SOIL ELECTRICAL CONDUCTIVITY LOGGING SERVICES (EC LOGGING)

Electrical conductivity (EC) logging is a rapid, innovative, and cost-effective way to conduct geo- hydrologic investigations with minimal sampling and disturbance of the surface and subsurface. BGS uses the Geoprobe Systems
Direct Image Soil Conductivity System with the Wenner or Dipole array configuration. The system provides a real-time display of the conductivity signal, probe depth, and speed of advancement as logging proceeds.

Conductivity readings are measured in milliSiemens/meter (Ms/m). The electrical conductivity of unconsolidated soils and sediments is a function of their grain size. Fine-grained materials, such as clays, have a higher conductivity than silty materials, which in turn have a higher conductivity than sands or gravels.

During logging, conductivity readings are taken every 0.05 feet. All data is stored in electronic format (ASCII) and can be accessed through a spreadsheet program, such as Excel, or imported into various graphing software programs. Hard copies can also be printed in the field.

Once the logs have been interpreted, this innovative technology for site characterization can be used to trace soil layers across a site, to aid in the construction of geologic cross sections, to define aquifers and aquatards, and to define other soil layers like clay or sand lenses. When accurate surface elevations are obtained at each EC location, the depths to formations or formation contacts can be translated to elevations. This information can be used to construct contour maps on formation contacts and to construct contour maps on upper surfaces of permeable units to define potential flow paths for contaminant transport. And this information can help when placing monitoring well screens and is a useful tool when groundwater profiling.

MIP SERVICES (MEMBRANE INTERFACE PROBE)

MIP, which stands for Membrane Interface Probe, is an in-situ volatile organic compound (VOC) logging system that is capable of detecting and measuring VOCs, without the need to physically collect soil samples. The system provides detailed information, such as the depth and thickness of VOC soil impact and soil type based on soil conductivity measurements. Much like the soil conductivity logging system, the MIP displays the information graphically in “real time” so that decisions can be made based on real data. MIP logging works in both unsaturated and saturated soils. Because the MIP tip is heated to maintain a constant temperature of 120o C, a drop in temperature often indicates that groundwater was encountered, which can be identified on the display screen.

The MIP probe is intended as a semi-qauntitative screening tool. This tool is perfect for plume delineation both horizontally and vertically. We have found this to be a great tool in determining what soil interval should be sampled for laboratory analyses. When logging in saturated soils, the information can be used to determine proper monitoring well screen placement and length. This tool is also useful in determining the soil interval, in which bio-enhanced material could be injected for remedial purposes. Currently, this system cannot determine what type of VOC is present or at what concentration, because of this it is best used when the type of VOC impact is known, such as BTEX, TCE, or PCE. It is believed that future technology will allow us to provide this information as well.

Detection of contaminants is performed using laboratory-grade gas chromatography detectors. BGS uses an FID, PID and ELCD to detect VOCs. In a single push of the rod string, the system displays VOC detection and soil conductivity information. This information can be printed in the field and correlated to other logs performed on site. Typically more than 300 feet can be logged in a day. The log data is stored electronically as an ASCII Tab Delimited format, which can be opened using a spreadsheet program or imported into various graphing software programs to provide subsurface contour maps and 3D maps.

"The Triad is an innovative approach to decision-making for hazardous waste site characterization and remediation. The Triad approach proactively exploits new characterization and treatment tools, using work strategies developed by innovative and successful site professionals. The Triad Resource Center provides the information hazardous waste site managers and cleanup practitioners need to implement the Triad effectively."