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fication are special problems found in cold climates. Airphoto examples of 
these problems are shown in fig. 6 where ice polygons indicative of permafrost 
along the Steese Highway in Alaska are designated by arrows; and in fig. 7. 
where soil flows are observed on the same highway. Fig. 8 shows a line location 
skirting relatively deep (12 to 18 feet) muskegs (M) on Mitkoff Island, Alaska. 
Geologic studies of tunnel and major bridge sites are special problems that 
can be assisted effectively by photo interpretation. Fig. 9 shows a tunnel site 
on the Quebec Cartier Mining Railway. Airphoto interpretation indicated 
that for the north portal area of the tunnel (toward Mile-33), the rock condition 
was such as to require lining in the tunnel, whereas for the rest of the tunnel,