science for a changing world

Prepared in cooperation with the

USDA Forest Service and

U.S. Environmental Protection Agency

Integrated Investigations of Environmental 

Effects of Historical Mining in the Basin and 

Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Professional Paper 1652

U.S. Department of the Interior 

U.S. Geological Survey
Cover. View from Eva May mine looking across Cataract Creek valley at Hoodoo Creek drainage. 

Photograph by D.A. Nimick.
Integrated Investigations of Environmental 

Effects of Historical Mining in the Basin 

and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E, Church, and Susan E. Finger

Prepared in cooperation with the

USDA Forest Service and

U.S. Environmental Protection Agency

Volume comprises Chapters A, B, C, D1-D10, E1-E3, F, and G, 

and an accompanying CD-ROM

Professional Paper 1652

U.S. Department of the Interior 

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat Director

U.S. Geological Survey, Reston, Virginia: 2004 

First printing: 2004

For sale by U.S. Geological Survey, Information Services 

Box 25286, Denver Federal Center 

Denver, CO 80225

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Telephone: 1-888-ASK-USGS

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Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

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Although this report is in the public domain, it contains copyrighted materials that are noted in the text. 

Permission to reproduce those items must be secured from the individual copyright owners.

ISBN = 0-607-94344-0
Ill

Volume Contents

A. Summary and conclusions from investigation of the effects of historical

mining in the Boulder River watershed, Jefferson County, Montana................................. 3

By U.S. Geological Survey 

B. The Boulder River watershed study, Jefferson County, Montana .................................... 13

By Stanley E. Church, David A. Nimick, Susan E. Finger, and

J. Michael O'Neill 

C. Synthesis of water, sediment, and biological data using hazard quotients

to assess ecosystem health..................................................................................................... 29

By Susan E. Finger, AVda M. Farag, David A. Nimick,

Stanley E. Church, and Tracy C. Sole

D. Watershed-Scale Characterization and Investigation of Processes

Responsible for Environmental Effects of Historical Mining 

Dl. Geologic framework..................................................................................................................49

By J. Michael O'Neill, Karen Lund, Bradley S. Van Gosen, 

George A. Desborough, Tracy C. Sole, and Ed H. DeWitt 

D2. Geophysical characterization of geologic features with environmental

implications from airborne magnetic and apparent resistivity data................................ 89

By Anne E. McCafferty, Bradley S. Van Gosen, Bruce D. Smith, and 

Tracy C. Sole 

D3. Mine inventory......................................................................................................................... 127

By E. Paul Martin 

D4. Metal leaching in mine-waste materials and two schemes for classification

of potential environmental effects of mine-waste piles.................................................... 137

By David L. Fey and George A. Desborough 

D5. Trace elements in water in streams affected by historical mining................................. 155

By David A. Nimick and Thomas E. Cleasby 

D6. Quantification of metal loading by tracer injection and synoptic

sampling, 1997-98.................................................................................................................... 191

By Briant A. Kimball, Robert L. Runkel, Thomas E. Cleasby, and 

David A. Nimick 

D7. Short-term variation of trace-element concentrations during base

flow and rainfall runoff in small basins, August 1999........................................................ 263

By John H. Lambing, David A. Nimick, and Thomas E. Cleasby 

D8. Trace elements and lead isotopes in streambed sediment in streams affected by

historical mining....................................................................................................................... 279

By Stanley E. Church, Daniel M. Unruh, David L. Fey, and Tracy C. Sole 

D9. Hydrogeology of the Boulder River watershed study area and 

examination of the regional ground-water flow system using 

interpreted fracture mapping from remote sensing data................................................. 337

By Robert R. McDougal, M.R. Cannon, Bruce D. Smith, and 

David A. Ruppert
IV

D10. Aquatic health and exposure pathways of trace elements.............................................. 369

By A'i'da M. Farag, David A. Nimick, Briant A. Kimball, 

Stanley E. Church, Don Skaar, William G. Brumbaugh, 

Christer Hogstrand, and Elizabeth MacConnell

E. Case Studies of Mining Sites within the Boulder River Watershed Study Area 

E1. Understanding trace-element sources and transport to upper Basin Creek

in the vicinity of the Buckeye and Enterprise mines......................................................... 401

By M.R. Cannon, Stanley E. Church, David L Fey, Robert R. McDougal, 

Bruce D. Smith, and David A. Nimick 

E2. Monitoring remediation—Have mine-waste and mill-tailings removal and

flood-plain restoration been successful in the High Ore Creek valley?........................ 457

By Sharon L. Gelinas and Robert Tupling 

E3. Geologic, geophysical, and seismic characterization of the Luttrell pit as a

mine-waste repository............................................................................................................ 475

By Bruce D. Smith, Robert R. McDougal, and Karen Lund

F. Evaluating the success of remediation in the Boulder River watershed...................... 495

By Susan E. Finger, Stanley E. Church, and David A. Nimick 

G. Digital databases and CD-ROM for the Boulder River watershed.................................. 503

By Carl L. Rich, David W. Litke, Matthew Granitto, Richard T. Pelltier, and

Tracy C. Sole
Summary and Conclusions from 

Investigation of the Effects of Historical 

Mining in the Boulder River Watershed, 

Jefferson County, Montana

By U.S. Geological Survey

Chapter A of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-A

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Introduction................................................................................................................................................... 3

Study Area...................................................................................................................................................^

Environmental Effects..................................................................................................................................4

Sources of Trace Elements......................................................................................................................... 9

Potential for Restoration.............................................................................................................................. 9

Figures

1. Map showing location of Boulder River watershed and watershed study area,

Montana........................................................................................................................................ 4

2. Photograph showing Eva May mine in Cataract Creek valley............................................. 5

3. Photograph showing mill tailings in High Ore Creek valley at Comet mine site................ 5

4-6. Maps showing:

4. Estimated distribution of trout in study area prior to start of large-scale

remediation activities..........................................................................................................6

5. Approximate concentrations of dissolved zinc during low streamflow

conditions, 1991-2000.......................................................................................................... 7

6. Concentrations of zinc in streambed sediment............................................................... 8

7-9. Photographs showing:

7. Crystal mine......................................................................................................................... 10

8. Bullion mine......................................................................................................................... 10

9. Buckeye flotation mill site before and after remediation............................................ 11

10. Graphs showing dissolved arsenic and zinc concentrations at mouth of High Ore

Creek, 1996-2000........................................................................................................................ 12
Chapter A

Summary and Conclusions from Investigation of the 

Effects of Historical Mining in the Boulder River 

Watershed, Jefferson County, Montana

By U.S. Geological Survey

Introduction

The Boulder River watershed is one of many watersheds 

in the western United States where historical mining has left 

a legacy of acid mine drainage and elevated concentrations of 

potentially toxic trace elements. Abandoned mine lands commonly are located on or affect Federal land. Cleaning up these 

Federal lands will require substantial investment of resources. 

As part of a cooperative effort with Federal land-management 

agencies, the U.S. Geological Survey implemented an Abandoned Mine Lands Initiative in 1997. The goal of the initiative was to use the watershed approach to develop a strategy 

for gathering and communicating the scientific information 

needed to formulate effective and cost-efficient remediation 

of affected lands in a watershed. The watershed approach is 

based on the premise that contaminated sites that have the 

most profound effect on water and ecosystem quality within 

an entire watershed should be identified, characterized, and 

ranked for remediation.

The watershed approach provides an effective means 

to evaluate the overall status of affected resources and helps 

to focus remediation at sites where the most benefit will be 

gained in the watershed. Such a large-scale approach can 

result in the collection of extensive information on the geology 

and geochemistry of rocks and sediment, the hydrology and 

water chemistry of streams and ground water, and the diversity 

and health of aquatic and terrestrial organisms. During the 

assessment of the Boulder River watershed, we inventoried 

historical mines, defined geological conditions, assessed fish 

habitat, collected and chemically analyzed hundreds of water 

and sediment samples, conducted toxicity tests, analyzed fish 

tissue and indicators of physiological malfunction, examined 

invertebrates and biofilm, and defined hydrological regimes. 

Land- and resource-management agencies are faced with 

evaluating risks associated with thousands of potentially harmful mine sites, and this level of effort is not always feasible 

for every affected watershed. The detailed work described in

this report can help Federal land-management agencies decide 

which characterization efforts would be most useful in characterization of other affected watersheds.

Study Area

The Boulder River watershed is located near the town 

of Basin in southwestern Montana (fig. 1). Our study area 

includes Basin, Cataract, and High Ore Creeks and the short 

reach of the Boulder River into which these tributaries flow. 

The watershed study area does not include the large upstream 

drainage of the Boulder River or the downstream reach of the 

Boulder River between Little Galena Gulch and the Jefferson 

River, even though the effects of historical mining are apparent through this reach. Many of the areas affected by historical 

mining in the Boulder River watershed are within the Beaverhead-Deerlodge National Forest or on land managed by the 

Bureau of Land Management (Church, Nimick, and others, 

this volume, Chapter B).

The Boulder River watershed study area encompasses 

the Boulder and Basin mining districts. Mining of ore deposits 

containing base metals (copper, lead, and zinc) and precious 

metals (primarily silver and some gold) started in the early 

1860s. The main period of mining was from about 1880 to 

1907, and peak production occurred during 1895-1903. 

Mining had generally ceased by the 1940s. Ore deposits were 

found primarily in polymetallic quartz-vein deposits, which 

are thin (less than 50 feet wide) and occur within granitic 

host rocks, which are widespread in the watershed (O'Neill 

and others, this volume, Chapter Dl). More than 140 inactive 

mines, such as the Eva May mine (fig. 2), and mining-related 

sites lie in the Boulder River watershed study area (Martin, 

this volume, Chapter D3). These sites include mines, where 

ore was recovered; prospects, where rock was removed in 

search of ore deposits; and mills, where ore was crushed and 

processed to concentrate the valuable metals.
4 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Boulder River 

watershed 

study area

Boulder River 

watershed 

study area

46°22'30" -

46° 15'

Base from U.S. Geological Survey 

1:100,000 Butte North, 1994

0 1 2 3 MILES

I———,—"-,———r1—————'

0 1 2 3 KILOMETERS

Figure 1. Location of Boulder River watershed and 

watershed study area, Montana. Elevations are in feet.

Environmental Effects

During historical mining, mine waste and mill tailings 

were discharged with little regard for any potential effect on 

the landscape or streams (fig. 3). Although most mining in the 

Boulder River watershed occurred nearly a century or more 

ago, effects on the environment are still present today. Physical manifestations of these effects were evident locally as land 

disturbances, unvegetated areas, and colorful mine drainage 

near mine and mill sites. At a watershed scale, these effects 

occurred primarily in streams, where aquatic organisms are 

affected downstream from the historical mine and mill sites.

In some mining districts, trace-element concentrations in 

soil, streambed sediment, stream water, and aquatic organisms 

were elevated long before any mining occurred because mineralized rocks were weathering and contributing acid and trace

elements to streams. However, in the Boulder River 

watershed, this was not the case (Nimick and Cleasby, this 

volume, Chapter D5; Church, Unruh, and others, this volume, 

Chapter D8). At present, acidic and trace-element-rich water 

within the study area is associated with

• mine adits that opened and exposed the quartz-vein 

deposits and channeled subsurface water to the surface, 

or

• dumps containing mineralized mine waste or mill 

tailings.

Prior to mine development, the quartz-vein deposits likely 

produced small amounts of acid, which were neutralized by 

the moderate acid-neutralizing potential contained in many 

of the rocks in the watershed (McCafferty and others, this 

volume, Chapter D2).

The most important environmental effect of historical 

mining in the watershed was impairment of aquatic life in 

streams. All species of fish were absent in stream reaches 

downstream from a few large mines because of the high 

trace-element concentrations caused by acid mine drainage 

(fig. 4). Farther downstream, trout were found in these highly 

contaminated reaches, but exposure to high trace-element 

concentrations affected the health of these fish. The presence 

of dissolved trace elements in the water column was shown to 

directly affect fish. Similarly, the presence of toxic trace 

elements in streambed sediment was shown to affect the 

aquatic food chain of fish and cause health effects through 

dietary exposure in trout (Farag and others, this volume, 

Chapter DIG).

Ongoing drainage from historical mine sites has degraded 

the quality of water in some stream reaches. In most streams, 

pH values were near-neutral to slightly alkaline, but a few 

small streams were acidic because of drainage from mine 

adits. Concentrations of cadmium, copper, lead, and zinc, 

which are the trace elements that most strongly affect aquatic 

organisms in watershed streams, commonly exceeded chronic 

aquatic-life standards established by the U.S. Environmental 

Protection Agency. The highest concentrations (fig. 5, zinc 

as example) were in streams downstream from three large 

inactive mines: Crystal mine in a tributary to Cataract Creek, 

Comet mine in High Ore Creek, and Bullion mine in a tributary to Jack Creek (Nimick and Cleasby, this volume).

Trace elements derived from mine waste and acidic 

drainage typically accumulate in streambed sediment. Similar 

to the pattern found for water, the highest concentrations of 

trace elements in streambed sediment occurred immediately 

downstream from the Comet, Crystal, and Bullion mines. For 

example, figure 6 shows the pattern of concentrations of zinc, 

which is one of the trace elements that strongly affect aquatic 

organisms. All major tributary basins (Basin, Jack, Cataract, 

and High Ore Creeks and Uncle Sam Gulch) and the Boulder 

River downstream from Basin Creek had concentrations of 

arsenic, copper, and lead that exceeded the apparent effects 

threshold for aquatic organisms. These effects were traced in 

the Boulder River for a distance of 55 miles downstream to 

the confluence with the Jefferson River (Church, Unruh, and 

others, this volume i.
Summary and Conclusions

Figure 2. Eva May mine in Cataract Creek valley, September 1998. Photograph by D.A. Nimick.

Figure 3. Mill tailings in High Ore Creek valley at Comet mine site, October 1996. Photograph by D.A. Nimick.
6 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112°221 3011

T8N

T7N

EXPLANATION

Distribution of trout

• None

H Uncertain

B Westslope cutthroat

• Rainbow, eastern brook, brown, or 

Yellowstone cutthroat

• No data

tt Inactive mine

T6N

46°15'

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

2 KILOMETERS

Figure 4. Estimated distribution of trout in study area prior to start of large-scale remediation activities.
Summary and Conclusions

112°22'30"

Boulder River 

watershed 

study area

T6N

EXPLANATION ~"

Ribbon Zinc, |ig/L

• > 1,000

• 100-1,000

• 30-100

• <30

K Inactive mine

R5W

Base from U.S. Geological Survey 

Digital line graphs, 1:100,000

R4W 

2 MILES

2 KILOMETERS

Figure 5. Approximate concentrations of dissolved zinc during low streamflow conditions, 1991-2000.
8 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

BUCKfYEAND T8N

ENTERPRISE

Boulder River 

watershed 

study area

EXPLANATION

Ribbon Zinc, ppm

• > 1,500

• 750-1,500 

EH 375-750

• 225-375

• <225

Inactive mine

R5W

Base from U.S. Geological Survey 

Digital line graphs, 1:100,000

R4W 

2 MILES I————i——"—i0 1 2 KILOMETERS

Figure 6. Concentrations of zinc in streambed sediment.
Summary and Conclusions

Sources of Trace Elements

Land-management agencies are charged with the task of 

remediating inactive mines in the Boulder River watershed. 

Numerous inactive mine sites contribute trace elements to 

streams in the study area. Therefore, the challenge facing the 

agencies is one of source determination. The highest concentrations of cadmium, copper, lead, and zinc in water, streambed sediment, and aquatic organisms occur just downstream 

from the Crystal, Bullion, and Comet mines. Because the 

concentrations below these mine sites are so high, the three 

sites clearly are the major sources of trace elements in the 

watershed. However, the main delivery mechanism for trace 

elements is not the same at each mine site. Study of streambed sediment demonstrated that much of the contaminated 

sediment in the Boulder River came from High Ore Creek 

(Church, Unruh, and others, this volume). The dam holding 

the mill tailings deposited in the High Ore Creek valley from 

the Comet mill (fig. 3) has been breached and the tailings 

extensively eroded and transported downstream into the 

Boulder River (Gclinas and Tupling, this volume, Chapter E2). 

Study of water quality demonstrated that Cataract and Basin 

Creeks contributed more than 80 percent of the dissolved cadmium and more than 50 percent of the dissolved copper and 

zinc to the Boulder River (Nimick and Cleasby, this volume). 

These and other data indicated that the Crystal mine (fig. 7) 

in Uncle Sam Gulch and Bullion mine (fig. 8) in a tributary 

to Jack Creek were the largest contributors of dissolved trace 

elements in the watershed (Kimball and others, this volume, 

Chapter D6). Based on detailed metal-loading studies, discharge from one or two adits was by far the most significant 

source of trace elements at each of these mine sites.

The overall conclusion from our analysis of trace-element 

sources is that three large mines appear to be the most important sources of trace elements in the Boulder River watershed 

(Finger, Farag, and others, this volume, Chapter C). Smaller 

loadings occur from some other sites, such as the Buckeye 

mine and mill and Enterprise mine in upper Basin Creek and 

the Hattie Ferguson, Boulder Chief, Ida M., and Eva May 

mine sites along Cataract Creek.

Potential for Restoration

Many of the mine sites identified as contributors of trace 

elements have been targeted for remediation by Federal 

land-management agencies. Large-scale remediation efforts 

began in 1997 at the Comet mine in High Ore Creek. The 

Montana Department of Environmental Quality removed the 

large quantity of mill tailings (about 500,000 yd3 or about 

750,000 tons) that had been impounded in the valley (fig. 3). 

In 1999, the Bureau of Land Management began removal and 

in-place treatment of tailings that had been washed downstream by floods and deposited on the High Ore Creek flood 

plain. The United States Department of Agriculture (USDA) 

Forest Service began remediation efforts at the Buckeye and

Enterprise mine site in 2000 (fig. 9) and at the Bullion mine 

in 2002. Part of the earlier planning efforts by USDA Forest 

Service had been location of suitable repository sites for safe 

storage of mine waste and mill tailings removed from historical mine sites. The U.S. Environmental Protection Agency 

(USEPA) has recently taken over the open pit at the recently 

closed Basin Creek mine and converted it to a regional repository (Smith and others, this volume, Chapter E3) for mine 

wastes in the Boulder River and other neighboring watersheds. 

Basin and Cataract Creeks were added to the National Priority 

List (Superfund) in 1999. Soon afterwards, USEPA began 

removing mine and mill waste within the town of Basin, and 

in 2002, began cleanup work at the Crystal mine. However, 

to date (2003), no work has been initiated to remediate acid 

drainage coming from mine adits such as those at the Crystal, 

Bullion, or Enterprise mines.

Monitoring is an important tool for evaluating the 

effectiveness of remediation efforts and assessing the extent 

of ecological restoration. Without collecting and analyzing 

comprehensive monitoring data, land managers cannot objectively evaluate how successfully a remedial action performs 

and whether remediation goals have been met. In the Boulder 

basin, the primary focus of the watershed approach has been 

on the identification of factors affecting the health and potential for recovery of the aquatic community and its supporting 

habitat. Ongoing monitoring of High Ore Creek has shown 

that remediation has substantially reduced dissolved zinc 

concentrations, but that dissolved arsenic concentrations have 

increased slightly, probably because the imported material 

used to amend mine wastes increases the solubility of arsenic 

(fig. 10). Monitoring has also recorded improvements in High 

Ore Creek after remediation (Gelinas and Tupling, this volume). Continued improvements in water quality and reduced 

sediment loading should result in improved survival, growth, 

and reproduction in the fish community. Future monitoring 

that incorporates biological and chemical measurements will 

be able to demonstrate the degree of success of all cleanup 

projects in the watershed. However, the success of ecological restoration will be determined not only by the degree of 

improvement achieved in the aquatic environment, but also 

by the recovery of associated flood-plain and riparian habitat 

within the watershed. Although not specifically addressed 

in this volume, the issues of revegetation of the riparian area 

and stabilization of the flood plain are important to land 

managers in the overall environmental restoration of an area. 

Monitoring the improvement of flood-plain and riparian soils 

after the physical removal of tailings can be accomplished 

by use of both geochemical characterization and soil toxicity assessments. Such monitoring can determine the potential 

for successful revegetation of an area. In addition, monitoring 

the health and recovery of wildlife communities dependent 

on this terrestrial habitat can provide valuable information on 

ecological restoration. Although economic limitations often 

result in the reduction or elimination of a monitoring program 

following cleanup, only through a well-designed and rigorously implemented monitoring program can the success of a 

remedial effort be validated (Finger, Church, and Nimick, this 

volume, Chapter F).
10 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

fcf

Figure 7. Crystal mine, June 1997. Acidic discharge drains from adit (out of view near lower right of 

photograph) to Uncle Sam Gulch on far left. Photograph by D.A. Nimick.

V- * -^ -' **&*9f -**>« - 9* -«-•**•> • • «;Jf7 .- 5 *4iio 

JL^ '^"- " -» *-. _• >.-?.'V?S'W-^^ afSftaEL-'ri* "^>^

Figure 8. Bullion mine, August 1998. Acidic drainage flows downhill from mine adit behind mine-waste piles in 

top center of photograph. Photograph by D.A. Nimick.
Summary and Conclusions 11

Figure 9. Buckeye flotation mill site, upper Basin Creek, before (top) and after (bottom) remediation. 

Photographs by Ray TeSoro.
12 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

40

30

y i 20

10

0 I I I I I I I I I I I i I I I I I I I I

2,500

< 2,000

z 1,500

1,000

z 500

I I I I i I I | I I 

Comet 

mine 

i remediation

I I TTT | I I I I I I I I 

High Ore 

Creek 

floodplain 

restoration

Zinc

l l I l l l i l l l I I I I II I I I I I I I I I I I I I I I I I I I I i i I I I i I

1996 1997 1998 1999 2000

Figure 10. Dissolved arsenic (top) and zinc (bottom) concentrations at mouth of High Ore Creek, 

1996-2000.
The Boulder River Watershed Study, 

Jefferson County, Montana

By Stanley E. Church, David A. Nimick, Susan E. Finger, and J. Michael O'Neill

Chapter B of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-B

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Introduction................................................................................................................................................. 15

Acknowledgments...................................................................................................................................... 17

Description of Study Area......................................................................................................................... 17

Hydrologic Setting............................................................................................................................. 17

Biologic Setting.................................................................................................................................. 19

Geologic Setting................................................................................................................................. 20

Mining History.................................................................................................................................... 20

Remediation Activities ..................................................................................................................... 23

Overview of this Volume............................................................................................................................23

References Cited........................................................................................................................................ 27

Figures

1. Index map of the two Abandoned Mine Lands study areas............................................... 16

2. Shaded relief map of the Boulder River watershed study area......................................... 18

3. Streamflow hydrograph for years 1996-2000........................................................................ 19

4. Simplified geologic map of the study area............................................................................ 21

5. Graphs showing historical record of production from the Basin-Cataract

mining district, 1902-1958......................................................................................................... 22
Chapter B

The Boulder River Watershed Study, Jefferson County,

Montana

By Stanley E. Church, David A. Nimick, Susan E. Finger, and J. Michael O'Neill

Introduction

Thousands of inactive hard-rock mines have left a legacy 

of acid drainage and toxic metals across mountain watersheds 

in the western United States. More than 40 percent of the 

watersheds in or west of the Rocky Mountains have headwater 

streams in which the effects of historical hard-rock mining are 

thought to represent a potential threat to human and ecosystem health. In many areas, unmined mineral deposits, waste 

rock, and mill tailings in abandoned mine lands (AML) may 

increase metal concentrations and lower pH, thereby contaminating the surrounding watershed and ecosystem. Streams 

near abandoned, inactive mines can be so acidic or metal laden 

that fish and aquatic insects cannot survive and terrestrial bird 

species are negatively affected by uptake of metals through 

the food chain. Although estimates of the number of abandoned, inactive mine sites vary, observers agree that the scope 

of this problem is huge, particularly in the western United 

States where public lands contain thousands of inactive mines. 

Clearly, remediation of Federal lands affected by inactive historical mines will require substantial investment of resources.

Numerous AML sites are located on or adjacent to public 

lands, or affect aquatic or wildlife habitat on public lands. In 

1995, personnel from a U.S. Department of the Interior and 

U.S. Department of Agriculture (USDA) interagency task 

force, including the Bureau of Land Management, National 

Park Service, USDA Forest Service, and U.S. Geological 

Survey (USGS), developed a coordinated strategy for the 

cleanup of environmental contamination from inactive historical mines associated with Federal lands. As part of the 

interagency effort, the USGS implemented an Abandoned 

Mine Lands Initiative to develop a strategy for gathering 

and communicating the scientific information needed to 

formulate effective and cost-efficient remediation of inactive historical mines on Federal land. Objectives of the AML 

Initiative included watershed-scale and site characterization,

understanding of the effect and extent of natural sources, and 

communication of these results to stakeholders, land managers, and the general public. Additional objectives included 

transfer of technologies developed within the AML Initiative 

into practical methods at the field scale and demonstration of 

their applicability to solve this national environmental problem 

in a timely manner within the framework of the watershed 

approach. Finally, developing working relationships with the 

private sector, local citizens, and State and Federal land-management and regulatory agencies will establish a scientific 

basis for consensus and an example for future investigations of 

watersheds affected by inactive historical mines.

The combined interagency effort has been conducted in 

two pilot watersheds (fig. 1), the upper Animas River watershed in Colorado (U.S. Geological Survey, 2000) and the 

Boulder River watershed in Montana. In selection of a pilot 

watershed in Montana for the AML Initiative, five candidate 

watersheds were considered. These watersheds were ranked on 

the basis of geologic factors, metal loading, the status of ongoing remediation activities, general knowledge of the candidate 

watersheds, and extent of Federal lands within the watershed. 

The Boulder River watershed was selected from these five 

candidate watersheds in May 1996.

Land-management and regulatory agencies face two fundamental questions when they approach a region or watershed 

affected by abandoned mines. First, with potentially hundreds 

of dispersed contaminated inactive historical mine sites, how 

should resources for prioritizing, characterizing, and restoring 

the watershed be invested to achieve cost-effective and efficient cleanup? Second, how can realistic remediation targets 

be identified, considering

• The potential for adverse effects from unmined 

mineralized deposits (including any effects that may 

have been present even under premining conditions 

or still may persist from unmined deposits adjacent to 

existing abandoned or inactive mines)
16 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Boulder River watershed 

study area

Figure 1. Location of the Boulder and Animas River watershed 

study areas in the western United States. Watershed boundaries are based on the 8-digit hydrologic units as defined by U.S. 

Geological Survey (1982).

• The possible impact of incomplete cleanup of specific 

inactive historical mine sites

• Other factors that may limit sustainable development of 

desired ecosystems?

To answer these questions, the Abandoned Mine Lands 

Initiative adopted a watershed approach rather than a siteby-site approach to characterize and remediate abandoned 

mines (Buxton and others, 1997). This approach is based on

the premise that watersheds affected by acid mine drainage 

in a State or region should be prioritized on the basis of its 

effect on the biologic resources of the watershed so that the 

resources spent on remediation will have the greatest benefit 

on affected streams. Within these watersheds, contaminated 

sites that have the greatest impact on water quality and ecosystem health within the watershed would then be identified, 

characterized, and ranked for remediation. The watershed 

approach establishes a framework in which interdisciplinary 

scientific knowledge and methods can be employed at similar inactive historical mine sites throughout the Nation. The 

watershed approach

• Gives high priority to actions most likely to significantly improve water quality and ecosystem health

• Enables assessment of the cumulative effect of multiple 

and (or) nonpoint sources of contamination

• Encourages collaboration among Federal, State, and 

local levels of government and stakeholders

• Provides information that will assist disposal-siting 

decisions

• Accelerates remediation and reduces total cost compared to remediating on a site-by-site basis

• Enables consideration of revenue generation from 

selected sites to supplement overall watershed remediation costs.

This report provides a detailed review of work conducted 

in the Boulder River watershed during 1996-2000. The 

objectives of this work were to

• Estimate premining geochemical baseline (background) 

conditions

• Define current geochemical baseline conditions

• Characterize processes affecting contaminant dispersal 

and effects on ecosystem health

• Develop remediation goals on the basis of scientific 

study of watershed conditions

• Transfer data and information to users in a timely and 

effective manner.

Expertise in water quality, hydrology, geology, geochemistry, geophysics, biology, mapping, and digital-data collection and management was applied during these investigations. 

Investigations were coordinated with stakeholders, the 

Montana Department of Environmental Quality, Montana 

Fish, Wildlife and Parks, Montana Bureau of Mines and Geology, U.S. Environmental Protection Agency, USDA Forest 

Service, and Bureau of Land Management, all of which are 

coordinating the design and implementation of remediation 

activities within the watershed.
The Boulder River Watershed Study 17

Acknowledgments

Our work would not have been possible without the 

assistance of individuals in several State and Federal agencies. 

We thank personnel in the following agencies:

Montana Fish, Wildlife and Parks, particularly Don 

Skaar, Ron Spoon, and Kurt Hill, for their assistance with 

collection and analysis of fisheries data.

U.S. Fish and Wildlife Service, particularly Elizabeth 

MacConnell, for assistance with analysis of fisheries data.

Montana Department of Environmental Quality, particularly Vie Anderson and Ben Quinones, for providing data on 

their agency's efforts to evaluate mine sites.

Montana Bureau of Mines and Geology, particularly 

John Metesh for data and discussions on particular mines and 

their impact on the environment, and Joel Hall for his assistance with merging of the two geologic maps.

U.S. Environmental Protection Agency, particularly 

Mike Bishop for his efforts to coordinate subsequent Superfund work in the Boulder River and Tenmile Creek watersheds, and Steve Way for providing U.S. EPA and unpublished 

contractor reports related to the Luttrell pit.

USDA Forest Service, particularly Robert Wintergerst, 

Ray TeSoro, David Ruppert, Grant Godbolt, and Pat Barringer, 

for GIS data sets and general information about the study area, 

and for arranging access to some private lands.

Bureau of Land Management, particularly Tim Bozorth 

and Mike Browne, for their support and information on environmental issues in the High Ore Creek basin.

We also thank Dan Adams, Basin Creek mine geologist, 

formerly of Pegasus Gold Corp., for his assistance with the 

report on the Luttrell pit (Smith and others, this volume, 

Chapter E3). Finally, we thank the land owners in the Boulder River watershed who allowed us access to their property 

during this study. We also thank the residents of the towns of 

Basin and Boulder, Mont., for their hospitality while we were 

conducting fieldwork in the area.

Funding for some of the site-characterization work in the 

study area was provided by the USDA Forest Service and 

U.S. Environmental Protection Agency.

Description of Study Area

The Boulder River watershed is located in southwestern 

Montana (fig. 1). The Boulder River watershed study area, as 

defined in this study, is the drainage area of three large tributaries (Basin, Cataract, and High Ore Creeks) and the 

approximately 9 mi reach of the Boulder River that extends 

from just upstream to just downstream of these tributaries. 

The watershed study area does not include the large upstream 

drainage of the Boulder River or the reach downstream to 

the Jefferson River, even though effects of historical mining 

are apparent through these reaches. Studies focused on the 

watershed; however, some added sampling and regional

investigations were conducted outside this study area to document the extent of enriched trace-element concentrations in 

adjacent areas and to provide reference localities unaffected 

by historical mining. The Basin and Cataract Creek basins are 

within the Beaverhead-Deerlodge National Forest, while much 

of the land in the High Ore Creek basin is managed by the 

Bureau of Land Management.

The watershed area is mountainous (fig. 2): elevations 

range from about 4,900 to 8,800 feet above sea level. Mean 

annual precipitation ranges from about 18 to 26 in./yr (Parrett, 

1997). Although the population varies seasonally as temporary 

residents move into the area during the summer, about 

200 people live year-around in the Boulder River watershed 

study area. Residents are engaged primarily in mining, 

logging, or tourism.

For ease of discussion, figure 2 includes various basin 

and subbasin boundaries where work in the study area was 

concentrated. In the Basin Creek basin, the upper Basin Creek 

subbasin and the Jack Creek subbasin contain the Buckeye and 

Bullion mine sites, respectively. The Cataract Creek basin is 

subdivided into the upper, middle, and lower Cataract Creek 

subbasins and the Uncle Sam Gulch subbasin, which contains 

the Crystal mine. The High Ore Creek basin has not been 

subdivided.

The trace elements in which we were particularly interested for this investigation were those related to the mineral 

deposits in the watershed and that occur in concentrations 

sufficiently high to cause concern about their potential effect 

on aquatic organisms. These trace elements include arsenic, 

cadmium, copper, lead, silver, and zinc. In contrast, other trace 

elements such as chromium, cobalt, strontium, titanium, and 

many others occur in rocks throughout the watershed but are 

not concentrated in the mineral deposits.

Hydrologic Setting

Streamflow in the Boulder River watershed study area is 

typical of mountain streams throughout the northern Rocky 

Mountains. Streamflow is dominated by snowmelt runoff, 

which typically occurs between April and June; this snowmelt 

runoff often is augmented by rain. Streamflow typically peaks 

in May or June and decreases as the shallow ground-water 

system drains. Spring runoff conditions extend into July. Low 

Streamflow conditions are typical from August to March 

(fig. 3). The nearest Streamflow gauging station is 5 mi downstream of the study area on the Boulder River near Boulder, 

Mont. Although the magnitude of Streamflow is less than at 

this gauging station, Streamflow in study area streams is 

proportional (based on drainage area) to that at the gauge and 

has similar seasonality.

Water quality in many study area streams is good; 

however, water quality is degraded by high trace-element 

concentrations in reaches downstream from some of the 

inactive mines. The major-ion chemistry of stream water 

varies depending on geology and the relative amount of mine 

drainage. Calcium or calcium-sodium bicarbonate water is the
18 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

1120 22'30"

2 MILES

0 1 2 KILOMETERS

Figure 2. Shaded relief map of Boulder River watershed showing the study area; Boulder River; the three main tributaries—Basin, 

Cataract, and High Ore Creeks, impacted by past mining in the study area; and selected subbasins. Basin Creek basin was subdivided 

into three subbasins: upper Basin Creek, which contains the Buckeye mine and the Basin Creek mine; Jack Creek subbasin, which 

contains the Bullion mine; and lower Basin Creek subbasin. Cataract Creek basin is subdivided into four subbasins: lower, middle, and 

upper Cataract Creek, and Uncle Sam Gulch subbasins. Drainage from the Crystal mine affects both the Uncle Sam Gulch and the 

lower Cataract Creek subbasins. High Ore Creek basin, which contains the Comet mine, was not subdivided. The generalized Boulder 

River watershed study area boundary is the area of these three targeted tributary drainages (outlined in black). Area south of Boulder 

River, containing Galena and Little Galena Gulches, is not included in this study. Luttrell pit at Basin Creek mine site southwest of Luttrell Peak is the U.S. ERA repository site for mine wastes from both Boulder River watershed and Tenmile Creek watershed to north.
The Boulder River Watershed Study 19

1,500 i—,—f

1,200 -

I-T-I——| i i i fulfil i——i i | > i i 

r

300 -

JFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJ 

1996 1997 1998 1999 2000

Figure 3. Daily mean streamflow during 1996-2000 at the Boulder River at Boulder, Mont. (USGS gauging station 06033000). Average annual peak flow is for water years 1929-72,1975, 1981, and 1985-2000. Shaded areas indicate periods of spring runoff, which 

was arbitrarily defined as streamflow greater than 150 cubic feet per second.

norm. Streams affected by inactive mines have larger proportions of sulfate. All but a few small streams receiving adit 

discharge have alkaline pH (Nimick and Cleasby, this volume, 

Chapter D5).

Near-surface ground-water flow is largely controlled by 

topography, by the distribution of unconsolidated Tertiary and 

Quaternary deposits that overlie the Boulder batholith (fig. 4), 

and by the decrease in hydraulic conductivity of geologic units 

with depth (McDougal and others, this volume, Chapter D9). 

Topography strongly controls the direction of ground-water 

flow and the location of discharge areas. Recharge primarily 

occurs on topographic highs, and greater amounts of recharge 

occur in areas with the greatest precipitation and hydraulic 

conductivity. Discharge, in the form of numerous seeps and 

small springs, occurs in topographic lows and at breaks in 

slope. The upper, thin unit of unconsolidated deposits has the 

largest hydraulic conductivity. Flow paths in this near-surface 

aquifer, from recharge to discharge areas, are short, commonly 

less than a few thousand feet. Regional ground-water flow is 

limited by the low permeability of the underlying bedrock, 

except in areas of high fracture intensity. The uppermost, fractured and weathered zone in the igneous bedrock has a smaller 

hydraulic conductivity than the overlying unconsolidated 

deposits but has a much greater hydraulic conductivity than 

the underlying unweathered granitic to granodioritic Butte 

pluton. Fractures are the major conduit for ground-water flow 

in bedrock, with more flow in the uppermost zone (about 

50 ft) where the fractures are weathered and fairly open.

Biologic Setting

Little historical information is available on biological 

communities in the Boulder River watershed (fig. 1), making 

it difficult to determine biological conditions in this watershed 

prior to mining. In recent years, however, a complete biological characterization of the watershed was done by the Montana 

Department of Fish, Wildlife and Parks (1989). Mule deer, elk, 

moose, and antelope are year-round residents in the Boulder 

River watershed, and black bear are present seasonally. Mink 

and beaver also are found in the river and riparian zone.

The Boulder River upstream from the town of Boulder 

(fig. 1) has a narrow flood plain, and the riparian vegetation 

is dominated by willow, alder, conifer, and, to a lesser extent, 

cottonwood and aspen. At the lower elevations, downstream 

from the town of Boulder, the river meanders with a gradual 

gradient; as a result, riparian vegetation consists of cottonwood, aspen, and willow. The river supports brook trout, 

brown trout, rainbow trout, and mountain whitefish; some 

tributaries of the Boulder River provide habitat for native 

westslope cutthroat trout. Other species, such as mottled 

sculpin, longnose dace, longnose sucker, and white sucker, 

also reside in the Boulder River.

Past mining activity has affected aquatic communities in 

this watershed. Gardner (1977) found that elevated concentrations of metals and sedimentation affected the distribution and 

abundance of aquatic invertebrates. Vincent (1975) and Nelson 

(1976) attributed reduced populations of trout in the lower 

Boulder River to elevated concentrations of metals in the water 

and streambed sediment.
20 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Geologic Setting

The geologic setting of a watershed provides a framework 

for understanding the scope and cause of environmental effects 

of historical mining. The geologic setting includes the main 

types of rock and their spatial distribution in the watershed, 

the degree of faulting and fractures in these rocks, and finally 

the type and location of the mineralized areas, ore deposits, 

and associated mines. These factors play an important role in 

determining the way the watershed responds to mine discharge 

and waste and in controlling the flow of ground water to and 

from these sites. In addition, understanding the rock composition and geologic architecture can help identify suitable 

mine-waste repository sites that have more abundant acid-neutralizing capacity but yet have limited geologic- or fracturecontrolled ground-water flow.

The Boulder River watershed is largely underlain by the 

Cretaceous Boulder batholith, which is a large mass of granitic 

rock that cooled and crystallized at depth, and the overlying 

Elkhorn Mountains Volcanics, which formed as the molten 

granitic magma erupted (fig. 4). This entire assemblage of 

granitic and volcanic rocks was later eroded so that lower 

elevation areas of the watershed, such as valley bottoms, 

generally are carved through granitic rocks while higher elevation areas, such as ridges and mountain tops, are formed in the 

overlying volcanic rocks.

The bulk of the Boulder batholith within the study area is 

the granitic to granodioritic Butte pluton (Becraft and others, 

1963; Ruppel, 1963; O'Neill and others, this volume, Chapter 

Dl). Most of the intrusive rocks are porphyritic and contain 

variable amounts of mafic minerals (5-15 percent biotite 

and hornblende; Ruppel, 1963) and vein calcite, all of which 

contribute to the acid-neutralization capacity of rocks in the 

watershed (Desborough, Briggs, and Mazza, 1998; O'Neill 

and others, this volume). The presence of these minerals may 

help explain why, in general, few streams in the study area 

are acidic even though acidic conditions existed at many mine 

sites. The Elkhorn Mountains Volcanics include welded tuff, 

tuff and flow breccia, and volcanic sandstone and conglomerate. The volcanic rocks are predominantly quartz latite to 

andesite and also include varying amounts of mafic minerals. 

Andesite intrusions within the Elkhorn Mountains Volcanics 

occur near the confluence of Basin and Jack Creeks (Ruppel, 

1963).

Small outcrops of the Lowland Creek Volcanics of 

Eocene age (Smedes and Thomas, 1965) and of quartz latite 

composition also are present but are restricted to the southern 

and eastern parts of the study area. In addition to volcanic 

rocks, the Lowland Creek Volcanics include tuffaceous sandstone and siltstone as well as structurally controlled northeasttrending dike swarms.

Unconformably overlying the older Elkhorn Mountains 

and Lowland Creek Volcanics are lower Oligocene rhyolitic 

flows (younger volcanic rocks in fig. 4), part of the nearby 

Avon volcanic field. Tertiary rhyolitic flows occur extensively 

in the western and northern parts of the study area (Becraft

and others, 1963; Ruppel, 1963). These rhyolitic rocks host the 

disseminated gold-pyrite ore deposit in the northern part of the 

study area near Luttrell Peak (location, fig. 2).

The Butte pluton is extensively jointed; the joints consist 

of three prominent sets that trend north or east or are subhorizontal (Ruppel, 1963; Becraft and others, 1963). Because 

the sets of joints in the Butte pluton commonly are filled with 

leucocratic veins that most likely represent late-stage magmatic fluids, Ruppel (1963) interpreted them to be related to 

batholithic cooling phenomena. This interpretation has been 

confirmed on the basis of new 40Ar/39Ar ages determined in 

this study (O'Neill and others, this volume; Lund and others, 

2002). Associated with the intrusion of these late-stage aplites 

is an altered leucocratic granite that is exposed in rubble in 

Uncle Sam Gulch upstream from the Crystal mine.

The batholithic rocks are cut by numerous faults and 

lineaments of uncertain age. Some of the faults are mineralized and host the largest ore deposits in the study area. Most of 

the faults trend east or northeast; a minor but important subset 

of faults and lineaments trends northwest (fig. 4). The northeast- and northwest-trending faults appear to be recurrently 

active, related to tectonic activity restricted to the northeasttrending Great Falls tectonic zone (O'Neill and Lopez, 1985) 

or to southwest-northeast-directed basin and range extension 

(Reynolds, 1979). The east-trending, strongly mineralized 

faults or shear zones appear to be related to emplacement of 

the Boulder batholith (Schmidt and others, 1990; O'Neill and 

others, this volume).

Acid-neutralizing potential of bedrock is an important 

control on water quality in mined areas. The granitic rocks that 

underlie much of the study area contain minerals that provide a moderate amount of acid-neutralizing potential. These 

minerals include iron and magnesium minerals (for example, 

biotite and hornblende) that formed when the magma was 

cooling, and calcite (calcium carbonate) that formed later after 

the magma cooled. These minerals are widely disseminated 

and provide significant and widespread acid-neutralizing 

capacity. The presence of these minerals may help explain 

why, in general, few streams in the study area are acidic even 

though acidic conditions existed at many mine sites.

Pleistocene glacial till is present on some of the upland 

surfaces in the study area. Till is present in many of the flat 

areas in the valleys, and lateral moraines are present along 

some of the valleys, such as along Jack Creek. Outwash 

deposits are present in a few of the larger valleys. Tertiary 

unconsolidated sand and gravel locally mantle upland surfaces 

in areas previously mapped as glacial deposits (Ruppel, 1963; 

J.M. O'Neill, written commun., 1999). Holocene fluvialalluvial and minor pond and bog deposits have accumulated in 

the study area along valley floors.

Mining History

The mineral deposits of the Boulder River watershed 

include disseminated deposits of auriferous pyrite, placer 

deposits of gold and tin, and a large number of base- and
The Boulder River Watershed Study 21

112°22'30" 112151

n 

n

n

EXPLANATION

Alluvium

Landslide deposits and 

glacial deposits

Younger volcanic rocks 

Lowland Creek Volcanics 

Elkhorn Mountains Volcanics 

Boulder batholith

Normal fault—Dashed where inferred; 

dotted where concealed

Generalized study area boundary

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

2 KILOMETERS

Figure 4. Generalized geology of Boulder River watershed study area (modified from O'Neill and others, this volume, 

Chapter D1, pi. 1). Dashed outline shows the area of the target drainages in the study area.
22 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

precious-metal-bearing quartz veins. Auriferous pyrite occurs 

in rhyolite on the divide between Tenmile and Basin Creeks 

at the Basin Creek mine (fig. 2). Most placer deposits are in 

coarse gravel deposits along upper Basin Creek downstream 

of the area of rhyolite outcrop (younger volcanic rocks, fig. 4; 

Becraft and others, 1963; Ruppel, 1963).

The ore deposits in the watershed occur primarily in thin 

veins, which formed as the last vestiges of molten rock from 

the cooling granitic body filled thin fractures and small faults 

in the solidified magma rock and overlying volcanic rocks. 

These ore deposits are called polymetallic quartz-vein deposits 

and were mined primarily for silver and for base metals 

(copper, lead, and zinc), although some contained economic 

quantities of gold. The inactive mines in the study area are 

located mostly along these veins. The polymetallic quartz 

veins typically are short, but some extend for as much as 

several miles. Most of the largest ore-bearing veins occupy 

east-trending Late Cretaceous extensional structures. The 

hydrothermal alteration common in and adjacent to all veins 

generally is confined to thin zones, typically about 1 ft thick 

and rarely more than a few feet thick. The veins contain abundant base-metal sulfides with high silvengold ratios. Pyrite 

is the most abundant sulfide mineral but had no economic 

value to miners. Other sulfide minerals, such as arsenopyrite, 

chalcopyrite, tetrahedrite, galena, and sphalerite, contained the 

metals that miners targeted.

The Boulder River watershed study area encompasses 

the Boulder and Basin mining districts. Mining in these 

districts started in the mid-1860s with the discovery of gold 

placer deposits. Production of placer gold reached a maximum 

between 1868 and 1872, although placer operations continued 

intermittently through about 1940. Roby and others (1960) 

reported that an estimated 845 fine ounces of placer gold were 

recovered between 1933 and 1938 from lower Basin Creek. 

A small amount of placer gold was also recovered from the 

Boulder River during this time period. Auriferous pyrite 

deposits that had been mined previously in small underground 

mines were mined briefly by open-pit and cyanide extraction 

at the Basin Creek mine in the early 1990s.

The first discoveries of base-metal vein deposits were 

made at about the same 1 ime as the first placer discoveries. 

Lead-silver ore was discovered at the Ada mine in the early 

1860s and gold was discovered at the Buckeye mine in 1868. 

After 1872, lode mining completely overshadowed placer 

mining. The main period of lode mining began about 1880, 

reached a peak between 1895 and 1903, and ended about 

1907. Production prior to 1902 is largely undocumented 

because records were not kept prior to Montana statehood. 

After 1907, mining was intermittent and largely restricted to 

a few mines, especially the Comet, Gray Eagle, Crystal, and 

Bullion mines, which yielded most of the ore mined in the 

study area (Martin, this volume, Chapter D3). Mining generally had ceased by the 1940s at these mines, but some production continued into the 1960s and 1970s. Figure 5 shows the 

recorded production from Jefferson County from approximately 1900 through 1958 from the Basin-Cataract mining

district (Roby and others, 1960). Many of the smaller mines 

and prospects were reopened from time to time after 1903 

for further exploration and for speculation, but none yielded 

appreciable quantities of ore (Becraft and others, 1963; Ruppel, 1963). Much of the mining occurred on privately owned 

(patented) mining claims. However, some mine, mill, and 

smelter sites, and some mill-tailings deposits, along with 

eroded tailings distributed along various reaches of stream 

channels and flood plains, are located on Federal land.

1900 1910 1920 1930 

YEAR

1940 1950 1960

CO•z. 

o

o

yD 

O 

EC

D1,000

100

10

1900 1910 1920 1930 

YEAR

1940 1950 1960

1,000,000

100,000

^ 10,000

D

o

DC

1,000

100

10

1900 1910 1920 1930 

YEAR

1940 1950 1960

Figure 5. Produced tonnage of copper, lead, and zinc; annual 

production, expressed as tons (2,000 Ib) of ore; and production 

of gold and silver, in troy ounces, from the Basin-Cataract mining 

district from 1902 to 1958 (Roby and others, 1960).
The Boulder River Watershed Study 23

In the 1800s and early 1900s, mills treated ores by crushing and grinding and then concentration by gravity separation, 

or, after about 1914, by flotation methods. Some of the larger 

mines had small stamp mills at the mine site. Ore from smaller 

mines was transported to off-site mills. Concentrates from 

these mills generally were transported to smelters in Basin 

or outside the Boulder River watershed (Metesh and others, 

1994).

More than 140 inactive mine-related sites lie in the Boulder River watershed study area (Martin, this volume). These 

sites include mines, where ore was recovered, and prospects, 

where rock was removed in search of ore deposits. Rock that 

was mined but that had insufficient economic value typically 

was left near the mine in waste-rock piles. Ore was stockpiled 

at mine sites for later transport to a mill, and some stockpiles 

remain in the watershed. Ore was crushed and processed at 

a mill to concentrate the valuable metals. Wastes from mills, 

called tailings, typically were discharged to areas, including 

valley bottoms, downhill from the mill. Many of the mine and 

mine-related sites in the study area had been inventoried for 

State and Federal agencies to help target likely mine and mill 

sites for remediation. Inactive mine-related sites affect streams 

through direct discharge of acid drainage from adits, seepage 

from waste-rock and tailings piles, and erosion of tailings piles 

and fluvial tailings deposits by storm runoff or streambank 

erosion.

Remediation Activities

Interest in reducing the environmental effects of the many 

inactive mines and prospects in the Boulder River watershed 

increased in the 1980s as the studies of the effects of historical mining on water quality increased. One of the first actions 

taken was the construction of a diversion channel in the 1980s 

to route High Ore Creek (fig. 2) around the large quantity of 

tailings deposited in the valley bottom at the Comet mine site. 

The State of Montana inventoried and ranked inactive mines 

in the study area (Montana Department of State Lands, 1995) 

and conducted a preliminary watershed analysis (Montana 

Department of Environmental Quality, 1997). Federal landmanagement agencies began planning for cleanup activities in 

the mid-1990s after the completion of inventories of inactive 

mines (Metesh and others, 1994, 1995, 1996; Marvin and 

others, 1997). Studies were conducted to locate suitable sites 

for small, local mine-waste repositories (Desborough and Fey, 

1997; Desborough and Driscoll, 1998; Desborough, Briggs, 

and Mazza, 1998; Desborough and others, 1998) as well as to 

site a larger regional repository at the Luttrell pit at the Basin 

Creek mine (fig. 2; Smith and others, this volume, Chapter 

E3). In 1997, the State of Montana began cleanup activities 

at the Comet mine, and large quantities of mill tailings in the 

High Ore Creek valley bottom were removed to the former 

open pit at the Comet mine site. In 1999, the BLM removed 

flood-plain tailings from the valley floor along the 4-mi reach 

between the Comet mine and the Boulder River (Gelinas and

Tupling, this volume, Chapter E2) to a new repository near 

the Comet mine. In 1999, the U.S. Environmental Protection 

Agency listed the Basin and Cataract Creek drainages and the 

adjacent Tenmile Creek drainage immediately to the north as 

Superfund sites on the National Priorities List. Also in 1999, 

the U.S. EPA and USD A Forest Service cooperatively developed the Luttrell pit as a repository for mine wastes that would 

be removed from sites in the Boulder River and Tenmile Creek 

watersheds. In 2000, the U.S. EPA continued moving mine 

wastes from the Tenmile Creek area to the Luttrell pit. The 

USDA Forest Service removed mine wastes and flood-plain 

tailings from the Buckeye and Enterprise mine area to the 

Luttrell pit in 2000.

Overview of this Volume

Chapters in this volume are arranged from general 

conclusions to more specific detailed and technical studies. 

The following summaries provide an overview and summary 

of the chapters contained in this report for those who have 

limited time or are unaware of which subjects presented in the 

volume would be most applicable to their interests. Chapter A, 

"Summary and Conclusions from Investigation of the Effects 

of Historical Mining in the Boulder River Watershed, Jefferson County, Montana," provides a brief summary of our major 

findings. Historical mining has elevated the concentrations 

of cadmium, copper, and zinc in surface water of the Boulder 

River watershed study area. Weathering of mine wastes, and 

particularly of mill tailings in the study area, has also resulted 

in elevated concentrations of arsenic, cadmium, copper, lead, 

and zinc in streambed sediment in Basin Creek downstream 

from the Buckeye and Enterprise mines, in Jack Creek downstream from the Bullion mine, in Uncle Sam Gulch downstream from the Crystal mine, in High Ore Creek downstream 

from the Comet mine, and in the Boulder River downstream 

from the Jib Mill site. Studies of fish in the stream reaches 

downstream of these sites indicate that fish cannot survive in 

the most severely affected reaches; chronic effects were documented where trace-element concentrations were significantly 

elevated. The Montana Department of Environmental Quality, 

Bureau of Land Management, USDA Forest Service, and 

U.S. Environmental Protection Agency initiated remediation 

planning of these sites following our initial characterization 

studies summarized in this volume.

Chapter C, "Synthesis of Water, Sediment, and Biological 

Data Using Hazard Quotients to Assess Ecosystem Health," 

by Susan E. Finger, Ai'da M. Farag, David A. Nimick, Stanley 

E. Church, and Tracy C. Sole, is a multidisciplinary synthesis of the studies conducted in the watershed, using what is 

called an ecological risk assessment approach. This approach 

explains the relevance of the combined studies, hydrologic, 

geologic, and biologic, in terms of remediation and recovery 

at the watershed level. This chapter evaluates the physical and 

chemical characteristics of the watershed that may limit the
24 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

recovery of those species that are negatively affected by historical mining. Specifically, it evaluates effects of trace-element 

exposure on fish communities. Such exposure can be from the 

water in which these organisms live and (or) through the food 

chain. The potential for adverse biological effects associated 

with elevated concentrations of cadmium, copper, and zinc 

in water and streambed sediment is assessed by comparison 

with aquatic regulatory standards for water and consensusbased sediment-quality guidelines. Ribbon maps showing the 

distribution of trace elements in stream water and streambed 

sediment demonstrate the severity of contamination in specific 

stream reaches within the study area. Chronic effects are documented in trout in some Boulder River tributaries.

Chapter D, consisting of "subchapters" D1-D10, provides the scientific basis for the conclusions and recommendations made in this volume. The subchapters describe detailed 

scientific studies focused on particular aspects of the Boulder 

River watershed study.

Chapter Dl, "Geologic Framework," by J. Michael 

O'Neill, Karen Lund, Bradley S. Van Gosen, George A. 

Desborough, Tracy C. Sole, and Ed H. DeWitt, summarizes the geology of the study area. Polymetallic quartz-vein 

deposits, which were emplaced along tensional structures 

in the Butte pluton, formed the sulfide ore veins that were 

exploited in the Basin and Boulder mining districts between 

1868 and about 1970. Premining water and streambed-sediment geochemistry was controlled by the composition of the 

granitic Butte pluton, which underlies most of the Boulder 

River watershed study area. In contrast, the water and streambed-sediment geochemistry today is significantly affected by 

the accelerated weathering of disturbed waste rock and mill 

tailings produced by historical mining. Studies of the chemistry of the rocks indicate that unaltered Butte pluton probably 

contained sufficient calcite to neutralize much of the acid 

generated by sulfides exposed prior to mining.

Chapter D2, "Geophysical Characterization of Geologic 

Features with Environmental Implications from Airborne 

Magnetic and Apparent Resistivity Data," by Anne E. 

McCafferty, Bradley S. Van Gosen, Bruce D. Smith, and Tracy 

C. Sole, summarizes aeromagnetic and resistivity geophysical data that were collected using airborne data sensors flown 

over the study area with a helicopter. The airborne geophysical 

data primarily reflect the mineralogy of the bedrock to depths 

of several hundred feet and are able to see through shallow 

ground cover. These data provide a more complete coverage of the bedrock features than can be mapped by standard 

geologic field methods. The airborne geophysical data were 

used to show where hydrothermal alteration events caused 

subtle changes in the mineralogy and chemistry of the Butte 

pluton. About 20 percent of the Butte pluton has been altered 

by hydrothermal activity, and these areas of altered rock would 

not constitute suitable sites for repositories for mine waste, 

because they have been leached of their acid-neutralizing 

potential by the hydrothermal alteration processes. The data 

provide one basis for the interpretation of the environmental 

geology of the watershed study area.

Chapter D3, "Mine Inventory," by E. Paul Martin, is an 

inventory of significant mines, mill sites, and prospects in the 

watershed study area. One hundred forty-three sites were identified from literature searches and then accurately located from 

digital orthophoto quadrangles (DOQs). Detailed site characteristics, including flow rates and pH of acid mine drainage, 

numbers of mine features, and size estimates of mill tailings 

and mine wastes, were compiled into a single database.

Chapter D4, "Metal Leaching in Mine-Waste Materials 

and Two Schemes for Classification of Potential Environmental Effects of Mine-Waste Piles," by David L. Fey and George 

A. Desborough, provides data on mine wastes from 10 mine 

sites in the study area. Mine-waste piles are of particular 

environmental concern because large quantities of acid and 

trace elements commonly leach from the rock material in these 

piles. These factors are key in determining how large an effect 

an individual mine-waste pile might have on the environment. A new surface-sampling procedure was developed that 

provided a statistically representative sample of an individual 

waste pile. These samples were analyzed for total and watersoluble trace-element content of each sample, the amount 

of specific minerals likely to release acid or trace elements, 

and the potential to produce or neutralize acid. Two waterleach methods for evaluating metal mobility were compared. 

The standard EPA 1312 protocol was compared with a less 

labor-intensive static leach method. Both methods gave similar 

results. Mineralogical studies of the samples indicated that the 

secondary sulfates anglesite and jarosite were present in about 

80 percent of the mine wastes, indicating active weathering in 

the mine waste. Results from these chemical analyses suggest 

that the mine-waste dumps represent an essentially infinite 

source of water-soluble trace elements and acid.

To help land managers prioritize these piles for remediation, the authors developed a ranking system based on the 

size of the pile and used results of the chemical analyses in 

developing the rankings. The ranking system was used to 

classify 19 waste piles that they had permission to sample. For 

the sampled mine sites, the ranking system showed that waste 

piles at the Buckeye, Bullion, Daily West, Cracker, and Boulder Chief mine sites had a high potential for environmental 

degradation, whereas piles at the Crystal and Sirius mine sites 

had intermediate potential, and piles at the Morning Marie and 

Waldy mine sites had low potential.

Chapter D5, "Trace Elements in Water in Streams 

Affected by Historical Mining," by David A. Nimick and 

Thomas E. Cleasby, describes surface-water chemistry in the 

watershed, focusing on variation in major-element chemistry 

and concentrations, loads, and sources of trace elements. Few 

stream reaches have pH less than 6.5 in contrast to what is 

typical of many other historical mining districts. Dissolved 

concentrations (0.45-micrometer filtered water) of cadmium, 

copper, lead, and zinc commonly exceeded aquatic-life standards downstream from inactive historical mine sites. Ribbon 

maps show the distribution of pH and metal concentrations 

in stream reaches in the watershed. The Bullion, Comet, and 

Crystal mine sites produced most of the dissolved
The Boulder River Watershed Study 25

trace-element load in the study area. Cataract Creek contributed larger dissolved loads than either Basin or High Ore 

Creeks.

Chapter D6, "Quantification of Metal Loading by Tracer 

Injection and Synoptic Sampling, 1997-98," by Briant A. 

Kimball, Robert L. Runkel, Thomas E. Cleasby, and David 

A. Nimick, describes the results from detailed metal-loading 

studies conducted in Cataract Creek, Uncle Sam Gulch, and 

the Bullion Mine tributary on Jack Creek. Individual sources 

of metals were identified and quantified from the downstream 

changes in metal loads in each study reach. Metal loads were 

calculated using data from the dilution of a tracer (sodium 

chloride) that was injected at the upstream end of each study 

reach and from metal concentration data determined in synoptic water-quality samples. The major sources of metal loadings for dissolved metals in these creeks were shown to be the 

Crystal mine adit flow on Uncle Sam Gulch and the Bullion 

mine adit flow on the Bullion Mine tributary. The Crystal mine 

adit flow provided a daily load of about 35 Ib of zinc to Cataract Creek whereas the zinc load from the Bullion mine adit 

was about 7 Ib per day. About one-third of the calculated zinc 

load in Cataract Creek came from unsampled inflows, possibly 

ground water, and about one-third was lost to colloidal deposition on the streambed.

Chapter D7, "Short-Term Variation of Trace-Element 

Concentrations during Base Flow and Rainfall Runoff in Small 

Basins, August 1999," by John H. Lambing, David A. Nimick, 

and Thomas E. Cleasby, details the short-term variation of 

arsenic, copper, manganese, and zinc concentrations in High 

Ore, Jack, and Cataract Creeks. Dissolved zinc concentrations 

varied by a factor of three in High Ore Creek over the 24-hour 

observation period. Maximum dissolved zinc concentrations 

occurred in early morning hours, whereas minimum concentrations occurred in the late afternoon. Interpretation of these 

data suggests that the cause of this variation may be the sorption of dissolved zinc onto paniculate material in the stream as 

temperature and pH of the water change throughout the day.

Concentrations of these trace elements were also shown 

to increase in response to runoff during rainfall. The lag time 

following onset of rainfall before the arrival of the peak concentration of dissolved metals was short, on the order of 

3 hours, whereas the decay curve following the rainstorm 

lasted 8-10 hours. Both phenomena, the changes in traceelement concentrations caused by daily fluctuations in temperature and the changes caused by a rainfall event, may have 

substantive effects on the toxicity of dissolved trace elements 

on aquatic life. At sites where the dissolved metal concentrations were measured late in the day, the daily variation would 

result in a calculated toxicity for aquatic life that would be 

underestimated. During periods following runoff from a summer thunderstorm, the calculated toxicity would be dependent 

on the time lag associated with runoff for each mine waste 

site.

Chapter D8, "Trace Elements and Lead Isotopes in 

Streambed Sediment in Streams Affected by Historical

Mining," by Stanley E. Church, Daniel M. Unruh, David L. 

Fey, and Tracy C. Sole, is a study of the present streambedsediment geochemistry of the watershed. Concentrations of 

arsenic, cadmium, copper, lead, and zinc exceed published 

sediment-quality guidelines in many of the streams downstream from historical mine sites. The effect of historical 

mining on trace-element concentrations in streambed sediment 

in the Boulder River can be followed all the way to the confluence with the Jefferson River 55 mi downstream from the 

Basin and Boulder mining districts. Studies of the concentrations of these trace elements in premining streambed sediment 

preserved in terrace deposits in the watershed show that these 

trace elements are concentrated in streambed sediments today 

by factors of 50 to 100 times more than were present in the 

streambed sediment prior to historical mining.

Lead isotopes provide a "fingerprint" that can be used 

to tie sources of metals to groups of mineral deposits. The 

signature from the poly metallic veins exploited in the Basin 

and Cataract Creek basins is different from that in the High 

Ore Creek basin at the Comet mine. The lead isotope data 

have been used to quantify the contributions of the inactive 

historical mines to Boulder River streambed sediment. These 

calculations indicate that (1) about 35 percent of the lead in 

streambed sediment of the Boulder River was derived from 

Basin Creek and the Jib Mill site located on the Boulder 

River immediately above the confluence of Basin Creek, 

(2) 13 percent of the lead in streambed sediment was derived 

from Cataract Creek, and (3) about 50 percent of the lead in 

streambed sediment was derived from High Ore Creek. Data 

from streambed sediment in a terrace immediately downstream 

from the Jib Mill indicate that ores from outside the district 

were milled at this site and contributed elevated trace-element 

concentrations to Boulder River streambed sediment.

Chapter D9, "Hydrogeology of the Boulder River Watershed Study Area and Examination of the Regional GroundWater Flow System Using Interpreted Fracture Mapping from 

Remote Sensing Data," by Robert R. McDougal, 

M.R. Cannon, Bruce D. Smith, and David A. Ruppert, 

describes a reconnaissance level study of ground-water flow 

in the study area. Ground water can play an important role 

in determining the extent of contamination in historically 

mined areas. If ground water moves freely, dispersal of trace 

elements can be large, whereas if ground-water movement is 

restricted, effects of historical mining can be more localized. 

A conceptual model of how ground water flows in the study 

area was developed based on observations made in the field 

near the Buckeye, Bullion, and Crystal mines. The model then 

was used to help interpret the metal-loading studies and field 

observations made by other scientists. Ground water occurs 

primarily in the surficial unconsolidated deposits that blanket 

much of the study area and in the upper 50 ft of the bedrock, 

where the fractures are open and allow flow. At depth, fractures in the bedrock are tight and restrict ground-water flow. 

Flow paths for ground water from areas of recharge to areas 

of discharge are generally short (less than 1,000 ft) because
26 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

of the shallow nature of the permeable rocks. Ground-water 

flow from adits appears to be the major contribution from 

the ground-water system; ground-water flow through major 

geologic structures does not appear to contribute significantly 

to water-quality degradation in the study area. This conceptual idea of ground-water flow was expanded by mapping of 

linear features visible on images of the watershed taken from 

satellites and aircraft. These linear features were assumed to 

represent the expression at the land surface of faults, joints, 

fractures, and mineralized veins that cut the bedrock. Quantification of the primary orientations, the average lengths, and the 

relative spatial frequency of the features allowed areas where 

recharge and discharge might be more likely to be identified.

Chapter DIG, "Aquatic Health and Exposure Pathways 

of Trace Elements," by A'ida M. Farag, David A. Nimick, 

Briant A. Kimball, Stanley E. Church, Don Skaar, William G. 

Brumbaugh, Christer Hogstrand, and Elizabeth MacConnell, 

assesses aquatic community health, food supply, and pathways 

of exposure for toxic trace elements in the aquatic ecosystem. 

Laboratory and field methods were applied to evaluate the 

effects of metals released by past mining activity on fish at 

the individual organism and the population levels. Population 

surveys confirmed the absence of fish in some reaches of the 

watershed near mine sites, but trout populations were documented downstream of these source areas. Instream experiments using caged trout showed that elevated concentrations 

of cadmium, copper, and zinc in the water column were associated with increased trout mortality at sites near mine-waste 

sources. Physiological changes in the gill tissue from these 

fish indicated that the cause of death was related to elevated 

trace-element concentrations in the water column. Assessment 

of resident trout revealed impaired health at a downstream 

site in lower Cataract Creek, where reduced fish population 

densities also occurred. Exposure pathways and partitioning 

of metals in the aquatic environment were determined by measurement of trace-element concentrations in water, colloids, 

streambed sediment, biofilm (that is, algae and bacteria that 

grow on rocks in the stream), invertebrates, and fish at many 

sites throughout the watershed. The interrelationship of the 

trace elements accumulating in these biotic and abiotic components suggests that copper, cadmium, and zinc concentrations 

increased in fish tissues as a result of direct exposure from 

water and sediment and from indirect exposure through the 

food chain. Through contact by these two pathways, the health 

of aquatic biota in the watershed has been compromised.

Chapter E, consisting of three "subchapters," describes 

site-specific studies that focused on important aspects of abandoned mine land remediation. The three subchapters describe 

site characterization of the Buckeye and Enterprise mine sites 

on upper Basin Creek, water-quality monitoring of the Comet 

mine on High Ore Creek, and geologic evaluation of the Luttrell pit mine-waste repository site at the Basin Creek mine.

Chapter El, "Understanding Trace-Element Sources 

and Transport to Upper Basin Creek in the Vicinity of the 

Buckeye and Enterprise Mines," by M.R. Cannon, Stanley E. 

Church, David L. Fey, Robert R. McDougal, Bruce D. Smith,

and David A. Nimick, describes detailed studies of the mine 

wastes and mill tailings at the Buckeye and Enterprise mines, 

in particular, their effect on water quality in upper Basin 

Creek. Geochemical studies of a mill-tailings site at the Buckeye mine indicated that weathering of processed sulfide wastes 

had resulted in widespread dispersion of oxidized materials 

containing high concentrations of arsenic, cadmium, copper, 

lead, and zinc on the Basin Creek flood plain. Trenching at the 

site showed that unoxidized sulfides existed at depth. Data for 

chemistry, water levels, and hydraulic characteristics from 

10 shallow ground-water wells showed that although concentrations of trace elements were high in ground water near 

the mill and Enterprise mine sites, ground-water discharge 

contributed only a small part of the trace-element load to 

upper Basin Creek. Ground geophysical studies helped define 

the extent of the inferred plume of contaminated ground water. 

Observations of the local hydrology indicated that saturation of the mill-tailings pile on the flood plain occurred in the 

spring during snowmelt, and as a result, trace elements were 

transported both in solution and as suspended sediment into 

upper Basin Creek during high flow. Mill tailings and waste 

rock were removed to the Luttrell pit repository during summer 2000.

Chapter E2, "Monitoring Remediation—Have MineWaste and Mill-Tailings Removal and Flood-Plain Restoration 

Been Successful in the High Ore Creek Valley?" by Sharon 

L. Gelinas and Robert Tupling, describes the cleanup actions 

taken by the Montana Department of Environmental Quality 

and the Bureau of Land Management in the High Ore Creek 

valley. The Comet mine operated as a small open-pit mine 

briefly during the early 1970s. Mill tailings were impounded 

in High Ore Creek. The tailings impoundment was breached, 

and eroded tailings contaminated High Ore Creek and the 

Boulder River. Water quality and streambed-sediment quality 

in High Ore Creek and the Boulder River are affected by trace 

elements leached from these dispersed mill tailings. The tailings impoundment and the High Ore Creek flood plain were 

reclaimed during the course of this study. Preliminary evaluation of water-quality data collected before and after cleanup 

indicates that dissolved zinc concentrations have decreased, 

whereas dissolved arsenic concentrations have increased. 

Variations of the concentrations of these trace elements indicate a significant change in dissolved trace-element concentrations downstream of High Ore Creek in the Boulder River, 

but the dissolved trace-element concentrations have not stabilized.

Chapter E3, "Geologic, Geophysical, and Seismic Characterization of the Luttrell Pit as a Mine-Waste Repository," 

by Bruce D. Smith, Robert R. McDougal, and Karen Lund, 

provides an evaluation of the geologic suitability of the Luttrell pit site as a mine-waste repository. The Basin Creek mine 

went into Chapter 11 Bankruptcy by Pegasus Gold Corp. in 

1999. The U.S. EPA eventually acquired the site and requested 

an evaluation of the geologic suitability of the site as a minewaste repository. Detailed drilling data, mine-site geology, and 

fracture density at the Basin Creek mine site were provided by
The Boulder River Watershed Study 27

Pegasus Gold for USGS evaluation of the site to determine the 

local geologic characteristics and suitability as a mine-waste 

repository. No evidence of recent faulting in the vicinity of the 

Luttrell pit was found. Historical seismic data were evaluated to determine that the risk of earthquakes at the proposed 

repository site was acceptable. Fracture analysis indicated 

areas where ground-water flow paths from the repository may 

intersect local structures; these areas were suggested as sites 

for monitoring wells for the repository. A brief summary of 

the liner and drain system engineered by independent contractors documents the level of protection provided to prevent 

escape of any potentially toxic wastes from the Luttrell minewaste repository site.

Chapter F, "Evaluating the Success of Remediation in 

the Boulder River Watershed," by Susan E. Finger, Stanley E. 

Church, and David A. Nimick, describes the potential for successful ecological restoration and recovery of the aquatic community in the study area. Successful restoration is influenced 

by both the removal of the residual levels of contamination 

and the establishment of physical or chemical conditions that 

will support desired or realistic biological communities. Any 

restoration action involves a certain amount of risk of failure, 

including the realities of natural environmental variability, 

the scale of the restoration effort, and external catastrophic 

influences such as flood or drought. Although the desire of 

land-management agencies may be for ecological recovery 

to a preexisting baseline condition, this is often not feasible. 

Numerous factors must be considered before identifying the 

restoration alternative that has the highest probability of success. The success of any restoration effort can be best documented via a well-designed monitoring program that collects 

physical, chemical, and biological information to provide a 

comparison with conditions prior to cleanup activities. 

Necessary monitoring activities are recommended to chart 

the progress of aquatic recovery following these remediation 

efforts.

Chapter G, "Digital Databases and CD-ROM for the 

Boulder River Watershed," by Carl L. Rich, David W Litke, 

Matthew Granitto, Richard T. Pelltier, and Tracy C. Sole, 

describes the content and format of the data and information 

contained on the accompanying CD-ROM. Included are a relational database, a GIS database, and various map, image, and 

graphic products created during the study. The relational database contains sample site data collected and produced for the 

study, and an inventory and description of mine-related sites 

located and compiled for the study. The GIS database contains 

the sample site data and the information for mine-related sites 

stored as data layers and associated tables. In addition, the GIS 

database contains base cartographic data and other thematic 

data layers collected or produced during this study, as well as 

data layers and information that resulted from use of a GIS to 

analyze the sample site, mine-related site, base cartographic, 

and thematic data.

References Cited

Becraft, G.E., Pinckney, D.M., and Rosenblum, Sam, 1963, 

Geology and mineral deposits of the Jefferson City quadrangle, Jefferson and Lewis and Clark Counties, Montana: U.S. 

Geological Survey Professional Paper 428, 101 p., 4 plates.

Buxton, H.T., Nimick, D.A., von Guerard, Paul, Church, S.E., 

Frazier, Ann, Gray, J.R., Lipin, B.R., Marsh, S.P., Woodward, Daniel, Kimball, Briant, Finger, Susan, Ischinger, 

Lee, Fordham, J.C., Power, M.S., Bunck, Christine, and 

Jones, J.W., 1997, A science-based, watershed strategy to 

support effective remediation of abandoned mine lands: 

Proceedings of the Fourth International Conference on Acid 

Rock Drainage, Vancouver, B.C., May 31-June 6, 1997, 

p. 1869-1880.

Desborough, G.A., Briggs, PH., andMazza, Nilah, 1998, 

Chemical and mineralogical characteristics and acidneutralizing potential of fresh and altered rocks and soils of 

the Boulder River headwaters in basin and Cataract Creeks 

of northern Jefferson County, Montana: U.S. Geological 

Survey Open-File Report 98^0, 21 p.

Desborough, G.A., Briggs, PH., Mazza, Nilah, and Driscoll, 

Rhonda, 1998, Acid-neutralizing potential of minerals in 

intrusive rocks of the Boulder batholith in northern Jefferson County, Montana: U.S. Geological Survey Open-File 

Report 98-364, 21 p.

Desborough, G.A., and Driscoll, Rhonda, 1998, Mineralogical 

characteristics and acid-neutralizing potential of drill core 

samples from eight sites considered for metal-mine related 

waste repositories in northern Jefferson County, Montana: 

U.S. Geological Survey Open-File Report 98-790, 6 p.

Desborough, G.A., and Fey, D.L., 1997, Preliminary characterization of acid-generating potential and toxic metal 

solubility of some abandoned metal-mining related wastes 

in the Boulder River headwaters, northern Jefferson County, 

Montana: U.S. Geological Survey Open-File Report 

97^78, 21 p.

Gardner, W.M., 1977, The effects of heavy metals on the 

distribution and abundance of aquatic insects in the Boulder 

River, Montana: Bozeman, Mont., Montana State University 

M.S. thesis, 84 p.

Lund, Karen, Aleinikoff, J.N., Kunk, M.J., Unruh, D.M., 

Zeihen, G.D., Hodges, W.C., duBray, E.A., and O'Neill, 

J.M., 2002, SHRIMP U-Pb and 40Ar/39Ar age constraints for 

relating plutonism and mineralization in the Boulder batholith region, Montana: Economic Geology, v. 97, p. 241-267.
28 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Marvin, R.K., Metesh, J.J., Bowler, T.P., Lonn, J.D., Watson, 

I.E., Madison, J.P., and Hargrave, P.A., 1997, Abandonedinactive mines program, U.S. Bureau of Land Management: 

Montana Bureau of Mines and Geology Open-File Report 

348, 506 p.

Metesh, J.J., Lonn, J.D., Duaime, T.E., and Wintergerst, Robert, 1994, Abandoned-inactive mines program, Deerlodge 

National Forest—Volume I, Basin Creek drainage: Montana 

Bureau of Mines and Geology Open-File Report 321, 131 p.

Metesh, J.J., Lonn, J.D., Duaime, T.E., Marvin, R.K., and 

Wintergerst, Robert, 1995, Abandoned-inactive mines 

program, Deerlodge National Forest—Volume II, Cataract 

Creek drainage: Montana Bureau of Mines and Geology 

Open-File Report 344, 201 p.

Metesh, J.J., Lonn, J.D., Marvin, R.K., Madison, J.P., and 

Wintergerst, Robert, 1996, Abandoned-inactive mines 

program, Deerlodge National Forest—Volume V, Jefferson 

River drainage: Montana Bureau of Mines and Geology 

Open-File Report 347, 179 p.

Montana Department of Environmental Quality, 1997, Watershed analysis of abandoned hardrock mine priority sites 

1997: Prepared by Pioneer Technical Services, Inc., Butte, 

Mont., and Integrated Geoscience, Inc., Helena, Mont., for 

the Mine Waste Cleanup Bureau, variously paginated.

Montana Department of Fish, Wildlife and Parks, 1989, Application for reservations of water in the Missouri River Basin 

above Fort Peck Dam—Volume 2, Reservations requests for 

waters above Canyon Ferry Dam: 620 p.

Montana Department of State Lands, 1995, Abandoned 

hardrock mine priority sites, 1995 summary report: 

Prepared by Pioneer Technical Services, Inc., Butte, Mont., 

for the Abandoned Mine Reclamation Bureau, variously 

paginated.

Nelson, FA, 1976, The effects of metals on trout populations 

in the upper Boulder River, Montana: Bozeman, Mont., 

Montana State University M.S. thesis, 60 p.

O'Neill, J.M., and Lopez, D.A., 1985, Character and regional 

significance of the Great Falls tectonic zone, east-central 

Idaho and west-central Montana: American Association of 

Petroleum Geologists Bulletin, v. 69, p. 437-447.

Parrett, Charles, 1997, Regional analysis of annual precipitation maxima in Montana: U.S. Geological Survey WaterResources Investigations Report 97-4004, 51 p.

Reynolds, M.W, 1979, Character and extent of basin-range 

faulting, western Montana and east-central Idaho, in Newman, G.W, and Goode, H.D., eds., Basin and Range symposium and Great Basin field conference: Rocky Mountain 

Association of Geologists, p. 185-193.

Roby, R.N., Ackerman, W.C., Fulkerson, F.B., and Crowley, 

FA., 1960, Mines and mineral deposits (except fuels), 

Jefferson County, Montana: Montana Bureau of Mines and 

Geology Bulletin 16, 120 p.

Ruppel, E.T., 1963, Geology of the Basin quadrangle, Jefferson, Lewis and Clark, and Powell Counties, Montana: 

U.S. Geological Survey Bulletin 1151, 121 p., 7 plates.

Schmidt, C.J., Smedes, H.W, and O'Neill, J.M., 1990, 

Syncompressional emplacement of the Boulder and 

Tobacco Root batholith (Montana-U.S.A.) by pull-apart 

along old fault zones: Geological Journal, v. 25, p. 305-318.

Smedes, H.W, and Thomas, H.H., 1965, Reassignment of the 

Lowland Creek Volcanics to Eocene age: Journal of Geology, v. 73, p. 508-510.

U.S. Geological Survey, 1982, A U.S. Geological Survey data 

standard, Codes for the identification of hydrologic units 

in the United States and the Caribbean outlying areas: U.S. 

Geological Survey Circular 878-A, 115 p.

U.S. Geological Survey, 2000, Interim report on the scientific 

investigations in the Animas River watershed, Colorado to 

facilitate remediation decisions by the U.S. Bureau of Land 

Management and the U.S. Forest Service, March 29, 2000, 

meeting, Denver, Colo.: U.S. Geological Survey Open-File 

Report 00-245, 34 p.

Vincent, E.R., 1975, Southwestern Montana fishery investigation, Inventory of waters of the project area: Bozeman, 

Montana Department of Fish and Game, Project F-9-R-23, 

Job I-a, 12 p.
Synthesis of Water, Sediment, and 

Biological Data Using Hazard Quotients 

to Assess Ecosystem Health

By Susan E. Finger, AVda M. Farag, David A. Nimick, Stanley E. Church, and 

Tracy C. Sole

Chapter C of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-C

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract................................................................^

Introduction .................................................................................................................................................31

Purpose and Scope........................................................................................................................... 32

Ecosystem Stressors..................................................................................................................................32

Exposure Pathways.................................................................................................................................... 34

Ranking Stream Reaches Using Hazard Quotients............................................................................... 34

Water ..........................................................._

Streambed Sediment......................................................................................................................... 36

Comparisons of Hazard Quotients and Biological Effects................................................................... 36

Summary...................................................................................................................................................... 47

References Cited........................................................................................................................................ 48

Figures

1. Map showing estimated distribution of trout prior to large-scale remediation

work in Boulder River watershed study area....................................................................... 33

2-4. Maps showing chronic hazard quotients for water for:

2. Cadmium.............................................................................................................................. 37

3. Copper.................................................................................................................................. 38

4. Zinc....................................................................................................................................... 39

5. Map showing estimated risk based on sum of chronic hazard quotients for

water for cadmium, copper, and zinc..................................................................................... 40

6-9. Maps showing hazard quotients for streambed sediment for:

6. Cadmium.............................................................................................................................. 41

7. Copper.................................................................................................................................. 42

8. Lead......................................_

9. Zinc...................................................................................................................................... 44

10. Map showing estimated risk based on sum of hazard quotients for streambed

sediment for cadmium, copper, and zinc............................................................................... 45

Tables

1. Chronic aquatic-life water-quality criteria for cadmium, copper, and zinc..................... 36

2. Comparisons of biological assessment endpoints with estimated risk

based on hazard quotients....................................................................................................... 47
Chapter C

Synthesis of Water, Sediment, and Biological Data Using

Hazard Quotients to Assess Ecosystem Health

By Susan E. Finger, ATda M. Farag, David A. Nimick, Stanley E. Church, and Tracy C. Sole

Abstract

The level of effort expended in the Boulder River watershed to assess the effects of trace elements on aquatic life 

is not feasible for land- and resource-management agencies 

when faced with evaluating risks associated with thousands of 

potential inactive historical mine sites. However, the comprehensive data set for the Boulder River watershed offered the 

opportunity to estimate potential ecological effects from measured geologic, geochemical, and hydrological conditions and 

to validate these estimates by comparing them with measured 

biological responses. Hazard quotients calculated with chronic 

water-quality criteria and with sediment probable-effects concentrations generally agreed with measurements of biology to 

designate the primary areas of potential hazard in the Boulder 

River watershed. Sampling sites that potentially represent high 

hazards to aquatic life included the Bullion Mine tributary, 

Jack Creek, Uncle Sam Gulch, Cataract Creek downstream 

from Uncle Sam Gulch, lower Cataract Creek (upstream 

from the Boulder River), High Ore Creek downstream from 

the Comet mine, and lower High Ore Creek (upstream from 

the Boulder River). Fish were absent from all of these sites 

except lower Cataract Creek, and poor survival during 96-hour 

survival experiments suggested that trout would be unable 

to survive in these stream reaches. Adult fish were present 

in lower Cataract Creek, but the biomass, density, and individual health of trout were adversely affected, suggesting that 

chronic effects on the fishery in Cataract Creek existed. The 

only exceptions to the agreement between hazard quotients 

for water and sediment were in the Bullion Mine tributary 

and Jack Creek, where the lower pH of the water reduced the 

ability of trace elements to sorb to colloids and streambed 

sediment. Therefore, consideration of pH is critical for the 

interpretation of water and sediment chemistry from regions of 

historical mining activity. Remediation of the major inactive 

mine sites in the basins upstream from the primary areas of 

potential hazard could include removal of mine wastes located 

on valley floors and reduction of trace-element loading from 

draining adits. Our hazard-quotient analyses suggest that such 

remediation could result in substantial improvement of ecological health in the watershed.

Introduction

The watershed approach provides an effective means to 

evaluate the overall status of ecological resources in an area 

affected by historical mining and helps focus remediation and 

restoration strategies on regions that will most benefit from 

recovery of the watershed. Such a large-scale approach can 

entail the collection of extensive information on geology and 

geochemistry, hydrology and water chemistry, and ecological structure, health, and organization within the watershed 

of concern. During the assessment of the Boulder River 

watershed, mines were inventoried, geologic conditions were 

defined, aquatic habitat was assessed, hundreds of water and 

sediment samples were chemically analyzed, toxicity tests 

were conducted, fish tissues and indicators of physiological malfunction were analyzed and assessed, invertebrates 

and biofilm were examined, and hydrological regimes were 

defined. This level of effort is not feasible for land- and 

resource-management agencies to undertake routinely when 

faced with evaluating risks associated with thousands of potential inactive historical mine sites. However, this comprehensive 

data set offers the opportunity to use geologic, geochemical, 

and hydrological conditions measured throughout the watershed to estimate potential ecological effects on the aquatic 

communities and to validate these estimates by comparing 

them with measured biological responses. Although the focus 

of this volume is on the health of the aquatic community, a 

similar watershed-level approach could be used to evaluate 

the potential health of the terrestrial flora and fauna, or to 

evaluate the potential problems that might be encountered in 

attempts to revegetate the riparian corridor. Standard methods 

are available for measuring effects on the survival, growth, and 

reproductive health of terrestrial organisms (USEPA, 1992). 

Similarly, standard procedures to evaluate toxicity of soils 

to plants could be combined with information on sediment 

geochemistry to establish conditions in the flood-plain and 

riparian corridor (Linder and others, 1993).

Ecological risk assessments evaluate the potential that 

adverse effects may occur as the result of exposure to one 

or more stressors. These assessments provide a framework 

for organizing and evaluating data and offer an approach
32 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

for environmental managers to consider available scientific 

information in determining a course of action. The ecological 

risk assessment approach was developed to address anthropogenic changes that have potentially undesirable outcomes such 

as adverse effects on an ecosystem. Therefore, this general 

approach is appropriate and useful in evaluation of the effects 

of inactive mine sites on ecological health. The level of complexity of a risk assessment may vary from highly quantitative to a qualitative process depending on the objectives of 

the project. The end result should provide a relative means to 

rank the potential for adverse effects in the environment at the 

individual, population, or community level.

Purpose and Scope

The purpose of this chapter is to present an integrated 

assessment of environmental conditions in the Boulder River 

watershed and rank those conditions based on their potential 

to influence the health and recovery of the aquatic community. 

Information from a range of geologic, geochemical, hydrological, and biological studies is evaluated within an ecological 

risk assessment framework.

Scientific information collected during our studies in the 

Boulder River watershed, standard U.S. Environmental Protection Agency assessment methods, and information from the 

scientific literature are combined to

• Identify stressors that influence ecosystem health

• Identify pathways of exposure

• Calculate hazard quotients for ranking severity of 

effects

• Compare the ranking to measured biological responses.

Ecosystem Stressors

Historical mining activity in the Boulder River watershed 

significantly affected the physical and biological nature of the 

region. Fish were absent from some areas in the watershed 

directly downstream of draining mine adits, but populations of 

brook trout (Salvelinusfontinalis), rainbow trout (Oncorhynchus mykiss), and cutthroat trout (Oncorhynchus clarki) 

occurred further downstream in tributaries and in the Boulder 

River (fig. 1). In addition, native populations of westslope 

cutthroat trout (Oncorhynchus clarkii lewisi) existed upstream 

of the Comet mine in the High Ore Creek basin (Farag and 

others, this volume, Chapter D10). Although current information suggests that both fish and invertebrate populations are 

adversely affected in the Boulder River watershed, absence of 

physical habitat does not appear to be a major limiting factor. 

The persistence of an aquatic community in some parts of the 

watershed provides a basis for future ecosystem restoration.

Contaminants in surface water and streambed sediment 

are major stressors on the aquatic ecosystem in the Boulder 

River watershed. Specifically, copper, lead, zinc, arsenic, 

cadmium, silver, and antimony are the major contaminants in 

the watershed. Elevated concentrations of these trace elements 

can be linked directly to historical mining at the Buckeye and 

Enterprise mines in upper Basin Creek, the Bullion mine on a 

tributary of Jack Creek, the area of Cataract Creek upstream 

from Uncle Sam Gulch, the Crystal mine in upper Uncle Sam 

Gulch, and the Comet mine in upper High Ore Creek (Martin, 

this volume, Chapter D3). Although some trace elements, such 

as copper and zinc, are essential to normal growth and development of aquatic life, excess concentrations of trace 

elements are associated with abnormal reproduction, growth, 

and development (Rand and Petrocelli, 1985). Our characterization of the Boulder River watershed documented concentrations of a range of trace elements in water, sediment, colloids, 

biofilm, benthic macroinvertebrates, and trout. This approach 

provided the information necessary to characterize exposure 

pathways and to document the extent and severity of contamination in the watershed as a result of the exposure of aquatic 

life to their environment.

In streambed sediment from the sites just described, 

concentrations of trace elements associated with ore deposits 

were substantially higher than concentrations in premining 

streambed sediment (Church, Unruh, and others, this volume, 

Chapter D8). Similarly, the Bullion, Crystal, and Comet mines 

also produced most of the dissolved trace-element load to the 

watershed. Cadmium, copper, and zinc concentrations were 

most commonly elevated in stream water downstream from 

these sites (Nimick and Cleasby, this volume, Chapter D5). 

However, pH of most streams was near neutral. In contrast 

to many regions where inactive mines occur, the mineralogical and textural character of the bedrock in the Boulder River 

watershed exhibits a widespread acid-neutralizing capacity, 

thus minimizing the presence of acid water drainage in the 

basin (O'Neill and others, this volume, Chapter Dl).

The contributions of streambed sediment from Basin and 

Cataract Creeks to the Boulder River were similar, but the 

impact of the contamination in streambed sediment from High 

Ore Creek dominated the concentrations of trace elements 

in streambed sediment of the Boulder River from High Ore 

Creek downstream to the Jefferson River (Church, Unruh, and 

others, this volume). In contrast, surface water from Cataract 

Creek contributed larger trace element loads to the Boulder 

River than either Basin Creek or High Ore Creek (Nimick 

and Cleasby, this volume). The major source of metal loading to Cataract Creek was the discharge to Uncle Sam Gulch 

from the Crystal mine adit. For example, about 75 percent of 

the zinc load to Cataract Creek came from Uncle Sam Gulch 

(Kimball and others, this volume, Chapter D6). The relative importance of streambed sediment from High Ore Creek 

contrasted with the importance of surface-water loading from 

Cataract Creek highlights the fact that both water and sediment 

quality must be considered when the potential for biological 

effects in an ecosystem is evaluated.
Hazard Quotients Used to Assess Ecosystem Health 33

V ^ ^J-EWIS AND CLARK CO

' J

<u 

Si 

CJ

, ^1 BUCKEYE AND 

ENTERfRISE

Boulder River 

watershed 

study area \

T8IM

T7N

T6N

EXPLANATION

Distribution of trout 

| None 

H Uncertain 

| Westslope cutthroat

| Rainbow, eastern brook,

brown, or Yellowstone cutthroat

• No data

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

Biological sites

Fish abundance and health assessment 

96-hour survival experiment 

Inactive mine

1 2 KILO METERS

Figure 1. Estimated distribution of trout prior to large-scale remediation work in Boulder River watershed study area.
34 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Exposure Pathways

In biological studies. Farag and others (this volume) 

suggest that the accumulation of trace elements in tissues 

of benthic macroinvertebrates and fish in the Boulder River 

watershed occurs through two pathways and is associated with 

adverse effects on the overall health of the watershed. Accumulation of trace elements in fish tissue results from direct 

exposure through water and sediment and indirect exposure 

through dietary pathways. Thus, the exposure pathways to 

trout include biofilm, benthic macroinvertebrates, water, colloids, and sediment.

Streambed sediment and surface water provide major 

pathways for transport and distribution of contaminants 

through the watershed and for direct exposure of the biological community. Exposure of an organism is dependent on the 

concentration of the trace elements in both the water and sediment pathways. Accumulation of trace elements and resulting 

toxicological responses are determined by both concentration 

and duration of exposure. Chemical data for individual waterquality samples reflect an instantaneous measure of conditions 

at a single point in time. Trace-element concentrations in 

streams may vary widely depending on time of day, streamflow, ground-water inflow, and season. Trace-element concentrations in streambed sediment have less temporal variability 

than concentrations in water because streambed sediment 

integrates contaminant conditions over an extended period of 

time. This integration occurs because coatings on sediment 

grains, particles, and colloidal material sorb trace elements 

from the water column. This geochemical reaction reduces the 

dissolved trace-element concentrations in water and increases 

concentrations in streambed material.

Iron and aluminum colloids, defined as particles between 

0.001 and 0.45 um (micrometers) in size, are transported 

downstream suspended in the water column. Because the 

association of colloids and trace elements is dynamic, trace 

elements may sorb and desorb frequently during downstream 

transport. These colloids may be trapped by biofilm on rock 

surfaces and may accumulate trace elements when they 

become available. Both colloids and biofilm (also referred to 

as aufwuchs) appear to play an important role in the movement of trace elements through the food chain. Farag and 

others (this volume) observed significant correlation between 

concentrations of arsenic, copper, lead, and zinc in colloids 

and biofilm, which indicates a possible relation between trace 

elements in the two components.

These exposure pathways are important in the Boulder 

River watershed because they provide multiple encounters 

between aquatic life and elevated concentrations of trace elements. As a result of these exposures, survival of trout may be 

limited in parts of the Basin and Cataract Creek basins and in 

High Ore Creek downstream from the Comet mine. Furthermore, the number of trout present and the health of individual 

fish are also affected in lower Cataract Creek.

Ranking Stream Reaches Using 

Hazard Quotients

Assessment of environmental hazards from trace-element 

exposure can be definitively accomplished by direct measurement of biological effects. To measure biological effects at 

all points in a stream system is usually impractical; therefore, 

ecological risk assessment methods have been developed to 

estimate environmental hazards associated with contaminant 

exposure. One of the basic strategies used to perform these 

types of assessments is to compare the environmental concentration of trace elements with a measured biological effect or 

no-effect level. Thus, estimates of trace-element concentrations in water or sediment may be compared to results from 

toxicological criteria, regulatory standards and guidelines, or 

individual threshold values that encompass the concentrationresponse relationship between a trace element and an organism. This is known as the quotient approach to hazard assessment (Urban and Cook, 1986). If the environmental 

concentration of a contaminant in an aquatic ecosystem 

exceeds an effect concentration, then a hazard exists. Similarly, if the environmental concentration is far below the 

no-effect level, then one may assume the hazard is minimal or 

not a threat.

Potential hazards in the Boulder River watershed were 

determined by use of hazard quotients to compare relative 

risks among reaches. For the assessment, we calculated hazard 

quotients (HQ) for individual trace elements in water or sediment by dividing the trace-element concentration for an environmental sample either by the U.S. Environmental Protection 

Agency (USEPA) chronic water quality criteria or by the 

sediment guideline for probable-effects concentration. If the 

HQ < 0.1, no adverse effect is expected. If 0.1 < HQ < 1, the 

hazard is low, but potential for adverse effects should be considered; and if 1.0 > HQ < 10, some adverse effect or moderate hazard is probable. If HQ > 10, high hazard is anticipated.

Hazard quotients were developed for water and streambed 

sediment from the Boulder River watershed study area. Based 

on the analysis of exposure pathways presented by Farag and 

others (this volume) and summarized in the preceding section, 

cadmium, copper, and zinc were the key metals that appear to 

cause toxicity in the watershed. In addition, arsenic and lead 

were measured in fish tissues and may contribute to hazards 

present in the watershed. For example, arsenic may contribute 

to morphological changes observed in skin of fish held in High 

Ore Creek (Farag and others, this volume).

Because water and streambed sediment were collected 

over a multi-year period during various hydrologic and geochemical conditions in the study area, we chose a subset of the 

data representing conditions most toxic to aquatic life for calculation of hazard quotients. These conditions coincide with 

low flow, which occurs from late summer through early spring 

(Church, Nimick, and others, this volume, Chapter B). In 

addition, only data collected prior to large-scale remediation 

efforts (which began in 1997 in the watershed) were selected.
Hazard Quotients Used to Assess Ecosystem Health 35

We constructed ribbon maps to depict individual hazard 

quotients for cadmium, copper, and zinc in water (figs. 2-4) 

and for cadmium, copper, lead, and zinc streambed sediment 

(figs. 6-9). Streams were color-coded upstream and downstream 

from the sample sites with calculated hazard quotients. The 

color codes were based on our knowledge of metal sources, 

metal attenuation, and expected dilution effects of tributaries. 

Because so many hazard quotients exceeded a value of 1 for 

the Boulder River watershed, the HQ interval between 1 and 10 

was divided into three categories to facilitate ranking of reaches. 

Note that the multiple colors, and hence, multiple intervals, were 

not chosen for biological relevance (that is, hazard quotients 

greater than 1 generally indicate that hazards may exist for 

biota), but were chosen to delineate reaches where restoration 

might provide the most significant benefits.

Hazard quotients are most useful in determination of either 

high or low risks and for relative comparisons of the potential 

for adverse effects among stream reaches. Hazard quotients 

estimate the hazard associated with individual rather than multiple trace elements and therefore do not account for additive, 

antagonistic, or synergistic interactions commonly associated 

with chemical mixtures. Hazard quotients based on measurements of environmental concentrations and measured biological 

effect or no-effect levels should not be used to evaluate hazards 

associated with elements that biomagnify such as selenium and 

mercury.

To address the issue of interactions of multiple contaminants in an aquatic system, Sprague and Ramsey (1965) suggested that the strength of a contaminant could be expressed as 

a fraction of its lethal concentration using a ratio identical to 

that now used in calculating hazard quotients. They referred to 

these values as toxic units. Sprague (1970) further suggested that 

the toxic unit for each element in a mixture could be calculated 

and these values summed to estimate the overall toxicity of the 

mixture. This approach assumes that elements exhibit the same 

modes of action and that the toxicity of mixtures is strictly additive. Nonetheless, it provides a reasonable and now commonly 

used approach for evaluating mixture toxicity. Furthermore, a 

compilation of results for 76 studies that assessed the toxicity 

of mixtures including elements such as copper, zinc, cadmium, 

mercury, nickel, and chromium demonstrated that the toxic unit 

approach closely approximated the toxicity of the mixture in 

87 percent of the cases. Lloyd (1982) concluded that although 

antagonistic and synergistic interactions definitely occur, the 

joint action of toxic mixtures of common trace elements is likely 

to be additive.

We constructed maps that show the summation of hazard 

quotients by site in an effort to exhibit the potential hazard from 

a combination of trace elements in water or sediment. These 

maps summed the individual hazard quotients for cadmium, 

copper, and zinc in water (fig. 5) and in sediment (fig. 10). It 

should be noted that the sum of the hazard quotients in many 

places was greater than 30 in water (fig. 5). Therefore, the color 

designations in the mixture hazard quotient maps reflect greater 

hazard quotients than those depicted in the maps for individual 

trace elements.

Water

For water, aquatic-life water-quality criteria established 

by the USEPA (1999, 2001) are suitable criteria for the "no 

adverse effect" concentration used in the denominator of the 

hazard quotient formula. These criteria are an estimate of the 

concentration of a trace element in surface water to which an 

aquatic community can be exposed briefly (acute criteria) or 

indefinitely (chronic criteria) without experiencing an adverse 

effect. Chronic criteria, which are determined from controlled 

laboratory experiments with a number of freshwater species, 

were used to calculate hazard quotients. Thus, a hazard quotient calculated using the chronic criteria (HQC) provides an 

assessment of potential chronic toxicity incorporating effects 

such as impairment of growth and reproductive success. These 

are the types of effects that likely occurred at sites such as 

lower Cataract Creek (Farag and others, this volume). Hazard 

quotients calculated with acute criteria revealed a pattern of 

degraded reaches similar to those identified by the HQC values. 

As a result, the hazard quotients computed using acute criteria 

are not presented.

We calculated the HQC for waterborne elemental concentrations using the ratio of the environmental concentration in a 

filtered (0.45-|Lim) water sample to the USEPA chronic waterquality criterion.

HQC = Elemental Concentration / USEPA Chronic 

Water-Quality Criterion (1)

Chronic aquatic-life water-quality criteria (table 1) 

were calculated as defined by U.S. Environmental Protection 

Agency (USEPA, 1999, 2001). The criteria are dependent on 

hardness (as mg/L CaCO3 ), which was calculated from measured concentrations of dissolved calcium and magnesium (in 

mg/L) using the following equation:

Hardness = ((Ca/40.08)+(Mg/24.31))*100 (2)

A single sample collected during low flow, which 

would represent the most toxic conditions to aquatic life, was 

selected for each water-quality sampling site. Approximately 

50 percent of the sites in the watershed were sampled in 

September 1997, and these data were used in the HQC calculations. For the sites not sampled during September 1997, data 

from a sample collected during September or October in 1996, 

1998, or 2000 were used, because streamflow conditions were 

similar to the September 1997 flows. However, only October 

1996 data were used for High Ore Creek and the Boulder 

River downstream of High Ore Creek, because remediation 

had started in the High Ore Creek basin in September 1997. 

Maps showing hazard quotients for cadmium, copper, and zinc 

in water are in figures 2-4, and the sum of the three calculated 

hazard quotient values is in figure 5.
36 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 1. Chronic aquatic-life water-quality criteria for cadmium, copper, and zinc. 1

Cadmium:

Cdchronic = (e (07852[ln(hardness«- 2715)) * [(1.101672-ln(hardness) * (0.041833)]

Copper:

CU = (C (°- 8545nn(hardness)]-1.702)\ * Q 

^ ^

Zinc:

Zn = (e (°- 8473 [ln(hardness)]=°-884> 1) * Q

chronic ^ ' «.

'U.S. Environmental Protection Agency (USEPA, 1999, 2001).

Streambed Sediment

For streambed sediment, the probable-effect concentration was used in the denominator of the hazard quotient formula. The probable-effect concentration is the concentration 

of a trace element above which harmful effects on sedimentdwelling organisms are expected to occur frequently (MacDonald and others, 2000). These consensus-based concentrations are reliable and predictive of sediment toxicity based on 

evaluation of samples on both a national and a regional basis.

We calculated the HQS for sediment elemental concentrations using the ratio of the environmental concentration 

in a total digest of a sediment sample to the probable-effect 

concentration.

HQS = Total Elemental Concentration / Probable Effects

Concentration (3)

The consensus-based probable-effect concentrations 

used in calculating these quotients were 4.98 ug/g cadmium, 

149 ug/g copper, 128 ug/g lead, and 459 ug/g zinc (MacDonald and others, 2000). Maps showing the hazard quotients 

for cadmium, copper, lead, and zinc in sediment are in 

figures 6-9, and the sum of the calculated hazard-quotient values for cadmium, copper, and zinc in sediment is in figure 10.

As was observed for water, the concentrations of trace 

elements in sediment were generally higher during low-flow 

than during high-flow conditions. These higher concentrations 

likely occur during the fall each year, so the 1996 data were 

used for environmental concentrations. Some sites were not 

sampled in 1996, and for these sites, 1997 or 1998 data were 

used. Streambed-sediment samples were analyzed for leachable and total trace-element concentrations; the total concentrations were used to calculate hazard quotients.

Comparisons of Hazard Quotients and 

Biological Effects

The hazard-quotient maps indicate that areas of potential 

hazard to biota exist in Basin Creek, Cataract Creek, and High

Ore Creek, the three main tributaries in the Boulder River 

watershed. Both chronic water and sediment hazard quotients 

show that the hazard potential is most widespread and extreme 

in Uncle Sam Gulch, lower Cataract Creek, and High Ore 

Creek.

The combined hazard quotients for chronic effects of 

surface water indicate highest concern for adverse effects on 

the biological community to be in Uncle Sam Gulch, Cataract 

Creek downstream from Uncle Sam Gulch, the Bullion Mine 

tributary, Jack Creek downstream from the Bullion Mine 

tributary, High Ore Creek downstream from the Comet mine, 

and, to a slightly lesser extent, lower High Ore Creek. The 

individual chronic hazard quotients are greater than 10 for 

cadmium, copper, and zinc in water in sections of Jack Creek, 

the Bullion Mine tributary, and Uncle Sam Gulch, and for cadmium and zinc in High Ore Creek downstream of the Comet 

mine (figs. 2-4}. Therefore, high hazard is anticipated in these 

reaches based on the concentrations of just one of these trace 

elements. As a result, these areas have combined chronic hazard quotients greater than 30, except lower High Ore Creek, 

which is 21-30 (fig. 5).

Chronic effects encompass nonlethal biological responses 

including reduced growth, reproductive impairment or failure, behavioral changes, or physiological malfunction. Any 

of these would result in reduced health at the individual or 

population level. In fact, fish health and biomass/density estimates (Farag and others, this volume) confirm that individual 

fish health and biomass/density were compromised at lower 

Cataract Creek. This is the same area that hazard quotients calculated with chronic water-quality criteria define as a potential 

high hazard for aquatic biota.

Comparisons of acute water-quality criteria to environmental concentrations in water demonstrate the same pattern 

of potential hazards as the chronic water-quality criteria (maps 

of hazard quotients calculated using acute criteria not presented). Acute criteria (and hazard quotients based on them) 

imply that significant mortality will result if aquatic life is 

exposed to water at sites in the Boulder River watershed just 

listed. These findings of potential hazard related to mortality agree with survival experiments performed by Farag and 

others (this volume). Westslope cutthroat trout held in Uncle 

Sam Gulch, Cataract Creek downstream from Uncle Sam
Hazard Quotients Used to Assess Ecosystem Health 37

112022'30" 11215'

JEFFERSON CO

^/ BUCKEY -AND 

ENTERPi '/S£

Three

Brothers

BEAVERHEAD-DEERLODGI 

NATIONAL FOREST

iAWKEYE

DIAMONDOCCIDENTAL

Boulder River 

watershed 

study area \

T8N

T7N

T6N

\

5^C~" Cardwelli) }

EXPLANATION

Hazard quotient

• >10

• 7-10

• 4-7 

D 1-4

R5W

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

R4W 

2 MILES

1 2 KILOMETERS

40 V Sample site 

v\ Inactive mine

Figure 2. Cadmium chronic hazard quotients for water.
38 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Boulder River 

watershed 

study area \

T8N

T7N

T6N

&

EXPLANATION 

Hazard quotient 

• > 10 

EJ 7-10 

El 4-7

n 1-4

R5W

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

R4W 

2 MILES

2 KILOMETERS

41 V Sample site 

$£ Inactive mine

Figure 3. Copper chronic hazard quotients for water.
Hazard Quotients Used to Assess Ecosystem Health 39

LEWIS AND CLARK CO

JEFFERSON CO 

BUCKEYE AND

BEAVERHEAD-DEERLODG 

NATIONAL FOREST

BLUE 

DIAMONDOCCIDENTAL

CRYSTAL!TM BLACK

BEAR

IDAM.

BOULDER 

CHIEF

BOUNDARY

Boulder River 

watershed 

study area \

Boulder River )

T8N

T7N

T6N

EXPLANATION 

Hazard quotient

• >10

• 7-10

• 4-7 

H 1-4

Base from U.S. Geological Survey 0 

digital line graphs, 1:100,000

0 1 2 KILOMETERS

46 V Sample site 

tt Inactive mine

Figure 4. Zinc chronic hazard quotients for water.
40 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112022'30"

Boulder River 

watershed 

study area \

T8N

T7N

T6N

EXPLANATION

Hazard quotient

• >30 4.0 Y Sample site 

E 21-30 f.

• 12-21 . 

CH 3-12

Inactive mine 

Mill site

Base from U.S. Geological Survey 0 

digital line graphs, 1:100,000

0 1 2 KILOMETERS

Figure 5. Estimated risk based on sum of chronic hazard quotients for water for cadmium, copper, and zinc. Mill site immediately 

upstream from confluence of Basin Creek with Boulder River shown for reference.
Hazard Quotients Used to Assess Ecosystem Health 41

112022'30"

Boulder River 

watershed 

study area \

T8N

T7N

T6N

EXPLANATION 

Hazard quotient

• > 10 

CD 7-10

• 4-7

n 1-4

K Inactive mine

R5W

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

R4W 

2 MILES

I————i——t—r0 1 2 KILOMETERS

Figure 6. Cadmium hazard quotients for streambed sediment.
42 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Boulder River 

watershed 

study area \

T8N

T7N

T6N

EXPLANATION

Hazard quotient

•• > 10 

I 7-10 

D 4-7

EH 1-4

^ Inactive mine

R5W

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

R4W 

2 MILES

I————i——"—r0 1 2 KILOMETERS

Figure 7. Copper hazard quotients for streambed sediment.
Hazard Quotients Used to Assess Ecosystem Health 43

112°22'30"

V .LEWIS AND CLARK CO

Boulder River 

watershed 

study area \

T8N

T7N

T6N

EXPLANATION 

Hazard quotient

• > 10

• 7-10

• 4-7 

d 1-4

R5W

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

R4W 

2 MILES

0 1 2 KILOMETERS

vv Inactive mine

Figure 8. Lead hazard quotients for streambed sediment.
44 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

11202Z3ff 1

Boulder River 

watershed 

study area \

T8N

T7N

T6N

EXPLANATION

Hazard quotient

• 7-10

• 4-7

n 1-4 

• <i

•% Inactive mine

R5W

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

R4W 

2 MILES

I————i——"-i

0 1 2 KILOMETERS

Figure 9. Zinc hazard quotients for streambed sediment.
Hazard Quotients Used to Assess Ecosystem Health 45

112°22'3011 1120 15'

Boulder River 

watershed 

study area \

T8N

T7N

T6N

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

0 1 2 KILOMETERS

EXPLANATION

Hazard quotient

• >30 

r~l 21-30

• 12-21 

CH 3-12

• <3

tt Inactive mine

• Mill site

Figure 10 . Estimated risk based on sum of hazard quotients for streambed sediment for cadmium, copper, and zinc. Mill site 

immediately upstream from confluence of Basin Creek with Boulder River shown for reference.
46 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Gulch (but not as far downstream as lower Cataract Creek), 

the Bullion Mine tributary, Jack Creek downstream from the 

Bullion Mine tributary, High Ore Creek downstream from the 

Comet mine, and lower High Ore Creek experienced extensive 

mortality in the 96-hr survival experiments (Farag and others, 

this volume).

If the chronic and acute water-quality standards provide 

the same pattern of potential hazard in the Boulder River 

watershed, then why do we see any fish in lower Cataract 

Creek? If trace-element concentrations at this site exceed the 

acute water-quality criteria, would it not be rendered completely uninhabitable by fish? Two explanations exist for this 

contradiction. First, the acute criteria were established for multiple species of aquatic life and focus on the survival of larval 

and swim-up stages that are generally believed to be the most 

sensitive to contaminant exposure. Adult fish were observed 

and collected in lower Cataract Creek. It is possible that early 

life-stage fish would not survive at this site.

Second, acclimation and avoidance behavior may explain 

the presence of fish in lower Cataract Creek whereas they 

were not observed immediately downstream from Uncle Sam 

Gulch. Farag and others (this volume) discuss the likelihood 

that fish collected in lower Cataract Creek have acclimated 

to metals in the water at that site. Additionally, the authors 

document that the cost of this acclimation may be exhibited by 

reduced biomass/density and physiological changes interpreted in a decline in overall fish health.

Furthermore, anecdotal observations during the in-place 

96-hr survival experiments provide evidence that an avoidance response occurs in sections of Cataract Creek. During the 

experiments, trout were observed in Cataract Creek upstream 

from Uncle Sam Gulch. These trout fed in a riffle located 

near the confluence and moved quickly back upstream if they 

were carried below the confluence. Several dead trout were 

also found downstream from the confluence with Uncle Sam 

Gulch. These observations are anecdotal and do not prove 

behavioral avoidance in this section of the stream, but they 

suggest the relevance of avoidance behavior in this area. It is 

possible that some fish in lower Cataract Creek overcame the 

avoidance response to respond to more immediate stressors 

such as the need for food (though amounts available may be 

less than at other sites with lesser concentrations of metals) 

and a lack of competition from other fish at that site.

Hazard-quotient maps for sediment (figs. 6-9) point to 

the same general areas of potential hazard as do the maps 

for water. Combined hazard quotients for sediment (fig. 10) 

indicate that the areas of highest concern for adverse effects on 

the biological community were in Uncle Sam Gulch and High 

Ore Creek downstream from the Comet mine, and to a lesser 

extent, High Ore Creek downstream from Peters Gulch. Additional areas of concern were Jack Creek downstream from an 

unnamed tributary draining the Jack Mountain area (figs. 9 

and 10), Cataract Creek downstream from Uncle Sam Gulch, 

and High Ore Creek between Bishop Creek and Peters Gulch. 

For each of these reaches, one or more of the hazard quotients 

for cadmium, copper, lead, or zinc exceeded 10. In the case of

High Ore Creek downstream from the Comet mine, the hazard 

quotient exceeded 10 for all four of these trace elements.

Although the hazard quotients calculated from the sediment data point to the same general areas of concern as those 

calculated from the water, the hazard quotients calculated from 

the sediment data for Jack Creek and the Bullion Mine tributary (hazard quotients are 3-21 with sediment data, fig. 10) 

were not as large as those calculated from water-quality data 

(hazard quotients > 30 with water data, fig. 5). Such differences may be attributed to the lower pH of surface water in the 

Bullion Mine tributary. If the pH of the water is slightly acidic, 

cadmium, copper, and zinc, but not lead and arsenic, remain in 

the water column rather than sorb onto colloidal particles. The 

pH of water in the Bullion Mine tributary was measured as 

low as 5.2 in August 1999 (Nimick and Cleasby, 2000). Therefore, the low pH of water at a site lowers the hazard quotients 

slightly in sediment versus water.

Evaluation of the ecological health of a stream is commonly based on the condition of its fisheries resources because 

fish represent the top of the food chain in streams and are considered an important resource to land managers and the public. 

Ecological health of a system is dependent on the chemical 

and physical conditions in the habitat. If hazard quotients are 

good estimators of ecological health, then biological conditions of individuals, populations, and communities should 

reflect interpretations similar to those derived from these 

simple ratio estimators.

The impaired health of the fish community in lower 

Cataract Creek corresponded to adverse effects suggested by 

the hazard quotient method of ranking. The HQC values for 

water suggested extreme hazard for aquatic life in Jack Creek, 

Bullion Mine tributary, Uncle Sam Gulch, and High Ore Creek 

downstream from the Comet mine. Fish survival was poor 

during 96-hr survival in-place experiments performed at these 

sites (Farag and others, this volume). These reaches should 

pose the most immediate concern for land managers. Also, the 

hazard quotients and the survival data may provide explanations about the presence or absence of fish species throughout 

the Boulder River watershed (fig. 1). Fish were not present in 

the Bullion Mine tributary, Uncle Sam Gulch, Cataract Creek 

downstream from Uncle Sam Gulch, and High Ore Creek 

downstream from the Comet mine. The combined hazard quotients for water agree with the 96-hr survival experiments and 

point to these reaches as areas of potential high hazard. Except 

for the Bullion Mine tributary and Jack Creek (as discussed 

previously), the sediment hazard quotients also indicate these 

as areas of potential high hazard. Therefore, biology measurements and hazard quotients calculated with water-quality 

criteria and sediment probable-effects concentrations provide a 

complete picture of the probable hazards that exist in the Boulder River watershed.

Furthermore, biomass of all species of trout was the 

smallest at the lower Cataract Creek site. The reduced fish 

population biomass and density cannot be explained by habitat 

differences alone (Farag and others, this volume). In addition, 

concentrations of most trace elements in the livers, gills, and
Hazard Quotients Used to Assess Ecosystem Health 47

whole-fish tissue of resident rainbow trout were the greatest 

in fish from the lower Cataract Creek site. The impairment 

of physiological function was also most pronounced in the 

rainbow trout from lower Cataract Creek. Similar effects on 

population biomass and density, tissue contamination, and 

physiological impairment were not detected at the lower Basin 

Creek site, nor did the quotient ranking indicate that they 

would occur. In addition, using total Ephemeroptera (mayflies), Plecoptera (stoneflies), and Tricoptera (caddis flies) taxa 

as indicators of macroinvertebrate health, Boyle and Gustina 

(2000) showed that macroinvertebrate communities in High 

Ore Creek, Jack Creek downstream from the Bullion Mine 

tributary, and Cataract Creek were the three sites most affected 

by historical mining in the Boulder River watershed.

Elevated trace-element concentrations were also measured in fish from lower Basin Creek and the Boulder River 

downstream from Galena Gulch (Farag and others, this 

volume). However, physiological changes and changes in 

biomass and density were not significant at those two sites. 

Therefore, the biological data suggest that these may be areas 

land-use managers should continue to monitor, but as shown 

by the hazard quotient for water and sediment, trace-element 

concentrations in these two areas do not represent the level 

of hazard noted in lower Cataract Creek. Some sections of 

the Boulder River have combined hazard quotients from 3 to 

12 for water and sediment (figs. 5 and 10), which suggests 

that some moderate hazard is possible in both lower Basin 

Creek and the Boulder River downstream from the mill site 

immediately upstream from Basin Creek. The combined 

ranking of information for both chronic water-quality criteria 

and sediment probable-effects concentrations identified the 

six most biologically impaired sites: Bullion Mine tributary, 

Jack Creek, Uncle Sam Gulch, Cataract Creek downstream 

from Uncle Sam Gulch, High Ore Creek downstream from 

the Comet mine, and lower High Ore Creek (table 2). These 

sites, where acute effects on organism survival are anticipated,

overlapped with sites where a high potential for chronic effects 

was estimated. We surmise that remediation efforts, including 

removal of mine wastes located on valley floors and reduction 

of trace-element loading from draining adits, of inactive mine 

sites in the basins draining to these six reaches will result in 

substantial improvement of ecological conditions in the watershed. Additionally, restoration efforts in the Cataract Creek 

basin are most likely to positively affect fish biomass, density, 

and individual health in lower Cataract Creek.

Summary

Hazard quotients calculated with chronic water-quality 

criteria and with sediment probable-effects concentrations 

generally agreed with measurements of biology to designate 

the primary areas of potential hazard in the Boulder River 

watershed (table 2). The sites where potential for high hazards 

to aquatic life exists included the Bullion Mine tributary, Jack 

Creek, Uncle Sam Gulch, Cataract Creek downstream from 

Uncle Sam Gulch, lower Cataract Creek (upstream from the 

Boulder River), High Ore Creek downstream from the Comet 

mine, and lower High Ore Creek (upstream from the Boulder 

River). Fish were absent from all of these sites except lower 

Cataract Creek, and poor survival during 96-hr survival experiments suggested that trout would be unable to survive in these 

locations. Adult fish were present in lower Cataract Creek, 

but the biomass, density, and individual health of trout were 

affected, which suggests that chronic effects on the fishery in 

Cataract Creek exist.

The only exception to the agreement between hazard quotients for water and sediment was in the Bullion Mine tributary and Jack Creek, where the lower pH of the water in the 

Bullion Mine tributary reduced the ability of trace elements 

to sorb to colloidal material in the sediment. Therefore, it is

Table 2. Comparisons of biological assessment endpoints with estimated risk based on hazard quotients.

[Hazard quotients calculated using chronic water-quality criteria (HQC) and sediment probable-effects concentrations (HQS). Endpoints not 

assessed are labeled N/AJ

Site

Uncle Sam Gulch

Cataract Creek downstream

from Uncle Sam Gulch.

High Ore Creek downstream

• from Comet mine.

Lower High Ore Creek

Lower Cataract Creek

Bullion Mine tributary

Jack Creek

Upper Basin Creek

Lower Basin Creek

Boulder River

HQC

High

High

High

High

High

High

High

Low

Low

Low

HQS

High

High

High

High

High

Low

Low

Low

Low

Low

Resident 

fish

Absent

Absent

Absent

Absent

Present

Absent

Absent

Present

Present

Present

Resident 

biomass/density 

effects

N/A

N/A

N/A

N/A

Yes

Yes

N/A

N/A

No

No

Resident 

fish health 

effects

N/A

N/A

N/A

N/A

Yes

N/A

N/A

N/A

No

No

Individual 

survival effects 

(96-hr tests)

Yes

Yes

Yes

^1

Yes ^

N/A

Yes

Yes

N/A

N/A

N/A
48 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

critical that pH be monitored to interpret water and sediment 

chemistry.

As a result of hazard-quotient analyses, we estimate that 

remediation could result in substantial improvement of ecological conditions in the Boulder River watershed study area. 

These efforts could include removal of mine wastes located 

on the valley floors of these basins and reduction of trace-element loading from draining adits of the major inactive mine 

sites in the basins upstream from the primary areas of potential 

hazard. With remediation, the likelihood that aquatic life will 

survive at sites where survival was minimal during 96-hr survival experiments will be improved. Additionally, remediation 

efforts in the Cataract Creek basin are most likely to positively 

affect fish biomass/density and individual health in lower 

Cataract Creek.

References Cited

Boyle, T.P., and Gustina, G.W., 2000, A strategy for use of 

multivariate methods of analysis of benthic macroinvertebrate communities to assess mine-related ecological stress, 

in ICARD 2000; Proceedings of the Fifth International 

Conference on Acid Rock Drainage, Volume 2: Society for 

Mining, Metallurgy, and Exploration, Inc.. p. 1425-1431.

Linder, Greg, Callahan, Clarence, and Pascoe, Gary, 1993, 

A strategy for ecological risk assessments for Superfund: 

Biological methods for evaluating soil contamination, in 

Hoddinott, K.B., ed., Superfund risk assessment in soil 

contamination studies: Philadelphia, Pa., American Society 

for Testing and Materials, ASTM STP 1158, p. 288-308.

Lloyd, R., 1982, The toxicity of mixtures of chemical to 

fish—An overview of European laboratory and field experience, in Bergman, H.L., Kimerle, R.A., and Maki, A.W., 

eds., Environmental hazard assessment of effluents: New 

York, John Wiley, 265 p.

MacDonald, D.D., Ingersoll, C.G., and Berger, T.A., 2000, 

Development and evaluation of consensus-based sediment 

quality guidelines for freshwater ecosystems: Archives of 

Environmental Contamination and Toxicology, v. 39, 

p. 20-31.

Nimick, D.A., and Cleasby, T.E., 2000, Water-quality data for 

streams in the Boulder River watershed, Jefferson County, 

Montana: U.S. Geological Survey Open-File Report 00-99, 

70 p.

Rand, G.M., and Petrocelli, S.R., 1985, Fundamentals of 

aquatic toxicology: New York, Hemisphere Publishing 

Corporation, 666 p.

Sprague, J.B., 1970. Measurement of pollutant toxicity to 

fish—II, Utilizing and applying bioassay results: Water 

Research, v. 4, p. 3-32.

Sprague, J.B., and Ramsey, B.A., 1965, Lethal levels of 

mixed copper-zinc solutions for juvenile salmon: Journal of 

Fisheries Research Board of Canada, v. 22, p. 425-^32.

Urban, D.L., and Cook, N.J., 1986, Hazard evaluation, Standard evaluation procedure, Ecological risk assessment: 

Washington, D.C., U.S. Environmental Protection Agency, 

EPA540-9-85-001.

U.S. Environmental Protection Agency (USEPA), 1992, 

Evaluation of terrestrial indicators for use in ecological 

assessments at hazardous waste sites. Corvallis, Oregon, 

U.S. Environmental Protection Agency, 600/R-92/183.

U.S. Environmental Protection Agency (USEPA), 1999, 

National recommended water quality criteria—Correction: 

Washington, D.C., Office of Water, EPA822-R-01-001, 

35 p.

U.S. Environmental Protection Agency (USEPA), 2001, 

Update of ambient water quality criteria for cadmium: 

Washington, D.C., Office of Water, EPA 822-R-01-001, 

35 p.
Geologic Framework

By J. Michael O'Neill, Karen Lund, Bradley S. Van Gosen, George A. Desborough, 

Tracy C. Sole, and Ed H. DeWitt

Chapter D1 of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-D1

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract........................................................................................................................................................ 53

Introduction................................................................................................................................................. 53

Previous Work.................................................................................................................................... 53

Setting .......................................................................................................................................................... 55

Regional Tectonic Setting................................................................................................................. 55

Contacts with Adjacent Rocks........................................................................................................ 57

Mode of Emplacement...................................................................................................................... 57

Tertiary Extensional Structures....................................................................................................... 58

Igneous Rocks............................................................................................................................................. 58

Upper Cretaceous Elkhorn Mountains Volcanics........................................................................ 58

Lower Member.......................................................................................................................... 59

Middle Member......................................................................................................................... 59

Upper Member.......................................................................................................................... 59

Chemical Composition.............................................................................................................59

Metamorphism..........................................................................................................................60

Ages ........................................................................................................................................63

Late Cretaceous Butte Pluton of the Boulder Batholith..............................................................63

Medium-to Coarse-Grained Phase....................................................................................... 63

Fine-Grained Porphyritic Phase.............................................................................................64

Aplite and Porphyry.................................................................................................................. 65

Chemical Composition.............................................................................................................65

Ages ........................................................................................................................................ 66

Relationship Between Late Cretaceous-Age Volcanic and Plutonic Rocks............................ 67

Comparison of Geochemical Data......................................................................................... 67

Emplacement History...............................................................................................................67

Internal Geometry of Butte Pluton......................................................................................... 67

Tertiary Volcanic Rocks.................................................................................................................... 67

Eocene Lowland Creek Volcanics.......................................................................................... 68

Eocene-Oligocene Helena Volcanic Rocks.......................................................................... 68

Miocene-Pliocene Volcanic Rocks........................................................................................68

Sedimentary Rocks.....................................................................................................................................69

Lower Tertiary Sedimentary Rocks................................................................................................. 69

Quaternary Deposits.........................................................................................................................71

Structural Geology and Tectonics............................................................................................................72

Introduction........................................................................................................................................ 72

Nondiastrophic Fracture Systems..................................................................................................73

Synemplacement Diastrophic Fracture Systems......................................................................... 75

Late Diastrophic Structures............................................................................................................. 78

Lineaments................................................................................................................................. 78

Dikes ........................................................................................................................................ 78

Faults ........................................................................................................................................ 78

Mineral Deposits......................................................................................................................................... 78
Late Cretaceous Mineralized Rock.................................................................................................79

Controlling Structures.............................................................................................................. 79

Polymetallic Quartz Veins........................................................................................................ 79

Alteration Envelopes................................................................................................................80

Origin of Mineralizing Fluids................................................................................................... 81

Comparison to Other Veins in the Butte Pluton ................................................................... 81

Age ........................................................................................................................................ 81

Tertiary Mineralization...................................................................................................................... 82

Lowland Creek Volcanics Mineralization............................................................................. 82

Helena Volcanic Rocks Mineralization ................................................................................. 82

Pervasive Alteration Systems.......................................................................................................... 82

Gold Placer Deposits.........................................................................................................................83

Tin Placer Deposits ........................................................................................................................... 83

Acid-Neutralizing Potential of Bedrock.................................................................................................. 83

Summary...................................................................................................................................................... 84

References Cited........................................................................................................................................ 85

Plates

[Plates in this report are on accompanying CD-ROM]

1. Geologic map of the Boulder watershed study area and vicinity, Powell, 

Jefferson, and Lewis and Clark Counties, Montana

2. Fence diagram showing correlation of Quaternary deposits in Buckeye 

Meadow, Basin Creek drainage, Jefferson County, Montana

Figures

1. Index map to area described in this report........................................................................... 54

2. Tectonic map of the Boulder batholith area showing major plutonic units and faults.. 56

3. Regional cross section showing interpreted relationship of main mass of Butte

pluton to faults ........................................................................................................................... 57

4. Classification diagram of samples of the Elkhorn Mountains Volcanics in the study 

area based on the R,R2-diagram of De La Roche and others (1980)................................. 60

5. Marker variation diagrams showing abundances of major oxides versus Si02 for

samples of the Elkhorn Mountains Volcanics....................................................................... 61

6. Marker variation diagrams showing abundances of major oxides versus Si02 for

samples of Butte pluton............................................................................................................ 62

7. Ternary diagram showing modes of rocks of Butte pluton in the study area.................. 64

8. Classification diagram of Butte pluton samples from the study area based

on the R^-diagram of De La Roche and others (1980)...................................................... 66

9. Classification diagram of samples of Eocene Lowland Creek Volcanics and of 

Eocene-Oligocene volcanic rocks from the Helena volcanic field in the study 

area based on the R^-diagram of De La Roche and others (1980)................................. 69
10. Marker variation diagrams showing abundances of major oxides versus Si02 for 

samples of Eocene Lowland Creek Volcanics and of Eocene-Oligocene 

volcanic rocks from the Helena volcanic field in the study area...................................... 70

11. Photograph showing prominent fracture systems in Butte pluton................................... 72

12. Contour diagram of joints in Butte pluton rocks from west half of the area

of plate 1...................................................................................................................................... 73

13. Diagrams of joints, dikes, veins, faults, and lineaments in the northern Elkhorn

Mountains east of the area of plate 1.................................................................................... 74

14. Diagram showing principal stress trajectories and net change in temperature in

the model system at 0,35,000, and 150,000 years after pluton emplacement................. 75

15. Rose diagrams showing trends of dikes, veins, shear zones, and nonmineralized

faults in the east half of the area of plate 1........................................................................... 76

16. Schematic diagram showing relationship of deep-seated fault zones to

synemplacement diastrophic fractures in the Butte pluton............................................... 77

17. Variation diagram showing relationship of selected metal oxides in Butte

pluton wallrocks and in alteration zones from two mines near the study area.............. 80

Tables

1. Acid-neutralizing potential for three samples of plutonic rocks with different 

calcite concentration and different concentrations of mafic minerals, and total 

acid-neutralizing potential.......................................................................................................84
Chapter D1 

Geologic Framework

By J. Michael O'Neill, Karen Lund, Bradley S. Van Gosen, George A. Desborough, Tracy C. Sole, 

and Ed H. DeWitt

Abstract

The Boulder River watershed study area is underlain by 

the Late Cretaceous Butte pluton of the Boulder batholith. The 

elongate, northeast-trending batholith is interpreted to have 

been emplaced in a slowly opening pull-apart along strike-slip 

faults that were active during tectonic development of the 

Cordilleran overthrust belt. Batholithic emplacement was 

accompanied by voluminous cogenetic volcanism; these volcanic rocks formed the roof of the intrusive complex and are 

now preserved as roof pendants within the study area. Subsequent erosion has exposed only the upper few thousand 

feet of the batholith, which is interpreted to be as much as 

10 miles thick. The exposed, upper part of the batholith is 

cut by two well-developed fracture systems. Fractures that 

developed during emplacement of the batholith are widely 

spaced and through-going; they are related to the dynamics of 

the pull-apart mechanism of pluton emplacement. These synemplacement fractures were commonly filled with late-stage 

magmatic fluids that crystallized to form aplitic to pegmatitic 

dikes commonly associated with thin polymetallic quartz 

veins. The second set of fractures appear to be related to cooling of the batholithic mass; they are unmineralized, closely 

spaced, and restricted to the outer margins of the batholith. 

The cooling fractures greatly influence near-surface groundwater flow in the study area.

The Butte pluton in the study area contains numerous 

polymetallic quartz-vein deposits as well as well-developed 

cooling fracture systems. Inactive mines and prospects in 

the watershed are located along widely spaced polymetallic 

quartz veins. Geochemical studies of plutonic rocks that host 

the polymetallic quartz-vein deposits have shown that iron- or 

magnesium-bearing minerals, an integral part of the mineralogic composition of the Butte pluton, are capable of neutralizing acidic waters. Prior to mine development, the polymetallic 

quartz-vein deposits were likely minor point-source acidproducing sites surrounded by rocks with high acid-neutralizing potential. Closely spaced cooling fractures that control 

the current hydrologic character of the area greatly assist the 

effectiveness of neutralizing potential of the bedrock. At present, acidic water within the study area is associated with 

(1) inactive mine adits that have opened and exposed the

quartz-vein deposits and channeled the flow of ground 

water, or (2) mine dumps and mill tailings that have concentrated mineralized rock waste.

Introduction

The Boulder River watershed study area is located in 

southwestern Montana approximately midway between Butte 

and Helena (fig. 1). The study area is in the north-central part 

of the laige Late Cretaceous Boulder batholith and is centered 

on the Basin and Boulder mining districts north and northeast 

of the town of Basin. The mining districts comprise numerous 

base- and precious-metal mines that explored thin polymetallic quartz veins filling fractures and small faults in the basins 

of Basin, Cataract, and High Ore Creeks, tributaries to the 

Boulder River (pi. L). The aim of this report is to characterize 

the geologic framework and associated mineral deposits in 

the watershed, to identify and prioritize the major contributors 

of acid mine drainage and deposit-related trace elements to 

primary streams and tributaries, and to assess the natural acidneutralizing capacity of the bedrock that hosts the polymetallic vein deposits.

The Boulder River study area is located in an area that 

was the focus of an earlier, comprehensive study undertaken 

by the U.S. Geological Survey in the 1950s and 1960s. The 

result of that original undertaking was the publication of 

numerous maps and reports on the geology of the central part 

of the Boulder batholith (fig. 1). The Boulder River study area 

was mapped and described in the maps and reports of Ruppel 

(1963) for the Basin 15-minute quadrangle and Becraft and 

others (1963) for the adjacent Jefferson City 15-minute quadrangle. This report is in many ways a summary of the previous 

work as it pertains to the Boulder River watershed study area. 

The reader is encouraged to refer to the previous reports for 

amplification of details of the geologic investigations.

Previous Work

Lindgren (1886) made the first study of the igneous rocks 

in this area. These igneous rocks were soon thereafter named
54 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

46° -

10 

I

20 30 MILES

Figure 1. Index map to area described in this report. Labels refer to publications of the U.S. Geological Survey (from Smedes, 

1966, fig. 1). Plate 1 covers the area of USGS publications Professional Paper 428 (Becraft and others, 1963) and Bulletin 1151 

(Ruppel, 1963).
Geologic Framework 55

the Boulder batholith by Weed (1887) in a study of the area 

around Butte. The Boulder River study area is included in a 

report by Knopf (1913) on the northern part of the Boulder 

batholith. During the 1950s and 1960s, the U.S. Geological 

Survey conducted geologic investigations of 13 quadrangles 

covering the north-central part of the Boulder batholith 

(fig. 1). The careful descriptive manner in which the plutonic 

rocks were described and depicted on these maps allowed us 

to compile consistent units across the batholith and provided 

a remarkable view of the geometry of the entire intrusive 

complex. The closely coordinated individual studies formed 

the basis for several batholith-wide topical studies, including 

chemistry (Tilling, 1968, 1973, 1974), timing (Tilling and 

others, 1968), magmatic evolution (Robinson and others, 1968; Rutland and others, 1989), emplacement models 

(Hamilton and Myers, 1967; Klepper and others, 1971), and 

regional tectonic syntheses (Robinson and others, 1968; 

Schmidt and others, 1990) that have been influential in the 

studies of magmatic systems and their settings. Mapping studies by Ruppel (1963) and Becraft and others (1963) as part 

of the Boulder batholith study form the basis of the geologic 

information used in our analyses and summary.

Setting

Western Montana is underlain by rocks that range in age 

from Archean to Quaternary. High-grade metamorphic rocks 

and lesser amounts of felsic plutonic rocks compose most of 

the Archean lithologic units exposed in cores of mountain 

ranges in the southwestern part of the State. Archean rocks 

were deformed in Paleoproterozoic time during the assembly and formation of the North American craton. A major 

Paleoproterozoic contractional suture zone between Archean 

cratonic provinces of the northern Rocky Mountains trends 

northeasterly across east-central Idaho and western Montana, 

into southern Saskatchewan. In Mesoproterozoic time, the area 

comprising western Montana and adjacent Idaho was the site 

of thick accumulations of sediment deposited in what is now 

known as the Belt basin. The basin trends north and extends 

from southwest Montana into British Columbia. The Helena 

embayment, an east-trending arm of the basin, projects eastward into west-central Montana; the embayment is bounded 

by high-angle faults on the north and south. Phanerozoic 

miogeoclinal rocks that cover Archean and Proterozoic rocks 

were complexly deformed in the Cretaceous. Large sheets of 

allochthonous rocks exposed in the western part of the State 

were thrust eastward and tectonically interacted with coeval 

Laramide uplifts of Precambrian basement rocks east of the 

overthrust belt. Batholithic rocks were also emplaced into 

these rocks during the Cretaceous; the Boulder batholith, the 

subject of this report, is one of the larger of these intrusive 

bodies.

The Boulder batholith is a plutonic complex consisting of a sequence of Cretaceous intrusions that evolved into

more silicic compositions through time (Knopf, 1963). The 

emplacement sequence of the Boulder batholith is from initial 

more mafic plutons to a voluminous intermediate-composition 

main batholithic phase to a final, minor late-stage, alkali-rich 

felsic pluton. Early mafic plutons are elongate east-west bodies at the northern and southern borders of the Boulder batholith (fig. 2); their emplacement was controlled by reactivated 

east-trending structures acting primarily as tear structures and 

lateral ramps during Late Cretaceous thrust faulting. The most 

voluminous, intermediate plutonic phase of the batholithic 

complex has historically been called the "Butte Quartz Monzonite." However, by use of more recent plutonic classification 

systems, the composition of this pluton is not quartz monzonite (see discussion on Butte pluton); thus the name Butte pluton will be adopted, following the usage of Schmidt and others 

(1990), to prevent confusion. The Butte pluton is about 10 mi 

wide and 32 mi long and forms the north-northeast elongated 

heart of the plutonic complex (fig. 2). The shape and location 

of the Butte pluton were probably controlled by tension related 

to geometry of interacting structures during Late Cretaceous 

thrust faulting (Schmidt and others, 1990). Late-stage felsic 

plutons crosscut the Butte pluton; their location may be controlled by the Butte-Helena fault zone (fig. 2, see discussion 

on mode of emplacement).

Regional Tectonic Setting

The structural setting of the Boulder batholith region1 

has been dominated by recurrent movement on three sets of 

steep faults (fig. 2): northwest-trending, northeast-trending, 

and east-trending sets. The northwest-trending fault set consists of about 30 separate faults spaced 3.5-6 mi apart. 

Some of these faults are vertical at the surface, but most dip 

50°-80° NE. Schmidt and Garihan (1986) concluded that these 

faults were down to the northeast during Mesoproterozoic 

time. They were reactivated as left-reverse, oblique-slip faults 

during east-west shortening of the thrust belt and adjacent 

Rocky Mountain foreland in the Late Cretaceous (Schmidt 

and Garihan, 1983). Most of these faults are restricted to the 

Tobacco Root and Highland Mountains, directly south of the 

Boulder batholith.

Faults of the northeast-trending set occur over a wide 

zone (120 mi) spanning both the thrust belt and the basement rocks of the foreland. O'Neill and Lopez (1985) have 

documented recurrent activity along this fault set, going back 

to at least Mesoproterozoic time; they named the fault trend 

the Great Falls tectonic zone (not labeled in fig. 2). McBride 

and others (1990) extended the zone to include thrusts in the 

Archean basement rocks of the Rocky Mountain foreland and 

showed that the thrusts had a component of right-lateral slip

'The following discussion of the kinematics of emplacement of the 

Boulder batholith is excerpted from Schmidt, Smedes, and O'Neill (1990). 

Minor additions to the original article herein are by O'Neill and are based on 

geologic observations made since that time.
56 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

EXPLANATION

Eocene Lowland Creek Volcanics

Butte Quartz Monzonite 

and related rocks

a Alaskite/aplite bodies 

b Butte pluton

Early tonalitic plutons

Late felsic plutons 

(including satellites)

re Rader Creek pluton

bp Burton Park pluton

U Unionville pluton

kr Kokoruda Ranch complex

m Mafic stock

Satellite plutons 

(unassigned)

Pioneer batholith

Upper Cretaceous Adel Mountains

Volcanics 

Upper Cretaceous Elkhorn Mountains

Volcanics 

Precambrian metamorphic basement

and Phanerozoic rocks

Anticline 

Syncline

Fault, undifferentiated—dashed where 

inferred

Thrust fault (frontal thrust belt)—Dashed 

where inferred; sawteeth on upthrust 

block

Thrust fault (basement-involved)— 

Sawteeth on upthrust block

Fault with strike-slip component— 

Barbs show direction of relative 

movement; U, upthrown side; D, 

downthrown side

Porphyritic granodiorite 

Climax Gulch pluton 

Moose Creek pluton 

Donald pluton 

Hell Canyon pluton

mm McCartney Mountain stock

tr Tobacco Root batholith

Im Lone Mountain laccolith

HELENA 

STRUCTURAL 

SALIENT

Figure 2. Tectonic map of the Boulder batholith area showing major plutonic units and faults (modified from Schmidt and others, 

1990, fig. 1). Inset map shows location. Unlabeled areas are Proterozoic and Phanerozoic rocks. RCS, Rader Creek screen. Cross 

section A-A' is shown in figure 3.
Geologic Framework 57

due to easterly-directed compression during the Late Cretaceous. More recently, O'Neill (1998) has described the architecture of the Great Falls tectonic zone across western Montana; he described the zone as a Paleoproterozoic collisional 

orogen and continental suture whose axis is now obscured 

beneath the Boulder batholith.

Major east-trending Mesoproterozoic faults or fault zones 

are inferred to be either buried or reactivated by thrusts along 

the southwest Montana transverse zone at the southern margin 

of the Helena structural salient (fig. 2) (Robinson, 1963; 

Schmidt and O'Neill, 1983). The zone is likely controlled by 

a major down-to-the-north normal fault zone, the Perry line of 

Harris (1957), that marked the southern margin of the Helena 

embayment of the Belt basin in Mesoproterozoic time. The 

westward projection of the line closely coincides with the 

southern margin of the Boulder batholith. Another, though less 

distinct, east-trending Proterozoic normal fault zone has been 

identified in the northern Helena salient (Winston, 1986). This 

fault zone, the Garnet line of Winston (1986), is interpreted to 

mark the north edge of the Mesoproterozoic Helena embayment. Late Cretaceous sinistral shear along the segment of the 

Garnet line fault zone that crosses the northern boundary of 

the Boulder batholith has produced a series of large northwesttrending en echelon folds in the Proterozoic and Phanerozoic 

rocks in that region.

In summary, the upper crust in the region of the Boulder 

batholith is crisscrossed by three sets of deeply penetrating 

faults that have been recurrently active since the Proterozoic.

Contacts with Adjacent Rocks

Fifteen plutons make up the Boulder batholith (fig. 2). 

Tonalitic plutons are products of the earliest stage of intrusive 

activity and are preserved dominantly along the north and 

south margins of the batholith. These plutons are the most 

mafic bodies in the batholith and occur as northwest-trending

and east-trending dike-like bodies. The intrusion of the earliest 

plutons appears to have been controlled by the intersection of 

east-trending faults that bound the Mesoproterozoic Helena 

embayment of the Belt basin on the north and south with the 

axial crustal suture zone within the Great Falls tectonic zone.

The Butte pluton, which underlies the entire study area, 

forms about 73 percent of the outcrop area of the Boulder 

batholith. It can be divided into eastern and western sectors 

separated by the Butte-Helena fault zone (fig. 2). In the south, 

the fault zone is 3 mi wide and separates the batholith from 

younger Lowland Creek Volcanics. In the north the zone is 

marked by northeast-trending late-stage plutons, small bodies of alaskite and pegmatite, and abundant late-stage fissure 

veins. This zone is interpreted to be one of deep-seated faulting associated with the axial suture of the Great Falls tectonic 

zone.

The eastern boundary of the Butte pluton has long been 

interpreted as having been emplaced along a preexisting northeast-trending fault that was partly obliterated by stoping. In 

several places the Elkhorn Mountains Volcanics are intensely 

sheared and recrystallized along the fault zone (Smedes, 1966; 

Prostka, 1966). In the north the fault appears to terminate 

abruptly against the east-trending Garnet line. On the south, it 

bends gradually westward and merges with the east-trending 

Perry line that marks the southern boundary of the batholith.

The east-west cross-sectional shape of the pluton is 

known only from gravity data of Biehler and Bonini (1969) 

and Burfeind (1967). The pluton is highly asymmetric and can 

be divided into two parts: (1) a relatively thin wedge-shaped 

body west of the Butte-Helena fault zone and (2) a thick, 

steep-sided pluton east of the fault zone (fig. 3).

Mode of Emplacement

Plutonic rocks west of the Butte-Helena fault zone appear 

to have been intruded as a laccolith that now has an

I Quaternary and 

I Tertiary sediments 

i Eocene Lowland 

Creek Volcanics

I Upper Cretaceous

I Butte Quartz Monzonite

I Upper Cretaceous 

I intrusive rocks

EXPLANATION

.. .. I Mesozoic and

Paleozoic rocks

m Cretaceous volcanic and sedimentary rocks

O Jurassic through 

LJ Cambrian rocks 

;—I Precambrian 

:L\ sedimentary rocks

I Precambrian

I metamorphic rocks

Figure 3. Regional cross section (line A-A' of fig. 2) showing interpreted relationship of main mass of Butte pluton to faults 

(modified from Schmidt and others, 1990, fig. 3).
58 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

extensive gently west dipping updomed roof of Elkhorn 

Mountains Volcanics and a few large roof pendants of prevolcanic sedimentary rocks (Smedes and others, 1988). This 

part of the batholith is clearly thinner than the eastern part and 

probably thins gradually westward. However, quite a different 

mode of intrusion seems to be required for the eastern part of 

the pluton (figs. 2, 3), because (1) this part of the batholith is 

a parallelogram in map view and is bounded on four sides by 

faults; (2) the roof apparently never contained any rocks older 

than the cogenetic Elkhorn Mountains Volcanics; and (3) the 

floor is interpreted to be a thrust belt decollement. We suggest 

that a rhombohedral pull-apart opened up within the Helena 

salient of the thrust belt during active eastward movement of 

the thrust sheets. Such a cavity may have formed by interaction of the thrust sheet above the basal decollement with the 

east-trending faults that bound the pluton on the north and 

south and with the northeast-trending faults that bound the 

rhombohedral mass on the east and west. Emplacement may 

have taken place episodically as a series of sheeted dikes.

The pull-apart is centered on the Butte-Helena fault zone 

that in turn is a Cretaceous manifestation of recurrent faulting 

above the Paleoproterozoic continental suture zone named the 

Great Falls tectonic zone. Thin-skinned, east-directed tectonic 

transport occurred in rocks north and south of the suture zone; 

however, thick-skinned basement deformation of the Rocky 

Mountain foreland occurred only southeast of the Great Falls 

tectonic zone. Thus, east-west crustal shortening southeast of 

the tectonic zone included both thick- and thin-skinned deformation, whereas to the northwest only thin-skinned deformation is recorded; hence east-directed tectonic transport of the 

crust was greater to the southeast. The deep-seated fault lines 

that bound the north and south sides of the Helena embayment 

of the Belt basin acted as accommodation zones that allowed 

a pull-apart to form along the crust-penetrating suture of the 

Paleoproterozoic collisional orogen. A progressively opening 

rhombohedral pull-apart was thus outlined by northeast- and 

east-trending faults, and this pull-apart was progressively filled 

from below by Butte pluton magmas. When pull-apart ceased 

and the rhomb-shaped part of the Butte pluton achieved its 

final form, the western, laccolithic part of the Butte pluton 

developed as the volume of magma exceeded the room available in the pull-apart region.

Tertiary Extensional Structures

In middle Eocene time, regional extension of the crust led 

to renewed eruption of calc-alkaline magmas along the ButteHelena fault zone to produce the Lowland Creek Volcanics 

(Tlv, figs. 2 and 3). In the early Oligocene, bimodal rhyolitebasalt volcanism of the Helena volcanic field was centered in 

the northwestern part of the batholith.

Igneous Rocks

Names for rock units used in the original reports (Becraft 

and others, 1963; Ruppel, 1963) are not used in this report 

in favor of using names that indicate textural and chemical character of the rocks. Because the plutonic rocks are all 

part of the same pluton and have the same general chemistry 

throughout the area, map units are defined on the basis of texture. Rock textures highlight cooling features of the pluton and 

are important for understanding the physical breakdown and 

chemical weathering of these rocks. Traditional modal data are 

available for the plutonic rocks, and these data are presented 

herein for comparison to other commonly used rock classification systems. However, because of the desirability of using the 

ground-water and surface-water chemistry of both the plutonic 

and volcanic rocks to relate rock type to other collaborative 

studies that are part of this project, we have chosen to discuss 

and compare the volcanic and plutonic rocks of the study area 

using their major-element chemistry. Thus, the major-element 

chemistry of the igneous rocks is presented and classification 

of the volcanic and plutonic rocks is based on systems used 

by De La Roche and others (1980). Using the same criteria 

to classify all the igneous rocks provides better comparison 

among rock types and includes the mafic minerals as part of 

the classification. Using mafic minerals as part of the classification system is pertinent to this study because mafic minerals 

are extremely important constituents in contributing to the 

acid-neutralizing potential of rocks in contact with acid-bearing water that issues both from exposed, unmined but mineralized areas, and from inactive mine workings.

Most of the rock units in the study area are Cretaceous 

igneous rocks. Previous work has shown that the Elkhorn 

Mountains Volcanics and the Boulder batholith are part of the 

same magmatic system (Roberts, 1953; Klepper and others, 

1957; Robinson, 1963; Smedes, 1966). In general, the Elkhorn 

Mountains Volcanics represent magma that reached the surface 

and erupted, forming a volcanic and volcanogenic layered 

sequence; the Boulder batholith represents the parent magma 

that crystallized beneath the Elkhorn Mountains Volcanics 

(Robinson and others, 1968; Rutland and others, 1989). Only 

two eruptive units of the Elkhorn Mountains Volcanics are 

present in the area of plate 1. The Boulder batholith in the area 

of plate 1 includes three textural phases of the Butte pluton, 

the largest pluton of the Boulder batholith. Younger, Eocene 

and Oligocene volcanic rocks and associated dikes are not 

related to the Boulder batholith but are related to later regionally important igneous events.

Upper Cretaceous Elkhorn Mountains Volcanics

The Elkhorn Mountains Volcanics are from 2.2 to 

3.0 mi thick and once covered about 10,000 mi2 (Smedes, 

1966), making this volcanic field one of the largest known ashflow volcanic fields (Lipman, 1984). The Elkhorn Mountains 

Volcanics are folded concordantly with the pre-volcanic rocks
Geologic Framework 59

and were thus erupted during and after contractional deformation. They were named and described from the Elkhorn Mountains (Klepper and others, 1957) located about 15 mi east of 

the study area. The volcanics are informally divided into three 

members: a lower unit of tuff, lapilli tuff, and tuff breccia; a 

middle unit mainly of welded tuff; and an upper unit of wellbedded tuffaceous sedimentary rocks. Small bodies of intrusive rocks are included with the Elkhorn Mountains Volcanics 

because they are thought to be the same age as the volcanics 

rather than part of the major intrusion of the Butte pluton.

Lower Member

The lower member does not crop out in the study area 

or in the area of plate 1 but is found to the east in the Elkhorn 

Mountains (Smedes, 1966). The lower member is andesitic 

tuff, flow breccias, and volcaniclastic rocks and is as much as 

4,900 ft thick. Andesitic ash-flow tuffaceous rocks are massive 

and commonly flow brecciated; some are slightly welded. 

Sedimentary rocks derived from these andesitic rocks range 

from sandstone to pebble and boulder conglomerate.

It is unlikely that the lower member was ever deposited 

in the study area, given that the batholith was intruded into an 

ever-opening pull-apart that formed after the lower member 

was deposited; the lower member is necessarily restricted to 

areas east and west of the Butte pluton.

Middle Member

The middle member is primarily dacitic welded tuff 

and also includes lapilli tuff, tuff breccia, and minor volcanic 

sandstone and conglomerate. The middle member may be as 

much as 8,200 ft thick (Smedes, 1966) and is the predominant 

member of the Elkhorn Mountains Volcanics in the study area 

and across the area of plate 1. Two welded tuff zones of which 

dacite is the most common rock type make up the middle 

member. Welded tuffs of the upper zone are light-greenishgray and medium-gray rocks. Groundmass is fine to very fine 

grained, and phenocrysts are mostly euhedral plagioclase and 

hornblende. Plagioclase composition is An30 35 (Ruppel, 1963). 

Plagioclase phenocrysts range from 0.5 to 3 mm long, and the 

mafic minerals are generally less than 1 mm across. 2 Welded 

tuffs of the lower zone are brownish gray or reddish gray. The 

groundmass is aphanitic to very fine grained. Plagioclase phenocrysts are 1-2 mm long, and biotite grains are found in trace 

amounts. Small lithic fragments of volcanic rock are common. In the welded tuffs, phenocrysts are commonly aligned 

parallel to welding features and flattened fragments of pumice 

and glass. Tuff breccia and lapilli tuff are more common in 

the lower parts of the middle member and probably represent 

unwelded or partly welded tuff of the same compositions.

2A11 microscopic measurements are given in millimeters rather than inches. 

To convert to inches, multiply by 0.04.

Local interbedded volcanic sandstone and conglomerate contain fragments of welded tuff and probably originated by local 

erosion of volcanic rocks between major volcanic eruptions.

The middle member crops out as roof pendants on the 

Butte pluton across the western part of the study area and 

as a weakly folded inlier on the east side of the study area. 

Throughout the study area, the base of the middle member has 

been partly assimilated by the intrusion.

Upper Member

The upper member of the Elkhorn Mountains Volcanics 

is primarily volcaniclastic material reworked from the lower 

members; it includes some tuff layers. The upper member 

is as much as 1,900 ft thick (Smedes, 1966). Dark-gray, 

thin-bedded to laminated, fine-grained andesitic mudstone to 

siltstone is the dominant rock type, interbedded with lesser 

amounts of andesitic sandstone to conglomerate and breccia. 

Andesitic sandstone contains subrounded to rounded grains 

that are well sorted. Breccia is probably of landslide or mudflow origin. Lapilli tuff and crystal tuff, which are interbedded 

with the fine-grained sedimentary rocks, document on-going 

volcanism.

Rocks of the upper member are found in and extending out of the southwestern part of the study area above the 

welded tuff of the middle member, and also along the east 

side of the study area. The base of the upper member is 

generally conformable with rocks of the middle member. The 

overlying Lowland Creek Volcanics lie on top of the upper 

member of the Elkhorn Mountains Volcanics across an angular 

unconformity.

Chemical Composition

Becraft and others (1963) reported the chemical analyses 

of two samples of tuff from the upper member of the Elkhorn 

Mountains Volcanics and one sample of same-age intrusive 

porphyry. Their tuff samples are andesite and rhyodacite in 

composition; the intrusive porphyry is a dacite (fig. 4). Ruppel 

(1963) reported the analyses of two welded tuffs and a metamorphosed welded tuff, with all three samples from the middle 

member. The two welded tuff samples are dacites (fig. 4). The 

metamorphosed welded tuff is compositionally a rhyolite 

(fig. 4). Ruppel (1963) suggested that the tuff was altered 

(silicified) after its deposition, perhaps by the intrusion of the 

Butte pluton. Desborough, Briggs, and Mazza (1998, 

table 1, p. 6-7) collected four samples of unaltered bedrock of 

the middle member of the Elkhorn Mountains Volcanics from 

the study area; these samples range from lati-andesite to dacite 

to rhyodacite in composition (fig. 4). Desborough, Briggs, and 

Mazza (1998, table 3, p. 11) also sampled silicified volcanic 

rocks of the Elkhorn Mountains Volcanics at Jack Mountain 

(fig. 5).

Similar to the rocks of the Butte pluton, samples of Elkhorn Mountains Volcanics show rather consistent and typical
60 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

1,500 -

1,000 1,500 2,000 2,500 3,000 

R! = 4,OOOSi - 11,000(IMa + K) - 2,000(Fe + Ti)

EXPLANATION

^ Samples of the upper member (n=2)

D Samples of the middle member (n=7) 

W Sample of related intrusive rock

Figure 4. Classification of samples of the Elkhorn Mountains Volcanics in the study area based on 

the R^-diagram of De La Roche and others (1980). Analytical data from Becraft and others (1963, 

table 1, p. 7), Ruppel (1963, table 2, p. 16), and Desborough, Briggs, and Mazza (1998, table 1, p. 6-7).

inverse relationships between silica content and concentrations 

of magnesium, calcium, phosphorus, and titanium (fig. 5); 

aluminum and manganese also show similar inverse trends. 

An association of these metals with mafic minerals is likely; 

therefore, the least silica rich rocks of the Elkhorn Mountains 

Volcanics likely contain relatively more mafic minerals.

A comparison of figures 5 and 6 shows that the range 

and magnitude of major-element concentrations are generally 

similar between the representative samples of the Butte pluton 

and the Elkhorn Mountains Volcanics. No modal data for the 

Elkhorn Mountains Volcanics have been published, mainly 

because the fine-grained nature of these rocks precludes 

mineral identification and volume estimates in petrographic 

sections.

Metamorphism

The Butte pluton intruded into the middle and upper 

members of the Elkhorn Mountains Volcanics, and, near contacts with plutonic rocks, the tuffs are contact metamorphosed 

to cordierite hornfels facies. The hornfels are very fine grained

rocks in which original textures have been destroyed, resulting 

in a dense impermeable rock. As for less dramatic metamorphic effects, low-grade contact metamorphism of the tuffs and 

welded tuffs formed quartz-sericite-alkali feldspar hornfels as 

much as 65 ft away from the contact. In these hornfels, Becraft 

and others (1963) and Ruppel (1963) observed that mafic 

minerals have been mostly destroyed and the remainder of the 

rock has been converted to sericitized feldspar phenocrysts 

and a groundmass of fine-grained intergrown sericite, quartz, 

and alkali feldspar. Pyrite and tourmaline in cavities and along 

fractures were introduced during or after formation of the 

hornfels. Wispy textures in these hornfels rocks in the western part of the study area are probably relict welding texture. 

Chemically, samples of this rock are much more silicic than 

unmetamorphosed samples (fig. 4), reflecting the importance 

of the hydrothermal introduction of silica as part of the metamorphism. Both the composition and texture of the hornfels 

considerably affect the chemical reactions between this rock 

and ground and surface water and the response of this rock 

to weathering. See section, "Acid-Neutralizing Potential of 

Bedrock, " p. 83 .
Geologic Framework 61

S 14

? 12

3" 10

10

0.25

0.20

0.15

0.10

0.05

a* i i i i i r

D

n

*

n

jk. s

*

D

•

56 60 64 68 72 76 80 84

Si0 2, IN WEIGHT PERCENT

F

1.0 

0.8 

0.6 

0.4 

0.2

g 0.10

O

S 0.08 i—

2 0.06

LU

| 0.04 

I 0.02

t

D

D

D

D

D

56 60 64 68 72 76 80 84 88 

Si02, IN WEIGHT PERCENT

EXPLANATION

^ Samples of the upper member (n=2)

D Samples of the middle member (n=7) 

W Sample of related intrusive rock

13 Samples of silicified volcanic rocks at Jack Mountain (n=7) 

collected by Desborough, Briggs, and Mazza (1998)

Figure 5. Marker variation diagrams showing abundances of major oxides versus Si02 for 17 samples of the Elkhorn Mountains 

Volcanics from the study area. Analytical data from Becraft and others (1963, table 1, p. 7), Ruppel (1963, table 2, p. 16), and 

Desborough, Briggs, and Mazza (1998, table 3, p. 11).
62 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

B 17

oc

£ 16 i—

1 15 

z 14

0 10 _N 13

g 2.5

o

S 2.0

i—

5 1.5

0.5

GHT

uj 0.25

o

£ 0.20 i—

I 0.15

UJ

I 0.10

n

n

n

3-

5.0 

4.5 

4.0 

3.5 

3.0

1.0 

0.8

0.6

^ 0.4

o" 0.2

p

S 0.10

o

§ 0.08 i—

| 0.06

z 0.04

I 0.02

n

D D

c

D

n n

n n

62 63 64 65 66 67 68 69 70 71 

Si0 2, IN WEIGHT PERCENT

62 63 64 65 66 67 68 69 70 71 

Si02, IN WEIGHT PERCENT

EXPLANATION

^ Samples from the fine-grained porphyritic unit (n=8)

• D Samples from the medium- to coarse-grained unit (n=22); 

open square, sample collected by Desborough, Briggs, 

and Mazza (1998)

Figure 6. Marker variation diagrams showing abundances of major oxides versus Si02 for 30 samples of Butte pluton in the 

study area. Chemical data from Becraft and others (1963, table 2, p. 10), Ruppel (1963, table 3, p. 26), and Desborough, Briggs, 

and Mazza (1998, table 1, p. 6-7).
Geologic Framework 63

Ages

Age determinations of rocks of the Elkhorn Mountains 

Volcanics have been obtained elsewhere in the region. Vertebrate and plant fossils found in the Elkhorn Mountains Volcanics are from the Campanian Stage of the Upper Cretaceous 

(Smedes, 1966). Only a few isotopic ages are reported and, of 

these, only two have been considered reliable. These are 

hornblende K-Ar ages, both from the lower member, thus 

recording the onset of volcanism. A sample of autoclastic 

breccia from near the base of the lower member from a site 

southeast of this study area resulted in reported dates of 

77.6±2.4 and 78.8±2.4 Ma (Robinson and others, 1968). 

Another sample from near the top of the lower member west 

of this study area resulted in a reported date of 77.6±2.4 Ma 

(Robinson and others, 1968). Fossils from welded tuffs near 

the top of the upper member are dated at 73 to 75 Ma and 

record the end of volcanism. Together these data indicate that 

volcanism occurred for about 5 m.y. from about 78 to 73 Ma 

(Robinson and others, 1968). More recent dating of Cretaceous fossil zones (Obradovich, 1993) suggests that volcanism, represented as volcaniclastic rocks of the underlying 

Slim Sam Formation, began about 81 Ma (Tysdal, 2000), thus 

extending the period of igneous activity.

Late Cretaceous Butte Pluton of the 

Boulder Batholith

Previous mapping in the study area by Ruppel (1963) and 

Becraft and others (1963) resulted in complex subdivision of 

granitic units based on grain size, amount of mafic minerals, 

outcrop color, and texture. Between the two maps, 19 map 

units were used to subdivide rocks of the Butte pluton. Units 

used for the present study are simplified to only three map 

units (pi. 1) for the following reasons.

Although the units designated by Ruppel and Becraft 

and others were used consistently where defined, they were 

not completely carried across both quadrangles. Additionally, 

gradational boundaries without identified contacts were used 

in some areas. Thus, distinctions among medium grained, 

coarse grained, and porphyritic or among the different color 

varieties were not made everywhere and could not be carried 

across the present study area without a great deal of additional 

field mapping.

Significantly, the previous reports make it abundantly 

clear that such effort is not warranted. Geochemical analyses 

and modal data for units show unequivocally that some units 

distinguished by texture or by color index could not be differentiated based on rock chemistry, and further, some units that 

have identical textures have different chemical signatures and 

modes. Thus, color was used by earlier workers to distinguish 

some otherwise chemically and texturally identical rocks 

(Becraft and others, 1963; Ruppel, 1963). Pink versus gray 

color in granite is, in some cases, indicative of later alteration 

of the rock by hydrothermal fluids. Where alteration has not

occurred, the pink color may reflect magmatic conditions, 

in particular, the oxidation state of iron in the feldspar. The 

previous authors make it clear that the chemical, modal, and 

textural data show no indication of separate magma sources or 

even of separate intrusive phases of the same magma (Becraft 

and others, 1963; Ruppel, 1963). To avoid confusion of the 

classification systems in these rocks with similar chemistry 

and to highlight internal features of the Butte pluton in the 

study area, map units used on plate 1 are defined mostly on 

the basis of texture. Thus, the complicated map units used by 

Becraft and others (1963) and Ruppel (1963) are not used in 

this study in favor of units that were mapped consistently by 

previous workers and those presented here that are deemed 

relevant to the present study.

