Environmental Considerations for Fly Ash Disposal

Recent concern about subsurface leaching from fly ash disposal sites has generated research to investigate this phenomenon. Among the constituents of the leachate are soluble heavy metals that are found in high concentrations on many fly ashes. This paper reviews those factors which are most important in heavy metal release and reports on some results from a leachate field investigation at an active disposal pond. The pH, which may be determined by the acid-base characteristics of the fly ash, degree of surface concentration of metals, presence of complexing agents, and soil physical and chemical properties are seen as the major considerations affecting leachate quality and quantity. Alternatives which include the use of lining materials, addition of chemicals to sluice water, conversion to a dry handling system, and selective mixing of fly ashes are considered as possible disposal strategies if greater control is deemed necessary.