STINK SINKS AND PERPETUAL POT HOLES: LIVING WITH GYPSITE KARST IN LARAMIE, WYOMING

A large part of Laramie, Wyoming, is built over gypsite, an earthy weathering product derived from thick sequences of gypsum bedrock in the underlying redbeds of the Permian Goose Egg and Triassic Chugwater formations. Both the gypsum bedrock and gypsite were mined for over 100 years, first for plaster and recently for cement. The gypsite deposits range up to 10 feet thick. Dissolution of the gypsite has produced dolines that contain ponds which have been incorporated into city parks. Sinkhole collapses in roads are caused by piping associated with leaking water and sewer lines. Soil instabilities under streets, gutters, sidewalks and foundations are caused by freeze-thaw swelling and dissolution of wetted gypsite. Networks of horizontal conduits dissolved in the gypsite allow for the rapid lateral migration of contaminants. The State of Wyoming has granted technical impracticability waivers for remediation of the karst networks that preclude isolating and removing the contaminants.