Based on replotting of modal data of Becraft and others 

(1963) and Ruppel (1963), samples from the Butte pluton plot 

in the granite field (fig. 7; Streckeisen, 1976) as it was originally classified (Weed, 1887; Knopf, 1957). Subsequent to the 

original work, these rocks were typically named quartz monzonite (Butte Quartz Monzonite of Becraft and others, 1963; 

Ruppel, 1963; and many others) due to a then popular igneous 

rock classification system (Johannsen, 1939; and see Knopf, 

1957). Alternatively, based on major-element chemistry in 

which all constituents of the rock are considered, samples of 

the Butte pluton from the study area plot in the granodioritetonalite fields (see discussion on "Chemical Composition").

Medium-to Coarse-Grained Phase

The dominant rock type in the study area is the mediumto coarse-grained hornblende-biotite phase of the Butte pluton; 

this phase (Kbm) underlies as much as 90 percent of the 

study area but is conspicuously absent in the vicinity of Jack 

Mountain. Even where not exposed on the surface, this rock is 

not deeply buried and underlies all other exposed rocks. Thus, 

the chemistry, grain size, and fracture patterns of the mediumto coarse-grained phase and the presence of hornblende and 

biotite are the most important factors in the environmental 

geology of the study area. The chemical and physical characteristics of this rock type dominate all other factors in controlling ground-water flow, ground-water chemistry, and acid-neutralizing potential of bedrock in the study area.

The medium- to coarse-grained phase is light to dark gray 

in fresh samples; some samples are pinkish gray or brownish 

gray as well. Modal counts published in Becraft and others 

(1963) and Ruppel (1963) have been replotted in figure 7 and 

show a spread of compositions across the part of the granite 

field (monzogranite) where plagioclase and potassium feldspar 

are present in subequal amounts. A few samples fall in the 

granodiorite field owing to a predominance of plagioclase 

over potassium feldspar. Plagioclase composition is in the 

range of An20-An50 ; plagioclase crystals are commonly rimmed 

by zoned albite in coarser grained rocks. Quartz makes up 

20-30 percent of the medium- to coarse-grained phase and is 

commonly strained. Mafic minerals are biotite and hornblende 

and represent from 5 to 14 percent of the rock. Generally,
64 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

QUARTZ

QUARTZ

MONZONITE

(quartz latite)

ALKALI 

FELDSPARS

10 35 65 90 PLAGIOCLASE

EXPLANATION

• Modes reported by Becraft and others (1963) 

o Modes reported by Ruppel (1963)

Figure 7. Modes of rocks of Butte pluton in the study area as counted from thin sections by Becraft and others (1963, fig. 3, p. 8) 

and Ruppel (1963, fig. 3, p. 23). Modes are plotted on modal classification diagram for plutonic rocks constructed by Streckeisen 

(1976); equivalent volcanic rock names are given in parentheses.

biotite slightly predominates over hornblende; biotite averages 3-7 percent and hornblende averages 1-7 percent. Relict 

augite is found in most samples. As much as 4 percent tourmaline is present. Sphene, magnetite, zircon, apatite, and allanite 

are common as trace minerals.

The medium- to coarse-grained phase is commonly equigranular, but minor areas of porphyritic texture with mediumand coarse-grained groundmass are found along the northern 

edge of the map area of plate 1. Based on mapping of Becraft 

and others (1963) and Ruppel (1963), the grain size in this 

unit forms a distinct pattern of coarser at deeper exposures as 

opposed to medium at higher positions relative to the original 

roof of the pluton. The porphyritic varieties noted in previous 

mapping are at the northern contact of the Butte pluton against 

the older, cogenetic Unionville pluton (Knopf, 1963). This 

porphyritic texture in the Butte pluton is presumably due to 

more rapid cooling near the roof and side of the magma body 

during crystallization.

Pegmatitic to aplitic segregations form knots in the 

medium- to coarse-grained phase, especially in the upper parts 

of this unit. The pegmatitic and aplitic segregations are feldspar and quartz intergrowths that can be either coarser or finer 

than the surrounding rock and also commonly include visible 

crystals of tourmaline and epidote. Some of these pegmatitic 

or aplitic knots have crystals terminating inward into poorly

formed miarolitic cavities. Where the knots or cavities are particularly common, the rock has locally been mapped as aplite 

bodies by the previous workers; in this study, these rocks 

are interpreted to be textural and compositional phases that 

formed due to liquid-rich bubbles near the top of the crystallizing magma. Miarolitic cavities indicate moderate to shallow 

emplacement and cooling of the magma at about 

2.5 mi beneath the paleosurface.

Fine-Grained Porphyritic Phase

The fine-grained porphyritic phase includes light- and 

dark-gray and pinkish-gray varieties and both porphyritic and 

equigranular varieties; this phase (Kbf) is most abundant in 

the study area in the vicinity of Jack Mountain. Phenocrysts 

are most commonly potassium feldspar, but one variety has 

plagioclase phenocrysts. Plagioclase composition is in the 

range of An30-An50 ; crystals are commonly zoned. Quartz 

makes up 20-30 percent of the fine-grained phase and is commonly strained. Mafic minerals are biotite and hornblende. 

Generally, biotite slightly predominates over hornblende; 

biotite averages 4-7 percent and hornblende averages 2-4 

percent. Sphene, magnetite, zircon, apatite, and allanite are 

common trace minerals.
Geologic Framework 65

The porphyritic fine-grained variety is composed dominantly of rocks with groundmass crystals of about 1 mm and 

phenocrysts as much as 30 mm.3 Some equigranular varieties with grain size of about 1 mm were originally mapped as 

separate units based on the textural difference. The groundmass in both porphyritic and equigranular varieties is formed 

of interlocking grains.

Other textural varieties in this unit include granophyre, 

porphyry, and minor aplite. In the granophyric variety, fine to 

very fine rosettes of quartz and graphic intergrowths of quartz 

and feldspar form most of the groundmass. In the porphyry 

variety, the groundmass is very fine and the appearance of 

the phenocrysts dominates the rock in hand specimen. Some 

small zones of aplite, rock having lower mafic mineral content 

and composed of a mosaic of quartz and feldspar grains, are 

included in this unit. In all these textural types, aplitic material 

forms knots and segregations associated with sparse, poorly 

formed miarolitic cavities. These textures indicate moderately 

shallow cooling at about 2.5 mi beneath the surface.

The fine-grained porphyritic variety and associated 

varieties are most commonly found at the highest elevations 

in the Butte pluton. They are located overwhelmingly near 

the contact of the Butte pluton with overlying roof rocks. 

This phase forms a chill margin to the rest of the pluton and, 

thus, crystallized before the coarser grained phases. In places 

where this relationship does not hold and the fine-grained 

phase appears to be surrounded by the coarser grained phases, 

this chill phase may represent rafts caused by the failure of 

the roof zone during emplacement of the still mobile coarser 

magma.

Aplite and Porphyry

The aplite and porphyry unit (Kba) includes rocks 

originally mapped as alaskite and pegmatite map units. When 

replotted (fig. 7), modal counts published in Becraft and 

others (1963) spread across the modal granite field with most 

samples falling in the part of the granite field (syenogranite) 

having higher concentration of potassium feldspar 

than plagioclase feldspar. These rocks have considerably 

higher silica content than the other phases with quartz composing 3 1-42 percent of the rock. Potassium feldspar makes 

up 30-65 percent, and sodic plagioclase makes up most of the 

rest of the rock. Biotite is the only common mafic mineral, and 

it is only present in trace amounts of less than 1 percent. Black 

tourmaline is common locally.

Textures in much of this unit are similar to those in the 

fine-grained porphyritic phase; the unit is distinguished from 

it on the basis of the very low mafic content. Although some 

sugary alaskitic textures do exist in the area, most of this unit 

has aplitic (fine-grained pegmatitic) or leucocratic porphyritic

3A11 microscopic measurements are given in millimeters rather than inches. 

To convert to inches, multiply by 0.04.

textures. Grain size of the aplite and porphyry matrix averages 

about 1 mm. However, some pegmatite with much coarser 

quartz and feldspar grains is also included in this unit. Finegrained to very fine grained rosettes of quartz and graphic 

intergrowths of quartz and feldspar are common.

The aplite and porphyry units form tabular bodies and 

dikes throughout the map area. East of the study area, on the 

east side of the area of plate 1, aplite dikes are common. These 

have strongly preferred northeast trends, although other orientations are also evident. These aplite dikes formed in steep 

joints. Aplite is also present as segregations that form knots 

at different scales: many knots are characteristically small but 

some are so extensive and intergrown that they were mapped 

as separate bodies. Many of the tabular aplite bodies throughout the map area are part of the fine-grained, chilled facies 

that formed near the top of the magma chamber rather than the 

usual late-stage segregations typical of aplite.

Chemical Composition

As part of this study, Desborough, Briggs, and Mazza 

(1998) collected 11 samples of unaltered Butte pluton bedrock 

in the Basin and Cataract Creek basins. The major-element 

compositions of their samples appear to overlap with those of 

the Butte pluton samples of Ruppel (1963, p. 26), as well as all 

but the four most silica rich rocks of Becraft and others (1963, 

table 2, p. 10), as shown in figures 6 and 8. Marker variation 

diagrams showing the rock chemistry of Butte pluton samples 

from all three studies (fig. 6) reveal a fairly consistent trend for 

a few elements. The concentrations of magnesium, calcium, 

phosphorus, and titanium show an inverse relationship with 

silica; that is, as silica content increased in the melt, magnesium, calcium, phosphorus, and titanium decreased. Marker 

variation diagrams by Tilling (1974, fig. 3, p. 3883), which 

display more than 250 chemical analyses of Boulder batholith 

rocks and its satellite plutons, show this same inverse relationship between silica and magnesium, calcium, phosphorus, and 

titanium.

In major-element composition, no distinct difference is 

evident between rocks of the fine-grained porphyritic unit and 

rocks of the medium- to coarse-grained unit (figs. 6 and 8). 

This similarity provides further evidence that these two units 

had a common magma source and probably do not represent 

separate intrusive events. Because of the similar compositions, 

the two units should have nearly the same acid-neutralizing 

potential in the study area. (See section, "Acid-Neutralizing 

Potential of Bedrock.")

The multi-element chemistry of the 11 Butte pluton 

bedrock samples collected by Desborough, Briggs, and Mazza 

(1998, table 1, p. 6-7) was examined with correlation statistics. Although this data set is not large enough to warrant 

confident statistical conclusions, a few interesting relationships were found. Calcium correlated very strongly with iron 

and scandium (correlation coefficient (R) of >0.9), strongly 

with vanadium and titanium (R>0.8), and well with magnesium, phosphorus, and manganese (R>0.7). Iron and titanium
66 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

1,500 -

1,000 1,500 2,000 2,500 

R! = 4,OOOSi -11,000(Na + K) - 2,000(Fe + Ti)

3,000

EXPLANATION

W Fine-grained porphyritic unit (n=8)

• D Medium- to coarse-grained unit (n=22); open squares indicate 

samples collected by Desborough, Briggs, and Mazza (1998)

if "Aplite" (n=2)

Figure 8. Classification of Butte pluton samples from the study area based on the R^-diagram 

of De La Roche and others (1980). Chemical data from Becraft and others (1963, table 2, p. 10, and 

table 5, p. 22), Ruppel (1963, table 3, p. 26), and Desborough, Briggs, and Mazza (1998, table 1, 

p. 6-7).

showed similar correlation matrices. A grouping of Ti-Sc-VCa-Fe-Y, and to a lesser extent, manganese, accounted for 

30 percent of the variation in the factor analysis. The grouping of Ca-Fe-Ti, associated with magnesium and phosphorus, 

may be explained by mafic minerals, such as: (1) the amphiboles tremolite [ideal formula Ca2Mg5Si8O22(OH)2], actinolite 

[Ca2(Mg, Fe)5Si8O22(OH)2], and hornblende [(Ca, Na)23(Mg, 

Fe, Al)5Si6(Si, A1)2O22(OH)2]; (2) sphene [CaTiO(SiO4j]; 

(3) biotite [K(Mg, Fe)3 (AlSi3O10(OH)2]; and (4) apatite 

[Ca5 (PO4)3 (F, Cl, OH)]. Note again the trends in figure 6, 

which suggest that as silica content increased in the normal 

crystallization of this plutonic melt, magnesium, calcium, 

phosphorus, and titanium concentrations decreased. Thus, 

silica-rich facies of the Butte pluton should contain relatively 

fewer mafic minerals, whereas less silica-rich facies should 

have relatively more mafic minerals.

Project research indicates that the mafic minerals within 

the Butte pluton contribute significantly to the acid-neutralizing potential of the watershed (Desborough, Briggs, Mazza, 

and Driscoll, 1998). Butte pluton rocks rich in mafic minerals

are thought to have higher capacity to neutralize acidic waters 

than plutonic and volcanic facies that are more silicic and 

have fewer mafic minerals. The relationship between mafic 

minerals and acid-neutralizing potential is discussed later in 

this chapter and in McCafferty and others (this volume, 

Chapter D2).

Ages

Rocks of the Boulder batholith have been dated previously by K-Ar methods (Knopf, 1956; McDowell, 1966; 

Robinson and others, 1968; Tilling and others, 1968) and 

preliminary Pb-alpha dating has also been done (Chapman and 

others, 1955). Previous K-Ar ages for the Boulder batholith 

are cooling ages that range from 78 to 70 Ma. The Pb-alpha 

ages obtained by Chapman and others (1955) on the Butte 

pluton were 71 Ma.

New U-Pb dating using SHRIMP techniques was done in 

conjunction with this study. The single age, from a sample collected from the central part of the Butte pluton near the trace
Geologic Framework 67

of the Butte-Helena fault zone, is 74.5±0.9 Ma. This new age 

indicates that the span of emplacement for most of the Boulder 

batholith is from about 82 to 74 Ma (Lund and others, 2002).

Relationship Between Late Cretaceous-Age 

Volcanic and Plutonic Rocks

Comparison of Geochemical Data

Rock chemistry indicates that most of the magma that 

formed the Elkhorn Mountains Volcanics was related to the 

mafic plutons of the Boulder batholith (Tilling, 1974). Significant mafic plutons, of relatively lesser volumetric importance 

in the Boulder batholith, are the Unionville pluton along the 

northern margin of the batholith directly north of this study 

area, the Kokoruda Ranch Complex on the northeast corner 

of the batholith, and the Burton Park and Rader Creek plutons 

near the southern margin of the batholith (fig. 2). Thus, rock 

chemical information suggests that most of the early magma 

of this volcano-plutonic complex was erupted and relatively 

little of it crystallized in the crust.

Chemical analyses indicate that only ash flows of the 

middle member of the Elkhorn Mountains Volcanics were 

derived from the same magma as the Butte pluton or related 

silicic intrusive rocks. Chemical compositions of ash flows of 

the middle member plot in a silicic and potassic extension of 

the field plotted for the Butte pluton and related silicic plutons 

(compare figs. 4 and 8). Thus, the middle member of the 

Elkhorn Mountains Volcanics and the Butte pluton had a common source, and the middle member is probably a differentiate 

of the magma that formed the Butte pluton and other closely 

related silicic plutons (Tilling, 1974; Lambe, 1981; Rutland, 

1986; Rutland and others, 1989). Further, a volumetrically 

small part of the volcanic rocks are related to the Butte pluton, 

which is overwhelmingly the most voluminous part of the 

Boulder batholith.

Emplacement History

The 78- to 72-Ma volcanic-plutonic episode began with 

eruption of volcanic ash that was water-worked and became 

incorporated into Upper Cretaceous volcanogenic sedimentary deposits of the Slim Sam Formation. Early, voluminous 

volcanism was coeval with injection of the oldest, more mafic 

magmas into the upper crust along older, deep-seated fault 

zones. Magma of this generation intruded Paleozoic and 

Mesozoic prevolcanic country rocks and cooled to form the 

mafic plutons concentrated along the northern and southern 

margins of the batholith; most of the magma of this generation 

erupted to form the lower member of the Elkhorn Mountains 

Volcanics. During the main stage, more silicic magmas were 

injected, probably as sheeted dikes, into the progressively 

forming structural pull-apart in the upper crust, forming the

voluminous Butte pluton. Because the void created by the 

pull-apart was an ongoing process, apparently less magma 

was available to be erupted to form the middle member of 

the Elkhorn Mountains Volcanics. The upper member of the 

Elkhorn Mountains Volcanics documents the waning stages 

of volcanism and the return to a sedimentary environment, as 

much of the material in the upper member is water-worked 

tuff and coarse volcanogenic sedimentary rocks. The magma 

that formed the Butte pluton clearly intruded its own cogenetic 

volcanic cover rocks; that the lower member of the Elkhorn 

Mountains Volcanics is absent in the study area is consistent 

with the dynamic opening of a pull-apart and consequent 

tectonic transport of early, lower member volcanics to the 

east. Thus, the presence of the contact between the Elkhorn 

Mountains Volcanics and the Butte pluton in the study area 

suggests that the exposures of coeval volcanic-plutonic rocks 

are at or near the structural top of the pluton where it intrudes 

its volcanic cover.

Internal Geometry of Butte Pluton

Becraft and others (1963) and Ruppel (1963) described, 

and plate 1 illustrates, a textural pattern of finer grained rocks 

at the top of the Boulder batholith. The overall pattern is of an 

original chill zone of fine-grained rock at the roof and more 

slowly cooled, coarse-grained zones at depth; finer grained 

rocks near or at the original roof of the pluton are more common in the laccolithic part of the pluton in the west part of the 

area of plate 1. In some places, the coarser phases are in direct 

contact with the overlying roof rocks, suggesting an unsolidified, mobile interior of the magma body intruded above the 

level of its earlier formed chilled border. The large number of 

aplite dikes in the Butte pluton on the east side of the map area 

in the main body of the pluton probably represents late waterrich segregations that migrated into joints. Some of the aplite 

bodies that were mapped as irregular sheets are interpreted to 

be part of the chilled facies that formed near the roof of the 

magma chamber. This silicic, water-rich phase either chilled 

against the roof or was injected into joints as they formed during the contraction related to cooling of the whole pluton. The 

chilled phases of the roof zone also show evidence of having 

been stoped (cut loose and rafted in the magma) and of being 

assimilated by still-mobile magmas, resulting in some irregular outcrop patterns.

Tertiary Volcanic Rocks

Tertiary volcanic and intrusive rocks of the study area 

were mapped and classified by Becraft and others (1963) 

and Ruppel (1963) into "quartz latite" and "rhyolite" groups. 

These workers agreed with Knopf (1913, p. 41) that the 

"rhyolite" and "quartz latite" seem to represent two distinctly 

different periods of volcanic activity. Becraft and others (1963) 

and Ruppel (1963) correlated the "quartz latite" group with a 

part of the Lowland Creek Volcanics of early Eocene in age, as
68 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

defined by Smedes and others (1962) southwest of the study 

area. "Rhyolite" rocks in the study area have been included in 

the early Oligocene Helena volcanic field of Chadwick (1978).

Eocene Lowland Creek Volcanics

Smedes (1962) named and described the Lowland Creek 

Volcanics for a thick sequence of volcanic rocks and associated intrusive dikes and plugs exposed north and west of 

Butte, Mont. Lowland Creek, the type locality of these rocks, 

drains into the Boulder River about 7.5 mi upstream from the 

town of Basin. The original extent of the volcanic field was a 

northeast-elongate zone of about 125 mi2 , more or less centered near Lowland Creek. The northeasternmost extent of the 

volcanic field was just east of the study area at Jefferson City. 

Radiometric K-Ar age determinations indicate the volcanics 

are Eocene in age, 50-48 Ma (Smedes and Thomas, 1965). 

New ^Ar/^Ar ages suggest that some of these rocks may be as 

old as 52 Ma (Ispolatov and others, 1996).

Lowland Creek Volcanics are a complexly intertongued 

and interlayered volcanic and volcaniclastic sequence nearly 

6,100 ft thick. The layered rocks, in general, consist of a basal 

conglomerate overlain by welded tuff deposits that compose 

more than half of the volcanic sequence. Lava flows and vitrophyre make up the uppermost part of the sequence.

Lowland Creek Volcanics are present only in the southernmost part of the watershed study area. Tuffaceous rocks 

underlie Pole Mountain northwest of Basin as well as the nose 

of a small ridge at the confluence of Cataract and Big Limber Creeks just east of Basin. The remaining Lowland Creek 

rocks occur as small plugs, phreato-magmatic breccia pipes 

and diatremes, and abundant northeast-trending dikes best 

exposed near High Ore Creek. These volcanic rocks rest on 

partly exhumed Butte pluton rocks as well as on the cogenetic 

Elkhorn Mountains Volcanics.

Based on normative quartz, potassium feldspar, and plagioclase calculated from chemical analyses, Becraft and others 

(1963) and Ruppel (1963) classified rocks from this group as 

quartz latites. Becraft and others (1963, table 7, p. 28) reported 

the chemical analyses of four samples of intrusive rocks of this 

group. Ruppel (1963, table 4, p. 49) reported the analyses of 

two volcanic rocks and one intrusive rock from this group. Use 

of the R^-diagram of De La Roche and others (1980) plots 

three of Becraft's samples in the rhyodacite field and one just 

into the rhyolite field (fig. 9); Ruppel's analyses of welded tuff 

and intrusive rock samples plot in the rhyodacite field (fig. 9). 

Ruppel's lapilli tuff sample plots well to the right of the alkali 

rhyolite field (fig. 9); the high silica content is probably due 

to silicification after deposition. In general chemical composition (refer to fig. 10), the rhyodacite welded tuff sample of 

Ruppel (1963) clusters with the four intrusive rocks of Becraft 

and others (1963). The rhyodacite intrusive rock of Ruppel 

(1963) appears to be compositionally intermediate between the 

rhyodacite of the Lowland Creek Volcanics and rhyolitic rocks 

of the Helena volcanic field (fig. 10).

Eocene-Oligocene Helena Volcanic Rocks

The Helena volcanic field includes rhyolitic rocks in the 

northern part of the Boulder batholith, as well as silicic flows 

west, northwest, and east of Helena at Avon, Mullan Pass, 

and Lava Mountain, respectively. Rocks from this field have 

yielded radiometric K-Ar ages between 37.3 and 35.8 Ma 

(Chadwick, 1978). Rocks in the northern part of the Boulder 

batholith, near or within the study area, have not been dated.

Rhyolitic rocks of the Helena volcanic field are present along the Continental Divide in the western and northern 

parts of the watershed study area (pi. 1). The rhyolite consists 

of volcanic flows and tuffs on the west and forms intrusive 

centers near the Basin Creek mine in the north. The rock is 

porphyritic with common sanidine and biotite phenocrysts. 

The rhyolite was erupted onto an erosion surface of low relief 

and rests unconformably on plutonic rocks of the Butte pluton, 

Elkhorn Mountains and Lowland Creek Volcanics, and the 

Eocene-Oligocene sedimentary rocks of the poorly exposed 

and unmapped Renova Formation.

On the RjR^-diagram of De La Roche and others (1980), 

the four published analyses for samples of the Eocene-Oligocene rhyolitic rocks of the Helena volcanic field plot in the 

alkali rhyolite field (fig. 9). These rocks include two samples 

of flows collected by Ruppel (1963), a sample of silicified 

rock collected from the southeast flank of Red Mountain 

directly north of the study area by Becraft and others (1963), 

and a sample of rhyolite from the top of Red Mountain 

reported by Clarke (1910, p. 80). In addition to higher silica 

content than the Eocene Lowland Creek Volcanics, the 

Eocene-Oligocene alkali rhyolites of the Helena volcanic field 

have generally lower amounts of aluminum, calcium, magnesium, and titanium, and higher sodium and potassium (fig. 10). 

A silica-rich sample of the Lowland Creek Volcanics, Ruppel's 

(1963) lapilli tuff sample (likely silicified), is chemically similar to the Helena volcanic rocks (fig. 10).

Miocene-Pliocene Volcanic Rocks

Although no volcanic rocks younger than the Helena 

volcanic rocks have been recognized from the central parts of 

the Boulder batholith, Ruppel (1963) described basalt in the 

northwestern part of the area of plate 1, and he included these 

rocks with the Elkhorn Mountains Volcanics. Basaltic flows 

and flow breccias rest unconformably on the Elkhorn Mountains Volcanics; basaltic intrusive rocks commonly intrude 

them as well. Ruppel (1963) commented that the basaltic 

rocks west of the Basin quadrangle are folded and faulted in 

a style similar to that of the Elkhorn Mountains Volcanics in 

the Basin quadrangle. Based largely on the structural similarity, Ruppel (1963) provisionally included the extrusive basalts 

with the Elkhorn Mountains Volcanics.

Basalts are known from the Avon area, directly northwest 

of the area of plate 1. Trombetta (1987), in his study of Helena 

rhyolitic rocks exposed near Avon, recognized that the basaltic 

rocks in this area are the youngest of the extrusive rocks and
Geologic Framework 69

1,500 -

(R 1 = 5,248)

(R, - 4,023)

1,000 1,500 2,000 2,500 

T = 4,OOOSi -11,000(Na + K) - 2,000(Fe + Ti)

3,000

EXPLANATION

4> Intrusive rocks related to Lowland Creek Volcanics, called

"quartz latite" (n=4) and collected by Becraft and others

(1963, table 7, p. 28) 

^ Lowland Creek Volcanics: lapilli tuff (n=l), welded tuff

(n=l), and intrusive rock (n=l) called the "quartz latite

group" and collected by Ruppel (1963, table 4, p. 49) 

A. Helena volcanics flow rocks called the "rhyolite group"

(n=2) and collected by Ruppel (1963, table 4, p. 49) 

O Altered rhyolite from the Helena volcanics from southeast

slope of Red Mountain collected by Becraft and others

(1963, table 8, p. 30) 

~^f Rhyolite from the Helena volcanics from top of Red

Mountain, as reported by Clarke (1910, p. 80)

Figure 9. Classification of samples of Eocene Lowland Creek Volcanics and of Eocene-Oligocene volcanic rocks 

from the Helena volcanic field in the study area based on the R^-diagram of De La Roche and others (1980).

are not genetically related to underlying rhyolitic rocks. We 

have no definitive data regarding the age of the basalt flows, 

flow breccias, and intrusive basaltic rocks in the map area; 

however, on the basis of crosscutting relations observed 

directly northwest of the study area (Trombetta, 1987), at least 

some basaltic rocks are likely late Tertiary in age. No basaltic 

rocks are present in the study area.

Sedimentary Rocks

Lower Tertiary Sedimentary Rocks

Sedimentary rocks of early Tertiary age were not recognized in the study area by previous workers. Today, due largely

to numerous new roads constructed to accommodate development of the Basin Creek mine in the northern part of the study 

area and extensive logging operations in the western part, new 

exposures of bedrock in roadcuts have allowed recognition of 

previously concealed sedimentary rocks. The newly recognized rocks consist of poorly cemented and layered, light-gray 

to tan sediment composed of sand and silt derived mainly from 

erosion of batholithic rocks. The newly discovered sedimentary deposits are preserved only where they are overlain by 

more resistant Eocene to lower Oligocene rhyolitic rocks of 

the Helena volcanic field in the western and northern parts of 

the study area.

The new exposures are extremely limited and of poor 

quality, and are not shown on plate 1. Along the Elk Gulch 

tributary of Joe Bowers Creek in the northwestern part of 

the study area, the upper 3-4 ft of the sedimentary unit has 

been exposed. The sediments are weakly layered and locally
70 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

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EXPLANATION

^ Intrusive rocks related to Lowland Creek Volcanics, called "quartz latite" (n=4) and collected

by Becraft and others (1963, table 7, p. 28) 

ML. Lowland Creek Volcanics: lapilli tuff (n=l), welded tuff (n=l), and intrusive rock (n=l) called

the "quartz latite group" and collected by Ruppel (1963, table 4, p. 49) 

/A Helena volcanics flow rocks called the "rhyolite group" (n=2) and collected by Ruppel

(1963, table 4, p. 49) 

V Altered rhyolite from the Helena volcanics from southeast slope of Red Mountain collected

by Becraft and others (1963, table 8, p. 30) 

W Rhyolite from the Helena volcanics from top of Red Mountain, as reported by Clarke (1910, p. 80)

Figure 10. Marker variation diagrams showing abundances of major oxides versus Si02 for 11 samples of Eocene 

Lowland Creek Volcanics and of Eocene-Oligocene volcanic rocks from the Helena volcanic field in the study area.
Geologic Framework 71

contain cut and fill sedimentary structures. Here, the overlying 

rhyolile has baked the underlying sedimentary rocks, resulting 

in a 6-in. thick, bright-red zone of oxidation at the contact. An 

exploratory hole dug at the base of the exposure revealed 2 ft 

of loosely consolidated arkosic sand; the base of the sand was 

not reached.

The maximum thickness of the sedimentary rocks is not 

known; thickness is variable, as the unit is not everywhere 

present, and probably does not exceed 50 ft. Maximum roadcut thicknesses of about 15 ft are present west of the study 

area in the Red Rock Creek drainage basin, west of Thunderbolt Mountain and outside the area shown on plate 1. The 

distribution of the sediment appears to have been controlled 

by early Tertiary topography in this area. The sedimentary 

deposits appear to have filled in lower areas, while higher 

areas remained uncovered.

Although these sedimentary rocks were not previously 

mapped in the study area below the Helena volcanic rocks, 

somewhat anomalous geologic conditions present at this geologic horizon can be interpreted to reflect the presence of these 

deposits. Abundant colluvial deposits, landslides, and unusually moist and wet soil conditions associated with bogs and 

springs are present in many places along the lower contact of 

the Helena volcanic rocks. We suggest that the localized masswasting deposits and unusual hydrologic conditions reflect the 

presence of concealed, poorly consolidated, porous, and easily 

weathered sedimentary units at this contact.

Lower Tertiary sedimentary rocks are common in 

southwestern Montana but are mostly found only in 

present-day basins. These basin-fill sediments are part of the 

Bozeman Group of Robinson (1963) and have been divided 

into the older Eocene-Oligocene Renova Formation and the 

younger Miocene-Pliocene Six Mile Creek Formation. The 

older Renova filled sedimentary basins of unknown extent 

that formed in the Eocene. The Renova basins were later 

segmented by late Tertiary-Quaternary basin-range faulting. 

The Renova is known primarily from sparse outcrops along 

the margins of these young basins. In only one other uplifted 

mountain range in this region are lower Tertiary basin-fill 

sediments known to be preserved—the Gravelly Range south 

of the study area (CTNeill and Christiansen, 2002; Luikart, 

1997). In the Gravelly Range, loosely consolidated sandstone 

and siltstone containing Eocene-Oligocene vertebrate fossils 

are preserved beneath resistant volcanic rock.

Quaternary Deposits

The most extensive surficial deposits in the study area 

are glacial accumulations of Pleistocene age. These deposits 

comprise mainly morainal debris and outwash. On the east 

the glacial drift is largely confined to the headwaters area and 

valley bottom of Cataract Creek. On the west, in the Basin 

Creek watershed, glacial till is extensive, covering gentle,

east-facing slopes from Pole Mountain to the Continental 

Divide as well as the broad valley bottoms of Basin and 

Jack Creeks and their smaller tributaries. Ruppel (1963) and 

Becraft and others (1963), in their discussion of glaciation, 

concluded that the glacial deposits represent the older of two 

major late Pleistocene periods of glaciation in southwest 

Montana. The older glacial period, now commonly referred 

to as Bull Lake episode, ended about 120,000 years ago. Bull 

Lake glaciation was more extensive and reached lower elevations than the younger Pinedale episode, which was restricted 

to only the highest alpine areas of the region, some 18,000 to 

10,000 years ago. The assignment of the glacial deposits to 

the older, Bull Lake period of glaciation in the study area was 

based largely on the 6 to 10 ft depth of weathering of the till, 

the lack of conspicuous, preserved glacial morphology, and the 

relatively low elevation of the deposits.

The till is composed mainly of locally derived plutonic 

and volcanic rocks. Because much of the till is deeply weathered, smaller clasts in the original till are poorly preserved and 

most have disintegrated into unsorted sand- and granule-size 

grains that now form the interstitial matrix for larger, less 

weathered boulders.

Glacial outwash is exposed only in the Basin Creek 

drainage of the study area, at the confluence of Basin and Jack 

Creeks, and along Basin Creek about 2 mi southeast of the 

confluence. The deposits consist of pebbles and cobbles interlayered with fine- to coarse-grained sand lenses. Additional 

deposits of relatively coarse grained outwash are concealed 

beneath younger, finer grained stream and bog deposits along 

the upper reaches of Basin Creek as well. During the course of 

this study, stream and flood-plain deposits along Basin Creek 

at Buckeye Meadow were sampled in 10 relatively closely 

spaced monitoring wells in the vicinity of the Buckeye mine. 

In this area, coarse braided stream deposits interpreted to 

represent, in part, glacial outwash are overlain by as much as 

10 ft of thin stream sand and gravel lenses interlayered with 

organic-rich sand, silt, and clay deposited in levees, bogs, and 

backswamps (pi. 2). One well (site 4a, pi. 2) drilled in these 

organic-rich sediments intersected the 6,845 year old Mazama 

ash at 3.6 ft depth.

Less widespread surficial deposits are also present 

throughout the study area. These deposits include stream 

alluvium, localized alluvial fan deposits, colluvium, talus 

deposits, and localized landslides. Solifluction or down-slope 

creep of many of the finer grained surficial deposits appears 

to be occurring at the present time. Relatively gentle slopes, 

extensive exposures of deeply weathered, porous glacial till 

locally superimposed on weakly consolidated lower Tertiary 

sedimentary rocks, and relatively thick winter snow pack combine to produce a large area of water-logged, unstable surface 

conditions that engender down-slope creep of unconsolidated 

sediment during periods of snow melt and high runoff.
72 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Structural Geology and Tectonics

Introduction

Fracture systems in igneous rocks are a prominent 

phenomenon recognized and described worldwide. Perhaps 

the most commonly recognized fractures are primary nondiastrophic cooling and contraction columnar joints characteristic of volcanic flows and intrusive rocks emplaced at shallow 

depths. Fractures can also reflect diastrophic processes that 

record structural and tectonic events. The Butte pluton of the 

Boulder batholith, well known for its locally spectacular fracture systems (fig. 11), appears to contain both nondiastrophic 

and diastrophic features. Prominent nondiastrophic fracture 

systems are well exposed because the level of erosion of the 

pluton is minimal, and only the outer skin of the magma body 

(1,500 ft or less), where cooling fractures are best developed, is exposed. The Cretaceous Boulder batholith was also 

intruded during Laramide time into one of the more complexly 

deformed tectonic regions of the American Cordillera. The 

Butte pluton can be considered unusual because it appears to 

contain both primary and secondary diastrophic structures. Primary diastrophic fractures are herein interpreted to represent

structures related to the mechanism of intrusion of the pluton; 

colinear secondary fractures are postemplacement structures 

formed throughout the Tertiary and Quaternary in response 

to reactivation of deep-seated, earlier formed structures. The 

origin and orientation of the fracture systems in the pluton, 

including the nondiastrophic cooling features, appear to be 

intimately tied to the mechanism of emplacement of the igneous body.

The origin of the fracture systems presented here follows 

years of discussion regarding the origin of vein systems in the 

Butte pluton. The most recent discussion of their origin was by 

Woodward (1986), who correctly observed that polymetallic 

quartz veins developed in an east-west compressional stress 

field within the Sevier orogenic belt. Woodward (1986) postulated that the northeast and northwest vein systems represented 

conjugate shears in such a stress field, whereas east-trending 

fractures, which host the quartz-vein deposits in the study 

area as well as at Butte, were extensional fractures oriented 

parallel to the maximum principal stress trajectories. Although 

this proposal would apply to a static, cooling body intruded 

into an ongoing contractional environment, we do not believe 

it to be compatible with the mechanism of emplacement of 

the batholith described previously, in the section, "Mode of 

Emplacement."

Figure 11. Prominent fracture systems in Butte pluton. View to north from Interstate 90 about 2 mi east of 

Homestake Pass south of the area of plate 1.
Geologic Framework 73

Nondiastrophic Fracture Systems

Nine major fracture systems are recognized in the 

Boulder batholith. The primary age of six of these systems is 

established by the observation that aplite (including pegmatite 

and alaskite) dikes and quartz veins follow them. Three of 

the six primary fracture systems, best exposed in the Basin 

quadrangle, were interpreted by Ruppel (1963), following the 

terminology of Balk (1948), as nondiastrophic cooling joints: 

they are cross joints, longitudinal joints, and primary flat-lying 

joints (fig. 12). In the Boulder batholith, cross joints are steep 

to nearly vertical east-trending fractures spaced from about 

5 to 10 ft. Longitudinal joints trend north and generally dip 

steeply west; spacing on these fractures is from 1 to 5 ft. These 

two nearly vertical joint sets have been intruded in various 

localities by thin dikes of aplite. Primary flat-lying joints, 

which mainly dip gently south, have locally been intruded by 

thick sheets of aplite. In coarser grained facies of the batholith, 

joint spacing of north-trending fractures increases to 15 ft, 

and east-trending fractures are spaced at intervals as much 

as 40 ft. Individual joints are rarely longer than about 30 ft; 

however, where one joint dies out, it is commonly overlapped 

by a parallel joint that either is entirely separate and less than 

1 in. to several inches away, or is connected by a transverse 

joint or joint set.

Joint sets of identical orientation and character were 

described by Smedes (1966) from the northern Elkhorn 

Mountains directly east of the study area (fig. 13). In that area, 

the north-trending set is the better developed of the two nearly 

vertical sets.

The three primary, nondiastrophic fracture sets just 

described appear to be genetically related to the emplacement 

and cooling history of the batholith. Theoretical,

two-dimensional calculations of the stress field in static, cooling magma bodies in the crust have been presented by Knapp 

and Norton (1987). Theoretical calculations of such a magma 

body reveal a radial and concentric stress field in which the 

maximum principal stress is in the radial position (fig. 14). In 

such a case, tension fractures related to the cooling, crystallization, and contraction of a magma body will be vertical at 

the top and rotate to horizontal along the sides of the crystallized, brittle pluton. Nearer to the molten center of the magma, 

maximum principal thermal stress trajectories are deflected to 

horizontal and become concentric around the cooling center. 

Fractures formed directly above the cooling center are flat 

lying or horizontal.

The east half of the Butte pluton has been interpreted to 

have been emplaced within an ever-widening, east-directed 

pull-apart in the Helena embayment that was bounded by steep 

fault abutments on the north, south, east, and west (figs. 2, 

3). Along the roof of the crystallized, yet still cooling pluton, the stress field described by Knapp and Norton (1987) 

likely applies (fig. 14); that is, the maximum principal stress 

trajectories are vertical and the least principal stress is horizontal. However, because the inferred pull-apart emplacement 

mechanism is not static but an ongoing process, maximum 

stress is unlikely to be radial around the body; the likelihood 

is that it remains vertical along the sides of this particular, 

eastward-expanding pluton. Thus, the least principal stress 

must be horizontal and oriented east-west. In this kinematic 

scenario the intermediate stress must also be horizontal and 

directed normal to the confining walls on the north and south. 

With this configuration of stress trajectories, well-developed 

north-trending fractures should be a prominent joint set in the 

pluton. In the likelihood that growth of a pull-apart follows 

the conventional wisdom of strike-slip fault displacement, the

EXPLANATION

Contours, 

in percent

Figure 12. Contour diagram of 493 joints in Butte pluton rocks from west half of the area of plate 1, equal area 

projection on lower hemisphere (from Ruppel, 1963, pi. 5).
74 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Figure 13. Summary diagrams of A, joints; B, alaskite, aplite, and pegmatite dikes; C, veins; and D, faults and lineaments in the northern Elkhorn Mountains east of the area of plate 1 (from Smedes, 1966, fig. 30). A, Contour diagram 

of poles of 283 joints in Butte pluton and point diagram of poles of 11 joints in the Kokoruda Ranch complex. Contours 

2-6-10(11) percent. Equal area projection of lower hemisphere. B, C, D, Each rosette is a statistical summary showing relative abundance (percent) of trends of all high-angle planar structures of a given type and is weighted according to length. B, Solid line, dikes in the Butte pluton (n=685); dashed line, dikes in the Kokoruda Ranch complex 

(n=42). C, Solid line, metalliferous quartz veins (n=192); dashed line, chalcedony veins (n=698). D, Solid line, faults 

(n=996); dashed line, lineaments (n=1,357).
Geologic Framework 75

— — - Go (minimum principal stress)

(maximum principal stress)

Figure 14. Principal stress trajectories and net change in temperature (°C) in the model 

system at 0,35,000, and 150,000 years after pluton emplacement (from Knapp and Norton, 

1987, fig. 6). Rectangular box represents hypothetical pluton measuring 3 km wide, 4.5 km 

high, and infinite in the third dimension. Trajectories are radial and tangential around the 

cooling center located at the top of the pluton at 35,000 years after emplacement

horizontal intermediate and least principal stresses seem likely 

to switch positions periodically during magma emplacement. 

North-south least principal stress orientation should lead to the 

development of east-trending fractures as well.

Directly above the partly molten cooling center of the 

pluton, the maximum and least principal stress trajectories 

are deflected and switch orientations: the maximum principal 

stress trajectories become horizontal and the least principal 

stress is vertical (fig. 14). In this stress configuration, prominent horizontal or flat-lying fractures should develop. Because 

the cooling and crystallization of an igneous body proceeds 

from the outer rind toward the center, the horizontal fractures are probably the first joint system to form. The common horizontal fractures and joints, often filled with aplite, 

probably formed earliest, in the elastic, upper parts of the 

pluton directly above the cooling center where the maximum 

principal stress was horizontal. Vertical joints, sparsely filled 

with aplite, formed later in solidified regions farther away 

from the cooling center of the magma; these joints formed in 

response to horizontal tensile stresses related to the position 

of the least principal stress and a nonradial vertical maximum 

principal stress. As such, the joints formed should be of three 

orientations: one early-formed horizontal set and two vertical 

sets trending north and east. As observed by Smedes (1966), 

the north-trending fractures, which reflect the east-directed 

pull-apart mechanism, are the prominent tensile fracture in the 

batholith.

Given the theoretical parameters presented by Knapp and 

Norton (1987) and the mechanism of emplacement interpreted 

by Schmidt and others (1990), the orientation of the three 

observed primary, nondiastrophic joint sets in the Boulder 

batholith seems to conform with the thermal stress field postulated to occur during magma cooling within a progressively 

opening, east-directed pull-apart zone.

Synemplacement Diastrophic Fracture Systems

Of the six primary fracture systems in the study area the 

three remaining systems are diastrophic and appear to be best 

developed and their included fractures more numerous on the 

east in the Jefferson City quadrangle. These three fracture systems are best developed farther east in the northern part of the 

Elkhorn Mountains (figs. 13 and 15). These fracture systems 

are intruded by large aplite (alaskite) dikes or thin chalcedony 

veins, or are shear zones that contain quartz veins and polymetallic mineral deposits. That these fracture systems contain 

late melt fractions from the Butte pluton indicates that they are 

primary structural features. (See section on "Age," p. 81.)

Large aplite (alaskite) dikes that extend for many hundreds of feet are the most prominent linear features in the area. 

The preferred orientation of these dikes in the Jefferson City 

quadrangle and adjacent Elkhorn Mountains is northeast 

(fig. 15A). Becraft and others (1963) observed a bimodal
76 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

30

20

30

40

50

60

20 10 N 10

30

20 10 N 10

30

40 .40

50 .50

60 ,60

B

10 N 10

10

10 N 10

.60

Figure 15. Trends of dikes, veins, shear zones, and nonmineralized faults in the east half of the area of plate 1 (from Becraft 

and others, 1963, figs. 29,30,31,32, and 33). All data plotted in 10° increments; all data are from Jefferson City quadrangle. A, 

trends of 513 steeply dipping alaskite dikes. B, trends of 255 steeply dipping chalcedony vein zones. C, trends of 142 nonmineralized faults and topographically expressed lineaments. D, trends of 182 shear zones. £, trends of 177 Tertiary quartz latite dikes.
Geologic Framework 77

northeast trend with two rose diagram maxima at N. 25°E. and 

N. 55°E. Their rose diagram reveals a small but conspicuous 

N. 25°W. preferred orientation as well. To the northeast in the 

Elkhorn Mountains, Smedes (1966) observed and recorded 

equal numbers of northeast- and northwest-trending aplite 

(alaskite) dikes (fig. 13). Becraft and others (1963) also examined and described chalcedony veins that are most common 

in the southern part of the study area. Preferred orientation of 

chalcedony veins is N. 55°-65°E. (fig. 155).

The most important fracture system, based on its economic significance, is marked by east-trending shear zones as 

much as 6 mi long (fig. 15D). The zones are unusual because, 

although they cut the overlying Elkhorn Mountains Volcanics, 

offset is not observed along them. Moreover, the shear zones 

terminate at the east edge of the batholith and do not extend 

into the adjacent country rock. Also, east-trending faults have 

not been mapped in the western, laccolithic part of the batholith. Northeast-trending dikes of the middle Eocene Lowland 

Creek Volcanics cut the shear zone, and they themselves are 

neither sheared nor altered. The east-trending shear zones have 

slickensided surfaces that indicate oblique-slip movement; 

most zones dip steeply north. The major east-trending zones in 

the study area host the major mineral deposits and sites of the 

largest mines. The Comet mine on the east in High Ore Creek

and the Morning Glory mine in Cataract Creek are along one 

of these major east-trending zones; a second major east-trending shear is the locus of the Crystal mine in Uncle Sam Gulch 

and the Bullion mine along the south fork of Jack Creek 

(pi. 1). All these mines are point sources for acidic mine 

and(or) metal-rich drainage in the study area (Nimick and 

Cleasby, this volume, Chapter D5).

These three primary fracture systems parallel the major 

fault systems that controlled the location and shape of the 

batholith. Their genesis is interpreted to be related to the 

emplacement mechanism of the batholith (fig. 16). In our summary of the emplacement history of the batholith, we noted 

that the structural setting of the batholith is dominated by three 

sets of deep-seated northeast-, northwest-, and east-trending 

faults that first formed in Proterozoic time. All three sets were 

active during emplacement of the batholith and controlled not 

only its geographic position and its shape, but also earlyformed fracture systems in the igneous mass.

Early-formed fractures directly south of the batholith 

are northwest-trending reverse faults that offset crystalline 

basement rocks of the Rocky Mountain foreland; these faults 

accommodated Laramide basement crustal shortening that 

terminated against the northeast-trending axial suture of the 

Great Falls tectonic zone beneath the batholith. Displacement

Pull-Apart

Synemplacement EW-, NW-, and 

NE-trending diastrophic fractures

CORDILLERAN FOLD 

AND THRUST BELT

LACCOLITHIC WESTERN 

PART OF BOULDER 

BATHOLITH

Northeast-trending 

sheeted dike injection 

in crustal pull-apart

Northwest-trending

basement faults accommodate

crustal shortening in Rocky Mountain foreland

Figure 16. Schematic diagram showing relationship of deep-seated fault zones, which controlled emplacement of the Boulder 

batholith, to synemplacement diastrophic fractures in the Butte pluton. Butte-Helena fault is directly over central part of Great Falls 

tectonic zone.
78 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

of basement rocks along northwest trends at the floor of the 

batholith during its emplacement is inferred to have displaced 

crystallized, brittle batholithic rocks. The cooling, still partly 

molten core of the batholith would also be affected by fault 

movement, which would have enhanced leakage of late-stage 

magmatic melts into newly formed fracture systems. Northeast-trending fractures filled with alaskite dikes and chalcedony veins are interpreted to reflect synthetic and antithetic 

fractures formed subparallel to the Butte-Helena fault zone as 

the pull-apart expanded eastward.

The east-trending shear zones are subparallel to the 

bounding faults on the north and south. As the pull-apart 

widened eastward, it carried with it partly cooled, brittle 

batholithic rocks. The east-trending shear zones, which host 

the polymetallic quartz vein deposits and are restricted to the 

batholith, outline eastward-elongate blocks of Butte pluton 

rocks carried eastward during tectonism. The east-trending shear zones are interpreted to be accommodation zones 

within the batholith that allowed coeval, yet slightly disparate, 

eastward advance of the plutonic rocks during growth of the 

pull-apart.

Late Diastrophic Structures

Of the nine major fracture systems recognized in the 

batholith, the last three are secondary systems that owe their 

origin to reactivation of preexisting structures. Tertiary and 

Quaternary recurrent movement along preexisting faults and 

fractures in southwestern Montana has been documented 

by previous workers (for example, Schmidt and Garrihan, 

1983; O'Neill and Lopez, 1985; O'Neill and others, 1986). In 

middle Eocene time, northeast-trending fracture systems were 

important in controlling the location of intrusion of numerous 

dike swarms and igneous plugs and stocks along the Great 

Falls tectonic zone from east-central Idaho, across southwestern Montana, including the Boulder batholith, and extending 

into the high plains of north-central Montana. A significant 

amount of faulting along northwest trends began in the Miocene that marked the initiation of Basin and Range extension 

in southwestern Montana (Reynolds, 1979). Directly south 

and southeast of the Boulder batholith, northwest-trending 

faults that cut the Highland Mountains have been reactivated 

to form a series of horsts and grabens that trend northwest into 

the batholith (O'Neill and others, 1986). Faults that controlled 

the emplacement of the batholith are precisely those that have 

been reactivated in Cenozoic time. As such, in the study area, 

primary diastrophic fracture sets that formed in the Cretaceous 

are colinear with younger, Tertiary and Quaternary nonmineralized fractures and faults, lineaments, and dike swarms within 

the batholith.

Lineaments

In the Basin and Jefferson City quadrangles, a pronounced rectilinear drainage pattern trends northeast and

northwest. Because the bedrock in these linear drainages is 

concealed by surficial deposits, the reason for such prominent 

zones of weakness is not known. Two prominent drainages, 

the main northwest-trending stem of Basin Creek and northeast-trending Jack Creek, are examples of lineaments in the 

study area. That the lineaments formed after the emplacement 

of the Butte pluton is clear because they extend across all 

phases of the pluton without interruption. Northeast-trending, 

elongate breccia pipes and northwest-trending shear zones 

occur along and parallel to the lineaments and are thought to 

be localized along the structurally weak zones that the 

lineaments represent.

Dikes

Eocene Lowland Creek dikes in the eastern part of the 

study area and a younger belt of Oligocene rhyolitic volcanic 

rocks on the west show a strong northeast trend. The emplacement of these rocks is inferrred to have been controlled by 

structurally weak zones defined by many of the parallel 

lineaments.

Faults

Quaternary and Tertiary faults are not particularly 

conspicuous in the study area. The only significant faults are 

northeast- and northwest-trending structures that parallel topographic lineaments. Two northeast-trending faults are present 

in the northern part of the study area. The northernmost fault 

is the larger and parallels the Continental Divide, passing 

just north of Old Baldy Mountain (pi. 1). This fault cuts all 

bedrock units and, significantly, displaces glacial deposits, 

disrupts postglacial drainage patterns, and is marked by prominent scarps as much as 300 ft high. A second fault along the 

northwest flank of Three Brothers displaces only batholithic 

rocks; it does not appear to displace swamp and bog deposits 

along its trace. A large, northeast-trending fault zone is present 

in the southern part of the study area in Big Limber Gulch 

and High Ore Creek. This fault zone is marked by pervasive 

alteration of plutonic and volcanic rocks, giving the rocks an 

orange-red hue along the trend. The fault drops volcanic rocks 

of both the Elkhorn Mountains and Lowland Creek Volcanics 

on the northwest side relative to plutonic rocks on the southeast side. Two northwest-trending shear zones in the vicinity 

of Pole Mountain are zones of crushed rock bounded by sharp, 

nearly vertical faults.

Mineral Deposits

The mine wastes of particular interest to this study are 

related to Late Cretaceous quartz-vein polymetallic sulfide 

mineralization and alteration systems. Eocene breccia-pipe 

and Miocene disseminated precious-metal mineralization and 

associated alteration systems are also present in the study area,
Geologic Framework 79

and the resultant metals and areas of altered rock have also 

contributed to the present-day surficial environment.

Late Cretaceous Mineralized Rock

The Late Cretaceous polymetallic sulfide veins in the 

study area are in the Basin and Boulder districts. These 

districts were important primarily for their gold and silver 

production. Lead and zinc made up the largest volume of the 

metals recovered, although zinc was not recovered in the early 

operations because it could not be smelted and had little commercial value. Volumetrically lesser amounts of gold, silver, 

and copper were recovered, as reported from smelter data, but 

these were the metals of the most value. All these polymetallic 

veins have associated pyrite, which generates acid waters in 

oxidizing, near-surface environments.

Polymetallic deposits in the study area were discovered in 

the late 1860s, but most of the production probably took place 

from about 1883 to 1907 (see Church, Nimick, and others, this 

volume, Chapter B). Sporadic mining activity has been ongoing in the study area in the years following until 1997. Most 

of the opening up of the veins from the surface rather than by 

adits has been done since World War II.

Controlling Structures

Narrow brecciated and sheared zones and related joint 

systems host the polymetallic pyritic quartz-vein mineral 

deposits that are important to this study. These mineralized 

shear/breccia zones trend from east-west to about N. 80°E. 

and are nearly vertical, as discussed in the section, "Structural 

Geology and Tectonics." The longest zone is the Comet-Gray 

Eagle zone, which is about 6 mi long; it extends from Cataract 

Creek to the upper part of the Boulder River valley (pi. 1). 

Most of these zones are complex features along which different short fault segments anastomose and overlap to form the 

larger structure.

These mineralized veins are near the top of the Butte 

pluton. The veins die out upward into the volcanic rocks, 

perhaps indicating less open fracturing in the volcanic rocks in 

comparison to the plutonic rocks. Additionally, that the fluids 

responsible for these mineralized veins were concentrated at 

the top of the pluton can be inferrred from the large number 

of mines located near or at the top of the plutonic rocks (pi. 

1). Mines at the upper contact of the pluton, such as Gray 

Eagle, Bluebird-Pen Yan, and Boulder Chief mines in or near 

the southeastern part of the study area, are associated with 

shear zones; but these deposits are also reportedly somewhat 

pod-shaped (Becraft and others, 1963). Preferential location of 

mineralized veins near the roof of the pluton may be a result 

of the Elkhorn Mountains Volcanics acting as a caprock or 

impermeable barrier above the pluton.

Many of the polymetallic quartz veins are cut by Eocene 

dikes related to the Lowland Creek Volcanics. In places, the

dikes follow the trend of the veins, even splitting and 

complicating the vein exposures. Where parallel to veins, 

margins of the dikes are sheared in many cases, indicating 

continued fault movement along some of these shear zones 

from Late Cretaceous through at least Eocene time.

Polymetallic Quartz Veins

Vein material has intruded fractured and sheared zones; 

the veins have sharp contacts against the intruded wallrock. 

Vein systems range from just a few inches across to 50 ft wide. 

Many of the veins are complexly anastomosing systems of 

veins and veinlets, even branching off into horsetail structures, 

rather than being a single simple vein (Becraft and others, 

1963). However, in general, they have a tabular geometry. A 

general appearance of layering is common, reflecting repeated 

introduction of mineralizing fluids.

Quartz is the dominant mineral in the veins. Most early 

quartz is milky gray, whereas quartz introduced later in the 

sequence is commonly white. Few open-space features such 

as cockscomb structure or crystal terminations are present in 

the quartz. Absence of these features in deposits of this type 

is generally considered to indicate mid-level (mesothermal) 

deposits formed at a depth of 1-2.5 mi (Lindgren, 1933).

Tourmaline, commonly in the form of radiating black 

needles, is intergrown with quartz and pyrite. Volumetrically, 

it is the second most important vein mineral; it was a major 

constituent of the early veins but decreased in prevalence in 

the later veins.

Pyrite is the most ubiquitous sulfide mineral; fine to 

medium grains are disseminated in the quartz-vein material 

and in the nearby wallrocks. Argentiferous galena and sphalerite were the principal ore minerals. Argentiferous galena is 

also disseminated in veins and wallrock, but the argentiferous 

sphalerite is confined to the quartz veins. Chalcopyrite is common whereas the abundance of tetrahedrite is highly variable. 

Arsenopyrite is also disseminated in quartz. Arsenic-rich 

arsenopyrite was often sorted onto dumps or left in slopes; if 

present in the ore, it resulted in operators being penalized at 

the smelters. Stibnite, bornite, cosalite, enargite, chalcocite, 

ruby silver, boulangerite, bournonite, and albandite also have 

been reported from these veins (Becraft and others, 1963).

In many deposits, pink-tinged carbonate veinlets, stringers, and networks crosscut the other vein materials and form 

the youngest phase of the mineralized quartz veins. The carbonate is dominantly dolomite but ranges in composition from 

calcite to ankerite.

Chalcedony veins and quartz-chalcedony veins are 

younger than the quartz veins. These are not sulfide bearing 

but do contain uranium minerals. In places, these veins occupy 

the same fracture systems as the sulfide-bearing quartz veins, 

but they are predominantly found on the east side of the area 

of plate 1, deeper in the Butte pluton, and with strongly dominant northeast trends (Becraft and others, 1963).
80 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Alteration Envelopes

The mineralized veins are accompanied by complex 

and overlapping alteration zones that range from 2 to 300 ft 

in width. In the simple veins with well-defined boundaries, 

alteration zones are distributed symmetrically about the vein. 

Sericitic, argillic, and chloritic alteration zones are present. 

Nearest the vein, a narrow (1 to 4 in.) greenish-gray sericite 

zone developed in the wallrocks. The sericitic alteration zone 

consists primarily of sericite and quartz. Depending on the 

amount of quartz in this zone, the contact with the vein itself 

may be gradational or sharp. Pyrite and lesser argentiferous 

galena are in places finely disseminated in the sericitic zone 

(Becraft and others, 1963). Tourmaline is present along with 

quartz in some localities. Some muscovite is present in addition to sericite; it probably formed as an alteration product 

of biotite. Original minerals and rock textures are largely 

destroyed.

The typical argillic zone is dull gray white and clay rich. 

Original mineral outlines and rock textures are preserved. 

Plagioclase is altered to montmorillonite with lesser amounts 

of kaolinite, sericite, quartz, epidote, and calcite. Biotite is 

altered to montmorillonite and kaolinite with lesser amounts 

of illite, ilmenite, chlorite, and sericite. Potassium feldspar is 

only partially altered to kaolinite. The argillic zone as much 

as 10-15 ft wide and gradational with the sericitic zone over a 

narrow distance of less than 2 in. (Becraft and others, 1963).

The chloritic zone is typically wider than the sericitic and 

argillic zones. Original minerals are partially preserved and 

rock textures remain; the rock is generally nonfriable. Plagioclase is only partly argillized and is altered to sericite along 

fractures. Biotite and hornblende are altered to chlorite, minor 

clays, magnetite, ilmenite, epidote, quartz, and calcite. Potassium feldspar is only slightly altered or fresh. The chloritic 

zone is as much as 4-12 in. wide. It is diffusely gradational 

with the argillic zone over about 1 ft and is more broadly 

gradational with fresh rock. The persistent long Comet-Gray 

Eagle vein system has large alteration envelopes that are in 

places more than 300 ft wide.

The bulk changes of chemistry resulting from the alteration of country rocks are of particular importance in the study 

of the capacity of the country rocks to neutralize acid water 

generated by the exposure of sulfide mineral deposits to 

weathering and oxidation. Chemical profiles from the data of 

Becraft and others (1963) for alteration zones at two deposits in the area are shown in figure 17. Whereas the calcium, 

magnesium, and sodium concentrations are slightly decreased 

in the chloritic zones, the argillic and sericitic zones show 

marked decreases in these elements. This change in rock 

chemistry is due to the loss of mafic minerals during alteration 

processes. This loss of mafic minerals in the alteration zones 

affects the ability of the altered rock to neutralize acidic water. 

(See section, "Acid-Neutralizing Potential of Bedrock.")

20 feet 4 feet

3raltered wall rock

Na2O

o 

cc

o

X

o

1 -

N 

CD 

O"

O "i_

CD

C

"CD

E

3 

O

pyritic &

thoroughly

sericitized

o DC

o 

X

o

"virtually 

unaltered"

MgO

argillized

B

Figure 17. Variation diagram showing relationship of selected 

metal oxides in Butte pluton wallrocks and in alteration zones from 

two mines near the study area (data from Becraft and others. 

1963, tables 11 and 12, p. 44 and 45). A, Bunker Hill mine; 

B, G. Washington mine.
Geologic Framework 81

Origin of Mineralizing Fluids

Observations at the Bluebird-Pen Yan mine near the 

eastern border of the study area, the mineralogy of pegmatitic 

knots and segregations present throughout the study area, 

the mineralogy of rocks at the roof zone of the pluton, and 

observations of the silicate mineralogy of the veins all bear 

on the question of the origin of the mineralizing fluids. At the 

Bluebird-Pen Yan mine, rosettes of tourmaline intergrown 

with pyrite are common (Winchell and Winchell, 1912). The 

character of samples found on the Bluebird-Pen Yan dump is 

that of a water-saturated, incompatible element-rich, metalrich fluid that concentrated at the roof of the pluton. Estimates 

indicate that the deposits extended only about 1,300 ft below 

the roof of the pluton (Elliott, 1996, p. 36). A simple sulfidemineral zonation with depth, resulting in relatively fewer 

precious metals at depth, has been noted (Billingsley and 

Grimes, 1918). Tourmaline is more prevalent in the deposits 

that formed at the highest parts of the Butte pluton; it is also 

common in the pegmatitic/aplitic segregations and knots that 

also formed in the upper parts of the pluton. Knopf (1913) and 

Billingsley and Grimes (1918) related the zoning of metals to 

depth below the roof of the pluton. The presence of tourmaline 

in all these areas and types of fluid-rich segregations in the 

Butte pluton suggests that the sulfide mineralizing fluids were 

similar to late-stage fluids that formed fluid-rich compositional and textural segregations of various sizes in rocks near 

the roof. This indicates that these mineral deposits are related 

directly to the Butte pluton and not to a younger igneous 

event.

Polymetallic quartz-vein deposits in the study area (Basin 

and Boulder mining districts) are similar to those in nearby 

districts. Vein deposits in mining districts in the drainages 

north of the study area (Knopf, 1913) are similar to those 

in the study area in terms of scale and mineralogy and are 

probably of the same origin. Districts having the most similar 

characteristics are Rimini to the north and Clancy to the northeast. Some deposits in the Elkhorn Mountains mining district 

to the east are also similar. Of the districts in the Butte pluton, 

the quartz-vein deposits in the study area (and at Rimini and 

Clancy) probably formed closest to the top of the mineralizing 

system and at the shallowest crustal depths. Deposits farther 

north, near Helena, had a thicker roof that included Mesozoic 

sedimentary rocks in addition to Elkhorn Mountains Volcanics. Some of the quartz-vein deposits near Helena are closely 

related to the emplacement of Eocene porphyritic dikes, and 

many appear to be more like precious-metal skarn deposits 

than polymetallic quartz-vein deposits.

Polymetallic precious-metal quartz-vein deposits in and 

near the study area are clearly simple vein deposits compared 

to the complex situation in the Butte district to the southwest. 

Although much excellent work has been done in the Butte 

district, timing of mineralization and origin of complexly overlapping vein and porphyry deposits have not yet been completely worked out. Current data suggest that products of early 

vein mineralization at Butte may turn out to have had an origin 

similar to that of the polymetallic quartz-vein deposits near the 

study area. The bulk of the mineralized rock at Butte—the porphyry copper and molybdenum deposits—is clearly younger, 

however; and judging by published age information (Miller, 

1973), the deposits are too young to be related to the Boulder 

batholith. Deposits in the Butte district are distant from roof 

rocks, indicating a setting in which veins formed deeper within 

the hosting Butte pluton than veins near the study area to the 

north.

Tourmaline is an important constituent of the quartz-vein 

and alteration assemblages in deposits in the districts near 

Basin (including Rimini and Clancy) and in deposits considered to be the oldest and most closely related to the Butte 

pluton in the Elkhorn district in the Elkhorn Mountains to the 

east (Smedes, 1966). These districts containing tourmaline are 

all proximal to the roof of the Butte pluton. Interestingly, tourmaline is not reported in the vein or porphyry systems at Butte 

(Sales and Meyer, 1949; Becraft and others, 1963). Geologic 

information suggests that early vein deposits, now exposed at 

Butte, may have formed at a greater depth and that porphyry 

deposits are younger (Meyer and others, 1968; Miller, 1973) 

than polymetallic quartz-vein deposits in the study area.

Comparison to Other Veins in the Butte Pluton Age

No dates are currently available for the polymetallic 

quartz-vein deposits of the study area. Likewise, no dates 

are available for the silver-rich vein deposits to the north in 

the Helena drainages, or for the silver-rich vein deposits that 

were mined early in the Butte district (prior to discovery of 

the rich copper-molybdenum porphyry deposits at depth). 

Relative age relations show that the polymetallic quartz veins 

are clearly older than chalcedony veins and Lowland Creek 

Volcanics. The best evidence for the ages of the polymetallic quartz-vein deposits in the study area is that they seem to 

be related to late-stage crystallization of the Butte pluton and 

thus probably date from about 74 Ma (Lund and others, 2002). 

Reported dates for thermal events related to porphyry copper-molybdenum deposits at Butte are between about 65 and 

56 Ma (Miller, 1973). Thus, the porphyry systems at Butte are 

significantly younger than all phases of the Boulder batholith 

and must be unrelated to the polymetallic quartz-vein deposits 

that are of interest in this study.
82 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Tertiary Mineralization

Lowland Creek Volcanics Mineralization

Diatreme-related mineral deposits in the study area 

are in phreato-magmatic units (Tic) associated with Eocene 

Lowland Creek volcanism. The diatremes crosscut rhyodacite 

ignimbrite flows of the Lowland Creek Volcanics and Late 

Cretaceous plutonic and volcanic rocks. Some of the diatremes 

formed in the same north-northeast fractures as dikes (Tli) that 

are associated with the Lowland Creek Volcanics, and some 

are cut by Lowland Creek-related dikes indicating a relation 

to Eocene volcanism. The diatremes are primarily matrix rich 

breccia with sand-sized tuffaceous and quartzo-feldspathic 

matrix and diverse breccia fragments. The angular to subrounded breccia fragments include clasts of Lowland Creek 

Volcanics, Elkhorn Mountains Volcanics, Butte pluton, and 

carbonized wood (Becraft and others, 1963; Ruppel, 1963; 

Sillitoe and others, 1985). The composition of fragments and 

matrix indicate that the diatremes intruded the three rock 

types. The specimen that contained wood fragments indicates 

that the diatremes were locally open to the surface as in a maar 

volcano (Sillitoe and others, 1985). The diatremes are from 

300 ft to about 2 mi in length and are known to continue at 

least 1,000 ft in depth below the present surface (Becraft and 

others, 1963; Sillitoe and others, 1985).

Mineralized material is in the form of disseminated 

sulfide minerals in the breccia matrix associated with quartz in 

vugs and veinlets. In places, most of the matrix itself is sulfide 

minerals. Multiple episodes of mineralization and brecciation 

are evident. Sulfide mineralogy is pyrite, sphalerite, galena, 

minor chalcopyrite, and rare electrum. With the exception of 

the absence of arsenopyrite, this mineralogy is similar to that 

of the earlier polymetallic quartz-vein deposits (Sillitoe and 

others, 1985). Other minerals occurring with the sulfides are 

quartz, manganocalcite, rhodochrosite, and siderite. Tourmaline is noticeably absent in deposits of this age as compared 

to the earlier quartz-vein deposits (Sillitoe and others, 1985). 

Alteration zones include central serialization with carbonate minerals, minor silicification, and kaolinite formation in 

plagioclase. A more distal propylitic zone includes chlorite, 

montmorillonite, and carbonate (Becraft and others, 1963; 

Ruppel, 1963; Sillitoe and others, 1985). Preliminary 40Ar/39Ar 

dating from this study suggests that mineralization took place 

about 53 Ma (M. Kunk, unpub. data, 2000).

Recent mining of this type of deposit has occurred at the 

Montana Tunnels mine (Sillitoe and others, 1985) across the 

drainage divide 2 mi east of the study area. This was an openpit bulk mining operation that mined lower grade disseminated gold, silver, lead, and zinc. An historical deposit called 

Montana Tunnels east of the study area and the much smaller 

Obelisk deposit on the south edge of the study area were both 

mined by adits for gold and silver in 1900 or before (Becraft 

and others, 1963).

Helena Volcanic Rocks Mineralization

Oligocene pyroclastic rhyolite tuffs of the Helena volcanic field host disseminated gold deposits at the head of the 

Basin Creek drainage. The volcanic rocks originated from 

vents aligned along an east-northeast trend, which are, from 

west to east, the peak southwest of the Josephine mine, the 

peak at Carlson mine, Luttrell Peak, and Red Mountain (Smith 

and others, this volume, Chapter E3). In the volcanic rocks 

near the vents, the circulation of localized late-stage, ore-bearing hydrothermal fluids was pervasive and resulted in disseminated gold deposits near vents. These deposits are probably 

about 28 m.y. old, and formed immediately following consolidation of the volcanic rocks (Chadwick, 1978).

The disseminated gold deposits formed in two types of 

environment. The simplest deposits are in zones of intense 

alteration in the rhyolite flow layers in this interbedded 

sequence of flow and pyroclastic layers. The more complex 

type of deposit is along the contact between the older rocks of 

the Butte pluton and the young rhyolite where hydrothermal 

fluids moved along the weathered surface of the older plutonic 

rocks and up into the base of the volcanic rocks. Some primary 

mineralized rock is in the weathered rocks of the Butte pluton 

and in the upper parts of fractures in it (Dan Adams, Pegasus 

Corporation, oral commun., 1999). Primary gold is in finely 

disseminated pyrite and possibly locally in arsenopyrite 

(Ruppel, 1963). Intense low-temperature argillic alteration 

resulted in destruction of feldspars to form clays, and in 

silicification in the mineralized zones. Secondary enrichment 

resulted from oxidation of the primary pyrite during weathering. Gold has been the only metal produced from this type of 

deposit, making these significantly different from older pluton-related polymetallic quartz-vein deposits in the study area.

The most recent mining of this type of deposit was at the 

Basin Creek mine, where bulk mining of low-grade mineralized rock was undertaken for gold in three relatively small 

open pits. This recent mining activity was centered over areas 

of high-grade gold mineralized rock and in areas of historical 

mining that explored deposits formed by weathering and secondary enrichment. The historical mines were Venus (Martin, 

this volume, Chapter D3) and Pauper's Dream and Porphyry 

Dike (nearby, in Tenmile Creek headwaters).

Pervasive Alteration Systems

Several areas in the study area have undergone pervasive 

alteration that is unrelated to known mineralized systems as 

shown previously (Becraft and others, 1963). A large area of 

hydrothermal alteration, which was not previously shown, is 

near Big Limber Gulch and Cataract and High Ore Creeks 

in the southern part of the study area (pi. 1). This alteration 

resulted in chloritization of biotite and destruction of plagioclase to form clay minerals. The alteration zone seems to be 

related to north-northeast-trending normal faults and smaller 

structures that controlled emplacement of late-stage
Geologic Framework 83

chalcedony veins as well as Eocene dikes related to the 

Lowland Creek Volcanics. This zone of pervasive alteration is 

of a much larger magnitude than the narrow alteration envelopes that formed around the Late Cretaceous polymetallic 

quartz-vein deposits. Additionally, the setting is quite different 

from areas of alteration at the top of the Butte pluton directly 

under the volcanic roof rocks, such as at Jack Mountain and 

the Occidental Plateau, where alteration is more clearly a 

direct magmatic process involving water-rich fluids at the top 

of the magma chamber. These pervasively alterated rocks in 

the southern part of the study area may be related to Eocene 

Lowland Creek volcanism rather than to the older polymetallic 

quartz-vein deposits.

Hydrogen and oxygen isotopic study of rocks in the 

Boulder batholith included rocks of the Butte pluton in 

the study area (Sheppard and Taylor, 1974; Tilling, 1977). 

Samples taken by Sheppard and Taylor (1974) near Basin were 

mostly in the zone of the Eocene Lowland Creek dike swarm 

and structures that controlled them. Sheppard and Taylor 

(1974) concluded that most of the alteration in the study area 

was the result of meteoric water that circulated after solidification of the Butte pluton. They envisioned this process taking 

place during the Late Cretaceous or early Tertiary. In the 

absence of dating of the alteration-zone mineralogy, their data 

and observations would also support an Eocene age for the 

pervasive alteration event.

The location, size, and chemistry of these pervasive zones 

of alteration could affect the ability of the country rocks to 

neutralize acidic water.

Gold Placer Deposits

Placer mining of alluvial and glacial deposits containing gold was the earliest mining in the study area (Church, 

Nimick, and others, this volume). Some placer mines were 

also in areas where weathering and oxidation resulted in 

secondary gold enrichment above lode or disseminated deposits. In these areas gravity separation methods were used to 

mine as much as 100 ft of the uppermost, strongly weathered 

rubble. The discovery and mining of placer deposits was an 

important exploration clue that indicated the presence of goldbearing lode deposits in the study area.

Tin Placer Deposits

Tin, in the form of cassiterite, is reported in goldbearing placers along upper reaches of Monitor, Tenmile, and 

Basin Creeks (pi. 1). The source of the cassiterite is believed 

to be the Oligocene rhyolite of the Helena volcanic field on 

the Continental Divide ridge near the Basin Creek mine area 

(Ruppel, 1963).

Acid-Neutralizing Potential of Bedrock

The acid-neutralizing potential (ANP) of bedrock is an 

important control on water quality in areas of inactive mines 

and mill tailings. In areas of polymetallic quartz-vein deposits, 

such as the Boulder River study area, acidic drainage water is 

caused chiefly by the oxidation of the common gangue mineral pyrite. Interest in understanding the surficial water-bedrock chemical interactions in the Boulder River study area was 

prompted by the fact that even though numerous pyrite-bearing mine-waste piles lie in the area (Metesh and others, 1994: 

Metesh and others, 1995; Desborough and Fey, 1997), only a 

few, small acidic stream reaches exist (Nimick and Cleasby, 

this volume, fig. 2). The Boulder River watershed appears to 

have a natural acid-neutralizing capacity, and that capacity 

must be controlled by the mineralogy of the bedrock.

Acid-neutralizing potential values reported herein are 

converted to "calcite equivalent" regardless of whether the 

acid-neutralizing mineral is calcite or other minerals. Calcite equivalent has become the standard usage for engineering practices and other purposes related to acid-neutralizing 

potential. For simplicity, consider that 1 g (gram) of calcite 

will neutralize 10,000 g (10 L (liters)) of acidic water of pH 

= 3.0. In another context, a cubic foot of rock with 1 weight 

percent of calcite could neutralize about 8.4 tons (7,660 L) of 

water of pH = 3.0 if all the calcite were available to react with 

the acidic water.

Ruppel (1963) studied about 250 thin sections of the 

Butte pluton and Elkhorn Mountains Volcanics in the west half 

of the area of plate 1, but he reported no carbonate minerals 

that might contribute to acid-neutralizing potential. However, 

large slabs (10X10 cm) of fresh plutonic rocks studied by 

Desborough, Briggs, and Mazza (1998), using alizarin-red 

chemical stain, revealed minor amounts of calcite. Calcite concentrations from approximately 0.1 to 1.6 weight percent were 

determined based on total carbon analyses for 15 bedrock 

samples. Leaching studies using acidic (pH = 2.90) minewaste leachate showed that the acid-neutralizing potential of 

these bedrocks was greater than could be accounted for by the 

dissolution of these small amounts of calcite. A second quantitative study (Desborough, Briggs, Mazza, and Driscoll, 1998) 

of three samples of plutonic rocks and their separated mineral 

fractions, using acidic mine-waste leachate and analysis of 

total carbon for calculating calcite concentrations, showed that 

mafic minerals such as biotite, chlorite, and tremolite have 

significant acid-neutralizing potential. Table 1 summarizes 

the most significant aspects of mineralogical, chemical, and 

acidic leaching studies of the three samples of plutonic rocks. 

These samples had different concentrations of calcite, different 

concentrations of mafic minerals, and only minor differences 

in total acid-neutralizing potential. Although sample FMT020
84 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 1. Acid-neutralizing potential for three samples of plutonic rocks with different calcite concentration 

and different concentrations of mafic minerals, and total acid-neutralizing potential.

[Data from Desborough, Briggs, Mazza, and Driscoll (1998)]

Sample No.

Weight percent calcite

ANP of rock due to silicates expressed in wt. percent calcite equivalence

Weight percent mafic minerals

Total calcite equivalent ANP of rock as wt. percent calcite

FMT020

1.4

4.7

5.2

6.1

FMT022

0.4

5.8

16.5

6.2

FMT032

1.0

7.2

16.4

8.2

had only 5.2 weight percent of mafic minerals, it had about 

2.6 weight percent of chlorite, whereas the other two samples 

(FMT022 and FMT032) had no chlorite (table 1) but had 

higher concentrations of mafic minerals (16.5 and 

16.4 percent, respectively). The sample with minor chlorite 

had significant acid-neutralizing potential because magnesium-rich chlorite (clinochlore) has more acid-neutralizing 

potential than the other mafic minerals, tremolite and biotite. 

For this reason, the range in weight percent calcite equivalent 

acid-neutralizing potential among the three samples studied 

differed by only 25 percent, whereas the concentration of 

mafic minerals was tripled in the chlorite-free samples.

The Elkhorn Mountains Volcanics have significant 

acid-neutralizing potential owing largely to abundant chlorite. 

Because they lie above the polymetallic quartz veins, they 

could have some impact on acid generated from veins, because 

water percolating through the volcanics down to mineralized 

zones would have increased acid-neutralizing capacity.

Rocks that have been altered by hydrothermal solutions, 

such as those immediately surrounding the small polymetallic quartz veins explored and (or) mined for metallic minerals during the last century, have negligible acid-neutralizing potential because mafic minerals are virtually absent. 

Although these veins and adjacent altered rock represent less 

than a few percent of the study area (Ruppel, 1963; Becraft 

and others, 1963), they are the localities where the mines 

are situated so their negligible acid-neutralizing potential is 

significant.

Extensive hydrothermally altered areas that are silicified 

and highly fractured, such as at Jack Mountain, have insignificant acid-neutralizing potential (Desborough, Briggs, and 

Mazza, 1998). However, this alteration includes andalusite and 

pyrophyllite and is thought to be unrelated to the formation of 

polymetallic quartz-vein deposits.

A study of mineralogy and acid-neutralizing potential of 

some Butte pluton and Elkhorn Mountains Volcanics was conducted to explore bedrock suitability for mine-waste repositories in the Basin Creek drainage (Desborough and Driscoll, 

1998). Four sites were core drilled by the USDA Forest Service in 1998. Two were near the Bullion mine wastes and two 

were near the Buckeye/Enterprise mine wastes. One site near 

the Bullion mine-waste piles was drilled into highly silicified 

and fractured Elkhorn Mountains Volcanics on Jack Ridge 

east of Jack Mountain; acid-neutralizing potential of samples

was low and equivalent to only 0.4 weight percent calcite. 

The cored samples in Butte pluton drilled at a site within a 

few hundred yards of the Bullion waste piles had much larger 

acid-neutralizing potential, equivalent to 2.0 weight percent 

calcite. The two sites cored near the Buckeye/Enterprise mine 

were silicified or silicified+pyrite-bearing altered Elkhorn 

Mountains Volcanics; their calcite equivalent acid-neutralizing 

potential was only about 0.5 weight percent and they were 

intensely fractured—characteristics undesirable for minewaste repositories.

Cored rocks that had the highest acid-neutralizing 

potential (for example, near Bullion mine) had abundant magnetite in heavy-mineral concentrates made from these rocks, 

whereas those with low acid-neutralizing potential contained 

no magnetite in the heavy-mineral concentrates (Desborough 

and Driscoll, 1998, table 1). This difference in magnetite 

concentration is probably due to the destruction of magnetite 

during hydrothernal alteration. This observation is important 

because airborne magnetic data for the study area show that 

the hydrothermally altered areas have a much lower magnetic 

susceptibility than igneous bedrock unaffected by hydrothermal alteration, and it allows potential discrimination of altered, 

and thus low ANP, bedrock from airborne geophysical surveys 

(McCafferty and others, this volume, Chapter D2).

Summary

The description of the geologic framework, the new 

interpretation of the bedrock geology, and the discussion 

of the tectonic and structural history of emplacement of the 

Boulder batholith presented in this report focus on geologic 

topics that bear greatest relevance to reclamation efforts by 

Federal land-management agencies entrusted with the remediation of inactive mine sites in the watershed study area. The 

interpretive geology is portrayed in a consistent, contemporary geologic context designed to tie the geologic conditions 

to geochemical results for water, sediment, and ultimately to 

biotic habitat. Discussion of the mineralogic and textural character of the Butte pluton gives insight into the scope 

of the significant, widespread acid-neutralizing capacity of 

the bedrock and documents why acidic water is not presently 

more prevalent within the study area. Additionally,
Geologic Framework 85

recognition that the polymetallic quartz-vein deposits are 

restricted to rocks within 1,000 ft or less of the roof of the 

Butte pluton suggests that prior to mining, any acid water 

that may have been generated was quickly neutralized by the 

subjacent plutonic rocks. Recognition of weakly consolidated 

Eocene, largely unexposed sediments buried beneath Tertiary 

volcanic rocks that now underlie the Continental Divide helps 

explain the hydrology of topographically perched boggy and 

swampy areas and associated solifluction processes observed 

within the study area. The mechanism of emplacement of the 

Boulder batholith is crucial to understanding (1) the nature of 

the narrow, widely spaced fractures that initially controlled the 

locus of polymetallic quartz-vein deposits as well as (2) the 

pervasive, closely spaced cooling fractures that control the current hydrologic character of the plutonic rocks (McDougal and 

others, this volume, Chapter D9). Closely tied to the understanding of tectonic controls of emplacement of the batholith 

is the recognition of the propensity for recurrent movement on 

synemplacement fault or fracture systems and the initiation of 

younger faults with preferred orientations subparallel to the 

older structures.

Understanding the bedrock composition and geologic 

architecture and the characteristics and mode of emplacement 

of polymetallic quartz-vein deposits is intended to guide the 

land-management agencies in the selection of suitable repository sites where acid-neutralizing potential is present and 

where movement of ground water through fractures is minimal. Prior to mine development these polymetallic quartz-vein 

deposits were likely minor acid-producing sources surrounded 

by rocks with high acid-neutralizing potential.

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Geophysical Characterization of Geologic 

Features with Environmental Implications 

from Airborne Magnetic and Apparent 

Resistivity Data

By Anne E. McCafferty, Bradley S. Van Gosen, Bruce D. Smith, and Tracy C. Sole

Chapter D2 of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-D2

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract........................................................................................................................................................ 93

Introduction................................................................................................................................................. 93

Purpose and Scope........................................................................................................................... 94

Airborne Geophysical Survey................................................................................................................... 95

Apparent Resistivity Data................................................................................................................. 95

Magnetic Data Enhancements........................................................................................................ 95

Reduction-to-Pole .................................................................................................................... 95

High-Pass Magnetic Anomaly................................................................................................ 96

Magnetic Susceptibility Model.............................................................................................. 97

Geophysical Signatures of Geologic Features .................................................................................... 100

Quaternary Unconsolidated Deposits.......................................................................................... 100

Eocene-Oligocene Helena Volcanic Rocks................................................................................. 101

Eocene Lowland Creek Volcanics................................................................................................. 104

Upper Cretaceous Elkhorn Mountains Volcanics...................................................................... 104

Late Cretaceous Butte Pluton Granitic Rocks............................................................................ 106

Late Cretaceous Polymetallic Quartz Veins ............................................................................... 106

Geologic Structures and Geophysical Trends ........................................................................... 107

Geology-Based Geoenvironmental Map .............................................................................................. 110

Acid-Neutralizing Potential............................................................................................................ 110

Estimating Acid-Neutralizing Potential............................................................................... 110

Acid-Neutralizing Potential of Rock Units.......................................................................... 114

Acid-Generating Potential.............................................................................................................. 115

Effect of Acid-Neutralizing Minerals on Aquatic Health .......................................................... 115

Calcium, Iron, and Geophysical Response.................................................................................. 115

Geophysical Magnetite Maps ................................................................................................................ 115

Magnetite Estimates from Magnetic Susceptibility Model...................................................... 116

Magnetite Estimates from 900-Hz Apparent Resistivity Data................................................... 116

Relationship of Magnetite to Alteration Processes................................................................... 116

Relationship of Magnetite to Environmental Rock Properties................................................. 118

Geophysical Refinement of Geoenvironmental Map.......................................................................... 120

Geophysics-Based Geoenvironmental Map............................................................................... 120

Geology- and Geophysics-Based Geoenvironmental Map...................................................... 120

Implications for Siting of Waste-Rock Repositories.................................................................. 123

Summary.................................................................................................................................................... 123

References Cited...................................................................................................................................... 124
Figures

1. Index map showing generalized Boulder River watershed study area

and area of airborne geophysical survey.............................................................................. 94

2-5. Maps showing:

2. 7,200-Hz apparent resistivity data.................................................................................... 96

3. Reduced-to-pole magnetic anomalies............................................................................ 97

4. High-pass magnetic anomalies........................................................................................ 98

5. Magnetic susceptibility and estimated volume-percent magnetite models

calculated from high-pass magnetic data..................................................................... 99

6. Sketch illustrating concept of bulk magnetic susceptibility versus outcrop

susceptibility............................................................................................................................. 100

7. Geologic map showing main lithologic units...................................................................... 101

8. Box plot showing electrical resistivity versus geologic unit............................................ 102

9. Box plot showing magnetic susceptibility versus geologic unit...................................... 103

10. Histograms showing geophysical probabilities for mineralized and

nonmineralized veins.............................................................................................................. 108

11. Rose diagrams showing geophysical gradient trends...................................................... 109

12. Graph showing relation of calcium and iron content to pH of acidic mine-waste

leachate for samples of several rock units......................................................................... 111

13. Histogram and box plot showing acid-neutralizing potential of geologic units............ 112

14. Geology-based geoenvironmental map showing relative acid-neutralizing 

and acid-generating potential of geologic units, based on percentages of 

calcium and iron ...................................................................................................................... 113

15. Map showing electromagnetic magnetite anomaly.......................................................... 117

16. Diagram showing persistence of minerals, geophysical signatures, and

relative acid-neutralizing potential in alteration zones..................................................... 118

17. Geophysics-based geoenvironmental map showing locations of inferred 

low acid-neutralizing potential, based on low values of volume-percent 

magnetite calculated from airborne geophysical data..................................................... 121

18. Geoenvironmental map showing combined geology- and geophysics-based

relative acid-neutralizing and acid-generating potential of rocks.................................. 122

Tables

1. Map symbols, descriptions, and average sum of percent calcium and iron 

from whole-rock chemical analyses of samples collected in and around 

the Boulder River watershed study area............................................................................. 105

2. Relative acid-neutralizing potential from analyses of surface and core rock

samples collected in and around the Boulder River watershed study area................. 119

NOTE ON CONVERSIONS:

The scientific standard for measurements in this report is the metric system. To convert meters 

to feet, multiply by 3.28. To convert kilometers to miles, multiply by 0.62

Chapter D2

Geophysical Characterization of Geologic Features with 

Environmental Implications from Airborne Magnetic and 

Apparent Resistivity Data

By Anne E. McCafferty, Bradley S. Van Gosen, Bruce D. Smith, and Tracy C. Sole

Abstract

High-resolution magnetic and apparent resistivity data 

collected from airborne geophysical surveys characterize 

aspects of geologic features in and near the Boulder River 

watershed that have important environmental consequences. 

Physical properties of bedrock expressed in the geophysical maps as magnetic and apparent resistivity anomalies are 

intrinsically related to mineralogical and chemical properties 

that have the potential to neutralize or produce acidic metalrich waters. In particular, assemblages of acid-consuming 

minerals are directly associated with varying amounts of the 

mineral magnetite. Magnetite is the main source for magnetic 

anomalies and, in part, resistivity anomalies. The recognition 

of the relationship of magnetite to geophysical anomalies, 

alteration mineral assemblages, and acid-neutralization and 

acid-generation potential is one of the most important results 

of this study. Mathematical transformations applied to the 

magnetic and resistivity data result in pseudo-mineral maps 

that display volume-percent magnetite and that facilitate 

direct estimates of the associated amounts of acid-consuming minerals present in most of the rock types in the Boulder 

River watershed. The geophysical magnetite maps infer areas 

in the watershed with varying degrees of acid neutralization 

and, in some cases, map the locations of the acid-generating 

rocks. Many areas with low- to zero-percent magnetite coincide with areas of known hydrothermal alteration, silica-rich 

rock, and (or) geologic units containing sulfide-rich mineral 

assemblages, such as the polymetallic quartz veins. Results 

suggest that about 30 percent of the volcanic and plutonic rock 

lacks appreciable minerals to provide neutralization for acidic 

water. In the absence of much subsurface drill data, the threedimensional capability of the geophysical data provides information on the environmental properties of bedrock at depth. 

This study demonstrates the utility of geophysical surveying 

to address issues surrounding water quality, aquatic health, 

and selection of safe waste-rock repositories. The methods 

and approaches employed in this study can be applied to other 

watersheds with similar plutonic regimes containing acidgenerating historical mines or source rocks.

Introduction

The watershed approach to study and remediate historical 

mining areas has many environmental and economic benefits 

(Buxton and others, 1997). Watersheds are much larger in 

area and have more diverse environmental characteristics than 

individual mine sites. Therefore, implementing a watershed 

approach requires a broader study framework than might be 

used at a single site. In particular, techniques that reduce the 

resources needed for watershed-scale data collection and 

facilitate data analysis over large areas are especially useful. 

Airborne geophysical surveying is one example of such a 

technique.

Several characteristics of airborne geophysical surveys 

make them particularly useful for studying watersheds containing historical mines. First, data are collected essentially 

continuously, providing the same type of information for the 

entire survey area. In comparison, other related field tools, 

such as ground geophysical surveys or geochemical sampling, may have access and logistical constraints and typically 

provide only a limited amount of information for discrete sites 

or small areas. Second, geophysical surveys provide a third 

dimension to surface-collected information, providing insight 

on geologic properties with depth. Although subsurface geology has an important bearing on a range of hydrogeologic and 

geochemical issues important to the study of these watersheds, adequate resources often are not available for extensive 

drilling. Airborne geophysical mapping is also not hindered 

by vegetative cover or unconsolidated deposits, which can 

obscure bedrock geology.

Airborne geophysical surveys traditionally have been 

used for mineral prospecting, for structural geology studies, 

and in some instances, for mapping plumes of contaminated 

ground water. To our knowledge, airborne geophysical surveying has not been used previously in abandoned mine land 

studies on watershed scales even though geophysical techniques have the potential to address several key environmental 

issues related to historical mining and repository siting. This 

study was undertaken to determine the utility of airborne 

geophysical surveys to assess environmental aspects of this
94 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

watershed. Results of this study define how the geophysical 

data relate to environmental properties for many types of rocks 

that crop out throughout much of southwest Montana. Therefore, we expect that these study results can be extrapolated to 

other mining areas with similar rock types.

During the last decade, significant research has focused 

on determining the environmental signature of metallic 

mineral deposits and their effect on water quality and aquatic 

and human health (du Bray, 1995; Wanty and others, 1999). 

Plumlee (1999) has provided a succinct summary on the 

"environmental signature" of mineral deposits and a discussion on key geologic characteristics that control the degree of 

impact of a mineral deposit on the environment. This report 

takes an analogous approach, but describes a methodology to 

evaluate the environmental signature of bedrock geology and 

its influence on mitigating the negative effects associated with 

acid-generating mineral deposits in the study area.

Purpose and Scope

The purpose of this report is to combine high-resolution airborne geophysical data with geologic information to 

address environmental aspects in watersheds affected by historical mining. In particular, magnetic and apparent resistivity 

data are used to characterize the amounts of acid-consuming 

mineral assemblages within specific plutonic and volcanic 

rock units in and near areas of historical mining. Acidneutralizing potential is an important environmental property 

of bedrock that has bearing on the effects of historical mine 

sites on aquatic environment and selection of suitable sites for 

mine-waste repositories.

The area covered by the airborne survey includes most 

of the Boulder River watershed study area and parts of the 

adjacent Tenmile and Prickly Pear Creek watersheds. Where 

appropriate, we distinguish between the Boulder River watershed study area and the larger geophysical survey area (fig. 1).

46°30' 112°22'30" 11215' 112°07'30"

46°22'30"

46°15'

Target

drainages of the 

Boulder River 

watershed study 

area

5 MILES

10 KILOMETERS

Figure 1. Boulder River watershed (part) and area of airborne geophysical survey.
Geophysics and Environmental Implications 95

Two geoenvironmental maps were produced to portray 

the relative degree of acid-neutralizing potential of bedrock. 

One map is based on geologic information and the other on 

airborne geophysical data. The first map was derived from 

rock-sample mineralogy, where acid-neutralizing potential 

was assigned to specific rock units based on amounts of 

acid-consuming minerals. The second map, derived from the 

geophysical data, shows acid-neutralizing potential as a function of magnetite abundance. Magnetite abundance correlates 

well with the abundance of acid-consuming minerals and can 

be estimated from the geophysical data by the application of 

mathematical transformations.

Finally, the study combines the geology- and geophysics-based geoenvironmental maps to spatially portray bedrock 

characteristics that are important controls on the impact of 

acid-generating mineral deposits on shallow subsurface and 

surface environments. The resultant map has important environmental implications for abandoned mine land issues in the 

Boulder River watershed.

Airborne Geophysical Survey

During December 1996, a high-resolution airborne geophysical survey was flown by helicopter over parts of the High 

Ore and Cataract Creek basins. The following year, a second 

survey was flown to augment the 1996 survey over the Basin 

Creek basin on the west and also over the east side of the 

study area. Geophysical data were acquired at the beginning of 

the Boulder River watershed study so that maps and derivative 

products could help researchers prioritize ground investigations. The two surveys were flown with identical specifications 

for compatibility and were digitally combined to form one 

data set that is analyzed in this report.

Magnetic and apparent resistivity data were collected 

along flightlines spaced 200 m apart and flown along an 

azimuth of 160°/340°. The electromagnetic (EM) field was 

measured with three frequencies (900. 7,200, and 56,000 Hz) 

using horizontal coplanar transmitting and receiving coils 

towed in a "bird" or sensor that varied in elevation but generally was located at approximately 30 m above the ground 

surface. The helicopter towed the sensor at higher altitudes in 

populated areas, or where higher altitudes were appropriate for 

safe flying, for example, over powerlines. The magnetic-field 

sensor was mounted 15m above the electromagnetic sensor.

Data were collected approximately every 3 m along the 

flightline. The flightline data for the magnetic anomaly and 

resistivity data were interpolated onto a 25 m interval grid. 

Digital flightline data, grids, and information on other derivative geophysical products from this survey are available on 

CD-ROM (Smith and others, 2000).

Apparent Resistivity Data

The electromagnetic sensor measures the electrical 

resistivity (or the reciprocal, conductivity) of rocks. The depth 

of investigation for EM measurements varies inversely as a 

square root of frequency and earth resistivity (Telford and 

others, 1976) with the highest frequency (56,000 Hz) having 

a depth of investigation from the surface to a few to 10 m. 

The mid-frequency (7,200 Hz) has a depth of investigation 

of approximately 30 m. The lowest frequency (900 Hz) can 

explore as deep as 60 m.

EM measurements can be affected by noise from cultural 

sources such as powerlines. For example, a series of linear 

anomalies caused by a large powerline in the southern part of 

the survey area is evident in the data for all three frequencies. 

In comparison to the other frequencies, noise from cultural 

sources is elevated in the 56,000-Hz data. However, noise is 

minimal in the 7,200- and 900-Hz resistivity maps and only 

data from these two frequencies were used in this report. A 

map showing apparent resistivities from the 7,200-Hz data 

is shown in figure 2. Resistivity signatures as defined in the 

7,200-Hz resistivity map were used to distinguish geologic 

units and structures. Data from the 900-Hz apparent resistivity 

were used to derive a pseudo-mineral map of magnetite.

Magnetic Data Enhancements

Aeromagnetic surveying is based on mapping variations 

in the local magnetic field, which are caused by changes in 

concentration of various magnetic minerals in surface and subsurface rocks. In order to emphasize magnetic features from 

sources in the shallow geologic environment, a number of data 

enhancement techniques were applied to the magnetic data. 

The purpose of the enhancements was to transform anomalies 

into forms that can be directly compared with important rock 

mineralogical properties. This section describes enhancements 

that (1) correctly positioned anomalies over their causative 

sources, (2) increased the resolution of small-scale anomalies 

related to near-surface magnetic sources, and (3) convened 

data to a model of magnetic susceptibilities for comparison 

with rock mineralogical properties.

Reduction-to-Pole

The study area is located at a geomagnetic latitude where 

magnetic anomalies are shifted slightly to the southwest from 

their sources (assuming induced magnetization) and are represented by an anomaly pair determined, in part, by the inclination of the present-day Earth's field. To correct anomalies for 

this offset in symmetry and position, a filter called reductionto-pole (RTF) was applied to the magnetic data (fig. 3) using 

programs available in Phillips (1997). Application of the RTF 

filter results in magnetic anomalies correctly positioned over 

their sources and, most importantly, allows for a more accurate 

interpretation of magnetic source location relative to geologic 

features.
96 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

46°30' 112°22'30" 11215' 112°07'30"

46°22'30"

4615'

Target 

drainages in the 

Boulder River 

watershed study 

area

5 MILES

10 KILOMETERS

Figure 2. 7,200-Hz apparent resistivity data showing lateral variations in electrical resistivity of rocks from surface elevations to 

approximate depth of 30 m. Data from this map were used to define resistivity characteristics of geologic units.

High-Pass Magnetic Anomaly

To aid interpretation of anomalies related to near-surface 

geologic units, a "match" filter was applied to the RTF data. 

Match filters facilitate first approximations of magnetic fields 

corresponding to sources at relative depths based on ranges 

of wavelengths. The filter was employed using methodology 

developed by Syberg (1972) with computer programs in Phillips (1997). Application of the filter for this study yielded a 

short-wavelength anomaly field that approximates the

magnetic response of a shallow magnetic source layer located 

within the upper 200 m of the Earth's crust (fig. 4).

We focused our analysis on the magnetic response from 

the shallowest depth layer, defined here as the "high-pass" 

magnetic anomaly, because this shallow layer is related to 

near-surface geologic units and processes important to this 

study. Additionally, the depth range of the shallowest magnetic 

source layer corresponds most closely to the depths of investigation of the apparent resistivity data and to the depths where 

acid-neutralization reactions most likely occur.
Geophysics and Environmental Implications 97

46°30'

112-151 112°07'30"

46°22'30"

46151

Target

drainages in the V

Boulder River

watershed study

area

5 MILES

10 KILOMETERS

Figure 3. Reduced-to-pole magnetic anomaly map. Data in this map were filtered to enhance magnetic anomalies associated 

with shallow magnetic sources (fig. 4} and produce models of magnetic susceptibilities and volume-percent magnetite (fig. 5).

Magnetic Susceptibility Model

A model of magnetic susceptibility was calculated from 

the high-pass magnetic anomaly data to approximate the 

causative physical property producing the anomaly field, and 

also as an intermediate step toward estimating volume-percent 

magnetite. Magnetic susceptibility is almost entirely related to 

the abundance of the mineral magnetite because other magnetic minerals such as pyrrhotite, maghemite, and ilmenite are 

scarce in rocks exposed in the Boulder River watershed study

area (Ruppel, 1963; Becraft and others, 1963). In addition, the 

susceptibility of magnetite is roughly 100 times the susceptibility of pyrrhotite (Dobrin and Savit, 1988). Therefore, we 

can be quite confident that the magnetic anomalies observed in 

the geophysical survey are overwhelmingly influenced by the 

distribution of magnetite.

Prior to estimating magnetic susceptibilities, we calculated a magnetization model from the high-pass anomaly data 

using a method from Blakely (1995) modified by 

J.D. Phillips (USGS, written commun., 2002). The method
98 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

117°77"3n" 46°30' 1ir^U

46°22'30"

46°15'

Target 

drainages in the 

Boulder River 

watershed study 

area

5 MILES

10 KILOMETERS

Figure 4. High-pass magnetic anomaly map calculated from reduced-to-pole magnetic anomaly data (fig. 3). Map emphasizes 

short-wavelength magnetic anomalies caused by lateral variations in magnetic properties of rocks exposed on the surface to 

approximate depths of 200 m.

inverts gridded magnetic anomaly data to magnetization 

estimates. For this study, we defined a 200 m thick rock layer 

with an upper surface represented by topography. The thickness was defined from the estimated thickness given from the 

matched filtering process. To obtain a first estimate of magnetization, the high-pass data were divided by an appropriate factor that produced reasonable magnetization estimates. 

These data were used as a first approximation to a magnetization model. The magnetic effect of the first approximation for 

magnetization was calculated, and the output magnetic field 

was scaled against the high-pass anomaly data for a best fit in

terms of least squares. A difference grid was produced by subtracting the magnetic field calculated from the first approximation from the high-pass data. Magnetic values in the error grid 

were scaled to appropriate magnetization values and added to 

the first approximation to create a second approximation. This 

process was repeated until a minimum difference between the 

calculated field and high-pass magnetic field was achieved. 

The magnetic anomaly field resulting from the final magnetization model contained errors of less than 2 gammas for more 

than 95 percent of the grid. We converted magnetizations to 

magnetic susceptibilities by dividing the magnetization values
Geophysics and Environmental Implications 99

by the total intensity of the geomagnetic field and assuming 

induced magnetizations. The magnetic susceptibility model is 

shown in figure 5.

The range in model susceptibility values is significantly 

narrower than the range of susceptibilities measured in either 

field observations during this study, or from results of

magnetic-property laboratory studies of Hanna (1969). Susceptibility measurements taken at outcrop can typically range 

over orders of magnitude and can do so within the same rock 

type over short distances (within a few centimeters in some 

cases). The discrepancy between field and model susceptibility values is not surprising, however, and is controlled in large

46°30'

112e22'30' 112°07'30"

46°22'30"

46°15'

Target 

drainages in the 

Boulder River 

watershed study 

area

EXPLANATION

• Rock sample location 

(Desborough, Briggs, and 

Mazza, 1998)

• Rock sample location 

(Desborough, Briggs, Mazza, 

and Driscoll, 1998)

Volume-percent magnetite (est) 

Apparent magnetic susceptibility 

(ess

1.7 1.8 >1.9 

0.0043 0.0045 >0.0048

5 MILES

0 5 10 KILOMETERS

Figure 5. Magnetic susceptibility and estimated volume-percent magnetite models calculated from high-pass magnetic data (fig. 4). 

Magnetic susceptibility characteristics for geologic units within airborne geophysical survey are given in figure 9. Values for percent 

magnetite at locations of rocks analyzed for acid-neutralizing potential are given in table 2. Low values of volume-percent magnetite 

(<1.4 percent) are shown in blue and infer areas of rocks with low acid-neutralizing potential. In contrast, red areas infer bedrock with 

high magnetite content and corresponding high acid-neutralizing potential.
100 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

part by scale. Field susceptibility measurements sample only 

a very small volume of rock, and values can vary greatly due 

to relatively small changes in magnetic mineral content. In 

contrast, the susceptibility model based on airborne surveying represents the integrated response of magnetic properties 

within a much larger volume of rock (illustrated in 

fig. 6). Magnetic susceptibilities from the model do, however, 

fall within the range of susceptibilities measured in laboratory 

and field. The model calculations are reasonable values for the 

types of plutonic and volcanic lithology present in the watershed, and they produce a magnetic field that closely approximates the observed field. These factors support the assumption 

that the model susceptibilities provide a reasonable representation of rock magnetic properties within the near surface.

Figure 6. Sketch illustrating concept of bulk magnetic 

susceptibility versus magnetic susceptibility measured at outcrop. Measurements taken from an airborne magnetic sensor 

integrate effects from a much larger volume of rock compared 

to measurements taken at outcrop.

Geophysical Signatures of 

Geologic Features

This section presents an overview of the apparent 

resistivity and magnetic susceptibility signatures for approximately 40 geologic units organized under six major lithologic 

groups. These groups include Quaternary deposits, EoceneOligocene Helena volcanic rocks, Eocene Lowland Creek 

Volcanics, Upper Cretaceous Elkhorn Mountains Volcanics, 

Late Cretaceous Butte pluton granitic rocks, and Late Cretaceous polymetallic quartz veins (fig. 7). In addition, statistical 

approaches were used to define geophysical signatures of the

polymetallic quartz veins and to quantify geophysical gradient 

trends related to geologic structures.

Geophysical signatures for the geologic units are presented as box plot diagrams that present summary statistics. 

The resistivity (fig. 8) and magnetic susceptibility (fig. 9) 

charts are effective visual tools to illustrate the range in 

physical property variation inherent in a single geologic unit, 

showing similarities, differences, and overlap in geophysical 

signature among multiple units. Interpretation of the physical 

property characteristics is described in terms of the geologic 

factors and processes that influence the range of resistivity and 

magnetic susceptibility values. The diagrams were produced 

by determining the physical property values that had overlap with a particular geologic unit from 100x100 m grids of 

geology (Ruppel, 1963; Becraft and others, 1963), 7,200-Hz 

resistivity (fig. 2), and magnetic susceptibility data (fig. 5).

Quaternary Unconsolidated Deposits

Unconsolidated deposits are mainly glacial deposits and 

alluvial sediments found primarily on the valley floors. Low 

electrical resistivities characterize the Quaternary deposits; 

values average approximately 180 ohm-m. In general, the 

surficial deposits are electrically conductive (resistivity lows) 

relative to bedrock because of contained water, interconnected 

pore space, and predominance of clays. The chemistry and 

amount of the contained water can be highly variable and have 

a significant effect on the electrical properties of rocks. For 

example, if interstitial water is dilute, that is, free from salinity 

and dissolved metals, and there is little connected pore space, 

high resistivities will result. Alternately, as is likely the case 

for most of these Unconsolidated deposits, the abundant pore 

space is connected and the sediments are saturated, resulting 

in a decrease in electrical resistivity.

There is considerable overlap between the resistivity of 

the Unconsolidated deposits and that of many other geologic 

units, especially the Tertiary volcanic units (fig. 8). This 

overlap can be attributed to similar amounts of clays, which 

developed either as part of hydrothermal processes or from 

low-temperature weathering processes. Both processes can 

produce clays with similar resistivity ranges (Telford and others, 1976). Local resistivity anomaly highs that occur in valley 

floors are interpreted to be the resistivity response of shallowly 

buried bedrock that projects from adjacent hill slopes.

Although resistivity anomalies are produced from electrical property changes in the Unconsolidated deposits, magnetic surveying is relatively insensitive to magnetic property 

changes in the sediments. Rather, the magnetic anomaly map 

is dominated by magnetic properties in the underlying bedrock 

because the Unconsolidated deposits are effectively magnetically transparent owing to the relatively thin mantle of unconsolidated deposits in comparison to the volumetrically large 

underlying bedrock ''Ruppel, 1963; Becraft and others, 1963). 

Although magnetite is present in the Unconsolidated deposits, 

the amount of magnetite is not sufficient to cause significant 

magnetic anomalies.
46°30' 112°22'30"

Geophysics and Environmental Implications

112°07'30"

101

46°22'30"

46°15'

Target 

drainages in the 

Boulder River 

watershed study 

area

[~j Alluvium, landslide and

glacial deposits >

SMILES

10 KILOMETERS

Figure 7. Main lithologic units within area of airborne geophysical survey over the Boulder River watershed study area and surrounding region. Generalized from Ruppel (1963) and Becraft and others (1963).

Eocene-Oligocene Helena Volcanic Rocks

Rocks mapped as rhyolite intrusives (Tri) in the Helena 

volcanic field are generally some of the most resistive rock 

units in the study area (fig. 8). The largest Tertiary intrusive 

body in the study area is exposed at Red Mountain (fig. 7). 

A sample of intrusive rhyolite from the top of Red Mountain 

contained more than 75 percent SiO2 . An altered counterpart 

to the fresh rhyolite collected on the southeast slope of Red 

Mountain contains a slightly higher (81 percent) but comparable amount of silica (Becraft and others, 1963, p. 30).

The large amplitude resistivity high (fig. 2), moderately low 

amplitude magnetic anomaly (fig. 4), and mineralogy at Red 

Mountain are evidence that silica-rich fluids were introduced 

as part of the alteration event. Silica-rich rocks typically have 

low magnetic susceptibility owing to their decreased magnetite content and high electrical resistivities (Telford and others, 

1976).

In contrast, intrusions that are part of the Helena volcanic 

field that exhibit a much different geophysical signature and 

show evidence of a hydrothermal event with more potassic-rich fluids exist in other parts of the airborne geophysical
2,000

C/3

CC

1,000

800

700

600500

400

o

^ 300

K 200LU CC

100

80

70

60

50

CO O) i"5 !!! O3 "O ^ CO -Q

E E - ^

C »-5?

CD 5f

EXPLANATION

[jjp Hydrothermally altered rock 

H Polymetallic quartz veins HI?] Butte pluton granitic rocks 

H Elkhom Mountains Volcanics I I Lowland Creek Volcanics 

LJ Helena volcanic rocks 

LJ Alluvium and glacial deposits! 90 75 50 25 10 

Percentiles

ooo

CD

n.

GEOLOGIC UNIT

Figure 8. Electrical resistivity characteristics from 7,200-Hz resistivity grid (fig. 2) for geologic units within airborne geophysical survey. Geologic unit symbols from Ruppel (1963) and Becraftand others (1963). Unit descriptions in table 1.
=i LU 

CO UJ

COo

0.0162 

(6.48)

0.0144 

(5.76)

0.0126 

(5.04)

0.0108 

(4.32)

0.0090 

(3.6)

0.0072 

(2.88)

0.0054 

(2.16)

0.0036 

(1.44)

0.0018 

(0.72)

0.00

ll

E E

GEOLOGIC UNIT

EXPLANATION

[~~| Hydrothermally altered rock

B Polymetallic quartz veins 

[~1 Butte pluton granitic rocks

Ly Elkhom Mountains Volcanics 

I I Lowland Creek Volcanics I I Helena volcanic rocks 

I I Alluvium and glacial deposits

T 90

75

5025 

-1- 10 

Percentiles

Figure 9. Magnetic susceptibility and volume-percent magnetite estimates shown in figure 5 modeled from high-pass magnetic anomaly data (fig. 4) for geologic units within airborne geophysical survey. Geologic unit descriptions from Ruppel (1963) and Becraft and others (1963) and in table 1.

CDo

fo'

CO

to

CD

I

3"3
104 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

survey area. The most prominent of these are located east of 

Bison Mountain and north of the Boulder River watershed 

study boundary, in the northwestern part of the airborne 

geophysical survey. Very large amplitude "bullseye" resistivity and magnetic anomaly highs ringed by distinct resistivity 

and magnetic anomaly lows (fig. 2 and fig. 3, respectively) are 

located here, representing both extremes in highest and lowest 

modeled magnetic susceptibilities and electrical resistivity 

values. Although undivided Tertiary rhyolite (Tr) is mapped 

here (Ruppel, 1963), we interpret the geophysical anomalies 

to represent the response of a vent area with a large intrusive 

body at shallow depth. Geologic evidence for other vent areas 

along a northeast trend occurs in this area (O'Neill and others, 

this volume, Chapter Dl). The resistivity anomaly high is 

interpreted to represent the electrical response of a more silicified cap over the intrusive center. Emplacement of the inferred 

intrusive has significantly altered the surrounding host rock 

resulting in the magnetic and resistivity lows that surround 

the circular geophysical highs. Additionally, the resistivity 

lows surrounding the source suggest that the hydrothermal 

fluids were not silica rich. Other areas with similar geophysical signatures occur over outcrops of undivided rhyolite rocks 

exposed at Lava Mountain and at Spruce Hills (fig. 7).

Eocene Lowland Creek Volcanics

Resistivity values have the greatest variability in rocks 

that form the Eocene Lowland Creek Volcanics. Relatively 

high resistivity values characterize the lapilli tuff (Til) unit 

of Ruppel (1963), whereas very low resistivities characterize 

the volcanic sandstone (TIs) unit of Ruppel (1963). Chemical analyses of a sample of Til (Ruppel, 1963, p. 49) showed 

exceptionally high percentage of silica, which is in agreement 

with the overall high resistivities that characterize this rock 

(fig. 8). Extremely low apparent resistivities occur over the 

volcanic sandstone unit (TIs). Average resistivity for this unit 

is 120 ohm-m and is consistent with resistivities expected for 

clays (Telford and others, 1976), which suggests that clays are 

well developed in this unit. Additionally, sedimentary rocks 

typically have lower resistivities compared to igneous rocks, 

owing to increased porosity.

The Lowland Creek Volcanics are characterized by low 

magnetic susceptibility values (fig. 9). The low values are the 

combined response from remanent magnetization and nonmagnetic mineralogy. Total magnetization is a vector sum of 

induced (also called normal) magnetization (Mn) and remanent 

magnetization (Af);

M I =M 

n +Mr

where normal magnetization is the product of the Earth's magnetic field (//) and magnetic susceptibility (k);

Mn = kH

The magnetic susceptibility model (fig. 5) was calculated assuming that remanent magnetization is not a dominant 

factor in the plutonic and volcanic rocks in the study area and 

that normal magnetization, which is primarily a function of

magnetic susceptibility, is the main contributor to magnetic 

anomalies in the study area. This is true for most rock types 

in the study area. However, remanent magnetization is present 

in some units within the Lowland Creek Volcanics (Hanna, 

1969), but it is of such low intensities that its contribution 

to total magnetization is minimal. Of more importance in 

explaining the magnetic anomaly lows (and low magnetic 

susceptibilities) that typify much of the outcrop of Lowland 

Creek Volcanics is the nonmagnetic mineralogy of the rocks. 

Average susceptibility for more than 80 outcrop measurements 

of Lowland Creek Volcanics is 0.00005 (cgs), which is 

20 times lower than average susceptibilities of Elkhorn Mountains Volcanics, and 50 times lower in value than average 

susceptibilities measured in Butte pluton granitic rocks.

A large area of magnetic lows occurs over outcrops of 

Lowland Creek Volcanics in the vicinity of the Wickes mining 

district, located southeast of the Boulder River watershed, 

where rocks are pervasively altered (Becraft and others, 1963). 

The cause of the magnetic anomaly and magnetic susceptibility lows is the destruction of magnetite due to introduction 

of hydrothermal fluids, which have chemically removed 

magnetite.

Upper Cretaceous Elkhorn Mountains Volcanics

The range of resistivity and the magnetic susceptibility values for the units of Elkhorn Mountains Volcanics are 

similar in overall geophysical character to those of the Butte 

pluton units. However, some notable differences can be seen. 

As discussed in O'Neill and others (this volume), only the ash 

flow deposits of the middle member of the Elkhorn Mountains 

Volcanics were derived from the relatively silica rich magma 

that produced the Butte pluton. The other volcanic units in the 

group were derived from more mafic phases of the Boulder 

batholith, are less voluminous, and lie outside the geophysical 

study area.

Three units were grouped on the generalized geologic 

map by O'Neill and others (this volume, pi. 1) to define the 

middle member, Kevm; these include Kva1, Kva2, and Kv2 

(table 1). The magnetic susceptibility ranges of the three map 

units (fig. 9) are almost identical, so a geophysical rationale 

exists for grouping these three units into one composite unit. 

Resistivity ranges for the three units also overlap (fig. 8). 

However, some areas of unit Kva2 have significantly higher 

resistivity values, suggestive of a more silica rich composition 

than the other two middle member map units have. Additionally, in the geology-based geoenvironmental map section 

(p. 110), we show that Kva2 is significantly different in 

chemical composition, enough to warrant a separate 

classification from the other units in this volcanic group.

Assuming that the middle member map units in the 

Elkhorn Mountains Volcanics were derived from a more silica 

rich phase of the Butte pluton, we expect that their magnetic 

susceptibilities would be lower and their resistivities higher 

in comparison with upper member units presumably derived
Geophysics and Environmental Implications 105

Table 1. Map symbols, descriptions, and average sum of percent calcium and iron from whole-rock chemical analyses of 

samples collected in and around the Boulder River watershed study area.

[Sum of calcium and iron reflects the presence of calcic and mafic mineral assemblages that provide significant ANP to low pH waters. 

Rocks with higher percentages of calcium and mafic minerals possess higher ANP. The chemical data are used to create the geologybased geoenvironmental map shown in figure 14. Relative ANP is defined in varying degrees: H, high; MH, moderately high; M, 

moderate; ML, moderately low; L, low. Leaders (--), samples not available for chemical analyses and no ANP assigned]

Geologi

Original12

ic map symbol

Generalized3

Description Percent Ca+Fe Relative ANP

Quaternary alluvium and glacial deposits

Qg1

QTst1

Qal1

Qst1

Qg

Qg

Qal

Qal

glacial deposits

gravel veneering strath

alluvium

fan gravel

-

~

-

-

-

-

-

-

Tertiary Helena volcanic rocks; rhyolite

Trl1

Tril,2

altered Tri2

Trf1 '2

Trb1

Tr12

Trl

Tri

Tri

Trf

Trb

Tr

lapilli tuff

intrusive

altered intrusive

flow

flow breccia

undivided

-

1.92

0.62

1.5 1

-

-

-

L

L

L

-

-

Tertiary Lowland Creek Volcanics; quartz latite

Tli 1

Tit1 -2

Tls 1

Til 1

Tlf1

Tied1

Tla1

Tli

Tit

Tls

Til

Tlf

Tied

Tla

intrusive rocks

tuff

sandstone

lapilli tuff

lava flow

clastic dikes

welded tuff

3.21 -2

-

-

0.5 1

—

-

3.21

ML

-

--

L

~

-

ML

Cretaceous Elkhorn Mountains Volcanics

Kvt1

Kvl 1

Kv1 '2

Ki2

Kvi 1

Kvib1

Kval 1

Kva2[

altered Kva2

Kv22

Kv32

Kvs 1

Kev

Kev

Kev

Kei

Kei

Kei

Kevm

Kevm

Kva2

Kevm

Kevu

Kevu

crystal tuff

lapilli tuff

undivided volcanics

rhyodacite porphyry

intrusive andesite

intrusive basalt

lower dark-gray and greenish-gray welded tuff

upper medium- and light-gray welded tuff

upper medium- and light-gray welded tuff

light-greenish-gray to light-gray welded tuffs

well-bedded dark-gray tuffs

andesitic sandstone

-

-

-

6.52

—

-

6.3 1 -4

5.1 1

1.34

6.14

9.1 2

-

-

--

-

MH

-

-

MH

M

L

MH

H

-

Cretaceous Butte pluton granitics

cm2

altered cm4

cl2

cla2

md1 -2

altered md4

Kbm

Kbm

Kbm

Kbm

Kbm

Kbm

undivided coarse and medium grained

undivided coarse and medium grained

coarse-grained light-gray biotite-hornblende

coarse-grained light-gray biotite-hornblende

medium grained dark gray

medium grained dark gray

6.32-4

2.32

5.82'4

6.52

5.7 1 '2-4

1.82

H

ML

MH

MH

MH

L
106 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 1. Map symbols, descriptions, and average sum of percent calcium and iron from whole rock chemical analyses of samples 

collected in and around the Boulder River watershed study area.—Continued

Geologic map symbol Description Percent Ca+Fe Relative ANP

Original1 -2 Generalized3

Cretaceous Butte pluton granitics — Continued

mda2

mdb1

mdc1

ml2

mla1 -2

mid1

g1

fll,2

fla1 -2

fib1 -2

flc2

fd1 -2

fda2

a2

Kbm

Kbm

Kbm

Kbm

Kbm

Kbm

Kbm

Kbf

Kbf

Kbf

Kbf

Kbf

Kbf

Kba

medium grained dark gray

medium grained medium gray with pink tint

medium grained with abundant mafic minerals

medium grained light gray

medium grained light gray, reddish-brown tint

medium grained light gray with abundant biotite

fine to medium grained, dark gray

fine grained light gray

fine grained light gray porphyritic

fine grained light gray with pink tint

fine grained light gray

fine grained dark gray

fine grained dark gray porphyritic

alaskite, aplite, and pegmatite

7.02

7.1 1

6.91

3.1 2

4.42-4

--

7.91

5.01 '2

--

4.61

4.32

5.01 -2

4.62

0.82

MH

MH

MH

ML

M

-

H

M

-

M

M

M

M

L

'Ruppel, 1963. 2Becraft and others, 1963. 3O'Neill and others, this volume. "Desborough, Briggs, Mazza, and Driscoll, 1998.

from a more mafic magma. However, the geophysical data 

suggest that the middle member units are more similar in 

geophysical character to the other units than the interpretation 

of the rock chemistry suggests.

Late Cretaceous Butte Pluton Granitic Rocks

In comparison to other granitic plutons of similar mineralogy, the Butte pluton is characterized by lower than normal 

resistivity values. The relatively low resistivity values initially 

puzzled us given that typical resistivities for similar granitic 

rocks are in the thousands of ohm-meters range (Telford and 

others, 1976). Resistivity for most of the Butte pluton granitic 

rocks ranges from approximately 300 to 800 ohm-m (fig. 8). 

The lower than average resistivity values determined from 

the airborne survey imply that the pluton has been greatly 

affected by surficial weathering, hydrothermal alteration, and 

fracturing within its upper 60 m. Clays, which result from 

either low-temperature weathering or hydrothermal processes, 

tend to lower the resistivity of igneous and volcanic rocks. 

Consequently, altered volcanic and plutonic granitic rocks are 

typically less resistive (more conductive) in comparison with 

their fresh unaltered state. Direct current electrical resistivity soundings made from ground measurements on the Butte 

pluton confirm that the electrical resistivity of the first 30 m is 

on the order of 200 to 300 ohm-m in many places, again much 

lower than expected (Smith and Sole, 2000).

Studies of magnetic properties of Butte pluton granites 

show that these rocks possess normal polarity and that intensities of remanent magnetization are negligible (Hanna and 

others, 1994). The intensities present in the form of normal

magnetizations are strong enough to contribute significantly 

to magnetic anomaly intensities. Consequently, magnetic 

anomalies over the pluton can be chiefly explained by magnetite content. Granite that contains more magnetite has a 

stronger magnetization and results in a more positive (larger 

amplitude) magnetic anomaly. In granite that has undergone 

chemical alteration, whether hydrothermal or deuteric, primary 

magnetite has been destroyed and the rock is associated with 

a more negative (lower amplitude) magnetic anomaly (Hanna, 

1969). Alteration typically causes conversion of magnetite to 

nonmagnetic, more highly oxidized and hydrated iron-oxide 

minerals such as limonite (Ruppel, 1963). In cases where 

redox conditions are reducing, magnetite can be destroyed as 

its iron is reduced. The resulting ferrous iron is combined with 

sulfur to form pyrite (Desborough and Driscoll, 1998). Overall, the resulting geophysical effect of the alteration processes 

is a reduction in magnetization and a corresponding lowering 

of the intensity of the magnetic anomaly. A detailed analysis 

of magnetite content within the environmentally important 

Butte pluton follows in a later section.

Late Cretaceous Polymetallic Quartz Veins

Two types of veins cut the Butte pluton granitic rocks of 

the study area. East-trending polymetallic quartz veins host 

the ore deposits exploited by mining. Generally northeast 

trending chalcedony veins that are not mineralized also cut the 

granitic rocks. Geologic characteristics associated with mining the east-trending polymetallic quartz veins exert the most 

negative impact on the surface-water quality in the Boulder 

River watershed study area. Water draining from mines, adits,
Geophysics and Environmental Implications 107

and waste associated with the polymetallic veins is a major 

source for acidic and metal-rich surface waters (Nimick and 

Cleasby, this volume, Chapter D5; Kimball and others, this 

volume, Chapter D6). Geophysical characteristics that define 

these mineralized veins include low magnetic susceptibilities (fig. 9) and moderately high resistivities (fig. 8). The 

statistical summaries presented in the resistivity and magnetic susceptibility diagrams are useful to view the range of 

physical properties that characterize a particular feature, but 

they do not allow for a comprehensive understanding of how 

"distinct" or characteristic these signatures are in comparison 

with geophysical signatures of other geologic features.

To quantify how characteristic (or not) low magnetic 

susceptibilities and high resistivities are of the mineralized 

veins, we applied a statistical approach using methodology 

developed by Lee and others (2001) to the resistivity (fig. 2) 

and magnetic susceptibility data (fig. 5). The approach uses a 

ratio of probabilities, also called weights (W), to describe the 

statistical likelihood of a class of a particular evidential layer 

having a spatial association with a given prototype area. For 

this study, the evidential layers are the magnetic susceptibility 

and resistivity data, and classes are defined as values within 

these data. Prototypes against which we compare the evidential layers include locations of polymetallic quartz veins and 

nonmineralized chalcedony veins (Ruppel, 1963; Becraft and 

others, 1963).

Weights fall within three general categories that describe 

the spatial association:

a positive spatial association exists if W> 1;

a negative spatial association exists if W< 1; and

a random association is present if W = l

To illustrate, a weight of 30 would suggest that a particular class, high values of resistivity, for example, within a 

geophysical data layer would be 30 times more likely to be 

associated with a particular mineral deposit than any other 

feature in the study region.

The geophysical signatures of nonmineralized chalcedony veins were examined to determine if the two vein types 

could be distinguished on a geophysical basis.

Histograms that describe the spatial association between 

the resistivity and magnetic susceptibility data and polymetallic quartz and chalcedony veins are shown in figure 10. 

Results show that moderately high resistivities, in the range 

of 1,750 to 2,500 ohm-m, characterize the polymetallic quartz 

veins. Resistivities for the nonmineralized chalcedony veins 

show a strong spatial association (W> 1) with a slightly 

lower resistivity range (1,050 to 1,700 ohm-m). High electrical resistivities that characterize both vein types may reflect 

the presence of resistive gangue minerals (quartz) and low 

porosity of the vein material.

Polymetallic quartz veins are characterized by very low 

magnetic susceptibilities (fig. 10). Model magnetic susceptibilities that characterize the mineralized veins range from 

-0.0059 to -0.0026 (cgs). This range of values is interpreted 

to be a combined effect of demagnetization of once magnetite-rich host rock from hydrothermal alteration processes and

the nonmagnetic mineralogy of the vein material. In contrast to 

the resistivity signature, no particular magnetic susceptibilities 

characterize the chalcedony veins as evidenced by the random 

spatial associations defined by weights that fluctuate around 

the value of 1 (fig. 10). The lack of distinct magnetic signature 

of the chalcedony can be attributed to the narrower alteration 

envelopes surrounding the chalcedony veins compared to the 

wider alteration envelopes surrounding the polymetallic quartz 

veins (Becraft and others, 1963). Fluids associated with the 

emplacement of the chalcedony veins only locally altered the 

country rock. In contrast, fluids associated with the emplacement of the polymetallic quartz veins had a more profound 

effect on the wall rock, resulting in larger alteration envelopes 

and greater modification of host rock magnetic mineralogy 

(Becraft and others, 1963).

Geologic Structures and Geophysical Trends

Obvious features in the geophysical maps are linear 

gradients that trend over kilometers. Many gradients and narrow elongate anomalies define faults and structures that map 

contacts between rocks with different resistivity or magnetic 

properties. Faults can be expressed as linear resistivity lows if 

the degree of fracturing is high (equivalent to high porosity), 

clay has developed from weathering or alteration processes, 

and (or) water is present. Alternately, fault zones that contain 

silicified fractures, are dry, and have little clay present commonly are expressed as resistivity highs. Resistivity values 

can be orders of magnitude higher in dry, unfractured rock in 

contrast to wet and fractured rock (Olhoeft, 1985). The magnetic expression of faults depends on the magnetic properties 

of the adjacent rocks. If a fault juxtaposes rocks with similar 

magnetic properties, no magnetic expression of the geologic 

contact is likely. However, if a nonmagnetic rock is adjacent to 

a highly magnetic rock type, a distinct magnetic gradient will 

mark the fault contact.

Geophysical gradient trends are defined as distinct linear 

and curvilinear elements that can be mapped from contours in 

the geophysical data (Grauch, 1988). Figure 11 shows geophysical trends calculated from grids of the 7,200-Hz apparent 

resistivity (fig. 2) and RTP magnetic anomaly data (fig. 3). 

Dominant geophysical trend directions are co-linear with the 

orientation of three major fracture systems in the region. These 

orientations include a set of northeast- and northwest-trending 

structures, and a third east-trending set. The three principal 

fracture systems likely reflect deep-seated and reactivated 

structures related to emplacement of the Boulder batholith and 

to have been active recurrently since the Proterozoic (O'Neill 

and others, this volume).

Dominant orientations of geophysical gradients are northwest and west-northwest. The northwest-trending gradients 

are partly co-linear with faults and lineaments mapped by 

Smedes (1966) and lineaments mapped from remote sensing 

data within and around the Boulder River watershed study area 

(McDougal and others, this volume, Chapter D9). Although
108 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

126 178 229 280 331 382

APPARENT RESISTIVITY, IN OHM-METERS 1550 3968

MAGNETIC SUSCEPTIBILITY, IN CENTIMETER-GRAM-SECONDS

Figure 10. Statistical probabilities (weights) that describe the spatial association between A, resistivity, or 

B, magnetic susceptibility and mineralized polymetallic (red) or nonmineralized (blue) veins. The greater the 

weight, the stronger the spatial association. Low values of magnetic susceptibility, in the range of -0.0049 to 

-0.0022, are two to fourteen times more likely to occur over the polymetallic veins than any other geologic feature 

in the study. Alternately, the nonmineralized veins have no characteristic magnetic susceptibility signature; a 

weak to random spatial association exists as evidenced by weights around the value of 1. Results of the modeling 

for resistivity data show that both vein types are strongly associated with moderately high values of resistivity.
Geophysics and Environmental Implications 109

60

EXPLANATION

Geophysical trends co-linear with: 

| Faults and lineaments (Smedes, 1966)

Structures host to Tertiary quartz 

latite dikes (Becraft and others, 1963)

East-west shear zones host to mineralized 

veins (Smedes, 1966; Becraft and others, 

1963)

Figure 11. Geophysical gradient trends from A, grids of reduced-to-pole magnetic anomaly (fig. 3) 

and B, 7,200-Hz apparent resistivity data (fig. 2); both plotted in 10 increments. Colors indicate increments of geophysical trends co-linear with trends of mapped geologic features.

the mapping performed by Smedes lies outside the Boulder 

River watershed study, a similar structural and geologic setting exists in our study area (O'Neill and others, this volume). 

The less dominant geophysical gradient trend direction is 

northeast, which is co-linear with trends of alaskite dikes and 

chalcedony veins mapped in the Jefferson City quadrangle 

(Becraft and others, 1963).

The preferred northwesterly trend in the geophysical data 

is not obvious in the geology or mapped structures for the area 

(Ruppel, 1963; Becraft and others, 1963) but is reflected in 

topography. Streams form a northeast-northwest rectilinear 

drainage pattern in parts of the study area, and some linear 

magnetic and resistivity lows follow segments of this drainage 

network. Details pertaining to the structures along the drainages are poorly understood because the structures are partly 

or entirely concealed by younger volcanic rock or surficial 

deposits.

One interpretation for the strong northwest-trending linear magnetic lows is destruction of magnetite in shear zones. 

Zones of major tectonic adjustment may be expressed in 

magnetic maps as linear magnetic anomaly lows, especially if

these zones were affected by recurrent thermal activity. Ruppel 

(1963) and Becraft and others (1963) interpreted the rectilinear 

drainage pattern to reflect structurally weak zones that have 

persisted as controlling structures since the Proterozoic. These 

zones are characterized by steeply dipping deep-seated faults 

that were first formed in the Proterozoic and reactivated during 

the emplacement of the Boulder batholith. The presence and 

distribution of elongate breccia pipes (Ruppel, 1963) provide 

supporting evidence of the northeast-trending structural zones. 

East-trending resistivity and magnetic anomaly gradients 

define a third trend set (fig. 11). These geophysical trends 

parallel shear zones that host the polymetallic mineralized 

veins. Unlike the northwest- and northeast-trending magnetic 

gradients, which mostly coincide with the drainages, the easttrending shear zones cross a variety of topography. Many of 

the mapped mineralized veins coincide with linear magnetic 

anomaly lows and likely reflect the destruction of magnetite 

in adjacent wall rock and the nonmagnetic mineralogy of the 

vein material.
110 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

A fourth minor gradient trend set in the magnetic and 

resistivity data generally is co-linear with structures host to 

Tertiary dikes (Becraft and others, 1963) (this report, fig. 11).

The spatial association of linear magnetic and resistivity trends in the watershed with known geologic structures 

strongly implies that geophysical gradients mark locations of 

faults and fractures. As is evident in the resistivity and magnetic anomaly maps for the watershed (figs. 1 and 2), linear 

geophysical gradients greatly outnumber structures mapped at 

the surface (O'Neill and others, this volume, pi. 1). Implications for fractures and faults as related to the important issue 

of ground-water flow and quality are discussed in McDougal 

and others (this volume).

Geology-Based Geoenvironmental 

Map

Impact of a mine or mineralized terrain on the environment is controlled in large part by the geologic landscape. The 

environmental behavior of geology in a mineralized terrain 

is effectively portrayed in a study that assessed the potential 

impact of mining in Montana on surface water quality (Lee 

and others, 2001). The statewide study used geologic, geochemical, and geophysical information in conjunction with a 

predictive methodology to model the environmental behavior 

of geologic units that host metal-sulfide-rich deposits. An 

important aspect of the study included an effort to predict the 

environmental behavior of geologic units by classifying rocks 

in terms of acid-neutralizing or acid-generating potential, 

which was based on estimated amounts of calcium- or sulfidebearing minerals expected for the various rock formations. 

Classifications used a ranking scheme (high, moderate, low) 

largely determined by knowledge provided by scientists with 

expertise and experience with Montana geology. The availability of new high-resolution geophysical data, detailed geologic 

maps, and whole-rock chemistry data in the Boulder River 

watershed study area allowed us to use an approach similar to 

the State study but at a more detailed scale.

Water quality is generally good in most of the major 

streams in the watershed based upon water-quality criteria 

established for aquatic life, although water quality is degraded 

downstream of some mine sites such as the Bullion, Crystal, 

and Comet mines (Nimick and Cleasby, this volume; Kimball 

and others, this volume). The effects of metal-rich, acidic mine 

drainage on surface water are thought to be naturally mitigated 

(Nimick and Cleasby, this volume) by acid-consuming minerals present in fresh granitic and volcanic rocks (Desborough, 

Briggs, Mazza, and Driscoll, 1998). Clearly, the mineralogy of 

the rocks in mine-waste piles and in those that underlie mine 

sites influences the quality of surface water and naturally exacerbates or mitigates the effects of high metal concentrations 

and acidity. We developed a geology-based geoenvironmental 

map portraying the rock unit characteristics to examine the

spatial relation between environmental characteristics of the 

geology and water quality.

Acid-Neutralizing Potential

Estimating Acid-Neutralizing Potential

Acid-neutralizing potential (ANP) is an important environmental property of rock units because it can greatly influence water quality in mineralized areas such as the Boulder 

River watershed. However, ANP is not mapped routinely by 

field geologists. Therefore, a method was needed to estimate 

ANP from geologic information traditionally collected in the 

field. For this study, we combined the geologic map units of 

Ruppel (1963) and Becraft and others (1963), based in large 

part on grain size and mineralogy within formations, with rock 

chemistry data to develop a geoenvironmental map showing 

ANP.

Ruppel (1963) and Becraft and others (1963) mapped the 

Butte pluton granitic rocks based on mineralogy, color, and 

grain size. Mineralogy and color are important for estimating 

ANP because these qualities have direct bearing on the abundance of mafic minerals related to acid-consuming mineralogical assemblages. Grain size is important not only because different grain-size phases contain different mineral assemblages 

but also because grain size influences the geophysical signature and allows geophysical data to distinguish rock units, as 

described in a later section.

In the Boulder River watershed study area, ANP is 

provided by a suite of acid-consuming minerals. Calcite is 

present in minor amounts as interstitial fillings in fresh Butte 

pluton granitic rocks (Desborough, Briggs, and Mazza, 1998). 

Calcite is an important acid-consuming mineral because of the 

acid-neutralizing potential of the carbonate ion. Mafic minerals—including biotite, hornblende, tremolite, chlorite, and 

feldspars—are also important (Desborough, Briggs, Mazza, 

and Driscoll, 1998) because acid is consumed and bicarbonate 

ions are produced as these minerals weather. In addition, some 

mafic minerals, such as biotite, tremolite, and chlorite, contain 

hydroxide ions. Both bicarbonate and hydroxide ions can 

neutralize acid and thus mitigate the effects of metals in water 

through chemical bonding.

Quantitative data on abundance of acid-consuming 

minerals are not available for the mapped rock units. However, 

chemical data for rock units are available. Concentration data 

for key major elements can be used as indicators of the abundance of the acid-consuming minerals. Calcium and (or) iron 

are important major elements in calcite, plagioclase feldspars, 

and mafic minerals but not in other minerals, such as quartz or 

potassium feldspar, which have little acid-neutralizing potential. Therefore, calcium and iron are used as indicator elements 

to estimate the relative ANP of the rock units mapped by Ruppel (1963) and Becraft and others (1963).
Geophysics and Environmental Implications 111

Iron and calcium percentages were obtained from (1) 

chemical analyses made during the original geologic mapping efforts that provide the geologic framework for this study 

(Ruppel, 1963; Becraft and others, 1963) and (2) analyses of 

samples and core analyzed for the Boulder River watershed 

study (Desborough, Briggs, and Mazza, 1998; Desborough, 

Briggs, Mazza, and Driscoll, 1998; Desborough and Driscoll, 

1998). Figure 12 shows the relation between ANP measured in 

leachate studies, and the sum of calcium and iron concentrations in samples of plutonic and volcanic rock units. Although 

traditional ANP data expressed in percent calcite equivalent 

are not available for these samples, results of a leach experiment that used an acidic (pH=2.9) leachate demonstrate the 

relation between calcium, iron, and pH.

Whole-rock chemistry data are available for 26 geologic 

units that cover approximately 70 percent of the geophysical survey area. Sampling is admittedly sparse and restricted 

to a meager one to four samples per unit. Although too few 

samples are available to determine statistical significance, in

principle, the rocks collected were considered representative 

of the overall unit. Consequently, we assume that the chemical 

signature is generally representative for a given unit. A listing 

of map symbols and descriptions for geologic units referred to 

in this report, as well as the average sum of calcium and iron 

concentrations, are given in table 1.

A relative ANP rank was assigned to each map unit on 

the basis of calcium and iron concentration. These data also 

are shown in figure 13 (top chart). Geologic units not sampled 

and therefore not assigned environmental characteristics 

include unconsolidated Quaternary alluvial and glacial deposits with unknown, or perhaps heterogeneous, acid-neutralizing 

potential.

Relative degrees of ANP are portrayed in the geoenvironmental map (fig. 14) as shades of green—lighter hues indicate 

rocks with high acid-neutralizing potential (relatively high percent of mafic and calcic minerals) whereas dark green infers 

rocks with relatively low ANP (low percentages of mafic and 

calcic minerals).

X

4 5 

PERCENT (Ca + Fe)

EXPLANATION

—— R2 = 0.751

0 Fresh Butte pluton granitic rocks

X Fresh Elkhorn Mountains Volcanics

• Altered Elkhorn Mountains Volcanics

Figure 12. Relation of calcium and iron content to pH of acidic mine-waste leachate after 24 hour exposure 

for fresh Butte pluton granitic rocks, Elkhorn Mountains Volcanics, and altered Elkhorn Mountains Volcanics 

(Desborough, Briggs, and Mazza, 1998).
RELATIVE ACID-NEUTRALIZING POTENTIAL RELATIVE ACID-NEUTRALIZING POTENTIAL

1 S 1 t 3 -^ cp =o ° "2 m __ 8 3 <P: - CXJ e 7T 

_ 0 «*»

<g c ^ g3 5 l~|1 30

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Q. 0 0 fJa 

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. • ^

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3 ° g S

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g. M

a CALCULATED VOLUME-PERCENT MAGNETITE =• 5

P r1 NJ CO .*• W "1 ^ 0 — fO GO

•«J •fr — » O5 CO O "»J ^^

—————————————————————————————— 1 ———————————————————————— "=222

I ———— P: —— ^— i ——— ^ —— - —— | n=7894

1 ——————— r. ——— •[ | n=1781

| ————————— 'f ——— m- ————— | n=3955

i 1 —————————— • ——— n=l

\ ——————— j —————— ! ———— '•i ——————— | n=1762

| ————— P i '~*——\ ———— 1 "=600

g— ? — ) — ^L. E . j _api " 190

( ——— jf-ln=M,

\ ————— -I' - ————— |r?=203

1 —————————— ! —— | ————— 1 "=2621

| ————————————— = —————————————— | n=2772

1 —————— | —————— n=7

; ; f*i

1 ———— ^IH ——— ^265

•r] n=\]Q

• \ H 1 "=1626

; hW *1098 j

_ , ____ ^TM § | —— [ | 1 —— | n= number of 100 x 100 m grid cells 

|j, 

0

W

S

W

g

y 

cm 

altered cm 

cl 

da 

md 

altered md 

mdamdb 

mdc 

ml 

mla

fl 

fib 

flc 

fd 

fda

PERCENT (Ca + Fe) ="

*. m en ~J oo CD c>

coarse-graine granitic rocks: Kbm h

J alter -d coarse-grained granitic roijks: Kbm

coarse-grained g/anitic rocks: Kbm

^

medium-grained biotite-hornblende: Kbm |1 ^^^^^j ——————————— y

^^^^^^^| altered •edium-gr 

rTiedium grained", dark gray: Kbm

ained biotite-hornb|ende: Kbr 

———————— f

medium grained, medium gray with pinK tint: Kom 

medium grained, medium gray: Kbm IT"

medium grained, reddish bro 

1

Miediunq grained, 

wn: Kbm \\

fine grained, light gray: Kbf 

fine-grained chlorite-epidote: Kbffine- .rained, li^ht-.ra. ,ior

fine flrained^ dark aray: Kbf

-H

LhyrY:Kbf(]

h

fine grained, dark cra>: Kbf \\

a |^^B aplite: Kba

Kva1 

Kva2 

altered Kva2 

Kv2 Kv3 

Ki

Tli Til 

Tla

Trf 

Tri 

altered Tri |

ightgray: Kbm

welded tuff lower member: Kevm IJl\

^^^^^Haltered welded 

welded tuffs: Kevm

interbedded tuffs: Kevu

tuff upper member: Kevm

1

=y

i

—— ' ——————— rhyodacite porphyry: Kei h

quartz latite intrusive

^J rhyollte lapllhtyn "juart^B^^^Ftuf^

j^H^^^A rhyoliteflow ^^^^^^IA rhyolite int 

^^laltvred rhyolite intrusi

i s

n as

I I'

• VI

o 

rusive £.

en

je

Helena 

Lowland Creek volcanic

Elkhorn 

1 ——————— Butte pluton granitic rocks ———————— I Vol

0) §.

, = 0 o- =

Q) 5'

V)

Environmenta1 Effects ofHistorical Mining, Bou

Ider RiveWatershed, Montana
46°30'

112°22'30"

Geophysics and Environmental Implications 113

112015' 112°07I30"

46°22'30"

46°15' -

Target

drainages in the 

Boulder River 

watershed study 

area

5 MILES

High

EXPLANATION ° 5 

. Relative acid-neutralizing potential ...................................... Low

10 KILOMETERS

Butte pluton

g, fine- to medium-grained

Elkhorn Mountains Volcanics

Kv3, interbedded tuffs

Butte pluton

cm, coarse-grained

Butte pluton

m I a, medium-grained 

fl, fine-grained

da, lighf-gray. biotite-hornblende TM>, fine-grained 

md, medium-gray, medium-grained TIC, tine-grained 

mda, dark-gray, medium-grained TM- fine-grained 

mdb, medium-gray, medium-grained fda ' fme-gramed 

mdc, medium-grained

Elkhorn Mountains Volcanics

Kval, welded tuff

Kva2, upper welded tuff

Kv2, welded tuff Relative acid-generating

Ki, rhyodacite porphyry potential: High

Butte pluton

altered cm, coarse-grained 

ml, medium-grained

Lowland Creek Volcanics

Tli, intrusive 

Tla, welded tuff

Butte pluton

altered md, medium-grained 

a, aplite

Elkhorn Mountains Volcanics

altered Kva2, upper welded tuff

Lowland Creek Volcanics

Til, lapilli tuff

Helena volcanic rocks

Tr, rhyolite,undivided 

Trf. rhyolite lava flow 

Tri, rhyolite intrusive 

altered Tri, rhyolite intrusive

Polymetallic quartz veins

Figure 14. Geology-based geoenvironmental map showing relative acid-neutralizing potential of geologic units based on 

percentages of calcium and iron (table 1 and fig. 13). Acid-generating polymetallic quartz veins also shown.
114 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Acid-Neutralizing Potential of Rock Units

The Butte pluton plays an important environmental role 

in the watershed. Geologically, it hosts the acid-generating 

polymetallic quartz vein deposits. Chemically, it contains 

minerals that provide significant acid-neutralization and thus 

has ANP comparable to that of many calcite-rich sedimentary 

rocks (Desborough, Briggs, and Mazza, 1998; Desborough, 

Briggs, Mazza, and Driscoll, 1998). This ANP likely is the 

reason that few streams in the Boulder River watershed study 

area have acidic pH (Nimick and Cleasby, this volume). 

Geographically, the Butte pluton is the largest pluton of the 

Boulder batholith, covering an area 17x51 km, which represents approximately 73 percent of the outcrop of the Boulder 

batholith in southwest Montana (O'Neill and others, this 

volume, pi. 1). It crops out in approximately 44 percent of 

the area covered by the geophysical survey, and 36 percent of 

the area within the Boulder River watershed; it also underlies 

younger rocks exposed at the surface.

Relative acid-neutralizing potential for the Butte pluton 

granitic rocks is variable but roughly correlates with age of 

emplacement; early-stage mafic intrusions have higher relative 

ANP compared to later stage silica-rich granitic phases 

(fig. 13). Rocks of the earliest stage of intrusion, designated 

as "g" in Ruppel (1963), have the highest relative ANP for 

all rocks in the Butte pluton and second highest relative ANP 

for rocks in the study area (fig. 13). The medium- to coarsegrained granitic rocks represent the most voluminous mafic 

phase of the pluton and are the dominant rock types in the 

study area, constituting more than 90 percent of the pluton outcrop. Most of the coarse- and medium-grained units 

contain 6-8 percent calcium and iron and are interpreted to 

have moderately high to high ANP (table 1). Volumetrically 

significant exceptions are the ml and mla units (table 1). 

These medium-grained units are rather widespread, making up 

approximately 7 percent of the area covered by the airborne 

survey, although much of the ml unit lies outside the Boulder 

River watershed in the adjacent Prickly Pear Creek watershed. 

Whereas most of the coarse- and medium-grained phases contain more than 6 percent iron and calcium, the ml unit 

is characterized by half as much iron and calcium. Both the 

ml and mla units are host to a number of mineralized veins. 

We would expect that acid- and metal-rich waters draining 

from veins hosted in these rocks would be neutralized, but not 

as quickly as similar contaminated water draining off veins 

hosted in the other coarse- and medium-grained phases of the 

pluton.

The fine-grained plutonic units (fl, fib, flc, fd, and fda) 

are chemically indistinguishable from each other and are characterized by iron and calcium contents that average 

4.5 percent. These facies would be interpreted to have consistently lower relative ANP than most of the medium- or coarsegrained phases.

The most silica rich units in the pluton consist of aplite. 

The aplites represent a less mafic, more alkali rich phase interpreted to have been formed from a later stage magma (Ruppel,

1963). Aplite is interpreted to have the lowest ANP of all the 

granitic phases in the pluton. It is also the least voluminous 

unit in the Butte pluton, at less than 2 percent of mapped 

outcrops.

Rock samples with the highest average percentage of iron 

and calcium and therefore interpreted to have highest ANP are 

those from rocks of the Elkhorn Mountains Volcanics 

(fig. 13). Samples of interbedded tuffs (Becraft and others, 

1963, map unit Kv3) contain an average of 9 percent calcium and iron. The area of outcrop for this unit is quite large, 

covering approximately 5 percent of the airborne geophysical 

survey area, although the majority lies outside the Boulder 

River watershed in the Prickly Pear Creek watershed to the 

east. Overall, the mineralogy of the Cretaceous volcanic units 

is similar to that for the Butte pluton because both are part 

of the same magmatic system (Roberts, 1953; Klepper and 

others, 1957: Robinson, 1963; Smedes, 1966). However, one 

unit of Elkhorn Mountains Volcanics has relatively low ANP 

in comparison with the other volcanics. Samples of the upper 

welded tuff unit (Kva2) that crops out near Jack Mountain and 

is presumably unaltered contain less than 2 percent calcium 

and iron (fig. 13), similar to the Tertiary volcanics and altered 

plutonic rocks with lowest ANP in the study. Altered samples 

of the same rock type (altered Kva2) taken near the top of 

Jack Mountain (Desborough, Briggs, and Mazza, 1998) show 

even lower percentages of calcium and iron (slightly more 

than 1 percent),

The acid-neutralizing effect of the Cretaceous and 

Tertiary volcanic units on metalliferous and acidic water draining the mineral deposits exposed by mining and waste piles 

is not as critical as that of the Butte plutonic rocks. This is 

because the Cretaceous and Tertiary volcanic rocks are located 

stratigraphically and topographically above the acid-generating mineralized veins. Nonetheless, water draining through 

and downgradient from these rock units would presumably 

have some mitigating effect on water quality (O'Neill and 

others, this volume).

Along with providing an in-place understanding of 

environmental characteristics of the geology, an environmental 

geology map can provide scientific information for other uses. 

For example, information provided on the map could be used 

to evaluate rock suitability for engineering purposes. Some 

units in the Elkhorn Mountains Volcanics may be suitable 

sources for material to line a waste-rock repository given other 

cost and logistic considerations. So, although the Elkhorn 

Mountains Volcanics do not have as direct an influence on 

water quality, their geologic characteristics do have 

implications for other uses.

Rocks with the lowest percentages of calcium and iron 

and interpreted to have the lowest ANP in the study include 

Tertiary volcanic units within the Lowland Creek Volcanics 

and the Helena volcanic field (fig. 13). The volcanic rocks 

are characterized by high silica content (Ruppel, 1963) that 

provides little acid neutralization.

A significant reduction in iron and calcium minerals 

occurs when a rock is altered by hydrothermal fluids
Geophysics and Environmental Implications 115

(Desborough, Briggs, and Mazza, 1998; Desborough and 

Driscoll, 1998), resulting in low ANP. Iron and calcium percentages from altered rock samples are shown in figure 13 for 

four rock types (cm, md, Kva2, and Tri). In all four cases, 

the percent of calcium plus iron is significantly lower in the 

altered sample (30 to 60 percent less) compared to its unaltered counterpart.

Acid-Generating Potential

Acid-generating sources in the watershed are Late Cretaceous polymetallic quartz veins and associated waste piles that 

contain abundant pyrite and varying amounts of other sulfide 

minerals (Ruppel, 1963; Becraft and others, 1963; O'Neill and 

others, this volume). The veins cover less than 1 percent of 

the surface area in the Boulder River watershed, but oxidation 

of mine waste caused by near-surface weathering and mining 

activity has produced metal-rich acidic water. The metal-laden 

water that enters the main drainages and tributaries (Nimick 

and Cleasby, this volume) adversely affects aquatic health 

(Farag and others, this volume, Chapter D10).

Evidence for other acid-generating sources occurs (1) in 

the Helena volcanic rocks near the Basin Creek mine where 

disseminated pyrite is associated with mineralization (Ruppel, 

1963) and (2) in altered Elkhorn Mountains Volcanics rocks 

near the Buckeye and Enterprise mines (O'Neill and others, 

this volume).

Effect of Acid-Neutralizing Minerals on 

Aquatic Health

The presence and quantities of iron and calcium in mafic 

and calcic minerals that are commonly found in the plutonic 

and volcanic rocks in the Boulder River watershed have a 

bearing on water quality and aquatic health. Iron or calcium is 

present in biotite (K(Mg,Fe+2)3 (Al,Fe+3)Si3O10(OH)2), tremolite 

(Ca2Mg5Si8O22(OH)2), and chlorite ((Mg, Fe+2,Fe+3 )6 

AlSi3O10(OH)g). These minerals also contain hydroxide ions 

(OH"), which have the ability to raise water pH and mitigate 

deleterious effects of metals in the water. When hydroxide 

ions are exposed to acidic water, they are free to combine with 

hydrogen ions (H+), raising the pH of the water. Chlorite has 

abundant hydroxide ions and is ubiquitous in the Butte pluton 

rocks. Chlorite is derived from primary mafic minerals such as 

hornblende and formed during regional metamorphism due to 

heating during late magmatic activity in the Boulder batholith.

Additionally, calcium is connected to the environmental 

signature of a rock through the role of bicarbonate ions 

(HCO3~) in the neutralizing process. Bicarbonate forms complexes with several potentially toxic metal ions (Cd, Cu, Zn), 

thereby reducing the toxicity of these metals in surface water 

to aquatic life. One source for bicarbonate is in minor amounts 

of interstitial calcite in fresh Butte pluton granitic rocks (Desborough, Briggs, and Mazza, 1998).

Calcium, Iron, and Geophysical Response

For volcanic and plutonic rocks in the Boulder River 

watershed study area, variations in calcium and iron content 

correlate with quantities of other minerals that strongly influence geophysical response, specifically silica and magnetite. 

Although electromagnetic and magnetic surveys are not sensitive to calcium content as such, elevated amounts of calcium 

correspond to a decrease in silica (fig. 5 in O'Neill and others, 

this volume). Silica acts as an electrical insulator; electrical 

current does not pass easily through it. Consequently, rocks 

with high amounts of silica will typically produce resistivity 

anomaly highs. Silica-rich rocks in the watershed study area 

also produce lower amplitude magnetic anomalies in comparison with more mafic rock phases, primarily owing to lower 

magnetite content.

As discussed in the previous section, iron in volcanic 

and plutonic rocks is derived from a number of minerals 

that provide acid neutralization. Iron is a main constituent in 

magnetite (Fe3O4), which does not provide acid neutralization 

but is present in association with the minerals that do. In the 

following section, we discuss the importance of magnetite in 

terms of geophysical signature and relate magnetite to acidneutralizing potential.

Geophysical Magnetite Maps

"Cored rocks that had the highest acid-neutralizing potential (for example, near Bullion mine) had 

abundant magnetite in heavy-mineral concentrates 

made from these rocks, whereas those with low 

acid-neutralizing potential contained no magnetite in 

the heavy-mineral concentrates" (O'Neill and others, 

this volume).

This section investigates the hypothesis presented by 

our colleagues—that magnetite content may be indicative of 

granitic rock alteration and thereby relate to a rock's ability to 

provide acid neutralization. By transforming the resistivity and 

magnetic anomaly data to maps of magnetite distribution, we 

can make the geophysical magnetite maps function as proxy 

ANP maps. In the previous section, information from rock 

chemistry provided a mineralogical rationale to define acidneutralizing potential. However, with so few rock samples and 

the presence of glacial, alluvial, and tree cover, variations in 

environmental properties of underlying bedrock were impossible to discern in the field for much of the study area. The 

detail provided in the geophysical survey and the ability of 

geophysical methods to "see" beneath much of the problematic vegetation and rock cover provide a means to continuously 

map major to minor variations in rock environmental properties. Information extracted from the geophysical survey can be 

used as an indirect measuring tool of mineralogical properties 

in that magnetite is used as an indicator for other important 

acid-consuming minerals.
116 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Magnetite Estimates from Magnetic 

Susceptibility Model

Magnetic susceptibility is, to a large degree, a measure of 

magnetite content. For rocks whose concentrations of magnetite lie between 0.1 and 10 percent, volume percentage of 

magnetite (Vm) can be estimated from susceptibility (k in cgs) 

with the following equation: 

Vm = 400 k (modified from Balsley and Buddington, 1958)

Estimates for volume percent magnetite were determined 

from the grid of magnetic susceptibility data using this equation. Model magnetic susceptibilities were given in relation 

to percent magnetite in the map shown in figure 5 and for 

geologic units in figure 9. Negative magnetic susceptibilities 

were set to zero.

Magnetite content derived from the magnetic susceptibility model was compared to magnetite content determined visually from thin sections for a limited number of rock samples. 

The lower chart in figure 13 shows rock sample percent 

magnetite for 12 rock samples (Becraft and others, 1963) compared to model susceptibilities. Analyses were available for 

nine Butte pluton units. Magnetite contents measured for the 

12 rock samples fall either within or very near the range for a 

given unit (fig. 13B), signifying that the susceptibility model 

is, at the very least, a reasonable representation of magnetite 

distribution in the watershed.

Magnetite Estimates from 900-Hz Apparent 

Resistivity Data

Magnetite, because of its electrical properties, is the only 

mineral that causes observed negative in-phase anomalies in 

horizontal coplanar resistivity data. As part of the airborne 

survey contract with the USGS, estimates of apparent volume 

percent magnetite are available (Smith and others, 2000). 

Magnetite estimates were determined by identification of 

negative in-phase anomalies in the 900-Hz resistivity data and 

by application of a calculation based on methodology in Fraser 

(1981). The estimates are apparent because they are based on 

a theoretical model and provide only a relative gauge of magnetite content. Estimates for magnetite are restricted to rocks 

located to a maximum depth of 60 m.

The method has limitations under certain geologic 

conditions. The greatest constraint for use of this method in 

our study area relates to the low resistivities of many of the 

volcanic rocks. Unreliable magnetite estimates result for rocks 

with resistivities of less than 500 ohm-m (Fraser, 1981). For 

this reason, only pixels within the EM magnetite grid that 

coincide with resistivities greater than 500 ohm-m are shown 

in figure 15, with the consequence that 46 percent of the area 

within the airborne geophysical survey was excluded. Most of 

the excluded area is over rocks within the Helena and Elkhorn 

Mountains volcanic fields. The low resistivities of the volcanic 

units are attributed to the greater development of clays from 

surface weathering and alteration processes.

Magnetite estimates in the EM magnetite model are 

unrealistically low in comparison with magnetite concentrations determined from rock sample modal analyses (Becraft 

and others, 1963; Desborough, Briggs, and Mazza, 1998) but 

are interpreted to reflect relative amounts of magnetite within 

rocks located within 60 m of the surface. Attenuated (low) EM 

magnetite values can occur in rocks that are very magnetic, 

where error from strong magnetic polarization exists, and over 

rocks where the electromagnetic sensor height exceeds 45 m 

(Fraser, 1981).

Within the Boulder River watershed study area, the 

granitic units of the Butte pluton are characterized by high EM 

magnetite values and are in general agreement with high percent magnetite values calculated from the magnetic anomaly 

data (fig. 9). Outside the watershed boundary, in the adjacent 

Prickly Pear Creek watershed to the east and Tenmile Creek 

watershed to the north, most of the Butte pluton outcrop is 

associated with very low to zero-percent apparent magnetite 

anomalies. Much of the low percent magnetite occurs over the 

ml unit, west of Lava Mountain, which also has a correspondingly low magnetic signature (fig. 9) and low percent magnetite as determined from rock sample analysis (fig. 13B).

Relationship of Magnetite to Alteration 

Processes

Mineralization, metamorphism, and magmatic processes 

have altered the original mineralogical composition of plutonic 

and volcanic rocks in the study area. Locations of altered 

Butte plutonic rocks related to Late Cretaceous mineralization were mapped in the eastern part of the study area but are 

limited to narrow envelopes surrounding a select number of 

mineralized veins studied in detail in the Jefferson City quadrangle (Becraft and others, 1963). As part of the detailed study 

of polymetallic quartz veins and wall rock alteration, Becraft 

and others (1963) collected samples of Butte pluton granitic 

rocks adjacent to well-exposed mineralized veins, sampling 

from the veins outward to rock least affected by alteration 

processes. Results of our study provide an understanding of 

the relationship between alteration mineral assemblages and 

magnetite abundance. Within the alteration envelope, three 

zones are observed and include, from most altered to least 

altered, a sericitic zone, an argillic zone, and a chloritic zone. 

"Least altered" describes granitic rocks that appear unaffected 

by surface weathering or sulfide mineralization. Mineralogical 

analyses show that within zones of argillic alteration, magnetite is absent. This concept is illustrated in figure 16.

Evidence for alteration of the original mineralogy due to 

metamorphism is present in units of the Elkhorn Mountains 

Volcanics where chemical analyses show metamorphosed 

samples are more silicic (less mafic) than unmetamorphosed 

samples (Ruppel, 1963). Metamorphism was caused by the 

intrusion of the Butte pluton into the Elkhorn Mountains Volcanics. The metamorphosed samples also show a
Geophysics and Environmental Implications 117

46°30

112007'30"

46°22'30" -

46°15' -

Target

drainages in the 

Boulder River 

watershed study 

area

Volume-percent magnetite 

(est.) EXPLANATION

• Rock sample location

(Desborough, Briggs, and 

Mazza, 1998)

• Rock sample location

(Desborough, Briggs, Mazza, 

and Driscoll, 1998)

5 MILES

10 KILOMETERS

Figure 15. EM magnetite anomaly calculated from 900-Hz resistivity data where resistivity is greater than 500 ohm-m. White areas 

within airborne geophysical survey are characterized by low resistivities and result in unreliable EM magnetite estimates. Values for 

percent magnetite are given at locations of rocks analyzed for acid-neutralizing potential (table 2). Low EM magnetite estimates are 

combined with areas of high resistivity to map locations of silica-rich rock units with inferred low acid-neutralizing potential.

significant (30-80 percent) decrease in iron oxides, which 

likely reflects a decrease in magnetite content as well.

Alteration in which hydrothermal fluids were dominantly 

silicic rather than potassic or alkalic is present in altered rocks 

within the Elkhorn Mountains Volcanics. Chemical analyses of altered rocks from the top of Jack Mountain show no 

magnetite present in heavy-mineral concentrates (Desborough, 

Briggs, and Mazza, 1998).

O'Neill and others (this volume) discuss two other 

alteration events that altered the mineralogy of some of the 

Butte plutonic rocks. Several areas mapped in the southern 

part of the study area contain zones of alteration, but no 

samples were collected to determine magnetite content.
118 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Minerals

Chlorite

Montmorillonite

Kaolinite

Sericite

Quartz

Pyrite

Magnetite

Relative acid-neutralizing potential 

High ——————————————————^ Low

EM magnetite anomaly intensity

High Low

Magnetic anomaly intensity 

Positive —————————————————>- Negative

Degree of alteration 

Least altered ———————————*- Most altered

Chloritic Argillic Sericitic

Figure 16. Persistence of minerals in alteration zones from a suite of Butte pluton 

rocks measured from polymetallic quartz veins (most altered) outward to granitic 

rocks least affected by alteration. Modified from Becraft and others (1963) to show 

persistence of magnetite, corresponding geophysical signatures, and relative acidneutralizing potential. Gradient regions indicate range of relatively high mineral 

abundance; solid lines indicate minor amounts of minerals.

