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In cooperation with the Southern Division Naval Facilities Engineering Command

Integrity of Production Wells and Confining Unit at the Naval Weapons Industrial Reserve Plant, Dallas, Texas, 1995

By S.A. Jones and Frederick L. Paillet

U.S. Geological Survey
Water-Resources Investigations Report 97–4047


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Contents

Abstract

Introduction

Purpose and Scope

Description of Study Area

Acknowledgments

Hydrogeologic Units

Shallow Alluvial Aquifer

Confining Unit

Deep Aquifers

Paluxy Aquifer

Twin Mountains Aquifer

Methods of Data Collection and Analysis

Water-Quality Sampling

Borehole Geophysical Logging

Integrity of Production Wells

Water-Quality Data

Volatile Organic Compounds

Semivolatile Organic Compounds

Pesticides and Polychlorinated Biphenyls

Total Petroleum Hydrocarbons

Trace Elements and Major Ions

Water-Level Data

Borehole Geophysical Data

Integrity of Confining Unit

Summary and Conclusions

Selected References

Figures

1.   Map showing location of study area and wells at the Naval Weapons Industrial Reserve Plant, Dallas, Texas
2.   Generalized section of north-central Texas showing geologic and hydrogeologic units
3.   Map showing trichloroethylene concentrations in the shallow alluvial aquifer at the Naval Weapons Industrial Reserve Plant, Dallas, Texas
4.   Graph showing concentrations of chromium, copper, lead, and zinc and the corresponding practical quantitation limit (PQL) at each sampling depth in the wells at the Naval Weapons Industrial Reserve Plant, Dallas, Texas
5.   Graph showing concentrations of iron and manganese and the corresponding secondary maximum contaminant level (SCML) at each sampling depth in the wells at the Naval Weapons Industrial Reserve Plant, Dallas, Texas
6.   Diagram showing sample cement-bond scores obtained from the acoustic signature log
7.   Log composite for well 1
8.   Log composite for well 2A
9.   Log composite for well 3A
10.   Log composite for well 4A
11.   Log composite for well 5A
12.   Example of enlarged-scale log composite for well 2A

Tables

1.   Geologic units and their water-yielding characteristics
2.   Well data for production and abandoned wells at the Naval Weapons Industrial Reserve Plant Dallas, Texas
3.   Constituents analyzed by contract laboratory and associated reporting limits
4.   Water-quality sampling data from production and abandoned wells at the Naval Weapons Industrial Reserve Plant, Dallas, Texas
5.   Geophysical logs used at the Naval Weapons Industrial Reserve Plant, Dallas, Texas
6.   Selected results of laboratory analysis of volatile organic compounds, semivolatile organic compounds, pesticides, polychlorinated biphenyls, and total petroleum hydrocarbons in ground-water samples from the Naval Weapons Industrial Reserve Plant, Dallas, Texas
7.   Selected results of field and laboratory quality-control samples from the Naval Weapons Industrial Reserve Plant, Dallas, Texas
8.   Selected field properties, major ions, dissolved solids, and total trace element concentrations in ground-water samples from the Naval Weapons Industrial Reserve Plant, Dallas, Texas
9.   Explanation of letters shown in figures 7–12

Abstract

Ground water in the shallow alluvial aquifer is contaminated at the Naval Weapons Industrial Reserve Plant, Dallas, Texas. Five production wells at the site are cased through the alluvial aquifer and underlying units and are screened in either the Paluxy or Twin Mountains aquifer. Three abandoned wells, originally completed in the Twin Mountains aquifer but filled with drilling mud in 1958, also penetrate the alluvial aquifer. The Paluxy and Twin Mountains aquifers are used for drinking-water supplies in and around the Dallas-Fort Worth metroplex.

Trichloroethylene and its degradation products, dichloroethylene and vinyl chloride, and the metal chromium previously have been detected in the shallow alluvial aquifer. Current (1995) analyses of water-quality samples taken from the static water column of the five production wells and one of the abandoned wells indicate no trichloroethylene, dichloroethylene, or vinyl chloride in the water column of these wells. Chromium was detected in all samples, but concentrations were less than the practical quantitation limit, which is the regulatory action level for this site.

The results of borehole geophysical log analysis indicate that two of the production wells could have vertically connected intervals where cement bonding in the well annulus is poor. The other production wells have overall good cement bonding. Temperature logs do not indicate flow behind casing except in the screened interval of one well. Geophysical logs show the Eagle Ford Shale ranges from 147 to 185 feet thick at the site. The Eagle Ford Shale has low permeability and a high plasticity index. These physical characteristics make the Eagle Ford Shale an excellent confining unit.

 


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