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An Integrated Geophysical and Hydraulic Investigation to Characterize a Fractured-Rock Aquifer, Norwalk, Connecticut

USGS Water Resources Investigation Report 01-4133

Prepared in cooperation with United Technologies Corporation

By John W. Lane, Jr., John H. Williams, Carole D. Johnson, Sister Damien Marie Savino, and F. P. Haeni



CONTENTS

Abstract
Introduction
   
Purpose and Scope
    Description of the Study Area
    Acknowledgments
Geophysical Methods
   
Conventional Geophysical Logging
    Optical-Televiewer Logging
    Borehole-Radar Reflection
    Cross-Hole Radar Tomography
    Azimuthal Square-Array Direct-Current Resistivity Sounding
Hydraulic Methods
   
Fluid-Resistivity Logging
    Temperature Logging
    Flowmeter Logging
Analysis of Hydraulic Data
   
Estimation of Specific Capacity and Transmissivity of Open Boreholes
    Estimation of Transmissivity and Hydraulic Head of Fracture Zones
Results: Integrated Interpretation of Geophysical and Hydraulic Logs
   
Foliation and Fractures
    Transmissive Fractures
    Identification of Large Fractures and Fracture Zones
    Azimuthal Resistivity Anisotropy
Results of Hydraulic Analyses
   
Hydraulic Head and Transmissivity for Individual Open Holes and Fracture Zones
    Hydraulic Connections
    Discrete-Zone Monitoring
Summary and Conclusions
References Cited

Appendix 1: Conventional Geophysical Logs from Selected Boreholes at the Study Area, Norwalk, Connecticut
Appendix 2:
Optical Televiewer Logs from Selected Boreholes at the Study Area,  Norwalk, Connecticut
Appendix 3:
Borehole-Radar Reflection Logs from Selected Boreholes at the Study Area,  Norwalk, Connecticut
Appendix 4:
Flowmeter Logs from Selected Boreholes at the Study Area, Norwalk, Connecticut

 

FIGURES

1. Map showing location of the study area, Norwalk, Connecticut
2. Map showing the study area in Norwalk, Connecticut, with borehole locations, equal-area stereonets showing the orientation of transmissive fractures, and lines representing known hydraulic connections between wells
3. Plot of equal-area stereonets of (a) foliation and (b) fractures, in 11 boreholes at the study area, Norwalk, Connecticut
4. Graph showing fracture intensity for interpreted fractures in 11 boreholes at the study area, Norwalk, Connecticut
5. Plot of caliper, specific conductance, and fluid temperature, under ambient and pumping conditions; modeled flow logs; and estimated fracture transmissivity for borehole MW-69, Norwalk, Connecticut
6. Plot showing locations of transmissive zones in several boreholes, with proposed locations of isolation packers in selected boreholes, Norwalk, Connecticut
7. Graph showing fracture intensity of transmissive fractures in 11 boreholes at the study area, Norwalk, Connecticut
8. Plot of 60-megahertz directional borehole-radar reflection log from borehole MW-71, Norwalk, Connecticut
9. Plot of 100-megahertz cross-hole borehole-radar tomography between boreholes MW-74 and MW-73, Norwalk, Connecticut
10. Graph showing results of azimuthal resistivity, Square Array 1, Norwalk, Connecticut

 

TABLES

1. Mean strikes and dips interpreted at the study area, Norwalk, Connecticut
2. Transmissivity and cross-hole drawdown in selected boreholes at the study area, Norwalk, Connecticut
3. Transmissivity of transmissive zones in selected boreholes at the study area, Norwalk, Connecticut
4. Estimated hydraulic-head difference of transmissive zones in selected boreholes at the study area, Norwalk, Connecticut


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Citation: Lane, J.W. Jr., Williams, J.H., Johnson, C.D., Savino, Sr. D.-M., and Haeni, F.P., 2002, An integrated geophysical and hydraulic investigation to characterize a fractured-rock aquifer, Norwalk, Connecticut: U.S. Geological Survey Water-Resources Investigation Report 01-4133, 97 p.

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