Geology Reference
In-Depth Information
14.3. PROVISION OF MUNICIPAL SERVICES AND
URBAN INFRASTRUCTURE
The provision of municipal services and urban infrastructure such as water supply and
sewage disposal are particularly diffi cult in permafrost regions. This is because systems
will freeze if left unprotected above ground yet it is costly and diffi cult to excavate trenches
either to depths below the seasonal-frost level or within permafrost. Therefore, pipes to
carry municipal services cannot be laid below ground, as is normally the case in non-
permafrost regions, because heat from the pipes will promote thaw of enclosing perma-
frost and subsequent subsidence and fracture of the pipe.
The construction of the town of Inuvik in the Mackenzie Delta, NWT, Canada, in the
early 1960s was an example of the careful manner in which the urban infrastructure must
be planned and constructed in permafrost regions. A major factor that governed the loca-
tion of the town was the presence of a large body of fl uvio-glacial gravel a few kilometers
to the south. This was used to place a gravel pad beneath the entire area of the proposed
townsite. Today, this aggregate source has been exhausted and future growth of the com-
munity depends upon exploitation of more distant aggregate sources with associated
higher costs of haulage.
At Inuvik, the provision of municipal services has been achieved through the use of
continuously-insulated aluminum boxes that run above ground on supports and link each
building to a central system (Figure 14.7A). These are termed utilidors. The cost of utilidor
systems is high, involving a fair degree of town planning and constant maintenance, and
can only be justifi ed in large settlements.
Another example is provided by the town of Dawson City, Yukon Territory, Canada.
There, the provision of municipal services was upgraded at considerable cost in the late
1970s and early 1980s by an alliance of Federal and Provincial government agencies. At
issue was the restoration and maintenance of historic buildings, and the adequate provi-
sion of utilities to the town. Prior to 1980, the city water distribution and sewage systems
were those that had been constructed in 1904. The town uses water from infi ltration wells
situated near the bank of the Klondike River. The distribution system consisted of wood-
stave pipes within gravel in the active layer; all were emplaced at depths shallower than
1.2 m. In winter, the water was heated by electricity to
5.5 °C and enough fl ow was main-
tained to prevent freezing by bleeding into each house. At the end of the circulation
system, the water temperature was about 1.1 °C. Needless to say, these antiquated water
and sewage systems required frequent repair due to seasonal-frost heave, settlement of
the pipes through thaw, and frost deterioration of the pipes. The electrical heating costs
were also high. Accordingly, a new system of underground services was installed. Trenches
were excavated to a minimum depth of 2.0 m and backfi lled with coarse (frost-stable)
gravel fi ll (Figure 14.7B) that was hauled to the site. Similar costly preventive measures
are now regarded as normal practice in many communities elsewhere in Canada, and in
Alaska, Svalbard, and northern Norway.
Sewage treatment is also problematic in many communities located in cold environ-
ments. Waste treatment plants are costly and most northern communities, in both North
America and Russia, cannot afford them. Haulage and direct dilution in adjacent rivers
or the sea are the solutions for many smaller settlements. Nearby lakes are sometimes
used as settling ponds but these are not always available and there are environmental
concerns since they may be used for fi shing or by wildlife. There is also the inevitable risk
of contamination of freshwater drinking supplies. Settling ponds, or sewage lagoons, are
used by larger communities but are costly to excavate and do not function well because
the low temperature inhibits bacterial decomposition. Furthermore, the lagoon may freeze
+
