EVAPORITE KARST GEOHAZARD MANIFESTATIONS IN PERMIAN STRATA, CULBERSON COUNTY, TEXAS

Karst development is extensive throughout the Ochoan evaporites of the Castile Formation within Delaware Basin of far west Texas and southeastern New Mexico. Specifically, failures on ranch to market roads are occurring with greater frequency as oilfield activities and associated heavy traffic have increased in Culberson County, Texas. These manifestations include road subsidence and collapse within the right of way which are coupled directly with karst development or indirectly through suffosion processes and road base compaction. Current research is focused on utilizing geophysical techniques, including both ground penetrating radar and resistivity, to delineate and characterize geohazard extent. These non-invasive subsurface characterizations have been correlated with physical excavations and GIS-based analyses, including LiDAR and imagery analyses, to identify regions of increased geohazard susceptibility.   Geohazards have been identified as being associated with: 1) direct associations with cave and solutional conduits; 2) dissolution of road base aggregate; 3) differential compaction of road base and underlying gypsic soils; 4) differential dissolution of bedrock, including secondary alteration of bedrock; 5) soil piping / suffosion; 6) intrastratal brecciation; and 7) anthropogenic alterations, including engineered structures and buried utility cables. Complicating delineation of current and future geohazard potentials is the complex, evolving speleogenetic system, which includes both extensive hypogene and hypergene karst development, including surficial manifestations of both collapse and solutional sinks that episodically infill and reopen as a result of gypsic soil mobilization. As geohazard delineation and characterization are refined, engineering solutions will be developed for potential mitigation.