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U.S. Geological Survey Open-File Report 2008-1382

Prepared in cooperation with the U.S. Bureau of Land Management

Environmental Impact of the Helen, Research, and Chicago Mercury Mines on Water, Sediment, and Biota in the Upper Dry Creek Watershed, Lake County, California

By James J. Rytuba, Roger L. Hothem, Jason T. May, Christopher S. Kim, David Lawler, Daniel Goldstein, and Brianne E. Brussee

2009

Abstract

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The Helen, Research, and Chicago mercury (Hg) deposits are among the youngest Hg deposits in the Coast Range Hg mineral belt and are located in the southwestern part of the Clear Lake volcanic field in Lake County, California. The mine workings and tailings are located in the headwaters of Dry Creek. The Helen Hg mine is the largest mine in the watershed having produced about 7,600 flasks of Hg. The Chicago and Research Hg mines produced only a small amount of Hg, less than 30 flasks. Waste rock and tailings have eroded from the mines, and mine drainage from the Helen and Research mines contributes Hg-enriched mine wastes to the headwaters of Dry Creek and contaminate the creek further downstream. The mines are located on federal land managed by the U.S. Bureau of Land Management (USBLM). The USBLM requested that the U.S. Geological Survey (USGS) measure and characterize Hg and geochemical constituents in tailings, sediment, water, and biota at the Helen, Research, and Chicago mines and in Dry Creek. This report is made in response to the USBLM request to conduct a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA - Removal Site Investigation (RSI). The RSI applies to removal of Hg-contaminated mine waste from the Helen, Research, and Chicago mines as a means of reducing Hg transport to Dry Creek.

This report summarizes data obtained from field sampling of mine tailings, waste rock, sediment, and water at the Helen, Research, and Chicago mines on April 19, 2001, during a storm event. Further sampling of water, sediment, and biota at the Helen mine area and the upper part of Dry Creek was completed on July 15, 2003, during low-flow conditions. Our results permit a preliminary assessment of the mining sources of Hg and associated chemical constituents that could elevate levels of monomethyl Hg (MMeHg) in the water, sediment, and biota that are impacted by historic mining.

Version 1.0

Posted April 28, 2009
Updated April 29, 2009

For additional information contact:
Jim Rytuba

Western Mineral Resources Science Center


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Suggested citation:

Rytuba, J.J., Hothem, R.L., May, J.T., Kim, C.S., Lawler, D., Goldstein, D., and Brussee, B.E., 2009, Environmental impact of the Helen, Research, and Chicago mercury mines on water, sediment, and biota in upper Dry Creek watershed, Lake County, California: U.S. Geological Survey Open-File Report 2008-1382, 59 p. [http://pubs.usgs.gov/of/2008/1382/].



Contents

Introduction

Mining History and Geology

Sample Locations and Methods

Analytical Methods

Results

Conclusions

Acknowlegments

References Cited


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