A high degree of variability often exists in refuse materials within the same disposal area, because individual prep plants often process several coal seams. Each seam may exhibit different mineralogical, chemical, and physical properties. This variability makes the development of uniform reclamation strategies difficult. Additional variability is introduced through weathering. Because coal refuse materials are primarily fresh, unweathered geologic materials that have been subjected to severe treatment during processing, sharp changes in physical and chemical properties are common over short periods of time. The pH of fresh refuse can change dramatically in a short period. We have observed the pH of a fresh, high-sulfur refuse change from to within a single month.