GNWT Transportation Monitoring Program

In the summer of 2016, the second phase of the Northwest Territories Transportation Monitoring Program (NWTTMP) supported by Transport Canada, was approved, with the goal to continue existing research as well as to initiate new research into the effects of climate change on permafrost and transportation infrastructure. Phase 2 of the program is made up of four components located throughout the Northwest Territories. These include two test sections along the newly constructed Inuvik to Tuktoyaktuk Highway to monitor the structural stability of highway embankments, the installation of 24 thermistors along both newly constructed sections of the highway and off right-of-way locations, monitoring alternative watercourse structures at various locations along the Inuvik to Tuktoyaktuk Highway and the Mackenzie Valley Winter Road, and four different sections along Highway No. 3 for testing and monitoring new rehabilitation techniques for roads constructed on discontinuous permafrost under warming conditions. The previous phase 1of the Monitoring Program commenced in 2015 and included two Inuvik to Tuktoyaktuk Highway permafrost research and development projects, a geotextile-reinforced deep fill embankment section and the implementation of an alternative plastic drainage culvert structure. Components of the program which have robust publicly available information will be explored further below. These include: two test sections along the newly constructed Inuvik to Tuktoyaktuk Highway, and a state-of-the-art ground temperature monitoring network along the Dempster- Inuvik to Tuktoyaktuk Highway (ITH) corridor.

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Understanding and Assessing Impacts

The Government of the Northwest Territories with support from Transport Canada’s Northern Transportation Adaptation Initiative (NTAI) have supported a number of projects aimed at understanding how climate driven warming in northern Canada is contributing to permafrost thaw an infrastructure challenges. These projects include implementing an applied permafrost research program for the Dempster – Inuvik to Tuktoyaktuk Highway (ITH) corridor, this acts as a precursor to adaptation action by producing a state-of-the-art ground temperature monitoring network. Other research projects include understanding the formation of aufeis (icings) on the ITH, surveying thaw-induced landslides along linear infrastructure in the Northwest Territories and examining the thermal and mechanical performance of embankments in the arctic following winter construction of the ITH. In this last case, near and long-term climate change models were considered in the project as well as broader insight related to northern temperature increases as outlined in the IPCC’s fifth assessment report.

Identifying Actions

Firstly, from the perspective of the Northern Transportation Adaptation Initiative research pertaining to the effects of climate change on northern infrastructure was lacking as of 2010, signalled by the existence of only two Canadian universities showing interest in the area of permafrost engineering. This preliminary survey likely influenced actions found in the Implementing an applied permafrost research program: The Dempster – ITH research corridor study such as the creation of an applied permafrost research hub. Researchers from Laval University, the University of Manitoba as well as a private consultant undertook a detailed literature review in order to inform actions taken as part of their study Structural stability of highway embankments along the ITH. The effect of the literature review was two-fold. Firstly, it allowed for a clear understanding of the challenges typically associated with Artic highway construction, among them, the frequent unavailability of ideal materials such a gravel. Secondly, the review also showed a wealth of information on embankment performance attributed to permafrost degradation, but that limited work has been done on the thawing of the frozen soil used in the construction of the embankment fill and how this influences performance. The study then looks to fill this gap through 3 years of monitored results of an on-going study to determine the thermal and mechanical performance of high-fill embankment sections constructed in the Arctic using frozen soil under winter conditions.

Implementation

As noted in the Short Description section above, the Northwest Territory’s Transportation Monitoring program has undertaken and implemented a number of actions since its inception in 2015, ranging from alternative plastic drainage culvert construction to programs monitoring alternative watercourse structures. Given the sheer number of actions and initiatives and considering available information, this section will highlight two sets of actions – those related to the introduction of wicking geotextile in highway embankment construction, as well as the creation of an applied permafrost research hub. The former was a result of efforts outlined in Structural stability of highway embankments along the ITH. The project created two 20m long test sections of road near kilometre 80 along the Inuvik to Tuktoyaktuk Highway. Of the two sections, one acted as the control while the other was treated with a geotextile. The construction and outfitting of both portions with monitoring instrumentation occurred in April of 2015. Implementing an applied permafrost research program: The Dempster – ITH research corridor outlines the establishment of numerous ground temperature monitoring sites since 2013 near or along the length of the almost 140km Inuvik Tuktoyaktuk Highway which complements a legacy of geotechnical and mapping products developed to design, construct and maintain the highway.

Outcomes and Monitoring Progress

In relation to the study titled Structural stability of highway embankments along the ITH produced three distinct findings. Firstly, temperature sensors have shown a warming trend in the embankment fill and foundation soil. This is attributed to warming air temperatures and heat trapped in the embankment during the winter months when the embankment slopes are covered with snow. Thawing of the previously compacted frozen soil may lead to reduction in shear strength available to resist traffic loading and increasing seasonal thaw depth at the toe might also lead to loss of support and cause instability in the embankment slopes. Second, the largest lateral displacements were recorded in the summer following construction of the embankments and attributed to thawing of the frozen soil at the slopes. Finally, Addition of the woven geotextiles with wicking as a secondary function to its primary purpose of reinforcement has reduced the lateral displacements as the embankment slope experiences seasonal freezing and thawing. Monitoring of the site is on-going to establish long-term trends with improved confidence. The introduction of a network of ground temperature monitoring sites aided by efforts through Implementing an applied permafrost research program: The Dempster – ITH research corridor has enabled the creation of a NWT Permafrost database, information in which will be publicly available to contribute to informed decision-making, climate change adaptation and risk management.

Next Steps

The project team associated with the study Structural stability of highway embankments along the ITH notes that monitored field results, together with the results of the laboratory tests conducted on the soil and geotextile, will be used to calibrate a coupled thermal–mechanical model to investigate the operating mechanisms contributing to the short- and long-term performance of the embankment test sections. Ultimately, results of this on-going research will assist in the development of improved guidelines for the design, construction, and maintenance operations of highway embankments in Arctic regions constructed under winter conditions. Authors of Implementing an applied permafrost research program: The Dempster – ITH research corridor identify a web to better enable access to the NWT Permafrost Database as forthcoming.

Resources

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Additional Resources