APPLYING GROUND PENETRATING RADAR TO IDENTIFY EVAPORITE KARST GEOHAZARDS ASSOCIATED WITH RM 652 IN CULBERSON COUNTY, TEXAS

Texas Ranch to Market 652 (RM652) stretches for 34 miles through northern Culberson County within the Delaware Basin. The study area is known to host significant evaporite karst geohazards throughout the Gypsum Plain (i.e. Castile Formation) which form beneath and immediately adjacent to the road. Karst geohazards associated with RM 652 are due to increased road traffic, related to growth in petroleum exploration and production in the area. Gypsum sourced from the Castile and Rustler formations was used to create the road base, which meteoric waters have easily dissolved while increases in gross weight of heavy traffic has accelerated solution and suffosion features. Characterization of compaction and dissolution beneath the road surface was undertaken through GPR, using the SIR 20 by GSSI. This study focuses on the first half meter of the subsurface, including road base material, as a result of the limitations of ground penetrating radar. RADAN 7, also by GSSI, was used to process data; geographic location and characterization of the karst landforms from GPR data was used to map geospatial distribution of geohazards.

Karstic geohazards identified in this study most commonly include extensive meteoric dissolution of road base, as well as traffic related compression of the road, primarily caused by the use of crushed gypsum as the aggregate road base. Other subsurface expressions commonly include suffosion features, both in the gypsic soil and Castile bedrock. Extensive geohazard formation is present in areas where the Castile Formation is close to the surface or in outcrop, and has definitive topographic relief, which aids the flow of water through the gypsum, rapidly dissolving it. Additionally, leaching of the gypsic soil and gypsum formations takes place in areas where water ponds following meteoric events. Of special note in this project is the Rustler Formation; in general it remains free of major geohazards; however, in portions of the formation, gypsic masses can be found which display significant geohazard formation.