Wastes generated by human activities range from relatively harmless substances such as food and paper waste to toxic substances such as paint, batteries, asbestos, healthcare waste, sewage sludge derived from wastewater treatment and high-level radioactive waste.
The process of storage, collection, transport, treatment and disposal of wastes all have the potential to pollute the environment and particularly groundwater due to uncontrolled migration of fluids derived from the wastes. A critical criterion in estimating potential groundwater pollution from waste disposal is the siting of waste treatment and disposal facilities.
The likelihood of disposed wastes polluting groundwater depends on the thickness of the unsaturated zone and the attenuation capacity of the overburden (loose unconsolidated material) underlying the site, since the quantity and concentration of leachate generated is a function of the access of water to the site. Thus, the potential for pollution of groundwater will be least at sites carefully selected to take advantage of the most favorable geological/hydrogeological conditions.