and aquifers east of Ski Hill Road
are unknown and their role in flow
beneath the landfill is undefined.
Surface water fills low areas where
the active layer is shallow (less than
1 . 0 m), and sometimes creates
marshes. This water probably con-
tributes little to the ground water in
either the suprapermafrost or sub-
permafrost aquifers. In addition,
those areas with a thin active layer
inhibit communication between
suprapermafrost aquifers and near-
surface ground water movement.
Directions of flow in such areas may,
therefore, differ from the deeper,
more continuous aquifers. Near-
surface flow is mainly limited to
deeply thawed areas beneath roads,
trails, artificial drainage ditches, and
former swales or channels. Near-
surface flow is only connected to the
subpermafrost aquifer where perma-
frost is absent, and it is seasonally
controlled by depths of freezing and
thawing. The combined effects of
permafrost frozen to bedrock and a
shallow active layer severely restrict
lateral ground water movement and
Figure 24. Idealized ground water flow patterns within and beneath
recharge of the subpermafrost or bed-
the landfill. Dashed arrows show potential migration pathways if con-
rock aquifers by suprapermafrost
taminants leach from the fill material. Diagram A shows the general
waters.
conditions along an east to west cross section in the northern half of
Water may be flowing through dis-
the fill area. Diagram B illustrates an east to west cross section in the
crete horizontal or vertical thawed
southern half of the fill area. Diagram C gives a north to south cross
zones in the permafrost, but we have
section through the middle of the fill area.
few data concerning this. Flow
through taliks will probably be highly
The movement of ground water and the migra-
variable in direction and rate, depending upon
tion of contaminants beneath the landfill (Fig. 24)
the size of the thaw zone, water sources, and local
depend on numerous factors, some of which are
hydraulic gradient. Ambiguous, intense reflections
as follows:
on GPR records of the interface between frozen
sediments and frozen bedrock suggest that water
The volume of water that seeps through the
may also be present in isolated "conduits" at this
fill material, leaching contaminants in the
interface. The number and dimensions of these
process.
interface taliks appear limited, but they could
The volume of water and leachate in surface
result in anomalous, but highly localized, devia-
runoff that enters laterally into the landfill
tions in flow.
through thawed materials adjacent to it.
The hydraulic gradient and flux of the sub-
regional aquifer.
CONCLUSION
The flux of water from the Birch Hill aquifer
Hydrogeological conditions in the north-
into near-surface and subpermafrost aqui-
central cantonment area are controlled primarily
fers.
by the distribution and geometry of discontinu-
In addition, the extent and depth of permafrost
ous permafrost, stratigraphic variability, and inter-
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