Considerations in the Extraction of Uranium from...Miocene Oakville Sandstone, South Texas. Digital Download

RI0126D. Considerations in the Extraction of Uranium from a Fresh-Water Aquifer: Miocene Oakville Sandstone, South Texas, by C. D. Henry, W. E. Galloway, and G. E. Smith. 36 p., 12 figs., 4 tables, 1 appendix, 1982. doi.org/10.23867/RI0126D. Downloadable PDF.

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ABSTRACT
The Miocene Oakville Sandstone is a major aquifer and uranium host beneath the Texas Coastal Plain. In 1976, approximately 6,000 acre-ft of ground water were withdrawn from the Oakville for municipal use. An additional but unknown amount was used for drinking water in rural areas, for livestock, and for irrigation. Potential sustained yield is many times greater. Present and future uranium mining by either surface or in situ methods could affect the availability and quality of Oakville ground water unless the mining is designed properly. This report discusses possible effects of mining, potential natural mitigation of these effects, and approaches to minimizing the impact of mining on the aquifer system. Conclusions are based on results presented in a series of reports, cited in following sections of this report, on physical stratigraphy, hydrology, and geochemistry of the Oakville Sandstone.

Both solution and surface mining may affect the availability of ground water by altering recharge characteristics and permeability. Because the volume of the aquifer affected by mining is small compared with its total volume, availability of Oakville ground water will probably not be reduced significantly, except in wells immediately adjacent to a mine. Mining may affect the quality of ground water by introducing chemicals that are not indigenous to the aquifer or by inducing chemical reactions that do not occur naturally or that occur at much slower rates. For example, most mining companies no longer use concentrated, ammonium-based leaches because of known problems in restoring water to its original chemistry. Natural and induced release of trace elements such as molybdenum is known to occur, but the geochemical controls on mobility and potential mitigating reactions in the aquifer are poorly understood.
Because the affected aquifer volume is small, any deterioration of water quality will probably be localized.

Observations and recommendations are presented on (1) regional and local baseline studies, (2) determination of aquifer sensitivity, (3) methods and goals of monitoring during and after mining, and (4) need for research on poorly understood aspects of mining impact. Such impacts include chemical reactions and processes that affect the long-term release of trace elements.

Keywords: aquifers, mining, Miocene, Oakville, South Texas, Texas Coastal Plain, uranium

CONTENTS

ABSTRACT

INTRODUCTION

URANIUM MINERALIZATION

URANIUM EXTRACTION PROCESSES

THE OAKVILLE AQUIFER

GEOLOGIC SETTING

USE OF OAKVILLE GROUND WATER

Current pattern of water use

Climate

Regional land use

INTERACTION OF MINING AND GROUND WATER

LIXIVIANT-MATRIX REACTIONS

POSSIBLE ALTERATION OF WATER QUALITY

Abandonment and restoration of solution mines that used an alkaline or neutral leach

Long-term effects

Excursion of an alkaline leach fluid

Acid leach fluids

QUANTIFICATION OF MINING IMPACTS

George West district

Ray Point district

OBSERVATIONS AND RECOMMENDATIONS

ACKNOWLEDGMENTS

REFERENCES

APPENDIX

FIGURES

1. Depositional elements of the Oakville fluvial system, central and southern Texas Coastal Plain

2. Stratigraphic section, South Texas uranium province

3. Uses of Oakville water, South Texas

4. Land and water use in the Oakville aquifer area, South Texas

5. Climatic variations within Oakville outcrop

6. Existing land use and vegetation zones within study area

7. Possibilities for the flow of water across or within geochemical zones of a uraniferous aquifer

8. Geologic setting, uranium deposits and mine areas, and interpreted direction of modern ground-water flux within the mineralized lower Oakville aquifer, George West district

9. Geologic setting, uranium deposits and mine areas, and interpreted direction of modern ground-water flux within the mineralized basal Oakville sand unit, Ray Point district

10. Dip-oriented cross section of Oakville sand, Ray Point district

11. Computer simulation of ground-water flow in a faulted aquifer-aquitard sequence

12. Summary of Oakville hydrology, land use, and consequent inferred aquifer sensitivity, South Texas Coastal Plain

TABLES

1. Public use of Oakville ground water

2. Average and range of Oakville ground-water quality

3. Analysis of in situ leach fluid, Oakville Sandstone, South Texas

4. Measured and calculated physical hydrologic parameters of principal Oakville mining districts

APPENDIX

Oakville water wells


Citation
Henry, C., Galloway, W. E., and Smith, G. E., 1982, Considerations in the Extraction of Uranium from a Fresh-Water Aquifer: Miocene Oakville Sandstone, South Texas: The University of Texas at Austin, Bureau of Economic Geology, Report of Investigations No. 126, 36 p.