Electrical Resistivity Studies Related to the Proposed Low Level Radioactive Waste Repository, Hudspeth County, Texas

As part of the site characterization effort for the proposed low-level nuclear waste disposal site north of Fort Hancock, Texas, the University of Texas at El Paso conducted an electrical resistivity survey of the area. This survey was contracted by the Texas Low-Level Radioactive Waste Authority. The intent is to repeat this survey annually if the site is licensed in order to monitor leachate migration.

A series of soundings were made, and profile readings were taken around the entire perimeter of the proposed site. The locations of these measurements are shown in Figure 1. The procedures outlined in Draft Regulatory Guide 6.7 of the Texas Department of Health were followed. A Price array configuration was used to make the measurements, and the Barnes layer method (Barnes, 1953) was used to calculate apparent subsurface resistivities. The voltage readings were generally the average of 4 measurements, but in a few cases, 16 measurements were averaged. Repeatability was excellent (1 or 2%) for a specific placement of the electrodes. However, movement of any electrode by 1 m created variations in readings of up to 100%, and variations of 50% were common. These results are to be expected considering the near-surface variability in terms of soil composition and water saturation, but they must be kept in mind if the survey is repeated in the future.