Hydrology - Water Resources Report 8
Geology, Ground Water, and Wells of Greenville County, South Carolina
H. Lee Mitchell
Reservoirs and streams are the main sources of water supply in Greenville County, S.C., but wells furnish water to about one-tenth of the county’s 132,000 households. About 20 percent of the wells are large-diameter, shallow, generally low-yielding bored wells that produce water form the saturated zone of the residual saprolite. The other 80 percent are mainly 6-inch drilled wells that produce their water from a network of bedrock fractures beneath the saprolite. The drilled wells have a median yield of less than 10 gallons per minute. The low yields discourage consideration of wells as realistic water supplies where large quantities are needed; however, yields are considerably higher for wells carefully sited and drilled for maximum production.
Information on 1,828 6-inch drilled wells and 566 24-inch bored wells was analyzed for this report. The median bored-well depth is 50 feet, and the median drilled-well depth is 200 feet. The median depth of drilled-well casings is 54 feet that is approximately the saprolite thickness.
For bored wells, the median water level is 27 feet below land surface, and for drilled wells it is 30 feet. Saturated thickness of the saprolite in bored wells has a median value of 26 feet. For drilled wells, the median saturated thickness is about 23 feet.
Topography is an important factor influencing the yield of drilled wells. Generally, wells in draws and valleys have higher yields than those on hillsides or hilltops. Proximity to lineaments is also helpful.
The ground water quality is generally good, with most wells having slightly acidic water; pH ranges from 5 to 7.8, but almost 90 percent of well samples had a pH of less than 7. Most of the water is soft, and elemental concentrations usually are low, although iron can sometimes be troublesome.
Many tools are available for improving the understanding of the Piedmont hydrogeology in Greenville County. These include borehole geophysical logs, water quality analyses, pumping tests, geological maps, and lineament analysis.
Copies of this report are available in the SCDNR's Columbia office.