Figure 10. Transect 94-78 with interpretation based on boreholes and other data. The transect
lies west of landfill and trends east to west (0660 m). This profile was obtained in March
1995 using 50-MHz antennas. Arrows in radar traces indicate bedrock reflectors.
The profiles of three transects (CR94-53, 98,
acquired in late March 1995, when the ground
and 69) are linked in Figure 11 to show several
was frozen from 3 to 4 m deep. They are represen-
characteristics of the site. Bedrock is a promi-
tative of GPR data and subsurface conditions
nent reflector at a depth of about 15 m at the 85-m
across the area, and illustrate typical features of
distance mark. This reflector steadily deepens to
the radar records. Boreholes used to interpret
the south, dropping sharply after about 500 m
the radar data are located on each profile figure.
distance. Permafrost extends into bedrock in the
Conditions in the area west of the landfill are
northern end, but at about 400 m distance, a weak
interpreted from several transects, including pro-
reflector suggests that unfrozen bedrock lies at a
file CR94-78, which trends eastwest and crosses
depth of 3040 m. At about 950 m distance, perma-
several features with contrasting subsurface
frost extends to about 32 m depth, with unfrozen
properties (Fig. 10). The ground is deeply thawed
sediments between it and the top of the bedrock,
on its eastern end (600650 m). Permafrost then
which is undetected, but must be greater than 50
thickens and extends to bedrock between the 600-
m deep.
and 90-m distance marks. Between 410 and 230
Transect 94-61 (Fig. 12) is about 1 km long,
m, the transect traverses a marshy area with a
trending south to north from River Road to the
prominent, abandoned slough between 290 and
base of Birch Hill, and lies directly west of the land-
250 m. Although much of the area was frozen to
fill (see Fig. 6). Only one borehole, that at 100 m
bedrock at the time of survey, the near-surface
distance north of River Road, encountered the
fine-grained sediments attenuated the signal and
bottom of the permafrost. At this location, the bot-
kept us from detecting the bedrock. A strong
tom of permafrost lies at about 38 m depth. The
subhorizontal return only marks the surface of
permafrost bottom rises south of 100 m, and dis-
bedrock at shallow depths, such as those ranging
appears at about 40 m distance, where there are
from 25 to 35 m along the far western end of the
unfrozen channel deposits under an artificially
profile. Bedrock is intermittently revealed on the
deepened drainage ditch. North of about 250 m,
eastern end at depths greater than 40 m.
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