The process of injecting contaminants and waste material into confined aquifers for waste disposal.

In order for this process to be safe, the following parameters are needed for the region:
-the presence of a confining layer which would prevent the migration of wastes into groundwater flow.
-an injection zone of high permeability to receive the wastes.
-poor-quality water within the aquifer (thus, the aquifer can't be used for anything else.

Unfortunately, it is hard to determine whether an aquifer is completely confined and upward seepage of wastes can occur causing groundwater contamination.

Adapted from Hydrology: An Environmental Approach by Watson and Burnett.