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U.S. Geological Survey, Scientific Investigations Report 2006-5303

Geochemical Characterization of Mine Waste, Mine Drainage, and Stream Sediments at the Pike Hill Copper Mine Superfund Site, Orange County, Vermont

By Nadine M. Piatak, Robert R. Seal II, Jane M. Hammarstrom, Richard G. Kiah, Jeffrey R. Deacon, Monique Adams, Michael W. Anthony, Paul H. Briggs, and John C. Jackson

In cooperation with the U.S. Environmental Protection Agency

ONLINE ONLY

Abstract

The Pike Hill Copper Mine Superfund Site in the Vermont copper belt consists of the abandoned Smith, Eureka, and Union mines, all of which exploited Besshi-type massive sulfide deposits. The site was listed on the U.S. Environmental Protection Agency (USEPA) National Priorities List in 2004 due to aquatic ecosystem impacts. This study was intended to be a precursor to a formal remedial investigation by the USEPA, and it focused on the characterization of mine waste, mine drainage, and stream sediments. A related study investigated the effects of the mine drainage on downstream surface waters. The potential for mine waste and drainage to have an adverse impact on aquatic ecosystems, on drinking- water supplies, and to human health was assessed on the basis of mineralogy, chemical concentrations, acid generation, and potential for metals to be leached from mine waste and soils. The results were compared to those from analyses of other Vermont copper belt Superfund sites, the Elizabeth Mine and Ely Copper Mine, to evaluate if the waste material at the Pike Hill Copper Mine was sufficiently similar to that of the other mine sites that USEPA can streamline the evaluation of remediation technologies. Mine-waste samples consisted of oxidized and unoxidized sulfidic ore and waste rock, and flotation-mill tailings. These samples contained as much as 16 weight percent sulfides that included chalcopyrite, pyrite, pyrrhotite, and sphalerite. During oxidation, sulfides weather and may release potentially toxic trace elements and may produce acid. In addition, soluble efflorescent sulfate salts were identified at the mines; during rain events, the dissolution of these salts contributes acid and metals to receiving waters. Mine waste contained concentrations of cadmium, copper, and iron that exceeded USEPA Preliminary Remediation Goals. The concentrations of selenium in mine waste were higher than the average composition of eastern United States soils. Most mine waste was potentially acid generating because of paste-pH values of less than 4 and negative net-neutralization potentials (NNP). The processed flotation-mill tailings, however, had a near neutral paste pH, positive NNP, and a few weight percent calcite. Leachate tests indicated that elements and compounds such as Al, Cd, Cu, Fe, Mn, Se, SO4, and Zn were leached from mine waste in concentrations that exceeded aquatic ecosystem and drinking-water standards. Mine waste from the Pike Hill mines was chemically and mineralogically similar to that from the Elizabeth and Ely mines. In addition, metals were leached and acid was produced from mine waste from the Pike Hill mines in comparable concentrations to those from the Elizabeth and Ely mines, although the host rock of the Pike Hill deposits contains significant amounts of carbonate minerals and, thus, a greater acid-neutralizing capacity when compared to the host rocks of the Elizabeth and Ely deposits.

Water samples collected from unimpacted parts of the Waits River watershed generally contained lower amounts of metals compared to water samples from mine drainage, were alkaline, and had a neutral pH, which was likely because of calcareous bedrock. Seeps and mine pools at the mine site had acidic to neutral pH, ranged from oxic to anoxic, and generally contained concentrations of metals, for example, aluminum, cadmium, copper, iron, and zinc, that exceeded aquatic toxicity standards or drinking-water standards, or both. Surface waters directly downstream of the Eureka and Union mines were acidic, as indicated by pH values from 3.1 to 4.2, and contained high concentrations of some elements including as much as 11,400 micrograms per liter (µg/L) Al, as much as 22.9 µg/L Cd, as much as 6,790 µg/L Cu, as much as 23,300 µg/L Fe, as much as 1,400 µg/L Mn, and as much as 3,570 µg/L Zn. The concentrations of these elements exceeded water-quality guidelines. Generally, in surface waters, the pH increased and the concentrations of these elements decreased downstream from the mines. The stream sediments also contained concentrations of trace elements such as cadmium, copper, selenium, and zinc that exceeded toxicity standards for aquatic life. The highest concentrations of metals were found directly downstream of the Eureka and Union mines, and concentrations decreased with increasing distance from the mines. The concentrations of metals in mine drainage and in stream sediments at the Pike Hill Superfund site were comparable to those found at the Elizabeth and Ely mines.

Contents

Abstract

Introduction

Site Information

Previous Studies

Objectives

Geologic Setting

Methods

Mine Waste

Sampling

Mineralogy

Bulk Geochemical Composition

Acid-Base Accounting

Leachate Chemistry

Water Sampling and Analysis

Stream-Sediment Sampling and Analysis

Sample Descriptions and Locations

Mine-Waste Samples

Water and Stream-Sediment Samples

Results and Discussion

Mine Waste

Mineralogy

Sulfates and Sulfides

Iron Oxides

Bulk Geochemistry

Acid-Base Accounting

Leachate Chemistry

Mine Drainage and Regional Surface Waters

Background Waters

Seeps and Mine Pools

Surface-Mine Drainage

Downstream Waters and Mine-Drainage Effects

Comparison with Elizabeth and Ely Surface Waters

Stream Sediments

Mineralogy

Bulk Geochemistry

Conclusions

Acknowledgments

References Cited

Figures

1-3. Maps showing:

4–9. Photographs showing:

10–24. Graphs showing:

Tables

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Geospatial Data

Shapefiles and DBF files created from tables and appendixes: 2006-5303.zip (88 KB)
Metadata (text file)

Suggested Citation:

Piatak, N.M., Seal, R.R., II, Hammarstrom, J.M., Kiah, R.G., Deacon, J.R., Adams, M., Anthony, M.W., Briggs, P.H., and Jackson, J.C., 2006, Geochemical characterization of mine waste, mine drainage, and stream sediments at the Pike Hill Copper Mine Superfund Site, Orange County, Vermont: U.S. Geological Survey Scientific Investigations Report 2006-5303, 120 p.

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