Alternative Title
NCKRI Symposium 2: Proceedings of the Thirteenth Multidisciplinary Conference on Sinkholes and the Engineering and Environmental Impacts of Karst
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Publication Date
May 2013
Abstract
pg(s) 151-159 Gypsum, a highly soluble rock, is readily dissolved to form karst features identical to those associated with limestones and dolomites. Investigations in Blaine County, in northwestern Oklahoma, evaluated potential problems that subsidence due to gypsum karst may pose for the proposed Watonga Wind-Power Project, a wind-turbine project just east of Watonga. Catastrophic collapse of a wind turbine is clearly unacceptable, and minor settlement could also be a risk. Differential settlement by even 3 cm across a 15-m-wide turbine foundation could lead to the turbine tilting out of tolerance, requiring remedial repairs. Gypsum beds of the Permian Blaine Formation underlie all parts of the Project Area, at depths ranging from 10 to 45 m below ground level. The Blaine Formation here is about 29 m thick: it consists of four gypsum beds, each 0.6 to 4 m thick, interbedded mainly with red-brown shales. The Blaine is overlain by the Permian Dog Creek Shale and by unconsolidated Quaternary sands, clays, and gravels that may obscure karst features. Field studies, aerial-photo analysis, and literature review show that there is no evidence of gypsum karst in the Project Area. Although lacking direct evidence of karst in or near the Project Area, we recognize there is some potential for subsidence due to dissolution of shallow gypsum. Additional mitigation of this risk can be achieved by placing wind turbines at sites where the gypsum beds are deepest: we believe that where gypsum is 25 m below ground level, or deeper, the risk related to gypsum karst is low. Placing turbines at sites where gypsum beds are less than 25 m deep would pose a medium or high risk. To minimize this risk, a map was prepared showing areas of low, medium, and high risk, related to potential gypsum karst. Open Access - Permission by Publisher See Extended description for more information.
Type
Conference Proceeding
Publisher
University of South Florida
Identifier
K26-01526
Recommended Citation
Johnson, Kenneth S.; Bangsund, William J.; and Hines, Neal A., "Gypsum karst and potential risk in siting wind turbines in Blaine County, Oklahoma NCKRI Symposium 2: Proceedings of the Thirteenth Multidisciplinary Conference on Sinkholes and the Engineering and Environmental Impacts of Karst" (2013). KIP Talks and Conferences. 63.
https://digitalcommons.usf.edu/kip_talks/63
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