WorldWide Drilling Resource

15 SEPTEMBER 2014 Exploring Karst Environments Compiled by Amy White, Associate Editor WorldWide Drilling Resource ® Some environments prove more challenging for drilling than others, and a karst is one of them. Karst is a land- scape or terrain which results from weathering of water-soluble rock types including limestone, dolomite, and gyp- sum. Sinkholes, caves, and underground drainage systems characterize a karst. Rainwater becomes acidic after mixing with carbon dioxide in the atmos- phere and soil. It drains into fractures in rock, dissolving the rock and creating a network of passages. As water contin- ues to flow, it erodes and enlarges pas- sages, allowing larger amounts of water to pass and wear away rock. Sinkholes can be of particular con- cern since they can have a sudden and dramatic effect, especially when occur- ring in an urban setting. Around 23,000 sinkholes have been identified in the U.S. Most sinkhole damage in the U.S. tends to occur in Alabama, Florida, Kentucky, Missouri, Pennsylvania, Tennessee, and Texas. Last year was termed “the year of the sinkhole.” Activity was unusually high, capturing media attention and rais- ing awareness of associated risks. once a home or business-owner notices signs of a sinkhole, such as cracked foundations and/or walls, their insurance pro- vider is notified and an investi- gation begins. Test bor- ing is an essen- tial part of the process. Drilling takes place to determine the nature of the soil. Samples are taken every five feet, then packaged and sent to a lab for analysis. Data from these core samples provides crucial infor- mation about soil conditions to engineers and property owners. Results from sub- surface borings, as well as surveys on the surface, reveal whether or not sinkhole activity is present. Certain precautions are required when drilling in a karst environment: 3 Depressions can open slowly, so the mast should be closely moni- tored for verticality. 3 Hand augers should have rub- ber handles due to electrical lines near houses. 3 Slight slopes should be careful- ly observed since they can cause a rig to topple. 3 Collapses can happen sudden- ly, so a kill switch and safety action plan are imperative. Features of a Karst system courtesy of esi.utexas.edu Photos courtesy of Larry Madrid, taken by WWDR during the National Drilling Association 2013 Conference in Orlando, Florida. " ; # 511-,(2 0) 20'5&43 %9 4+(3( ,/( $/5)$&452(23 ; 08 029'0/ # ! : : $8 $,- 3$-(3 *,6(/3,/4(2/$4,0/$- &0. "(% ,4( 777 *,6(/3,/4(2/$4,0/$- &0. WorldWide Drilling Resource ®