U.S. EPA Removal Action Projects
Geoprobe Systems® Machines
Subsurface investigation activities performed by the Illinois EPA’s Office of Site Evaluation (OSE) are completed predominantly using two Agency owned Geoprobe Systems® direct push machines (Models 5400 & 6600). Geoprobe Systems® direct push machines are hydraulically powered units that use both static force and percussion to advance sampling and logging tools into the subsurface. The Geoprobe Systems® direct push machines provide the OSE the capability of collecting soil, groundwater, and soil gas samples, installing 2-inch monitoring wells using conventional rotary system techniques, installing prepack monitoring wells and piezometers using direct push techniques, coring concrete, and advancing direct sensing instrumentation. Geoprobe Models have made collecting soil and groundwater samples much easier and more efficient, even reaching depths in excess of 100 feet!
When completing soil borings using the Geoprobe Systems® machines, a 4 or 5 foot Macro-Core® Sampler is repeatedly advanced into the subsurface to obtain soil cores. The subsurface material is maintained by a plastic liner located inside the Macro-Core® Sampler. The subsurface soil core may be inspected, analyzed in the field, and sampled for laboratory analysis following removal of the plastic liner and soil core from the Macro-Core® Sampler.
X-Ray Fluorescence (XRF)
The X-Ray Fluorescence (XRF) analyzer uses high-energy primary x-ray photons emitted from an x-ray tube react with individual atoms in the sample, that respond by “fluorescing” or emitting their own secondary x-rays. The XRF detector captures these fluorescent x-rays and processes the information to determine element-specific concentrations in soil directly beneath the instrument. The results of the analysis are very accurate and immediately available to field personnel. The XRF has proven to be a useful tool in depicting the extent of metals contamination for site characterization and remediation, as well as eliminating areas for further analysis. Illinois EPA primarily uses XRF for its ability to measure metal concentrations in soils and sediments at sites being evaluated.
The Geonics EM-61 is a twin coil, high sensitivity metal detector which is used to detect ferrous and non-ferrous metallic objects below the ground surface. The EM-61 uses a powerful transmitter to generate a pulsed primary magnetic field, which induces eddy currents in nearby metal objects and is then measured by the twin coils. It can detect a 55-gallon metal drum 3 meters below the ground surface, yet is still sensitive enough to filter out surface metals such as fences, buildings, cars, etc. Illinois EPA has found the EM-61 to be extremely useful in determining if underground storage tanks have been removed from older sites, or are still in the ground.
The results from the EM-61 can be overlain onto maps to provide a better understanding of where buried metal objects may be located in relation to other site features.
Membrane Interface Probe (MIP)
The Membrane Interface Probe (MIP) is a direct sensing instrument designed by Geoprobe Systems® to measures the electrical conductivity of subsurface materials and detect the presence of Volatile Organic Compounds (VOCs). The MIP is used by the Illinois EPA’s Office of Site Evaluation (OSE) to provide immediate feedback on the presence of VOCs in soil and groundwater without having to collect samples and wait for laboratory analytical results. Results obtained using the MIP assist the OSE in identifying contaminated soil horizons and aquifers from which laboratory analytical samples may be collected. The electronic conductivity of the subsurface materials recorded by the MIP can be used to identify changes in soil type. This system offers several benefits including detecting contaminants in coarse and fine soils, contaminants in saturated and unsaturated soils, as well as detecting chlorinated and non-chlorinated Volatile Organic Compounds (VOC) contaminants. Multiple MIP logs produced at a site are beneficial in determining the source area of a contamination, movements of contaminants, depth of contaminants, and are especially important in selecting remediation treatment procedures.