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Hydraulic Properties of the Surficial Aquifer at Five Selected Sites in the Little Contentnea Creek Basin, North Carolina, 2002–03

Scientific Investigations Report 2005–5238
By Douglas G. Smith and Melinda J. Chapman

Full Text

Abstract

Aquifer tests of the surficial aquifer were conducted from June 2002 to June 2003 at selected sites in the Little Contentnea Creek drainage basin in the Coastal Plain Physiographic Province of North Carolina. These tests were designed to evaluate the variability of unconfined, surficial aquifer properties at selected sites across the Little Contentnea Creek basin and determine if relations exist between the hydraulic properties of the surficial aquifer and the topographic setting. Five sites were tested in three generalized topographic or geomorphic settings—upland or hilltop (one site), hillside or slope (two sites), and valley flat or flood plain (two sites).

Each aquifer test was conducted by continuously pumping water from the surficial aquifer at a constant rate for a period of 24 to 72 hours. For each test, water was withdrawn from one well that was constructed to fully penetrate the surficial aquifer. Water levels were measured in the pumping well and in multiple observation wells at each test site. Pumping rates for the five aquifer tests ranged from 1.8 to 13.6 gallons per minute. Water-table depths measured under static conditions at the five test sites ranged from about 1.4 to 10.8 feet below land surface. The saturated thickness of the surficial aquifer at most test sites generally was less than 19 feet, and the lower boundary of the surficial aquifer (top of the uppermost confining layer) generally was less than 25 feet below land surface.

Estimates of transmissivity at the five test sites ranged from 55 to 500 feet squared per day. Hydraulic conductivity values were not estimated from aquifer-test data because of the large reductions in saturated thickness, which ranged from about 25 to 56 percent. Based on slug tests, hydraulic conductivity estimates at the five test sites ranged from 3 to 21 feet per day. Specific yields calculated for the test sites ranged from less than 1 percent to 10 percent. The lowest estimated transmissivity (55 feet squared per day) was determined for a site that was located in a valley-flat setting. The highest estimated transmissivity (500 feet squared per day) determined during this investigation was at one of the hillside sites. The lowest estimated hydraulic conductivity was determined for one of the hillside settings. The highest hydraulic conductivity estimate determined was at one of the valley-flat sites. Using results from the five sites tested in the Little Contentnea Creek basin, no relation was identified between topographic setting and hydraulic properties of the surficial aquifer.

Smith, D.G., and Chapman, M.J., 2005, Hydraulic properties of the surficial aquifer at five selected sites in the Little Contentnea Creek basin, North Carolina, 2002–03: U.S. Geological Survey Scientific Investigations Report 2005–5238, 104 p.