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Texas Water Science Center

Two-Dimensional Resistivity Investigation Along West Fork Trinity River, Naval Air Station-Joint Reserve Base Carswell Field, Fort Worth, Texas, October 2004

By Sachin D. Shah and Gregory P. Stanton

U.S. Geological Survey
Data Series 178

In cooperation with the U.S. Air Force, Aeronautical Systems Center,
Environmental Management Directorate, Wright-Patterson Air Force Base, Ohio


Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB) at Fort Worth, Tex., constitutes a government-owned, contractor-operated facility that has been in operation since 1942. Contaminants, primarily volatile organic compounds and metals, have entered the ground-water-flow system through leakage from waste-disposal sites and manufacturing processes. Ground water flows from west to east toward the West Fork Trinity River. During October 2004, the U.S. Geological Survey conducted a two-dimensional (2D) resistivity investigation at a site along the West Fork Trinity River at the eastern boundary of NAS–JRB to characterize the distribution of subsurface resistivity. Five 2D resistivity profiles were collected, which ranged from 500 to 750 feet long and extended to a depth of 25 feet. The Goodland Limestone and the underlying Walnut Formation form a confining unit that underlies the alluvial aquifer. The top of this confining unit is the top of bedrock at NAS–JRB. The bedrock confining unit is the zone of interest because of the potential for contaminated ground water to enter the West Fork Trinity River through saturated bedrock. The study involved a capacitively-coupled resistivity survey and inverse modeling to obtain true or actual resistivity from apparent resistivity. The apparent resistivity was processed using an inverse modeling software program. The results of this program were used to generate distributions (images) of actual resistivity referred to as inverted sections or profiles. The images along the five profiles show a wide range of resistivity values. The two profiles nearest the West Fork Trinity River generally showed less resistivity than the three other profiles.

Table of Contents



Purpose and Scope

Description of the Study Site

Hydrogeologic Units and Contaminant History

Alluvial Aquifer

Goodland-Walnut Confining Unit

Trichloroethene (TCE) Contamination

Methods of Investigation

Capacitively-Coupled Resistivity

Borehole Geophysics

Resistivity Profiles



Appendix 1—Field Inversion Results of Capacitively-Coupled Data, NAS–JRB study site, Fort Worth, Texas

1.1 Line 1

1.2 Line 2

1.3 Line 3

1.4 Line 4

1.5 Line 5

Appendix 2—Natural Gamma and Induction Conductivity Borehole Geophysical Logs, NAS–JRB study site, Fort Worth, Texas

2.1 Well MW–09

2.2 Well MW–12

2.3 Well WHGLTA036

2.4 Well WHGLTA037


1–4. Maps showing:
  1. Location of Naval Air Station-Joint Reserve Base Carswell Field (NAS–JRB), Fort Worth, Texas, and resistivity investigation site
  2. Location of two-dimensional (2D) capacitively-coupled resistivity profiles and wells, NAS–JRB study site, Fort Worth, Texas
  3. Water-table (potentiometric surface) of the alluvial aquifer and general directions of ground-water flow, NAS–JRB, Fort Worth, Texas, fall 2002
  4. Extent of trichloroethene (TCE) plume in the alluvial aquifer, NAS–JRB, Fort Worth, Texas, October 2002
5. Diagrams showing field inversion results of capacitively-coupled data (actual resistivity) at common resistivity scale for lines 1–5, NAS–JRB study site, Fort Worth, Texas


1. Well completion information for wells logged during October 2004, NAS–JRB study site, Fort Worth, Texas

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