The report, the fourth of five volumes, focuses on utilization of coal ash and FGD wastes. With increasing utilization of coal, generation of these wastes is expected to grow, but at a slower rate than generation, thus increasing the volume of wastes sent to disposal. Many uses for coal ash have been developed in three categories: as fill material; in the manufacture of cement, concrete, and pavements; and in miscellaneous uses such as ice control and blasting grit. In 1977, about 21% of the 61.6 million tons of coal ash generated was utilized. Current R and D projects on ash focus on understanding existing uses and developing new uses including mineral recovery. FGD wastes are not presently used in the U.S. Potential FGD utilization options may include use as gypsum substitutes, as fillers and soil conditioners, in cement and concrete manufacture, and construction of artificial reefs. Technical, environmental, and institutional barriers (the last being the most important) constrain utilization. Data gaps remain in quality requirements for using coal ash and FGD wastes in specific applications and understanding the institutional constraints to utilization.