USGS Scientific Investigations Report 2008-5055
Prepared in cooperation with the North Carolina Department of Environment and Natural Resources, Division of Water Quality
By Charles G. Pippin, Melinda J. Chapman, Brad A. Huffman, Matthew J. Heller, and Melissa E. Schelgel
U.S. Geological Survey Scientific Investigations Report 2008-5055, 89 pages (Published online, July 2008. Version 1.1 published online, December 2008. Version 1.1 incorporates several editorial changes and is a considerably smaller file.)
This report is available online in PDF format:
SIR 2008-5055 (
) (6.6 MB)
A 6-year intensive field study (2000–2005) of a
complex, regolith-fractured bedrock ground-water system
was conducted at the Langtree Peninsula research station on
the Davidson College Lake Campus in Iredell County, North
Carolina. This research station was constructed as part of
the Piedmont and Mountains Resource Evaluation Program,
a cooperative study being conducted by the North Carolina
Department of Environment and Natural Resources and the
U.S. Geological Survey. Results of the study characterize
the distinction and interaction of a two-component ground-water
system in a quartz diorite rock type. The Langtree
Peninsula research station includes 17 monitoring wells and
12 piezometers, including 2 well transects along high to
low topographic settings, drilled into separate parts of the
ground-water-flow system. The location of the research station
is representative of a metaigneous intermediate (composition)
regional hydrogeologic unit. The primary rock type is mafic
quartz diorite that has steeply dipping foliation. Primary and
secondary foliations are present in the quartz diorite at the site,
and both have an average strike of about N. 12° E. and dip
about 60° in opposite directions to the southeast (primary) and
the northwest (secondary). This rock is cut by granitic dikes
(intrusions) ranging in thickness from 2 to 50 feet and having
an average strike of N. 20° W. and an average dip of 66° to
the southwest. Depth to consolidated bedrock is considered
moderate to deep, ranging from about 24 to 76 feet below land
surface. The transition zone was delineated and described in
each corehole near the well clusters but had a highly variable
thickness ranging from about 1 to 20 feet. Thickness of the
regolith (23 to 68 feet) and the transition zone do not appear to
be related to topographic setting. Delineated bedrock fractures
are dominantly low angle (possibly stress relief), which were observed
to be open to partially open at depths of as much as 479 feet below land surface. Well yields ranged from about
3 to 50 gallons per minute. The connection of fracture zones
at depth was demonstrated in three bedrock wells during a
48-hour aquifer test, and drawdown curves were similar for all
three wells.
General findings of this study help characterize ground-water flow in the Piedmont and Mountains ground-water systems. Ground-water flow generally is from high to low topographic settings. Ground-water flow discharges toward a surface-water boundary (Lake Norman), and vertical hydraulic gradients generally are downward in recharge areas and upward in discharge areas. Dominant water types are calcium-bicarbonate and are similar in all three zones (regolith, transition zone, and bedrock) of the ground-water system. Results of continuous ground-water-quality monitoring indicate that ground-water recharge may occur seasonally over a period of several months or after heavy rainfall periods over a shorter period of a few to several weeks.
Abstract
Introduction
Background
Program Objectives
Purpose and Scope
Description of the Study Area
Previous Studies
Acknowledgments
Methods of Investigation
Research Station Design and Monitoring
Investigation Field Methods
Climate Data
Well and Surface-Water Station Numbering System
Hydrogeologic Setting
Regional Geology
Local Geology
Ground-Water System Characteristics
Ground-Water Levels
Aquifer Hydraulic Properties
Ground-Water Flow
Ground-Water Quality
Continuous Monitoring Data
Results from Periodic Water-Quality Sampling
Summary
References
Appendix 1. Geologic core descriptions from the Langtree Peninsula research station
Appendix 2. Geophysical logs and images showing lithologies and fracture zones tapped by bedrock wells
To view the PDF document, you need the Adobe Reader installed on your computer. (A free copy of the Adobe Reader may be downloaded from Adobe Systems Incorporated.)
Suggested citation: Pippin, C.G., Chapman, M.J., Huffman, B.A., Heller, M.J., and Schelgel, M.E., 2008, Hydrogeologic setting, ground-water flow, and ground-water quality at the Langtree Peninsula research station, Iredell County, North Carolina, 2000–2005: U.S. Geological Survey Scientific Investigations Report 2008–5055, 89 p. (available online at http://pubs.water.usgs.gov/sir2008–5055)
For more information, please contact Melinda J. Chapman.
U.S. Department of the Interior |
U.S. Geological Survey
Persistent URL: http://pubs.water.usgs.gov/sir2008-5055
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