Building and maintaining highways in the NWT has never been straightforward, but it is becoming more difficult in the face of climate change.
Construction firms must now contend with challenges like degrading permafrost in addition to long existing factors like remote locations and high costs.
“Climate change continues to challenge the design, construction, maintenance and operations of Northern infrastructures due to disturbances within the permafrost,” said a spokesperson for the GNWT’s Department of Infrastructure (INF). “The degradation of permafrost can dramatically influence the surface conditions on the active layer of the earth. The active layer is composed of soil materials that thaw and refreeze seasonally. This layer varies in thickness and is situated directly on top of the permafrost layer. As permafrost thaws, the ground surface is negatively impacted, causing abrupt changes such as landslides, water drainage issues, thaw slumps, settlements and structure failures.”
The threat of forest fires and floods also complicates the construction and maintenance of the territory’s highways, the spokesperson added, but efforts are already underway to adapt to the many challenges created by climate change.
The GNWT has been involved in several research and development projects aimed at finding “more sustainable design, construction and maintenance techniques.” That includes collaborations with the universities of Alberta, Manitoba, Toronto, Ottawa and Waterloo, as well as Carleton University, Kingston University, the Royal Military College, and other research institutes like the National Research Council, BGC Engineering and TetraTec.
Some of those research efforts have been focused on the Inuvik to Tuktoyaktuk Highway, where an “alternate watercourse crossing structure” and a “geosynthetic reinforcement high-fill embankment” have both been tested.
The alternate watercourse crossing structure project aims “to help maintain ground temperatures at stream crossing sites, and to manage the impact of this disruption on highways using high-density polyethylene (plastic) culverts.”
The geosynthetic reinforcement high-fill embankment project is intended to “improve the structural stability of high-embankment fills.”
Testing has also been underway on Highway 3, which connects Yellowknife to Fort Providence.
“In 2012, four test sections designed by BGC Engineering on behalf of INF were constructed along Highway 3,” the territorial government spokesperson said. “The test sections were part of a research project intended to evaluate rehabilitation techniques for roads constructed on warming, ice-rich, permafrost. During construction, each test section was equipped with instruments to continuously measure ground temperatures.
“Information gathered from the test sections has been able to inform better roadway designs, construction and maintenance methods,” they added. “These include use of geotextile and geo grid reinforced fill, milder embankment slopes, proper drainage systems, and replacement of embankment shoulder fills with clean cobbles, which helps keep the ground temperatures cool along the shoulder of the highway.”
Last December, the federal government announced a contribution of up to $1.6 million for a University of Alberta project to map permafrost and ground ice along the Mackenzie Valley Highway and Inuvik-Tuktoyaktuk Highway, “using tools that will create a better understanding of the influence of surface and groundwater on permafrost soils and aggregate resources.”
Tom Taylor, Local Journalism Initiative Reporter, NWT News/North