DEVELOPMENT OF A COVER SYSTEM TO MINIMIZE PERCOLATION

An environment impact study was conducted to support the expansion of the J.R. Simplot Smoky Canyon Mine located in southeast Idaho. Selenium is a contaminant of concern in the run of mine (ROM) material. To address the issue of selenium leaching from the ROM into ground water, a cover system was designed to minimize percolation by using materials available at the mine. Development of the cover system consisted of material characterization, assignment of initial and future material properties, creation of a 100-year meteorological database, and multiple numerical modeling simulations. The synthesis of this data into the model resulted in a layered cover system of three materials with a total thickness of six feet. The cover system is predicted to limit percolation to approximately 15 mm per year, or approximately 2% of the annual average precipitation, resulting in the protection of ground and surface water resources. This paper describes the process and methodology undertaken to develop the cover system in the approved record of decision.