Connecting the Dots: Combining Geotechnical and Geophysical Investigation Methods to Characterize Permafrost Soils along a 170 km-long All-Season Road in the Northwest Territories

ABSTRACT: Tetra Tech Canada Inc. (Tetra Tech) conducted a geotechnical and geophysical investigation program (the Program) for a proposed 170-km long all-season road (ASR) linking the Prairie Creek Mine to the Nahanni Butte Access Road in the southwest corner of the Northwest Territories. The proposed ASR will cross varying terrain that includes discontinuous permafrost with the potential occurrence of karsts, thermokarsts, sink holes, and thaw slumps. The objective of the Program was to collect subsurface geotechnical and permafrost data along the proposed ASR as well as investigate areas of interest along the route. The Program utilized a combination of geotechnical and geophysical methods for subsurface data collection and permafrost characterization. This combined approach for the Program reduced the number of boreholes and testpits, resulting in lower environmental impact and costs. The geotechnical and geophysical results were then input into a data web map, which was used to share spatial data as well as subsurface logs and profiles.