>1.03.0 m Thaw
Thawed
Based Upon Limited Data
Above Permafrost
Permafrost Absent
Speculative; Data Lacking
≤ 1.0 m Thaw Annually
>3.0 m Thaw
Active Landfill Area
Above Permafrost
Above Permafrost
Figure 16. Characteristic depths of thaw and the locations of unfrozen zones in the north-central area of the cantonment.
Deep thaw zones above permafrost are commonly associated with disturbed terrain, while thin active layers characterize
undisturbed terrain covered by vegetation. Areas with shallow active layers (less than 1.0 m) severely reduce ground
water movement and result in divergent flow patterns. Unfrozen materials are generally in former channels and sloughs,
as is evident by their map patterns. Permafrost and aquifer distribution below the landfill are based upon interpretations
from historical aerial photographs using data from the terrain surrounding the site. Very few subsurface data exist east of
Ski Hill Road. Note that small, shallow drainages are not identified, thaw depths may exceed the cited depths by two to
three times, and the unfrozen zones have peripheral shallow and deep thaw zones that may be omitted for clarity. This
map was created on unrectified aerial photographs taken on 20 May 1993.
area. The depth to bedrock presumably continues
increase sharply at about several hundred meters
to increase south of River Road but there are only
distance south of Birch Hill. Comparing the depth
a limited number of borehole measurements in
to bedrock (Fig. 18) with the depth to the bottom
this area.
of permafrost (Fig. 15b) shows that unfrozen sedi-
Contouring of the depth to bedrock data tells
ments from a few meters to over 25 m thick under-
us that sediments bury gullies or valleys that were
lie perennially frozen materials over much of the
15
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