Hydrology - SCWRC Report 174

Pumping Tests of the Coastal Plain Aquifers in South Carolina

With a Discussion of Aquifer and Well Characteristics

By
Roy Newcome, Jr.
1993

ABSTRACT

Results of more than 470 pumping tests are available for determining aquifer and well characteristics in the Coastal Plain aquifers of South Carolina. Only one-tenth of these are multiwell tests that permit calculation of the storage coefficient. All the tests provide values for aquifer transmissivity, and nearly all provide well specific capacity and well efficiency.

Counties of the Coastal Plain are unevenly represented in numbers of pumping tests, Horry County having the most (95) and Chesterfield County the fewest (2). All the significant aquifers are represented, with sand beds in the Middendorf and Black Creek Formations of Cretaceous age and limestone in the Floridan aquifer of Eocene age yielding most of the ground water pumped and having the most tests.

Practically all the tests were made at wells in confined aquifers. The Floridan aquifer in Beaufort and Jasper Counties (southern tip of the State) has the highest transmissivity, in places reaching 500,000 gpd/ft (gallons per day per foot of aquifer width). The second-best water-bearing unit, and the one having the greatest areal extent, is the Middendorf Formation. Tests of multiscreened wells in its aquifers have produced transmissivity values with a median of 21,000 gpd/ft. In pumping tests of the Black Creek aquifers the median transmissivity was 12,000 gpd/ft. Median values for the remaining aquifers generally were less than 5,000 god/ft.

Various shortcomings, in procedures as well as in test conditions, render many tests unusable. Most of the shortcomings can be overcome or avoided relatively easily, leading to a higher percentage of "good" and "excellent" tests. Currently (1992), half the tests analyzed are rated as "poor" and another quarter as only "fair" by the rating system presented.


Copies of this report are available in the SCDNR's Columbia office.