich’in communities are the most at risk of permafrost thaw with warm (-1°C to Do I live in a community that is sensitive to -3°C) ice-rich permafrost. Minor changes in permafrost thaw? pg 8 temperature or surface conditions can cause Some tree and plant species can be indicators the ice to melt causing thaw settlement. of permafrost.