ABSTRACT
Ground-water has several unique characteristics that make ground-water pollution a particular challenge to clean up. Ground-water is formed when rain-water percolates through the soil and into underground reserves called aquifers. These occur in layers of rocks such as sandstone or gravel that are porous and permeable enough to store water and let it flow through them easily, or in fractured rock such as granite or basalt. Once in the aquifers, ground-water can remain there for tens to thousands of years before eventually making its way out and into streams, rivers, lakes and oceans.
