Selenium is a metallic-like substance that is vital to good diet but harmful in large amounts in food or water.
selenium
- Selenium is a naturally occurring element located in the soils and rocks all over the world.
- Generally, Southeastern Idaho is deficient in selenium. However, elevated selenium is located in some of the rocks below the surface that must be removed in order to access phosphate ore. Non- phosphate bearing soil and rocks is called overburden, which is removed by large equipment before access to phosphate ore in the ground is possible.
- Selenium has many chemical forms; some are mobile in the environment others are not. The greatest risk is associated with the forms that are mobile in the environment.
- During mining in Southeastern Idaho, selenium can become mobile in the environment after rocks that contain elevated selenium are disturbed or brought to the surface. To manage this potential, the material that is elevated in selenium must be separated and buried under overburden that contains no selenium.
- Because the industry and the governmental agencies that regulate industry were unaware of the selenium risk prior to 1996, overburden containing selenium was not separated from overburden containing no selenium, nor was the overburden containing selenium buried as it was removed. In fact, due to its soil-like characteristics, the material that was elevated in selenium was required by the agencies to be used as topsoil. Therefore, the phosphate industry is addressing certain areas at historic mines where this overburden may be releasing selenium to the environment. (See the associated fact sheet entitled, “What is Simplot doing about selenium contamination?”)
- New mining techniques, commonly referred to as “best management practices” (BMP’s), that were put in place after 1996 are proving to be effective in managing the potential release of selenium from overburden.
- For the extension of the Smoky Canyon Mine, Simplot has proposed a protective cover system that goes beyond what is predicted to be necessary to help eliminate the potential risk of selenium. The cover provides an extra measure of protection. (see the Final Environmental Impact Statement for Smoky Canyon Mine, Panels F and G)
