ABSTRACT
Many of the world’s largest aquifers reside in fractured consolidated media. Studies have shown that even media traditionally considered to be of low permeability, such as shale and granite, are fractured to the extent that signicant groundwater ow may occur. In North America, there are many locales at which bedrock of either sedimentary or crystalline origin is used for either domestic or commercial water supply. In many geological settings, the lack of a protective layer of low-permeability clays or clay tills makes these water supplies particularly vulnerable to groundwater contamination.
