Acid mine drainage abatement resulting from pressure grouting of buried bituminous mine spoils

A 37 acre surface coal mine located in Clinton County, PA, was mined and reclaimed between 1974 and 1977. Buried pyrite-rich pit floor cleanings and tipple refuse were found to be producing severe acid mine drainage (AMD). The pyritic material is located in discrete piles or pods in the backfill. The pods and the resulting contaminant plumes were initially defined using geophysical techniques and confirmed by drilling. The approach taken was to use a cementitious grout, composed of fluidized bed combustion (FBC) ash and water, which would be placed in a manner which would prevent water and oxygen from contacting the pyritic materials. Statistically significant water quality improvements have been noted as a result of the grouting. After four years of post-grouting monitoring, reductions in concentrations of most of the mine drainage parameters range from 40 to 90%.