Geoscience Reference
In-Depth Information
vulnerable if a spill occurs at the wrong time in the wrong
place.
Table 24.2
lists the range of disturbance of Arctic
ecosystems which comes from oil and gas development.
Although the areas of direct impact are mostly small, the
cumulative impact of large developments can affect larger
areas. The indirect impact can lag behind construction by
many years, and the total area eventually disturbed can
greatly exceed the original site. Spills, thermokarst and
flooding are important impacts of all activities, and result
from permafrost melting and the disruption of drainage
lines. The impacts on aesthetics and 'wilderness' are
universal. The other impacts listed are mostly self-
explanatory. Perhaps the area where least is known is the
cumulative impact on wildlife, particularly land mammals
and birds, both wildfowl and land birds. The effect of
human activities and noise on breeding, calving and
migration routes is not well researched. It is certain,
however, that there will be a negative impact on wildlife
populations. The passage of tankers or supply ships in
Arctic pack ice, for example, leaves a jumble of broken ice
('freeboard') which can also disrupt the movements of
native people as they travel over the polar ice.
The trans-Alaska pipeline (TAP) is the most famous oil
pipeline in the Arctic (
Plates 24.21-
2
)
, though there is also
a smaller 27 cm diameter pipeline from Norman Wells,
North West Territories, Canada, to Zama, Alberta, as well
as several oil pipelines in European Russia and north-west
Siberia. TAP runs from the Prudhoe Bay oilfields to the
ice-free port of Valdez for a distance of 1,280 km. Over
half the distance is underlain by permafrost, much of
which was unforeseen, with the result that the original
estimate of $0.9 billion had risen to $6.3 billion by
completion in 1977. Although delays and cost increases
were ascribed to the activities of native peoples and
environmental groups, much was due to failure to
recognize the problems of the ice-rich permafrost. TAP is
a remarkable engineering achievement. The temperature
of the oil in the pipe is 65
C, and for more than half its
length it is above ground. The supporting members have
been drilled into the permafrost, and each has an
automatic refrigeration system which maintains the
permafrost around the footing (
Plate 24.21
).
The beam
supporting the pipe is wide enough to allow the pipe to
move laterally with temperature changes. For those
sections where the pipeline is buried, special insulation
coatings 10 cm thick surround the pipe, and in
particularly sensitive areas refrigeration pipes are installed
in the trench below the pipeline to ensure minimal
drainage to the permafrost (
Plate 24.22
).
Gas pipelines differ from the oil pipelines. Most tundra
soils exhibit the process of 'frost heave' whereby water
moves to the point of freezing ('the freezing front') and
becomes incorporated into the freezing material. This
process can cause the soil to double in volume, and is
additional to the well known expansion of water on
freezing of 9 per cent (see
Chapter 15).
Natural soils vary
greatly in their susceptibility to heave, so the effects may
induce bending in any buried pipeline. In permafrost
areas the temperature of gas in a buried pipeline must be
below 0
Activity
Disturbances
Impacts
All activities
Spills
Thermokarst
Aesthetics
Wilderness
Flooding
Oilfields
Prospecting wells
Air pollution
Production wells
Rubbish
Distribution pipes
Drilling wastes
Gravel pads
Gravel pads
Storage tanks
Wildlife impact
C. If it were not, the pipe would cause thawing
and subsidence. However, where the pipe with its chilled
gas passes through patches of unfrozen ground, freezing
occurs around the cold pipe, causing heave.
In the tundra along the coast of north-west Siberia the
exploitation of the natural gas resources is in an early
stage. The plan is for hundreds of gas wells to produce gas
for processing plants, which will pipe the gas to the
European Union. Early indicators are that development
activity has had adverse effects on the tundra. Drilling sites
were not initially on pads, resulting in thermal degrada-
tion, subsidence and the formation of ponds due to heat
loss from buildings ('thermokarst'). On a much larger
scale is the widespread degradation caused by tracked
Transport corridors
Roads
Roadside dust
Pipelines
Drainage disruption
Tanker routes
Noise
Wildlife impact
'Freeboard'
Seismic trails
Off-road vehicles
Vegetation
Soils
Materials sites
Gravel quarries
Vegetation
Soils
Camps
Rubbish
Vegetation
Sewage
Soils
Services
Pads
