Automation of geophysical surveys used in assessment of hazardous waste

Geophysical surveys generally involve non-invasive measurements made from the ground surface to assess subterranean physical formations. These surveys can serve to locate subsurface contamination or assist in understanding the potential movement of these materials in groundwater. Oak Ridge National Laboratory has recently merged two technologies to automate geophysical measurements. The terrain conductivity meter (Geonics EM-31) measures subsurface conductivity detecting anomalies such as water-filled trenches or buried water or gas lines. The Ultra Sonic Ranging and Data System was developed to locate a surveyor on a specified area using triangulation with ultrasonic time-of-flight positioning. The surveyor's position is transmitted once a second to a microcomputer in the field. Simultaneously, the measurement taken by the surveyor's portable instrument is also transmitted to the microcomputer using a radio frequency link. Up to 3,600 paired measurements and locations can be stored directly in a microcomputer for analysis each hour. This represents a significant advance over conventional techniques by providing more data with fewer errors (related to transcription of information) in which the data can be analyzed in the field. Output from the analysis includes report-ready tables, two-dimensional contour plots, and three-dimensional mesh plots. With these plots, areas of high subsurface conductivity can be readily more » visualized while in the field so that any additional data needed can be obtained sooner with less cost. 3 refs., 3 figs. « less