GEOPHYSICAL EQUIPMENT
TPI operates two GSSI 400 MHz GPR units. The GPR unit functions by transmitting electromagnetic pulses into the ground from a joint transmitter/receiver box. These pulses of energy are then reflected back to the unit based upon varying electrical properties of the subsurface. The data are processed and displayed on the screen as a continuous cross-section in real time. In order to provide our clients with the greatest degree of certainty possible, we use GPR as one tool in our multifaceted on-site approach.
GPR
The Geonics EM-61 is the ideal metal detector for projects related to potential unknown underground storage tanks (USTs) and other buried metallic objects. By linking the EM data collection with a sub-meter Trimble GPS unit, we are able to simultaneously collect EM and GPS data. This benefits our clients by allowing us to operate in the most time efficient manner possible without the hassle of the standard grid setup. Our EM data are presented to the client in the final report in a clear and concise manner, which includes the GPS coordinates of suspect anomalies for further investigation. You will be able to navigate back to any detected anomaly long after the paint has faded and the pin flags have blown away.
EM-61/TW6 EM
RadioFrequency Line Location
Line locating is performed primarily with a Radiodetection 4000 RF transmitter/receiver set. The transmitter emits a specific electromagnetic signal that is indirectly induced or directly conducted onto a metallic line. The receiver is configured to detect that same signal, and the line is then traced and marked on the ground based upon the receiver’s response. Nonmetallic lines may also be located by snaking a small, independent transmitter (“sonde”) down accessible lines with a steel tape.
Suspect you’re dealing with a sinkhole issue? Need depth-to-bedrock or depth-to-water table information? Trying to delineate a backfilled stream-channel? Maybe you’re interested in the subsurface distribution of electrically conductive contaminants? These are the types of projects where we would suggest a resistivity survey. TPI conducts subsurface resistivity surveys using the AGI SuperSting R8 IP Earth Resistivity and IP Meter. The SuperSting unit measures the voltage drop of an induced electrical current across numerous electrodes as it travels through subsurface. The resistivity data are then processed and examined for evidence of significant subsurface features including bedrock surfaces, perched groundwater tables, cavities/sinkholes, or potential contaminant plumes. *Available upon request*.
TPI is also able to collect down-hole soil conductivity data by combining an electrical conductivity probe with one of our direct-push rigs. Down-hole EC profiling is
particularly useful in the efficient determination of soil grain size (permeable sands vs
impermeable clays), water content, and metal content. *Available upon request*.
Resistivity/Conductivity