A Natural-Potential Survey Around
Lemon Lane Landfill, Bloomington, Indiana
for
Westinghouse Electric Corporation/CBS
Bloomington Project
April/May 1998
EXECUTIVE SUMMARY
A natural-potential (NP) survey was conducted around the perimeter
of Lemon Lane Landfill in Bloomington, Indiana during April 1998. The survey
was performed in order to map possible groundwater conduits conducting water
to the Landfill site, and to locate likely pathways connecting the Landfill
to Illinois Central Spring, where low level pcb's have been detected.
The NP survey around the Landfill identified at least 24 anomaly trends
indicative of underlying groundwater conduits in carbonate rock. Around
the east, north and west sides of the Landfill, a number of possible pathways
for water were deduced from stacked NP profiles. In addition, crosslines
within the west and north blocks revealed trends that roughly paralleled
the landfill boundaries, suggesting a series of fractures concentric to
the sink beneath the fill. Anomaly trends of the East Block coincided with
existing depressions of the ground surface. Residual NP contours expressed
the combined anomaly trends of primary and cross-lines of the West Block,
while in the North Block the four north/south anomaly trends were discerned
in the contour portrayal.
On the south side of the Landfill, between the railroad and the cemetery
gardens, at least eight anomaly trends have been identified. These features
trend generally southeastward, but whether or not water within the underlying
structures flows in that direction within all of the trends is uncertain.
A major anomaly trend can be traced from Illinois Central Spring northwestward
to the cemetery, where it appears to bifurcate. Other possible tributaries
are evident in the stacked profiles. The anomaly trend coincides with deep
sinkholes up-gradient from the spring and culminates in an M-shaped anomaly
over the spring orifices. The main anomaly trend is clearly portrayed as
a series of NP highs in the residual NP contour map of the Southeast Block.
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