Hydrology - SCWRC Report 156

Ground-Water Conditions in the Santee Limestone and Black Mingo Formations Near Moncks Corner, Berkeley County, South Carolina

By
J. Kevin Meadows
1987

ABSTRACT

Rapid growth in and near Moncks Corner, Berkeley County, South Carolina, has escalated ground water use from the Santee Limestone Black Mingo aquifer system and caused water levels to decline in wells. Some residents with wells in these two units have had water availability problems.

The Tertiary-age Cooper Formation, Santee Limestone, and Black Mingo Formation compose a hydrologic system that supplies most of the ground water in the study area. The Cooper Formation is a confining unit that produces artesian conditions in the underlying Santee Limestone and Black Mingo Formation. Ground-water withdrawal in the Santee comes mostly from the lower part, called the Moultrie Member. Ground-water withdrawal in the Black Mingo comes mostly from sand and limestone beds in the upper part of the unit. Data indicate that these two water-yielding zones are hydraulically connected. Most wells are open to both zones.

Specific capacities of Santee-Black Mingo wells average 2 gallons per minute per foot, or less. Most 6-inch diameter and larger wells produce at least 100 gallons per minute. Transmissivity varies, but it generally ranges between 300 and 700 feet squared per day. Water from wells open to both units is a hard, alkaline, calcium or sodium bicarbonate type in the northern half of the study area, and a soft, more mineralized, sodium bicarbonate type in the southern half. Water quality deteriorates with depth below the uppermost sand beds of the Black Mingo.

Since 1970, static water levels have declined about 20 feet in the northern half of the study area and about 50 feet in the southwestern part. At present rates of decline (2-3 feet per year), pumping water levels in high-capacity wells will be low enough in the year 2000 that dewatering of the Santee-Black Mingo may occur locally.

Below the Santee-Black Mingo aquifer system, the Peedee, Black Creek, and Middendorf Formations contain aquifers available for use. Of these, the Black Creek and Middendorf are the most productive. Wells could yield as much as 1,000 gallons per minute. Static water levels would be at or above land surface. The water would be a soft, sodium bicarbonate type, similar to Santee-Black Mingo water.


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