Relationship of Magnetite to Environmental 

Rock Properties

Magnetite provides a means to connect geophysical signatures with important environmental rock properties. Geochemical investigations conducted as part of the Boulder River 

watershed study illustrate the connection between the presence 

of magnetite and corresponding acid-neutralizing potential 

for Butte pluton granitic rocks and other rock types. Rock 

samples of fresh and altered rock collected from drill core as 

well as surface outcrop samples were chemically analyzed 

to determine mineralogical characteristics associated with 

acid-neutralizing potential (Desborough and Driscoll, 1998; 

Desborough, Briggs, and Mazza, 1998; Desborough, Briggs, 

Mazza, and Driscoll, 1998). Table 2 compares the results of 

the leachate studies to determine ANP with values for percent 

magnetite as calculated from the geophysical data. Localities 

of the leachate samples are shown on the magnetic susceptibility model (fig. 5) and the EM magnetite map (fig. 15).

Although too few samples were analyzed to provide 

confident statistical conclusions, we can make some relevant 

and consistent observations regarding presence of magnetite, 

acid-neutralizing potential, and geophysical signature. For 

the 12 samples of unaltered Butte pluton granitic rock that lie 

within the airborne survey area, relatively high values from 

the EM magnetite anomaly data (0.24-0.86 percent, with an 

average of 0.44 percent) correspond with high acid-neutralizing potential as calculated from whole-rock chemistry. Percent 

magnetite derived from the magnetic susceptibility data for 

fresh Butte pluton rocks ranges from 1.12 to 1.83 percent, with 

an average value of 1.55 percent. All samples of these fresh 

rocks contain magnetite in the heavy-mineral concentrates. 

Unfortunately, no samples of altered Butte pluton granitic 

rocks were analyzed for acid-neutralizing potential.

Percent magnetite calculated from the apparent resistivity data for unaltered Elkhorn Mountains Volcanics shows that 

these rocks have slightly higher EM magnetite anomaly values 

(average 0.09 percent) than their altered counterparts (average 0.03 percent). Magnetite estimates for sample localities
Geophysics and Environmental Implications 119

Table 2. Relative acid-neutralizing potential from analyses of surface and core rock samples collected in and around the 

Boulder River watershed study area.

[Volume-percent magnetite values calculated from the EM magnetite data (fig. 15) and magnetic susceptibility model (fig. 5) are given at each sample 

location to illustrate the relation between the presence of magnetite, geophysical data, and relative acid-neutralizing potential. Leaders (—), unreliable 

EM magnetite estimates owing to high rock conductivity. Geologic map symbols in parentheses are described in table 1]

Outcrop or drill core sample and acid-neutralizing analysis information

Sample

FB007B1

FB007B2 

FB007B3

FB013

FB010

FMT012

FMT020

FMT021

FMT022

FMT031

FMT032

FMT034

FB035

FMT036

JM023

JM024

JM025

BMW

JRW

BKW

BPW

Depth

(ft)

Surface

Surface

Surface

Surface

Surface

Surface

Surface

Surface

Surface

Surface

Surface

Surface

Surface

Surface

Surface

1-40

24-66

25-62

15-39

Geologic unit

Butte pluton (md)

Butte pluton (cl)

Butte pluton (cl)

Elkhorn Mountains Volcanics (Kv2)

Butte pluton (mla)

Butte pluton (cl)

Butte pluton (cl)

Elkhorn Mountains 

Volcanics (Kval)

Butte pluton (mla)

Butte pluton (cm)

Elkhorn Mountains 

Volcanics (Kval)

Elkhorn Mountains 

Volcanics (Kva2)

Elkhorn Mountains 

Volcanics (Kva2)

Elkhorn Mountains 

Volcanics (Kva2)

Elkhorn Mountains 

Volcanics (Kva2)

Butte pluton (cl)

Elkhorn Mountains

Volcanics (Kva2)

Elkhorn Mountains 

Volcanics (Kva2)

Butte pluton (md)

Degree of 

alteration

Unaltered

Unaltered

Unaltered

Unaltered

Unaltered

Unaltered

Unaltered

Unaltered

Unaltered

Unaltered

Unaltered

Unaltered

Altered

Altered

Altered

Unaltered

Altered

Altered

Unaltered

Heavy minerals

'Magnetite, zircon, pyrite (< 1 ppm)

'Magnetite, zircon, pyrite (< 1 ppm)

'Magnetite, hornblende, zircon, pyrite 

(< 1 ppm)

'Magnetite, pyrite (< 1 ppm)

3Magnetite

4 Magnetite, chlorite, apatite, zircon, 

biotite, tremolite, pyrite (< 1 ppm)

3Magnetite

4 Magnetite, chlorite, apatite, zircon, 

biotite, tremolite, pyrite (< 1 ppm)

3Magnetite

4 Magnetite, chlorite, apatite, zircon, 

biotite, tremolite

4 Magnetite, chlorite, apatite, zircon, 

biotite, tremolite, pyrite (< 1 ppm)

4 Magnetite, chlorite, apatite, zircon, 

biotite, tremolite, pyrite (< 1 ppm)

4Pyrite

4Pyrite

4Pyrite

2 Magnetite, zircon

2 Zircon

2 None, pyrite abundant

2 Magnetite, zircon, pyrite

Relative 

ANP

High

High

High

High

High

High

High

High

High

High

High

High

Low

Low

Low

High

Low

Low

High

Volume-percent 

magnetite estimated 

from geophysical data

900-Hz 

apparent 

resistivity

0.24

0.86

0.29

—

0.27

0.61

0.45

0.10

0.27

0.58

0

0.18

0.06

0.05

0

0.37

0.09

—

0.37

High-pass 

magnetic 

anomaly

1.47

1.79

1.49

1.78

1.60

1.46

1.61

1.53

1.50

1.12

1.56

1.76

1.40

1.39

1.51

1.63

1.40

1.16

1.83

'Heavy-mineral concentrates from Desborough and Fey, 1997. 

2Heavy-mineral concentrates from Desborough and Driscoll, 1998. 

'Heavy-mineral concentrates from Desborough, Briggs, and Mazza, 1998. 

4Heavy-mineral concentrates from Desborough, Briggs, Mazza, and Driscoll, 1998.
120 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

FMT012 and BKW are not available from the EM magnetite 

data owing to low resistivities at these locations. Magnetite 

estimates from the magnetic susceptibility data (fig. 5) for 

four samples of unaltered Elkhorn Mountains Volcanics average 1.65 percent. Alternatively, consistently lower values for 

(magnetic data) magnetite occur for the five samples of altered 

Elkhorn Mountains Volcanics (average 1.37 percent). Samples 

of altered Elkhorn Mountains Volcanics contain no magnetite 

as determined from the heavy-mineral concentrates (Desborough, Briggs, Mazza, and Driscoll, 1998; Desborough and 

Driscoll, 1998).

Associations between alteration mineral assemblages, 

magnetite, geophysical anomaly signature, and acid-neutralizing potential for alteration zones mapped in Butte pluton 

granitic rocks are summarized in figure 16. Magnetic susceptibility and EM magnetite anomaly intensity progressively 

decrease as granitic rocks are altered to argillic levels. Rocks 

having undergone alteration to sericitic levels are characterized 

by low magnetic susceptibility and EM magnetite anomalies 

near zero. Compositional changes in the granitic rocks caused 

by progressively higher degrees of alteration coincide with 

the absence of magnetite and chlorite. Chemically, the lack of 

chlorite also corresponds to a decrease in the acid-neutralizing 

potential of the rock (Desborough, Briggs, and Mazza, 1998; 

Desborough, Briggs, Mazza, and Driscoll, 1998).

Geophysical Refinement of 

Geoenvironmental Map

Geophysics-Based Geoenvironmental Map

A geophysics-based geoenvironmental map (fig. 17) 

infers locations of surface and shallow subsurface bedrock 

with low magnetite content. Geophysical magnetite lows were 

determined on geologic and statistical criteria. Solid red in 

figure 17 defines pixels with values of 0 percent from the EM 

magnetite grid (fig. 15) combined with resistivities greater 

than 500 ohm-m from the 900-Hz resistivity grid (not shown). 

Geologically, these areas coincide with mapped outcrops 

enriched with silica and low in magnetite from either primary 

mineralogy or from introduction of silica-rich hydrothermal 

fluids (Ruppel, 1963; Becraft and others, 1963). Examples 

include (1) altered rocks with known low acid-neutralizing 

potential such as the altered Elkhorn Mountains Volcanics at 

Jack Mountain (Desborough, Briggs, and Mazza, 1998) or 

(2) rocks interpreted to have low acid-neutralizing potential 

such as the silica-rich Tertiary rhyolite at Red Mountain. Other 

solid red areas in figure 17 are interpreted to share analogous 

electrical properties and map similar rock types.

Pixels with values less than 1.4 percent in the magnetic 

susceptibility magnetite grid (fig. 5) are shown in the red 

pattern in figure 17. Lowermost magnetite content (less than

1.4 percent) was defined statistically for most rock types 

(fig. 9). Geologically, results best characterized mapped outcrop of altered rocks (Becraft and others, 1963; O'Neill and 

others, this volume). Other areas corresponding to magnetic 

susceptibility magnetite lows include parts of the study area 

expected to contain altered rocks such as clusters of polymetallic quartz veins and contact zones between the Butte 

plutonic rocks and younger volcanic units. Many of the main 

streams and tributaries are coincident with linear geophysical 

magnetite lows, which may be sites that provide little or no 

neutralization to acidic water draining from the mined areas 

and thus may not aid mitigation of toxic metal loads to aquatic 

life. Coincidence of geophysical magnetite lows with polymetallic veins suggests that some of the low-percent magnetite 

domains are mapping locations of acid-generating rocks that 

are depleted in magnetite from intense sulfidization.

Geology- and Geophysics-Based 

Geoenvironmental Map

Combining the geophysics- and geology-based geoenvironmental maps provides maximum detail in bedrock acidneutralizing potential. The combined geoenvironmental map 

(fig. 18) is a portrayal of the underlying geologic "landscape" 

that influences surface- and ground-water quality, the natural 

mitigation of metals and acidity, and, ultimately, the health 

of the ecosystem. Optimal geologic conditions are present 

where rocks with high acid-neutralizing potential (lightest 

green shades in figs. 14 and 18) do not overlap with geophysical magnetite lows or polymetallic quartz veins. Least 

desirable conditions may exist where polymetallic quartz 

veins lie within, uphill, or up gradient from rocks with low 

acid-neutralizing potential. These conditions identify places in 

the watershed that may be environmentally problematic to the 

mitigation of acidic metal-rich water.

Results of our study show that approximately 30 percent 

of the geophysical survey areas include rocks sufficiently 

depleted in magnetite to have low acid-neutralizing potential. 

Approximately 20 percent of the Butte pluton rocks within the 

Boulder River watershed study area are defined with low acidneutralizing potential. From an environmental context, these 

areas characterize rocks that should not provide significant 

mitigation to acidic water draining downhill or down gradient 

from mined or undisturbed mineralized rocks. We also expect 

that, in areas containing altered Butte pluton, the potential 

for mitigation of metals toxic to aquatic life is reduced due to 

lack of calcic and mafic minerals to provide bicarbonate and 

hydroxide ions.

Large, contiguous areas of geophysical magnetite lows 

occur over volcanic rocks in the Eocene Lowland Creek 

and Eocene-Oligocene Helena volcanic fields. The largest 

area covered by geophysical magnetic lows is located in the 

southeastern part of the study area over silicic rocks within the 

Lowland Creek volcanic field (figs. 7 and 17). The geophysical data were especially useful in these rocks as no
Geophysics and Environmental Implications 121

46°301

112°22'30"

46°221 30"

46°15'

Target 

drainages in the 

Boulder River 

watershed study

5 MILES

0 5 10 KILOMETERS

EXPLANATION 

Rocks with inferred low volume-percent magnetite (< 1.4 percent) calculated from aeromagnetic data

If Rocks with inferred low volume-percent magnetite (0 percent) and high resistivity (> 500 ohm-m) calculated 

from airborne 900-Hz resistivity

Figure 17. Geophysics-based geoenvironmental map showing locations of inferred low acid-neutralizing potential based on low 

values of volume-percent magnetite calculated from airborne geophysical data.
122 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

46°30' n2°i5' 112°07'30"

46°22'30'

46°15'

Target

drainages in the 

Boulder River 

watershed study

5 MILES

EXPLANATION

HIGHRelative acid-neutralizing potential 

—————— LOW LOW

10 KILOMETERS

Relative acid-generating potential 

HIGH

Percent (Ca + Fe) 

Geologic data

I magnetic I resistivity!

Volume-percent magnetite

(est.) 

Geophysical data

Geologic data

Figure 18. Combined geology- and geophysics-based geoenvironmental map showing relative acid-neutrahzmg and acid-generating potential of rocks inferred from rock mineralogy (fig. 14) and volume-percent magnetite calculated from airborne magnetic and 

apparent resistivity data (fig. 17). White areas, no data available.
Geophysics and Environmental Implications 123

mineralogical data were available to determine amounts of 

acid-consuming minerals. Other large areas, in association 

with geophysical magnetite lows, occur within Tertiary volcanic rocks in the northern part of the study area. Evidence that 

these rocks are also low in acid-neutralizing potential is present in low calcium and iron (fig. 13) and high silica content.

of surface and shallow ground water. If a land-use manager 

is restricted to a particular tract of ground in which to bury 

metal-sulfide waste rock, the environmental geology map can 

be one layer, among others, that provides geologic guidance 

as to which "host" rocks provide the better environmental 

controls.

Implications for Siting of Waste-Rock 

Repositories

Maps that portray pertinent environmental geologic 

characteristics, such as the map derived from this study 

(fig. 18), could be an information layer used in decisionmaking processes for locating geologically favorable wasterock repositories. Cleanup of inactive mines is an important 

goal of State and Federal land-management agencies. The 

primary environmental impact of inactive mines is degraded 

surface-water quality in streams (Nimick and Cleasby, this 

volume) and resultant impairment of aquatic habitat caused by 

metals (Farag and others, this volume). Mine waste and mill 

tailings are the main contributor of metals to surface drainages 

in the study area (Church, Unruh, and others, this volume; 

Nimick and Cleasby, this volume). Therefore, an important 

component of any restoration plan will be finding one or more 

suitable repository sites where mill tailings and mine wastes 

could be consolidated and safely stored.

In the early stages of the project (1996-1999), providing 

information to land managers regarding geologically suitable 

repository sites for mine waste and mill tailings was a priority. The USDA Forest Service together with geophysicists, 

geologists, and geochemists from the U.S. Geological Survey 

evaluated particular sites chosen by both groups to determine 

their suitability for storing the mine wastes in the watershed. 

However, during the course of the study, the unexpected 

bankruptcy of Pegasus Mining and the existing presence of 

the Luttrell pit at their mining operation (Smith and others, 

this volume, Chapter E3) made the process of repository siting moot. The USDA Forest Service and U.S. Environmental 

Protection Agency have a joint agreement to move mine waste 

from the Boulder River watershed and adjacent Tenmile Creek 

watershed into the Luttrell pit, located along the Continental 

Divide between the two watersheds.

Although not a current issue in the Boulder River watershed, repository siting within the larger context of the Departments of the Interior and Agriculture efforts to coordinate 

restoration activities at other Federal lands affected by inactive 

mines is a current issue being faced in many watersheds in the 

western United States. Exercises to characterize the environmental properties of geologic units, such as the techniques 

presented here, provide a scientific strategy for repository 

siting in other areas where safe mine-waste storage is an issue. 

For example, placing a repository in rock that is located at or 

near a ground-water recharge area in bedrocks with little or no 

ANP could potentially result in disruption or destabilization 

of underground portions of a repository and contamination

Summary

This report presents an empirical approach to extend the 

knowledge of geologic characteristics that exert fundamental 

controls on the natural environment with depth. In particular, 

high-resolution airborne geophysical data are used to map the 

surface and shallow subsurface distribution of acid-neutralizing minerals in igneous bedrock.

Enhancement techniques applied to the aeromagnetic 

anomaly data result in maps that emphasize magnetic rock 

properties in the uppermost surface to shallow subsurface. The 

statistical summaries describing the magnetic susceptibility 

and apparent resistivity signature for approximately 

40 geologic units allow for comparison of geophysical variability within and across geologic units and provide a basis 

for discussion of important factors controlling the anomaly 

signature. Geophysical analyses show that the polymetallic 

quartz veins are distinctively characterized by very low magnetic susceptibilities and moderately high resistivities. Trends 

of geophysical gradients are co-linear with mapped structures 

and faults.

The geology-based geoenvironmental map, derived 

from mineralogical and geochemical data, shows variability 

in relative acid-neutralizing potential as a function of mafic 

and calcic mineral abundance. Representative rock samples 

used to produce the geology-based geoenvironmental map 

are limited in number but considered sufficient to provide an 

understanding of acid-neutralizing potential. Granitic and most 

volcanic rocks that are fresh or unaltered have abundant mafic 

and calcic minerals with significant acid-neutralizing potential. In contrast, rocks that are silica rich and (or) have been 

intensely altered by hydrothermal solutions have negligible 

amounts of mafic minerals, insignificant amounts of calcite, 

and little acid-neutralizing capacity. Known sources for acidic 

metal-rich water in the Boulder River watershed are the Late 

Cretaceous polymetallic quartz veins and associated mine 

waste. Potential acid-generating source rock may include areas 

of Tertiary volcanic rocks containing disseminated pyrite.

This study demonstrates that magnetite acts as a relative 

gauge for corresponding amounts of mafic and calcic minerals 

in igneous rocks that provide significant acid neutralization to 

acidic and metal-rich waters. In fresh (unaltered) Tertiary and 

Cretaceous granitic and volcanic rocks, magnetite is a common accessory mineral (Ruppel, 1963; Becraft and others, 

1963) and is associated with mineral assemblages that provide 

relative degrees of acid neutralization (Desborough, Briggs, 

and Mazza, 1998; Desborough, Briggs, Mazza, and Driscoll,
124 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

1998). Where the igneous rocks are altered, the rock is devoid 

of magnetite and there is a corresponding depletion in acidneutralizing potential.

Magnetite is ubiquitous in nearly all the Cretaceous- and 

Tertiary-age volcanic and plutonic rocks exposed in the Boulder River watershed. Although magnetite is a minor mineral 

constituent, it provides an easily measured property that can be 

correlated to measurable percentages of important acidneutralizing minerals.

Mathematical filters convert magnetic anomaly and 

apparent resistivity data to pseudo-mineral maps to show surface and shallow subsurface distribution of magnetite. Magnetite is the main source for magnetic anomalies and contributes 

to the resistivity response of a rock. Magnetite estimates from 

the magnetic susceptibility model data are within realistic ranges when compared to values determined from rock 

samples. Estimates from the apparent resistivity data, however, 

are consistently lower in comparison with magnetite measurements from rock samples but are used in this report to reflect 

relative amounts of magnetite within rocks.

The geophysical magnetite models outline areas interpreted to indicate near-surface rocks lacking or depleted 

in magnetite. The magnetite depletion can be the result of 

high-temperature alteration of primary minerals or a silica-rich 

mineral composition. Absence of magnetite corresponds to 

low amounts of acid-consuming minerals. In some cases, low 

values in the geophysical magnetite data correspond with locations of acid-generating source rock such as sulfide-metal-rich 

veins. Alternately, areas with high values of magnetite from 

the geophysical models are interpreted to represent rocks associated with significant amounts of acid-consuming minerals.

The geophysical refinement to the geology-based geoenvironmental map results in an improved understanding of the 

spatial distribution of bedrock environmental characteristics. 

This report provides a summary of the geophysical signatures 

and geoenvironmental characteristics of volcanic and plutonic 

units, many of which extend well beyond the Boulder River 

watershed study area and crop out commonly throughout 

southwest Montana. Consequently, the methodology described 

here can be applied to watersheds that are geologically similar 

to the study area and which have water-quality degradation 

caused by historical mining like that in the Boulder River 

watershed.

References Cited

Balsley, J.R., and Buddington, A.F., 1958, Iron-titanium oxide 

minerals, rocks, and aeromagnetic anomalies of the Adirondack area, New York: Economic Geology, v. 53, no. 7, 

p. 777-805.

Becraft, G.E., Pinckney, D.M., and Rosenblum, Sam, 1963, 

Geology and mineral deposits of the Jefferson City quadrangle, Jefferson, and Lewis and Clark Counties, Montana: 

U.S. Geological Survey Professional Paper 428, 101 p.

Blakely, R.J., 1995, Potential theory in gravity and magnetic 

applications: London, Cambridge University Press.

Buxton, H.T., Nimick, D.A., von Guerard, Paul, Church, S.E., 

Frazier, Ann, Gray, J.R., Lipin, B.R., Marsh, S.P., Woodward, Daniel, Kimball, Briant, Finger, Susan, Ischinger, 

Lee, Fordham, J.C., Power, M.S., Bunck, Christine, and 

Jones, J.W, 1997, A science-based, watershed strategy to 

support effective remediation of abandoned mine lands: 

Proceedings of the Fourth International Conference on Acid 

Rock Drainage, Vancouver, B.C., May 31-June 6, 1997, 

p. 1869-1880.

Desborough, G.A., Briggs, PH., and Mazza, Nilah, 1998, 

Chemical and mineralogical characteristics and acidneutralizing potential of fresh and altered rocks and soils of 

the Boulder River headwaters in Basin and cataract Creeks 

of northern Jefferson County, Montana: U.S. Geological 

Survey Open-File Report 98^0, 21 p.

Desborough, G.A., Briggs, PH., Mazza, Nilah, and Driscoll, 

Rhonda, 1998, Acid-neutralizing potential of minerals in 

intrusive rocks of the Boulder batholith in northern 

Jefferson County, Montana: U.S. Geological Survey 

Open-File Report 98-0364, 21 p.

Desborough, G.A., and Driscoll, Rhonda, 1998, Mineralogical 

characteristics and acid-neutralizing potential of drill core 

samples from eight sites considered for metal mine related 

waste repositories in northern Jefferson, Powell, and Lewis 

and Clark counties, Montana: U.S. Geological Survey 

Open-File Report 98-790, 6 p.

Dobrin, M.B., and Savit, C.H., 1988, Introduction to geophysical prospecting, Fourth Edition: New York, McGraw Hill, 

867 p.

du Bray, E.A., 1995, Preliminary compilation of descriptive 

geoenvironmental mineral deposit models: U.S. Geological 

Survey Open-File Report 95-0831, 272 p.

Fraser, D.C., 1981, Magnetite mapping with a multicoil airborne electromagnetic system: Geophysics, v. 46, no. 11, 

p. 1579-1593.

Grauch, V.J.S., 1988, Statistical evaluation of linear trends in 

a compilation of aeromagnetic data from the southwestern 

U.S.: Geological Society of America Abstracts with 

Programs, v. 10, no. 7, p. A327.

Hanna, W.F., 1969, Negative aeromagnetic anomalies over 

mineralized areas of the Boulder batholith, Montana: U.S. 

Geological Survey Professional Paper 650-D, p. 159-167.
Geophysics and Environmental Implications 125

Hanna, W.F., Hassemer, J.H., Elliott, I.E., Wallace, C.A., and 

Snyder, S.L., 1994, Maps showing gravity and aeromagnetic anomalies in the Butte I°x2° quadrangle, Montana: 

U.S. Geological Survey Miscellaneous Investigations Series 

MapI-2050-I, scale 1:250,000.

Klepper, M.R., Weeks, R.A., and Ruppel, E.T., 1957, Geology 

of the southern Elkhorn Mountains, Jefferson and Broadwater Counties, Montana: U.S. Geological Survey Professional 

Paper 292, 82 p.

Lee, G.K., McCafferty, A.E., Alminas, H.V., Bankey, Viki, 

Frishman, David, Knepper, D.H. Jr., Kulik, D.M., Marsh, 

S.P., Phillips, J.D., Pitkin, J.A., Smith, S.M., Stoeser, D.B., 

Tysdal, R.G., and Van Gosen, B.S., 2001, Montana geoenvironmental explorer: U.S. Geological Survey Digital Data 

Series DDS-65.

Olhoeft, G.R., 1985, Low-frequency electrical properties: 

Geophysics, v. 50, no. 12, p. 2492-2503.

Phillips, J.D., 1997, Potential-field geophysical software for 

the PC, version 2.2: U.S. Geological Survey Open-File 

Report 97-725, 34 p.

Plumlee, G.S., 2000, The environmental geology of mineral 

deposits, in Plumlee, G.S., and Logsdon, J.J., eds., The 

environmental geochemistry of mineral deposits—Part A, 

Processes, techniques, and health issues: Society of Economic Geologists, Reviews in Economic Geology, v. 6A, 

p. 77-116.

Roberts, W.A., 1953, Notes on the alaskite rocks in the Boulder batholith near Clancy, western Montana: Northwest 

Science, v. 27, p. 121-124.

Robinson, G.D., 1963, Geology of the Three Forks quadrangle, Montana, with descriptions of igneous rocks by 

H. Frank Baraett: U.S. Geological Survey Bulletin 988-F, 

p. 121-141.

Ruppel, E.T., 1963, Geology of the Basin quadrangle, Jefferson, Lewis and Clark, and Powell Counties, Montana: 

U.S. Geological Survey Bulletin 1151, 121 p.

Smedes, H.W, 1966, Geology and igneous petrology of the 

northern Elkhorn Mountains, Jefferson and Broadwater 

Counties, Montana: U.S. Geological Survey Professional 

Paper 510, 116 p.

Smith, B.D., Labson, V.F, and Hill, Pat, 2000, Airborne geophysical survey in the Boulder River watershed, Jefferson 

and Lewis and Clark counties, Montana: U.S. Geological 

Survey Open-File Report 00-240, one CD-ROM.

Smith, B.D., and Sole, T.C., 2000, Schlumberger DC resistivity soundings in the Boulder watershed, Jefferson and Lewis 

and Clark Counties, Montana: U.S. Geological Survey 

Open-File Report 00-0110, available at 

URL http://pubs.usgs.gov/of/2000/ofr-00-0110A

Syberg, F.J.R., 1972, A Fourier method for the regionalresidual problem of potential fields: Geophysical Prospecting, v. 20, p. 47-75.

Telford, W.M., Geldart, L.P., Sheriff, R.E., and Keys, D.A., 

1976, Applied geophysics: Cambridge, U.K., Cambridge 

University Press.

Wanty, R.B., Berger, B.R., and Plumlee, G.S., 1999, Geoenvironmental models, in Fabbri, A.G., ed., Proceedings, 1998 

NATO Advanced Studies Institute Workshop on Geoenvironmental Models of Mineral Deposits: Dordrecht; Boston, 

L. Kluwer Academic Publishers.

Mine Inventory

By E.Paul Martin

Chapter D3 of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-D3

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract.............................................................................................................^^

Introduction............................................................................................................................................... 129

Methodology.............................................................................................................................................. 129

Data............................................................................................................................................................. 129

Discussion.................................................................................................................................................. 135

References Cited...................................................................................................................................... 135

Figures

1. Map showing mine inventory for Boulder River watershed study area......................... 130

Tables

1. Site-specific data for mines and prospects in the Boulder River watershed

study area................................................................................................................................. 131
Chapter 03 

Mine Inventory

By E.Paul Martin

Abstract

An inventory of inactive and historical mines and minerelated sites in the Boulder River watershed study area was 

compiled from existing State and Federal sources. Site 

locations were spatially verified using digital orthophoto 

quadrangles to ensure an accurate geographically referenced 

inventory. The inventory also provides, where available, 

descriptive information, compiled from published sources, 

that supports the environmental evaluation of the effect of 

historical mining in the study area. This information includes 

the presence and the pH of flowing water from an adit, the 

presence and estimated volume of mine waste and mill tailings, and estimates of past production. These data provide 

site-specific information about potential anthropogenic contributions of deposit-related trace elements observed within the 

watershed.

Introduction

This chapter describes the mine inventory compiled for 

the Boulder River watershed study area. One of the most 

important facets of characterizing watersheds affected by 

historical mines is determining the location of as well as 

information about the mines, mills, and other mine-related 

sites. Every site in the watershed represents a potential source 

of deposit-related trace elements that could affect water quality and ecosystem health through direct drainage, seepage, 

erosion, or runoff. Within the Boulder River watershed, abundant and comprehensive data are available from several previous investigations. However, these data had not previously 

been compiled into one database, and many of the inventoried 

sites had only approximate locations.

The objective of this inventory is to create a database of 

mine-related sites that are accurately positioned and attributed 

in order to provide information to answer important questions about mine-site and stream remediation. The inventory 

combines geographically referenced locations and descriptive 

information in a format that lays the foundation for answering 

environmental and remediation questions using geographic 

information system (GIS) technology. The inventory comprises significant mines and mine-related sites in the Basin 

Creek, Cataract Creek, and High Ore Creek basins (major

tributaries of the Boulder River), and in the areas drained by 

the portion of the Boulder River from the mouth of Basin 

Creek to High Ore Creek. (See Church, Nimick, and others, 

this volume, Chapter B, fig. 2.)

Methodology

The process used to determine the representative location for a mine-related site included the following steps. Data 

from the State of Montana, United States Department of 

Agriculture (USDA) Forest Service, Bureau of Land Management (BLM), and U.S. Geological Survey (USGS) databases 

provided an initial site data and localities list. These data were 

combined into one digital layer, and each site location was 

resolved to one representative point based on 1993 and 1998 

digital orthophoto quadrangles (DOQs). Some mine-related 

sites contained multiple adits, shafts, and prospects, yet 

only one point location was captured to "best" represent the 

inventory site. Also, in some cases, the site location had to be 

determined strictly from a written description because not all 

of the historical data were georeferenced. Using digital orthophoto quadrangle (DOQ) image plots containing the resolved 

mine locations, USDA Forest Service and USGS personnel in 

Montana verified and revised the localities of the mine-related 

sites based on limited site visits, survey plats, and local knowledge of the area. Field inventories conducted by the Montana 

Bureau of Mines and Geology (Metesh and others, 1994, 

1995, 1996; Marvin and others, 1997; Roby and others, 1960), 

the Montana Department of State Lands (1995), the Montana 

Department of Environmental Quality (1997), and the U.S. 

Geological Survey (Elliott and others, 1992) represent the 

sources for the descriptive data.

Data

Figure 1 shows 143 mine-related sites included in the 

inventory. Factors for inclusion or exclusion in the inventory 

focused on a site's contribution to environmental degradation, 

the physical hazard risk, past production volumes, and simply 

whether a site had a known name. The number for each site in 

figure 1 references a unique identifier for the study. Within the
130 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112°22'30"

NATIONAL FOREST BOUNDARY

Boulder River 

watershed study a re

\

\

EXPLANATION

100 Mine-related site 

* with Amli mine id

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

1 2 KILOMETERS

Figure 1. Mine inventory for Boulder River watershed study area.

mines database, this identifier is an item called Amli_mine_id 

and allows mine-related sites to be associated with scientific 

data and selected field sample sites. (See Rich and others, 

this volume, Chapter G, for a complete explanation of this 

relationship and how to access the mine inventory and project 

databases.)

Table 1 presents the descriptive information for each site 

in the inventory. The name field is self-explanatory. The next 

fields are the unique identifier just referenced and the geographic coordinates. The location status field provides a relative measure of how accurately the site has been positioned. 

The shafts and adits fields give an indication of the extent of
Table 1. Site-specific data for mines and prospects in the Boulder River watershed study area.

[Amli_mine_id in the database is Site No. (fig. 1); verif., verified; apprx., approximated; gpm, gallons per minute; undeterm., value not known; quantities expressed in units u

pounds; yd3 , cubic yard; —, no data. Blank spaces for flow rate and pH reflect the logical extension of a value of zero for the number of flowing adits or "no data" for the num

very large, greater than $5,000,000 or greater than 250,000 tons of ore; large, $500,000 to $5,000,000 or 25,000 to 250,000 tons of ore; medium, $50,000 to $499,000 or 2,50

than $50,000 or less than 2,500 tons of ore. Production data from Elliott and others (1992)]

Site name

Ada

Adelaide

Apollo

Aurora

Bakama

Basin Belle

Basin Creek

Basin Creek Placer

Basin Gold & Silver

Basin Mill/Atwater Complex

Big Limber

Bishop Creek

Black Bear

Blue Diamond-Occidental

Boulder Chief

Boulder Vestal

Buckeye

Bullion

Buster

Carlson

Cataract

Cataract Creek Placer

Cataract Tailings

Columbus

Comet

Comstock Group

Condor Lodes

Copper King Prospect

Cracker

Crescent

Crystal

Site 

No. 

(fig.D

l

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

W. longitude

112154.451

112 1625.629

112139.840

1121833.120

1121052.765

1121648.482

1121745.423

1121730.120

112 160.840

112 15 18.860

112 1359.880

112 1157.715

1121438.040

1121055.075

1121231.599

112 149.592

1121741.413

112 1739.106

112 1557.829

112 185.700

1121350.880

112 13 13.080

1121353.040

1121654.822

112 100.120

1121235.015

112 13 56.585

112136.094

112 149.960

1121444.160

112 1538.160

N. latitude

462145.312

46 17 9.374

46 21 6.840

46186.840

46 22 25.637

46 17 12.195

46 25 17.565

46 17 39.840

46 19 57.000

46 16 18.769

46 17 17.880

461821.774

462057.120

46 21 28.896

461948.616

46 17 18.893

46 23 50.974

462121.458

461646.635

462511.959

46 20 24.000

46 21 59.040

462017.160

46 17 15.693

461834.920

46 16 14.072

461835.971

46 17 7.453

46 19 24.960

462518.120

46 20 52.080

Location 

status

verif.

verif.

verif.

verif.

verif.

verif.

apprx.

apprx.

apprx.

verif.

apprx.

apprx.

verif.

verif.

verif.

apprx.

verif.

verif.

apprx.

verif.

verif.

verif.

verif.

verif.

verif.

verif.

verif.

apprx.

verif.

verif.

verif.

Shafts

1

-

-

-

-

-

-

--

-

-

-

--

1

--

1

--

1

1

-

-

2

-

--

-

2

~

1

~

--

2

multiple

Adits

8

2

1

5

1

2

-

-

-

--

-

1

2

3

2

1

multiple

4

-

-

3

-

-

3

--

1

1

~

1

1

2

No. of flowing 

adits

multiple

0

-

0

0

0

-

-

-

--

~

1

2

2

1

--

0

2(1 sampled)

-

-

2

--

-

0

--

-

-

--

1

1

1

Flow rate

west adit, <0.5 gpm

east adit, —

-

-

Blue Diamond = 2 gpm

Occidental = 7 gpm

0.1 gpm

7 gpm

-

12 gpm

5 gpm

36 gpm

pH

6.67

2.57

-

-

6.55

-

2.63

2.58

-

7.39

3.15

3.21

Mill 

existence

no

no

-

no

-

no

-

-

-

yes

-

-

no

no

yes

-

yes

yes

-

-

yes

-

-

no

yes

-

--

--

no

yes

no

q

1,

-

-

-

-

2,

--

-

-

-

-

-

3,

1,

90

14

--

6,

42

-

-

-

-

-

-

21

--

--

-

4,0

8,4

--
Table 1. Site-specific data for mines and prospects in the Boulder River watershed study area.—Continued

Site name

Custer

Daily West

Delia Prospect

Doris

Double Shaft

Dumortierite Prospect

East Katie

Eldorado and Plateau

Elmer

Enterprise

Eva May

Eva May Tailings

Evening Star & Golden Assets

First Shot

Freeburg

Golconda/Reliance

Golden Glow/Lula Bell

Golden Thread

Gray Eagle

Gray Lead

Great Shield Uranium

Hanna

Hattie Ferguson

Hawkeye

Hector

Hiawatha

Hidden Treasure

High Ore

Highland

IdaM.

Ida May

Independence

Jack Creek Mill Tailings

Jack Creek Ridge

Jessie

Site 

No. 

(fig.D

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

W. longitude

1121336.840

1121742.458

112 13 25.155

1121630.609

1121628.823

1121841.650

112 15 52.972

112 13 21.000

112 15 5.425

1121738.340

11213 18.335

112 13 13.080

11215 14.117

112169.840

1121241.160

112 12 10.840

1121630.561

1121048.290

1121152.627

1121420.989

1121426.880

1121359.160

1121450.102

1121652.292

1121646.352

11213 18.836

112 15 13.599

1121150.459

1121649.280

1121244.629

1121346.999

1121349.080

112 19 17.659

1121859.886

1121659.117

N. latitude

46 18 15.120

46 17 44.402

461953.847

461657.986

462358.126

46 21 54.704

46 16 17.553

46 24 45.000

461854.133

46 23 49.534

46 20 55.908

462048.120

461951.716

46 21 29.880

461849.781

461643.878

462451.941

46 18 45.904

461849.037

46 21 37.343

46 21 45.000

46 20 49.920

46 19 57.704

46 22 37.938

46 17 40.388

46 18 17.682

46 18 16.391

46 17 43.494

461648.478

46 19 50.040

462510.141

4617 11.040

46 21 17.864

46 22 0.864

46 16 57.573

Location 

status

verif.

verif.

verif.

verif.

verif.

apprx.

verif.

verif.

verif.

verif.

verif.

verif.

verif.

verif.

verif.

verif.

verif.

apprx.

verif.

verif.

apprx.

apprx.

verif.

verif.

verif.

verif.

apprx.

verif.

verif.

verif.

verif.

apprx.

verif.

verif.

verif.

Shafts

l

--

--

--

4

--

1

4

--

1

1

-

--

--

--

--

-

--

1

--

--

-

1

-

--

1

--

--

--

0

1

--

-

--

--

Adits

1

2

--

2

--

--

--

1

1

1

1

--

--

-

--

2

2

--

4

2

--

-

4

1

2

3

--

1

5

1

0

--

-

-

-

No. of flowing adits

0

0

--

0

--

-

-

0

0

1

1

-

--

--

--

-

--

--

1

1

--

--

2

1

--

--

--

--

--

1

0

--

-

--

--

Flow rate

-

5gpm

--

3gpm

0.5 gpm

2.9 gpm

--

2 gpm

pH

3.18

6.67

6.98

7.39

7.02

7.09

--

5.43

Mill existence

--

--

-

-

no

no

--

no

--

--

yes

--

--

-

--

no

no

-

--

yes

--

--

no

no

no

--

-

--

--

no

-

--

--

--

--

Dump 

quantity

--

300 tons

-

4,470 yd3

--

--

--

--

-

22,930 yd3

92,000 yd3

--

--

--

--

--

--

--

73,000 yd3

--

-

--

-

--

100 tons

--

-

--

--

--

-

--

-

--

--
Mine Inventory 133

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Mine Inventory 135

the workings at that site. The number of flowing adits, the flow 

rate, and the pH of the discharge represent important pointsource information. In numerous cases, either the site did not 

have a flowing adit or data were not available for the flow 

rate and pH. The mill existence field indicates the historical 

presence or absence of a mill at the site. The dump quantity 

and tailings quantity fields provide a measure of the amount of 

waste rock or mill tailings at each site (again, the sources did 

not necessarily document this descriptor for every site). The 

past production field shows each site's output in relative terms. 

The following provides a measure of the value or magnitude 

of production based either upon the value of the ore shipped 

(expressed in units of $1,000) or tonnage produced (expressed 

in units of 1,000 tons): very large, greater than $5,000,000 or 

greater than 250,000 tons of ore; large, $500,000-$5,000,000 

or 25,000-250,000 tons of ore; medium, $50,000-$499,000 or 

2,500-24,000 tons of ore; small, less than $50,000 or less than 

2,500 tons of ore; no or undetermined production. Monetary 

figures represent value at time of production (Elliott and 

others, 1992).

Discussion

The Boulder River watershed study area contains numerous prospects and smaller mine-related localities not inventoried for this study. Whereas the potential exists for any one 

of these sites to adversely affect ecosystem health, the data 

sources and field investigations suggest that this inventory is 

comprehensive in terms of identifying the significant historical 

mines and mine-related sites.

Some historical mine sites contain large underground 

workings or have multiple shafts and adits over an area. 

Regardless of complexity, the inventory represents each site 

with a single location.

The decision to encode the location status field in table 

1 with "verified" or "approximate" was determined by a comparison of the source description and field diagrams with the 

DOQs and locations symbolized on existing maps. A verified 

value means that USDA Forest Service and USGS personnel 

in Montana checked the mine-related location and agreed on 

its position with a high degree of confidence.

The values in table 1 represent a choice of values from 

multiple sources. Discounting the unique identifier, the 

geographic coordinates, and the location status, the values for 

any particular column do not necessarily originate from the 

same source. For example, the number of adits for the Ada 

mine originates from source A, and the number of adits for 

the Bullion mine originates from source B. Likewise for any 

particular mine, the values for each of the columns may derive 

from different sources. All data sources are referenced herein.

References Cited

Elliott, I.E., Loen, J.S., Wise, K.K., and Blaskowski, M.J., 

1992, Maps showing locations of mines and prospects in 

the Butte 1 degree x 2 degree quadrangle, western Montana: 

U.S. Geological Survey Miscellaneous Investigations Series 

Map I-2050-C, 2 plates, scale 1:250,000, and pamphlet, 

147 p.

Marvin, R.K., Metesh, J.J., Bowlers, T.P., Lonn, J.D., Watson, 

I.E., Madison, J.P., and Hargrave, P.A., 1997, Abandonedinactive mines program, U.S. Bureau of Land Management: 

Montana Bureau of Mines and Geology Open-File Report 

348, 506 p.

Metesh, J.J., Lonn, J.D., Duaime, T.E., and Wintergerst, Robert, 1994, Abandoned-inactive mines program, Deerlodge 

National Forest—Volume I, Basin Creek drainage: Montana 

Bureau of Mines and Geology Open-File Report 321, 131 p.

Metesh, J.J., Lonn, J.D., Duaime, T.E., Marvin, R.K., and 

Wintergerst, Robert, 1995, Abandoned-inactive mines 

program, Deerlodge National Forest—Volume II, Cataract 

Creek drainage: Montana Bureau of Mines and Geology 

Open-File Report 344, 201 p.

Metesh, J.J., Lonn, J.D., Marvin, R.K., Madison, J.P., and 

Wintergerst, Robert, 1996, Abandoned-inactive mines 

program, Deerlodge National Forest—Volume V, Jefferson 

River drainage: Montana Bureau of Mines and Geology 

Open-File Report 347, 179 p.

Montana Department of Environmental Quality, 1997, Watershed analysis of abandoned hardrock mine priority sites 

1997: Prepared by Pioneer Technical Services, Inc., Butte, 

Mont., and Integrated Geoscience, Inc., Helena, Mont., for 

the Mine Waste Cleanup Bureau, variously paginated.

Montana Department of State Lands, 1995, Abandoned 

hardrock mine priority sites, 1995 summary report: 

Prepared by Pioneer Technical Services, Inc., Butte, Mont., 

for the Abandoned Mine Reclamation Bureau, variously 

paginated.

Roby, R.N., Ackerman, W.C., Fulkerson, F.B., and Crowley, 

F.A., 1960, Mines and mineral deposits (except fuels), 

Jefferson County, Montana: Montana Bureau of Mines and 

Geology Bulletin 16, 120 p.

U.S. Geological Survey/USDA Forest Service - published 

maps and map/field materials:

Basin quadrangle - l:24,000-scale - 1985 provisional edition.
136 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Basin quadrangle - 1:24,000-scale - 1996 USGS/USFS Mount Thompson - 1:24,000-scale - 1996 USGS/USFS 

edition. edition.

Bison Mountain - 1:24,000-scale - 1985 provisional edition. Three Brothers - l:24,000-scale - 1985 provisional edition.

Chessman Reservoir - l:24,000-scale - 1985 provisional Thunderbolt Creek - l:24,000-scale - 1985 provisional 

edition. edition.

Mount Thompson - 1:24,000-scale - 1985 provisional edition. Thunderbolt Creek - 1:24,000-scale - 1996 USGS/USFS

edition.
Metal Leaching in Mine-Waste 

Materials and Two Schemes for 

Classification of Potential Environmental 

Effects of Mine-Waste Piles

By David L Fey and George A. Desborough

Chapter D4 of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-D4

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract....................................................................................................................................................

Introduction............................................................................................................................................... 139

Purpose and Scope......................................................................................................................... 140

Sample Collection and Preparation....................................................................................................... 140

Bulk Surface Samples..................................................................................................................... 140

Two-Inch Diameter Vertical Core.................................................................................................. 140

Location of Mine-Waste Sites................................................................................................................ 140

Geochemistry and Mineralogy of Mine Wastes.................................................................................. 143

Mineralogy........................................................................................................................................ 143

Mixed-Acid Digestion Method ...................................................................................................... 144

Passive Leach Method ................................................................................................................... 144

EPA-1312 Leach Method (Synthetic Precipitation Leach Procedure-SPLP)........................ 144

Net Acid Production (NAP) Method............................................................................................. 145

Effects of Weathering on Dump Surface Material.............................................................................. 145

Classification Schemes for Mine-Waste Piles.................................................................................... 148

Classification of Mine-Waste Piles in the Boulder River Watershed.............................................. 149

Summary and Conclusions...................................................................................................................... 152

References Cited...................................................................................................................................... 152

Figures

1. Map showing Boulder River watershed study area, and localities of bulk

surface mine-waste samples................................................................................................ 141

2. Photograph of lower (largest) waste dump at Bullion mine............................................. 143

3. Photograph of soluble salt goslarite coating mine waste................................................ 144

4. Generalized cross section of tailings sampled by cores at Buckeye flotation mill...... 147

5. Box plots of silver, lead, copper, zinc, cadmium, and arsenic in tailings core

from Buckeye mine site.......................................................................................................... 147

6. Graph showing net acid production of waste samples versus sum of dissolved

As+Cd+Cu+Zn+Pb from EPA-1312 leach.............................................................................. 149

7. Graph showing net acid production of waste samples versus dissolved iron

from EPA-1312 leach............................................................................................................... 150

8. Map of Boulder River watershed study area showing mine-waste piles ranked

by water-quality degradation potential................................................................................ 151

Tables

1. Site numbers, site names, sample descriptions, and estimated size of mine-waste 

piles sampled in the Boulder River watershed study area............................................... 142

2. Site numbers, names, pH of passive leach, net acid production, selected metals 

in both leaches; iron, sulfate, and specific conductance of EPA-1312 leach, and 

classification scores of wastes by Method 1 and Method 2............................................ 146
Chapter 04

Metal Leaching in Mine-Waste Materials and Two 

Schemes for Classification of Potential Environmental 

Effects of Mine-Waste Piles

By David L Fey and George A. Desborough

Abstract

Surface waste material was collected from 19 metalmining-related dumps at 10 sites in the Boulder River watershed study area. Leach and acidity analyses of waste material 

provided a foundation for the development of two classification schemes for evaluating the potential environmental effect 

of mine-waste piles. Mineralogical and geochemical analyses 

of a vertical core of tailings at a mill site showed a distinction 

in the amount of deposit-related elements between surface and 

buried waste material.

Mineralogy of bulk surface samples was determined 

primarily by X-ray diffraction. Anglesite and jarosite were 

present in about 80 percent of the waste piles. Sphalerite and 

arsenopyrite, both common primary minerals in the mineral 

deposits, were not present in the mine-waste samples. Goslarite (a zinc sulfate) and scorodite (iron arsenate) were identified in the field. Total-digestion inductively coupled plasmaatomic emission spectroscopy (ICP-AES) elemental and X-ray 

diffraction analyses of a core from the Buckeye flotation tailings revealed that most of the pile contained oxidized tailings 

composed of secondary minerals produced during weathering 

and sparse to no original sulfide minerals; the bottom of the 

core contained a layer of primary sulfide minerals. Comparison of concentrations in the sulfide and oxidized layers in this 

core demonstrated that significant leaching of deposit-related 

trace elements had occurred in the oxidized layer, with some 

elements migrating downward.

The surface samples were subjected to two leaching 

techniques to determine the concentration of water-soluble, 

deposit-related trace elements in the dump materials. Net acid 

production, an indication of the ability of a material to produce acid when oxidized over a long period of time, was also 

determined. The sum of the concentrations of deposit-related 

elements (Ag+As+Cd+Cu+Pb+Zn) in these leachates, when 

plotted against either the leachate pH or the net acid-production value, provided two schemes for classifying these mine 

wastes. Metal-mining wastes in the study area had classifications ranging from low potential to high potential for causing

environmental degradation. The leach and acidity tests showed 

that material with net acid potential greater than 20 pounds 

CaCO3 per ton equivalent will release high concentrations of 

iron, arsenic, cadmium, copper, lead, and zinc, and produce 

leachates with low pH.

The two classification schemes derived from the chemical and waste-pile-size data provide a means to compare the 

potential of the waste piles in a watershed to cause environmental degradation. These methods are meant to provide 

numerical means of evaluating and comparing wastes, but do 

not incorporate such factors as proximity to ground or surface water, presence of surface water, or draining adit water 

flowing over or infiltrating into the piles. These factors must 

be considered by land managers along with the classification 

results.

Introduction

Metal-mining-related wastes in the Boulder River 

watershed study area cause detrimental effects on water quality because of acid generation and toxic-metal solubilization 

(Nimick and Cleasby, this volume, Chapter D5; Cannon and 

others, this volume, Chapter El). Mining-related wastes also 

contribute to contamination of streambed sediment through the 

fluvial transport and deposition of tailings and the settling of 

metal-rich colloidal material (Church, Unruh, and others, this 

volume, Chapter D8).

Veins enriched in base and precious metals were explored 

and mined in the Basin, Cataract, and High Ore Creek basins 

for a period of more than 70 years. Extracted minerals 

included galena, sphalerite, pyrite, chalcopyrite, tetrahedrite, 

and arsenopyrite. Most of the metal-mining waste sites in 

the study area were identified and described by the Montana 

Bureau of Mines and Geology (Metesh and others, 1994; 

Metesh and others, 1995; Marvin and others, 1996). In 1997, 

we collected composite surface samples from sites in the 

Basin and Cataract Creek basins to identify, characterize, and 

classify waste sources.
140 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Purpose and Scope

The purpose of this chapter is to describe various geochemical and mineralogical studies to help understand and 

assess the potential geochemical effect of mine-waste piles 

in the Boulder River watershed study area. Material from the 

surface of waste piles was sampled and analyzed to determine 

the minerals and elements present in waste piles. A core was 

collected from one waste pile to determine whether surface 

samples have different trace-element composition and mineralogy from samples collected at depths. Finally, chemical and 

physical attributes of waste piles were combined to construct 

two classification schemes to rank the potential environmental 

hazard of runoff from mine-waste piles. The goals of this part 

of the Boulder River watershed study were to:

• Characterize the mineralogy and geochemistry of mine 

wastes

• Demonstrate the geochemical differences between 

surface and subsurface material in mine-waste piles

• Develop a classification scheme or schemes to assess 

the potential environmental effect of runoff from 

mine waste

• Apply the classification schemes to the sampled 

mine-waste piles.

Sample Collection and Preparation

Bulk Surface Samples

Mine-waste samples (exploration waste, dump material, 

or mill tailings) were collected from the surface of 19 waste 

piles at 10 sites in the Boulder River watershed study area. 

Surface material was collected for analysis because it is what 

is exposed to air, rain, and snowmelt runoff infiltration. Material from each site was collected from 30 or more randomly 

selected 3-ft cells across the top and sides of a dump to a depth 

of approximately 3 in. using four to six randomly selected 

2-3 oz scoops per cell. This collection method is designed to 

reduce the sampling error (also called the fundamental error; 

Smith and others, 2000). Samples were dry sieved in the 

field to obtain a minus-0.08 in. (<2 mm) fraction. The minus0.08 in. fraction was deemed to be the most reactive to water 

in short-term exposures. Coarser material was discarded. The 

resulting composite sample typically contained 2-4 Ib of mine 

waste. The minus-0.08 in. fraction was split in the laboratory 

using a Jones splitter. One fraction was further split into a 

l/2 Ib sample that was used for (1) bulk chemical analysis (after 

sieving to minus-80 mesh (<190 |im) and grinding to minus200 mesh (<75 urn)); (2) X-ray diffraction (XRD) analysis 

to determine mineralogy; (3) analysis of heavy-mineral

concentrates to identify high-density minerals; (4) leaching 

tests to determine amounts of soluble deposit-related elements; 

and (5) net acid production (NAP) tests (after grinding to 

minus-200 mesh (<75 um)).

Two-Inch Diameter Vertical Core

At the Buckeye mill tailings site, we also drove a 2-in. 

PVC pipe about 6 ft through the thickest part of the tailings. 

In the laboratory, core samples were described and subdivided 

into subsamples (by depth) according to visually identified 

differences in mineralogy, organic content, and apparent 

oxidation zones. The subsample material was sieved to 

minus-100 mesh (<150 um), analyzed for bulk chemistry, 

and examined with XRD for mineralogy. Analyses from this 

core illustrate the leaching of trace elements as sulfidic waste 

weathers; they are discussed in more detail in the section on 

effects of weathering on dump surface material and in Cannon 

and others (this volume).

Location of Mine-Waste Sites

We sampled and analyzed material from selected sites 

likely to have moderate to high impact on the environment, 

and to which we had access (either public land or private land 

with permission). We did not sample all possible waste sites, 

and so the rankings derived from the classification schemes 

discussed herein serve as applied examples of those schemes, 

and not a definitive ranking of all mine-waste sites in the study 

area.

Metesh and others (1995) inventoried 37 waste sites from 

historical records in the Basin Creek basin and visited 28. 

They sampled 14 sites. Of those 14, we visited and sampled 

5 sites. Our sampling plan was based on assessing which sites 

were likely to contribute adversely to the quality of water and 

sediment in the study area. Some sites were deemed too small, 

too distant from any surface water (for example, the Morning mine), or too inaccessible for remediation (Hector mine). 

Other sites showed no significant impact on nearby streambed sediment (for example, Lady Lieth and Winter's Camp 

mines), and so were not sampled. Metesh and others (1995) 

inventoried 57 sites in the Cataract Creek basin, visited 54, 

and sampled 27. We collected samples at five sites, using the 

criteria just listed to screen sites. The Crescent mine is accessible only by foot, and although it has visible mine discharge, 

it had negligible effect on sediment in upper Cataract Creek, 

based on streambed sediment analyses (Church, Unruh, and 

others, this volume). Similarly, effect on sediment of Hoodoo 

Creek (tributary to Cataract Creek) from the Blue DiamondOccidental mine was minimal. The Phantom mine-waste pile 

on Cataract Creek was very small (200 tons). One site not 

sampled but which should have been was the Morning Glory 

tailings. This site is on the west bank of Cataract Creek and 

contained approximately 6,000 tons of material (Metesh and
Metal Leaching and Potential Environmental Effects of Mine Waste 141

others, 1995). However, Metesh and others (1995) concluded We collected 19 bulk surface samples from mine-waste

that the pile did not appear to contribute to the degradation of piles at 10 mine sites located in the Basin and Cataract Creek

Cataract Creek, and that the mineralogy of the material sug- basins (fig. 1). The estimated sizes of the waste piles are in

gested little potential for metals to be released. table 1.

112°22'30"

v Flotation tailings

BEAVERHEAD-DEERL ODGE 

NATIONAL FOREST

Boulder River 

watershed study area

MORNING MARIE

o

Boulder River . watershed {

T8N

T7N

T6N

EXPLANATION

Mine site sampled by bulk surface method Base from U.S. Geological Survey 

digital line graphs, 1:100,000

0 1 2 KILOMETERS

Figure 1. Boulder River watershed study area, and localities of bulk surface mine-waste samples (sites numbered as in Martin, this 

volume, Chapter D3).
142 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 1. Site numbers, site names, sample descriptions, and estimated size of mine-waste 

piles sampled in the Boulder River watershed study area.

[Site numbers are from Martin (this volume, table 1)]

41 

17

18

15

142

94

29

33

119

31

Site No. and name

Enterprise mine 

Buckeye mine

Bullion mine

Boulder Chief mine

Waldy mine

Morning Marie mine

Cracker mine

Daily West mine

Sirius mine

Crystal mine

Sample description, 

bulk surface sample

Brown waste from Enterprise mine 

Light-gray waste from Buckeye mine 

Light-gray tailings from flat near creek

Uppermost dump, upper adit 

Middle dump, middle adit 

Lower dump, lower adit 

Small dump near lowest adit

Upper tailings impoundment

Lower tailings impoundment

Waste above adit from open cut 

Waste from below mine adit

Waste dump at adit

Waste piles from adit

Waste from adit

Yellow waste near creek bed

Waste dump at adit

Altered rock along east side of open cut

Altered rock along west side of open cut

Waste at ore bins near creek

Estimated size 

(tons)

5,000 

10,000 

8,400

6,000 

7,000 

12,000 

500

1,200

3,600

3,500 

3,500

700

1,000

4,000

300

5,000

20,000

10,000

4,000

In the Basin Creek basin, we visited the following sites 

and collected samples as noted:

• Buckeye mine area near the head of Basin Creek; two 

samples

• Enterprise mine area (just upstream of the Buckeye 

mine on Basin Creek); one sample

• Bullion mine area, above a small tributary to Jack 

Creek (the Bullion mine tributary); six samples

• Daily West mine, along Basin Creek about 3 mi 

upstream from the town of Basin; one sample.

In the Cataract Creek drainage basin, we visited the 

following sites and collected samples as noted:

• Crystal mine, near the head of Uncle Sam Gulch 

(tributary of Cataract Creek); three samples

• Sirius mine; one sample

• Morning Marie mine, along Cataract Creek upstream 

of Uncle Sam Gulch; one sample

• Cracker mine, along Cataract Creek upstream of Uncle 

Sam Gulch; one sample

• Boulder Chief mine, about ll/2 mi east of Cataract 

Creek and ll/2 mi south of Hoodoo Creek; two samples

• Waldy mine, in Big Limber Gulch about 2 mi upstream 

from Cataract Creek; one sample.

The High Ore Creek basin is also in the study area. 

However, we did not collect samples from the Comet mine, 

the largest mining operation in that drainage, because it was 

scheduled for remediation.
Metal Leaching and Potential Environmental Effects of Mine Waste 143

Figure 2. View of lower (largest) waste dump at Bullion mine, looking north. Distance across dump is about 

200 feet (60 m). Loading chute seen at center of picture. Mill was below dump, to the north.

Geochemistry and Mineralogy of 

Mine Wastes

Mineralogy

Minerals in the bulk surface samples of mine waste were 

determined by X-ray diffraction (copper radiation) of 2-oz 

samples of the minus-0.08-in. (<2 mm) fraction after pulverizing in a Spex mill to minus-200 mesh (<75 |um). Both 

anglesite and jarosite were present in about 80 percent of the 

samples. Whereas anglesite is chemically simple (PbSO4 ), 

jarosite may be chemically complex. Studies of members of 

the alunite-jarosite family of minerals by Scott (1987) showed 

that the general formula for jarosite is AB3 (XO4)2 (OH)6 ; the 

large cation (A) may be Na, K, Ag, NH4, H3O, Ca, Pb, Ba, Sr, 

or Ce, and the B sites may be occupied by Al, Fe, Cu, or Zn. 

The anion (XO4) may be SO4, PO4, AsO4 , SbO4, CrO4, or SiO4 . 

For our samples, the dominant X-ray diffraction pattern was 

that of the jarosite family, with SO4 as the major anion with 

some possible AsO4 substitution where arsenic was abundant. 

The major cations appeared to be K, Pb, and H3O based on 

scanning electron microscopy and energy-dispersive X-ray 

fluorescence analysis.

Heavy-mineral concentrates were obtained by mechanical panning of a 1-oz fraction of each minus-0.08 in. (<2mm) 

split in order to concentrate high-density minerals such as 

pyrite, galena, and sphalerite. These minerals were identified 

by X-ray diffraction, X-ray fluorescence, and optical microscopy. Although sphalerite (ZnS) and arsenopyrite (FeAsS) are 

common primary hydrothermal minerals in the ore deposits 

of the study area (Billingsley and Grimes, 1918), we found 

no arsenopyrite in the heavy-mineral concentrates from any 

sample and only trace amounts of sphalerite in one sample.

White botryoidal crusts of goslarite (ZnSO4 «7H2O) were 

found underneath an overhang on the largest waste pile at 

the Bullion mine (fig. 3). Thus, we suspect that zinc resides 

chiefly in this soluble zinc sulfate, and possibly in gunningite 

((Zn, Mn)SO4 -H2O). Scorodite, a highly water-soluble iron 

arsenate (FeAsO4 *2H2O), was abundant on the surface of one 

waste pile at the head of Jack Creek, about 1 mile north of 

the Bullion mine. Scorodite is the most commonly occurring 

oxidized secondary mineral derived from arsenopyrite. The 

absence of primary zinc- and arsenic-bearing minerals and the 

presence of these two secondary minerals suggest that most 

of the zinc- and arsenic-bearing primary sulfide minerals had 

been converted to more soluble sulfate or arsenate phases by 

weathering. This weathering took place since the cessation of 

mining, a period of 50-100 years.
144 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Figure 3. Soluble salt goslarite (ZnS04»7H2 0) coating mine waste, Bullion mine. This easily dissolved mineral 

formed in place from leaching of zinc from waste pile; it was protected here from rain by an overhanging cut in 

the waste pile. Field of view in photograph is about 1 ft across.

Mixed-Acid Digestion Method

A mixed-acid digestion technique was used to provide 

bulk analyses of surface mine-waste samples and the core 

subsamples. We used the results to illustrate the geochemical 

difference between dump surface material (mostly oxidized) 

and material at depth (partially oxidized or unoxidized). A 

0.2 g portion of material was subjected to a mixed-acid digestion using, in sequence, HC1, HNO3 , HC1O4 , and HF acids 

(Crock and others, 1983; Briggs, 1996). The resulting solution was analyzed for 40 elements using inductively coupled 

plasma-atomic emission spectroscopy (ICP-AES). The digestion dissolves sulfides and most silicates and oxides; resistant 

or refractory minerals such as zircon, spinels, and some tin 

oxides are only partially dissolved. Samples of standard reference material (SRM) were digested and analyzed with the 

mine-waste samples. These standards were SRM-2704, SRM2709, SRM-2710, and SRM-2711, available from the National 

Institute of Standards and Technology. Analytical results for 

the bulk surface materials are in Fey, Desborough, and Finney 

(2000), and results for the 2-in. core from the Buckeye site 

are in Cannon and others (this volume) and the database (Rich 

and others, this volume, Chapter G). A statistical summary of 

mean values, median values, and standard deviations for multiple analyses of the reference materials, and comparisons with 

certified values appear in Fey, Unruh, and Church (1999).

Passive Leach Method

A passive leach procedure was also applied to the bulk 

surface mine-waste materials, and the results were used in 

one of the waste classification schemes discussed herein. A 

100-g sample was exposed to 2 L of laboratory deionized 

water (pH of 5.0±0.2) in an open 4-L beaker. Samples were 

left at rest for 1 hour and then gently stirred for 5 seconds to 

prevent stratification of the leachate. The pH of the leachate 

was measured after 24 hours, and then a 60-mL sample of the 

leachate was filtered through a Gelman 0.45-|um filter using 

a disposable 60-mL syringe (Desborough and Fey, 1997), 

acidified with six drops of ultra-pure HNO3 , and refrigerated 

prior to analysis by ICP-AES. The data for the passive leach 

procedure are in Desborough and Fey (1997).

EPA-1312 Leach Method (Synthetic Precipitation 

Leach Procedure-SPLP)

This procedure was used on the bulk surface mine-waste 

materials, and the results were used in one of the waste classification schemes discussed below. A 100-g sample of mine 

waste was placed in a 2.3-L polyethylene bottle. Two liters 

of an extract solution were added, resulting in a 1:20 sample/ 

extract ratio, with 300 cm3 of headspace. The extract solution 

was made from deionized w ater acidified to a pH of 4.2 with
Metal Leaching and Potential Environmental Effects of Mine Waste 145

a 1-percent aqueous solution of 60/40 v/v H2SO4/HNO3 . The 

capped bottles were placed on an end-over-end (tumbling) 

rotating agitator at 30 rpm for 18 hours. The leachates were 

then pressure filtered through a 0.7-um filter (USEPA, 1986). 

A 100-mL aliquot of filtered solution was acidified with 

ultra-pure HNO3 and analyzed for 25 elements by ICP-AES 

(Briggs and Fey, 1996) and for sulfate (as sulfur) by ICP-AES. 

Specific conductance and pH were determined on the unacidified bulk filtered leachate. All data are in Fey, Desborough, 

and Finney (2000).

Net Acid Production (NAP) Method

This test was applied to the bulk surface mine-waste 

materials, and the results are used in one of the classification 

schemes herein. A 1.0-g sample of pulverized, minus-200 

mesh material was digested with a solution of 30 volumepercent hydrogen peroxide to oxidize pyrite and pyrrhotite, 

thereby producing sulfuric acid (Lapakko and Lawrence, 

1993). The produced acidic solution reacted with the bulk 

sample, releasing additional acidity from water-soluble salts 

(present as a result of wetting-drying cycles on the mine-waste 

pile). The solution also reacted with acid-consuming minerals 

such as carbonates, biotite, chlorite, and epidote. The solutions 

were heated to near-boiling for 1 hour, cooled, and filtered. 

The filtrate was then titrated to a pH of 7 with 0.1M NaOH. 

A calculated net acid production (NAP) is expressed in terms 

of Ib-equivalent CaCO3 per ton of mine waste. This NAP is 

meant to represent the net long-term or total potential of a 

material to produce acid over an unspecified period of weathering. The NAP analyses are in table 2.

Effects of Weathering on Dump 

Surface Material

In this study, we collected surface samples at 10 waste 

sites. Factors that can influence the resulting analytical values 

are numerous. One factor is the surface inhomogeneity of the 

material sampled. We addressed that factor by collecting many 

subsamples from at least 30 cells across the surfaces of waste 

piles and mixing them into one composite sample. Another 

factor leading to variation is inhomogeneity on a vertical scale 

within a waste pile. The surface zone typically is composed 

of oxidized material that has been exposed to the environment 

for 50 years or more. The concentrations of deposit-related 

trace elements are usually lower in surface waste material 

than in material from deeper inside a pile due to accelerated weathering and leaching at the surface. Other concerns 

related to differential weathering of dumps include slope 

aspect (north-facing or south-facing) and top versus sides, but 

we did not address these particular distinctions in this study. 

Material from below the surface is less likely to be completely 

oxidized, and material from deep within a pile can contain

a large proportion of the original sulfide minerals. Hence, 

surface sampling is likely to produce a sample biased towards 

lower metal content, but one that represents the material that 

determines the chemical composition of surface runoff. Deep 

sampling would provide a sample that yields a higher metal 

content and that better represents the long-term potential for 

future metal release. However, deep sampling is both technically difficult and expensive. We collected a 6-ft long core 

from the thickest part of the Buckeye tailings, and through 

geochemical analyses, we show the distinction between surface sampling and depth sampling. The processes of element 

mobility and dispersion of metals represented by this core are 

discussed in Cannon and others (this volume).

Production records from Roby and others (1960) indicate 

that ore was last produced at the Buckeye mine in 1939. Rossillon and Haynes (1999) suggested that reprocessing of ores 

using flotation took place in the early 1940s, resulting in the 

waste we investigated from the flood plain near the Buckeye 

mine. Thus, the study of this core examines the results of a 

60-year experiment, showing the effect of annual saturation 

and weathering of mine wastes in a temperate environment. 

The 2-in. core provided an opportunity to examine the tailings chemistry vertically from the present surface to a depth 

of about 6 ft. Throughout most of the flood-plain area that is 

covered by waste, the tailings were thin (generally less than

2 ft thick) and oxidized. The 6-ft core encountered a layer of 

unoxidized sulfidic tailing about 20 in. thick at a depth of

3 ft (fig. 4). The sulfide zone was near the bottom of the tailings deposit, resting on stream-deposited sand and gravel in 

a buried wetland. Although some initial inhomogeneity may 

have existed in the deposition of these reprocessed tailings, 

they all were likely deposited as sulfidic material; the difference in chemistry between the oxidized and sulfidic tailings 

now likely reflects the relative mobility of metals as they were 

weathered and oxidized from the original sulfide minerals. We 

analyzed, by mixed-acid digestion and XRD, 26 subsamples 

from this core: 14 from the upper, oxidized zone, 8 from the 

sulfide zone, and 4 from the contaminated flood-plain sediment beneath the tailings. We distinguished the zones in 

the core by visual inspection, descriptions of the core intervals, and mineralogy of the subsamples. The oxidized zone 

contained no visible sulfides and no pyrite based on XRD 

(although traces of sphalerite were found by XRD of samples 

concentrated by panning). The sulfide tailings zone had visible 

sulfides, and pyrite was identified by XRD. Sample descriptions, mineralogy by XRD, and concentrations of selected 

elements in mixed-acid digestions are in table 1 of Cannon and 

others (this volume).

The analyses for silver, lead, copper, zinc, cadmium, and 

arsenic are summarized in the box plot in figure 5. The median 

values are instructive to demonstrate the relative mobilities of 

the elements. The median silver values for the oxidized and 

the sulfide tailings were nearly identical (67 ppm vs. 

70 ppm). This indicates that silver was not mobile in this 

surficial weathering environment. Lead shows a 33 percent 

decrease from the sulfide to the oxidized zone (15,000 ppm
Table 2. Site numbers, names, pH of passive leach, net acid production (NAP), sum of five trace elements (As+Cd+Cu+Pb+Zn) in both leaches; iron

specific conductance of EPA-1312 leach, and classification scores of wastes by Method 1 and Method 2.

Site 

Site No. and name

41 Enterprise mine

17 Buckeye mine

18 Bullion mine

15 B oulder Chief mine

142 Waldy mine

94 Morning Marie mine

29 Cracker mine

33 Daily West mine

119 Sirius mine

31 Crystal mine

pH, passive 

leach 

standard units

3.75

3.33 

3.25

2.94 

3.08 

3.74

3.62

3.92

3.90

6.78

3.23

6.60

3.65

3.46

2.75

3.33

5.93

4.76

3.84

NAP, 

Ib/ton

12

42 

10

34 

36 

8

8

6

6

0

12

4

6

26

68

16

0

2

8

Specific 

conductance, 

1312 leach 

|uS/cm

106

240 

210

597 

315 

230

107

60

61

119

333

202

96

185

1,090

240

87

60

78

Sulfate, 

1312 leach 

mg/L

16

44 

37

120 

130

85

21

8.8

7.9

15

67

55

18

47

280

55

31

24

29

Sum of 

metals, 

passive leach

100

2,500 

13,000

4,100 

6,000 

3,600

42

150

230

41

6,600

27

100

7,800

36,000

2,000

750

270

1,800

Sum of 

metals, 

1312 leach

330

11,000 

13,000

5,700 

7,100 

5,400

190

480

650

66

11,000

28

200

14,000

34,000

9,400

710

260

3,100

Dissolved 

iron, 

1312 leach

mg/L

190

1,700 

1,200

9,700 

5,400 

130

120

210

360

80

1,000

33

22

34

22,000

620

190

26

37

R

M

sc
(1) generalized core of 

study area tailings

Metal Leaching and Potential Environmental Effects of Mine Waste 147

(2) core from thickest section of 

Buckeye tailings

oxidized tailings

underlying contaminated flood-plain sediment

Figure 4. Generalized cross section of tailings sampled by cores at Buckeye flotation mill. Tailings consisted predominantly of oxidized waste material and were sampled as per core number 1. At thickest part of Buckeye flotation tailings, a 

sulfide layer remaining at depth was sampled as per core number 2. Copper, zinc, cadmium, and arsenic can migrate and 

are removed by annual flooding of the site during spring runoff (Cannon and others, this volume).

vs. 10,000 ppm). This means that some lead was lost from the 

oxidized tailings (Cannon and others, this volume). Note that 

anglesite (lead sulfate, a weathering product) was present in all 

of the oxidized tailing samples.

Copper, zinc, and cadmium all show dramatic differences 

between the sulfide and oxidized tailings zones. The median 

copper value for the sulfide tailings was 2,800 ppm, whereas it

was only 88 ppm in the oxidized tailings. The median copper value from a premining baseline core taken at site 7B 

from the meadow south of Basin Creek was 29 ppm (Church, 

Unruh, and others, this volume, table 3); the oxidized tailings zone in our core contained barely three times the copper 

concentration over the local background. These results show 

that the majority of copper originally present in the tailings

z iuu,uuu 

o

_l

^

oc i n nnn

CO

oc

z 1,000

z~ 

o

^_

o? 100 hz

z 

o

0 10 hz

^

LJJ

UJ ,

: T ifinnn

* ' ~i— -i—

mnnn ..f* 1 ;; 15,000 _ ^^RJ r iu,uuu —— «=- fa,,, . j ^ i^ H

: -1- E^A:*I /,boU g gijQ

9 RDD : ;g;a?t'"' -i- / Z,OUU r j -r .

> .Sp ,., ; - —— 1 —— •-,

' •' •'' 7/10 1

-L. r4

-\ — "*~ i 1 I pp

. | ^J"T |'I:S:*:| Bggg| Ij4

67 1 70 ^ ^P 

1 T/

CH Oxidized tailings

U Sulfide tailings

Ag Pb Cu Zn Cd As

Figure 5. Box plots of silver, lead, copper, zinc, cadmium, and arsenic concentrations in tailings core from 

Buckeye mine site. Upper bar represents 90th percentile of population; upper line of box represents 75th 

percentile; middle line represents 50th percentile (median); lower line represents 25th percentile; lower bar 

represents 10th percentile. Numbers by the boxes are median values Plot shows that silver is essentially 

immobile, lead is slightly mobile, and that copper, zinc, cadmium, and arsenic can be mobilized by near-surface weathering processes.
148 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

was leached from the oxidized zone. The median values for 

zinc were 7,650 ppm and 740 ppm, respectively. The zinc 

concentration in the oxidized tailings was only 10 percent of 

the concentration in the sulfide tailings, so we conclude that 

zinc, like copper, was weathered out of and dispersed from the 

upper tailings. The local background concentration for zinc, 

also taken from the core at site 7B, was 190 ppm. Cadmium is 

geochemically similar to zinc and showed a similar response. 

The median value for cadmium in the sulfide tailings was 

54 ppm, whereas in the oxidized tailing it was 4 ppm. Similar to zinc, the cadmium concentration in the oxide tailings 

zone was about 10 percent the concentration contained in the 

sulfide tailings zone. It is important to note that the traceelement concentrations in the sulfide tailings zone probably 

do not represent the original concentrations, as some losses 

from weathering may have occurred in the sulfide tailings 

zone as well. For example, anglesite (lead sulfate, a weathering product) was also present in most of the sulfide tailings 

subsamples, indicating that weathering processes were active 

in the subsurface sulfide tailings zone.

Arsenic concentrations in the oxidized zone were highly 

variable, but the median value was lower than in the sulfide 

zone. The median values were 6,350 and 16,000 ppm, respectively. The lowest concentration of arsenic in the oxidized 

tailings was only 500 ppm. Concentrations of arsenic in the 

contaminated flood-plain sediment below the sulfide tailings 

were relatively high (about 2,000 ppm). Together, these observations suggest that much but not all of the arsenic had been 

leached from the oxidized tailings, that arsenic was somewhat 

mobile in the sulfidic tailings, and that some of the mobilized 

arsenic accumulated in the flood-plain sediment.

These geochemical results demonstrate two important 

issues. First, surface material on mine-waste piles has undergone weathering by surface processes. Second, collection 

of surface samples leads to analyses that underestimate the 

deposit-related metals in the mine-waste dumps (except silver, 

which appears to be chemically immobile).

Classification Schemes for 

Mine-Waste Piles

One of the objectives of collecting and studying mine 

waste from the study area was to develop and apply a classification method, based on chemical and physical parameters, 

to help land managers prioritize mine-waste sites in terms of 

removal or remediation. Values for total-metal content, watersoluble metals, mineralogy, net acid production, pH of leach 

solutions, and size all are important in describing a particular 

material's tendency to affect water that it contacts. Over the 

course of the study, we developed two methods to classify 

mine-waste piles in the Boulder River watershed study area.

The first method (Method 1) was described in Desborough and Fey (1997) and utilized the pH of the passive leach 

solutions, the sum of dissolved deposit-related elements (ZDE)

(£As+Cd+Cu+Pb+Zn in ug/L) in the passive leach solutions, 

and the estimated size (in tons) of the waste dump. Four 

classes were defined for the acidity component: for pH > 6.0, 

class 0; for pH between 4.5 and 6.0, class 1; for pH between 

3.5 and 4.5, class 2; and for pH <3.5, class 3. Similarly, for 

the sum of dissolved elements, four classes were defined: for 

£DE <500 ug/L, class 0; for ZDE between 500 and < 1,000 

ug/L, class 1; for ZDE between 1,000 and 5,000 ug/L, class 

2; and for £DE >5,000 ug/L, class 3. The size factor has three 

classes: for size <500 tons, class 1; for size between 500 and 

2,500 tons, class 2; and for size >2,500 tons, class 3. These 

size classes were defined for this study; other watersheds may 

have waste piles with far greater ranges in size. The sum of the 

class numbers for each parameter (pH, SDE, size) gives a classification number between 1 (low potential for water-quality 

degradation) and 9 (high potential). The classification numbers 

based on Method 1 for the waste piles are listed in table 2.

A second ranking method (Method 2) has been developed that considers the effects of (1) the net acid production 

(NAP), (2) the sum of dissolved deposit-related elements (also 

£As+Cd+Cu+Pb+Zn) in the leach solution following the EPA1312 leach method, (3) the concentration of dissolved iron in 

the EPA-1312 solution, and (4) estimated size. This ranking method was described in Fey, Desborough, and Church 

(2000). The approach is similar to Method 1, which utilized 

element concentration data from the passive leach. The difference is that Method 2 does not consider the pH of the passive 

leach solution (a short-term snapshot of hydrogen ion activity 

mostly resulting from the dissolution of water-soluble salts) as 

the "acidity parameter," but rather utilizes the total long-term 

net acid production (NAP), as determined by the hydrogenperoxide oxidation of sulfides in the sample.

There are two chemical components to Method 2: a plot 

of SDE from the EPA-1312 leach solutions against the NAP, 

and a plot of dissolved iron from the EPA-1312 leach solutions 

against the NAP. A plot of the NAP, expressed as Ib CaCO3 

per ton, versus the SDE from the EPA-1312 leach solutions 

was developed from data for about 110 mine-waste samples 

collected from the Animas River study area in Colorado, and 

the Boulder River watershed study area (Fey, Desborough, 

and Church, 2000). Only the samples from the Boulder River 

study area are shown here (fig. 6). We delineated four classes 

of samples: Group 1, which has low NAP (<20 Ib CaCO3/ton) 

and < 1,000 ug/L ZDE; Group 2, which has low NAP and 

moderate SDE (between 1,000 and 5,000 ug/L); Group 3, 

which has low NAP and high IDE (>5,000 ug/L); and Group 

4, which has high NAP (>20 Ib CaCO3 /ton) and high 2DE 

(>5,000 ug/L). No samples plotted in the lower right-hand area 

in the diagram of high NAP and low SDE.

The second chemical indicator considered in Method 2 

was the dissolved iron content of the EPA-1312 leach solutions. Iron is an important constituent in the mine wastes and 

the leach solutions because considerable amounts of pyrite 

(or its oxyhydroxide weathering products) are found in many 

mine wastes. Fey, Desborough, and Church (2000) showed 

that samples from the Boulder River watershed study area can
Metal Leaching and Potential Environmental Effects of Mine Waste 149

contain as much as 0.05 percent of their iron in water-soluble 

form. Dissolved iron in water results in well-defined acute and 

chronic toxicity, regardless of alkalinity (Colorado Department 

of Health, 1984). Therefore, we added dissolved iron as one of 

parameters in the ranking criteria. Because the dissolved iron 

concentration of a leachate can overwhelm the signal from 

the EDE, we plot it on a separate figure (fig. 7). We classified 

the data points into three groups: Group 1, having NAP less 

than 20 Ib CaCO3 /ton and dissolved iron less than 1,000 [ag/L; 

Group 2, having NAP less than 20 Ib CaCO3/ton and dissolved 

iron greater than 1,000 [ag/L; and Group 3, having NAP 

greater than 20 Ib CaCO3/ton and dissolved iron greater than 

1,000 [ag/L. Figure 7 shows these classes. Only one out of 

twenty-one samples plotted in the lower right hand portion of 

the diagram, representing the unusual condition of relatively 

high acidity and a low dissolved iron concentration. This 

sample was from the Cracker waste pile.

The size classes were the same as for Method 1: for size 

<500 tons, class 1; for size between 500 and 2,500 tons, class 

2; and for size >2,500 tons, class 3. Figures 6 and 7 combine 

to show that if the NAP is above 20 Ib CaC(X/ton, the mine

waste is likely to produce high concentrations of dissolved 

trace elements in leach solutions.

Method 2 sums the class numbers for the sum of dissolved metals and NAP (four classes), dissolved iron and NAP 

(three classes), and the size (three classes). The sum of these 

three criteria then yields an estimate of a mine-waste pile's 

potential to adversely affect water quality, with a rank of 3 

indicating little potential and a rank of 10 indicating the highest potential. The classification numbers based on Method 2 

for the waste piles are listed in table 2.

Classification of Mine-Waste Piles in 

the Boulder River Watershed

We apply here both classification schemes to the bulk 

surface samples that we collected from mine sites in the Boulder River watershed study area (fig. 8). The sample sites are 

depicted with symbols of three different colors, representing 

the relative potential for the materials to affect water quality.

1,000,000

g= 100,000

Q_ 

CO

DC 

CD 

O 

DC 

CJ

_Q 

Q_

CJ

-o+

CJ

+

CO

10,000

1,000

100

10

GroupS

Group 2

Group 1

Group 4

20 200 

NET ACID PRODUCTION, IN POUNDS CaCOo PER TON

2,000

Figure 6. Net acid production (NAP) of waste samples versus the sum of dissolved concentrations of As+Cd+Cu+Pb+Zn from 

EPA-1312 leach solutions. NAP is a measure of long-term acid producing potential of waste material. Samples with NAP greater than 

20 Ib/ ton CaC03 equivalent generally have the sum of metals greater than 5,000 ug/L for mine wastes from the type of polymetallic 

vein deposit in the Boulder River watershed.
150 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Q_ 

CO

<

or

CD

o 

or 

o

1,000,000

100,000

^ 10,000

o

<

CM 

CO

O 

QC

O 

LJJ

O 

CO 

CO

1,000

100

10

Group 2

Group 1

GroupS

20 

NET ACID PRODUCTION,

200 

POUNDS CaC03 PER TON

2,000

Figure 7. Net acid production (NAP) of waste samples versus dissolved iron from EPA-1312 leach solutions. Samples with 

NAP greater than 20 Ib/ton CaC03 equivalent generally have dissolved iron greater than 1,000 ug/L for wastes from the type of 

polymetallic vein deposit in the Boulder River watershed.

In this illustration, the size of the waste pile has been incorporated into the color of symbol used.

The classification results reveal that the Buckeye minewaste pile had the highest potential for affecting the nearby 

environment. With Method 1 this pile scored 8 on a scale of 

1 to 9. On the basis of Method 2 the Buckeye mine-waste pile 

scored 10 on a scale of 3 to 10. Flotation tailings from the 

reprocessed gravity tailings of the Buckeye mine, deposited 

on the north side of Basin Creek, also presented a significant 

problem. These tailings scored 9/9 and 8/10, respectively, on 

the basis of Method 1 and Method 2. The waste pile at the 

Enterprise mine, near the Buckeye mine/mill complex, scored 

a moderate 5/9 and 5/10.

At the Bullion mine, there were three large waste piles, 

termed the upper, middle, and lower waste sites. The upper 

and middle waste piles scored high. On the basis of Method 

1, they scored 8/9 and 9/9; using Method 2, both scored high, 

10/10. The lower waste pile of the Bullion mine complex 

was the largest, and also scored high. Its classification scores 

were 7/9 and 8/10. During a rainfall event on August 2, 1999, 

overland flow was observed at the Bullion mine site. After 

an initial decrease, dissolved zinc concentrations increased 

by about three fold in the Bullion Mine tributary, presumably 

from the dissolution of easily soluble zinc salts (Lambing and 

others, this volume, Chapter D7). This observation confirms

that mine-waste piles can have a direct, short-term effect on 

water quality in receiving streams.

In addition to the three large waste piles, two former 

tailings impoundments were farther downstream along Bullion Mine tributary. These tailings were different from the 

unmilled mine wastes in the three large dumps; the difference 

is reflected in the classification scores. The tailings had been 

leached of much of their original metal content (table 2), and 

so their classification scores were moderate. The upper tailings impoundment scored 4/9 and 4/10, and the lower tailings 

impoundment scored 5/9 and 5/10. A small (500 ton) dump 

near the two former tailings impoundments had classification 

scores of 4/9 and 3/10.

Along Uncle Sam Gulch, waste from ore bins upstream 

from the adit at the Crystal mine scored moderately high (6/9 

and 6/10). Material collected from the large exploration cut in 

the hilltop above the mine had very low acidity and low leachable metals. The scores for this surface material were 6/9 and 

6/10 (east side) and 5/9 and 5/10 (west side). After a rainfall 

event on August 4-5, 1999, zinc concentrations in Uncle Sam 

Gulch increased by a factor of about 1.8 (Lambing and others, 

this volume).

The Sirius mine had low acidity, moderately high 

summed metal content, and low dissolved iron. Its scores were 

8/9 and 7/10. The Cracker mine dump was close to Cataract
Metal Leaching and Potential Environmental Effects of Mine Waste 151

112°22'30" 1120 15'

BEAVERHEAD-DEER 

NATIONAL FOREST

Boulder River 

watershed study area

\

T8N

T7N

T6N

EXPLANATION 

High potential for water-quality degradation

Intermediate potential for water-quality degradation 

Low potential for water-quality degradation

R5W

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

2 KILO METERS

Figure 8. Boulder River watershed study area with mine-waste piles ranked by water-quality degradation potential. Green sites, low 

potential; blue sites, intermediate potential; red sites, highest potential for water quality degradation. This ranking using chemical data 

and size does not incorporate nonquantified data such as presence of draining adits, surface water in contact with dumps, or distance 

to streams. Sites numbered as in Martin, this volume.
152 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Creek, contained moderately large tonnage (4,000 tons), and had 

low dissolved iron but high summed dissolved trace elements. 

The classification scores were 9/9 and 8/10. The Daily West 

dump, despite its small size, has the most available soluble acid 

and metals of any of the wastes studied in this report. In addition, 

the waste pile is located in the flood plain of Basin Creek. The 

classification scores were high (7/9 and 8/10) but would have 

been higher if the dump were larger.

The waste from below the adit of the Boulder Chief mine 

was classified high, with scores of 9/9 and 8/10. This site was 

situated more than l/2 mi from the nearest first-order tributary, and 

Cataract Creek was more than I mi away. However, the metalloading study for Cataract Creek detected input from the Boulder 

Chief mine (Kimball and others, this volume, Chapter D6).

The waste piles from both the Morning Marie (Cataract 

Creek) and Waldy (Big Limber Gulch) mines were small, and 

had low acidity, low dissolved summed metals, and low dissolved 

iron. The scores from the two classification methods were 4/9 and 

4/10 for the Morning Marie waste pile and 2/9 and 4/10 for the 

Waldy waste pile.

An important factor not included in this numerical ranking 

model is the proximity to a stream of a particular waste dump. 

Assigning a numerical value to this factor is difficult, as several 

aspects may influence the severity of the impact from waste 

material. Water draining from an adit and over a waste pile, or 

surface water flowing over or through the waste and directly into 

a nearby creek constitutes a direct flow path for impact of that 

waste pile on stream water. This should be a primary, non-numerical factor to be considered in ranking waste dumps for removal. 

Proximity to a stream or body of water is also important, as storm 

or snowmelt runoff can easily transport acid and dissolved metals 

or metal-sorbing colloidal materials directly to surface water. 

In two studies of waste-material impact on surface water in the 

Animas River, Colo., watershed, Nash (1999a, 1999b) emphasized the importance of field observations of these kinds of flow 

paths. Knowledge of local ground water, the influence of fracture 

control on ground-water flow, and waste permeability is also 

important.

Summary and Conclusions

Metal-mining waste was collected by bulk surface sampling 

at 10 sites in the Boulder River watershed study area. Mineralogical analyses revealed that 80 percent of the samples contained 

anglesite and jarosite. Primary sulfide minerals were rare: only 

trace amounts of sphalerite and no arsenopyrite, although these 

minerals had been reported as abundant by early reports. The 

minerals goslarite (a zinc sulfate) and scorodite (iron arsenate) 

were found in the field. Mineralogical and whole-sample analyses 

of core samples from the thickest part of the flotation tailings 

at the Buckeye site demonstrated the relative mobilities of six 

deposit-related elements over a 60+ year period of annual weathering cycles. Silver is essentially chemically immobile, lead is

nearly immobile, and copper, zinc, cadmium, and arsenic 

can be mobilized in the surface weathering environment.

Two classification methods for mine-waste piles were 

developed. These schemes were based on geochemical data 

derived from two leach methods and waste-pile size. The 

geochemical parameters were pH and soluble metal content 

(As+Cd+Cu+Pb+Zn) from a passive leach, and NAP, 

soluble metal and soluble iron content from an EPA-1312 

leach. Applying these methods to the Boulder River watershed study area reveals that waste piles from the Buckeye 

mine/mill, the Bullion mine/mill, the Daily West mine, the 

Cracker mine, and the Boulder Chief mine had high potential for environmental degradation. Wastes from the Crystal 

mine and the Sirius mine had an intermediate potential, and 

wastes from the Morning Marie and the Waldy mines had 

low potential for environmental degradation.

References Cited

Billingsley, P., and Grimes, J.A., 1918, Ore deposits of the 

Boulder batholith: American Institute of Mining and 

Metallurgical Engineers Transactions, v. 58, p. 284-361.

Briggs, P.H., 1996, Forty elements by inductively coupledplasma atomic emission spectrometry, in Arbogast, 

B.F., ed., Analytical methods manual for the Mineral 

Resources Program: U.S. Geological Survey Open-File 

Report 96-525, p. 77-94.

Briggs, PH., and Fey, D.L., 1996, Twenty-four elements 

in natural and acid mine waters by inductively coupled 

plasma-atomic emission spectrometry, in Arbogast, B.F., 

ed., Analytical methods manual for the Mineral Resource 

Surveys Program, U.S. Geological Survey: U.S. Geological Survey Open-File Report 96-525, p. 95-101.

Colorado Department of Health, 1984, Basic standards and 

methodologies: 3.1.0 (5CCR 1002.8).

Crock, J.G., Lichte, F.E., and Briggs, P.H., 1983, Determination of elements in National Bureau of Standards 

geologic reference materials SRM 278 obsidian and 

SRM 688 basalt by inductively coupled plasma-atomic 

emission spectroscopy: Geostandards Newsletter, v. 7, 

p. 335-340.

Desborough, G.A., and Fey, D.L., 1997, Preliminary 

characterization of acid-generating potential and toxic 

metal solubility of some abandoned metal-mining related 

wastes in the Boulder River headwaters, northern Jefferson County, Montana: U.S. Geological Survey Open-File 

Report 97^78, 21 p.
Metal Leaching and Potential Environmental Effects of Mine Waste 153

Fey, D.L., Desborough, G.A., and Church, S.E., 2000,

Comparison of two leach procedures applied to metal-mining related wastes in Colorado and Montana and a relative 

ranking method for mine wastes, in ICARD 2000; Proceedings of the Fifth International Conference on Acid Rock 

Drainage, Volume 2: Society for Mining, Metallurgy, and 

Exploration, Inc., p. 1477-1487.

Fey, D.L., Desborough, G.A., and Finney, C.J., 2000,

Analytical results for total-digestions, EPA-1312 leach, and 

net acid production for twenty-three abandoned metal-mining related wastes in the Boulder River watershed, Northern 

Jefferson County, Montana: U.S. Geological Survey OpenFile Report 00-114, 17 p.

Fey, D.L., Unruh, D.M., and Church, S.E., 1999, Chemical 

data and lead isotopic compositions in stream-sediment 

samples from the Boulder River watershed, Jefferson 

County, Montana: U. S. Geological Survey Open-File 

Report 99-575, 147 p.

Lapakko, K., and Lawrence, L.W., 1993, Modification of the 

net acid production (NAP) test, in Proceedings of the 

Seventeenth Annual British Columbia Mine Reclamation 

Symposium, Port Hardy, British Columbia, May 4-7, 1993: 

p. 145-159.

Marvin, R.K., Metesh, J.J., Bowler, T.P., Lonn, J.D., Watson, 

J.E., Madison, J.P., and Hargrave, P.A., 1997, Abandonedinactive mines program, U.S. Bureau of Land Management: 

Montana Bureau of Mines and Geology Open-File Report 

348, 506 p.

Metesh, J.J., Lonn, J.D., Duaime, T.E., and Wintergerst, Robert, 1994, Abandoned-inactive mines program, Deerlodge 

National Forest—Volume I, Basin Creek drainage: Montana 

Bureau of Mines and Geology Open-File Report 321, 131 p.

Metesh, J.J., Lonn, J.D., Duaime, T.E., Marvin, R.K., and 

Wintergerst, Robert, 1995, Abandoned-inactive mines 

program, Deerlodge National Forest—Volume II, Cataract 

Creek drainage: Montana Bureau of Mines and Geology 

Open-File Report 344, 201 p.

Nash, J.T., 1999a, Geochemical investigations and interim 

recommendations for priority abandoned mine sites on 

USDA Forest Service lands, Mineral Creek watershed, San 

Juan County, Colorado: U.S. Geological Survey Open-File 

Report 99-170, 40 p.

Nash, J.T., 1999b, Geochemical investigations and interim 

recommendations for priority abandoned mine sites, BLM 

lands, Upper Animas River watershed, San Juan County, 

Colorado: U.S. Geological Survey Open-File Report 

99-323, 45 p.

Roby, R.N., Ackerman, W.C., Fulkerson, F.B., and Crowley, 

FA., 1960, Mines and mineral deposits (except fuels), 

Jefferson County, Montana: Montana Bureau of Mines and 

Geology Bulletin 16, 122 p.

Rossillon, M., and Haynes, T., 1999, Basin Creek Mine Reclamation Heritage Resource Inventory 1998, Volume I: Butte, 

Mont., Renewable Technologies, Inc., 126 p. [Submitted to 

Beaverhead-Deerlodge National Forest, Dillon, Montana.]

Scott, K.M., 1987, Solid solution in, and classification of, gossan-derived members of the alunite-jarosite family, northwest Queensland, Australia: American Mineralogist, v. 72, 

p. 178-187.

Smith, K.S., Ramsey, C.A., and Hageman, PL., 2000, Sampling strategy for the rapid screening of mine-waste dumps 

on abandoned mine lands, in ICARD 2000; Proceedings of 

the Fifth International Conference on Acid Rock Drainage, 

Volume 2: Society for Mining, Metallurgy, and Exploration, Inc., p. 1456-1462.

U.S. Environmental Protection Agency (USEPA), 1986, 

Test methods for evaluating solid waste, Volumes I and II 

(SW-846) Third Edition, November, Updates are available 

through Revision 2B, published April 4, 1995.

Trace Elements in Water in Streams 

Affected by Historical Mining

By David A. Nimick and Thomas E. Cleasby

Chapter D5 of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-D5

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract...................................................................................................................................................... 159

Introduction............................................................................................................................................... 159

Purpose and Scope......................................................................................................................... 159

Previous Investigations.................................................................................................................. 161

Data Collection................................................................................................................................. 161

General Water Chemistry............................................................................................................... 162

Water-Quality Standards................................................................................................................ 163

Trace Elements in Water......................................................................................................................... 164

Ribbon Maps..................................................................................................................................... 164

pH...........................................^

Trace-Element Partitioning............................................................................................................. 165

Relation of Streamflow and Concentration................................................................................. 168

Trace-Element Concentrations...................................................................................................... 170

Zinc........................................................................................................................................... 171

Cadmium................................................................................................................................... 174

Copper...................................................................................................................................... 174

Lead.......................................................................................................................................... 180

Arsenic..................................................................................................................................... 180

Aluminum................................................................................................................................. 180

Concentration Trends During 1996-2000...................................................................................... 184

Sources of Trace Elements..................................................................................................................... 184

Mining-Related Sources................................................................................................................. 184

Premining Background Sources................................................................................................... 186

Trace-Element Loading to the Boulder River.............................................................................. 186

Summary.................................................................................................................................................... 189

References Cited...................................................................................................................................... 189

Figures

1. Map showing water-quality sites and selected inactive mines in Boulder River

watershed study area, Montana........................................................................................... 160

2. Photograph showing flood-plain tailings eroding at Jack Creek during snowmelt

runoff upstream from site 19, May 1997............................................................................... 162

3. Map showing approximate values of pH during low-streamflow conditions, 

1991-2000...............................................^

4. Photograph showing acidic water in Bullion Mine tributary, August 1998.................... 167

5. Photograph showing Cataract Creek at Basin during high-streamflow conditions, 

June 1997, and low-streamflow conditions, October 1996............................................... 168

6. Graphs showing relation of Streamflow to dissolved trace-element concentrations 

at five sites, 1996-2000............................................................................................................ 169

7. Graphs showing relation of Streamflow to dissolved and total-recoverable

trace-element concentrations in Cataract Creek, 1996-2000.......................................... 171
8. Photograph showing Crystal mine, June 1997.................................................................... 172

9. Photograph showing Bullion mine, June 1997.................................................................... 172

10-18. Maps showing approximate concentrations of:

10. Dissolved zinc during low-streamflow conditions (July-March), 

1991-2000.................................................^

11. Total-recoverable zinc during high-streamflow conditions (April-June), 

1996-2000........................,.........................^

12. Dissolved cadmium during low-streamflow conditions (July-March),

1991-2000........................................................................................................................... 176

13. Total-recoverable cadmium during high-streamflow conditions (April-June), 

1996-2000..,...........,...................................^

14. Dissolved copper during low-streamflow conditions (July-March),

1991-2000........................................................................................................................... 178

15. Total-recoverable copper during high-streamflow conditions (April-June),

1996-2000........................................................................................................................... 179

16. Total-recoverable lead during high-streamflow conditions (April-June), 

1996-20M....................................................»

17. Dissolved arsenic during low-streamflow conditions (July-March),

199&-2000........................................................................................................................... 18

18. Total-recoverable arsenic during high-streamflow conditions (April-June),

1996-2000........................................................................................................................... 183

19. Graphs showing temporal profiles of dissolved zinc concentration and

streamflow at five sites, 1996-2000...................................................................................... 185

20. Hydrograph for Boulder River at Boulder and sampling dates for

water-quality data used for analysis of trace-element loading at five sites,

water year 1997........................................................................................................................ 187

21. Photograph showing Boulder River below Little Galena Gulch during

spring runoff, June 1997......................................................................................................... 188

Tables

1. Aquatic-life standards for selected trace elements in the Boulder River

watershed................................................................................................................................. 163

2. Results of linear regression and Kendall's correlation for trend tests of

dissolved zinc concentration for five sites in the Boulder River watershed................. 186

3. Estimated annual streamflow and annual loads of dissolved trace elements

for five sites in the Boulder River watershed, water year 1997....................................... 188

Chapter 05

Trace Elements in Water in Streams Affected by

Historical Mining

By David A. Nimick and Thomas E. Cleasby

Abstract

Investigation of trace elements in water of the Boulder 

River watershed provided information to (1) delineate stream 

reaches having elevated concentrations of trace elements, 

(2) determine sources of the trace elements, (3) understand 

the transport of dissolved and paniculate forms of trace elements, (4) evaluate the potential for trace-element toxicity to 

biota, and (5) establish a long-term water-quality monitoring 

plan. Water-quality data collected in and near the watershed 

during 1996-2000, as well as historical data, were used for the 

assessment.

Concentrations of trace elements associated with ore 

deposits in the watershed varied greatly, with the highest 

concentrations occurring in small streams downstream from a 

few inactive mines. Cadmium, copper, lead, and zinc concentrations in streams affected by historical mining commonly 

were higher than aquatic-life standards. Concentrations 

exceeded acute aquatic-life standards by as much as 200-fold. 

Few stream reaches had acidic pH (less than 6.5). Of all of 

the inactive mines in the watershed, the Bullion, Crystal, and 

Comet mine sites produced most of the trace-element load 

to the watershed and had the largest effect on trace-element 

concentrations in streams. Cataract Creek, which drains the 

Crystal mine, contributed larger dissolved trace-element loads 

to the Boulder River than either Basin or High Ore Creeks, 

which drain the Bullion and Comet mines, respectively.

Introduction

More than 140 inactive mines and 15 mills are scattered 

throughout the Basin, Cataract, and High Ore Creek basins in 

the Boulder River watershed study area (fig. 1), but knowledge about the individual or cumulative effects of these sites 

on streams in the watershed is limited. Water is the main 

transport mechanism for trace elements derived from historical 

hard-rock mining areas and serves as the habitat for aquatic 

organisms that may be exposed to potentially toxic concentrations. Therefore, assessing the distribution, magnitude, and

sources of trace elements in water is an integral component of 

any study of the environmental effects on aquatic ecosystems 

in watersheds that contain inactive mines. Understanding 

the distribution and magnitude of trace elements in streams 

throughout an affected watershed is important for prioritizing remediation activities and establishing restoration goals. 

Characterization of trace-element sources and pathways is 

essential for planning effective and cost-efficient remediation. 

Integrating water-quality data with streambed-sediment data 

and biological measures of aquatic health then allows assessment of the vulnerability of aquatic ecosystems to the effects 

of historical mining in the study area.

Purpose and Scope

This report assesses the concentrations, sources, and 

loads of mining-related trace elements in streams draining 

historical mining areas in the Boulder River watershed near 

the town of Basin in southwestern Montana. Trace elements 

of particular interest were those which are associated with the 

ore deposits in the watershed and which can pose a toxic risk 

to aquatic life. Trace-element concentrations and associated 

physical and chemical data were determined for water samples 

from 64 sites during 1996-2000. These data are presented in 

the database (Rich and others, this volume, Chapter G and 

accompanying CD-ROM). In addition, we utilized waterquality data presented by Kimball and others (this volume, 

Chapter D6) and historical water-quality data (Nimick and 

Cleasby, 2000, table 4).

To help us characterize environmental conditions in 

streams of the Boulder River watershed, we set goals of 

determining the seasonal and spatial distribution of traceelement concentrations in surface water throughout the 

watershed, and then identifying the significant mining- and 

nonmining-related source(s) of those trace elements. Source 

areas were determined from concentration gradients showing 

downstream changes in trace-element concentrations in water 

and from trace-element loads revealing areas where major 

increases occurred in the mass of elements transported. We 

distinguished mining- and nonmining-related sources of trace
160 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112°22'30"

EXPLANATION

Water-quality site and number

V U.S. Geological Survey

Base from U.S. Geological Survey 

Digital line graphs, 1:100,000

62 Z KILOMETERS

25M

• Montana Bureau of Mines and Geology 

name CRYSTAL <

Figure 1. Water-quality sites and selected inactive mines in Boulder River watershed study area, Montana.
Trace Elements in Stream Water 161

elements in mineralized watersheds by comparing water-quality data to the location of mined areas and geologic units.

The water-sampling program conducted during this study 

had four objectives. The first objective was to determine what 

mining-related trace elements occurred at concentrations that 

were potentially toxic *o aquatic organisms. To accomplish 

this objective, we analyzed samples from selected sites during 

the early part of the study for a large suite of trace elements. 

The second objective was to characterize the range of concentrations of the potentially toxic trace elements throughout 

the watershed both spatially and seasonally. To accomplish 

this objective, samples were collected once during high-flow 

conditions and once during low-flow conditions at many sites 

throughout the watershed. To efficiently evaluate many sites 

in the watershed, samples from some sites were analyzed only 

for total-recoverable zinc, because zinc is associated with the 

watershed's ore deposits and occurs more frequently in detectable concentrations in surface water than the other depositrelated trace elements. The third objective was to characterize 

trace-element loads at five key sites in the watershed during a 

complete hydrologic cycle. For this objective, samples were 

collected 13 times during 1996-97 over a wide range of flow 

conditions. The fourth objective was to establish a waterquality monitoring program to determine long-term seasonal 

and annual variations near areas where remediation activities had been planned by State and Federal agencies. This 

last part of the water-sampling program was initiated in 

1997 before any remediation started, so that pre-remediation 

conditions could be documented. Sampling at five key sites 

in the watershed continued during 1998-2000 but at a lower 

frequency than in 1997. Long-term monitoring sites also were 

established downstream from the Bullion, Crystal, Comet, and 

Buckeye mines as well as the reach of Cataract Creek between 

Uncle Sam Gulch and Hoodoo Creek. Results for this fourth 

objective are reported in this chapter for the five key sites as 

well as for the Comet mine by Gelinas and Tupling (this volume, Chapter E2) and for the Buckeye and Enterprise mines 

by Cannon and others (this volume, Chapter El).

Trace elements of particular concern for this study were 

those typically associated with polymetallic veins (Becraft 

and others, 1963; Ruppel, 1963), which were the primary 

rocks mined in the watershed. These trace elements include 

antimony, arsenic, cadmium, copper, gold, iron, lead, silver, 

and zinc. In contrast, trace elements that are not associated 

with polymetallic vein systems are called rock-forming trace 

elements and include chromium, strontium, vanadium, and the 

rare-earth elements.

Previous Investigations

The first systematic assessment of the effects of historical 

mining on water quality in the Boulder River watershed took 

place in the 1970s (summarized by Ken Knudson, consulting 

biologist, Helena, Mont., written commun., 1984). Results 

showed that trace-element concentrations were higher in High

Ore Creek than in Basin or Cataract Creeks. No streamflow 

data were collected and therefore loads could not be calculated. In 1985, Phillips and Hill (1986) sampled 14 sites 

during spring runoff. Results indicated that, although concentrations were high in High Ore Creek (as noted by Knudson, 

written commun., 1984), the load of trace elements contributed by Cataract Creek to the Boulder River was greater than 

the load from High Ore Creek because of the much larger 

streamflow in Cataract Creek. The Montana Bureau of Mines 

and Geology collected water-quality samples from numerous sites throughout the watershed as part of the inventories 

of inactive mines completed in the mid-1990s for the USD A 

Forest Service (Metesh and others, 1994, 1995, 1996) and 

Bureau of Land Management (Marvin and others, 1997). Data 

from these mine-inventory reports were useful for characterizing the range and distribution of trace-element concentrations 

throughout the watershed because many sites were sampled.

Data Collection

Water-quality samples for this study were collected from 

64 sites (fig. 1) between October 1996 and October 2000. 

Water-quality sites were located throughout the study area on 

both small and large streams and at locations upstream and 

downstream from selected inactive mines. We also collected 

samples at three sites on the Boulder River (sites 59, 61, and 

62) downstream from the study area to determine the extent of 

trace-element enrichment from the Basin and Boulder mining 

districts.

Reference sites were selected in drainages that had a 

geologic setting similar to that of the study area except without 

mineralized rocks. We sampled these sites to establish a reference for water-quality comparison with mineralized areas. No 

sites were available in unmined, mineralized zones to indicate 

natural background conditions in the study area. Reference 

sites (fig. 1) included the Boulder River upstream from the 

Boulder River watershed study area (site 1), Red Rock Creek 

(site 2), and the Little Boulder River (site 60).

The area upstream from site 1 is underlain by Late 

Cretaceous plutonic rocks of the Boulder batholith as well as 

the Late Cretaceous Elkhorn Mountains Volcanics and Eocene 

Lowland Creek Volcanics (Wallace, 1987). Little historical 

mining took place in this area of the Boulder River watershed 

(Elliott and others, 1992). The areas upstream from 

site 2 (Red Rock Creek) and site 60 (Little Boulder River) are 

underlain by Late Cretaceous plutonic rocks of the Boulder 

batholith and the Elkhorn Mountains Volcanics (Wallace, 

1987). Elliott and others (1992) did not indicate any historical mines or prospects in these two areas, but small producing 

historical mines did exist in the Little Boulder River basin 

upstream from the sampling site. However, with the exception 

of one placer mine, these mines and prospects are not close to 

the Little Boulder River.

Methods of data collection and analysis, as well as 

quality-assurance data, are in Nimick and Cleasby (2000).
162 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

The types of data collected included streamflow, field measurements of physical and chemical properties, suspendedsediment concentration, and analytical results for major ions, 

nutrients, and dissolved and total-recoverable trace elements. 

Streamflow was measured according to methods described 

by Rantz and others (1982). Water samples typically were 

collected from multiple verticals across the stream using 

depth- and width-integration methods. These methods provide 

a vertically and laterally discharge-weighted sample that is 

representative of the entire flow through the cross section of 

a stream. Grab samples were collected when streamflow was 

too low to allow use of a depth-integrating sampler. Sampling 

equipment consisted of standard USGS depth-integrating 

suspended-sediment samplers (models DH-81, DH-48, and 

D-74TM), which are either constructed of plastic or coated 

with a nonmetallic epoxy paint; both types are equipped with 

interchangeable nylon nozzles for sampling a wide range of 

stream depths and velocities.

General Water Chemistry

Without elevated trace-element concentrations, the 

water in almost all streams in the Boulder River watershed 

study area generally is not toxic to aquatic organisms and 

water quality would be considered good. Concentrations of 

dissolved solids were low (generally less than 120 mg/L), 

presumably because the granitic and volcanic rocks in the 

watershed weather relatively slowly, producing few solutes, 

and because ground water has a relatively short residence time 

in the local flow paths in the bedrock (McDougal and others, 

this volume, Chapter D9). Dissolved solids concentrations 

were higher, ranging as high as 273 mg/L, in streams such as 

Bullion Mine tributary, Uncle Sam Gulch, and High Ore Creek 

where mine-drainage effects were most pronounced.

The major-ion chemistry of streams varied depending on 

the geology of their drainage basins and the relative amount of 

mine drainage they received. The Boulder River above Kleinsmith Gulch (site 3) and the Little Boulder River (site 60) had 

a calcium-sodium bicarbonate type water. Basin Creek had 

a similar water type during high flow, but during low-flow 

conditions, the water was a calcium-magnesium bicarbonatesulfate type, with the addition of sulfate indicating the effects 

of mine drainage. Streams that are upstream from most mining and drain the interior of the study area, such as Jack Creek 

above the Bullion Mine tributary, High Ore Creek above the 

Comet mine, and Cataract Creek above Uncle Sam Gulch, had 

a calcium bicarbonate type water. Cataract Creek downstream 

from Uncle Sam Gulch also had calcium bicarbonate type 

water, although the proportion of sulfate was greater than it 

was upstream. High Ore Creek at the mouth had calcium sulfate-bicarbonate water, showing the effects of mine drainage.

Hardness is an important property of water because 

the toxicity of some trace elements increases as hardness 

decreases. Hardness values were relatively low (12-87 mg/L) 

year-round in most streams throughout the study area.

Values in High Ore Creek downstream from the Comet mine 

and Galena Gulch were higher, ranging from 44 to 180 mg/L. 

Hardness values typically were lowest during high flow, such 

as during spring runoff, owing to dilution; they were highest 

during low flow.

We measured the concentration of suspended sediment 

routinely in samples collected for this study during 1996-2000 

because transport of trace elements in the particulate fraction 

can be important, particularly during high flow (fig. 2). 

Suspended-sediment concentrations typically were low 

(generally less than 7 mg/L) during low flow in streams both 

upstream and downstream of mined areas. Concentrations of 

suspended sediment were slightly higher in streams such as 

the Bullion Mine tributary (site 17), Uncle Sam Gulch (site 

43), and High Ore Creek (site 56) that were most affected by 

mining. Low-flow suspended-sediment concentrations were 

as high as 15 mg/L in these streams, likely resulting from the 

presence of colloidal material produced during neutralization of 

acidic mine drainage. Suspended-sediment concentrations during high-flow conditions were higher, ranging as high as

Figure 2. Flood-plain tailings eroding at Jack Creek during 

snowmelt runoff upstream from site 19, May 1997.
76 mg/L in the Boulder River above Kleinsmith Gulch (site 

3) and lower Basin and Cataract Creeks (sites 24 and 47). In 

High Ore Creek, the maximum concentration (86 mg/L) was 

similar except for a March 1999 sample (308 mg/L) that likely 

was affected by remediation activities. High-flow suspendedsediment concentrations generally were higher in the Bullion Mine tributary (site 17), Jack Creek (site 19), Uncle Sam 

Gulch (site 43), and the Boulder River below Little Galena 

Gulch (site 58), where maximum values ranged from 99 to 

174 mg/L.

Water-Quality Standards

One of the most important reasons for characterizing 

water quality in streams affected by historical mining is to 

determine whether trace elements occur at concentrations that 

may be toxic to aquatic organisms. The relative magnitude 

of trace-element concentrations in water in various stream 

reaches can be evaluated by comparing measured concentrations with State and Federal aquatic-life standards. Except for 

aluminum, standards issued by the State of Montana (Montana 

Department of Environmental Quality, 1999) are applicable

Trace Elements in Stream Water 163

to the total-recoverable concentration of each trace element, 

whereas Federal standards (U.S. Environmental Protection 

Agency, 1999) are applicable to the dissolved concentration. 

Dissolved concentrations are defined by the regulatory agencies as the concentration in a 0.45-jj.m filtrate. For aluminum, 

the Montana standards are applicable to the dissolved concentration and the U.S. Environmental Protection Agency (EPA) 

standards are applicable to the total-recoverable (unfiltered) 

concentration. Aquatic-life standards for some metals (such 

as cadmium, copper, lead, and zinc) that are found regularly 

in the Boulder River watershed are dependent on hardness. 

Table 1 shows the range of hardness values measured in different streams in the watershed and the corresponding range of 

hardness-adjusted values for the State and Federal acute and 

chronic aquatic-life standards. In general, the lower values of 

the aquatic-life standards applied when streamflow was high 

because hardness values in the Boulder River watershed were 

lowest during these high-flow periods. Metals generally are 

more toxic to aquatic organisms than to humans. Humanhealth standards (Montana Department of Environmental 

Quality, 1999) for cadmium (5 j^g/L), copper (1,300 j^g/L), 

lead (15 jig/L), and zinc (2,100 jig/L) typically are higher than 

the hardness-adjusted aquatic-life standards for the watershed.

Table 1. Aquatic-life standards for selected trace elements in the Boulder River watershed.

[Abbreviations: Mg/L, micrograms per liter; pm, micrometer; mg/L, milligrams per liter]

Constituent

Hardness (mg/L)

Boulder River, Basin Creek, and Cataract Creek

Minimum

12

Maximum

87

High Ore Creek1

Minimum

44

Maximum

180

Acute aquatic-life standard (ug/L)2

Aluminum3'4

Arsenic3

Cadmium

Copper

Lead

Zinc

750

340

1.0/0.5

3.8/1.8

14/6.0

37/19

750

340

3.9/3.7

12/12

68/55

106/104

750

340

1.8/1.8

6.5/6.2

29/26

60/58

750

340

8.8/8.1

24/23

173/122

197/193

Chronic aquatic-life standard (ug/L)2

Aluminum3

Arsenic3

Cadmium

Copper

Lead

Zinc

87

150

0.8/0.4

2.9/1.5

0.5/0.2

37/20

87

150

2.2/2.0

8.3/8.0

2.7/2.2

106/105

87

150

1.3/1.2

4.6/4.4

1.1/1.0

60/59

87

150

3.9/3.5

15/15

6.7/4.7

197/194

'Includes Galena Gulch, in which the geology is similar to High Ore Creek.

2The first number is the Montana aquatic-life standard (Montana Department of Environmental Quality, 1999). The second 

number is the EPA standard (U.S. Environmental Protection Agency, 1999). Except for aluminum, Montana aquatic-life standards 

refer to total-recoverable concentrations, whereas EPA aquatic-life standards refer to dissolved (0.45-fxm filtration) concentrations. 

For aluminum, the Montana standards refer to dissolved (0.45-^m filtration) concentrations and EPA standards refer to totalrecoverable concentrations. When hardness is less than 25 mg/L, the Montana standard computed for a hardness of 25 mg/L applies.

3Aquatic-life standards for aluminum and arsenic are not dependent on hardness. Only one value is listed because the Montana 

and EPA standards are the same.

"Montana and EPA standards for aluminum apply when pH values are between 6.5 and 9.0.
164 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Arsenic is not as toxic to aquatic organisms as the other 

trace elements at similar concentrations, and human-health 

standards for arsenic are lower than aquatic-life standards. 

The Montana human-health standard of 18 [o,g/L (Montana Department of Environmental Quality, 1999), the EPA 

maximum contaminant level of 50 [o,g/L (U.S. Environmental 

Protection Agency, 1999), and the proposed maximum contaminant level of 10 [o,g/L are much lower than the acute and 

chronic aquatic-life standards for arsenic (340 and 150 |J,g/L, 

respectively).

Trace Elements in Water

We characterized the magnitude and extent of trace 

elements in surface water in the Boulder River watershed by 

systematic sampling of streams throughout the study area during a wide range of hydrologic conditions, comparing metal 

concentrations to aquatic-life standards, estimating annual 

loading of trace elements to the main streams in the watershed, 

and analyzing concentration data for temporal trends. We also 

made water-quality measurements in reference streams draining subbasins underlain by unmineralized rock of the same or 

similar lithologic units as those in the Boulder River watershed 

study area.

Water samples initially were analyzed for a broad suite 

of trace elements. Concentrations of some elements, such as 

beryllium, chromium, mercury, nickel, and silver, consistently 

were near or less than the minimum reporting level of the analytical laboratory or less than the applicable aquatic-life standard; routine analysis for these trace elements therefore was 

discontinued early in the study. Other elements, particularly 

the metals cadmium, copper, lead, and zinc, had concentrations greater than the applicable aquatic-life standards at many 

sites downstream from inactive mines. Therefore, this report 

focuses on these metals, as well as arsenic, which is pervasive throughout the watershed. Historical water-quality data 

collected during 1991-97 from inventories of inactive mines 

(Metesh and others, 1994, 1995, 1996; Marvin and others, 

1997; summarized in Nimick and Cleasby, 2000, table 4) and 

other investigations also were used to characterize study-area 

streams.

The data described herein were collected either as part 

of a periodic sampling program (most of the 1996-2000 data) 

or as part of a one-time sampling event (most of the historical 

data). These types of sampling programs are designed to provide a broad overview of water-quality conditions in a watershed or a record of water quality at one or more sites over a 

long time period. Other water-quality sampling programs with 

different purposes also were conducted during this investigation of the Boulder River watershed. Although an integral part 

of the watershed study, results of these programs are reported 

elsewhere in this volume. These other sampling programs 

included synoptic-sampling studies of closely spaced sites 

along specific stream reaches where more detailed information

on trace-element loading was needed (Cannon and others, this 

volume, Chapter El; Kimball and others, this volume, Chapter 

D6) and hourly sampling during 1- to 2-day periods at selected 

sites to document effects of diel (24-hour) cycles or storm 

runoff on trace-element concentrations (Lambing and others, 

this volume, Chapter D7).

Ribbon Maps

Ribbon maps are used in this chapter to display the large 

amount of trace-element data collected and compiled during 

this study for water-quality sites throughout the watershed. 

These maps use colors to indicate the approximate range in 

concentration of a specific constituent in different stream 

reaches and different hydrologic conditions. The maps also 

are useful for assessing exceedances of water-quality criteria 

throughout the watershed (table 1). A common assessment 

method in some studies is to compare each trace-element 

concentration in a water-quality sample to a specific standard. 

Summarizing this type of information for many samples from 

multiple sites would be tedious, especially when some criteria, 

such as aquatic-life standards for metals, vary depending on 

hardness. Ribbon maps, on the other hand, provide a way 

to summarize and display this information if the concentration ranges used in the maps bracket values for water-quality criteria. Although the ribbon maps are less specific and 

less precise than tabulated data, they may be more useful for 

evaluating exceedances on a watershed scale. A ribbon map 

can be used to display the range of all the data for the constituent, only data for a specific period, or only data for specific 

hydrologic conditions.

Ribbon maps were constructed for arsenic, cadmium, 

copper, lead, and zinc concentrations in water. The color coding for each map is similar. The concentration ranges represented by each color are the same for the dissolved (0.45-[jm 

filtration) and total-recoverable concentration maps for an 

individual trace element but differ among the trace elements. 

The only exception is for cadmium, where the concentration 

ranges represented by blue and green are not the same on the 

dissolved and total-recoverable maps because the lower minimum reporting level for the analytical method for dissolved 

cadmium provided more definition relative to the aquatic-life 

standards.

The concentration ranges depicted by color coding on 

the ribbon maps are considered approximate because the 

data were limited, most sites were sampled only once or a 

few times, and samples were collected over a 10-year period 

(1991-2000) and at different streamflow conditions. Therefore, the data likely did not represent the full range of concentrations. Similarly, concentrations at some sampling sites 

extended over more than one concentration range. At these 

sites, the median concentration value for the available data was 

used to designate the appropriate concentration range for the 

site. Minimum reporting levels for historical data were higher 

than for the 1996-2000 data. At sites where only historical
Trace Elements in Stream Water 165

data less than the minimum reporting level were available, the 

assumption was made that concentrations at the site were in 

the lowest (blue) concentration range. Owing to the limited 

number of sampling sites, the exact location where a traceelement concentration changed from one concentration range 

to the next was roughly estimated based on likely dilution 

effects from tributary inflows; therefore, the location of these 

color changes is considered approximate. Despite these 

limitations, ribbon maps have the benefit of summarizing data 

from many water samples and thereby provide an overall 

picture of trace-element concentrations in various stream 

reaches of the watershed.

Separate ribbon maps were constructed for dissolved and 

total-recoverable trace-element concentrations because the 

importance of these two fractions is different during different streamflow conditions. Dissolved concentrations of some 

trace elements tended to be higher during low flow than during 

high flow because the effect of dilution is minimal during low 

flow. In contrast, total-recoverable concentrations tended to 

be higher during high flow (particularly for arsenic, copper, 

and lead) because trace-element-enriched streambed sediment 

is entrained during high flow. In addition, during low flow, 

little paniculate or colloidal material was transported by most 

streams in the study area, and total-recoverable concentrations 

were approximately equal to the dissolved concentrations. 

Therefore, ribbon maps show either dissolved concentrations 

during low flow or total-recoverable concentrations during 

high flow. Because streamflow data were not available for 

some of the concentration data and because of the difficulty 

in determining whether flow was high or low for any given 

site in a particular year, we defined high flow as occurring 

during April-June and low flow during July-March. On the 

basis of the 58-year streamflow record for the Boulder River 

near Boulder (USGS streamflow-gauging station number 

06033000, site 59), spring runoff (streamflow greater than 

150 ftVs at this site) generally occurs between mid-April and 

June. Runoff periods during 1996-2000 are shown in Church, 

Nimick, and others (this volume, Chapter B, fig. 3).

For all ribbon maps, concentrations increase as the color 

changes from blue through green and yellow to orange and 

red. Reaches colored blue had concentrations either less than 

most water-quality criteria or less than the laboratory minimum reporting level applicable to most of the water-quality 

samples collected during 1996-2000. Concentration ranges 

represented by green and yellow were chosen to broadly 

represent applicable water-quality criteria. For arsenic, the 

applicable criteria were the Montana human-health standard 

(18 jig/L) and the EPA maximum contaminant level (50 jag/L). 

For metals, the freshwater acute and chronic aquatic-life 

standards (table 1) were used to define concentration ranges. 

Aquatic-life standards (table 1) are dependent on hardness, 

which generally is dependent on streamflow. Standards based 

on the measured hardness in the Boulder River and Basin and 

Cataract Creeks were used because these basins constitute 

most of the study area. Hardness values in High Ore Creek 

tended to be higher than in the other study area streams

(table 1); therefore, the aquatic-life standards were somewhat 

higher than the color-coded values. Green reaches had concentrations within or near the range of the Montana and EPA 

chronic aquatic-life standards. Concentrations in the yellow 

reaches were higher and ranged from about the maximum of 

the chronic standards up to about the maximum values of the 

acute standards. For arsenic, green reaches had detectable 

concentrations less than the Montana human-health standard, 

and yellow reaches had concentrations between the Montana 

human-health standard and the EPA maximum contaminant 

level. For zinc, acute and chronic aquatic-life standards were 

nearly equal (table 1); consequently, green color-coding was 

not used. Orange reaches had trace-element concentrations 

that almost always exceeded the maximum value of the acute 

standard (maximum contaminant level for arsenic) and ranged 

up to 10 times the maximum value of this standard. Red 

reaches had concentrations that exceeded this standard by 

more than 10 times. Data used to construct the ribbon maps 

consisted of data for 1996-2000 collected for this study (Rich 

and others, this volume, Chapter G and accompanying 

CD-ROM) and data for 1991-97 compiled from the Ground 

Water Information Center database at the Montana Bureau of 

Mines and Geology (Nimick and Cleasby, 2000, table 4).

PH

In many mining-affected watersheds, streams have low 

pH values owing to acidic mine drainage. However, few 

stream reaches in the Boulder River watershed were acidic 

(fig. 3), and pH values were near-neutral to slightly alkaline 

everywhere except in isolated circumstances, where acid 

discharge from inactive mines affected small streams. The 

primary acidic (pH values less than 6.5) reaches were in 

Uncle Sam Gulch downstream from the Crystal mine and the 

Bullion Mine tributary (fig. 4) downstream from the Bullion 

mine. Rocker Creek downstream from the Ada mine also was 

somewhat acidic (pH of 5.8). Although other inactive mine 

sites had acidic drainage, the paucity of acidic stream reaches 

in the watershed likely results from acid-neutralizing capacity provided by mafic minerals and secondary calcite in the 

granitic rocks of the Boulder batholith (Desborough and Fey, 

1997; Desborough, Briggs, and Mazza, 1998; Desborough and 

others, 1998; Desborough and Driscoll, 1998).

Trace-Element Partitioning

Trace elements transported in a stream are either dissolved or in a paniculate form. This partitioning is important 

for studies of streams affected by mine drainage because 

toxicity depends greatly on the chemical form of each trace 

element, with the dissolved form typically being more toxic 

than particulate forms (Brown and others, 1974; Erickson 

and others, 1996). Dissolved species of trace elements are 

analyzed in filtered water samples whereas concentrations of 

particulate forms are determined by the difference between
166 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112022'30" 112-151

BUCKEYE 

01 7 AND

ENTERPRISE

-83

EXPLANATION

Approximate range of pH values, in standard 

units

Water-quality site and pH value or range of 

values, in standard units

7.6-8.4 ,

Base from U.S. Geological Survey 

Digital line graphs. 1-100,000

2 KILCMETEBS

7.4.

CRYSTAL.

V U.S. Geological Survey

Montana Bureau of Mines and Geology

Inactive mine and name

Figure 3. Approximate values of pH during low-streamflow conditions (July-March), 1991-2000. Site locations and numbers are 

shown in figure 1. Values of pH for Bullion Mine tributary and Uncle Sam Gulch were defined by data from Kimball and others 

(this volume) and are not shown.
Trace Elements in Stream Water 167

Figure 4. Acidic water in Bullion Mine tributary, August 1998. Bullion mine is on bare 

hillslope (top center of photograph).

total-recoverable (unfiltered) and filtered concentrations. 

Dissolved species include ionic forms (for example, Zn2+) 

and aqueous ion pairs (for example, ZnHCO3+). These forms 

are not retained by normal filtration, which typically uses a 

0.45-|um pore-size filter, or by ultrafiltration. which typically 

uses a 10,000-Dalton nominal (about 0.001-|um) pore-size 

filter. Particulate forms include colloidal material and coarser 

particles that can settle to the streambed. Colloidal material 

is too fine to settle unless it aggregates and often is defined 

operationally as particles ranging in size from 0.001 to 1 |tim 

(Rees and Ranville, 1990). Large quantities of colloidal material, typically oxyhydroxides of aluminum, iron, and manganese, form as acidic inflows are neutralized in the receiving 

stream (Chapman and others, 1983; Kimball and others, 1995; 

Schemel and others, 2000). The colloidal material aggregates, 

settles to the streambed, and coats the streambed material, 

which subsequently can be entrained and transported downstream during high flow (Church and others, 1997). Although 

0.45-|um filtration is commonly used to separate the dissolved 

and particulate fractions in water-quality studies, trace-element concentrations in a 0.45-|um filtrate may be higher than 

the actual dissolved fraction because some colloids can pass 

through the filter (Kimball and others, 1995). Ultrafiltration 

can be used to determine concentrations of actual dissolved 

trace elements (Kimball and others, 1995). In this study, 

aliquots of selected water samples collected in 1996-98 were 

filtered through 0.45-|um and 10,000-Dalton pore-size filters to 

determine the possible presence and role of the colloidal fraction in transporting trace elements (D.A. Nimick, unpub. data).

The general pattern of trace-element partitioning among 

unfiltered samples (total-recoverable concentrations) and 

10,000-Dalton and 0.45-|tim filtrates from the Boulder River

watershed depended primarily on the trace element and, to a 

lesser extent, on the proximity of the sampling site to principal 

source areas. Limited data indicate that aluminum and iron 

were almost entirely associated with colloidal or particulate 

material in streams both upstream and downstream from historical mining areas in the study area. Many total-recoverable 

aluminum and several total-recoverable iron concentrations 

were at least 100 |tig/L or higher, whereas concentrations of 

aluminum and iron in ultrafiltrates typically were much lower. 

Limited data also indicate that cadmium and zinc partitioned 

mostly to the dissolved (ultrafiltrate) phase, particularly during 

low flow. In contrast, lead partitioned almost exclusively to 

the colloidal or particulate fraction during most flow conditions. Large amounts of arsenic and copper also partitioned 

to the solid phase but, unlike lead, arsenic and copper also 

were present in substantial proportions in the dissolved phase. 

During high flow, the partitioning of many trace elements 

shifted with increased proportions of each trace element in 

the particulate or colloidal phase because of entrainment of 

streambed sediment.

Differences in concentrations between 0.45-|tim filtrates 

and ultrafiltrates varied between trace elements. Iron concentrations typically were two- to three-fold (or more) higher in 

0.45-jum filtrates than in ultrafiltrates. indicating a substantial 

portion of colloidal iron in most streams. In contrast, concentrations of arsenic, cadmium, and zinc in 0.45-|tim filtrates 

typically were similar or only 10-20 percent higher than in 

ultrafiltrates, indicating that only small amounts of these 

trace elements were present as colloidal material even though 

colloidal iron was present. Thus, concentration data for 

0.45-jum filtrates generally can be assumed to be representative of dissolved arsenic, cadmium, and zinc concentrations.
168 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Partitioning of copper in 0.45-|j,m filtrates and ultrafiltrates is 

not known because of copper contamination introduced during 

the 0.001-jam filtration. Partitioning of lead also is not known 

because concentrations in one or both filtrates typically were 

less than the minimum reporting level. On the basis of these 

evaluations, data for 0.45-|j,m filtrates are used in this report to 

define dissolved concentrations of trace elements.

Relation of Streamflow and Concentration

Streamflow is an important factor in controlling traceelement concentrations as well as the proportion of dissolved 

and colloidal or particulate trace elements being transported 

(fig. 5). Tn many streams, dissolved (filtered) concentrations typically decrease as Streamflow increases owing to 

dilution. Total-recoverable concentrations typically increase 

during high flow because colloidal and particulate material 

is entrained from the streambed or eroded from streambanks. 

However, these general relations are not universal. Therefore, 

the streamflow-concentration relations need to be determined 

for each trace element.

The relation between Streamflow and dissolved 

(0.45-|j,m filtration) trace-element concentrations is shown in 

figure 6 for five sites in the Boulder River watershed. At one 

site (site 56, High Ore Creek), data are segregated into a preand a post-remediation period to illustrate remediation effects 

on water quality. At Boulder River below Little Galena Gulch 

(site 58), Cataract Creek (site 47), and High Ore Creek (site 

56, pre-remediation), dissolved cadmium and zinc concentrations decreased as Streamflow increased during snowmelt 

runoff. This relation is expected because cadmium and zinc 

are likely to exist in the dissolved phase (Smith, 1999). For 

High Ore Creek (site 56) this generalization applies to the 

period before September 1997, when remediation activities 

began at the Comet mine (Gelinas and Tupling, this volume). 

The decrease in dissolved cadmium and zinc concentrations with increased Streamflow at these three sites suggests 

that the sources of these metals were relatively constant, for 

example from ground-water or adit discharge, as opposed to 

leaching of mine wastes or tailings either in piles or in fluvial 

deposits, where loading would be expected to increase during snowmelt or storm runoff. This relation did not hold for 

Boulder River above Kleinsmith Gulch (site 3) or for Basin 

Creek (site 24). At these sites, cadmium and zinc concentrations did not change appreciably with increased Streamflow, 

perhaps because upstream loading of these metals was relatively insignificant and concentrations were controlled more 

by desorption from streambed sediment. Dissolved arsenic 

concentrations generally did not vary with Streamflow at most 

sites, probably because concentrations were low and, as shown 

in a later section, because arsenic is derived from the entire 

watershed and not primarily from the mined areas. In High 

Ore Creek, post-remediation dissolved arsenic concentrations 

during low flow are higher than pre-remediation concentrations and decrease with increased Streamflow. Dissolved

Figure 5. Cataract Creek at Basin (site 47) during highstreamflow conditions, June 1997 (top), and low-streamflow 

conditions, October 1996 (bottom).

copper concentrations increased at all five sites as Streamflow 

increased. This pattern, which is the reverse of the pattern for 

cadmium and zinc at sites 58, 47, and 56 (pre-remediation), 

likely is an artifact of filter pore size. Copper is more likely 

to exist in the particulate or colloidal phase than in the dissolved phase (Smith, 1999). Colloidal material is more readily
Trace Elements in Stream Water 169

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: o 0 ^ :

— o ~

r <§>

8or5b

«. * . ° ^

- ^ % „• M = ,»• • •*/•

7 • • * ~

- —

1 * 1,

_

~ • Basin Creek (site 24) ~

r O Cataract Creek (site 47)

, , , , i , ,ii , ,1,1,1,1 i ,,,,,,.

7,000

5,000 

4,000

3,000

2,000

1,000

700

500

400

300

200

inn

-_ 0 High Ore Creek (site 56) j 

: post-remediation :

~ • High Ore Creek (site 56) ~ 

pre-remediation

— —

- '* ..« i

o

: o : _ •* _

: O O O O O O\ :

0

r ° o -

0

o

0 0

-

, 1,11,11! , ,,,,,,, I I,,,,,,"

100 1,000 1 10 100 1,000 0.1 

STREAMFLOW, IN CUBIC FEET PER SECOND

Figure 6. Relation of streamflow to dissolved (0.45-|u,m filtration) trace-element concentrations at five sites, 1996-2000. 

Dissolved cadmium concentrations for the Boulder River above Kleinsmith Gulch (site 3) were less than the minimum 

reporting levels and are not shown.
170 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

entrained from the streambed during high flows than during 

low flows and, thus, more colloids would move in suspension 

in the water column during high flow. Because some colloidal 

material can pass through the 0.45-fim filter used in this study, 

copper concentrations in 0.45-nm filtrates would be expected 

to increase as streamflow increases.

The relation between streamflow and dissolved and 

total-recoverable concentrations is not the same for each trace 

element during low-flow and high-flow conditions. Figure 

7 shows the relation between streamflow and dissolved and 

total-recoverable trace-element concentrations for Cataract 

Creek (site 47). These relations are typical for other watershed streams with elevated trace-element concentrations. 

Total-recoverable and dissolved concentrations of aluminum 

and iron increased greatly with streamflow. Copper and manganese total-recoverable concentrations increased moderately 

with increasing flow. Although dissolved copper increased 

as total recoverable copper increased, dissolved manganese 

remained relatively constant as flows changed and total-recoverable manganese increased. The patterns for arsenic and lead 

are somewhat similar to that of manganese. Dissolved arsenic 

concentrations were consistently low (2-5 fig/L) during all 

flow conditions, but total-recoverable arsenic concentrations 

increased about 10-fold during high flow. Similarly, dissolved 

lead concentrations were consistently low (<1-1 fig/L), but 

total-recoverable concentrations increased as much as 20-fold 

during high flow. These increases in total-recoverable arsenic 

and lead concentrations indicate that arsenic and lead may be 

associated with the hydrous metal oxide coatings on streambed sediment and transported when colloids are resuspended 

during high flow (Church, Unruh, and others, this volume, 

Chapter D8). Total-recoverable concentrations of cadmium 

and zinc were only slightly higher than dissolved concentrations, indicating that, although suspended sediment was 

enriched in cadmium and zinc (Church, Unruh, and others, 

this volume, fig. 12), the amount of paniculate cadmium and 

zinc in the water column was small relative to the dissolved 

fraction. This relation demonstrates that these metals strongly 

partition to the dissolved phase.

Seasonal differences in streamflow are an important 

factor affecting the severity and timing of aquatic toxicity. 

The importance of understanding these factors is demonstrated 

in figure 7 using aluminum, cadmium, copper, lead, and zinc 

data for Cataract Creek (site 47). These graphs show the 

EPA hardness-adjusted aquatic-life standards for each water 

sample. Total-recoverable copper concentrations increased 

from 13 to 90 fig/L and total-recoverable lead concentrations 

increased from less than 1 to 22 fig/L as streamflow increased 

from 1.9 to 168 ft3/ s. In contrast, hardness (not shown) and 

the aquatic-life standards for copper and lead decreased as 

streamflow increased. Similar to copper and lead, total-recoverable aluminum concentrations also increased with streamflow from 12 to 952 fig/L and exceeded the acute aquatic-life 

standard during high flow. The implication of these trends 

is that the toxicity of copper and lead is much greater during

high flow. For cadmium and zinc, concentrations decreased 

about three- to four-fold as streamflow increased. The 

aquatic-life standards for cadmium and zinc also decreased 

as streamflow increased, but the decreases in these standards 

were somewhat less than for concentration. Therefore, 

the degree of aquatic toxicity for cadmium and zinc was 

slightly greater during low flow, although the difference 

between high-flow and low-flow toxicity for cadmium and 

zinc was not nearly as great as it was for copper and lead. 

Part of the convergence of the aquatic-life standards and 

concentrations of cadmium and zinc at high-flow results 

from the regulatory restriction that hardness-adjusted aquatic 

standards do not continue to decrease as hardness decreases to 

values less than 25 mg/L, which happened every spring during 

snowmelt runoff in Cataract Creek.

Trace-Element Concentrations

Trace-element concentrations in streams of the Boulder 

River watershed varied greatly, with the highest concentrations occurring in small streams downstream from just a few 

of the inactive mines in the watershed. The lowest concentrations generally were in stream reaches upstream from areas of 

historical mining or in headwater streams where small inactive 

mines had little effect. Cadmium, copper, lead, and zinc concentrations commonly exceeded chronic aquatic-life standards. 

The highest concentrations were in streams downstream 

from three large inactive mines: the Crystal mine (fig. 8) in a 

tributary to Cataract Creek, the Bullion mine (fig. 9) in a tributary to Jack Creek, and the Comet mine in High Ore Creek 

(Gelinas and Tupling, this volume, fig. 3). Downstream from 

these three mines, the chronic aquatic-life standard for at least 

one metal associated with the watershed's ore deposits was 

exceeded at all sampling sites, including sites in the Boulder 

River between Basin Creek and the Jefferson River.

The magnitude and distribution of trace elements in water 

are shown by ribbon maps for zinc, cadmium, copper, lead, 

and arsenic. Of these, zinc probably provides the best overall 

indicator for several reasons. First, concentration data for dissolved and total-recoverable zinc are available for more sites 

than for other trace elements. Second, zinc is a mobile metal 

that occurs at many sites in concentrations well above the 

minimum reporting level; however, concentrations of zinc are 

relatively low in areas unaffected by mining. Finally, exceedances of aquatic-life standards typically are larger for zinc than 

for other trace elements. Therefore, zinc is very useful for 

assessing the effects of mine drainage in the watershed. For 

some sites, only total-recoverable zinc concentration data were 

available; these data also were used to construct the dissolved 

zinc ribbon map because zinc occurs primarily in the dissolved phase and the total-recoverable concentrations provide 

an upper limit on the dissolved zinc concentrations at the sites 

with limited or no dissolved zinc data.
Trace Elements in Stream Water 171

IUU

70

50 

40

30

20

10

7

5

4

3

2

100

cc 

| 70

E 50

s «

1 30

cc

CD

g 20

CO

5

z:

z- 10

0

fe 7

*5 

1 5

o 4

Z:

0 3 

0 J

2

500

400

300

200

100

70

50

40

30

20

10

i i [ i i i i 1 1 i i , i i i 1 1 1

1 ARSENIC -I

[ 2

^L_

- -

.

*\ -

\ • i

r % ~

7 •••• • -

" 2 OC"rv, 0 0 0 0 <p _

- • mPo oo- o ° o 0-

-_ COPPER ' * *_

1 ~ 1

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- • ^ O O °)° <§-

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~ n •

: § 8 ;

- 4t4- -

: + \ + + '-

+ ~-

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. 1,111,1 , , , i , i 1 1 1

~ MANGANESE ~

— —

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,,,,,, ,1 , ,,,,1,1

AUUU

1,000

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1,000

500

200

100

50

20

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1.000

700

500

400

300

200

100

70

50

40

30

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ALUMINUM

f chronic standard t:

A A0

• ^ -

•

acute standard O _

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.> * °^

_ * 0 °°

-

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: o .99,,,,, , , , ,,,,, '-

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chronic standard •

T « *•

- % -

• •

•o o

Oo"

r • o °°° -

:- t -

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: ;

- »*fc ^

1 ® a •

r *° a • *"^

; "Soo^;

oL + + %++ + j

- ++ + J

7 Acute and chronic + ^+-fHK

- (not shown) standards

" are equal

10

7

5

4

3

2

1

0.7

0.5 

0.4

100 

70 

50

40

30

20

10

7 

5

4

3

2

1

0.7

0.5

0.4

1

i , i , , i 1 1 1 i , , i , , > , |

: CADMIUM :

f ~

— —

- * Cp -

L • W L

- +-&& » • -

•_ + T+ * «0 • •:

: x x ^xx x ++ ? $*•*:

- x xX ^ *+&

X ^ X >}<«-

J ,,,,,, 1 , 1 1 1 1 1 1 1

, 1 , 1 1 . 1 1 1 1 1 , , , , I 1 1 

r LEAD -

- ++ \+ + ~.

-

~ + ++ + *:

-__ • j;

[ • \~\

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- X X x • ;

.•

r • xx x

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T , ,,,,,, ,1 , ,,,,,,,!

10 100 20

STREAMFLOW, IN CUBIC FEET PER SECOND

EXPLANATION

O Dissolved concentration

• Total-recoverable concentration

+ EPA acute aquatic-life standard

x EPA chronic aquatic-life standard

Zinc

100 200 100 200

STREAMFLOW, IN CUBIC FEET PER SECOND

Figure 7. Relation of streamflow to dissolved (0.45-fim filtration) and total-recoverable trace-element concentrations 

in Cataract Creek (site 47), 1996-2000. Dissolved lead data are not shown because concentrations were equal to or less 

than minimum reporting level of 1 u.g/L U.S. Environmental Protection Agency (EPA) aquatic-life standards vary with 

hardness for cadmium, copper, lead, and zinc; standards for manganese have not been established. Standards for 

arsenic are not shown because they are much higher than measured concentrations.

Dissolved zinc concentrations during low flow (fig. 10) 

ranged from <1 |ug/L at some sites to 21,000 |ug/L in Uncle 

Sam Gulch below the Crystal mine (site 44M). At sites in 

areas upstream from historical mining and in many headwater 

areas that were mined, dissolved zinc concentrations generally 

were <50 |ug/L, and at most sites, the concentrations were 

<10 Lig/L.

Three inactive mines (Crystal, Bullion, and Comet) had 

a profound effect on zinc concentrations in the watershed. 

Downstream from these mines, zinc concentrations were as

high as 50-200 times the acute aquatic- life standard 

(19-197 |ug/L, table 1). Discharge from the adit at the Crystal 

mine increased dissolved zinc concentrations in Uncle Sum 

Gulch from 12 |ug/L upstream from the mine to 58,600 |ug/L 

downstream from the mine (Kimball and others, this volume). 

Zinc concentrations were elevated throughout Uncle Sam 

Gulch, although dilution from tributaries decreased dissolved 

concentrations during low flow to 1,750-5,730 |ug/L at the 

mouth (site 43). The Bullion Mine tributary (site 17) had 

dissolved zinc concentrations ranging from 2,130 to 5,820 

|ug/L, which elevated concentrations in Jack Creek to 205-405 

|ug/L at the mouth. The Comet mine site had a similar effect
172 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

&&£ X&, •*-. *

Figure 8. Crystal mine, June 1997. Acidic discharge drains from adit (out of view near lower 

right of photograph) to Uncle Sam Gulch on far left.

Figure 9. Bullion mine, June 1997. Primary adits are on hillslope denuded by mine wastes 

above Bullion Mine tributary, which flows from right to left at edge of trees at center right of 

photograph. Acid discharge from one adit flows downslope in lower right corner.

on High Ore Creek. Upstream from the Comet mine (site 49), 

zinc concentrations were low, ranging from <1 to 

54 fig/L. However, at all sites on High Ore Creek downstream 

from the mine, dissolved zinc concentrations were much 

higher, ranging from 388 to 5,214 fig/L prior to the start of 

remediation activities (Gelinas and Tupling, this volume). 

The effect of drainage from each of these three mines 

extended far downstream (fig. 10). For example, the zinc

loading from Uncle Sam Gulch affected concentrations in 

Cataract Creek downstream to its mouth. Dissolved zinc 

concentrations during low flow, from 191 to 634 fig/L at the 

mouth, were always higher than the acute aquaticlife standard (19-104 |ig/L, table 1) in this lower reach of 

Cataract Creek. Zinc loading from Bullion Mine tributary 

increased dissolved zinc concentrations in Jack Creek from 

12.3-33 fig/L (site 16) to between 205 and 1,280 fig/L
Trace Elements in Stream Water 173

112022'30"

^DI/OTVI .

Lnfo IML

Vs

EXPLANATION

Approximate range of dissolved zinc concentrations, 

in micrograms per liter

_____ > 100-1,000 ————— <30

Water-quality site and dissolved zinc concentration 

or range of concentrations, in micrograms per liter

73-208^ u.s. Geological Survey

• Montana Bureau of Mines and Geology 

\ Inactive mine and name

Base from U.S. Geological Survey 

Digital line graphs. 1:100,000

2 KILOMETERS

Figure 10. Approximate concentrations of dissolved zinc during low-streamflow conditions (July-March), 1991-2000. Site locations 

and numbers are shown in figure 1. Values in red are supplemental total-recoverable zinc concentrations for sites where dissolved 

zinc data are limited or do not exist. Concentration data from Kimball and others (this volume), although not shown, were used to 

define color coding for Bullion Mine tributary and Uncle Sam Gulch.
174 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

(sites 19 and 63) and, farther downstream, to 35-91 |ug/L at 

the mouth of Basin Creek (site 24). Fluvial tailings along Jack 

Creek (Church, Unruh, and others, this volume) upstream and 

downstream from site 19 might be an additional source of zinc 

and other trace elements at downstream sampling sites.

The effect of drainage from these three mines continued 

downstream into the Boulder River, where dissolved zinc 

concentrations during low flow increased incrementally downstream from Basin, Cataract, and High Ore Creeks. Upstream 

from Basin Creek, concentrations in the Boulder River were 

1-6 |ug/L, whereas concentrations ranged from 25 to 70 |ug/L 

between Basin and Cataract Creeks. Between Cataract and 

High Ore Creeks, concentrations were higher, ranging from 

55 to 159 |ug/L. Finally, downstream from High Ore Creek, 

concentrations in the Boulder River ranged from 73 to 

208 |ug/L. On the basis of one sampling episode during 

low flow, dissolved zinc concentrations exceeded the acute 

aquatic-life standard downstream from the Basin and Boulder 

mining districts almost to the Jefferson River (fig. 10).

Other inactive mines contributed dissolved zinc to 

streams in the Boulder River watershed during low flow but 

not to the same degree as in those reaches affected by the 

Crystal, Bullion, and Comet mines. In the Cataract Creek 

basin upstream from Uncle Sam Gulch, dissolved zinc concentrations were 100 |ug/L or higher in four unnamed tributaries between Uncle Sam Gulch and Hoodoo Creek, in Rocker 

Creek downstream from the Ada mine, and in the headwater 

portion of Cataract Creek downstream from the Ida May mine. 

In upper Basin Creek, the Buckeye and Enterprise mines were 

a source of trace elements (Cannon and others, this volume). 

Dissolved zinc concentrations in upper Basin Creek downstream from these mines (site 8) generally were less than about 

40 fig/L. Similarly, mines in upper Big Limber Gulch and 

Hoodoo Creek in the Cataract Creek basin appear to be the 

cause of slightly elevated dissolved zinc concentrations during 

low flow (fig. 10).

Total-recoverable zinc concentrations during high flow 

(fig. 11) tended to be lower than dissolved concentrations during low flow, particularly in reaches where zinc concentrations 

were elevated. Concentrations in Basin Creek downstream 

from the Buckeye and Enterprise mines were an exception to 

this generalization. In this reach, loading of zinc and other 

trace elements was substantial during spring runoff, resulting 

in higher concentrations during high flow (Cannon and others, 

this volume). In reaches relatively unaffected by historical 

mining, such as Cataract Creek upstream from Hoodoo Creek, 

total-recoverable zinc concentrations were low during high 

flow (generally less than 50 |ug/L) but slightly higher than 

low-flow dissolved concentrations.

Cadmium

The spatial distribution of dissolved cadmium concentrations during low flow (fig. 12) was similar to the distribution 

of dissolved zinc concentrations, indicating that sources of 

cadmium and zinc were similar. Cadmium concentrations

exceeded the acute aquatic-life standard (0.4-3.9 |ig/L, 

table 1) in many of the same reaches where zinc exceeded this 

standard, particularly in headwater areas near inactive mines. 

However, in comparison to zinc, dissolved cadmium concentrations were not as elevated above the acute aquatic-life standard. This is shown by the lesser extent of yellow-, orange-, 

and red-colored reaches on the dissolved cadmium ribbon map 

(fig. 12) compared to the zinc map (fig. 10). Uncle Sam Gulch 

and the Bullion Mine tributary are the only red reaches on the 

cadmium ribbon map, whereas other stream reaches are red 

on the zinc map. Because the relative degree of exceedance of 

the aquatic-life standard was smaller for cadmium concentrations than zinc concentrations, exceedances of the cadmium 

standards did not extend as far downstream below major 

sources as did exceedances of the zinc standard. For instance, 

dissolved cadmium concentrations at the mouth of Basin 

Creek barely exceeded 0.4 |ug/L (fig. 12). Although cadmium 

concentrations in the Boulder River increased incrementally 

downstream through the study area, aquatic-life standards 

were only exceeded downstream from Cataract Creek. Similar 

to zinc, total-recoverable cadmium concentrations during high 

flow (fig. 13) generally were lower than dissolved concentrations during low flow except in Basin Creek downstream from 

the Buckeye and Enterprise mines.

Copper

Dissolved copper concentrations during low flow 

(fig. 14) exceeded the acute aquatic-life standard (1.8- 

12 |ug/L, table 1) by more than 10 times (red color) downstream from the Bullion and Crystal mines in the Bullion Mine 

tributary and Uncle Sam Gulch, respectively. In contrast, 

concentrations in High Ore Creek downstream from the Comet 

mine were much lower (2-8 |ug/L). Although High Ore Creek 

is colored green on the dissolved copper ribbon map, indicating exceedance of the chronic criteria for other parts of the 

watershed where hardness values are lower, none of the lowflow concentrations actually exceeded the hardness-adjusted 

standard. The small amount of copper relative to zinc and 

cadmium that leaches from the Comet mine area probably 

results from the different ore body at this site compared to the 

polymetallic veins that compose ore bodies near the Crystal 

and Bullion mines (O'Neill and others, this volume, Chapter 

Dl). The copper loading from the Bullion Mine tributary 

increased copper concentrations in Jack Creek and, farther 

downstream, in Basin Creek. Similarly, the copper loading 

from Uncle Sam Gulch affected Cataract Creek downstream 

to its mouth. Similar to cadmium and zinc, dissolved copper 

concentrations in the Boulder River were enriched downstream 

from Basin Creek; concentrations generally ranged between 

the acute and chronic aquatic-life standards. Dissolved copper concentrations in the Boulder River were highest in the 

reach between Cataract and High Ore Creeks and decreased 

downstream from High Ore Creek. Total-recoverable copper 

concentrations during high flow (fig. 15) typically were higher 

than dissolved copper concentrations during low flow, most
Trace Elements in Stream Water 175

112°22'30" 1120 15'

Base from U.S. Geological Survey 

Digital line graphs, 1:100,000

2 KILOMETERS

V>

EXPLANATION

Approximate range of total-recoverable zinc concentrations, 

in micrograms per liter

Water-quality site and total-recoverable zinc concentration 

or range of concentrations, in micrograms per liter

760-1,600 ,_. ..„ _ . . .„ V U.S. Geological Survey

Inactive mine and name

Figure 11. Approximate concentrations of total-recoverable zinc during high-streamflow conditions (April-June), 1996-2000. 

Site locations and numbers are shown in figure 1.

CRYSTAL
176 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112°22'30" 112-151

EXPLANATION

Approximate range of dissolved cadmium concentrations, 

in micrograms per liter

Water-quality site and dissolved cadmium concentration or 

range of concentrations, in micrograms per liter

0.6-7.0

Base from U.S. Geological Survey 

Digital line graphs, 1:100,000

2 KILOMETERS

CRYSTAL

5.3 ,

V U.S. Geological Survey

Montana Bureau of Mines and Geology

vs Inactive mine and name

Figure 12. Approximate concentrations of dissolved cadmium during low-streamflow conditions (July-March), 1991-2000. 

Site locations and numbers are shown in figure 1.
Trace Elements in Stream Water 177

112°22'30" 112-151

CRYSTAL

EXPLANATION

Approximate range of total-recoverable cadmium concentrations, 

in micrograms per liter

Water-quality site and total-recoverable cadmium concentration or 

range of concentrations, in micrograms per liter

3-7

V U.S. Geological Survey

' Inactive mine and name

Base from U.S. Geological Survey 

Digital line graphs. 1:100,000

2 KILOMETERS

Figure 13. Approximate concentrations of total-recoverable cadmium during high-streamflow conditions (April-June), 1996-2000. 

Site locations and numbers are shown in figure 1.
178 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

1120 22'30"

HAWKEYE 

VV

VINDICATOR 

<5

CRYSTAL,

EXPLANATION

Approximate range of dissolved copper concentrations, 

in micrograms per liter

Water-quality site and dissolved copper concentration or 

range of concentrations, in micrograms per liter

/? 4Q

V U.S. Geological Survey

49

• Montana Bureau of Mines and Geology

. Inactive mine and name

Base from U.S. Geological Survey 

Digital line graphs. 1.100,000

2 KILOMETERS

Figure 14. Approximate concentrations of dissolved copper during low-streamflow conditions (July-March), 1991-2000. Site locations and numbers are shown in figure 1. Concentration data from Kimball and others (this volume), although not shown, were used 

to define color coding for Bullion Mine tributary and Uncle Sam Gulch.
Trace Elements in Stream Water 179

112C22'30" 112-151

CRYSTAL.

EXPLANATION

Approximate range of total-recoverable copper concentrations, 

in micrograms per liter

Water-quality site and total-recoverable copper concentration or 

range of concentrations, in micrograms per liter

9-38

V U.S. Geological Survey

' Inactive mine and name

Base from U.S Geological Survey 

Digital line graphs, 1:100,000

0 1 2 KILOMETERS

Figure 15. Approximate concentrations of total-recoverable copper during high-streamflow conditions (April-June), 1996-2000. 

Site locations and numbers are shown in figure 1.
180 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

likely because copper partitions more strongly than zinc or 

cadmium to the paniculate phase, thus enriching stream sediment, which is transported during high flow.

Lead

Dissolved lead concentrations in almost all parts of the 

study area were less than the minimum reporting level and 

are not shown on a ribbon map. The only sites where dissolved lead concentrations were typically higher than the minimum reporting level during low flow were the Bullion Mine 

tributary (site 17), where concentrations ranged from <1 to 

8.7 |ag/L, and Uncle Sam Gulch just downstream from the 

Crystal mine (site 44M), where the concentration was 

78.6 p,g/L. Both sites had acidic pH values (fig. 3).

Similar to copper, total-recoverable lead concentrations 

during high flow (fig. 16) were higher than during low flow 

because lead partitions strongly to the colloidal or particulate 

phase. Total-recoverable lead concentrations generally ranged 

between the chronic and acute aquatic-life standards (yellow 

color) throughout most of the watershed downstream from 

not only the Bullion, Crystal, and Comet mines, but also the 

Buckeye and Enterprise mines on upper Basin Creek and the 

Eva May mine on upper Cataract Creek.

Arsenic

Dissolved arsenic was present at low concentrations in 

both mined and unmined parts of the study area and in reference streams in other parts of the watershed. Concentrations 

during low flow (fig. 17) were not substantially elevated in 

any stream. Dissolved concentrations were much lower than 

the chronic aquatic-life standard (150 ug/L) throughout the 

watershed and exceeded the Montana human-health standard 

(18 ug/L) only locally. Dissolved arsenic concentrations 

generally ranged from 1 to 5 p,g/L at almost all sampling sites 

in the study area, as well as in areas upstream from historical 

mining (sites 1, 2, 49, and 60, fig. 1). Few sites had concentrations less than the minimum reporting level (1 ug/L). Concentrations in lower Basin Creek as well as in the Boulder River 

downstream from the study area were slightly higher, ranging 

as high as 9 p,g/L. These higher concentrations in Basin Creek 

appear to come from mining- and nonmining-related sources 

near the Buckeye and Enterprise mines (Cannon and others, this volume) as well as in Jack Creek, and possibly other 

tributaries. The higher dissolved arsenic concentrations in 

the Boulder River downstream from the study area appear to 

result from sources near or downstream from Boulder. Three 

stream reaches had concentrations higher than the Montana 

human-health standard of 18 p,g/L: Basin Creek downstream 

from the Buckeye and Enterprise mines (site 8), an unnamed 

and unmined tributary to Uncle Sam Gulch (site 42), and High 

Ore Creek downstream from the Comet mine (sites 52, 53, and 

56). Mine wastes, mill tailings, and fluvial deposits appear

to be the source of arsenic in High Ore Creek (Gelinas and 

Tupling, this volume). However, arsenic in Basin Creek near 

the Buckeye and Enterprise mines appears to be derived not 

only from mined areas, where the median arsenic concentration in mine wastes exceeds 1 weight percent (Church, Unruh, 

and others, this volume, table 2), but also from unmined areas 

(Cannon and others, this volume). The unnamed tributary to 

Uncle Sam Gulch drains an unmined area; therefore, the 

arsenic, which presumably is leaching naturally from arsenicrich geologic sources, in this drainage is nonmining related.

The spatial pattern of total-recoverable arsenic concentrations during high flow (fig. 18) was much different from the 

pattern for low-flow dissolved concentrations. The high-flow 

total-recoverable concentrations were higher than low-flow 

dissolved concentrations (fig. 17) at almost all sites having 

data for both flow conditions. No other trace element, with 

the exception of lead, had such a large difference between the 

low-flow dissolved and high-flow total-recoverable concentrations. The maximum dissolved arsenic concentration in the 

watershed during low flow was 44 p,g/L, whereas the maximum total-recoverable concentration during high flow was 

760 p,g/L. The chronic aquatic-life standard (150 ^ig/L) was 

equaled or exceeded at one or more sites downstream from 

the Buckeye, Bullion, Crystal, or Comet mines. Whereas 

the effect of historical mining areas is not readily apparent in 

the dissolved arsenic map (fig. 17), the effect is very apparent in the total-recoverable map (fig. 18). Because arsenic in 

mine drainage adsorbs to streambed sediment quickly (Smith, 

1999), dissolved concentrations during low flow are low. 

However, during high flow, arsenic-rich sediment is entrained 

within the water column and produces the high total-recoverable concentrations observed during this study. This same 

process also is the cause of the high concentrations of totalrecoverable lead during high-flow conditions in the watershed

Aluminum

Aluminum is not discussed in detail and ribbon maps 

are not presented because aluminum concentrations, unlike 

concentrations of other trace elements, do not appear to be 

overly toxic in the watershed. The toxicity of aluminum in 

neutral to alkaline surface water is not well understood (U.S. 

Environmental Protection Agency, 1999, p. 19), and therefore 

the established aquatic-life standards may be conservative. 

Typically, the primary concern regarding aluminum toxicity 

is not in reaches with neutral to slightly alkaline pH but rather 

in reaches that are mixing zones where acidic water rich in 

dissolved aluminum is neutralized, resulting in the formation 

of aluminum hydroxide colloids. These colloids can then coat 

the streambed and the gills of aquatic organisms.

Dissolved aluminum concentrations during low flow 

were consistently low in almost all streams. Concentrations 

only exceeded the chronic aquatic-life standard of 87 |ug/L in 

the Bullion Mine tributary and the upper and middle reaches
Trace Elements in Stream Water 181

1120 22'30" 112"15'

Base from U.S. Geological Survey 

Digital line graphs. 1:100.000

2 KILOMETERS

EXPLANATION

Approximate range of total-recoverable lead concentrations, 

in micrograms per liter

Water-quality site and total-recoverable lead concentration or 

range of concentrations, in micrograms per liter

7 7 ynn

V U.S. Geological Survey

CRYSTAL xx fi. . . X Inactive mine and name

Figure 16. Approximate concentrations of total-recoverable lead during high-streamflow conditions (April-June), 1996-2000. 

Site locations and numbers are shown in figure 1.
182 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112°22'30" 112-151

Base from U.S. Geological Survey 

Digital line graphs. 1:100,000

CRYSTAL.

EXPLANATION

Approximate range of dissolved arsenic concentrations, 

in micrograms per liter

_____ > 18-50

Water-quality site and dissolved arsenic concentration or 

range of concentrations, in micrograms per liter 

11-44

V U.S. Geological Survey

^ Inactive mine and name

1 2 KILOMETERS

Figure 17. Approximate concentrations of dissolved arsenic during low-streamflow conditions (July-March), 1996-2000. 

Site locations and numbers are shown in figure 1.
Trace Elements in Stream Water 183

112°22'30"

CRYSTAL,

EXPLANATION

Approximate range of total-recoverable arsenic concentrations, 

in micrograms per liter

> 18-50 ————— <;5

Water-quality site and total-recoverable arsenic concentration or 

range of concentrations, in micrograms per liter

18-200 TJ U.S. Geological Survey 

Inactive mine and name

Base from U.S. Geological Survey 

Digital line graphs, 1:100,000

1 2 KILOMETERS

Figure 18. Approximate concentrations of total-recoverable arsenic during high-streamflow conditions (April-June), 1996-2000. 

Site locations and numbers are shown in figure 1.
184 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

of Uncle Sam Gulch on the basis of data collected by Kimball 

and others (this volume) and data for sites 17 and 43 (Rich 

and others, this volume). These reaches generally were acidic, 

and therefore dissolved concentrations of aluminum and other 

metals would be expected to be elevated. Total-recoverable 

aluminum concentrations during low flow typically were 

somewhat higher than dissolved concentrations, and exceeded 

the chronic aquatic-life standard at sites in Basin Creek 

(site 8), Jack Creek (site 19), Uncle Sam Gulch and Cataract 

Creek (sites 43 and 44), and High Ore Creek (site 56) downstream from the Buckeye, Bullion, Crystal, and Comet mines, 

respectively. The maximum total-recoverable low-flow concentration at these sites was 570 (ig/L, which did not exceed 

the acute aquatic-life standard of 750 (ig/L.

Total-recoverable aluminum concentrations typically 

were highest during high flow, exceeding the acute aquatic-life 

standard (750 (ig/L) in some samples from many sites, including some sites in streams upstream from mining activities. 

