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Geoprobe®
Direct Push
Services
GeoCore currently
utilizes a 2003 Geoprobe® 540UD probing machine mounted on a 2003
Ford F350 truck for direct push soil and groundwater sampling
capabilities. This probing machine is extremely versatile in
performing continuous soil sampling, electrical conductivity logging,
discrete interval soil sampling and discrete interval groundwater sampling
in unconsolidated sediments. Due to its small size and 4-wheel drive
capability, this unit is able to access difficult sampling locations.
 Some
of the advantages of the Geoprobe® 5400 are:
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Direct
push sampling with little or no investigative derived waste and
minimal disruption to property.
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Small
4x4 truck access to difficult terrain.
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Fast
efficient setup and sampling allowing for a high volume of samples
collected per day.
Tooling
which is provided with this rig consists of 1.25” probe rods, macro-core
sampler, discrete interval macro-core sampler, electrical conductivity
logging and screen point groundwater.
The
Geoprobe® 5400 is a compact, convenient, hydraulically powered
percussion-probing machine. It can be swiftly folded out the truck
for operation. The Geoprobe® uses static force and a percussion
hammer to advance small-diameter sampling tools. It provides an
economical way to carry out sampling operations and generally operates at
depths of 30 to 60 feet; but, depending on soil conditions, can go deeper.
Sampling is efficient with 10 to 30 sample locations per day. Stroke is 54
inches, enabling the Geoprobe® to accept a variety of probe rod lengths.
The probing tools not only create small diameter holes that minimize
surface disturbance, but little cuttings are produced during the sampling
process. Tools can be interchanged at any time.
Direct Push Electrical Conductivity Logging
A
percussion soil probe system designed for direct sensing of soil
conductivity. The probe is approximately 1-1/8 inches in diameter
with isolated contacts. The probe is advanced into the ground by a
hydraulically powered pushing and percussion mechanism. A signal cable
attached to the probe is run through the inside of the rod to a laptop
computer-based data recording system. Depth measurements are obtained from
a stringpot system configured to measure the distance from the driving
mechanism to the ground surface. Data derived from this system is used to
both determine the depth of the probe and the probing speed. Conductivity
measurements are displayed with respect to depth in near-real-time on the
computer screen. Data was recorded in spreadsheet format and downloaded at
the end of each field day.
High
conductivities are associated with clayey soils, low conductivities with
sandy and gravely soils, and sand/silt/clay mixtures have conductivities
that lie somewhere in between. Conductivity levels change somewhat from
one sample location to the next; however, the clayey soils at the site
tend to have conductivities in the range of 60 to 140 mS/m and the sands
about 30 to 40 mS/m, with gravels generally showing a conductivity dip of
about 5 to 10 units below the level for a sandy soil. Because the
conductivity varies somewhat for a given soil type between sample
locations, comparing the conductivity log with a soil boring log or CPT
soil classification log is essential to properly interpret the
conductivity log. Changes in conductivity are caused by changes in soil
type, water content, and soil or groundwater contamination. Accordingly,
when used alone, the conductivity log leaves some doubt regarding an
accurate soil classification. It is quite effective, however, at
delineating changes in the subsurface properties.
Macro-Core soil sampling
The
Macro-Core soil sampler collects core samples of unconsolidated materials
1-1/2 inch in diameter. These unconsolidated materials may include soils,
sediments and waste materials or mixtures of these. The device works best
in medium to fine grained cohesive materials such as silty/clay soils or
sediments. When using the plastic core catchers, the Macro-Core catcher
can also be used to sample medium to coarse grained sandy materials with
some fine to medium gravels.
The Macro-Core sample can be used with an open nose cone in stable soils
or a closed nose cone in unstable materials to prevent unwanted materials
from entering the sampler till the sampling depth has been reached.
The
Macro-Core soil sample can be captured in clear plastic liners. The liners
are inserted into the sampling tool prior to being pushed into the soil.
The most common types are PETG and PVC liners. These are clear and give
you a good view of the soil cross section after retrieval. PVC plastic
core catchers can be used in the end of these liners for sampling
unconsolidated soils
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