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Case
Histories
Resistivity
Profiling
Landfill
Depth Profiling
Recently, we
were asked to conduct a high
resolution resistivity survey to
determine depth to bottom
of fill and landfill areas at a huge
Brownfield project in Arizona. Profiles
were conducted at
areas of suspected debris landfills and
areas of uncompacted fills to
compliment proposed environmental
and geotechnical drill sites.
The native formation at the site was an
electrically resistive conglomerate.
This
profile was conducted as a baseline
study, since historical records
indicated that it had not been
disturbed. As
you can see, there is a fairly shallow
layer of fill (1.5
meters)
over the more resistive native.
This
profile was conducted in an area of
suspected buried trash. As you can see,
large bull's-eye areas of high
conductivity exist.
These
areas are interpreted to be metal and other
conductive land fill debris and are up to
depths of more than 16 meters.
This
profile was conducted along a river bank
in an area where a cut bank was reportedly
filled, but not compacted.
As
it turned out, the fill was more conductive
then the native soil and the cut bank is
easy to recognize.
This
profile was conducted in an area of
suspected concrete and rock debris. As
you can see, large Bull's-eye areas of
higher resistivity exist.
These
areas are interpreted to be buried
concrete and decorative boulders and
extend to depths of up to 20 meters.
Some
benefits to consider:
-
This
survey work was conducted
despite ongoing operations
at the several properties.
-
These
surveys can be conducted in
endangered
habitat sensitive areas.
-
No
permitting is required for
conducting these surveys, and
therefore, can be scheduled
ahead of drilling.
-
When
conducted in conjunction with
exploratory borings or test
pits, it can increase the
overall extent of subsurface
information as well as aid
in boring and test pit location.
.
Southwest
Geophysics
has used Resistivity
Surveys to:
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Map
Faults
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Map
fracture zones for water well sighting
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Map
large karst voids and sea caves
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Find
depth to groundwater, in certain
specific situations
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Generally
characterize subsurface geology.
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Aid environmental contamination
flow projects when used to evaluate
locations of paleo stream
channels or fault zones.
-
Find
buried bedrock valleys, which can be
an important source of groundwater in
unconfined aquifers.
-
Vertical
joints or cracks, which can indicate
subsidence features.
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