For example, the median total-recoverable aluminum concentration during high-flow conditions in the Boulder River was 

the same (560 |ag/L) upstream (site 3) and downstream 

(site 58) from the study area. This value also was higher 

than the median high-flow total-recoverable concentrations 

(370-445 (ig/L) at the mouths of Basin, Cataract, and High 

Ore Creeks. These data indicate that the primary source of 

aluminum was not related to historical mining. In addition, 

although total-recoverable aluminum concentrations exceeded 

the acute and chronic aquatic-life standards in many parts of 

the watershed during high flow, the distribution of total-recoverable aluminum does not correlate well with stream reaches 

where aquatic health is thought to be impaired (Farag and others, this volume, Chapter D10).

Concentration Trends During 1996-2000

Temporal trends in trace-element concentrations can be 

caused by changes in hydrologic conditions over multi-year 

periods (for example, several dry years followed by several 

wet years) or by changes in loading resulting from remediation 

activities in mined areas. Changes due to varying hydrologic 

conditions do not necessarily imply that contaminant supply 

has changed, but rather just indicates fluctuating delivery and 

transport rates. Actual trends caused by a physical change 

in either contaminant supply or delivery process are more 

readily detected by statistically accounting for the effect of 

flow variation. Trace-element concentration data collected 

during 1996-2000 for this study at five key sites in the study 

area were analyzed statistically for trends. Generally, a 4-year 

period is too short to demonstrate systematic trends. However, 

some preliminary trends are discernible in the concentration 

data.

Temporal profiles of dissolved zinc concentrations during 1996-2000 are depicted in figure 19 for five sites in the 

watershed. These graphs show the full range of concentration

variation over the sampling period, seasonal patterns related to 

streamflow, and year-to-year patterns over the 4-year period. 

Trend tests were performed on these data sets to estimate the 

probability that the data exhibit a temporal trend. Because 

apparent trends are sometimes indicated by the seasonal 

change in concentration caused by streamflow variations, concentration data frequently are adjusted prior to the trend test 

to account for the variation due to streamflow. In this case, 

streamflow adjustment was incorporated into the trend test 

by using a linear regression of streamflow and concentration. 

The residuals from this regression were then evaluated for 

temporal trends (table 2) using the non-parametric KendalFs 

tau correlation (Helsel and Hirsch, 1992).

Variations in dissolved zinc concentrations in the Boulder 

River above Kleinsmith Gulch during 1996-2000 indicated no 

statistical trend. As a result, the magnitude of zinc load for a 

given flow did not vary appreciably during the study period. 

Presumably, loading of other trace elements from similar areas 

underlain by unmineralized rock upstream from the study area 

may also have shown little change. Similarly, dissolved zinc 

data for Basin and Cataract Creeks appear to have had no trend 

during 1996-2000. The absence of zinc concentration trends 

is consistent with the lack of remediation activity in the Basin 

and Cataract Creek basins. In contrast, dissolved zinc concentrations for High Ore Creek and the Boulder River below Little 

Galena Gulch exhibited a decreasing trend during 1996-2000. 

These trends and the related remediation activities conducted 

in 1997-2000 in the High Ore Creek valley are discussed in a 

subsequent chapter (Gelinas and Tupling, this volume).

Sources of Trace Elements

Mining-Related Sources

Although the Boulder River watershed has more than 

140 inactive mines and 15 mills (Martin, this volume, Chapter D3), only a few are significant sources of trace elements 

to streams. The downstream concentration profiles depicted 

in the ribbon maps (figs. 10-18) clearly show the influence 

of the Comet, Crystal, and Bullion mines (and, to a lesser 

extent, the Buckeye and Enterprise mines) on trace-element 

concentrations in the watershed. Ribbon maps depicting 

trace-element concentrations in streambed sediment also show 

the influence of these mines (Church, Unruh, and others, this 

volume). Waste rock was present at each of these mines, and 

mill tailings were present at three of these mines. Runoff 

from and erosion of these mine wastes likely contributed to 

the trace-element load discharged from these sites. Analysis 

of metal leaching from selected waste piles demonstrated 

that mine-waste materials at the Bullion and Buckeye mines 

had a high potential to impact streamwater quality (Fey and
Trace Elements in Stream Water 185

Boulder River above Kleinsmith Gulch (site 3)

— 400

Bn-tn-l— ETI |gf* :i-. LI i'g—i—i—f--ai

Basin Creek (site 24) 120 i—i—i—;—i—i—i -r -1—i—i—i—i

Cataract Creek (site 47)

Streamflow^ ,.-:

'ii}--t—t—I—H'' ji.jii 5 : i I'ET' till

High Ore Creek (site 56)

Streamflow^/ * ~\

i i I i i i -I-.*. t"i i i i i I i , i r...u-i I I I J -. t.f I I I I I I I i I I ill J

Boulder River below Little Galena Gulch (site 58)

FFF1--B-—<R1 I !'l j Pil l'B---h--f-- —R' I f t

2,700

1,800 -

7.5

- 5.0

- 2.5

100

1,500

1,000

500

ONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASO 

1996 1997 1998 1999 2000

Figure 19. Temporal profiles of dissolved zinc concentration and streamflow at five sites, 1996-2000. Shaded areas 

indicate periods of high streamflow during spring runoff. Lines connecting the data points are for visual generalization 

of temporal patterns and do not imply actual knowledge of concentrations or streamflow between sampling dates.
186 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 2. Results of linear regression and Kendall's correlation for trend tests of dissolved zinc concentration for five sites 

in the Boulder River watershed.

Site 

number

(fig.D

3

24

47

56

58

Station name

Boulder River above Kleinsmith Gulch

Basin Creek

Cataract Creek

High Ore Creek 

Boulder River below Little Galena 

Gulch.

Linear regression of Kendall's correlation, 

dissolved zinc concentration residuals and time 

and streamflow data pairs1 Conclusion2

Slope

0.207

200

-3.04

.134 

-2.32

R2

0.006

.001

.952

.007 

.803

T

-0.059

-.039

-.028

-.362 

-.536

p value

0.692

.780

.853

.0081 

.0002

No trend.

No trend.

No trend.

Decreasing trend. 

Decreasing trend.

'The p value indicates the probability of obtaining the computed T value if no temporal trend in the data exists. Thus, small p values (generally 

less than about 0.05) indicate temporal trends, whereas large p values indicate no temporal trends. Decreasing trends are associated with negative 

values of T.

2Trend tests are based on a short-term (4-year) dataset; consequently, conclusions regarding trend are considered preliminary.

Desborough, this volume). At the Crystal mine, adit discharge 

was sufficient to make this mine the most significant source 

of trace elements in the watershed. Detailed investigations of 

trace-element sources are reported for the Crystal and Bullion 

mines (Kimball and others, this volume) and the Buckeye and 

Enterprise mines (Cannon and others, this volume). Remediation activities started in late 1997 in the Comet mine area in 

the High Ore Creek basin; consequently, a detailed investigation of trace-element sources was not conducted there for this 

study.

The ribbon maps (figs. 10-18) show that effects from historical mining exist in stream reaches other than those affected 

by the Comet, Crystal, Bullion, Buckeye, and Enterprise 

mines. In particular, inactive mines along Cataract Creek and 

in tributaries to Cataract Creek contribute sufficient copper, 

zinc, and, in some cases, cadmium to increase concentrations 

in these reaches to levels near aquatic-life standards.

Premining Background Sources

Watersheds that experienced historical mining activity 

also contain undisturbed mineralized rocks that might weather 

and contribute acid and trace elements to streams. These 

mineralized rocks can be either mineral deposits or surrounding rock affected by hydrothermal alteration. Differentiating between trace-element loads derived from undisturbed 

geologic sources and mining-affected sources is essential for 

the mining-related contribution to be put in perspective. In 

addition, land managers can use information on the relative 

contributions of trace elements from undisturbed geologic 

sources and mining-related sources in a watershed for prioritizing subbasins for remediation and for establishing postremediation water-quality goals.

In the Boulder River watershed, sources of cadmium, 

copper, lead, and zinc in undisturbed areas appear to be 

small because concentrations of these metals in water are not 

elevated at reference sites upstream from mining activities or 

even in some headwater drainages with inactive mines. This

conclusion is reasonable for two reasons. First, mineralized 

veins and surrounding zones affected by hydrothermal alteration, which contain pyrite and other sulfide minerals that are 

the source of trace elements associated with ore deposits, have 

limited areal extent in the watershed. Second, the acid-neutralizing capacity provided by mafic minerals and secondary 

calcite in the Boulder batholith limits the migration of acidic, 

metal-rich water produced by oxidation of the veins and 

altered rock (Desborough, Briggs, Mazza, and Driscoll, 1998; 

Desborough, Briggs, and Mazza, 1998). However, premining 

water-quality data do not exist for stream reaches downstream 

from mined areas; hence, the reasons stated are somewhat 

speculative. Arsenic, on the other hand, appears to have small 

but pervasive sources throughout the undisturbed parts of the 

watershed.

Trace-Element Loading to the Boulder River

Early biological studies in the watershed (Vincent, 

1975; Nelson, 1976) postulated that trace-element loads from 

Basin, Cataract, and High Ore Creeks affected fisheries in 

the Boulder River. We determined the relative importance of 

each of the three major tributaries as contributors of dissolved 

trace elements to the Boulder River by estimating the annual 

streamflow and loads of dissolved trace elements during water 

year 1997 (October 1996 through September 1997). This 

loading analysis used only data for water year 1997 (fig. 20) 

because data were collected less frequently in subsequent 

years and because remediation activities began at the Comet 

mine along High Ore Creek in late 1997, which affected traceelement loads from this stream to the Boulder River (Gelinas 

and Tupling, this volume).

The annual loads of dissolved trace elements from Basin 

Creek (site 24), Cataract Creek (site 47), and High Ore Creek 

(site 56), and at sites on the Boulder River upstream (site 3) 

and downstream (site 58) of these tributary streams, were estimated in a multi-step process utilizing water-quality data for 

13 sample sets collected between October 1996 and September
Trace Elements in Stream Water 187

2,000

1,000 

a

3 700

LLJ 

C/0

E 500

£: 400

UJ

LU inn LL. 300 

o

CO

3 200

10 L

A Full sampling event (five sites)

O Abbreviated sampling event 

(less than five sites)

Period used to estimate 

load during runoff 

(April 14-July 22)

0 IM D 

1996

JFMAMJJAS 

1997

Figure 20. Hydrograph for Boulder River at Boulder (site 59) and sampling 

dates for water-quality data used for analysis of trace-element loading at 

five sites, water year 1997.

1997 and the daily mean streamflow record for a nearby site 

on the Boulder River (site 59, USGS streamflow-gauging station 06033000; Shields and others, 1998). First, a regression 

model relating daily mean streamflow at the gauging station 

to instantaneous streamflow measured at the time of sampling 

was developed for each sampling site. Second, the flow relation for each site was applied to the daily mean flows at the 

gauging station to construct a daily flow record for water year 

1997 for each site. Third, a set of regression models relating instantaneous streamflow at the time of sampling to the 

concentration of each trace element was developed. Fourth, 

these regression models were used with the estimated daily 

streamflow values for each site to estimate daily trace-element concentrations. Fifth, daily loads for each trace element 

were estimated by multiplying estimated daily streamflow and 

concentration. Finally, daily loads were summed for the year 

to estimate the annual loads for water year 1997 at each site 

(table 3).

Basin, Cataract, and High Ore Creeks together contributed 33 percent of the annual streamflow in the Boulder River 

(site 58) at the downstream end of the study area (fig. 21), 

roughly in proportion to their total drainage area compared to 

the drainage area upstream from the Boulder River below

Little Galena Gulch. The dissolved arsenic load contributed 

by the three tributaries was 38 percent of the load at site 58, 

about the same proportion as streamflow, indicating that the 

mineralized rocks in the study area contribute little if any 

excess dissolved arsenic. In contrast, the three tributaries 

contribute nearly all the dissolved cadmium load (89 percent) 

and zinc load (83 percent) and more than half of the dissolved 

copper load (56 percent). On an annual basis, Cataract Creek 

contributes more cadmium, copper, and zinc to the Boulder 

River than Basin and High Ore Creeks. The contribution of 

cadmium and copper from Cataract Creek was more than 

twice as large as the load from Basin Creek, and from 6 to 

almost 40 times greater than the load from High Ore Creek. 

The load of dissolved zinc from Cataract Creek was almost 

1.5 to 2 times as large as the loads from Basin and High Ore 

Creeks. High Ore Creek contributed little dissolved copper, 

accounting for only 1 percent of the load at site 58. Most of 

the dissolved trace-element load in Basin and Cataract Creeks 

was transported during runoff. In contrast, the High Ore 

Creek basin, which has lower mountains and therefore less 

snowmelt runoff from its headwaters, contributed almost half 

of its streamflow and trace-element load outside of the snowmelt runoff period.
188 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Figure 21. Boulder River below Little Galena Gulch (site 58) during spring runoff, 

June 1997.

Table 3. Estimated annual streamflow and annual loads of dissolved trace elements for five sites in the Boulder River 

watershed, water year 1997.

[Numbers in parentheses are negative. Period used to estimate load during runoff for 1997 was April 14 to July 22. >, greater than; 

<, less than; —, not applicable]

Station name Site number

(see fig. 1)

Boulder River

above Kleinsmith Gulch.

Basin Creek

Cataract Creek

High Ore Creek

Unaccounted for

Boulder River

below Little

Galena Gulch.

Site number

(fig.D

3

24

47

56

-

58

i

3

24

47

56

--

58

Streamflow Dissolved arsenic

Annual Percent of Percent of Annual load. Percent of Percent of 

stream-flow streamflow at streamflow in tons load at site 58 load during 

(acre-feet) site 58 during runoff runoff period 

period

31.7 xlO6

8.32 xlO6

6.40 x 106

0.596 x 106

0.0456 x 106

47.0 x 106

67

18

14

1

(<1)

100

Dissolved cadmium

Annual

load, in

tons

<0.012

.015

.041

.007

>.004

.071

Percent

of load at

site 58

<17

21

58

10

>6

100

Percent of

load during

runoff period

81

88

65

5

--

70

Annual

load, in

tons

0.521

.334

.710

.011

.324

1.90

83

86

84

55

—

82

0.422

.173

.082

.029

.033

.739

Dissolved copper

Percent

of load at

site 58

27

18

37

1

17

100

Percent of

load during

runoff period

87

94

88

67

--

84

Annual

load, in

tons

0.47

2.05

4.13

2.96

1.37

11.0

57

23

11

4

4

100

87

88

83

51

--

80

Dissolved zinc

Percent

of load at

site 58

4

19

38

27

12

100

Percent of

load during

runoff period

85

84

63

36

-

60

'Unaccounted for streamflow and loads were calculated by subtracting the sum of the values for sites 3, 24, 47, and 56 from the value for site 58. 

The resulting value could represent unsampled inflows or be an artifact of the analysis. Percents may not total to exactly 100 due to rounding.
Trace Elements in Stream Water 189

Summary

Concentrations, sources, and loads of trace elements in 

streams affected by historical mining in the Boulder River 

watershed near Basin in southwestern Montana were investigated during this study. Study results are essential for land 

managers to plan effective and cost-efficient remediation, 

prioritize remediation activities, and establish restoration 

goals. Specific objectives were to determine which trace 

elements associated with ore deposits in the watershed 

occurred at levels that potentially could be toxic to aquatic 

organisms, characterize trace-element concentrations throughout the watershed, identify primary source areas by quantifying trace-element loads at key sites in the watershed, and 

establish a water-quality monitoring program to determine 

long-term seasonal and annual variations near areas where 

remediation activities were likely. The study focused on those 

trace elements associated with the polymetallic veins exploited 

by historical mining.

The magnitude and extent of trace elements in the Boulder River watershed were assessed by systematic sampling of 

streams throughout the area during a wide range of hydrologic 

conditions, comparison of trace-element concentrations to 

aquatic-life standards, estimation of annual loading of trace 

elements to the main streams in the watershed, and analysis 

of concentration data for temporal trends. Water-quality 

measurements also were made in reference streams draining 

unmineralized subbasins underlain by the same or similar lithologic units. Almost all streams in the Boulder River watershed had near-neutral to alkaline pH and, except for elevated 

trace-element concentrations, generally good water quality.

Trace-element concentrations in streams of the Boulder 

River watershed varied greatly; the highest concentrations 

occur in small streams downstream from a few of the inactive mines in the watershed, and the lowest concentrations are 

generally in stream reaches upstream from areas of historical 

mining or in headwater streams where small inactive mines 

had little effect. Cadmium, copper, lead, and zinc concentrations commonly exceeded chronic aquatic-life standards. 

Zinc exceeded these standards to a greater degree than did 

the other metals. The highest concentrations were in streams 

downstream from three large inactive mines: the Crystal mine 

in Uncle Sam Gulch, the Comet mine in High Ore Creek, and 

the Bullion mine in a tributary to Jack Creek. Downstream 

from these three mines, the chronic aquatic-life standard for at 

least one trace element associated with the metal ore deposits 

in the watershed was exceeded at all sampling sites, including 

sites in the Boulder River between Basin Creek and the Jefferson River. Because hardness decreases while concentrations 

increase, the toxicity of copper and lead was much higher 

during high flow compared to low flow. Toxicity of cadmium 

and zinc also was slightly higher during high flow compared 

to low flow.

In the Boulder River watershed, sources of cadmium, 

copper, lead, and zinc in undisturbed areas appear to be small;

however, arsenic is pervasive at low concentrations throughout 

the watershed. Basin, Cataract, and High Ore Creeks together 

contributed 33 and 38 percent of the annual streamflow and 

dissolved arsenic, respectively, at the downstream Boulder 

River site, roughly in proportion to their percentage of the total 

drainage area. In contrast, the three tributaries contributed 

nearly all the dissolved cadmium (89 percent) and zinc 

(83 percent) as well as more than half of the dissolved copper 

(56 percent). On an annual basis, Cataract Creek contributed 

more cadmium, copper, and zinc than either Basin Creek or 

High Ore Creek.

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190 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

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97^78, 21 p.

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I.E., Madison, J.P., and Hargrave, PA., 1997, Abandonedinactive mines program, U.S. Bureau of Land Management: 

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348, 506 p.

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Wintergerst, Robert, 1996, Abandoned-inactive mines 

program, Deerlodge National Forest—Volume V, Jefferson 

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70 p.

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toxicity of copper and zinc in the Boulder River drainage, 

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250.

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Quantification of Metal Loading by 

Tracer Injection and Synoptic Sampling, 

1997-98

By Briant A. Kimball, Robert L Runkel, Thomas E. Cleasby, and David A. Nimick

Chapter D6 of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-D6

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract...................................................................................................................................................... 197

Introduction............................................................................................................................................... 197

Purpose and Scope......................................................................................................................... 197

Methods..................................................................................................................................................^

Tracer Injections and Stream Discharge..................................................................................... 198

Synoptic Sampling and Analytical Methods............................................................................... 199

Principal Components Analysis..................................................................................................... 200

Constituent Loads............................................................................................................................ 200

Subbasin Studies..................................................................................................................................... 201

Cataract Creek Basin...................................................................................................................... 201

Study Area and Experimental Design.................................................................................. 201

Chemical Characterization of Synoptic Samples.............................................................. 201

Load Profiles............................................................................................................................ 206

Locations of Major Loading .................................................................................................. 216

Unsampled Inflow................................................................................................................... 216

Attenuation of Load................................................................................................................ 216

Uncle Sam Gulch Subbasin............................................................................................................ 216

Study Area and Experimental Design.................................................................................. 216

Chemical Characterization of Synoptic Samples.............................................................. 221

Load Profiles............................................................................................................................ 224

Locations of Major Loading .................................................................................................. 236

Unsampled Inflow................................................................................................................... 236

Attenuation of Load................................................................................................................ 236

Bullion Mine Tributary Subbasin................................................................................................... 237

Study Area and Experimental Design.................................................................................. 237

Chemical Characterization of Synoptic Samples.............................................................. 242

Load Profiles............................................................................................................................ 248

Locations of Major Loading .................................................................................................. 248

Unsampled Inflow................................................................................................................... 248

Attenuation of Load................................................................................................................ 248

Discussion.................................................................................................................................................. 260

Sources of Metals........................................................................................................................... 260

Processes Affecting Metals.......................................................................................................... 260

Implications...................................................................................................................................... 260

Summary.................................................................................................................................................... 260

References Cited...................................................................................................................................... 261

Figures

1. Map showing location of study reach, selected inactive mines or prospects, and

selected sampling sites, Cataract Creek drainage............................................................ 202
2-4. Graphs of data along Cataract Creek, August 1997, showing:

2. Injected chloride concentration and calculated discharge...................................... 205

3. Variation of alkalinity, calcium, and sulfate concentrations with distance............ 207

4. Variation of aluminum, copper, iron, and zinc concentrations with distance......... 208

5. Biplot of principal component scores for synoptic samples and loadings for

chemical constituents, Cataract Creek, August 1997........................................................ 209

6-11. Graphs and bar charts for Cataract Creek, August 1997, showing variation of 

load with distance, and changes in load for individual stream segments, 

for the following:

6. Sulfate.................................................^

7. Zinc...................................................^

8. Manganese........................................................................................................................212

9. Aluminum............................................................................................................................ 213

10. Copper................................................................................................................................. 214

11. lron........................................................»

12. Map showing location of stream segments and inflows for synoptic sampling,

Uncle Sam Gulch, August 1998.............................................................................................. 218

13-15. Graphs of data along Uncle Sam Gulch, August 1998, showing:

13. Variation of chloride concentration and calculated discharge with distance...... 220

14. Variation of pH and sulfate with distance.................................................................... 222

15. Variation of aluminum, copper, iron, and zinc concentrations with distance........ 223

16. Biplot of principal component scores for synoptic samples and loadings

for chemical constituents, Uncle Sam Gulch, August 1998.............................................. 225

17-25. Graphs and bar charts for Uncle Sam Gulch, August 1998, showing variation 

of load with distance and changes in load for individual stream segments, 

for the following:

17. Strontium............................................................................................................................ 226

18. Sulfate ................................................................................................................................227

19. Cadmium............................................................................................................................ 228

20. Manganese........................................................................................................................ 229

21. Zinc..............................................................................................................TM

22. Iron.....................................................^

23. Aluminum...........................................................................................................................232

24. Copper................................................................................................................................233

25. Lead ....................................................................................................................

26. Diagrams showing mass transfer of metals between dissolved and colloidal

phases, Uncle Sam Gulch, August 1998............................................................................... 238

27. Map showing location of stream segments and inflows for synoptic sampling,

Bullion Mine tributary, September 1998............................................................................... 240

28-30. Graphs of data along Bullion Mine tributary study reach, September 1998, showing:

28. Variation of chloride concentration and calculated discharge with distance ...... 241

29. Variation of pH with distance......................................................................................... 243

30. Variation of aluminum, copper, iron, and zinc concentrations with distance........ 244

31. Photograph of Bullion Mine tributary showing turbid nature of stream water

owing to colloidal suspension of solids, September 1998................................................ 245
32. Biplot of principal component scores for synoptic samples and loadings for

chemical constituents, Bullion Mine tributary, September 1998..................................... 247

33-42. Graphs and bar charts for Bullion Mine tributary, September 1998, showing 

variation of load with distance and changes in load for individual stream 

segments, for the following:

33. Cadmium............................................................................................................................249

34. Manganese........................................................................................................................ 250

35. Zinc...................................................^

36. Sulfate..............................................^

37. Strontium............................................................................................................................ 253

38. Aluminum........................................................................................................................... 254

39. Copper................................................................................................................................ 255

40. Nickel.................................................................................................................................. 256

41. Iron...................................................................................................................................... 257

42. Lead ..................................................................................................................................

Tables

1. Segment number, distance along study reach, source, site description, 

and selected water-quality characteristics of water from synoptic sampling 

sites, Cataract Creek, August 13,1997................................................................................. 203

2. Average composition of groups from principal components analysis of synoptic

samples, Cataract Creek, August 1997................................................................................. 206

3. Change in load for individual stream segments and summary of load calculations, 

Cataract Creek, August 1997.................................................................................................. 217

4. Segment number, source, distance along study reach, site description, and 

field data for water from synoptic sampling sites, Uncle Sam Gulch, 

August 29,1998......................................................................................................................... 219

5. Average chemical composition of groups from principal components analysis

of synoptic samples, Uncle Sam Gulch, August 1998........................................................ 221

6. Change in load for individual stream segments and summary of load calculations 

for selected solutes, Uncle Sam Gulch, August 1998........................................................ 235

7. Segment number, distance along study reach, source, site description, site 

number, and field and chemical data for water from synoptic sampling sites, 

Bullion Mine tributary, September 1,1998........................................................................... 239

8. Median composition of groups from principal components analysis for synoptic

sampling sites, Bullion Mine tributary, September 1998................................................... 246

9. Change in load for individual stream segments and summary of load calculations 

for selected solutes, Bullion Mine tributary, September 1998......................................... 259
METRIC CONVERSION FACTORS AND ABBREVIATIONS

Multiply

foot (ft) 

cubic foot per second (ftYs) 

pound (Ib)

By

0.30481 

28.317 

.45

To obtain

meter (m) 

liter per second (L/s) 

kilogram (kg)

Temperature in degree Celsius (°C) can be converted to temperature in degree Fahrenheit (°F) by using the 

following equation:

°F = 9/5°C+32.

The following terms and abbreviations also are used in this report:

kilograms per day (kg/day) 

milligram per liter (mg/L) 

microgram per liter (^ig/L) 

millimoles per liter (mM/L) 

milliliters per minute (mL/min) 

milligram per second (mg/s)

Chapter D6

Quantification of Metal Loading by Tracer Injection and

Synoptic Sampling, 1997-98

By Briant A. Kimball, Robert L Runkel, Thomas E. Cleasby, and David A. Nimick

Abstract

Determination of the best sites for remediation of mine 

drainage requires an understanding of metal contributions 

from all sources in a watershed. A hydrologic framework to 

study metal loading in selected streams of the Boulder River 

watershed of Montana was established by a series of massloading studies of three impacted stream reaches. Each study 

used the tracer-dilution method in conjunction with synoptic 

sampling to determine the spatial distribution of discharge and 

concentration. Discharge and concentration data were then 

used to develop mass-loading profiles for the various metals of 

interest. Discharge and load profiles (1) identify the principal 

sources of load to the streams; (2) demonstrate the importance 

of unsampled, dispersed subsurface inflows; and (3) estimate 

the amount of attenuation. The two major sources of metal 

loading to the streams are the Crystal mine adit discharge in 

Uncle Sam Gulch and the Bullion mine adit in the Bullion 

Mine tributary. Other sources are small in comparison to these 

two. Along the 40,905-foot study reach of Cataract Creek, 

21.2 kilograms per day of zinc were added to the stream. 

About 75 percent of this load came from Uncle Sam Gulch, 

a principal tributary. By comparison, the adit discharge from 

the Bullion mine accounted for 2.8 kilograms per day of zinc, 

which was only about 20 percent of the zinc load coming from 

the Crystal mine adit in Uncle Sam Gulch.

About 34 percent of the zinc load in Cataract Creek 

occurred as unsampled inflow, including part of the load from 

Uncle Sam Gulch. Along the study reach, about 34 percent of 

the zinc load was removed to the stream bed. Similar details 

are available for other metals in each of the three streams 

studied. This watershed approach provides a detailed snapshot 

of metal load for the watershed to support remediation decisions, and quantifies processes affecting metal transport.

Introduction

Land-management agencies in the Boulder River watershed of Montana are charged with the task of reclaiming

abandoned mine lands. Numerous inactive mines contribute 

substantial metal loads and acidic waters to the streams that 

drain the Boulder River watershed. The affected streams are 

headwater systems that gain substantial amounts of water 

as they flow down valley. Sources of additional water range 

from well-defined tributary inflows to diffuse ground-water 

inflows that are not visible. The water quality associated with 

these sources also varies dramatically, from dilute mountain 

springs to metal-rich water emanating from mineralized areas. 

The challenge facing land-management agencies is thus one 

of source determination: For a given stream, what sources of 

water are most detrimental to water quality? This question is 

of paramount importance to land managers who must implement remedial actions subject to fiscal constraints.

The approach used in these studies to address the problem of source determination is based on two well-established 

techniques: the tracer-dilution method and synoptic sampling. 

The tracer-dilution method provides estimates of stream 

discharge that are in turn used to quantify the amount of water 

entering the stream through tributary and ground-water inflow. 

Synoptic sampling of instream and inflow chemistry provides 

a spatially detailed "snapshot" of stream-water quality. When 

used in unison, these techniques provide a description of the 

watershed that includes both discharge and concentration. Discharge and concentration data can then be used to determine 

the mass loading associated with various sources of water. 

Sources representing the greatest contributions in terms of 

mass loading can then be the target of remedial action.

Purpose and Scope

The purpose of this chapter is to describe the application 

of the combined tracer-dilution and synoptic-sampling method 

to selected stream reaches within the Boulder River watershed. 

Application of the method results in a set of mass-loading 

curves that illustrate the spatial distribution of the various 

inflow sources and the effects of the sources on instream water 

quality. The mass-loading curves are used to answer three 

basic questions. First, which sources have the greatest effect 

on stream-water quality in terms of the greatest contributions 

to constituent loads? Sources determined to be substantial in
198 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

terms of mass loading could be the subject of further study and 

candidates for remedial action. Second, are there substantial 

inflows that are primarily composed of diffuse ground-water 

inflow? Stream subreaches that are dominated by groundwater loading may not be amenable to remediation due to the 

lack of a well-defined surface-water inflow. Third, is there 

substantial instream attenuation of metal loads? Attenuation of 

metal loads by geochemical processes should be considered as 

part of the remedial design.

This chapter begins with a detailed account of the studies 

conducted on individual stream reaches within the watershed 

and the associated mass-loading curves. These studies were 

conducted over two field seasons (1997-98) during low flow. 

Despite the focus on the low-flow period, differences in the 

flow regimes arise as a result of yearly variability. The studies in Uncle Sam Gulch and the Bullion Mine tributary were 

conducted during a 2-week period in 1998.

Methods

The combined tracer-dilution and synoptic-sampling 

method has been applied to many streams in the Rocky Mountains (Bencala andMcKnight, 1987; Kimball, Broshears, and 

others, 1994; Kimball, 1997; Kimball and others, 1999, 2001, 

2002). The studies described herein were undertaken during 

low-flow conditions (generally August and September). Application of the method to low-flow conditions is an appropriate 

focus for two reasons. First, the mass-loading profile at low 

flow reflects the importance of metal sources that enter the 

stream on a continuous basis. Remedial actions that address 

the sources identified at low flow will, therefore, improve 

water quality during the entire year. Second, the pattern of 

metal loading at low flow indicates which sources contribute 

to high concentrations during the winter months when the 

most toxic conditions likely occur (Besser and Leib, 1999). 

During the winter months, the extent of dilution of mine 

drainage is less than during higher flow, and limits of toxicity are more likely to be exceeded (Besser and others, 2001). 

Although dissolved metal loads are greater during snowmelt 

runoff, true dissolved metal concentrations generally are lower 

(Nimick and Cleasby, this volume, Chapter D5) and the risk to 

aquatic life is not as great.

Tracer Injections and Stream Discharge

Quantifying discharge in mountain streams by the 

traditional velocity-area method1 (Rantz and others, 1982) is 

compromised because of the roughness of the streambed and 

the variability caused by pools and riffles (Jarrett, 1992). 

Further, a substantial percentage of discharge may flow

'Velocity-area discharge method. Physical measurement of discharge made 

by dividing a cross section of the flowing stream into at least 20 area increments and measuring velocity at the center of each increment. The sum gives 

the total discharge at that cross section.

through porous areas of the streambed that make up the 

hyporheic zone (Zellweger and others, 1989). Measurement 

of discharge with the velocity-area method does not account 

for flow through the hyporheic zone2 , and discharge estimated 

by that method may result in an underestimate of metal loads 

(Zellweger and others, 1989; Kimball, 1997). Another limitation of the velocity-area method for the characterization of 

metal loads is the time and personnel requirements associated 

with each discharge measurement. In the studies described 

herein, numerous (about 30-50) instream samples were collected during a single day to characterize stream chemistry at 

steady state. Velocity-area discharge measurements made in 

conjunction with sample collection at a large number of sites 

are limiting, if not impossible.

The tracer-dilution method is an alternative means of estimating discharge (Kilpatrick and Cobb, 1985). The tracer-dilution method uses an inert tracer that is continuously injected 

into the stream at a constant rate and concentration. With 

sufficient time, all parts of the stream, including side pools 

and the hyporheic zone, will become saturated with the tracer. 

Instream concentrations at a specific distance downstream will 

become constant (Kimball, 1997). When the stream reaches 

this condition during a tracer-injection, it is at a "plateau 

concentration." Decreases in plateau concentration along the 

length of the stream reflect the dilution of tracer by additional 

water entering the channel from surface and ground-water 

inflows. This dilution allows for the calculation of discharge 

at each stream site. Application of the tracer-dilution method 

addresses both of the problems previously noted: (1) the tracer 

enters porous areas of the streambed such that flow through 

the hyporheic zone also is measured; and (2) collection of 

tracer samples when plateau concentrations are achieved 

provides the ability to obtain discharge estimates at numerous 

stream sites.

Successful implementation of the tracer-dilution method 

is dependent on two factors. First and foremost, the injected 

tracer must be transported through the stream reach in a 

conservative manner; concentrations of the tracer should be 

unaffected by biogeochemical reactions. Previous studies 

have documented the transport and chemistry of inorganic 

salt tracers (Bencala and others, 1990; Broshears and others, 

1993; Zellweger, 1994). Because of the conservative behavior of chloride in most natural waters and the availability of 

inexpensive sodium chloride salt, NaCl was used in the studies 

described herein. A second important factor is the ability to 

maintain a constant rate of injection during the study. For the 

studies described here, tracer injections were controlled with 

precision metering pumps linked to a Campbell CR-10 data 

logger. Use of the data logger provides a means to maintain a 

constant injection rate as battery voltage decreases. Additional 

details on specific tracer injections are included in the "Subbasin Studies" section.

2Hyporheic zone. That area of the streambed alluvium that contains at least 

10 percent stream water as a result of exchange with the stream.
Quantification of Metal Loading 199

Kilpatrick and Cobb (1985) presented a simple massbalance equation that considers the concentration and injection rate of the added tracer. Discharge at the first synoptic site 

downstream from the injection is given by:

QD =

(1)

where QINJ = the injection rate,

CINJ = the injectate concentration,

CD = the tracer concentration at the plateau, and

C0 = the naturally occurring concentration of the

tracer upstream from the injection.

This equation is based on two assumptions: that (1) 

negligible inflow enters the stream between the injection site 

and the first synoptic site, and (2) the injection concentration 

is much greater than C0. Discharge estimates at the remaining 

synoptic sites are given by:

QD =

Q — C

(2)

where CL = tracer concentration in the inflow waters entering a specified subreach,

Cv = the plateau tracer concentration for the synoptic 

site immediately upstream, and

Qu = the stream discharge for the synoptic site 

immediately upstream.

Inflow chloride concentrations in some subreaches 

represent well-defined surface inflows that are easily sampled. 

In other subreaches, inflow waters may be primarily diffuse ground-water inflows that are difficult or impossible to 

sample. These subreaches require estimation of the chloride 

inflow concentration, a process that can lead to uncertainty 

in discharge calculations. For the three studies described 

here, chloride values in subreaches that are dominated by 

unsampled ground-water inflow had to be estimated. The 

uniformity in surface-inflow chloride concentrations has a 

negligible effect on discharge estimates. Note that the problem 

of estimating chloride for systems with variable background 

concentrations may be avoided by conducting a pre-synoptic 

sampling of the stream (Kimball and others, 2001). At the 

start and end of the injection, samples generally are collected 

manually at intervals of 5 or 10 minutes at three to five sites, 

chosen from among the synoptic sampling sites, to define the 

arrival and departure of the tracer. During the plateau period, 

hourly samples are taken by automatic samplers at the same 

sites, which are called transport sites. These samples provide 

information for transport modeling and allow for resolving 

temporal effects from storms that could occur during synoptic 

sampling.

Synoptic Sampling and Analytical Methods

The spatial distribution of metal sources may be characterized by synoptic sampling. Under ideal conditions, samples 

at all of the sampling locations would be collected simultaneously, providing a description of stream-water quality at steady 

state. Personnel limitations generally preclude simultaneous 

sample collection, but the synoptic studies described in the 

following text provide an approximate means of describing 

steady-state conditions. This approximation is achieved by 

the collection of samples throughout a relatively short period 

(less than 8 hr) and by conducting the studies during low-flow 

conditions such that the effects of diurnal flow variation are 

minimized. By approximating steady-state conditions, synoptic sampling provides a spatially intensive "snapshot" of chemistry and discharge that is used to quantify instream loads.

During a synoptic study, samples are collected at several 

stream and inflow sites. Stream sites along the study reach are 

spaced such that they bracket the sampled inflows and areas 

of likely subsurface inflow. Subreaches that are bracketed by 

two adjacent stream sites are referred to as stream segments. 

The intent of this bracketing is to capture the changes in load 

that are attributable to visible surface inflow and (or) diffuse 

subsurface inflow within each segment. At this level of spatial 

detail, changes in stream chemistry and discharge between 

stream sampling sites reflect a net metal load for specific 

segments, although the loads cannot always be attributed to 

specific sources.

For each of the following studies, stream and inflow 

samples were collected at numerous predetermined locations, beginning at the downstream end of the study reach and 

ending upstream of the tracer-injection. This downstreamto-upstream sampling order was followed in order to avoid 

disturbing streambed materials. Inflow and stream sites that 

were considered well mixed were sampled by using grab techniques. Stream sites that were not well mixed were sampled 

by equal width integration3 (Ward and Harr, 1990). Water 

temperature was measured on site and the collected samples 

were transported to a central location for further processing. 

Samples were processed at a central location to measure pH 

and specific conductance and to divide the sample into the following bottles: a raw (unfiltered) unacidified sample (RU), a 

raw acidified sample (RA), a filtered unacidified sample (FU), 

a filtered acidified sample (FA), and a ultrafiltered acidified 

sample (UFA).

Specific conductance and pH were determined from 

the RU sample within hours of sample collection. Filtration 

included tangential-flow filtration through 0.45-|am membranes (FU and FA samples) and ultrafiltration by using a 

10,000-Dalton molecular weight membrane (UFA sample).

3Equal-width integration. Sample collected by moving a depth-integrating 

sampler, like a USGS DH-81, down and up at a constant rate at equal increments of width across a stream. Thus, those parts of the stream that have 

greater discharge will fill the bottle the most.
200 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Metal concentrations for the RA, FA, and UFA samples were 

determined by inductively coupled plasma-atomic emission 

spectrometry (Lichte and others, 1987). Anion concentrations 

were determined from FU samples by using ion chromatography (Kimball and others, 1999). Ferrous iron was determined 

colorimetrically from the UFA samples (Kimball and others, 

1992), and total alkalinity was determined by titration.

Use of two filter sizes provides for three different operationally defined concentrations for each metal. The unfiltered 

sample (RA) provides a measure of the total-recoverable metal 

concentration (dissolved + colloidal), and the ultrafiltrate concentration (UFA) is considered the dissolved metal concentration. The 0.45-|um concentration (FA) is used for comparison 

purposes. Colloidal metal concentrations are defined as the 

difference between the total-recoverable (RA) and the ultrafiltrate metal concentrations (UFA) for stream samples (Kimball 

and others, 1995).

Principal Components Analysis

An important objective of synoptic sampling is to 

recognize patterns or chemical characteristics that indicate 

the sources of mine drainage. Water-rock interactions with 

different mineral assemblages in source areas create distinct 

chemical signatures among the inflows. The signatures may 

produce groups of inflow samples that are distinguished by 

their similarities. Groups of stream samples may be linked 

to inflow groups, indicating which inflows influence stream 

chemistry. Distinctions among inflow groups also may lead to 

an understanding of differences in drainage from mined and 

nonmined areas.

Patterns in the chemistry, including the pH, of synoptic 

samples are displayed by using Principal Components Analysis (PCA). A principal component represents a transformed 

axis that is a linear combination of the original variables 

(Daultrey, 1976; Davis, 1986). The transformation to a new 

axis is not statistical, but is simply a rotation (in multi-dimensional space) that orients the data points so that we observe the 

greatest amount of difference (or variance) among them. The 

rotation does not change the relation of one sample to another; 

it only changes how we view the samples. For example, if the 

surface of a framed picture were given jt, y, and z coordinates 

to represent its surface morphology, PCA would rotate the 

picture so that one would be looking at it straight on instead of 

at some angle. The x and y variables (height and width of the 

picture) are much greater than the depth (which would mostly 

be due to the frame). Conceptually, PCA rotates chemical data 

in a similar manner, and this helps one visualize the greatest distinctions among groups of samples. It also emphasizes 

distinct outlier samples. The first two principal components 

generally show enough of the variance in a data set to distinguish groups among the samples. Each sample is related to a 

principal component by its score on that component, which is 

the coordinate of the original data point on the new principal 

component axis.

PCA also can emphasize the physical and chemical processes that are responsible for the distinctions among groups 

of samples. Each chemical constituent has a correlation to the 

new principal components, called a loading in the jargon of 

PCA. These correlations can be expressed as arrows or vectors 

on a plot of sample scores. By combining the classification 

information of scores with the process information from loadings, a biplot is created. Biplots are used to present results of 

PCA for each mass-loading study.

Chemical reactions and mixing processes often result in 

linear relations among chemical constituents. To emphasize 

the linear relations among variables, the chemical concentration of each constituent, expressed in millimoles per liter, 

was log transformed. This improves correlations that may be 

related to stoichiometries of particular chemical reactions. It 

is the products of chemical reactions that end up as dissolved 

constituents in the stream and are sampled in a water-quality 

study. Mole ratios of those products provide mass-balance 

evidence of the water-rock reactions that may account for the 

observed chemistry. PCA calculations were carried out with 

the U.S. Geological Survey Statpac programs that include 

special scaling options to improve the biplot (Grundy and 

Miesch, 1987).

Constituent Loads

Given estimates of stream discharge and metal concentration, solute load at each stream site can be quantified as the 

simple product of discharge and concentration. This calculation leads to a longitudinal profile of the sampled instream 

load. Any change in load between a pair of stream sites 

accounts for the gain or loss of solute load for that segment. 

Gains in solute load imply the existence of a source for the 

solute that reaches the stream between the two stream sites. 

Instream load also can decrease within a stream segment, indicating a net loss of the solute as a result of chemical or biological processes. The sum of all the increases in load between 

sampling sites along the study reach produces cumulative 

instream load. At the end of the study reach, the cumulative 

instream load is an estimate of the total load of solute added to 

the stream; this estimate is likely a minimum estimate because 

it only measures the net loading between sites. Some of the 

load in that stream segment could be lost through attenuation 

within an individual stream segment.

The change in discharge between stream sites is used in a 

second approach to calculating loads. The change in discharge 

between two stream sites, multiplied by solute concentration of an inflow sample, provides an estimate of the inflow 

load for a stream segment. The sum of the inflow loads for all 

sampled inflows provides a longitudinal profile of the cumulative inflow load, which indicates how well the sampled inflows 

account for the load measured within the stream. The cumulative instream and cumulative inflow profiles are equivalent if 

the sampled inflows are representative of the inflows that enter 

the stream. This situation rarely occurs, however, because
Quantification of Metal Loading 201

inflows to streams include both surface and subsurface inflow. 

Greater subsurface concentrations would cause the profile of 

cumulative instream load to be more than the profile of cumulative inflow load.

Load profiles provide not only information to evaluate the 

location and magnitude of metal loading to the stream, but also 

help in understanding and quantifying watershed processes. 

The loading profile is a view from the stream; it accounts for 

the loads that actually reach the stream. A particular mine adit 

away from the stream may have a greater load at its adit, but 

if that load is attenuated before it reaches the stream, it is not 

accounted for within the load profile. Thus, inflow samples are 

obtained near the stream to represent the net delivery of metals 

to the stream from various sources. The three ways to account 

for loads from the watershed are based on instream and inflow 

loads. First, the sampled instream load provides information 

about the relative importance of metal sources in terms of 

which stream segments contribute the greatest loads. The level 

of detail from synoptic sampling allows individual increases, 

measured in each stream segment, to be viewed in the context 

of the whole watershed. Second, the difference between the 

cumulative instream and cumulative inflow loads provides 

information about the location of unsampled, or possible 

ground-water inflows. Third, the difference between the cumulative instream load and the sampled instream load provides 

information about the extent of attenuation of solutes. All this 

information is available on the scale of individual stream segments and the scale of the entire study reach.

Subbasin Studies

Complete chemical data for synoptic samples that were 

collected in each of the subbasin studies are presented in the 

database on CD-ROM. A description of sampling sites and 

summaries of chemical data are presented here for each subbasin. Locations of all the mines discussed in this chapter are 

in Martin (this volume, Chapter D3).

Cataract Creek Basin

Study Area and Experimental Design

The experimental design of the tracer-injection study in 

Cataract Creek is described in Cleasby and others (2000). The 

study reach started 3,000 ft upstream from Hoodoo Creek and 

ended at the confluence with the Boulder River (fig. 1); the 

total distance is more than 40,000 ft and was divided into 

44 stream segments. Inflow samples were collected in 20 of 

the stream segments; 23 inflows were sampled in all. Downstream distance for each of the segments and inflows, along 

with site descriptions, are listed in table 1.

A sodium chloride tracer with a chloride concentration 

of 133,200 mg/L was injected at a rate of 435 mL/min. This 

provided a clear chloride signal that was elevated above background concentrations (fig. 2). Because the inflow chloride 

concentrations were low, but not constant, equation 2 was 

used to calculate discharge (fig. 2). The increase in discharge 

along the study reach was 12.5 ft3/s. Discharge increased by 

4.8 ft3/s in those segments that had no inflow samples; this 

was 38 percent of the total increase in discharge, which was a 

considerable ground-water component to the increase in flow. 

The path of the creek generally follows the structural control 

of a major fault (O'Neill and others, this volume, Chapter Dl, 

pi. 1), and the reach is predicted to be a gaining reach based on 

the lineament and fracture-density analysis of McDougal and 

others (this volume, Chapter D9).

Chemical Characterization of Synoptic Samples

Synoptic sampling of inflows provides a range of chemistry that affects the stream and provides a context for the 

changes in stream chemistry and solute loads. In a watershed 

affected by mine drainage that has outcrops of rocks with acidneutralizing capacity, inflow chemistry can range from acidic 

and metal-rich to alkaline and essentially metal-free. Both 

kinds of inflow chemistries can affect the stream chemistry.

Stream water in Cataract Creek was a calcium bicarbonate type, reflecting the chemical weathering of bedrock in the 

watershed (Nimick and Cleasby, this volume, Chapter D5). 

The tracer overwhelmed baseline concentrations of sodium 

and chloride in the stream. The baseline concentrations of 

inflows, however, were approximately 3 mg/L sodium and 

0.3 mg/L chloride. This baseline chloride concentration was 

about 10 times lower than the chloride concentration at the 

final stream sampling site (fig. 2). The alkalinity of Cataract 

Creek remained nearly constant along the entire reach (fig. 3). 

Concentration of the other major ions increased slightly 

downstream from Uncle Sam Gulch; changes in calcium 

and sulfate were the greatest (fig. 3). Calcium concentrations upstream from Uncle Sam Gulch averaged 12.4 mg/L, 

and 15.0 mg/L downstream; sulfate concentrations averaged 

9.1 mg/L upstream and 16.8 mg/L downstream. The greater 

change in sulfate mostly represents the mine-drainage inputs 

from Uncle Sam Gulch.

Several metals occurred with measurable concentrations. 

Aluminum, copper, iron, manganese, and zinc concentrations 

were substantially above detection limits. Cadmium, nickel, 

and lead concentrations mostly were near limits of detection. 

Although no great variation occurred in major-ion concentrations or pH along the study reach, substantial differences did 

occur in metal concentrations upstream and downstream from 

Uncle Sam Gulch, with higher concentrations occurring downstream (fig. 4). Concentrations of aluminum, copper, 

and zinc that were less than the detection limits are not 

plotted; therefore, the lines are not all continuous. Average
202 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

46°20'

46°

,•YT-1

Crystal

JEFFERSON CO

Tracer-injection 

unnamed mine 1

s Apollo ,., I

"^\ J2,490 

"5 Eva May t 3,050

/ 4,400^3,450"?? 

Cataract y( 3,850 

andtailifigs «/'" 4,660 

^;5C^ T-2

"\ 10,655/X v 4,940 

1*K605 'J

Hattie v Lower 

Ferguson^ Hattie

fj . L/nc/e

Sam

'

/- 14,055

714,855

v/' > 

15,660, ^

? T-3 //

>,X U645 ' '-'

"<V V.

Boulder 

Chief

18",545 x' 

19 730 >* ""-...- - '

**i-^5f Morning Glory 

20,050^19,700

Q\ ST-4 

/ ( 24,715

26,371^

r,J. 27,773^'

Ouster

Hiawatha \

BEAVERHEAD-DEERLODGE 

NATIONAL FOREST

%>^ 29,757 ''^ X *1 "i,V" ' —"" "TM"" t~~ '/*"" / 

j 's Mantle / !. •'

T-5l ),-x^ 

34,105 !

] «ZV"34,155 

/?t/?/? ^ South Mantle

Basin

T-6 

40,905

34,105

EXPLANATION

— Sampling site and distance 

downstream from injection 

site, in feet

T-5 _ Tracer-monitoring site and distance 

downstream from injection 

site, in feet

Phantom ., 3C Inactive mine or prospect

T7N 

T6N

R5W

1 MILE

I

T

1 KILOMETER

Figure 1. Location of study reach, selected inactive mines or prospects, and selected sampling sites, Cataract Creek 

drainage (modified from Cleasby and others, 2000).
Quantification of Metal Loading 203

Table 1. Segment number, distance along study reach, source, site description, and selected water-quality characteristics of 

water from synoptic sampling sites, Cataract Creek, August 13,1997.

[Dist, distance, in feet along the study reach; source: S, stream; RBI, right-bank inflow; LBI, left-bank inflow; Q, discharge, in liters per second;

T, temperature, in degrees Celsius; pH, in standard units; Ksc, specific conductance, in microsiemens per centimeter; Cl, chloride, in milligrams per liter]

Segment 

number

SOI

T01

S02

803

T02

S04

T03

805

T04

S06

S07

T05

SOS

S09

T06

S10

Sll

S12

S13

T07

S14

T08

S15

T09

S16

T10

Til

S17

T12

S18

S19

S20

T13

S21

T14

T15

S22

S23

S24

S25

S26

T16

S27

S28

S29

T17

S30

S31

Dist

150

160

850

1,370

1,615

1,690

1,691

2,490

3,050

3,450

3,850

4,400

4,660

4,940

4,941

5,940

6,800

7,900

8,700

8,820

9,220

9,225

10,380

10,655

11,055

11,605

11,795

12,115

12,120

13,255

14,055

14,855

14,860

15,655

15,660

15,845

16,845

17,645

18,545

19,245

19,700

19,730

20,050

20,730

21,130

21,315

21,715

22,315

Source

S

RBI

S

S

RBI

S

RBI

S

LBI

S

S

RBI

S

S

RBI

S

S

S

S

RBI

S

RBI

S

RBI

S

RBI

LBI

S

LBI

S

S

S

LBI

S

RBI

RBI

S

S

S

S

S

RBI

S

S

S

LBI

S

S

Site description

First site below injection

Right-bank inflow

Tl transport site in canyon

Above right-bank mine dump

Right-bank inflow from mine dump

Below mine dump at Apollo mine

Right-bank inflow

Above mine dump at Eva May mine

Hoodoo Creek on left bank

Below Hoodoo Creek

Above Eva May mine tailings

Eva May tailings inflow

Adjacent to Eva May tailings pile

T2 transport site below Eva May mine

From pipe under road

Below curve with overbank tailings

Along bend

Below old cabin

Below mine dump, at Cataract mine tailings

Below Cataract mine dump

Adjacent to Cataract mine tailings

Cataract mine tailings with iron stains

End of large flood plain

Right-bank inflow

Adjacent to ponded water on right bank

Inflow with iron stains

Boulder Chief and Ida M. mines

Above large clear-cut area

Left-bank inflow

Above Lower Hattie Ferguson mine

Below Lower Hattie Ferguson mine

Above left-bank inflow

Left-bank inflow

Below Upper Hattie Ferguson mine

Upper Hattie Ferguson mine

Right-bank inflow

Below inflows

T3 transport site below logging-road ford

Above biological sampling site

Above Morning Glory mine

Below Morning Glory mine

Uncle Sam Gulch

Below Uncle Sam Gulch

Below cabin and tailings pile on right bank

Check for reaction below Uncle Sam Gulch

Waste-rock piles on both banks

Along cascades below small mine dumps

Above rock wall

Q

111

4.0

121

124

4.0

130

0.1

130

40.0

170

174

8.0

182

185

2.0

187

189

191

193

5.0

198

3.5

205

10.0

215

4.5

4.5

224

7.0

231

236

239

3.0

242

4.0

4.0

250

261

270

276

276

50.0

326

336

336

2.0

338

338

pH

7.71

7.62

7.85

7.82

7.59

7.87

7.81

7.83

7.75

7.82

7.83

7.48

7.83

7.73

7.71

7.74

7.74

7.80

7.71

7.26

7.66

7.20

7.52

7.51

7.38

6.61

7.57

7.68

7.63

7.77

7.82

7.81

7.89

7.44

7.59

7.45

7.81

7.72

7.80

7.64

7.83

7.32

7.63

7.81

7.61

8.10

7.83

7.80

Ksc

110

70

108

106

190

107

175

107

106

106

105

100

106

107

92

108

107

108

108

65

108

88

110

57

109

130

122

109

143

111

113

113

84

112

116

135

113

114

116

116

116

134

119

118

118

409

118

118

Cl

8.28

<.l

8.26

8.08

<.l

7.72

<.l

7.74

<.l

5.99

5.85

<.l

5.61

5.52

<.l

5.46

5.42

5.37

5.31

<.l

5.20

<.l

5.02

<.l

4.81

<.l

<.l

4.63

<.l

4.49

4.42

4.37

<.l

4.31

<.l

<.l

4.19

4.05

3.93

3.85

3.92

<.l

3.30

3.22

3.22

<.l

3.21

3.21
204 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 1. Segment number, distance along study reach, source, site description, and selected water-quality characteristics of 

water from synoptic sampling sites, Cataract Creek, August 13,1997.—Continued

Segment 

number

T18 

T19 

S32 

S33 

T20 

S34 

S35

S36

Segment 

number

T21

S37

S38

S39

T22

S40

S41

S42

S43

T23

S44

S45

Dist Source Site description

22,565 LBI Left-bank inflow 

22,715 LBI Left-bank inflow 

22,915 S Below small inflow 

23,715 S At old lean-to 

24,495 RBI Draining oxbows 

24,715 S T4 transport site above canyon 

25,215 S Above start of canyon

26,335 S Above Deer Creek

Dist

26,370

26,590

26,970

27,775

29,760

29,970

31,470

32,970

34,105

34,155

34,355

40,905

Source

RB

S

S

S

LB

S

S

S

S

LB

S

S

Site description

Deer Creek

Below Deer Creek

Below large concrete bridge

Below second wooden bridge

Left-bank inflow

Below old cabin on right bank

Along cascade reach

Wide section of canyon

T5 transport site above Big Limber Gulch

Big Limber Creek

Below Big Limber Creek

T6 transport site Cataract Creek at mouth

Q

11.0

360

361

364

13.0

377

382

387

394

36.0

430

472

Q pH Ksc

0.1 7.77 222 

0.1 7.19 220 

338 7.65 120 

342 7.74 123 

3.0 7.20 279 

345 7.65 123 

349 7.70 124

349

T

11.5

13.5

13.5

13.5

11.5

13.5

13.5

13.5

13.5

14.5

14.0

14.8

pH

8.14

7.88

8.01

8.23

8.48

7.40

7.82

7.84

8.00

7.84

7.83

126

Ksc

188

126

126

126

500

126

128

128

128

280

130

131

Cl

<.l 

<.l

3.21 

3.18 

<.l 

3.16 

3.13

3.13

Cl

<.l

3.05

3.04

3.02

<.l

2.99

2.96

2.93

2.89

<.l

2.79

2.59

concentrations of total-recoverable aluminum increased from 

less than 50 to about 80 fig/L at S27 (fig. 44). All of the filtered copper concentrations were less than detection, and only 

a few sites downstream from Uncle Sam Gulch had totalrecoverable concentrations greater than detection (fig. 45). 

Copper concentrations of Uncle Sam Gulch and Big Limber 

Gulch were greater than 100 fig/L. Total-recoverable concentrations of iron decreased from 300 to 249 fig/L (fig. 4C). 

Filtered and total-recoverable zinc concentrations were near 

detection limits from the injection site to the area of the Eva 

May mine tailings (SOS). Downstream from SOS, zinc concentrations were measurable all the way to S26, upstream 

from Uncle Sam Gulch. Downstream from Uncle Sam Gulch, 

filtered zinc concentration increased an average of 34 to 

461 |Ug/L (fig. 4D). Concentrations of total manganese 

increased from an average of 12 to 75 |Ug/L at S27, and had 

a pattern similar to that of zinc. Concentrations of cadmium, 

lead, and nickel were too low to observe patterns.

Nimick and Cleasby (this volume, Chapter D5) indicate 

those parts of Cataract Creek where metal concentrations 

exceeded instream aquatic life standards for acute and chronic 

toxicity. The tracer-study results are comparable to their 

findings.

The importance of the iron and aluminum colloids is 

seen by their impact on other metals. Total-recoverable 

copper concentrations were substantially higher downstream 

from Uncle Sam Gulch, most likely because copper was 

sorbed to the iron colloids (fig. 45). Total-recoverable zinc 

concentrations increased from near the detection limit to an 

average of 461 fig/L downstream from Uncle Sam Gulch, 

and about 14 percent of that total-recoverable zinc was 

transported in the colloidal phase (fig. 4D). The presence of 

copper and zinc in the colloidal material could have effects 

on the chronic toxicity of the stream (Clements, 1994; Besser 

and others, 2001). The colloidal concentrations contribute 

to the high concentrations of copper and zinc in the bed 

sediments downstream from Uncle Sam Gulch (Church and 

others, this volume, Chapter D8).

On the basis of principal components analysis (Kimball and others, 2001), differences in chemical composition 

among inflows along Cataract Creek distinguish five groups 

among the synoptic samples (fig. 5). Three of these groups 

represent both stream and inflow samples, and two include 

only inflows. The combination of stream and inflow samples 

in a group may explain two conditions. First, for stream 

samples collected upstream of mine-drainage inflows, the 

chemical character of the stream samples should resemble
Quantification of Metal Loading 205

DC

LLJ

Hi

DC 

LLJ 

Q_

C/5

DC 

CD

LU 

O

z 

o 

o

LU 

Q

DC

g

n: 

o

Chloride, stream 

I Chloride, inflow

Chloride, smoothed stream

—*— Discharge, stream 

Discharge, inflow

5,000 10,000 15,000 20,000 25,000 30,000 35,000 

DISTANCE ALONG STUDY REACH, IN FEET

40,000

0

45,000

Figure 2.

table 1.

Injected chloride concentration and calculated discharge, Cataract Creek, August 1997. Numbers are segment numbers,

inflows that drain the same unaltered bedrock in the catchment. Second, where an inflow dramatically changes the 

character of the stream water, that inflow may determine the 

character of stream samples for some distance downstream 

until additional inflows or instream chemical reactions cause 

further change.

The vectors indicate the chemical differences among 

groups of samples (fig. 5). For example, samples that plot to 

the upper left are higher in metals, while samples that plot to 

the upper right have higher concentrations of the alkaline-earth

metals and sulfate. Group 1 represents samples somewhat 

affected by mining, and includes samples upstream from 

Hoodoo Creek and inflow T08 (table 2). Group 2 includes 

most stream sites upstream from Uncle Sam Gulch and most 

of the inflows along that reach. These samples plot in the 

direction of slightly greater metal concentrations than group 

1, and several of these inflows are draining areas that include 

tailings. Group 2 represents inflows and stream sites upstream 

from Uncle Sam Gulch that have higher concentrations of 

alkaline-earth metals and sulfate. Group 3 represents the
206 Environmental Effects of Historical Mining, Boulder River Watershed, Montana 

Table 2. Average composition of groups from principal components analysis of synoptic samples. Cataract Creek, August 1997.

[pH, in standard units; all concentrations in milligrams per liter]

Solute Group 1 

Limited effects of 

mining, upstream 

from Hoodoo Creek

Number of samples

pH

Sulfate

Calcium

Magnesium

Aluminum

Cadmium

Copper

Iron

Manganese

Nickel

Lead

Strontium

Zinc

13

7.70

10.8

12.5

2.43

.040

.003

.019

.222

.033

.003

.002

.U95

.154

Group 2 

Stream samples 

upstream from 

Uncle Sam Gulch

24

7.63

12.7

13.7

2.68

.043

.005

.021

.248

.047

.004

.003

.118

.243

Group 3 

Stream samples 

downstream from 

Uncle Sam Gulch

20

7.76

13.3

14.6

2.92

.039

.003

.022

.311

.062

.003

.002

.105

.234

Group 4 

Inflows affected 

by alkaline-earth 

weathering

9

7.64

29.9

33.4

5.74

.025

.005

.028

.086

.145

.001

.001

.233

.173

Group 5 

Inflows from 

Big Limber Gulch 

area

2

8.29

38.3

48.3

9.46

.001

.001

.003

.004

.031

.001

.001

.370

.001

change in composition downstream from Uncle Sam Gulch. 

The sample from Uncle Sam Gulch, T16, was the only inflow 

sample in group 3. It is grouped with the downstream samples 

because it has a great influence on the chemistry of those 

stream samples. Stream samples in group 3 plot between the 

stream samples of group 2 and inflow T16; this indicates the 

change that resulted from the inflow of Uncle Sam Gulch. The 

vectors around T16 indicate that it is mostly a shift in cadmium, copper, manganese, and zinc. Groups 4 and 5 include 

only inflow samples, representing higher concentrations of 

alkaline-earth metals and sulfate, but not contributing metals.

Load Profiles

A summary of the net change in load for each segment is 

listed in table 3, along with a summary of calculations for the 

whole study reach. Cumulative instream loads provide the best 

estimate of the total loading for an element in a study reach. 

The cumulative instream load for the selected constituents 

in table 3 varies considerably. Sulfate load was the greatest, 

more than 720 kg/day, while copper load was only 2 kg/day. 

Among the metals, zinc had the greatest cumulative load, with 

17 kg/day. The details of this loading are illustrated in load 

profiles and bar charts showing summaries of surface inflow, 

unsampled inflow, and net losses for individual stream segments (figs. 6-11).

There are differences among the profiles of metal and 

sulfate loading along the study reach of Cataract Creek. The 

two extreme profiles were those of sulfate (fig. 6) and zinc 

(fig. 7). The profile of sulfate shows loading in many stream 

segments all along the study reach. The resulting profile is a

broad gradual increase in the cumulative instream load, punctuated by the tributary inflows at Hoodoo Creek (S06), Uncle 

Sam Gulch (S27), and Big Limber Gulch (S44). The most 

plausible cause of this profile is the contribution from weathering reactions throughout the watershed. Sulfate most likely has 

a mineralogical residence in sulfide minerals associated with 

alteration in the watershed. However, it is most likely more 

widespread than the metals associated with ore deposits.

At the other extreme, zinc loading was dominated by a 

large loading in one stream segment, the inflow of Uncle Sam 

Gulch (fig. 7). There were a few other, much smaller loads 

from stream segments, but none compares with the loading 

from Uncle Sam Gulch. This pattern results from the adit 

drainage of the Crystal mine into Uncle Sam Gulch (Nimick 

and Cleasby, this volume, Chapter D5).

These two patterns of sulfate and zinc load profiles 

represent different mixtures of weathering processes and mine 

drainage in the watershed. Profiles of other metals have some 

differences from these two that mostly result from the conservative or reactive behavior of the metals once they have been 

added to the stream. Manganese loading was similar to that 

of zinc, and the load from the segment containing Uncle Sam 

Gulch (S27) dominated the profile (fig. 8). Downstream from 

Uncle Sam Gulch, the manganese load decreased slightly, but 

no transfer of manganese to the colloidal phase took place. 

Instead, manganese was lost to the streambed, probably 

through sorption to streambed materials. A similar pattern was 

observed for manganese in Little Cottonwood Creek, Utah, 

where the pH was comparable to that of Cataract Creek 

(Kimball and others, 2001).
Quantification of Metal Loading 207

200

Alkalinity, stream 

Alkalinity, inflow 

Calcium, stream 

Calcium, inflow 

Sulfate, stream 

Sulfate, inflow

7,000 14,000 21,000 28,000 35,000

DISTANCE ALONG STUDY REACH, IN FEET

Figure 3. Variation of alkalinity, calcium, and sulfate concentrations with distance. Cataract Creek, August 1997.

42,000
208 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

4 (WS) ipmO J«»qu<n Big

(iES) laaJD Jaaa

(LZS) IPIIQ "<BS spun

«• 

*

(6is)auiui uosnBjaj SIUBH

(SOS) sBLi|iBj AB|/\| BA3

(90S) 1«»JD oopooH

1 1 1 1 lAl t

(90S) >|aa-"D oopooH

,,, , , , i IIMI |

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(6 IS) 8U!UJ uosnBjaj SJUBH

(90S) 'laa-'D oopooH

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(90S) 133-0 oopooH

I i i I i

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LU 

DC

O

z 

o

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<

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o

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i.

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(6LS) sujUJ uosn6jaj ajUBH 1

(80S) s6u!l!Bl ABWBA3 :

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8 o

00 <f w 2

DC 

Q

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LU 

O

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U31H U3d SI/MVUDOyOII/M Nl 'NOI1VU1N30NOO
Quantification of Metal Loading 209

-3 -2

SCALED PRINCIPAL COMPONENT 1 LOADINGS 

-101234567 10

\J

4

3

LJJ 

CC

O 9

0

(/)

esi

hZ

LJJ

§1

D_

O

0

_1

oJ O

0

z

DC 

D_

Q

O

(/)

-2

-3

-4

*• Group 

"& Group

^ Group

^ Group

O Group

~ & "& Group

A O Group

O ^ !f "A" Group ^ O 0°

O

0 0° °t

»

Cadmium Zmc O

^X. /Manganese Sulfete + 

Copper .^^ ^

*C vi 7

\. ^«L / Magnesium

Aluminum ^^ ^^\ / ^^^ Strontium

^^v^^A /^^^^^ Calcium

^s^^\ fj^P'^

Iron -^ ——— __^^^^^

Nickel^^;^^^

1 I 1 1 1 I 1 I 1 ,

1

1, inflows

2

2, inflows

3

3, inflows ~~

4

5, inflows

pt w

~

X^ft^ Hydrogen ion <{>

^r. ^0^PP^

Lead A ^

A

o ^

" f * * * *

*

1 I I I I 1 I I I I 1 I I I I

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0

Z

CC.

D_

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-3

yl

5 6 7 8 9 10

SCALED PRINCIPAL COMPONENT 1 SCORES

Figure 5. Biplot of principal component scores for synoptic samples and loadings for chemical constituents, Cataract Creek, 

August 1997.
210 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

<

Q 

CC.

C/)

800

700

600

•-A— Dissolved instream load 

"•"- Cumulative instream load 

~"~ Cumulative inflow load

21,000 28,000 35,000 42,000

200

Si 150 

a.

c/)

DC

O

_J

5

I

o

100

Surface-water inflow 

I\X1 Dispersed, subsurface inflow 

I I Loss

Q 50 

O

C/)

_LL

B

7,000 14,000 21,000 28,000

DISTANCE ALONG STUDY REACH, IN FEET

35,000

V) •

\ \ \ \ \ \ \ \

42,000

Figure 6. Variation of A, sulfate load with distance, and B, changes in load for individual stream segments, Cataract Creek, 

August 1997.
Quantification of Metal Loading 211

IO

16

Q 

cc 14

LU 

Q_

C/D 12

^f

S 10

0

5 8

Z

O 6

^

O

_i

0 4

Z

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2

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-

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0

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0} 

03k_

; o

! o 

o

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X

—A— Dissolved instream load 

— T— Colloidal instream load

— ^— Total instream load 

— ^ Cumulative instream load 

—— — Cumulative inflow load

00 

0

C/5

>

o

s-

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CO

03

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n:

f»^^^dc•B.^

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C/5

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1

01

U

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M

,,,,,,. t~n

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t

A 0 7,000 14,000 A

18

< 16

Q

LU 14

Q_

C/D

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DCS 10

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I 0

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_ 1 1 . 1 1 1 1 1 1 1 1

_

• i

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- l\\1 Dispersed, subsurface inflow

^^| Loss

~-

~

_

-

_

-

-

_

L

-

• i i i i i i i i i i

0 6,000 12,000

B

, ,

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24,000 30,000 36,000 42,000

DISTANCE ALONG STUDY REACH, IN FEET 

Figure 7. Variation of A, zinc load with distance, and B, changes in load for individual stream segments, Cataract Creek, August 1997.
212 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

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6,000 12,000 18,000 24,000 30,000 

DISTANCE ALONG STUDY REACH, IN FEET

36,000 42,000

Figure 8. Variation of A, manganese load with distance, and B, changes in load for individual stream segments, Cataract Creek, 

August 1997.
Quantification of Metal Loading 213

DC

LJJ 4 

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—A— Dissolved instream load 

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—— • Total instream load 

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6,000 12,000 18,000 24,000 30,000 

DISTANCE ALONG STUDY REACH, IN FEET

36,000 42,000

Figure 9. Variation of A, aluminum load with distance, and B, changes in load for individual stream segments, Cataract Creek, 

August 1997.
214 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

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18,000 24,000 30,000 36,000 42,000

DISTANCE ALONG STUDY REACH, IN FEET

Figure 10. Variation of A, copper load with distance, and B, changes in load for individual stream segments, Cataract Creek, 

August 1997.
Quantification of Metal Loading 215

14

>• 12

DC 

LU

10

Dissolved instream load 

Colloidal instream load 

Total instream load 

Cumulative instream load 

Cumulative inflow load

CN

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DISTANCE ALONG

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STUDY REACH, IN FEET

LO

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42,000

Figure 11. Variation of A, iron load with distance, and B, changes in load for individual stream segments, Cataract Creek, 

August 1997.
216 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Loading profiles of aluminum, copper, and iron were 

mixtures between the sulfate and zinc profiles. Substantial 

loads of aluminum entered the stream at Uncle Sam Gulch 

(S27) and segment S44 (fig. 9A). Most of the aluminum that 

entered the stream at Uncle Sam Gulch was transported downstream as colloidal aluminum (figs. 4A, 9A). Copper loading 

mostly occurred at Uncle Sam Gulch (segment S27; fig. 10). 

Downstream from there, the copper was mostly present as 

colloidal copper, but there appeared to be some transformation 

between dissolved and colloidal phases in response to downstream inflows. There was a loss of copper load to the streambed between Uncle Sam Gulch and Big Limber Gulch, which, 

in part, was due to loss in the iron colloids.

The iron profile (fig. 11A) indicates a relatively small 

increase in load from Uncle Sam Gulch (segment S27); the 

greatest loading was from upstream sources (segment SOI). 

Because iron is reactive in mine-drainage settings, there very 

likely was attenuation of iron concentrations as water traveled 

from sources at adits or seeps to the stream (Kimball, Broshears, and others, 1994). Unsampled inflow of iron occurred 

in segment S28, downstream from Uncle Sam Gulch. This corresponds to unsampled inflow of sulfate (fig. 6B), and could 

indicate weathering of pyrite in tailings piles along the stream 

in that area. Because most of the iron load was colloidal, 

losses such as that downstream from segment S28 very likely 

involved the transformation of dissolved to colloidal iron and 

then settling of aggregated colloids and (or) entrapment in the 

algae covering streambed cobbles, as indicated by Church. 

Unruh, and others (this volume, Chapter D8).

Locations of Major Loading

The cumulative instream load listed in table 3 is the best 

estimate of the total metal loading along the study reach. 

Although differences are seen among metal loading profiles, 

their similarities identify the locations where most of the 

metal loading occurs. Locations of the major contributions 

to Cataract Creek are indicated in table 3 by color shading. 

There were five locations where most of the loading occurred. 

The greatest loading occurred with the inflow of Uncle Sam 

Gulch (S27). This inflow accounted for 64 percent of the 

aluminum load, 66 percent of the copper load, 21 percent of 

the iron load, 96 percent of the manganese load, 92 percent of 

the zinc load, and 24 percent of the sulfate load (table 3). Iron 

(38 percent) and manganese (4 percent) loads were important 

at the beginning of the study reach (segment SOI). The other 

constituents were also present (table 3). The Eva May tailings 

(segment SOS) contributed to the load of zinc (2 percent). The 

inflow of Big Limber Gulch (segment S44) accounted for aluminum (14 percent), iron (8 percent), and sulfate (8 percent). 

Mines and mineralized rock in that drainage could account for 

these loads (O'Neill and others, this volume, pi. 1; McCafferty and others, this volume). Finally, loads of copper (24 

percent), iron (10 percent), and sulfate (10 percent) increased 

in the large segment represented by the sample at the mouth of

Cataract Creek (S45). Little is known about possible sources 

in this segment.

Unsampled Inflow

The principal locations of unsampled inflow include 

Uncle Sam Gulch (SI7), segment S28 downstream from Uncle 

Sam Gulch, and segment S45 between Big Limber Gulch and 

the mouth of Cataract Creek. The unsampled inflow from 

Uncle Sam Gulch consisted of sulfate (fig. 6B) and zinc 

(fig. IB). Downstream from Uncle Sam Gulch, a substantial 

tailings pile lies along Cataract Creek in segment S28, and this 

could be the source of iron and sulfate loading to the stream 

in that segment. Little is known about the last stream segment, 

S45, where there was unsampled inflow of copper, iron, and 

sulfate because there was no access to the stream along that 

reach.

Attenuation of Load

Along the length of the study reach, substantial attenuation only occurred for copper (30 percent) and iron 

(25 percent, table 3); most of the constituents were transported 

to the Boulder River once they entered Cataract Creek. Attenuation of copper and iron occurred downstream from Uncle 

Sam Gulch (figs. 105 and 115), after the load had greatly 

increased. This was likely a result of the loss of colloidal iron 

to the streambed through settling of aggregated colloids or 

through entrapment by algae on the streambed cobbles.

Uncle Sam Gulch Subbasin

Results of the tracer-injection study in Cataract Creek 

indicated that Uncle Sam Gulch was the principal source of 

metal loading to the stream. A tracer-injection study was done 

during low-flow conditions in late August 1998 to investigate 

the source of metals and the patterns of metal loading.

Study Area and Experimental Design

The study reach began upstream from the Crystal mine, 

near the headwaters of the stream, and continued to the mouth 

of Uncle Sam Gulch, where the stream discharges into lower 

Cataract Creek (fig. 12). Synoptic sampling sites defined 

36 stream segments. Stream segment numbers are listed in 

table 4, but the detailed descriptions of these sites are found in 

the database (Rich and others, this volume, Chapter G). Fourteen inflows were sampled in 13 of these segments.

A sodium chloride solution of 161,200 mg/L chloride was 

injected at a rate of 92 mL/min for a 48.7-hour period starting 

at 16:50 MDT on August 27, 1998. During the course of the 

injection, difficulties with the pumps complicated the interpretation of the chloride profile downstream from the injection.
Quantification of Metal Loading 217

Table 3. Change in load for individual stream segments and summary of load calculations, Cataract Creek, August 1997.

[Distance, in feet along the study reach; Al, aluminum; Cu, copper; Fe, iron; Mn; manganese; Zn, zinc; SO4, sulfate; all values of load are in kilograms per day; 

percentages are percent of cumulative instream load; color of cell indicates rank of load: red, first; orange, second; yellow, third; green, fourth; blue, fifth; 

negative values of load indicated in red type with parentheses]

Segment 

number

SOI

S02

S03

S04

805

S06

S07

SOS

S09

S10

Sll

S12

S13

S14

S15

S16

S17

S18

S19

S20

S21

S22

S23

S24

S25

S26

S27

S28

S29

S30

S31

S32

S33

S34

S35

S36

S37

S38

S39

S40

S41

S42

S43

S44

S45

Site descriptions

First site below injection

Tl transport site in canyon

Above right-bank mine dump

Below mine dump at Apollo mine

Above mine dump at Eva May mine

Below Hoodoo Creek

Above Eva May mine tailings

Adjacent to Eva May tailings pile

T2 transport site below Eva May mine

Below curve with overbank tailings

Along bend

Below old cabin

Below mine dump, at Cataract mine tailings

Adjacent to Cataract mine tailings

End of large flood plain

Adjacent to ponded water on right bank

Above large clear-cut area

Above Lower Hattie Ferguson mine

Below Lower Hattie Ferguson mine

Above left-bank inflow

Below Upper Hattie Ferguson mine

Below inflows, checking water inflow

T3 transport site below logging-road

Above biological sampling site

Above Morning Glory mine

Above Uncle Sam Gulch, below Morning Glory

mine

Below Uncle Sam Gulch

Below cabin and tailings pile on right bank

Check for reaction below Uncle Sam Gulch

Along cascades below small mine dump

Above rock wall

Below small inflow

At old lean-to

T4 transport site above canyon

Above start of canyon

Above Deer Creek

Below Deer Creek

Below large concrete bridge

Below second wooden bridge

Below old cabin on right bank

Along cascade reach

Wide section of canyon

T5 transport site above Big Limber Gulch

Below Big Limber Gulch

Cataract Creek at mouth

Cumulative instream load

Cumulative inflow load

Percent inflow

Unsampled inflow

Percent unsampled

Attenuation

Percent attenuation

Distance Al Cu

150 ifl.227 0.131 |

850 0.038 ^^^^

1,370 H^|

1,690 0.066

2,490 0.084 *

3,450 mo^ frpfv^

3,850

4,660

4,940

5,940

6,800

7,900

8,700

9,220

10,380

11,055

12,115

13,255

14,055

14,855

15,655

16,845

17,645

18,545

19,245

19,700 (0.149)

20,050 ^^^^^^H|

20,730 (0.180) |

21,130

21,715

22,315

22,915 (0.105)

23,715

24,715

25,215 (0.113)

26,335 (0.113)

26,590

26,970

27,775

29,970

31,470 (0.110)

32,970 (0.096)

34,105

34,355 fc.448 ^^^J

40,905 ^^||

3.08 2.03

4.08 2.11

132 104

<0 <0

<1 <1

0.254 0.612

8 30

Fe Mn Zn

^^^^^^•~O078

(0.038)

(0.016)

0.007

0.778 0.068

(M07

iHHI

0.299

(0.081) 0.083

0.103

(0.418) |

——^mmm

^^^^^

(1-71)

(0.076) (0.342)

(1.24)

• 1

11.9 2.68 17.0

9.09 2.75 14.9

77 103 88

2.77 < 0 2.09

23 < 1 12

2.92 0.157 2.05

25 6 12

so4

67.6

3.09

2.80

3.53

36.3

4.87

13.2

7.25

5.89

6.85

6.27

4.92

4.82

4.78

5.14

6.51

12.9

10.5

1^

7.39

••

17.0

(39.4)

11.8

20.3

30.7

19.3

15.6

30.4

•

722

540

75

182

25

39.4

5
218 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112° 16'54.716" 

46°21'8.074"-

46° 18" 43.189"

S01 - Start .of 

injection

T02 

Crystal 

mine 

adit

520 (T2 transport site)

521

22

T08 Jack

Mountain

tributary

S25 Downstream from 

Jack Mountain 

tributary

EXPLANATION

S27 Stream sampling site

T12 A Inflow sampling site

S34

S36 

End of 

study reach

0.5 1 MILE

0 0.5 1 KILOMETER

Figure 12. Location of stream segments (indicated by alternating colors) and inflows for synoptic sampling. 

Uncle Sam Gulch, August 1998.
Quantification of Metal Loading 219

Table 4. Segment number, source, distance along study reach, site description, and field data for water from synoptic sampling sites, 

Uncle Sam Gulch, August 29,1998.

[Dist, distance, in feet along the study reach; source: S, stream; LBI, left bank inflow, RBI, right bank inflow; pH, in standard units; Ksc, specific conductance, 

in microsiemens per centimeter; Q, discharge, in liters per second; Cl, chloride, in milligrams per liter]

Segment 

number

SOI

S02

S03

S04

SOS

S06

T01

S07

SOS

S09

S10

T02

Sll

S12

S13

S14

T03

S15

S16

S17

T04

S18

SI9

S20

S21

T05

T06

S22

T07

S23

S24

T08

S25

S26

S27

T09

S28

T10

S29

Til

S30

T12

S31

S32

S33

S34

T13

S35

T14

S36

Dist

0

278

305

592

702

780

792

957

,152

,314

,399

,413

,461

,560

,661

,764

,829

,866

2,026

2,273

2,286

2,727

3,170

3,777

4,365

4,650

4,763

4,915

5,264

5,830

6,068

6,088

6,213

7,417

8,270

8,374

9,200

9,400

9,588

10,289

10,856

11,006

11,724

12,795

14,540

15,314

15,671

15,971

16,471

17,095

Source

S

S

S

S

S

S

LBI

S

S

S

S

RBI

S

S

S

S

RBI

S

S

S

LBI

S

S

S

S

RBI

RBI

S

RBI

S

S

RBI

S

S

S

LBI

S

RBI

S

LBI

S

LBI

S

S

S

S

LBI

S

RBI

S

Description

Upstream from injection

First site below injection

Stream site, no description

Channel converges

Below several small

Tl transport site

tailings piles

Left bank tributary from old prospect

At steep waste rock pile

Below deep cuts eroding banks

At toe of waste rock pile

Above Crystal adit discharge

Right bank Crystal adit inflow

Below Crystal mine adit

Below Crystal waste rock pile

At edge of treatment pond

At treatment pond pipe

Right bank inflow from waste rock

Below obvious mining disturbance

Below mining disturbance (2)

Below mining disturbance (3)

Left bank tributary, low conductance

Below left bank inflow

Stream near road

T2 transport site — edge of clear cut

Stream at lower conductance

Right bank tributary

Right bank seep with iron precipitate

At boggy area along right bank

Right bank tributary near road

T3 transport site

Upstream from Jack Mountain tributary

Jack Mountain tributary (right bank)

Below Jack Mountain tributary

At heavy vegetation. low gradient

At small clearing near road

Left bank inflow from marshy area

T4-Upstream from old cabin

Right bank tributary by cabin

Near road below cabin inflow

Left bank tributary

Split in stream

Left bank tributary

Stream below dilution inflow

Below tailings

T5 transport site — upstream end of culvert

Below power line crossing

Left bank tributary

Below tributary near road

Right bank tributary draining wet area

Uncle Sam at mouth

Site identifier

SAMO

SAM278

SAM305

SAM592

SAM702

SAM780

SAM792

SAM957

SAM 11 52

SAM1314

SAM 1399

SAM1413

SAM 1461

SAM 1560

SAM 1661

SAM 1764

SAM 1829

SAM 1866

SAM2026

SAM2273

SAM2286

SAM2727

SAM3170

SAM3777

SAM4365

SAM4650

SAM4763

SAM4915

SAM5264

SAM5830

SAM6068

SAM6088

SAM6213

SAM7417

SAM8270

SAM8374

SAM9200

SAM9400

SAM9588

SAM 10289

SAM 10856

SAM 11 006

SAM 11 724

SAM 12795

SAM 14540

SAM15314

SAM 15671

SAM 15971

SAM 16471

SAM 17095

pH

7.18

7.26

7.45

Ksc

45

45

220

7.47 1,045

7.43 2,340

7.24 2,210

7.04

7.29

7.29

7.13

7.05

3.21

3.27

3.25

3.23

3.20

2.83

3.19

3.17

3.14

7.26

78

,838

,535

,356

,302

,164

,195

,204

,210

,195

,563

,205

.189

,182

56

3.22 1,065

3.30

3.32

3.44

6.97

6.71

3.48

6.83

3.53

3.58

7.17

4.81

4.91

5.13

6.95

6.62

7.61

6.74

7.24

7.14

7.50

6.89

7.28

7.29

7.32

7.84

7.36

7.74

6.62

878

774

732

80

123

686

139

642

621

63

243

229

222

116

211

91

201

147

194

114

183

181

177

176

165

184

217

180

Q

0.07

0.07

0.09

0.10

0.27

0.28

0.03

0.31

0.28

0.37

0.43

2.27

2.70

2.71

2.71

2.74

0.04

2.77

2.81

2.89

0.25

3.14

3.90

4.48

4.71

0.19

0.37

5.28

0.47

5.75

5.65

10.12

15.76

17.14

17.41

1.22

18.63

1.60

20.23

0.77

20.99

3.43

24.42

25.51

26.42

27.08

5.58

32.65

4.14

36.80

Cl

4.00

4.29

50.1

279

650

606

3.94

509

390

345

325

4.84

50.7

54.6

51.6

53.7

7.50

54.4

52.4

51.2

3.41

40.9

25.0

20.0

20.2

5.40

6.66

21.3

6.80

24.1

22.1

4.21

10.1

10.5

9.86

4.85

5.05

6.22

8.34

5.56

8.00

5.82

7.54

7.38

7.37

7.22

5.44

6.93

0.94

6.79
CHLORIDE CONCENTRATION, IN MILLIGRAMS PER LITER

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DISCHARGE, IN CUBIC FEET PER SECOND
Quantification of Metal Loading 221

Although the decrease of chloride concentration appeared to 

be systematic, a "wave" of chloride moved through the study 

reach during the synoptic sampling, indicated by the increase 

of chloride at the first few sampling sites (fig. 13). Because 

of these complications, chloride and sulfate ratios around 

inflows, along with velocity-area discharge measurements, 

were used to calculate the increase of flow due to individual 

inflows. The resulting calculated discharge ranged from 0.004 

to 1.3 ft-Vs (fig. 13). Most of this increase was from Jack 

Mountain tributary (T8). Discharge increased only 0.07 ftVs in 

those segments that had no sampled inflow, only 10 percent of 

the total increase, and so the explicit amount of ground-water 

inflow was small.

Chemical Characterization of Synoptic Samples

Changes in stream-water chemistry along Uncle Sam 

Gulch were distinct and occurred over short distances in 

response to acidic and neutral inflows. The abrupt changes of 

pH along the study reach indicate where the changes occurred 

(fig. 14). Upstream from the Crystal mine, pH was greater than 

7.0, sulfate concentration was less than 25 mg/L, and metal 

concentrations were relatively low (fig. 15). With the addition 

of the adit drainage (T2), and the spring from the mine wasterock pile (T3), pH dropped substantially, to less than 3.5, 

and sulfate increased to greater than 550 mg/L. Metal concentrations increased to greater than 10,000 (jg/L aluminum, 

10,000 |ug/L copper, 40.000 ug/L iron, and 60,000 ug/L zinc 

(fig. 15). Baseline sediment chemistry also indicates the 

impact from mining (Church, Unruh, and others, this volume, 

figs. 4-10). Inflow from Jack Mountain tributary increased 

the pH to 4.81 in segment S25, and pH continued to increase 

to 5.13 by the end of segment S27. Farther downstream, after 

additional neutral inflows at T9 and T10, the pH increased to 

6.74 at segment S29. Within the reach of increasing pH, from 

segment S25 to S27, dissolved concentrations of the metals 

decreased and colloidal concentrations increased. Iron colloids, however, started forming upstream from the inflow of 

Jack Mountain tributary; the total-recoverable iron was greater 

than the two filtered concentrations (fig. 15CJ. At the higher 

pH there was a steady formation of aluminum and iron colloids as water moved downstream (fig. 15,4, C). As the 

colloids formed, dissolved copper concentrations decreased 

and most of the copper became associated with the colloidal 

phase (fig. \5B). Concentrations of dissolved zinc exceeded 

chronic water-quality criteria at all sites downstream from 

the Crystal mine adit, as noted by Nimick and Cleasby (this 

volume, Chapter D5).

Table 5. Average chemical composition of groups from principal components analysis of synoptic samples. Uncle Sam Gulch, 

August 1998.

[LD, less than detection limit; all values in milligrams per liter, except pH, which is in standard units]

Group 1 

Stream

., . , from S1 Number of __ 

. . . to S3, samples or solute upstream

from acid 

inflows

Number of

samples

pH

Calcium

Magnesium

Sulfate

Aluminum

Cadmium

Copper

Iron

Manganese

Nickel

Lead

Strontium

Zinc

3

7.30

5.44

.957

6.11

.121

.002

.007

1.11

.067

.001

.009

.066

.047

Group 1 

Unaffected 

inflows

2

7.15

9.29

1.47

9.31

.032

.002

.008

.242

.069

LD

LD

.070

.085

Group 2 

Stream 

site S4, 

unaffected 

by acid 

inflows

1

7.47

9.84

1.67

10.0

.045

.003

.015

.499

.084

.001

.001

.121

.121

Group 2 

Inflows 

unaffected 

by mining

10

7.26

17.3

3.18

15.9

.017

.004

.027

.139

.409

LD

LD

.131

.157

Group 3 

Stream 

from S5 

to S10, 

affected 

bulldozed 

area

6

7.24

23.6

3.84

10.1

.037

.006

.023

.232

.075

.001

.001

.271

.232

Group 4 

Stream 

from S11 

to S18, 

affected 

by 

Crystal 

mine 

adit

6

3.21

54.3

15.5

507

12.4

.771

12.4

36.0

11.9

.054

.243

.267

56.7

Group 4 

Most 

acidic 

inflow, 

including 

Crystal 

mine 

adit

2

3.02

62.0

19.7

706

17.3

.891

15.6

43.0

16.4

.065

.134

.270

71.4

Group 5 

Stream 

between 

S19and 

S24

6

3.44

35.2

9.43

293

7.86

.453

7.36

10.5

7.19

.030

.188

.212

33.7

Group 6 

Stream 

between 

S25 and 

S31

7

6.03

17.6

4.24

78.4

1.83

.119

1.93

1.03

1.87

.008

.042

.126

8.92

Group 7 

Stream 

between 

S32 and 

S36

5

7.17

18.2

4.07

53.1

.683

.072

.731

.284

.949

.006

.001

.134

5.60
pH, IN STANDARD UNITS

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SULFATE CONCENTRATION, IN MILLIGRAMS PER LITER
20,000

16,000 - 50,000 Ultrafiltrate 0.45-micrometcr filtrate 

Total-recoverable Inflows

Ultrafiltratc0.45-micrometer filtrate 

Total-recoverable 

* Inflows

S25

Downstream from 

Jack Mountain tributary

S25

Downstream from 

Jack Mountain tributary

Ultrafiltrate

- 0.45-micrometer filtrate

— Total-recoverable 

• Inflows

Ultrafiltrate

0.45-micrometer filtrate Total-recoverable 

Inflows

S25

Downstream from 

Jack Mountain tributary

S25

Downstream from 

Jack Mountain tributary

18,000

O 09o1 

5'

3,000 6,000 9,000 12,000 15,000

DISTANCE ALONG STUDY REACH, IN FEET

a ooo 6,000 9,000 12,000 15,000 

DISTANCE ALONG STUDY REACH, IN FEET

18,000 0) 0.

CO

Figure 15. Variation of A, aluminum, B, copper, C, iron, and D, zinc concentrations with distance, Uncle Sam Gulch, August 1998.
224 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

These substantial changes in stream chemistry and the 

variability of inflows resulted in a classification of seven 

groups of samples by PCA (fig. 16). Six of the groups represent variations in stream-water chemistry, with associated 

inflows, and one represents inflows unaffected by mining or 

alteration (table 5). The biplot provides a reasonable interpretation of the chemical variation among synoptic samples from 

Uncle Sam Gulch. Two sets of stream sites (groups 1 and 3) 

are unaffected by discharge from the Crystal mine adit and 

plot to the right on the biplot (fig. 16). All the vectors indicate 

increasing concentrations to the right; the vectors for metals 

from the mine are very similar and so they are only identified as a group. Samples to the left of the biplot are opposite 

all the vectors, and have the lowest concentrations. Group 1 

contains two inflow samples (T01 and T04) that resulted from 

the same weathering reactions that produced the stream-water 

chemistry upstream from segment S04. An extensive amount 

of disturbance resulted from bulldozing of soil up the mountain on the right bank of the stream. Inflow water that drained 

the disturbed area contributed high calcium, sulfate, and some 

zinc (group 3). With the inflow of adit discharge and water 

from the waste-rock pile (inflows T02 and T03), the chemistry shifted to reflect the acidic, metal-rich character of those 

inflows (group 4), far to the right of the biplot. Variations 

among stream samples in groups 5, 6, and 7 represent dilution by the non-mining inflows as water moved downstream. 

With greater dilution, the chemical character of the stream 

water becomes increasingly more like the inflows of group 2; 

samples plot progressively to the left downstream. Thus, in 

groups 5, 6, and 7 segment numbers increase from right to left, 

indicating a sequential dilution. The large jump from group 5 

to 6 results from the inflow of Jack Mountain tributary (T08), 

which is one of the group 2 inflows (fig. 16).

Load Profiles

Colloids were responsible for much of the metal transport 

in Uncle Sam Gulch (fig. 15). Load profiles reflect dynamic 

changes between dissolved and colloidal phases along the 

study reach (figs. 17-25). A summary of load calculations 

for each solute is listed in table 6. A distinction is evident 

between the loading profile of strontium and those of the 

other metals. Although the Crystal mine adit in stream segment S11 contributed a substantial load of strontium, it was 

not the largest loading among the stream segments (fig. 17). 

Similar to the strontium profile in Cataract Creek, the profile 

in Uncle Sam Gulch most likely represents weathering from 

non-mined sources. However, all the metals and sulfate had 

similar loading profiles in segment SOI. Downstream from the 

Crystal mine adit, however, individual profiles of metal loading differed because of the conservative or reactive nature of 

the different metals.

The pattern of strontium loading indicated more segments contributing to the load than most other constituents 

(fig. 17; table 6). Although drainage from the Crystal mine

adit in segment S11 contributes a substantial strontium load, 

other segments were equally important. Unlike the sulfate 

loading in Cataract Creek, sulfate loading in Uncle Sam Gulch 

was derived substantially from one source, the Crystal mine 

adit in segment S11 (fig. 18). Other locations of sulfate loading throughout the watershed were minor (fig. 18B). A small 

amount of unsampled inflow occurred in segments SI9, S20, 

and S26, but most of the sulfate loading was accounted for by 

the sampled inflows. One similarity between profiles of sulfate 

and strontium was the increase in load in the last two stream 

segments of the study reach (segments S35 and S36). The 

source of these loads may be a large fault that intersects the 

stream in segment S35 (O'Neill and others, this volume, pi. 1). 

Some of the metal loads also increased in segment S35, near 

the end of the study reach.

Downstream from the inflow of the Crystal mine adit, 

cadmium, manganese, nickel, and zinc were mostly conservative. These metals had fewer sources than strontium and 

sulfate. The principal source of cadmium load was the inflow 

from the Crystal mine adit (fig. 19). At segment S35, near 

the confluence with Cataract Creek, there was a substantial 

increase in cadmium load, which was all in the colloidal 

phase. Profiles of manganese (fig. 20) and zinc (fig. 21) load 

were similar to that of cadmium. The principal source of 

loading for both metals was inflow from the Crystal mine 

adit (T02, segment SI 1). Manganese load increased slightly 

with the inflow of Jack Mountain tributary. Manganese load 

decreased downstream from segment S30. but zinc load did 

not. Zinc had unsampled inflow at segment S19 and segment 

S26, one segment downstream from Jack Mountain tributary. The instream load of both metals was substantial at the 

confluence with Cataract Creek, which is consistent with the 

contribution of Uncle Sam Gulch on the loads in Cataract 

Creek (figs. 7 and 8).

Other metals were reactive downstream from the Crystal 

mine adit (SI 1). Iron was the most reactive (fig. 22); aluminum (fig. 23), copper (fig. 24), and lead (fig. 25) were reactive 

downstream from the inflow of Jack Mountain tributary (S25). 

The adit of the Crystal mine was essentially the only measurable source of iron load along the study reach; however, 

sources downstream from the adit could have been masked 

by a net negative change in iron load within individual stream 

segments due to loss from the water column (fig. 22). Downstream from the adit inflow the profile of iron load differed 

from profiles of the other solutes because of a continuous 

decrease in total iron load. Upstream from Jack Mountain 

tributary, the iron load was mostly in the dissolved phase and 

decreased by about 80 percent from segment S11 to segment 

S24. Downstream from Jack Mountain tributary, there was 

essentially a complete transformation of iron from the dissolved to the colloidal phase, and the colloidal phase was 

dominant all the way to the confluence with Cataract Creek. 

Downstream from Jack Mountain tributary, ferrihydrite is 

probably the iron phase being precipitated at the higher pH 

(Bigham and Nordstrom, 2000). Loss of iron load along the
Quantification of Metal Loading 225

(/)

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SCALED PRINCIPAL COMPONENT 1 LOADINGS 

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tributary (T08)

*

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Adit discharge 

constituents

Calcium 

Strontium

<S> Group 1

* Group 1, inflows

* Group 2

* Group 2, inflows

o Group 3

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* Group 5

* Group 6

* Group 7

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SCALED PRINCIPAL COMPONENT 1 SCORES

Figure 16. Biplot of principal component scores for synoptic samples and loadings for chemical constituents, Uncle Sam Gulch, 

August 1998.
226 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

0.5

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trS °-4

tr 

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Cumulative instream load 

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DISTANCE ALONG STUDY REACH, IN FEET

15,000 18,000

Figure 17. Variation of A, strontium load with distance, and B, changes in load for individual stream segments. Uncle Sam Gulch, 

August 1998.
i" &• CHANGE IN LOAD, IN KILOGRAMS PER DAY SULFATE LOAD, IN KILOGRAMS PER DAY

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228 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

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Figure 19. Variation of A, cadmium load with distance, and B, changes in load for individual stream segments, Uncle Sam Gulch, 

August 1998.
> 31

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230 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

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Figure 21. Variation of A, zinc load with distance, and B, changes in load for individual stream segments, Uncle Sam Gulch, 

August 1998.
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234 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

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DISTANCE ALONG STUDY REACH, IN FEET

15,000 18,000

Figure 25. Variation of A lead load with distance, and B, changes in load for individual stream segments, Uncle Sam Gulch, 

August 1998.
Quantification of Metal Loading 235

Table 6. Change in load for individual stream segments and summary of load calculations for selected solutes. 

Uncle Sam Gulch, August 1998.

[Distance, in meters along the study reach; Al, aluminum; Cu, copper; Fe, iron; Pb, lead; Mn, manganese; Sr, strontium; 

Zn, zinc; SO4, sulfate; cumulative instream load, cumulative inflow load, unsampled load, and attenuation in kilograms per day; 

numbers in red with parentheses indicate a loss of load; color of cell indicates the segments with the greatest load: red, largest 

load; orange, second largest; yellow; third; green, fourth; blue, fifth]

Segment number Distance

SOI

S02

S03

S04

805

S06

S07

SOS 

S09

S10

Sll 

S12

S13

S14

S15

S16

S17

S18

S19

S20

S21

S22

S23

S24

S25

S26

S27

S28

S29

S30 

S31

S32

S33

S34 

S35

S36

Cumulative instream load

Cumulative inflow load

Percent inflow load

Unsampled inflow

Percent unsampled 

inflow

Attenuation

Percent attenuation

0

278

305 j

592

702

780

957

1,152 

1,314

1,399

1,461 | 

1,560

1,661

1,764

1,866

2,026

2,273

2,727

3,170 

3,777

4,365

4,915

5,830

6,068

6,213

7,417

8,270

9,200

9,588

10,856 

11,724

12,795

14,540

15,314 

15,971

17,095

Al

0.000

.000

(.001)

.001

(.000) 

(.001)

.001

o nn ^^^^•^^

(-447)

(.320)

(.629)

.342

V.-r^f

3.33

3.00

90

.329

10

1.88

56

Cu

0.000

(.000)

j .000

' .000

.001

(.000)

(.000)

P .060 *

P, 3.05

(-751)

(.327)

.265

,.^.,

3.32

3.05

92

.268

8

1.64

49

Fe

0.001

.001

.019

.004

(.004) 

.001

10.6

(1.08)

(.702)

(1.11)

0.5-57

o

(1.03)

(.320)

Jy^j

(.368)

(.313)

(.263)

(-524)

(.140)

0.160 •

v-^,

11.7

10.6

91

1.06

9

9.81

84

Pb Mn

0.000 0.000

.000

.000 .001

rnom /nm.

.000 .002

(.001) 

.000

.055 2.90

017 '

.272

(.022)

(.053) (.212)

• 2.87

,.TM,

.073 3.71

.053 2.88

72 78

.020 .823

28 22

.073 .953

100 26

Sr

0.000

.000

.001

.003

.001

.002

.002

.001

.052 B

.009 | 

.006

.009

.061

.015

^^^m

P .044 f

.182

\.\j-r\JI

.412

.328

80

.084

20

.000

0

Zn

0.000

(.000)

.001

.000

.004

.001

(.001) 

.003

, 13.9

(1.02)

f/7721!

Uzu-i

.841

I

2.87

——— '•

18.3

13.5

74

4.85

26

5.43

30

SO,

0.010

.039

.019

.019

.151

.026

(.030) 

.081

.043 ^m

13.5

8.25

(13.6)

12.3

12.0 I

169

160

94

9.33

6

13.6

8
236 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

study reach is consistent with the relatively small contribution 

of iron load from Uncle Sam Gulch to Cataract Creek (fig. 11).

Most of the aluminum load also entered the stream in 

the adit discharge of the Crystal mine (fig. 23). One additional increase was measurable in segment S35, and it was 

unsampled inflow for aluminum as it was for other metals. 

Higher pH downstream from Jack Mountain tributary caused a 

complete change in aluminum load from the dissolved 

to the colloidal phase. Unlike the transformation of iron, this 

change in aluminum phase occurred along the next 2,000 ft of 

stream. The colloidal aluminum load subsequently decreased 

downstream to about half the amount present before the 

transformation.

Copper loading resembled that of aluminum; the major 

source was the adit inflow from the Crystal mine, and load 

decreased substantially downstream from Jack Mountain 

tributary (fig. 24). For copper, the decrease in load was not as 

abrupt as for iron. Instead, there was a gradual transformation 

from dissolved to colloidal copper after sorption to iron and 

perhaps aluminum colloids between segments S25 and S29. 

The percentage of total-recoverable copper that is in the colloidal form increased systematically with pH, in a manner very 

similar to a sorption isotherm (Smith, 1999). The increase in 

copper load at segment S35 was an increase in colloidal, rather 

than dissolved, copper. The unsampled inflow of copper likely 

occurred as dissolved copper that was sorbed to iron colloids 

during the time of transport through the stream segment.

The loading profile of lead differed from those of the 

other metals because some of the loading occurred downstream from the inflow from the Crystal mine adit (segment S20), and not just from the adit inflow (fig. 25). The 

greatest increase occurred in segment S20, from unsampled 

inflow. Downstream from Jack Mountain tributary, the lead 

load decreased, but in a pattern more like copper indicating 

gradual sorption rather than precipitation. In stream segment 

S32, essentially the entire lead load was gone from the water 

column, possibly due to the increase of instream pH in this 

segment. The loss of lead is consistent with the increase of 

lead concentration in the bed sediments (Church and others, 

this volume, fig. 5).

Locations of Major Loading

Inflow from the Crystal mine adit at segment SI 1 

dominated the loading of all the constituents except strontium 

(table 6). Loading from the adit accounted for more than 

90 percent of the aluminum, copper, and iron; more than 

70 percent of the lead, manganese, zinc, and sulfate; but only 

13 percent of the strontium load. Segment S35, which was 

almost to the mouth of Uncle Sam Gulch, was the next most 

substantial source for loads for several constituents. This is the 

location of a major fault and several veins that have not been 

mined (O'Neill and others, this volume, pi. 1). Segment S20 

was a source for 23 percent of the lead load. The inflow of 

Jack Mountain tributary, accounted for by segment S25, was a 

source for iron, manganese, strontium, and sulfate.

Unsampled Inflow

Unsampled inflow was less than 30 percent for all the 

constituents. The greatest amount of unsampled inflow was 

for lead (28 percent), manganese (22 percent), and strontium (20 percent). For lead (fig. 25fi), the unsampled inflow 

occurred in segment S20 (fig. 25B). The source of this loading 

is unknown, but likely is associated with ground water from 

the Crystal mine or the waste-rock pile. Unsampled inflow 

for manganese (fig. 20B) occurred in segments S25 and S35, 

and for strontium (fig. \1B) it mostly occurred in segment 

S35, but there were several segments with a small amount of 

unsampled inflow. The small amount of unsampled inflow for 

zinc and sulfate reflects a general lack of widespread alteration 

of rocks in the watershed.

Attenuation of Load

Most of the attenuation of metals in Uncle Sam Gulch 

occurred downstream from Jack Mountain tributary. About 

50 percent of the aluminum (fig. 23A) and copper (fig 24A), 

more than 80 percent of the iron (fig. 22A), and all of the lead 

(fig. 25A) that entered Uncle Sam Gulch were removed from 

the water column by the end of the study reach (table 6). This 

metal attenuation resulted in the accumulation of colloidal 

floe on the streambed. In the Animas River watershed, Church 

and others (1997) quantified a large increase in the load of 

colloidal floe that was transported, or flushed, by high flows 

during snowmelt runoff. About 30 percent of the manganese 

and zinc loads were removed (table 6), but only 8 percent of 

the sulfate load and less than 1 percent of the strontium load 

were removed.

The attenuation of iron started immediately downstream 

from the adit inflow (fig. 22). The geochemical behavior of 

iron makes its loading profile different from that of other metals. The profile indicates that only segment SI 1 was a major 

source of loading; the net gain for all but three other segments 

was negative or near zero. This does not mean, however, that 

there were no contributions from other stream segments. 

Because the transformation of dissolved to colloidal iron 

occurred rapidly with respect to transport of the metals in the 

stream (Kimball, Broshears, and others, 1994), most of the 

colloidal iron can be lost through aggregation, settling, and filtering through the streambed within the same stream segment 

where it enters (Grundl and Delwiche, 1993; Packman and 

others, 2000). Thus, there could have been contributions or 

iron load in other stream segments, but if the iron entering the 

stream is rapidly transformed to colloidal iron and removed 

from the water column, there is no accounting of that mass 

loading at this stream-segment scale.

Load profiles help to quantify the mass transfer of chemical reactions in the stream. Changes in load indicate the timing 

and mechanisms of precipitation and sorption reactions in the 

context of stream transport (Kimball, Bencala, and Broshears, 

1994). The dominant reactions affecting metals downstream 

from Jack Mountain tributary were the formation of iron and
Quantification of Metal Loading 237

aluminum colloids. At the low pH upstream from Jack Mountain tributary, Desborough and others (2000) determined that 

the iron precipitate was schwertmannite. Bigham and Nordstrom (2000) discussed the steps in the formation of schwertmannite, and the final step is represented as:

8Fe3++SO-.2+14H O=Fe_O_(OHX.(SO,)+22HH (3)

Downstream from Jack Mountain tributary, at a higher 

pH, the precipitate was ferrihydrite:

Fe3++3OH~=Fe(OH)3 s

(4)

The change may be due to a more positive surface charge 

on the iron colloid at low pH, favoring anion sorption. Attenuation of aluminum, on the other hand, begins with a transformation from dissolved to colloidal aluminum, probably 

through the formation of polynuclear aluminum complexes at 

low temperature (Baes and Mesmer, 1976):

.3+ ,<3x-yH+H+

(5)

Downstream from the inflow of Jack Mountain tributary 

where the pH increased above 5.5, this transformation begins 

(fig. 24). As the complex grows it becomes too large to pass 

through the 10,000 Dalton filter and can be considered colloidal. A crystalline mineral phase, like gibbsite (A1(OH)3 s), 

would occur with aging on the streambed.

Loads of dissolved iron and dissolved aluminum were 

transformed from the dissolved to the colloidal phase in segments S25 through S28, downstream from Jack Mountain 

tributary (fig. 26). In each successive stream segment the total 

load was constant; before the loss of any load, only the portion 

of the colloidal phase increased. By adding in the amount of 

the colloidal phases lost to the streambed, the mass balance 

was still constant. After transport to segment S28, both aluminum and iron were completely transformed to the colloidal 

phase. Once the colloidal iron was present, dissolved copper 

started to change to colloidal copper, most likely from sorption to the iron solids. Often it is not possible to distinguish 

if copper is removed by sorption or coprecipitation (Fulghum 

and others, 1988), but these data clearly point toward sorption, rather than coprecipitation, as the mechanism of copper 

removal, because copper was transformed only after the iron 

colloid had formed. At segment S30, the dissolved and colloidal copper loads were nearly equal, and by segment S32 there 

was a loss of copper load to the streambed. By accounting for 

the dissolved, colloidal, and lost copper loads, the total copper 

remained constant and the mass balance indicates that the 

mass transfer between phases occurred in the water column.

Comparison of copper mass transfer (figs. 24 and 26) 

clearly indicates that the transformation of copper from the 

dissolved to the colloidal phase occurred after the formation of 

the aluminum and iron colloids. The moles of copper sorbed 

were less than one tenth of the moles of aluminum or iron 

formed, but this was a substantial quantity of mass transfer. 

Webster and others (1998) have shown that a high sulfate 

percentage in iron hydroxides increases the sorption capacity 

of the iron phase; schwertmannite has a higher sulfate percentage. This profile and timing strongly indicate that the process 

for copper removal is sorption rather than coprecipitation, 

according to a general reaction, using ferrihydrite:

Cu2++2H+sFe(OH) «2H++Cu2+=Fe(OH)

•J^a

(6)

where = indicates bonding to a solid surface. Runkel and others (1999) have simulated sorption of copper to iron colloids 

in a mine-drainage stream, showing that it is a reversible 

reaction.

Bullion Mine Tributary Subbasin

Mine drainage that affects a small tributary of Jack Creek, 

called the Bullion Mine tributary in this report, originates from 

the same ore body that was mined at the Crystal mine in Uncle 

Sam Gulch (fig. 12). The adit of the Bullion mine discharges 

to the Bullion Mine tributary where it is a small stream, and 

the impact of the mine drainage is substantial. A mass-loading 

study was done during low-flow conditions in early September 

1998 to investigate the source of metals and the patterns of 

metal loading.

Study Area and Experimental Design

Stream samples defined 33 segments and bracketed a 

total of 11 inflows along the study reach (fig. 27). Site 

numbers and descriptions of stream and inflow sites 

are listed in table 7 for reference; detailed field and chemical data for these sites are in the database (Rich and others, 

this volume). A sodium chloride solution, with 79,040 mg/L 

chloride, was injected into the Bullion Mine tributary at a rate 

of 0.0017 L/s for 36 hours, starting at 10:00 MDT on August 

30, 1998. Chloride concentration decreased systematically 

downstream from the injection, indicating those stream 

segments that contributed water to the stream (fig. 28). Calculated discharge ranged from 0.12 to 0.80 ftVs (fig. 28). The 

largest inflow was Jack Creek (site Tl 1) with a calculated discharge of 0.52 ftVs. Jack Creek represented 65 percent of the 

total streamflow. Stream segments that had sampled inflows 

accounted for 88 percent of the total increase in streamflow, 

and discharge increased 0.20 ftVs in those segments that 

had no sampled inflow. This indicates that a minimum of 

12 percent of the total increase in streamflow was unsampled 

inflow, on the basis of tracer information.
238 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

_- < 2.5 Q Q 

< cr -

vj '-'-'20 — — 1 Q_

^ (/)

D ^ 1.5-

< 2 0.5 -

z

0 -

< 3 " Q

Q" ^

cc

SI 2 :

z< -

0 g 2§ J

z

0-

TM" 4

S25

i 

S25

1

iBl ^^B?

i

S26

S26

i 

S27

I 

S27

^•5 Loss

1 —— 1 Colloidal 

1 1 Dissolved

i 

S28

^^^^^_

1 —— 1 Colloidal 

1 1 Dissolved

i 

S28

'

<

Q

tr *5

UJ <

o_ oc

Q_ CD

O O

3-

2-

1 -

0

S25 S28 S30 S32 

Figure 26. Mass transfer of metals between dissolved and colloidal phases, Uncle Sam Gulch, August 1998.
Quantification of Metal Loading 239

Table 7. Segment number, distance along study reach, source, site description, site number, and field and chemical data for water 

from synoptic sampling sites, Bullion Mine tributary, September 1,1998.

[Dist, distance, in feet along the study reach; source: S, stream; LBI, left bank inflow; RBI, right bank inflow; pH. in standard units; Ksc. specific conductance, in microsiemens per centimeter: Q. discharge, in liters per second; Cl, chloride, in milligrams per liter]

Segment 

number

SOI

S02

S03

S04

S05

T01

T02

S06

S07

SOS

S09

T03

S10

Sll

T04

S12

S13

S14

S15

S16

S17

S18

S19

S20

T05

S21

S22

T06

S23

T07

S24

T08

T09

S25

S26

S27

S28

S29

S30

T10

S31

Til

S32

S33

Dist

0

150

235

296

341

346

359

383

437

485

540

582

627

726

733

793

856

945

1,025

1,109

1,197

1,264

1,404

1,522

1,554

1,672

1,808

1,874

1,990

1,992

2,155

2,157

2,191

2,278

2,585

2,951

3,457

3,958

4,729

5,245

5,338

5,339

5,454

6,019

Source

S

S

S

S

S

LBI

LBI

S

S

S

S

LBI

S

S

LBI

S

S

S

S

S

S

S

S

S

RBI

S

S

LBI

S

LBI

S

LBI

RBI

S

S

S

S

S

S

LBI

S

RBI

S

S

Description

Above injection site

Below injection site

Tl transport site below injection

At start of mining disturbance

Above acidic inflows

Left bank inflow from mine

Second acid inflow

Below acidic inflows — logjam

Stream below acidic inflows

Below rock dam in small pond

At pine over creek

Left bank inflow

Below high conductance inflow

Upstream from bedrock control

Left bank near end of tailings

Downstream of log at meander

At large boulder control

Stream

Above breached settling dam

At breached dam

At convergence of stream channels

Stream

At meander bend

At logjam

Right bank tributary

Pool upstream from log jam

Upstream from rock falls

First high pH left bank inflow

Below high pH inflow

Second high pH left bank inflow

T2 transport site

Left bank tributary

Right bank tributary

At narrow point in canyon

Stream

Stream

Downstream from steep gradient

Stream

Stream

Left bank inflow

T3 transport site — near mouth

Jack Creek

Jack Creek below Bullion Mine tributary

Jack Creek above tailings impoundment

Site Number

BullO

Bull 150

Bull235

Bull296

Bull341

Bull346

Bull355

Bull383

Bull437

Bull485

Bull540

Bull582

Bull627

Bull726

Bull733

Bull793

Bull856

Bull945

Bull 1025

Bull 11 09

Bull 11 97

Bull 1264

Bull 1404

Bull 1522

Bull 1554

Bull 1672

Bull 1808

Bull 1874

Bull 1990

Bull 1992

Bull2155

Bull2157

Bull2191

Bull2278

Bull2585

Bull295 1

Bull3457

Bull3958

Bull4729

Bull5245

Bull5338

Bull5339

Bull5454

Bull6019

pH

6.82

7.07

7.08

6.89

6.88

2.78

2.83

3.61

3.55

3.63

3.60

3.52

3.52

3.58

4.61

3.52

3.56

3.52

3.56

3.58

3.63

3.75

3.71

3.66

6.72

3.73

3.68

6.79

3.73

6.83

3.85

6.40

6.50

4.14

4.11

4.39

4.20

4.32

4.34

6.33

4.64

6.77

6.60

6.70

Ksc

67

171

168

167

169

1,827

1,829

419

439

443

448

1,185

473

418

532

478

477

476

476

478

475

468

471

458

81

454

456

190

450

129

413

162

67

360

357

349

348

338

319

54

310

152

151

Q

3.3

3.3

3.3

3.3

3.4

0.17

0.35

3.9

3.9

4.0

4.0

0.20

4.2

4.2

0.02

4.2

4.2

4.3

4.4

4.5

4.5

4.5

4.5

4.6

0.00

4.6

4.7

0.00

4.7

0.45

5.2

0.37

0.37

5.9

5.9

6.1

6.1

6.3

6.6

0.32

6.9

15

22

23

Cl

0.28

33.5

31.8

32.0

31.1

2.94

3.46

26.9

26.5

26.2

26.1

1.54

24.5

24.8

0.73

24.2

23.4

23.3

22.4

23.2

22.7

22.4

22.1

21.9

0.26

21.3

21.3

0.41

20.9

0.27

18.8

0.36

0.20

16.5

16.7

16.3

16.2

15.3

14.9

0.20

13.9

0.22

4.17

4.00
240 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112° 18'33.121" 

46° 22'0.409"

112° 17'33.402'

46°21'6.109"

S33

S32 T11

T10

S31 - Mouth of Bullion Mine tributary 

k S30 7549

A

End of

injection

reach

Unnamed tributary

x

»

7084

EXPLANATION

S27 Stream segment

T5

Inflow site

7269 Mountain peak—Number 

is elevation of peak, in 

feet above sea level

7269

Start of injection 

reach

Drainage from 

collapsed adit

Collapsed

Bullion mine

adit

0 0.25 

I

0.5 MILE

0 0.5 KILOMETER

Figure 27. Location of stream segments (indicated by alternating colors) and inflows for synoptic sampling, Bullion Mine 

tributary, September 1998.
Quantification of Metal Loading 241

35

Stream chloride 

Inflow chloride 

Stream discharge 

Inflow discharge

- 0.1

1,000 2,000 3,000 4,000 5,000 

DISTANCE ALONG STUDY REACH, IN FEET

6,000

0

7,000

Figure 28 Variation of chloride concentration and calculated discharge with distance along the study reach, Bullion Mine 

tributary, September 1998.
242 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Chemical Characterization of Synoptic Samples

The impact of inflows from the Bullion mine adit was 

evident from the variation of pH along the study reach in the 

Bullion Mine tributary (fig. 29). Three acidic inflows (T01, 

T02, and T03) caused a large decrease in pH (Metesh and 

others, 1994). Within this same area of the stream are old 

mill tailings that may affect the stream chemistry, along with 

the drainage from the collapsed adit (Fey and others, 2000). 

Near-neutral pH inflows at T05 through T09 only raised 

the pH slightly. Downstream from the confluence with Jack 

Creek, the pH returned to neutral, as indicated by Nimick and 

Cleasby (this volume, fig. 2). Changes in dissolved and colloidal metal concentrations occurred at the same locations as the 

changes in pH (fig. 30). The greatest increase in concentration 

for each of the metals was at segment S06, downstream from 

inflows T01 and T02. Both the filtered concentrations and the 

total-recoverable concentrations of aluminum, copper, and 

zinc increased (fig. 30/4, C, D), indicating that these metals 

were present as truly dissolved metals at this low pH. The concentration decreased at segment S25 owing to inflows. At this 

point, there were small differences between filtered and totalrecoverable concentrations, indicating colloidal concentrations. Concentrations of these metals remained nearly constant 

until the inflow of Jack Creek, where concentration decreased 

substantially (segment S32), and aluminum and copper were 

transformed to colloidal concentrations. Only a small part of 

the zinc was transformed to the colloidal form. Nimick and 

Cleasby (this volume) have noted where concentrations of zinc 

exceeded water-quality criteria at sites downstream from the 

Bullion mine adit inflows.

Most of the iron occurred as colloidal solids (fig. 305), as 

indicated by the large difference between the total-recoverable 

and the ultrafiltrate concentrations. At site S06, downstream 

from the first acidic inflow, the colloidal iron concentration 

was 11 mg/L and the dissolved concentration was 5 mg/L. 

From that point on downstream, the water was noticeably 

cloudy due to colloidal solids (fig. 31), which were most likely 

schwertmannite due to the low pH of the stream. Downstream 

from the inflow of Jack Creek, iron concentrations were lower, 

but a greater percentage of the total-recoverable iron occurred 

as colloidal iron.

The difference between iron and the other metals resulted 

from the low pH of the Bullion Mine tributary (fig. 29). At 

S06, the pH was 3.61, which was sufficiently high for iron precipitation, but too low for the precipitation of aluminum (Nordstrom and Ball, 1986; Bigham and Nordstrom, 2000). This

pH also was too low for any substantial sorption of copper or 

zinc to the iron colloids (Smith, 1999). Downstream from Jack 

Creek, at segment S32, the pH increased to 6.60, causing substantial formation of aluminum colloids and sorption of copper 

(fig. 30/4, C), but the pH was not high enough for sorption of 

zinc (fig. 30D). At this higher pH, however, a clear distinction 

existed between unfiltered and 0.45-um filtered concentrations 

of aluminum, copper, and zinc. This indicates a continuum of 

colloid sizes, and that the 0.45-um membrane was not effective in separating the colloidal and dissolved concentrations, as 

observed in many other streams affected by acid mine drainage (Kimball and others. 1992: Kimball and others, 1995).

Clear chemical distinctions among stream and inflow 

samples were distinguished by principal components analysis 

into seven groups (table 8). Inflows were part of four different 

groups. The most dilute inflows were grouped with the stream 

samples that were upstream from any mining influence. All 

these samples represent the results of weathering catchment 

bedrock that is unaffected by alteration or mining (group 1). 

One of these inflows was Jack Creek (T10), which drains a 

much larger area than the Bullion Mine tributary but results in 

this same dilute chemical composition as the most upstream 

samples in the Bullion Mine tributary (table 8). A second set 

of inflows (group 7) differed from the dilute inflows because 

they had higher calcium and sulfate concentrations, possibly reflecting some effects of mine waste or a change in the 

mineralogy that they drain. A third group of inflows (group 6) 

includes the acidic inflows that had such a strong effect on the 

stream.

Three groups of stream samples occurred downstream 

from the acidic inflows. Group 2 was immediately downstream from T01 and T02, and reflects the change to acidic, 

metal-rich stream water. In the biplot (fig. 32), this group 

generally lies along a line between inflows T01 and T02 and 

the dilute samples of group 1. Downstream from inflow T03 

a change occurred in the stream-water chemistry to higher 

concentrations of calcium and sulfate, and group 3 plots to the 

upper right of group 2 in the direction of inflow T03 (group 3). 

Downstream from inflows T08 and T09, a change to a higher 

pH occurred, and concentrations of several metals decreased 

(group 4). Segments S32 and S33 (group 5), downstream from 

Jack Creek, were quite different because of the dilution by 

Jack Creek and the instream chemical reactions that occurred 

in the mixing zone. Thus, changes in stream chemistry were 

quite systematic in response to the inflows. Details of these 

changes among groups will be illustrated by profiles of metal 

loading.
pH, IN STANDARD UNITS

vw

^^

"

CD'

r+o'3O

-a

^ |.rr

Q. C/j'r+ 033

O

n>

CD

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CD

l-fCT

crHCD

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T3

Kf CD

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CD

— *

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C/)

TMl

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m

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^

.

0 

0o

o0o

00

00o

^

00

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O CO ^ (Jl CD •xj 0

, , 1 , . , 1 , , , 1 , , , 1 , , ,

00 X - -* N) A— '^

— ------ «»-- -.-. ---^ ————————————— i- ........................................... .....9..... .......................... 

H y Acidic inflows (S06)

CO ^ 

^

^^ , ""

: V a 

"

^ 

0

^ (Jl t 

^

/ H 

§ A H - V o ^ ^ R 

- 

*x T2 transport site (S24) co § * ^ 

— ^^t _^fc

• ^^«*^T^ "^^ ^^ ^

^*^*"*^-Aw ^^

Narrow point in canyon (S25) /

: \ 

j

- ^ ° ~

i \ |l *T \ s i

^ > ^ ^ ^ CD

Sj!j 55^^ ^"Sl^3 || ||

01 m S S

\ Q) =*. _| __ 01 D o 

j

Jack Creek (S32) 

A

\

^

_ _ , , , , 1 , , , 1 , , , 1 , , , 1 , , ,

o

5'

a 

Io

0) Q.

(O
100

0.1

0.01

1E-3

1E-4

0 1,000

A

1,000 . i ,

100 r10

0.1

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•Ultrafiltrate• 0.45-micrometer filtrate• Total recoverable 

Inflows

c _ 'n inc CM

I*

5

100

10

2,000 3,000 4,000 5,000 6,000

0.01

1E-3

1E-4 

7,000 0

C

Ultrafiltrate0.45-micrometer filtrate 

Total recoverable 

Inflows

100 - 0.1

1,000 2,000 3,000 4,000 5,000 6,000 

DISTANCE ALONG STUDY REACH, IN FEET

1E-3 

7,000 0

D

• Ultrafiltrate• 0.45-micrometer filtrate• Total recoverable 

Inflows

1,000 2,000 3,000 4,000 5,000 6,000 7,000

Ultrafiltrate

0.45-micrometer filtrate 

• Total recoverable 

Inflows

S6

CDtw8CO

o

O

I

09

1,000 2,000 3,000 4,000 5,000 6,000 

DISTANCE ALONG STUDY REACH, IN FEET

7,000

Figure 30. Variation of A, aluminum; B, iron; C, copper; and D, zinc concentrations with distance, Bullion Mine tributary, September 1998.
Quantification of Metal Loading 245

Figure 31. Bullion Mine tributary showing turbid nature of stream water owing to colloidal suspension of solids, September 1998. Length of photo area is about 1 m.
246 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 8. Median composition of groups from principal components analysis for synoptic sampling sites, Bullion Mine tributary, 

September 1998.

[pH, in standard units; Dis, dissolved; LD, less than detection; Col, colloidal; all concentrations in milligrams per liter; -, no data]

Number of 

samples or 

solute

Number of 

samples

PH

Calcium

Magnesium

Sodium

Chloride

Sulfate

Aluminum

Cadmium

Copper

Iron

Lead

Manganese

Nickel

Strontium

Zinc

Phase

Dis

Dis

Dis

Dis

Dis

Dis

Dis

Col

Dis

Col

Dis

Col

Dis

Col

Dis

Col

Dis

Col

Dis

Col

Dis

Dis

Col

Group 1 

Unaffected stream 

sites

5

6.89

7.88

1. 73

21.2

31.8

7.43

LD

.049

.002

LD

LD

LD

LD

.061

LD

LD

.001

.002

LD

LD

.063

.011

LD

Group 1 

Unaffected 

inflows

4

6.61

9.50

2.31

2.72

.210

5.11

.013

-

.002

-

.004

-

.005

-

LD

-

.001

-

LD

-

.068

.022

-

Group 2 

Stream 

after inflows T1 

andT2

6

3.62

19.0

5.91

17.9

26.2

131

2.18

.048

.068

.001

1.20

.004

4.74

10.4

.029

LD

3.02

.015

.014

.002

.095

6.06

LD

GroupS 

Stream 

after 

inflow T3 

to inflow 

T8

16

3.65

24.9

7.47

15.8

22.4

160

2.80

.043

.087

LD

1.46

LD

5.01

8.48

.042

.007

3.82

LD

.020

.002

.115

7.90

.004

Group 3 

Inflow T4, 

acidic, 

but 

higher pH

1

4.61

63.7

15.2

4.23

0.730

273

1.89

-

.151

-

1.31

-

.107

-

.111

-

4.37

-

.049

-

.258

17.7

-

Group 4 

Stream 

from S25 

toS28

4

4.17

25.1

7.03

12.8

16.4

136

2.12

.177

.073

.004

1.15

.069

3.24

6.56

.031

.009

3.00

.165

.016

.005

.119

6.66

.479

Group 5 

Jack 

Creek 

samples

2

6.65

15.5

3.93

4.91

4.08

41.4

.024

.483

.019

.002

.043

.235

.005

1.58

LD

LD

.645

.016

.002

.003

.088

1.68

.181

Group 6 

Drainage 

from Bullion mine 

adit

3

2.82

89.2

33.7

5.27

2.94

1,100

17.9

-

.556

-

10.6

-

158

-

.382

-

25.1

-

.142

-

.310

47.4

-

Group 7 

Inflows 

T6, T7, 

andTS 

with 

higher pH

3

6.79

21.2

4.76

2.76

0.360

36.1

LD

-

.007

-

.011

-

.004

-

LD

-

.017

-

LD

-

.095

.446

-
Quantification of Metal Loading 247

C/) 

LU 

CC.

O 

o

C/)

LU

z 

o

Q_

O 

o

D_ 

O

z

CC 

Q_

Q 

LU

O 

C/)

-1

3.0

2.5

2.0

1.0

0.5

0.0

-0.5

-1.0

-1.

SCALED PRINCIPAL COMPONENT 1 LOADINGS 

1234

T07 

*

S01

S02 

Q H 

S03

T10

I I I I I I

J06

_T08

a Group 1

* Group 1 inflows

^ Group 2

O Group 3

* Group 3 inflows

<*> Group 4

* Group 5

* Group 6

* Group 7

S25

T03 -

S28

Strontium

S04

S05

C/) 

CD

Z

O

3

CN

O 

Q_

O 

O

DO

0 ?

CC 

Q_

Q 

LU

O 

C/)

-1

-6-5-4-3-2-1012345 

SCALED PRINCIPAL COMPONENT 1 SCORES

Figure 32. Biplot of principal component scores for synoptic samples and loadings for chemical constituents, 

Bullion Mine tributary, September 1998.
248 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Load Profiles

Loading profiles of metals in the Bullion Mine tributary 

are comparable to those in Uncle Sam Gulch, mostly because 

of the distinct sources of metals and the chemical reactions 

that transformed metals downstream from neutral-pH inflows. 

Changes in the load for each individual stream segment are 

illustrated in figures 33 through 42; and a summary of load 

calculations is shown in table 9. There were three characteristic patterns of loading profiles among the solutes in the 

Bullion Mine tributary: (1) solutes that were conservative all 

along the study reach, (2) solutes that were conservative and 

then reactive transport downstream from Jack Creek, and 

(3) solutes that was reactive along the entire study reach.

Cadmium (fig. 33). manganese (fig. 34). zinc (fig. 35), 

and sulfate (fig. 36) were mostly conservative along the entire 

study reach. For each of these solutes, the greatest loading 

occurred downstream from the acidic inflows in segments 

S06 and S10, and for manganese and zinc additional loading 

occurred in segment S25 (table 9). Because this latter increase 

in load occurred as an increase of colloidal manganese and 

zinc (figs. 34A and 35A), it may have been caused by stirring up of the streambed colloids during sampling. However, 

a clear increase in strontium load was observed in that same 

stream segment (fig. 37), and strontium load would not likely 

increase from stirring up of the bottom. Downstream from 

segment S25, there was some loss of manganese load to 

the streambed in segment S27, and a similar small amount 

occurred downstream from the confluence with Jack Creek at 

segment S32.

Aluminum (fig. 38), copper (fig. 39), and nickel (fig. 40) 

loads were similar to cadmium, manganese, zinc, and sulfate 

except that downstream from the confluence with Jack Creek 

(S32), they were more reactive. Their loads changed from 

almost completely dissolved in the Bullion Mine tributary to 

almost completely colloidal in Jack Creek. This is consistent 

with the change in pH from less than 5.0 to greater than 6.0 

that occurred as the two streams mixed (fig. 29).

Iron (fig. 41) and lead (fig. 42) were reactive along the 

entire study reach. Load profiles for dissolved and colloidal 

iron indicate the importance of the acidic inflow at TO 1 

(fig. 4L4). Because cadmium, copper, and iron reactions and 

loss to the streambed occurred on a time scale of transport 

within individual stream segments, their net instream load is 

less than the inflow load or is negative. Thus, the cumulative 

instream load is less than the cumulative inflow load (table 9). 

For example, the inflow load of iron increased 7.17 kg/day for 

segment S06, but instream load increased only 5.46 kg/day. 

The difference of 1.71 kg/day would be the amount of iron 

precipitation to the streambed. Travel time through the segment was less than 2 minutes, pointing out the rapid reaction 

of the iron precipitation and aggregation to form colloidal 

particles (Grundl and Delwiche, 1993; Kimball, Broshears, 

and others, 1994). Downstream from Jack Creek, a complete 

transformation of dissolved to colloidal iron occurred 

(fig. 41A); colloidal iron load increased by 0.72 kg/day and

the dissolved load decreased by 0.81 kg/day; the difference 

was from additional loss to the streambed.

The lead profile (fig. 42) also indicated reactive transport through the study reach. Total load clearly increased at 

each of the acidic inflows. Some of the lead changed between 

dissolved and colloidal phases in response to increases in pH 

downstream from site S25. Downstream from Jack Creek, all 

the lead was removed from the water column to the streambed, 

sorbed to the iron colloids.

Locations of Major Loading

Similarities among the loading profiles indicate two 

principal locations of the metal loading along the Bullion 

Mine tributary. The greatest loading for all the constituents 

except strontium was in segment S06 (table 9). Segment S10 

also received substantial loading. Inflows T01. T02, and T03, 

which are in segments S06 and S10, drain the Bullion mine 

adit, and their surface flow was traced back to the collapsed 

adit. From segment S15 to segment S25, metal loading was 

minimal. At segment S25, loads increased for several of the 

metals (table 9). This could be due to the narrowing of the 

canyon at that point (table 8), which may have forced some 

subsurface water into the stream channel.

Unsampled Inflow

Because the Bullion mine adit was the primary source of 

metals in the watershed, there was relatively little unsampled 

inflow in the Bullion Mine tributary (table 9). Unsampled 

inflow generally occurred at the same locations as the principal surface-water loadings, indicating that some of the flow 

from the adit had seeped into the ground but was still contributing to the load. Nickel and lead had the highest percentages 

of unsampled inflow (table 9).

Attenuation of Load

Downstream from the principal inflows of metals at T01, 

T02, and T03, attenuation of most of the metals was relatively 

slight. For cadmium, manganese, zinc, sulfate, copper, nickel, 

and iron, the inflow load exceeded the instream load at S06, 

which most likely means that there was some removal of these 

solutes that is not accounted for in the calculation of attenuation in table 9. At the low pH of Bullion Mine tributary, the 

removal of sulfate with iron could indicate the formation of 

schwertmannite as the streambed precipitate (Bigham and 

Nordstrom, 2000).

Colloidal iron was lost from the water column during 

transport downstream (fig. 41). The loss most likely involves a 

sequence of aggregation in the water column and then entrapment by biofilm on the streambed cobbles (Besser and others, 

2001). Packman and others (2000) have proposed that colloids 

can be strained from the water column by the streambed as 

hyporheic exchange of water takes place during transport.
Quantification of Metal Loading 249

0.040

< 0.035 

cc

LLJ

°- 0.030

CC 0025

O

5 0.020

z

9 0.015

D

^ 

Q

O

0.010

0.005

0 

A

0.030

Q 0.025 

CC

LLJ 

Q_

^ 0.020

CC 

0 

P 0.015

CO 

0

(/)

o

Mo

T3 'o

_<

-

Tr./t llrt

**

FFfai

1 

1

1

&. ^ A ^ \

A

E o ^

o «~ *± ^

-^ IS 

E S aCO 0 > g

£^ o °

4-< *— 1- (-

|.5 |8 

11 Z .£

Q co

^

/

*7tnrtntnlr7*in^TT7T7im'V i^ v-4

k--^

^^

1, i 1 , , / rnl

— ———— ^4. —————

— A— Dissolved instream load 

—v— Colloidal instream load 

••"••••" Total instream load 

^^— Cumulative instream load 

^^— Cumulative inflow load

, • i KrJ i , , ,^ , . i , 1 • Vi , 1 ! 1 F?!^

-

^-A

c7 ~

CO 

C/)

^^

CD -

6

It

O 

CO ->

^^^ 

7\ , , , , 1 , , , ,

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

Q 

O

0.010

0.005

LLJ 

0

z 

<

X

o

-0.005 

B

CO

o

^^| Surface-water inflow

l\\1 Dispersed, subsurface inflow

^^1 Loss

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

DISTANCE ALONG STUDY REACH, IN FEET

Figure 33. Variation of A, cadmium load with distance, and B, changes in load for individual stream segments, Bullion Mine tributary, 

September 1998.
250 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

1.50

E 1 -25

D_ 

CO

CCCD O

Q 

<

O

CO 

LJJ

Z

<

CD

Z

25

JO

7C

50 

>5

-

- coo

C/}

- O

• c

- o

-

;!

I

p

^

,,,,,,,.,,,,,,, ,^

/1

^ 10

C CN ol*

E

— ••-* P*]L _

E > ^ CO 

> CO O

co _O -jr

£; *C "~ CO ~ 

p- C«3

0 'o

Q CO

;

X

k A,.X ^

^ A ———

- A — Dissolved instream load 

— T— Colloidal instream load

^^— Total instream load

^^— Cumulative instream load

^^— Cumulative inflow load

» Vv

i i 1 i i i iV/i • * • if-\ i < • fi— ] • , , i i i i* i i 1 i

A/

-

~

b ^^

-

—

C\T 

CO

Jfi.

(I) -

CD

0

CO -3

j.-.-rrf. .,,-

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

1.4

CC 

LU 

D_

CO

1.2 -

1.0 -

co 

o

CO ^B Surface-water inflow 

IXX^ Dispersed, subsurface inflow 

I I Loss

0.8 -

0.6 -

0.4 -

CC 

CD 

O

Z 

Q 

O

Z

— 0.2 -

LJJ

CD 

Z 

< 0

o

-0.2

B

ws

R

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 

DISTANCE ALONG STUDY REACH, IN FEET

Figure 34. Variation of A, manganese load with distance, and B, changes in load for individual stream segments, Bullion Mine 

tributary, September 1998.
Quantification of Metal Loading 251

A

2.5

Q

DC 2.0

UJ

< 1.5

CC

^.fj^i.^fA^^^^jL- '

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

O

Z 

0

1.0

g 0.5

Z

UJ

Z 0

X

o

-0.5 

0

B

Figure 35.

September

f 1 Surface-water inflow

I\V1 Dispersed, subsurface inflow

1 —— lLoss

S25 Downstream - 

inflows neutral 

CD

6

E__ !r

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 

DISTANCE ALONG STUDY REACH, IN FEET

Variation of A, zinc load with distance, and B, changes in load for individual stream segments, Bullion Mine tributary, 

1998.
252 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

80

DC 

LU 

D_ 60

C/> 

^ 

<

DC 

O 

O

rr 40

Q 

<

O

SULFATE

N) 

0

o o

Q CD

, ,^^^^A i T. -1 r!. i ..... i .... i .... i ..... i

Dissolved instrearn load 

Cumulative instrearn load 

Cumulative inflow load

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

DC 

LU 

o_

DC 

(D 

O

Q 

O

CJ

^^| Surface-water inflow

IXXI Dispersed, subsurface inflow

CHI Loss

CO

J_

B

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 

DISTANCE ALONG STUDY REACH, IN FEET

Figure 36. Variation of A, sulfate load with distance, and B, changes in load for individual stream segments, Bullion Mine 

tributary, September 1998.
Quantification of Metal Loading 253

0.16

>-

<

Q 0.14

DC

LLJ

D_

03 °- 12

^

<

S 0.10

0

_l

^ 0.08

z

d

< 0.06

O

_l

^>

D 0.04

H

z

g 0.02

I- 4 

(A)

T;

~

-

CD

O 

C/J

- §

O

>+-

c

o 

T3

O

r**! J 

Z-tri-rtfrt

1

E^5f

i i i

E o" -^ tn

1 i 5 I

Co ^ VJ

0) 5= O >

to '~ ra TO

c « 2 «

^ T3 C 

O 'o

° TO ^

g-^KJ?

M^^^

• T "*"*-

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1 CN

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|i "77 —

—A— Dissolved instream load 1 ju

— T— Colloidal instream load 1 ^

•^^— Total instream load 1 CD ~

•^^ Cumulative instream load 1 "^

•^^TM Cumulative inflow load 1

I

1

1

1 _

1

^r "

-

^^^p

vr ^^^^^~ '

U — yww/v^or^rvv^^vy n*r> — v — v — * — y ———— y ———— * ————— ? ————— * —————————————————— * ————————————— 

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

A

0.12 | ——————————————————————————————————————————————————————————————————————

>-

Q

Q- 0.10

LLJ

D_

^

< 0.08

CC

(D

0

^ 0.06

Z

o"

O 0.04 _i

z

LLJ

2 0.02 |

•

CM

1 ———————————————————————————————————————————— 1 °°

1 1 Surface-water inflow ¥L

IXX^ Dispersed, subsurface inflow |

1

1^1 I^B

1

I

^^H

H

5 0 I

-w w LO • -

< 

~r 

1 

• 

- ^H ° *~ LO * ^ S 111^1 5 1 |l? SB H :

B

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 

DISTANCE ALONG STUDY REACH, IN FEET

Figure 37. Variation of A, strontium load with distance, and B, changes in load for individual stream segments. Bullion Mine 

tributary, September 1998.
254 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

1.25

Q

E 1.00

CO

cc

(D 0.75

O

Q 0.50 

O

D

Z 0.25

-

•

-

• <o

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CO

•^ • $ '-

. o

M-

:!

• ^

•

•

_

-

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f

I

•

I

t^

/

^ Aj^A^ " A ^ ^^ ^

E o" *; IH

° CO CO

E CO 5 O JSV.

i: "c t c

w — co 5°

i •- z c o •"!

Q co

/

I

^ — A ^^

\

L i I i i i M.

1 1 1 1

—A— Dissolved instrearn load

— v— Colloidal instrearn load

^— • Total instream load

^— - Cumulative instream load

——— Cumulative inflow load

i , l-trJ I • • *J i h.l i ! . i/i i i

, ,\7,

1

1

r^\

CN

CO

CO

0)

<J

o

-3

•

_

b —— A

II , , , , 1 i , , ,

A

1.0

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

Q

cc 0.8

LU

CO

DC 

CD 

O

0.6

0.4

Q

g 0.2

Z

LLJ 

(D

X 

CJ

-0.2

B

I I Surface-water inflow

fxXI Dispersed, subsurface inflow

i i Loss

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500 

DISTANCE ALONG STUDY REACH, IN FEET

Figure 38. Variation of A, aluminum load with distance, and B, changes in load for individual stream segments, Bullion Mine tributary, 

September 1998.
Quantification of Metal Loading 255

0.6

\

- CD

~ CO

• ^

• J°

<+—

c 

o

^^^^^^g

A4*

E o

E¥ eg 

S .-2 'o to

""^ ^ c 

co ^ £ —A— Dissolved instream load

| !"2 t ^ — T— Colloidal instream load 

o co z c ^^~ Total instream load 

——— Cumulative instream load 

-^TM— Cumulative inflow load

rv

~ —— A

1 \ 

\

\ 

\

\ 

\

1 CN

oo -

CD

£

1 O 

' °

II , , , , 1 , , . ,

0.5 -

0.4 -

<

Q

DC 

LU 

Q_

C/D 

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<

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^ 0.3 -

Q

< 0.2

_i

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LU 

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o °' 1

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500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

<

Q

DC 

LLJ 

D_

C/D 

^ 

<

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O

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0.6

0.5 -

0.4 -

0.3 -

0.2 -

0.1 -

-0.1

B

^| Surface-water inflow 

l\\^ Dispersed, subsurface inflow

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 

I

5,500 6,000 6,500 

DISTANCE ALONG STUDY REACH, IN FEET

Figure 39. Variation of A, copper load with distance, and B, changes in load for individual stream segments, Bullion Mine tributary, 

September 1998.
256 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

0.021

< 0.018 

Q

—A- Dissolved instream load

— r— Colloidal instream load 

^^— Total instream load

— ^— Cumulative instream load

CM 

CO

</D

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

.010

-0.004

B

^^| Surface-water inflow

l\\1 Dispersed, subsurface inflow

^^| Loss

8

T

CO 

CO 

(/D

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

DISTANCE ALONG STUDY REACH, IN FEET

Figure 40. Variation of A, nickel load with distance, and B, changes in load for individual stream segments, Bullion Mine tributary, 

September 1998.
Quantification of Metal Loading 257

1 f.

< 10

Q

DC

LU 

Q.

05 8

|

DC 

CD

3 6

Z

§ 4

0

z

O 9

DC

n v

_

*

•

. to 

o 

• CO

. o

M—

c

0 

- T3

: 3

_

_

.•

h>*M

H^HBl

^

•• 1 ..

