Permafrost and ground ice conditions reported during recent geotechnical investigations in the Mayo district, Yukon territory

The Mayo District, Yukon Territory, lies in the widespread discontinuous permafrost zone. Permafrost thicknesses of up to 40 m have been measured in valleys, and of 135 m at higher elevations. Many observations of ground ice have been made by placer miners, but generally these are unrecorded. Recently, over 200 shallow geotechnical boreholes have been drilled in the area in association with municipal or highway construction. Ground ice is usually encountered at undisturbed sites within 4 m of the surface. In the main valleys at elevations below 1100 m a.s.l. coarse, clastic, outwash materials, sand dunes and slopes with southerly aspect are usually frost‐free. Stripping of vegetation for construction or placer mining leads to permafrost degradation, but permafrost can re‐establish as vegetation regenerates. Ground temperatures at Mayo and Keno Hill indicate a geothermal flux of over 0.1 W/m2. Copyrigh