USGS Georgia Water Science Center

USGS Open-File Report 2004-1366

Methods and Hydrogeologic Data from Test Drilling and Geophysical Logging Surveys in the Lawrenceville, Georgia, Area

This report is available online in pdf format (2 MB): USGS OFR 2004-1366 (Opens the PDF file in a new window. )

Lester J. Williams, Phillip N. Albertson, Donna D. Tucker, and Jaime A. Painter

U.S. Geological Survey Open-File Report 2004-1366, 38 pages (Published 2004)


Optical televeiwer image.Thirty-two wells, ranging in depth from 180 to 630 feet, were used to study the bedrock lithology, fracture, and water-yielding characteristics in the Lawrenceville, Georgia, area. These data were compiled to determine what geologic structures, if any, contribute to the development of increased permeability and high ground-water yield in the area. Methods used in this study include test-well drilling, geophysical logging and borehole-camera surveys, flowmeter surveys, aquifer testing, packer testing, and water-level monitoring.

Water-bearing fractures identified in open boreholes of wells include: joints, open joints, and zones of joint concentration; foliation partings and major foliation openings along foliation and layering of the rock; dissolution openings along mineral infillings; and irregular voids and fractures. Most of the joints observed in the boreholes appeared as tight hairline fractures and typically were not significant water-bearing zones. Moderate to small amounts of water—from 1 to 5 gallons per minute (gal/min)—are produced from open, steeply-dipping joints and zones of joint concentration. Foliation partings and major foliation openings, which form "foliation parallel-parting systems" in the area, yielded large quantities of water to open boreholes. Foliation partings typically yielded from 1 to 15 gal/min, with a maximum value of about 63 gal/min. In some boreholes, groups of foliation partings form significant water-bearing zones yielding as much as 50 gal/min. Major foliation openings yield substantially more water than the smaller foliation partings, with a typical range from 50 to 100 gal/min. Major foliation openings are the primary water-producing features responsible for high-yield wells in the area. In a few wells, dissolution openings along mineral infilled joints or veins had yields as much as 35 gal/min, indicating the potential importance of dissolution features in the bedrock.

Flowmeter surveys, aquifer tests, packer tests, and water-level monitoring provided additional hydrologic information on water-bearing fractures in the study area. These data were used to help confirm the depth and yield contribution from various types of water-bearing fractures, indicate the hydraulic characteristics of these fractures, and show the hydraulic response of the aquifer system to pumping.

Borehole-camera images showing down-hole view and side viewCollectively, the data from this study indicate that foliation parallel-parting systems, consisting of discontinuous zones of foliation partings and major foliation openings, strongly influence the yields of wells in the Lawrenceville area. Wells tapping these systems are capable of sustaining large ground-water withdrawals for extended periods of time, as indicated from the continuous operation of the Rhodes Jordan Wellfield since 1995. Open-hole water levels, flowmeter surveys, and preferential drawdown parallel to foliation and compositional layering all indicate a general hydraulic confinement of foliation parallel-parting systems, and indicate a strong lithologic and structural control on the development of these water-bearing fracture systems.

Foliation parallel-parting systems are easily identified in boreholes using geophysical methods described in this report. The yield potential of foliation parallel-parting systems within an individual topographic basin or several topographic basins can be large, depending on the areal extent of the water-bearing zones and the interconnectivity of these zones with sources of recharge.




Purpose and Scope

Description of the Study Area

Water Use

Geologic Setting

Hydrogeologic Setting

Well-Naming System

Supplemental Data on CD–ROM


Methods of Data Collection and Analysis

Test-Well Drilling

Air-Percussion Rotary Drilling and Well Construction

Lithologic Sampling and Determination of Rock Type

Well Development and Short-Term Yield

Geophysical Logging and Borehole-Camera Surveys

Caliper Logging

Natural-Gamma Logging

Resistivity Logging

Fluid-Temperature and Fluid-Resistivity Logging

Borehole-Televiewer Imaging

Borehole-Camera Surveys

Characterization of Fractures in Open Boreholes

Determination of Type, Depth, and Orientation of Fractures

Identification of Water-Bearing Fractures

Estimating Yield Contribution from Individual Water-Bearing Fractures

Estimating Yield during Drilling

Flowmeter Surveys

Aquifer Testing

Packer Testing

Water-Level Monitoring

Hydrogeologic Data

Fracture Data

Individual Fracture Yield

Joints, Open Joints, and Zones of Joint Concentration

Foliation Partings and Major Foliation Openings

Dissolution Openings

Irregular-Shaped Voids and Fractures

Flowmeter Surveys

Aquifer-Test Data

Aquifer-Test Yield, Drawdown, and Recovery

Direction and Magnitude of Drawdown

Packer-Test Data

Water-Level Data

Summary and Conclusions

References Cited



This report is available online in pdf format (2 MB): USGS OFR 2004-1366 (Opens the PDF file in a new window. )
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