Unique Well Construction in a Weathered Pegmatite of the Georgia Piedmont
Harman, H. Dan, Jr.
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Groundwater in the Georgia Piedmont is routinely found in the saprolite of the uppermost aquifer and in fractured igneous and metamorphic rocks of the bedrock aquifer. Within the bedrock aquifer, fractures are normally the groundwater migration pathways which yield water to wells. These fractures are open spaces in consolidated rock which can be easily drilled and developed by air rotary drilling. The air rotary technique is the typical drilling method for bedrock wells in the Georgia Piedmont. This paper describes an abnormal hydrogeological case in which a water-bearing weathered pegmatite was encountered beneath solid rock, and which required a unique well construction to enable the use of the local groundwater. Pegmatite is an igneous rock of hydrothermal origin which has been injected into an existing rock. Pegmatite is usually a consolidated rock and is composed of various minerals and may include quartz, muscovite mica, feldspar and garnet plus many others.