Clayey barrier assessment for impoundment of domestic waste leachate (southern Ontario) including clay–leachate compatibility by hydraulic conductivity testing
The current use of engineered clayey barriers to control the chemical flux entering the groundwater adjacent to landfill sites is discussed. New analytical methods to predict flux–time relationships controlled by advection and diffusion are presented briefly, followed by an assessment of macropore flow problems inherent in laboratory and especially field-compacted clays.The clay–leachate compatability of southern Ontario (Sarnia) clays is then assessed with respect to domestic waste leachate using hydraulic conductivity as the assessment tool. The dominant role of channel flow through macropores, even in very carefully controlled laboratory samples, is emphasized, as is the critical role of soil smectite and vermiculite in retardation of species such as K+ from domestic leachate.The Sarnia brown and grey clays seem compatible with domestic waste leachate at least with respect to hydraulic conductivity, k. In spite of extensive K+ retardation, leachate effected a slight decrease in k of the water-compacted brown and grey samples, a feature also observed recently for the contaminated grey clay zone at a field site. Key words: clay barriers, hydraulic conductivity, compatibility, domestic leachate, channel flow, potassium retardation, migration modelling.