The Multidisciplinary Conference on Sinkholes and the Engineering and Environmental Impacts of Karst, generally called “The Sinkhole Conference,” is the longest-running international conference of its type. Since 1984, engineers, geologists, hydrologists, land managers, biologists, and many others have gathered at these meetings to exchange cutting-edge information on karst and its many benefits and challenges. Abstracts may be submitted until 15 August 2017, after which will be the time to submit your papers to accompany your abstracts. The papers of past Sinkhole Conferences have made those proceedings highly sought and widely cited. We expect the proceedings of the upcoming meeting will be the best yet.
Following flooding in September 2013, several areas along Lakewood Road and Lake Road in northern Eddy County, New Mexico, were damaged by multiple sinkhole collapses. Pettigrew & Associates contracted NCKRI to conduct electrical resistivity (ER) surveys for cavities to guide road repairs. NCKRI agreed to conduct this research to assist in solving a threat to public safety in addition to collecting additional geophysical data, to include in its database for future detailed studies of ER data collection methods and analyses.
The sinkholes in the study area, cover collapse sinkholes, form by the piping of soil and alluvium into underlying karstic cavities. Their position along the two roads is the result of drainage channels along either side of each road, which have promoted groundwater recharge in these linear areas for many years. The piping of the unconsolidated materials created cavities in the alluvium that slowly stoped up toward the surface and into the soil. The flood of September 2013 focused substantially greater flow down into the soil in the channels until the cavities became sufficiently large and unstable to collapse and breach the surface. A visual survey of the area by Pettigrew and NCKRI personnel on 12 February 2014 supported this hypothesis, finding that collapse and related features appeared to diminish with distance from the roads (Figure 1). Subsequent interviews with Lakewood residents revealed additional karstic fissures and sinkholes occurring several tens of meters from the roads, but still indicating the majority were concentrated along the drainage channels.
This study examines “caves and karst” because not all caves and related features are karstic. Pseudokarst collectively describes cavernous landscapes and features formed by non-karstic processes. Pseudokarst caves formed by wind, stream, and sea and lake erosion of cliffs, fracturing of rock and soil, and out-washing of sediment from under a cap of harder material are typically small compared to karst caves. Volcanic caves, notably lava tubes formed by the draining of molten rock beneath a cooled, solidified roof, can be long and complex.
In October 2012, Intrepid Potash Company was in the process of constructing a well pad, access road, and pipeline for an injection well as part of a larger potash solution mining project in eastern Eddy County, New Mexico. During excavation of the pipeline trench, Intrepid employees discovered a small cavity (Figure 1) that extended approximately 1 m below ground level and opened into a cave approximately 8 m long by 5 m wide and extending to a maximum depth of about 10 m. Observations of the cave interior (Figure 2) by Bureau of Land Management (BLM) personnel indicate that the cave is formed entirely in compacted gypsiferous soil, not bedrock, and that the cave might be deeper and more extensive than their preliminary examination indicated.
On July 16, 2008, a brine well cavity in northern Eddy County, New Mexico abruptly collapsed. The resulting sinkhole engulfed the brine well and associated structures, and ultimately grew to ~111 m in diameter with an estimated depth of 45 m. Jim’s Water Service, an oil field service company, had been solution-mining the Salado Formation by injecting fresh water down the well and circulating it through the 86-m thick section of halite until the water reached saturation. The resulting brine was then pumped to the surface and sold as oil field drilling fluid. The brine well operated on state trust land under permit from the New Mexico Oil Conservation Division (NMOCD). The collapse became known as the JWS Sinkhole after the well operator. Less than four months later, on November 3, another brine well collapse occurred in northern Eddy County north of the small community of Loco Hills, forming a sinkhole of similar dimensions. The Loco Hills brine well was also a solution mining operation in the Salado Formation on state trust land. Figure 1 shows the location of these two collapses, the position of a seismometer that recorded the JWS Sinkhole collapse (Land and Astor, 2009; Land, 2011), and the location of the I&W brine well, which is the subject of this report.
Las Cruces is one of the largest towns in the department of Petén in northern Guatemala (Figure 1). Heavy rainfall associated with a hurricane in 2008 and a tropical depression in 2010 caused severe flooding, resulting in displacement of 7,000 residents. An Engineers Without Borders (EWB) team began investigations of the area to evaluate the potential for constructing a drainage channel around the north and west side of town to mitigate future flood events. However, they recognized the possibility for intersecting caves along that route that might complicate or defeat their efforts and asked the National Cave and Karst Research Institute (NCKRI) to assist with this humanitarian effort by evaluating the potential for underlying caves. EWB (2010) provided the data specific to the Las Cruces area described below in this report.