Design of a monitoring network to detect the effects of land use on ground water quality and describe the contaminant flow system in the Piedmont of North Carolina
Proceedings of the Sixth National Symposium and Exposition on Aquifer Restoration and Ground Water Monitoring
By Douglas A. Harned
Abstract
The U.S. Geological Survey is investigating the relation of ground
-water quality and land use in the combined regolith and fractured rock
ground water system of the North Carolina Piedmont. The study provides a
description of the flow system, review of available data, and hypothesis
formulation, used to determine a water-quality monitoring network design
for detailed study of selected areas.
The Piedmont of North Carolina covers an area of approximately
20,000 square miles, or about 38 percent of the State. About half of the
population within the Piedmont of North Carolina uses ground water for
water supply. The igneous and metamorphic rocks of the Piedmont are
mantled nearly everywhere by a cover of their own weathering products.
The solid bedrock grades upwards into unweathered fractured rock,
covered by a transition zone of highly-fractured, partially weathered
rock, clay-rich-saprolite, and the soil. The fractured bedrock,
transition zone, saprolite, and soil make up a complex aquifer system.
A review of available ground water quality data for the Piedmont
shows a lack of information about organic compounds and trace metals that
may be present in ground water. In addition, there is little information
about variation of ground water quality with depth.
There are two principal hypotheses to be tested during the study:
(1) the amount and type of ground water contamination in the system can
be related to land use, and (2) the transition zone between bedrock and
regolith, when present, serves as a primary transmitter of ground water
and dissolved contaminants.
The water-quality monitoring network design covers basins with five
land uses in North Carolina. Monitoring of basins containing old
industrial, new industrial, downtown urban, residential in Mecklenburg
County, and agricultural land uses in Guilford County, will help define
the relation of ground water quality to land use. Water samples will be
collected from a network of wells augered into the top of the saturated
zone. Sampling wells open to different depths in the regolith and
fractured rock system will help test the hypothesis that the transition
zone is a primary transmitter of contaminated ground water. Sampling of
streams during base flow will accompany sampling of wells.
Citation:
Harned, D.A., 1986, Design of a monitoring network to detect the effects of land use on ground water quality and describe the contaminant flow system in the Piedmont of North Carolina, in Proceedings of the Sixth National Symposium and Exposition on Aquifer Restoration and Ground Water Monitoring, Columbus, Ohio, May 19-22, 1986: Dublin, Ohio, National Water Well Association, p. 120-137.
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