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Quantification of Metal Loads by Tracer Injection and Synoptic Sampling in Daisy Creek and the Stillwater River, Park County, Montana, August 1999

In cooperation with the

U.S. DEPARTMENT OF AGRICULTURE-FOREST SERVICE

Cover Photograph: 
Headwaters of Daisy Creek in the New World Mining District near Yellowstone National Park, Montana.  
The McLaren Mine is on the right and Fisher Mountain is on the left in the background.  
View is upstream from sampling site 1,340 and shows the upstream, low-gradient part of the study reach.  
Photograph by J.H. Lambing, U.S. Geological Survey.

Water-Resources Investigations Report 00-4261
Helena, Montana, 2001

By David A. Nimick and Thomas E. Cleasby


Abstract

A metal-loading study using tracer-injection and synoptic-sampling methods was conducted in Daisy Creek and a short reach of the Stillwater River during baseflow in August 1999 to quantify the metal inputs from acid rock drainage in the New World Mining District near Yellowstone National Park and to examine the downstream transport of these metals into the Stillwater River. Loads were calculated for many mainstem and inflow sites by combining streamflow determined using the tracer-injection method with concentrations of major ions and metals that were determined in synoptic water-quality samples.

Water quality and aquatic habitat in Daisy Creek have been affected adversely by drainage derived from waste rock and adit discharge at the McLaren Mine as well as from natural weathering of pyrite-rich mineralized rock that comprises and surrounds the ore zones. However, the specific sources and transport pathways are not well understood. Knowledge of the main sources and transport pathways of metals and acid can aid resource managers in planning and conducting effective and cost-efficient remediation activities.

The metals cadmium, copper, lead, and zinc occur at concentrations that are sufficiently elevated to be potentially lethal to aquatic life in Daisy Creek and to pose a toxicity risk in part of the Stillwater River. Copper is of most concern in Daisy Creek because it occurs at higher concentrations than the other metals. Acidic surface inflows had dissolved concentrations as high as 20.6 micrograms per liter (μg/L) cadmium, 26,900 μg/L copper, 76.4 μg/L lead, and 3,000 μg/L zinc. These inflows resulted in maximum dissolved concentrations in Daisy Creek of 5.8 μg/L cadmium, 5,790 μg/L copper, 3.8 μg/L lead, and 848 μg/L zinc.

Significant copper loading to Daisy Creek occurred only in the upper half of the stream. Sources included subsurface inflow and right-bank (mined side) surface inflows. Copper loads in left-bank (unmined side) surface inflows were negligible. Most (71 percent) of the total copper loading in the study reach occurred along a 341-foot reach near the stream’s headwaters. About 53 percent of the total copper load was contributed by five surface inflows that drain a manganese bog and the southern part of the McLaren Mine. Copper loading from subsurface inflow was substantial, contributing 46 percent of the total dissolved copper load to Daisy Creek. More than half of this subsurface copper loading occurred downstream from the reaches that received significant surface loading.

Flow through the shallow subsurface appears to be the main copper-transport pathway from the McLaren Mine and surrounding altered and mineralized bedrock to Daisy Creek during base-flow conditions. Little is known about the source of acid and copper in this subsurface flow. However, possible sources include the mineralized rocks of Fisher Mountain upgradient of the McLaren Mine area, the surficial waste rock at the mine, and the underlying pyritic bedrock.

Contents

INTRODUCTION

Purpose and Scope

Description of study area

Acknowledgments

METHODS OF DATA COLLECTION

Tracer injection

Supplemental streamflow measurements

Synoptic sampling

Quality assurance

TRACER-INJECTION RESULTS

Downstream travel and dilution

Determination of streamflow

SYNOPTIC-SAMPLING RESULTS

pH and major-ion concentrations

Metal concentrations

QUANTIFICATION OF LOADS

Major ions

Metals

METAL SOURCES

SUMMARY AND CONCLUSIONS

FIGURES

TABLES

REFERENCES CITED

CONVERSION FACTORS, VERTICAL DATUM, ABBREVIATED UNITS AND ACRONYMS

FULL TEXT OF THE REPORT (pdf)

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and does not imply endorsement by the U.S. Government

For additional information, write to:

District Chief, U.S. Geological Survey, 3162 Bozeman Avenue, Helena, MT 59601-6456

Copies of this report may be purchased from:

U.S. Geological Survey, Branch of Information Services, Box 25286, Denver, CO 80225-0286

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