,,,,,,,.,,,,,,,,

E n° r-*- +±InLT5

t! CO .E ^

P f 1-

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£^ o °

4-> &- ^. C~ 

(/) ~ 1- iS

C .0 TO g

O 'o •—

f~\ 03

/

_y

^

y\ 

A .Af^ ^\ *\ ^\ A A ^

t A A A. A

^J**A

, , , I , , , , I , , , , I , ,

— A— Dissolved instream load

— v— Colloidal instream load

— — Total instream load

— • — Cumulative instream load

——— Cumulative inflow load

^^__

' ^\ __ T _ ~~~~^

'- A —— A .^^^

^~^^'A - ————— A

~~~ — — A— —— -—A

\

"

•

.

-

-

~

—

-

-

-

_

CN 

CO

CO

0)

CD _

O

"o

CD -3

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 lAl l_ I L 1 K 1 1 1 1

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

A

8 | ————————————————————————————————————————————————————————————————————

^-

< 7

Q

DC

LU 

CL 6

05

< 5 ^^ *J

DC

CD

° *

o"- 3

0 2

Z

LU 1

CD

Z

<

<J

to

O

CO

_

-

.

TM

-

"

^^| Surface-water inflow -

IXX^ Dispersed, subsurface inflow

•• Loss -

-

•

-

1

' 1 i

• LD

• LD CM

• r- CO ^H co ^B f\l H N ho

JP M KN

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

B

DISTANCE ALONG STUDY REACH, IN FEET

Figure 41. Variation of A, iron load with distance, and B, changes in load for individual stream segments. Bullion Mine tributary. 

September 1998.
258 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

—A Dissolved instream load

—T— Colloidal instream load 

^—• Total instream load

—^— Cumulative instream load

——— Cumulative inflow load

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000 6,500

>-

Q 0.015

CC 

LLI

Q_

CO 0.010

^

<£

5 0.005

O

\/

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< -0.005 

O

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CJ

-0.020

....,,

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-

(

^

(

FF( ^

$TV

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-

2 (vj t ! Surface-water inflow

^ 55 l\\1 Dispersed, subsurface inflow

/ / 1 —— lLoss ^

/ V)

/ TM f\^\ T/ CM \

" X

El N\: ^-TU 1 ^ -

. 1 , , . . 1 , , , , 1 . , , , 1 , . . . 1 , , , , 1 . . . , 1 . . . , 1 , , . . 1 , , , 1, 1 . . . . 1 , , . .

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 6,000

B

DISTANCE ALONG STUDY REACH, IN FEET

Figure 42. Variation of A, lead load with distance, and B, changes in load for individual stream segments, Bullion Mine tributary. 

September 1998.

6,500
Quantification of Metal Loading 259

Table 9. Change in load for individual stream segments and summary of load calculations for selected solutes, Bullion 

Mine tributary, September 1998.

[Distance, in feet along the study reach; Al, aluminum; Cu, copper; Fe, iron; Mn, manganese; Ni, nickel; Pb, lead; Sr, strontium; Zn, zinc; SO4, 

sulfate; cumulative instream load, cumulative inflow load, unsampled load, and attenuation in kilograms per day; numbers in red with parentheses 

indicate a loss of load; cell color indicates the segments with the greatest load: red, largest load; orange, second largest; yellow, third; green, fourth; blue, fifth]

Segment number

SOI 

S02 

S03 

S04 

S05

S06

S07

SOS

S09

S10

Sll

S12

S13

S14

S15

S16

S17

S18

S19

S20

S21

S22

S23

S24

S25

S26

S27

S28

S29

S30

S31

S32

S33

Cumulative instream load

Cumulative inflow load

Percent inflow load

Unsampled inflow

Percent unsampled load

Attenuation

Percent attenuation

Distance

0 

150 

235 

296 

341

383

437

485

540

627

726

793

856

945

1,025

1,109

1,197

1,264

1,404

1,522

1,672

1,808

1,990

2,155

2,278

2,585

2,951

3,457

3,958

4,729

5,338

5,454

6,019

Al

0.007 

.005 

.021

.019

! .637

.149

.158

.147

(.157)

(.109)

1.14

1.04

91

.105

9.2

.286

25

Cd Cu Fe

0.001 0.000 0.006 

.000 .001 .006 

uuuut (.001) ^||^ 

(.026) 

.005 .020

.020 .380 5.46

^n^

.UU6 .0/3

.603

| .064 §.789

(.859)

(.383)

(.316)

(-482)

(.315)

(.096)

(.313)

.027 .569 6.92

.035 .577 7.19

131 101 104

(.008) (.008) (.270)

(31) (1.4) (3.9)

.000 .096 2.69

1.4 17 39

Mn Ni Pb

0.001 0.000 0.000 

.002

(.001) .005 

.013 (.005)

.961 .004 .010^

m .117 .002 ^

^^^V -003 ^HB

(.010)

.004

.002 (.005)

.152* |

(.152) (.003)

(.002)

^^^| (.005)

0.007

(.165) (.003) (.018) |

••

1.46 .017 .047

1.42 .010 .025

97 59 53

.047 .007 .022

3.2 41 47

.318 .008 .043

22 45 91

Sr Zn

o.onj 0.005

(.002) 

(.000) 

.001 

.024

.011 1.68

^^m

.148

.005 §PB^

.004

.191

.005

^^H .441

—.211

(-451)

••

.147 3.56

.141 3.08

96 87

.006 .480

4.0 13

.000 .454

.0 13

so.

1.92 

.126 

.112

.573

"3S.T^

I 3.33

3.44

3.41

C37^

(4.24)

4.00

4.61 J

4.81 '

77.8

76.0

98

1.80

2.3

4.24

5
260 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Downstream from the inflow of Jack Creek, substantial 

attenuation occurred for copper, manganese, nickel, and lead 

(figs. 39, 34, 40, and 42). These metals most likely sorbed 

to iron and aluminum colloids. As the colloidal material was 

removed, the metal loads decreased. Cadmium, zinc, aluminum, and iron (figs. 33, 35, 38, and 41) were transformed 

from dissolved to colloidal phases but were not substantially 

removed from the water column; their total-recoverable concentrations remained nearly constant.

Discussion

On the basis of the three tracer-injection studies, we can 

make some generalizations about sources of metals within the 

Boulder River watershed and discuss the major processes that 

affect the metal transport. Because copper and zinc adversely 

affect the aquatic life, this discussion will focus on those two 

metals.

Sources of Metals

Surface-water inflows were the principal source of the 

copper and zinc loads. Unsampled inflow of copper was 

23 percent of the total cumulative load in Cataract Creek, but 

only 8 percent in Uncle Sam Gulch, and less than detection 

in the Bullion Mine tributary (tables 3, 6. and 9). Unsampled 

inflow of copper in Cataract Creek occurred only in the last 

large stream segment between Big Limber Creek and the 

mouth (fig. 105). Because access for sampling was not given, 

we do not know if a source in that segment could have been 

sampled. Unsampled inflow for zinc load ranged from 12 to 

26 percent in the three study reaches, indicating that most of 

the zinc loads also were surface-water inflows.

This surface-water inflow is dominated by drainage from 

the Crystal and Bullion mine adits in both Basin and Cataract 

Creeks at low flow (tables 3, 6, and 9). Nimick and Cleasby 

(this volume) had a similar conclusion, based on more widespread watershed sampling. Other sources of metals in these 

watersheds are minimal in comparison to these adit drainages. The tracer-injection studies were conducted at different 

times and under slightly different conditions, but they provide 

a picture of loading during base-flow conditions that can be 

compared among the streams. Loading of copper and zinc 

from the Bullion Mine adit was 0.50 and 2.69 kg/day, respectively. By comparison, loading from the Crystal Mine adit was 

3.05 and 13.9 kg/day for copper and zinc; or about five times 

greater. Loadings of copper and zinc reaching the Boulder 

River from Cataract Creek are greater than loads from Basin 

Creek (Nimick and Cleasby, this volume), which is consistent 

with these differences in loading.

Processes Affecting Metals

Metal attenuation, particularly in Uncle Sam Gulch 

and the Bullion Mine tributary, resulted from inflows of 

near-neutral pH water downstream from the principal metal 

sources. Those elements that are more reactive in the streams, 

principally aluminum, copper, iron, and lead, were lost to 

the streambed in Uncle Sam Gulch. Although they were not 

lost to the same extent in the study reach of the Bullion Mine 

tributary, they were affected by attenuation downstream from 

the confluence with Jack Creek. Attenuation may continue in 

Basin Creek (Nimick and Cleasby, this volume). A substantial 

amount of the manganese and zinc that entered the streams 

from both mine adits was transported all the way to the Boulder River and likely affects aquatic health there.

Metals that are lost to the streambed can be flushed 

downstream during periods of snowmelt runoff or storms 

(Church and others, 1997). Thus, attenuation of the metals 

does not mean that the metals are no longer a concern for 

aquatic health. As part of the streambed material, these 

metals can enter food pathways to aquatic organisms (Farag 

and others, this volume, Chapter D10). This has also been 

documented in other streams affected by mine drainage (Clements, 1994; Besser and others, 2001).

Implications

Loading profiles that have been documented from the 

tracer-injection studies have important implications for possible remediation. When metal loading in a watershed is 

dominated by several discrete sources, and those sources contribute a high percentage of the total loads, the most effective 

approach to remediation would obviously be to focus on those 

identified sources. Remediation efforts of the many smaller 

sources of metals would have only limited impact on stream 

recovery. The lack of regional alteration that can produce 

widespread metal loading also simplifies remediation options.

Summary

Tracer-injection and synoptic sampling methods were 

used to quantify the locations and magnitude of loading to 

selected reaches of three streams in the Boulder River 

watershed study area in Montana. Tracer studies helped 

identify the location of major sources of metal loading to the 

streams, the extent of loading from subsurface sources, and 

the extent of attenuation downstream from the sources. Along 

the 40,905-ft study reach of Cataract Creek, 21.2 kg/day of 

zinc were added to the stream. About 75 percent of this load 

came from Uncle Sam Gulch, a principal tributary. The major 

source of metal loading to Uncle Sam Gulch was the Crystal 

mine adit discharge. The Bullion Mine adit discharge was the 

principal source to the Bullion Mine tributary of Jack Creek. 

Other sources were small in comparison to these two. The adit
Quantification of Metal Loading 261

discharge from the Bullion mine accounted for 2.8 kg/day of 

zinc, which was only about 20 percent of the zinc load coming 

from the Crystal mine adit in Uncle Sam Gulch. Both adit discharges drain the same mineral deposit and contribute acidic, 

metal-rich water to the receiving streams. Most of the loading 

was from identifiable surface inflows, but part of the total load 

of each metal was contributed by subsurface inflow. During 

transport in Uncle Sam Gulch and the Bullion Mine tributary, much of the iron and aluminum was transformed from 

dissolved to colloidal phases downstream from the inflows of 

neutral-pH tributaries. This colloidal material affects the transport of other metals that sorb to the colloids. Deposition of this 

material on the streambeds provides a route for metals to enter 

the food web and create a condition of chronic toxicity for fish 

downstream. These two mine-adit sources likely have the most 

impact on the aquatic health of the Boulder River watershed.

References Cited

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cations: New York, John Wiley, 489 p.

Bencala, K.E., and McKnight, D.M., 1987, Identifying instream variability—Sampling iron in an acidic stream, in 

Averett, R.C., and McKnight, D.M., eds., Chemical quality 

of water and the hydrologic cycle: Chelsea, Mich., Lewis 

Publishers, Inc., p. 255-269.

Bencala, K.E., McKnight, D.M., and Zellweger, G.W., 1990, 

Characterization of transport in an acidic and metal-rich 

mountain stream based on a lithium tracer injection and 

simulations of transient storage: Water Resources Research, 

v. 26, p. 989-1000.

Besser, J.M., Brumbaugh, W.G., May, T.W., Church, S.E., and 

Kimball, B.A., 2001, Bioavailability of metals in stream 

food webs and hazards to brook trout (Salvelinus fontinalis) 

in the Upper Animas River watershed, Colorado: Archive of 

Environmental Contamination and Toxicology, v. 40, 

p. 48-59.

Besser, J.M., and Leib, K.J., 1999, Modeling frequency of 

occurrence of toxic concentrations of zinc and copper 

in the Upper Animas River, in Morganwalp, D.W., and 

Buxton, H.T., eds., U.S. Geological Survey Toxic Substances Hydrology Program—Proceedings of the Technical Meeting, Charleston, S.C., March 8-12, 1999, Volume 

1, Contamination from hardrock mining: U.S. Geological 

Survey Water-Resources Investigations Report 99-4018A, 

p. 75-81.

Bigham, J.M., and Nordstrom, D.K., 2000, Iron and aluminum hydroxysulfates from acid sulfate waters, in Alpers, 

C.N., Jambor, J.L., and Nordstrom, D.K., eds., Sulfate 

minerals—Crystallography, geochemistry, and environmental significance: Mineralogical Society of America, 

Reviews in Mineralogy and Geochemistry, 

v. 40, p. 351-403.

Broshears, R.E., Bencala, K.E., Kimball, B.A., and 

McKnight, D.M., 1993, Tracer-dilution experiments and 

solute-transport simulations for a mountain stream, Saint 

Kevin Gulch, Colorado: U.S. Geological Survey WaterResources Investigations Report 92-4081, 18 p.

Church, S.E., Kimball, B.A., Fey, D.L., Ferderer, D.A., 

Yager, T.J., and Vaughn, R.B., 1997, Source, transport, 

and partitioning of metals between water, colloids, and 

bed sediments of the Animas River, Colorado: U.S. Geological Survey Open-File Report 97-151, 135 p.

Cleasby, T.E., Nimick, D.A., and Kimball, B.A., 2000, 

Quantification of metal loads by tracer-injection and 

synoptic sampling methods in Cataract Creek, Jefferson 

County, Montana, August 1997: U.S. Geological Survey 

Water-Resources Investigations Report 00-4237, 39 p.

Clements, W.H., 1994, Benthic invertebrate community 

responses to heavy metals in the Upper Arkansas River 

basin, Colorado: Journal of the North American Benthological Society, v. 13, no. 1, p. 30-44.

Davis, J.C., 1986, Statistics and data analysis in geology, 

Second Edition: New York, John Wiley, 646 p.

Daultrey, S., 1976, Principal components analysis: Concepts and Techniques in Modern Geography 8, Institute 

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Desborough, G.A., Leinz, R.W, Sutley, S.J., Briggs, PH., 

Swayze, G.A., Smith, K.S., and Breit, George, 2000, 

Leaching studies of schwertmannite-rich precipitates 

from the Animas River headwaters, Colorado, and Boulder River headwaters, Montana: U.S. Geological Survey 

Open-File Report 00-004, 16 p.

Fey, D.L., Church, S.E., and Finney, C.A., 2000, Analytical 

results for Bullion Mine and Crystal mine waste samples 

and bed sediments from a small tributary to Jack Creek 

and from Uncle Sam Gulch, Boulder River watershed, 

Montana: U.S. Geological Survey Open-File Report 

00-031, 63 p.

Fulghum, J.E., Bryan, S.R., Linton, R.W., Bauer, C.F., and 

Griffis, D.P., 1988, Discrimination between adsorption 

and coprecipitation in aquatic particle standards by surface analysis techniques—Lead distributions in calcium 

carbonates: Environmental Science & Technology, v. 22, 

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262 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Grundl, T., and Delwiche, J., 1993, Kinetics of ferric oxyhydroxide precipitation: Journal of Contaminant Hydrology, 

v. 14, p. 71-97.

Grundy, W.D., and Miesch, A.T., 1987, Brief descriptions of 

STATPAC and related statistical programs for the IBM 

personal computer—Documentation: U.S. Geological Survey Open-File Report 87^11-A, 34 p.

Jarrett, R.D., 1992, Hydraulics of mountain rivers, in Yen, 

B.C., ed., Channel flow resistance centennial of Manning's 

formula: International Conference of the Centennial of 

Manning's and Kuichling's Rational Formula, Littleton, 

Colo., Water Resources Publications, p. 287-298.

Kilpatrick, FA., and Cobb, E.D., 1985, Measurement of discharge using tracers: U.S. Geological Survey Techniques of 

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sampling to measure metal loading from acid mine drainage: U.S. Geological Survey Fact Sheet FS-245-96.

Kimball, B.A., Bencala, K.E., and Broshears, R.E., 1994, 

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Button, A., ed., Toxic substances in the hydrologic sciences: 

Minneapolis, Minn., American Institute of Hydrology, 

p. 80-94.

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Investigations Report 89-4150, 20 p.
Short-Term Variation of Trace-Element 

Concentrations during Base Flow and 

Rainfall Runoff in Small Basins, 

August 1999

By John H. Lambing, David A. Nimick, and Thomas E. Cleasby

Chapter D7 of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-D7

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract...................................................................................................................................................... 267

Introduction............................................................................................................................................... 267

Purpose and Scope.........................................................................................................................268

Methods............................................................................................................................................ 268

Diel Variation of Trace-Element Concentrations during Base Flow................................................. 269

High Ore Creek................................................................................................................................. 269

Other Streams..................................................................................................................................270

Correlation of Zinc Concentrations with Field Parameters...................................................... 270

Streamflow............................................................................................................................... 270

pH..................................................^

Dissolved Oxygen................................................................................................................... 272

Specific Conductance............................................................................................................ 272

Water Temperature................................................................................................................ 273

Variation of Zinc Concentrations during Rainfall Runoff.................................................................... 273

Jack Creek Basin............................................................................................................................. 273

Cataract Creek Basin...................................................................................................................... 274

Implications of Short-Term Variation in Trace-Element Concentrations......................................... 275

Summary.................................................................................................................................................... 277

References Cited...................................................................................................................................... 277

Figures

1. Map showing location of study area and sampling sites ................................................ 268

2-6. Graphs showing:

2. Diel variation of dissolved arsenic, copper, manganese, and zinc

concentrations in High Ore Creek, August 2-4,1999 ................................................ 269

3. Diel variation and correlation of dissolved zinc concentrations

in High Ore Creek, August 2-4,1999, with selected field parameters .................... 271

4. Variation of dissolved zinc concentrations during rainfall runoff in 

Bullion Mine tributary and Jack Creek below Bullion Mine tributary, 

August 2-3,1999............................................................................................................... 274

5. Variation of dissolved zinc concentrations during rainfall runoff in 

Uncle Sam Gulch and Cataract Creek below Uncle Sam Gulch, 

August 4-5,1999............................................................................................................... 275

6. Hypothetical diel variation of dissolved zinc concentrations in Boulder River

resulting from inflow of High Ore Creek....................................................................... 276
CONVERSION FACTORS, VERTICAL DATUM, ABBREVIATED UNITS

Multiply By To obtain 

cubic foot per second (ftVs)__________0.028317 cubic meter per second______

Temperature can be converted to degrees Celsius (°C) or degrees Fahrenheit (°F) by the following 

equations:

°C = 5/9(°F-32) 

°F = 9/5°C + 32

Sea level: In this report, "sea level" refers to the National Geodetic Vertical Datum of 1929 (NGVD of 

1929)—a geodetic datum derived from a general adjustment of the first-order level nets of both the United 

States and Canada, formerly called Sea Level Datum of 1929.

ug/L microgram per liter

ug/L/hour microgram per liter per hour

urn micrometer

uS/cm microsiemens per centimeter at 25 degrees Celsius

mg/L milligram per liter

Chapter D7

Short-Term Variation of Trace-Element Concentrations 

during Base Flow and Rainfall Runoff in Small Basins, 

August 1999

By John H. Lambing, David A. Nimick, and Thomas E. Cleasby

Abstract

Water-quality data for the Boulder River watershed of 

southwest Montana indicated that dissolved zinc concentrations vary cyclically throughout the day during base flow. To 

provide insight into the pattern and magnitude of traceelement concentration changes during a 24-hour (diel) cycle, 

water samples were collected hourly in three small tributary 

basins of the Boulder River watershed that drain abandoned 

mine lands. Hourly zinc variations were examined at five 

sites in High Ore, Jack, and Cataract Creeks; arsenic, copper, 

and manganese also were analyzed at the High Ore Creek 

site. Dissolved zinc concentrations in High Ore Creek varied 

by about 400 (ig/L (micrograms per liter) during a 24-hour 

cycle, representing about a three-fold change in concentration. 

Another type of short-term variation in zinc concentrations 

was documented when rainstorms produced runoff over mine 

wastes during the sampling of base flow at four sites. Within 

1 to 5 hours following the onset of intense rain, dissolved 

zinc concentrations increased rapidly at all four sites, 

ranging from a 670 ^ig/L increase in Cataract Creek below 

Uncle Sam Gulch to a 6,200 (ig/L increase in a tributary below 

the Bullion mine. Short-term variations of trace-element 

concentrations caused by either diel cycles or rainfall runoff 

can potentially affect interpretation of trace-element sources, 

long-term trends, and biological risk.

Introduction

Periodic sampling conducted during 1997-99 to describe 

water-quality conditions on a watershed scale (Nimick and 

Cleasby, this volume. Chapter D5) provided insufficient data 

to characterize two important phenomena: diel (24-hour) 

variation in trace-element concentrations during base flow 

and changes induced by short-duration rainstorm events. Diel 

cycles have been noted in other streams affected by metals 

(McKnight and others, 1988; Brick and Moore, 1996; Nimick

and Cleasby, 2001) and arsenic (Fuller and Davis, 1989) 

derived from mine wastes, as well as naturally occurring 

arsenic (Nimick and others, 1998). The specific mechanism 

causing diel concentration changes is not known, but the effect 

likely results from a combination of geochemical, biological, 

and physical processes that affect the partitioning of trace elements between the dissolved and solid phases. Such processes 

that occur regularly during the course of a 24-hour cycle could 

produce systematic temporal patterns in trace-element concentrations, thereby causing analytical results to vary depending 

on the time of day that samples are collected. Water-quality 

data collected for Cataract Creek (Cleasby and others, 2000) 

and High Ore Creek (Nimick and Cleasby, 2000) indicated 

that relatively large variations of dissolved zinc concentrations 

were occurring at different times of the day during base flow. 

This phenomenon warranted further investigation because 

diel concentration changes might affect synoptic load calculations and subsequent interpretation of trace-element sources, 

detection of long-term trends, and reliable evaluations of the 

effectiveness of remediation efforts. In addition, diel cycles 

in concentrations of potentially toxic constituents could affect 

assessment of biological exposure risks.

Short-term and potentially large variations in traceelement concentrations also can be caused by rainfall runoff 

that flushes trace elements from mine wastes into stream 

channels. This type of pulse event has been documented in 

mining areas where waste rock or mill tailings are exposed, 

or where historical floods have redistributed tailings along 

the flood plain (Lambing, 1991; Nimick and Moore, 1991; 

Smith and others, 1998). Because of the inherent difficulty 

in sampling short-lived and localized storm events, little 

quantitative information exists on the duration and magnitude of elevated trace-element concentrations that can occur 

in response to the overland flushing of mine waste. Tailings 

erosion and transport, however, can be an extremely important 

influence in mining-impacted watersheds, as this mechanism 

of metal delivery to the stream is presumed to be responsible 

for fishkills noted in other mining areas (Lambing, 1991; U.S. 

Environmental Protection Agency, 1999).
268 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Hourly sampling was conducted at five sites in three 

tributary basins of the Boulder River watershed during August 

1999 (fig. 1) to quantify short-term variation in traceelement concentrations associated with diel cycles. Dissolved 

zinc was chosen as the primary trace element for analysis 

because it typically is present at detectable concentrations in 

the tributary basins, is known to display diel cycles (Brick and 

Moore, 1996), and can be toxic to aquatic life. Although the 

study was not originally designed to sample rainstorm runoff, 

rainstorms over two of the three basins produced runoff during 

sampling that provided a unique opportunity to characterize 

an important hydrologic condition that occurs irregularly, is 

short-lived, and is logistically difficult to sample.

Boulder River 

watershed 

study 

area

Boulder River

watershed

study

area

112*20'

LEWIS AND 

CLARK CO 112-10'

46°22'3Q'

56

EXPLANATION 

T Water-quality site and 

number

Base from U.S Geological Survey 

1:100,000 Butte North, 1994

SMILES

2 3 KILOMETERS

Figure 1. Location of study area and sampling sites. Site 

numbers are those assigned by Nimick and Cleasby (this 

volume). Altitude shown in feet.

Purpose and Scope

The original purpose of this investigation was to collect 

data on diel changes in trace-element concentrations during 

base flow at five sites in three small basins—Jack, Cataract, 

and High Ore Creeks—that drain abandoned mine lands in the 

Boulder River watershed study area (fig. 1). The intent was 

to utilize these data to define temporal patterns and quantify 

magnitudes of trace-element concentration changes. This 

information could help to resolve whether load variations 

determined from synoptic sampling represented source inputs 

or sampling artifacts. Samples were collected hourly over 

1.5- to 2-day periods to document the changes in dissolved 

zinc concentrations during base-flow conditions. Samples 

from the High Ore Creek site also were analyzed for dissolved 

arsenic, copper, and manganese to examine if concentrations of other trace elements exhibited diel cycles. In addition, field parameters known to exhibit diel cycles in aquatic 

environments (streamflow, pH, dissolved oxygen, specific 

conductance, and water temperature) were measured hourly 

to identify associations with zinc concentrations that could be 

potentially useful for understanding the process or processes 

controlling diel variations.

During the collection of hourly samples in the Jack and 

Cataract Creek basins, localized rainstorms produced runoff 

that interrupted base flow. However, the hourly samples of 

runoff collected during and following these rainstorms provided data characterizing the variations of dissolved zinc 

concentrations in response to a short-duration storm. The 

investigation was thus effectively expanded to include an 

assessment of rainfall runoff over mine wastes. Consequently, 

this report documents short-term changes in zinc concentrations and related parameters resulting from two distinct 

processes.

Methods

Automated pumping samplers were used to collect waterquality samples at hourly intervals at each site. The intake 

of each sampler was placed in a riffle near midstream where 

the stream was well mixed. Samples were processed within 

4 hours of collection according to procedures described by 

Wilde and others (1998). Samples were filtered through a 

0.1-jim (micrometer) plate filter and acidified using ultrapure 

nitric acid. Field measurements of pH, dissolved oxygen, 

specific conductance, and water temperature were recorded 

hourly at each site with a multiparameter meter according to 

procedures described in Wagner and others (2000). At each 

site, the meter was submerged in the stream near the intake of 

the pumping sampler.

Several different methods were used for the measurement 

of streamflow during this study. Streamflow was determined hourly in High Ore Creek by tracer dilution methods 

using procedures described by Kimball (1997). Samples for 

trace-element analyses from High Ore Creek were collected
Short-Term Variation of Trace-Element Concentrations 269

upstream from the tracer-injection point and were unaffected 

by the chloride solution. At the other four sites, streamflow 

values were determined periodically either by current-meter 

measurements (Cataract and Jack Creek sites) or with a 

Parshall flume (Uncle Sam Gulch and Bullion Mine tributary 

sites).

Most samples were analyzed for dissolved zinc by the 

U.S. Geological Survey (USGS) National Water Quality 

Laboratory in Denver, Colo. Most samples from the High Ore 

Creek site also were analyzed by the USGS for other selected 

trace elements (arsenic, cadmium, copper, and manganese) 

and for chloride (to calculate hourly streamflow values). 

Dissolved trace elements were determined by inductively coupled plasma-mass spectrometry, and dissolved chloride was 

determined by ion chromatography. Analytical procedures are 

described in Garbarino and Taylor (1996) and Fishman (1993).

Diel Variation of Trace-Element 

Concentrations during Base Flow

During sampling in the Jack and Cataract Creek basins, 

rainfall runoff prevented full characterization of diel cycles 

under base-flow conditions. No significant rainfall or overland runoff was observed during sampling in the High Ore 

Creek basin; consequently, data for this site represent the most 

complete description of the base-flow diel cycle of traceelement concentrations. Hourly data for High Ore Creek were 

examined to determine temporal patterns and the magnitude 

of dissolved trace-element concentration changes, with zinc 

being the primary element evaluated.

High Ore Creek

The diel variation of dissolved zinc concentrations in 

High Ore Creek (site 56, fig. 1) over a 53-hour period during 

August 2-4, 1999, is shown at the bottom of figure 2. The 

variation over the approximately 2-day period was relatively 

consistent, displaying a distinct symmetry in both magnitude 

and timing during the daily rise and fall of concentrations. 

The difference between the minimum and maximum zinc 

concentrations was about 400 ug/L during the period of sampling. The minimum concentrations were about 210 jug/L and 

occurred in the early evening at about 1700 hours. The maximum concentrations also were similar on both days, ranging 

from about 580 to 630 u,g/ L. The maximum concentrations 

represented about a three-fold increase over the minimum and 

lasted about 2 hours in the early morning shortly after sunrise 

(from about 0600 to 0800 hours). Concentrations increased 

relatively gradually on the rising limb, followed by a more 

rapid concentration decrease on the falling limb. The average 

rate of concentration change during the falling limb (about 

45 jag/L/hour) was slightly greater than that during the rising 

limb (about 30 ug/L/hour).

0600 1200 

234 

1800 2400 0600 1200 1800 2400 0600 1200 18 

AUGUST 1999

Figure 2. Diel variation of dissolved (0.1 -urn filtration) arsenic, 

copper, manganese, and zinc concentrations in High Ore Creek 

(site 56), August 2-4,1999.

In addition to zinc, diel variations of dissolved arsenic, 

copper, and manganese concentrations are shown in figure 

2 to allow comparison of temporal patterns and magnitude 

of change. These data for base-flow conditions in High Ore 

Creek indicate that diel cycles exist to varying degrees for 

each of the four trace elements shown. In general, two patterns are evident: manganese and zinc display similar timing of concentration changes during the day, while arsenic 

and copper have nearly the opposite timing of concentration maxima and minima relative to zinc. Manganese is the 

most similar to zinc in the proportional magnitude of its diel
270 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

cycle. For example, the diel range of zinc concentrations was 

approximately three-fold (about 200 to 600 ng/L) and the 

maximum and minimum concentrations generally occurred at 

about 0700 and 1700 hours, respectively. Similarly, the diel 

range for manganese concentrations (35 to 87 fig/L for the 

first-day cycle) was about 2.5-fold for most of the sampling 

period, although an anomalous increase in manganese concentrations during the last few hours of the second day may not 

be representative of the typical diel pattern. The maximum 

and minimum dissolved manganese concentrations occurred at 

about 0800 and 1800 hours, respectively. In contrast, the diel 

range for arsenic and copper concentrations was somewhat 

less than for manganese or zinc, varying only about 1.5-fold 

between the minimum and maximum concentrations. Concentrations of arsenic and copper also were substantially lower, 

with arsenic ranging from 22 to 33 [j,g/L and copper ranging 

from about 3 to 4 (j.g/L. The differences in timing of the diel 

concentration cycles for arsenic and copper relative to those 

for manganese and zinc indicate that either different processes 

are driving the concentration changes, or that the instream 

supply of arsenic and copper, possibly attached to colloids 

or metal-hydroxide coatings on streambed sediment, is more 

limited and cannot support a large shift in partitioning between 

the dissolved and particulate phases under the ambient physical and chemical conditions in the stream.

Other Streams

Base-flow conditions at the other four sites (sites 17, 19, 

43, and 44, fig. 1) lasted only for about the first 10 to 12 hours 

of hourly sampling before the onset of rainfall runoff (between 

about 1600 and 1800 hours on August 2 and 4). Zinc concentration data for these short pre-rainfall sampling periods 

generally follow the same pattern observed at High Ore Creek: 

maximum values occurred in early morning, followed by 

decreasing values through late morning and afternoon. The 

magnitude of the variations, however, was minor compared to 

that for High Ore Creek.

In the Jack Creek basin, the differences between the 

minimum and maximum zinc concentrations during the prerainfall period (about 0600 to 1800 hours on August 2) were 

about 250 to 300 ^g/L at both the Bullion Mine tributary 

(from 3,900 to 4,150 ^g/L) and Jack Creek mainstem (from 

722 to 1,010 Mg/L). Although the magnitude of variation was 

similar at both sites, the pre-rainfall concentration difference 

represented only about a 6 percent change at the Bullion Mine 

tributary, but more than a 40 percent change at the Jack Creek 

site. The limited variability in diel zinc concentrations at the 

Bullion Mine tributary may be due to the low ambient pH 

(about 5.2 during base flow), which could prevent geochemical partitioning between the dissolved and particulate phases.

In the Cataract Creek basin, differences between the 

minimum and maximum concentrations during the 

pre-rainfall period (about 0700 to 1800 hours on August 4) 

were 660 ^ig/L (from 4,330 to 4,990 pg/L) in Uncle Sam

Gulch and about 100 ^ig/L (from 628 to 731 ^ig/L) in Cataract 

Creek. These concentration differences represent about a 

15 percent variation at both sites.

Because the pre-rainfall data for the Jack and Cataract 

Creek basins span the period from about 0600 to 1800 hours, 

the full range of the zinc diel cycle likely was encompassed 

because that general time interval included the diel minimum 

and maximum values at High Ore Creek. If this assumption 

is correct, then the diel changes in zinc concentrations in the 

Jack and Cataract Creek basins are proportionally much less 

than the 3-fold change observed for High Ore Creek.

Correlation of Zinc Concentrations with 

Field Parameters

The correlation of diel variations of dissolved zinc concentrations and selected field parameters in High Ore Creek 

(fig. 3) was examined to provide insight into possible causes 

of the diel zinc cycles. Field parameters such as streamflow, 

pH, dissolved oxygen, specific conductance, and water temperature are easily measured, are known to exhibit diel cycles, 

and might be associated with geochemical processes that 

control the diel zinc cycle. In addition, identification of strong 

correlations between field parameters and zinc concentrations could provide a basis for developing either mathematical 

methods or sampling strategies to minimize the effect of diel 

variations on data sets used to interpret trace-element sources, 

long-term trends, and biological risk.

The strength of relations was evaluated by the coefficient of determination (R2), which expresses the proportion of 

total variation in the dependent variable (Y) that is explained 

by regression with the independent variable (X). Also, the 

closeness in patterns of change and timing of maximum and 

minimum values was considered indicative of whether diel 

fluctuations in zinc concentrations have a strong likelihood of 

a direct geochemical association with the field parameter.

Streamflow

Concurrent diel variations in streamflow and dissolved 

zinc concentration in High Ore Creek are shown in figure 3A. 

Streamflow during the 2-day period showed a nearly 1.5-fold 

diel variation, ranging from about 0.6 to 0.9 ft3/s (cubic feet 

per second). In many streams, flow increases commonly are 

associated with dilution and decreasing solute concentrations, but the timing of the diel streamflow variations in High 

Ore Creek relative to those of dissolved zinc concentrations 

does not support a dilution effect. Rather, the timing of peak 

dissolved zinc concentrations (around 0600 to 0800 hours) 

coincides with the rising limb of the diel flow increase.

The relation between streamflow and dissolved zinc concentration in High Ore Creek was weak (R2 = 0.29) and had 

a positive slope, indicating that dissolved zinc concentrations 

increase as flow increases. Dissolved metal concentrations 

that increase with flow have been observed in other streams
Short-Term Variation of Trace-Element Concentrations 271

O ^ Q 119- 2

3iVA 1.0

0.8

°

¥ 0.6

- 0.4

O Zinc

A Streamflow

600

800

600

400

200

800

600

- 400

200

R2 =0.29

o o

, ,I?,CCP I Q I , i ,?, i M i i i i i i i i i i i i i i i , i 200

0.5 0.6 0.7 0.8 0.9 1.0

INSTANTANEOUS STREAMFLOW, IN CUBIC FEET PER SECOND

800

600

200

R2 =0.45 -

8.1 8.2 8.3 

pH, IN STANDARD UNITS

8.4

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Hi

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O o DC >- 9 LU 

X b °- an O < en 8-°

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LU 5 <

> if cc 7.5

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6.5

800

600 ^ 600

200 o 200

R2 =0.67

6.5 7.0 7.5 8.0 8.5

DISSOLVED OXYGEN CONCENTRATION,

IN MILLIGRAMS PER LITER

- 600

800

600

400

200

R2 =0.55

295 305 315 325 335 345 355 

SPECIFIC CONDUCTANCE, IN MICROSIEMENS 

PER CENTIMETER AT 25 DEGREES CELSIUS

800

- 600

- 400

200

2400 1200 

234

2400 1200 2400 1200 2400

AUGUST 1999

Figure 3. Diel variation and correlation of dissolved (0.1- 

(site 56), August 2-4,1999, with selected field parameters 

D, specific conductance; f, water temperature.

800

600

400

200

R2 =0.86 -

10 12 14 16 18 20 22 

WATERTEMPERATURE, IN DEGREES CELSIUS

urn filtration) zinc concentrations in High Ore Creek 

A, streamflow; B, pH; C, dissolved oxygen;

that are contaminated with mine and mill wastes (J.H. Lambing, unpub. data, 2000). Such increases in dissolved zinc 

concentration may result from entrainment of zinc-enriched 

tailings during runoff, followed by dissolution of weakly 

sorbed particulate zinc to a soluble form. The diel sampling in 

High Ore Creek, however, was conducted during base flow. In

the absence of overland runoff to entrain zinc-enriched 

tailings, an instream source of zinc is more likely to be causing 

the diel cycle.

A possible flow-related explanation for a zinc diel cycle 

is associated with the ground water residing in the alluvium 

below and adjacent to the stream channel. If ground water
272 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

was enriched in dissolved zinc, then an instream zinc diel 

cycle could result as diel variations in evapotranspiration 

from the flood plain change the amount of ground water 

discharging to the stream throughout the day. For example, 

if ground-water discharge to the stream is greater at night 

because less ground water is discharged to the atmosphere 

by evaporation and transpiration, then the instream flow and 

concentration of dissolved zinc could simultaneously increase. 

The concurrent increase in streamflow and zinc concentration 

during an approximately 6-hour period from about midnight to 

0600 hours (fig. 3A) may support this concept. However, the 

temporal patterns of streamflow and concentration are not 

sufficiently in unison to assume that ground-water inflow 

could be solely responsible for the zinc diel cycle. Also, the 

ground water was not sampled; therefore, the potential for zinc 

enrichment by ground water is only speculated.

pH

Concurrent diel variations in pH and dissolved zinc 

concentration in High Ore Creek are shown in figure 3B. The 

minimum pH values generally are reached within a few hours 

after sunset (about 2000 hours), similar to when minimum 

values for streamflow are observed. Unlike streamflow, however, pH is maintained at a relatively constant value throughout the night. Near sunrise (about 0600 hours), pH begins to 

rise, almost simultaneously as zinc concentrations begin to 

fall. Values of pH reach a maximum around mid-afternoon, 

which corresponds well with minimum zinc concentrations. 

The increase in pH from the nighttime minimum was relatively minor in High Ore Creek, representing less than 0.3 of 

a pH unit (range of 8.08 to 8.34). The maximum pH value 

was maintained only for about 2-4 hours, unlike the nighttime minimum that was maintained for about 10-12 hours. 

Although the pH minimum was maintained as an extended 

plateau rather than continuing to decline, the time interval 

spanning the minimum pH values coincided fairly well with 

the interval of increasing zinc concentrations.

The relation between pH and dissolved zinc concentration 

was slightly stronger (R2 = 0.45) than that for streamflow and 

dissolved zinc, with a negative slope indicating that dissolved 

zinc concentrations increase as pH decreases. This inverse 

correlation is typical of the solubility exhibited by many metals. The lower pH during the night possibly could solubilize 

particulate zinc from the instream colloidal fraction or streambed sediment to achieve a cyclical nighttime increase. If this 

is the case, however, the increased zinc solubility is occurring 

over a very narrow range of pH values.

Dissolved Oxygen

Concurrent diel variations in dissolved oxygen and dissolved zinc concentrations in High Ore Creek are shown in 

figure 3C. Dissolved oxygen concentrations varied by less 

than 2 mg/L (milligrams per liter), ranging from about 6.7

to 8.4 mg/L. The maximum dissolved oxygen concentration 

occurred around 0800 hours, while the minimum occurred 

near 1700 hours. The dissolved oxygen concentrations likely 

were responding primarily to water temperature because 

concentrations began dropping in mid-morning as the water 

warmed and oxygen solubility decreased. This pattern of 

decreasing dissolved oxygen concentrations during the day 

generally is the opposite of biologically productive streams 

with substantial photosynthetic activity. Metal concentrations 

in the stream probably inhibit aquatic plant growth, thereby 

suppressing photosynthetic oxygen production. The temporal patterns of dissolved oxygen and zinc concentrations had 

generally similar symmetry and their maximum and minimum 

concentrations coincided within 1 hour of each other.

The relation between dissolved oxygen and dissolved 

zinc concentrations in High Ore Creek was fairly strong 

(R2 = 0.67) and displayed a positive slope, indicating that 

dissolved zinc concentrations increase as dissolved oxygen 

concentrations increase. The strength of the relation and the 

relatively close match in diel variation indicate that dissolved 

oxygen concentration might be a useful surrogate for estimating diel cycles in zinc concentrations. However, the relation 

might have been merely coincidental because the oxygen 

variations were responding almost entirely to water temperature. In addition, the multiple biological and physical factors 

influencing dissolved oxygen concentrations may complicate 

straightforward interpretation of diel effects.

Specific Conductance

Concurrent diel variations in specific conductance and 

dissolved zinc concentrations in High Ore Creek are shown in 

figure 3D. Specific conductance, which commonly correlates 

well with major-ion concentrations, was examined to indicate 

if a correlation also existed for trace concentrations typical 

of most metals. The maximum specific conductance values 

generally occurred within several hours of the maximum zinc 

concentrations, thereby indicating that major-ion solutes may 

respond to the same physical or geochemical process influencing zinc concentrations. The relation between specific conductance and dissolved zinc concentrations in High Ore Creek 

was moderately strong (R2 = 0.55) and had a positive slope, 

indicating that zinc concentrations increase as conductance 

increases. Specific conductance values generally increased 

through the night, which corresponds to the pattern observed 

for dissolved zinc concentrations and, to a lesser extent, for 

streamflow. However, the diel patterns for specific conductance, streamflow, and dissolved zinc concentrations in High 

Ore Creek are not sufficiently in unison to support the concept 

that constituent-enriched ground water flowing to the stream is 

primarily responsible for driving the diel concentration cycle.

An abrupt increase in specific conductance occurred 

during the second day of the sampling period from about 0500 

to 0900 on August 4, followed by a rapid decrease for the 

next 4 hours until the end of sampling. These values appear 

to be anomalous relative to the preceding diel patterns. If
Short-Term Variation of Trace-Element Concentrations 273

the values for the last 9 hours of sampling are omitted, the R2 

for the regression relation between specific conductance and 

dissolved zinc concentrations increases to 0.75. Although this 

stronger correlation may indicate a more direct link between 

processes driving diel cycles in both major ions and dissolved 

zinc, the several-hour lag between conductance and zinc 

minima and maxima implies that other mechanisms may be 

exerting primary control over the diel zinc concentration cycle. 

Of note regarding the anomalously high conductance values 

during the last 9 hours of sampling is that a nearly identical pattern was observed for dissolved manganese (fig. 2). 

Other trace elements and field parameters did not display this 

anomalous pattern.

Water Temperature

Concurrent diel variations in water temperature and 

dissolved zinc concentration in High Ore Creek are shown in 

figure 3E. The relation between water temperature and dissolved zinc concentrations in High Ore Creek was very strong 

(R2 = 0.86) and substantially better than the relation between 

zinc and any of the other field parameters. The negative 

slope of the relation indicates that dissolved zinc concentrations increase as water temperatures decrease. The timing of 

temperature maxima and zinc minima is nearly concurrent, 

which would be expected based on the strong inverse correlation. Maximum temperatures occurred in late afternoon, 

which closely matched the timing of minimum dissolved zinc 

concentrations (about 1700 hours). Similarly, minimum temperatures occurred in early morning within an hour or so of the 

maximum dissolved zinc concentrations (about 0700 hours).

A possible temperature-related explanation for a zinc diel 

cycle is geochemical adsorption-desorption reactions acting 

on zinc-enriched colloids or streambed sediments. Studies of solution equilibria using thermodynamic principles 

(Machesky, 1990; Barrow, 1992; Trivedi and Axe, 2000) indicate that cation adsorption onto particulate material increases 

as temperature increases, and decreases as the temperature 

decreases. Thus, during the night and early morning when 

water temperatures decrease, adsorption of divalent metals 

such as zinc would decrease, thereby resulting in higher dissolved zinc concentrations as the water cools. This pattern of 

increasing zinc concentration was observed in High Ore Creek 

throughout the night until shortly after sunrise: dissolved 

zinc concentrations reached a maximum in the early morning 

(0600 to 0800 hours) within an hour or so of the minimum 

water temperature (0700 to 0800 hours). As water temperature increased throughout the morning and afternoon, adsorption onto colloids or streambed sediment would increase and 

progressively remove zinc from solution, thereby causing a 

corresponding decrease in dissolved zinc concentration during 

the afternoon. This conceptual process was consistent with 

observed data, whereby dissolved zinc concentrations reached 

a minimum coincident with maximum water temperatures.

Variation of Zinc Concentrations 

during Rainfall Runoff

Localized rainstorms over parts of the Boulder River 

watershed on August 2 and 4, 1999, created short-term overland runoff that affected streamflow conditions during the 

diel sampling investigation. As a result of increased flows, 

the base-flow diel cycle for dissolved zinc concentrations was 

obscured by both dilution effects and the inputs of additional 

zinc via runoff over wastes from inactive mines. Data from 

the hourly samples provide a temporally intensive characterization of changes in zinc concentrations over an approximately 1.5-day period in the Jack and Cataract Creek basins. 

The magnitude and duration of zinc concentration changes 

during rainfall runoff also may indicate how other metals 

associated with mine wastes or tailings might respond during 

short-term flushing events.

Rainfall volumes, intensity, and duration were not measured during the storms. However, changes in streamflow 

were periodically documented during the sampling period by 

stage readings and current-meter flow measurements. Because 

of the short period of runoff and the relatively minor increases 

in streamflow, the zinc loads derived from rainfall runoff were 

presumed to be small relative to loads transported by the much 

larger and sustained runoff during spring snowmelt. However, because instream dilution is minimal during low-flow 

conditions, increases in trace-element concentrations during 

rainfall runoff may be greater than those during either spring 

snowmelt runoff or base-flow diel cycles. Data from such a 

hydrologic condition, therefore, provide a valuable reference 

to short-term changes in biological exposure risks.

Jack Creek Basin

In the Jack Creek basin, streamflows in Bullion Mine 

tributary and Jack Creek below Bullion Mine tributary (sites 

17 and 19, fig. 1) were affected by rainfall runoff during the 

diel sampling period. Variations in dissolved zinc concentrations at both sites over a 36-hour period during August 2-3, 

1999, are shown in figure 4.

At about 1800 hours on August 2, heavy rain began 

falling in the Jack Creek basin and lasted for about 4 hours. 

Within an hour after the start of the rainstorm, overland runoff 

was observed. The largest measured streamflow in Jack Creek 

during the sampling period was 2.22 ft3/s, but streamflow was 

estimated by stage readings to have increased 5-fold from 

about 1 to 5 ft3/s. Although flows were not measured during 

runoff in Bullion Mine tributary, overland runoff also was 

observed at this nearby site, presumably increasing flow in a 

manner similar to that of Jack Creek. The initial effect of this 

runoff was a rapid decrease of about 1,000 (ig/L in dissolved 

zinc concentrations in Bullion Mine tributary during the first 

2-3 hours of heavy rain (fig. 4). The zinc concentration also 

decreased rapidly by about 400 |ig/L in Jack Creek,
274 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

10,000

8,000

: £ 6,000

o ic

So 4,000

Q 2,000

ZINC

O O O O

9- O O O O O

Jack Creek (site 19)

0400 0800 1200 1600 2000 2400 0400 0800 1200 1600 2000

2 3 

AUGUST 1999

Figure 4. Variation of dissolved (0.1 -urn filtration) zinc concentrations during rainfall runoff 

in Bullion Mine tributary (site 17) and Jack Creek below Bullion Mine tributary (site 19), 

August 2-3,1999. Heavy rain began falling at about 1800 hours on August 2.

beginning about an hour after the decline began in the Bullion 

Mine tributary and continuing during the 2-3 hour period of 

initial rainfall runoff. The decreases in dissolved zinc concentrations at both sites were likely the result of dilution from 

overland runoff draining from upland headwater areas containing relatively few sources of waste rock or tailings.

After the initial 2-3 hours of runoff and concentration 

decreases at both sites, dissolved zinc concentrations increased 

rapidly over the following 1-2 hours, presumably resulting 

from dissolution of soluble zinc sulfate salts such as goslarite 

(Fey and Desborough, this volume, Chapter D4, fig. 3) 

from waste rock and tailings at the Bullion mine. At the 

Bullion Mine tributary, zinc concentrations increased by 

about 6,200 ng/L (from 2,880 to 9,100 ng/L) during a 2-hour 

period. At Jack Creek, zinc concentrations increased by 

nearly 1,000 ng/L (from 346 ng/L to 1,320 pg/L) during a 

1-hour period. Because the timing of both concentration peaks 

was nearly identical (fig. 4), inflow from the Bullion Mine 

tributary likely contributed most of the zinc to Jack Creek 

during this rainfall event. It is not known how far downstream 

the peak concentrations measured in the Jack Creek mainstem 

below Bullion Mine tributary were maintained until dilution 

from other tributaries or overland runoff from non-mined areas 

caused concentrations to decrease.

Dissolved zinc concentrations at both sites decreased 

from their peaks as sharply as they had risen. The temporal 

pattern of declining zinc concentrations was very similar at 

both sites, with concentrations decreasing for the next 4 hours 

to values similar to those observed during the initial periods of 

runoff (fig. 4). After reaching a post-peak minimum concentration at both sites at about 0300 hours on August 3, zinc 

concentrations gradually began increasing over the next several hours before stabilizing at near pre-rainfall values.

Cataract Creek Basin

In the Cataract Creek basin, streamflows in Uncle Sam 

Gulch and Cataract Creek below Uncle Sam Gulch (sites 43 

and 44, fig. 1) also were affected by rainfall runoff during the 

diel sampling period. Variations in dissolved zinc concentrations at both sites over a 35-hour period during August 4-5, 

1999, are shown in figure 5.

Beginning at about 1800 hours on August 4, a gradual 

but steady increase in dissolved zinc concentrations began in 

Cataract Creek and lasted for about 6 hours. A light rain was 

falling at the time. During this same period, zinc concentrations increased and decreased irregularly in Uncle Sam Gulch, 

possibly indicating sporadic runoff volumes and accompanying dilution effects, or variable quality of runoff from different 

parts of the basin. A relatively large increase in dissolved zinc 

concentration occurred in Cataract Creek between 2400 and 

0100 hours on August 5, but only a small increase occurred 

in Uncle Sam Gulch during this time. The concentration 

increases in Cataract Creek likely originated from sources 

upstream from Uncle Sam Gulch, such as the Morning Glory 

mine or Cataract mine and tailings (fig. 1).

Shortly after the onset of heavy rain during the night, 

zinc concentrations increased irregularly between about 2400 

and 0500 hours at both sites on Uncle Sam Gulch and Cataract Creek. The sharpest increase occurred between 0300 and 

0500 hours in Uncle Sam Gulch. Zinc concentrations during 

the 5-hour period increased by about 3,100 (j,g/L (from 4,040 

to 7,130 ng/L) in Uncle Sam Gulch and about 670 pg/L (from 

779 to 1,450 p,g/L) in Cataract Creek, with concentrations 

at both sites peaking at the same time and at nearly identical 

proportions (nearly a 2-fold increase). The uniformity in timing and proportionality of concentration increases at the two 

sites strongly indicates that Uncle Sam Gulch was the primary 

source of zinc input to Cataract Creek during this runoff event.
Short-Term Variation of Trace-Element Concentrations 275

8,000

Z rr"

Q QJ 6,000

£oc 

z£ 

Sco

§| 4,000

co z 2,000 Q -

ZINC

ooooooooo

Cataract Creek (site 44) 

—0-O O O Q0400 0800 1200 1600

4

2000 2400 0400 

AUGUST 1999

0800 1200

5

1600 2000

Figure 5. Variation of dissolved (0.1-urn filtration) zinc concentrations during rainfall 

runoff in Uncle Sam Gulch (site 43) and Cataract Creek below Uncle Sam Gulch (site 44), 

August 4-5,1999. Rain began falling about 1800 hours on August 4.

It is not known how far downstream the peak concentration of 

dissolved zinc in Cataract Creek was maintained.

Dissolved zinc concentrations at both sites decreased 

from their peak concentrations as rapidly as they had risen. 

Within 3 hours of their peaks, concentrations in Cataract 

Creek and Uncle Sam Gulch decreased to levels similar to 

those measured during the pre-rainfall period. Concentrations 

continued to gradually decrease at both sites for several hours, 

eventually stabilizing within about 8-10 hours after the peak.

Implications of Short-Term Variation in 

Trace-Element Concentrations

Efforts to characterize trace-element concentrations in 

streams draining abandoned mine lands typically rely upon 

data collected at widely dispersed locations and over a broad 

range of hydrologic conditions. These data are used to 

establish baseline conditions, indicate the locations of major 

sources of trace-element inputs, detect long-term trends for 

evaluating remediation effectiveness, evaluate potential risks 

to aquatic biota, and provide information on how streamflow 

conditions and season influence concentrations. But if shortterm variability of metal or other constituent concentrations 

is substantial and persistent, interpretations of source inputs, 

trends, or biological exposure risks may be susceptible to 

error due to inadequate characterization by routine sampling 

strategies where samples are widely spaced in time. Large 

diel cycles in trace-element concentrations, and rapid concentration increases caused by rainfall runoff, pose difficulties in 

assessments of trace-element sources or long-term trends, and 

thereby produce uncertainty for resource managers attempting 

to prioritize areas for cleanup, design remedial treatments, or 

evaluate remediation effectiveness. The information obtained 

during these short-term sampling episodes in the Boulder

River watershed may not quantitatively relate to other similar sites, but the patterns of variation observed can provide 

an awareness of potential factors to consider when studies to 

characterize streams draining abandoned mine lands are being 

planned.

Diel cycles of zinc or other trace-element concentrations 

can complicate comparison of loads determined during synoptic sampling because of the difficulty in resolving whether 

load differences between successive sites are the result of 

actual inputs or simply an artifact of sampling time. Synoptic sampling to identify spatially discrete source areas (for 

example, Kimball and others, this volume, Chapter D6) commonly is conducted during base flow when a steady-state input 

of constituent loads is assumed. However, if the steady-state 

assumption is not met and concentrations at a site vary widely 

during the course of a day, then comparisons of load differences between sites may under- or over-estimate actual inputs 

if successive sites are sampled many hours apart and at different phases of a diel concentration cycle. Under this condition, 

interpretations of some trace-element sources could be invalidated. In High Ore Creek, the diel variation (fig. 2) was small 

for copper (about 1 (j,g/L) and moderate for arsenic (about 

10 (J-g/L). Consequently, the effect on synoptic load calculations and source interpretations for these elements is relatively 

small. The larger diel variations for manganese (about 

80 |ag/L) and zinc (about 400 (j,g/L) could affect interpretations of synoptic loads and inputs along stream reaches. 

Therefore, unless the diel effect is accounted for by either 

design of a synoptic sampling schedule that minimizes time 

differences between successive sites, or by mathematical normalization of analytical results, the only stream reaches that 

can reliably be considered as a source of trace-element input 

are those where between-site concentration differences exceed 

the diel rate of change.

Similar to the effect on synoptic load determinations, 

evaluations of long-term trends at a site could be complicated
276 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

in streams having large diel variations if samples collected 

periodically over multiple years were obtained at different 

times of the day. The variable sampling times would result in 

different phases of the diel cycle being sampled and a potentially wide range of concentrations representing base-flow 

conditions. The wide range of time-dependent concentrations 

caused by the natural variability of diel concentration cycles 

could obscure the presence of an actual trend, or mistakenly 

indicate a trend where none exists.

If same-time sampling over multiple years is not practical, a possible approach to facilitate interpretation of diel 

variation is to develop a means to mathematically normalize 

ambient concentrations. Although water temperature may 

not be the sole, or even predominant, control on diel cycling 

of dissolved zinc concentrations, its strong correlation with 

dissolved zinc concentrations makes it a potentially good 

surrogate to normalize sample concentrations to an equivalent 

concentration at a standard reference temperature. Because 

concentrations of zinc can vary widely from site to site, a dieladjustment method needs to be independent of the magnitude 

of concentration. Presumably, such a method would be based 

on a proportional rate of change of concentration relative to 

temperature or other surrogate parameters. With further study, 

mathematical-adjustment methods might be developed that 

are process-based and applicable to a wide range of stream 

conditions.

In terms of biological exposure, diel cycles of traceelement concentrations could have sustained but difficult-todetect impacts on aquatic biota. A chronic stress conceivably 

could be imposed on aquatic biota if trace-element concentrations regularly exceeded aquatic-life standards, even if only 

for portions of each day. Characterization of short-lived 

exceedances may be difficult, however, using data obtained 

from routine sampling strategies that assume a discrete value 

measured in a sample represents a consistent level of exposure 

throughout the day.

A hypothetical example of the effect of diel zinc loading 

from High Ore Creek on dissolved zinc concentrations in 

the Boulder River during base flow is illustrated in 

figure 6. In this example, estimated diel variations of dissolved zinc concentrations in the Boulder River resulting solely from the inflow of High Ore Creek have been 

constructed from mass-balance calculations using the diel 

variations in zinc load from High Ore Creek and the instream 

flow and background zinc concentration in the Boulder River 

(Nimick and Cleasby, 2000). This estimate of the diel loading 

effect indicates a maximum increase of about 20 [ig/L (from 

about 10 to 30 [ig/L) of dissolved zinc in the Boulder River 

resulting from the inflow of this one tributary. Although this 

level of increase is not sufficient to cause exceedances of 

aquatic-life criteria for zinc, similar diel effects from loading 

of other trace elements, cumulative diel effects from multiple 

tributaries draining abandoned mine lands, or more substantial 

loading effects from storm runoff during low flow could cause 

receiving streams and their biota to be adversely impacted on 

short-term time scales that are difficult to document.

Data from the sampling of rainfall runoff provide clear 

evidence that runoff from waste rock or tailings into streams 

can result in rapid and large increases of dissolved zinc concentrations that are sufficient to greatly increase biological risk 

in the vicinity of source areas. The sharp increases noted for 

dissolved zinc presumably could occur for other trace elements that are prevalent in mine wastes of the Boulder River 

watershed. This local increase is likely maintained for some 

distance downstream, although the magnitude and spatial 

extent have not been quantified. Sampling such episodes of 

trace-element input to quantify the magnitude, spatial extent, 

and duration of biological risk can be very difficult logistically 

due to the short-lived and localized nature of storm runoff. 

Opportunistic sampling such as occurred in this study, or the 

use of automated pumping samplers triggered by a continuously monitored surrogate, may be the only feasible means to

LU 5

Q o

30

ZINC

0600 1200 

234

1800 2400 0600 1200 1800 2400 0600 1200 1800

AUGUST 1999

Figure 6. Hypothetical diel variation of dissolved (0.1-um filtration) zinc concentrations 

in Boulder River resulting from inflow of High Ore Creek.
Short-Term Variation of Trace-Element Concentrations 277

characterize the site-specific responses to the flushing of trace 

elements from abandoned mine lands into streams.

Whether the cause of short-term variation in trace-element concentrations is a diel cycle or localized rainfall runoff, 

the downstream cumulative effect is of concern. Depending 

on the magnitude of loads delivered and the dilution capacity 

of the receiving stream, cyclical diel peak loads in tributaries 

or the flushing of waste rock and tailings by rainfall runoff 

may sufficiently impact the chemistry of both local and more 

distant stream reaches to temporarily exceed thresholds for 

biological impairment. The short-term variation of zinc 

concentrations may not have much practical consequence for 

evaluating biological risk in those tributaries where aquaticlife criteria for acute toxicity are consistently exceeded. But 

inflows from such impacted tributaries may have pronounced 

effects downstream in Basin Creek or the Boulder River 

mainstem, both of which support a trout fishery (Farag and 

others, this volume). Biological risks, including possible 

lethality, would be especially pronounced for the pulse of trace 

elements delivered by rainfall runoff during low flows when 

concentrations increase to a greater extent and more rapidly 

than from the diel cycle.

Summary

Variations in trace-element concentrations on a 24-hour 

(diel) basis in streams draining historical mining areas can, 

if sufficiently large and persistent, affect interpretations of 

trace-element sources, long-term trends, and biological risk. 

In this study, hourly samples were collected at five sites in 

August 1999 to quantify short-term variation of dissolved 

trace-element concentrations associated with base-flow diel 

cycles in three small basins that drain abandoned mine lands 

in the Boulder River watershed. The zinc diel cycle in High 

Ore Creek over a 53-hour period during base flow was relatively consistent, with zinc concentrations varying by about 

400 |ug/L between the maximum and minimum. Maximum 

concentrations (about 580 to 630 jag/L) occurred shortly after 

sunrise (between 0600 to 0800 hours) and represented about 

a three-fold increase over the minimum concentration (about 

210 |tig/L), which occurred in the early evening at about 

1700 hours. The maximum rate of zinc concentration change 

was about 45 |ug/L/hour on the falling limb of the diel cycle. 

At High Ore Creek, samples also were analyzed for dissolved 

arsenic, copper, and manganese, all of which exhibited diel 

cycles to varying degrees. The manganese cycle was the 

most similar to zinc in both symmetry and proportionality of 

concentration differences (about a 2.5-fold range in concentration). The diel cycles for arsenic and copper were proportionally smaller (about a 1.5-fold range in concentration), and the 

timings of concentration minima and maxima were nearly 

opposite to those for zinc and manganese.

Selected field parameters (streamflow, pH, dissolved 

oxygen, specific conductance, and water temperature) also

were measured hourly to identify correlations that might 

provide insight into possible geochemical associations with 

the zinc diel cycle. Zinc concentrations generally increased as 

streamflow increased; therefore, dilution was not indicated to 

be the cause of the diel cycle. An inverse correlation between 

pH and dissolved zinc concentrations exhibited fairly good 

concurrence in the timing of maxima and minima, possibly 

indicating a geochemical association. The correlation between 

water temperature and dissolved zinc concentration was stronger than that observed for any of the other field parameters; 

dissolved zinc concentrations increased as water temperatures 

decreased. The inverse symmetry of diel variations for dissolved zinc concentrations and water temperature coincided 

closely in time. This observation corresponds well to solution 

equilibria using thermodynamic principles, which indicates 

that zinc can undergo adsorption-desorption reactions with 

paniculate material (colloids and streambed sediment) as 

water temperature changes. With further study, it might be 

possible to utilize one or more field parameters as surrogates 

to normalize zinc concentrations to minimize the effect of diel 

variation on data sets used to interpret trace-element sources, 

long-term trends, and biological risk.

During the diel sampling period, rainstorms over the 

Jack and Cataract Creek basins produced runoff that obscured 

the base-flow diel cycles but provided a unique opportunity 

to document zinc variations during rainfall runoff. Rapid 

increases in dissolved zinc concentrations over 1-5 hour 

intervals ranged from about 670 |ug/L in Cataract Creek below 

Uncle Sam Gulch to about 6,200 |ug/L in Bullion Mine tributary of the Jack Creek basin. Data from this sampling provide 

clear evidence that runoff from waste rock or tailings into 

streams can result in rapid and large increases of dissolved 

trace-element concentrations that are sufficient to increase the 

potential for biological risk in the vicinity of source areas.

Whether the cause of short-term variation of instream 

trace-element concentrations is a diel cycle or localized 

rainfall runoff, data reported herein show that the cumulative 

effect of trace-element loading from mining-affected tributaries on downstream reaches is of concern. Depending on 

the magnitude of loads delivered and the dilution capacity of 

receiving streams, impacts to water quality may be sufficient 

to exceed thresholds for biological impairment or lethality, 

both locally and for extended distances downstream from the 

trace-element source.

References Cited

Barrow, N.J., 1992, A brief discussion of the effect of 

temperature on the reaction of inorganic ions with soil: 

Journal of Soil Science, v. 43, p. 37-45.

Brick, C.M., and Moore, J.N., 1996, Diel variation of trace 

metals in the upper Clark Fork River, Montana: Environmental Science and Technology, v. 30, p. 1953-1960.
278 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Cleasby, T.E., Nimick, D.A., and Kimball, B.A., 2000, 

Quantification of metal loads by tracer-injection and 

synoptic-sampling methods in Cataract Creek, Jefferson 

County, Montana, August 1997: U.S. Geological Survey 

Water-Resources Investigations Report 00-4237, 39 p.

Fishman, M.J., 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water 

and fluvial sediments: U.S. Geological Survey Open-File 

Report 93-125, 217 p.

Fuller, C.C., and Davis, J.A., 1989, Influence of coupling of 

sorption and photosynthetic processes on trace element 

cycles in natural waters: Nature, v. 340, p. 52-54.

Garbarino, J.R., andTaylor, H.E., 1996, Inductively coupled 

plasma-mass spectrometric method for the determination of 

dissolved trace elements in natural water: U.S. Geological 

Survey Open-File Report 94-358, 49 p.

Kimball, B.A., 1997, Use of tracer injections and synoptic 

sampling to measure metal loading from acid mine drainage: U.S. Geological Survey Fact Sheet FS-245-96, 8 p.

Lambing, J.H., 1991, Water-quality and transport characteristics of suspended sediment and trace elements in streamflow 

of the upper Clark Fork basin from Galen to Missoula, 

Montana, 1985-90: U.S. Geological Survey WaterResources Investigations Report 91^139, 73 p.

Machesky, M.L., 1990, Influence of temperature on ion 

adsorption by hydrous metal oxides, in Melchior, D.C., and 

Bassett, R.L., eds., Chemical modeling of aqueous systems 

II: Washington, D.C., American Chemical Society 

Symposium Series 416, p. 283-292.

McKnight, D.M., Kimball, B.A., and Bencala, K.E., 1988, 

Iron photoreduction and oxidation in an acidic mountain 

stream: Science, v. 240, p. 637-640.

Nimick, D.A., and Cleasby, T.E., 2000, Water-quality data for 

streams in the Boulder River watershed, Jefferson County, 

Montana: U.S. Geological Survey Open-File Report 00-99, 

70 p.

Nimick, D.A., and Cleasby, T.E., 2001, Quantification of 

metal loads by tracer injection and synoptic sampling in 

Daisy Creek and the Stillwater River, Park County, 

Montana: U.S. Geological Survey Water-Resources 

Investigations Report 00^261, 51 p.

Nimick, D.A., and Moore, J.N., 1991, Prediction of watersoluble metal concentrations in fluvially deposited tailings sediment, upper Clark Fork valley, Montana, U.S.A.: 

Applied Geochemistry, v. 6, p. 635-646.

Nimick, D.A., Moore, J.N., Dalby, C.E., and Savka, M.W, 

1998, The fate of geothermal arsenic in the Madison and 

Missouri Rivers, Montana and Wyoming: Water Resources 

Research, v. 34, p. 3051-3067.

Smith, J.D., Lambing, J.H., Nimick, D.A., Parrett, Charles, 

Ramey, Michael, and Schafer, William, 1998, Geomorphology, flood-plain tailings, and metal transport in the upper 

Clark Fork valley, Montana: U.S. Geological Survey WaterResources Investigations Report 98^170, 56 p.

Trivedi, P. and Axe, L., 2000, Modeling Cd and Zn sorption to 

hydrous metal oxides: Environmental Science and Technology, v. 34, p. 2215-2223.

U.S. Environmental Protection Agency, 1999, Ecological 

risk assessment, Clark Fork River operable unit, Milltown 

sediments/ Clark Fork River Superfund Site, Public Review 

Draft, Volume 1: Prepared by ISSI Consulting Group, Inc., 

Denver, Colo., for USEPA Region VIII, December 1999, 

variously paged.

Wagner, R.J., Mattraw, H.C., Ritz, G.C., and Smith, B.A., 

2000, Guidelines and standard procedures for continuous 

water-quality monitors—Site selection, field operation, calibration, record computation, and reporting: U.S. Geological 

Survey Water-Resources Investigations Report 00-4252, 

53 p.

Wilde, F.D., Radtke, D.B., Gibs, Jacob, and Iwatsubo, R.T., 

1998, National field manual for the collection of waterquality data: U.S. Geological Survey Techniques of WaterResources Investigations, book 9, Chapters A1-A9.
Trace Elements and Lead Isotopes in 

Streambed Sediment in Streams Affected 

by Historical Mining

By Stanley E. Church, Daniel M. Unruh, David L Fey, and Tracy C. Sole

Chapter D8 of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-D8

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract................................................................^

Introduction.............................................................................................^^

Purpose and Scope......................................................................................................................... 284

Previous Geochemical Investigations................................................................................................... 284

Sample Collection and Preparation....................................................................................................... 285

Streambed Sediment...................................................................................................................... 285

Suspended Sediment...................................................................................................................... 285

Premining Sediment ....................................................................................................................... 285

Sample Analysis........................................................................................................................................ 289

Geochemical Methods.................................................................................................................... 289

Lead Isotopic Methods................................................................................................................... 289

Dendrochronology and the Historical Record............................................................................ 289

Trace Elements in Streambed Sediment............................................................................................... 289

Geochemical Mapping Using Streambed-Sediment Data................................................................. 290

Estimating the Premining Geochemical Baseline from Regional Geochemical Data.......... 290

Regional Geochemical Mapping—The Late 1970s Geochemical Baseline.......................... 290

Current Studies of Streambed Sediment—Definition of Sources of Contaminants............. 291

Geochemical Baseline Maps from Streambed Sediment, 1996-1999.................................... 292

Basin Creek.............................................................................................................................. 297

Cataract Creek........................................................................................................................ 300

High Ore Creek........................................................................................................................ 302

Boulder River........................................................................................................................... 302

Summary.................................................................................................................................. 305

Premining Geochemical Baseline.......................................................................................................... 305

Basin Creek....................................................................................................................................... 306

Cataract Creek.................................................................................................................................311

High Ore Creek................................................................................................................................. 311

Boulder River.................................................................................................................................... 311

Boulder River Watershed............................................................................................................... 314

Lead Isotopic Results............................................................................................................................... 314

Basin Creek...................................................................................................................................... 317

Cataract Creek................................................................................................................................. 319

High Ore Creek................................................................................................................................. 322

Boulder River.................................................................................................................................... 322

Calculation of the Effect of Historical Mining on the Streambed Sediment in the

Boulder River............................................................................................................................... 325

Comparison of the Boulder River Watershed Streambed-Sediment Data with

Sediment-Quality Guidelines ........................................................................................... 330

Summary.................................................................................................................................................... 332

References Cited...................................................................................................................................... 333
Figures

1. Map showing localities of current and previous sediment samples..............................286

2. Map showing localities where stream-terrace sites were sampled for premining 

streambed sediment, as well as several mine and mill sites also sampled for 

this study...................................................................................................................................287

3. Photographs of four stream-terrace deposit sites............................................................. 288

4-6. Regional geochemical maps from total-digestion data from NURE streambedsediment data, contrasted with concentrations in streambed sediment from 

major tributaries:

4. Copper................................................................................................................................293

5. Lead ....................................................

6. Zinc.................................._

7. Regional geochemical map for total arsenic from analysis of streambed sediment 

from Butte 1°x 2° study contrasted with concentrations in streambed 

sediment from major tributaries............................................................................................ 294

8-10. Ribbon maps showing concentrations of:

8. Silver, from total-digestion data from streambed sediment...................................... 295

9. Cadmium, from total-digestion data from streambed sediment............................... 295

10. Leachable iron in streambed sediment........................................................................ 296

11-13. Diagrams showing concentrations of copper, lead, zinc, arsenic, silver,

cadmium, and antimony, and their effect on streambed sediment of Boulder River:

11. Streambed sediment from Basin Creek and its tributaries....................................... 299

12. Streambed sediment from Cataract Creek and its tributaries.................................. 301

13. Streambed sediment from High Ore Creek and its tributaries.................................. 303

14. Concentration profiles of copper, zinc, lead, and arsenic determined from total

and partial digestion of streambed sediment in Boulder River........................................ 304

15-18. Plots of geochemical dataforthe elements copper, lead, zinc, arsenic, iron, 

and manganese from cores for determination of premining geochemical 

baseline in streambed sediment from:

15. Basin Creek basin............................................................................................................. 309

16. Jack Creek basin.............................................................................................................. 310

17. Uncle Sam Gulch basin and High Ore Creek basin..................................................... 312

18. Boulder River watershed in the Basin and Boulder mining districts....................... 313

19-22. Ribbon maps showing concentrations of elements in premining streambed 

sediment of the Boulder River watershed study area:

19. Copper................................................................................................................................315

20. Lead....................................................................................................................................315

21. Zinc............................................^^^

22. Arsenic .............................................................................................................................. 316

23. Plot of concentration of lead versus isotopic composition of lead (206Pb/204 Pb) 

showing the dominant effect of mixing of contaminant lead derived from 

mining on isotopic composition of leachable lead in streambed sediment................... 319
24-27. Profile plots of lead isotopic composition and lead concentration determined in 

streambed sediment with respect to:

24. Boulder River and Basin Creek...................................................................................... 320

25. Boulder River and Cataract Creek................................................................................. 321

26. Boulder River and High Ore Creek................................................................................. 323

27. Boulder River.....................................................................................................................324

28. Plot of the calculated percent deposit-lead contamination added to the 

streambed sediment of the Boulder River by the addition of tailings from the 

Jib Mill site and streambed sediment from Basin Creek, Cataract Creek, and 

High Ore Creek......................................................................................................................... 328

29. Ribbon map showing calculated percentages of deposit lead in streambed

sediment today......................................................................................................................... 329

Tables

1. Trace-element data from streambed sediment from tributary drainages that

have little impact from past mining in the Boulder River watershed, Montana............ 291

2. Statistical summaries of the mine waste data.................................................................... 298

3. Descriptions of sites sampled for possible premining geochemical baseline, 

age control, and determination of premining concentrations of selected 

deposit-related trace elements at those sites.................................................................... 307

4. Estimates of contaminant and premining baseline lead isotopic compositions

from Boulder River watershed study area .......................................................................... 318

5. Calculated copper, zinc, arsenic, and lead contributions from Basin, Cataract,

and High Ore Creeks to Boulder River................................................................................. 326

6. Summary of screening level concentrations proposed as possible measures

for sediment-quality guidelines............................................................................................. 331

7. Sites where the leachable deposit-related trace-element concentrations in

streambed sediment from the study area exceed recommended screening levels.... 332
Chapter 08

Trace Elements and Lead Isotopes in Streambed Sediment

in Streams Affected by Historical Mining

By Stanley E. Church, Daniel M. Unruh, David L Fey, and Tracy C. Sole

Abstract

Assessment of deposit-related and rock-forming trace 

elements in Streambed sediment in the Boulder River watershed has provided the data necessary to delineate stream 

reaches having elevated contaminant concentrations in 

tributary streams, to determine anthropogenic sources of 

contaminated Streambed sediment, to understand the transport 

of dissolved and particulate trace elements, and to establish 

the streambed-sediment framework needed to evaluate toxicity 

to aquatic biota. Concentrations of the suite of deposit-related 

trace elements—copper, lead, zinc, arsenic, silver, cadmium, 

and antimony—were elevated in modern Streambed sediment 

in the Boulder River downstream from the confluence with 

Basin, Cataract, and High Ore Creeks. The major sources of 

these contaminants were tied directly to historical mining. 

All major tributary basins, Basin Creek, Jack Creek, Cataract 

Creek, Uncle Sam Gulch, and High Ore Creek, and the Boulder River downstream from the confluence of Basin Creek, 

had concentrations of leachable copper, lead, and arsenic 

in modern Streambed sediment that exceeded the apparent 

effects threshold for aquatic biota. In the Boulder River, 

these effects can be traced for a distance of about 55 river 

miles downstream to the confluence with the Jefferson River. 

Concentrations of cadmium and zinc exceeded the apparent 

effects threshold in Streambed sediment in the Boulder River 

downstream from the confluences of Cataract and High Ore 

Creeks. Everywhere within the three basins downstream from 

the major mines, the concentrations of all the deposit-related 

trace elements exceeded the screening level concentration for 

aquatic biota.

Comparison of the concentrations of this suite of depositrelated trace elements in Streambed sediment today with that 

in premining Streambed sediment from terrace deposits in the 

flood plains of these streams showed that the concentrations of 

the deposit-related trace elements were substantially elevated, 

from several to more than 100 times that prior to historical 

mining. Lead isotopic data from these two media indicated 

that the effect of mineralized rock on the streambed-sediment 

geochemistry prior to mining was small, but nevertheless 

greater than the concentrations of deposit-related trace

elements in tributaries unaffected by historical mining or 

mineralized rock.

Two different sources of deposit lead were defined by 

the lead isotopic data, one representing the polymetallic vein 

deposits in both the Basin and Cataract Creek basins, and a 

second at the Comet mine in the High Ore Creek basin. Calculations of the extent of the contamination of the Streambed 

sediment in the Boulder River indicate about 35 percent of 

the lead contamination was introduced by Streambed sediment from Basin Creek and the Jib Mill, about 15 percent was 

derived from Cataract Creek, and about 50 percent was from 

High Ore Creek. Contaminants carried in Streambed sediment 

from High Ore Creek dominated the concentrations of depositrelated trace elements in stream sediment of the Boulder River 

below the confluence downstream to the Jefferson River. Data 

from suspended sediment, when compared with that from the 

Streambed sediment, indicated that copper and zinc were being 

actively and differentially transported in the suspended-sediment phase relative to arsenic and lead.

Introduction

Streambed-sediment geochemical studies have been 

used in mineral exploration programs for more than 50 years, 

using the principle that the presence of elevated trace-element 

concentrations at a locality or localities may be an indication 

of undiscovered mineral deposits upstream. Erosion of these 

mineral deposits or the altered rock surrounding them provides 

evidence of their presence at specific sites in the watershed. 

In the case of historical mining districts such as the Basin and 

Boulder districts discussed here, no historical data exist to 

indicate either what the concentrations of several important 

trace elements in water or Streambed sediment might have 

been prior to mining, or whether aquatic life was present in 

or downstream of these historical mine and mill sites. This 

report examines the concentrations and sources of selected 

trace elements in Streambed sediment in the Boulder River and 

its major tributaries near the town of Basin in southwestern 

Montana.
284 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Ruppel (1963) and Becraft and others (1963) described 

the mineralogy of the veins that were mined in the Boulder 

River watershed study area. In general, the miners exploited 

polymetallic quartz veins containing pyrite, galena, sphalerite, 

chalcopyrite, arsenopyrite, and minor amounts of tetrahedrite. 

For purposes of this report, we focus on the distribution of a 

subset of trace elements that are specifically associated with 

these polymetallic vein deposits: copper, lead, zinc, arsenic, 

silver, cadmium, antimony, and gold. We refer to this traceelement suite as the deposit-related trace elements. In contrast, 

trace elements that are not associated with and enriched in the 

polymetallic vein deposits are herein referred to as rock-forming trace elements and include chromium, cobalt, strontium, 

titanium, vanadium, the rare-earth elements, and many others.

Fundamental time-frame differences are present in the 

data obtained from different sample media collected in the 

Boulder River watershed study. Water-quality data provide an 

instantaneous measure of the concentrations of constituents 

in the water column in a dynamic system. Concentrations of 

dissolved trace elements in water varied widely depending on 

streamflow conditions, ground- and surface-water flow, daily 

variations caused by plant uptake, and instream geochemical reactions (Nimick and Cleasby, this volume, Chapter 

D5; Lambing and others, this volume, Chapter D7; Kimball 

and others, this volume, Chapter D6). Suspended-sediment 

samples, which also included colloidal material, provided 

data on the concentrations of trace elements in the sediment 

fraction being transported in the water column. In contrast, 

streambed-sediment samples integrated conditions at a sample 

site over a longer time period because the streambed deposits 

were composed of detrital material transported and deposited 

during high flow as well as additional material that accumulated at the site during low-flow conditions (Church, Nimick, 

and others, this volume, Chapter B, fig. 3). This additional 

material included colloidal material composed of amorphous 

oxyhydroxides of aluminum, iron, and manganese that either 

coated these detrital grains or coalesced and settled to the 

streambed. These coatings and colloids contained and continued to sorb the deposit-related trace elements, effectively lowering their dissolved concentrations in water. Both processes, 

grain coating and colloidal settling, and continued sorption by 

these reactive aluminum, iron, and manganese oxyhydroxide 

surfaces, enriched the streambed sediment with deposit-related 

trace elements. This enrichment process continued throughout 

low-flow periods and caused concentrations of the depositrelated trace elements to increase with time during low-flow 

conditions for a period of several months each year following 

spring runoff.

Purpose and Scope

Major objectives of this study were four-fold.

• The primary goal was to characterize one aspect of 

the current aquatic environmental conditions in the 

Boulder River watershed—that is, to determine the

present-day spatial distribution of deposit-related trace 

elements in streambed sediment throughout the watershed. This objective was achieved through geochemical 

analysis of streambed-sediment samples collected at 

63 sites throughout the basin during low flow over the 

3-year period from 1996 through 1998.

A second objective was to identify those mining sites 

that provide the major contributions of deposit-related 

trace elements to the streams. This objective was 

achieved through spatial analysis of contributions of 

these deposit-related trace elements from mine sites to 

streambed sediment in specific stream reaches.

A third objective was to determine the premining 

geochemical baseline—that is, the concentrations of 

the deposit-related trace elements in streambed sediment that predate historical mining. Determination of 

the premining geochemical baseline was necessary 

to define the minimum concentrations of the depositrelated trace elements that feasible remediation efforts 

might be expected to achieve. This goal was achieved 

by sampling of streambed sediment in tributaries 

located upstream from past mining activities and by 

sampling premining fluvial deposits in old stream 

terraces. However, we were limited by the distribution, 

preservation, and recognition of, as well as access to, 

these old stream-terrace deposits downstream from 

historical mining sites. Dendrochronology and historical records have been used to provide a chronology for 

these terrace deposits (Unruh and others, 2000).

A fourth objective was to quantify the deposit-related 

trace-element contribution to the streambed sediment 

today from historical mine sites within the watershed. The data sets could then be used to evaluate the 

elevated deposit-related trace-element concentrations 

found in water and their potential detrimental effects 

on aquatic habitat in the Boulder River study area 

(Nimick and Cleasby, this volume; Farag and others, 

this volume, Chapter D10; Finger, Farag, and others, 

this volume, Chapter C).

Previous Geochemical Investigations

Analytical results for major- and trace-element concentrations in streambed sediment have been reported from two 

previous studies: the Butte l°x 2° study (McDanal and others, 

1985; Elliott and others, 1992) conducted from 1975 to 1983, 

and the National Uranium Resource Evaluation (NURE) program conducted from 1976 to 1977 (Aamodt, 1978; Broxton, 

1980; Van Eeckhout, 1981). In both studies, streambed sediment was collected from small, first-order tributaries, as indicated on l:24,000-scale topographic maps, with drainage areas 

of about 1 to 4 or more mi2 , in order to evaluate the sources
Trace Elements and Lead Isotopes in Streambed Sediment 285

of deposit-related trace elements for mineral exploration. Not 

all first-order tributary streams within the Boulder River study 

area were sampled in the NURE or the Butte 1° x 2° studies. Analytical results from the NURE studies were used to 

develop regional geochemical maps for copper, lead, and zinc; 

and results from the Butte 1° x 2° study were used to develop 

the regional geochemical map for arsenic. These geochemical 

maps provide a regional geochemical baseline circa the late 

1970s for the Boulder River watershed study area. Sample 

localities are shown in figure 1. These regional geochemical maps showed the effects of past mining on the first-order 

tributary drainages and defined an area within the study area 

with elevated concentrations of copper, lead, zinc, and arsenic. 

The regional geochemical maps were used to focus the current 

study on critically affected stream reaches.

The NURE data (Broxton, 1980; Van Eeckhout, 1981) 

also indicated that the Boulder batholith contained elevated 

concentrations of uranium. The uranium is in pitchblende in 

chalcedony veins that occur with the base- and precious-metal 

polymetallic veins in the Boulder batholith in the study area 

(Ruppel, 1963; Becraft and others, 1963). No new data have 

been collected on the occurrence and distribution of the 

uranium-bearing minerals in these veins.

Sample Collection and Preparation

Streambed Sediment

Streambed-sediment samples were collected from 38, 

31, and 18 sites, respectively, in October 1996, July 1997, and 

July 1998 at a total of 63 separate localities on Basin, Cataract, 

High Ore, and Jack Creeks, Uncle Sam Gulch, and the Boulder and Little Boulder Rivers, or their first-order tributaries 

(fig. 1). Some samples were collected from outside the study 

area to sample basins with the same geology, to determine 

the geochemical baseline in unmineralized streams, and to 

evaluate the downstream limits of effects in the Boulder River. 

Streambed-sediment samples were collected during low-flow 

conditions, thus ensuring collection of colloidal material in 

the Streambed sediment. At each sampling site, Streambedsediment samples were collected, using a plastic scoop, from 

the surfaces of fluvial sediment deposits in pool or low-velocity areas on both sides of the stream along a 100-150 foot 

reach. The samples were composited, wet sieved with ambient 

stream water to pass through a 10-mesh (<2 mm) stainless 

steel screen, and collected in a plastic gold pan. About 6.5 Ib 

of material was sealed in plastic containers at the site. During 

the 1996 sampling, a few Streambed-sediment samples from 

the first-order tributary basins were collected to both augment 

and verify previous work conducted in the NURE and Butte 

1° x 2° regional geochemical studies (fig. 1). Seven pairs of 

Streambed-sediment samples, one each from the north and 

south sides of the Boulder River, were collected upstream and

downstream of the confluences of Basin, Cataract, and High 

Ore Creeks (sites 5S, 6S, 8S, 9S, US, 12S, and 13S; fig. 1).

In the laboratory, the samples were air dried and sieved 

to minus 100-mesh (<150 um) to correspond directly with the 

procedure used in the NURE study (the Butte 1° x 2° study 

used minus-80-mesh sediment), and split for analysis (Fey, 

Unruh, and Church, 1999). The sample material analyzed 

constitutes the very fine sand, silt, and clay size fractions of 

the fluvial sediment in the active stream channel. Results are 

in the database (Rich and others, this volume, Chapter G).

Low-flow conditions in the watershed, defined as less 

than 150 ft3/s at U.S. Geological Survey gauging station 

06033300 located 2 mi east of Boulder, started in mid-July in 

each of the 3 years Streambed sediment was sampled (Church, 

Nimick, and others, this volume, fig. 3). The 1996 samples 

were collected about 3 months after the onset of low flow, 

whereas the 1997 and 1998 samples were collected shortly 

after the spring-runoff period. The samples collected in the 

latter 2 years are therefore not directly comparable to the 

data from the 1996 data set because of differences in the time 

period after runoff for accumulation of colloidal components 

at the sampling sites. In general, the latter two data sets contain lower concentrations of the deposit-related trace elements, 

although they exhibit the same trends as were found in the 

1996 data set. In construction of the trace-element maps, the 

1996 data were used wherever possible. This choice particularly affects sites 7S, 10S, and 14S on the Boulder River 

(fig. 1).

Suspended Sediment

In May 1997 during spring runoff, D.A. Nimick collected 

suspended-sediment samples from six localities (fig. 1) using a 

DH-74-TM sampler and width- and depth-integrated sampling 

procedures. Approximately 8 L of water were collected. After 

the suspended sediment settled in plastic containers, it was 

collected and air dried for analysis (Fey, Unruh, and Church, 

1999).

Premining Sediment

Stream terraces were sampled at a number of localities 

(fig. 2) in the study area using either trenches or cores through 

stream deposits preserved in cutbanks along the creeks and 

river (Unruh and others, 2000). The terrace deposits were generally composed of poorly sorted fluvial silt, sand, and gravel 

containing lithic clasts ranging in size up to 12 in. in diameter 

(fig. 3). Because no discernible stratigraphy was preserved in 

the gravel deposits, samples were taken in 6- to 12-in. intervals 

throughout the exposed terrace section. We dug back into the 

terrace deposit at least 8 in., carefully removing any materials 

that might have been deposited on the surface or cut bank of 

the terrace by historical floods that might have contaminated 

the sample. We removed unvegetated sand and gravel deposited on top of the terrace deposits unless covered by a
286 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112°22'30"

T8N

Boulder River 

watershed study area

EXPLANATION

2/5

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

30S

A Streambed-sediment locality sampled by U.S. Geological Survey

1 2 MILES 

_I

2 KILOMETERS

Suspended-sediment locality sampled by U.S. Geological Survey 

D Streambed-sediment locality sampled during MURE program

• Streambed-sediment locality sampled by U.S. Geological Survey, Butte 1° x 2° study

• Jib Mill site

Figure 1. Localities where suspended-sediment and streambed-sediment samples were collected during current study, and where 

streambed-sediment samples were collected in Butte 1° x 2° and NURE studies during the 1970s. Some small tributaries sampled 

during Butte ]°x2° study are not shown. Prior to this study, no samples were collected from the major tributaries or Boulder River. 

The Jib Mill site is also shown.
Trace Elements and Lead Isotopes in Streambed Sediment 287

1120 22'30"

_ I LEWIS AND CLARK CO 

r -~,

S/BUCKEYEAND I 

ENTERPRISE

Boulder River 

watershed study area

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

2 KILOMETERS

EXPLANATION

16B 9 Stream-terrace locality sampled by U.S. Geological Survey

$£ Mine-waste locality sampled by U.S. Geological Survey

A Fluvial tailings locality or mill site sampled by U.S. Geological Survey

• Jib Mill site

Figure 2. Localities where stream-terrace sites were sampled for premining streambed sediment to determine premining 

geochemical baseline. Also shown are several mine and mill sites sampled for this study that were localities of the primary point 

sources of contamination reaching the streams Fluvial tailings deposits and selected mine sites were also sampled.
288 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Figure 3. Stream-terrace deposit sites. A, Terrace sampled on Basin Creek (near site 706). Notice 

mottled iron staining in layer below the well-developed soil horizon and above the gravel indicating 

postdepositional oxidization and possible movement of iron in the terrace sediments. 6, Terrace site 

sampled at beaver dam impoundment on upper Jack Creek downstream from Bullion Mine tributary 

(site 746). Note thick deposit of fluvial tailings from blowout of the mill tailings dams at the Bullion mine. 

Core sample was taken using a 2-in.-diameter PVC pipe near base of a 99-year-old Lodgepole pine 

buried in the dam during construction. C, Flood-plain gravel deposit on Uncle Sam Gulch downstream 

from Crystal mine (site 776). The premining baseline core (foreground) was taken between two large 

stabilizing roots of a 252-year-old Ponderosa pine harvested in 1983. Stainless steel coring probe used 

for the 1-in. diameter cores is lying on top of stump. Note contaminated water and streambed sediment 

in Uncle Sam Gulch (background). D, fluvial deposits from near site 6B, downstream from High Ore 

Creek on the Boulder River. Uppermost layer above white zone and in root zone contaminated by postmining overbank sediment. Cottonwood growing on river bank at this locality gave dendrochronological 

age of 60 years.
Trace Elements and Lead Isotopes in Streambed Sediment 289

well-developed soil horizon to prevent contamination by 

recently deposited gravel and silt. We took a minimum of three 

samples at each site to provide some measure of reproducibility of the analytical data, or to discern a geochemical trend 

in the data from the site. Where the analytical results were not 

consistent between samples collected at the same site, not all 

the results were used to estimate the premining geochemical 

baseline. The gravel samples were dry sieved in the field to 

pass a 2-mm stainless steel screen, and sent to the laboratory 

for further processing.

In the laboratory, the samples were air dried if needed, 

sieved to pass 100-mesh (<150 jam), and split to ensure 

homogeneity (Fey, Unruh, and Church, 1999). The sample 

material analyzed constitutes the very fine safld, silt, and clay 

size fractions of the premining fluvial sediment; results are in 

Unruh and others (2000) and in the database (Rich and others, 

this volume).

Sample Analysis

Geochemical Methods

Geochemical data for the streambed-sediment, suspended-sediment, and terrace samples were determined using 

inductively coupled plasma-atomic emission spectrometry 

(ICP-AES) from a mixed mineral-acid total digestion (Briggs, 

1996; Church, 1981) and from a partial-digestion method 

using 2M HC1-1 percent H2O2 (Fey, Unruh, and Church, 

1999). This partial digestion or leach was designed to dissolve 

the aluminum, iron, and manganese oxyhydroxide component 

of the streambed sediment and isolate the deposit-related trace 

elements contained in this component of the streambed sediment from those trace elements in the rock-forming phases 

of the streambed sediment found in the total digestions of the 

residual phases (Rich and others, this volume). Total-digestion data were used for the geochemical maps (figs. 8-9) so 

that the data collected in this study are comparable with those 

from previous studies (figs. 4-7), whereas the partial-digestion 

data have been used to make the concentration versus distance 

diagrams (figs. 11-14) that showed the streambed-sediment 

geochemistry profiles. All analytical results are available in 

the database (Rich and others, this volume).

Lead Isotopic Methods

Lead isotopic analyses of the streambed sediment were 

done on the partial-digestion solutions using standard lead 

isotopic methods (Fey, Unruh, and Church, 1999; Unruh and 

others, 2000). Results are reported in terms of the lead isotope 

ratio to 204Pb, the isotope of lead that has no radioactive parent. 

All analytical results are in the database (Rich and others, this 

volume).

Dendrochronology and the Historical Record

We used historical data and dendrochronology to 

constrain the ages of premining gravel in terrace deposits used 

to determine the premining geochemical baseline. The dendrochronological data provide minimum ages for the terrace 

deposits whereas the historical data provide ages of structures 

or events within the mining district. Historical data for the 

Basin and Cataract mining districts were reviewed by 

Rossillon and Haynes (1999), who provided this work under 

contract with the USDA Forest Service.

Dendrochronological analysis was conducted by the 

Laboratory of Tree-Ring Research, University of Arizona, 

Tucson, Ariz.; the results are in Unruh and others (2000). 

Dates from live trees provided a minimum age of the terrace. 

Dates from dead standing trees sampled also provided only a 

minimum age, but with a larger uncertainty. Construction of 

a dendrochronological record from live trees to allow dating 

of dead trees was not achieved. The climate of the basin was 

sufficiently constant through time that a distinctive tree-ring 

structure versus time curve could not be constructed (Jeff 

Dean, Laboratory of Tree-Ring Research, University of Arizona, written commun., 1999). Development of a mature soil 

horizon on terraces was used in a qualitative sense to estimate 

the relative age and maturity of stream-terrace deposits.

Trace Elements in Streambed Sediment

Deposit-related trace elements derived from acidic drainage and mine waste as well as from mineralized but unmined 

sources typically accumulate in the streambed sediment downstream from inactive, historical mines. In the Boulder River 

watershed study area, these trace elements were concentrated 

in the colloidal phase and the grain coatings of the streambed 

sediment. As seen from the data, the difference between the 

concentrations of the deposit-related trace elements in the 

total-digestion data and data from the residual silicates clearly 

showed that the deposit-related trace elements were concentrated in and associated with the iron oxyhydroxide component 

of the streambed sediment. Downstream concentration profiles 

for streambed sediment, constructed using the partial-digestion 

data, were used to delineate stream reaches that had elevated 

deposit-related trace-element concentrations, to locate sources 

of contaminated material, and to help understand the transport 

of dissolved and particulate trace elements. In addition, we 

used concentration data to evaluate the potential toxicity of 

deposit-related trace elements in streambed sediment to biota 

(Farag and others, this volume).

The measured concentrations of deposit-related trace 

elements in the streambed sediment varied with the velocity of 

the flow regime. The colloidal component and the suspended 

sediment tended to settle out of suspension in low-velocity reaches in the stream or river. Thus, the deposit-related 

trace-element concentrations were susceptible to temporal
290 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

variability caused by sorption to grain coatings and colloids, 

and by deposition of the suspended sediment during low flow. 

They were also dependent upon the frequency of summer 

storms because the increased flow may mobilize some fraction 

of the colloidal component that had settled to the streambed. 

In general, one would not expect temporal variability to affect 

spatial variation of the geochemical signature obtained from a 

streambed-sediment survey within a watershed as long as the 

entire sample suite was collected over a short time frame 

(barring a summer rainstorm during the sample collection 

period). No such rainfall event occurred during any of the 

three streambed-sediment sampling efforts in the Boulder 

River watershed (Church, Nimick, and others, this volume, 

fig. 3).

Downstream profiles of deposit-related trace-element 

concentrations in streambed sediment in the Boulder River 

watershed study area were similar to the concentration profiles 

observed for surface water for copper, lead, zinc, and cadmium 

(Nimick and Cleasby, this volume). The highest concentrations of leachable and total deposit-related trace elements in 

streambed sediment occurred immediately downstream from 

the large mines, the Buckeye, Bullion, Crystal, and Comet 

mines (fig. 2), whereas concentrations of these deposit-related 

trace elements were near average crustal abundance values 

in rocks underlying subbasins where mineral deposits have 

not been found. Copper, lead, zinc, arsenic, cadmium, and 

antimony were concentrated in the leachable phase, indicating 

sorption to the hydrous aluminum, iron, and manganese grain 

coatings and colloids in streambed sediment. Concentrations 

of trace elements not associated with the mineral deposits (for 

example, chromium, cobalt, strontium, titanium, vanadium, 

and the rare-earth elements) were similar throughout the 

watershed where underlain by the same rock type.

Geochemical Mapping Using 

Streambed-Sediment Data

Estimating the Premining Geochemical Baseline 

from Regional Geochemical Data

The geochemical baseline for the Boulder River watershed study area today was evaluated using geochemical data 

from small tributaries from both the current and previous studies. Data from these small tributaries where the drainage basin 

is underlain by unmineralized rocks of the Boulder batholith 

and the Elkhorn Mountains Volcanics (O'Neill and others, this 

volume, Chapter Dl) provided but one measure of the geochemical baseline prior to historical mining. Tributary streams 

sampled in the earlier studies that had near-crustal-abundance 

trace-element concentrations were generally not resampled. 

Reference sites located in drainages that had a geologic setting 

similar to the study area were sampled outside the study area 

to provide data for comparison with mineralized areas. At site

IS on the upper Boulder River (fig. 1), the drainage basin is 

underlain by Cretaceous plutonic rocks of the Boulder batholith and the coeval Elkhorn Mountains Volcanics (Wallace, 

1987). Elliott and others (1992) indicated one large past-producing mine, several small historical mines with no known 

production, and several prospects in the headwaters of the 

Boulder River substantially upstream of the sampling site. At 

site 19S on the Little Boulder River (fig. 1), the basin is underlain by Cretaceous plutonic rocks of the Boulder batholith 

and the coeval Elkhorn Mountains Volcanics (Wallace, 1987). 

Elliott and others (1992) indicated that a small gold placer, 

several prospects, and several small past-producing historical 

mines were located in the Little Boulder River basin upstream 

of the sampling site. With the exception of the placer mine, 

these mines and prospects were not close to the Little Boulder 

River. At site 2S (fig. 1), the drainage basin is underlain by 

Cretaceous plutonic rocks of the Boulder batholith and the 

coeval Elkhorn Mountains Volcanics on the north side of the 

Boulder River, but by the younger Lowland Creek Volcanics 

of Eocene age on the south side of the Boulder River (Wallace, 

1987). Elliott and others (1992) indicated little past mining in 

this area of the Boulder River watershed.

Thirty-five streambed-sediment sites from the NURE 

study (Aamodt, 1978; Broxton, 1980; Van Eeckhout, 1981) 

were located within the Boulder River watershed study area 

(fig. 1). Many of these sites were on first-order tributary 

streams shown on l:24,000-scale topographic maps (fig. 1). 

Results for copper, lead, and zinc from 16 streambed-sediment samples from the NURE study and 11 samples collected 

from the Boulder River watershed study area are summarized 

in table 1. Samples were restricted to those collected from 

tributary drainages generally underlain by rocks of the Butte 

pluton that appeared to have little or minimal effects from past 

mining activities. Arsenic was not analyzed, and only a few 

cadmium and silver concentrations were determined or were 

above the limit of detection in streambed sediment analyzed 

during the NURE study. Median and mean concentrations 

for this suite of trace elements are in reasonable agreement 

between the two data sets. The standard deviation of the data 

sets is small when compared to the median value. The median 

and mean concentrations of the deposit-related trace elements are near or below average crustal abundance values for 

cadmium, copper, and silver, and were elevated above crustal 

abundance values for arsenic, lead, and zinc (table 1). We 

used the median values determined from these two studies to 

define one measure of the premining geochemical baseline in 

the Boulder River watershed and to compare with enrichment 

for this same suite of trace elements downstream from inactive 

mine sites in the Boulder River watershed study area.

Regional Geochemical Mapping— 

The Late 1970s Geochemical Baseline

Regional geochemical maps of the study area were 

constructed from the streambed-sediment data from first-order
Trace Elements and Lead Isotopes in Streambed Sediment 291

Table 1. Trace-element data from streambed sediment from tributary drainages that have little impact from past mining in the 

Boulder River watershed, Montana.

[<, value below specific limit of detection (ICP-AES; this study); n.a., not analyzed; --, no data calculated; No. of sites does not include censored 

arsenic values in the new data set or censored zinc values in the NURE data set; crustal abundance data from Fortescue (1992)]

Copper

ppm

Lead Zinc

ppm ppm

Arsenic

ppm

Cadmium

ppm

Silver

ppm

New Boulder study

Median

Mean

Std. dev.

No. of sites

21

23

12

11

47 150

50 164

24 65

11 11

35

32

12

10

<2

<2

—

-

<2

<2

—

--

NURE study

Median

Mean

Std. dev.

No. of sites

46

45

18

16

31 147

37 146

16 54

16 12

n.a.

n.a.

n.a.

—

<5

<5

—

—

<5

<5

-

-

Boulder River watershed geochemical baseline

Median

Mean

Std. dev.

32

36

19

35 150

42 155

21 59

35

32

12

<2

<2

—

<2

<2

—

Crustal abundance 68 13 76 1.8 0.16 0.08

tributary drainages sampled in the NURE or Butte 1° x 2° 

studies using the procedures described in Smith (1994) and 

Smith and others (1997). The data sets for copper, lead, zinc, 

and arsenic were each gridded using 3,281-ft (1,000-m) cells 

from a block of data with a large margin surrounding the Boulder River watershed study area to ensure that the interpolation 

of the geochemical data surface was not affected by "edge 

effects." Contoured geochemical maps were constructed from 

the gridded data using approximate multiples of crustal abundance (Fortescue, 1992; table 1) for four of the deposit-related 

trace elements. Sample localities appear in figure 1. The maps 

were trimmed to produce the regional geochemical base maps 

(figs. 4-7). Data from both regional geochemical studies were 

used to focus the investigations of the environmental effect of 

past mining activities in the study area. No regional geochemical maps were constructed for silver and cadmium because the 

data were censored below the detection limit of 2 ppm, which 

was substantially above the crustal abundance value (table 1).

Current Studies of Streambed Sediment— 

Definition of Sources of Contaminants

Total-digestion streambed-sediment data collected from 

the main tributaries (Basin, Cataract, High Ore, and Jack 

Creeks, and Uncle Sam Gulch) during this study have been 

used to produce the ribbon maps superposed on the regional 

geochemical base maps of the Boulder River watershed

study area (figs. 4-7) to provide the basic framework for the 

interpretation of the distribution of the deposit-related trace 

elements. The deposit-related trace elements were derived 

from the weathering of both altered and unaltered rock 

(O'Neill and others, this volume; McCafferty and others, this 

volume, Chapter D2) as well as mine waste and mill tailings 

(Fey and Desborough, this volume, Chapter D4; Martin, this 

volume, Chapter D3). Ribbon maps for silver and cadmium 

are presented as figures 8 and 9. Values on the ribbon reflect 

the concentration of the deposit-related trace element measured at the nearest downstream sample site. Exceptions to 

this procedure have been made where additional field data 

supported these changes: (1) data from site 4S on the Boulder River were assumed to apply downstream to the Jib Mill 

site (figs. 1 and 2); (2) data from site 46S on upper Cataract 

Creek were assumed to apply to the reach of Cataract Creek 

upstream from the Eva May mine (near the confluence with 

Hoodoo Creek) to site 46S; (3) data from site 51S were 

assumed to apply to the reach between site 51S and the confluence with Big Limber Gulch; and (4) data from site 58S, in the 

headwaters of High Ore Creek, were assumed to apply to the 

entire reach upstream from the Comet mine. Data from sites 

7S, 10S, and 14S on the Boulder River, which were collected 

in 1997 and 1998, were collected much earlier in the summer following the onset of low-flow conditions than those 

streambed-sediment samples collected from the Boulder River 

in 1996, so whenever in conflict with the data from the 1996 

sampling, the 1997-98 data were not used to construct the
292 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

ribbon maps. Leachable iron concentrations determined using 

the partial-digestion data have been used to show that iron-rich 

sediment accumulates downstream from the major mine sites 

in the watershed (fig. 10). Some of the areas of high leachable 

iron concentrations were downstream from mine sites and corresponded to areas of low pH observed in the stream reaches at 

low flow (Nimick and Cleasby, this volume, fig. 3).

Rock-forming trace elements, such as chromium, cobalt, 

strontium, vanadium, titanium, and the rare-earth elements, 

showed no abrupt changes in concentration in the streambed 

sediment downstream from the major mines in the watershed in either the NURE, Butte 1° x 2°, or our data sets. This 

indicated that the source of the deposit-related trace-element 

enrichment found in some streambed-sediment samples 

downstream from historical mining sites in the study area was 

associated with past mining of the mineral deposits, as was • 

shown in studies in other watersheds affected by historical 

mining activity (for example, Church and others, 1993, 1997). 

In the terrace deposits, as will be shown later, premining geochemical baseline data (with the exception of one site) did not 

show such profound enrichment of the deposit-related trace 

elements.

Streambed sediment was sampled at several localities 

in the Boulder River watershed for 2 or 3 consecutive years 

to evaluate the temporal stability of the geochemical maps. 

The data set was not sufficiently large to provide a rigorous statistical test, but it was sufficient to provide a general 

overview of the stability of the geochemical maps. In general, 

rock-forming trace-element concentrations were stable at the 

±10 percent level, whereas the deposit-related trace elements, 

which were controlled by the percentage of colloidal material 

in the streambed sediment, varied substantially between the 

1996 and the 1997 and 1998 data sets as discussed in paragraph 1 of this section. Data used for the geochemical profile 

diagrams (figs. 11-13) and streambed-sediment ribbon maps 

(figs. 4-10) were primarily from samples collected during the 

1996 field season. The concentrations of the deposit-related 

trace elements in the 1997-98 data sets generally were lower 

than those in the 1996 data set because of the difference in 

time frames for accumulation of colloids at these sites.

Geochemical Baseline Maps from Streambed 

Sediment 1996-1999

Studies of streambed sediment affected by mine drainage 

in other watersheds (Church and others, 1993, 1997; Kimball 

and others, 1995; Nordstrom and Alpers, 1999; Smith, 1999; 

Desborough and others, 2000) have shown that trace elements 

were sorbed to grain coatings and to iron and aluminum colloids, that is, hydrous iron oxyhydroxides (for example, ferrihydrite), iron oxysulphates (for example, schwertmannite), and 

aluminum oxysulphates. The results from the present study 

indicate that the mineralogical residence site for the sorbed 

deposit-related trace elements was the grain coatings and colloids formed in the water column during mixing of the acidic

drainage with more neutral water. Enrichment of iron from 

colloidal transport and settling on the streambed is a function of the pH of the water, sorption of deposit-related trace 

elements to the grain coatings and colloids, and the velocity 

of the stream. The enrichment of colloidal iron is shown on 

the ribbon map of leachable iron (fig. 10). Strongly elevated 

concentrations of leachable iron occurred in the stream reaches 

below the Comet, Crystal, and Bullion mines. The elevated 

concentrations of metals in Hoodoo and Rocker Creeks 

also may reflect past mining activity. Strongly elevated concentrations of leachable iron in upper Cataract Creek 

(fig. 10) appear to be related to wetland areas in the headwaters. Comparison of the partial-digestion data to crustal abundance is problematic because published crustal abundance data 

were determined from total-digestion results. Therefore, in the 

discussion following, enrichments of the deposit-related trace 

elements are expressed using the total-digestion data, whereas 

discussions of mechanisms of enrichment are drawn from the 

partial-digestion data. Partial-digestion concentrations were 

generally lower than the total-digestion concentrations because 

the deposit-related trace elements in rock-forming particles 

and sulfide grains, with the exception of galena, were not dissolved by the partial digestion.

Deposit-related trace elements were concentrated in the 

reaches of the major tributaries and creeks where leachable 

iron concentrations were generally greater than the 75th percentile (2.0 wt. percent or 20,000 ppm iron) downstream from 

major mine sites in the Boulder River watershed study area. 

Copper concentrations in streambed sediment below the Crystal and the Comet mines exceeded 20 times crustal abundance 

and affected Uncle Sam Gulch and Cataract Creek, and High 

Ore Creek, respectively, to their confluence with the Boulder 

River (fig. 4). Elevated concentrations of lead occurred in 

streambed sediment immediately downstream from the Buckeye and Bullion mine sites and affected upper Basin and Jack 

Creeks downstream to their confluence (fig. 5). In the stream 

reaches downstream from the Crystal mine, lead concentrations of greater than 140 times crustal abundance affected 

Uncle Sam Gulch and Cataract Creek for several miles downstream from the mine site to the confluence with the Boulder 

River. Streambed sediment in Cataract Creek between the confluence of Hoodoo Creek and Uncle Sam Gulch downstream 

from the Eva May mine had an elevated lead concentration 

in excess of 19 times crustal abundance. Lead concentrations 

exceeded 400 times crustal abundance in streambed sediment 

in High Ore Creek downstream from the Comet mine and in 

the Boulder River for at least 2 miles downstream from the 

confluence with High Ore Creek (fig. 5).

In general, the distribution of arsenic (fig. 7) and silver 

(fig. 8) in streambed sediment follows that of lead, although 

silver was more quickly attenuated than lead by instream processes. Elevated concentrations of zinc (fig. 6) and cadmium 

(fig. 9) were more dispersed downstream from the major mine 

sites than were copper, lead, arsenic, and silver, which reflect 

the tendency of cadmium and zinc to sorb less strongly than 

copper, lead, arsenic, and silver to the hydrous iron oxide
112°22'30" 112°22'30"

EXPLANATION

Contour Ribbon Lead, ppm

en • > 400

en a 200-400

dl 100-200• 60-100

en • <6o

EXPLANATION

Contour Ribbon Copper, ppm

• > 1,300

Cn _d 650-1,300

n O 325-650

en 1 200-325

en • < 200

R5W

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

1 2 KILOMETERS

f

0.ie ^

£

0 1 2 KILOMETERS

Figure 4. Regional geochemistry for copper from total-digestion data from NURE 

streambed-sedimentdata (Broxton, 1980) showing contrast with copper concentrations 

in Streambed sediment from major tributaries. White, sample density insufficient to allow 

projection of geochemical surface using a 3,281-ft (1,000-m) grid-cell density. Dark-red 

square, Jib Mill site.

Figure 5. Regional geochemistry for lead from total-digestion data from NURE streambedsediment data (Broxton, 1980) showing contrast with lead concentrations in Streambed sediment from major tributaries. White, sample density insufficient to allow projection of geochemical surface using a 3,281-ft (1,000-m) grid-cell density. Dark-red square, Jib Mill 

site.

CO

I.

CD3.
112'22'30" 1120 22'30" 112*15'

. BQUNP

X—I & S. v

* .«>«., ffiS

Boulder River • 

watershed /

EXPLANATION 

Contour Arsenic, ppm Ribbon Arsenic, ppm 

>115 • > 1,000 

35-100 O 250-1,000 

<35 D 50-250 

<50

Digital line graphs, 1:100,000

Io' I.0900oCD 30 1'I

ffICD

CL

EXPLANATION

Contour Ribbon Zinc, ppm

• • > 1,500I I • 750-1,500CH E3 375-750O • 225-375

I—I • < 225

Base from U.S. Geological Survey Digital line graphs, 1:100,000 0 1 2 KILOMETERS

Figure 6. Regional geochemistry for zinc from total-digestion data from NURE streambed-sediment data (Broxton, 1980) showing contrast with zinc concentrations in streambed sediment from major tributaries. White, sample density insufficient to allow projection of geochemical surface using a 3,281-ft (1,000-m) grid-cell density. Dark-red square, Jib Mill site.

Figure 7. Regional geochemistry for total arsenic from analysis of streambed sediment from Butte 1 0 x2°study(McDanal and others, 1985) showing contrast with arsenic 

concentrations in streambed sediment from major tributaries. White, sample density insufficient to allow projection of geochemical surface using a 3,281-ft (1,000-m) grid-cell density. Dark-red square, Jib Mill site.
2,/fENT 

V / X • «

EXPLANATION 

Cadmium, ppm

> 10 5-10 

B 2-5 

<2

T6N

1 2 KILOMETERS

Figure 8, Concentrations of silver from total-digestion data from streambed sediment Figure 9. Concentrations of cadmium from total-digestion data from streambed sedicollected from major tributaries during current study. Dark-red square, Jib Mill site. ment collected from major tributaries during current study. Dark-red square, Jib Mill site.

CD 3-
296 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112°22'30"

LJWISANDCLARKICO

JEFFERSON CO

• 

BULL ON I

, #\ CRYSTAL

Boulder River 

watershed study area

\

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

Boulder River ; 

watershed '

T8N

T7N

T6N

2 KILOMETERS

EXPLANATION 

Iron, percent

>s.o

2.0-3.0 

1-4-2.0 

> 1.4

Figure 10. Concentrations of leachable iron in streambed sediment from major tributaries (leachate data). Box plot shows 

distribution of leachable iron data; 75th percentile is 2.0 weight percent or 20,000 ppm, the 90th percentile is 3.0 weight percent, or 

30,000 ppm. Dark-red square, Jib Mill site.
Trace Elements and Lead Isotopes in Streambed Sediment 297

phases (Smith, 1999; Schemel and others, 2000). These same 

trends were seen in comparison of dissolved cadmium and 

zinc data with lead and arsenic in surface water (Nimick and 

Cleasby, this volume). Elevated cadmium and zinc concentrations (10 to more than 20 times crustal abundance) from 

the Bullion mine affected the lower reaches of Jack Creek 

and Basin Creek downstream from the confluence of Jack 

Creek. Elevated cadmium and zinc concentrations from the 

Crystal mine affected Uncle Sam Gulch and Cataract Creek 

downstream from Uncle Sam Gulch. The Boulder River had 

also been affected downstream from Cataract Creek. High 

Ore Creek downstream from the breached tailings dam at the 

Comet mine (Gelinas and Tupling, this volume, Chapter E2) 

had elevated concentrations of cadmium and zinc that affected 

streambed sediment in High Ore Creek as well as the Boulder 

River for about 2 miles downstream from the confluence.

Partial-digestion data for copper, lead, zinc, arsenic, 

silver, cadmium, and antimony are plotted as a function of 

river distance in figures 11-13. Distance is expressed in miles 

downstream from the confluence of Basin Creek with the 

Boulder River, which was assigned an arbitrary value of 

15 miles (25 km). Samples from the principal tributary streams 

are plotted relative to the distance upstream from the confluence of the tributary with the stream it intersects. Streambedsediment data from other tributary streams not affected by 

mining are not shown, but they are summarized in table 1. The 

tie lines show the substantial influx of deposit-related trace 

elements in the stream from particular mine sites as well as 

the dispersive effect of downstream transport and dilution by 

uncontaminated sediment from other tributary basins. This 

dispersive effect can also be seen on the ribbon maps 

(figs. 4-10). The concentrations of the deposit-related trace 

elements in the seven pairs of streambed-sediment samples 

from the north and south sides of the Boulder River (sites 55, 

6S, 8S, 95, 775, 725, and 735; fig. 1) were averaged to produce 

the ribbon maps and the geochemical profile diagrams (figs. 

4-10, 11-13). The data from the Boulder River streambed 

sediment are plotted on all of the geochemical profile diagrams (figs. 11-13) so that the streambed-sediment contribution from each of the three principal tributaries to the Boulder 

River can be evaluated. Additional amounts of deposit-related 

trace elements were being contributed by both the dissolved 

and suspended loads (Nimick and Cleasby, this volume).

Major sources of mine waste sampled during this study 

(fig. 2) are also indicated on the geochemical profile diagrams. From the study of mine sites, Fey and Desborough 

(this volume) identified and ranked several major mine sites 

that contained substantial concentrations of deposit-related 

trace elements. Statistical data for deposit-related trace-element concentrations from five sites are summarized in table 2. 

Samples from three of the sites, Bullion, Buckeye, and Comet, 

represent a large enough number of mill tailings samples to 

be statistically meaningful. We use the 75th percentile as an 

estimate of the concentration of the contaminants in figures 

11-13 because mixing with soil and streambed sediment in 

many of the samples had reduced the concentrations of the

deposit-related trace elements. Therefore, the median value 

was judged to not be a good indicator of the concentration of 

the deposit-related trace elements from the source.

Basin Creek

Geochemical data for leachable copper, lead, zinc, 

arsenic, silver, cadmium, and antimony from streambed 

sediment from the Basin Creek geochemical profile are in 

figure 11. In addition to the data from the Boulder River, three 

stream reaches are distinguished on this diagram: (1) Basin 

Creek, a major contaminated tributary of the Boulder River, 

(2) Jack Creek, and (3) the unnamed tributary to Jack Creek 

that drains the Bullion mine, hereafter referred to as Bullion 

Mine tributary (fig. 2). Three major anthropogenic sources 

of deposit-related trace elements lie along Basin Creek: the 

Buckeye and Enterprise mines in the headwaters of Basin 

Creek, the Bullion mine in the headwaters of the Bullion Mine 

tributary, and the Bullion smelter reservoir on lower Jack 

Creek (site 75#, fig. 2). Mill tailings and mine waste from 

both the Buckeye and Enterprise mine sites and the Bullion 

mine site received high rankings. Both were recommended for 

remedial action (Fey and Desborough, this volume).

Exposed sulfidic wastes from the Buckeye and Enterprise 

mines caused an increase in deposit-related trace-element 

concentrations in streambed sediment (site 275 at about river 

mi 2; fig. 11) in the upper reaches of Basin Creek (Cannon and 

others, this volume, Chapter El). Metesh and others (1994) 

reported surface water draining from this site with a pH of 

3.12. Cannon and others (this volume) reported pH values of 

3.1 to 4.1 that varied by season at this site. Copper, lead, zinc, 

and arsenic in the total-digestion data from site 275 below the 

Buckeye and Enterprise mines were enriched by factors of 4.1, 

46, 4.5, and 129 respectively over the geochemical baseline 

(table 1). Concentrations of the deposit-related trace elements 

in streambed sediment decreased steadily until upstream from 

the confluence with Jack Creek at site 24S (river mi 7.5). The 

Bullion mine (fig. 2), on the Bullion Mine tributary of Jack 

Creek, was the major source of streambed-sediment contamination in Jack Creek (river mi 6). Metesh and others (1994) 

reported mine adit drainage at this site with a pH of 2.58, and 

Desborough and others (2000) reported schwertmannite, a 

hydrous iron sulfate, in streambed sediment below the Bullion 

mine. Schwertmannite forms in acidic waters in the pH range 

of 2.8 to 4.5 (Bigham and others, 1996). Concentrations of 

copper, lead, zinc, and arsenic were enriched in streambed 

sediment below the Bullion mine (site 335) by factors of 10, 

25, 4.6, and 66 respectively (table 1). Fluvial tailings in overbank deposits downstream (355-375), presumably deposited 

after the breach of the tailings impoundments at the mine site, 

had deposit-related trace-element concentrations that substantially exceeded the enrichment factors found downstream 

(345-365) along Bullion Mine tributary. The addition of sediment from upper Jack Creek was responsible for the dilution 

of the deposit-related trace-element concentrations in streambed sediment immediately downstream from the confluence
298 Environmental Effects of Historical Mining, Boulder River Watershed, Montana 

Table 2. Statistical summaries of the mine waste data.

[75th percentile was used as the best estimate of the composition of the contaminant]

Statistical data Copper Lead Zinc

ppm ppm ppm

Arsenic

ppm

Cadmium

ppm

Silver

ppm

Jib Mill tailings 1 (n= 18)

Minimum

25th percentile

Median

75th percentile

Maximum

250 200 110

310 300 200

360 330 250

470 360 340

790 470 520

280

360

400

460

550

<2

<2

<2

<2

<2

<2

<2

<2

<2

<2

Bullion Mill tailings2 (n= 155)

Minimum

25th percentile

Median

75th percentile

Maximum

44 190 61

92 1,900 130

140 2,600 170

280 4,700 250

2,700 16,000 18,000

230

2,000

2,500

4,600

13,000

1

8

11

20

150

6

21

27

50

130

Buckeye Mill tailings3 (n = 67)

Minimum

25th percentile

Median

75th percentile

Maximum

28 120 76

100 2,200 160

160 9,800 250

260 17,000 450

4,800 93,000 28,000

210

6,400

13,000

20,000

63,000

3

33

69

118

370

3

22

56

87

290

Crystal mine wastes2 (n = 9)

Minimum

25th percentile

Median

75th percentile

Maximum

190 510 360

220 830 630

400 1,000 640

660 1,500 770

1,600 2,300 8,000

840

1,500

2,400

3,400

11,000

<2

<2

<2

<2

<2

6

7

9

13

26

Comet Mill tailings" (n= 149)

Minimum

25th percentile

Median

75th percentile

Maximum

30 90 200

500 4,600 1,400

830 9,200 2,400

1,300 15,000 5,300

4,300 59,000 50,000

67

3,900

6,000

8,000

22,000

2

11

20

57

740

8

65

110

160

460

'Unruh and others (2000). 

2Fey and others (2000). 

3Fey, Church, and Finney (1999). 

4Fey and Church (1998).

of Bullion Mine tributary with Jack Creek. Impoundment of 

these tailings and streambed sediment in an abandoned beaver 

pond at site 14B just downstream from the confluence with 

the Bullion Mine tributary, and in an old reservoir at site 15B 

(upstream from site 415), which was built to provide water for 

the Bullion smelter that operated from 1904 to 1906 (Rossillon and Haynes, 1999), trapped contaminated sediment in the 

lower reaches of Jack Creek.

Jack Creek provided a large contribution to the streambed 

sediment in Basin Creek, as can be seen by the major increase 

in deposit-related trace-element concentrations at the confluence of Jack Creek with Basin Creek at about river mi 7.6

(site 26S, fig. 11). Deposit-related trace-element concentrations decreased slowly downstream in streambed sediment 

of Jack Creek from the confluence with the Bullion Mine 

tributary to the confluence with Basin Creek. The streambed 

sediment in Jack Creek was highly enriched in leachable iron 

(fig. 10) resulting from the acid mine drainage from the Bullion mine (Kimball and others, this volume).

The effect of deposit-related trace elements from the Bullion mine on the streambed sediment concentrations of copper, 

zinc, arsenic, and cadmium in Basin Creek downstream from 

the confluence with Jack Creek substantially overwhelmed the 

deposit-related trace-element concentrations in the streambed
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CONCENTRATION, IN PPJVI

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CONCENTRATION,

09crCDO.c/>CDn.CD
300 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

sediment that were derived from the Buckeye and Enterprise 

mines. Concentrations of three trace elements increased substantially downstream from the confluence of Jack Creek with 

Basin Creek (sites 24S and 265): copper from 29 to 130 ppm, 

zinc from 380 to 580 ppm, and arsenic from 140 to 330 ppm, 

in the total-digestion data and copper from 24 to 210 ppm, 

zinc from 290 to 840 ppm, and arsenic from 98 to 430 ppm in 

the partial-digestion data. Lead concentrations in the streambed sediment remained relatively constant at about 200 ppm 

in the total-digestion data, but lead concentrations increased in 

the partial-digestion data from 170 to 320 ppm. Differences in 

the total-digestion data and the partial-digestion data probably 

are not analytical but are more likely the result of the difference in sample size used for the analytical procedure (0.2 g for 

the total digestion versus 2.0 g for the partial digestion; Fey, 

Unruh, and Church, 1999). These differences between data 

sets are generally not large or very important in an absolute 

sense because the data always exhibit the same trends. The 

differences are largely the result of the "nugget effect," that is, 

an observed difference when elements are concentrated in a 

single grain, in this case the deposit-related trace elements in 

the iron colloids.

Downstream from the confluence of Basin Creek with 

Jack Creek, deposit-related trace-element concentrations were 

diluted by uncontaminated streambed sediment that had lower 

concentrations of deposit-related trace elements entering Basin 

Creek from other tributary drainages. At the confluence of 

Basin Creek and Boulder River (site 375), copper, lead, and 

arsenic concentrations in streambed sediment decreased from 

130 to 93 ppm, from 210 to 160 ppm, and from 330 ppm to 

110 ppm, respectively. Zinc concentrations increased slightly 

downstream from the confluence with Jack Creek from 580 to 

600 ppm. Concentrations of leachable zinc in streambed sediment were about 900 ppm downstream and decreased near the 

confluence with the Boulder River to about 600 ppm.

As shown in figure 11, the data from the suspended sediment from the Boulder River upstream from the confluence 

with Basin Creek (4S) and from Basin Creek just upstream 

from the confluence (305) with the Boulder River indicated 

that the total concentration of deposit-related trace elements 

in the suspended sediment was very similar to that found in 

the leachable phase of the streambed sediment in the stream 

reach where the suspended sediment was sampled. Such a 

correlation would be expected since the suspended sediments 

are dominated by the colloidal components extracted during 

the partial digestion. Concentrations of deposit-related trace 

elements were elevated relative to where they were collected 

because the suspended-sediment samples, which were collected in May 1997, represented streambed sediment that had 

accumulated upstream during low flow in 1996.

Cataract Creek

In addition to the data from the streambed-sediment 

study, extensive water-quality data have been collected 

(Nimick and Cleasby, this volume) and a metal-loading

study conducted on Cataract Creek (Kimball and others, this 

volume; Cleasby and others, 2000). The results of the metalloading study clearly showed little effect on the streambedsediment geochemistry of Cataract Creek by past mining 

upstream from the Eva May mine, located near the confluence 

of Hoodoo Creek (river mi 10.5, fig. 12). Rocker Creek was 

contaminated by past mining in its headwaters (probably from 

the Ada mine), but little of that deposit-related trace-element 

contamination was transported into Cataract Creek as streambed sediment as evidenced by the NURE data from lower 

Rocker Creek (Broxton, 1980). The contamination likely was 

trapped in the low gradient reach of Rocker Creek upstream 

from the confluence and diluted by the relatively uncontaminated streambed sediment in Cataract Creek upstream from 

the Eva May mine site. In the reach from the Hoodoo Creek 

confluence (using the data from site 46S, river mi 10) 

downstream to Uncle Sam Gulch (site 49S, river mi 12.5), 

streambed-sediment concentrations of copper increased from 

47 to 190 ppm, lead from 47 to 240 ppm. zinc from 280 to 

610 ppm, and arsenic from 63 to 150 ppm. In the leachable 

phase, partial-digestion data for copper increased from 

44 to 110 ppm, lead from 49 to 220 ppm, zinc from 250 to 

440 ppm, arsenic from 41 to 96 ppm, silver from <1 to 

5 ppm, and cadmium from 1.5 to 2.7 ppm. The increase in the 

deposit-related trace-element concentrations in the streambed 

sediment, by about a factor of four in this stream reach, was 

not caused by streambed sediment from Hoodoo Creek or by 

the influx of tailings from the Eva May mine site, even though 

direct field evidence showed transport of tailings from the Eva 

May mine site into Cataract Creek. The August 1997 metalloading study (Kimball and others, this volume; Cleasby and 

others, 2000) indicated that the Cataract mine and mill tailings 

sites and the upper and lower Hattie Ferguson mine sites were 

probable sources of deposit-related trace elements in this 

reach. Additional sources of mine waste on private property, 

to which we did not have access, were located along Cataract 

Creek near the stream bank, such as the Morning Glory mine 

(Martin, this volume).

The Crystal mine (fig. 2, table 2), located in the headwaters of Uncle Sam Gulch (fig. 12, river mi 10), was the major 

source of deposit-related trace elements in the streambed 

sediment of Cataract Creek (table 2). Mine wastes from the 

Crystal mine were ranked as a moderate source of depositrelated trace elements (Fey and Desborough, this volume). 

Copper, lead, zinc, arsenic, silver, and cadmium concentrations in streambed sediment increased dramatically directly 

below the mine (sites 54S and 555, river mi 10.5). Additional 

enrichments of copper and zinc occur at the confluence of 

Uncle Sam Gulch with Cataract Creek (site 575, river 

mi 12.5), but lead and arsenic concentrations decrease. 

Desborough and others (2000) reported the presence of 

schwertmannite in streambed sediment from Uncle Sam Gulch 

immediately downstream from the Crystal mine adit. The pH 

of Uncle Sam Gulch downstream from the Crystal 

mine was 3.2-3.5 (Metesh and others, 1995; Nimick and 

Cleasby, 2000), which is within the pH stability field of
Trace Elements and Lead Isotopes in Streambed Sediment 301

CATARACT CREEK

5,000

D_ 

D_

< 

DC

o 

o

500

50

D_ 

D_

-1,000

o

2 

O

100

10

D_ 

Q_

^ 1,000

<CC

o 

o

100

10

Copper

5 10 15 20 

DISTANCE, IN MILES

5 10 15 20 25 

DISTANCE, IN MILES

Zinc

5 10 15 20 25 

DISTANCE, IN MILES

Arsenic

0 5 10 15 20 25 

DISTANCE, IN MILES

30

	EXPLANATION

• Boulder River sediment

A Boulder River suspended sediment

• Cataract Creek sediment

A Cataract Creek suspended sediment

• Crystal mine

• Little Boulder River sediment

• Uncle Sam Gulch sediment

A Uncle Sam Gulch, suspended sediment

o_ 

o_

<

DC

o 

o

30

30

10

<

DC

C_)

z 

o

30

10 15 20 

DISTANCE, IN MILES

25 30

5 10 15 20 25 

DISTANCE, IN MILES

30

1

X Antimony

0 5 10 15 20 25 

DISTANCE, IN MILES

30

Figure 12. Concentrations of copper, lead, zinc, arsenic, silver, cadmium, and antimony determined in the 

partial digestion of streambed sediment from Cataract Creek and its tributaries, and their effect on streambed sediment of Boulder River. Trace-element concentrations determined for major sources within the 

watershed are also shown. Data are plotted against distance; upstream always to left regardless of actual 

direction stream flows. Samples that represent streambed sediment from active stream or river channel are 

indicated by discrete solid symbols and connected by tie lines. Concentrations of antimony, cadmium, and 

silver are censored at 2 ppm and arsenic at 5 ppm.
302 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

schwertmannite (Bigham and others, 1996); pH increased to 

7.3 ± 0.2 at the confluence with Cataract Creek at low flow 

(Nimick and Cleasby, this volume, fig. 3). The enrichment of 

deposit-related trace elements in the streambed sediment of 

Uncle Sam Gulch upstream from the confluence with Cataract 

Creek at site 57S is as follows: copper, 72; lead, 26; and zinc, 

25; and arsenic, 37 times the geochemical baseline (table 1). 

Suspended-sediment concentrations collected from site 57S 

(river mi 12.5) exceeded the concentrations of deposit-related 

trace elements in streambed sediment with enrichment factors 

of 93 for copper, 24 for lead, 32 for zinc, and 49 for arsenic 

relative to the geochemical baseline (table 1). Suspendedsediment concentrations decreased by a factor of 2 to 3.5 at 

site 57S. Enrichment factors in the streambed sediment at site 

53S are as follows: copper, 14 fold; lead, 13 fold; zinc, 6.7 

fold; and arsenic, 17 fold. Relative to the suspended-sediment 

concentrations at site 53S, the concentrations in the suspended sediment were similar for lead, arsenic, and silver, but 

enriched by a factor of 2 for copper, a factor of 3 for zinc, and 

a factor of 3.5 for cadmium. These enrichment factors indicate 

that differential transport of these three deposit-related trace 

elements occurred in the suspended-sediment load.

The streambed sediment contributed by Uncle Sam Gulch 

increased the concentrations of deposit-related trace elements 

in streambed sediment in Cataract Creek downstream from the 

confluence (site 505, river mi 12.6). Copper was enriched from 

6 to 20, lead from 7 to 14, zinc from 4 to 15, and arsenic from 

4 to 16 times the geochemical baseline (table 1). Depositrelated trace-element concentrations in suspended sediment at 

site 508 were substantially elevated upstream from the concentrations in streambed sediment, which indicated that much of 

the deposit-related trace-element load was transported in the 

suspended sediment as colloids. Little change was evident in 

the concentrations of copper (420 ppm, a 13-fold enrichment), 

lead (320 ppm, a 9-fold enrichment), zinc (1,450 ppm, a 

10-fold enrichment) and arsenic (460 ppm, a 13-fold enrichment) in streambed sediment in Cataract Creek between Uncle 

Sam Gulch (site 505) and the Boulder River (site 535). We 

interpret these data to indicate that the Crystal mine site on 

Uncle Sam Gulch was the major source of contaminants in 

Cataract Creek. Results from the metal-loading study (Cleasby 

and others, 2000; Kimball and others, this volume) showed 

that Uncle Sam Gulch was the source of 92 percent of the zinc 

load and 66 percent of the copper load in Cataract Creek.

High Ore Creek

The major source of deposit-related trace elements in 

streambed sediment of High Ore Creek was the Comet mine 

(Fey and Church, 1998), an open-pit mine with extensive 

underground workings located near the headwaters (fig. 2). 

A tailings dam constructed across the drainage adjacent to 

the Comet mine was breached (Gelinas and Tupling, this 

volume). Mill tailings had washed downstream from the mine 

site, contaminating the High Ore Creek watershed (river mi 

16; Rich and others, this volume). The tailings in the breached

impoundment were removed in 1998 by the Montana Department of Environmental Quality and stored in the open pit 

at the Comet mine. The downstream fluvial tailings were 

removed by the U.S. Bureau of Land Management during 

the course of this study (Gelinas and Tupling, this volume). 

Downstream of the breached tailings dam, streambed sediment 

had deposit-related trace-element concentrations of 2,000 ppm 

copper, 5,700 ppm lead, 17,000 ppm zinc, 8,100 ppm arsenic, 

52 ppm silver, and 150 ppm cadmium (site 59S, river mi 20; 

fig. 13). Enrichment relative to the geochemical baseline values (table I) was: copper, more than 60-fold; zinc, more than 

110-fold; lead, more than 160-fold, and arsenic, cadmium, and 

silver by more than 200-fold. Sediment from Bishop Creek, 

the major tributary entering High Ore Creek between sites 

60S and 61'S (river mi 17), resulted in some dilution of the 

deposit-related trace elements in streambed sediment of High 

Ore Creek. Deposit-related trace-element concentrations in 

streambed sediment at the mouth of High Ore Creek (site 63S, 

river mi 21) were reduced to about 740 ppm copper, 1,600 

ppm lead, 10,000 ppm zinc, 4,300 ppm arsenic, 34 ppm silver, 

and 69 ppm cadmium in October 1996 when High Ore Creek 

was first sampled. In general, copper was diluted by a factor of 

2.7, lead by a factor of 3.6, zinc by a factor of 1.7, and arsenic 

by a factor of 1.9. Overbank deposits of fluvial tailings from 

the Comet mine, identified on the basis of the lead isotopic 

signature (Rich and others, this volume), were found on a 

low terrace at site 14S on the Boulder River. These deposits 

probably formed during the breach of the mill tailings dam 

at the Comet mine site. High Ore Creek was a minor source 

of streambed sediment, but it was a major source of depositrelated trace-element contaminants to the streambed sediment 

of the Boulder River.

Boulder River

Streambed-sediment samples were collected systematically at sites along the Boulder River upstream, through, and 

downstream of the Basin and Boulder mining districts, about 

100 ft upstream and downstream from the confluences of 

Basin, Cataract, and High Ore Creeks. At sites 5S, 6S, 8S, 

95, I IS, 725, and 13S, samples were collected from both the 

north and south sides of the Boulder River. Only the average 

values from these sites are shown in figure \4A. The objective 

of this sampling plan was to evaluate the efficiency of mixing of sediment from the major tributaries and the effect of 

flow and velocity on the accumulation of colloidal material on 

the streambed of the Boulder River. Samples from the north 

and south sides of the Boulder River had major differences in 

concentrations: higher concentrations of leachable iron and 

deposit-related trace elements occurred in streambed sediment 

deposited on the lower velocity side of the reach where colloidal particles settled. Basin, Cataract, and High Ore Creeks 

enter the Boulder River from the north. As shown by the data 

(Rich and others, this volume), mixing in the fluvial system at 

a distance of 100 ft downstream from the confluence was not 

complete at that distance from any of the three confluences.
Trace Elements and Lead Isotopes in Streambed Sediment 303

HIGH ORE CREEK

Q_ 

Q_

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DC

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,000

100

10

5 10 15 20 25 30 

DISTANCE, IN MILES

10,000 r

1,000 r

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£ 10,000

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10 15 20 25 

DISTANCE, IN MILES

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10 15 20 25 

DISTANCE, IN MILES

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DISTANCE. IN MILES

	EXPLANATION

•••" Boulder River sediment

A Boulder River suspended sediment

• Comet Mill tailings

A Fluvial tailings (Comet Mill)

•^— High Ore Creek sediment

• Little Boulder River sediment

5 10 15 20 25

DISTANCE, IN MILES

5 10 15 20 25 

DISTANCE, IN MILES

^ 10

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Antimony

5 10 15 20 25 

DISTANCE, IN MILES

30

Figure 13. Concentrations of copper, lead, zinc, arsenic, silver, cadmium, and antimony determined in the 

partial digestion of streambed sediment from High Ore Creek and its tributaries, and their effect on streambed 

sediment of Boulder River. Trace-element concentrations determined for major sources within the watershed 

are also shown. Data are plotted against distance; upstream always to left regardless of actual direction 

stream flows. Samples that represent streambed sediment from active stream or river channel are indicated 

by discrete solid symbols and connected by tie lines. Concentrations of antimony, cadmium, and silver are 

censored at 2 ppm and arsenic at 5 ppm.
304 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

10,000 E I , , . I

Cataract

n . Creek Basin q:tp co Creek blteWs 

Site 31s

14.0 16.0 18.0 20.0 

DISTANCE, IN MILES

22.0 24.0

1,000 r

cc

LLJ 

D_

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CC.

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Basin and Boulder mining districts 

i.i.i, i

30 40 

DISTANCE. IN MILES

60 70

Figure 14. Concentration profiles of copper, zinc, lead and arsenic. A, Determined in the total digestion 

of streambed sediment in Boulder River. Data plotted against distance, upstream always to left. Data for 

samples from both north and south sides of river at sites 55, 6S, 8S, 35, 11S, 12S, and /35have been averaged to provide a continuous profile of element concentrations in Boulder River streambed sediment. 

Concentration data from Basin Creek (site 3/5), Cataract Creek (site 535), and High Ore Creek (site 635) 

are shown as diamonds to indicate concentrations of these deposit-related trace elements in streambed 

sediment that was added by the three major tributaries. Concentrations of arsenic are censored at 5 ppm. 

B, Determined from partial digestion of streambed sediment in Boulder River. Arsenic profile (not shown) 

closely mimics that of lead.
Trace Elements and Lead Isotopes in Streambed Sediment 305

Concentrations of copper, lead, zinc, and arsenic were not 

systematically higher on either the north or the south side of 

the Boulder River.

The distributions of copper, lead, zinc, and arsenic in 

Boulder River streambed sediment showed similar abundance 

patterns; concentrations increased downstream from each 

of the confluences (fig. 14A). Variation between sites downstream of the confluences was within the variation we would 

expect from stream-sediment sampling. The increase in concentrations at site 55, upstream from the confluence of Basin 

Creek, can be explained by contributions from the Jib Mill 

site and several small prospects in the area between sites 4S 

and 55 (fig. 1). Downstream from the confluence with Basin 

Creek (site 65), the deposit-related trace-element concentrations decreased slightly. This is reasonable in view of the fact 

that the deposit-related trace-element concentrations in Basin 

Creek at site 3IS were similar for arsenic and zinc and lower 

for copper than those in the Boulder River at site 55 (fig. 14A). 

Only lead appeared to be significantly enriched in Basin Creek 

relative to the Boulder River. Downstream from the Basin 

Creek confluence, deposit-related trace-element concentrations in Boulder River streambed sediment decreased by more 

than a factor of two (except lead) at site 75 (river mi 16.2). 

Samples from site 75 were collected in 1997 from a deep pool 

that had accumulated significantly more detrital sediment 

relative to other sites sampled on the Boulder River. Thus, the 

decrease in deposit-related trace-element concentrations at 

this site was atypical of the other sites used for comparison. A 

minor increase in deposit-related trace-element concentrations 

occurred between sites 6S and 8S; it was not significant.

Deposit-related trace-element enrichment between sites 

10S and 775 (both upstream from High Ore Creek) appears 

to be confined primarily to copper and zinc. The downstream 

enrichment of the more soluble metals suggested that the 

enrichment at site 775 was most likely due to sedimentation of 

colloidal particles and sorption processes within the Boulder 

River rather than enrichment from an outside source. Samples 

from site 705 were collected in 1997.

Deposit-related trace-element concentrations increased 

dramatically immediately downstream from High Ore Creek 

(site 725, fig. 14A) and continued to increase for at least 

0.5 mile to site 7 3S (river mi 20.7). Deposit-related traceelement concentrations then decreased significantly at site 

14S (1997 data; river mi 21.7), but increased at site 755 (river 

mi 23). We had difficulty in obtaining sample material at site 

14S, which was on the outside of a meander where streambed 

sediment did not tend to accumulate. The data between sites 

73S and 755 showed a gradual decrease in concentration; these 

data were used to define the concentration trend for the ribbon 

maps (figs. 4-9).

The effect of historical mining within the Basin mining district on the concentrations of copper, lead, and zinc in 

streambed sediment of the Boulder River is clear from 

fig. 145. Note the substantial increase in concentrations of 

these deposit-related trace elements in the streambed sediment 

of the Boulder River as it flowed through the Basin and

Boulder mining districts. Note also that lead concentrations 

were diluted as a function of distance downstream from the 

mining districts (that is, downstream from river mi 40). 

Arsenic also showed the same trend as lead but is not plotted in figure 145. Concentrations of both copper and zinc 

increased downstream, albeit at different rates. Both metals 

have been shown to be toxic to fish in the watershed (Farag 

and others, this volume). This phenomenon also was observed 

in the Animas River watershed (Church and others, 1997) and 

in the Arkansas River watershed (Church and others, 1993; 

Kimball and others, 1995); it reflects the transport, sorption, 

and subsequent deposition of colloidal particles from the water 

column to the streambed sediment. The effect of historical 

mining activity on aquatic habitat may extend for many river 

miles downstream from a historical mining district.

Summary

One of the primary goals of this study was to characterize the deposit-related trace-element distributions and show 

the impact of historical mining on streambed sediment in 

the Boulder River watershed study area. The data presented 

clearly indicate significant enrichment of the deposit-related 

trace elements copper, lead, zinc, arsenic, silver, cadmium, and 

antimony in streambed sediment in the major tributary streams 

downstream from historical mine sites. We have identified the 

major sources of the deposit-related contaminants: Jack Creek 

downstream from the Bullion mine and upper Basin Creek 

downstream from the Buckeye mine are the most severely 

affected reaches in the Basin Creek basin. Uncle Sam Gulch 

immediately downstream from the Crystal mine is the most 

severely affected tributary on Cataract Creek, and it affected 

Cataract Creek from the confluence with Uncle Sam Gulch to 

the Boulder River. High Ore Creek is severely affected from 

the Comet mine to its confluence with the Boulder River. The 

Boulder River has been impacted by streambed sediment from 

all three of the major tributaries as well as by milling of ore 

at the Jib Mill site on the Boulder River near the Basin Creek 

confluence. Thus we have identified the major point sources 

of contamination within the Boulder River watershed and 

fulfilled the second goal of this study. Differential transport of 

copper and zinc in the suspended sediment and deposition of 

colloids in the low-velocity zones of the Boulder River have 

resulted in irregularly dispersed deposits of contaminated 

streambed sediment in the Boulder River downstream from the 

confluences of the three major tributaries.

Premining Geochemical Baseline

Determination of the sources of deposit-related trace elements in the streambed sediment and terrace deposits requires 

careful evaluation of all possible sources. In addition to those 

identified at some historical mine sites as just described, these 

other sources include the unaltered rocks in the Boulder River
306 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

watershed study area, the altered areas in the Butte pluton, 

and the unmined vein deposits that still exist within the study 

area. Of these, only the hydrothermally altered zones have 

not been discussed. The geologic character of hydrothermal 

alteration in the Butte pluton clearly indicates that unmined 

sources of elevated deposit-related trace-element concentrations are limited. O'Neill and others (this volume) summarize 

alteration studies of earlier workers. Polymetallic veins were 

emplaced along shear zones subsequent to cooling of the Butte 

pluton. The total width of the veins and the alteration zones is 

measured in terms of a few feet (maximum width about 50 ft). 

Argillic and sericitic alteration occurred on the outer fringes 

of the veins where chlorite replaces mafic minerals in the 

pluton. Silica replacement and deposition were characteristic 

along vein walls, and sulfide minerals were restricted to the 

mineralized veins. Becraft and others (1963) defined areas of 

alteration in the Butte pluton that were not associated with the 

mineralization that produced the polymetallic vein deposits. 

McCafferty and others (this volume) mapped the distribution of the chlorite-rich, magnetite-poor altered rocks in the 

pluton and showed that they parallel known structural features 

in the Boulder batholith (O'Neill and others, this volume; 

McDougal and others, this volume, Chapter D9). Sources of 

deposit-related trace elements, other than the veins exploited 

by historical mining, were therefore largely restricted to those 

mineralized veins that had not been mined. Because of the 

limited extent of geologic sources for elevated concentrations 

of deposit-related trace elements, the most logical sources of 

contamination are the fluvial deposits of postmining age along 

stream reaches in the watershed. Therefore, minimum values 

were used when the depth profile plots of the geochemical 

data from stream terrace deposits suggested that the samples 

might have been contaminated by postmining fluvial processes.

Determination of the premining geochemical baseline in 

the historical mining districts within the study area was a necessary goal of this project so that we could define minimum 

target concentrations for the deposit-related trace elements that 

feasible remediation efforts might be expected to achieve. 

Elevated deposit-related trace-element concentrations in 

mining districts commonly are found in soils and streambed deposits prior to mining. The fundamental and difficult 

question to answer in historical mining districts is: What 

were these baseline concentrations of the deposit-related 

trace elements prior to mining? To evaluate the data collected 

from these localities (fig. 2), concentration profiles of eight 

major and trace elements (iron, manganese, copper, lead, zinc, 

arsenic, silver, and cadmium) were graphed, and the concentration-versus-depth profiles examined and interpreted from 

sample descriptions of sediment grains (Unruh and others, 

2000; Rich and others, this volume). Depth profile plots of the 

data for six of these elements from several of the sites studied 

appear as figures 15-18 together with plots of the enrichment 

ratio for copper, lead, zinc, and arsenic (that is, the observed 

concentration of the deposit-related trace element divided by 

the geochemical baseline value for the trace element; data

from table 1). Site descriptions, age control, and premining 

geochemical baseline data for six deposit-related trace elements are summarized in table 3. Identification and interpretation of the geochemical data from premining terraces that 

contained streambed sediment unaffected by either subsequent 

erosion and deposition, ground-water movement, or infiltration 

of contaminated surface waters in the streams resulted in the 

following general observations:

1. Gravels sampled from terraces that have no vegetation 

or established soil profile are young, that is, postmining (circa 

1870; Ruppel, 1963), and have consistently proven to be contaminated by deposit-related trace elements . These included 

samples from sites 2B and 3B on the Boulder River, site 11B 

on Basin Creek, site 13B on Jack Creek, site 16B on Uncle 

Sam Gulch, and sites 18B and 19B on High Ore Creek (fig. 2).

2. Samples from other terraces showed evidence of 

contamination, either from onlap deposition of sediment on 

the terrace, or by infiltration of contaminated surface waters 

in the streams. In this case, the data showed distinct trends 

of deposit-related trace-element enrichment as a function of 

depth. As one approached the low-flow-water-level depth in 

the core, concentrations of the deposit-related trace elements 

increased (for example, see site 2B, fig. 18).

3. Ground-water movement may also have caused 

changes in deposit-related trace-element concentrations that 

vary as a function of element mobility. The deposit-related 

trace elements are listed in table 3 in inferred increasing element mobility from left to right (Fey and Desborough, this 

volume). Iron and manganese profiles with depth were used as 

a qualitative measure of ground-water movement of depositrelated trace elements in the cores (figs. 15-18). Precipitation of iron-oxide coatings on grain surfaces was used as an 

independent indicator of this process and was also indicated in 

the figures (for example, site 7B, fig. 15). Ribbon maps (figs. 

19-22) show premining concentrations of copper, lead, zinc, 

and arsenic in streambed sediment for the major tributaries 

and the Boulder River. Stream reaches with no data are also 

indicated on the maps. Premining geochemical background 

concentrations for both silver and cadmium in streambed 

sediment were below the limit of detection (< 2 ppm) everywhere within the study area.

Basin Creek

Premining geochemical baseline data for the depositrelated trace elements in streambed sediment were determined 

successfully at sites 7B through 10B (figs. 2 and 15). Additional data determined from streambed sediment that underlies the mill tailings at the Buckeye mine site on upper Basin 

Creek were also used to determine the premining geochemical 

baseline (Rich and others, this volume; Cannon and others, 

this volume). At site 7B, ground-water movement in the upper 

2 ft of the core had resulted in movement of the depositrelated trace elements. Only those data from samples below 

2.5 ft in depth showed a consistent pattern and were used to
Trace Elements and Lead Isotopes in Streambed Sediment 307

Table 3. Descriptions of sites sampled for possible premining geochemical baseline, age control, and determination of premining 

concentrations of selected deposit-related trace elements at those sites.

[Site localities in figure 2; LFWL = low-flow water level in adjacent stream; age data from Laboratory for Tree-ring Research, Univ. of Arizona, Tucson, Ariz., 

reported in Unruh and others (2000); nd, no data; description of Mazama ash at site B-7 in O'Neill and others, this volume, plate 2]

Site Description Age control No. 

samples

Ag 

ppm

As 

ppm

Pb 

ppm

Cu 

ppm

Zn 

ppm

Cd 

ppm

Boulder River

IB

2B

3B

4B

5B

6B

Terrace gravel, about 2 ft above LFWL,

minimal vegetation.

Terrace gravel, about 4 ft above LFWL,

no vegetation.

Discontinuous terrace gravel deposits

along north bank of river.

Terrace gravel, about 15 ft above

LFWL.

Terrace gravel, about 12 ft above

LFWL.

Terrace gravel, about 8 ft above LFWL,

well-developed soil profile.

nd

nd

nd

nd

nd

Live cottonwood, 60 years

old; sediments pre-1940.

1

1

nd

3

1

3

<2

<2

<2

<2

<2

57

24

36

46

59

40

34

67

74

70

100

52

67

43

70

110

150

100

140

210

<2

<2

<2

<2

<2

Basin Creek

Buckeye

Mill site

7B

8B

9B

10B

11B

Bullion

Mill site

12B

13B

14B

Sediments from cores beneath fluvial

tailings at mill site.

Core taken in meadow south of Buckeye mill site, soil about 1 ft above

LFWL.

Core from stream terrace, South Fork

of Basin Creek, well-developed soil

profile.

Core from stream terrace on Basin

Creek, about 6 ft above LFWL, good

soil profile.

Core from stream terrace on Basin

Creek, about 3 ft above LFWL, good

soil profile.

Terrace gravel, about 4 ft above LFWL,

no vegetation.

Sediments from cores beneath fluvial

tailings at mill site.

Core from stream terrace, about 2 ft

above LFWL, well-developed soil

profile.

Core from stream terrace, about 3 ft

above LFWL, no vegetation.

Core from sediments beneath beaver

dam. Beaver pond flooded with mill

tailings. There is no historical record

of this flood event.

nd

Mazama ash encountered

at base of core; sediment

circa 6,845 years B.P.

nd

nd

nd

nd

nd

nd

nd

Live Lodgepole pine,

99 years old, pre-1900;

dead tree in dam,

87 years old, sediment is

4

5

8

4

7

nd

4

nd

3

<2

<2

<2

<2

<2

<2

<2

--

<2

31

26

23

28

31

120

53

-

130

39

79

63

52

57

110

35

-

58

53

29

24

39

19

85

56

--

34

180

190

110

200

150

150

250

-

210

2

<2

<2

2

<2

<2

<2

-

2

15B Core from reservoir built for Bullion 

smelter, which was on county tax 

rolls 1903-1905; smelter operated 

1904-1906 (Rossillon and Haynes, 

1999).

pre-1840 if one assumes 

that the tree was killed in 

forest fire of 1934. 

Dead tree 251 years old, 

pre-1652 sediment 

assuming tree was cut 

down in 1903 at time of 

dam construction.

<2 110 60 72
308 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 3. Descriptions of sites sampled for possible premining geochemical baseline, age control, and determination of premining 

concentrations of selected deposit-related trace elements at those sites.—Continued

Site Description Age control No. Ag As Pb Cu Zn Cd 

samples ppm ppm ppm ppm ppm ppm

Cataract Creek

16B Core from stream terrace near miner's 

cabin, surface covered with mill 

tailings.

nd nd

17B Core from stream gravels taken beneath 3-ft diameter Ponderosa 

old tree, terrace about 1 ft above pine cut down in 1983, 

LFWL. 252 years old, sediment 

pre-1731.

4 <2 220 190 110

High Ore Creek

Comet 

Mill site 

18B

19B

Median 

values

Sediments from cores beneath fluvial 

tailings downstream from mill site. 

Core through fluvial tailing deposit, no 

vegetation. 

Core through terrace deposit, 3 ft above 

LFWL, no vegetation.

nd 

nd 

nd

Summary

nd

4 < 2 32 48 32 160 <2 

1 <2 120 220 130 

nd

<2 46 60 53 160 <2

determine the premining geochemical baseline values at this 

site. The enrichment ratio did not exceed 3.5 in this section 

of the core for any of the deposit-related trace elements. At 

about 4 ft depth at this site in a separate core, we encountered 

Mazama ash, which was dated at 6,845 years B.P. (O'Neill 

and others, this volume, pi. 2). The montaine basin where this 

sample was taken was dammed by a terminal glacial moraine 

downstream from the Buckeye mill tailings site and the basin 

filled with postglacial sediment. Downstream on the South 

Fork of Basin Creek at site 8B, none of the deposit-related 

trace elements exceeded an enrichment ratio of two and all 

data were used (not shown in fig. 15). At site 9B, on the main 

channel of Basin Creek upstream from the confluence with 

the South Fork of Basin Creek, we found an abrupt transition 

between sediment indicating premining geochemical baseline 

and sediment that had been contaminated by historical mining. 

Samples from below 2.7 ft depth were used to indicate premining geochemical baseline values and had enrichment ratios of 

2 or less. In contrast, sediment from above 2.5 ft depth showed 

evidence of ground-water movement of the deposit-related 

trace elements; copper, lead, arsenic, and cadmium were 

generally enriched in the sediment in this upper section of the 

core by a factor of more than 5. Zinc, which was relatively 

more mobile, and to some extent copper, have been leached 

out of the core particularly at the upper level above 1 ft depth. 

At site 1 OB, on Basin Creek downstream from the confluence 

with Jack Creek, all the data from the terrace deposits at this 

site were used. Profile plots of deposit-related trace-element 

concentrations were relatively constant in spite of the fact that 

we observed iron-oxide coatings on the grains below 2.5 ft 

and manganese had moved in this terrace deposit. At site 10B,

enrichment factors were always less than 2. Site 11B was from 

a low terrace gravel with no vegetative cover. All data indicate 

that the streambed sediment from this terrace was contaminated and postmining in age. Because site 11B was the farthest 

downstream site on Basin Creek, we used the data from site 

10B for the premining geochemical baseline in streambed sediment for the reach downstream from site 1 OB when preparing 

the premining geochemical ribbon maps (figs. 19-22).

On Jack Creek, we investigated terrace deposits at sites 

12B through 15B (fig. 2). We also obtained data from the cores 

taken through the tailings below the Bullion mine site (Rich 

and others, this volume). At site 12B, we sampled contaminated fluvial sediment that overlies uncontaminated streambed 

sediment (fig. 16). Enrichment factors for the deposit-related 

trace elements in the lower section of the core below 6 in. 

did not exceed 2, whereas above that depth in the core, they 

were highly variable, approaching 4 to 5 for the more mobile 

deposit-related trace elements copper and zinc. The mill tailings dam at the Bullion mine site was breached and flotation 

mill tailings flushed downstream in an event of unknown age. 

Fluvial tailings deposits exposed along Bullion Mine tributary have had much of the original content of copper and zinc 

leached out (Rich and others, this volume). The core from site 

12B was one locality where these metals have been sorbed by 

the older sediment. Site 13B (not shown in fig. 16) was in a 

young terrace with no vegetation on the surface of the terrace. 

All the streambed sediment in this terrace was deposited after 

the onset of mining and was contaminated. At site 14B, we 

cored beneath the dam of an abandoned beaver pond that had 

been flooded during the breach of the mill tailings dam 

(fig. 35). The minimum age of the premining streambed
Trace Elements and Lead Isotopes in Streambed Sediment 309

O_

0

0.5 

1.0

i- 1-5

LLJ 

LLJ

"- 2.0

z

£ 2.5

QS 3.0 

3.5 

4.0 

4.5

0

0.5 

1.0

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LLJ

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£ 2.0

LLJ 

Q

2.5 

3.0 

3.5

200 400 600 800 1,000 1,200 1,400 

CONCEI\rmATION, IN PPM

Site SB

200 400 600 800 1,000 1,200 

CONCEI\rmATION, IN PPM

500 1,000 1,500 

CONCENTRATION, IN PPM

2,000

O_

O_

0.5

ENRICHMENT RATIO

Premining

geochemical

baseline

Iron-oxidecoated grains

ENRICHMENT RATIO

50

Figure 15. Plots of geochemical data for the elements copper, lead, zinc, arsenic, iron, and manganese from 

cores taken at sites 7B, 9B, and WB (fig. 2) for determination of premining geochemical baseline in streambed 

sediment from Basin Creek basin. Uppermost soil interval was not analyzed; top is ground surface. Presence 

of iron-oxide coatings on grains was interpreted to be indicative of ground-water movement of depositrelated trace elements that would compromise geochemical baseline concentration data. Intervals in each 

core used for determination of the premining geochemical baseline are indicated; data are summarized in 

table 3. Geochemical data from core at site 8B were very similar to that from site WB. Site 11B yielded no 

usable data.
310 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

0.2

_ 0.4

LU 

LU 

LL.

* 0.6

Q_ 

LU

D 0.8 

1.0 

1.2

0

0.25

0.50

0.75

t 1.00

LU 

LL.

z 1.25 

E 1.50

Q_ 

LU

D 1.75 

2.00 

2.25 

2.50

0

0.5 

1.0

2.0

2.5

3.0

3.5

Site 12B

500 1,000 1,500 2,000 

CONCENTRATION, IN PPM

2,500

500 1,000 1,500 2,000 2,500 3,000 3,500 

CONCENTRATION, IN PPM

0.2 

0.4 

0.6 

0.8 

1.0

1.2

I

0

0.25

0.50

0.75

fc 1.00

LU

LL.

z 1.25 

£ 1.50

LU

D 1.75 

2.00 

2.25 

2.50

0

0.5 

1.0

LU

K 1.5

z

£ 2.0

LU 

O

2.5

3.0

Contaminated 

sediments

Premining 

geochemical 

baseline

0.5 50

ENRICHMENT RATIO

Premining

geochemical

baseline

0.5 50

ENRICHMENT RATIO

5,000

3.5

0 1,000 2,000 3,000 4,000 0.5 50

CONCENTRATION, IN PPM ENRICHMENT RATIO

Figure 16. Plots of geochemical data for the elements copper, lead, zinc, arsenic, iron, and manganese 

from cores taken at sites 12B, 14B, and 756 (fig. 2) for determination of premining geochemical baseline in 

streambed sediment from Jack Creek basin. Uppermost soil interval was not analyzed; top is ground surface. 

Presence of iron-oxide coatings on grains was interpreted to be indicative of ground-water movement of 

deposit-related trace elements that would compromise geochemical baseline data. Intervals in each core used 

for determination of the premining geochemical baseline are indicated; data are summarized in table 3. All data 

from site 736 indicated that only contaminated sediment was present in this core. We used only the minimum 

value from the geochemical data from site 756, which should be considered an estimate of the premining 

geochemical baseline in this reservoir.
Trace Elements and Lead Isotopes in Streambed Sediment 311

sediment in this core below the beaver dam is 99 years on 

the basis of the tree-ring count of a dead Lodgepole pine(?) 

growing in and partially buried by the beaver dam. Concentrations of the deposit-related trace elements decrease abruptly at 

a depth of 1.3 ft. Enrichment ratios in the lower section of the 

core for copper, lead, and zinc were less than 2 and for arsenic 

were between 3 and 4. At site 15B, we sampled streambed 

sediment trapped in a water reservoir on Jack Creek built in

1903 to supply the Bullion smelter. According to Rossillon 

and Haynes (1999), the Bullion smelter operated between

1904 and 1906. The sediment sample was taken adjacent to 

a Douglas-fir stump dated at 251 years. Because the stump 

was within a few hundred feet of the dam and Douglas-fir are 

sparse in this Lodgepole pine forest, the tree was probably 

cut down at the time of construction in 1903 for use in the 

dam, which was built entirely of Douglas-fir logs. Only the 

lowermost sample interval was used to estimate the premining 

geochemical baseline at the site (pre-1652). All other samples 

in the core through reservoir sediment had elevated enrichment 

factors for copper. lead, and arsenic that exceeded 5. Zinc was 

leached out of the sediment in the reservoir impoundment and 

showed variable enrichment ratios. This reservoir constitutes 

a large, reversible source of fluvial mine tailings that will 

contaminate water and streambed sediment in Jack Creek for 

many decades unless remediated.

Cataract Creek

The concentrations of deposit-related trace elements 

in streambed sediment of Cataract Creek upstream from the 

confluence with Uncle Sam Gulch were not investigated 

because most of the area is on private property and because 

data from streambed sediment collected in the stream indicated only a small enrichment in deposit-related trace-element 

concentrations. One potential source of contaminants, the Eva 

May mine, had been partially remediated prior to this study. 

No sites where terrace gravel would accumulate due to the 

steepness of the gradient of this reach of Cataract Creek were 

identified downstream from the confluence of Uncle Sam 

Gulch. In Uncle Sam Gulch, no usable data were obtained 

from the core from site 16B (fig. 2). At site I7B, located in a 

clear-cut in the flood plain of Uncle Sam Gulch, streambed 

