USING COAL COMBUSTION BYPRODUCTS IN MINE RECLAMATION: EFFECTS ON GROUNDWATER

Electric utility response to certain amendments of the Clean Air Act has resulted in the production of several types of alkaline coal combustion byproducts. Alkaline combustion byproducts are gaining increasing usage for acid mine drainage mitigation as research leads to a better understanding of their beneficial applications. This paper discusses three such projects using FGD for in-situ treatment of acid mine drainage in an underground coal mine, reclaiming a gravel pit with class C ash and using FBC ash as a cap and cover medium in an acid producing coal mine. Monitoring indicated that the FGD mine fill treated AMD parameters and other metal ions without increased risk of contamination from other elements. Increases were limited to soluble salt constituents: Ca, Na, K, Cl and SO4 without approaching regulatory limits. Placing class C ash in the gravel pit resulted in down gradient contamination of an otherwise high quality aquifer and the FBC cap controlled AMD without mobilizing other, toxic elements. The results indicate the importance of understanding the treatment objective and matching the appropriate CCB to the groundwater setting.