Technical Improvements in Dipole Geoelectric Survey Methods

After five years of private research, the Dipole Method (ASTM D7007) has been vastly improved with technology that allows for superior quality control. Many companies performing the dipole method take exception to the ASTM requirement to record the voltage potential data, instead locating holes in real time as the survey progresses. The only commercial dipole equipment currently available does not include data recording capabilities. Per ASTM D7007, ASCII data files can be requested by the client, but the files would simply be a log of voltage potential measurements, which is not meaningful to a layperson. Recent advances in the Dipole Method equipment include a GPS-based data recording system and software in order to download the data and create an iso-potential map throughout the survey area. Potential hole locations are clearly shown as a bull's eye pattern in the voltage potential field. In addition, the equipment uses a proprietary technology, which allows the operator to greatly reduce the background noise. When the background noise can be reduced, the signal produced by a hole is not only amplified, but it can be seen more easily and from further away. The increased sensitivity of the new technology is presented in this paper through calibration curves produced for a given hole size using both the existing and the new technology. The new technology shows that the Dipole Method can be performed with both increased sensitivity as well as the production of survey documentation, which can ensure the quality of the survey and provide a means for quality control documentation. The abilities of the new technology presented in this paper will be increasingly important as national standards develop. This paper presents the capabilities of this dipole equipment for the first time.