sediment was cored from between the roots of a 3-ft diameter 

Ponderosa pine that had been cut down in 1983 (Robert Wintergerst, USDA Forest Service, written commun., 1998). The 

tree was 252 years old, indicating that the streambed sediment 

predates the onset of mining by more than a century (circa 

1731). Instead of the expected low values, concentrations of 

copper, lead, zinc, arsenic, and cadmium were elevated and 

varied with depth (fig. 17). Only silver had a low concentration approaching the local geochemical baseline (table 1). Iron 

concentrations were constant and were not enriched, whereas 

manganese concentrations were highly variable and showed 

enrichment near the top of the core above 1 ft in depth (that 

is, above the ground-water table). Arsenic and copper were

enriched above 1 ft in depth, whereas zinc was enriched below 

that zone with enrichment factors exceeding 10. Copper concentrations between 1.5 and 2.3 ft were enriched by factors of 

2-4, arsenic and lead by factors of 5-7, and zinc was enriched 

by about a factor of 7 over three of the cored intervals. These 

data represented the best estimate of the premining geochemical baseline in Uncle Sam Gulch prior to mining. We interpret 

these data to indicate that the vein exploited at the Crystal 

mine probably was exposed at the surface and that depositrelated trace elements were being actively eroded into the 

stream at the site prior to discovery about 1883 (Rossillon and 

Haynes, 1999).

High Ore Creek

The premining geochemical baseline was not successfully determined at either site J8B or 19B (fig. 2). At both 

sites, the terrace gravel had no vegetation cover on the surface 

and proved to be contaminated young terrace gravel. At site 

18B, we used the minimum concentrations from the base of 

the core, although these concentrations are merely an estimate of what the premining geochemical baseline might have 

been (fig. 17). Cadmium and zinc concentrations were clearly 

contaminated by ground-water movement of these two metals. Additional premining geochemical baseline data were 

obtained from streambed sediment cored from beneath the 

fluvial mill tailings below the Comet mine site and are summarized in table 3.

Boulder River

Six terrace gravel sites were sampled along the Boulder 

River (sites IB through 6B; fig. 2); the data for three of these 

sites, 2B, 4B, and 6B, illustrate the results (fig. 18). Site 3B 

contained no usable data and was postmining in age. At sites 

IB, 2B, and 5B, the lowermost samples had elevated depositrelated trace-element concentrations (fig. 18). Whether this 

was (1) the result of surficial contamination by young sediment with the existing sand and gravel on the banks, which 

were not removed because we failed to dig back far enough 

into the gravel deposit, or (2) the result of movement of metals 

and colloids into the gravel deposits from the contaminated 

surface waters was not tested. At sites IB, 2B, and 5B, only the 

data from the least contaminated interval were used. This was 

the top interval at sites IB and 5B, and the middle interval at 

site 2B (fig. 18). Site 2B is located immediately downstream 

from the Jib Mill site (fig. 2) and likely contained overbank 

deposits contaminated by mill tailings on top of the terrace 

gravel. As will be shown in "Lead Isotopic Results," lead 

isotope data from site 2B prove the value of this approach. 

The concentrations of the deposit-related trace elements in 

the upper intervals from sites IB and 5B were very similar to 

those from site 6B and are not shown in figure 18. Sites 4B 

and 6B were both large, vegetated terrace deposits that gave 

very consistent results. The terrace at site 6B is a minimum
312 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

0

0.25

0.50

0.75

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LL.

z 1.25 

^ 1-50

LLJ

Q 1.75 

2.00 

2.25 

2.50

0

0.25

0.50

0.75

£ 1.00

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Site 17B

2,000 4,000 6,000 

CONCENTRATION, IN PPM

8,000

Site 18B

2,000 4,000 6,000 8,000 10,000 12,000 

CONCENTRATION, IN PPM

Copper

Lead

Zinc

Arsenic

Iron/100

Manganese

0 2,000 4,000 6,000 8,000 10,000 

CONCENTRATION, IN PPM

0

0.25

0.50

0.75

1.00

1.25

1.50

1.75

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0

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2.50

2.75

10 

ENRICHMENT RATIO

100

_L

10

ENRICHMENT RATIO

100

0.5 5 50 

ENRICHMENT RATIO

500

Figure 17. Plots of geochemical data for the elements copper, lead, zinc, arsenic, iron, and manganese 

from cores taken at site 776 (fig. 2) for determination of premining geochemical baseline in streambed sediment from Uncle Sam Gulch basin, and at sites 18B and 19B in High Ore Creek basin. Uppermost soil interval 

was not analyzed; top is ground surface. Presence of iron-oxide coatings on grains was interpreted to be 

indicative of ground-water movement of deposit-related trace elements that would compromise geochemical 

baseline data. Intervals in each core used for determination of the premining geochemical baseline are indicated on the figures; data are summarized in table 3. Samples for site 16B were contaminated. No convincing 

evidence for a premining baseline was determined in High Ore Creek basin from cores taken at sites 18B and 

19B.
Trace Elements and Lead Isotopes in Streambed Sediment 313

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Site 2B

0 200 400 600 800 1,000 1,200 1,400 

CONCENTRATION, IN PPM

Site 4B

200 400 600 800 

CONCENTRATION, IN PPM

1,000

500 1,000 1,500 

CONCENTRATION, IN PPM

2,000

0.5 

1.0 

1.5

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Copper

Lead

Zinc

Arsenic

Iron/100

Manganese

Premining geochemical 

baseline

Contamination 

rom Jib Mill site

0.5 50

ENRICHMENT RATIO

6.0 

6.5 

7.0 

7.5 

8.0 

8.5 

9.0 

9.5

10.0

3.0

3.5

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6.0

1

Copper

Lead

Zinc

Arsenic

Iron/100

Manganese

0.5 50

ENRICHMENT RATIO

T

.Contaminated 

sediments

Copper

Lead

Zinc

Arsenic

Iron/100

Manganese

0.5 50

ENRICHMENT RATIO

Figure 18. Plots of geochemical data for the elements copper, lead, zinc, arsenic, iron, and manganese 

from cores taken at sites 2B, 4B, and 6B (fig. 2) for determination of premining geochemical baseline in 

streambed sediment from Boulder River watershed in the Basin and Boulder mining districts. Uppermost soil 

interval was not analyzed; top is ground surface. Presence of iron-oxide coatings on grains was interpreted 

to be indicative of ground-water movement of deposit-related trace elements that would compromise geochemical baseline data. Intervals in each core used for determination of premining geochemical baseline 

are indicated on the figures; data are summarized in table 3. All samples from site 36 were contaminated.
314 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

of 60 years old, on the basis of dendrochronological age of a 

large cottonwood tree that was growing on the terrace deposit. 

Samples were taken from the exposed root zone in the terrace 

cut bank. The uppermost interval was composed of a silt layer 

and may represent a flood deposit rather than local terrace 

gravel. Including the data from the silt layer does not significantly affect the premining geochemical baseline ribbon maps 

of figures 19-22.

Boulder River Watershed

Ribbon maps of the premining geochemical baseline for 

the watershed are shown in figures 19-22. The data used are 

both in table 3 and taken from the current geochemical maps 

in areas where past mining had little effect (figs. 4-7). The 

same concentration intervals were used as in the previous 

maps to facilitate comparisons of the conditions in the Boulder 

River watershed today with those prior to mining (Rich and 

others, this volume). Premining geochemical baselines for 

all the deposit-related trace elements were in the lowest two 

concentration ranges everywhere except downstream from the 

Crystal mine site in Uncle Sam Gulch.

In contrast to the data from unmined and probably 

unmineralized tributaries in table 1, the premining geochemical baseline determined from terrace deposits in the Basin and 

Boulder mining districts was higher than reported in table 1. 

Premining geochemical baseline concentrations for copper 

ranged from 19 to 150 ppm with a median value of 53 ppm; 

lead ranged from 34 to 220 ppm with a median value of 60 

ppm; zinc ranged from 100 to 250 ppm with a median value of 

160 ppm; arsenic ranged from 23 to 220 with a median value 

of 46 ppm (35 ppm in table 1); silver was always < 2 ppm; and 

cadmium ranged from <2 to 2 ppm with a consensus value of 

<2 ppm. These median values are 65 percent higher for copper, 60 percent higher for lead, 30 percent higher for arsenic, 

but only 6 percent higher for zinc than those given in table 1. 

The agreement between the two methods for determination 

of the premining geochemical baseline is remarkable. Use of 

either set of geochemical baseline values would make little 

difference in terms of evaluating the toxic effect of historical mining on aquatic life in the three major tributaries in the 

Boulder River watershed study area. The data demonstrate 

the feasibility of using terrace deposits of premining age to 

determine streambed-sediment geochemistry prior to the onset 

of mining in a historical mining district. The independent 

determination of premining geochemical baseline from 

premining terrace deposits fulfills the third goal of this study. 

The two methods for the determination of premining geochemical baselines, that is, the use of premining sediments 

preserved in terrace deposits, and the use of stream sediment 

from unaffected tributaries in a historical mining district, 

provide compelling evidence that the watershed would have 

supported aquatic life prior to mining.

Lead Isotopic Results

Lead isotopic analyses of all streambed sediment, sediment cores, and selected premining terrace sediment were 

completed to determine if metals in the present-day streambed-sediment samples were derived from past mining activities. Four isotopes of lead exist in nature, three of which 

change directly as a function of time through the radioactive 

decay of uranium and thorium: 2()6Pb is the daughter product 

of decay of 238U, 207Pb is the daughter product of decay of 235U, 

and 208Pb is the daughter product of decay of 232Th. However, 

204Pb has no radioactive parent. Thus, the isotopic composition of lead in rocks in the Earth's crust (that is, 20f)Pb/204Pb, 

2()7pb/2()4pb and 208pb/204pb) changes regularly with time as uranium and thorium undergo radioactive decay. When mineral 

deposits are formed, lead is separated from the parent uranium 

and thorium isotopes and the lead isotopic composition of 

the hydrothermal fluid is "frozen" into the sulfide minerals, 

usually in galena, within the mineral deposit. This mineral 

deposit lead isotope signature will then differ from that of the 

host rocks underlying a watershed because the lead in the host 

rocks continues to change with time whereas the lead in the 

mineral deposit remains fixed.

The isotopic composition of lead in streambed sediment reflects mixtures of lead from many discrete sources: 

the mineral deposits, unmined altered rock surrounding those 

deposits, the unmineralized rocks underlying the watershed, 

mine-waste dumps near mine adits, and mill tailings produced 

during the processing of ore. Physical transport of detrital 

material derived from erosion and mixing of all these materials combine to make up the streambed sediment. In addition, 

aqueous or colloidal transport of deposit-related trace elements 

from mined sites to the stream, and precipitation by mixing, 

:sorption to the colloids and grain coatings, and subsequent settling of the colloids to the streambed also contribute depositrelated trace elements to the streambed.

In order for the lead isotopic data to be useful, it must be 

possible (1) to measure the isotopic compositions of all suspected sources of lead as well as the premining geochemical 

baseline, and (2) to determine the lead isotopic composition of 

the contaminant. Moreover, (3) the lead-isotopic composition 

of the contaminants must be distinct from that of uncontaminated or premining geochemical baseline (Church and others, 

1997).

The lead isotopic values in the present study area form 

single arrays on lead isotopic correlation plots (that is,

206pb/204pb versus 207pb/204pb and 206pb/204pb versus 208pb/204pb

plots). This was because the lead in most of the streambedsediment samples was contained in minerals derived from the 

Butte pluton of the Boulder batholith or the associated Elkhorn 

Mountains Volcanics. The variations observed among the 

samples reflect variations in U/Pb among the different rocks 

and ores, which were derived from a common source during 

melting that formed the batholith and subsequent mineralization (O'Neill and others, this volume; Lund and others,
112°22'30" 112°22'30"

EXPLANATION 

Copper, ppm

• > 1,300

• 650-1,300H 325-650• 200-325• <200• No data 46° 15'

EXPLANATION 

Lead, ppm

• >400

• 200^100 

KB 100-200• 60-100• <60

• No data

Base from U.S. Geological Survey digital line graphs, 1:100,000

Figure 19. Concentrations of copper (ppm) in premining streambed sediment (solid dot) of 

Boulder River watershed study area. Stream reaches shown in gray, no data. Concentration intervals are same as in figure 4 Note that all stream reaches where we determined premining geochemical baseline have concentrations of copper below 200 ppm, that is, 

less than six times baseline value of 32 ppm (table 1). Dark-red square, Jib Mill site.

Base from U.S. Geological Survey 0 digital line graphs, 1:100,000 l~

R4W 

I 2 MILES

1 2 KILOMETERS

Figure 20. Concentrations of lead (ppm) in premining streambed sediment (solid dot) of 

Boulder River watershed study area. Stream reaches shown in gray, no data. Concentration intervals are same as in figure 5. Note that many stream reaches where we have been 

able to determine premining geochemical baseline have concentrations of lead below 

80 ppm, that is, about twice the baseline value of 35 ppm (table 1), with the exception of the 

reach downstream from Crystal mine in Uncle Sam Gulch at site 775. Dark-red square, Jib 

Mill site.

m 

tonE

o •a!.I0)COCD

a.

n 2.

u en
f J BUCKCYEAN ENTEI*PRISE

EXPLANATION

Arsenic, ppm

• > 1,000• 250-1,000 

50-250 

<50 

No data

EXPLANATION 

Zinc, ppm

• > 1,500• 750-1,500 

d! 375-750

• 225-375

• <225

• No data

~aDOO

I

ni-<D

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

R4W 

1 2 MILES

2 KILOMETERS

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

R4W 

1 2 MILES

Figure 21. Concentrations of zinc (ppm) in premining streambed sediment (solid dot) of 

Boulder River watershed study area. Stream reaches shown in gray, no data. Concentration intervals are same as in figure 6. Note that many stream reaches where we have been able to determine premining geochemical baseline have concentrations of zinc below 

200 ppm, that is, less than 1.5 times the baseline value of 150 ppm (table 1), with the exception of the reach downstream from Crystal mine in Uncle Sam Gulch at site 17B. Dark-red 

square, Jib Mill site.

Figure 22. Concentrations of arsenic (ppm) in premining streambed sediment (solid dot) 

of Boulder River watershed study area. Reaches shown in gray, no data. Concentration intervals the same as in figure 7. Note that many stream reaches where we have been 

able to determine premining geochemical baseline have concentrations of arsenic below 50 ppm (table 1; arsenic has a median value of 35 ppm). However, downstream from Bul lion and Crystal mines, arsenic concentrations were elevated. Dark-red square, Jib Mill 

site.
Trace Elements and Lead Isotopes in Streambed Sediment 317

2002). Consequently, the lead isotopic data will be represented 

exclusively using206Pb/204Pb values throughout the ensuing 

discussion.

Lead isotopic data showed an inverse relationship with 

lead concentrations (fig. 23). The highest 206Pb/2MPb values 

from drainage basins underlain largely by rocks of the Butte 

pluton of the Boulder batholith (18.1-18.2) and lowest lead 

concentration values (<60 ppm) were found among some of 

the premining streambed-sediment samples collected either 

from tributaries upstream from major mines or from the Boulder River upstream from Basin Creek. Streambed-sediment 

samples from sites 3S and 4S (between river miles 12.5 and 

14.5, fig. 24A) along the Boulder River showed anomalously 

high ^Pb/^Pb values of 18.3-18.4. These streambed-sediment samples were collected downstream from where the 

Boulder River cuts through a large dike of Eocene Lowland 

Creek Volcanics (O'Neill and others, this volume, pi. 1). 

These Eocene rocks are younger than and have a different 

source than the Boulder batholith. As a result, they had a more 

radiogenic lead isotopic composition; that is, they had a higher 

^Pb/^Pb value than the rocks that make up the majority of 

the Boulder River watershed study area. Lead isotopic data 

from these two sites were used as an estimate of the uncontaminated streambed sediment in the Boulder River immediately upstream from the Jib Mill and Basin Creek, but they 

were not used to calculate average premining baseline lead 

isotopic values in streambed sediment anywhere else within 

the study area (table 4).

The lead data in figure 23 clearly indicated two principal 

sources of deposit-related lead. Streambed-sediment samples 

containing high concentrations of lead (for example, samples 

from High Ore Creek with lead concentrations > 1,000 ppm) 

showed a relatively constant ^Pb/^Pb value of 18.06. We 

interpret this value to represent the 206Pb/204Pb value of depositrelated contaminant lead from the Comet mine in this drainage. In contrast, the highest concentrations of lead in the Basin 

and Cataract Creek basins were characterized by a 206Pb/204Pb 

value of 17.90-17.93. Because sampling was limited at each 

of the mines in the Basin and Cataract Creek basins, we used 

the average of the highest lead samples (that is, lead concentrations greater than 1,000 ppm and ^Pb/^Pb value of 17.91) 

collected from these two basins to represent the lead isotopic 

composition of the contaminant lead for both the Basin and 

Cataract Creek basins (fig. 23, table 4). Comparison of the 

deposit lead signatures from the mining districts with the data 

from the geochemical baseline site 2B downstream from the 

Jib Mill (206Pb/204Pb value of 17.73) is clear evidence that the 

low lead isotopic value from this site is not from mines in the 

Basin and Boulder mining districts.

One unfortunate aspect of the relationship among virtually all samples to a common source is that the total range of 

206Pb/204Pb values among the samples was only about 

1.7 percent, varying from ^Pb^Pb of 17.9 to 18.2 (fig. 23, 

excluding the streambed sediment apparently derived from 

the Eocene Lowland Creek Volcanics). This means that, when 

even comparatively small amounts of deposit-related lead are

added to the streambed sediment, the 206Pb/204Pb value of the 

streambed sediment will rapidly approach that of the deposit 

lead. Consequently, we were not able to resolve the small isotopic differences created by the addition of deposit lead from 

other downstream sources within the study area.

Lead isotopic data from modern streambed-sediment 

samples and from the premining terrace appear as figures 

24-27; data are in the database (Rich and others, this volume). 

Individual mine localities are indicated in the figures, plotted 

by distance (river mi).

Basin Creek

The lead isotopic compositions of streambed sediment 

from Basin Creek are compared with those of the Boulder 

River in figure 24A. All Basin Creek streambed-sediment 

samples had lower ^Pb/^Pb values than those of the Boulder 

River upstream from the Basin mining district. As Basin Creek 

flowed past the Buckeye mine, the 206Pb/204Pb value decreased 

from 18.0 to 17.9. The 206Pb/2MPb progressively increased 

downstream as a result of both settling out of colloidal phases 

rich in deposit-related trace elements and dilution by streambed sediment derived from nonmineralized rock in the Basin 

Creek basin. At the confluence with Jack Creek, the 206Pb/204Pb 

value decreased from 18.0 to 17.92 as a result of contaminant 

lead contributed by Jack Creek. Downstream of this confluence to the confluence of Basin Creek with the Boulder River, 

the ^Pb/^Pb value progressively increased as a result of 

dilution by streambed sediment from unmineralized subbasins 

drained by other tributaries to Basin Creek (fig. 24A, E).

The effects of the Buckeye and Bullion mines on the 

206Pb/204Pb value and the lead concentrations in the streambed 

sediment of upper Basin Creek and the Bullion Mine tributary, respectively, are readily apparent (fig. 24B, C). Lead 

isotopic values decreased and lead concentrations increased 

significantly as the streams flowed past these mine sites. The 

lead concentration and isotopic values in streambed sediment 

upstream from these mines (sites 20S and 32S) were similar 

to those found in premining streambed sediment from terrace 

samples collected along these streams.

In contrast, the streambed-sediment samples from Jack 

Creek collected upstream from the confluence with the Bullion 

Mine tributary (site 38S) had elevated lead concentrations and 

comparatively low 206Pb/204Pb values. These results suggest 

that either historical mining activity or exposed mineralized 

rock also influenced the deposit-related trace-element concentrations and lead isotopic characteristics of upper Jack Creek. 

In any case, the 206Pb/204Pb value of streambed sediment in 

Jack Creek was already so similar to those of the contaminant sources (^Pb/^Pb of 17.91-17.92) upstream from the 

confluence with the Bullion Mine tributary that the addition of 

streambed sediment from the Bullion Mine tributary was not 

discernible in the lead isotopic data (fig. 245). However, the 

addition of leachable lead from the Bullion Mine tributary to 

Jack Creek had a large effect on the concentration of lead as
318 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 4. Estimates of contaminant and premining baseline lead isotopic compositions from 

Boulder River watershed study area.

[Data are from Fey, Unruh, and Church (1999) and Unruh and others (2000); data are in database, Rich and others, this volume]

Sample Site Sample type Pbppm 206pb/204pb

Baseline, Boulder River upstream from Basin Creek

97-BM-115

98-BMS-113

96-BM-121

Mean Value

3S

3S

4S

Streambed sediment

Streambed sediment

Streambed sediment

20

24

20

21

18.263

18.318

18.425

18.389

Baseline, Boulder River downstream from Basin Creek

96-BM-107

97-BM-102sl

97-BM-120

97-BM-108sl

98-BMS-115

99BMB-102a

99BMB-103c

99BMB-108a

98BMB-406a-e

98BMB-401cdfh

98BMB-402jkl

98BMB-403eghi

98BMB-407b-f

97BMB(S)-122efgh

97BMF-131(9fgl3ef)

Mean Value

22S

32S

44S

54S

58S

IB

2B

5B

7B

8B

9B

10B

12B

13B

Streambed sediment

Streambed sediment

Streambed sediment

Streambed sediment

Streambed sediment

Stream terrace

Stream terrace

Stream terrace

Stream terrace

Stream terrace

Stream terrace

Stream terrace

Stream terrace

Stream terrace

Core through fluvial tailings, 

Comet Mill.

61

59

36

34

31

48

34

51

33

39

33

36

33

42

33

40

18.185

18.079

18.213

18.055

18.227

18.190

18.123

18.114

18.096

18.126

18.099

18.122

18.163

18.094

18.101

18.132

Deposit-related lead, Basin and Cataract Creeks

96-BM-136

96-BM-115

97-BM-104G

96-BM-114

97-BM-106G

96-BM-116

96-BM-118

Mean Value

21S

34S

35S

37S

55S

57S

Streambed sediment

Streambed sediment

Fluvial tailings

Bullion smelter waste

Fluvial tailings

Streambed sediment

Streambed sediment

1,600

1,400

12,000

1,300

2,600

1,900

920

17.895

17.927

17.925

17.897

17.923

17.921

17.925

17.916

Deposit-related lead, High Ore Creek

96-BM-101

96-BM-102

96-BM-102d

Mean Value

59S

60S

60S

Streambed sediment

Streambed sediment

Streambed sediment

5,700

1,900

2,000

18.069

18.062

18.064

18.065

well as other deposit-related trace elements in Streambed sediment downstream from the confluence with the Bullion Mine 

tributary (fig. 11).

With the exception of the two most-upstream samples 

(sites 20S and 32S), the streambed-sediment samples from 

both Jack and Basin Creeks showed elevated lead concentrations and low 206Pb/2MPb relative to Streambed sediment from

premining terraces (fig. 24B, Q. Although the 

value and lead concentration in Streambed sediment from 

Basin Creek progressively approached those of the premining 

samples as a function of distance downstream, the contaminants in Basin Creek still exerted a significant influence on 

streambed-sediment geochemistry at the confluence with the 

Boulder River (river mi 15, fig. 24A).
Trace Elements and Lead Isotopes in Streambed Sediment 319

JO 

D_

O

CNI

JO

Q_ 

CO

o

CNI

18.4 

18.3 

18.2 

18.1 

18.0 

17.9 

17.8

17.7 

1C

i- * "^ "^ ^

"^ Lowland Creek Volcanics 

i 206 Pb /204 Pb = 1826 -18.42

: m ^ ^

7 •• Premining baseline

- • T-- 206 Pb/ 204 Pb = 18.08 -18.23 

MfSB A High Ore Creek

: ^'iSC^mi.P" ~ ~ _ _ _ 206Pb/204Pb =

I O JlfS'^*^ /\ — -y^- __ __ rr Basin and Cataract 

<^V 9+~ + O ^LO O" CT Cree|< contaminant

7 ^-* ——— ——— ——— - 206pb/204p b =

17.90-17.93

: , * , ...,,, , , . ...... . . . ...... . . . ...

1 100 1,000 10,000 1C

^

10,0

LEAD CONCENTRATION, IN PARTS PER MILLION

EXPLANATION

+ Cataract Creek

O Uncle Sam Gulch

*, High Ore Creek

• Premining stream terraces

• Boulder River above High Ore Creek 

G Boulder River below High Ore Creek

• Basin Creek

O Jack Creek and Bullion Mine tributaries

X Extraneous lead from Jib Mill site(?)

Figure 23. Plot of concentration of lead versus isotopic composition of lead ( 206Pb/204Pb) showing the dominant 

effect of mixing of contaminant lead derived from mining on isotopic composition of leachable lead in streambed 

sediment. Analytical error for lead isotopic data is smaller than the symbol. Note limited range in lead isotopic 

compositions.

Cataract Creek

The ^Pb/^Pb values in Cataract Creek streambed sediment decreased progressively downstream from premining 

baseline values at river mi 6 (fig. 25A, site 44S) to essentially 

contaminant values at the confluence with Uncle Sam Gulch 

(river mi 13, sites 49S and 505). Deposit-related trace-element-rich streambed sediment derived from tributaries such as 

Hoodoo and Rocker Creeks and mines such as the Eva May, 

Cataract, and Hattie Ferguson in upper Cataract Creek (Martin, this volume) contributed to the deposit-like lead isotopic 

signature in the streambed sediment at site 49S (river mi 12.5). 

Consequently, the effect of streambed sediment derived from 

Uncle Sam Gulch on the ^Pb/^Pb value downstream from 

the confluence with Cataract Creek was nearly undiscernible 

in the lead isotope data. Only a slight decrease in the 206Pb/ 

204Pb value and an increase in lead concentration in streambed 

sediment were observed downstream from the confluence 

(fig. 25B, Q. The interpretation of the data from site 505

was further complicated by the fact that mine waste from 

the Morning Glory was in and along Cataract Creek over an 

extended area upstream and downstream from the confluence 

with Uncle Sam Gulch (Martin, this volume).

The influence from the Crystal mine on the depositrelated trace-element load in the streambed sediment of Uncle 

Sam Gulch is clearly evident in figure 25B, C. The lead concentration increased from 34 ppm upstream from the Crystal 

mine to 1,900 ppm downstream, whereas 206Pb/204Pb value 

decreased from 18.06 to 17.92. The 206PbP4Pb value remained 

relatively constant all the way downstream to the confluence 

with Cataract Creek and lead concentrations decreased by 

about a factor of 2. Downstream from the confluence with 

Uncle Sam Gulch, lead in the streambed sediment of Cataract Creek decreased only slightly toward premining baseline 

values: the ^Pb/^Pb value increased to 17.95 whereas lead 

concentrations decreased to 310 ppm upstream from the confluence of Cataract Creek with the Boulder River. Although 

the lead isotopic composition of deposit lead in Cataract Creek
320 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

o 

o

Q

18.5

18.4

18.3

18.2

18.1

18.0

17.9

17.8

18.2

18.1

18.0

17.9

Boulder River 

Basin Creek

5.0 10.0 15.0 20.0 

DISTANCE, IN MILES

25.0 30.0

1,000

100

10

E C

BUCKEYE 

•MINE ^

BULLION 

MINE

• Basin Creek 

Jack Creek 

Bullion Mine tributary

Premining terraces 

Basin Creek

Premining terraces 

Jack Creek and 

Bullion Mine 

tributary

2.0 4.0 6.0 8.0 10.0 

DISTANCE, IN MILES

12.0 14.0 16.0

Figure 24. Profile plots of lead isotopic composition (A B) and lead concentration (C) determined in 

streambed sediment. A, 206Pb/204Pb versus distance on Boulder River and Basin Creek. B, 206Pb/204Pb 

versus distance on Basin Creek, Jack Creek, and the Bullion Mine tributary. C, Concentration of lead in 

streambed sediment on Basin Creek, Jack Creek, and the Bullion Mine tributary versus distance.
Trace Elements and Lead Isotopes in Streambed Sediment 321

_a 

Q_

-Q

a_

_a

Q_

.a

a_

18.5

18.4

18.3

18.2

18.1

18.0

17.9

17.8

18.3

18.2

18.1

18.0

17.9

Boulder River 

Cataract Creek

: A

Hoodoo

Creek "^ Uncle Sam Gulch

5.0 10.0 15.0 20.0 

DISTANCE, IN MILES

25.0 30.0

<

DC

1,000

100

10

CRYSTAL 

MINE

B

H——I——h H——I——h

CRYSTAL 

MINE

EVA MAY 

MINE

Cataract Creek 

Uncle Sam Gulch 

Rocker Creek 

Hoodoo Creek

Premining terrace 

Uncle Sam Gulch

6.0 8.0 10.0 12.0

DISTANCE, IN MILES

14.0 16.0 18.0

Figure 25. Profile plots of lead isotopic composition (A B) and lead concentration (C) determined 

in streambed sediment. A, 206Pb/204Pb versus distance on Boulder River and Cataract Creek. B, 206Pb/ 

204 Pb versus distance on Cataract Creek and Uncle Sam Gulch. C, Concentration of lead in streambed sediment of Cataract Creek and Uncle Sam Gulch versus distance. Note small difference in lead 

isotopic composition versus the great difference in lead concentration in premining versus modern 

streambed sediment in Uncle Sam Gulch.
322 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

near the Eva May mine site and in Hoodoo Creek was identical to that from the Crystal mine, the very large increase in 

lead concentration in streambed sediment today downstream 

from the confluence with Uncle Sam Gulch indicated that 

the Crystal mine was the major source of contaminants in the 

Cataract Creek basin.

As mentioned previously, we were not able to obtain any 

premining stream-terrace samples from Cataract Creek. Lead 

isotopic data obtained from a single premining terrace sample 

(17B) on Uncle Sam Gulch are shown in figure 25B, C. The 

lower than normal 206Pb/204Pb value of 17.99 was in accord 

with higher than normal deposit-related trace-element concentrations observed at this site (fig. 17). The data indicate that a 

significant amount of lead was in the streambed sediment prior 

to mining if the sample from the base of the core at site I7B 

was not contaminated by past mining.

High Ore Creek

The Comet mine site on High Ore Creek (river mi 

15.9) contributed the bulk of the deposit-related trace elements to streambed sediment in this basin. The 2WlPb/204Pb 

value decreased markedly from 18.23 in streambed sediment 

upstream to 18.07 downstream from the mine (fig. 26A B). 

Lead concentrations (fig. 26C) increased dramatically from 

about 30 ppm to 5,700 ppm over this same interval. Downstream from the Comet mine, the 206Pb/204Pb value remained 

relatively constant at 18.06-18.07 to the confluence with the 

Boulder River. Lead concentrations decreased from 1,600 to 

1,000 ppm but were still strongly elevated relative to premining concentrations (table 1). Note that the composition of 

contaminant deposit lead from the Basin and Cataract Creeks 

was lower than that from the Comet mine, so the lead isotopic composition of streambed sediment in the Boulder River 

increased to the deposit-lead value at the Comet mine 

(table 4. fig. 23) downstream from the confluence with High 

Ore Creek.

Samples from two of the cores that penetrated through 

the fluvial tailings immediately downstream from the Comet 

mine (fig. 2) have been used to estimate premining baseline 

values for streambed sediment in High Ore Creek. One of the 

samples had a 206Pb/204Pb value of 18.10 and contained 33 ppm 

lead, very similar to premining baseline values throughout 

the study area. The other had an elevated lead concentration 

(110 ppm) and somewhat lower 206Pb/204Pb value of 18.08. 

Because these samples were overlain by tailings, the possibility that lead migration through the sediment column may have 

affected even the sample with the lowest lead concentration 

must be considered. In any case, present-day lead concentrations in streambed sediment in High Ore Creek prior to 

the removal actions, which began in 1997, appeared to be 

30-150 times those in streambed sediment prior to mining 

(tables 1 and 4).

Boulder River

Lead isotopic data for the entire 70-mile segment of the 

Boulder River are summarized in figure 27A. The 206Pb/204Pb 

values were lowest through the historical mining district and 

progressively increased downstream from the district. At a 

distance of approximately 45 miles downstream from the 

Basin and Boulder mining districts (site 785; river mi 68), the 

206Pb/2()4Pb finally approached the baseline value at site 75 in 

the Boulder River (river mi 0.5). However, if the 206Pb/204Pb 

value of 18.27 in streambed sediment from the Little Boulder 

River was a reasonable indication of sediment unaffected by 

mining activity (site 795, river mi 30), then we would conclude that the contribution of deposit lead was still evident 

at site 7<S5, forty-five miles downstream from the Basin and 

Boulder mining districts near the confluence with the Jefferson 

River (fig. 27).

The effects of each of the tributaries on the 206Pb/204Pb 

value and lead concentration of Boulder River streambed 

sediment can be evaluated from figure 27. Lead derived from 

the Jib Mill (and associated tailings) and Basin Creek caused 

a pronounced decrease in the 2()6Pb/2()4Pb value and an increase 

in lead concentration in Boulder River streambed sediment. 

It was not possible to isolate the contributions from these two 

sources because mill tailings apparently derived from the Jib 

Mill were found downstream of the confluence of Basin Creek 

and the Boulder River. Furthermore, numerous small prospects 

in the area, as well as construction debris from a railroad grade 

and interstate highway, have all caused at least some disruption to the normal sedimentation processes, if not a direct 

contribution to the sediment load in the Boulder River. Lead 

isotope data from site 2B (fig. 2) demonstrated that the use 

of the minimum concentration from the core at this site was 

the correct approach to determination of the uncontaminated 

geochemical baseline in stream-terrace deposits. Geochemical 

data from the site (fig. 18) indicate a minimum in all depositrelated trace-element concentrations at a depth of 2.6 ft. The 

206Pb/2()4Pb from the three lowest sampled intervals was 17.726, 

which plotted below the field of the deposit leads from the 

Basin and Boulder mining districts (fig. 23), indicating an 

extraneous source of lead and copper associated with the Jib 

Mill. In contrast, the sample from the 2.6 ft depth had a concentration of 34 ppm and a 2()6Pb/2(MPb value of 18.123, which 

plots in the field of uncontaminated sediment from the study 

area (fig. 23).

Streambed sediment derived from Cataract Creek caused 

an abrupt increase in both the 206Pb/204Pb and lead concentration in the streambed-sediment sample collected immediately 

downstream (site 95, fig. 1, river mi 17) of the confluence of 

Cataract Creek with the Boulder River. The lead concentration 

in the Boulder River streambed sediment decreased at site 705 

(river mi 17.5) to values close to those obtained just upstream 

from the confluence (site 85).
Trace Elements and Lead Isotopes in Streambed Sediment 323

_Q

o_

_Q

o_

.0 

Q_

_Q 

Q_

< 

cc

18.5

18.4

18.3

18.2

18.1

18.0

17.9

17.8

18.3

18.2

18.1

Boulder River 

High Ore Creek

COMET MINE

I A

5.0 10.0 15.0 20.0 

DISTANCE, IN MILES

25.0 30.0

S 18.0

17.9

1,000

100

o

z 

o 

o 

o

25 10

COMETMINE

High Ore Creek

Cores through fluvial tailings 

High Ore Creek

- c

14.0 15.0 16.0 17.0

DISTANCE, IN MILES

18.0 19.0 20.0

Figure 26. Profile plots of lead isotopic composition (A, B) and lead concentration (C) determined in 

streambed sediment. A, 2D6Pb/204Pb versus distance on Boulder River and High Ore Creek. B, 206Pb/204Pb 

versus distance on High Ore Creek. C, Concentration of lead in streambed sediment from High Ore 

Creek versus distance. Note small difference in lead isotopic composition relative to the large difference in lead concentration in premining versus modern streambed sediment in High Ore Creek.
324 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

-Q 

Q_

.a 

D_

s

18.5

18.4

18.3

18.2

18.1

18.0

17.9

17.8

18.5

18.4

18.3

18.2

18.1

18.0

17.9

A

'Basin anqBoulder

I mining 

districts I

10.0 20.0 30.0 40.0 

DISTANCE, IN MILES

50.0 60.0 70.0

Q_ 

Q_

<C 

DC

LLJ 

CJ

o

CJ

100

10

High Ore

Cataract Creek 

Creek

Boulder River

Premining terraces 

Boulder River

B

Basin 

Creek

10.0 12.0 14.0 16.0 18.0 20.0 22.0

DISTANCE, IN MILES

24.0 26.0 28.0

Figure 27. Profile plots of lead isotopic composition (A, B) and lead concentration (C) 

determined in streambed sediment. A, 206Pb/204Pb versus distance on Boulder River, fi, 

206Pb/204Pb at larger-scale intervals for streambed sediment on Boulder River and premining terrace deposits (sites in fig. 18). C, Concentration of lead in streambed sediment today 

and in streambed sediment from premining terrace samples versus distance on Boulder 

River.
Trace Elements and Lead Isotopes in Streambed Sediment 325

At the confluence with High Ore Creek, lead concentrations in Boulder River streambed sediment increased by more 

than a factor of two and remained elevated through river mi 

28 (fig. 21Q. The 206Pb/204Pb values increased slightly from 

18.02 to 18.05 and remained relatively constant at the latter 

value through river mi 28, indicating a predominance of the 

lead from the Comet mine in the streambed sediment of the 

Boulder River downstream from the confluence with High Ore 

Creek.

Throughout the Basin and Boulder mining districts, 

all 206Pb/204Pb values in modern streambed sediment were 

uniformly lower than those from the streambed sediment from 

premining terraces (fig. 275), probably because of contamination from historical mines, mills, and smelters in the mining 

districts. This is in spite of the fact that the lead concentrations, at least upstream from High Ore Creek, were quite 

similar between the premining and present-day data sets (fig. 

TIC). Significant increases in lead concentrations in presentday streambed sediment in the Boulder River were apparent 

downstream from the confluence of all three tributary streams, 

but were most pronounced downstream from the confluence 

with High Ore Creek (fig. 27C).

The effect of the deposit-related trace elements in the 

streambed sediment was estimated on the basis of the increase 

in trace-element concentrations in the streambed sediment of 

the Boulder River using the following equation, assuming bulk 

mixing:

C)]xlOO (1)

where PS is the percent of the total sediment contributed by 

tributary C to the receiving stream at site B,

C, is the concentration of the trace element in streambed A

sediment in the river upstream from the confluence with the 

tributary C,

CD is the concentration of the trace element in streamD

bed sediment in the river downstream from the confluence 

with the tributary and

Cc is the concentration of the trace element in the tributary stream C at its confluence.

The amount of a deposit-related trace-element contaminant 

in streambed sediment in the river that was contributed by 

the tributary was estimated from the following equation, also 

assuming bulk mixing:

Pc = Ps xCc/CB (2)

Calculation of the Effect of Historical 

Mining on the Streambed Sediment in 

the Boulder River

Bulk mixing calculations were used to estimate the 

contribution of contaminated streambed sediment from each 

of the three basins to the streambed sediment of the Boulder 

River. These calculations, however, assume uniform, wellmixed end members, which we have shown was not the case 

from our sampling of the north and south banks of the Boulder 

River downstream from the confluences of the three principal tributaries. Sampling variability also adds an additional 

source of error that had not been evaluated because replicate 

samples were not collected in any one year during this study. 

Furthermore, the calculation errors associated with the small 

spread of the entire lead isotopic data set result in some 

mathematical limitations. However, the calculations are useful 

to evaluate the scale of the heterogeneity in the sampling and 

to portray the overwhelming effect that the contamination 

from past mining in the three basins had on the fine-grained 

(<150 |am) streambed sediment and contaminant loads in the 

Boulder River. Comparisons of the data for copper and zinc, 

which were transported largely in the dissolved and suspended 

phases (Nimick and Cleasby, this volume; Kimball and others, 

this volume), with the data for lead and arsenic, which were 

transported largely as colloidal components of the streambed 

sediment and as grain coatings on detritus in the streambed 

sediment, are useful in our understanding of the transport of 

contaminants in the suspended- and streambed-sediment loads. 

The data also provided valuable information on the mixing 

zones downstream from stream confluences.

where Pc is the percent contaminant contributed by the tributary and PS ,CC , and CB are defined as in eq. 1.

An independent method of estimating Pc for lead was 

obtained from the lead isotopic data (Church and others, 1997) 

using the following equation:

(3)

where Ppb is the percent lead contributed by the tributary C to 

the river,

RA is the 206Pb/204Pb in the river upstream of the confluence with tributary C,

Ra is the ^Pb/^Pb in the river downstream of the conD

fluence with the tributary, and

Rc is the ^Pb/^Pb in tributary C upstream from the 

confluence.

Values used for A, B, and C in these equations are indicated in table 5.

Although this method is based on mass and is therefore 

independent of trace-element concentrations and the mechanisms of transport, estimates may be uncertain as a result of 

the small isotopic differences found among RA, RB, and Rc 

relative to the precision of the individual measurements of 

these lead isotopic ratios. This was especially true for very 

small contributions (that is, RA « /?fl) and very large contributions (that is, RB « Rc) from C. It was also true in the situation 

where contributions of C to previously contaminated sediment 

are similar (that is, RA xRB « Rc).

Calculations were made, using equations 1, 2, and 3 and 

the 1996 total-digestion data, to determine the effects of each 

of the three main tributaries on the streambed-sediment geochemistry of the Boulder River. These results are summarized 

in table 5. Calculations were made for several site "5"
326 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

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Trace Elements and Lead Isotopes in Streambed Sediment 327

localities to evaluate the effects of the tributaries both immediately downstream from the confluence and farther downstream. We used the concentrations and 206Pb/204Pb value of the 

tributary sample closest to the confluence of the Boulder River 

as site "C" (sites 31S, 53S, and 63S; figs. 1 and 14).

The choice of sites upstream of the confluence (that is, 

site "A") for each of the tributaries was somewhat problematic 

because the downstream concentration profiles (fig. 145) do 

not progressively increase in the Boulder River. Whereas it 

would have been simple to dismiss this irregularity as due to 

sample heterogeneity, we interpreted the data as a transport 

phenomenon in the Boulder River. Sediment collected immediately upstream and downstream from the confluences have 

previously been shown to be quite heterogeneous depending 

upon the side of the river on which the sample was collected. 

Also, samples collected midway between tributary confluences 

generally showed atypically low deposit-related trace-element 

concentrations that may not be representative of the river segment between the tributaries because these sites were collected 

in 1997 and 1998, so year-to-year variation was also present 

in the data set. Consequently, we used the 1996 total-digestion data from the sites immediately upstream of each of the 

confluences of Cataract and High Ore Creeks as "site A" for 

these two tributaries (table 5).

The effects of streambed sediment derived from Basin 

Creek on the Boulder River were distinguished from the 

effects of mill tailings contributed by the Jib Mill on the basis 

of the lead isotopic data measured in the terrace at site 2B. 

However, because the Jib Mill site is private property and was 

not sampled, we cannot quantitatively separate the contributions from Basin Creek and the Jib Mill site. We have chosen 

site 4S as site "A" for the calculations for Basin Creek (table 5, 

fig. 1). The marked increase in deposit-related trace-element 

concentrations between sites 4S and 5S and the calculations 

in table 5 suggest that the Jib Mill contributed significant 

amounts of copper and zinc and more modest amounts of 

arsenic and lead to the streambed sediment of the Boulder 

River. This observation from the streambed-sediment data 

calculations was supported by the analysis of the chemical 

data from core 2B (fig. 18) sampled downstream from the Jib 

Mill, which showed increased concentrations of copper and 

zinc in the lower portions of the core, and by the lead isotopic 

data from this section of the core, which indicated that ore 

from outside the Basin and Boulder mining districts was processed at the Jib Mill (fig. 23). The percent sediment contribution (eq. 1) calculated for Basin Creek from the arsenic data 

agreed well using either site 6S or 8S as the downstream site 

(48 and 46 percent respectively, table 5) and compared well 

with calculations using the lead data from site 8S (51 percent). 

Calculations of the percent contaminant for both lead and arsenic (eq. 2) agreed well using both downstream sites ranging 

between 74 and 89 percent. These values also agreed well with 

the calculated percentage of deposit lead (83 and 88 percent) 

from the lead isotope data (eq. 3). All calculations indicated 

an unaccounted-for contribution of copper and zinc, which we 

attribute to the Jib Mill site (see data from site 2B, fig. 18).

Calculations for the percent sediment (eq. 1) and the percent contaminant (eq. 2) using the copper and zinc data were 

much higher, ranging from about 97 to 120 percent for PcCu 

and PfZn. However, calculated copper contributions 

(PsCu) were very large, ranging from 184 to 265 percent 

(table 5). We interpret these data to indicate that a large component of copper was being contributed from an unsampled 

location between 4S and 5S, probably the Jib Mill site. Basin 

Creek (site 3IS) was apparently a lesser contributor of depositrelated trace-element contamination to the Boulder River than 

the Jib Mill site.

The effects of streambed sediment contributed by Cataract Creek to the Boulder River have been calculated using the 

data from sites 8S, 9S, and 53S (table 5, fig. 1). Concentrations 

of all four deposit-related trace elements increased significantly in streambed sediment downstream of the confluence 

with Cataract Creek at site 9S. Calculations of the percentage 

of contaminant (PJPb) and the percentage of deposit lead (Ppb) 

for site 9S were also in good agreement at 49 and 46 percent 

respectively. The calculated percent sediment increased using 

the 1996 total-digestion data for zinc, lead, arsenic, and copper 

from 19 to 33 percent of the sediment contributed by Cataract 

Creek (table 5). The calculated percent contaminant increased 

in a similar fashion ranging from 49 to 67 percent. Higher 

values for arsenic and copper indicate preferential transport of 

these two trace elements in the water or suspended sediment of 

Cataract Creek.

The effects of streambed sediment contributed by High 

Ore Creek to the Boulder River have been calculated using 

the data from sites US, 12S, and 63S (table 5, fig. 1). Calculations for site 12S, immediately downstream from High Ore 

Creek (figs. 1 and 145) suggested that, whereas the percent 

sediment contributed by High Ore Creek was in the range of 8 

to 13 percent using the zinc, arsenic, and lead concentrations 

(P,Zn, P<As, and Pfb), 51 to 88 percent of the contaminants 

in streambed sediment of the Boulder River were contributed 

by the streambed sediment from High Ore Creek (table 5, 

fig. 1). At site 13S approximately 0.6 mi downstream from 

High Ore Creek where the differences between concentration 

and lead isotopic data were reduced between the two different sites from the north and south sides of the river, calculated 

contaminant contributions from High Ore Creek ranged from 

72 to 97 percent for all deposit-related trace elements and 

90 percent deposit-lead contaminant. At site 15S, about 

3.3 mi downstream, the calculated percentages using the arsenic, lead, and the lead isotopic data were 86, 62, and 76 percent respectively, whereas the calculations for zinc and copper 

were substantially lower, 52 and 15 percent respectively.

Evidence for preferential transport of copper and zinc 

relative to lead (shown previously in fig. 14A) and the inconsistent results for these two elements as shown in table 5 indicated that the lead isotopic data generally represented the best 

estimates of overall deposit-related trace-element contributions to the streambed sediment in the Boulder River. In most 

instances, the percent contribution calculated from the arsenic 

and lead concentration data was in reasonably good agreement
328 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

with that calculated from the 206Pb/204Pb data. Calculations of 

streambed-sediment contributions from Cataract and High Ore 

Creeks were probably best estimated from the arsenic and lead 

data. However, reliable estimates for the Basin Creek contribution cannot be made because of the influence of the Jib Mill at 

the confluence.

The effects of the three tributaries on the lead in the 

streambed sediment of the Boulder River are summarized 

in more detail in figure 28. The effect of past mining on the 

streambed sediment in the Boulder River increased progressively as the Boulder River flowed through the Basin and 

Cataract mining districts. It is evident from figures 28 and 29 

that High Ore Creek contributed the largest fraction of depositrelated lead to the Boulder River. Downstream from High Ore 

Creek through site 15S, about 3.3 mi downstream from High 

Ore Creek, more than 70 percent of the lead in the streambed 

sediment was traced to deposit lead from historical mining 

activity in the Boulder River watershed study area.

Estimates of the percentage of deposit-related lead at any 

site within the area can be made using 206Pb/204Pb data and 

equation 3. The appropriate RA and Rc values are in table 4, 

and the RD values were those measured at the individual sites.

D

The calculated percent deposit-lead values (Pph values, eq. 3) 

are shown as a ribbon map, figure 29. Because we expressed 

the lead isotopic data in terms of percent

contaminant deposit lead, the two different identified isotopic 

signatures for the deposit leads, one from Basin Creek and 

Cataract Creek basins, and a second from High Ore Creek 

basin (fig. 23), were normalized out of the data in figure 28. 

In using these data, however, we were not able to distinguish 

between deposit-related lead that had weathered from outcrops of mineralized rock and lead introduced into the stream 

from historical mining wastes or mill tailings. Consequently, 

although the calculated Pph values may closely approximate 

contaminant lead contributions downstream from major mines, 

these values are not, in a strict sense, percentages of lead 

introduced by historical mining. However, in the absence of 

data indicating a large, undefined source of deposit-related 

trace elements in the study area, the calculated percentages 

provided a good estimate of the contaminants introduced into 

the aquatic habitat today by past mining practices.

The highest percentages of deposit-related lead were 

found downstream of the major mines in the area. Concentrations of lead in streambed sediment from Basin Creek 

decreased to some extent as shown by higher 206Pb/204Pb values 

downstream from both the Buckeye mine and the confluence 

with Jack Creek, but 50-75 percent of the lead present in the 

streambed sediment of Basin Creek at its confluence with the 

Boulder River was deposit-related lead.

o 

cc

100

90

80

70 

ol

-_ 60

o

£ 50

1 40

O

0 30 o

LLJ

20

10

i i i I 

Boulder River

5S&6S

us 

Cataract Creek

High Ore Creek

Site 4S

Basin Creek and Jib

14.0 16.0 18.0 20.0 

DISTANCE, IN MILES

22.0 24.0

Figure 28. Plot of the calculated percent deposit-lead contamination added to the streambed sediment of the Boulder River by the addition of tailings from the Jib Mill site and streambed sediment from Basin Creek, from streambed 

sediment from Cataract Creek, and from streambed sediment from High Ore Creek.
Trace Elements and Lead Isotopes in Streambed Sediment 329

112°22'30"

T8N

T7N

Boulder River 

watershed stud

T6N

EXPLANATION

Contaminant lead, percent

^ >90 

H 75-90

• 25-50

• <25

Base from U.S. Geological Survey 

digital line graphs, 1:100,000

1 2 KILOMETERS

Figure 29. Ribbon map showing calculated percentages of deposit lead in streambed sediment today (table 5). Dark-red square, 

Jib Mill site.
330 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

The highest proportions of deposit-related lead in the 

Cataract Creek drainage were found downstream from the 

Eva May mine site, in Uncle Sam Gulch downstream from 

the Crystal mine, and in Cataract Creek downstream from 

Uncle Sam Gulch. The 206Pb/204Pb values in streambed sediment downstream from this confluence increased only slightly 

before Cataract Creek enters the Boulder River.

The Comet mine on High Ore Creek represents the 

dominant source of deposit-related lead in this basin. The 

calculated percentages of deposit-related lead remain greater 

than 90 percent from the Comet mine to the confluence with 

the Boulder River.

Downstream from site 755 on the Boulder River, calculations become very tentative owing to the lack of data from surrounding rocks or streambed sediment from other tributaries to 

the Boulder River. The Little Boulder River, a principal tributary that enters the Boulder River just downstream from site 

765 (river mi 28) had 206Pb/204Pb values similar to or slightly 

higher than those of premining baseline values estimated in 

table 4. If we assume that the estimated premining baseline 

values in table 4 are valid downstream from site 755 and that 

no other sources of deposit-related lead occur downstream, 

then calculations can be made as for figures 28 and 29. 

Results suggest that as much as 80, 50, and 13 percent of 

the lead in streambed sediment of the Boulder River at sites 

765 (river mi 27), 775 (river mi 41), and J8S (river mi 68) 

respectively is deposit-related lead. Thus, we have quantified 

the contaminant contributions of the major tributaries to the 

Boulder River, fulfilling the fourth goal of the study.

Comparison of the Boulder River Watershed 

Streambed-Sediment Data with SedimentQuality Guidelines

Sediment-quality guidelines for trace-element concentrations in streambed sediment have only recently been defined 

and are not currently regulated. Various measures of biologic 

response to elevated concentrations of deposit-related trace 

elements in sediment are summarized in table 6 (Jones and 

others, 1997; MacDonald and others, 2000). Different 

definitions are used to define the effect of sediment-borne 

contaminants on aquatic life (see the footnotes, table 6). For 

the purposes of this discussion, we adopt the terminology used 

in MacDonald and others (2000). The Threshold Effect 

Concentration (TEC) is defined as the "contaminant concentration below which harmful effects on sediment-dwelling 

organisms were not expected," whereas the Probable Effect

Concentration (PEC) is defined as the "contaminant concentration above which harmful effects on sediment-dwelling 

organisms were expected to occur frequently" (MacDonald 

and others, 2000, p. 21). For the elements antimony and 

silver, no TEC or PEC values have been determined. For these 

elements, we use the Screening Level Concentration (SLC) 

values (table 6), defined as "the highest concentration that 

can be tolerated by approximately 95 percent of the benthic 

fauna"(EPA, 1996).

For most of the deposit-related trace elements investigated in this watershed, the ranges of the TEC (or SLC) and 

PEC concentrations were significantly below those found in 

the streambed sediment from the Boulder River watershed 

study area. Leachable concentrations of the potentially toxic 

trace elements investigated in this study are those concentrations either sorbed or loosely bound in the iron-oxyhydroxide 

fraction of the streambed sediment. Leachable trace-element 

concentrations were compared with the sediment-quality 

guidelines at four sites on the Boulder River, at the mouths 

of the three major tributaries, and below the major mine sites 

(table 7). Concentrations of arsenic and lead exceeded the PEC 

sediment-quality guidelines in streambed sediment throughout the Basin, Cataract, and High Ore Creek basins and in the 

streambed sediment in the Boulder River immediately downstream from their confluences except at site 6S for lead downstream of the Basin Creek confluence. Copper concentrations 

exceeded PEC values in Basin Creek below the Bullion Mine 

tributary, in Uncle Sam Gulch and Cataract Creek downstream 

to the confluence in the Boulder River, and in the Boulder 

River downstream from Basin Creek to the confluence with 

the Little Boulder River (river mi 27). Copper concentrations 

exceeded the TEC everywhere in the study area downstream 

from historical mining. Zinc and cadmium concentrations 

exceeded the PEC in streambed sediment downstream from 

the Buckeye mine on Basin Creek, and exceeded the TEC 

elsewhere throughout the Basin Creek basin downstream from 

historical mining. Zinc and cadmium concentrations in streambed sediment exceeded the PEC everywhere in the Cataract 

Creek and High Ore Creek basins. Zinc exceeded the PEC 

and cadmium exceeded the TEC in the streambed sediment of 

the Boulder River downstream from the confluence with the 

Little Boulder River because of the sorption of zinc to freshly 

precipitated colloidal fraction of the streambed sediment (see 

fig. \4B). Silver and antimony concentrations exceeded the 

SLC values in streambed sediment everywhere within the 

study area downstream from historical mining sites where the 

concentrations in streambed sediment exceed the analytical 

limits of detection.
Table 6. Summary of screening level concentrations proposed as possible measures for sediment-quality guidelines.

[Concentrations in parts per million, ppm; --, no value recommended; bold values are recommended consensus values]

ARCS1 

TEC2 PEC3

Antimony

Arsenic

Cadmium

Copper

Iron

Lead

Silver

Zinc

--

12.1

0.592

28

--

34.2

--

159

--

57

11.7

77.7

--

396

--

1,532

Ontario MOE4 

Low Severe

--

6

0.6

16

20,000

31

-

120

--

33

10

110

40,000

250

--

820

EPA-IV 

SLC5

12

7.24

1

18.7

--

30.2

2

124

OSWER 

SLC8

--

8.2

1.2

34

--

47

~

150

Range 

of SLC7

12

7-12

0.6-1.0

16-34

20,000

30-47

2

120-160

Range 

ofAET8

--

33-57

10-12

78-110

40,000

250-400

--

820-1,532

Consen

TEC9

--

9.79

0.99

31.6

--

35.8

--

121

'ARCS - Assessment and Remediation of Contaminated Sediments Project, EPA Region IV, Great Lakes Program (U.S. EPA, 1996).

2TEC -Threshold Effect Concentration, the contaminant concentration below which harmful effects on sediment-dwelling organisms were 

3PEC - Probable Effect Concentration, the contaminant concentration above which harmful effects on sediment-dwelling organisms were e

frequently.

4Ontario MOE - Low, the lowest effect level of screening level concentration (5th percentile); Severe, severe effect level of screening leve

centile; Persuad and others, 1993).

5EPA-IV - Ecological screening values for sediments (U.S. EPA, 1995).

6OSWER - Office of Solid Waste and Emergency Response (U.S. EPA, 1996) screening level concentrations.

7SLC - Screening Level Concentration, the highest concentration of a contaminant that can be tolerated by approximately 95 percent of the 

8AET - Apparent Effects Threshold, that concentration above which statistically significant biologic effects always occur.

9Consensus-based TEC from MacDonald and others (2000); predicted TEC shown accurately predicts no toxic effect more than 80 percen

trace elements in table except for arsenic where the TEC shown accurately predicts no toxic effect 74 percent of the time (n=150).

10Consensus-based PEC from MacDonald and others (2000); predicted PEC shown accurately predicts a toxic effect 90 percent or more of 

trace elements in table except for arsenic where the PEC shown accurately predicts a toxic effect 76.9 percent of the time («=150). 
332 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 7. Sites where the leachable deposit-related trace-element concentrations in streambed sediment from 

the study area exceed recommended screening levels.

[Concentrations of trace elements copper, lead, zinc, arsenic, and cadmium are in italics where they exceed the TEC and in bold where 

they exceed the PEC concentration (from table 6, consensus-based values); and for silver and antimony, concentrations are in italics where 

they exceed the SLC concentration (from table 6, U.S. EPA-IV Screening Level Concentrations)]

Location

Boulder River upstream from Basin Creek

Basin Creek downstream from Buckeye 

Mill.

Bullion Mine tributary downstream from 

the Bullion mine.

Jack Creek at confluence

Basin Creek at confluence

Boulder River downstream from the 

confluence with Basin Creek.

Uncle Sam Gulch at confluence

Cataract Creek at confluence

Boulder River downstream from the 

confluence with Cataract Creek.

High Ore Creek downstream from the 

Comet Mill.

High Ore Creek

Boulder River downstream from the 

confluence with High Ore Creek.

Boulder River upstream from the confluence 

with Little Boulder River.

Little Boulder River

Boulder River at river mi 40

Boulder River at confluence with Jefferson 

River.

Site

4S

21S

34S

24S

31S

6S

57S

53S

9S

59S

63S

13S

16S

19S

17S

18S

Cu 

ppm

25

120

340

24

93

190

2,400

420

235

1,600

540

285

380

17

86

92

Pb 

ppm

20

1,600

1,400

170

162

49

790

320

135

5,900

1,400

460

220

22

83

50

Zn 

ppm

120

680

350

290

585

425

3,700

1,450

725

14,000

6,100

1,500

420

85

490

700

As 

ppm

14

4,000

4,400

98

125

35

900

460

105

5,300

4,200

350

230

14

57

15

Cd 

ppm

<1

5

1.6

2

5.3

3.1

41

15

4.7

140

21

14.5

2.2

<1

1.4

4.7

Ag 

ppm

<1

6.9

12

<1

<1

<1

5.4

3.7

3.1

45

22

9.6

4.3

<1

1.3

<1

Sb 

ppm

<3

34

16

<3

<3

<3

9.2

3

<3

25

4.9

<3

<3

<3

<3

<3

Summary

Assessment of deposit-related and rock-forming trace elements in streambed sediment in the Boulder River watershed 

has provided the data necessary to delineate stream reaches 

having elevated contaminant concentrations that exceeded 

recommended action levels for streambed sediment, to determine anthropogenic sources of deposit-related trace elements 

that contaminated sediment, to understand the transport of 

dissolved and paniculate trace elements, and to establish the 

streambed-sediment framework needed to evaluate toxicity to 

aquatic biota.

Concentrations of the suite of deposit-related trace 

elements copper, lead, zinc, arsenic, silver, cadmium, and 

antimony were elevated in modern streambed sediment in the 

Boulder River downstream from the confluence with Basin, 

Cataract, and High Ore Creeks. The major sources of these 

contaminants can be tied directly to historical mining at the 

Buckeye and Enterprise mines in upper Basin Creek, the 

Bullion mine on a small tributary of Jack Creek and sediment

trapped in beaver ponds and a small reservoir on Jack Creek, 

the area of Cataract Creek just upstream from the confluence 

with Uncle Sam Gulch, the Crystal mine in upper Uncle Sam 

Gulch, and the Comet mine in upper High Ore Creek. The Jib 

Mill site immediately upstream from the confluence of Basin 

Creek with the Boulder River was also implicated as a source 

of these contaminants, especially of elevated concentrations 

of copper in the Boulder River at the confluence with Basin 

Creek.

Downstream from the confluence of Basin Creek, 

concentrations of leachable arsenic and copper exceeded the 

probable effect concentration, and lead, zinc, silver, cadmium, 

and antimony exceeded the threshold effect concentration, 

in modern streambed sediment of the Boulder River. Downstream from the confluence with Cataract Creek to the confluence with the Little Boulder River, streambed sediment in 

the Boulder River contained concentrations of copper, lead, 

zinc, arsenic, and at most sites, cadmium that exceeded the 

probable effect concentration in streambed sediment. All of 

the major tributary basins, Basin Creek, Jack Creek, Cataract Creek, Uncle Sam Gulch, and High Ore Creek, also
Trace Elements and Lead Isotopes in Streambed Sediment 333

had concentrations of copper, lead, and arsenic in streambed 

sediment downstream of these major mines to their confluence 

that exceeded the probable effects concentration. Everywhere 

within the three basins downstream from the major mines, 

the concentrations of all the deposit-related trace elements 

exceeded the sediment-quality guidelines (table 7).

Comparison of the concentrations of this suite of depositrelated trace elements in streambed sediment today with that 

in premining streambed sediment from terrace deposits in the 

flood plains of these streams showed that the concentrations 

of the deposit-related trace elements were substantially 

elevated in streambed sediment today, from several to more 

than 100 times that prior to historical mining activities. Lead 

isotopic data from these two media indicate that the effect of 

mineralized rock on the streambed-sediment geochemistry 

prior to mining was small relative to what we can see today.

Two different sources of deposit lead were defined by 

the lead isotopic data, one representing the polymetallic vein 

deposits in both the Basin and Cataract Creek basins, and a 

second at the Comet mine in the High Ore Creek basin. Calculations of the extent of the contamination caused by historical 

mining activity using both the arsenic and lead concentration 

data and the lead isotopic data gave similar results. In contrast, 

calculations using the copper and zinc data gave higher percentages, some exceeding 100 percent. These results indicate 

that the copper and zinc were being actively and differentially 

transported in the suspended-sediment phase and were being 

precipitated to the streambed sediment as a function of velocity of the stream reach often miles downstream from their 

source. The contribution of contaminant lead, as shown in 

figure 28, to streambed sediment of the Boulder River from 

Basin Creek was about 35 percent and from Cataract Creek 

about 15 percent. However, the contribution of contaminant 

lead to streambed sediment of the Boulder River from High 

Ore Creek was about 50 percent. The contamination from 

High Ore Creek dominated the concentrations of depositrelated trace elements in stream sediment of the Boulder River 

below the confluence downstream to the Jefferson River.

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Robert, 1995, Abandoned-inactive mines program, Deerlodge National Forest—Volume II, Cataract Creek Drainage: Montana Bureau of Mines and Geology Open-File 

Report 344, 201 p.

Nimick, D.A., and Cleasby, T.E., 2000, Water-quality data for 

streams in the Boulder River watershed, Jefferson County, 

Montana: U.S. Geological Survey Open-File Report 00-99, 

70 p.

Nordstrom, D.K., and Alpers, C.N., 1999, Geochemistry of 

mine waters, in Plumlee, G.S., and Logsdon, M.J., eds., The 

environmental geochemistry of mineral deposits—Part A, 

Processes, techniques, and health issues: Society of Economic Geologists, Reviews in Economic Geology, v. 6A, 

p. 133-160.

OSWER (Office of Solid Waste and Emergency Response, 

Environmental Protection Agency), 1996, Ecotox thresholds: ECO Update, v. 3, p. 1-12.

Persuad, D., Jaaugmagi, R., and Hayton, A., 1993, Guidelines 

for the protection and management of aquatic sediment 

quality in Ontario: Ontario Ministry of the Environment and 

Energy, 30 p.

Rossillon, Mitzi, and Haynes, Tom, 1999, Basin Creek mine 

reclamation heritage resource inventory 1998, unpublished 

report prepared for the Beaverhead-Deerlodge National 

Forest, Dillon, Mont., 126 p.

Ruppel, E.T., 1963, geology of the Basin quadrangle,

Jefferson, Lewis and Clark, and Powell Counties, Montana: 

U.S. Geological Survey Bulletin 1151, 121 p.

Schemel, L.E., Kimball, B.A., and Bencala, K.E., 2000, 

Colloid formation and metal transport through two mixing 

zones affected by acid mine drainage near Silverton, 

Colorado: Applied Geochemistry, v. 15, p. 1003-1018.

Smith, K.S., 1999, Metal sorption on mineral surfaces—An 

overview with examples relating to mineral deposits, in 

Plumlee, G.S., and Logsdon, M.J., eds., The environmental 

geochemistry of mineral deposits—Part A, Processes, techniques, and health issues: Society of Economic Geologists, 

Reviews in Economic Geology, v. 6A, p. 161-182.

Smith, S.M., 1994, Geochemical maps of copper, lead, and 

zinc, upper Arkansas River drainage basin, Colorado: 

U.S. Geological Survey Open-File Report 94-408, 15 p.

Smith, S.M., Church, S.E., and Green, G.N., 1997, Effects of 

geology and mining activity on sediment geochemistry of 

the Arkansas River drainage basin, Colorado: Explore, 

no. 96, p. 6-10, 14.
Trace Elements and Lead Isotopes in Streambed Sediment 335

Unruh, D.M., Fey, D.L., and Church, S.E., 2000, Chemical 

data and lead isotopic compositions of geochemical baseline 

samples from streambed sediments and smelter slag, lead 

isotopic compositions in fluvial tailings, and dendrochronology results from the Boulder River watershed, Jefferson 

County, Montana: U.S. Geological Survey Open-File 

Report 00-38, 75 p.

U.S. Environmental Protection Agency, 1995, National sediment inventory; Documentation of derivation of freshwater 

sediment quality: Washington, D.C., Office of Water, EPA 

Report.

U.S. Environmental Protection Agency, 1996, Calculation and 

evaluation of sediment effect concentrations for the amphipod Hyalella azteca and the midge Chironomus riparius: 

Chicago, 111., Great Lakes National Program Office, EPA 

Report 905-R96-008.

Van Eeckhout, E.M., 1981, Utilizing the geochemical data 

from the National Uranium Resource Evaluation (NURE) 

Program; an evaluation of the Butte Montana quadrangle, 

Montana: Grand Junction, Colo., U.S. Dept. of Energy, 

GJBX-58(81), 67 p.

Wallace, C.A., 1987, Generalized geologic map of the

Butte l°x 2° quadrangle, Montana: U.S. Geological Survey 

Miscellaneous Field Studies Map MF-1925, scale 

1:250,000.

Hydrogeology of the Boulder River 

Watershed Study Area and Examination of 

the Regional Ground-Water Flow System 

Using Interpreted Fracture Mapping from 

Remote Sensing Data

By Robert R. McDougal, M.R. Cannon, Bruce D. Smith, and David A. Ruppert

ChapterD9of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-D9

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract...............................................................^

Introduction............................................................................................................................................... 341

Purpose and Scope..................................................................................................................................343

Hydrogeologic Setting .............................................................................................................................343

Elkhorn Mountains Volcanics........................................................................................................ 343

Boulder Batholith ............................................................................................................................ 344

Tertiary Volcanics............................................................................................................................ 344

Unconsolidated Deposits .............................................................................................................. 344

Ground-Water Recharge and Discharge..................................................................................... 345

Methods of Investigation......................................................................................................................... 345

Conceptual Model of Ground-Water Flow................................................................................... 345

Linear Feature Mapping ................................................................................................................. 345

Results and Analysis................................................................................................................................ 352

Conceptual Model of Ground-Water Flow................................................................................... 352

Linear Feature Analysis.................................................................................................................. 354

Conclusions and Discussion................................................................................................................... 361

References Cited...................................................................................................................................... 368

Figures

1. Site map for hydrogeologic study of the Boulder River watershed................................ 342

2. Landsat 5 scene comparing unfiltered band 4 with image filtered to enhance

northeast-trending features................................................................................................... 346

3. Landsat 5 scene to which a principal components transformation was applied,

and directionally filtered to enhance northeast-trending linear features..................... 348

4. IRS-1C panchromatic satellite image directionally filtered and bit error filter

applied....................................................................................................................................... 349

5. Shaded relief Digital Elevation Model images showing illumination from two

different directions.................................................................................................................. 350

6. Site map showing 7.5-minute quadrangle boundaries, linear feature mapping

quadrants, and approximate area of the Butte-Helena fault zone................................. 351

7. Conceptual ground-water model and depiction of flow regimes.................................... 353

8. Map showing linear features, Boulder River watershed study area.............................. 357

9. Rose diagrams representing orientations of all linear features and all linear

features weighted by length.................................................................................................. 358

10. Length filtered rose diagrams of linear features in several ranges of lengths............. 359

11. Rose diagrams showing linearfeature orientation arranged by quadrants

shown in figure 6...................................................................................................................... 360
12-17. Contour maps of:

12. Linear feature spatial frequency.................................................................................... 362

13. Linear feature length........................................................................................................ 363

14. Linear feature intersections........................................................................................... 364

15. Combined linear feature spatial frequency and intersections................................. 365

16. Combined linear feature spatial frequency and total length..................................... 366

17. Combined linear feature spatial frequency and intersections, and areas

of mapped shallow ground water.................................................................................. 367

Tables

1. Summary statistics for mapped linear features................................................................. 354

2. Summary statistics for orientations of mapped linear features...................................... 355

3. Summary of main orientations of mapped linear features............................................... 356

Chapter D9

Hydrogeology of the Boulder River Watershed Study Area 

and Examination of the Regional Ground-Water Flow 

System Using Interpreted Fracture Mapping from 

Remote Sensing Data

By Robert R. McDougal, M.R. Cannon, Bruce D. Smith, and David A. Ruppert1

Abstract

This investigation describes the shallow unconsolidated 

and upper fracture-controlled ground-water flow regimes in 

the Boulder River watershed, and uses remote sensing data to 

map linear surface features that are interpreted as fractures and 

are assumed to be associated with regional fracture controlled 

subsurface flow. Ground water in the Boulder River watershed 

occurs primarily in saturated unconsolidated deposits and 

the upper portion of a fractured bedrock aquifer. The hydraulic properties of the bedrock aquifer, at depth, are largely 

unknown. However, along fault zones, mineralized zones, and 

some large fractures, the hydraulic conductivity may be significant. A conceptual model of ground-water flow was developed based on hydrogeologic characteristics of aquifers investigated near the inactive Buckeye, Bullion, and Crystal mines, 

and on observations of ground-water discharge from granitic, 

volcanic, and unconsolidated rock units throughout the Basin 

Creek and Cataract Creek drainages. The direction of shallow 

ground-water flow can be modeled as the gradient of topographic slope. Deeper ground-water flow likely is a function 

of fracture width, continuity, and interconnectivity, and likely 

is partly controlled by the heterogeneous and anisotropic 

orientation of fractures. Four remote sensing data sets, used as 

base images, provided a range of spatial resolutions for linear 

feature mapping. Endpoint data from mapped linear features, 

used in a 2-D orientation analysis, enabled us to determine 

primary orientations of lineaments from rose diagrams and 

to produce contour maps of linear feature characteristics. A 

contour map of combined linear feature spatial frequency 

and intersections was compared with a map of wetland-soils 

areas to identify correlated areas of high fracture occurrence 

and areas where the potentiometric surface is close to the land

'United States Department of Agriculture (USDA) Forest Service, 

Beaverhead-Deerlodge National Forest, Butte, Mont.

surface. The mapped lineaments show a consistent east-west 

primary orientation. The greatest linear feature spatial 

frequency, length, and frequency of intersections occurred 

on the Continental Divide at the northern boundary of the 

Boulder River watershed study area. The observation of highest interpreted fracture frequency on the Continental Divide is 

significant in that this area may provide potential recharge for 

fracture-controlled ground water. The comparison of highest 

interpreted fracture frequency with areas of mapped shallow 

ground water shows a correlation in several locations between 

potential areas of recharge to the fractured granitic aquifer and 

areas of discharge, or wet soils. The description of the groundwater regime and the identification of areas of high interpreted 

fracture frequency are components of the ground-water system 

that should be considered in the design of strategies for mine 

remediation.

Introduction

The Boulder River watershed is representative of mountainous terrains in the western United States where ground 

water occurs in unconsolidated Quaternary alluvial and colluvial deposits, and in fractures in underlying plutonic rocks. 

The crystalline bedrock aquifers commonly have significantly 

lower hydraulic conductivity and storage potential than the 

unconsolidated aquifers, except where substantial secondary 

fracture permeability exists.

Based on field observations near the inactive Buckeye, 

Bullion, and Crystal mines, and on observations of groundwater discharge from granitic, volcanic, and unconsolidated 

rock units throughout the Basin Creek and Cataract Creek 

drainages (fig. 1), the hydraulic characteristics and flow 

regimes of the upper part of the ground-water system in the 

Boulder River watershed are relatively well understood. The 

hydraulic properties of the fractured bedrock aquifer and its
342 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112°

46°30

46° 15'

Generalized boundary of 

the Boulder River watershed 

study area

BEAVERHEADDEERLODGE 

NATIONAL 

FOREST

Base modified from U.S. Geological Survey 1:250,000 

Butte, 1947, and White Sulphur Springs, 1958

10 MILES

_I

10 KILOMETERS

Figure 1. Site map for hydrogeologic study of the Boulder River watershed.
Hydrogeology and Examination of Regional Ground-Water Flow 343

contribution to the regional ground-water system, however, 

have not been well characterized. Similarly, the relative importance of shallow (local) and deep (regional) ground-water flow 

as pathways for transporting metals from mining-related and 

natural sources to streams in the watershed is not well understood. Detailed synoptic streamflow measurements indicated 

that ground water discharges to streams in several locations in 

the study area (Kimball and others, this volume, Chapter D6).

This investigation describes the shallow unconsolidated, 

and upper fracture-controlled ground-water flow regimes 

within the Boulder River watershed study area, and uses 

remote sensing data to map linear surface features in approximately 528 mi2 of the watershed and surrounding area. The 

mapped linear features identified in this study are interpreted 

to represent the surface expression of faults, joints, and other 

fractures in the Butte pluton and overlying volcanic rocks. The 

regional and subregional structurally controlled ground-water 

flow regimes are assumed to be associated with the orientation 

of these linear features.

Previous studies have shown that mineral deposits and 

hydrothermal fluid flow in many mining districts occur along 

linear trends that can range in length from tens of feet to tens 

of miles in length (Rowan and Wetlaufer, 1975). Remote sensing data, such as Landsat Thematic Mapper (TM) data, have 

successfully been used to evaluate the relationship between 

mineral deposits and linear structural features (Sabins, 1987). 

Concepts from these previous studies have been applied in 

this study to examine the potential relation between fracture 

systems and ground-water flow. The statistical analysis of 

linear feature orientation presented here is intended to provide 

a general view of the potential regional flow directions in 

the bedrock aquifer by identifying primary azimuths of 

mapped linear features. To identify and map all structural 

features from remotely sensed data is not possible, because of 

ground resolution limitations, vegetation cover, and alluvial or 

colluvial cover. It is also not possible, in most cases, to 

differentiate types of linear features. That is, is the linear 

feature the surface expression of a fault, fracture, joint, or 

mineralized vein? Mapped linear features from these data sets 

provide a representation of the spatial distribution and orientation of bedrock fractures, and that of fractures in overlying 

volcanic rocks. Therefore, maps of this type should be interpreted as a statistical sample of the naturally occurring linear 

features in a region (Knepper, 1996).

Purpose and Scope

The purpose of this investigation is to provide a conceptual representation of the ground-water system in the Boulder 

River watershed study area. The objectives of the study are to

• Develop a conceptual model of ground-water flow for 

the purpose of describing the relative magnitude of 

ground-water flow systems in various rock units.

Map linear features from remote sensing imagery. The 

linear features are assumed to represent the spatial 

distribution, spatial frequency, and orientation of faults, 

joints, and fractures associated with structurally controlled ground-water flow.

Compare a contour map of combined linear feature 

spatial frequency and intersections with a wet soils 

coverage representing areas of inferred shallow ground 

water. Areas that have high fracture frequency and wet 

soils may be areas of recharge or discharge for 

fracture-controlled ground-water flow.

Evaluate how the ground-water flow systems may 

affect mine-site remediation in the watershed.

Hydrogeologic Setting

Igneous rocks of the Cretaceous Elkhorn Mountains 

Volcanics and cogenetic Boulder batholith, and Tertiary volcanic rocks, crop out over most of the Boulder River watershed 

study area and adjacent areas (O'Neill and others, this volume, 

Chapter Dl). In places, the igneous rocks are overlain by 

unconsolidated surficial deposits of various origin, including 

glacial drift, stream alluvium, bog deposits, and mass-wasting deposits. Hydrogeologic characteristics of the thin and 

porous surficial deposits are vastly different from those of the 

underlying massive, low-permeability igneous rocks. Characteristics such as permeability, fracture density, degree of 

weathering, and thickness and extent of geologic units have a 

major control on location and magnitude of ground-water flow 

systems in the region.

Elkhorn Mountains Volcanics

The Elkhorn Mountains Volcanics are present on many 

of the higher ridges and peaks in the northwestern part of the 

study area, on Jack Mountain in the central part of the study 

area, and in the Mount Thompson area near the headwaters of 

High Ore Creek. Primary permeability of the volcanic rocks 

is very low; however, where the rocks were examined on Jack 

Mountain and in the northern part of the Basin Creek drainage, 

they were highly fractured with many open and intersecting 

fractures. Samples of Elkhorn Mountains Volcanics collected 

on Jack Mountain by Desborough and others (1998) were 

intensely fractured at intervals of about 4 in. or less and were 

silicified. Core holes drilled on Jack Mountain (Maxim Technologies, Inc., 1999) revealed that fractures in the subsurface 

generally were clay filled, and a slug test in one of the holes 

indicated a hydraulic conductivity of 0.3 ft/day. Nearly all 

hydraulic conductivity of the volcanic rocks is a result of the 

intense fracturing. Based on observed fracture systems, the 

Elkhorn Mountains Volcanics in the northern and central parts 

of the study area have small ground-water storage capacity 

with low to moderate hydraulic conductivity, largely dependent on the degree of clay filling in the fractures.
344 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Boulder Batholith

Plutonic, granodioritic rocks of the Butte pluton of the 

Boulder batholith underlie most of the study area and extend 

for many miles beyond the study area boundary. Nearly all 

permeability of the Butte pluton is the result of fracturing and 

near-surface weathering. Plutonic rocks in outcrop generally 

are highly fractured and have three prominent sets of closely 

spaced joints. Observations of nearly 500 joints in the plutonic 

rocks documented a prominent joint set that trends about east 

and dips steeply north, a set that trends about north and most 

commonly dips steeply west, and a set that trends east and 

most commonly dips gently south (Ruppel, 1963). The joints 

are spaced from a few inches to many feet apart. In the Basin 

7.5-minute quadrangle, the north-trending steep joints are 

from about 1 to 5 ft apart and the east-trending steep joints are 

from 5 to 10 ft apart. Individual joints are rarely more than 

30 ft long, but where one joint dies out it commonly is overlapped by a parallel joint that is entirely separate or that is 

connected by a linking transverse joint (Ruppel, 1963).

Outcrops of the Butte pluton are characterized by large 

open fractures caused by weathering along existing joints 

(O'Neill and others, this volume, fig. 11). In many areas, joints 

in the rocks have sufficiently weathered to leave large, freestanding, rounded boulders. Weathering of the plutonic rocks 

decreases rapidly with depth, which is clearly evident in many 

road cuts, mine workings, excavations, and drill holes. In areas 

examined, the upper 5 ft of rock typically contain open joints. 

From about 5 to 50 ft in depth, the plutonic rock grades from 

slightly weathered to unaltered rock; most joints become tight; 

and many are filled with clay. Below about 50 ft, rocks of the 

Butte pluton typically are fractured, although most fractures 

are extremely tight, and weathering is observed only on some 

fracture surfaces. Exceptions to these general characteristics 

are found along fault zones, mineralized zones, and some large 

fractures.

Hydraulic conductivity of the granodioritic rocks of the 

Butte pluton typically is very low. At a core hole drilled south 

of the Bullion mine, hydraulic conductivity measured from 

a slug test was about 0.02 ft/day (Maxim Technologies Inc., 

1999). At another core hole on the Continental Divide 2.5 mi 

north of the study area, the hydraulic conductivity of the plutonic rocks was about 0.04 ft/day, as determined from a slug 

test (Maxim Technologies Inc., 1999). Water wells drilled into 

the granodioritic rocks typically have small yields, although 

well yields are highly variable and range from 0 to as much 

as 100 gallons per minute (Montana Department of Natural 

Resources and Conservation, unpublished data). Well yield is 

highly dependent on degree of fracturing and connection of 

the fractures to sources of recharge.

Tertiary Volcanics

Tertiary volcanic rocks are present in relatively small 

areas of the Boulder River watershed study area and include

quartz latite of Eocene age and rhyolite of Oligocene-Eocene 

age. Quartz latite of the Lowland Creek Volcanics is present in 

several small outcrops near the town of Basin; rhyolitic rocks 

crop out near the Continental Divide in the northwestern part 

of the study area (O'Neill and others, this volume). Most of 

the joints in the Tertiary volcanic rocks are primary joints and 

partings resulting from flowage and cooling (Ruppel, 1963). 

Columnar joints are common in outcrops of rhyolite and 

quartz latite welded tuff. Platy jointing parallel to flow laminae 

is common in rhyolite and results in weathered outcrops that 

have the appearance of rock rubble. Typically, the permeability 

and hydraulic conductivity of these types of volcanic rocks are 

relatively low (Freeze and Cherry, 1979). However, in areas 

where fracturing occurs, there can be a wide range of secondary permeability that largely is dependent on the degree of 

fracturing and amount of clay in fractures.

Unconsolidated Deposits

Unconsolidated deposits, consisting chiefly of Quaternary glacial deposits and stream alluvium, mantle a large part 

of the bedrock surface in the upper valleys of Basin Creek 

and Cataract Creek. Glacial deposits in the study area include 

bouldery till, outwash, and lake sediments, with till being by 

far the most abundant (O'Neill and others, this volume). The 

glacial deposits are reported to be early Wisconsin in age, 

equivalent to the Bull Lake stage of glaciation in the Wind 

River Mountains of Wyoming (Ruppel, 1963). Other young 

Unconsolidated deposits include small areas of colluvium, 

talus, landslide, and bog deposits. Thickness of Unconsolidated 

deposits ranges from less than 1 ft to more than 31 ft in some 

stream valleys as observed in road cuts and drill holes in the 

study area.

In the northwest part of the study area, arkosic sand 

and silt deposits underlie Oligocene-Eocene volcanic rocks, 

with weakly consolidated early Tertiary sedimentary rocks 

also present. Due to the weakly consolidated character of 

these rocks, anomalous hydrologic conditions exist along the 

Continental Divide at the base of the rhyolitic volcanic rocks. 

Unusually moist and wet soil conditions associated with bogs 

and springs are typical along the base of the rhyolitic volcanics 

(O'Neill and others, this volume).

Most surficial Unconsolidated deposits are fairly thin, 

whereas the weakly consolidated Tertiary deposits may be 

as much as 45 ft thick. These deposits are important local 

aquifers because of their relatively large hydraulic conductivity and porosity. All of these deposits are readily recharged 

by precipitation, and many small springs and seeps discharge 

from Unconsolidated deposits near or along their contact with 

underlying bedrock. Discharge from the springs typically 

varies from peak flow in the spring or early summer to low 

flow or no flow by late summer. These flow characteristics 

are typical of springs fed by local ground-water flow systems. 

Hydraulic conductivity of Unconsolidated deposits, measured 

from slug tests at nine wells near the Buckeye mine, ranged
Hydrogeology and Examination of Regional Ground-Water Flow 345

from 0.03 to 40 ft/day, with a median of 0.2 ft/day (Cannon 

and others, this volume, Chapter El, table 5). The lowest 

measured hydraulic conductivity values were in till; the highest value was in alluvial sand.

Ground-Water Recharge and Discharge

Recharge to aquifers primarily occurs from snowmelt 

and large precipitation events in spring and early summer. 

Recharge likely occurs on most topographic highs, and greater 

amounts of recharge are in areas with the highest precipitation 

and highest hydraulic conductivity. The water table is near 

land surface in much of the study area, including highelevation ridges and slopes, as observed from wells and 

springs. Discharge in the form of numerous small springs and 

seeps occurs in topographic lows, at abrupt breaks in slope, 

and at geologic contacts where there is a downward decrease 

in hydraulic conductivity. Ground-water flow paths in the 

upper aquifers, from recharge to discharge areas, are generally 

short—commonly less than a few thousand feet. Most active 

ground-water circulation occurs in unconsolidated deposits 

and the upper 50 ft of fractured bedrock.

Nearly all discharges observed in mine workings, road 

cuts, exploration pits, and natural springs were characterized 

as discharge from local ground-water flow systems based on 

characteristics such as topographic position, seasonal variation 

in flow, water quality, and geologic source. Water contained in 

fractures within the upper 50 ft of plutonic rocks generally is 

part of the local ground-water flow system and, on a macroscopic scale, flow direction in the rock is likely controlled 

largely by topography.

Discharge from regional flow systems was not observed 

within the study area. A very small part of annual recharge 

likely enters deep, regional flow systems through some fault 

and large fracture zones. Regional ground-water flow would 

be constrained by the very low hydraulic conductivity of the 

granodioritic bedrock, and would occur only as the result of 

secondary permeability along faults and fractures. Direction 

of flow within the regional system is presumably controlled 

by geologic structure and topography. Possible discharge areas 

for regional flow originating in the study area are Broadwater 

hot springs on the north end of the Butte pluton west of Helena 

and the Prickly Pear Creek valley east of the study area, in the 

vicinity of Alhambra hot springs (fig. 1).

Base-flow discharge of streams that drain the study area 

is sustained by ground-water flow from unconsolidated deposits and the upper zone of fractured and weathered bedrock. 

The small ground-water discharge available from the shallow 

aquifers and the lack of regional ground-water discharge to the 

streams are evident in the small base flow and steep recession 

curves of stream hydrographs (Church, Nimick, and others, 

this volume, Chapter B, fig. 3). Base flow of Basin Creek, 

Cataract Creek, and High Ore Creek, determined from winter 

measurements made from 1996 to 2000, averaged 

0.11 ftVs from each square mile of drainage area. The baseflow discharge is equivalent to 1.5 in. of runoff per year from 

the entire drainage area.

Methods of Investigation

Conceptual Model of Ground-Water Flow

Theoretical and mathematical ground-water flow concepts documented by Hubbert (1940), Toth (1963), and Freeze 

and Witherspoon (1966, 1967) form the basis of modern 

ground-water modeling. Data requirements for model development include (1) hydraulic conductivity distribution of 

the geologic units within the drainage basin, (2) geometry of 

the basin, including variations in topography and location of 

basin boundaries, and (3) configuration of the water table as 

determined from measurements of water levels in wells and 

by the measurement of elevation of recharge and discharge 

areas. A conceptual model of steady-state ground-water flow 

in the Boulder River watershed was constructed through 

the application of theoretical ground-water flow concepts to 

observed hydrogeologic properties of rocks and topographic 

and hydrologic characteristics of the study area. Included in 

the model are representations of typical flow regimes within 

the watershed.

Linear Feature Mapping

Four data sets, Landsat Thematic Mapper (TM), India 

Remote Sensing satellite (IRS 1-C) panchromatic, U.S. 

Geological Survey Digital Orthophoto Quads (DOQ), and 

U.S. Geological Survey Digital Elevation Models (DEM), 

were used to generate base images for mapping linear features. 

The different spatial resolutions of these data sets facilitated 

identification of linear features at various scales, ranging in 

length from a few hundred feet to several miles. All image 

processing and enhancement was performed using ENVI® 

(Environment for Visualizing Images, Research Systems Inc.. 

1998).

Images produced from the Landsat TM data2 (94 ft 

(30 m)3 spatial resolution) were processed to enhance linear 

surface features by applying directional convolution filters to 

the images to emphasize north-south-, east-west-, northeastsouthwest-, and northwest-southeast-trending linear features, 

and features adjacent to these principal directions (fig. 2). 

In all of the images where directional filters were used (TM, 

IRS, and DOQ), a user-defined addback value of 75 percent 

of the original image was selected. A principal components 

(PC) transformation was applied to maximize the variance of 

the TM multispectral data. This process is useful for identifying less correlated information in the data set which may

2The Landsat 5 scene was obtained from EROS Data Center and is part 

of the Multi-Resolution Land Characteristics (MRLC) data set. Entity ID 

number: MBP03902806281994. Image acquisition date: June 28, 1994. Path 

39, row 28.

3The spatial resolution of remote sensing data is usually reported in metric 

units.
346 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Figure 2. Comparison of unfiltered Landsat Thematic Mapper (TM) band 4 image (top) and TM band 4 image filtered to enhance 

northeast-trending features (bottom). In each image pair, the white outline is enlarged in the upper right view.
Hydrogeology and Examination of Regional Ground-Water Flow 347

be overwhelmed by the highly correlated topographic and 

albedo effects (Sabins, 1987). After inspection of the six 

resulting principal component images, PC-3 was selected 

because it provided the most suitable base image for mapping. 

Directional filters were applied to the image, as previously 

described, to enhance linear features (fig. 3). Lineaments considered to represent faults, fractures, or other geologic structures were mapped from each TM base image and included in 

a vector coverage. The endpoint map and image coordinates 

for each vector were recorded. The same mapping procedure 

was used for all the other data sets.

The IRS panchromatic data4 (16 ft (5 m) spatial resolution) were filtered to reduce the effects of nonperiodic banding 

in the image. This noise is the result of sensitivity variations 

in the IRS satellite's "push-broom" detector array. A bit error 

filter (Eliason and McEwen, 1990) was used to minimize the 

resulting noise. The residual banding, however, could not be 

completely removed without degrading the image. The resulting image was directionally filtered to enhance linear features 

as previously described (fig. 4). Because of the northeastsouthwest trend of the residual banding, the image was not 

used to map linear features oriented in this direction.

Six DOQ images5 (3.3 ft (1 m) spatial resolution), corresponding to the 7.5-minute topographic quadrangles covering the study area, were directionally filtered as previously 

described. The resulting images, having the highest spatial 

resolution, were used to identify the smallest mappable linear 

features.

When linear features are mapped from satellite or aerial 

imagery, an important consideration is that visual bias will 

be introduced by the direction of solar illumination. Linear 

features that are oriented parallel to the direction of solar 

illumination are often not as easily identified as those oriented 

perpendicular to this direction, where shadowing becomes 

more prominent. To minimize this effect, a DEM (33 ft 

(10 m) spatial resolution) was used to produce two shaded 

relief images that could be artificially illuminated from any 

selected direction, and using any selected sun elevation angle 

(fig. 5). The solar illumination azimuths are 124° for the TM 

data, 148° for the IRS data, and 120° for the DOQ data. Based 

on this predominantly southeastern illumination direction of 

the data sets, the shaded relief images were illuminated from 

0° and 45°, with a solar elevation angle of 45°.

The geographic coordinates (recorded as Universal 

Transverse Mercator (UTM) coordinates) of the endpoints of 

each mapped vector were used to calculate the azimuth and 

length of each linear feature. These data were used in a 2-D 

orientation analysis (RockworksTM, Rockware ® Inc., 1999) 

to determine primary orientations of lineaments from rose diagrams and to produce contour maps of linear feature characteristics. Rose diagrams are polar histograms, which represent

"IRS-1C Pan Image acquired from Space Imaging Inc. path/row/section: 

252/036/A & 252/036/B. acquisition date: 7-16-97(a) & ll-13-97(b).

5This data set is from the National Technical Means (NTM) declassified 

archives. The images, as received, have been degraded to 3.3 ft (1 m) spatial 

resolution.

the two-dimensional (horizontal plane) orientations of mapped 

linear features. The statistical parameters of sample size (AO, 

maximum percentage, mean percentage, vector mean azimuth 

(direction), standard deviation, confidence interval, and 

R-magnitude were calculated for each diagram. The maximum 

percentage is the histogram class with the greatest frequency, 

while the mean percentage is the class containing the average 

frequency. The confidence interval represents the interval on 

either side of the mean azimuth that most likely (using a 

95 percent confidence level) contains the true mean direction. 

The R-magnitude values are standardized to range from 0 to 1 

and are a measure of the magnitude of the azimuth mean. Data 

sets with a large dispersion about the mean have small values 

for R (values near 0), and data sets that are tightly grouped 

around the mean have a large value for R (values near 1).

Rose diagrams were produced to display the primary 

orientations of linear features. Petals in each rose diagram 

were either sized proportional to the length of the lineaments 

(total length of linear features within a 10° class range) or 

sized proportional to the spatial frequency of the lineaments 

within a 10° class range. The linear feature data were filtered 

using length groupings of 3.3-1,640 ft (1-500 m)6, 1,640- 

3,281 ft (500-1,000 m), 3,281-9,843 ft (1,000-3,000 m), and 

9,843-26,247 ft (3,000-8,000 m). Length-proportional rose 

diagrams were produced for each length group. The length 

groupings are meant to compare the orientations of short, short 

to medium, medium to long, and long length ranges of linear 

features.

The northeast-trending Butte-Helena fault zone divides 

the study area roughly into a southeastern region of synemplaced diastrophic fractures of the Butte pluton, and a western 

laccolithic region (O'Neill and others, this volume). The study 

area was divided into four quadrants (fig. 6), and rose 

diagrams of linear feature spatial frequency were plotted for 

each quadrant. Linear features were assigned to the quadrant 

that contained the midpoint of the linear feature. The rose 

diagrams corresponding to the four quadrants are intended to 

illustrate differences in linear feature orientation associated 

with differing geologic subregions and environments.

Contour maps of the spatial frequency, length, occurrence 

of intersections, combined spatial frequency and intersections, 

and combined spatial frequency and length were produced by 

interpolating the linear feature data using the kriging7 gridding method (Surfer 7 ®, Golden Software, Inc.). In a spatial 

frequency grid, the value assigned to each grid cell represents 

the number of linear features that lie in the cell. This number includes lines that originate in the cell, end in the cell, 

and pass through the cell. In a length grid, the value for each

6The linear feature data were originally recorded as endpoints in UTM 

coordinates, and the length groupings were based on calculated lengths from 

the metric coordinates. Therefore, metric units are also shown here.

7Kriging is a geostatistical gridding method that is often used to produce 

contour maps from irregularly spaced data. Kriging attempts to express trends 

suggested in the data by taking into account what is known about the spatial 

characteristics of the data (Isaaks and Srivastava, 1989).
348 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

513QOOO 5125000

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Hydrogeology and Examination of Regional Ground-Water Flow 349

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350 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Figure 5. Shaded relief Digital Elevation Model (DEM) images artificially illuminated from 0° azimuth (top) and 

45° azimuth (bottom) (area shown corresponds to previous figures).
5 

co

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Figure 6. Site map showing USGS 7.5-minute quadrangle (1:24,000 scale) boundaries (green), linear feature mapping quads (yellow), and approximate area of 

the Butte-Helena fault zone (blue).
352 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

cell represents the total lengths, added together, of all linear 

features that pass through the cell. The total length of each 

linear feature is calculated, not just the length of the section 

of the feature that lies within the cell. In an intersection grid, 

the value for each cell represents the number of intersections 

of linear features that occur within the cell. Each contour map 

was made using a grid cell size of 2,500 ft on each side. This 

grid cell size was selected, based on the results of various test 

dimensions, to minimize false map features produced by the 

gridding algorithm.

Contour maps combining spatial frequency and intersection data, and spatial frequency and length data were produced 

to show where these features occur together. Values for linear 

feature spatial frequency, intersections, and length were 

normalized, that is, the values from each data set were divided 

by their maximum value so that all values would range from 0 

to 1. The data were then combined to produce the values that 

were contoured in the combination maps. In terms of groundwater flow, areas with greater combined spatial frequency and 

intersections may identify where greater hydraulic connection 

in the bedrock aquifer exists, assuming fractures are hydraulically conductive. Areas where greater spatial frequency and 

linear feature length are coincident represent deeper groundwater circulation. Longer linear features likely represent 

fractures extending to greater depths, and therefore, deeper 

ground-water circulation, again assuming that the fractures are 

hydraulically conductive.

The contour map depicting linear feature spatial frequency and intersections was combined with a map of shallow 

ground water and wetland areas. This map is a derivative product from a land-type inventory of the Beaverhead-Deerlodge 

National Forest (D. Ruppert, unpub. data, 1980); it shows 

areas where ground water occurs at or near the land surface. 

Some of the water associated with areas of high water tables 

has been observed on the ground and on aerial photos as originating from seeps and springs oriented along linear features. 

These linear features are interpreted as being associated with 

bedrock structures. The purpose of combining these maps is to 

identify where zones of inferred high fracture frequency and 

areas where the potentiometric surface is close to the land surface coincide. These correlated areas may represent recharge 

to or discharge from fractured rock.

Results and Analysis

Conceptual Model of Ground-Water Flow

Geologic units in the Boulder River watershed study area 

can be grouped, based on their relative hydraulic conductivity, 

into three hydrogeologic units that correspond to three layers 

of a conceptual ground-water flow model (fig. 7). The upper 

model layer represents unconsolidated deposits and has the 

largest hydraulic conductivity. The second model layer

represents the upper fractured and weathered zone in the 

granodioritic bedrock: it has a smaller hydraulic conductivity 

than the unconsolidated deposits but a much greater hydraulic conductivity than underlying unweathered Butte pluton. 

Fractured rocks of Elkhorn Mountains Volcanics and Tertiary 

volcanics also are included in the second model layer of 

rocks having intermediate hydraulic conductivity. The third 

or lowest layer of the conceptual model represents the very 

low hydraulic conductivity of the Butte pluton. The crystalline 

rocks are likely fractured at depth, but fracture permeability 

undoubtedly decreases with depth. The exception to this low 

permeability might occur in fault zones where hydraulic conductivity in fractures might increase. This three-layer conceptual model oversimplifies the hydraulic properties of rocks in 

the study area; however, it preserves important hydraulic characteristics, which are that hydraulic conductivity is greatest 

in the upper unconsolidated alluvium and generally decreases 

with depth. The hydrogeologic properties of the Butte pluton 

are the primary factors that limit development of regional 

ground-water flow systems in the study area.

Topography determines the upper geometry of the 

ground-water basin and is a major control on direction of 

ground-water flow in a basin such as the Boulder River 

watershed, where at depth no extensive high permeability 

unit exists. The steep hummocky terrain of the study area, 

combined with the decrease in hydraulic conductivity of 

geologic units with depth, results in the formation of mostly 

shallow, localized ground-water flow systems (Toth, 1963; 

Freeze and Witherspoon, 1967). Direction of shallow groundwater flow in the study area can be modeled as the gradient of 

topographic slope. Mathematical analysis (Freeze and Witherspoon, 1967) has shown that changes in topographic slope, 

combined with decreasing hydraulic conductivity with depth, 

will focus ground-water discharge at breaks in slope and at 

geologic contacts, similar to those observed in the Boulder 

River watershed. A conceptual three-layer model of decreasing hydraulic conductivity with depth also is consistent with 

the generally shallow depths to ground water observed in 

the study area. In the conceptual model of ground water just 

outlined, the upper layer of rocks has the greatest hydraulic 

conductivity and transports the greatest amount of ground 

water per unit volume of aquifer on an annual cycle. The second layer of rocks, having intermediate hydraulic conductivity, 

transports a smaller amount of ground water than the upper 

layer. The third layer of rocks, in which hydraulic conductivity is very low, transports the least amount of water annually, 

even though the amount of water stored within this unit may 

be large.

The ground-water flow regimes included in the conceptual model (fig. 7) are typical of conditions in the watershed; 

the views are meant to represent various settings for groundand surface-water interaction and to depict the geologic controls on basin hydraulics. Figure 1A illustrates an area where 

principal recharge is through unconsolidated alluvium, with 

secondary recharge through surface fractures. Ground-water 

discharge in this flow regime is to springs that occur at the
B

Linear feature 

(fracture)

Spring

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7 *TV ^S;"jppm:,^,(j.ii|i^ . .-' -'

EXPLANATION

Unconsolidated deposits ^ 

(model layer 1 - high hydraulic conductivity)

Fractured Lowland Creek Volcanics

(model layer 2 - moderate hydraulic conductivity)

Fractured Elkhorn Mountains Volcanics 

(model layer 2 - moderate hydraulic conductivity) 

Upper fractured or weathered zone 

T!l of the Boulder batholith (model layer 2 - low to 

moderate hydraulic conductivity)

Plutonic rocks of the Boulder batholith

and intrusives (model layer 3 - low hydraulic conductivity)

Variously oriented faults, fractures, 

and joints

Direction of ground-water flow

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Figure?. Conceptual ground-water model and depiction of flow regimes in the Boulder River watershed (cross sections are for purposes of illustration and are not to scale). 

Areas corresponding to views are noted in text.
354 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

contact between unconsolidated alluvium and plutonic rocks, 

and to a channel whose location was likely controlled by 

bedrock fractures. Cataract Creek near the confluence of 

Uncle Sam Gulch is an example of this type of stream.

Figure IB illustrates a flow regime where ground-water 

recharge occurs at a topographic high, in fractured Elkhorn 

Mountains Volcanics (analogous to conditions at Jack Mountain), and in the fractured Lowland Creek Volcanics. Groundwater discharge in this regime is to springs at the contact 

between the Cretaceous and Tertiary volcanics, and the contact 

of the Elkhorn Mountains Volcanics and underlying plutonic 

rocks.

The flow regime in Figure 1C depicts ground-water 

recharge occurring in unconsolidated alluvium, fractured 

Elkhorn Mountains Volcanics, and throughgoing fractures 

in volcanic and plutonic rocks. Discharge is to wetlands and 

adjacent streams in glacial valley fill (analogous to Buckeye 

Meadows), and to springs that occur at breaks in slope and the 

contact between volcanic and plutonic rocks.

Figure ID illustrates a ground-water flow regime where 

recharge occurs in exposed fractured and weathered plutonic 

rocks, fractured Lowland Creek Volcanics. and unconsolidated 

alluvium. Discharge in this regime is to springs located at the 

contact between Tertiary volcanics and plutonic rocks, and to 

streams in unconsolidated alluvium. Examples of this flow 

regime are the lower Basin Creek valley, upstream from the 

town of Basin, and upper Cataract Creek meadows.

Linear Feature Analysis

Linear features were mapped within the Boulder River 

watershed study area and in areas surrounding the study area 

(fig. 8). A total of 563 features were mapped. These linear features are interpreted as representing the surface expression of 

faults, joints, other fractures, and mineralized veins. Statistical 

summaries of length and orientation are in tables 1 and 2. 

The mapped linear features range in length from 671 ft to 

26,070 ft, with a mean of 4,902 ft. The mean orientation 

(azimuth) of all mapped features is 79.92°. The primary and 

secondary orientations and other minor trends of linear features are summarized in table 3.

A rose diagram summarizing the orientations of all 

mapped linear features is shown in figure 9A. Figure 9B has a 

similar rose diagram in which the orientations were weighted 

according to each feature's length. Both rose diagrams show 

two primary trend sets with azimuths of 65° and 105°. The 

length weighted rose diagram was compared to rose diagrams 

of lineament and fault orientation analysis results from a previous study (Smedes, 1966) of the northern Elkhorn Mountains 

(adjacent to and northeast of the area of this study). These 

diagrams show the orientation of 996 faults and 1,357 lineaments that were mapped from field observations and aerial 

photos, and weighted by length. The comparison with linear 

feature orientations (fig. 9B) shows a correlated trend of faults 

to the northeast, and of lineaments to the east-northeast. There

is little correlation in the prominent trend of fault orientation 

to the southeast. However, the average angle of illumination 

of the remote sensing base images, as described preceding, is 

co-linear with this trend, and linear features oriented in this 

direction would be less discernible.

The length filtered rose diagrams indicate that short to 

moderate-length linear features (fig. IOA and lOfi) generally 

trend to the northeast and east-northeast. The moderate- to 

long length features, ranging from 3,280 to 26,250 ft 

(1,000 to 8,000 m) (fig. 10C and 10D) also have two primary 

trend sets, with a predominant orientation to the east-southeast 

and a secondary orientation to the east-northeast.

The mapped lineaments grouped by quadrant 

(fig. 1 IA-D) have a consistent east-west primary mean 

azimuth direction similar to that seen in the length filtered 

rose diagrams. The primary and secondary orientations in the 

quadrant-grouped diagrams are typically about 100°-110° 

and 70°-80°. A minor orientation in figure 1 \A and 11 C is 

20°-30 , and in figure 11D is 30 -40°. In a previous study of 

the Jefferson City 15-minute quadrangle (Becraft and others, 

1963), a northeast primary trend of nonmineralized faults and 

topographically expressed lineaments (fig. 11£) was observed. 

Minor trends are at 0°-10°, 90°-100°, and 140°-150°. 

The Jefferson City 15-minute quadrangle corresponds to the 

eastern part of this study (quadrants 2 and 4, fig. 6). In order 

to compare trends from the same area, linear features from 

quadrants 2 and 4 were combined and the rose diagram from 

Becraft and others (1963) was overlaid (fig. 11£). There are 

correlated trends to the northeast and east, and to a lesser 

extent, to the southeast. The trend at 0°-10° shown in the rose 

diagram from Becraft and others (1963) is not well correlated.

Mapping quadrant 1 (fig. 6) covers an area corresponding 

with a portion of the laccolithic western part of the Boulder 

batholith, northwest of the Butte-Helena fault zone (O'Neill 

and others, this volume, fig. 16). Part of the area is overlain 

with Elkhorn Mountains Volcanics. Mapping quadrant 4 is 

southeast of the Butte-Helena fault zone and includes areas of 

the Butte pluton, Elkhorn Mountains Volcanics, and Lowland

Table 1. Summary statistics for mapped 

linear features.

Mean

Standard error

Median

Mode

Standard deviation

Range

Minimum

Maximum

Sum

Count

4,902 ft 

157ft 

3,600 ft 

3,678 ft 

3,713ft 

25,400 ft 

671ft 

26,070 ft 

2,759,538 ft 

563
Table 2. Summary statistics for orientations of mapped linear features.

[--, when length filtering is deactivated, minimum and maximum length are not applicable]

Rose diagram

fig. 9A

fig. 9B

fig. 10A

fig. 105

fig. 10C

fig. 10D

fig. 11A 

Quadrant 1

fig. 115 

Quadrant 2

fig. 11C 

Quadrant 3

fig. 11D 

Quadrant 4

Calculation 

method

Frequency

Length

Length

Length

Length

Length

Frequency

Frequency

Frequency

Frequency

Length 

filtering

Deactivated

Deactivated

Activated

Activated

Activated

Activated

Deactivated

Deactivated

Deactivated

Deactivated

Minimum 

length 

(feet)

..

--

3.3

1,640

3,281

9,843

--

--

--

--

Maximum 

length 

(feet)

..

--

1,640

3,281

9,843

26,247

--

--

-

--

Sample 

size

563

563

51

192

264

56

196

150

99

118

Maximum 

percentage

13.3

18.3

15.9

11.6

15.8

30.3

12.8

18.7

16.2

14.4

Mean 

percentage

5.6

5.6

7.7

5.6

5.9

9.1

5.6

5.6

5.9

5.9

Mean 

azimuth 

(degrees)

79.92

83.79

63.20

77.17

84.32

88.32

74.30

85.55

79.90

81.72

Relative 

standard 

deviation 

(percent)

3.54

4.51

5.06

3.56

3.31

9.27

3.65

5.14

3.82

3.80

Co

i

(d
356 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 3. Summary of main orientations of mapped linear features.

All linear features

All linear features weighted by 

length.

Mean 

azimuth 

(degrees)

79.92

83.79

Primary orientation 

(degrees)

100-110

100-110

Secondary 

orientation 

(degrees)

70-80

70-80

Other minor 

trends 

(degrees)

20-30

30-40

Length filtered

3. 3- 1,640 ft (1 -500m)

1,640-3,281 ft (500-1,000 m)

3,281-9,843 ft (1,000-3,000 m)

9,843-26,247 ft (3,000-8,000 m)

63.20

77.17

84.32

88.32

20-40

60-70

100-110

90-110

50-60

90-110

60-80

60-70

70-80

20-30

30-40

30-40

Grouped by quadrant

Quadrant 1 (NW)

Quadrant 2 (NE)

Quadrant 3 (SW)

Quadrant 4 (SE)

74.30

85.55

79.90

81.72

100-110

100-110

90-100

70-80

70-80

60-80

20-30

100-120

20-30

130-140

50-80

30-40
Hydrogeology and Examination of Regional Ground-Water Flow 357

51 40000 513QOOO 5125000

00
Confidence 

interval

Mean azirri

00

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Figure 9. Rose diagrams representing A, orientations of all linear features, and B, all linear features weighted by length. The confidence interval represents the interval on 

either side of the mean azimuth that most likely (using a 95 percent confidence level) contains the true mean direction. Rose diagrams from a previous study (Smedes, 1966) of 

the northern Elkhorn Mountains showing the orientation of 996 faults (solid red line) and 1,357 lineaments (dashed red line) are shown in view B.
Hydrogeology and Examination of Regional Ground-Water Flow 359

270- 14 12 10 8 6 r

- V '' -AW .//>.•*:-^

270- 10 -90 270

B D

Figure 10. Length filtered rose diagrams of linear features A, 3.3-1,640 ft (1-500 m) in length; B, 1,640-3,281 ft (500-1,000 m) in 

length; C, 3,281-9,843 ft (1,000-3,000 m) in length; D, 9,843-26,247 ft (3,000-8,000 m) in length. The mean azimuth and confidence 

interval are shown for each diagram.
360 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Figure 11. Rose diagrams showing linear feature orientation arranged by quadrants shown in figure 6. A, quadrant 1; 

B, quadrant 2; C, quadrant 3; D, quadrant 4. The mean azimuth and confidence interval are shown for each diagram, £, rose 

diagram (red) from a previous study (Becraft and others, 1963) in the Jefferson City 15-minute quadrangle of the trends of 

142 nonmineralized faults and topographically expressed lineaments overlaid on combined linear feature orientation of 

quadrants 2 and 4.
Hydrogeology and Examination of Regional Ground-Water Flow 361

Creek Volcanics. The trends of mapped linear features for 

these two quadrants are similar (fig. 1 \A and 1 ID), with the 

exception of a minor trend oriented to the north-northwest in 

quadrant 1. The similarity of linear feature orientation in these 

two quadrants suggests a consistent pattern of fracturing northwest and southeast of the Butte-Helena fault zone.

Quadrant 2 and quadrant 3 (fig. 6) represent the northeastern and southwestern portion, respectively, of the ButteHelena fault zone within the study area. Linear features in 

the northeast quadrant (fig. 1 IB) show two primary trend sets 

similar to the orientation of spatial frequency distribution for 

the entire study area (fig. 9A). The southwest quadrant (fig. 

11C) has primary east-west (90°-100°) and north-northeast 

(20 -30 ) orientations, with minor classes trending eastnortheast (50°-80°) and southeast (140°-160°). These orientation classes are consistent with the synemplaced diastrophic 

fracture orientations of the Butte pluton (O'Neill and others, 

this volume). Because of the more dispersed orientations in 

this quadrant, fracture-controlled ground-water flow directions 

would also be expected to be more diffuse.

Within the Boulder River watershed study area, the 

greatest occurrence of linear feature spatial frequency, length, 

and intersection frequency (figs. 12-14) was mapped near the 

Continental Divide at the northern boundary of the study area 

between Old Baldy and Lava Mountains. Other areas of high 

linear feature spatial frequency are indicated in the central part 

of the watershed near the Crystal mine, in the north part of the 

watershed near the Buckeye mine, and in the south part of the 

watershed east of Basin (fig. 12). Longer linear features also 

occur in the central part of the watershed near the Crystal and 

Bullion mines and in the southern part of the watershed 

(fig. 13). Combined contour maps of linear feature spatial frequency and intersections (fig. 15), and spatial frequency and 

length (fig. 16) show similar results, with an area of high combined spatial frequency and length west of the Bullion mine.

Areas of relatively dense linear features overlap with 

areas of mapped shallow ground water (fig. 17) in several 

locations. An instance is seen in the northern part of the 

watershed between Old Baldy Mountain and Lava Mountain. Old Baldy Mountain is mapped as an area of high linear 

feature spatial frequency and is flanked on the east and south 

by areas where the water table is near the land surface. Similar 

occurrences of this correlation are seen in the central part of 

the watershed near the Crystal and Bullion mines, and in the 

northwest part of the study area near Basin Creek. Areas of 

high linear feature spatial frequency on either flank of the 

Continental Divide and in other topographically high areas 

likely have enhanced ground-water recharge through the 

fractures in volcanic and plutonic rocks. Adjacent areas of 

inferred shallow ground water represent potential discharge in 

unconsolidated alluvium, fractured volcanics, and fractured 

plutonic rocks.

Conclusions and Discussion

Based on field observations at the Buckeye, Bullion, and 

Crystal mines and the ground-water flow concepts outlined 

here, ground-water flow to mines in the Boulder River watershed study area is primarily local in origin. Ground-water flow 

to underground workings, such as those at the Bullion and 

Crystal mines, primarily comes from infiltration of shallow 

ground water from rocks above the mine workings and from 

interception of surface runoff into mine trenches and pits. 

Ground water that enters mine workings through lateral flow 

from fractured plutonic rocks is a relatively small percentage of the total water entering mines. Remediation efforts 

that eliminate ponded surface water near mine workings 

and reduce infiltration and surface runoff to caved adits and 

trenches would significantly reduce the quantity of shallow 

ground water entering mine workings. The relatively small 

amount of ground water that enters underground mine workings from deeper fractures in plutonic rocks probably could 

not be eliminated or even significantly reduced through any 

surface remediation efforts. Given the probable long residence 

times for deep circulation and relatively high acid-neutralizing 

potential (Desborough and others, 1998) of the plutonic rocks, 

fracture-controlled ground water at depth likely would not 

adversely affect surface water quality in the watershed.

The primary surface-water flow direction (Basin Creek, 

Cataract Creek, and High Ore Creek) in the watershed is to 

the south into the Boulder River. Shallow ground water in the 

unconsolidated aquifer likely follows a similar flow direction, 

which is primarily topographically controlled. However, the 

predominant east-west orientation, and the orientation of other 

minor trends, of mapped linear features, assumed associated 

with fractures, may have a significant influence on structurally 

controlled shallow ground-water flow directions. The orientation of bedrock linear structural features likely affects the flow 

direction of deeply circulating regional ground-water flow. 

The rose diagrams presented in this study indicate that the orientations of mapped linear features at the surface are co-linear 

with the orientation of geophysical gradients in the subsurface (McCafferty and others, this volume). This suggests that 

some linear structures extend to considerable depth, and that 

ground-water storage at depth is potentially large.

The high linear feature frequency indicated in areas along 

the Continental Divide is significant in that these areas represent potential recharge to fracture-controlled ground water 

in both the Boulder River watershed and the Tenmile Creek 

watershed to the north. The higher occurrence of mapped 

linear features could identify potential recharge sources for 

fracture-controlled ground water, consistent with the conceptual model presented in this study.

The results of this study provide a conceptual understanding of the ground-water and surface-water relationships in the 

watershed, identify possible fracture-controlled ground-water 

recharge areas associated with near-surface structures, and 

map areas of greatest linear feature spatial frequency. These 

components should be considered in any mine-site restoration 

strategy or in identifying suitable locations for mine-waste 

repositories.
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366 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

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368 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

References Cited

Becraft, G.E., Pinckney, D.M., and Rosenblum, Sam, 1963, 

Geology and mineral deposits of the Jefferson City quadrangle, Jefferson and Lewis and Clark Counties, Montana: 

U.S. Geological Survey Professional Paper 428, 101 p., 

18 plates.

Desborough, G.A., Briggs, PH., and Mazza, N., 1998, Chemical and mineralogical characteristics and acid-neutralizing 

potential of fresh and altered rocks and soils of the Boulder 

River headwaters in Basin and Cataract Creeks of Northern 

Jefferson County, Montana: U.S. Geological Survey OpenFile Report 98-40, 21 p.

Eliason, E.M., and McEwen, A.S., 1990, Adaptive box filters 

for removal of random noise from digital images: Photogrammetric Engineering & Remote Sensing, v. 56, no. 4, 

p. 453.

Freeze, R.A., and Cherry, J.A., 1979, Groundwater: 

Englewood Cliffs, N.J., Prentice-Hall, Inc., 604 p.

Freeze, R.A., and Witherspoon, P.A., 1966, Theoretical analysis of regional groundwater flow—I, Analytical and numerical solutions to the mathematical model: Water Resources 

Research, v. 2, no. 4, p. 641-656.

Freeze, R.A., and Witherspoon, P.A., 1967, Theoretical analysis of regional groundwater flow—II, Effect of water table 

configuration and subsurface permeability variation: Water 

Resources Research, v. 3, no. 2, p. 623-634.

Hubbert, M.K., 1940, The theory of ground-water motion: 

Journal of Geology, v. 48, no. 8, pt. I, p. 785-944.

Isaaks, E.H., and Srivastava, R.M., 1989, An introduction to 

applied geostatistics: New York, Oxford, 561 p.

Knepper, D.H., 1996, Interpreted linear features from Landsat 

Thematic Mapper images, Southern Ute Indian Reservation, 

Colorado, in Geology and resources of the Paradox Basin, 

Utah: Utah Geological Association Guidebook 25.

Maxim Technologies Inc., 1999, Final engineering evaluation of potential repository sites, Beaverhead-Deerlodge 

and Helena National Forests, Lewis and Clark, Powell, and 

Jefferson Counties, Montana: Helena, Mont., prepared for 

USDA Forest Service, Region I, Missoula, Mont., variously 

paged.

Research Systems, Inc., 1998, Boulder, Colorado, ENVI, The 

Environment for Visualizing Images.

Rockware, Inc., 1999, Golden, Colorado, RockWorks99.

Rowan, L.C., and Wetlaufer, P.H., 1975, Iron-absorption 

band analysis for the discrimination of iron-rich zones: 

U.S. Geological Survey, Type III Final Report, Contract 

S-70243-AG.

Ruppel, E.T., 1963, Geology of the Basin quadrangle,

Jefferson, Lewis and Clark, and Powell Counties, Montana: 

U.S. Geological Survey Bulletin 1151, 121 p., 7 plates.

Sabins, F. F, 1987, Remote sensing principles and interpretation, Second Edition: New York, Freeman.

Smedes, H.W., 1966, Geology and igneous petrology of the 

northern Elkhorn Mountains, Jefferson and Broadwater 

Counties, Montana: U.S. Geological Survey Professional 

Paper 510, 116 p.

Toth, J., 1963, A theoretical analysis of groundwater flow in 

small drainage basins: Journal of Geophysical Research, 

v. 68, no. 16, p. 4795-4812.
Aquatic Health and Exposure Pathways 

of Trace Elements

By ATda M. Farag, David A. Nimick, Briant A. Kimball, Stanley E. Church,

Don Skaar, William G. Brumbaugh, Christer Hogstrand, and Elizabeth MacConnell

Chapter D10 of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-D10

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract......................................................................................................................................................373

Introduction............................................................................................................................................... 373

Purpose and Scope......................................................................................................................... 375

Previous Studies.............................................................................................................................. 376

Acknowledgments........................................................................................................................... 376

Methods ......................................................................

Aquatic Health.................................................................................................................................. 376

Survival Experiments.............................................................................................................. 376

Fish Biomass, Density, and Physiology............................................................................... 377

Statistical Analyses................................................................................................................ 377

Exposure Pathways......................................................................................................................... 377

Statistics................................................................................................................................... 378

Results........................................................................................................^^

Aquatic Health.................................................................................................................................. 378

Survival Experiments.............................................................................................................. 378

Water Chemistry—Survival Experiments.................................................................. 379

Fish Biomass and Density Estimates................................................................................... 379

Habitat Characterization of Fish Abundance Sites........................................................... 381

Water Chemistry—Resident Fish Biomass/Density and Health............................ 382

Tissue Trace Elements........................................................................................................... 385

Metallothionein ...................................................................................................................... 385

Lipid Peroxidation................................................................................................................... 386

Exposure Pathways......................................................................................................................... 386

Water ......................................................................_

Colloids.........................................................................................................................

Sediment.................................................................................................................................. 389

Biofilm ...................................................................................................................................... 389

Benthic Macro in vertebrates................................................................................................ 390

Fish Tissues.............................................................................................................................. 390

Relationships among Components ..................................................................................... 391

Discussion.................................................................................................................................................. 394

Aquatic Health.................................................................................................................................. 394

Exposure Pathways......................................................................................................................... 395

Summary.................................................................................................................................................... 397

References Cited...................................................................................................................................... 398

Figures

1. Map of Boulder River watershed showing biological sampling sites used to

assess aquatic health and exposure pathways................................................................. 374

2. Histogram of survival of hatchery cutthroat trout placed in various tributaries

of Boulder River for as long as 96 hr during 1998 and 1999.............................................. 378
3. Photomicrograph views of gill sections of cutthroat trout held in the 

Little Boulder River (reference site), Middle Cataract Creek, and upper 

High Ore Creek during the 1999,96-hour survival experiment......................................... 380

4. Graph showing comparisons of growth of trout in three tributaries in

Boulder River watershed........................................................................................................ 383

Tables

1. Biological sampling sites, Boulder River watershed......................................................... 375

2. Physical and chemical data for stream sites during the 96-hour survival

experiments.............................................................................................................................. 381

3. Size ranges and biomass/density estimates of brook, rainbow, and cutthroat

trout in tributaries and mainstem of the Boulder River..................................................... 382

4. Weighted usable area of stream for brook and rainbow trout fry, juveniles,

and adults.................................................................................................................................. 383

5. Physical and chemical data for stream sites where fish health was assessed, 

1996-99..........................................................................._

6. Mean trace-element concentrations in fish, 1998............................................................. 385

7. Metallothionein concentrations in gill and liver samples of resident rainbow

trout, 1997.................................................................................................................................. 386

8. Lipid peroxidation of tissues sampled from resident rainbow trout, 1997...................... 386

9. Median trace-element concentrations in water, 1996-99................................................ 387

10. Mean trace-element concentrations in colloids and ultrafiltrates during

low-flow conditions, 1996-98................................................................................................. 388

11. Leachable trace-element concentrations in composite streambed sediment,

1998............................................................................................................................................389

12. Mean trace-element concentrations in biofilm, 1998........................................................ 390

13. Mean trace-element concentrations in invertebrates, 1998............................................ 391

14. Correlation coefficients for trace-element concentrations measured in water, 

sediment, colloids, biofilm, benthic macroinvertebrates,fish gill, fish liver, 

and whole fish, 1996-99 ......................................................................................................... 392

Chapter 010

Aquatic Health and Exposure Pathways of Trace Elements

By ATda M. Farag, David A. Nimick, Briant A. Kimball, Stanley E. Church, Don Skaar, 1 William G. Brumbaugh, 

Christer Hogstrand,2 and Elizabeth MacConnell3

Abstract

Historical mine adits, mill tailings, and waste-rock dumps 

in the Boulder River watershed, Montana, are sources of 

trace elements to streams. Biological studies were undertaken 

to characterize the aquatic health of fisheries and the exposure pathway of these trace elements in watershed streams. 

Aquatic health was assessed by measuring the survivability of 

hatchery fish, measuring the biomass and density of resident 

fish, and documenting the physiology of fish exposed to trace 

elements. Pathways of exposure were assessed by determining trace-element concentrations in water, sediment, biofilm, 

invertebrates, and fish tissues and by defining relations among 

these components.

Instream survivability experiments at sites that had no 

resident trout and were downstream from inactive mines indicated that elevated concentrations of filtered cadmium, copper, 

and zinc were associated with increased mortality as well as 

hypertrophy (swelling), degeneration (dying), and necrosis 

of epithelial cells in gills of hatchery trout. In lower Cataract 

Creek, a site farther downstream, the health of resident trout 

was impaired. A decrease in the number of trout per acre indicated population-level effects; and increased metallothionein, 

increased products of lipid peroxidation, and elevated concentrations of trace elements in fish tissues indicated individuallevel effects.

The concentrations of cadmium, copper, and zinc in 

water and those of arsenic, cadmium, copper, lead, and zinc in 

sediment in some watershed streams were sufficient to affect 

aquatic life. Concentrations of arsenic, copper, cadmium, lead, 

and zinc in invertebrates from lower Cataract Creek (63, 339, 

59, 34, and 2,410 ug/g (dry weight, respectively)) were greater 

than concentrations in invertebrates from the Clark Fork River 

watershed, Montana (19, 174, 2.3, 15, and 648, respectively), 

where these trace elements were associated with reduced survival, growth, and health of cutthroat trout fed diets composed 

of the Clark Fork River invertebrates. The concentrations of 

all trace elements, except cadmium, in colloids and biofilm

'Montana Fish, Wildlife, and Parks, Helena, Montana.

2Kings College, London, England.

3U.S. Fish and Wildlife Service, Bozeman, Montana.

were significantly correlated, which suggests that transfer of 

trace elements associated with colloids to biological portions 

of biofilm is an important pathway in which trace elements 

associated with abiotic components are first presented to biotic 

components. The interrelationship of trace elements accumulating in the abiotic and biotic components sampled suggests 

that copper, cadmium, and zinc concentrations increased in 

fish tissues as a result of direct exposure from water and sediment contact and indirect exposure through the food chain. 

Apparently, trace elements have made contact with biota 

through these two pathways and have thereby compromised 

the overall aquatic health of the Boulder River watershed.

Introduction

Environmental effects of historical mining in a watershed 

typically are manifested as impairment of the health of aquatic 

life in streams. The health of fisheries usually is considered 

an important aquatic life issue because fish represent the top 

of the food chain in streams and because fish are a resource of 

considerable interest to land managers and the public. Aquatic 

health of the fisheries in a watershed can be defined in multiple ways. For example, direct measures of the reduced survivability of fish or reduced levels of fish biomass or density 

may indicate the inability of a watershed to support an optimal 

population size. However, to explain possible mechanisms of 

this population-level impairment and to establish a cause-andeffect relationship between a stressor (for example, concentrations in tissues or "tissue dose" of trace elements) and the 

effects at the population level (for example, reduced biomass/ 

density), the health of individual fish must be studied. Understanding the pathways of trace-element exposure can further 

establish the cause-and-effect relationship between stressors 

and the particular concentrations accumulated in the aquatic 

components (biofilm, invertebrates, and fish). Interpretation 

of trace-element concentrations in these components can help 

define the overall health of the aquatic life in a watershed and 

provide a baseline for comparisons following remediation 

activities.

In the Boulder River watershed, Basin, Cataract, and 

High Ore Creeks (fig. 1) have elevated trace-element
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EXPLANATION EXPLANATION

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Fish abundance and health assessment 

96-hour survival experiment

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Figure 1. Biological sampling sites used for assessing aquatic health (left) and exposure pathways (right) in Boulder River watershed, Montana.
Aquatic Health and Exposure Pathways of Trace Elements 375

concentrations in water and streambed sediment, and trace-element loads from these streams affect trace-element concentrations in the Boulder River (Church, Unruh, and others, this 

volume, Chapter D8; Nimick and Cleasby, this volume, Chapter D5). All species of fish are absent from stream reaches 

downstream from a few draining mine adits in the watershed, 

but populations of brook trout (Salvelinus fontinalis), rainbow 

trout (Oncorhynchus mykiss), and cutthroat trout (Oncorhynchus clarki) reside farther downstream (Robert Wintergerst, 

United States Department of Agriculture (USDA) Forest 

Service, Missoula, Mont., oral commun., 1997). Additionally, viable populations of native, genetically pure, westslope 

cutthroat trout (Oncorhynchus clarkii lewisi) exist in High Ore 

Creek upstream from the Comet mine (fig. 1).

Purpose and Scope

This report examines the aquatic health of fisheries and 

the exposure pathways of trace elements in streams draining 

historical mining areas of the Boulder River watershed near 

Basin in southwestern Montana. Multiple investigations were 

conducted to fulfill the following biological objectives:

• Determine the survivability of westslope cutthroat trout 

in stream reaches that lacked fish

Table 1. Biological sampling sites, Boulder River watershed.

• Determine the biomass, density, and health of resident 

fish

• Characterize the pathway and partitioning of trace elements in water, sediment, biofilm, benthic macroinvertebrates, and fish

• Define the role of water, colloids, and sediment in the 

transfer of trace elements to aquatic life.

The first objective, to determine the survivability of 

westslope cutthroat trout in stream reaches that lacked fish, 

was important for documenting the maximum trace-element 

concentrations that would not be acutely toxic to fish. Some 

fishless reaches in Jack Creek, Uncle Sam Gulch, and High 

Ore Creek coincided with trace-element concentrations of 

filtered Cd (cadmium) greater than 50 |ug/L (micrograms per 

liter) and as much as 5,000 |ug/L of filtered Zn (zinc) in water 

(Nimick and Cleasby, this volume, figs. 11 and 14). Instream 

experiments to determine the survivability of cutthroat trout 

were conducted at seven sites (table 1; fig. 1). Additionally, 

the concentrations of whole-body ions (such as calcium, potassium, sodium) and histological changes in fish that occurred 

during the survival studies were investigated because they 

could provide insight about the mechanisms causing acute 

toxicity. Whole body calcium, potassium, and sodium could

Site ID 

(fig.D

LBR

BMT

JC

USG

UCC

MCC

LCC

UHO

LHO

LBC

UBR

BRRC

BRBC

BRCC

BRGG

Reference - 

Site name site

Little Boulder River x

Bullion Mine tributary

Jack Creek downstream from

Bullion Mine tributary.

Uncle Sam Gulch

Cataract Creek upstream from

Uncle Sam Gulch.

Cataract Creek downstream from

Uncle Sam Gulch.

Cataract Creek at mouth

High Ore Creek downstream

from Comet mine.

High Ore Creek at mouth

Basin Creek near mouth

Boulder River upstream from x

Trapper Creek.

Boulder River downstream from x

Red Rock Creek.

Boulder River downstream from

Basin Creek.

Boulder River downstream from

Cataract Creek.

Boulder River downstream from

Galena Gulch.

Assessments

Biofilm, Survival experiment

Fish invertebrates 1000 IQQQ

XXX

1 iJiJQ t UiJJ

X X

XXX

X X

X

XXX

X X

X

XXX

X X

X X

X X

X

X

X X
376 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

indicate upsets in ionoregulatory status as a result of metal 

exposure. Histological examinations could provide insight 

about acute changes in tissues, especially gills, which might 

result during the survivability experiments.

Our second objective was to determine the biomass, density, and health of fish in streams and in the mainstem of the 

study area. Trace-element exposure can affect aquatic 

biota and the overall ecological health of a river system 

(Farag and others, 1995). No assessments of individual fish 

health had been previously performed in the Boulder River. 

Surveys of fish biomass and density, measures of physiological function, and trace-element concentrations in tissues at 

five sites (table 1; fig. 1) were used to provide a picture of 

exposure related to physiological malfunction and any resulting decrease in fish populations. In addition, we used measures 

of metallothionein and products of lipid peroxidation (see 

results for definitions of these measurements) to define physiological malfunction. Then we interpreted these physiological 

malfunction data with data on trace-element concentrations in 

tissues and with data on fish biomass and density to determine 

the overall ecological health of sites in our study area within 

the Boulder River watershed.

Our third and fourth objectives were established to define 

the exposure pathways of trace elements. These objectives 

were to characterize the pathway and partitioning of trace 

elements in water, sediment, biofilm (also referred to 

aufwuchs, and consists of abiotic and biotic materials that 

form a surface layer on rocks in streams), invertebrates, 

and fish, and to define the influence of water, colloids, and 

sediment in the transfer of trace elements to aquatic life. To 

meet these objectives, we collected samples for trace-element 

analysis from both abiotic and biotic components throughout 

the watershed. Biofilm and benthic macroinvertebrates were 

collected from 12 sites; fish tissues were collected from 5 sites 

(table 1; fig. 1).

Previous Studies

Although aquatic health had not been previously rigorously studied in the Boulder River watershed, investigations 

of the effects of mining on aquatic life in the Boulder River 

began in 1975. Nelson (1976) found reductions in the survival 

of fish eggs during an egg bioassay and reductions in fish 

populations at sites on the Boulder River below Cataract Creek 

and High Ore Creek. Gardner (1977) found that the invertebrate community diversity in the Boulder River at a station 

downstream from High Ore Creek was reduced compared to 

an upstream station on the Boulder River located downstream 

from Red Rock Creek. In both studies, the differences between 

sites upstream and downstream of High Ore Creek were attributed to the greater concentrations of zinc in the water at the 

site below High Ore Creek.

In the 1990s, other investigations of the watershed were 

initiated to define the fitness of aquatic life in the Boulder 

River watershed. Gless (1990) designated Basin Creek a

"stream of concern," Cataract Creek as "degraded," and High 

Ore Creek as "extremely degraded." These classifications 

were based on elevated concentrations of arsenic in the water 

column and the rare presence of aquatic life in some stream 

reaches. Gless (1990) observed iron stains and dead vegetation 

as high as 4.5 ft above the stream banks of Cataract Creek. 

Martin (1992) documented elevated concentrations of 

cadmium, copper, and zinc in water, sediment, aquatic invertebrates, and fish in the Cataract Creek drainage and related 

these concentrations to the sources of trace elements in the 

drainage.

Acknowledgments

The authors thank Thomas E. Cleasby for assistance with 

water-sample and fish-tissue collections; Jack Goldstein, Dave 

Harper, and Brad Mueller for assistance during collections 

of biology samples and performance of toxicity experiments; 

Michele Williams for assistance with measurements of lipid 

peroxidation; Ron Spoon and Kurt Hill for assistance during 

biomass/density and habitat assessments; and Mark Ellesieck 

and Darren Rhea for statistical assistance and graphics.

Methods

Aquatic Health

Assessing aquatic health of fisheries involved investigations that measured survivability of hatchery trout in instream 

experiments, measured fish biomass and density, assessed 

fish physiology, and statistical analysis of the data. Farag and 

others (2003) have provided more complete details of the 

methods described herein.

Survival Experiments

The survival of westslope cutthroat trout from the 

Washoe Park State Fish Hatchery, Anaconda, Mont., was 

determined with 96-hr in-situ experiments at five sites downstream from large inactive mine sites in Basin and Cataract 

Creek basins and in lower High Ore Creek (fig. 1) during 

low-flow conditions in 1998. We repeated the experiment in 

1999 and added a sixth site in upper High Ore Creek. This 

site was added because of its close proximity to the Comet 

mine site, where remediation efforts were underway (Gelinas 

and Tupling, this volume, Chapter E2). This site also was in 

close proximity to a native population of westslope cutthroat 

trout living upstream of the Comet mine. A site on the Little 

Boulder River (fig. 1, LBR), which lacked significant historical mine activity, was selected as a reference site.

Twenty Age-1 fish were placed at each site, with five fish 

in each of four 4-L polyethylene enclosures. We investigated 

the whole-body ion status of sampled fish during 1998 to 

determine if ionoregulatory failure due to elevated
Aquatic Health and Exposure Pathways of Trace Elements 377

concentrations of trace elements in the water column was the 

cause of death. During 1999, additional experimental fish were 

held at each site, and the tissues were processed by standard 

histological methods and examined by light microscopy.

Water quality was monitored at each site during the 96-hr 

survival experiments. Specific conductance, pH, and dissolved oxygen were measured onsite, and water samples were 

analyzed for total hardness and filtered and total-recoverable 

trace elements (Lambing and others, this volume, Chapter D7; 

Nimick and Cleasby, this volume).

Fish Biomass, Density, and Physiology

Five sites were selected to study resident fish population 

and physiology. The three tributary sites were upper Boulder 

River (UBR, reference site), lower Cataract Creek (LCC), 

and lower Basin Creek (LBC) (fig. 1). The two mainstem 

sites were the Boulder River downstream from Red Rock 

Creek (BRRC, reference) and downstream from Galena Gulch 

(BRGG). The differences in flow between the tributary and 

mainstem sites required that different methods be used to 

study populations in these two types of sites. Multiple-pass 

depletion was used to estimate populations in the smaller, 

tributary sites, and mark-recapture techniques were used to 

estimate populations in the mainstem sites (Zippen, 1958). 

Fish were collected by electrofishing. Total lengths and 

weights were recorded, and scales were collected to define the 

length at age.

Using methods described by Platts and others (1983), 

depth, velocity, substrate, and microhabitat features were 

measured at sites sampled for fish abundance. Weighted 

usable area was calculated from these parameters using the 

PHABSIM models (Platts and others, 1983). Calculated 

weighted usable area was used to differentiate the available 

habitat among sites. Suitability indices (SI) for all brook trout 

life stages were from Chapman (1995), rainbow trout fry SI 

values were from Raleigh and others (1984), and rainbow trout 

juvenile and adult SI values came from Ken Bovee (oral commun., 1997) for the South Platte River, Colo. Water-quality 

conditions were monitored periodically between October 1996 

and September 1999 at the five fish-health-assessment sites 

(Nimick and Cleasby, this volume).

Thirteen to twenty-five rainbow trout of 8 ± 1.7 inches 

(mean ± 1 a) and 0.20 ± 0.14 pounds were collected from 

each site for physiological analyses during low flow in 1997. 

Each fish was pithed, and a necropsy was performed immediately to define any gross abnormalities (for example, nodules 

on internal organs, discolored or frayed gills; Goede, 1989). 

Samples of gill and liver were dissected from each fish and 

immediately frozen with liquid nitrogen. Five additional rainbow trout (same size as preceding) were collected from each 

site and frozen for measurements of whole-body trace-element 

concentrations. At least five composite samples of each tissue 

from each site were prepared in the laboratory by combining tissues from two to five fish. To define the physiological 

condition of fish from the sites, concentrations of tissue trace

elements, products of lipid peroxidation, and metallothionein 

were measured in aliquants of the composite samples. Arsenic, 

cadmium, copper, lead, and zinc were measured in gills, livers, 

and whole fish (n > 5 for each tissue type). Quality control 

included measurements of predigestion spikes, postdigestion 

spikes, digestion replicates, and reference tissue samples.

Statistical Analyses

Data for tissue trace-element concentrations, metallothionein, products of lipid peroxidation, length at age, and 

fish biomass/density estimates were analyzed with one-way 

analysis of variance (SAS Institute, 1989). We tested the data 

for equality of variances with the Levene test after transforming the data when necessary. Means were compared using a 

Fischer least significant difference test with a statistical criterion of a = 0.05. We did not statistically analyze the survival 

data.

Exposure Pathways

We collected water, sediment, biofilm, and invertebrates 

from 12 sites within the Boulder River watershed (table 1) to 

examine the pathway of metals in abiotic and biotic components of streams. Five sites were on the mainstem Boulder 

River (UBR, BRRC, BRBC, BRCC, and BRGG) and seven 

sites were on tributaries (UBR, LHO, LCC, MCC, UCC, LBC, 

and JC; fig. 1). BRRC was a reference for the mainstem sites. 

Data from UBR (characteristics were similar to tributaries) 

and LBR were combined as a reference for the tributary sites. 

Once the boundaries of a site were established, we collected 

samples of biofilm and invertebrates at four riffle localities at 

the site (n = 4). Methods of sample collection and data analysis are summarized herein. A more complete description of 

these methods is in Farag and others (work in progress).

Water samples were collected periodically during 

1996-99 at all sites. Water temperature, specific conductance, 

pH, and streamflow were measured at the time of sampling 

(Nimick and Cleasby, this volume). Water samples were 

analyzed for total-recoverable (unfiltered) and filtered 

(0.45-|um pore-size) trace-element concentrations. We determined colloidal concentrations of trace elements in the water 

column indirectly by subtracting an ultrafiltered trace-element 

concentration (0. l-|um, or 10,000 Dalton, pore size) from a 

total-recoverable trace-element concentration. A composite 

sediment sample was collected at each site over a 100-150 ft 

reach by means of a plastic scoop (Church, Unruh, and others, 

this volume). We collected biofilm by gently scraping the surface of rocks collected from the near-shore streambed. Macroinvertebrates were sampled with a 3-mm mesh net attached to 

a 2 x 4-ft frame. The substrate in approximately 65 ft2 of riffle 

upstream from the net was overturned, and the dislodged macroinvertebrates were collected in the net. Fish were collected 

as described in the preceding section. (See "Fish Biomass, 

Density, and Physiology.")
378 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Statistics

Concentrations of trace elements measured in water, 

sediment, biofilm, invertebrates, gill, liver, and whole fish collected from the test sites were compared to concentrations in 

samples collected from the reference sites. Data from multiple 

reference sites were combined into one group and are referred 

to as the pooled reference (REF). Multiple reference sites 

were not sampled for gill, liver, and whole fish. Data for all 

sites were tested for homogeneity of variance and transformed 

when necessary. Under the assumption of equal variances, 

an Analysis of Variance (ANOVA) was performed to test for 

differences between means. If any difference was detected, 

Dunnett's one-tailed t-test (Dunnett, 1955) was used to make 

comparisons between each experimental site and the reference 

site for each trace element. Regressions also were performed 

to define correlations of trace-element accumulation among 

water, sediment, colloids, biofilm, and fish.

Results

Aquatic Health

Survival Experiments

Survival of caged westslope cutthroat trout at 96 hours 

was less at all test sites (table 1) than at the Little Boulder 

River reference site during 1998 and 1999 (fig. 2). Except survival at the lower High Ore Creek site, which was 33 percent 

during 1999, survival at 96 hr was 0 percent at all experimental sites during both years. In most cases, survival was affected 

in 24 to 48 hr during 1999. Fish died more quickly at Jack 

Creek and middle Cataract Creek during 1999 as compared 

to 1998. In the two most extreme cases, cutthroat trout placed 

in Uncle Sam Gulch and the Bullion Mine tributary died in 5 

and 8 hr, respectively, during 1999. Survival was reduced to 5 

percent at upper High Ore Creek at 72 hr, and the experiment 

at this site was ended at that time.

The concentrations of whole-body ions in fish in 1998 did 

not differ significantly among sites (reference site included).

1998 1999

n

Oh 24h 48 h 72 h 96h 

TIME

Oh 24h 48 h 72h 96h 

TIME

EXPLANATION 

QLBR

• BMT 

D JC

nusc

• MCC 

OLHO

• UHO - 1999 only

Figure 2. Survival of hatchery cutthroat trout placed in various tributaries of Boulder River for as long as 96 hr during 1998 and 1999.
Aquatic Health and Exposure Pathways of Trace Elements 379

Concentrations of ions ranged from 22,500 to 24,900 jag Ca/g, 

12,000 to 15,100 |ag K/g, and 2,050 to 3,180 jag Na/g, with the 

highest concentrations noted in fish from Uncle Sam Gulch. 

The histological analyses during 1999 indicated that degeneration (dying) and necrosis (death) of gill epithelia was the 

most significant tissue lesion. Excessive mucus production and 

hypertrophy (swelling) also were noted in gill epithelia of fish 

from the test sites (fig. 3). Spongiosis, a condition of edema 

and necrosis, was also observed in the nares (nasal sensory 

organ) of fish held in the test sites. Additionally, excessive 

mucus was noted in the skin of fish from all test sites. There 

was some hypertrophy in the gill lamellae and abundant mucus 

in the nares of fish held at the reference site, but these changes 

were less severe than those at the test sites. The proliferation 

of epithelial cells noted in gills of fish from both the upper 

and lower High Ore Creek sites indicates that toxicity was less 

acute at these sites, consistent with the longer times to death 

at these sites in 1999. Additionally, the pseudobranch offish 

from lower High Ore Creek contained cystic (fluid-filled) 

areas, an abnormal condition not noted at other sites. We noted 

dark longitudinal coloration in the skin at death for fish at the 

High Ore Creek sites. This discoloration was about 0.5 cm 

wide and was observed across the length of the fish. Correspondingly, an increased accumulation of melanocytes was 

noted in the skin of fish collected from lower High Ore Creek.

Water Chemistry—Survival Experiments

Water chemistry was variable in stream reaches where 

96-hr survival experiments were performed in 1998 and 1999. 

The onsite experiments were performed between mid-July and 

early August, but streamflow conditions were different each 

year. During the 1999 experiments, streams had low-flow conditions typical of late summer, whereas the 1998 experiments 

were conducted near the end of spring runoff. Streamflow 

was higher during the 1998 experiments, and trace-element 

concentrations generally were lower in 1998 than in 1999. In 

both years, almost all the cadmium and zinc was in the filtered 

(0.45 (am) fraction, and copper was divided about equally 

between the filtered and particulate phases. Therefore, filtered 

concentrations of cadmium, copper, and zinc are presented 

(table 2). Concentrations of arsenic and lead generally were 

low relative to concentrations of the other trace elements 

(<3 jag As/L except LHO and UHO with 22-33 jag As/L; 

<1 (ag/L for Pb/L except BMT with 3.1 jag Pb/L), and the data 

are not presented. The pH values were neutral to slightly basic 

(7.0-8.3) except for the site on Bullion Mine tributary, where 

pH was 5.2-5.4. The temperature range was 11°-2FC for all 

sites.

The relationship between trace-element concentrations 

and mortality followed a consistent pattern; higher concentrations resulted in greater and more rapid mortality. At the 

reference site on the Little Boulder River (LBR), hardness 

(48-56 mg/L) and trace-element concentrations (<0.3 jag 

Cd/L, 2 (ag Cu/L, 2-5 (ag Zn/L) were low. Water-quality conditions at this reference site were similar in 1998 and 1999.

However, streamflow was 4-8 times higher during the experiments in 1998 than in 1999 in the Jack and Cataract Creek 

drainages. Consequently, constituent concentrations were 

higher in 1999 at the four sites in these two drainages (BMT, 

JC, USG, MCC). In 1999, concentrations of cadmium, copper, 

and zinc were about 100 percent higher and hardness values 

were about 50 percent higher than the corresponding 1998 

levels at each site. Hardness measured generally higher at the 

two High Ore Creek sites (LHO and UHO 130-140 mg/L) 

compared to all other sites. Concentrations of trace elements 

were similar at the two sites on High Ore Creek in 1999 and 

somewhat higher at lower High Ore Creek in 1998 compared 

to 1999, apparently as a result of streamflow (table 2).

Results of hourly sampling in 1999 indicated that filtered 

zinc concentrations typically varied at many sites (Lambing and others, this volume). These variations resulted from 

normal diel concentration cycles and from the effect of storm 

runoff, which occurred during the toxicity experiments in Jack 

Creek in 1999. Diel cycles resulting in 2- to 3-fold changes 

in dissolved cadmium and zinc concentrations have been 

documented at several sites in and near the study area and are 

thought to be caused by the effect of water temperature and 

pH on the partitioning of cadmium and zinc between dissolved 

and sorbed phases (Fuller and Davis, 1989; Lambing and others, this volume). Therefore, a wide range of concentrations 

may occur daily at each site.

Fish Biomass and Density Estimates

Of the three tributaries studied, the combined biomass 

of all species of trout observed (on either an areal or a lineal 

basis) was the smallest at the lower Cataract Creek site 

(table 3). There were 12 ± 3.5 Ib/acre at lower Cataract Creek 

versus 60±4.9 Ib/acre at the upper Boulder River site and 

37±1.9 Ib/acre at the lower Basin Creek site. Brook and rainbow trout were the two trout species found in the tributaries; 

brook trout were the most common species of fish at the upper 

Boulder River site, whereas rainbow trout were the most common species of fish present at the lower Cataract Creek site. 

However, both species were present in about equal numbers in 

lower Basin Creek. The species composition in lower Cataract 

Creek and lower Basin Creek seemed to generally reflect the 

composition of the nearest mainstem sites; the Boulder River 

site near Red Rock Creek had a similar composition to that 

in lower Basin Creek, and the Boulder River site near Galena 

Gulch was similar to that in lower Cataract Creek. Although 

there was a trend of less biomass at the Boulder River site 

near Galena Gulch (BRGG) compared to the reference site 

upstream from the affected study reach (BRRC), the difference 

was not significant (table 3). There were no significant differences among lengths at age calculated from scales of rainbow 

trout samples from the three tributary sites (fig. 4), nor was 

there a difference in length at age between fish sampled from 

the mainstem sites (data are not presented). The observations 

for density (number per 1,000 ft) have the same pattern as 

biomass results for all sites (table 3).
380 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Figure 3. Gill tissue of trout held during the 1999,96-hr survival experiment. A, Gill section of a cutthroat trout held at Little Boulder 

River site (reference). Section is 5 urn thick, stained with hematoxylin and eosin, x 250. B, Gill section of a trout held at Middle Cataract 

Creek site. Top arrow points to hypertrophied cells; bottom arrow points to degenerate epithelial cell. Section is 5 urn thick, stained with 

hematoxylin and eosin, x 250. C, Gill section of a trout held at upper High Ore Creek site. Arrow points to excessive mucus. Section is 

5 urn thick, stained with hematoxylin and eosin, x 250.
Aquatic Health and Exposure Pathways of Trace Elements 381

Table 2. Physical and chemical data for stream sites during the 96-hour survival experiments.

[Trace-element concentrations are for filtered samples; median values are listed when multiple samples were collected 

during an experiment]

Site 

(%1)

LBR - Reference

BMT

JC

USG

MCC

UHO

LHO

Sample 

date

7/21/98

8/2/99

7/21/98

8/2/99

8/3/99

7/21/98

8/2/99

7/21/98

8/2/99

8/4/99

7/21/98

8/2/99

8/4/99

8/3/99

7/21/98

8/2/99

Cadmium

(ug/D

<0.3

<0.3

20

38

35

3.4

8.0

22

75

59

4.4

9.6

9.3

2.5

3.7

2.0

Copper

(ug/L)

2.0

2.4

113

557

314

33

51

84

377

206

34

48

48

3.7

5.0

3.6

Zinc 

(ug/L)

2.0

2.5

2,160

3,970

3,920

377

656

1,830

5,730

4,840

391

714

651

550

987

459

pH (standard 

units)

7.9-8.1

8.0-8.2

7.4

5.2-5.4

5.9

7.7-7.8

7.0-7.4

7.6

7.3

7.5

7.8-8.2

7.9

7.8-7.9

8.2

8.1-8.3

8.1-8.3

Hardness 

(nig CaCtyL)

48

56

39

66

-

29

44

41

-

63

36

-

48

140

130

140

Streamflow

(tf/s)

6.4

2-.5

1.1

0.02

-

32.5

1.1

4.9

-

0.71

20.5

-

4.6

0.35

1.8

0.71

Fish species observed at the five fish-abundance sites 

during 1997-99 included three native species (longnose sucker 

Catostomus catostomus, mottled sculpin Cottus bairdi, and 

mountain whitefish Prosopium williamsoni) and four nonnative species (Yellowstone cutthroat trout, rainbow trout 

Salmo gairderi, eastern brook trout Salvelinusfontinalis, and 

brown trout Salmo truttd). The mainstem sites had a greater 

number of species than did the tributary sites. Most of the 

brown trout and mountain whitefish captured in the mainstem 

(in 1998 and 1999) were in spawning condition and may have 

migrated from sites farther downstream. Mottled sculpin were 

found at the upper Boulder and the lower Basin Creek tributaries, and mountain whitefish were found at lower Basin Creek. 

Neither mottled sculpin nor whitefish were found at lower 

Cataract Creek. None of the rainbow, cutthroat, or brook trout 

collected from the tributary sites appeared to be spawning.

Habitat Characterization of Fish Abundance Sites

The habitat of the tributary sites differed in many ways. 

The lower Cataract Creek site had a higher stream gradient 

(2.7 percent) than the other tributary sites (2.0 and 1.1 percent 

for UBR and LBC, respectively) as well as a higher percent of 

habitat described as riffles (94 percent as compared to 

70 percent for UBR and 60 percent for LBC). Lower Cataract 

Creek had the widest bankfull channel width (80 ft) and a corresponding lower mean depth and velocity than the other sites.

All sites were similar in having a fair amount of canopy cover 

(13.4-19.8 percent), little woody debris (0.1-1.4 percent), low 

levels of embeddedness (1.3-1.4 percent), and small amounts 

of undercut bank (1-4 percent) or overhanging vegetation 

(1-4 percent). For the mainstem sites, the Boulder River near 

Galena Gulch had a much higher percentage of riffles 

(84 percent) than the Boulder River near Red Rock Creek 

(38 percent), even though the Boulder River near Galena 

Gulch site had a slightly lower gradient (0.8 percent vs. 

1.2 percent). Both sites were characterized as having no pool 

habitat, and the sites were also similar in the amount of canopy 

cover, woody debris, embeddedness, bank cover, undercut 

banks, and overhanging vegetation. Mean velocity at the Boulder River near Red Rock Creek site was slightly higher 

(1.04 ft/s) than that at the Boulder River near Galena Gulch 

(0.99 ft/s). Boulder River near Galena Gulch is a larger stream, 

having a bankfull channel width of 114 ft, compared to only 

68.6 ft for the Boulder River near Red Rock Creek. Microhabitat was quantified in terms of weighted usable area from 

one set of measurements taken along 10 or 11 transects at each 

site in late September-early October 1998. Large amounts of 

available habitat are reflected by large amounts of weighted 

usable area. Therefore, observed excessive differences in 

weighted usable area among sites would suggest that habitat is 

responsible for differences in biomass/density estimates. For 

both brook and rainbow trout, the weighted usable area in the 

tributaries was greatest in lower Basin Creek for fry and
382 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 3. Size ranges and biomass/density estimates of brook, rainbow, and cutthroat trout in tributaries and 

mainstem of the Boulder River.

[The estimates were performed during late July (1997) and early October (1998 and 1999), and numbers are reported with standard 

error in parentheses; "*" indicates significant difference from reference atp = 0.05]

Site(fig.l)

Size range 

(inches) No./1,000ft No./acre Pounds/acre

Tributaries

UBR - Reference 

1997

1998

1999

Mean

LBC 

1997

1998

1999

Mean -

LCC 

1997

1998

1999

Mean

2.7-12.4

2.0-9.6

2.4-10.2

1.6-13.2

2.0-10.5

1.7-11.1

2.7-8.3

1.4-8.6

3.3-8.6

214 (53)

212.4(19)

325 (19)

144 (23)

210(8)

381(13)

41 (14)

142 (12)

94(3)

551 (137)

547 (49)

837 (50)

645 (96)

404 (63)

591 (22)

1,070(35)

688 (198)

74(25)

257 (21)

171 (5)

167 (152)*

57(13)

53 (4.6)

70 (4.0)

60.0 (4.9)

55 (7.7)

55 (2.8)

61 (1.9)

56.8 (1.9)

5.2(1.8)

14(1.2)

17 (0.5)

12 (3.5)*

Boulder River

BRRC - Reference

1998

1999

Mean

4.2-11.8

3.9-12.5

148 (30)

219(15)

275 (18) (37)

180(37)

227 (48)

31 (6.1)

50 (5.4)

40 (9.3)

BRGG

1998

1999

Mean

4.2-12.6

4.3-13.8

177(10)

227 (17)

200(15)

156 (9)

178 (22)

19(1.1)

27 (2.5)

225 (4.2)

juveniles, and greatest for adults in upper Boulder River. 

Lower Cataract Creek had the lowest weighted usable area 

for each life stage (table 4). In the mainstem, weighted usable 

area for juveniles and adults was greatest for both species in 

Boulder River near Galena Gulch, but the weighted usable 

area for fry was greatest for both species at Boulder River near 

Red Rock Creek.

Water Chemistry—Resident Fish Biomass/Density and 

Health

Data from water samples collected in 1996-97 at the five 

biomass/density and fish-health sites indicated that filtered 

and total-recoverable concentrations of Al, Sb, As, Ba, Be, Cr, 

Co, Fe, Mn, Hg, Mo, Ni, U, Ag, and U (Nimick and Cleasby, 

this volume) were either less than method-detection levels or 

less than concentrations established by the U.S. Environmental

Protection Agency (1999, 2001) to protect aquatic life. In contrast, concentrations of Cd, Cu, Pb, and Zn (table 4) frequently 

were elevated at sites downstream of the historical mining 

activity (LBC, LCC, and BRGG).

Trace-element concentrations generally were low 

(table 5) during all flow conditions at the sites (UBR and 

BRRC) upstream of historical mining activities. At Boulder River near Red Rock Creek, concentrations of copper 

exceeded the acute and chronic aquatic-life standard in 2 of 

4 samples measured for filtered and 6 of 10 samples measured 

for total-recoverable copper during high flow. Some totalrecoverable lead concentrations also exceeded the chronic 

but not acute aquatic-life standard at Boulder River near 

Red Rock Creek. Trace-element concentrations were higher 

at the other three sites. The highest concentrations of trace 

elements occurred at the lower Cataract Creek site, where
Aquatic Health and Exposure Pathways of Trace Elements 383

240

220

200

<£ 180

LJJ 

LJJ

| 160

^ 140

i—

CD

S 120 

_i

o 100 i—

80

60

40

EXPLANATION

-•- Upper Boulder River (UBR)

-O- Lower Basin Creek (LBC) 

~V~ Lower Cataract Creek (LCC)

1.0 2.0 3.0 

AGE (YEAR)

4.0

Figure 4. Comparisons of growth of trout in three tributaries in Boulder River watershed. Means are 

presented as symbols and ± standard deviations are represented with bars.

filtered cadmium, copper, and zinc concentrations exceeded 

acute standards in every sample. Filtered zinc concentrations 

also exceeded acute standards in all samples from lower Basin 

Creek and Boulder River near Galena Gulch. Concentrations 

of cadmium and copper frequently exceeded standards during

high flow at these two sites and at Boulder River near Galena 

Gulch during low flow as well.

Concentrations of filtered cadmium and zinc at the lower 

Cataract Creek site were similar to concentrations associated with mortality in the 96-hr survival experiments. Median 

concentrations (table 5) at this site were higher than at middle

Table 4. Weighted usable area (ft2 WUA) per 1,000 ft2 of stream for brook and rainbow trout fry, juveniles, 

and adults.

[WUA based on the product of suitability index values for depth, velocity, and substrate; Fry (<2 inches), Juveniles (2-8 inches), 

and Adults (>8 inches)]

Site 

(fig.D

UBR

LBC

LCC

BRRC

BRGG

Fry

4.6

5.2

4.5

4.1

2.2

Brook trout

Juvenile

5.6

5.6

5.6

2.5

2.5

Adult

27.2

25.7

19.7

14.5

21.3

Fry

20.6

23.6

17.8

12.4

18.1

Rainbow trout

Juvenile

9.6

15.6

8.6

16.0

23.3

Adult

3.7

3.1

2.1

5.3

6.0
TableS. Physical and chemical data for stream sites where fish health was assessed. Boulder River watershed, Montana, 1996-99.

[Median filtered (flit.) and total-recoverable (total) trace-element concentrations are listed, and n represents the number of samples collected on different dates throughout the flow 

Site 

(fig.D

UBR 

BRRC 

LBC 

LCC 

BRGG

UBR 

BRRC 

LBC 

LCC 

BRGG

n

2 

10 

10 

11 

11

2 

8 

7 

7 

8

Streamflow

(fe/s)

14-81 

106-724 

14-251 

14-170 

177-1,049

4-4 

7-25 

4-7 

4-7 

18-35

pH

7.6-8.1 

7.6-8.2 

7.0-8.0 

6.8-8.0

7.5-8.2

8.0

7.4-8.3 

7.5-8.2 

7.5-8.3 

7.7-8.5

Hardness 

(mg/L as 

CaC03)

21-38 

22-50 

12-35 

18-54 

19-48

52-53 

54-61 

39-42 

59-69 

61-68

Filtered trace-element concentration, median (ng/L)

Arsenic Cadmium

Total

4.0 

5.5 

11 

17 

12

2.5 

3.0 

7.0 

4.8 

6.0

Filt. Total

High-flow conditions

2.5 <1 

3.3 <1 

4.0 <1 

3.4 1.8 

4.0 <1

Low-flow conditions

2.0 <1 

2.4 <1 

4.0 <1 

3.0 5.0 

5.0 <1

Filt.

<0.3 

<0.3 

0.4 

1.3 

0.3

<0.3 

<0.3 

0.4 

4.9 

0.8

Copper Lead

Total

3 

5 

12 

46 

20

1.5 

1.4 

4.0 

24 

10

Filt. Total Fi

1.5 <1 < 

3.3 1.1 < 

8.7 2.6 < 

33 6.7 < 

11 5.9 <

1.7 <1 < 

3.0 <1 < 

22 <1 < 

9.0 <1 <
Cataract Creek and Jack Creek during the 1998 experiments 

in which 100 percent mortality was observed at 96 hr. Filtered 

trace-element concentrations at the other four fish-assessment 

sites during low flow were considerably less than the concentrations associated with mortality in the survival experiments 

(tables 2 and 5).

Tissue Trace Elements

Concentrations of most trace elements in the livers of 

resident rainbow trout were greatest in fish from lower Cataract Creek (table 6). Concentrations in the livers of rainbow 

trout from lower Cataract Creek were higher than 1,000 jug 

Cu/g, 60 ug Cd/g, and 13 jug As/g (dry wt). Concentrations of 

trace elements in the livers of fish from lower Basin Creek and 

Boulder River near Galena Gulch also were elevated above 

those measured at the reference sites (UBR and BRRC). In 

general, the pattern of metal accumulation in livers was LCC 

> LBC > BRGG > BRRC > UBR (table 6). In an exception to 

this pattern, the greatest concentration of lead was in fish from 

Boulder River near Galena Gulch.

The pattern of trace-element concentrations in livers was 

similar to the pattern in gills (table 6). The greatest concentrations of copper, cadmium, and zinc were in the gills of fish 

from lower Cataract Creek (>20 jug Cu/g, >60 |jg Cd/g, and 

>700 jug Zn/g) (table 6). Whereas lesser concentrations of copper and greater amounts of zinc occurred in the gill compared

Aquatic Health and Exposure Pathways of Trace Elements 385

to the liver, the concentrations of cadmium in livers and gills 

of fish from lower Cataract Creek were nearly identical. As 

was noted for liver, the greatest concentrations of lead were in 

gills from fish at Boulder River near Galena Gulch. However, 

unlike liver, there was no significant accumulation of arsenic 

in the gills.

The pattern of trace-element accumulation described for 

livers and gills was similar in whole fish. Again, the greatest 

concentrations of most trace elements in whole fish were in 

samples from lower Cataract Creek, where 22 jag Cu/g, 

4.9 jug Cd/g, and 8 jug As/g were measured (table 6). Although 

less cadmium was observed in the whole body versus liver 

and gill, the mean cadmium concentration in whole fish from 

lower Cataract Creek was 4.9 ^ig/g. There was no significant 

accumulation of lead in whole fish.

Metallothionein

Physiological malfunction can be defined with measurements of metallothioneins and products of lipid peroxidation 

(Farag and others, 1994, 1995). These measurements have 

been associated with reduced growth in laboratory experiments (metallothioneins: Dixon and Sprague, 1981; Roch and 

McCarter, 1984; Marr and others, 1995; lipid peroxidation: 

Woodward and others, 1995) and with exposure to trace elements (metallothioneins: Dixon and Sprague, 1981; Roch and

Table 6. Mean trace-element concentrations in fish, 1998.

[Means followed by the same letter (within a tissue) are not significantly different at p = 0.05; standard error of the mean is in parentheses]

Trace-element concentration, mean (ug/g dry weight)1

Site(fig.l) Arsenic Cadmium Copper Lead Zinc

Gill

UBR

LBC

LCC

BRRC

BRGG

2.7 (0.4)a

3.1 (0.5)a

2.8 (0.4)a

1.3 (0.4)b

1.3(0.04)b

0.79 (0.04)a

30.1 (0.2)b

71.4 (3.9)c

3.2(1.6)a

25.7(1.2)b

5.6 (1.9)ab

7.7 (0.1 )b

21.5 (1.9)c

4.3 (0.1)a

5.6 (0.2)ab

0.3 (0.9)a

1.2(0.1)b

1.3 (0.1 )bc

0.4 (0.2)a

1.7 (0.2)c

667 (162)a

845 (148)abc

744 (103)abc

404 (89)b

1,070 (179)c

Liver

UBR

LBC

LCC

BRRC

BRGG

2.7 (0.3)a

7.2(1.0)b

13.8 (0.5)c

2.0 (0.4)a

4.8 (0.4)d

1.5 (0.2)a

29.2 (2.3)b

70.6 (4.9)c

7.1 (2.4)a

20.7 (2.7)d

125 (22)a

488 (83)b

1,010 (100)c

319 (106)a

548 (74)d

0.60 (0.01)a

0.29 (0.03)b

0.37 (0.03)b

0.09 (0.03)a

0.54 (0.08)c

110(3)

174 (3)

262(13)

126 (8)

204 (14)

Whole fish

UBR

LBC

LCC

BRRC

BRGG

1.7(0.6)ac

6.0(1.7)*

8.0(1.2)b

0.9(0.1)c

3.5 (1.0)abc

0.15(0.01)a

2.7 (0.4)b

4.9 (0.3)c

0.16(0.02)a

2.4 (0.3)b

5.2 (0.2)

13(1.1)

22(2.1)

7.7 (0.8)

14.3 (0.7)

<0.25

2.1(1.1)

1.2 (0.28)

0.26 (0.01)

0.88 (0.05)

104 (4.4)

318(24)

353 (9.8)

105 (8.1)

309 (28)

'Different letters designate a significant difference among sites atp<0.05 within a trace element for mainstem and tributaries.
386 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

