0
100
200 m
Birch Hill
Building
1173
Quarry
N
Boundary Separating
Assemblages of Surficial
Alluvial Sediments
Approximate Trends
to Former Swales,
d
rR
Channels and Levees
e
Riv
Figure 5. Assemblages of alluvial deposits distinguished by the trends of the point bars, swales, former
channels, and levees north of the Chena River. Cross-cutting relationships of these features indicate the relative
ages of the surficial deposits.
(Fig. 1 and 3). The Tank Farm is located on the
est sediments within this area, however, are those
southsouthwest slope of Birch Hill where per-
bordering River Road (Fig. 5) and within the Test
mafrost is probably absent owing to its southern
Grid area. As is discussed in a later section, there
exposure. Drilling shows that the Tank Farm area
is no clear relationship between the ages of sedi-
is generally blanketed by accumulations of eolian
ments and the extent of permafrost development,
silt (loess). This silt overlies a 1- to 3-m-thick zone
which further complicates predictions of locations
of moderately to highly weathered schist, which
and extents of frozen zones. Prominent sloughs,
grades into unweathered schistose bedrock at
however, tend to be zones of partial or complete
depth. The Truck Fill Stand lies south of the Tank
thaw and may therefore be significant pathways
Farm in an area of alluvial deposits.
of groundwater flow.
Arcuate patterns or meander scrolls on 1949
Canol Road and the adjacent pipeline extend
aerial photographs confirm the alluvial origins of
southeast towards the Chena River within a
the sediments, and cross-cutting relationships pro-
cleared right-of-way (Fig. 1). There is significant
vide evidence on relative ages of different depos-
thaw beneath the road and pipeline, with the top
its (Fig. 4). The most prominent features within
of permafrost generally at depths of 7 to 13 m
the site reflect a meandering channel migrating
(Lawson et al. 1993). The pipeline crosses the river
towards the northeast, with the youngest depos-
at the railroad bridge and terminates at the Rail
its existing in the outer-most loop, which encircles
Off-Load Facility (ROLF), an area of point bar
most of the site. Paleocurrents were presumably
and swale deposits within a convex, northward
in a counter-clockwise direction around this loop.
loop in the Chena River (Fig. 1). More detailed
Cross-cutting the earliest deposits of this sequence,
descriptions of each site and historical accounts
however, are the northsouth trending swales near
of contaminant sources are given by Ecology and
the western post boundary, indicating possibly
Environment (1994).
secondary channel cut-offs or sloughs. The young-
5
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