Electrical Resistivity Methods for Delineation of Potential Karst Geohazards Along FM 2185, Culberson County, Texas

Extensive karst development within the Delaware Basin poses a significant geohazard threat to infrastructure. The dissolution of evaporite strata of the Castile and Rustler formations have led to manifestations of multiple karst geohazard phenomena including sinkholes, subsidence features, and caves. The study area is located within the Gypsum Plain in Culberson County, Texas and includes outcrops of Castile and Rustler strata that host gypsum karst geohazards. Land reconnaissance surveys conducted during summer of 2019 documented numerous surficial manifestations of karst features proximal to Farm to Market Road 2185 (FM 2185).

A 48-kilometer segment of FM 2185 was investigated using Capacitively-Coupled Resistivity (CCR) and Direct-Current Resistivity (DCR) methods to characterize and delineate karst features that do not manifest surficially but pose potential geohazard concerns. CCR data was acquired using the Geometrics OhmMapper G-858 resistivity system, which uses a dipole-dipole configuration composed of five receivers connected by 2.5-meter coaxial cables and a transmitter offset of 2.5 meters. In combination with the medium analyzed, this geometric configuration enabled resistivity soundings up to 5 meters deep. Two dimensional DCR data was collected with a SuperSting (R8/IP) multi-electrode earth resistivity meter using 112 electrodes with 2-meter spacing and a dipole-dipole array configuration. This enabled a depth of investigation of up to 73 meters in depth. Data was processed using AGI's (Advanced Geometrics Inc.) EarthImager 2D software and used to delineate karst-related cavities and subsidence features in the shallow subsurface within the study area.