USGS

WRD Colorado District

Application of Tracer-Injection Techniques to Demonstrate Surface-Water and Ground-Water Interactions Between an Alpine Stream and the North Star Mine, Upper Animas River Watershed, Southwestern Colorado

By Winfield G. Wright and Bryan Moore

Available from the U.S. Geological Survey, Branch of Information Services, Box 25286, Denver Federal Center, Denver, CO 80225, USGS Water-Resources Investigations Report 03-4172, 29 p., 17 figs.

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The citation for this report, in USGS format, is as follows:
Wright, Winfield G., and Moore, Bryan, 2003, Application of Tracer-Injection Techniques to Demonstrate Surface-Water and Ground-Water Interactions Between an Alpine Stream and the North Star Mine, Upper Animas River Watershed, Southwestern Colorado: U.S. Geological Survey Water-Resources Investigations Report 03-4172, 29 p.


Abstract

Tracer-injection studies were done in Belcher Gulch in the upper Animas River watershed, southwestern Colorado, to determine whether the alpine stream infiltrates into underground mine workings of the North Star Mine and other nearby mines in the area. The tracer-injection studies were designed to determine if and where along Belcher Gulch the stream infiltrates into the mine. Four separate tracer-injec-tion tests were done using lithium bromide (LiBr), optical brightener dye, and sodium chloride (NaCl) as tracer solu-tions. Two of the tracers (LiBr and dye) were injected con-tinuously for 24 hours, one of the NaCl tracers was injected continuously for 12 hours, and one of the NaCl tracers was injected over a period of 1 hour. Concentration increases of tracer constituents were detected in water discharging from the North Star Mine, substantiating a surface-water and ground-water connection between Belcher Gulch and the North Star Mine. Different timing and magnitude of tracer breakthroughs indicated multiple flow paths with different residence times from the stream to the mine. The Pittsburgh and Sultan Mines were thought to physically connect to the North Star Mine, but tracer breakthroughs were inconclusive in water from these mines. From the tracer-injection tests and synoptic measure-ments of streamflow discharge, a conceptual model was devel-oped for surface-water and ground-water interactions between Belcher Gulch and the North Star Mine. This information, combined with previous surface geophysical surveys indicat-ing the presence of subsurface voids, may assist with decision-making process for preventing infiltration and for the remedia-tion of mine drainage from these mines.


Contents

Abstract

Introduction

Description of Study Area

Purpose and Scope

Previous Studies

Water-Quality Sampling

Surface Geophysics

Methods of Study

Tracer-Injection Methods

Continuous-Injection Tests

Slug-Injection Test

Sample Collection

Discharge Determinations

Interpretation of Tracer-Injection Data

Results of Tracer Recovery and Discharge Measurements

Tracer Recovery at the North Star Mine

Continuous-Injection Tests

Slug-Injection Test

Tracer Recovery at Other Sites

Discharge of Springs, Streams, and Mine Outflows

Surface-Water and Ground-Water Interactions at the North Star Mine

Summary

References Cited

Appendix—Supplemental Information

Laboratory Analytical Methods

Instrument Calibrations

Quality Assurance

 

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