CRyOfRONT: News and Views from the Far North
Earth and ice – the blessed and cursed materials of the far north By Ken Johnson, NTWWA Director
The theme of the 2011 conference (“Cycles”) has elements in common with the far north such as the seasons – there are only two: ‘frozen’ and ‘not frozen.’ The ‘not frozen’ season is very short in the far north. Associated with these two seasons are elements of nature which play a critical and challenging role in design, construction, and management of water related infrastructure – earth and ice. The cycle of earth and ice has been known and studied for over a century – the first significant consideration of earth and ice in the far north was during the construction of the White Pass and Yukon Railway, where permafrost challenged the construction of this historical project. The second significant consideration of earth and ice in the far north was during the construction of the Alaska Highway. Although neither of these projects were water related, they were landmarks for the work undertaken today in the far north. Earth is a fundamental building material to water infrastructure across the north. For the work in my scope of technical practice, earth provides the retention structures of a sewage lagoon, the berm structures for landfills, and the cover material for buried water and sewer. The major challenge associated with the use of the
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Road constructed on frozen ground on the Alaska Highway in 1941, using logs as an insulating layer and structural support.
earth in the far north is that it generally does not function well when mixed with ice, and for the majority of the year (frozen season) it is not useable because it is ‘hard as a rock’ – during this period of time it is often “cursed.” However, during the brief not frozen season, earth becomes the focus of significant activity as it is excavated, screened, moved, piled and compacted as part of most water infrastructure related projects – during this time it is often “blessed.” Nothing is ever absolute, particularly in the
far north, and as much as mixing earth and ice is not a particularly good practice, it does have a beneficial scenario. A limited amount of moisture in earth produces a low permeability material which is beneficial for lagoon structures, and may provide a retaining structure to limit the flow of contaminated runoff from landfills. On the other hand, ice is generally not a fundamental building material because during the not frozen season it has a tendency to melt if it is not protected by earth or other means of insulation.
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Ice is, however, a material of great importance during the frozen season because it provides a means of transportation which is unique to the far north. The ice roads of the north and the ice road truckers have become of bit of a cult phenomenon in the reality television world. The accessibility provided by ice is beneficial to water related projects because it provides access for the construction of water infrastructure – during this period of time it is often “blessed.” By virtue of its nature ice may also provide a direct benefit to water related infrastructure because it stabilizes biological materials from movement and degradation during the frozen period – no movement and degradation means little or no environmental impact. In crude terms this scenario is referred to as the creation of the “shitcycle.” This attribute makes ice “blessed”, however, as the ice will eventually melt; but during the transition period of freezing and thawing the ice behaves in a very particular manner and purifies itself. A principle for water retaining structures such as pipes in the far north is that they should be designed for ‘when’ it freezes, not ‘if’ it freezes. Ice in a pipe makes it “cursed” and creates a challenging situation to thaw. As much as technology and the ‘synthetic world’ may influence the nature of the work of water professionals in the south, earth and ice are and will remain dominating factors for the work of water professionals in the far north.
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Earth lagoon structure in Grise Fiord, Nunavut, which includes berms constructed with a freeze back of core to create a low permeability structure.
Insulated pipe loaded for delivery to the far north.
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