Geology Reference
In-Depth Information
The problem is least acute in regions of discontinuous permafrost, where extensive
alluvial deposits provide an abundant source of groundwater. For example, in Fairbanks,
Alaska, most houses rely on small diameter private wells (see Péwé, 1983c, pp. 67-85).
However, in many areas of continuous permafrost, the permafrost is several hundred
meters deep. In certain parts of Siberia, perennial springs that are fed by sub-permafrost
water constitute the sole water source. In historic times, these sites assumed a religious
signifi cance from aboriginal (Yakut) peoples. In most areas of thick permafrost, drilling
is either not possible, since the hole would freeze, or too costly. As a result, surface water
bodies, particularly those which do not freeze to their bottoms in winter, must be utilized.
Great care must be taken to prevent contamination. It follows that the supply of water is
a severe limitation to any large-scale permanent settlement in many periglacial environ-
ments. For example, the water-supply problems at Sachs Harbour, a small Inuit community
of approximately 250 people on southwest Banks Island, Canada, are reasonably typical.
There, the water supply is derived from a lake approximately 3 km from the town. It is
trucked every 3-4 days, by water tanker, to individual homes, which have indoor storage
containers. Contamination is a problem and the size of the lake, one of the few deep
enough not to freeze to its bottom during winter, limits growth of the community.
(A)
(B)
Figure 14.10.
Historic buildings at Dawson City, Yukon Territory, are built upon ice-rich and
warm permafrost. (A) An abandoned building, approximately 85 years old, experienced severe thaw
settlement in the central (previously heated?) part of the building. (B) A heritage building restored
by Parks Canada and placed upon non-frost-susceptible granular fi ll following removal of ice-rich
permafrost. Note the adjacent modern fi re hydrant that required deep burial (see Figure 14.7B) of
municipal services.
Figure 14.9.
Thaw subsidence, road sagging, and sewer-pipe breakages are persistent problems
along Franklin Avenue in downtown Yellowknife. (A) Cross-section along Franklin Avenue showing
geology and permafrost conditions prior to reconstruction of sewer lines in 1990. From Wolfe
(1998). (B) Diagram indicating the previous road surface levels, the location of the 1967 service
mains, the locations of the new (1990) service mains, the limit of the thaw bulb beneath the road,
and the locations of the insulated polystyrene layers installed. Source: unpublished data, NorthTech
Consulting Ltd.