McCarter, 1984; Marr and others, 1995; lipid peroxidation: 

Wills, 1985; Stern, 1985; DiGiulio and others, 1989).

Metallothioneins are proteins that bind metals, such as 

copper, cadmium, and zinc (Hogstrand and Haux, 1991; Stegeman and others, 1992). Because metallothionein synthesis 

and concentrations increase when fish are exposed to metals, 

the induction of these proteins indicates metal exposure in 

fish. The induction of metallothioneins in trout also has been 

associated with slowed growth of trout that maintain induced 

metallothionein concentrations (Marr and others, 1995). 

Therefore, elevated metallothionein concentrations also may 

indicate reduced fitness of trout.

Concentrations of metallothionein were greatest in the 

livers of rainbow trout from lower Cataract Creek (921 fig/g). 

The mean concentration of metallothionein in livers of fish 

from lower Cataract Creek was significantly greater than that 

in livers of fish from the reference site on the upper Boulder 

River (UBR, table 7). A trend toward greater metallothionein 

appeared in livers of fish from lower Basin Creek compared to

Table 7. Metallothionein concentrations in gill and 

liver samples of resident rainbow trout, 1997.

[Values are reported as mean with 2 CT error in parentheses; means 

followed by the same letter (within a tissue) are not significantly 

different atp = 0.05; n = 5 for all sites except BRGG, where n = 6; 

metallothionein concentration in |ag/g wet weight]

Metallothionein (ug/g)

Site(fig.l)

Tributaries

UBR - Reference

LBC

LCC

Boulder River

BRGG - Reference

BRGG

Gill

9.37ab (0.63)

7.61a (1.00)

12.0b (1.18)

12.4b (0.52)

11.1* (1.15)

Liver

31.2a ( 7.70)

597ab (289)

92 l b (216)

271 ab (195)

293* ( 60.5)

the reference site, but this finding was not significant. The gills 

generally had small concentrations of metallothionein, and 

concentrations in gills measured at lower Basin Creek were 

less than those collected from lower Cataract Creek and Boulder River near Galena Gulch. Concentrations of metallothionein in livers or gills of fish from the mainstem sites (BRRC 

and BRRG) showed no significant differences.

Lipid Peroxidation

Elevated concentrations of products of lipid peroxidation 

indicate cell death and tissue damage (Farag and others, 1995). 

Cell membranes are composed of polyunsaturated fatty-acid 

side chains and generally have a fluid composition. However, 

these side chains are targets of lipid peroxidation, a process 

that changes the structural integrity of the cell membrane and

may ultimately result in cell death and tissue damage (Halliwell and Gutteridge, 1985; Wills, 1985). Trace elements 

that exist in more than one valence state, such as copper, may 

initiate lipid peroxidation (Wills, 1985). Trace elements may 

also initiate lipid peroxidation because they inhibit antioxidant enzymes such as glutathione peroxidase and transferase 

(Reddy and others, 1981). The amounts of products of lipid 

peroxidation measured with 340-nm excitation in the livers 

of rainbow trout from lower Cataract Creek were significant 

compared to amounts measured in livers of rainbow trout 

from upper Boulder River (table 8). No difference in the mean 

amount of products of lipid peroxidation was found in livers 

of fish from the two mainstem sites (BRRC and BRGG). 

There was no significant difference in lipid peroxidation in 

the gills of fish among tributary or mainstem sites. Products of 

lipid peroxidation also were measured with 360-nm excitation. Although a trend appeared of increased products of lipid 

peroxidation measured with 360-nm excitation, the difference 

was not significant (data not presented).

Exposure Pathways

Water

In stream water, concentrations of arsenic and lead 

were greatest at lower High Ore Creek (table 9, total recoverable of 64 u.g/L and 54 u.g/L respectively) during high 

flow. Copper concentrations also were greater at most sites 

during high flow, although the highest total-recoverable 

concentrations at any site occurred during low flow at Jack 

Creek (140 fig/L). Unlike arsenic and lead, the concentrations 

of cadmium and zinc were greater during low rather than high

Table 8. Lipid peroxidation of tissues sampled from 

resident rainbow trout, 1997.

[Values are reported as mean with 2 CT error SEM in parentheses; 

means followed by the same letter (within a tissue) are not 

significantly different atp = 0.05; n - 5 for all sites except 

site BRGG, where n = 6]

Site 

(fig.D

Tributaries

UBR - Reference

LBC

LCC

Boulder River

BRRC - Reference

BRGG

Relative intensity1

Gill

73. l a (8.19)

66.4a (6.91)

73. 8a (3.77)

79.2a (6.57)

73. l a (4.09)

Liver

114a (5.31)

115- (H.7)

141b ( 7.28)

125ab (11.9)

127ab ( 4.63)

'Note: Lipid peroxidation is expressed as the fluorometric measurement 

(relative intensity) of a chloroform extract of tissue. The relative intensity 

was measured at 340-nm excitation and 435-nm emission when 0.05 ng/mL 

of quinine sulfate measured 322 with settings to measure gill and 136 with 

settings to measure liver (Farag and others, 2003). Different letters designate 

a significant difference among sites atp<0.05 within a trace element for 

mainstem and tributaries.
Table 9. Median trace-element concentrations in water, 1996-99.

[n = number of samples collected on different dates throughout the flow condition; Tot = total recoverable concentration; Filt = concentration in 0.45-(j,m filtrate; RE

for LBR and UBR site and REF 2 = BRRC]

Site 

(fig.D

n

Streamflow 

(ftVs)

Hardness 

(mg/L 

CaC03)

Trace-element concentration, median (pg/L)

Arsenic

Tot Filt

Cadmium

Tot Filt

Copper

Tot Filt

Lead 

Tot Filt 

High-flow conditions

Tributaries

Ref 1

Mainstem

Ref 2

LBR

UBR

LHO

LCC

MCC

UCC

LBC

JC

BRRC

BRBC

BRCC

BRGG

2

2

15

11

7

6

10

6

10

2

2

11

69-94

15-83

1.8-6.8

13-168

17-186

15-121

15-251

4.4-35

106-725

94-436

106-513

175-1,050

19

21-38

74-150

18-54

18-37

17-37

12-35

19-38

22-50

24-47

24-47

19-48

6.0 3.0

4.0 2.5

64 13

17 3.4

15 3.0

3.5 2.3

12 5.2

32 3.0

5.4 3.3

7.0 4.4

8.2 4.1

12 4.0

<1 <0.1

<1 <0.3

4.9 2.4

1.8 1.3

3.3 2.3

<1 <0.3

5.2 .5

3.5 3.2

<1 <0.3

<1 <0.3

<1 .4

<1 .3

6.5

3

17

46

62

8.9

14

59

5.0

9.2

15

23

2.0

1.5

5.8

33

33

7.2

10

32

3.3

7.2

11

12

3.0

<1

54

6.7

13

3.0

4.7

9.6

1.2

1.9

2.5

8.5

<1 

<1 

<1 

<1 

<1 

<1 

4.7 

<1 

<1 

<1 

<1 

<1 

Low-flow conditions

Tributaries

REF1

Mainstem

REF 2

LBR

UBR

LHO

LCC

MCC

UCC

LBC

JC

BRRC

BRBC

BRCC

BRGG

6

2

8

8

5

4

8

4

9

2

2

9

2.4-6.3

2.3-3.8

0.52-1.3

1.9-5.4

3.6-4.6

2.8-5.0

3.1-5.8

.86-1.2

8.6-25

25-28

26-33

17-36

37-56

52-53

140-170

59-69

48-57

43-52

39-42

44-51

54-61

55-59

57-60

61-68

2.0 2.0

2.5 2.0

33 17

4.0 3.1

3.5 2.0

2.7 2.4

7.1 4.6

18 1.9

3.0 2.5

4.0 3.5

4.2 3.7

6.0 5.0

<1 <0.1

<1 <0.3

4.5 3.9

5.0 4.7

9.4 8.9

<1 .3

<1 .4

12 11

<1 <0.3

<1 <0.3

<1 .6

<1 .8

5.0

1.5

4.6

24

82

4.6

4.1

140

1.4

9.4

12

10

2.0

<1

3.1

20

53

4.5

3.0

69

1.6

7.9

9.2

8.9

<1

<1

6.8

<1

2.0

<1

<1

4.1

<1

<1

<1

<1

<1 

<1 

<1 

<1 

<1 

<1 

<1 

<1 

<1 

<1 

<1 

<1 
388 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

flow. Zinc concentrations were greatest at lower High 

Ore Creek during low flow (1,970 ug/L) (table 9). The 

greatest concentrations of cadmium were measured at Jack 

Creek (12 ug Cd/L) and middle Cataract Creek (9.4 ug Cd/L) 

during low flow. The pH ranged from 7.0 to 8.5 at all sites 

regardless of flow (Nimick and Cleasby, this volume).

Colloids

The presence of colloids in the water column is indicated 

most clearly by the high concentration of colloidal iron 

(table 10) and, to a lesser extent, aluminum (data not presented) at most sites including the reference sites. These data 

support the conclusion of Church, Unruh, and others (this 

volume) that, based on an analysis of suspended sediment 

collected during high flow in 1997, much of the sediment in 

watershed streams is iron oxyhydroxide colloidal material. 

This colloidal material has a large capacity for sorbing trace 

elements, and the degree of metal enrichment varies among 

sites.

The general pattern of partitioning of trace elements 

between dissolved (0.001 um) and colloidal fractions in the 

water column depended primarily on the trace element and, 

to a lesser extent, on the proximity of the sampling site to a 

source of trace elements. Almost all iron and lead were present in the colloidal fraction, whereas cadmium and zinc were 

primarily dissolved. Large amounts of arsenic and copper also

partitioned to the colloidal phase, but unlike lead, arsenic and 

copper also existed in the dissolved phase.

The spatial pattern of colloidal trace-element concentrations generally was the same as for trace-element concentrations in water and sediment in that the highest colloidal 

concentrations were directly downstream from inactive mines. 

Trace-element-rich acidic water draining from mines in the 

Boulder watershed study area is neutralized in mixing zones 

in streams, producing substantial loads of metal-rich colloids 

rich in trace elements. These colloids then can be transported 

long distances downstream (Kimball and others, this volume, 

Chapter D6). Substantial colloid loads occurred in the Bullion 

Mine tributary (BMT) and Jack Creek (JC) downstream from 

the Bullion mine, in Uncle Sam Gulch (USG) and Cataract 

Creek (MCC) downstream from the Crystal mine, and in High 

Ore Creek (UHO and LHO) downstream from the Comet mine 

(table 10). For the 12 main sampling sites, the highest concentrations of colloidal trace elements were at lower High Ore 

Creek (0.5 ug/L Cd, 8.2 ug/L Pb, and 322 ug/L Zn) and Jack 

Creek (24 ug/L As and 74 ug/L Cu). Concentrations 

at sites nearer inactive mines (BMT, USG, and UHO) were 

even higher, and often exceeded 1 mg/L for iron and zinc 

(table 10). Colloidal concentrations of arsenic, copper, lead, 

and zinc increased in the Boulder River in a step-wise downstream pattern as each of the three mining-affected tributaries 

entered the mainstem.

Table 10. Mean trace-element concentrations in colloids and ultrafiltrates during low-flow conditions, 1996-98.

[Dis = dissolved concentration in ultrafiltrate; Col = concentration in colloidal fraction; REF 1 = pooled value for LBR and UBR site; REF 2 = BBRC; 

*, ancillary sampling site near an inactive mine]

Site 

(fig.D

Tributaries 

LBR

REF 1 UBR

LHO

LCC

MCC

UCC

LBC

JC

BMT*

USG*

UHO*

Mainstem

REF 2 BRRC

BRBC

BRCC

BRGG

Trace-element concentration, mean (ug/L)

n

2

3

3

3

4

3

3

3

3

3

1

2

3

3

3

Arsenic 

Dis Col

<3

2.6

14

3.2

<3

<3

5.6

<3

<1

<1

8

3.6

4.4

4.5

5.0

1.0

1.4

14

2.2

3.5

1.5

4.6

24

27

6

102

1.5

1.2

1.5

7.0

Cadmium 

Dis Col

0.1

<0.1

4.2

4.0

6.5

0.3

0.4

9.0

45

43

6

<0.1

0.2

0.5

0.7

0.4

<0.3

0.5

<0.3

<0.3

0.2

0.1

0.3

1

1

<0.3

0.4

0.4

<0.3

0.3

Copper 

Dis Col

2.5

<1

2.5

16

27.5

5.3

5.1

41

469

141

1

2.5

8.4

10

8.0

<3

1.2

3.2

15

38

<1

2.6

74

87

256

9

<2

1.2

2.8

8.7

Iron 

Dis Col

<50

<50

<50

<50

<50

<50

<50

33

748

<10

<1

48

39

<50

<50

225

193

197

95

204

135

107

857

1,940

196

1,600

490

316

270

283

Lead 

Dis Col

0.4

0.4

0.5

0.3

0.5

0.3

0.1

0.5

2

0.5

<1

0.3

0.3

0.4

0.5

<!

<1

8.2

1.2

1.7

<1

1.8

4.5

13

8

44

0.4

0.2

0.1

0.6

Zinc 

Dis Col

<2

<2

1,750

329

546

56

54

942

5,000

3,520

4,390

2

35

65

112

<10

<10

322

22

73

5

11

88

270

350

710

3

5

15

41
Aquatic Health and Exposure Pathways of Trace Elements 389

Sediment

In streambed sediment, the concentrations of all trace 

elements except copper were highest at lower High Ore Creek 

(740 ng As/g, 14 ng Cd/g, 1,100 ng Pb/g, and 3,400 ng Zn/g) 

(table 11). The concentrations of arsenic, cadmium, and zinc 

in Cataract and Basin Creeks were 2 to 5 times less than 

concentrations in lower High Ore Creek but were still much 

higher than the concentrations at the reference site on the 

upper Boulder River (UBR). The concentrations of cadmium 

were similar in Cataract Creek (9.3 jig/g at MCC and 11 jig/g 

at LCC) compared to lower High Ore Creek. The highest copper concentrations were in Cataract Creek (450 |ig/g at MCC, 

440 ng/g at LCC) followed by Jack Creek (180 |ig/g at JC) and 

High Ore Creek (140 ng/g at LHO).

In the Boulder River, trace-element concentrations in 

sediment generally were less than in the tributaries. However, concentrations of all trace elements, except cadmium at 

BRBC, were greater at the three downstream mainstem sites 

compared to the reference site (BRRC). For instance, arsenic 

concentrations were 99 jig/g at Boulder River near Galena 

Gulch, far higher than the 8.3 ng/g measured at Boulder River 

near Red Rock Creek upstream from the area of historical 

mining.

Biofilm

Trace-element concentrations in biofilm decreased at 

sites farthest downstream from historical mining areas 

(table 12). The greatest concentrations of cadmium, copper, 

and lead were in Jack Creek (all data presented as |ig/g±a; 

70±5; 4,620±860; 885±84 respectively) followed by middle 

Cataract Creek (60±22; 1,940±850; 660±150 respectively), 

then lower High Ore Creek (41±3; 321±9; 1,100±30 respectively). The concentrations of these trace elements decreased 

substantially downstream in Basin Creek (LBC) but were still 

18-23 times greater than the concentration for the combined 

reference (REF 1) used for the tributary sites. Concentrations 

of these trace elements in biofilm were significantly less at 

lower Cataract Creek compared to the middle Cataract Creek 

site. However, the downstream site in Cataract Creek (LCC) 

yielded elevated concentrations of trace elements compared to 

the combined reference. Biofilm from upper Cataract Creek 

(UCC) had concentrations of trace elements less than those 

of lower Cataract Creek but greater (though not significantly) 

than the combined reference. The concentrations of cadmium 

and lead but not copper were significantly elevated in biofilm 

from lower High Ore Creek compared to the combined 

reference.

Table 11. Leachable trace-element concentrations in composite streambed sediment, 1998.

[REF 1 = pooled value for LBR and UBR site and REF 2 = BRRC]

Site 

(fig.D

Tributaries LBR 

UBR

Arsenic Cadmium Copper 

(ug/g) (ug/g) (ug/g)

20 < 

13 <

:1 13 

:1 7.8

Lead

(ug/g)

26 

10

Zinc

(ug/g)

100 

40

REF1 17 <1 10 18 70

LHO

LCC

MCC

UCC

LBC

JC

Mainstem BRRC 

REF 2

BRBC

BRCC

BRGG

740

580

250

96

140

330

8.3

20

55

99

14

11

9.3

3.0

3.9

4.2

<1

<1

3.2

2.8

140

440

450

110

98

180

16

38

110

84

. 1,100

390

280

220

150

190

13

27

80

99

3,400

1,300

930

440

640

490

74

180

430

490
390 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Biofilm from lower High Ore Creek had the greatest concentrations of arsenic and zinc (all data presented as 

ug/g±a, 3,300±400 and 18,100±1,700 respectively) followed 

by Jack Creek (2,600±170 and 6,210±170 respectively) and 

middle Cataract Creek (1,700±700 and 6,000±2,240 respectively). Concentrations of arsenic and zinc decreased farther 

downstream at lower Cataract Creek and lower Basin Creek 

but were still greater than 26 times the concentrations at the 

reference site.

Elevated concentrations of trace elements persisted in 

the mainstem of the Boulder River. The arsenic concentration 

in biofilm at Boulder River near Galena Gulch was 262 ug/g. 

The zinc concentrations at Boulder River near Galena Gulch 

were similar to the concentrations measured at lower Cataract 

Creek (3,200±250 versus 3,870±420), although the concentrations of arsenic in biofilm from the mainstem downstream 

from Cataract Creek (BRCC) were less than that from lower 

Cataract Creek (67±3 versus 731 ±67). The concentrations of 

trace elements in biofilm from the Boulder River downstream 

from Basin Creek and downstream from Cataract Creek also 

were elevated compared to concentrations at the reference site 

(BRRC, REF 2).

Benthic Macro in vertebrates

The concentrations of trace elements were generally 

less in benthic macroinvertebrates compared to the biofilm, 

but invertebrates from many of the test sites had concentrations greater than at the reference site (tables 12 and 13). This 

trend was apparent at sites throughout the watershed even in

the absence of extensive statistical significance. Furthermore, 

some of the greatest concentrations of cadmium, copper, and 

lead were observed in the lower portion of Cataract Creek (all 

data presented as ug/g± a, 59±5; 340±130; 34±16 respectively). In general, though concentrations of trace elements 

persisted in invertebrates from sites on the Boulder River, they 

were less than concentrations of invertebrates from the tributaries. One exception to this observation was lead; invertebrates from Boulder River near Galena Gulch had the greatest 

mean concentration of lead measured in the watershed. These 

results demonstrate that trace elements were being transported 

downstream and were transferred to the food chain.

Fish Tissues

As stated in a preceding section (see "Fish Biomass, 

Density, and Physiology"), mean concentrations of trace elements, especially arsenic, cadmium, and copper, were greatest 

in gill, liver, and whole fish from lower Cataract Creek (table 

6). The concentrations of cadmium in the gill, liver, and whole 

fish from lower Cataract Creek were magnitudes greater than 

that found in the reference, upper Boulder River (90 times for 

gill, 47 times for liver, 33 times for whole fish). Likewise, the 

concentrations of copper in fish from lower Cataract Creek 

ranged from 4 to 8 times the concentrations in fish from the 

reference. Although concentrations of trace elements were 

less in fish from the mainstem, elevated arsenic, cadmium, 

and zinc were measured in fish as far downstream as Boulder 

River near Galena Gulch.

Table 12. Mean trace-element concentrations in biofilm, 1998.

[Standard error of the mean is in parentheses, and n = sample size; REF 1 = pooled value for LBR and UBR sites, REF 2 = BRRC]

Trace-element concentration, mean (ng/g dry weight)1

Site 

(fig.D

Tributaries LBR

UBR

REF1

LHO

LCC

MCC

UCC

LBC

JC

Mainstem REF 2

BRBC

BRCC

BRGG

n

4

4

8

4

4

4

4

4

4

4

4

4

4

Arsenic

17.7(1.4)

17.8 (2.0)

17.7(l.l)a

3,300 (400)d

731 (67)ab*

1,700 (700)bc

130 (13)a

475 (77)ab*

2,600 (170)cd

15.3(1.2)a

37.6 (4. l)a*

67.1 (2.9)b

262(12)c

Cadmium

1.0(0.1)

0.7(0.1)

0.8(0.1)a

41.2(2.7)bcd

30.6 (4.5)abcd*

60 (22)cd

23 (12)abc*

16.6 (2.7)ab*

70.3 (4.5)d

0.54 (0.06)a

3.3 (0.5)a*

10.5 (2.4)b

17.4(1.5)c

Copper

25(4)

15(2)

20 (3)a

321 (9)ab*

853 (96)ab*

1,940 (850)b

260 (56)ab*

369 (62)ab*

4,620 (860)c

23 (2)a

89 (14)b

170 (18)c

270 (16)d

Lead

12(3)

12(1)

12(l)a

1,100 (30)e

389 (46)te

660 (150)cd

256 (89)ab*

281 (29)ab*

885 (84)de

12.2 (0.9)a

32.3 (2.3)ab*

50.0 (7.5)b

278 (9)c

Zinc

99 (15)

62(8)

81(ll)a

18,100 (l,700)c

3,870 (420)ab*

6,000 (2,240)b

2,360 (660)ab*

2,320 (350)ab*

6,210 (170)b

141 (34)a

619 (95)ab*

1,240 (180)b

3,200 (250)c

'Different letters designate a significant difference atp<0.05 within a trace element for mainstem and tributary sites; * indicates a significant difference 

at /?<0.05 between specified site and reference only.
Aquatic Health and Exposure Pathways of Trace Elements 391 

Table 13. Mean trace-element concentrations in invertebrates, 1998.

[Standard error of the mean (2 CT) is in parentheses; n = sample size; REF 1 = pooled value for LBR and UBR sites; and REF 2 = BRRC]

Site 

(fig.D

Tributaries LBR

UBR

REF1

LHO

LCC

MCC

UCC

LBC

JC

Mainstem REF 2

BRBC

BRCC

BRGG

Trace-element concentration, mean (pg/g dry weight)1

i}

4

4

8

4

4

4

4

4

4

4

4

4

4

Arsenic

2.3 (0.3)

3.7 (1.0)

3.0 (0.5)a

60(1 1)*

63 (27)bc

80.1 (7.3)c

7.5 (2.9)ab

21.5(1.4)abc*

77 (29) c

4.6 (0.3)a

5.3 (0.3)a

13.1 (2.0)ab*

26.7 (8.8)b

Cadmium

3.7 (0.4)"

0.9 (0.2)"

2.3 (0.6)a

16.7 (0.8)b

59.3 (5.4)d

35.0 (5.4)c

15.9 (3.2)b

18.1 (1.3)b

10.0 (2.8)ab*

l.l(0.3)a

10.6 (5.7)ab*

16.2(2.1)b

11.7(3.0)ab*

Copper 38 a)**

30(1)**

34 (2)a

74 (4)ab*

340 (130)c

268 (35)te

77 (4)ab*

92 (6)abc *

319(89)bc

29(l)a

85 (5)b

111 (7)b

98 (16)b

Lead

1.2(0.2)

1.0 (0.3)

1.2(0.2)a

36 (6)b

34 (16)b

24.1 (2.0)ab*

11.2(4.4)ab*

12.4 (0.7)ab*

12.6 (9.9)ab*

1.6(0.1)a

3.3 (0.4)a*

8.5(1.5)a*

38 (18)a*

Zinc

340 (27)**

235 (18)"

288 (25)a

3,090 (75)d

2,410 (420)cd

2,070 (290)"°

1,050 (200)a*

929 (80)a*

580 (144)a

237(ll)a

584(81)b

977 (127)c

669 (66)bc

'Different letters designate a significant difference atp<0.05 within a trace element for mainstem and tributary sites.

* indicates a significant difference at p<0.05 between specified site and reference only.

**indicates a significant difference atp<0.05 between pooled reference sites.

Relationships among Components

Significant correlations were observed among the metal 

concentrations measured in the various abiotic and biotic 

components sampled in the Boulder River watershed. The 

concentrations of all trace elements, except lead, measured 

in low-flow total, filtered, or dissolved water correlated with 

concentrations in biological components (table 14). Significant 

correlations between water and biology were more frequent 

for cadmium, copper, and zinc than for arsenic. Copper and 

zinc measured in total, filtered, or dissolved water correlated 

with colloids, biofilm, and macroinvertebrates. However, arsenic in total water rather than filtered or dissolved correlated 

more significantly with colloids and biofilm. Because 

r < 0.884 for biofilm and total arsenic, the amount of variation 

explained by the corresponding r2 values (not listed) is less for 

arsenic than was generally observed for cadmium, copper, and 

zinc. No significant correlations were observed between arsenic in water and arsenic in fish, although cadmium, copper, 

and zinc in water were significantly correlated to fish tissues. 

Copper in the water was directly correlated to gill, liver, and 

whole fish; cadmium was directly correlated to gill and liver; 

and zinc was directly correlated to liver. Therefore, cadmium, 

copper, and zinc accumulated in various levels of the food 

chain and directly in fish from the water column.

Some significant correlations were found between trace 

elements in water and sediment, but r values ranged from 

0.537 to 0.877 and correspond to generally smaller r2 values. 

These small r2 values indicate that these correlations explain 

less variation than was generally observed between trace elements in water and biology. Some of the strongest correlations

between trace elements in water and sediment were observed 

for zinc and cadmium in low-flow dissolved water (r = 0.877 

and 0.857, respectively).

Concentrations in sediment correlated directly with 

biology for all trace elements. Trace elements in sediment 

correlated with biofilm and (or) macroinvertebrates for all 

trace elements, and the r ranged from 0.667 to 0.952. The 

strongest correlations were for zinc in biofilm (r = 0.952) and 

macroinvertebrates (r = 0.899). Additionally, cadmium and 

copper concentrations in sediment were correlated directly to 

gill, liver, and whole fish (r>0.922). Arsenic concentrations 

in sediment were correlated directly to concentrations in liver 

and whole fish (r = 0.978 and r = 0.882, respectively). Zinc 

concentrations in sediment were correlated to zinc concentrations in liver (r = 0.953). These results indicate that sediment, 

in addition to water, appears to provide a source of trace elements to aquatic resources in the Boulder River watershed.

Concentrations of trace elements in colloids were correlated to concentrations in biofilm for all trace elements, 

except cadmium, at/?>0.01 with r>0.900 for copper, lead, and 

zinc and r = 0.819 for arsenic. The corresponding r2 values for 

most of the correlations indicate that much of the variation in 

the data is explained. Concentrations of arsenic, copper, and 

zinc in colloids also were correlated to macroinvertebrates but 

at/?>0.05 rather than/?>0.01, and the corresponding r values 

were <0.760. Colloids also correlated directly with liver and 

whole fish for copper and with whole fish for lead.

Biofilm and macroinvertebrates were correlated to one 

another for arsenic, copper, lead, and zinc. However, all r were 

<0.828 and indicated small corresponding values for r2 ; as 

a result, small amounts of variation were explained. Biofilm
392 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 14. Correlation coefficients for trace-element concentrations measured in water, sediment, colloids, biofilm, benthic macroinvertebrates, fish gill, fish liver, and whole fish, 1996-99.

[Concentrations in water: Total = total recoverable concentration, Filt = concentration in 0.45-(im filtrate, Dis = dissolved concentration in ultraflltrate, LF = low 

flow; Inverts = benthic macroinvertebrates; probability values in parentheses; «; = number of water, sediment, colloid, biofilm, and invertebrate samples included 

in correlations with fish tissues; n2 - number of gill, liver, or whole fish concentrations used in the same correlations. Bold type, significance atp<0.01; underline atp<0.05; standard type designates significance atp<0.10. Correlations not significant above p<0.10 not presented]

n Total LF Filt LF Dis Sediment Colloids Biofilm n, n2 Gill Liver Whole

fish

Arsenic

Total LF

Filt LF

Dis

Sediment

Colloids

Biofilm

Inverts

Gill

Liver

Whole

fish

12

12

12

12

12

12

12

5

5

5

0.852

(0.0004)

—————— 0.764

(0.0273)

0.754 

(0.0047)

0.771

(0.0033)

0.884

(0.0001)

0.522 

(0.0817)

0.976

(<0.0001)

0.677 

(0.0156)

~

0.619 

(0.0318)

-

55-

55

55

55

0.522 

(0.0816)

0.809 0.819

(0.0962) (0.0011)

0.769 0.647 0.828 

(0.0035) (0.0231) (0.0009)

—

~—

-

_

__

0.978

(0.004)

-

0.971

(0.006)

0.965

(0.008)

--

"""

-

_

__

0.882 

(0.048)

-

0.994

(0.001)

0.898 

(0.039)

-

0.960

Cadmium

Total LF

Filt LF

Dis

Sediment

Colloids

Biofilm

Inverts

Gill

Liver

Whole

fish

4

9

10

8

8

12

12

5

5

5

0.998

(<0.0001)

0.986

(<0.0001)

0.537 

(0.0717)

--

0.943

(<0.0001)

-

0.984

(<0.0001)

0.771 0.857 

(0.0254) (0.0032)

—

0.960 0.932

(<0.0001) (0.0003)

0.733 0.656 

(0.0246) (0.0456)

0.888

(0.044)

0.928

(0.023)

o s —————— 0.941

(0.017)

~ , 0990 

(0.001)

35-

0.852 0.971

(0.0072) " " (0.006)

0.687 0.983

(0.0596) " " (0.003)

—

0.916

(0.029)

0.943

(0.016)

0.954

(0.012)

0.996

(0.001)

-

0.942 

(0.017)

0.993

(0.001)

0.994

(0.001)

—

_

0.855

(0.065)

0.873

(0.053)

0.952 

(0.013)

-

0.996

(0.001)

0.938 

(0.019)

0.985

(0.002)

0964 \f»^\f^

(0.008)

Copper

Total LF

FiltLF

12

12

11

0.986

(<0.0001)

0.975

(<0.0001)

0.987

(<0.0001)

0.929 

(0.023)

0.908

(0.033)

0.897

(0.039)

0.952 

(0.013)

0.957

(0.011)

0.990

(0.001)

0.940 

(0.018)

0.943

(0.016)

0.984

(0.003)
Aquatic Health and Exposure Pathways of Trace Elements 393

Table 14. Correlation coefficients for trace-element concentrations measured in water, sediment, colloids, biofilm, benthic macroinvertebrates, fish gill, fish liver, and whole fish, 1996-99.—Continued

Sediment

Colloids

Biofilm

Inverts

Gill

Liver

Whole fish

n

12

9

12

12

5

5

5

Total

—

0.994

(<0.0001)

0.983

(O.OOOl)

0.770

(0.0034)

Filt LF

0.611 

(0.0350)

0.974

(<0.0001)

0.949

(O.OOOl)

0.830

(0.0008)

Dis

0.605 

(0.0350)

0.972

(<0.0001)

0.951

(O.OOOl)

0.867

(0.0003)

Sediment Colloids Biofilm

--

0.992

(O.OOOl)

0.859 0.760 0.761

(0.0003) (0.0174) (0.0041)

«.

5

4

5

5

n2

5

5

5

5

Gill

0.989

(0.002)

0.853 

(0.066)

0.942 

(0.017)

0.981

(0.003)

_

--

Liver

0.946 

(0.015)

0.931 

(0.021)

0.966

(0.008)

0.953

(0.012)

0.888

(0.045)

—

Whole

fish

0.922 

(0.026)

0.932 

(0.021)

0.968 

(0.007)

0.940

(0.020)

0.857

(0.063)

— 0991 '• ——

(0.001)

Lead

Total LF

Filt LF

Dis

Sediment

Colloids

Biofilm

Inverts

Gill

Liver

Whole fish

3

0

12

12

9

12

12

5

5

5

—

--

--

--

—

0.591 

(0.0941)

--

0.875

(0.0020)

0.808 0.920

(0.0015) (0.0004)

0.667 0.640

(0.0178) " (0.0249)

0

0

0

5

4

5

5

5

5

5

5

5

5

5

—

--

0.889 

(0.044)

0.921

(0.026)

-

-

—

--

-

--

-

-

0.951

(0.013)

~

--

--

Zinc

Total LF

Filt LF

Dis J.-'lo

Sediment

Colloids

Biofilm

Inverts

Gill

Liver

Whole fish

9

12

10

12

10

12

12

5

5

5

1.000

(<0.0001)

0.995

(<0.0001)

0.835

(0.0007)

0.928

(<0.0001)

0.946

(<0.0001)

0.694 

(0.0124)

0.922

(<0.0001)

0.827 

(0.0009)

0.918

(0.0002)

0.941

(<0.0001)

0.691 

(0.0128)

0.877 

(0.0009)

0.957

(<0.0001)

0.969

(<0.0001)

0.699 

(0.0246)

0.930

(<0.0001)

0.952 0.983

(<0.0001) (O.OOOl)

0.899 0.709 0.804 

(<0.0001) (0.0218) (0.0016)

3

5

4

5

4

5

5

5

5

5

5

5

5

5

_

--

0.847 

(0.070)

--

--

--

0.948

(0.014)

0.946

(0.015)

0.945

(0.015)

0.953 

(0.012)

--

0.967

(0.007)

0.911 

(0.031)

--

~

__

0.876 

(0.051)

--

0.970

(0.006)

--

--

0.904

(0.035)
394 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

and invertebrates were directly correlated with gill, liver, and 

whole fish for cadmium, and copper; liver and whole fish for 

arsenic; liver for zinc; and gill for lead. Concentrations of all 

trace elements, except lead, in liver correlated with those measured in whole fish. Concentrations in gill were also correlated 

to liver concentrations for cadmium. However, concentrations 

between gill and whole fish were not correlated for any of the 

metals measured.

Discussion

This study provides evidence that populations of fish 

are unlikely to survive in close proximity to some inactive 

mine sites in Basin, Cataract, and High Ore Creeks. Limited 

survival in some stream reaches of these basins appears to be 

related to elevated concentrations of trace elements present 

in the water column. Furthermore, the health and biomass/ 

density of resident fish in lower Cataract Creek may be compromised as a result of exposure routes that include water, 

sediment, and diet. In addition, one route in the dietary pathway may begin with colloids suspended in the water column.

Aquatic Health

The multiple tools we used to investigate the effects of 

historical mining in the Boulder River watershed allow us to 

define where trace elements affect the aquatic health of the 

watershed. In the most extreme cases, where concentrations 

of trace elements were greatest in the water column, population-level effects existed and fish survival was poor. The 

relation between trace-element concentrations and mortality 

was consistent, and greater trace-element concentrations were 

associated with greater and more rapid mortality.

The association between fish mortality and the elevated 

concentrations of trace elements in the water provides evidence that trace elements caused the observed mortalities. 

Water-quality criteria have been established by the U.S. 

Environmental Protection Agency (1999, 2001) for the chronic 

and acute protection of aquatic life. Although the water-quality criteria are hardness dependent, we can calculate standards 

for the average hardness measured at various sites in this 

watershed. The acute aquatic-life standards are 12 jag Cu/L 

and 82 jag Zn/L in Basin and Cataract Creeks at a hardness of 

66 mg/L. The toxicity of some metals is alleviated by elevated 

hardness in the water. (See Finger, Farag, and others, this 

volume, Chapter C, for more complete discussion.) Therefore, 

the greater hardness values at lower High Ore Creek (LHO, 

140 mg/L) may explain why survival was slightly better in this 

stream.

The hypertrophy noted in gills of fish in this study is 

consistent with the edema noted previously in the secondary lamellae of rainbow trout exposed to 40 mg Zn/L for 3 hr 

(Skidmore and Tovell, 1972). Skidmore and Tovell (1972) also 

observed severe curling of the secondary lamellae, a finding

not unlike the "twisting" that was noted in the gills of fish 

collected from middle Cataract Creek (MCC), where concentrations of zinc ranged from 400 to 700 \ig/L. Cutthroat trout 

near death experienced excess mucus production in this study. 

Handy and Eddy (1991) suggested that excess mucus production is part of a "general stress response" in rainbow trout. 

Therefore, ionoregulatory upset (though we could not measure 

this upset directly) was the likely cause of hypertrophy (swelling), degeneration (dying), and necrosis (death) of epithelial 

cells in the gills. And, mucus production occurred simultaneously as a general response to stress.

The concentrations of cadmium, copper, and zinc in 

water at lower Cataract Creek are near the concentrations 

reported at middle Cataract Creek site, where mortality was 

observed during in-place experiments. Therefore, resident fish 

in lower Cataract Creek may have acclimated to the elevated 

concentrations of trace elements. Simultaneously, a metabolic 

cost of acclimation may be expressed at lower Cataract Creek 

as acclimation coincides with a decreased mass (though not 

decreased growth) of trout in lower Cataract Creek.

Metallothioneins are proteins that bind trace elements 

such as copper, cadmium, and zinc and may play a role in the 

acclimation of fish to trace elements (Stegeman and others, 

1992). Marr and others (1995) demonstrated that a physiological cost of acclimation exists for brown trout in the Clark Fork 

River, Mont., where trout acclimated to trace elements in the 

river had elevated concentrations of metallothionein in their 

livers and grew less than trout not acclimated to the trace elements. Furthermore, Dixon and Sprague (1981) concluded that 

decreased growth was a result of the metabolic costs associated with acclimation to copper in the laboratory. Trout from 

lower Cataract Creek had elevated metallothionein in their 

livers. Similar to Marr and others (1995), metallothionein was 

greatest in the livers of fish that also had the greatest concentrations of trace elements in the liver.

Further evidence of the compromised health of resident fish in lower Cataract Creek was the greater amounts 

of products of lipid peroxidation in the livers. Peroxidation 

of fatty-acid side chains in cell membranes can change the 

structural integrity of cell membranes and may lead to cell 

death and tissue damage (Halliwell and Gutteridge, 1985; 

Wills, 1985). These findings imply that the livers of trout in 

lower Cataract Creek were compromised and this state was 

associated with elevated concentrations of trace elements in 

the liver. The concentrations of arsenic, copper, cadmium, 

lead, and zinc in livers of trout from lower Cataract Creek also 

were elevated above the concentrations in the livers of fish 

from the reference site (UBR). In fact, the >1,000 jag Cu/g in 

the livers of fish from lower Cataract Creek was much greater 

than the upper limit of an effect concentration of 480 |ig Cu/g 

suggested by Farag and others (1995) for the Clark Fork River, 

Mont.

The extent of the reduced fish biomass and density at 

lower Cataract Creek cannot be explained by habitat differences. The mass of trout per 1,000 ft in lower Cataract Creek 

was only 28 percent of the mass calculated for the reference
Aquatic Health and Exposure Pathways of Trace Elements 395

site (UBR). This biomass difference between lower Cataract Creek and the reference site was much greater than the 

difference in weighted usable area. For all three lifestages 

(fry, juvenile, and adult), lower Cataract Creek had an average of 91 and 78 percent of the weighted usable area that the 

reference site had for brook and rainbow trout, respectively. 

That habitat differences are sufficient to explain the reduced 

biomass/density at lower Cataract Creek is thus unlikely.

We observed decreases in the density and mass per 

1,000 ft at lower Cataract Creek but did not observe differences among sites in the lengths-at-age. However, the lower 

density of trout at lower Cataract Creek may have masked the 

growth-suppressing effects of trace elements. A situation of 

less competition for resources may result when fish are present in lower densities. Jenkins and others (1999) found that 

growth of individual brown trout increased as a result of lower 

densities. During electrofishing activities on Cataract Creek, 

we only collected fish from what we observed to be the most 

energy-efficient feeding locations, which may have allowed 

for good growth (Bachman, 1984).

We also documented elevated concentrations of arsenic, 

cadmium, copper, lead, and zinc in the tissues of trout from 

lower Basin Creek (LBC) and Boulder River at Galena Gulch 

(BRGG). Lowe and others (1985) and Schmitt and Brumbaugh (1990) reported the 85th percentile (values for which 

85 percent of samples are below) of 1.1 ng As/g, 0.33 (ig 

Cd/g, 5.0 ng Cu/g, 1.31 |ug Pb/g, and 201 \ig Zn/g of whole 

fish collected from more than 100 stations across the United 

States (80 percent moisture was assumed to calculate (ig/g dry 

weight). The mean concentrations of trace elements in whole 

fish collected from lower Cataract Creek, lower Basin 

Creek, and Boulder River near Galena Gulch exceed these 

85th percentiles. Therefore, cadmium was >121, >60, and 

>60 times, respectively, than the 85th percentiles for lower 

Cataract Creek, lower Basin Creek, and Boulder River near 

Galena Gulch, respectively. Also, the amount of arsenic in 

whole fish from lower Cataract Creek, lower Basin Creek, 

and Boulder River near Galena Gulch was 8, 6, and >3 times, 

respectively, greater than the 85th percentiles.

Although the concentrations of trace elements in fish 

from lower Basin Creek and Boulder River near Galena Gulch 

were greater than in fish sampled from across the country 

(Lowe and others, 1985; Schmitt and Brumbaugh, 1990), the 

concentrations were not as great as those noted in lower Cataract Creek. Moreover, we did not observe significant changes 

in mass of trout per acre, metallothionein, or lipid peroxidation 

at lower Basin Creek or Boulder River near Galena Gulch 

(tables 3, 7, and 8). Therefore, the impacts of trace elements 

at these two sites were less than the impacts at lower Cataract 

Creek. This study provides a baseline of data for future monitoring. Monitoring plans that include lower Basin Creek and 

Boulder River near Galena Gulch, as remediation proceeds in 

Basin and High Ore Creeks, could document improved conditions or else changes caused by inadvertent releases of trace 

elements downstream when the tailings are disturbed.

The target organ of arsenic toxicity is the skin (Goyer, 

1986), and arsenic is elevated in sediment, invertebrates, 

and fish at Boulder River near Galena Gulch (tables 5, 10, 

and 11). The dark coloration and the increased accumulation of melanocytes observed in the skin of fish held at lower 

High Ore Creek (located upstream of BRGG) during the 

onsite 96-hr survival experiments may have been caused by 

the elevated arsenic present at this site. Obvious changes in 

coloration were observed during the necropsy evaluations, but 

histological evaluations would be necessary to observe more 

subtle changes such as increased numbers of melanocytes. 

Additionally, color changes during necropsies may not always 

be observed because melanocyte regulation and control are 

lost immediately at death. For these reasons, we suggest that 

histological analyses be added to future assessments of aquatic 

health in an effort to document any tissue pathology more 

completely.

Exposure Pathways

Another goal of this study was to characterize the pathway and partitioning of trace elements into water, sediment, 

biofilm, benthic macroinvertebrates, and fish. This pathway 

documents the routes of trace-element exposure to fish that 

appear to have caused the impaired health status that we 

observed. Not only were trace elements elevated in all three 

of the tributaries of concern (Basin, Cataract, and High Ore 

Creeks), but also, trace elements accumulated in all components and accumulated to the greatest extent at sites nearest 

inactive mines. Furthermore, the pathway has resulted in 

concentrations of trace elements in water and sediment that 

may adversely affect the aquatic health in the Boulder River 

watershed.

Median concentrations of cadmium, copper, and zinc in 

stream water at most sites exceeded acute and chronic aquaticlife standards (U.S. Environmental Protection Agency, 1999, 

2001). In the Boulder River watershed, hardness generally 

was < 50 mg CaCO3 /L at all sites except lower High Ore 

Creek. At 50 mg/L hardness, a conservative estimate for the 

Boulder River watershed, the standards are (acute/chronic) 

1.0/0.15 ng Cd/L, 7.0/5.0 ng Cu/L, and 66/65 ng Zn/L. These 

general guidelines suggest that the water quality of most of 

the tributary sites and even some of the mainstem sites (zinc at 

BRCC and BRGG) was sufficiently degraded to cause detrimental effects to aquatic life.

As was observed in the water column, cadmium, copper, 

and zinc were elevated in sediment throughout the Boulder 

River watershed. Additionally, arsenic and lead persisted in 

the sediment though concentrations of these trace elements 

generally were not elevated in the filtered fraction of the water 

column. Although sediment-quality criteria have not been 

established, several researchers have suggested concentrations 

to be used as sediment-quality guidelines. MacDonald and 

others (2000) determined that guidelines of 33 (ig As/g, 

4.98 [ig Cd/g, 149 ng Cu/g, 128 ng Pb/g, and 459 ng Zn/g
396 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

would protect benthic macroinvertebrates from toxicity of 

these trace elements. These consensus-based guidelines for 

freshwater sediment correctly predicted no toxicity for invertebrates during the majority of laboratory investigations (correct 

prediction 74 percent for As, 80 percent for cadmium, 

82 percent Cu, lead, and zinc). In the Boulder River watershed, sediment from all tributary sites exceeded the consensusbased guidelines for arsenic and lead, and the consensus-based 

guideline for arsenic was exceeded on the mainstem as far 

downstream as Boulder River near Galena Gulch. All tributary 

sites with the exception of upper Cataract Creek exceeded 

the consensus-based guideline for zinc. And several of the 

tributary sites exceeded the consensus-based guidelines for 

cadmium and copper. Therefore, this study suggests that the 

pathway of trace elements in the Boulder River watershed 

would lead to invertebrate toxicity in the watershed. This finding that invertebrate toxicity may be present in the Boulder 

River watershed is supported further by Boyle and Gustina 

(2000). These researchers defined the invertebrate community 

structure at some of the same sites investigated during this 

study and observed a depleted number of EphemeropteraPlecoptera-Tricoptera (EPT) taxa in High Ore Creek, lower 

Cataract Creek, and Jack Creek.

Colloids and biofilm appear to play a critical role in the 

pathway of trace elements to the food chain. Colloidal iron 

oxyhydroxides are formed immediately downstream of mine 

drainage mixing zones and are involved in the downstream 

transport of copper, lead, and zinc (Schemel and others, 2000). 

The association of colloids and trace elements is dynamic, 

and the trace elements may adsorb or desorb frequently as 

pH changes in mixing zones during transport. Therefore, the 

formation of iron colloids may play an important role in the 

transport of trace elements downstream and in the transfer of 

trace elements to biofilm.

During transport downstream, colloids commonly are 

trapped by biofilm on rock surfaces. Newman and Mclntosh 

(1989) questioned the bioavailability of trace elements associated with iron oxyhydroxides. However, we suggest that the 

transfer of trace elements associated with iron colloids to 

biological components of biofilm is an important pathway 

where trace elements associated with abiotic components are 

first presented to biotic components. Significant accumulations 

may occur if only small portions of these trace elements are 

bioavailable. The significant correlations we observed between 

concentrations of arsenic, copper, lead, and zinc in colloids 

and biofilm support the hypothesis that colloids transport trace 

elements, at least in part, to biofilm. And, we have documented that arsenic, in addition to copper, lead, and zinc, as 

documented by Schemel and others (2000), likely is transported downstream by colloids. Furthermore, trace elements in 

biofilm are associated with both the abiotic and biotic components present in biofilm (Newman and others, 1983, 1985). 

This association suggests that biofilm is a critical link in the 

movement of trace elements directly into the food chain.

Biofilm also may accumulate trace elements by means 

other than the exposure received from colloids. This appears

especially evident for cadmium and zinc. The concentrations of these trace elements were greater in filtered water in 

comparison to concentrations in colloids. We observed strong 

correlations between dissolved metal in water and biofilm for 

cadmium but not between colloids and biofilm. This suggests that water may be the primary source of the cadmium in 

biofilm. Dissolved zinc concentrations were greater than zinc 

concentrations in colloids, and the correlations were strong 

among water, colloids, sediment, and biofilm for zinc. This 

suggests that biofilm may receive zinc from water, colloids, 

and sediment.

Large concentrations of trace elements were observed 

in biofilm throughout the Boulder River watershed. In fact, 

arsenic and copper concentrations were greater in the Boulder 

River watershed than in the Coeur d'Alene River watershed in 

Idaho (Farag and others, 1998). The largest arsenic concentration in biofilm from the Coeur d'Alene River watershed was 

155 |jg/g at Cataldo, just downstream of the boundary for a 

Natural Resource Damage Assessment, while arsenic concentrations of 3,300 jag/g and 2,600 jag/g were found at High 

Ore Creek and Jack Creek, respectively. Zinc and cadmium 

concentrations were similar between some sites in the Coeur 

d'Alene and Boulder River watersheds. For example, there 

was slightly more zinc in the biofilm collected from High 

Ore Creek (18,100 |Jg/g) than was observed at Pinehurst 

(11,600 ng/g), a site within the boundary for the Natural 

Resource Damage Assessment of the Coeur d'Alene River 

watershed. Also, cadmium concentrations were similar at Jack 

Creek (70 |Jg/L) and at Nine Mile, a site defined as a significant source of trace elements for the Coeur d'Alene River 

watershed. We note that concentrations of lead found in the 

Coeur d'Alene River watershed are still among the greatest documented. The concentrations of lead in biofilm from 

many sites in the Boulder River watershed were higher than 

concentrations at the reference site (for example, 1,100 jag/g 

at High Ore compared to 12.1 jag/g at the reference site), but 

lead concentrations in biofilm from the Coeur d'Alene River 

watershed were magnitudes greater (for example, 27,200 jag/g 

at Nine Mile).

Not only were concentrations of trace elements in invertebrates elevated throughout the Boulder River watershed when 

they were compared to reference concentrations, but they were 

also elevated compared to composite invertebrate samples 

collected from other sites in the West where historical mining 

activities have occurred. In fact, the concentrations of arsenic, 

cadmium, copper, lead, and zinc in invertebrates from lower 

Cataract Creek (63, 59, 340, 34, and 2,410 |jg/g, respectively) 

were greater than the concentrations in invertebrates from the 

Clark Fork River watershed (19, 2.3, 174, 15, and 648, respectively) that were associated with reduced survival, growth, and 

health of cutthroat trout fed diets composed of these invertebrates from the Clark Fork River watershed (Farag and others, 

1994; Woodward and others, 1995).

Silver Bow Creek is a tributary of the Clark Fork River 

in western Montana. Historically, mine tailings were deposited 

along Silver Bow Creek, and some of the greatest
Aquatic Health and Exposure Pathways of Trace Elements 397

concentrations of trace elements in invertebrates in the Clark 

Fork River watershed were recorded in this stream. Arsenic 

concentrations in invertebrates from Jack Creek (77 ug/g) 

were 2 times the concentrations measured in invertebrates 

from Silver Bow Creek (34 ug/g before remediation of the 

area). And, zinc concentrations in invertebrates at lower High 

Ore Creek and lower Cataract Creek (3,090 and 2,410 ug/g, 

respectively) were greater than the amount of zinc measured 

in invertebrates from Silver Bow Creek (1,660 ug/g; Poulton 

and others, 1995). However, copper concentrations at Silver 

Bow Creek were considerably greater (1,380 ug/g) than those 

observed in invertebrates from the Boulder River watershed 

(for example, 340 ug/g, LCC).

As we noted in the case of biofilm, the concentrations of 

some trace elements in macroinvertebrates from the Boulder 

River watershed exceeded the concentrations in the Coeur 

d'Alene River watershed. Concentrations of arsenic and 

copper in invertebrates from Jack Creek (77 and 319 ug/g, 

respectively) were greater than in invertebrates collected from 

the Coeur d'Alene River watershed near Pinehurst (42 and 

34 ug/g, respectively). However, the mean concentration of 

lead in invertebrates from the Coeur d'Alene River watershed 

at Cataldo was 292 ug/g, and as was noted with biofilm, this 

concentration of lead is magnitudes greater than those measured in invertebrates collected in the Boulder River watershed. Some of the largest concentrations of lead in aquatic 

life in the intermountain western United States continue to be 

documented in the Coeur d'Alene River watershed.

The pattern of accumulation in the components measured 

during this study differed from patterns previously observed. 

During a pathway investigation of the Coeur d'Alene River 

watershed, Farag and others (1998) found that the pattern of 

trace-element concentrations (from greatest to least) to be as 

follows: biofilm and sediment > macroinvertebrates > whole 

fish. However, during this investigation of the Boulder River 

watershed, the order of concentrations was biofilm > macroinvertebrates > sediment > fish tissues > water and colloids. In 

fact, the concentrations of trace elements in biofilm during this 

study were often greater than the concentrations in sediment. 

This could result from the entrapment of colloid-bound trace 

elements by the biofilm, and this entrapment may tend to integrate the water-column concentrations over time.

The final goal of this study was to define the influence of 

water, colloids, and sediment in the transfer of trace elements 

to aquatic life. A clear interdependency among the components measured during this study exists, and all components 

that were measured appear to be important in the movement 

of trace elements up the food chain. The numerous significant correlations of trace-element concentrations among the 

various components support this interpretation. However, the 

primary pathway varied with the trace element. For example, 

copper, cadmium, and zinc appear to have moved directly to 

biota (biofilm, invertebrates, and (or) fish tissues) from water 

and sediment. In fact, not only did trace-element concentrations in biofilm increase with concentrations in water and 

sediment, but concentrations of trace elements in fish tissues

also increased directly with concentrations in water and sediment. Therefore, concentrations of these trace elements appear 

to have increased in fish tissues as a result of direct exposure from water and sediment contact and indirect exposure 

through the food chain. The pathway of arsenic was slightly 

different, because, although arsenic accumulated in colloids 

and biofilm directly from water, arsenic did not accumulate in 

fish tissues directly from the water. The movement of lead into 

biological components appeared to be the result of a pathway 

that began with sediment because there were no correlations 

for lead between water and the other components.

Correlations between water and sediment were less 

significant than expected; two possible explanations for this 

observation arise. First, colloids present in the water and on 

sediment particles may affect the concentrations and diminish 

the strength of correlations. Iron colloids also are likely to be 

present in biofilm, and concentrations of most trace elements 

in biofilm were correlated with water and (or) sediment. If 

colloids made up a significant portion of the biofilm, these 

correlations of water and sediment with biofilm may have 

resulted in part from the significant colloid presence. A second 

possibility is the spatial aspect of the process by which trace 

elements are transferred from the water column to sediment. 

The process occurs as colloids form in mixing zones and then 

trace elements react with the colloids; this all occurs during 

transport downstream. Thus, a sample at a single site may not 

reflect the whole process, and correlations may not be good. 

Where a sequence of samples was collected in Uncle Sam 

Gulch during a metal-loading study (Kimball and others, this 

volume), the process was evident, but any single sample would 

not have indicated the process.

In summary, the pathway of trace elements to fish in the 

Boulder River watershed clearly included water, sediment, 

biofilm, and benthic macroinvertebrates. Trace elements accumulated in all of these components and to the greatest extent 

at sites nearest historical mining activities. The concentrations 

of trace elements in water and sediment routinely were such 

that aquatic life was affected at several sites in the watershed. 

Finally, the interrelationship of the trace elements accumulating in the various components suggests that fish were exposed 

to trace elements both directly from water and sediment and 

indirectly through the food chain.

Summary

Water quality in Bullion Mine tributary, Jack Creek, 

middle Cataract Creek, Uncle Sam Gulch, and to a lesser 

degree lower and upper High Ore Creek may have rendered 

the survival of trout unlikely at these sites and may have acted 

as a barrier that limited fish migration to upstream reaches in 

the Boulder River watershed. Additionally, because biomass/ 

density was decreased, and metallothionein, products of lipid 

peroxidation, and tissue trace-element concentrations were 

simultaneously increased in resident fish at lower Cataract
398 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Creek, we conclude that the aquatic health of lower Cataract 

Creek was compromised. Furthermore, the association of 

elevated trace-element concentrations in tissue, water, and 

sediment has led us to conclude that trace elements were the 

cause of the compromised aquatic health in lower Cataract 

Creek. Therefore, resident fish populations would benefit 

greatly if remediation efforts were directed to minimize the 

concentrations of trace elements in the water, sediment, and 

biota of lower Cataract Creek downstream from Uncle Sam 

Gulch.

The concentrations of trace elements in water and sediment routinely were such that aquatic life was affected at 

several sites in the watershed. And, the concentrations of 

arsenic, cadmium, copper, lead, and zinc in invertebrates 

from lower Cataract Creek were greater than the concentrations in invertebrates from some sites in the Clark Fork River 

watershed, Montana, where high trace-element concentrations 

were associated with reduced survival, growth, and health of 

cutthroat trout fed diets composed of these Clark Fork River 

invertebrates (Farag and others, 1994; Woodward and others, 1995). Arsenic concentrations in invertebrates from Jack 

Creek and zinc concentrations in invertebrates from lower 

High Ore Creek and lower Cataract Creek were greater than 

the concentrations of these trace elements in invertebrates 

from Silver Bow Creek, a tributary with some of the greatest 

invertebrate trace-element concentrations in the Clark Fork 

River watershed.

Finally, the interrelationship of the trace elements 

accumulating in the components measured suggests that fish 

were exposed to trace elements both directly from water and 

sediment and indirectly through the food chain. It appears that 

trace elements have contacted biota through these two pathways to compromise the overall aquatic health of the Boulder 

River watershed. One first step in the food-chain pathway 

seems to be associated with trace elements transferring from 

colloids to biofilm.

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impairment of free ranging brown trout exposed to metals in 

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Farag, A.M., Woodward, D.F., Goldstein, J.N., Brumbaugh, 

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associated with mining waste in sediments, biofilm, benthic 

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metallothionein: Comparative Biochemistry and Physiology, v. 100C,p. 137-141.

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20-31.

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metals-acclimated brown and rainbow trout exposed to 

metals representative of the Clark Fork River, Montana: 

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quality, sediments, invertebrates and fish located in Uncle 

Sam Gulch, Cataract Creek and the Boulder River, northern 

Jefferson County, Montana: Butte, Mont., Montana College 

of Mineral Science and Technology M.S. thesis, 

117 p.

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in the upper Boulder River, Montana: Bozeman, Mont., 

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of aufwuchs as a monitor of bioaccumulation: Environmental Pollution, v. 60, p. 83-100.

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monitor bioaccumulation of arsenic, cadmium, chromium, 

copper and zinc: Water Research, v. 19, p. 1157-1165.

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a biomonitor for lead levels in two New Jersey reservoirs: 

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U.S. Department of Agriculture, Intermountain Forest and 

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M.L., and Brumbaugh, W.G., 1995, Relations between 

benthic community structure and metals concentrations in 

aquatic macroinvertebrates, Clark Fork River, Montana: 

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Fourth Edition, Volume 2: Gary, N.C., SAS Institute.

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protein systems as indicators of chemical exposure and 

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Chelsea, Midi., Lewis Publishers, p. 235-335.
400 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

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C.E., and Bergman, H.L., 1995, Metals-contaminated 

benthic invertebrates in the Clark Fork River, Montana— 

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p. 82-90.
Understanding Trace-Element Sources 

and Transport to Upper Basin Creek in the 

Vicinity of the Buckeye and 

Enterprise Mines

By M.R. Cannon, Stanley E. Church, David L Fey, Robert R. McDougal, 

Bruce D. Smith, and David A. Nimick

Chapter E1 of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

In cooperation with the

United States Department of Agriculture (USDA) Forest Service

Professional Paper 1652-E1

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract................................................................^

Introduction............................................................................................................................................... 407

Purpose and Scope.........................................................................................................................407

Description of Study Area.............................................................................................................. 409

Sources of Trace Elements..................................................................................................................... 409

Flotation-Mill Tailings...................................................................................................................... 410

Geochemistry of Tailings....................................................................................................... 410

Total-Digestion Data...................................................................................................... 411

Leachate Data................................................................................................................411

Arsenopyrite................................................................................................................... 416

Dispersion of Tailings on the Flood Plain............................................................................ 417

Shallow Subsurface Sources........................................................................................................ 417

Electromagnetic Survey of Conductive Materials............................................................ 418

Magnetic Survey of Shallow Anomalies............................................................................. 420

Direct-Current Resistivity Soundings of Conductive Materials...................................... 421

Transport of Trace Elements to Upper Basin Creek............................................................................ 426

Ground Water................................................................................................................................... 426

General Geohydrologic Setting............................................................................................ 426

Test Wells .................................................................................................................................426

Water Levels and Flow Directions....................................................................................... 428

Water Quality and Trace-Element Loads............................................................................ 428

Streambed Sediment in Basin Creek............................................................................................ 433

Surface Water.................................................................................................................................. 433

Flow Characteristics of Basin Creek................................................................................... 440

Water Quality and Synoptic Sampling ................................................................................ 440

Trace-Element Loads in Basin Creek................................................................................... 446

Summary and Conclusions...................................................................................................................... 453

References Cited...................................................................................................................................... 454

Figures

1. Map showing location of Buckeye and Enterprise mines near upper Basin Creek,

Mont........................................................................................................................................... 408

2. Photograph showing flotation mill active during the 1940s and associated 

tailings on flood plain of Basin Creek at Buckeye and Enterprise mines, 

October 1996............................................................................................................................. 409

3. Map showing location of mill tailings and core holes on flood plain of upper

Basin Creek............................................................................................................................... 410

4. Graphs showing relation of selected trace-element concentrations in total

digests to depth in the 2-in. core through mill tailings, upper Basin Creek.................. 414

5. Graphs showing relation of selected trace-element and sulfate concentrations

in leachate to depth in the 2-in. core through mill tailings, upper Basin Creek............ 416
6. Box plots showing range and distribution of silver and strontium

concentrations in total digestions of 1-in. cores along main traverse through

mill tailings, upper Basin Creek............................................................................................. 418

7. Graphs showing relation of strontium and selected trace-element 

concentrations in total digests of 1-in. cores through mill tailings, upper 

Basin Creek...............................................................................................................................419

8-11. Maps showing:

8. Location of electromagnetic (EM) survey grid and test wells.................................. 420

9. Contours of deep subsurface apparent conductivity measured using an

EM-34 along upper Basin Creek.................................................................................... 421

10. Contours of shallow subsurface apparent conductivity measured using an

EM-31 along upper Basin Creek.................................................................................... 422

11. Location of total-field magnetic survey lines and direct-current resistivity

soundings........................................................................................................................... 423

12. Graphs showing results of total-field magnetic survey...................................................... 424

13. Section showing subsurface conductivity from direct-current resistivity

soundings.................................................................................................................................. 425

14. Map showing location of test wells and configuration of water table,

August 3,1999........................................................................................................................... 427

15. Map showing location of streambed-sediment and surface-water sampling sites,

upper Basin Creek...................................................................................................................439

16. Graph showing monthly distribution of mean annual streamflow of Boulder River..... 441

17. Graph showing relation of dissolved zinc concentration and streamflow

for Basin Creek below Buckeye mine, 1996-99.................................................................. 441

18. Photograph showing snowmelt runoff from flotation-mill tailings entering upper

Basin Creek near site 12B, May 27,1999............................................................................. 442

19. Graph showing streamflow in upper Basin Creek, May 28,1999.................................... 446

20-27. Graphs showing dissolved load in upper Basin Creek, May 28,1999:

20. Aluminum...........................................................................................................................449

21. Arsenic...............................................................................................................................449

22. Cadmium............................................................................................................................450

23. Copper................................................................................................................................450

24. Iron..................................................................................................................................... 451

25. Lead.................................................................................................................................... 451

26. Manganese........................................................................................................................452

27. Zinc..................................................................................................................................... 452

Tables

1. Mineralogy and concentrations of selected major and trace elements 

in core intervals from a 2-in. diameter core in mill tailings along upper 

Basin Creek............................................................................................................................... 412

2. Specific conductance, pH, and concentrations of sulfate and selected 

trace elements in leachate from various depth intervals of core samples 

collected from the mill tailings along upper Basin Creek................................................. 415
3. Well-completion data for test wells near upper Basin Creek.......................................... 427

4. Water levels, pH, and specific conductance of ground water from test

wells near upper Basin Creek............................................................................................... 429

5. Hydraulic properties of unconsolidated deposits along upper Basin Creek................. 431

6. Concentrations of major ions and dissolved trace elements in ground water

near upper Basin Creek.......................................................................................................... 432

7. Estimated dissolved trace-element loads discharged to upper Basin Creek 

during low flow from shallow ground water in the vicinity of the Buckeye and 

Enterprise mines......................................................................................................................433

8. Streamflow and water-quality data for upper Basin Creek, 1996-99............................. 434

9. Dissolved trace-element loads in upper Basin Creek upstream of and

downstream of the Buckeye and Enterprise mines, October 16,1998........................... 439

10. Concentrations of leachable iron and selected trace elements in streambedsediment samples, upper Basin Creek................................................................................. 440

11. Synoptic streamflow and water-quality data for upper Basin Creek and

tributaries, May 28,1999......................................................................................................... 443

12. Dissolved trace-element loads for upper Basin Creek and tributaries,

May 28,1999.............................................................................................................................447
CONVERSION FACTORS AND DATUM

Multiply

foot (ft) 

inch (in.)

mile (mi)

acre

square foot (ft2 ) 

square mile (mi2 )

cubic foot (ft3) 

cubic yard (yd3)

cubic foot per day (ft^d) 

cubic foot per second (ft^/s)

By

Length

0.3048 

2.54 

25.4 

1.609

Area

0.4047

0.09290 

2.589

Volume

28.3168 

0.7646

Flow

0.028317 

0.028317

Hydraulic Conductivity

To obtain

meter (m) 

centimeter (cm) 

millimeter (mm) 

kilometer (km)

hectare

square meter 

square kilometer

liter 

cubic meter

cubic meter per day 

cubic meter per second

foot per day 

foot squared per day (ft2/d)

0.3048

Transmissivity

0.0929

meter per day

meter squared per day

Temperature can be converted to degrees Celsius (°C) or degrees Fahrenheit (°F) by the following equations:

°C = 5/9 (°F - 32) 

°F = 9/5 (°C) + 32

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD29); horizontal 

coordinate information is referenced to the North American Datum of 1927 (NAD27).

Chapter E1

Understanding Trace-Element Sources and Transport to 

Upper Basin Creek in the Vicinity of the Buckeye and 

Enterprise Mines

By M.R. Cannon, Stanley E. Church, David L. Fey, Robert R. McDougal, Bruce D. Smith, and David A. Nimick

Abstract

The Buckeye mine and adjacent Enterprise mine, located 

about 10 miles north of Basin, Montana, were intermittently 

operated in the late 1800s and early 1900s. Upper Basin Creek 

flows next to acid-generating pyritic rocks and the tailings left 

from the mining and milling operations. Overland runoff from 

the mine area is rich in trace elements and measurably affects 

water quality in upper Basin Creek, primarily during spring 

snowmelt and high streamflow. Detailed studies of the sources 

of trace elements and modes of transport to upper Basin Creek 

were needed to aid in designing remediation.

Geochemical analyses of core samples from areas of mill 

tailings identified zones containing the highest concentrations 

of trace elements. Geophysical surveys identified areas of high 

conductivity that could result from ground water containing 

high concentrations of dissolved solids. Ground-water samples 

from test wells identified areas containing high concentrations 

of dissolved aluminum, arsenic, cadmium, copper, iron, lead, 

manganese, and zinc.

During spring runoff, dissolved trace-element loads measured in upper Basin Creek were largely derived from small 

tributary inflows draining the area of the Buckeye and Enterprise mines. Runoff from the mine area caused concentrations 

of copper, lead, and zinc in upper Basin Creek to exceed the 

State of Montana aquatic-life standards. For all trace elements 

except arsenic, ground water contributed only a small part of 

the dissolved trace-element load to upper Basin Creek.

Introduction

The Buckeye and Enterprise mines in the upper Basin 

Creek area of west-central Montana are two of many inactive 

or abandoned metal mines that were intermittently operated 

in the late 1800s and early 1900s. Wastes left from the mining

and processing of ore include pyritic rocks and tailings from 

gravity and flotation mills. Most of the flotation-mill tailings were deposited in the flood plain of upper Basin Creek, 

on lands now administered by the Beaverhead-Deerlodge 

National Forest (fig. 1). Upper Basin Creek, which flows along 

the southern margin of the mill tailings, receives surface-water 

and ground-water discharge from the tailings and areas around 

the mines. That discharge is rich in trace elements and measurably affects water quality in Basin Creek. State of Montana 

water-quality standards for aquatic life are exceeded in Basin 

Creek, downstream from these mines, during times of high 

runoff.

The United States Department of Agriculture (USD A) 

Forest Service and U.S. Environmental Protection Agency 

identified the need for remediation of the Buckeye and Enterprise mine area; however, the size of the affected area and the 

number of potential trace-element sources made the planning 

of remediation complex. The site contained multiple potential 

sources of trace elements, which could be transported via 

surface- and ground-water pathways to upper Basin Creek. 

Potential sources of trace elements included an adit that 

discharged acidic water, piles of waste rock near the mines, 

tailings from an early mill that were located on a hillslope 

adjacent to the Basin Creek valley floor, and flotation-mill tailings on the flood plain of upper Basin Creek.

Purpose and Scope

The purpose of this report is to present data and results 

from a comprehensive investigation of trace-element sources 

and transport to upper Basin Creek from surface and ground 

water near the Buckeye and Enterprise mines. The investigation was conducted by the U.S. Geological Survey in 1998-99. 

Prior to the comprehensive investigation near the mines, surface water and streambed sediment were sampled to determine 

the extent, magnitude, and seasonal patterns of trace-element
408 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Boulder River watershed study area

S

U.S. GEOLOGICAL SURVEY 

STREAMFLOW-GAUGING 

STATION 06033000

112° 20' LEWIS AND 

CLARK CO

46°22'30" -

BEAVEJRHEAD-DEERLODGE \ 

AT1ONAL FOREST-""^ N

46° 15'

Base from U.S. Geological Survey 

Butte North, MT, 1100,000.1994

Basin r j^^^

A

/^~n !l% ~

3 MILES

0 1 2 3 KILOMETERS

Figure 1. Location of Buckeye and Enterprise mines near upper Basin 

Creek, Mont. Altitude in feet.

concentrations in a large part of the Basin Creek drainage 

(Nimick and Cleasby, 2000; Fey, Unruh, and Church, 1999). 

Results of those samples indicated that the area of the Buckeye 

and Enterprise mines was contributing trace elements to upper 

Basin Creek through the transport of acidic, trace-elementrich water and sediment. Seasonal samples from upper Basin 

Creek indicated that the greatest concentrations and loads of 

trace elements occurred during spring runoff and much smaller 

concentrations occurred during low streamflow. Those initial 

water and sediment samples from upper Basin Creek clearly 

showed a need for a more thorough characterization of traceelement sources and mechanisms of transport to the stream.

The scope of the investigation was limited to public lands 

in upper Basin Creek that are adjacent to the Buckeye and 

Enterprise mines. To better understand the sources 

of trace elements and mechanisms for transport to upper 

Basin Creek, a multidisciplinary approach was used that 

examined (1) geochemistry of mill tailings and streambed 

sediment, (2) geophysical properties of tailings, alluvial sediments, and pore water, (3) ground-water flow and quality, and 

(4) surface-water flow and quality. Results of the investigation 

were used to aid in the development of efficient and costeffective remediation plans for the mine site and adjacent area 

of public lands. Remediation activities at the site were conducted in 2000-01 by the USD A Forest Service.
Trace-Element Sources and Transport to Upper Basin Creek 409

Description of Study Area

The Buckeye and Enterprise mines are located in upper 

Basin Creek about 10 mi north of the town of Basin in 

Jefferson County, Mont. (fig. I). The Buckeye mine was intermittently operated from 1868 to 1908, although the principal 

period of mining activity was from 1896 to 1903 (Ruppel, 

1963). The ore vein, which contained gold-bearing pyrite and 

minor quantities of silver-bearing galena, was worked through 

shafts that were sunk to a depth of 100-200 ft. The adjacent 

Enterprise mine was operated at about the same time, but was 

closed before 1900. The Enterprise mine had a 400-ft vertical 

shaft that accessed an ore vein similar to the one at the Buckeye mine. The 5-ft thick Buckeye ore vein and the adjacent 

smaller veins are nearly vertical and apparently occupy fault 

zones trending N. 85° W. within the Butte quartz monzonite 

(Ruppel, 1963). During the time of mine operation, ore from 

the mines was processed by a gravity mill located at the Buckeye site. In the 1940s during World War II, a flotation mill was 

built on the flood plain of Basin Creek (fig. 2) to reprocess 

the old tailings from the gravity mill (Roby and others, 1960; 

Metesh and others, 1994). An estimated 5,000 cubic yards of 

flotation tailings and sandy material accumulated in the Basin 

Creek flood plain (Fey, Church, and Finney, 1999) as a result 

of activities at the flotation mill. These flood-plain tailings 

occupied about 3.3 acres in an irregularly shaped area of about 

200 by 750 ft.

Altitudes within the study area range from about 

7,020 ft along Basin Creek at the west end of the study area to 

7,100 ft at the mine workings. Basin Creek drops about 

20 ft as it meanders for a distance of about 4,300 ft from east 

to west through the study area. Because of its relatively high 

altitude, the area receives nearly 30 in. of precipitation per 

year, much of it falling as snow from late October through 

May (U.S. Department of Agriculture, 1981).

Sources of Trace Elements

Several potential sources of trace elements were present at the Buckeye and Enterprise mines and adjacent area. 

Sources included a mine adit discharging water, piles of pyritic 

waste rock on private property, and dispersed deposits of mill 

tailings on public land along upper Basin Creek The size of 

the area affected by elevated concentrations of trace elements 

such as arsenic, cadmium, copper, lead, and zinc that are 

associated with the mineral deposit was unknown. To assess 

the lateral and vertical extent of the affected area, detailed 

geochemical studies were conducted on the mill tailings and 

soils on the flood plain of upper Basin Creek, and geophysical 

surveys were used to examine properties of subsurface 

materials along upper Basin Creek and the surrounding area.

Figure 2. Flotation mill active during the 1940s and associated tailings on flood plain of Basin 

Creek at Buckeye and Enterprise mines, October 1996. Buckeye mine is behind mill near clearing in trees. Enterprise mine is in trees on right side of photograph.
410 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Flotation-Mill Tailings

The distribution, thickness, and volume of flotation-mill 

tailings as well as underlying fluvial sediment with elevated 

trace-element concentrations were estimated by Fey, Church, 

and Finney (1999) from 35 shallow cores collected from the 

flood plain of upper Basin Creek (fig. 3) in 1997. These cores 

were 1 inch in diameter and typically as much as 24 inches 

in length. The cores were subdivided into 196 samples on the 

basis of visual identification of differences in mineralogy, 

organic content, and degree of oxidation. Each sample was 

analyzed by geochemical and binocular-microscopic methods. 

Trace-element concentrations and mineralogy determined 

from these analyses were used to distinguish contaminated 

and uncontaminated material and to estimate the volume of 

the contaminated material (Fey, Church, and Finney, 1999). 

Further investigation of the mill tailings was warranted to 

determine the source of trace elements in underlying ground 

water, whether the tailings had potential for further oxidation 

and associated release of acid and trace elements, and what 

processes cause lateral and vertical dispersion of trace elements in the tailings and across the flood plain.

Geochemistry of Tailings

The geochemistry of the flotation-mill tailings was examined by detailed analysis of a core (2 inches in diameter and 

79 in. long) collected from the thickest part of the mill tailings 

in July 1998. This core, as well as a nearby exploratory 

trench (approximately 10 ft long and 7 ft deep), revealed a 

zone of oxidized waste that graded downward into unoxidized, 

pyrite-rich waste near the base of the tailings. The core was 

subdivided into 27 samples. Sample descriptions as well as 

geochemical and mineralogical data from the core are in 

table 1. The data indicate four distinct sections corresponding to the oxidized zone (the upper 22 in.), the partly oxidized 

zone (22-41 in.), the unoxidized pyritic zone (41-62 in.), and 

buried soil developed in flood-plain sediment (62-79 in.). At 

the base of the mill tailings, buried wetland grasses overlie 

the top organic-rich layer of the buried soil. Geochemical and 

mineralogical data for the 2-in. core are used to demonstrate 

how the tailings weathered and how trace elements were mobilized, redistributed within the core, and, in some cases, leached 

out of the tailings. The mechanisms by which trace elements 

were released by weathering and dispersed through the flood 

plain can be understood by examination of the differences 

in element concentrations (from the 1-in. cores) in total- and 

leach-digestions as well as the distribution of primary and 

secondary minerals and their relative abundance within the 

cores.

112°18'0r 112°17'54" 1120 17'40"

46°231 46"

4B°231 39"

EXPLANATION

| | Approximate area of mill tailings on flood plain of 

Basin Creek

• Location of 2-inch mill tailings core hole—Core sample 

number 98BMF109, tables 8 and 9

Location of 1-inch mill-tailings core hole

BUCKEYE 

MINE X>\

ENTERPRISE 

MINE /

,- ve \ ,-; £

400 FEET

100 METERS

Figure 3. Location of mill tailings and core holes on flood plain of upper Basin Creek
Trace-Element Sources and Transport to Upper Basin Creek 411

Total-Digestion Data

The samples from the 2-in. core were processed using 

a total-digestion procedure that used a mixture of strong 

acids (Fey and others, 2000). Concentrations of major elements such as calcium, sodium, iron, and aluminum clearly 

show the difference between mill tailings and the underlying 

buried soil and reflect differences in the mineralogy of these 

two units (table 1). These differences in element concentrations are caused by the large difference in proportions of the 

deposit-related minerals found in the rocks that were milled 

and the rock-forming minerals typically found in the premining flood-plain sediment beneath the tailings. Other differences in element concentrations were caused by oxidation of 

the abundant sulfide minerals (such as pyrite) in the tailings 

and leaching of the oxidation byproducts. Calcium and sodium 

were present in the tailings at very low concentrations, but in 

the underlying soil zone they were present at concentrations 

one to two orders of magnitude higher. This pattern largely 

reflects the original compositions of the tailings and underlying buried soil, with much smaller amounts of feldspar and 

other rock-forming minerals in the tailings compared to the 

soil. Aluminum exhibited a somewhat similar but less distinct 

pattern. Aluminum concentrations were lower in the tailings 

(1.6-4.4 percent) and higher in the underlying soil (5.2-9.0 

percent), again reflecting the larger proportion of rock-forming 

minerals in the buried soil.

Within the tailings, variations in iron and aluminum 

concentrations with depth reflect processes that affected 

the tailings after their deposition on the flood plain. Iron is 

hosted primarily in pyrite, which likely was distributed fairly 

uniformly throughout the original tailings. However, iron 

concentrations in the core were lower in the oxidized zone 

(less than 1 percent) and higher in the unoxidized pyritic zone 

(2.6-5.6 percent). This pattern likely developed because pyrite 

and other sulfide minerals in the upper part of the tailings pile 

were oxidized and their constituents leached from the oxidized 

zone. The wide range in iron concentrations within just the 

unoxidized pyritic zone reflects the variable amount of quartz, 

the dominant silicate mineral in the tailings, which diluted the 

amount of pyrite present in individual layers sampled in the 

zone. Aluminum concentrations were higher in the oxidized 

zone (3.5-4.4 percent) than in the unoxidized pyritic zone 

(1.7-3.6 percent). The aluminum distribution is also a result 

of the leaching of the sulfide-oxidation byproducts. As these 

components were removed, aluminum, which was not leached, 

was concentrated in the oxidized zone, primarily in kaolinite 

that formed during weathering.

Similar to the major elements, the distribution of trace 

elements in the core (fig. 4) reflects the original mineralogy 

as well as subsequent processes that differentially mobilized 

and sequestered the trace elements. Strontium and silver 

concentrations, like calcium, sodium, and iron concentrations, 

reflect the original composition of the tailings and buried soil. 

In the tailings, strontium concentrations were low and silver 

concentrations were high, whereas this pattern was reversed

in the buried soil. Strontium represents the rock-forming trace 

elements typical of the underlying premining flood-plain 

sediment, whereas silver represents the deposit-related trace 

elements that were concentrated in the tailings.

Arsenic, cadmium, copper, lead, and zinc are the trace 

elements that pose risk to aquatic life in Basin Creek (Farag 

and others, this volume, Chapter D10). These elements were 

enriched in the tailings (fig. 4B, C) but had distinctly different mobilities during oxidation and weathering in place. 

Silver is a relatively immobile trace element during oxidation 

and weathering. The uniform distribution of silver through 

the tailings (fig. 4Q indicates that the tailings had a fairly 

uniform composition as they were dumped from the flotation mill and that, initially, the tailings in the core likely were 

homogeneous. Therefore, comparing the distributions of the 

trace elements of concern to the distribution of silver provides 

useful information about the weathering processes. Lead, like 

silver, is relatively immobile (fig. 4Q. Arsenic (fig. 4Q is 

more mobile during weathering than silver and lead but less 

mobile than cadmium, copper, and zinc (fig. 4B). Moderate to 

large increases in concentrations of trace elements occurred 

at the boundary between the oxidized zone and the partly oxidized zone (22 in. depth) and, for most trace elements, at the 

boundary between the partly oxidized zone and the unoxidized 

pyritic zone (41 in.). Concentrations also were high, particularly for arsenic, cadmium, copper, and zinc, near the top layer 

of the buried soil (64.3 in.). These increases were produced by 

downward leaching of the trace elements mobilized by sulfide 

oxidation in the oxidized zone. Some of the leached trace 

elements were sequestered as organic complexes at the top of 

the buried soil, which presumably had very low trace-element 

concentrations prior to deposition of the tailings. Below the 

organic material in the buried soil, concentrations of trace elements of concern decreased markedly over a distance of a few 

inches (fig. 4). Concentrations of arsenic, which behaves as an 

anion, and zinc, which remains mobile up to a pH of about 8, 

decreased gradually with depth reflecting their greater mobility and greater penetration into the buried soil horizon.

Leachate Data

The samples from the 2-in. core also were processed 

using a passive-leach procedure (Fey and others, 2000). 

Deionized water was used as the leachate and was mixed at a 

20:1 mass ratio with the sample. The samples were leached for 

24 hours without agitation to simulate the dissolution reactions 

that probably would occur when sulfidic tailings are exposed 

to surface water. Data are in table 2 and figure 5. Leachate 

from all intervals in the core was acidic, indicating that sulfide 

oxidation was occurring and that acid and trace elements 

would be mobile in the tailings and at least parts of the buried 

soil. The pH of the leachate solutions was slightly higher in 

the oxidized zone (pH from 3.41 to 3.68) than in the partly 

oxidized zone and unoxidized pyritic zone (pH from 2.53 to 

3.09). In the buried soil below the tailings, the pH increased 

with depth. Specific conductance and sulfate concentration
412 Environmental Effects of Historical Mining, Boulder River Watershed, Montana 

Table 1. Mineralogy and concentrations of selected major and trace elements in core intervals from a 2-in. diameter core in

[Core intervals expressed as the midpoint of the depth in the core from the surface (corrected for compaction). Major-element concentrations expressed in 

weight percent (parts per hundred); trace-element concentrations expressed in parts per million; minerals identified by XRD listed in order of decreasing 

abundance; cm, centimeter; mm, millimeter; ppm, parts per million; tr., trace; XRD, X-ray diffraction; <, less than minimum reporting level; --, not analyzed]

Sample 

No.

Depth

(midpoint, in

inches)

Sample description High-density minerals, 

identified by XRD

Minerals, in addition to quartz and 

mica identified by

XRD

Aluminum 

(weight

percent)

Oxidized zone

98BMF109-Aa

98BMF109-Ab

98BMF109-AC

98BMF109-Ad

98BMF109-Ba1

98BMF109-Bb1

98BMF109-BC1

1.8

5.3

8.6

11.8

15.0

17.9

20.8

Light-gray/pale-yellow tailings, medium sand

Coarse tailings, sand sized to 1 mm

Unsorted tailings with clay-size matrix

Unsorted tailings with clay- size matrix

Light-gray tailings, poorly sorted into

0.52-cm thick beds, coarse

grains to 2 mm.

anglesite, tr. sphalerite

anglesite, tr. sphalerite

anglesite, tr. sphalerite

anglesite, tr. sphalerite

anglesite, tr. sphalerite

anglesite, tr. sphalerite,

gold

anglesite, tr. sphalerite

orthoclase

anglesite, kaolinite

anglesite, kaolinite

anglesite, kaolinite

anglesite, kaolinite

anglesite, orthoclase

anglesite

4.4

4.3

4.2

4.2

3.8

3.5

3.6

Partly oxidized zone

98BMF109-Ca

98BMF109-Da

98BMF109-Ea

98BMF109-Fa

98BMF109-Ga

98BMF109-Ha

98BMF109-Ia

23.2

25.4

28.2

31.1

34.4

37.5

39.7

Pale-yellow fine-grained tailings, 90 percent

"clay" size.

Pale-yellow/cream tailings, coarse- and finegrained.

Pale yellow/gray, coarse and fine grained

Bright-yellow sand, unsorted tailings

Pale-yellow cream tailings with lenses of sulfide

grain, layered.

Light-gray light-yellow fine to coarse oxidized 

sulfide tailings.

Yellow, medium sand tailings

anglesite

anglesite

anglesite

anglesite

anglesite

anglesite

anglesite

anglesite

anglesite

anglesite

anglesite

anglesite

anglesite

anglesite, scorodite

4.0

2.8

2.5

1.9

2.2

1.8

1.6

Unoxidized pyritic zone

98BMF109-Ja

98BMF109-Ka

98BMF109-La

98BMF109-Ma

98BMF109-Mb

98BMF109-Na

98BMF109-Oa

42.4

45.5

48.8

52.2

54.9

57.1

59.9

Cream and dark-gray, sulfides, fine sand

Light- and dark-gray, sulfides, fine sand

Fine sand with gray sulfides

Pale-yellow tailings, some gray sulfides, medium 

to coarse sand, moderately sorted.

Pale-yellow tailings, some gray sulfides, medium 

to coarse sand, moderately sorted.

Light-dark-gray tailings, fine sand, pyrite

Cream, poorly sorted fine- sand size tailings

pyrite, anglesite

pyrite, anglesite

pyrite, anglesite

pyrite, anglesite

pyrite, anglesite

pyrite, anglesite

pyrite

anglesite, pyrite

pyrite, anglesite,

sphalerite

sphalerite, pyrite,

anglesite

pyrite, anglesite

pyrite, anglesite

pyrite, anglesite

pyrite, anglesite

3.3

2.6

1.8

1.7

2.0

3.2

3.6

Buried soil

98BMF109-P

98BMF109-Qa

98BMF109-Qb

98BMF109-Qc

98BMF109-Qd

98BMF109-Qe

62.0

64.3

67.8

71.5

75.0

78.0

Organic layer

Soil, dark brown at top

Light brown at bottom

Soil

Soil

Soil

-

tr. pyrite

none

none

zircon, tr. hornblende

zircon, tr. hornblende

~

halloysite, plagioclase

montmorillonite,

kaolinite, plagioclase

montmorillonite,

kaolinite, plagioclase

montmorillonite,

kaolinite, plagioclase

montmorillonite,

kaolinite, plagioclase

5.2

7.6

9.0

8.9

8.7
mill tailings along upper Basin Creek.

Trace-Element Sources and Transport to Upper Basin Creek 413

Calcium

(weight

percent)

Iron

(weight

percent)

Potassium

(weight

percent)

Sodium

(weight

percent)

Arsenic

(ppm)

Cadmium

(ppm)

Copper

(ppm)

Lead

(ppm)

Manganese

(ppm)

Silver

(ppm)

Strontium

(ppm)

Zinc

(ppm)

Oxidized zone

0.02

.02

.02

.01

.009

.009

.01

0.86

.82

.80

.78

.63

.57

.62

2.1

2.1

2.0

2.0

1.8

1.6

1.7

0.05

.04

.04

.03

.02

.01

.009

1,600

1,700

1,300

1,400

500

480

640

2

<2

<2

<2

<2

<2

<2

54

35

47

43

38

66

60

6,100

7,500

6,900

7,400

5,000

8,300

7,000

140

140

130

140

120

120

120

52

48

48

62

42

92

64

25

24

26

21

15

9

7

280

210

260

180

170

240

210

Partly oxidized zone

.01

.008

.009

<.005

.008

.006

<.005

1.8

1.6

1.6

2.8

2.3

1.7

4.4

1.9

1.3

1.2

.89

1.0

.86

.75

.02

.007

.007

<.005

.009

<.005

<.005

13,000

11,000

13,000

26,000

21,000

16,000

44,000

9

9

7

10

15

13

19

110

110

200

270

360

250

400

37,000

22,000

14,000

12,000

15,000

16,000

20,000

190

140

120

94

120

99

86

190

110

110

64

98

70

88

20

12

13

8

14

14

9

1,400

1,500

1,200

1,600

2,600

2,300

3,000

Unoxidized pyritic zone

.009

.01

<.005

<.005

.006

.02

.01

4.0

5.6

4.6

3.1

2.6

4.3

3.6

1.6

1.2

.88

.78

.94

1.5

1.7

.01

.01

<.005

<.005

<.005

.01

.02

18,000

31,000

22,000

14,000

13,000

20,000

13,000

48

70

60

27

31

64

44

2,900

3,200

2,000

790

1,000

4,300

2,700

58,000

52,000

26,000

12.000

9,100

19,000

8,600

180

160

110

92

92

140

130

300

220

120

52

34

80

59

16

10

6

6

8

20

18

6,900

9,800

9,000

4,400

4,700

8,400

5,600

Buried soil

.27

.56

1.1

1.0

1.2

1.8

2.1

3.7

4.2

3.8

.60

.98

1.4

1.4

1.7

.26

.52

.80

.80

1.1

9,400

2,500

2,300

2,300

1,900

190

17

2

7

9

3,200

43

50

75

90

500

110

160

160

440

190

350

680

700

610

2

<2

<2

<2

<2

59

110

220

190

230

12.000

6,400

3,300

1,100

820
414 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

10 100 

CONCENTRATION, IN PARTS PER MILLION

1.000 10 100 1,000 

CONCENTRATION, IN PARTS PER MILLION

10,000

EXPLANATION

Concentration, in parts per million 

Arsenic (As)

——— Cadmium (Cd)

——— Copper (Cu)

——— Lead (Pb)

——— Manganese (Mn)

——— Silver (Ag)

——— Strontium (Sr)

——— Zinc(Zn)

Geochemical zones in the mill tailings, 

and underlying sediment, in inches

Oxidized zone (0-22) 

Partly oxidized zone (22-41) 

Unoxidized pyritic zone (41-62) 

Buried soil zone (62-79)

10 100 1,000 10,000 60,000 

CONCENTRATION, IN PARTS PER MILLION

Figure 4. Relation of selected trace-element concentrations in total digests to depth in the 2-in. core through 

mill tailings, upper Basin Creek. Concentrations of silver in samples below 64.3 in. were less than minimum 

reporting level of 2 parts per million and are not shown. A, strontium, manganese; B, cadmium, copper, zinc; 

C, silver, arsenic, lead.

in the leachate were well correlated (fig. 5, R2 = 0.88). Both 

sulfate concentration and specific conductance increased in 

the leachate with depth in the tailings and decreased in the 

buried soil. Iron concentrations in the leachate were low in the 

oxidized zone and high in the unoxidized pyritic zone. Iron 

concentrations in the oxidized zone were low because the iron 

had been leached out of the oxidized zone as shown by the 

total-digestion data.

Leachate data reflect the mobility of trace elements during oxidization of the tailings, with arsenic being the most 

mobile (concentration increase of about three orders of magnitude through the tailings); cadmium, copper, and zinc less 

mobile; and antimony, lead, and silver least mobile 

(fig. 5). The presence of native sulfur (identified visually) and 

the very soluble hydrous iron arsenate, scorodite, in the partly

oxidized zone (table 1) indicates that the mobility of the trace 

elements was limited with depth by low permeability in tailings. The immobility of lead is clearly shown by the presence 

of anglesite (lead sulfate, which is relatively insoluble) in the 

oxidized and partly oxidized zones (table 1). No jarosite (ironrich, hydrous potassium aluminum sulfate) was observed in 

the core, perhaps because insufficient potassium was available 

to form this mineral. Muscovite, which contains potassium, 

was sparse in the flotation wastes, so mobile potassium was 

not readily available to form jarosite. Deposit-related trace elements generally were sequestered at the top of the buried soil 

horizon immediately below the organic layer (62 in.), with the 

exception of manganese, zinc, and arsenic, which had elevated 

concentrations throughout the buried soil (fig. 5).
Table 2. Specific conductance, pH, and concentrations of sulfate and selected trace elements in leachate from various depth intervals of core samples collected from the mill 

tailings along upper Basin Creek.

[Core intervals expressed as the midpoint of the depth in the 2-in. diameter core from land surface (corrected for compaction). ICP. inductively coupled plasma; jag/L, micrograms per liter; fjS/cm, microsiemens 

per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; <, less than minimum reporting level; --, not analyzed (organic layer)]

Depth 

Sample (midNo, point, 

in inches)

Specific

conduc- .. . 

. pH of tanceof ... 

. . 4 leachate leachate

(uS/cm)

ICP1 

Sulfate

(mg/L)

ICP2 ICP3 ICP3 ICP3 

Aluminum Antimony Arsenic Cadmium

(Mg/L) (Mg/D (Mg/L) (Mg/L)

ICP1 

Copper

(Mg/D

ICP2 

Iron 

<Mg/L)

ICP3 ICP2 

Lead Manganese

(Mg/D (Mg/D

ICP2 ICP1 

Silver Strontium

(Mg/L) (Mg/L)

ICP1 

Zinc

<Mg/U

Oxidized zone

98BMF109-Aa 1.898BMF109-Ab 5.398BMF109-Ac 8.698BMF109-Ad 11.898BMF109-Ba 15.098BMF109-Bb 17.9

98BMF109-Bc 20.8

189

127

111

124

116

122

131

3.413.563.633.623.683.67

3.62

35

26

23

23

2323

24

200

98

73

120

96

120

56

150150

54

100

240500

580

71692538

28

6781

15

13

9.8

7.5

9.38.27.8

440450

640

670

710

490

390

44

9.25.0

14

586882

12,00015,000

17,00018,000

18,00018,00018,000

33

18

11

5.3

5.75.23.7

22

10

5.4

6

15

24

17

18

13

1212

8.9

8.2

5.3

3,4002,500

,800,300,900,600

,700

Partly oxidized zone

98BMF109-Ca 23.2

98BMF109-Da 25.4

98BMF109-Ea 28.2

98BMF109-Fa 31.198BMF109-Ga 34.498BMF109-Ha 37.5

98BMF109-Ia 39.7

610760

900

1,3301,350

860

1,320

3.09

2.942.902.772.752.82

2.73

97

120160

260240

160

230

590

560730

820

570

150190

1,6001,5001,7001,900

2,100

1,700

1,200

250210

230

370

630

1,800

5,200

415166

100

9967

88

2,0003,5005,600

11,000

11,000

7,700

10,000

2,2005,100

10,000

25,000

18.000

8,300

13,000

9,5007,400

6,100

5,000

4,7005,4004,800

14

17

23

3231

21

27

530240

68

5569

40

41

4.0

2.6

4.0

3.5

5.1

4.0

3.4

Unoxidized pyritic zone

98BMF109-Ja 42.4

98BMF109-Ka 45.598BMF109-La 48.898BMF109-Ma 52.298BMF109-Mb 54.998BMF109-Na 57.198BMF109-Oa 59.998BMF109-P 62.098BMF109-Qa 64.398BMF109-Qb 67.898BMF109-Qc 71.598BMF109-Qd 75.098BMF109-Qe 78.0

3,280

2,170

1,3301,050

1,350

2,5902,100 -- 4,400

1,830

760370

290

2.53

2.823.02

2.95

2.902.762.79 --2.843.43

3.88

4.144.15

900

770

440270

350

900670 -2,200

840330

140

110

1,600

780210210

480

3,400

4,200 - 200,000

46,000

3,500

740

580

1,700

1,200

720380

330

600

530 -71

11

113.5

14

24,000

18,00012,000

8,400

7,400

14,00015,000

Buried soil -- 65,000

6,600

2,100

3,600

1,200

1,000

1,500

900

490

640

1,7001,200 -- 9,700

580

285185

87,00088,000

46,000

22,000

35,000

140,000

96,000 -- 120,000

440

45

36

26

94,000

83,000

45,000

23,000

26,000

100,000

74,000 -- 19,000

1,500

180

65

50

3,000

3,500

4,1004,400

4,000

3,200

4,000 -780

130

44

13

35

280

300

190

120180

540530 -- 5,300

8,600

12,000

7,2005,900

3

<2<2

<2

<2<2<2 --<2<2

<2

<2

<2

15

3.42.16.77.67.05.3 --120

260

380310

270

8,400

13,000

18,000

31,000 if32,000 cp

22,000 E!

31,000 1

CD

280,000 g»

310,000 =

170,000 CD

83,000 £

120,000 a.

270,000 =f

180,000 3•a 

oa.

0 720,000 c

320,000 ?

86,000 5

12,000 a?

7,600 ='

'Inductively coupled plasma-atomic emission 

spectrometry data used at higher concentrations.

spectrometry (ICP-AES) data. ^Inductively coupled plasma-mass spectrometry (ICP-MS) used at low concentrations; inductively coupled plasma-atomic emission 

•'Inductively coupled plasma-mass spectrometry data.
416 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

5.000

1.000 1,500 2.000 

SULFATE, IN MILLIGRAMS PER LITER

2.500 10 100 1.000 10.000 

CONCENTRATION, IN MICROGRAMS PER LITER 

(sulfate, in milligrams per liter)

100,000 200.000

Cd Zn

Oxidized 

zone

soil 

zone

- 50

10 100 1,000 10.000 100.000 700,000 0.1 10 100 1.000 10.000 100,000

CONCENTRATION, IN MICROGRAMS PER LITER

Concentration, in micrograms per liter

EXPLANATION

• Aluminum (Al)

• Antimony (Sb) 

Arsenic (As)

• Cadmium (Cd)

• Copper (Cu)

• Iron (Fe)

Lead (Pb) 

Manganese (Mn) 

Silver (Ag)

• Sulfate (804), milligrams 

per liter

• Zinc (Zn)

CONCENTRATION, IN MICROGRAMS PER LITER

Geochemical zones in the mill tailings, 

in inches

Oxidized zone (0-22) 

Partly oxidized zone (22-41) 

Pyritic zone (41-62) 

Buried soil zone (62-79)

Figure 5. Relation of selected trace-element and sulfate concentrations in leachate to depth in the 2-in. core through 

mill tailings, upper Basin Creek. Sample numbers and analytical results are presented in table 2 and in Rich and others 

(this volume, Chapter G). Concentrations of silver in samples below 45.5 in. were less than minimum reporting level of 

2 micrograms per liter and are not shown.

Arsenopyrite

Early descriptions of ore from the Buckeye and Enterprise mines identified arsenopyrite as a significant mineral. 

However, no arsenopyrite was identified by X-ray diffraction of bulk samples or the high-density-mineral concentrates from the 2-in. core (table 1). Arsenopyrite generally 

is absent from most of the mine wastes present in the Basin 

mining district (Desborough and Fey, 1997). In addition, no

arsenic minerals were identified in the unoxidized pyritic zone 

(table 1) that would account for the arsenic concentrations of 

11,000^44,000 parts per million (ppm) (1.1 to 4.4 percent) in 

the partly oxidized zone (fig. 4; table 1). Too much arsenic is 

present in the pyritic zone of the core to be incorporated into 

pyrite and, therefore, the arsenic must be hosted in another 

mineral. Arsenic could possibly be present as an amorphous 

phase in the pyritic zone and, therefore, not detected by X-ray 

diffraction (XRD).
Trace-Element Sources and Transport to Upper Basin Creek 417

Dispersion of Tailings on the Flood Plain

Descriptions of the 1-in. core samples (Fey, Church, and 

Finney, 1999) indicated that the majority of these samples 

looked more like flood-plain sediment than like tailings, even 

though many of the samples had high concentrations of the 

deposit-related trace elements. These observations indicate 

that the tailings were subjected to various weathering and 

dispersion processes after their deposition in the 1940s. Tailings likely were mobilized and transported away from the 

original pile by physical processes (wind or water erosion) 

and then redeposited and mixed with sediment on the flood 

plain or transported to Basin Creek. In addition, trace elements 

have been mobilized and leached by water from the tailings by 

chemical processes. Portions of these trace elements then were 

precipitated or adsorbed before reaching Basin Creek, thus 

increasing trace-element concentrations in flood-plain sediment. The effects of this physical and chemical dispersion on 

the flood-plain surface can be examined using the total-digestion geochemical data from both the 1-in.-diameter cores 

(fig. 3; Fey, Church, and Finney, 1999) and the 2-in.-diameter 

core (table 1). The 1-in. cores provide spatial data over a large 

part of the flood-plain area affected by tailings, whereas the 

2-in. core provides detailed vertical information.

The contrast in silver and strontium concentrations 

provides a useful tool to differentiate between tailings and 

underlying premining flood-plain sediment and to understand 

physical and chemical dispersion processes. The contrast in 

concentrations was clear in the 2-in. core (fig. 4), in which 

tailings had low strontium (6-26 ppm) and high silver concentrations (34-300 ppm) while premining flood-plain sediment 

(buried soil) had high strontium (59-420 ppm) and low silver 

(<2-2 ppm) concentrations. However, only 11 of the 196 

one-inch core samples had strontium concentrations less than 

30 ppm and silver concentrations greater than 2 ppm. These 

11 samples likely contained essentially pure tailings because 

the 11 samples were from the cores collected nearest the 2-in. 

core, which was located in the thickest part and presumably 

near the center of the tailings pile. The proportion of tailings 

in the other 185 one-inch core samples apparently was much 

less. Figure 6 shows box plots of strontium and silver concentrations for each of the 1-in. cores from the main traverse line 

(fig. 3). The coincidence of low strontium concentrations and 

high silver concentrations for the two 1-in. cores next to the 

2-in. core near the center of the mill-tailings pile is apparent. 

Cores farther away from the 2-in. core had higher strontium 

and lower silver concentrations, indicating that the material 

at these sites was mostly flood plain sediment unaffected by 

tailings.

Figure 7 shows the relation between concentrations of 

strontium and other trace elements in the top layers of each 

of the 1-in. cores. The data are ordered from left to right in 

the graph on the basis of increasing strontium concentration, 

which also indicates a greater proportion of flood-plain

sediment relative to tailings. In figure 7A, silver and lead, 

which behave similarly and were shown to be less chemically 

mobile in the 2-in. core (fig. 4C and 5), show marked decrease 

in concentration as strontium concentration increases. This 

pattern suggests that silver and lead were dispersed primarily 

by physical transport of tailings away from the original pile. 

In contrast, concentrations of arsenic, cadmium, copper, and 

zinc (fig. IB, C) do not decrease as markedly as lead and silver 

concentration. These elements were shown to be more easily 

mobilized by chemical processes from the oxidized tailings 

than were lead and silver (figs. 4 and 5). Therefore, these 

elements most likely were dispersed to a greater extent by a 

chemical process involving mobilization, transport, and redeposition within the tailings area. Manganese, however, shows 

different behavior (fig. ID}: its concentration increases slightly 

as strontium concentration increases. This trend is opposite the 

concentration trend exhibited by most other trace elements and 

suggests that manganese is not derived from the tailings but 

from another source, such as ground water, that could affect all 

portions of the flood plain.

Shallow Subsurface Sources

Surface-geophysical surveys were conducted during 

the summers of 1998 and 1999 to examine the location and 

extent of shallow subsurface materials with high electrical 

conductivity, which could be related to elevated trace-element 

concentrations in the mill tailings along upper Basin Creek 

and the surrounding area. Defining the extent of potentially 

contaminated ground water also was a primary purpose of the 

geophysical investigations. Shallow subsurface materials were 

examined with a combination of electromagnetic, magnetic, 

and direct-current resistivity methods.

An electromagnetic (EM) survey was used to map the 

distribution of conductive materials in the mill tailings and 

in the underlying and surrounding valley-fill sediments and 

bedrock. Generally, in this type of environment, areas of high 

conductivity are caused by the presence of wet clays in soils 

or by high dissolved-solids concentrations in ground water. 

Magnetic metallic objects such as buried pipes, cables, or 

milling artifacts can cause conductive anomalies. A total-field 

magnetic reconnaissance survey was used to locate any metallic objects in the subsurface and differentiate them from areas 

with wet clays or high dissolved-solids concentration. Buried 

metallic objects are distinguishable because they are both 

conductive and magnetic.

Direct-current (DC) resistivity soundings were made on 

the tailings and adjacent areas to examine the vertical distribution of conductive material and to estimate the depth to 

bedrock beneath the tailings. Resistivity data were converted 

to the reciprocal values with units of conductivity so that they 

could be correlated directly with the electromagnetic (EM) 

data.
418 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

WEST EAST

500

100

SILVER - Site of 2-inch core

J:

T

WEST EAST

500

rt^T

STRONTIUM

" Site of 2-irch core

EXPLANATION

^^^--' Maximum value 

T———— 90th percentile

—75th percentile

— Median

— 25th percentile

— 10th percentile 

^Minimum value

Figure 6. Range and distribution of silver and strontium concentrations in total digestions of 1-in. cores along main 

traverse through mill tailings, upper Basin Creek. Minimum concentration shown for silver is minimum reporting level of 

2 parts per million. Location of main traverse line and sample sites shown in figure 3. Each core was divided into four to 

seven samples. Data are in Fey, Church, and Finney(1999).

Electromagnetic Survey of Conductive Materials

An electromagnetic (EM-34) survey conducted in 

1998 and electromagnetic (EM-31) surveys conducted in 

1998-99 were used to map subsurface conductivity of the 

mill tailings and the surrounding meadows and forested areas. 

These surveys measured the distribution of conductive materials in the subsurface at depths from about 10 to 100 ft.

Measurements of conductivity at varying depths were achieved 

by use of two different EM instruments, with a horizontal 

and vertical transmitter/receiver dipole orientation for each 

instrument. In the horizontal magnetic dipole (HMD) orientation, the transmitter and receiver coils are perpendicular to the 

ground. In the vertical magnetic dipole (VMD) orientation, 

the transmitter and receiver coils are positioned parallel to the 

ground, resulting in a greater depth of exploration. The
Trace-Element Sources and Transport to Upper Basin Creek 419

100,000

10,000

1.000

100

10

1

70,000

10.000

1,000

100

10

1

50,000

10,000

1,000

100

•-• "V •.••.% . . •

' * r • • .» • * -. . «...

EXPLANATION

• Arsenic

• Cadmium

• Copper

• Lead

• Manganese

• Silver

• Strontium

• Zinc

1,000

100

D

OBSERVATIONS

Figure 7. Relation of strontium and selected trace-element concentrations in total digests of 

1-in. cores through mill tailings, upper Basin Creek. A, silver and lead; B, arsenic and copper; C, 

cadmium and zinc; D, manganese. Only data for samples from the contaminated zones of these 

cores are shown to reduce amount of data plotted. Contaminated zones were defined by Fey, 

Church, and Finney (1999) and included upper portion of each core where concentration of cadmium, copper, lead, silver, or zinc exceeded average crustal abundance values by about 

10-50 times, depending on the trace element. Cadmium and silver concentrations reported as less 

than 2 parts per million are not plotted.

Geonics EM-34 has variable coil spacing that ranges from 33 

ft (10 m) to 131 ft (40 m). For this survey, the EM-34 spacing 

was set at 33 ft, resulting in an approximate exploration depth 

of 49 ft in the VMD orientation, and an approximate depth of 

25 ft (McNeill, 1980) in the HMD orientation. The Geonics 

EM-31 has a fixed intercoil spacing of 12 ft, which results in

an exploration depth of approximately 20 ft in the VMD orientation, and approximately 10 ft in the HMD orientation. Data 

collected by each of these instruments will hereinafter be 

referred to based on their relative exploration depths, deep 

(EM-34) and shallow (EM-31). A survey grid (fig. 8) that 

covered the tailings and adjacent area was constructed with an 

origin point near the thickest part of the tailings.
420 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112G 17'54" 112°17'47" 112 0 17'33"

460 23'46M

46°23'39"

EXPLANATION

i i Approximate area of mill tailings on flood

plain of Basin Creek 

| | Area of EM-34 survey

|__| Area of EM-31 survey 

O Location of grid origin (0,0) for EM surveys 

Grid point for EM surveys

c

• Test well and number

ENTERPRISE 

MINE Ox

EM-31 survey 

shown in detail 

in figure 10

EM-34 survey 

shown in detail 

in figure 9

400 FEET

100 METERS

Figure 8. Location of electromagnetic (EM) survey grid and test wells.

Contours of the deep and shallow survey data show a 

high positive apparent-conductivity anomaly near the surveygrid origin (figs. 9B and 10). The 2-in. core collected near the 

conductivity anomaly encountered several layers about 1 in. 

thick of oxidized and unoxidized sulfides (table 1). Laboratory 

measurements of sulfide layers from the core show that the 

conductivity is on the order of 1,000 millisiemens per meter 

(mS/m) (D.V. Smith, written commun., 1999). The anomaly 

near the grid origin likely is the result of these highly conductive sulfide layers.

Contours of the deep VMD data show a negative conductivity anomaly near the survey-grid origin (fig. 9/4). Buried 

magnetic metallic objects or lateral heterogeneities in layered 

deposits typically can result in similar responses. Another 

possibility is that the conductivity values, indicated in the core 

analysis, are high enough to allow for the low-inductionnumber approximation to be invalid. At high conductivity values (greater than 100 mS/m), the approximation of the linear 

relationship between instrument response and terrain conductivity becomes invalid and the reading becomes negative. This 

effect typically is more pronounced in the VMD orientation 

(McNeill, 1980).

The shallow contour maps (fig. 10) show three areas 

where subsurface conductivities substantially increase. First, 

an anomaly interpreted as a body of conductive material 

extends from the area of the survey-grid origin to the

southwest toward Basin Creek (fig. 10/4). This anomaly, in 

terms of depth, position, and conductivity, is consistent with 

the potentiometric surface and direction of ground-water flow 

at the mill-tailings site on the flood plain (tig. 14, presented 

in ground-water section). Second, the shallow contour map of 

VMD data shows an area of high conductivity in the northeast part of the survey area, south of the Enterprise mine. The 

higher conductivity observed in this area may be the result 

of elevated concentrations of major ions and trace elements 

in the ground water. A seep of red-colored water in the area 

of this anomaly was observed in July 1999. Third, an area of 

relatively high conductivity (fig. 10/4) is indicated southwest 

of and on the other side of Basin Creek from the mill tailings 

in an area of wet meadows. Lithologic and geochemical data 

from cores or boreholes in this area are not available, but the 

conductivity could be the result of mill tailings deposited in 

this area during high streamflow. However, the higher conductivity more likely is caused by the presence of conductive 

clays or organic material, or both, in the meadow soil.

Magnetic Survey of Shallow Anomalies

During the summer of 1999, a total-field magnetic survey 

of the north-south and east-west base lines (fig. 11) was conducted using a proton precession magnetometer (Telford and 

others, 1990). Three measurements were taken at 33-ft (10-m)
Trace-Element Sources and Transport to Upper Basin Creek 421

B

EXPLANATION

IB Contour-Shows magnitude and extent of 

subsurface apparent conductivity (EM-34) 

in millisiemens per meter. Contour interval 

3 millisiemens per meter

+ Geophysical survey station-10-meter spacing

APPARENT CONDUCTIVITY 

(Millisiemens per meter)

Figure 9. Deep subsurface apparent conductivity measured using an EM-34 along upper Basin Creek. A, vertical magnetic dipole; 

B, horizontal magnetic dipole.

intervals and averaged to account for temporal variations in 

the Earth's magnetic field. This survey was intended to detect 

buried magnetic metallic objects that might cause the local 

EM anomalies.

Of particular interest was the area near the grid origin 

where EM results indicated an area of high conductivity 

caused either by a buried conductive metallic object or by 

lateral heterogeneity in the layered mill tailings. The totalfield magnetic survey indicated several metallic objects near 

the surface that caused local magnetic anomalies along the 

north-south magnetic survey line. However, no substantial 

magnetic anomalies were found along the east-west line, and 

no substantial magnetic anomalies were found in the area of 

the grid origin (fig. 12). Therefore, buried magnetic metallic 

objects are not a likely source of the high conductivity anomalies in the area of the grid origin. The likely source of the high 

conductivities is a zone of layered sulfides in the mill tailings.

Direct-Current Resistivity Soundings of 

Conductive Materials

Direct-current (DC) resistivity soundings were conducted 

in eight locations using an SAS DC resistivity system made by 

ABEM Instrument AB, Sweden, and a Schlumberger electrode 

array (Smith and Sole, 2000). Seven of these soundings were 

made on and near the main area of mill tailings (fig. 11) to 

provide detailed information about the subsurface variations 

and to possibly define the depth to bedrock. One additional 

sounding was made in an area of exposed granite bedrock 

about 2 mi northwest of the tailings (not shown in fig. 11) to 

directly measure the resistivity of bedrock. The sounding data 

(McDougal and Smith, 2000) were interpreted using software 

from Interpex (RESIX-IP version 2.14; Interpex, 1993).

Subsurface conductivity as interpreted from the DC 

soundings is shown in figure 13. Data from soundings DCS-1
422 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

- + + + +J

B

1 +++++++++++++++

APPARENT CONDUCTIVITY 

(Millisiemens per meter)

400 FEET

100 METERS

EXPLANATION

^H Contour—Shows magnitude and extent of 

subsurface apparent conductivity (EM-31) 

in millisiemens per meter. Contour interval 

3 millisiemens per meter

+ Geophysical survey station—10-meter spacing

Figure 10. Shallow subsurface apparent conductivity measured using an EM-31 along upper Basin Creek. 

A vertical magnetic dipole; B, horizontal magnetic dipole.

and DCS-3 (fig. 11) were not used because lateral heterogeneities affected the interpretation. For each sounding, the 

estimated subsurface conductivity was assumed to be located 

at the midpoint of the interpreted subsurface layer. The layer 

thickness increases at an approximately logarithmic rate 

because the resolution decreases at a similar rate. Consequently, the depths to points of estimated subsurface conductivity (sounding data points, fig. 13) increase logarithmically.

The estimate of the conductivity of the last layer should be 

taken as relatively resistive or conductive because the soundings did not approach a constant value asymptotically at large 

electrode spacings.

A conductive anomaly at a depth of about 25 ft exists in 

the center of the section (fig. 13) at DCS-2. The anomaly is 

interpreted to be a body of conductive material, most likely 

ground water with high dissolved-solids concentrations. A
Trace-Element Sources and Transport to Upper Basin Creek 423

112° 1TW 112G 17'40" m°1733"

46°23'46"

46°23'39"

EXPLANATION

Approximate area of mill tailings on flood 

plain of Basin Creek

Total-field magnetic survey line

-A' Trace of section-Subsurface conductivity 

section shown in figure 13

Location of direct-current resistivity sounding 

and number-One site about 2 miles northwest of 

tailings not shown

Test well and number

ENTERPRISE 

M,NE *

Rl ICKFYf400 FEET

100 METERS

Figure 11. Location of total-field magnetic survey lines and direct-current (DC) resistivity soundings.

relatively high subsurface conductivity anomaly also exists at 

DCS-6. This anomaly is located between the Enterprise mine 

and upper Basin Creek.

The sounding made on a nearby bedrock outcrop to the 

northwest of the tailings (DCS-8) showed that the conductivity 

of shallow bedrock is about 5 mS/m. None of the subsurface 

conductivities are this low except perhaps for DCS-2, DCS-4, 

and DCS-5 (fig. 13). Consequently, granite underlying the mill

tailings, with similar electrical properties as the outcropping 

area, may lie more than 98 ft deep. However, the granite in 

the stream valley likely is more weathered and has a higher 

volume of water than the outcrop area of DCS-8. Also, the 

underlying granite aquifer could have fractures that contain 

clays or that have water with high dissolved-solids content, 

which would produce higher conductivities and consequently 

place its depth at less than 98 ft.
424 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

SOUTH

950

900

North-South Survey Line NORTH

£o 850

650 

-500 -450 -400 -350 -300 -250 -200 -150 -100 -50 0 50 100 150 200 

STATIONS. IN FEET

WEST

950

900

& 850

650

East-West Survey Line

DCS3

EAST

-500 -450 -400 -350 -300 -250 -200 -150 -100 -50 0 50 100 150 200

STATIONS, IN FEET

Figure 12. Results of total-field magnetic survey.
VERTICAL EXAGGERATION X4

EXPLANATION

^1 Contour-Shows magnitude and extent 

of subsurface apparent conductivity in millisiemens per meter. Contour interval is 3 millisiemens per meter

+ Sounding data point

Figure 13. Subsurface conductivity from direct-current resistivity soundings. Trace of section shown in figure 11.

400 FEET

100 METERS

9996

93908784

8178757269

66636057545148

4542

3936333027242118

1512

9630

APPARENT CONDUCTMTV 

(MUlistemens per meter)

55 

n 

cpmCDCD

3.C/Je I

CD 

(A

B)

ea. S1CDCO 03 (ACDJT
426 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Transport of Trace Elements to Upper 

Basin Creek

Ground-water movement and surface-water runoff are the 

primary means of transport of trace elements from sources in 

the area of the Buckeye and Enterprise mines to upper Basin 

Creek. Studies were made of the local ground-water flow systems, quality of ground water, surface-water runoff, and quality of surface water to evaluate trace-element loads transported 

to upper Basin Creek by ground and surface water.

Ground Water

Ground-water resources along the upper Basin Creek 

valley and the area of the Buckeye and Enterprise mines were 

examined to identify aquifers and determine their characteristics, define ground-water and surface-water interaction along 

upper Basin Creek, and evaluate effects of acidic drainage 

on quality of ground water. Trace-element loads entering 

Basin Creek from acidic ground water in the study area were 

estimated to evaluate the effects of ground-water discharge on 

trace-element concentrations and loads in upper Basin Creek.

General Geohydrologic Setting

Two distinct aquifers, with vastly different hydraulic 

characteristics and flow systems, exist in the study area. One 

aquifer is a fractured bedrock system, composed of fractured, 

weathered, and mineralized granitic rocks of the Boulder 

batholith; the second aquifer is an unconsolidated porous 

system composed of till, alluvium, colluvium, organic-rich 

wetland deposits, and volcanic ash. The unconsolidated deposits underlie the flood plain of Basin Creek and overlie granitic 

rocks of the Boulder batholith.

Bedrock underlying the study area was originally mapped 

as Butte quartz monzonite of Late Cretaceous or Paleocene 

age (Ruppel, 1963). Recent studies have classified the Butte 

pluton as a medium- to coarse-grained hornblende-biotite 

granodiorite-tonalite (O'Neill and others, this volume, Chapter 

Dl). Fractures in the bedrock are numerous and include 

several steeply dipping sets of joints and one gently dipping set. Ruppel (1963) reported that one prominent joint set 

trends about east and dips steeply north, and one set trends 

about north and dips steeply west. Individual joints in the 

rock are rarely more than 30 ft long, but where one joint dies 

out, it commonly is overlapped by a parallel joint that either 

is entirely separate from the other, or that is connected by a 

linking transverse joint. Joints are open and weathered where 

they are exposed in outcrops. However, with increasing depth, 

joints typically become tighter and less weathered or contain 

clay.

Hydraulic conductivity of the bedrock aquifer is directly 

related to the number, size, clay content, and degree of connection of joints. Hydraulic conductivity is greatest near the

bedrock surface and decreases substantially within 5-50 ft of 

the surface, based on observations of fractures in outcrops, 

road cuts, core holes, and wells in the Boulder batholith. Most 

ground-water flow within the bedrock aquifer is in the uppermost fractured and weathered zone. Deeper fractures within 

the batholith can be saturated, as observed in a 100-ft-deep 

core hole 4 mi southeast of the study area, but fracture width 

and hydraulic conductivity generally are very small. Recharge 

from precipitation and snowmelt readily infiltrates the upper 

zone of weathered rock; shallow ground water follows the 

general topographic gradient and discharges to nearby seeps, 

springs, and streams. Discharge from the weathered bedrock 

commonly is observed at abrupt changes in topographic slope 

and at the contact between highly weathered and jointed rock 

and underlying rock that is less weathered. In the Buckeye 

study area, ground-water flow in the bedrock aquifer follows 

short flow paths from areas of recharge on slopes near the 

mines to areas of discharge along the valley margins and into 

sediments of the upper Basin Creek valley. Ground-water discharge, in the form of large seeps, was observed near the base 

of the bedrock hillsides south and southwest of the Buckeye 

and Enterprise mines. The ground-water discharge observed 

at this site is consistent with the conceptual model of groundwater flow as presented by McDougal and others (this volume, 

Chapter D9).

Saturated unconsolidated deposits that include till, alluvium, colluvium, wetland deposits, and volcanic ash form a 

heterogeneous aquifer that is hydraulically connected to Basin 

Creek. The unconsolidated deposits that compose the flood 

plain range from less than I ft to more than 30 ft thick and are 

overlain by mill tailings near the Buckeye mine. Bouldery till 

makes up a large part of the unconsolidated deposits. The till 

is exposed near the valley margin south of Basin Creek and 

along the stream banks about 1,200 ft downstream from the 

Buckeye flotation-mill tailings. Till overlies bedrock within 

much of the Basin Creek valley, and a small moraine at the 

lower end of the study area likely formed a natural dam to 

postglacial Basin Creek. Sediments that accumulated upstream 

from the moraine included stream-laid silt, sand, and gravel; 

organic-rich silt and clay; and volcanic ash from the eruption 

of Mount Mazama, about 6,845 years before present. Geologic 

and hydrologic characteristics of the unconsolidated-deposits 

aquifer were explored with shallow test wells.

Test Wells

Nine test wells (fig. 14; table 3) were drilled in the study 

area by Maxim Technologies Inc., under a contract with the 

USDA Forest Service. The wells were drilled into the unconsolidated deposits in the flood plain of Basin Creek to characterize the aquifer, to determine directions of ground-water 

flow, and to measure the quality of ground water. Seven of the 

test wells were installed in the area mantled by or adjacent to 

mill tailings. The test wells were installed using hollow-stem 

auger methods and were constructed of 2-in. diameter PVC 

(polyvinyl chloride) casing and screen, with 6-in. diameter
Trace-Element Sources and Transport to Upper Basin Creek 427

112°18'01" 112°17'54" 112°17'47" 112°17'40"

1 1 1 1

EXPLANATION

1 _ J Approximate area of mill tailings on 

flood plain of Basin Creek

—— 7,027 -- Water table contour -Dashed where 

approximately located. Interval is 1 foot BULKtYt 

8 MINE ^ 

• Test well and number

® Survey site for water-surface altitude 

46°23'46" — -^ —— Direction of ground-water flow

,,, |f), —7,03

^ B ; _ ~^f^^r\

'\ ^_ 6_ "^>V-, : : ir\ i--y \ ._, x"^^^-,c~^~^^"^'^ -<%>/ X-. 

x., f ^ _--' ] NX^\X**': : ; : '%£/N (f\

/ ~' ( -/ f \ ' \\^^

46"23'39" — 1 \ 1 \

1 1 1 1

Datum is from NATIONAL GEODETIC VERTICAL DATUM OF 1929 °,

0

Figure 14. Location of test wells and configuration of water table, August 3, 1999. 

Table 3. Well-completion data for test wells near upper Basin Creek.

[Data from Maxim Technologies, Inc., unpub. data, 1998]

... „ .. . ... . . .4 . Altitude of Drilled depth of p . . . Well No. Latitude Longitude ... „ Screen interval 

... ... .. r.f land surface well ., .

{flg' 14) N' W' (feet) (feet) (feet)

1 462344 1121737 7,038.6 10.8 5.6-10.6 

2 462343 1121741 7,039.7 24.8 16.7-21.7 

3 462342 1121742 7,034.8 11.0 5.5-10.5 

4 462340 1121743 7,032.5 31.0 26-31 

5 462340 1121742 7,032.8 8.5 3.5-8.5 

6 462342 1121746 7,032.5 10.0 4.5-9.5 

7 462341 1121746 7,032.3 11.0 5.5-10.5 

8 462342 1121748 7,032.0 13.0 5.5-10.5 

9 462347 1121733 7,043.6 17.0 10-15 

10 462339 1121743 7,034.2 5.0 4-5

112°17'33"

1 ) 

ENTERPRISE S 

MINE K> ^)

r* f ^

&i ^ - "5, 

\ & ) *«

^JA J\' 

\

i

400 FEET i

100 METERS

Height of cas- Interval of 

ing above land bentonite seal 

surface (feet below land 

(feet) surface)

2.8 0-3.6 

2.8 0-14.0 

3.0 0-3.7 

3.1 0-23.8 

3.0 0-2.2 

3.2 0-3.7 

2.9 0-4.7 

2.8 0-4.4 

2.3 0-8.9 

2.2 none1

'Sealed with cuttings.
428 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

steel protective casing at the surface. Each well screen was 

packed with silica filter sand and the entire annular space 

above the sand was sealed with bentonite. One additional shallow well (well 10) was drilled south of Basin Creek using a 

hand auger. Well 10 was installed in an area where an electromagnetic survey indicated moderately high values of conductivity and the possibility of ground water affected by acidic 

drainage from the Buckeye mill-tailings site.

Water Levels and Flow Directions

Water levels in test wells were measured periodically 

between December 1998 and August 1999 (table 4). Waterlevel data show that the water table is near land surface 

under the Basin Creek flood plain and in the area containing 

flotation-mill tailings. During part of the year, ground water 

saturates much of the mill tailings along Basin Creek. Water 

levels generally are highest in May and June, which also is 

when snowmelt and rain generally increase water depth and 

streamflow in upper Basin Creek. At well 6, measurements 

made in May and June documented water levels above land 

surface. Ground water was observed seeping from the ground 

in the vicinity of well 6 during that time.

A contour map showing the configuration of the water 

table (fig. 14) and direction of shallow ground-water flow was 

prepared using water-level measurements made on August 

3, 1999. Water-level data for the contour map were collected 

from 10 wells and from water-surface altitudes of Basin 

Creek, surveyed at nine locations within the study area. Watersurface altitudes in Basin Creek were similar to water-table 

altitudes measured in shallow wells (wells 5 and 7) near the 

stream, indicating hydraulic connection between the stream 

and flood-plain sediments.

In the upstream part of the study area in the vicinity of 

wells 1 and 9, ground water flows southwesterly toward Basin 

Creek. Ground water probably moves from the vicinity of the 

Enterprise mine toward wells 1 and 9, and to Basin Creek, as 

inferred from the topographic slope in that area.

Water-level data from wells 2 through 8 indicate that 

ground water follows a curved flow path as it moves south 

and west through the area of mill tailings on the flood plain of 

Basin Creek. Ground water moves southward from the general 

area of the Buckeye mine toward wells 2 and 3 and then 

moves predominantly westward along the flood plain in the 

area of wells 4, 7, and 8. During low streamflow conditions 

(July through March), little or no ground water discharges to 

Basin Creek adjacent to or immediately downstream from the 

mill tailings. In the area of wells 4, 5, 7, and 10, water-level 

data indicate that some water may be moving from Basin 

Creek into the flood-plain deposits.

During higher streamflow conditions (generally late 

April, May, and June), water levels in wells are at their peak 

for the year. Based on synoptic streamflow measurements in 

May 1999, the high water table during spring and early summer does not cause a measurably larger discharge of ground 

water directly into Basin Creek than during low flow,

probably because the stream also is at a higher stage at that 

time. It was observed that during higher water levels, water 

seeps out of the ground in the western and northwestern parts 

of the tailings deposits and that seepage drains into small 

tributaries flowing into Basin Creek.

Hydraulic properties of the unconsolidated-deposits aquifer were estimated from aquifer tests conducted at the nine test 

wells. Aquifer tests were made using a slug-injection method; 

changes in head were measured with a submersible pressure 

transducer and programmable data logger. Aquifer test data 

were analyzed using the curve-matching method of Cooper 

and others (1967). Results of aquifer tests are presented in 

table 5. Hydraulic conductivity values determined from the 

aquifer tests ranged over 3 orders of magnitude, from 0.03 to 

40 ft/d. The median hydraulic conductivity was a relatively 

small 0.22 ft/d, reflecting the large amount of silt and clay in 

the sediments underlying the Basin Creek flood plain.

During low flow, discharge of ground water from the 

unconsolidated-deposits aquifer to Basin Creek is minimal. 

The water-table configuration and flow directions drawn from 

water-level data collected in August 1999 (fig. 14) show that 

ground water discharges to Basin Creek in the stream reach 

upstream from the mill tailings (area 1, fig. 14), but not in the 

area of mill tailings (area 2, fig. 14). Ground-water discharge 

to Basin Creek or rate of ground-water flow through sediments underlying the Basin Creek flood plain can be estimated 

from the gradient of the water table, cross-sectional area of 

the aquifer, and hydraulic conductivity of the sediments. The 

rate of ground-water discharge into Basin Creek within area 

1 is about 25 ft3/d, assuming an average gradient of 0.017, an 

aquifer cross-sectional area of 6,900 ft2 (15 ft x 460 ft), and 

an average hydraulic conductivity of 0.21 ft/d (wells 1 and 9). 

The calculated rate of ground-water discharge within area 1 

applies to discharge from the northwest side of Basin Creek 

and does not include discharge from the south side of the 

stream.

During low flow, Basin Creek receives little or no 

ground-water discharge through the area of mill tailings 

(area 2, fig. 14). Water-table contours in figure 14 indicate that 

near Basin Creek, ground water flows predominantly to the 

west, nearly parallel with the stream. The rate of ground-water 

flow through the upper 15 ft of sediments in the vicinity of 

wells 3 through 8 during low flow is about 220 ft3/d. 

The calculated flow rate is for the cross section between 

Basin Creek and well 6, and assumes a gradient of 0.007 

(4 ft/570 ft), an aquifer cross-sectional area of 3,750 ft2 

(15 ft x 250 ft), and an average hydraulic conductivity of 

8.6 ft/d (average for wells 3-8, table 3).

Water Quality and Trace-Element Loads

Quality of ground water in deposits underlying the Basin 

Creek flood plain was determined by analysis of samples 

collected at 10 test wells (fig. 14). Seven of the ten test wells 

(wells 2-8) were in the area of mill tailings, one well (well 10) 

was south of Basin Creek, and two wells (wells 1 and 9) were
Trace-Element Sources and Transport to Upper Basin Creek 429

Table 4. Water levels, pH, and specific conductance of ground water from test wells near upper Basin 

Creek.

[|u.S/cm, microsiemens per centimeter at 25 degrees Celsius; -, no data]

Well No. _ 4 /i- 4/n Date (fig. 14)

1 12-01-98

02-23-99

04-19-99

05-20-99

05-24-99

06-07-99

06-14-99

08-03-99

2 12-01-98

02-23-99

04-19-99

05-20-99

05-24-99

06-07-99

06-14-99

08-03-99

3 12-01-98

02-23-99

04-19-99

05-20-99

05-24-99

06-07-99

06-14-99

08-03-99

4 12-01-98

02-23-99

04-19-99

05-20-99

05-24-99

06-07-99

06-14-99

08-03-99

5 12-01-98

02-23-99

04-19-99

05-20-99

05-24-99

06-07-99

06-14-99

08-03-99

6 12-01-98

02-23-99

04-19-99

05-20-99

05-24-99

06-07-99

Water level, 

below or above (+) 

land surface 

(feet)

2.51

2.62

.41

.16

—

-

.18

2.65

7.66

7.83

6.38

5.02

-

—

5.28

7.10

3.78

3.86

2.98

2.90

—

—

3.12

3.82

1.54

1.65

.91

.68

—

—

.95

1.60

1.90

2.03

1.21

.90

—

—

1.24

2.03

1.46

1.52

.43

+.21

—

—

pH 

(standard 

units)

4.7

3.8

-

-

4.0

3.4

—

--

8.4

8.2

—

--

7.4

7.2

-

--

4.9

3.6

-

—

4.2

5.9

-

-

7.4

8.0

-

-

7.8

7.8

—

--

5.8

6.0

-

-

3.6

3.7

—

--

6.6

6.5

—

—

6.4

6.9

Specific conductance 

(jiS/cm)

758

768

—

—

529

556

—

--

505

447

-

--

416

414

--

-

1,260

1,690

-

—

1,200

1,110

--

-

516

443

—

--

445

409

—

--

147

136

—

--

1,530

1,800

-

-

388

364

-

-

371

386
430 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 4. Water levels, pH, and specific conductance of ground water from test wells near upper Basin 

Creek.—Continued

Well No. _ . 

it- <fli Date (fig. 14)

6 (cont.) 06-14-99

08-03-99

7 12-01-98

02-23-99

04-19-99

05-20-99

05-24-99

06-07-99

06-14-99

08-03-99

8 12-01-98

02-23-99

04-19-99

05-20-99

05-24-99

06-07-99

06-14-99

08-03-99

9 12-01-98

02-23-99

04-19-99

05-20-99

05-24-99

06-07-99

06-14-99

08-03-99

10 07-30-99

08-03-99

Water level, 

below or above (+) 

land surface 

(feet)

+.22

1.54

1.74

1.88

1.12

1.02

-

-

1.20

1.85

4.58

4.62

4.01

3.16

-

-

3.48

4.44

2.26

2.29

1.03

.49

-

-

.76

2.43

_

3.45

pH 

(standard 

units)

-

-

5.9

5.4

-

-

5.7

6.6

-

-

6.3

6.5

-

-

6.2

7.1

-

-

7.0

6.9

-

--

6.6

6.1

-

-

6.5

-

Specific conductance 

(liS/cm)

-

-

342

290

-

-

256

330

-

-

381

273

-

-

390

427

-

-

920

924

-

-

903

911

-

-

167

-

northeast of the mill tailings between Basin Creek and the 

Enterprise mine (fig. 14). Before the wells were sampled for 

chemical analysis in June and July 1999, they were purged on 

three occasions with a hand bailer. The wells were purged and 

sampled for pH and specific conductance in December 1998, 

and February and May 1999 (table 4).

Water samples were collected from wells 1-9 on June 

7, 1999, and from well 10 on July 30, 1999, and analyzed for 

common ions and dissolved (0.45-micrometer (|im) filtration) 

trace elements (table 6). Samples from wells 1, 3, and 5 had 

relatively low pH and elevated concentrations of dissolved 

trace elements, indicating effects from acid drainage. Well 1,

which is located northeast of the mill tailings, had water with a 

pH of 3.4 when sampled in June 1999. Water from well 1 had 

relatively high concentrations of dissolved aluminum, cadmium, copper, lead, manganese, and zinc (table 6). The largest 

dissolved lead concentration analyzed from the 10 wells was 

36 micrograms per liter (|ig/L) from well 1.

Water from well 3, located near the center of the mill 

tailings, had a pH of 5.9 when sampled in June 1999, although 

a sample taken in February 1999 had a pH of 3.6 (tables 4 and 

6). Water from well 3 had high dissolved concentrations of 

dissolved aluminum, arsenic, iron, manganese, and /inc. The
Trace-Element Sources and Transport to Upper Basin Creek 431

Table 5. Hydraulic properties of unconsolidated deposits along upper Basin Creek.

fft/d, foot per day; ft2/d, foot squared per day]

Well No. 

(fig. 14)

1

2

3

4

5

6

7

8

9

Transmissivity 

(ftVd)

1.0

.19

3.0

.25

200

.16

8.3

46

1.1

Hydraulic 

conductivity

(ft/d)

0.20

.04

.60

.05

40

.03

1.7

9.2

.22

Average horizontal 

hydraulic gradient in 

area of well 

(August 1999}

0.010

.018

.005

.003

.003

.018

.015

.015

.024

Geologic description of 

unconsolidated deposits 

in screen interval

Silty sand, sandy clay.

Sandy, gravelly clay (till).

Sandy silt.

Silty sand, sandy clay.

Silty fine to coarse sand, sandy clay.

Clayey sand, silty sand, gravel, weathered rock.

Silty, clayey sand.

Silty sand, gravel, cobbles.

Silty sand with some gravel.

largest arsenic concentration analyzed from the 10 wells was 

19,000 ug/L from well 3.

Water from well 5 had a pH of 3.7 and relatively 

high concentrations of dissolved aluminum, arsenic, 

cadmium, copper, lead, manganese, and zinc. Of the 10 wells 

sampled, well 5 had the highest concentrations of aluminum 

(55,200 ug/L), cadmium (220 ug/L), copper (2,290 ug/L), and 

zinc (49,100 ug/L).

Wells 2,4, 6, 7, and 8 were completed in the area of mill 

tailings between the Buckeye mine and Basin Creek. Water 

samples collected from these five wells in June 1999 had pH 

values that ranged from 6.6 at well 7 to 7.8 at well 4. Concentrations of dissolved aluminum, cadmium, copper, lead, 

and zinc were relatively low in water samples from wells 2, 

4, and 6. Wells 2 and 4 are the deepest of the 10 wells and are 

completed in parts of the aquifer not directly affected by acid 

drainage. Well 6 is located at the northwestern margin of the 

mill tailings, upgradient from flow paths in the mill tailings, 

and also is not directly affected by acid drainage. Water from 

well 7 had relatively high concentrations of dissolved arsenic 

(680 ug/L) and iron (27,000 ug/L). Well 8 had a large concentration of dissolved zinc (10,300 ug/L).

Well 9, located south of the Enterprise mine, had a dissolved zinc concentration of 292 ug/L when sampled in June 

1999. Well 10, located south of Basin Creek in an area not 

disturbed by mining, had relatively low concentrations of dissolved trace elements, except for arsenic (45 ug/L) and iron 

(15,000 ug/L).

Loads of trace elements reaching Basin Creek from 

shallow ground water can be estimated from trace-element 

concentrations sampled at wells and rates of ground-water 

flow through the upper part of the aquifer. For the stream 

reach upstream from the mill tailings (area 1, fig. 14), calculated ground-water discharge into Basin Creek is about 

25 ft3/d during low flow. The calculated ground-water discharge applies to the upper 15 ft of deposits, which contains 

most of the poor-quality water from acid drainage. Estimated

trace-element loads to Basin Creek in area 1 are shown in 

table 7 and are based on the average trace-element concentrations at wells 1 and 9. Within area 2 of Basin Creek, groundwater flow predominantly is to the west, parallel to Basin 

Creek. During low flow, the dissolved trace-element load in 

ground water is not discharging directly to Basin Creek adjacent to the mill tailings (area 2) but likely enters Basin Creek 

downstream, probably within a zone from 500 to 1,200 ft west 

of the mill tailings. Flood-plain deposits are pinched off by a 

glacial moraine about 1,200 ft down valley from the mill tailings, favoring the discharge of ground water from the floodplain deposits into Basin Creek in that area. Trace-element 

loads to Basin Creek from area 2 (table 7) are based on the 

average trace-element concentration at wells 3, 5, 6, 7, and 8 

and the rate of ground-water discharge of about 220 ft3/d during low flow.

Downstream increases in trace-element loads measured 

in upper Basin Creek through the Buckeye study area during low flow also can be used to evaluate the ground-water 

contribution to trace-element loads in Basin Creek. Water 

samples collected upstream (site 4B, fig. 15) and downstream 

(site 22B) from the mine area during low flow on October 16, 

1998, showed substantial increases in some concentrations of 

dissolved aluminum, arsenic, manganese, and zinc (table 8). 

Dissolved aluminum increased from 2.3 ug/L above the mines 

to 12 ug/L below the mines, dissolved arsenic increased from 

1 ug/L to 14 ug/L, dissolved manganese increased from 8 ug/L 

to 52 ug/ L, and dissolved zinc increased from 7 ug/L to 26 

ug/L. Combining streamflow measurements with trace-element concentrations to compute instantaneous loads (table 9) 

indicated that dissolved aluminum load increased from 2.4 

grams per day (g/d) above the mines to 19.4 g/d below the 

mines, dissolved arsenic load increased from 1.0 g/d to 22.6 

g/d, dissolved copper load increased from <1 g/d to 3.2 g/d, 

dissolved manganese load increased from 8.4 g/d to 84.0 g/d, 

and dissolved zinc load increased from 7.4 g/d to 42.0 g/d.
432 Environmental Effects of Historical Mining, Boulder River Watershed, Montana 

Table 6. Concentrations of major ions and dissolved trace elements in ground water near upper Basin Creek.

, micrograms per liter; ^iS/cm, microsiemens per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; <, less than minimum reporting level]

Well No. 

(fig. 14)

1

2

3

4

5

6

7

8

9

10

Date

06-07-99

06-07-99

06-07-99

06-07-99

06-07-99

06-07-99

06-07-99

06-07-99

06-07-99

07-30-99

Specific ... .. .^ .. 

r . . u Alkalinity, „ . . Mag- conduct- pH, . . Calcium, i- ij / * laboratory .. . . nesium, 

ance, field (stan- , .. dissolved .. . . 

.... . . .. , (mg/L as , ... dissolved field dardumts) » (mg/L)

(|j.S/cm) 3

556 3.4 <1 64

414 7.2 79 43

1,110 5.9 <1 160

409 7.8 213 46

1,800 3.7 <1 240

386 6.9 125 44

330 6.6 16 31

427 7.1 29 45

911 6.1 94 140

167 6.5 64 14

11

14

32

11

36

9.5

8.1

11

27

4.6

Sodium, 

dissolved 

(mg/L)

5.3

17

21

25

17

14

4.9

9

16

5.9

_ t . Sulfate, Potassium, .. . . 

.. . . dissolved dissolved , ,. /mn/l » (mg/L as (mg/L) S(y

2.4

4.5

1.4

7.9

1

5.3

1.5

<.l

6.5

.8

270

120

1,100

6.2

1,100

56

100

160

390

<0.1

Well No. 

(fig. 14)

1

2

3

4

5

6

7

8

9

10

Chloride, 

dissolved 

(mg/L)

0.7

1.5

1.6

4.4

8.8

3.6

1

2.3

.8

.9

Dissolved 

solids, Aluminum, Arsenic, Cadmium, Copper, 

sum of dissolved dissolved dissolved dissolved 

constitu- (|ag/L) (|ag/L) (^g/L) (jag/l) 

ents (mg/L)

350 4,780 4 40 820

250 4 6 <1 1

1,300 307 19,000 <1 2

230 3 26 <1 <1

1,400 55,200 68 220 2,290

220 2 2 <1 <1

190 8 680 <1 <1

250 272 28 5 1

630 2 15 5 1

65 18 45 <1 <1

Iron, 

dissolved

(^ig/L)

1,300

55

130,000

310

1,400

5,900

27,000

9,200

1,300

15,000

Lead, 

dissolved

(l^g/L)

36

<1

3

<1

20

<1

<1

<1

<1

<1

Manganese, 

dissolved

(m/L)

6,060

1,310

7,080

256

6,770

3,770

2,230

2,290

1,140

135

Zinc, 

dissolved

(WJ/L)

4,850

9

12,200

1

49,100

9

9

10,300

292

2
Trace-Element Sources and Transport to Upper Basin Creek 433

Table 7. Estimated dissolved trace-element loads 

discharged to upper Basin Creek during low flow 

from shallow ground water in the vicinity of the 

Buckeye and Enterprise mines.

[g/d, grams per day]

Trace 

element

Aluminum

Arsenic

Cadmium

Copper

Iron

Lead

Manganese

Zinc

Load from 

areal

(g/d)

1.69

.007

.016

.290

.920

2 .025

2.55

1.82

Load from 

area 21

(g/d)

69.5

24.7

2 .28

2 2.85

216

2 .031

27.6

89.1

'Load from area 2 likely enters upper Basin Creek downstream from tailings area.

Tor values that were reported as less than the minimum 

reporting level of 1 (ig/L, the value of 1 (ig/L was used to 

calculate an average trace-element concentration.

The increased load of trace elements in Basin Creek 

in the Buckeye study area during this base-flow period likely 

is primarily from ground-water discharge. These traceelement-load data collected during low flow support the calculations of ground-water discharge and verify that the volume 

of trace-element-rich ground water that enters Basin Creek 

near the mines is small. However, this ground-water discharge 

has a marked effect on concentrations in the stream due to the 

large concentrations of trace elements in the ground water and 

the small streamflow in Basin Creek. The loads contributed 

by ground water in areas 1 and 2 (table 7) can account for 

essentially all of the load increase during low flow in the study 

reach below the mines.

Dissolved trace elements entering Basin Creek from 

ground water generally do not cause the trace-element concentrations in Basin Creek to exceed the State of Montana acute 

aquatic-life standards during low flow. Dissolved and totalrecoverable zinc concentrations (26 and 42 |ug/L) at site 22B 

below the Buckeye mine (sample of October 16, 1998) were 

near the chronic and acute aquatic-life standard of 40 |ug/L 

(Montana Department of Environmental Quality, 1999).

During spring snowmelt and resulting high streamflow, 

ground water with high dissolved trace-element concentrations (table 6) discharges from the mill tailings and increases 

the trace-element load in Basin Creek. The water table is at or 

near land surface during snowmelt. Shallow ground water and 

overland runoff leach the entire thickness of tailings and carry 

dissolved trace elements toward Basin Creek. Ground water 

seeps out of the upper part of the saturated tailings, combines 

with overland runoff, and flows into very small tributaries 

which discharge into Basin Creek. Shallow ground water 

also discharges directly to Basin Creek through diffuse bank 

seepage. Trace-element concentrations of these small

tributaries were sampled during high runoff in May 1999 

and are discussed in subsequent sections of this report.

Streambed Sediment in Basin Creek

Streambed-sediment samples were collected at six 

sites along Basin Creek (fig. 15) (Fey, Unruh, and Church, 

1999). The minus-80-mesh (<0.18 mm) fraction was 

analyzed for leachable trace elements (Rich and others, this 

volume) to determine the location and magnitude of potential effects from the mine area. Trace-element concentrations in streambed-sediment samples are influenced by the 

input of material eroded upstream of the sample site as well 

as by the formation and subsequent deposition of colloidal 

material on the streambed during periods of low streamflow. Downstream increases in the concentrations of iron 

and trace elements are readily apparent in the streambedsediment data summarized in table 10 and indicate that the 

Buckeye and Enterprise mine area is a source of iron and 

trace elements transported to Basin Creek and deposited 

on the streambed. The concentrations of antimony, arsenic, 

lead, and silver increase dramatically in the downstream 

direction, particularly between sites 21bS and 21cS, which 

are adjacent to the central part of the flotation-mill tailings. 

The location of these increases indicates the importance 

of the flotation-mill tailings as a source of trace elements 

that presumably have been transported via both surface 

water and ground water to Basin Creek. Ferricrete deposits 

(iron-hydroxide-cemented lithic deposits) on the north bank 

of Basin Creek at sites 21bS and 21cS provide additional 

evidence that iron has been transported by ground water 

from the mill-tailings area to Basin Creek. In contrast to 

antimony, arsenic, lead, and silver, the increases in concentrations of cadmium, copper, and zinc in streambed sediment are less dramatic, probably because these latter trace 

elements partition less strongly to the colloidal and particulate phases (Church and others, 1997; Schemel and others, 

2000; Nimick and Cleasby, this volume, Chapter D5).

Surface Water

Basin Creek, a tributary of the Boulder River, drains 

the Buckeye study area and surrounding lands. Upper Basin 

Creek enters the study area from the east, is joined by a 

small south-flowing tributary near the Enterprise mine, 

and flows westerly through the study area (fig. 15). At 

the tributary confluence (near site 4B) above the Buckeye 

mine, upper Basin Creek has a drainage area of 1.51 mi2 ; 

land-surface altitudes within this drainage area range from 

about 7,060 to 8,568 ft. The small south-flowing tributary 

(Enterprise Mine tributary) that joins upper Basin Creek in 

the eastern part of the study area (site 3T) has a drainage 

area of 0.32 mi2 and land-surface altitudes that range from 

7,060 to 7,580 ft. The combined drainage area of upper 

Basin Creek at the mouth of this tributary is 1.83 mi2 .
434 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 8. Streamflow and water-quality data for upper Basin Creek, 1996-99.

[ftVs, cubic feet per second; °C, degrees Celsius; ng/L, micrograms per liter; ^S/cm, microsiemens per centimeter at 25 degrees Celsius; 

mg/L, milligrams per liter; mm, millimeter; — , no data; <, less than minimum reporting level]

Site

No. Site Ct 4. 

... .. , Station name (fig. No.

15)

4B 5 Basin Creek above Buckeye mine, near Basin

3T 6 Enterprise Mine tributary near Basin

6B 7 Basin Creek below Enterprise Mine tributary,

near Basin

22B 8 Basin Creek below Buckeye mine, near Basin

Date

10-16-96

09-25-98

10-16-98

05-28-99

09-13-99

10-16-98

05-28-99

09-13-99

05-27-97

04-30-98

05-07-98

10-16-98

05-28-99

09-13-99

10-16-96

05-27-97

04-30-98

05-07-98

09-25-98

10-16-98

05-28-99

09-13-99

SediSpe- ment 

.,. susCITIC Stream- Tern- pH, Sedi- pended. Hardflow, . „. pera- field ment, diam- ness duct- , , „ Time mstan- ture, stan- sus- eter mg/L 

ance taneous ,. ..' water dard pended (percent as

(ftYs) ,1, (°C) units) (mg/L) finer CaC03 ) 

(MS( than 

cm) 0.062 

mm)

1030

1345

1045

1010

1115

1055

1030

1030

1130

1100

1315

1340

0945

1130

1010

1045

1015

1445

1215

1315

0840

1250

-

0.44

.43

7.9

.34

.05

1.7

.009

12

5.0

10

.48

9.2

.37

.51

15

6.3

17

.49

.66

13

.35

78

79

76

37

79

87

42

104

42

55

45

75

39

80

82

44

57

49

80

75

39

82

-

5.0

1.0

2.0

5.0

1.0

6.0

4.0

4.0

0.0

-

.5

2.5

5.0

0.0

5.0

3.0

3.0

8.0

.5

2.0

11.0

-

7.6

7.8

8.1

7.8

8.3

7.1

7.9

—

7.0

7.7

7.7

7.2

7.8

7.3

7.1

7.3

7.0

7.8

7.6

6.7

7.9

-

29

1

-

-

1

-

-

—

8

48

1

-

-

1

10

16

74

4

4

-

--

-

99

80

-

-

67

~

-

-

66

46

75

-

-

62

36

32

77

79

82

-

-

-

32

31

16

~

36

16

-

—

23

18

31

16

-

34

16

23

17

32

27

16

-

'Site number previously published in Nimick and Cleasby (2000).
Trace-Element Sources and Transport to Upper Basin Creek 435

Table 8. Streamflow and water-quality data for upper Basin Creek, 1996-99.—Continued

Site 

No. 

(fig. 

15)

4B

3T

6B

22B

Date

10-16-96 

09-25-98

10-16-98

05-28-99

09-13-99

10-16-98

05-28-99

09-13-99

05-27-97

04-30-98

05-07-98

10-16-98

05-28-99

09-13-99

10-16-96

05-27-97

04-30-98

05-07-98

09-25-98

10-16-98

05-28-99

09-13-99

Calcium

(mg/L)

9.5

9.0

4.8

-

10

4.8

--

„

6.7

5.4

9.0

4.8

~

10

4.8

6.8

5.0

9.3

7.7

4.7

-

Magnesium 

(mg/L)

2.1

2.1

1.0

-

2.6

1.0

-

__

1.5

1.2

2.1

1.0

-

2.3

1.1

1.5

1.1

2.2

1.8

1.0

--

Sodium 

(mg/L)

2.2

2.0

1.1

--

2.5

1.3

-

__

1.3

1.1

2.1

1.2

-

2.3

1.2

1.3

1.1

2.2

2.0

1.2

-

Potassium 

(mg/L)

1.1

1.1

.68

-

1.0

.64

-

._

1.0

.77

.94

.67

-

1.0

.67

1.2

.91

.99

.83

.68

-

Alkalinity, 

laboratory 

(mg/L as 

CaC03)

32

31

15

-

35

11

-

_

19

14

31

14

-

32

12

20

10

31

29

13

-

Sulfate 

(mg/L as 

S04)

6.8

6.7

2.7

-

7.1

6.6

-

„

6.5

5.8

6.8

3.5

~

8.7

7.6

7.1

8.7

7.8

7.5

4.7

-

Chloride Fluoride 

(mg/L) (mg/L)

0.19 <0.10

.24 <.10

.24

~

.26 <.10

.84

-

__

.23 <.10

.27 <.10

.21 <.10

.21

-

.30 <.10

.19 <.10

.28 <.10

.22 <.10

.19 <.10

.22 <.10

.22

..

Silica 

(mg/L)

14

14

-

-

11

-

-

_.

8.9

7.2

13

-

-

13

9.6

8.9

7.8

14

13

-

-

Dissolved 

solids, 

calculated

(mg/L)

55

53

-

-

55

-

-

__

38

31

53

~

-

57

33

40

32

56

51

-

-
436 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 8. Streamflow and water-quality data for upper Basin Creek, 1996-99.—Continued

Site 

No. 

(fig. 

15)

4B

3T

6B

22B

Date

10-16-96 

09-25-98

10-16-98

05-28-99

09-13-99

10-16-98

05-28-99

09-13-99

05-27-97

04-30-98

05-07-98

10-16-98

05-28-99

09-13-99

10-16-96

05-27-97

04-30-98

05-07-98

09-25-98

10-16-98

05-28-99

09-13-99

Aluminum, 

dissolved

(ug/U

8.3

2.3

52

-

3.8

160

-

—

149

102

13

66

-

22

225

154

219

13

12

120

__

Aluminum, 

total 

recoverable 

(ug/L)

1,300

17

185

-

21

440

-

—

350

900

<10

220

-

—

430

430

1,300

90

72

300

_

AntiArsenic, mony, 

.. dis- dis- . . 

. . solved solved . „ .

(H9/U (MB/l1

<1 3

<1 1

2

-

<1 <1

3

--

—

<1 3

<1 7

<1 2

2

-

3 16

2 13

3 29

7 38

4 21

2 14

10

_

Arsenic, 

total 

recoverable 

(ug/L)

4

2

4

-

3

8

-

_.

5

10

2

3

-

19

36

52

500

24

30

25

__

D - Beryl- Barium, .. 

.. hum, dis- .. 

• j dis- solved . . 

, „ . solved

( "9/L) (ug/L)

8.1 <1

4.7 <1

..

--

5.5 <1

--

-

_.

6.1 <1

5.5 <1

4.7 <1

-

-

5.0 <1

6.1 <1

7.9 <1

8.3 <1

5.8 <1

4.3 <1

-

_

n . Cad- „. Chro- Cad- . Chro- mium, . mium, mium, . . . mium, ^ ^ . 

.. total .. total dis- dis- 

. . recov- . . recov- solved ,, solved .. 

, ... erable , ... erable

'"S"11 (MB/I) l"«/l1 (MB/L)

<0.3 <1 <1

<.3 <1 <1

<.3 <1

-

<.3 <1 <1

1.9 2

-

_.

<.3 <1 <1

.5 <1 <1

<.3 <1 <1

.4 <1

-

.2 <1 <1 <1

1.2 1 <1 <1

.8 <1 <1

1.4 2 <1

<.3 <1 <1

<.3 <1 <1

.6 <1

—
Trace-Element Sources and Transport to Upper Basin Creek 437

Table 8. Streamflow and water-quality data for upper Basin Creek, 1996-99.—Continued

Site No. 

(fig. 

15)

4B

3T

6B

22B

Cobalt,

n * dis- Date . . solved

(ug/D

10-16-96 

09-25-98 <1

10-16-98 <1

05-28-99

09-13-99

10-16-98 <1

05-28-99

09-13-99

05-27-97

04-30-98 <1

05-07-98 <1

10-16-98 <1

05-28-99

09-13-99

10-16-96 <1

05-27-97 <1

04-30-98 <1

05-07-98 <1

09-25-98 <1

10-16-98 <1

05-28-99

09-13-99

Copper, 

dissolved 

(ug/D

<!

<1

2

~

<!

11

~

—

9

5

<1

4

-

2

18

11

18

2

2

9

__

Copper, 

total 

recoverable

3

<1

2

--

<1

14

--

__

9

7

<1

3

-

4

18

12

40

3

3

11

„

Iron, 

dissolved

(ug/L)

17

48

61

-

50

79

~

__

190

160

103

54

-

130

180

240

240

93

88

100

__

Iron, , , 

, , , Lead, total .. disrecov- . . 

,. solved erable , .. >

(ug/L) 'M9

1,200 <1

71 <1

240 <1

-

190 <1

460 <1

-

„

600 <1

2,000 <1

130 <1

230 <1

-

170 <1

530 10

880 7.7

3,200 23

250 <1

380 <1

350 5.4

__

Lead, 

total 

recoverable

(ug/L)

7

<1

1

~

<1

1

-

—

1

7

<1

<1

~

3

24

28

340

2

9

17

—

. .... Manga- Lithium, 

.. nese, dis- .. i j dis- solved . . 

. . . solved

13

8

3

-

54

178

-

._

184

229

28

39

--

<4 65

<4 136

187

306

48

52

85

_.

Manganese, 

total 

recoverable 

(ug/L)

46

<10

11

-

73

220

-

—

200

330

26

43

-

70

140

200

410

55

74

91

—
438 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 8. Streamflow and water-quality data for upper Basin Creek, 1996-99.—Continued

Site No. 

(fig. 15)

4B

3T

6B

22B

., Mercury, Molyb- ... . . Nickel, c.. Mercury, . . . f . F Nickel, 4 . , Silver, 

.. total denum, .. total .. 

n . dis- .. dis- dis- Date . . recov- dis- . . recov- . . solved ., . . solved . . solved 

, ... erable solved . ... erable . ...

to9/U i..n n\ ,..n n\ (Mg/U / «/n (Mg/U \ug/L) (Mg/U (M9/'-)

10-16-96 

09-25-98 - - <1 <1 - <1 

10-16-98 -- - <1 <1 - <1

05-28-99

09-13-99

10-16-98 - - <1 <1 - <1

05-28-99

09-13-99

05-27-97

04-30-98 - - <1 1 - <1

05-07-98 - - <1 1 - <1

10-16-98 -- - <1 <1 - <1

05-28-99

09-13-99

10-16-96 <0.1 <0.1 <1 <1 <1 <1

05-27-97 - <.l <1 <1 <1 <1

04-30-98 - - <1 1 - <1

05-07-98 - - <1 <1 - <1

09-25-98 - - <1 <1 - <1

10-16-98 - - <1 <1 - <1

05-28-99

09-13-99

Silver, ... ,. A A . Uranium, Zinc, total .. .. dis- disrecov- . . . . 

. . solved solved erable .... , ... (ug/L) (Mg/U

<1 3 

<1 7

6

~

<1 15

234

-

„

<1 129

<1 109

<1 12

49

-

<1 <1 39

<1 <1 173

<1 140

<1 218

<1 24

<1 26

90

-

Zinc, 

total 

recoverable

(Mg/U

20 

10

<40

-

21

250

-

100

130

140

15

52

-

40

180

150

270

30

42

95

-
Trace-Element Sources and Transport to Upper Basin Creek 439

Table 9. Dissolved trace-element loads in upper Basin Creek 

upstream and downstream of the Buckeye and Enterprise 

mines, October 16,1998.

[g/d, grams per day; <, less than]

Trace element

Aluminum

Arsenic

Cadmium

Copper

Iron

Lead

Manganese

Zinc

Instantaneous load 

upstream1

(g/d)

2.4

1.0

2<.4

2<1

50.5

2<1.2

8.4

7.4

Instantaneous load 

downstream1 

(g/d)

19.4

22.6

<.5

3.2

142

2<1.6

84.0

42.0

'Site 4B used to represent load upstream of the mines, instantaneous 

streamflow was 0.43 fVVs; site 22B used to represent load downstream, 

instantaneous streamflow was 0.66 fWs.

2For concentrations that were reported as less than the minimum 

reporting level, the value of 1 |ig/L for lead and copper and 0.3 (ig/L for 

cadmium was used to calculate a maximum value for the load.

112°17'54" 112°17'47" 112°17'40"

46°23'4G"

4B G 23'39"

EXPLANATION

ENTERPRISE 

MINE /<

Streambed-sediment sampling site and number

21 cS © Basin Creek

Surface-water sampling site and number

6B • Basin Creek

3TO Tributaries

BUCKEYE 

MINE 6

025B

23T

15T U 14T

400 FEET

0 100 METERS

Figure 15. Location of streambed-sediment and surface-water sampling sites, upper Basin Creek.
440 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 10. Concentrations of leachable iron and selected trace elements in streambed-sediment samples, upper Basin Creek. 1

[A 2M HCI, 1-percent H2O2 solution was applied to streambed-sediment samples which dissolved amorphous iron oxyhydroxide phases. Concentrations in parts per million (micrograms/gram); <, less than minimum reporting level]

Site No. 

(fig. 15)

20S

21aS

21bS

21cS

21dS

21eS

Date

July 1998

July 1997

July 1997

July 1997

July 1997

October 1996

Antimony

<3

<3

<3

33

40

34

Arsenic

34

170

600

3,000

3,000

4,000

Cadmium

<1

2.8

1.7

2.1

3.2

5.0

Copper

16

61

50

79

99

120

Iron

16,000

22,000

21,000

20,000

28,000

33,000

Lead

64

160

410

1,200

1,600

1,600

Silver

<1

1.4

3.0

6.5

8.6

6.9

Zinc

160

500

390

350

460

680

'Data from Fey, Unrah, and Church (1999, table 7).

As upper Basin Creek flows through the study area to site 

22B, it receives drainage from an additional 0.71 mi2 area, of 

which 0.634 mi2 is situated south of Basin Creek and 0.076 

mi2 is situated in the vicinity of the Buckeye and Enterprise 

mines on the north side of Basin Creek. The total drainage 

area of Basin Creek below Buckeye mine (to site 22B) is 

2.54 mi2 .

Flow Characteristics of Basin Creek

Streamflow in Basin Creek near the Buckeye and Enterprise mines was measured periodically at sites 4B, 6B, and 

22B between October 1996 and September 1999 (table 8). The 

highest measured flows were in May 1997, 1998, and 1999. 

The maximum measured Streamflow in Basin Creek was 17 

ftVs at site 22B below the Buckeye mine on May 7, 1998. The 

lowest flows were measured on September 13, 1999, when 

Streamflow in Basin Creek below the Buckeye mine was 0.35 

ft3/s. Monthly distribution of annual runoff of Basin Creek can 

be estimated from long-term records for the streamflowgauging station Boulder River at Boulder, Mont, (station 

number 06033000). Based on 1929-98 Streamflow records for 

the Boulder River gauge, mean monthly Streamflow is greatest 

in May and second greatest in June (U.S. Geological Survey, 

issued annually). May accounts for nearly 34 percent of the 

mean annual Streamflow and June accounts for nearly 29 

percent (fig. 16). For the period August through March, each 

month accounts for less than 5 percent of the mean annual 

Streamflow of the Boulder River. The monthly Streamflow 

pattern of Basin Creek in the study area likely is similar to the 

monthly Streamflow pattern of the Boulder River.

Water Quality and Synoptic Sampling

Analyses of water samples collected from upper Basin 

Creek, at various dates and Streamflow conditions, documented higher concentrations of dissolved trace elements at 

higher streamflows (table 8). For example, dissolved zinc 

concentrations in Basin Creek below the Buckeye mine (site 

22B) ranged from 24 ug/L during low flow on September 25, 

1998, to 218 ug/L during high flow on May 7, 1998. The relationship between dissolved zinc concentration and Streamflow 

in Basin Creek below the Buckeye mine is shown in figure 17. 

A similar pattern of higher concentration of dissolved trace 

elements with larger Streamflow was observed for aluminum, 

cadmium, copper, lead, and manganese.

Dissolved trace-element concentrations that are higher 

in Basin Creek at high Streamflow than at low Streamflow 

indicate that substantial amounts of dissolved trace elements 

sufficient to overcome dilution effects are delivered to the 

stream during high flow. Observations of Streamflow and overland runoff made at the study area during periods of snowmelt 

in April and May 1999 indicated that tailings and waste rock 

are probable sources of dissolved trace elements (fig. 18). On 

April 19, 1999, upper Basin Creek contained considerable ice, 

snow, and slush, restricting flow in the stream and creating 

ponds of water on the flood plain and mill tailings. These 

ponds were saturating the mill tailings, and ground-water 

levels were rising to near land surface, as indicated by water 

levels in test wells located on the flood plain (fig. 14; 

table 4). On May 20, 1999, snow was rapidly melting and 

overland runoff was considerable from areas around the 

Buckeye and Enterprise mines and from the mill tailings. 

Runoff from the mines and tailings was discharging directly
Trace-Element Sources and Transport to Upper Basin Creek 441

35

30

25

^ 20

O

15

10

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

Figure 16. Monthly distribution of mean annual streamflow of Boulder River (streamflow-gauging 

station 06033000, fig. 1).

240

£ 220

Z]

E 200

D. 

(/)

< 180

DC

O

g 160 

O

Z 140

Z

2 120

DC

£ 100

LLJ 

O

o 80

O

o

Z 60

40

20

0

—— Linear regression line

+ Water sample analyzed for 

zinc concentration

6 8 10 12 

STREAMFLOW, IN CUBIC FEET PER SECOND

14 16 18

Figure 17.

1996-99.

Relation of dissolved zinc concentration and streamflow for Basin Creek below Buckeye mine.
442 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Figure 18. Snowmelt runoff from flotation-mill tailings entering upper Basin Creek near 

site 12B, May 27,1999.

into Basin Creek; some of the runoff had a pH value as low as 

3.08, as measured onsite with a portable pH meter.

Water quality was sampled and streamflow was measured 

in upper Basin Creek and all tributaries on May 28, 1999, 

to determine concentrations and loads of trace elements at 

numerous sites in upper Basin Creek near the Buckeye and 

Enterprise mines during high streamflow in order to identify 

the primary sources of trace elements. Water-quality samples 

were collected and streamflow measured at 25 sites in a short 

period between 0800 and 1130 hours under uniform hydrologic conditions to provide a synoptic characterization of 

downstream changes. Physical properties measured in the field 

at the time of streamflow measurement were water temperature, specific conductance, and pH. Tributaries to Basin Creek 

were identified as entering from the right bank (bank with 

mining wastes) or left bank (bank with no mining wastes). 

Water analyses included major ions as well as dissolved and 

total-recoverable trace elements. Dissolved trace elements 

were determined from samples filtered through 0.1-um membrane filters. Water-quality and streamflow data for all sites 

are listed in table 11, and site locations appear in figure 15.

During the synoptic sampling of May 28, 1999, streamflow in Basin Creek ranged from 7.9 ft3/s above the Buckeye 

mine (site 4B) to 12 ftVs at the most downstream site (25B). 

Tributary inflows ranged from 0.005 ftVs (site 9T) to 1.65 ftVs 

(site 3T, Enterprise Mine tributary). A plot of the measured 

streamflow in Basin Creek and its tributaries shows that nearly 

all increases in flow in Basin Creek during a runoff condition 

could be accounted for by tributary inflow (fig. 19). Some 

small changes in streamflow between measurement sites may 

be attributed to ground water; however, the changes are so

small that they are within the measurement error of the methods used to measure streamflow. The difference between the 

measured streamflow in Basin Creek at site 25B and the sum 

of the measured streamflow at site 4B plus all tributary inflows 

was 0.44 ftVs, or 3.6 percent of the streamflow at site 25B.

The quality of water sampled at the 25 synoptic sites 

(fig. 15) ranged from good-quality water typical of local, 

undisturbed mountain streams to acidic, trace-element-rich 

runoff that exceeds Montana aquatic-life standards for 

acute toxicity. Sites with good-quality water that could be 

considered as reference sites representative of undisturbed 

areas were Enterprise Mine tributary above the Enterprise 

mine (site IT), Basin Creek above Buckeye mine (site 4B), 

and several tributaries to Basin Creek from the left bank 

(sites 14T, 18.5T, and 19T). Water from these undisturbed sites 

is characterized by nearly neutral pH, hardness values of 16 

milligrams per liter (mg/L) or less, and low dissolved metal 

concentrations (dissolved cadmium <0.3 ug/L; dissolved copper from 1.8 to 2.9 ug/L; dissolved lead from <0.3 to 0.7 ug/L; 

and dissolved zinc from 1.4 to 3.0 ug/L).

Water from tributaries that drained waste rock or mill 

tailings had high concentrations of dissolved trace elements 

(table 11) when sampled on May 28, 1999. The highest 

concentrations of dissolved trace elements were: aluminum, 

34,800 ug/L at site 7T; arsenic, 985 ug/L at site 17T; cadmium, 142 ug/L at site 2T; copper, 1,700 ug/L at site 7T; iron, 

12,000 ug/L at site 17T; lead, 6,470 ug/L at site 11T; manganese, 23,500 ug/L at site 7T; and zinc, 17,800 ug/L at site 2T. 

Tributaries draining waste rock near the Enterprise and Buckeye mines (sites 2T, 7T, 9T) had the highest concentrations 

of dissolved aluminum, cadmium, copper, manganese, and
Table 11. Synoptic streamflow and water-quality data for upper Basin Creek and tributaries. May 28,1999.

[Right bank, bank containing mining wastes; left bank, bank with no mining wastes. E, estimated; ft3/s, cubic feet per second; °C, degrees Celsius; |^g/L, micrograms per lite

per centimeter at 25 degrees Celsius; mg/L, milligrams per liter; <, less than minimum reporting level; --, no data]

Site No. 

(fig. 15)

IT

2T

3T

4B

6B

7T

8B

9T

10T

11T

12B

13B

14T

1ST

16B

17T

18B

18.5T

19T

20T

21T

22B

23T

24T

25B

Site description

Enterprise Mine tributary

Tributary to Enterprise Mine tributary

Enterprise Mine tributary

Basin Creek above Buckeye mine

Basin Creek below Enterprise Mine tributary

Basin Creek tributary, right bank

Basin Creek

Basin Creek tributary, right bank

Basin Creek tributary, right bank

Basin Creek tributary, right bank

Basin Creek

Basin Creek

Basin Creek tributary, left bank

Basin Creek tributary, left bank

Basin Creek

Basin Creek tributary, right bank

Basin Creek

Basin Creek tributary, left bank

Basin Creek tributary, two inflow points from left bank

Basin Creek tributary, left bank

Basin Creek tributary, right bank

Basin Creek below Buckeye mine

Basin Creek tributary, right bank

Basin Creek tributary, three inflow points from left bank

Basin Creek

Streamflow, 

instantaneous

(ff/s)

1.52

.012

1.65

7.87

9.22

.018

9.89

.005

.014

.018

10.7

10.2

.58

.01

11.1

.021

10.8

.175

1.18

.020

.066

12.5

.015

.156

12.2

Temperature, 

water

(°C)

4.0

16.5

6.0

2.0

2.5

10.0

3.0

9.0

6.5

5.5

2.0

4.0

8.0

5.0

3.0

14

3.0

—

5.0

7.0

8.5

2.0

7.0

.5

1.5

Specific 

conductance 

(pS/cm)

29

702

42

37

38

849

40

566

383

375

41

42

39

30

42

504

42

42

25

32

25

39

28

23

39

pH, 

field 

(standard 

units)

7.7

4.0

7.1

8.1

7.2

3.4

7.3

3.9

4.1

3.3

7.3

7.2

6.9

6.1

7.0

3.1

7.0

6.7

6.2

6.0

5.1

6.7

5.7

6.1

7.0

Hardness, 

total 

(mg/L as 

CaCOJ

12

240

16

16

16

148

17

153

125

30

17

17

16

11

16

31

17

15

9

12

5

16

8

8

16

C

d
Table 11. Synoptic streamflow and water-quality data for upper Basin Creek and tributaries, May 28,1999.—Continued

Site No. 

(fig. 15)

IT

2T

3T

4B

6B

7T

8B

9T

10T

11T

12B

13B

14T

1ST

16B

17T

18B

18.5T

19T

20T

21T

22B

23T

24T

25B

Sodium, 

dissolved 

(mg/L)

1.2

3.7

1.3

1.1

1.2

5.6

1.2

4.3

3.6

4.4

1.2

1.2

1.7

1.3

1.2

3.0

1.2

1.7

1.1

1.0

1.5

1.2

2.0

1.1

1.2

Potassium, 

dissolved

(mg/L)

0.6

3.6

.6

.7

.7

1.5

.7

2.3

2.0

1.7

.7

.7

.9

.6

.7

1.8

.7

1.0

.9

1.0

.7

.7

1.0

1.0

.7

Sulfate, 

dissolved 

(mg/L as S04 )

1.5

370

6.6

2.7

3.5

496

4.6

290

180

94

4.8

5.2

2.6

3.4

--

127

5.2

3.0

2.3

1.6

—

4.7

5.5

2.2

4.6

Chloride, 

dissolved 

(mg/L)

0.2

.6

.8

.2

.2

1.3

.2

1.2

.5

.6

.2

.2

2.2

.3

<.l

.5

.2

.3

.2

.4

—

.2

.6

.3

.2

Alkalinity, 

laboratory 

(mg/L as 

CaC03)

12

<1

11

15

14

<1

11

<1

<1

<1

14

14

13

9.2

<1

<1

14

14

9.0

12

—

13

5.5

8.2

13

Aluminum, 

dissolved

(Mg/L)

76

9,980

159

52

66

34,800

124

14,600

5,130

1,350

143

127

29

57

112

1,780

126

140

64

78

94

117

94

69

123

Aluminum, 

total recoverable

231

10,300

444

185

221

32,800

272

14,200

5,360

1,800

299

318

48

136

323

1,880

305

59

148

99

—

303

205

97

289

Arsenic, 

dissolved

(Mg/L)

2.3

45

2.8

2.2

2.1

123

2.4

271

118

280

3.4

4.2

4.0

22

5.3

985

7.9

3.1

1.6

33

182

9.7

153

15

10

Arsenic

total reco

erable

(Mg/D

2.3

50

7.5

3.8

3.3

146

3.2

447

183

5,190

7.6

16

6.2

32

20

2,270

23

2.9

3.2

33

—

25

220

17

24
Table 11. Synoptic streamflow and water-quality data for upper Basin Creek and tributaries, May 28,1999.—Continued

Site No. 

(fig. 15)

IT

2T

3T

4B

6B

7T

8B

9T

10T

11T

12B

13B

14T

1ST

16B

17T

18B

18.5T

19T

20T

21T

22B

23T

24T

25B

Cadmium, 

total 

recoverable

(pg/L)

<i

141

2.1

<1

<1

127

<1

67

24

24

<1

<1

<1

<1

<1

41

<1

<1

<1

<1

--

<1

1.6

<1

<1

Copper, 

dissolved

(pg/L)

2.8

740

11

2.1

3.7

1,700

7.5

1,090

478

434

8.5

10

1.8

5.2

9.3

757

10

2.9

2.1

7.1

26.1

9.4

40

4.5

9.2

Copper, 

total 

recoverable

(ug/L)

2.8

792

14

1.8

3.5

1,740

7.7

1,060

524

526

9.9

12

1.7

6.5

12

790

12

2.6

2.4

7.4

--

11

44

5.0

11

Iron, dissolved

(pg/L)

64

402

79

61

54

5,020

70

3,190

362

1,490

77

60

126

98

70

12,000

95

—

118

147

166

101

194

79

107

Iron, 

total 

recoverable

(pg/L)

208

384

465

240

230

4,450

256

3,050

430

7,970

268

278

300

229

353

12,900

323

—

267

165

-

355

588

97

360

Lead, dissolved

(pg/L)

<0.3

17

<.3

<.3

<.3

26

.5

481

586

6,470

2.4

3.9

<.3

3.2

3.0

3,160

7.3

.7

<.3

5.9

46

5.4

9.4

2.3

5.0

Lead, 

total 

recoverable

(pg/L)

<i

17

1.1

1.1

<1

28

1.2

470

552

10,100

5.8

14

<1

9.7

14

3,000

21

<1

<1

6.3

-

17

28

2.9

16

Manganese, 

dissolved

(pg/L)

2.1

11,900

178

3.4

39

23,500

102

7,520

2,590

1,010

102

113

6.5

21

105

907

103

14

11

20

63

85

64

7.0

84

Manganese, 

total recoverable 

(pg/L)

14

11,100

217

10

43

20,900

105

7,060

2,460

995

105

116

10

29

112

876

107

5.0

11

22

--

90

64

6.2

88

Zinc, d

solve

(pg/

1.4

17,8

234

5.9

49

15,9

89

6,93

2,86

3,02

94

108

2.2

18

99

5,52

10

2.9

3.0

29

157

90

19

25

88
446 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

14

13

12

11

Q 

LU

cc 9

LLJ 

Q.

LU 8

L1J

LJ_

CJ

5 7

CJ

1 6

1 6

LLJ 4 

DC

to

3

2

1

0

• Streamflow from tributary 

» Streamflow in Basin Creek

O Sum of measured Streamflow 

from tributaries and at site 4B

i i i I

4B 3T 6B 7T 8B 9T 10T 11T 12B 13B 14T 15T 16B 17T 18B 18.5T19T 20T 21T 22B 23T 24T 25B

SITE NUMBER

Figure 19. Streamflow in upper Basin Creek, May 28,1999.

zinc; tributaries draining mill tailings (sites 11T, 17T), had the 

highest concentrations of dissolved arsenic and lead. Tributary 

2IT, which drains from the northern margin of the mill tailings 

and enters Basin Creek downstream from the mill tailings, also 

had high concentrations of dissolved arsenic and lead.

Total-recoverable trace-element concentrations were 

similar to dissolved concentrations for most samples, indicating that the soluble phase was more predominant than 

the particulate phase, even during runoff conditions. Small 

differences between dissolved and total-recoverable concentrations were observed for cadmium, copper and zinc. Some of 

the largest differences between dissolved and total-recoverable 

concentrations were observed for aluminum, arsenic, iron, and 

lead. The large differences between dissolved and total-recoverable concentrations indicate that aluminum, arsenic, iron, 

and lead were being removed from solution and forming colloidal precipitates, which likely settle to the streambed. These 

observations are consistent with the data from the streambed 

sediments (table 10), which show large concentration increases 

for arsenic and lead from upstream of the Enterprise mine to 

downstream of the mill tailings.

Metals entering Basin Creek from tributaries during the 

runoff conditions of May 1999 caused increased concentrations that exceeded several aquatic-life standards for the State 

of Montana. Total-recoverable copper concentrations exceeded 

the acute aquatic-life standard of 3.8 ug/L for the reach of 

Basin Creek between sites 8B and 25B. Total-recoverable lead

concentrations exceeded the chronic aquatic-life standard of 

0.54 ug/L in the reach of Basin Creek between sites 12B and 

25B. Total-recoverable zinc concentrations exceeded the acute 

aquatic-life standard of 37 ug/L for the reach between sites 

6B and 25B. The extent to which these metal concentrations 

exceeded aquatic-life standards farther downstream in Basin 

Creek is unknown.

Trace-Element Loads in Basin Creek

Instantaneous loads of dissolved trace elements were 

calculated using Streamflow and trace-element concentration 

data from each site sampled during the synoptic measurements 

on May 28, 1999. Trace-element loads (table 12) are reported 

in grams per day (g/d), and were calculated by multiplying 

Streamflow (ft3/s) times dissolved trace-element concentration 

(ug/L) times a units-conversion factor of 2.4466. For cadmium 

and lead concentrations that were less than the minimum 

reporting level, loads were calculated using the value for the 

minimum reporting level, and these loads are reported as lessthan values in table 12.

Streamflow measurements and water-quality samples 

collected during snowmelt runoff on May 28, 1999, showed 

large increases in dissolved trace-element loads in Basin Creek 

through the area of the Buckeye and Enterprise mines. Streamflow in Basin Creek increased from 7.87 ft3/s upstream of the 

Buckeye mine (site 4B) to 12.2 ftVs at the most downstream
Table 12. Dissolved trace-element loads for upper Basin Creek and tributaries, May 28, 1999.

[Right bank, bank containing mining wastes; left bank, bank with no mining wastes; ft3/s, cubic feet per second; g/d, grams per day; <, less than; >, greater than]

Site No. _.. . _. 

... .._. Site description Time

IT

2T

3T

4B

6B

7T

8B

9T

10T

11T

12B

13B

14T

1ST

16B

17T

18B

18.5T

19T

20T

21T

22B

23T

24T

25B

Enterprise Mine tributary 1105

Tributary to Enterprise Mine tributary 1050

Enterprise Mine tributary 1130

Basin Creek above Buckeye mine 1010

Basin Creek below Enterprise Mine tributary 0945

Basin Creek tributary, right bank 0925

Basin Creek 0920

Basin Creek tributary, right bank 0915

Basin Creek tributary, right bank 0900

Basin Creek tributary, right bank 0840

Basin Creek 0815

Basin Creek 1105

Basin Creek tributary, left bank 1055

Basin Creek tributary, left bank 1045

Basin Creek 1015

Basin Creek tributary, right bank 0955

Basin Creek 0935

Basin Creek tributary, left bank 0935

Basin Creek tributary, two inflow points from left bank 0915

Basin Creek tributary, left bank 0900

Basin Creek tributary, right bank 0855

Basin Creek below Buckeye Mine 0840

Basin Creek tributary, right bank 0830

Basin Creek tributary, three inflow points from left bank 0820

Basin Creek 0800

INCREASE BETWEEN SITES 4B AND 25B

NOTE:

Streamflow,

instantaneous

(ftVs)

1.52

.012

1.65

7.87

9.22

.018

9.89

.005

.014

.018

10.7

10.2

.58

.01

11.1

.021

10.8

.175

1.18

.020

.066

12.5

.015

.156

12.2

4.3

Aluminum 

load

(g/d)

282

293

643

1,002

1,499

1,533

2,993

178

176

59.6

3,743

3,163

41.4

1.40

3,042

91.3

3,315

59.8

185

3.82

15.2

3,572

3.46

26.4

3,676

2,674

Arsenic

load

(g/d)

8.59

1.31

11.4

41.6

46.2

5.40

58.6

3.32

4.04

12.4

89.7

104

5.73

.54

145

50.6

209

1.34

4.50

1.60

29.3

295

5.60

5.69

306

264

Cadmium 

load

(g/d)

<1.12

4.16

7.50

<5.78

9.02

4.73

14.5

.70

.82

1.00

18.3

25.1

<.42

<.01

19.0

1.94

21.1

<.13

<.87

<01

.19

18.3

.05

<.ll

18.6

>12.8

Copper

load

(g/d)

10.6

21.7

43.4

41.3

83.0

75.0

181

13.3

16.4

19.1

223

255

2.62

.13

251

38.9

276

1.25

6.13

.35

4.21

287

1.46

1.71

276

235

Iron

load

(g/d)

239

11.8

318

1,166

1,218

221

1,685

39.0

12.4

65.6

2,024

1,486

179

2.39

1,887

617

2,498

126

341

7.19

26.9

3,078

7.11

30.3

3,192

2,026

Le

lo

(g/

<1

.5

<1

<5

<6

1.

12

5.

20

28

61

96

<.

.0

80

1

19

.3

<.

.2

7.

1

.3

.8

14

>1

Loads were computed from unrounded streamflow values to obtain greater resolution of small differences between sites.
448 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

measurement site (site 25B), which is an increase of 4.3 ft3/s 

or 55 percent. Figures 20-27 illustrate downstream changes of 

dissolved trace-element loads and streamflow for each of the 

eight trace elements analyzed in the synoptic samples from 

May 28, 1999. Loads are depicted for Basin Creek, individual 

tributaries, and the cumulative sum of the trace-element loads 

from site 4B plus tributaries.

Comparison of dissolved trace-element loads within 

Basin Creek with the cumulative sum of dissolved traceelement loads from tributaries indicated that dissolved traceelement loads in Basin Creek at the downstream end of the 

study area (site 25B) were largely derived from tributary 

inflows draining the Buckeye and Enterprise mines during runoff conditions. Comparison of the loads in Basin Creek and its 

tributaries also indicated that ground water and diffuse streambank seepage contributed only a small part of the dissolved 

trace-element load to Basin Creek during runoff. Arsenic was 

the only trace element to indicate that a substantial component 

of the load was from ground-water discharge or seepage from 

saturated stream banks directly into Basin Creek during runoff.

Arsenic is widespread in surface and ground water in the area, 

including water draining from the south side (left bank) of 

Basin Creek, as indicated by water-quality samples from well 

10 and tributaries 14T, 19T, and 24T (tables 6, 11, and 12). 

Part of the arsenic load in ground water thus likely originates 

on the south side of Basin Creek, in the area not disturbed by 

mining, because of the naturally occurring arsenic in that area.

The sum of measured loads of dissolved lead from all 

sampled tributaries was substantially larger than the loads in 

Basin Creek at downstream site 25B. The sum of measured 

loads of dissolved lead from the tributaries was more than 

three times as large as the load of dissolved lead at site 25B 

(fig. 25). The sum of measured loads of dissolved aluminum 

and cadmium from the tributaries ranged from about 10 to 

30 percent, respectively, larger than the load at site 25B 

(figs. 20 and 22). Load inputs greater than the instream loads 

of Basin Creek indicate that dissolved aluminum, cadmium, 

and lead from tributaries were precipitating or forming colloids within Basin Creek and subsequently settling to the 

streambed.
Trace-Element Sources and Transport to Upper Basin Creek 449

4,500

4,000

3,500

3,000

2,500

2,000 -

1,500

1,000 -

500 -

: DISSOLVED ALUMINUM

I I Aluminum load from Enterprise

Mine tributary 

H Aluminum load from right bank

tributaries 

• Aluminum load from left bank

tributaries

« Streamflow in Basin Creek 

A Aluminum load in Basin Creek 

O Sum of measured aluminum

loads from tributaries plus

load at 4B

10 8

4 g

4B 3T 6B 7T 8B 9T 10T 11T 12B 13B 14T 15T 16B 17T 18B18.5T19T 20T 21T 22B 23T 24T 25B

