The report, the third of five volumes, focuses on trends in generation of coal ash and FGD wastes (together comprising FGC wastes) and the characteristics of these wastes. With increasing use of coal, the generation of FGC wastes is expected to increased dramatically: to about 115 million tons of coal ash and 38.7 million tons of FGD wastes by the year 2000. Most of these wastes will be disposed of on land. Data on the chemical characteristics of fly ash, bottom ash, and both treated and untreated FGD wastes in this report include data on principle components, composition ranges for trace components, and leaching behavior. Based on the characteristics of FGD wastes, a categorization of these wastes is also presented. Ongoing programs on chemical characterization are assessed. The fundamental physical properties of FGC wastes are density, size, and crystal morphology. The critical physical and engineering properties are those relating to handling characteristics, placement and filling characteristics, long-term stability, and pollutant mobility. The report includes information on index properties, consistency-water retention, viscosity vs. water content, compaction/compression behavior, dewatering characteristics, strength parameters, permeability, and weathering characteristics. Further efforts in this area are recommended: key is data from full-scale disposal sites.