The physical and chemical characteristics and engineering properties of power plant bottom ash, a byproduct produced from the combustion of coal, are presented. Laboratory studies included evaluation of chemical and index properties, permeability, compaction, shear strength, and compressibility. The results of these tests conducted on Indiana bottom ashes are compared with representative values obtained for granular soils. The leaching behavior of bottom ash and its effects on ground water quality have been studied by laboratory extraction techniques. The findings suggest that untreated bottom ash may be used as a fill material, including backfill for retaining structures, highway embankments, and structural fills.