Electrical Conductivity (E)
Geoprobe.com describes Electrical Conductivity:
Soil conductivity and resistivity (the inverse of conductivity) have long been used as tools to classify soils. The power of this tool stems from the fact that higher electrical conductivities are representative of finer grained sediments, such as silts or clays, while sands and gravels are characterized by distinctly lower electrical conductivities. A few site specific core samples, either from discrete depths or a continuous core, can be used to verify the lithology represented by electrical conductivity values at a site. The electrical logs are then correlated across the site to show changes in thickness or elevation of lithologic units of interest. Soil conductivity logging continues to increase in usage because conductivity logging can be efficiently performed with the highly mobile and cost-effective percussion probing equipment. . . the Direct ImageR Electrical Conductivity (EC) System.
EC logs are used to define zones of lower conductivity, equivalent to coarser grained, more permeable sediments, which will allow the movement of contaminants (hydrocarbons, chlorinated VOCs, or metals) in the subsurface. The lithologic information gathered with the Conductivity System can be used to aid the investigator in understanding the movement and location of contaminants in the subsurface. This information will also assist in the proper placement of monitoring or extraction wells.
Membrane Interface Probe (MIP)
Geoprobe.com describes Membrane Interface Probe:
The Membrane Interface Probe (MIP) is a screening tool with semi-quantitative capabilities acting as an interface between the contaminates in the subsurface and gas phase detectors at the surface (Figure 1). The membrane is semi-permeable and is comprised of a thin film polymer impregnated into a stainless steel screen for support. The membrane is approximately 6.35mm in diameter and may be easily replaced. The membrane is placed in a heated block attached to the probe. This block is heated to approximately 100-120 degrees C and is raised at the leading edge to protect the membrane. Heating the block helps accelerate diffusion of the contaminate through the membrane.
Diffusion occurs because of a concentration gradient between the contaminated soil and the clean carrier gas behind the membrane. A constant gas flow of 35-45 mL/min sweeps behind the membrane and carries the contaminants to the gas phase detectors at the surface. Travel time from the membrane interface to the detector(s) is approximately 30-45sec (depending on the length of trunkline and flow rate).
The ability to detect a contaminant is determined by the type of detectors being used. Any laboratory grade gas phase detector with an analog output of 1-5V may be used. Most commonly used detectors include photoionization detector (PID), electron capture detector (ECD) and the flame ionization detector (FID). Each detector is designed for sensitivity to a group or type of contaminant. The ECD is used for chlorinated (TCE, PCE) contaminant detection, PID is best used for the detection of aromatic hydrocarbons (BTEX compounds), and the FID is best used for straight chained hydrocarbons (methane, butane). These detectors may be used in series with the least destructive detector being first and the most destructive detector coming last. The MIP system can process four detector signals at one time. These detector signals, in conjunction with the time in which a contaminant takes to return to the surface, are graphed versus depth.
The detector information and the electrical conductivity of the soil are graphed by the FC4000 field instrument. This allows the operator to determine the location of the contaminant, the relative concentration of the contaminant and the soil in which the contaminant is located. The MIP log can be used to determine the depth at which a monitoring well should be placed, at what depth samples need to be collected, or the interval for injection of remediation materials.
Hydraulic Profiling Tool
Geoprobe.com describes Membrane Interface Probe:
The Hydraulic Profiling Tool (HPT) allows the user to create fast, continuous, real-time profiles of soil hydraulic properties in both fine- and coarse-grained material. The HPT uses a sensitive, downhole transducer to measure the pressure response of the soil to injection of water. One primary use of this tool is to locate and define preferential migration pathways for contaminants in the subsurface. It can also be used to target zones for injection of remediation material. In addition, the HPT can be used to select well screen intervals, evaluate locations to conduct slug tests, and measure static water conditions across a site.
NOVA CPT Tools
Geoprobe.com describes NOVA CPT Tools:
The new NOVA CPT equipment integrates easily with the GeoprobeR 6622CPT machine which was designed specifically for pushing CPT, as well as having standard GeoprobeR direct push sampling capabilities using a hydraulic percussion hammer. Using RW (Radio Wave) NOVA, the user can push cones through the center chuck system while collecting cordless cone data real-time via a RW antenna. Communication between the cone and data acquisition is automatic. By integrating these two major components, expect to see improved efficiency in CPT. Setup and pushing capability will be easier for CPT soundings using the 6622CPT with automatic anchor placement, wireless remote control for tracks, throttle, & rear blade, and center pushing through a CPT clamp system. NOVA CPT adds to the advancements by offering two cordless options for operators where data can be acquired at 18-bit resolution through either RW or sound data transmission approaches.