| Title | Evaluation of threshold freezing conditions for winter road construction over discontinuous permafrost peatlands, subarctic Canada |
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| Author | Sladen, W E; Wolfe, S A ; Morse, P D |
| Source | Cold Regions Science and Technology vol. 170, 102930, 2019 p. 1-11, https://doi.org/10.1016/j.coldregions.2019.102930 |
| Image |  |
| Year | 2019 |
| Alt Series | Natural Resources Canada, Contribution Series 20180329 |
| Publisher | Elsevier |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf; html |
| Province | Northwest Territories; Nunavut |
| NTS | 85I/09; 85I/10; 85I/11; 85I/12; 85I/13; 85I/14; 85I/15; 85I/16; 85P/01; 85P/02; 85P/03; 85P/04; 85P/05; 85P/06; 85P/07; 85P/08 |
| Area | Tibbitt Lake; Cameron River; Gordon Lake; Tibbitt to Contwoyto Winter Road |
| Lat/Long WENS | -114.0000 -112.0000 63.5000 62.5000 |
| Subjects | surficial geology/geomorphology; geophysics; Nature and Environment; Science and Technology; Transport; permafrost; ground ice; periglacial features; organic deposits; peatlands; ice conditions; ice
thickness; snow; floods; temperature; ground temperatures; logging techniques; thermal analyses; surface waters; lakes; Canadian Shield; Road construction; Road safety |
| Illustrations | location maps; tables; time series; profiles; plots |
| Program | Climate Change
Geoscience Permafrost |
| Released | 2019 11 02 |
| Abstract | Winter roads provide an important transportation service in northern regions. The Tibbitt to Contwoyto Winter Road (TCWR), traversing subarctic Canada, is the busiest heavy-haul road in the world with
as many as 10,900 truckloads per season. In addition to lake-ice thickness, trafficability on the TCWR depends upon adequate freezeback of overland portages, which are primarily peatlands underlain by discontinuous permafrost. We investigate
threshold requirements for the initiation of winter road operations in this region and assess the use of a recommended 305 °C-day air-freezing index (FDD305a) value as an operational predictor of ground freezing at 30 cm depth, the desired depth to
allow winter road construction to commence. Snow compaction and flooding were found to enhance freezeback of portages with early winter overland flow having a similar effect. The majority of winter road portages were not adequately frozen to a depth
of 30 cm by FDD305a. Our results indicate that for drained and wet peatlands in this discontinuous permafrost environment, an FDDa threshold of 1100 °C-days is more appropriate than the 305 °C-day threshold. However, TCWR winter road operators
presently plan the construction of the winter road by a calendar date rather than by evaluation of the air-freezing index. This practice results in a conservative approach to the start of the construction season, close to 1100 °C-days with a higher
percentage of sites frozen to 30 cm depth than would be if the 305 °C-day air-freezing index was used as a guideline. In addition, the use of low-pressure vehicles for snow compaction during the start of the construction season is an effective
adaptation practice to accelerate freezing penetration. |
| Summary | (Plain Language Summary, not published)
Winter roads are seasonally constructed roads servicing remote communities and resource development sites in northern Canada. The lake ice and frozen
ground provide stable surfaces for vehicular traffic that would otherwise not be possible. Guidelines require 30 cm of frozen ground to support heavy equipment and use 305 air freezing degree-days (FDD305a) as the threshold to start winter road
construction over land. This paper investigates the ground thermal conditions at 30-cm depth in discontinuous permafrost peatlands on and off right-of-way along the Tibbitt to Contwoyto Winter Road (TCWR). During the study period, the FDD305a
threshold was insufficient for frost penetration to 30-cm depth in wet peatlands typical of the subarctic Canadian Shield. The current calendar date threshold used by the TCWR does however, provide sufficient time for adequate frost
penetration. |
| GEOSCAN ID | 313314 |
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