Geotechnical Characterization of Peatlands for a Remote Road Development Project in Northern Ontario, Canada

ABSTRACT: Webequie First Nation, located approximately 525 km north of Thunder Bay, Ontario, is developing an all-season road between the community of Webequie and the Ring of Fire mineral exploration area, approximately 110 km to the east. The Webequie Supply Road (WSR) Project is the first Indigenous-led environmental assessment in Ontario. Once completed, the WSR will offer year-round access between the community and the promising future mining area. It will also provide an all-season link to Marten Falls First Nation and the provincial highway system to the south via the Northern Road Link and Marten Falls Community Access Road projects. Beginning in 2018, studies have been conducted to characterize extensive peatland terrain crossed by proposed alternative road routes to assist with route selection and engineering design. Studies began with remotely sensed terrain analysis to identify peatland types and delineate their boundaries, followed by ground truthing with visual assessment, hand probes and non-intrusive geophysics. In fall 2024, a geotechnical testing program was completed using a hand-operated heli-portable drill, vane shear testing and cone penetrometer (CPT). Integrated drilling and CPT data provide valuable peat characteristics including degree of humification (von Post classification), physical properties (e.g., woody vs non-woody, size and types of fibers), groundwater levels, undrained shear strength, and peak and remolded vane shear strength. Disturbed and undisturbed peat samples and underlying mineral soil were collected for lab analysis. Study results demonstrate the effective integrated implementation of these low-impact investigation methods in terms of cost, environmental impact, field logistics and data quality.