SITE NUMBER

Figure 20. Dissolved aluminum load in upper Basin Creek, May 28,1999.

350

DISSOLVED ARSENIC

L~J Arsenic load from Enterprise

Mine tributary 

Arsenic load from right bank

tributaries 

• Arsenic load from left bank

tributaries

® Streamflow in Basin Creek 

A Arsenic load in Basin Creek

O Sum of measured arsenic 

loads from tributaries plus 

load at 4B

4B 3T 6B 7T 8B 9T 10T 11T 12B 13B 14T 15T 16B 17T 18B18.5T19T 20T 21T 22B 23T 24T 25B

SITE NUMBER

Figure 21. Dissolved arsenic load in upper Basin Creek, May 28,1999.
450 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

30

25

20

15

<r

DISSOLVED CADMIUM

I I Cadmium load from Enterprise

Mine tributary 

S: Cadmium load from right bank

tributaries

• Cadmium load from left bank 

tributaries

* Streamflow in Basin Creek 

A Cadmium load in Basin Creek 

O Sum of measured cadmium

loads from tributaries plus

load at 4B

11 o 

10 I

4 uj 

cc

4B 3T 6B 7T 8B 9T 10T 11T 12B 13B 14T 15T 16B 17T 18B18.5T19T 20T 21T 22B 23T 24T 25B

SITE NUMBER

Figure 22. Dissolved cadmium load in upper Basin Creek, May 28,1999. For cadmium concentrations that were less than minimum reporting level of 0.3 ug/L, load values are plotted using minimum 

reporting level.

350

300

250

200

150

100

50

DISSOLVED COPPER

I I Copper load from Enterprise 

Mine tributary

• Copper load from right bank 

tributaries

• Copper load from left bank 

tributaries

• Streamflow in Basin Creek 

A Copper load in Basin Creek 

O Sum of measured copper

loads from tributaries plus

load at 4B

I 

10 I

6

4 UJ 

OC

to 

3

2

1

4B 3T 6B 7T 8B 9T 10T 11T 12B 13B 14T 15T 16B 17T 18B18.5T19T 20T 21T 22B 23T 24T 25B

SITE NUMBER

Figure 23. Dissolved copper load in upper Basin Creek, May 28,1999.
Trace-Element Sources and Transport to Upper Basin Creek 451

3,500

3,000

2,500

£

Q 

EC

£ 2,000

V)

- 1,500 

Q

1,000

500

DISSOLVED IRON

I I Iron load from Enterprise

Mine tributary 

if! Iron load from right bank

tributaries 

• Iron load from left bank

tributaries

» Streamflow in Basin Creek 

A Iron load in Basin Creek 

O Sum of measured iron loads

from tributaries plus load

at4B

J

10 8

6

4B 3T 6B 7T 8B 9T 10T 11T 12B 13B 14T 15T 16B 17T 18B18.5T19T 20T 21T 22B 23T 24T 25B

SITE NUMBER

Figure 24. Dissolved iron load in upper Basin Creek, May 28,1999.

500

450 -

DISSOLVED LEAD

CH Lead load from Enterprise

Mine tributary 

Lead load from right bank

tributaries 

Lead load from left bank

tributaries 

Streamflow in Basin Creek

A Lead load in Basin Creek 

O Sum of measured lead loads

from tributaries plus load

at4B

3T 6B 7T 8B 9T 10T 11T 12B 13B 14T 15T 16B 17T 18B18.5T19T 20T 21T 22B 23T 24T 25B

SITE NUMBER

Figure 25. Dissolved lead load in upper Basin Creek, May 28,1999. For lead concentrations that were 

less than minimum reporting level of 0.3 ug/L, load values are plotted using minimum reporting level.
452 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

3,000

2,500 -

2,000

< 1,500

1,000

500 -

DISSOLVED MANGANESE

I I Manganese load from Enterprise

Mine tributary 

Manganese load from right bank

tributaries 

• Manganese load from left bank

tributaries

» Streamflow in Basin Creek 

A Manganese load in Basin Creek 

O Sum of measured manganese

loads from tributaries plus

load at 4B

10 8

9 £

QL

IQ I I I

a UJ

UO 

7 m

CJ

6 1

,i

4 uu

4B 3T 6B 7T 8B 9T 10T 11T 12B 13B 14T 15T 16B 17T 18B18.5T19T 20T 21T 22B 23T 24T 25B

SITE NUMBER

Figure 26. Dissolved manganese load in upper Basin Creek, May 28,1999.

3,500

3,000

2,500

2,000

^ 1,500

Q

1,000

500 -

DISSOLVED ZINC

I I Zinc load from Enterprise

Mine tributary 

H Zinc load from right bank

tributaries 

• Zinc load from left bank

tributaries

» Streamflow in Basin Creek 

A Zinc load in Basin Creek 

O Sum of measured zinc loads

from tributaries plus load

at4B

O

6 ^

5 S

4 LLJ

3

2

1

0

co

4B 3T 6B 7T 8B 9T 10T 11T 12B 13B 14T 15T 16B 17T 18B18.5T19T 20T 21T 22B 23T 24T 25B

SITE NUMBER

Figure 27. Dissolved zinc load in upper Basin Creek, May 28,1999.
Trace-Element Sources and Transport to Upper Basin Creek 453

Summary and Conclusions

The Buckeye and Enterprise mines are located in upper 

Basin Creek about 10 mi north of the town of Basin in Jefferson County, Mont. Pyritic ore from the mines was processed 

by a gravity mill located at the Buckeye mine site; gravity-mill 

tailings were later reprocessed through a flotation mill located 

on the flood plain of Basin Creek. Flotation-mill tailings on 

the flood plain occupy an area of about 3.3 acres and have a 

volume of about 5,000 cubic yards.

Basin Creek flows along the southern margin of the mill 

tailings and receives surface- and ground-water runoff from 

the mine areas and tailings, predominantly during spring 

snowmelt. The runoff from the mine areas and mill tailings measurably affects the quality of water in Basin Creek. 

The USDA Forest Service and U.S. Environmental Protection Agency have identified the need for remediation of the 

Buckeye and Enterprise mine area. To effectively remediate 

the impacts of historical mine wastes on Basin Creek and to 

measure the effectiveness of proposed mine-waste cleanup, it 

was necessary to determine sources of trace elements and their 

pathways of transport to the stream.

Chemical analyses of core samples from mill tailings, 

soils beneath the tailings, and leachate from samples 

prepared from a core showed four distinct geochemical 

zones: an oxidized and leached zone (the upper 22 in.), a 

partly oxidized zone (22-41 in.), an unoxidized pyritic zone 

(41-62 in.), and the buried soil horizon (62-79 in.). The 

unoxidized pyritic zone contained the highest concentrations 

of trace elements, whereas concentrations of most trace elements rapidly decreased with depth in the buried soil beneath 

the tailings.

Surface geophysical surveys, including electromagnetic, 

direct-current resistivity, and total-field magnetic methods, 

were used to examine the location and extent of high conductivity possibly related to trace-element contamination. 

Subsurface conductivity was mapped using EM-31 and EM-34 

terrain conductivity measuring systems. The conductivity surveys measured the variation in subsurface conductivity from 

about 10 to 100 ft. Areas of high conductivity can result from 

sediments containing wet clay or high dissolved-solids concentrations in ground water. Direct-current resistivity soundings were used to quantify subsurface conductivity variations 

and to estimate the depth to bedrock. Total-field magnetic 

measurements were used to identify magnetic metals in the 

subsurface.

The EM surveys identified three areas of relatively 

high apparent conductivity and detected a conductive plume 

extending from the northeast part of the mill tailings to the 

southwest, toward the stream. This plume correlates well with 

the potentiometric surface and direction of ground-water flow, 

and with water-quality data from the monitoring wells in and 

around the tailings. The electromagnetic data also indicate 

that ground water with a high dissolved-solids concentration 

probably has migrated downward. Conductive zones also were

identified south of the Enterprise mine and in an area of wet 

meadows southwest of the Buckeye tailings.

Total-field magnetic measurements indicated that buried 

magnetic objects were not a likely source of high conductivity 

near the EM survey grid origin. Therefore, the high conductivity anomaly is likely the result of the highly conductive sulfide 

layers that were observed in core samples from the same area.

Data from the direct-current soundings are interpreted 

to be a body of conductive material, most likely ground water 

with a high dissolved-solids content near the center of the 

Buckeye tailings and below the Enterprise tailings near well 9. 

The anomaly is slightly deeper than shown in the EM surveys, 

which may indicate downward movement of dissolved solids. 

Direct-current resistivity soundings also indicate that depth to 

bedrock is likely greater than 98 ft.

Two aquifers exist in the study area. One aquifer is 

fractured bedrock of the Boulder batholith, and the second 

aquifer is unconsolidated deposits consisting of till, alluvium, 

colluvium, organic-rich swamp deposits, and volcanic ash. 

The unconsolidated deposits range from less than 1 ft to more 

than 30 ft thick and are overlain by mill tailings in the vicinity of the Buckeye mine. The unconsolidated-deposits aquifer 

overlies granitic rocks and is hydraulically connected to Basin 

Creek. Test wells were installed in the unconsolidated-deposits 

aquifer to determine direction of ground-water flow, hydraulic 

characteristics, and water quality.

Ground water containing high concentrations of dissolved 

aluminum, arsenic, cadmium, copper, iron, lead, manganese, 

and zinc underlies the area of mill tailings and some of the 

area between the Enterprise mine and Basin Creek. Discharge 

of trace-element-laden ground water from the mine and milltailings areas into upper Basin Creek is small during low flow, 

but appears to account for essentially all of the instream load 

increase in upper Basin Creek during low flow. Traceelement loads from ground water elevate the concentrations 

of trace elements in upper Basin Creek, although the State of 

Montana aquatic-life standards generally are not exceeded 

during low flow. At times of snowmelt runoff, ground-water 

levels are near land surface over much of the mill-tailings area, 

and ground water saturates the tailings. This ground water, 

containing high concentrations of dissolved trace elements, 

seeps out of the tailings and into small tributaries that drain 

into Basin Creek.

Analyses of water samples collected from upper Basin 

Creek and tributaries, at various dates and streamflow conditions, documented higher concentrations of dissolved trace 

elements at higher streamflows. To determine concentrations 

and loads of trace elements in Basin Creek near the Buckeye 

and Enterprise mines during high streamflow for the purpose 

of identifying major sources, synoptic water-quality samples 

were collected for analysis and streamflow measurements 

were made in upper Basin Creek and all tributaries on May 28, 

1999. Water quality was sampled and streamflow was measured at 25 sites, between 0800 and 1150 hours, under uniform 

hydrologic conditions. Water samples were analyzed for water 

temperature, specific conductance, pH, common ions,
454 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

hardness, alkalinity, dissolved trace elements, and total-recoverable trace elements. The quality of water sampled at the 

25 synoptic sites ranged from good-quality water typical of 

local, undisturbed mountain streams to trace-element-rich 

runoff that exceeded State of Montana aquatic-life standards 

for acute toxicity. The highest measured concentrations of dissolved trace elements were aluminum, 34,800 |Ug/L at site 7T; 

arsenic, 985 |ug/L at site 17T; cadmium, 142 |ug/L at site 2T; 

copper, 1,700 |ug/L at site 7T; iron; 12,000 |ug/L at site 17T; 

lead, 6,470 |ug/L at site 11T; manganese, 23,500 |ug/L at 

site 7T; and zinc, 17,800 |dg/L at site 2T.

Tributaries draining waste rock near the Enterprise and 

Buckeye mines (sites 2T, 7T, 9T) had the highest concentrations of dissolved aluminum, cadmium, copper, manganese, 

and zinc; tributaries draining the mill tailings (sites 11T, 17T), 

had the highest concentrations of dissolved arsenic and lead. 

One tributary (21T), which drains from the northern margin of 

the mill tailings and enters Basin Creek downstream from the 

tailings, also had high concentrations of dissolved arsenic and 

lead.

During the May 1999 synoptic sampling, dissolved 

trace-element loads in Basin Creek at the downstream end of 

the study area (site 25B) were largely derived from tributary 

inflows draining the area of the Buckeye and Enterprise mines. 

For all trace elements except arsenic, ground water contributed 

only a small part of the dissolved load to Basin Creek during 

that period of snowmelt runoff. The sum of measured loads of 

dissolved aluminum, cadmium, and lead from tributaries was 

moderately to substantially larger than the sum of the loads 

in Basin Creek at downstream site 25B, indicating that these 

elements were precipitating or forming colloids within Basin 

Creek and subsequently settling to the streambed.

Metals entering Basin Creek from tributaries caused 

some of the State of Montana aquatic-life standards to be 

exceeded during runoff conditions of the synoptic sampling 

in May 1999. Copper exceeded the acute aquatic-life standard 

for the entire reach of Basin Creek between sites 8B and 25B. 

Lead exceeded the chronic aquatic-life standard in the reach 

of Basin Creek between sites 12B and 25B. Zinc exceeded the 

acute aquatic-life standard for the reach between sites 6B and 

25B. The extent to which these metal concentrations exceeded 

aquatic-life standards farther downstream in Basin Creek is 

unknown.

References Cited

Church, S.E., Kimball, B.A., Fey, D.L., Ferderer, D.A., 

Yager, T.J., and Vaughn, R.B., 1997, Source, transport, and 

partitioning of metals between water, colloids, and bed 

sediments of the Animas River, Colorado: U.S. Geological 

Survey Open-File Report 97-151, 135 p.

Cooper, H.H., Jr., Bredehoeft, J.D., and Papadopulos, I.S., 

1967, Response of a finite diameter well to an instantaneous 

charge of water: Water Resources Research, v. 3, no. 1, 

p. 263-269.

Desborough, G.A., and Fey, D.L., 1997, Preliminary characterization of acid-generating potential and toxic metal 

solubility of some abandoned metal-mining related wastes 

in the Boulder River headwaters, northern Jefferson County, 

Montana: U.S. Geological Survey Open-File Report 

97^78, 21 p.

Fey, D.L., Church, S.E., and Finney, C.J., 1999, Analytical 

results for 35 mine-waste tailings cores and six bedsediment samples, and an estimate of the volume of 

contaminated material at Buckeye meadow on upper 

Basin Creek, northern Jefferson County, Montana: 

U.S. Geological Survey Open-File Report 99-537, 59 p.

Fey, D.L., Desborough, G.A., and Church, S.E., 2000, 

Comparison of two leach procedures applied to metalmining related wastes in Colorado and Montana and a 

relative ranking method for mine wastes, in ICARD 2000; 

Proceedings of the Fifth International Conference on Acid 

Rock Drainage, Volume 2: Society for Mining, Metallurgy, 

and Exploration, Inc., p. 1477-1487.

Fey, D.L., Unruh, D.M., and Church, S.E., 1999, Chemical 

data and lead isotopic compositions in stream-sediment 

samples from the Boulder River watershed, Jefferson 

County, Montana: U.S. Geological Survey Open-File 

Report 99-575, 147 p.

Interpex, 1993, RESIX-IP version 2.0 users manual: Golden, 

Colo., Interpex Limited, 150 p.

McDougal, R.R., and Smith, B.D., 2000, Ground geophysical study of the Buckeye mine tailings, Boulder watershed, 

Montana: U.S. Geological Survey Open-file Report 

00-0371,56 p.

McNeill, J.D., 1980, Electromagnetic terrain conductivity measurement at low induction numbers: Mississauga, 

Ontario, Canada, Geonics Limited, Technical Note TN-6.

Metesh, J.J., Lonn, J.D., Duaime, T.E., and Wintergerst, Robert, 1994, Abandoned-inactive mines program, Deerlodge 

National Forest—Volume I, Basin Creek drainage: Montana 

Bureau of Mines and Geology Open-File Report 321, 131 p.

Montana Department of Environmental Quality, 1999, 

Montana numeric water quality standards: Helena, Mont., 

Planning, Preservation, and Assistance Division, Standards 

and Economic Analysis Section Circular WQB-7, 41 p.

Nimick, D.A., and Cleasby, T.E., 2000, Water-quality data for 

streams in the Boulder River watershed, Jefferson County, 

Montana: U.S. Geological Survey Open-File Report 00-99, 

70 p.
Trace-Element Sources and Transport to Upper Basin Creek 455

Roby, R.N., Ackerman, W.C., Fulkerson, KB., and Crowley, 

F.A., 1960, Mines and mineral deposits (except fuels), 

Jefferson County, Montana: Montana Bureau of Mines and 

Geology Bulletin 16, 122 p.

Ruppel, E.T., 1963, Geology of the Basin quadrangle, Jefferson, Lewis and Clark, and Powell Counties, Montana: 

U.S. Geological Survey Bulletin 1151, 121 p.

Schemel, L.E., Kimball, B.A., and Bencala, K.E., 2000, 

Colloid formation and metal transport through two mixing 

zones affected by acid mine drainage near Silverton, Colorado: Applied Geochemistry, v. 15, p. 1003-1018.

Smith, B.D., and Sole, T.C., 2000, Schlumberger DC resistivity soundings in the Boulder watershed, Jefferson and Lewis 

and Clark Counties, Montana: U.S. Geological Survey 

Open-File Report 00-110, 31 p.

Telford, W.M., Geldart, L.P., and Sheriff, R.E., 1990, Applied 

geophysics, Second Edition: New York, Cambridge 

University Press, 770 p.

U.S. Department of Agriculture, Soil Conservation Service, 

1981, Average annual precipitation Montana, based on 

1941-1970 base period: Prepared in cooperation with 

Montana Department of Natural Resources and Conservation, Water Resources Division, Helena, Mont., 13 p.

U.S. Geological Survey, issued annually, Water resources data, 

Montana: Helena, Mont., U.S. Geological Survey WaterData Report, pages vary.

Monitoring Remediation—Have 

Mine-Waste and Mill-Tailings Removal 

and Flood-Plain Restoration Been 

Successful in the High Ore Creek Valley?

By Sharon L Gelinas and Robert Tupling

Chapter E2 of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-E2

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract..................................................................................................................................................

Introduction............................................................................................................................................... 461

Purpose and Scope.........................................................................................................................463

Pre-Remediation Environmental Setting............................................................................................... 463

Remediation Along the High Ore Creek Valley..................................................................................... 464

Evaluation of Remediation....................................................................................................................... 467

Temporal Trends............................................................................................................................... 467

Pre- and Post-Remediation Concentration Profiles................................................................... 468

Statistical Analysis.......................................................................................................................... 468

Summary.................................................................................................................................................... 471

References Cited...................................................................................................................................... 472

Figures

1. Map showing location of High Ore Creek, Mont, with water-quality monitoring

sites and inactive mine locations.......................................................................................... 462

2-6. Photographs showing:

2. Mill tailings in High Ore Creek valley at Comet mine site before large-scale

remediation activities, October 1996............................................................................. 464

3. Comet Mill and open-pit mine before large-scale remediation activities,

October 1996...................................................................................................................... 465

4. High Ore Creek valley at Comet mine site after remediation activities,

August 1998....................................................................................................................... 465

5. Comet Mill and mine site after remediation activities, August 1998........................ 466

6. Reconstructed reach of High Ore Creek downstream from Comet mine site,

December 1999................................................................................................................. 466

7-10. Graphs showing:

7. Dissolved zinc concentrations and streamflow in four reaches of

High Ore Creek, 1993-2000.............................................................................................. 467

8. Dissolved zinc concentrations in High Ore Creek, September 1993 and

April 2000............................................................................................................................ 470

9. Dissolved arsenic concentrations and pH at mouth of High Ore Creek, 

1996-2000..................................................^

10. Regression relation of dissolved zinc concentrations and streamflow for 

pre- and post-remediation periods at five long-term monitoring sites in 

Boulder River watershed, 1996-2000............................................................................472
Tables

1. Trace-element data for High Ore Creek, April 28,2000..................................................... 469

2. Results of multivariate analysis of variance of dissolved zinc concentrations 

and streamflow for selected sites in Boulder River watershed for 1993-97 

and 1997-2000 periods............................................................................................................ 471

CONVERSION FACTORS

Multiply

acre

cubic foot per second (ftVs)

cubic yard (yd3)

foot (ft)

mile (mi)

ounce (oz)

pound (Ib)

By

4,047

0.028317

0.7646

0.8048

1.61

28.35

453.6

To obtain

square meter

cubic meter per second

cubic meter

meter

kilometers

gram

gram

Chapter E2

Monitoring Remediation—Have Mine-Waste and 

Mill-Tailings Removal and Flood-Plain Restoration Been 

Successful in the High Ore Creek Valley?

By Sharon L Gelinas 1 and Robert Tupling2

Abstract

Mining activity in the High Ore Creek basin produced 

mine wastes and mill tailings that resided in waste dumps 

or were dispersed along the flood plain by fluvial transport. 

These sources of arsenic and metals degraded water quality, 

contaminated streambed sediment, and negatively affected the 

health of aquatic biota. Comet mine, the largest mine in the 

basin, produced the majority of the waste rock and mill 

tailings. Evaluation of environmental data collected by the 

Montana Department of State Lands, the Montana Bureau 

of Mines and Geology, and the U.S. Geological Survey led 

to large-scale remediation in the High Ore Creek valley that 

included both removal actions and in-place treatments. 

Monitoring data collected before and after remediation provide a basis for documenting the effects of cleanup actions on 

trace-element concentrations.

A preliminary evaluation of pre- and post-remediation data indicates that dissolved zinc concentrations have 

decreased in High Ore Creek. Dissolved arsenic concentrations apparently have increased, presumably owing to desorption and leaching associated with liming of waste materials. 

Multivariate analysis of variance (MANOVA) has shown that 

post-remediation dissolved zinc concentrations at the mouth of 

High Ore Creek and in the Boulder River below Little Galena 

Gulch decreased significantly from pre-remediation concentrations, although concentrations in High Ore Creek are not 

yet stable. Continued monitoring can determine the effects 

of remediation on trace-element concentrations in High Ore 

Creek and the Boulder River ecosystem.

Introduction

Historical mining in the High Ore Creek basin 

produced wastes enriched in trace elements. Consequent

'Environmental Careers Organization, Boston, Mass. 

2Montana Tech of the University of Montana, Butte, Mont.

environmental effects were sufficiently severe to warrant some 

of the first abandoned mine lands (AML) remediation activities in Montana. Waste rock and mill tailings produced at the 

Comet mine (fig. 1), one of the largest in the Boulder River 

watershed, were deposited across High Ore Creek. Erosion of 

these materials by the stream resulted in extensive deposition 

of tailings on the High Ore Creek valley floor and the Boulder 

River flood plain (Marvin and others, 1997). Leaching of acid 

and trace elements, such as arsenic and metals, from these 

mine wastes degraded water quality sufficiently to effectively 

eliminate fish from High Ore Creek and impaired fisheries 

in the Boulder River (Farag and others, this volume, Chapter 

D10; Pioneer Technical Services, Inc., 1999). The Comet 

mine area was given a high priority for cleanup by the State of 

Montana (Montana Department of State Lands, 1995) because 

of impacts to water quality and the local fisheries. Largescale remediation efforts were initiated by State and Federal 

agencies in 1997 to improve riparian and aquatic conditions in 

High Ore Creek.

The Comet mine, located near the headwaters, was the 

largest and most productive mine in the High Ore Creek 

basin. It produced about 3,117,770 oz of silver; 42,440 oz 

of gold; 2,235,680 Ib of copper; 28,535,230 Ib of lead; and 

23,486,020 Ib of zinc during its intermittent operation from 

1880 to 1941 (Marvin and others, 1997). The mining operation included 18,000 ft of underground workings, a 900-ft 

shaft, and a large open pit (Elliott and others, 1992). Ore was 

processed onsite. In 1931, a new mill was built near the Comet 

mine to process the ore from this and other nearby mines. 

However, the mill closed a short time after the Comet mine 

ceased operations in 1941 (Becraft and others, 1963).

Large quantities of waste rock and mill tailings were 

left in and near High Ore Creek after the mine closed. One 

dump containing about 150,000 yd3 of mine waste rock was 

located in an upland area east of the open pit; this dump 

covered 3.4 acres. Two other dumps together containing about 

227,000 yd3 and covering 5.0 acres were left in the High Ore 

Creek valley. In addition, two impoundments containing about 

196,500 yd3 of mill tailings covering 5.5 acres were located 

in the valley bottom, blocking the premining stream channel 

(Pioneer Technical Services, Inc., 1997).
462 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

46°18'45" —

46°15' —

cj2 sedimentation pond 

Bureau of Land 

Management 

^-^.Repository

Base from U.S Geological Survey 

Digital line graphs, 1:100,000 2 MILES

2 KILOMETERS

S Map area

EXPLANATION

WATER-QUALITY MONITORING 

SITES AND NUMBER

56, 

79M

WQ3 

COMET

V U.S. Geological Survey

V Montana Bureau of Mines 

and Geology

T Montana Tech

5? Inactive mine and name

O Open pit

Figure 1. Location of High Ore Creek, Mont, with water-quality monitoring sites and 

locations of inactive mines.

In addition to the Comet mine, several small mines 

were located in the High Ore Creek basin (fig. 1; Martin, 

this volume, Chapter D3, fig. 1). The Grey Eagle mine was 

the largest of these smaller mines, producing primarily silver 

(about 2,090 oz) from 1897 to 1941 from about 10,000 ft of 

underground workings (Elliott and others, 1992; Marvin and 

others, 1997). The Silver Hill mine adjoined the Comet mine 

and had underground workings with one shaft (Elliott and

others, 1992). The Golconda/Reliance and King Cole mines, 

located adjacent to High Ore Creek downstream from the 

Comet mine, produced mainly silver, copper, and lead (Marvin 

and others, 1997).

At the smaller mines in the High Ore Creek basin, waste 

rock was the primary mining waste left after mining ceased, 

because the ore was processed at the Comet mill or transported 

out of the basin. Six dumps containing about 2,000 yd3 of
Monitoring Remediation Success in High Ore Creek Valley 463

mine waste rock were located at the Silver Hill mine (Pioneer 

Technical Services, Inc., 1997). One dump, approximately 

73,000 yd1 in size, was located at the Grey Eagle mine 

(Montana Department of State Lands, 1995). One dump (about 

4,300 yd3 covering 0.26 acres) was located on the east bank 

of High Ore Creek at the King Cole mine. Two dumps (about 

1,500 yd1 covering 0.22 acres), one on either side of High Ore 

Creek, were located at the Golconda/Reliance mine (Marvin 

and others, 1997).

Purpose and Scope

The purpose of this chapter is to describe the pre-remediation environmental setting and cleanup activities and to 

present a preliminary evaluation of the remediation based on 

post-remediation monitoring data. The pre-remediation environmental setting was determined from data compiled from 

the Montana Department of State Lands, the Montana Bureau 

of Mines and Geology (MBMG), and this study. Water-quality 

data collected from 1993 through 2000 at nine MBMG sites, 

four U.S. Geological Survey (USGS) sites, and nine Montana 

Tech (Montana Tech of the University of Montana) sites were 

used to evaluate remediation success.

Pre-Remediation Environmental 

Setting

The Montana Department of State Lands (1995) and 

Marvin and others (1997) inventoried mine wastes at inactive 

mines to identify and prioritize mine sites with environmental 

hazards. Site inventories included sampling tailings, waste 

rock, adit discharge, seeps, stream water, and streambed 

sediment. These inventory investigations, along with Boulder 

River watershed characterization data collected by the USGS, 

describe in detail the pre-remediation environmental conditions in the High Ore Creek basin.

Trace elements such as arsenic, cadmium, copper, lead, 

manganese, mercury, silver, and zinc generally existed at 

elevated concentrations in the waste-rock dumps and tailings 

impoundments at the Comet mine (Church, Unruh, and others, 

this volume, Chapter D8, table 2), and in the waste rock at the 

Silver Hill, Grey Eagle, King Cole and Golconda/Reliance 

mines. These elevated concentrations were much higher than 

premining baseline data determined by Church, Unruh, and 

others (this volume, table 3). Water flowing through waste 

rock and mill tailings produced acid mine drainage. The potential to produce acid mine drainage was determined by acidbase accounting. If the sum of the potential acidity and the 

potential neutralizing capacity was negative, then the site was 

considered a potential acid producer. Two of the waste-rock 

dumps and one tailings impoundment at the Comet mine site 

and the waste rock at the Silver Hill and Golconda/Reliance 

mines were considered potential acid producers (Montana

Department of State Lands, 1995; Pioneer Technical Services 

Inc., 1997, 1999).

Streamside tailings as much as several feet thick covered 

the banks and flood plain of High Ore Creek for several hundred feet downstream from the Comet mine. Farther downstream, the tailings became thinner and discontinuous. An 

estimated 32,000 yd1 of tailings covered more than 21 acres 

of the High Ore Creek flood plain (Marvin and others, 1997; 

Pioneer Technical Services, Inc., 1999). Analysis of 42 fluvial 

tailings cores showed elevated concentrations of arsenic, 

cadmium, copper, lead, silver, and zinc along High Ore Creek 

between the Comet mine and the Boulder River. A substantial 

fraction (from 25 to 100 percent) of the trace elements were in 

the leachable phase (Fey and Church, 1998; Rich and others, 

this volume, Chapter G).

Streambed sediment had elevated concentrations of 

arsenic, cadmium, copper, lead, silver, and zinc. Copper 

concentrations were more than 50 times greater than estimated background levels, whereas arsenic, cadmium, lead, 

and zinc concentrations were more than 100 times greater than 

estimated background levels. Concentrations in streambed 

sediment decreased downstream in High Ore Creek, particularly below the confluence with Bishop Creek. At the mouth 

of High Ore Creek, the median concentrations in samples 

collected during 1996-98 were 4,300 ppm (parts per million) 

arsenic, 30 ppm cadmium, 480 ppm copper, 1,600 ppm lead, 

and 6,800 ppm zinc. In contrast, median concentrations in 

streambed-sediment samples collected in the Boulder River 

watershed from areas unaffected by mining were 35 ppm 

arsenic, <2 ppm cadmium, 32 ppm copper, 35 ppm lead, and 

150 ppm zinc (Fey and others, 1999; Church, Unruh, and 

others, this volume; Rich and others, this volume).

Concentrations of dissolved cadmium and zinc in water 

from High Ore Creek during 1993-97 were elevated and 

consistently exceeded aquatic-life standards, while concentrations of dissolved copper and lead commonly were less than 

these standards. During pre-remediation low-flow conditions, 

average concentrations of dissolved cadmium and zinc (site 

56, fig. 1) were 4.3 and 2,050 |ug/L (micrograms per liter), 

respectively, which exceeded the State of Montana chronic 

aquatic-life standards of 3.5 and 177 ng/L, respectively (average hardness of stream samples collected during pre-remediation low flow used for calculating standards). During preremediation spring runoff, average dissolved concentrations of 

cadmium and zinc were 2.6 and 789 (ig/L, respectively (Rich 

and others, this volume), which exceeded the State of Montana 

acute aquatic-life standards of 2.3 and 111 (ig/L, respectively 

(average hardness during pre-remediation high flow used for 

calculating standards). Although trace-element concentrations 

were high in High Ore Creek, pH was consistently greater 

than 7.

Dissolved cadmium and zinc concentrations decreased 

downstream from the Comet mine during high- and low-flow 

conditions. Dilution by tributary inflow appears to have been 

a major factor in the decreases. Limited data for Bishop Creek 

and Peters Gulch showed low trace-element concentrations in
464 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

these tributaries. During low flow, total-recoverable zinc 

concentrations in the two tributaries were 20 and 40 

respectively, whereas concentrations were 30 and <10 

respectively, during spring runoff (Rich and others, this volume).

Although zinc concentrations in Bishop Creek were 

low relative to the mainstem, the Grey Eagle mine is a possible source that could contribute trace elements to High Ore 

Creek during high flow (Pioneer Technical Services, Inc , 

1999). Overland runoff and high flows can transport sediment 

enriched with trace elements from waste-rock dumps at the 

Grey Eagle mine downstream to High Ore Creek. Similarly, 

the waste rock at the King Cole and Golconda/Reliance mines 

also might have degraded water quality by contributing sediment during high flow (Marvin and others, 1997).

Upstream from the Comet mine, High Ore Creek contains 

a pristine fisheries environment, which includes a native population of westslope cutthroat trout and a diverse population of 

macroinvertebrates (Gless, 1990; Pioneer Technical Services, 

Inc., 1999). The waste rock and tailings in the High Ore Creek 

valley bottom at the Comet mine blocked fish passage and 

thereby isolated the westslope cutthroat trout from the rest of 

the Boulder River watershed where introduced species of trout 

occur. Presumably, westslope cutthroat trout inhabited all of 

High Ore Creek before mining.

Downstream from the Comet mine, High Ore Creek 

was considered extremely degraded by Gless (1990) based 

on the limited diversity of the macroinvertebrate population 

and elevated arsenic concentrations in water. This part of the 

stream did not support a fishery (Pioneer Technical Services, 

Inc., 1999; Farag and others, this volume). In addition, studies 

by Nelson (1976), Knudson (Ken Knudson. consulting

biologist, Helena, Mont., written commun., 1984), and Phillips 

and Hill (1986) demonstrated that fish populations decreased 

in the Boulder River downstream from High Ore Creek owing 

to degraded water quality resulting primarily from high traceelement concentrations.

At the mouth of High Ore Creek, biological data indicated that trace elements were accumulating in biofilm, macroinvertebrates, and fish (Farag and others, this volume). During 

an experiment exposing fish to ambient stream water, survival 

rates of juvenile westslope cutthroat trout were very low owing 

to elevated concentrations of copper and zinc (Farag and others, this volume). Elevated arsenic concentrations caused dark 

coloration and an increased number of melanocytes on fish 

skin (Farag and others, this volume).

In summary, the pre-remediation environmental data 

showed that the large amount of waste rock and tailings near 

the Comet mine and acid drainage from these wastes caused 

elevated trace-element concentrations in water from High 

Ore Creek and in flood-plain and streambed-sediment deposits along High Ore Creek downstream to the Boulder River. 

In addition, waste rock near the Grey Eagle and Golconda/ 

Reliance mines could have contributed to the elevated traceelement concentrations in water and in flood-plain and streambed-sediment deposits.

Remediation Along the High Ore 

Creek Valley

Based on chemical and biological environmental data, 

the Comet mine wastes and mill tailings (figs. 2, 3) were

Figure 2. Mill tailings in High Ore Creek valley at Comet mine site before large-scale remediation 

activities, October 1996. Photograph by D.A. Nimick.
Monitoring Remediation Success in High Ore Creek Valley 465

Figure 3. Comet Mill and open-pit mine before large-scale remediation activities, October 1996. 

Photograph by DA Nimick.

considered a high priority by the Stale of Montana and the 

Bureau of Land Management (BLM) for remediation. The 

Montana Department of Environmental Quality (MDEQ) 

started preliminary remediation work at the Comet mine site 

in 1995. Initially, the efficiency of the existing sediment pond 

was improved, a new treatment pond was constructed below 

the sediment pond, and other erosion-control barriers were 

installed (Pioneer Technical Services, Inc., 1997). Large-scale 

remediation efforts began in September 1997. From

September to December 1997, waste rock and mill tailings 

filling the original channel and adjacent valley bottom of High 

Ore Creek and 1 ft of the underlying native soil near the mine 

were excavated and moved to the existing open pit, which was 

used as an unlined repository (figs. 4, 5). From May through 

July 1998, other waste-rock materials were amended onsite 

with lime. During the second phase, planned to start in 2001, 

about 1,700 ft of High Ore Creek will be reconstructed to 

restore the channel to its approximate premining position and

Figure 4. High Ore Creek valley at Comet mine site after remediation activities, August 1998. The 

creek has been redirected and the area regraded. Photograph by DA Nimick.
466 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Figure 5. Comet Mill and mine site after remediation activities, August 1998. Waste rock and tailings have been removed, and the open pit has been used as a repository. Photograph by 

DA Nimick.

condition through the Comet mine site. Upon completion of 

this project, approximately 430,500 yd3 of waste will have 

been removed (Pioneer Technical Services, Inc., 1997).

Because High Ore Creek had been eroding and transporting mill tailings from the Comet mine site for many years, 

the area downstream from the Comet mine to the Boulder 

River also was targeted for remediation. In fall 1999, the BLM 

restored 3.73 mi of High Ore Creek on BLM and private land

by removing about 5,800 yd3 of waste rock and about 28,000 

yd3 of mill tailings from the valley bottom (Pioneer Technical 

Services, Inc., 1999). Upstream from Bishop Creek, floodplain and streambed-sediment deposits were removed, the 

High Ore Creek channel was reconstructed, and clean material 

was imported to backfill the excavated areas (fig. 6). Downstream from Bishop Creek, waste rock and flood-plain deposits were either removed or amended in place with lime, but the

Figure 6. Reconstructed reach of High Ore Creek downstream from Comet mine site, December 

1999. Photograph by J.H. Lambing.
Monitoring Remediation Success in High Ore Creek Valley 467

stream channel was not disturbed. All excavated 

wastes were placed in an unlined repository (fig. 1) with a 

multi-layered cap, south of the Comet mine (Pioneer Technical 

Services, Inc., 1999).

Evaluation of Remediation

The long-term pattern of trace-element concentrations 

in High Ore Creek will determine whether the remediation in 

the basin has been successful. Decreasing concentrations over 

time should eventually result in improved riparian and aquatic 

conditions. Trace-element concentrations were assessed by 

graphing temporal trends for four sites, by comparing

longitudinal concentration profiles for similar flow conditions 

before and after cleanup, and by statistical analysis.

Temporal Trends

Water-quality samples were collected at or near four 

USGS sites (fig. 7) on High Ore Creek from September 1993 

through October 2000 (Marvin and others, 1997; Nimick and 

Cleasby, 2000; Tupling, 2001; Rich and others, this volume). 

Data for these samples show the initial effect of the MDEQ 

and BLM remediation projects. Dissolved and total-recoverable copper and lead concentrations commonly were less than 

aquatic-life standards both before and after remediation and 

are not discussed here in further detail. Dissolved and totalrecoverable cadmium, manganese, and zinc concentrations had

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1995 1996 1997 1998 2000

EXPLANATION 

• Dissolved zinc 

A Streamflow

Figure 7. Dissolved zinc concentrations and streamflow in four reaches of High Ore Creek, 1993-2000. Data 

from Marvin and others (1997), Nimick and Cleasby (2000), Tupling (2001), and Rich and others (this volume). 

Zinc concentrations reported as less than the minimum reporting level of 1 jig/L are plotted as 1 |ig/L
468 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

similar patterns of temporal variation. Dissolved zinc concentrations, discussed here, illustrate the effects of remediation.

Dissolved zinc concentrations upstream from the Comet 

mine site (site 49) did not change from 1997 through 2000 and 

were consistently low (less than 55 ng/L). However, dissolved 

zinc concentrations at two sites (sites 52 and 53) between the 

Comet mine and Bishop Creek generally decreased after the 

beginning of large-scale cleanup in 1997 (fig. 7). Dissolved 

zinc concentrations near the mouth of High Ore Creek 

(site 56) also appear to have decreased after the beginning of 

large-scale cleanup. Samples collected on March 25, 1999, at 

sites 53 and 56 reflect early spring snowmelt runoff, which 

had anomalously high concentrations of dissolved zinc as well 

as other trace elements and suspended sediment (not shown in 

fig. 7). Sampling was not conducted during similar snowmelt 

runoff conditions prior to large-scale remediation activities. 

Therefore, the effect of remediation activities on zinc concentrations during early snowmelt runoff cannot be evaluated.

Pre- and Post-Remediation Concentration 

Profiles

An objective way to look at the effects of the Comet mine 

remediation is to compare pre- and post-remediation traceelement concentrations along High Ore Creek during similar 

flow conditions. Data collected by MBMG in September 1993 

(Marvin and others, 1997) and Montana Tech in April 2000 

(table 1; Tupling, 2001) as part of a post-reclamation study 

funded by the BLM clearly show the effects of cleanup 

(fig. 8). Based on limited data, streamflow in April 2000 

(1.7 ftVs at site WQ3, fig. 1) probably was similar to the flow 

in September 1993 (1.3 ft3/ s at site 81M, fig. 1). Again, dissolved zinc is discussed here to illustrate a pattern that was 

similar for dissolved cadmium and manganese. Figure 8 shows 

that dissolved zinc concentrations represented by two sample 

sets collected during similar hydrologic conditions decreased 

at essentially all sampling sites between 1993 and 2000. The 

largest decreases between 1993 and 2000 occurred at sites in 

the reach between the Comet and King Cole mines. However, 

the increase in dissolved zinc concentrations downstream from 

the Comet mine site in 2000 relative to site WQ15 above the 

mine indicates that the mine site is still a source of dissolved 

zinc to High Ore Creek. From Bishop Creek to the mouth 

of High Ore Creek, concentrations in 2000 remained essentially uniform, unlike in 1993 when concentration increases 

occurred downstream from Peters Gulch and the Golconda/ 

Reliance mine sites.

Concentrations of dissolved zinc exhibit diel cycles 

in High Ore Creek, with concentrations fluctuating by as 

much as a factor of 3 between early morning and late afternoon (Lambing and others, this volume, Chapter D7). These 

cycles potentially could have a large effect on comparisons 

of concentration data, such as those in figure 8, collected on 

different sampling dates. Sites downstream from Peters Gulch 

(fig. 8) were sampled at about the same time of day during the

September 1993 and April 2000 sampling episodes. Although 

the same sites were not sampled each year, the sampling time 

for each site sampled in 2000 was within 60 minutes of the 

sampling time for nearest site sampled in 1993. Temporal 

concentration variations attributable to diel cycles during a 

60-minute period are only a fraction of the total diel variation and, therefore, would not be large enough to eliminate or 

reverse the apparent decrease in concentration shown by the 

post-remediation data in figure 8. Sites between Peters Gulch 

and the Comet mine were not sampled at similar times during 

the two sampling episodes. Sites were sampled in mid- to late 

morning in September 1993, when concentrations would be 

near their maximum diel values, whereas sites were sampled 

in mid- to late afternoon in April 2000, when concentrations 

would be near the diel minimum values. Therefore, the apparent decrease in concentration shown in figure 8 may be much 

less than shown. These data demonstrate the importance of 

understanding diel cycles when trends in trace-element 

concentrations are being assessed.

In contrast to dissolved zinc, dissolved arsenic concentrations apparently increased since large-scale remediation began 

in 1997. In particular, concentrations at the mouth of High 

Ore Creek (site 56) not only have increased from pre-remediation levels, but values that typically were less than the State 

of Montana human-health standard of 18 ug/L have increased 

to post-remediation values that typically are higher than this 

standard (fig. 9). One explanation for this phenomenon is that 

sorption onto particulates, which is an important control on 

arsenic mobilization, has decreased. Sorption is dependent on 

pH, and arsenic desorption increases as pH increases (Pierce 

and Moore, 1982). However, the pH of High Ore Creek does 

not appear to have increased after remediation began 

(fig. 9), so the arsenic probably is not derived from desorption 

of arsenic from streambed sediment. A more likely explanation of these increases in dissolved arsenic in the stream is 

that the lime used to amend waste rock at the mine site and 

flood-plain deposits downstream from Bishop Creek resulted 

in an increase in pH in these materials. The higher pH likely 

mobilized arsenic, which then leached into High Ore Creek.

Statistical Analysis

A preliminary statistical analysis of water-quality data 

was done by segregating available data into two sets representing pre- and post-remediation periods. Data for September 

1997 were designated as the last pre-remediation sampling 

data. Multivariate analysis of variance (MANOVA) was used 

to compare the combined means of the logarithmically transformed trace-element concentrations and streamflow values. 

Dissolved zinc concentrations were used to represent the 

general differences between pre- and post-remediation metal 

concentrations.

Data for five monitoring sites in the Boulder River 

watershed (fig. 1, sites 3, 24, 47, 56, and 58) were used to 

evaluate the preliminary effects of the Comet mine cleanup
Table 1. Trace-element data for High Ore Creek, April 28,2000. 1

[ft3/s, cubic feet per second; |ag/L, micrograms per liter; <, less than minimum reporting level; —, no data]

Site No.

WQ3

WQ4

WQ5

WQ7

WQ9

WQ10

WQ11

WQ15

Streamflow, 

Station name instantaneous

(ftYs)

High Ore Creek near mouth 1 .7

High Ore Creek at cabin residence —

High Ore Creek downstream from Peters Gulch —

High Ore Creek downstream from Bishop 

Creek. ~

High Ore Creek upstream from Bishop Creek —

High Ore Creek downstream from reconstruction.

High Ore Creek downstream from Comet mine 

and above reconstruction.

High Ore Creek upstream from Comet mine —

Arsenic, 

dissolved

(ug/L)

21.8

19.9

19.0

13.5

18.6

14.5

11.4

1.69

Arsenic, 

total 

recoverable

(ug/D

47.7

57.9

61.6

40.8

48.0

18.4

15.8

2.1

Cadmium, 

dissolved

(ug/L)

2.76

2.67

2.66

2.51

3.97

5.82

6.44

<2

Cadmium, 

total 

recoverable

(ug/L)

3.78

3.92

4.11

3.48

4.92

5.94

6.22

<2

Copper, 

dissolved 

(ug/L)

3.1

3.56

4.02

2.04

2.59

<2

<2

<2

Copper, 

total 

recoverable

(ug/L)

10.8

12.1

12.8

9.98

10.1

3.1

2.84

<2

Lead, 

dissolved

(ug/L)

<2

<2

<2

<2

<2

<2

<2

<2

to

'Data from Tupling (2001).
470 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

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EXPLANATION

Data from Montana Bureau of Mines and Geology, September 1993

(Man/in and others, 1997) and site number 

Data from Montana Tech, April 2000 (Tupling, 2001) and site number

Figure 8. Dissolved zinc concentrations in High Ore Creek, September 1993 and April 2000.

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Figure 9. Dissolved arsenic concentrations and pH at mouth of High Ore Creek (site 56), 

1996-2000.
Monitoring Remediation Success in High Ore Creek Valley 471

on the Boulder River and High Ore Creek relative to other 

tributaries and upstream portions of the watershed. Results 

of the MANOVA tests determined that the combined means 

of dissolved zinc concentrations and streamflow at three sites 

unaffected by remediation (sites 3, 24, and 47) were not significantly different between the two time periods (before and 

after September 1997) (table 2). In contrast, High Ore Creek 

(site 56) and the Boulder River below Little Galena Gulch 

(site 58) had significantly different means between the two 

periods, indicating that dissolved zinc concentrations had 

changed.

Figure 10 shows ordinary least squares regression relations between streamflow and dissolved zinc concentrations 

for both pre- and post-remediation at the five Boulder River 

watershed sites. Basin Creek and Cataract Creek showed very 

little change in the relation between the two time periods. 

The upper site on the Boulder River (site 3) displayed some 

variation, but maintained consistently low concentrations. The 

most downstream site on the Boulder River (site 58) displayed 

a clear post-remediation downward shift in zinc concentrations at low streamflows (less than 100 ftVs), but tended to 

converge with the pre-remediation relation at higher flows 

(greater than 100 ft3/s). One notable feature is that High Ore 

Creek post-remediation data are highly scattered, indicating 

that dissolved zinc concentrations have not stabilized since 

remediation activity ended. With time, a stronger relation 

between streamflow and concentration might be expected to 

develop as remediated areas physically stabilize and hydrologic and geochemical equilibrium is established. Continued 

monitoring, especially at High Ore Creek and the Boulder 

River below Little Galena Gulch, would provide the necessary 

data to better demonstrate and quantify the overall change in 

trace-element concentrations and, ultimately, to determine the 

degree to which remediation was successful in improving the 

health of aquatic biota.

Summary

Inactive historical mines and a mill in the High Ore 

Creek valley produced wastes enriched in trace elements that 

degraded water quality and eliminated fish in High Ore Creek 

downstream from the Comet mine. These environmental 

effects were sufficiently severe to warrant remediation activities for abandoned mine lands in the basin. Pre-remediation 

environmental data showed that waste rock, mill tailings, 

fluvial tailings deposits, and streambed sediment contained 

elevated trace-element concentrations. MDEQ removed waste 

rock and tailings at the Comet mine site in 1997-98 and plans 

to finish reclaiming the mine site in 2001. BLM removed 

Comet mill tailings from the flood plain upstream from 

Bishop Creek, reconstructed the stream channel, and amended 

the waste rock and mill tailings with lime downstream from 

Bishop Creek.

A preliminary evaluation of pre- and post-remediation 

water-quality data from four sites along High Ore Creek has 

shown decreased dissolved zinc concentrations through time 

at the three sites below the Comet mine since large-scale 

remediation started. Downstream profiles of dissolved zinc 

concentrations at multiple sites along High Ore Creek in 

1993 and 2000 showed consistently lower concentrations in 

2000 throughout the entire reach of High Ore Creek below 

the Comet mine. In contrast, dissolved arsenic concentrations 

apparently have increased since remediation started, most 

likely owing to desorption and leaching associated with the 

pH effects of liming. Comparison of pre- and post-remediation regression relations between streamflow and dissolved 

zinc concentrations at five sites throughout the Boulder River 

watershed indicate that zinc concentrations at the mouth of 

High Ore Creek and the Boulder River below Little Galena 

Gulch have decreased since remediation started, although concentrations in High Ore Creek are not yet stable. Continued 

environmental monitoring would provide the necessary data to 

demonstrate and quantify the change in trace-element concentrations that can ultimately determine whether 

remediation was successful.

Table 2. Results of multivariate analysis of variance of dissolved zinc concentrations and streamflow for selected sites in 

Boulder River watershed for 1993-97 and 1997-2000 periods.

Site No. Station name

3 Boulder River above Kleinsmith Gulch, near Basin

24 Basin Creek at Basin

47 Cataract Creek at Basin

56 High Ore Creek near Basin

58 Boulder River below Little Galena Gulch, near Boulder

Level of significance 

(p-value)1

0.154

.403

.340

.010

.003

Conclusion 

(a = 0.05)

Means were equal.

Means were equal.

Means were equal.

Means were not equal.

Means were not equal.

'A p-value less than 0.05 indicates a significant difference between means.
472 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

50

10

Boulder River above 

Kleinsmith Gulch (site 3}

O

500

100 -

Basin Creek (site 24)

O

1 10

1,000

100

50

500

10

100 1,000 1

5,000

10 100 1,000

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^90

O 1,000

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100

High Ore Creek (site 56)

O

00

O

0.1

100

10

Boulder River below

Little Galena Gulch (site 58)

1 10 

STREAMFLOW, IN CUBIC FEET PER SECOND

100

EXPLANATION

• Pre-remediation along High Ore Creek 

O Post-remediation along High Ore Creek

10 100 1,000 

STREAMFLOW, IN CUBIC FEET PER SECOND

10,000

Figure 10. Regression relation of dissolved zinc concentrations and streamflow for pre- and post-remediation periods at five 

long-term monitoring sites in Boulder River watershed, 1996-2000.

References Cited

Becraft, G.E., Pinckney, D.M., and Rosenblum, Sam, 1963, 

Geology and mineral deposits of the Jefferson City quadrangle, Jefferson and Lewis and Clark Counties, Montana: 

U.S. Geological Survey Professional Paper 428, 100 p.

Elliott, J.E., Loen, J.S., Wise, K.K., and Blaskowski, M.J., 

1992, Maps showing locations of mines and prospects in 

the Butte 1 degree x 2 degree quadrangle, western Montana: 

U.S. Geological Survey Miscellaneous Investigations Series 

Map I- 2050-C, 2 sheets, scale 1:250,000.

Fey, D.L., and Church, S.E., 1998, Analytical results for 

42 fluvial tailings cores and 7 stream sediment samples 

from High Ore Creek, northern Jefferson County, Montana: 

U.S. Geological Survey Open-File Report 98-215,49 p.
Monitoring Remediation Success in High Ore Creek Valley 473

Fey, D.L., Unruh, D.M., and Church, S.E., 1999, Chemical 

data and lead isotopic compositions in stream-sediment 

samples from the Boulder River watershed, Jefferson 

County, Montana: U.S. Geological Survey Open-File Report 

99-575, 147 p.

Gless, E.E., 1990, Biological and chemical baseline studies along the Boulder River and its tributaries in Jefferson 

County, Montana: Prepared by E.E. Gless, Montana College 

of Mineral Science and Technology, Butte, Mont., as a 

report to the Jefferson County Commissioners, variously 

paged.

Marvin, R.K., Metesh, J.J., Bowler, T.P., Lonn, J.D., 

Watson, J.E., Madison, J.P., and Hargrave, PA., 1997, 

Abandoned-inactive mines program, U.S. Bureau of Land 

Management: Montana Bureau of Mines and Geology 

Open-File Report 348, 506 p.

Montana Department of State Lands, 1995, Abandoned 

hardrock mine priority sites, 1995, summary report: 

Helena, Mont., prepared for Abandoned Mine Reclamation 

Bureau by Pioneer Technical Services, Inc., Butte, Mont., 

variously paged.

Nelson, FA., 1976, The effects of metals on trout populations 

in the Upper Boulder River, Montana: Bozeman, Mont., 

Montana State University M.S. thesis, 60 p.

Nimick, D.A., and Cleasby, T.E., 2000, Water-quality data for 

streams in the Boulder River watershed, Jefferson County, 

Montana: U.S. Geological Survey Open-File Report 00-99, 

70 p.

Phillips, Glenn, and Hill, Kurt, 1986, Evaluations of sources 

and toxicity of copper and zinc in the Boulder River drainage, Jefferson County-1985: Montana Department of Fish, 

Wildlife and Parks, Pollution Control Information Series, 

Technical Report 4, 28 p.

Pierce, M.L., and Moore, C.B., 1982, Adsorption of 

arsenite and arsenate on amorphous iron hydroxides: 

Water Research, v. 16, p. 1247-1253.

Pioneer Technical Services, Inc., 1997, Final expanded 

evaluation/cost analysis for the Comet mine site: Butte, 

Mont., prepared for Montana Department of Environmental 

Quality, Abandoned Mine Reclamation Bureau, variously 

paged.

Pioneer Technical Services, Inc., 1999, Final expanded engineering evaluation/cost analysis for the High Ore Creek 

stream side tailings reclamation project: Butte, Mont., 

prepared for Montana Department of Environmental 

Quality, Abandoned Mine Reclamation Bureau, variously 

paged.

Tupling, Robert, 2001, Reclamation of the High Ore Creek 

watershed: Butte, Mont., Montana Tech of the University of 

Montana M.S. thesis, 133 p.

Geologic, Geophysical, and Seismic 

Characterization of the Luttrell Pit as a 

Mine-Waste Repository

By Bruce D. Smith, Robert R. McDougal, and Karen Lund

Chapter E3 of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

In cooperation with the

U.S. Environmental Protection Agency

Professional Paper 1652-E3

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract.................................................................^

Introduction............................................................................................................................................... 477

Purpose and Scope.........................................................................................................................478

Setting ............................................................................................................................................... 478

Methods ............................................................................................................................................478

Geological Characterization................................................................................................................... 480

Setting ............................................................................................................................................... 480

Faults ............................................................................................................................................... 481

Joints ............................................................................................................................................... 482

Airborne Magnetic and Electromagnetic Data.................................................................................... 482

Seismicity.......................................................................................................^

Helena Earthquakes of 1935........................................................................................................... 484

Earthquake Data.............................................................................................................................. 486

Interpreted Fracture Mapping from Remote Sensing Data............................................................... 487

Linear Feature Analysis.................................................................................................................. 488

Hydrological Implications............................................................................................................... 489

Conclusions............................................................................................................................................... 493

References Cited...................................................................................................................................... 493

Figures

1. Map showing location of the Luttrell mine-waste repository, in the Boulder River

watershed................................................................................................................................. 479

2. North-south cross section near north end of Luttrell pit.................................................. 481

3. Color-shaded relief map of reduced-to-pole magnetic anomalies for Luttrell

pit study area............................................................................................................................ 483

4. Color-shaded relief map of 7,200 Hz apparent conductivity for Luttrell pit

study area................................................................................................................................. 485

5. Isoseismal map from main shock of Helena earthquake of October 18,1935............... 486

6-8. Maps showing:

6. Peak acceleration in percent of gravity that has a 10 percent probability

of being exceeded in 50 years........................................................................................ 487

7. Earthquake epicenters in Rocky Mountain region defining Intermountain

seismic belt and Centennial tectonic belt.................................................................... 488

8. Earthquake epicenters and fault plane (nodal) solutions for Helena area............. 489

9. Rose diagrams and statistical analysis of lineament orientations in Luttrell pit

study area................................................................................................................................. 490

10. Digital map showing wet soils in the study area draped over a digital elevation

model and combined with mapped lineaments.................................................................. 491

11. Color map of 7,200 Hz apparent conductivity superimposed with linear features

described in this study............................................................................................................ 492
Chapter E3

Geologic, Geophysical, and Seismic Characterization of

the Luttrell Pit as a Mine-Waste Repository

By Bruce D. Smith, Robert R. McDougal, and Karen Lund

Abstract

Integrated geologic and geophysical studies conducted 

near the Luttrell pit at the former Basin Creek mine provide 

geotechnical information that characterizes the area of the 

mine-waste repository. The geologic setting, fracture patterns, 

potential ground-water flow paths, and historical seismicity 

were examined using mining company records, geologic and 

geophysical data, and remote sensing images. Interpretation 

and analysis of airborne geophysical data suggest a much 

greater structural and lithologic complexity than indicated by 

the geologic mapping. The bedrock in the immediate area of 

the Luttrell pit does not have high acid-neutralizing potential 

as interpreted from the airborne geophysical data. Although 

the region is an area of high seismic activity, little historical 

seismic activity has been recorded near the pit. Regional stress 

suggests that northeast-trending fractures may be preferentially open but local stress conditions at the mine-waste repository are unknown. Although faults in the area were active 

before and after mineralization, no recent movement was 

evident in the structures exposed by the pit mining. Structures 

inferred from geologic mapping, from airborne geophysical data, and from lineaments mapped using remote sensing 

images define a northeast-trending structural zone located 

0.25 miles south of the pit. This zone may influence the local 

flow of ground water in fractures and would be a possible 

area for bedrock ground-water monitoring. The potential for 

enhanced ground-water recharge or discharge may be greater 

in areas where the geophysical data indicate high electrical 

conductivity and mapping indicates the presence of linear 

features or structures.

Introduction

Mine wastes and mill tailings produced during historical 

mining activities commonly were discarded with little regard 

for any potential effect on the landscape and resources. Runoff 

from or direct erosion of these wastes is a primary cause 

of environmental degradation in many watersheds, like the

Boulder River watershed, that have been affected by historical mining. Repositories are a common type of facility used 

to consolidate and contain mining wastes. Repository-siting 

studies are therefore an important component of investigations designed to characterize abandoned mine lands prior to 

remediation activities.

Siting of repositories requires consideration of a complex 

array of environmental, economic, engineering, and political 

factors. As a part of the overall siting investigation, geotechnical studies (geology, geophysics, seismicity, and linear feature 

mapping) can provide important information for assessing 

each of these factors. Geologic information provides the basic 

framework for understanding the underpinnings of the repository and is critical for understanding the hydrogeology and 

potential fate of any contaminants released from the repository. Geologic information also provides information on the 

presence of faults and potential seismicity of the area. Geophysical data are useful for examining the subsurface geology of an area in greater detail than is possible from surface 

mapping. Geophysics and geochemistry provide a means to 

estimate surface and subsurface acid-neutralizing potential. 

Linear feature mapping using remote sensing images provides 

additional detail not easily obtained from traditional geologic 

mapping.

In the late 1990s, land-management agencies considered 

several potential repository sites near major historical mines 

in the Boulder River watershed for consolidation of mine 

wastes. Initial studies of some of these sites demonstrated 

that the region's granitic bedrock could neutralize potential 

releases of acidic leachate (Desborough and Driscoll, 1998). 

However, further investigation of these sites was curtailed 

when the opportunity arose to utilize an open pit at the former 

Basin Creek mine. The Luttrell pit is centrally located (fig. 1) 

as well as sufficiently large to contain historical mining wastes 

from several drainage basins. The agencies initiated investigations to identify and evaluate geotechnical characteristics that 

would affect site engineering. Reported here are results from 

those studies which have implications for the potential fate of 

contaminant releases and the possibility of earthquake activity 

destabilizing the repository.
478 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Purpose and Scope

This report describes and interprets selected geotechnical characteristics in the area of the Luttrell pit mine-waste 

repository, which are important considerations in engineering 

design. In particular, the goals of the report are to

• Describe the geology, alteration, mineralization history, 

joints, and faults

• Examine airborne geophysical data to determine the 

nature of subsurface rocks and geologic structures

• Provide preliminary conclusions about possible seismic 

hazards, and

• Interpret linear features from remote sensing images to 

identify possible structures that could control groundwater flow paths to or from the repository site.

Setting

The Luttrell pit was one of three open pits at the Basin 

Creek mine, which is located on the Continental Divide near 

the northern boundary of the Boulder River watershed study 

area (fig. 1). The site is near the headwaters of several drainage basins (fig. 1) where historical mining has occurred.

Gold was mined by underground and open-pit heap-leach 

operations in various locations within 1 mi of the Luttrell pit 

(fig. 1) intermittently from about 1892 to 1991. From 1915 to 

1926, the Basin Creek underground mine was operated by the 

Anaconda Minerals Company. During 1988 and 1989, Pangea 

Resources Ltd. conducted the first open-pit heap-leach operations, called the Columbia and Paupers pits, in the general 

location of the Paupers Dream mine southwest of the Luttrell 

pit. Pegasus Gold Corporation purchased the mine operations 

in 1989 and formed Basin Creek Mining, Inc. (a wholly owned 

subsidiary). The Paupers and Columbia pits were backfilled 

during mining of the Luttrell pit and subsequently capped with 

clay from the site (Dan Adams, Basin Creek Mine, Inc., oral 

commun., 1999); the Luttrell pit had not been backfilled when 

mining ceased in 1991.

Based on the results of our work and other studies, use 

of the Luttrell pit as a mine-waste repository began in 1999. 

During 1999 and 2000 approximately 140,000 loose cubic 

yards of mine-waste material was placed in individual cells. 

Each cell has a composite liner and a leachate collection and 

removal system (URS, Greiner Woodward Clyde, written 

commun., November 1999). The repository has room for additional wastes that will be removed from nearby inactive mines 

and mills in the future.

Methods

The geologic description in this chapter was compiled 

from published mapping (Ruppel, 1963), unpublished data

primarily from Pegasus Gold Corporation reports, and observations made during geologic field investigations (O'Neill and 

others, this volume, Chapter Dl). M.W. Reynolds (Thamke, 

2000) compiled geologic mapping of bedrock in the Helena 

area including the Luttrell pit area.

Airborne magnetic and electromagnetic surveys were 

flown over the site in 1996 and 1997 (Smith, McCafferty, and 

McDougal, 2000; McCafferty and others, this volume, Chapter 

D2). The airborne geophysical data along flightlines have been 

gridded with a 120-ft cell size, which is about 1/5 of the flightline spacing (Smith, Labson, and Hill, 2000). This cell size 

was required because of the difference between the flightline 

separation (600 ft) and the sampling interval along flightlines 

at 9 ft. The gridded data have been used to produce color maps 

discussed here.

The total-field airborne magnetic data have been processed and reduced to the pole as described by McCafferty and 

others (this volume). Reduction to the pole produces magnetic 

maps where the causative source for magnetic anomalies is 

directly beneath the high or low. Magnetic highs are caused by 

a greater abundance of magnetic minerals (primarily magnetite) in comparison to surrounding lithology. Conversely, relative magnetic lows are caused by an absence of magnetic minerals relative to surrounding lithology. McCafferty and others 

(this volume) give additional details about geologic features 

and processes that can be associated with magnetic anomalies. 

In addition, they give a statistical estimation of the magnetic 

properties of the geologic map units and their distribution in 

the Boulder River watershed.

Electromagnetic data were reduced to apparent resistivities (Eraser, 1978) and converted to apparent conductivities 

at three frequencies (900 Hz, 7,200 Hz, and 56,000 Hz). The 

apparent conductivity was computed based on a homogeneous half space (an electrically conductive and homogeneous 

Earth). The use of the term "apparent" reflects the fact that the 

Earth is not homogeneous and the calculated conductivities 

are an estimate of the true electrical conductivity. The depth 

of investigation varies inversely as a function of frequency and 

conductivity of the subsurface (Spies, 1989). For rocks that 

have an intermediate conductivity (5 millisiemens per meter), 

the lowest frequency provides information from a depth of at 

least 200 ft. The highest frequency provides information from 

a depth of 10-30 ft. In this study, the apparent conductivity 

map at 7,200 Hz was used because it provides information 

from an intermediate depth (30-100 ft), which is the zone that 

typically would immediately underlie a mine-waste repository.

Electrical conductivity of subsurface materials is determined by a variety of physical and electrochemical properties 

of the underlying rock and pore fluids (Olhoeft, 1985). Pore 

fluids affect subsurface conductivity primarily because of the 

charged ions that are dissolved in the water. Conductivity of 

the pore fluid increases as the dissolved-solids concentration 

increases. Therefore, the presence of ground water creates 

higher conductivity in rocks below the water table than in 

similar but unsaturated rocks above the water table. If ground 

water has high concentrations of dissolved solids, subsurface
The Luttrell Pit as a Mine-Waste Repository 479

10 MILES 

_I

10 KILOMETERS

Figure 1. Location of the Luttrell mine-waste repository, in the Boulder River watershed. Base modified from U.S. Geological Survey 

1:250,000 Butte, 1947, and White Sulphur Springs, 1958.
480 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

conductivity can be much higher than in rocks with fresh 

(potable) water. The amount of pore space (porosity) in rocks 

also can affect subsurface conductivity because conductivity 

increases as more pore space within rocks is filled with fluids. 

Mineralogy of rocks is important in determining subsurface 

conductivity. For instance, the presence of clay tends to 

increase conductivity. In addition, some clay minerals such as 

montmorillonite that have large cation exchange capacity can 

have higher electrical conductivity than clay minerals such 

as kaolinite that have small cation exchange capacity. Glacial 

moraines, some types of soil, and weathered volcanic rocks 

can contain significant amounts of clay minerals. Massive or 

interconnected metallic mineral deposits are another cause of 

high conductivity. Power lines, some fences, and pipelines also 

can cause high conductivity anomalies. McCafferty and others (this volume) estimated the apparent electrical properties 

associated with each of the mapped geologic units.

Seismicity interpretations were based on published peak 

ground acceleration, epicenter, and isoseismal maps (Neumann, 1937). These data were compared with Quaternary fault 

maps to determine location of active faults near the Luttrell pit 

and to predict earthquake activity of faults mapped in and near 

the study area. These data also were used to predict geologic 

controls of active faults and possible local surface disturbances 

during earthquakes.

Fracture studies were based on published data (Ruppel, 1963; Becraft and others, 1963) as well as mapping and 

interpretation of linear features from remote sensing imagery. 

Two data sets were used to generate base images for lineament 

mapping. Landsat Thematic Mapper (TM) («100 ft spatial 

resolution) and India Remote Sensing (IRS) 1-C panchromatic 

(17 ft spatial resolution) data were processed and filtered to 

enhance linear features (McDougal and others, this volume, 

Chapter D9). Linear features considered to represent faults, 

fractures, or other linear geologic features were mapped as a 

vector coverage from each base image. The azimuth and line 

length were calculated from the endpoints of each mapped 

vector. A digital map showing wet soil types (wetland areas; 

McDougal and others, this volume) was draped over a digital 

elevation model (DEM) and combined with the map of linear 

features to identify areas where there is an overlap of a high 

occurrence of fractures and saturated soils. These are areas of 

possible ground-water recharge or discharge.

Geological Characterization

Setting

Geologic information provides the basic framework for 

assessing many important geotechnical and hydrologic characteristics of a potential repository site. The Basin Creek mine 

(fig. 1) is in the northern part of the Late Cretaceous Boulder 

batholith-Elkhorn Mountains Volcanics complex, which is an 

important geologic feature of west-central Montana (O'Neill

and others, this volume). The Basin Creek mine site is underlain at depth by the Butte pluton of the Boulder batholith 

(Lund and others, 2002). The Late Cretaceous volcano-plutonic complex was intruded and overlain by Eocene dikes and 

volcanic rocks of the Lowland Creek Volcanics episodes and 

by Eocene-Oligocene volcanic necks and volcanic rocks of the 

Helena volcanic field (O'Neill and others, this volume, pi. 1).

At the Basin Creek mine, a series of Eocene-Oligocene 

purplish-gray and purple pyroclastic rhyolite tuffs and flows 

(O'Neill and others, this volume, pi. 1) of the Helena volcanic 

field overlie the Butte pluton and are the primary host of the 

gold deposits. These rhyolitic rocks are commonly porphyritic 

and contain phenocrysts of sanidine and biotite. They are characterized by spherulitic and fiamme textures of welded tuffs. 

The rocks are dated about 34 Ma (Chadwick, 1978; O'Neill 

and others, this volume) and originated as deposits from local 

vents near the Basin Creek mine. Recognized vents are in an 

east-northeast-trending zone and include, from west to east, 

the peak west of the Josephine mine, Pauper Peak, Luttrell 

Peak, and Red Mountain (O'Neill and others, this volume). 

The Eocene-Oligocene rhyolites were deposited nonconformably on the Late Cretaceous Butte pluton. Prior to deposition 

of the rhyolites, the plutonic rocks were exposed to erosion 

and weathering from about Late Cretaceous to late Eocene 

(for as long as 38 m.y.), and a thin carbonaceous clay was 

locally deposited on them (O'Neill and others, this volume). 

This clay was probably developed in a basin which was later 

in-filled by the Helena volcanic rocks, which metamorphosed 

the clay to shale (Dan Adams, Basin Creek Mine, Inc., written 

commun., 1999). This young sediment is age equivalent to the 

Oligocene siltstone and sandstone described by O'Neill and 

others (this volume). After deposition of the volcanic materials, a north-trending set of minor down-to-the-west normal 

faults dropped the depositional contact zone to the west (fig. 

2). Hydrothermal mineralization and alteration followed the 

faulting. The Paupers and Columbia pits are located entirely in 

the Eocene-Oligocene pyroclastic rhyolites. The Luttrell pit, 

the westernmost pit, is in the faulted contact zone between the 

rhyolitic rocks and the underlying plutonic rocks (O'Neill and 

others, this volume).

Disseminated gold deposits exploited at the Luttrell pit 

were localized primarily along the contact between plutonic 

and Helena volcanic rocks: hydrothermal fluids moved along 

the weathered upper surface of the plutonic rocks, up the 

minor down-to-the-west normal faults, and into the base of 

the rhyolites (fig. 2). The hydrothermal solutions resulted in 

argillic alteration that changed feldspars to clays throughout 

the mineralized areas, including most of the Luttrell pit area. 

Mineralization at the Basin Creek mine produced disseminated 

pyrite and cassiterite in the host rocks. Gold occurs as inclusions in pyrite (and possibly arsenopyrite) grains as well as 

free gold in zones where the pyrite had oxidized. The EoceneOligocene deposits at the Basin Creek mine are notably 

different in mineralogy from Late Cretaceous quartz-vein and 

Eocene breccia-pipe mineral deposits found elsewhere in the 

Boulder River watershed (O'Neill and others, this volume; 

Lund and others, 2002).
The Luttrell Pit as a Mine-Waste Repository 481

WEST EAST

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Figure 2. North-south cross section near north end of Luttrell pit, showing geologic interpretation and gold values exceeding 0.01 

oz/ton from drill hole data (provided by Pegasus Gold Corporation). Dashed lines are interpreted surfaces and faults, queried where 

uncertain. No horizontal scale.

Faults

The presence of faults, particularly possible active faults, 

near a mine-waste repository is important in characterizing the 

area because they present important engineering constraints. 

Faults also can be conduits for or barriers to ground-water 

flow and therefore can significantly influence the hydrology 

of a repository site. The northeast-trending Butte-Helena fault 

zone is an important structural feature in the regional tectonic 

setting of the Luttrell pit (O'Neill and others this volume, 

fig. 1). McDougal and others (this volume, fig. 6) suggest that 

the pit is located near the north edge of this structural zone. 

On a more local scale, Ruppel (1963) described four types of 

faults that can occur in the area of the Luttrell pit: (1) easttrending fault zones, (2) north-trending faults, (3) north 20° 

east-trending faults, and (4) northeast- and northwest-trending faults. The latter faults have been the most recently active 

since they offset glacial deposits. They also control some postglacial drainages and are marked by prominent fault scarps 

50-300 ft high.

The largest mapped fault near the Luttrell pit is an eastnortheast-trending normal fault that traverses the south side 

of the Basin Creek mine and cuts the upper Basin and Banner 

Creek basins (O'Neill and others, this volume, pi. 1). This 

fault is shown on the Basin quadrangle mapped by Ruppel

(1963) and continues a short distance to the east-northeast in 

the geologic map of the Jefferson City quadrangle (Becraft and 

others, 1963). It is grouped with the northeast-trending faults 

described by Ruppel (1963). In general more faults are shown 

on the Basin quadrangle (Ruppel, 1963) than on the Jefferson 

City quadrangle map (Becraft and others, 1963), reflecting the 

presence of more geologic units to show offset. Our geologic 

interpretation is that a fault zone controls the northeast trend of 

Eocene-Oligocene vents. Consequently we have extended the 

fault shown by Ruppel (1963) and Becraft and others (1963) 

east-northeast to the general area of Chessman Reservoir. The 

fault zone that contains this structure is likely composed of 

several other structures that may have different traces associated with the different ages and possibly styles of faulting. The 

entire northeast-trending fault zone is covered, so the eastnortheast fault shown by O'Neill and others (this volume, 

pi. 1) is approximately located.

Interpretation of the geologic map suggests that four 

periods of movement have taken place along this fault from 

middle Tertiary through Holocene time and that the direction 

of movement may have reversed through time. Characteristics 

of the fault which suggest this are:

1. The fault parallels the Eocene-Oligocene vents located 

along the east-northeast trend from the peak west of 

the Josephine mine to Red Mountain, suggesting that
482 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

the fault was active before the Eocene-Oligocene eruption and may have served as a conduit for the magmas 

and hydrothermal mineralizing fluids.

2. The Eocene-Oligocene rhyolites are preferentially 

preserved north of the fault, indicating post-Oligocene 

(but pre-Pleistocene) down-to-the-north offset after 

deposition of the rhyelite.

3. The fault also appears to bound the Basin Creek basin 

along its north edge and may have controlled preservation of glacial deposits on the south side. This would 

indicate a possible episode of Pleistocene movement.

4. As mapped by O'Neill and others (this volume, pi. 1), 

the fault cuts the glacial deposits in upper Basin Creek 

with down-to-the-south movement. Thus, it may have 

had a fourth episode of movement that included Holocene postglacial activity.

In summary, the long east-northeast-trending fault is 

part of a larger fault zone that trends northeast. The normal 

faulting has been active, at least intermittently, for more than 

34 m.y. as well as within the last 10,000 years. Therefore, 

future movement within the fault zone is possible.

A second set of faults in the Luttrell pit area consists of a 

north-trending zone of minor, down-to-the-west faults 

(fig. 2) that cut the contact between the Butte pluton and overlying rhyolitic rocks. Movement along these faults preceded 

mineralization, which took place about 34 Ma. That the faults 

do not offset mineralized rocks indicates that no movement 

has occurred on these particular faults since mineralization. 

Therefore, movement along these faults is highly unlikely 

to occur in the future. Other short northwest- and northeasttrending faults also cut the contact between the Eocene-Oligocene rhyolites and the Late Cretaceous plutonic rocks (O'Neill 

and others, this volume, pi. 1). These do not appear to be part 

of larger fault systems or zones, have only minor offsets, and, 

from our data, likely have not been active since 35 Ma.

Joints

Joints or fractures occur in almost all rocks. The orientation, intensity, and permeability of joints are important factors 

in controlling movement of ground water as well as leachate 

that may be lost from a repository. Orientation and intensity 

of joints are characteristics that are relatively easy to define. 

Estimating the permeability of fractured rock requires a more 

detailed investigation that was beyond the scope of this study.

The Eocene-Oligocene rhyolites that host the Basin 

Creek mine are relatively free of joints in comparison to either 

the Late Cretaceous Elkhorn Mountains Volcanics (O'Neill 

and others, this volume, pi. 1) or the Butte pluton. Many of the 

joints in the Eocene-Oligocene volcanic rocks are primary features that include cooling joints, some of which are columnar 

joints. The other common types of joints are platy joints that

formed secondarily along the flow and compaction layering in 

the pyroclastic rocks (Ruppel, 1963).

The underlying plutonic rocks of the Butte pluton have a 

complex joint pattern (O'Neill and others, this volume, fig. 11) 

and are more extensively weathered along these surfaces. Several major and minor joint sets have been reported (Ruppel, 

1963). Joints of a steeply dipping north-trending set are generally spaced about 1-5 ft apart and those of a steeply dipping 

east-trending set are spaced about 5-10 ft apart. Joints of the 

gently dipping east-trending set are spaced about 1-15 ft apart. 

Several other orientations of joints are present but are not as 

common. Many joints are probably related to shrinkage during 

cooling of the magma, and some have been intruded by latestage aplite dikes (Becraft and others, 1963; Ruppel, 1963). 

The preferred orientation of the joint sets indicates that they 

formed in response to regional stress patterns either during 

or after cooling (O'Neill and others, this volume). Although 

jointing is pervasive in the Butte pluton, most joints are 

thought to be tight at depths greater than about 50 ft. Therefore, we hypothesize that little ground water moves through 

the pluton relative to the amount that flows in the overlying 

shallow unconsolidated deposits and weathered plutonic rocks 

(McDougal and others, this volume).

Airborne Magnetic and 

Electromagnetic Data

Airborne magnetic and electromagnetic data for the Basin 

Creek mine area (Smith, Labson, and Hill, 2000; McCafferty 

and others, this volume) provide additional information about 

the subsurface lithology, structure, and ground water of the 

area. Reduced-to-the-pole magnetic field data are shown as a 

color-shaded relief map (fig. 3). The sun angle used to produce 

the shading is from the northwest in order to enhance northeast-trending features. McCafferty and others (this volume) 

give a detailed discussion of the interpretation of the magnetic 

field data, some of which also appears herein. Figure 4 is a 

color-shaded relief map (northwest illumination) of the 

7,200 Hz apparent conductivity for the Luttrell repository 

study area.

A number of linear features are defined by anomalous 

conductivity and magnetization (figs. 3, 4) that we interpret 

primarily as faults or lithologic contacts. Many more linear 

features are imaged in the geophysical data than are shown as 

mapped structures on the geologic map (O'Neill and others, 

this volume, pi. 1). The main reason for this greater density 

of possible structural features in the geophysical maps is that 

much of the bedrock in the watershed is covered by glacial or 

other surficial deposits and is thus not mappable by surface 

inspection.

None of the linear features shown by geophysical maps in 

figures 3 and 4 trend through the Luttrell pit. Thus, although 

numerous small faults have been mapped in the area by mine 

geologists (fig. 2), none appear either to have a geophysical
The Luttrell Pit as a Mine-Waste Repository 483

112°20' 112°17'30"

Chessman 

Reservoir

. Scott 

Reservoir

Figure 3. Color-shaded relief map of reduced-to-pole magnetic anomalies for Luttrell pit study area. Red filled circle 

is the location of the mine-waste repository. Dashed line shows linear feature discussed in text. A part of the linear 

feature is shown in the enlargement to give greater detail (no scale).
484 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

signature or to be part of a regional structure defined by a 

geophysical signature.

A linear geophysical feature observed about 1,600 ft 

south of the Luttrell pit is defined by remarkably intense 

and narrow (less than 150 ft) magnetic low and conductivity 

high anomalies (dashed line, figs. 3, 4). The northeast-trending feature is obvious on 1:24,000-scale geophysical maps, 

portions of which are shown at a smaller scale in figures 3 

and 4. An enlargement of a portion of the geophysical map is 

shown in each figure in order to better display its character. 

Though many other linear and curvilinear features are seen on 

the airborne geophysical maps, these anomalies are important 

not only for their relatively unique geophysical signature but 

also for their correlation with geologic features, as discussed 

herein. The narrow magnetic low is probably caused by 

alteration that has destroyed magnetic minerals along a possible structural zone. The relative high conductivity might 

be associated with alteration that produced clays, or water 

with high concentrations of dissolved solids in ground water 

along a structure, or both. No unusually high concentrations 

of dissolved solids have been measured in springs around the 

area. Therefore, the anomalously high specific conductance 

of shallow ground water is not a likely cause of the electrical 

conductivity high. If the high conductivity is caused by moist 

clays, then the linear feature might be a subsurface barrier to 

ground-water flow.

The long fault south of Luttrell pit that trends east-northeast toward Chessman Reservoir (O'Neill and others, this 

volume, pi. 1) probably controlled the spatial location of intrusive rocks. Small, closed magnetic high and apparent conductivity low anomalies probably caused by the young, shallow 

intrusive igneous rocks define the east-northeast trend of the 

structure shown on the geologic map. This trend may indicate 

discrete structures that could control local ground-water flow 

in the crystalline rocks. The west end of this east-northeast 

geologic feature merges with the more northeast-trending 

narrow magnetic and apparent conductivity anomaly west of 

Scott Reservoir.

McCafferty and others (this volume) give an extensive 

discussion of the acid-neutralizing potential (ANP) of different 

lithologies in the Boulder River watershed. In summary, high 

ANP is associated with bedrock that has both high magnetic 

signature and low electrical conductivity. Conversely, low 

ANP is associated with rocks having low magnetization and 

high electrical conductivity. Desborough, Briggs, and Mazza 

(1998) and Desborough, Briggs, and others (1998) presented 

results of geochemical tests for ANP of soils and bedrock in 

the Boulder River watershed that were used by McCafferty 

and others (this volume) to develop an environmental geologic 

map of the study area.

Figures 3 and 4 show that the Luttrell repository (red dot 

in figures) is located in an area of moderate magnetic field 

and low apparent conductivity. Consequently, the area has low 

ANP based on the geophysical signature. This interpretation 

is supported by the observed high hydrothermal alteration of 

the Helena volcanics and the underlying Butte pluton. This

style of alteration would remove minerals that produce ANP 

(Desborough, Briggs. and Mazza, 1998).

Seismicity

Earthquakes have the potential both to compromise the 

integrity of mine-waste repositories and to cause release of the 

stored waste or leachate. Therefore, the seismicity of the area 

near the Luttrell pit is an important geotechnical parameter 

in site selection and repository design. The seismic characteristics of the area are particularly important because large 

earthquakes took place about 50 mi northwest of the Luttrell 

pit in 1925 (magnitude 6.6) and 1935 (magnitudes 6.25 and 

6.0; Stickney and others, 2000). The repository is located in 

a highly active tectonic belt. Information on regional seismicity was obtained from reports of damage from nearby 

earthquakes, earthquake data, and maps of Quaternary faults. 

Unfortunately, little information about modern seismic activity 

within the Boulder batholith or the study area is available.

Helena Earthquakes of 1935

Devastating earthquakes occurred in 1935 within 12 mi 

of Helena, Mont. A sequence of four earthquakes with magnitudes greater than 5.5 took place between October 12 and 

November 28. The main shock of magnitude 6.25 occurred 

October 18 (Neumann, 1937; Stickney and others, 2000). The 

Mercalli intensities in the Helena area ranged from VI to VIII; 

observed damage from VIII intensity earthquakes is described 

by Neumann (1937, p. 36) as:

"***slight in specially designed structures; considerable in ordinary substantial buildings, with partial 

collapse; great in poorly built structures. Panel walls 

thrown out of frame structures. Fall of chimneys, 

factory stacks, columns, monuments, walls. Heavy 

furniture overturned. Sand and mud ejected in small 

amounts. Changes in well water. Persons driving 

motorcars disturbed."

Most of the damage from the 1935 Helena earthquakes 

was from ground shaking and not ground breakage. Newspaper accounts of the earthquake damage (O'Brian and Nava, 

1998) indicate no reported damage in underground mines 

and little damage in areas underlain by the Boulder batholith 

during the Helena earthquakes. There were some reports of 

boulders falling in the mountainous areas (Schmidt, 1986).

The Luttrell pit is located approximately on the margin 

of the area of highest intensity activity on the isoseismal map 

constructed from data on the 1935 Helena earthquake (fig. 5). 

Because the isoseismal lines have been generalized, and based 

just on damage reports described, it is doubtful that the intensity of disturbance was as high as shown on the map in areas 

underlain by rocks of the Boulder batholith.
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486 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

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WASHINGTO

44

Figure 5. Isoseismal map from main shock of Helena earthquake of October 18,1935 (Neumann, 1937). Luttrell pit (solid circle) is 

located just on margin of highest magnitude disturbance.

Earthquake Data

A map depicting peak ground acceleration with a 

10 percent probability of being exceeded over a 50-year period 

for Montana is in figure 6. Peak ground acceleration is shown 

in various levels of percent gravity (% g), ranging from less 

than 2 to more than 30 percent. This map can be viewed as a 

generalized seismic hazard map, where the highest peak acceleration is associated with the highest earthquake hazard. For 

the entire United States, the highest peak ground acceleration, 

greater than 100 percent gravity, occurs along the San Andreas 

fault system in California. In the Rocky Mountain region, the 

arcuate north-south Intermountain seismic belt has a high seismic hazard; in local areas in the Yellowstone Park region, peak 

ground acceleration could exceed 30 percent gravity. In the 

area of the Luttrell repository, peak acceleration is expected to 

be between 10 and 15 percent gravity.

In a regional context, the Luttrell pit is located within the 

Intermountain seismic belt and north of its intersection with 

the Centennial tectonic belt. These two tectonic features are 

defined by local faulting and earthquake epicenter distribution (fig. 7). Stickney and Bingler (1981) suggested that the 

Centennial tectonic belt poses the greatest seismic hazard in 

the area. This is also an area of high acceleration probability, 

as shown in figure 6. The tectonic feature is far enough to the 

south of the Luttrell pit that it is not a consideration in the 

seismic risk assessment of the mine-waste repository site.

A more detailed local map of earthquake epicenters is 

shown in figure 8. The sedimentary and younger volcanic 

rocks surrounding the Boulder batholith are sites of most of 

the recent earthquake epicenters (Stickney, 1998; Stickney and 

others, 2000). In general, the regional stress patterns in southwest Montana produce northeasterly expansion (Freidline and 

others, 1976). Recent fault plane solutions (Stickney, 1998; 

fig. 8) are consistent with northeast expansion, but this
The Luttrell Pit as a Mine-Waste Repository 487

CANADA 

UNITED

Figure 6. Peak acceleration in percent of gravity (% g) that has a 10 percent probability of being exceeded in 50 years. Modified 

from Montana Bureau of Mines and Geology (2001 a) at URL http://mbmgquake.mtech.edu/seismicity_in_montana.html.

direction of expansion is difficult to extrapolate to the faulting 

in the Luttrell pit area, for the following reasons: The younger 

faults in the batholith are normal faults rather than strike-slip 

faults defined by the fault plane solutions in figure 8. In addition, the fault plane solutions may not represent earthquakes 

within the batholith. However, the northeast regional expansion may indicate that northwest-trending faults may be preferentially open and more likely to be ground-water flow paths 

in the bedrock. A few faults that have a northwest trend are 

located 3 mi northwest of the Luttrell pit (O'Neill and others, 

this volume, pi. 1).

No regional-scale Quaternary faults have been mapped 

near the Luttrell pit (O'Neill and others, this volume, pi. 1; 

Stickney and others, 2000). The northwest-to-southeast-trending Bald Butte fault zone (fig. 8) is about 15 mi northeast of 

the mine-waste respository area, as shown by a recent geologic 

compilation (Thamke, 2000). This fault zone is suspected 

to be the source of the 1935 earthquakes (Schmidt, 1986). 

The youngest interpreted ground breakage along the faults is 

Pleistocene (Stickney and Bingler, 1981). No record exists of 

seismically active faults near the Basin Creek mine. In addition, no ground breakage features that would indicate recent 

activity on faults were noted in our fieldwork in the immediate 

area of the pit.

Epicenter locations (fig. 8) for earthquakes in the Helena 

area from 1982 through 1996 (Stickney, 1998) show few 

epicenters that come within 2 mi of the Luttrell pit. Earthquakes in the area southeast of Helena (fig. 8) are as large 

as magnitude 5 (Stickney, 1998) and may be associated with 

exposed local Quaternary faults (Stickney and others, 2000;. 

The earthquakes may also be associated with the ButteHelena fault zone (O'Neill and others, this volume), a regional 

tectonic feature. Earthquake hypocenters are poorly known, in 

part because the distribution of seismic stations was not ideal, 

and epicenter localities are uncertain. Schmidt (1986) stated 

that the Helena earthquakes occurred at a depth of about 

10.5 mi, which is as deep as the Boulder batholith (O'Neill 

and others, this volume).

Interpreted Fracture Mapping from 

Remote Sensing Data

The statistical analysis of the orientation of interpreted 

linear features and their orientation presented here provides 

a general view of possible directions of preferential local 

ground-water flow in the bedrock aquifer by identifying
488 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

> '--- -^ 

Lewis & Ciarfr^

V- ^**

r ^ ^ 

^•0 MissQula

Centennial Tectonic

200 KILOMETERS

Figure 7. Epicenters from earthquakes in Rocky Mountain region defining the Intermountain seismic belt and the Centennial 

tectonic belt. Modified from Montana Bureau of Mines and Geology (2001 b) at URL http://mbmgquake.mtech.edu/interm_s_b.html.

principal azimuths and locations of possible fractures. McDougal and others (this volume) give a detailed analysis of linear 

features and their hydrologic interpretation for the Boulder 

River watershed. The discussion of fracture orientation here is 

similar, but focuses on a smaller area near the Luttrell pit.

To identify and map all fractures and faults from remotely 

sensed data is not possible because of ground resolution limitations, vegetation cover, and glacial or other surficial cover. In 

most cases, to determine if a linear feature marks the surface 

expression of a fault, fracture, joint, mineralized vein, or lithologic contact is also impossible. Mapped linear features used 

in this study provide a representation of the spatial distribution 

and orientation of bedrock fractures near the Luttrell pit minewaste repository. The interpretation is a statistical sample of 

naturally occurring linear features that could be related to 

surface expression of structures.

Linear Feature Analysis

The lineament azimuths, calculated from the geographic 

coordinates of the endpoints of each mapped vector, were used 

to generate rose diagrams for the Luttrell pit study area. Rose 

diagrams are polar histograms, which represent distribution of

the two-dimensional (horizontal plane) orientations of mapped 

linear features. The statistical parameters of total number of 

data points (TV), maximum percentage, mean percentage, standard deviation, vector mean (direction), R magnitude, standard 

error of the mean, and the Rayleigh probability distribution 

were calculated for each diagram (McDougal and others, this 

volume). The R magnitude is a measure of the strength of the 

vector mean. Data sets with a large dispersion about the mean 

have small values for R, and data sets that are tightly grouped 

around the mean have a large value for R. The Rayleigh test 

was used to calculate uniformity within the data set. In this 

case, the chosen significance level was 0.1 (90 percent confidence interval). If the calculated value is less than 0.1, then 

the conclusion can be made that the data are non-uniform and 

show a preferred orientation (McEachran, 1990).

The diagram representing the primary lineament orientation (fig. 9A) for the Luttrell pit study area shows a vector 

mean of 81.2°. The small confidence angle of 7.5 1 °, R magnitude of 0.564, and Rayleigh value of 0.00 indicate that the data 

have a moderate vector mean strength, and a strong preferred 

orientation. However, note in figure 9A that the distribution is 

strongly bimodal with peaks in the rose diagram at 85° 

and 105°.
The Luttrell Pit as a Mine-Waste Repository 489

112°45'

BOULDER BATHOLITH 

GENERAL OUTLINE

Figure 8. Earthquake epicenters and fault plane (nodal) solutions for the Helena area (Stickney, 1998). Fault plane solutions for 

selected earthquakes are shown as circles whose solid areas denote direction of compression. Larger and darker symbols for epicenters show greater magnitudes for earthquakes.

Secondary lineament orientation was plotted by filtering out the azimuths within the vector mean of the primary 

bimodal orientation described preceding. The resulting 

diagram (fig. 95) shows a possible secondary orientation with 

a vector mean of 39.6°. The larger confidence angle (31.32°) 

and Rayleigh value, and smaller R magnitude, indicate that the 

filtered data set is less preferentially oriented than the primary 

trend. A possible tertiary trend lies between approximately 

110° and 140°. The 39.6° trend correlates with the general 

trend of the apparent conductivity and magnetic geophysical 

anomalies (dashed line in figs. 3 and 4). The interpreted geologic structure in the area of Scott and Chessman Reservoirs 

(O'Neill and others, this volume, pi. 1) trends northeast 55°, 

which corresponds to the main secondary orientation in 

figure 9. These linear features, together are collinear with the 

northeast-trending fault zone described in the geologic section.

Hydrological Implications

Ground-water flow near the Luttrell pit likely is consistent with the regional ground-water flow model developed 

for the Boulder River watershed (McDougal and others, this 

volume). Hydrologic characteristics of the bedrock north of 

the Luttrell pit have been described by Thamke (2000). The 

highest hydraulic conductivity occurs in the upper unconsolidated deposits and shallow weathered bedrock, which together 

form an unconfined aquifer. Oligocene sediments deposited 

locally on the Butte pluton (O'Neill and others, this volume) 

constitute a relatively unknown (not mapped) aquifer. Hydraulic conductivity generally decreases dramatically with depth 

within the rhyolitic rocks of the Helena volcanic field because 

fractures are filled with clays produced during weathering of 

the volcanic rocks. In the Basin Creek mine area, the Helena 

volcanic rocks are the host to mineralization which has
490 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Boulder Basin - primary lineament orientation

N =205 

Class interval = 10 degrees 

Maximum percentage = 18.5 

Mean percentage = 5.56 Standard deviation = 5.46

Statistics

Vector mean = 81. 2 

Conf. angle = 7.51 

R magnitude = 0.564 

Rayleigh = 0.0000

Boulder Basin - secondary lineament orientation

A/- 71 

Class interval = 10 degrees 

Maximum percentage = 23.9 

Mean percentage = 7.69 Standard deviation = 6.19

Statistics

Vector mean = 39.6 

Conf. angle = 31.32 

R magnitude = 0.247 

Rayleigh = 0.0132

Figure 9. Rose diagrams and statistical analysis of lineament orientations in the Luttrell pit study area. A, primary lineament orientations; B, secondary lineament orientations.

accompanied intense alteration to clays; this clay alteration 

significantly reduced hydraulic conductivity. The clay has 

been used to construct a cap designed to reduce infiltration 

into the back-filled Paupers and Columbia pits (Dan Adams, 

Basin Creek Mine, Inc., oral commun., 1999).

In the underlying fractured granodioritic bedrock 

aquifer, hydraulic conductivity decreases because joints and 

fractures become increasingly tight with increasing depth. In 

areas of greater fracture density near fault zones, permeability 

may be somewhat higher. The direction of shallow groundwater flow is controlled by the hydraulic gradient, which 

likely mimics the topographic slope. Locally, topography 

slopes away from the Luttrell pit generally in all directions, 

and therefore, shallow ground water likely flows in all directions away from the pit. The direction of deeper ground-water 

flow also is a function of the hydraulic gradient, which may be 

controlled to some extent by fracture orientation. The regional 

and subregional fracture geometry observed in outcrops is 

generally heterogeneous and anisotropic, and the local groundwater flow regime near the Basin Creek mine is assumed to be 

associated with the orientation of these fractures. Recharge to 

the local ground-water system comes primarily from

approximately 30 in. mean annual precipitation (mainly as 

snowfall). Intense rainstorms in spring and summer can contribute sudden influxes of recharge.

The results of the lineament orientation analysis indicate 

that ground-water flow, assuming some control by fracture 

permeability, could have a preferred flow direction to the 

east-northeast or west-south west, depending on the hydraulic 

gradient. Secondary and tertiary preferred flow directions to 

the northeast (southwest) and east-southeast (west-northwest), 

respectively, also are indicated by the rose diagrams.

The wet soils map (fig. 10) shows an area of inferred 

shallow ground water to the southwest of the Basin Creek 

mine site. Note that detailed soil mapping is not available 

north of the Boulder River watershed. This zone of wet soils 

coincides with a relatively high density of mapped linear 

features that indicate possible fractures, which may function as 

conduits for ground-water flow. This area of possible shallow 

ground water lies along the northeast fracture zone discussed 

in the previous geologic and geophysical sections. Observed 

springs in the area could also be associated with a lithologic 

contact between the Helena volcanics and the underlying Butte 

pluton. Potentiometric surface maps based on monitoring well
The Luttrell Pit as a Mine-Waste Repository 491

112018'45

1 KILOMETER

Figure 10. Digital map showing wet soils (blue) in the study area (McDougal and others, this volume) draped over a digital elevation model (DEM) and combined with mapped lineaments (black lines; McDougal and others, this volume) for Luttrell pit study area. 

Red dot, Luttrell pit.

data in and around the Basin Creek mine indicate groundwater flow directions to the north-northwest, northeast, and 

southwest (Olympus Environmental Science and Engineering, 

Inc., 1996). The combination of the wet soils map and linear 

feature orientation suggests that some ground water could 

flow from the Luttrell pit area to the southwest, and suggests 

a possible location where subsurface ground water could be 

monitored.

A high density of linear features also occurs at the Continental Divide south of the Luttrell pit (McDougal and others, 

this volume). This part of the northeast-trending structural

zone could serve to recharge possible fracture-controlled 

ground water in the area of the mine-waste repository, as it is 

an area of high topography.

Figure 11 shows interpreted linear features and mapped 

structures superimposed on 7,200 Hz apparent electrical 

conductivity. The intersections of areas of high electrical 

conductivity and interpreted linear features mark possible 

areas of ground-water discharge or recharge. High electrical 

conductivity may be caused by wet soils and rocks, and linear 

features may indicate fractures that control ground-water 

storage or flow. Increased fracturing may indicate increased
492 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

112°20' 112°12'30" 11Z101

3 KILOMETERS

LOW

Figure 11. Color map of 7,200 Hz apparent conductivity superimposed with the linear features described 

in this study. Red dot, Luttrell pit.
The Luttrell Pit as a Mine-Waste Repository 493

interconnectedness and therefore increased permeability in 

the bedrock. The area of the Luttrell pit mine-waste repository 

does not show any of the features that would indicate local 

ground-water discharge or recharge.

Conclusions

Geologic studies indicate that faulting has occurred at 

least intermittently near the Luttrell pit from before the Oligocene through the Holocene. There is no evidence of recent 

rejuvenation of faults beneath the mine-waste repository, as 

drill information from premining development indicates that 

mineralized rocks are not offset by structures. An east-northeast-trending normal fault on the south of the Basin Creek 

mine has had a complex movement history from at least middle Tertiary through Holocene and may have localized bedrock 

fracturing. This structure is grouped with northeast-trending 

structures described in detail by Ruppel (1963). The northeast 

trend probably is a fault zone with a collinear trend with the 

Butte-Helena fault zone described by O'Neill and others (this 

volume) that controls the location of young intrusive rocks.

The airborne magnetic and electromagnetic survey provides information about variations in subsurface lithologies 

and structures. Many previously unknown structural trends 

are suggested from the geophysical data, but none actually 

intersect the pit area. A major northeast-trending linear feature 

defined by a narrow low magnetic and high conductivity 

signature starts about 0.25 mi southwest of the pit and trends 

northeast just south of Scott Reservoir. Another geophysical 

trend is associated with the east-northeast structure inferred 

from geologic mapping. Potential sites for fracture-controlled 

springs are indicated by the intersection of lineaments and 

high subsurface conductivity. None of these areas occur at the 

Luttrell pit. The airborne geophysical data interpretation in 

terms of environmental geology suggests that the mine-waste 

repository site is located in an area of low acid-neutralizing 

potential (McCafferty and others, this volume).

A high seismic hazard characterizes the region surrounding the Luttrell pit owing to (1) its location in the Intermountain seismic belt, (2) large historical earthquakes in the nearby 

Helena area, and (3) continuing earthquake activity in the 

Helena area and an area southeast of the mine-waste repository. Fault plane solutions for deep earthquakes suggest that 

northwest-southeast extension might cause northeast-trending 

fractures to be preferentially open. However, current stress 

patterns within shallow plutonic rocks and the younger volcanic rocks are a matter of speculation. Newspaper accounts 

(O'Brian and Nava, 1998) describing damage from the 1935 

Helena earthquakes did not indicate any impact on the mines 

that were actively operating in the Boulder batholith. Therefore, seismic hazard at the pit is considered low.

No major lineaments that trend through the Luttrell pit 

were identified from remote sensing images or airborne geophysical data. Analysis of linear feature orientations suggests 

that preferential paths of ground-water flow have a primary 

azimuth to the east-northeast or west-southwest. Possible 

secondary and tertiary preferential flow azimuths may be to 

the northeast (southwest) and east-southeast (west-northwest) 

respectively. Wet soils and lineament maps suggest a possible preferential ground-water flow southwest of the Luttrell 

pit that could be considered in design of monitoring activities around the repository. Coincidence of linear features and 

subsurface high electrical conductivity might indicate areas of 

ground-water recharge or discharge. No such areas occur at 

the Luttrell pit mine-waste repository.

References Cited

Becraft, G.E., Pinckney, D.M., and Rosenblum, Sam, 1963, 

Geology and mineral deposits of the Jefferson City quadrangle. Jefferson and Lewis and Clark Counties, Montana: U.S. 

Geological Survey Professional Paper 428, 101 p.

Chadwick, R.A., 1978, Geochronology of post-Eocene 

rhyolitic and basaltic volcanism in southwestern Montana: 

Isochron/West, v. 5, p. 25-28.

Desborough, G.A., and Driscoll, Rhonda, 1998, Mineralogical 

characteristics and acid-neutralizing potential of drill core 

samples from eight sites considered for metal-mine related 

waste repositories in northern Jefferson, Powell, and Lewis 

and Clark counties, Montana: U.S. Geological Survey 

Open-File Report 98-790, 6 p.

Desborough, G.A., Briggs, PH., and Mazza, Nilah, 1998, 

Chemical and mineralogical characteristics and acid-neutralizing potential of fresh and altered rocks and soils of the 

Boulder River headwaters in Basin and Cataract Creeks of 

northern Jefferson Co., Montana: U.S. Geological Survey 

Open-File Report 98^10, 21 p.

Desborough, G.A., Briggs, PH., Mazza, Nilah, and Driscoll, 

Rhonda, 1998, Acid-neutralizing potential of minerals in 

intrusive rocks of the Boulder batholith in northern Jefferson Co., Montana: U.S. Geological Survey Open-File 

Report 98-364, 21 p.

Fraser, D.C., 1978, Resistivity mapping with an airborne multicoil electromagnetic system: Geophysics, v. 43, 

p. 114-172.

Freidline, R.A., Smith, R.B., and Blackwell, D.D., 1976, Seismicity and contemporary tectonics of the Helena, Montana 

area: Bulletin of the Seismological Society of America, 

v. 66, p. 81-95.
494 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Lund, Karen, Aleinikoff, J.N., Kunk, M.J., Unruh, D.M., Zeihen, G.D., Hodges, W.C., du Bray, E.A., and O'Neill, J.M., 

2002, SHRIMP U-Pb and 40Ar/39Ar age constraints for 

relating plutonism and mineralization in the Boulder batholith region, Montana: Economic Geology, v. 97, p. 241-267.

McEachran, D.B., 1990, Rosy 2-D orientation analysis for the 

Macintosh, users manual: Rockware Earth Science Software, 19 p.

Montana Bureau of Mines and Geology, 2001a, Seismicity 

in Montana. Accessed December 3, 2001, at URL 

http://mbmgquake.mtech.edu/seismicity _in_montana.html.

Montana Bureau of Mines and Geology, 200 Ib, Intermountain 

Seismicity Belt. Accessed December 3, 2001, at URL 

http://mbmgquake.mtech.edu/interm_s_b.html.

Neumann, Frank, 1937, United States earthquakes, 1935: 

U.S. Department of Commerce, Coast and Geodetic Survey, 

90 p.

O'Brian, E.H., and Nava, S.J., 1998, Personalizing the earthquake threat in the Intermountain Region, Technical Report 

to the U.S. Geological Survey for grant 1434-95-G-266, 

78 p.

Olhoeft, G.R., 1985, Low-frequency electrical properties: 

Geophysics, v. 50, no. 12, p. 2492-2503.

Olympus Environmental Science and Engineering Inc., 1996, 

Basin repository evaluation report for the Basin Creek mine, 

Jefferson and Lewis & Clark Counties, Montana: Report 

prepared for Abandoned Mine Reclamation Bureau, 

Montana Department of Environmental Quality, 33 p.

Ruppel, E.T., 1963, Geology of the Basin quadrangle, Jefferson, Lewis and Clark, and Powell Counties, Montana: U.S. 

Geological Survey Bulletin 1151, 121 p.

Schmidt, R.G., 1986, Geology, earthquake hazards, and land 

use in the Helena area, Montana—A review: U.S. Geological Survey Professional Paper 1316, 64 p.

Smith, B.D., Labson, V., and Hill, P., 2000, Airborne geophysical survey in the Boulder watershed, Jefferson and Lewis 

and Clark counties, Montana: U.S. Geological Survey 

Open-File Report 00-240.

Smith, B.D., McCafferty, A.E., and McDougal, R.R., 2000, 

Utilization of airborne magnetic, electromagnetic, and 

radiometric data in abandoned mine land investigations, 

in ICARD 2000; Proceedings of the Fifth International 

Conference on Acid Rock Drainage, Volume 2: Society for 

Mining, Metallurgy, and Exploration, Inc., p. 1525-1530.

Spies, B.R., 1989, Depth of investigation in electromagnetic 

sounding methods: Geophysics, v. 54, p. 872-888.

Stickney, M.C., 1998, Seismic source zones in Southwest 

Montana: U.S. Geological Survey grant number 

1434-95-G-2628, unpublished report, U.S. Geological 

Survey library, Denver, Colo., 32 p.

Stickney, M.C., and Bartholomew, M.J., 1987a, Seismicity and 

late Quaternary faulting of the northern Basin and Range 

Province, Montana and Idaho: Bulletin of the Seismological 

Society of America, v. 77, p. 1602-1625.

Stickney, M.C., and Bartholomew, M.J., 1987b, Preliminary 

map of late Quaternary faults in Western Montana: Montana 

Bureau of Mines and Geology Open-File Report 186, 

scale 1:500,000.

Stickney, M.C., and Bingler, E.G., 1981, Earthquake hazard 

evaluation of the Helena Valley area, Montana: Montana 

Bureau of Mines and Geology Report MBMG-83, 52 p.

Stickney, M.C., Haller, M.K., and Machette, M.N., 2000, Quaternary faults and seismicity in western Montana: Montana 

Bureau of Mines and Geology Special Publication 114, 

scale 1:500,000.

Thamke, J.N., 2000, Hydrology of the Helena area bedrock, 

west-central Montana, 1993-1998, with a section on 

Geologic setting and a generalized bedrock geologic 

map, by M.W. Reynolds: U.S. Geological Survey WaterResources Investigations Report 00-4212, 119 p.
Evaluating the Success of Remediation in the 

Boulder River Watershed

By Susan E. Finger, Stanley E. Church, and David A. Nimick

Chapter F of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-F

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract................................................................^

Introduction ...............................................................................................................................................497

Purpose and Scope.........................................................................................................................498

Monitoring Strategies.............................................................................................................................. 498

Monitoring Tools.............................................................................................................................. 499

Factors Influencing Restoration Success............................................................................................ 499

Monitoring in the Boulder River Watershed ........................................................................................ 501

Summary.................................................................................................................................................... 501

References Cited...................................................................................................................................... 501

Tables

1. Examples of biological components and corresponding parameters that

may be measured to evaluate progress of ecological recovery..................................... 500
Chapter F

Evaluating the Success of Remediation in the

Boulder River Watershed

By Susan E. Finger, Stanley E. Church, and David A. Nimick

Abstract

Historical mining has resulted in contamination of land, 

water, and biological resources in many areas of the Boulder 

River watershed. Other chapters in this volume have characterized the extent and severity of this contamination and have 

presented an ecological risk-based synthesis concluding that 

areas downstream from the Comet, Crystal, and Bullion mines 

were among the most contaminated in the watershed. Federal 

and State land managers have targeted these sites, among others in the watershed, for remediation. Monitoring can provide 

a means to determine the success of remedial activities and the 

rate or extent of recovery of the ecosystem. Monitoring tools 

should include measures of physical, chemical, and biological 

conditions similar to measurements used in the pre-remediation watershed assessment. Factors including the geology, 

water quality, and presence of a biological community for 

recolonization will determine the rate of success of ecological restoration. In addition to the reduction of trace-element 

concentrations in water and streambed sediment, restoration of 

a healthy riparian corridor is essential to ecological recovery 

of the aquatic environment. The importance of monitoring in 

documenting the success of remediation is often overlooked 

because of funding limitations. However, a well-designed and 

carefully implemented monitoring program is an extremely 

valuable means not only to evaluate the success of an 

ongoing project, but also to document ways to improve success in future restoration activities.

Introduction

Historical mining has resulted in contamination of land, 

water, and biological resources in many areas of the Boulder 

River watershed. Other chapters in this volume have characterized the extent and severity of this contamination (Nimick and 

Cleasby, this volume, Chapter D5; Church, Unruh, and others, 

this volume, Chapter D8) and have presented an ecological

risk-based synthesis concluding that areas downstream from 

the Comet, Crystal, and Bullion mines were among the most 

contaminated in the watershed (Finger, Farag, and others, 

this volume, Chapter C). Pre-remediation assessment studies 

demonstrated that fish were absent from many of these stream 

reaches, and where fish populations did exist, their health had 

been compromised (Farag and others, this volume, Chapter 

DIG). The potential for biological recovery in this aquatic 

environment is dependent on successful remediation of historical mine wastes and mine drainage in affected areas in the 

Boulder River watershed.

Mine and mill site remediation has been initiated at 

several locations throughout the Boulder River watershed 

(this volume, Chapter A). In 1997, remediation efforts began 

at the Comet mine in High Ore Creek. The Montana Department of Environmental Quality removed about 500,000 yd3 of 

mill tailings from a breached tailings repository in the High 

Ore Creek valley (Gelinas and Tupling, this volume, Chapter 

E2). In 1999, the Bureau of Land Management began removal 

and in-place treatment of tailings deposits on the High Ore 

Creek flood plain. The USDA Forest Service also initiated 

remediation efforts at the Buckeye and Enterprise mine site 

in 2000 and at the Bullion mine in 2002. The USEPA began 

remediation activities in the Basin Creek and Cataract Creek 

basins after these areas were added to the National Priority 

List (Superfund) in 1999. Mining wastes were removed from 

the town of Basin, and in 2002, remediation was started at the 

Crystal mine. However, as of 2003, no work has been initiated 

to reduce or eliminate acidic drainage coming from mine adits 

such as those at the Crystal, Bullion, or Enterprise mines.

The terms remediation and restoration are closely linked, 

but they refer to distinct phases in the process of ecological 

recovery. Remediation is the cleanup of a contaminated area. 

Remedial actions remove or isolate contaminants from the 

environment. These actions are critical to promoting the recovery of both the terrestrial and aquatic ecosystems. Remediation 

at mine sites can involve the in-place treatment or physical 

removal of mine waste and mill tailings from a stream, its 

associated flood plain, and the terrestrial landscape.
498 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Remediation at these sites can also involve actions that reduce 

or eliminate metal and acid loading from draining mines. 

Actual cleanup activities may cause adverse effects on the 

environment that must be addressed early in the planning 

phases of a project, because some remedial options may preclude achievement of restoration goals. Successful remedial 

actions result from risk-management decisions that are based 

on cost-benefit analyses that evaluate the potential outcomes 

of various alternatives ranging from a simple "no action" 

alternative to more costly and complicated alternatives such 

as complete removal of contaminated material. Performance 

measures for successful remediation might include (1) major 

sources of contamination in the watershed have been reduced 

or eliminated, (2) trace-element concentrations in water no 

longer exceed acute or chronic criteria for aquatic life, 

(3) trace-element concentrations in streambed sediment no 

longer exceed sediment-quality guidelines, (4) stream banks 

have been stabilized and erosion has been minimized, and 

(or) (5) flood-plain revegetation has reduced or eliminated the 

transport of contaminated sediment, mine waste, or mill tailings downstream.

Completion of this remediation or cleanup process marks 

the beginning of the restoration phase of ecosystem recovery. 

Restoration is the process of returning an ecosystem to a close 

approximation of its historical condition prior to a physical 

or chemical disturbance (National Research Council, 1992). 

Although an injured ecosystem may never return to conditions identical to those that existed prior to mining, it may 

be restored to conditions that are functionally equivalent to 

those of the previous environment. The underlying goal of 

restoration is ecological recovery. This goal must be ecologically realistic and based on the geologic, hydrologic, and 

biologic characteristics of the watershed. Achievement of this 

goal is contingent on restoration of the ecosystem's structure 

and function both locally and within a broader landscape or 

watershed context. Therefore, in an area affected by historical mining, an understanding of premining conditions in 

the watershed is required (Church, Unruh, and others, this 

volume). Although successful remediation actions, such as 

physical removal of mine waste and mill tailings or reduction 

in acidic mine drainage, may be part of the restoration process, 

these remedial steps do not necessarily ensure that ecological 

recovery will occur. Restoration may require such things as 

creation of viable fisheries habitat, restocking a stream with 

fish, reintroduction of terrestrial species, or revegetation of the 

flood plain to compensate for ecological losses. Performance 

measures for successful restoration might include (1) selfsustaining populations of fish throughout the watershed,

(2) successfully reproducing colonies of nesting birds, and (or)

(3) a healthy riparian corridor.

Monitoring is an important but often undervalued and 

underutilized tool for determining the success of remedial 

efforts and assessing ecological recovery. Adequate and 

appropriate monitoring procedures are the most direct measure 

of the success of remedial strategies and the resulting rates 

of recovery for populations, communities, or ecosystems.

However, monitoring rarely receives the attention necessary to 

develop and implement a successful plan. Following remediation of a site, funding limitations often reduce the frequency 

of monitoring or eliminate it completely. Kondolf and Micheli 

(1995) indicated that despite increased commitment to stream 

restoration, postrestoration monitoring has generally been 

neglected as well. Monitoring plans need not be exhaustive or 

complex. Rather, they need to be designed to address specific 

questions and applied in a consistent manner.

Purpose and Scope

The purpose and scope of this chapter are to identify 

factors that influence ecological recovery and discuss the 

appropriate procedures and tools for monitoring the success of 

remediation and restoration in the Boulder River watershed. 

We describe different types of monitoring, the questions each 

type is intended to address, and the endpoints that should be 

considered as a part of their design. Information from this 

chapter should have broad applicability to other watersheds 

impaired by historical mining.

Monitoring Strategies

Monitoring is an important tool for evaluating the success 

of remediation and restoration efforts and assessing the 

overall status of ecological recovery. Without collecting and 

analyzing comprehensive monitoring data, land managers cannot objectively evaluate the success of a remedial or restoration action or determine whether remediation and restoration 

goals have been met. As a tool, monitoring provides information for four basic purposes:

• Performance evaluation—This strategy is used to 

evaluate project implementation and ecological 

effectiveness.

• Trend assessment—This strategy includes an extended 

sampling plan to identify changes across spatial and 

temporal scales.

• Risk assessment—This strategy is used to identify 

hazard sources, causal relationships, and resource 

injury within an ecosystem.

• Baseline characterization—This strategy is used to 

quantify ecological conditions prior to an actual disturbance. It may also be used to collect information at a 

reference site to determine premining baseline conditions for a comparable disturbed habitat.

The type and extent of necessary monitoring will depend 

on specific management objectives (Kondolf, 1995). In the 

case of a historical mining area, the strategy most appropriate for evaluating the success of remediation and restoration 

would be performance evaluation. The three components of
Evaluating the Success of Remediation 499

performance evaluation include (1) implementation monitoring, (2) effectiveness monitoring, and (3) validation monitoring. Implementation monitoring addresses the question: "Were 

the remediation and restoration measures properly executed?" 

Exploring this question may yield valuable information that 

will help with potential refinement of remediation or restoration practices. Effectiveness monitoring addresses the question: "Did remediation and restoration measures achieve 

the desired results?" Monitoring variables should focus on 

indicators that document achievement of desired conditions. 

Variables should be sensitive enough to detect change, should 

be both detectable and measurable, and should have statistical 

validity. This level of monitoring is more time consuming than 

implementation monitoring. However, if effectivenessmonitoring data indicate that restoration goals are not being 

met, problems can be evaluated in a timely manner, and 

ecologically beneficial adjustments can be made to the 

remediation and restoration designs. The most costly level of 

monitoring is validation monitoring. This addresses the question: "Are the underlying assumptions used in the remediation 

and restoration designs and the cause-effect relationships correct?" This level of monitoring is usually performed when the 

desired results of the remediation or restoration actions are not 

occurring and when further corrective action has not achieved 

the desired results. This level of monitoring requires scientific 

expertise to design and implement.

Monitoring Tools

Monitoring involves measurement of chemical, physical, 

and biological parameters to evaluate the magnitude of change 

that occurs following remedial and restoration activities and to 

estimate the rate of recovery of an ecosystem. A comprehensive list of all potential variables available for use in a monitoring program would be overwhelming. Therefore, we present 

a refined list of the types of monitoring variables applicable to 

an ecosystem affected by historical mining activities. An ideal 

monitoring program would include a combination of these 

chemical, physical, and biological variables.

Biological communities provide an integrated response 

to the chemical and physical attributes of their environment. 

Understanding the response of the biological community to 

remediation and restoration activities is the most important 

outcome of monitoring. Important physical and chemical 

variables that may significantly affect the quality of aquatic 

habitat include temperature, turbidity, dissolved oxygen, pH, 

alkalinity/acidity, hardness, nutrients, flow, channel characteristics, spawning gravel/interstitial space, pool/riffle ratio, 

shade, in-stream cover, bed material load, dissolved constituents, and suspended solids. For a remediated historical mining 

area, chemical variables would include measures of traceelement concentrations in water, in streambed sediment, and in 

biota deemed problematic during the assessment phase of the 

project. For the chemical analysis of water, measurement of 

the fraction (total recoverable or dissolved) that relates

specifically to national or State water-quality criteria or that 

may be linked to bioavailability is most valuable in determining potential habitat improvement.

Ultimately, the goal of mine and mill site remediation 

is to restore a healthy self-sustaining ecosystem. This success can be documented through measurement of biological 

endpoints (table 1). Selection of biological measurements is 

generally determined by the species at risk. For example, in 

the Boulder River watershed, land managers are interested in 

establishing a healthy ecosystem that would support a successful trout fishery. In this case, measures of successful ecological restoration could include assessment of fish population 

densities, survival and health of individual fish (Karr, 1981; 

Farag and others, this volume), trace-element concentrations in 

biofilm and invertebrates, and indices of health of the aquatic 

invertebrate community (Klemm and others, 1990; Pflakin and 

others, 1989). If the species of interest were fish-eating birds 

such as kingfishers or eagles, focus should be on the traceelement concentrations in the tissues of fish and on the reproductive health of the birds of interest.

Factors Influencing Restoration 

Success

Successful ecological restoration of a stream or river that 

has been adversely affected by mining is dependent on the 

suitability of both the physical and chemical conditions in the 

aquatic environment. The basic geologic character of a mining 

area strongly influences the water quality and the biological 

community that can exist in an ecosystem. Therefore, knowledge of the geology of a region is critical to defining achievable restoration goals. Not only do the streambed sediment, 

mine waste, and mill tailings represent sources and sinks for 

contamination in the watershed (Church, Unruh, and others, this volume) prior to remediation, but also the nature of 

the mineral content, buffering capacity, acidity, and organic 

richness of rocks in the watershed all influence the ability of 

an ecosystem to recover following remediation. In addition 

to toxicological issues associated with sediment contamination, excessive sedimentation in the streambed can physically 

limit suitable habitat for survival and reproduction of benthic 

invertebrates and fish. If remediation addresses removal of 

contaminated sediment from the stream and flood plain, repair 

of the stream channel, and stabilization of the stream banks 

and flood plain, then underlying geologic characteristics of 

the region, such as the acid-neutralization capacity of the 

rocks in the Boulder River watershed (McCafferty and others, 

this volume, Chapter D2; McDougal and others, this volume, 

Chapter D9), or the particle size distribution of sediment in the 

streambed, will determine the potential for recovery of habitat 

that will support a healthy aquatic community and lead to the 

reestablishment of a healthy riparian corridor.

In an aquatic system, both the quality and the quantity 

of water also influence the ability of a system to recover. The
500 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 1. Examples of biological components and corresponding parameters that may be measured to evaluate 

progress of ecological recovery.

Biological component Parameter

Primary productivity

Aquatic invertebrate community

Fish community

Riparian wildlife/terrestrial community

Riparian vegetation

Periphyton or biofilm density

Aquatic macrophytes species and density

Concentration of trace elements

Species composition

Numbers of individuals

Diversity

Biomass

Concentration of trace elements

Species composition

Age class distribution

Fish health assessment

Population density

Concentration of trace elements

In-stream exposure experiments

Amphibian/reptile species composition

Amphibian/reptile population density

Mammal species composition

Mammal population density

Mammal health assessment

Passerine bird species composition

Passerine bird population density

Passerine bird reproductive health

Fish-eating bird species composition

Fish-eating bird health and population density

Species composition

Condition

Successional changes

Soil toxicity assessment __________

water serves as a primary pathway of contaminant exposure 

for the biological community as well as a means to transport 

contamination downstream through the watershed. Remediation of targeted mine sites should result in reduction of potential contaminant load in watershed streams. During the initial 

assessment of the Boulder River watershed, many aspects of 

water and sediment chemistry, geology, hydrology, biology, 

and ecology were characterized. Although it was important to 

determine the status of the biological community in the watershed during this assessment phase, chemical variables such as 

trace-element concentrations in water and sediment were used 

to calculate hazard quotients for identifying areas of concern 

(Finger, Farag, and others, this volume). These quotients were 

useful in focusing attention on general stream reaches to target 

for remediation. For aquatic environments impacted by historical mining, significant scientific literature linking biological 

exposure and effects exists, thus making the ecological risk 

assessment approach useful for anticipating adverse effects 

on the biological community. Actual measures of fish health,

population status, and toxicological assessment of larval fish 

survival (Farag and others, this volume) provided confirmation 

of effects predicted from physical measures. Overall, the measurement of physical variables during the assessment phase 

was extremely important for determining sources and extent of 

contamination in the watershed and for assessing the severity 

of contamination at specific sites.

If the remedial activities in any watershed are adequate, 

the effects of sources of contamination will be eliminated 

or greatly reduced. The potential for successful ecological 

restoration will then be greatest where healthy biological 

communities (1) exist in the watershed outside the zone of 

contamination and (2) are capable of recolonizing previously 

impaired stream reaches. This is the case in the Boulder River 

watershed where fish and invertebrates inhabit many stream 

reaches within the watershed (Finger, Farag, and others, this 

volume, fig. 1). Potentially, reestablishment of the native 

trout species is even possible because a reproductively viable 

population of westslope cutthroat currently exists in High Ore
Evaluating the Success of Remediation 501

Creek upstream from the Comet mine. Successful remediation 

and restoration of stream reaches affected by the Comet mine 

could lead to successful ecological recovery of this species 

by providing habitat where these native trout can survive and 

reproduce. However, some type of physical barrier would be 

necessary in High Ore Creek to prevent the migration and 

resultant competition of more aggressive brook and rainbow 

trout from the Boulder River.

tailings can be accomplished through use of both geochemical 

characterization and soil toxicity assessments. Such monitoring can determine the potential for successful revegetation of 

an area. In addition, monitoring the health and recovery of 

wildlife communities dependent on this terrestrial habitat can 

provide valuable information on ecological recovery. Only 

through a well-designed and rigorously implemented monitoring program can the success of a remedial effort be validated.

Monitoring in the Boulder River 

Watershed

In the Boulder River watershed, the primary focus of the 

watershed approach has been on the identification of factors 

affecting the health and potential for recovery of the aquatic 

community and its supporting habitat. Ongoing monitoring 

of High Ore Creek has shown that remediation has substantially reduced dissolved zinc concentrations, but that dissolved 

arsenic concentrations have increased slightly (Gelinas and 

Tupling, this volume). Continued improvements in water quality and reduced sediment loading should result in improved 

survival, growth, and reproduction in the aquatic community.

The selection of appropriate monitoring endpoints for use 

in the Boulder River watershed can be determined based on 

the watershed assessment. The same variables used to document impairment to the watershed can provide a measure of 

ecological recovery following remediation. These variables 

would include, at a minimum, concentrations of arsenic, 

cadmium, copper, lead, and zinc in water samples collected 

over a range of flow conditions, trace-element concentrations 

in streambed sediment and biofilm collected at low flow, 

in-stream exposures with larval fish, fish population assessment, and measures of fish health. Monitoring sites should 

correspond to those used in the watershed study with the 

possible addition of sites in areas of anticipated recovery. This 

approach would support the establishment of monitoring sites 

downstream of the Bullion mine on Bullion Mine tributary 

and on Jack Creek, downstream of the Crystal mine on Uncle 

Sam Gulch, on Cataract Creek upstream and downstream of 

the confluence with Uncle Sam Gulch, downstream of Comet 

mine on High Ore Creek, and at several locations on the Boulder River.

Future monitoring that incorporates biological and chemical measurements will be able to demonstrate the degree of 

success of remediation projects in the watershed. However, the 

success of any ecological recovery will be determined not only 

by the degree of improvement achieved in the aquatic environment, but also by the recovery of associated flood-plain and 

riparian habitat within the watershed. Although not specifically addressed in this volume, the issues of revegetation of 

the riparian area and stabilization of the flood plain are important to land managers in the overall environmental restoration 

of an area (Kondolf, 1995). Monitoring the improvement of 

flood-plain and riparian soils after the physical removal of

Summary

Monitoring includes measures of chemical, physical, 

and biological parameters to evaluate the magnitude of change 

that occurs following remedial activities and to estimate the 

rate of recovery of an ecosystem. Historical mining activities 

have resulted in the degradation of fisheries and their supporting habitat in the Boulder River watershed. As a result of 

remediation in the watershed, improvements in water quality 

and reduced trace-element concentrations in streambed sediment should result in ecological recovery, improved physical 

habitat, and greater survival, growth, and reproduction rates in 

the aquatic community. The presence of trout in some stream 

reaches in the Boulder River watershed provides a local source 

of fish to repopulate areas where no fish were present prior to 

remediation.

The selection of appropriate monitoring endpoints to 

evaluate recovery in the Boulder River watershed can be 

determined based on the physical, chemical, and biological 

measurements used during the pre-remediation watershed 

assessment. This would include, at a minimum, measures of 

cadmium, copper, lead, zinc, and arsenic in water samples 

collected at high and low flows, measures of bed sediment 

concentrations at low flow, and chemical analysis of biofilm 

at low flow, in-stream exposures with larval fish, fish population assessment, and measures of fish health. Monitoring sites 

should correspond to those used in the watershed study with 

the possible addition of sites in areas of anticipated recovery.

References Cited

Karr, J.R., 1981, Assessment of biotic integrity using fish 

communities: Fisheries, v. 6, p. 21-27.

Klemm, D.J., Lewis, P.A., Fulk, F, and Lazorchak, J.M., 

1990, Macroinvertebrate field and laboratory methods for 

evaluating the biological integrity of surface waters, 

EPA/600/4-90-030: U.S. Environmental Monitoring 

Systems Laboratory, Cincinnati, Ohio.

Kondolf, G.M., 1995, Five elements for effective evaluation of 

stream restoration: Restoration Ecology, v. 3, p. 133-136.
502 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Kondolf, G.M., and Micheli, E.R., 1995, Evaluating stream 

restoration projects: Environmental Management, v. 19, 

p. 1-15.

National Research Council, 1992, Restoration of aquatic 

ecosystems—Science, technology, and public policy: 

Washington, D.C., National Academy Press, 552 p.

Plafkin, J.L., Barbour, M.T., Porter, K.D., Gross, S.K., and 

Hughes, R.M., 1989, Rapid bioassessment protocols for use 

in streams and rivers, EPA444/4-89-001: U.S. Environmental Protection Agency, Washington, D.C.
Digital Databases and CD-ROM for the 

Boulder River Watershed

By Carl L Rich, David W. Litke, Matthew Granitto, Richard T. Pelltier, and 

Tracy C. Sole

Chapter Got

Integrated Investigations of Environmental Effects of Historical 

Mining in the Basin and Boulder Mining Districts, Boulder River 

Watershed, Jefferson County, Montana

Edited by David A. Nimick, Stanley E. Church, and Susan E. Finger

Professional Paper 1652-G

U.S. Department of the Interior 

U.S. Geological Survey
Contents

Abstract...................................................................................................................................................... 505

Introduction............................................................................................................................................... 505

Purpose and Scope......................................................................................................................... 505

Acknowledgments........................................................................................................................... 507

Base Cartographic Data.......................................................................................................................... 507

SiteData.........................................................................................................................................^

Sample-Site Data............................................................................................................................. 510

Mine-Related Site Data .................................................................................................................. 512

Geoscientific Data....................................................................................................................................513

Geologic Data................................................................................................................................... 513

Geochemical Data for Streambed Sediment and Water........................................................... 513

Biological Data................................................................................................................................. 514

Geophysical Data............................................................................................................................. 514

Remote Sensing Data...................................................................................................................... 514

Relational Database................................................................................................................................. 515

Contents of Database...................................................................................................................... 515

Database Structure.........................................................................................................................515

Data Viewer Software..............................................................................................................................520

Boulder River Watershed CD-ROM....................................................................................................... 521

References Cited...................................................................................................................................... 522

Figures

1-3. Maps showing:

1. Geographic extent of database for Boulder River watershed study....................... 506

2. Selected data within the eight-quadrangle area from the Boulder River

watershed CIS database................................................................................................. 508

3. Distribution of Boulder River watershed study sample sites.................................... 511

4. Diagram of primary tables in the relational database and the relationships

between tables.........................................................................................................................519

5. Graphical view of the qseIZnSynopticData query.............................................................. 519

6. Tabular reformatted results of the qseIZnSynopticData query........................................ 520

7. Directory tree structure for the Boulder River watershed CD-ROM............................... 521

Tables

1. Base cartographic data coverages in the Boulder River watershed GIS database.... 509

2. Elevation and elevation-derived grids in the Boulder River watershed GIS

database.................................................................................................................................... 510

3. File names for site data in various formats......................................................................... 512

4. Geologic maps and geochemical, biological, geophysical, and remote sensing

data in the Boulder River watershed GIS database.......................................................... 516

5. Data sources for sample-site data in the Boulder River watershed relational

database.................................................................................................................................... 518
Chapter G

Digital Databases and CD-ROM for the

Boulder River Watershed

By Carl L Rich, David W. Litke, Matthew Granitto, Richard I Pelltier, and Tracy C. Sole

Abstract

A large amount of digital data was produced as part of 

the Boulder River watershed study. Included are biologic, 

hydrologic, geochemical, geologic, and base cartographic 

data. Most were collected in the Basin Creek, Cataract Creek, 

and High Ore Creek subbasins of the Boulder River watershed, and in the portion of the Boulder River into which these 

creeks flow. A lesser amount was collected throughout the 

remainder of the Boulder River watershed. The data were 

converted to a common projection. Hydrography and road 

features, sample-site locations, and inactive mine and minerelated site locations were revised using digital orthophoto 

quadrangle (DOQ) imagery. The data are available, in formats 

compatible with widely used commercial software, on a 

CD-ROM that accompanies this volume. The data and the 

CD-ROM are described in this chapter.

Introduction

Digital datasets were an integral component of work 

conducted by U.S. Geological Survey scientists to understand 

issues related to inactive mines in the Boulder River watershed 

in southwest Montana. A large amount of information was 

produced as part of this multidisciplinary study. Analyses of 

the digital data layers have produced many results that are 

described and illustrated in the numerous maps and images 

that are provided in other chapters of this volume.

Data were obtained as part of various topical studies of 

the Boulder River watershed. During these studies, samples 

of many media, including rocks, soils, water, and aquatic life, 

were collected and analyzed. Other data sources used in this 

investigation included previous USGS regional studies, and 

the work of other Federal and State agencies. The different 

types of information were gathered from several different 

platforms including helicopters, fixed-wing aircraft, satellites, 

and ground fieldwork.

To make this information useful to others, the various 

datasets have been converted to a common map projection, 

and to formats compatible with widely used commercial software. The localities of the sample-site data were revised using 

digital orthophoto quadrangle (DOQ) image files. The data 

are organized in descriptive tables presented in this chapter, 

and in a digital relational database and a geographic information system (GIS) database on a CD-ROM that accompanies 

this volume. In addition, the CD-ROM provides data viewing 

software for elementary spatial comparisons and analysis of 

the various layers.

Purpose and Scope

The purpose of this chapter is to provide a comprehensive review of the digital data that were generated as part of 

the Boulder River watershed study, and which are placed on 

the CD-ROM that accompanies this volume. Included are a 

relational database, a GIS database, map, image, and graphic 

products created during the study, and two data viewers that 

allow visual spatial comparisons and analysis of the data. The 

relational database contains biologic, hydrologic, geochemical, and geologic sample-site data collected and produced 

for the Boulder River watershed study, and an inventory and 

description of mine-related sites located and compiled for 

the study. The GIS database contains the same sample-site 

data and mine-related site information stored as data layers 

and associated tables, as well as base cartographic, geologic, 

hydrologic, geochemical, and geophysical data in vector and 

raster formats.

The base cartographic data cover the Basin, Bison Mountain, Chessman Reservoir, Jefferson City, Mount Thompson, 

Three Brothers, Thunderbolt Creek, and Wickes 7.5-minute 

quadrangles at a level of detail similar to U.S. Geological 

Survey l:24,000-scale topographic maps. Geologic, 

geochemical, and geophysical data (collectively referred to in 

this chapter as "Geoscientific Data") also exist within these 

same eight quadrangles. The sample sites and mine-related
506 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

sites are located primarily within the Basin Creek, Cataract 

Creek, and High Ore Creek watersheds, and along the approximately 9-mile reach of the Boulder River that extends from 

just upstream to just downstream of these tributaries. There 

are also less detailed base data, and some sample-site data, 

throughout the remainder of the entire Boulder River watershed.

The Boulder River watershed GIS database contains data 

for various layers and scales over areas of varying extent, 

including the Boulder River watershed study area as previously defined in Church, Nimick, and others (this volume, 

Chapter B), an eight-quadrangle area which includes the 

"Boulder River watershed study area," and the Boulder River 

watershed in its entirety. Figure 1 shows the area of the

112°00'

EXPLANATION 

Boulder River and tributaries 

Boulder River watershed 

Targeted drainages in the 

Boulder River watershed

Eight-quadrangle area

MONTANA

W) Boulder River watershed

6 KILOMETERS

Figure 1. Geographic extent of database for Boulder River watershed study.
Digital Databases for the Boulder River Watershed 507

targeted drainages of the northern part of the Boulder River 

watershed.

The data are available on the CD-ROM in formats from 

the software used to create them, and in several other formats 

including ASCII textfiles. ESRI shapefiles, .dbf files, and 

TIFF image files. The x,y coordinates of the Arclnfo coverages, ESRI shapefiles, and TIFF image files are in UTM 

(Universal Transverse Mercator) meters, zone 12. and are cast 

on the North American Datum of 1927 (NAD27). The FieldSites table in the relational (Access) database also contains 

the longitude and latitude values of the field site locations in 

decimal degrees, also in NAD27.

The main body of this chapter begins with a synopsis of 

the various data layers organized under three broad themes, 

including (1) base cartographic data, (2) sample-site data 

and mine-related site data, and (3) data layers pertaining to 

geologic, geochemical, biologic, geophysical, and remote 

sensing information. (This third group of data layers is collectively referred to in this chapter as "Geoscientific Data.") 

A brief description of the utility of the data is given followed 

by a descriptive table that includes relevant information about 

individual data files. This synopsis of the data is followed by 

an explanation of the relational database. The report concludes 

with a description of the data viewer software that is provided 

on the CD-ROM and an explanation of the content and format 

of the CD-ROM itself.

Acknowledgments

The authors acknowledge the assistance of Paul Martin, 

Rick Poss, Stewart Wright, John Erickson, Steve Howard, 

Earl Wilson, and Eric Wong in the creation of the base cartographic data for the Boulder River watershed CIS database.

Base Cartographic Data

In general, the base cartographic data were initially collected from the eight 7.5-minute U.S. Geological Survey topographic maps mentioned previously, and then revised where 

possible using 1993 and 1998 digital orthophoto quadrangles 

(DOQ's). DOQ's were not available for the Wickes and 

Jefferson City quadrangles; however, the Boulder River watershed study area is entirely contained within the remaining 

six quadrangles. When available, U.S. Geological Survey 

Digital Line Graph (DLG) files were used as the initial source, 

but where necessary, data were scanned or digitized from 

stable-base separates of the appropriate 7.5-minute topographic map. These topographic maps were all 1985 Provisional Editions. During the 5-year period of this study, newly 

revised (1996) versions of the Thunderbolt Creek, Basin, 

Mount Thompson, and Wickes quadrangles were released to 

the public. A visual inspection of these maps was performed, 

and information in the CIS database was updated where 

appropriate.

Base cartographic layers created as just described include 

hydrography, roads and trails, miscellaneous transportation, 

hypsography (vector topographic contours), administrative and 

political boundaries, Public Land Survey System (PLSS), and 

cultural features. The hydrography and roads and trails layers 

were revised using DOQ files as just described. The remaining 

layers were not, and thus their content reflects the content of 

the 7.5-minute topographic maps. The location and description 

of inactive mines and mine-related features were of utmost 

importance to this study, and are described separately later in 

this chapter and in detail in the Mine Inventory chapter (Martin, this volume. Chapter D3). The Boulder River watershed 

study area boundary layer was created from the hypsography 

and hydrography layers. Figure 2 shows selected base cartographic data and the outline of the target drainages in the 

Boulder River watershed.

The base cartographic data vector layers exist on the 

Boulder River watershed CD-ROM as export files of Arclnfo 

coverages in the /bldr_cd/gis_db/basecart/eOO directory, and as 

ESRI shapefiles in the /bldr_cd/gis_db/basecart/shape directory. A complete list of base cartographic data coverages and 

the data themes they contain is in table 1. Due to shapefile 

naming restrictions, the names of some of the shapefiles are 

abbreviated versions of their corresponding Arclnfo coverage 

names. For a complete listing of the shapefile names, see the 

/bldr_cd/gis_db/basecart/README.txt file on the CD-ROM 

which accompanies this volume.

The first 16 coverages listed in table 1 contain data that 

lie entirely within the eight-quadrangle area. The Administrative Boundaries theme contains USDA Forest Service boundaries but does not include inholding boundaries. The Political 

Boundaries theme contains county boundaries, those being 

the only political boundaries that exist in the eight-quadrangle 

area.

In addition to the naturally occurring features contained 

in the Hydrography theme, there are lines labeled as "network 

flow lines," which connect streams where they flow into and 

out of lakes and marshes. These lines and all lines representing streams have been created from beginning to end in the 

downstream direction. Thus, by using all the linear features 

that represent streams, along with the "network flow lines," 

one can perform network flow modeling. The Springs theme 

contains all springs shown on the 7.5-minute topographic 

maps for the eight-quadrangle area, plus 13 others located as 

part of this study.

A typical USGS DLG Miscellaneous Culture Features 

file would contain the contents of the Miscellaneous Culture 

Features theme, the Miscellaneous Culture Point Features 

theme, and the Mine-related Point Features from Topographic 

Maps theme. Because of the importance of mine-related 

sites to this study, they were separated from the other cultural point features and stored in a separate coverage called 

M1NE_TOPO_PTS. This coverage contains all mine-related 

point features exactly as they are shown on the 7.5-minute 

topographic maps. A separate coverage. MINE_SITES. which 

was created using the digital orthophoto quadrangle files and
508 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

1120151

46°22'30M

46°15'

EXPLANATION i)_i2j MILES

Hydrography 0 2 4 KILOMETERS 

'•- —-- Roads

s—' Targeted drainages in the Boulder River watershed 

—— Quadrangle boundary

Figure 2. Selected data within the eight-quadrangle area from the Boulder River watershed GIS database.

a wide variety of other sources, is described briefly in this 

chapter under the "Site Data" section, and in greater detail in 

Martin (this volume, Chapter D3).

As previously mentioned, most of the data gathered for 

the Boulder River watershed study was collected within the 

eight-quadrangle area. However, a few samples were collected 

within the portion of the Boulder River watershed that lies 

outside the eight-quadrangle area. The last seven coverages 

listed in table 1 contain less-detailed data that cover the entire 

Boulder River watershed. These coverages were created to 

serve as visual reference for the data collected outside the 

eight-quadrangle area. The vast majority of the Boulder River 

watershed lies within Jefferson County, except for one very 

small portion of Broadwater County at the southeast edge of 

the watershed. The Basin-wide County Boundaries theme 

delineates this small section of county boundary. The Basinwide Hydrography theme contains the Boulder River and 

selected tributaries, and the Basin-wide Highways theme contains major highways within and near the Boulder watershed. 

The Jefferson River theme contains a section of the Jefferson 

River that lies just upstream and just downstream from the 

mouth of the Boulder River. The Subbasins theme contains

selected subbasin boundaries within the watershed, as selected 

by project scientists for the purpose of meaningfully interpreting the data collected for the study.

Other related base cartographic data in the GIS database 

include an elevation grid created directly from USGS 

10-meter Digital Elevation Model (DEM) files, and individual 

Digital Raster Graphic (DRG) files of the topographic maps. 

Slope grids in percent and degrees, and aspect and shadedrelief grids were also derived from the elevation grid. All of 

the elevation-related grids are listed in table 2. The elevation and elevation-derived grids exist on the CD-ROM in the 

/bldr_cd/gis_db/basecart/elev directory as a compressed tar 

file (elevation.tar.gz), which when uncompressed produces 

an entire Arclnfo workspace containing all of the elevationrelated grids. The elevation and elevation-derived data also 

exist as TIFF files on the Boulder River watershed CD-ROM 

in the /bldr_cd/gis_db/basecart/elev directory. Additionally, 

the raw elevation data values also exist in that directory in a 

flat, ASCII file called elevation, ascii.

For more detailed information describing the sources, 

creation and content of the base cartographic data in the Boulder River watershed GIS database, see the metadata located
Digital Databases for the Boulder River Watershed 509

Table 1. Base cartographic data coverages in the Boulder River watershed GIS database.

Coverage name

ADMINBND

HYDRO

HYPSO

MINE_TOPO_PTS

MISC_CUL

MISC_CUL_PTS

MISCTR

PLACE_NAMES

PLSS

POLBND

QUADS

Q8OUTLINE

ROADS

SPRINGS

STUDY_AREA_BD

USFS_CFF_OWN

ALL_BLDR_COBD

ALL_BLDR_HY

ALL_BLDR_RD

ALL_BLDR_USFS

ALL_BLDR_WSHD

JEFFRIVER

SUBBASINS

Theme

Administrative Boundaries

Hydrography

Hypsography

Mine-related Point Features from Topographic 

Maps

Miscellaneous Culture Features

Miscellaneous Culture Point Features

Miscellaneous Transportation Features

Place Names

Public Land Survey System

Political Boundaries

Quadrangle Boundaries

Outline of Eight-Quadrangle Area

Roads

Springs

Study Area Boundary

USDA Forest Service Cartographic Feature 

File (CFF) Ownership Lines

Basin-wide County Boundaries

Basin- wide Hydrography

Basin- wide Highways

Basin-wide USDA Forest Service Boundaries

Boulder River Watershed

Jefferson River

Subbasins

File name

adminbnd.eOO

hydro.eOO

hypso.eOO

mine_topo_pts.eOO

misc_cul.eOO

misc_cul_pts.eOO

misctr.eOO

place_names .eOO

plss.eOO

polbnd.eOO

quads.eOO

qSoutline.eOO

roads. eOO

springs.eOO

study_area_bd.eOO

usf s_cff_own . eOO

all_bldr_cobd.eOO

all_bldr_hy.eOO

all_bldr_rd.eOO

all_bldr_usfs.eOO

all_bldr_wshd.eOO

jeffriver.eOO

subbasins.eOO

Data format

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage

Arclnfo vector coverage
510 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 2. Elevation and elevation-derived grids in the Boulder River watershed GIS database.

Grid name

ELEVATION

HILSHD

SLOPE_DEGREE

SLOPE_PERCENT

ASPECT

Theme

Elevation

Shaded Relief

Slope in Degrees

Percent Slope

Slope Aspect

File name

elevation.tar.gz

elevation.tar.gz

elevation.tar.gz

elevation.tar.gz

elevation.tar.gz

Data format

Arclnfo grid

Arclnfo grid

Arclnfo grid

Arclnfo grid

Arclnfo grid

on the CD-ROM accompanying this volume, in the /bldr_cd/ 

gis_db/basecart/meta directory. Because the ESRI shapefile 

versions of the base cartographic data were created from the 

Arclnfo coverages, and due to shapefile naming limitations, 

the shapefiles in some cases have abbreviated versions of 

the coverage names listed in table 1. These differences are 

fully described in the README.txt file in the /bldr_cd/ 

gis_db/basecart directory on the CD-ROM. The CD-ROM is 

described at the end of this chapter in the Boulder River watershed CD-ROM section.

Site Data

As part of the watershed approach, many kinds of 

scientific data were collected in the Boulder River watershed 

study area for site characterization, analysis, and monitoring 

purposes. A wide range of rock, sediment, water, and biological samples was collected, measured, and analyzed, and an 

inventory of mine-related sites and descriptions was compiled. 

In order to have a single, integrated and standardized collection of project information, all data were integrated spatially 

using a GIS, and conceptually using a relational database. 

Field sampling sites that should be considered co-located for 

analysis purposes were grouped together resulting in 

425 Analysis Sites. Inactive mines and other mine-related 

features are represented as 143 Mine Sites. Associations 

between Field Sites and Mine Sites were defined and represented as relationships in the databases. The sample-site and 

mine-site data are available on the Boulder River watershed 

CD-ROM in a relational (Access) database, in a GIS (Arclnfo) 

database, and in several other formats.

Sample-Site Data

Figure 3 shows the distribution of the sample sites for 

the Boulder River watershed study. The majority of sites are 

in the area of targeted drainages in the Boulder River watershed; some are elsewhere in the Boulder River watershed; a 

few are outside the Boulder River watershed, but within the 

eight-quadrangle area. (See figure 1 for the spatial relationship 

of these three areas.) For detailed localities of specific sample 

sites, see the appropriate chapter of this volume, as listed in 

table 5 in the "Relational Database" section, or extract the 

FIELD_SITES data from the accompanying CD-ROM.

As previously mentioned, the sample-site data and minerelated site data exist in a number of different formats on the 

CD-ROM accompanying this volume. The file names of the 

data as they exist in the various formats are shown in table 3. 

Owing to differences in the allowed lengths of file names and 

attribute names, some of the Arclnfo, ESRI shapefile, and .dbf 

file names and attribute names are abbreviated versions of 

those that exist in the analogous relational (Access) database 

tables. These differences are delineated in the README.txt 

file on the Boulder River watershed CD-ROM in the /bldr_cd/ 

gis_db/sitedata directory.

The coverage, file, and attribute names used in the 

remainder of this section are from the Arclnfo GIS database. 

Access relational database table and attribute names are used 

in the "Relational Database" section later in this chapter.

The sample data exist in the GIS database as two point 

feature data layers (FIELD_SITES and ANALYSIS_SITE) 

and 10 associated tables. The FIELD_SITES data layer 

contains one point feature for each sample site. Attributes for 

each site include a unique identifier called SITENUMBER, 

various information provided by the person who collected the 

sample(s) at the site, and locational information generated by 

the GIS. A table called LOC_MASTER contains the attributes 

ELEVATION, TOWNSHIP, RANGE, SECTION, LITHOLOGY, STRATJJNIT (stratigraphic unit), GEOL_AGE 

(geologic age), and SUBBASIN for each sample site. Values 

for these attributes were assigned by using the GIS to perform 

spatial overlays with the FIELD_SITES coverage and the 

appropriate base cartographic and geologic coverages.

Sample sites that are considered co-located for purposes 

of spatial analysis are assigned the same value for an identifier 

called AMLI_ANALYSIS_ID. Because the location chosen to 

represent the "analysis site" is not always exactly the 

same as that of the sample sites that are logically considered 

to be co-located there, a second point feature data layer, 

ANALYSIS_SITE, is used to contain the locations of the 

analysis sites. The same attributes that were added to the 

FIELD_SITES data layer using spatial overlay were also 

added to the ANALYSIS_SITE data layer.

Because the AMLI_ANALYSIS_ID exists in the attribute 

tables for both the FIELD_SITES and ANALYSIS_SITE 

data layers, the two can be related to each other and to other 

data tables containing actual sample data and results. The 

relationship between the two point feature data layers is 

one-to-many, since more than one field site can have the same 

AMLI ANALYSIS ID. In order to aid GIS users not familiar
Digital Databases for the Boulder River Watershed 511

112" DO 1

EXPLANATION

Sample site

Boulder River and tributaries

Boulder River watershed

024 6 KILOMETERS

Figure 3. Distribution of Boulder River watershed study sample sites.

with techniques for dealing with one-to-many relationships, 

the attribute table for the ANALYSIS_SITE data layer also 

contains the SITENUMBERs of the field sites associated with 

each analysis site.

A table called FS_MS_ASSOCS contains a list of field 

sites that are associated with specific mine-related sites. There 

are 18 such relationships in the table, with the identifiers 

SITENUMBER and mine-related site AMLI MINE ID listed

for each relationship. For a complete description of the inventory of mining-related sites created for this study, see Martin 

(this volume).

There are eight other tables that contain the actual sample 

data and results, as well as various characteristics of the 

samples and results. These tables were initially created using 

the Access relational database and then converted to INFO 

files and .dbf files for inclusion in the GIS database. These
512 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 3. File names for site data in various formats.

Export files for Arclnfo coverages 

or Info files

analysis_site.eOO 

(coverage)

Analytic_meth.eOO 

(Info file)

field_sites.eOO 

(coverage)

fs_ms_assocs.eOO 

(Info file)

lab_name.eOO 

(Info file)

loc_master.eOO 

(Info file)

mine_sites.eOO 

(coverage)

mine_sites.eOO

(mine_sites.aditflow is part of 

mine_sites coverage )

parameter.eOO 

(Info file)

project.eOO 

(Info file)

qual_result.eOO 

(Info file)

result.eOO 

(Info file)

sample.eOO 

(Info file)

Sample_media.eOO 

(Info file)

Shapefiles or 

dBASE files

anlysite.shp

an_meth.dbf

fldsite.shp

fmsassoc.dbf

labname.dbf

locmastr.dbf

minesite.shp

msadflow.dbf

parametr.dbf

project.dbf

qualres.dbf

result, dbf

sample.dbf

sampmed.dbf

Access tables

SpatialAnalysisSites

AnalyticMethod

FieldSites

FieldSiteMineSiteAssocs

LabName

LocationMaster

MineSites

MineSitesAditFlow

Parameter

Project

QualitativeResult

Result

Sample

SampleMedia

ASCII tables

SpatialAnalysisSites. tab

AnalyticMethod.tab

FieldSites.tab

FieldSiteMineSiteAssocs.tab

LabName. tab

LocationMaster.tab

MineSites. tab

MineSitesAditFlow.tab

Parameter.tab

Project.tab

QualitativeResult. tab

Result.tab

Sample.tab

SampleMedia.tab

tables are described in the "Relational Database" section of 

this chapter. Effective use of the data in many of these tables 

requires dealing with one-to-many relationships. The relationships between the primary sample and results tables are shown 

in figure 4, and explained in the "Relational Database" section 

of this chapter. A bitmap file (relationship_diagram.bmp) 

containing a complete diagram of the relationships of all the 

files in the Boulder River watershed relational database exists 

on the accompanying CD-ROM in both the /bldr_cd/rel_db 

and /bldr_cd/gis_db/sitedata directories. Because effective 

use of the sample-site data requires an understanding of these 

relationships, this diagram is important for users of the GIS 

database, as well as for users of the relational database.

The FIELD_SITES and ANALYSIS_SITE coverages 

exist on the Boulder River watershed CD-ROM as export files 

in the /bldr_cd/gis_db/sitedata/eOO directory. Ten other tables 

containing information about, and data collected at, the field 

sites also exist in that directory as INFO files. These coverages 

and tables also exist as ESRI shapefiles and .dbf files,

respectively, in the /bldr_cd/gis_db/sitedata/shape and /bldr_ 

cd/gis_db/sitedata/dbf directories.

Mine-Related Site Data

An inventory of inactive mines and mine-related sites in 

the Boulder River watershed study area was compiled from 

existing State and Federal sources. In some cases, multiple 

shafts, adits, prospects, and disturbed areas were located at a 

given site, but in each case a single point location was chosen 

to best represent the site. The location of each mine-related 

site was verified where possible with digital orthophoto quadrangle (DOQ) images, and by persons with local knowledge of 

the area.

A number of descriptive attributes were gathered from 

a variety of sources and assigned to the mine-related sites 

wherever available. One hundred forty-three mine-related sites 

are stored in an Arclnfo coverage called MINE_SITES, which 

exists on the Boulder River watershed CD-ROM as an export
Digital Databases for the Boulder River Watershed 513

file in the /bldr_cd/gis_db/sitedata/eOO directory. There is also 

an Arclnfo lookup table called MINE_SITES.ADITFLOW, 

which contains information about flowing adits that 

exist at some of the mine-related sites. The MINE_ 

SITES.ADITFLOW lookup table is part of the MINE_SITES 

coverage, and is therefore contained in the mine_sites.eOO file. 

A detailed description of the mine inventory data is in Martin 

(this volume).

In addition, the MINE_SITES coverage and related tables 

are also available on the Boulder River watershed CD-ROM as 

an ESRI shapefile and .dbf files, respectively, in the /bldr_cd/ 

gis_db/sitedata/shape and /bldr_cd/gis_db/sitedata/dbf directories. The mine-related site data are also part of the Boulder 

River watershed relational database, which is described later in 

this chapter.

Geoscientific Data

Geologic Data

Two geologic maps were generated from the original 

geologic map products of Ruppel (1963) and Becraft and 

others (1963). The first map is a reinterpretation of bedrock 

geology and is described in O'Neill and others (this volume, 

Chapter Dl). Four data files are provided to create this map. 

All data are provided in both Arclnfo Export format and ESRI 

shapefile format. The first data file is the geology polygon and 

line file (geology.eOO, geologyp.shp, and geologyl.shp). This 

data file updates previously published maps by providing a 

geologic framework in the context of current geologic nomenclature and modern knowledge for geologic units in the Boulder River watershed. The second data file depicts the geologic 

structure (faults.eOO and faults.shp). This line file contains the 

faults that have been mapped in the geologic map area. The 

third data file is an alteration coverage (alter.eOO and alter.shp). 

This is a polygon file that shows areas of probable Late Cretaceous alteration. The fourth data file shows the veins that have 

been mapped for the geologic area (veins.eOO and veins.shp). 

All of these data files are provided in Arclnfo export format in 

the /bldr_cd/gis_db/geosci/geology/eOO directory, as well as in 

ESRI shapefile format in the /bldr_cd/gis_db/geosci/geology/ 

shape directory. O'Neill and others (this volume) provide a 

comprehensive discussion of geologic features. A PDF format 

map file also is provided (geol_pll.pdf). It is located in the 

/bldr_cd/gis_db/geosci/geology/pdf directory. Throughout 

this volume, this geologic map is listed and described as plate 

1. O'Neill and others (this volume) also contains a second 

oversize image, which is listed and described as plate 2. The 

illustration is a fence diagram correlating Quaternary deposits 

in the area of the inactive Buckeye mine. It is provided on the 

CD-ROM as a PDF in the /bldr_cd/gis_db/geosci/geology/pdf 

directory and is named geol_pl2.pdf. The topographic base 

was simplified for inclusion under the geology in plate 1.

A PDF of the complete topographic base is provided in the 

/bldr_cd/gis_db/geosci/geology/pdf directory and is named 

topobase.pdf.

The second geologic map provides a reinterpretation 

of study area geology in a geoenvironmental context, as 

described by McCafferty and others (this volume, Chapter 

D2). This map depicts geologic units in terms of their relative 

acid-neutralizing potential based on mineralogical data and 

acid-leachate studies. Geologic units with higher acid-neutralizing potential are shown in lighter shades of green, and units 

with relatively low acid-neutralizing potential are shown in 

darker greens. This map (e_geo.tif) is provided in GeoTIFF 

format. It is located in the /bldr_cd/gis_db/geosci/geophys/ 

geotiff directory.

Geochemical Data for Streambed 

Sediment and Water

Eleven files provided in the geochemistry section depict 

geochemical data for streambed sediment and water. The 

original geochemical data consisted of concentration data for 

trace elements in either sediment or water. These data were 

reinterpreted as hazard quotients to indicate the relative hazard 

of the trace elements to aquatic biota. These hazard quotients 

are presented in "ribbon" maps that illustrate the distribution 

of hazard quotients of selected trace elements as a band of 

color that runs along the streams and resembles a ribbon. The 

relative magnitude of the hazard quotient is depicted with different colors. Development of the hazard-quotient ribbon maps 

is described in more detail by Finger, Farag, and others (this 

volume, Chapter C).

The geochemistry section contains five streambed-sediment ribbon maps. The elements shown and their corresponding file names are: cadmium (sed_cd.eOO and sed_cd.shp), 

copper (sed_cu.eOO and sed_cu.shp), lead (sed_pb.eOO and 

sed_pb.shp), zinc (sed_zn.eOO and sed_zn.shp) and a combination of cadmium, copper, and zinc data (sed_all.eOO and 

sed_all.shp). A map is provided that shows the localities of all 

the streambed-sediment sample sites (sed.eOO and sed.shp). 

All these files are provided in Arclnfo export format in the 

/bldr_cd/gis_db/geosci/geochem/eOO directory, as well as in 

ESRI shapefile format in the /bldr_cd/gis_db/geosci/geochem/ 

shape directory.

This section also contains four water geochemical data 

maps. The elements shown and their corresponding file names 

are: cadmium (wat_cd.eOO and wat_cd.shp), copper (wat_ 

cu.eOO and wat_cu.shp), zinc (wat_zn.eOO and wat_zn.shp) and 

a combination of cadmium, copper, and zinc data (wat_all.eOO 

and wat_all.shp). A map is provided that shows the localities 

of all the water sample sites (water.eOO and water.shp). All 

these files are provided in Arclnfo export format in the /bldr_ 

cd/gis_db/geosci/geochem/eOO directory and in ESRI shapefile 

format in the /bldr_cd/gis_db/geosci/geochem/shape directory. 

Chapter D5 (Nimick and Cleasby) in this volume contains a 

detailed description of the water geochemical data.
514 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Biological Data

The one map provided in this section shows the estimated distribution of trout prior to 1997. This file illustrates 

the distribution of trout by type in the watershed (fish.eOO and 

fish.shp). The map is based on two types of biological sample 

sites. The first type of sample site is the fish abundance and 

health assessment; the second type is the 96-hour survival 

experiment. This file is provided in Arclnfo export format in 

the /bldr_cd/gis_db/geosci/biologic/eOO directory and in ESRI 

shapefile format in the /bldr_cd/gis_db/geosci/biologic/shape 

directory. Chapter DIG (Farag and others) in this volume contains a detailed description of the biological data.

Geophysical Data

Images of magnetic anomaly and apparent resistivity data 

and related interpretive products are part of the work described 

in McCafferty and others (this volume, Chapter D2) and are 

provided in the /bldr_cd/gis_db/geosci/geophys/geotiff directory on the accompanying CD-ROM. Vector files that define 

the extent of the airborne geophysical survey are available in 

Arclnfo export format (gp_poly.eOO) in the /bldr_cd/gis_db/ 

geosci/geophys/eOO directory, and in ESRI shapefile format 

(gp_poly.shp) in the /bldr_cd/gis_db/geosci/geophys/shape 

directory.

The images provided on the CD-ROM were derived from 

grids of data collected along closely spaced (200 m) flightlines 

as part of a high-resolution airborne geophysical survey over 

the Boulder River watershed area. The images provide a depiction of the magnetic anomaly and apparent resistivity fields 

but do not allow for detailed data manipulations or interpretation at specific sites. The reader is referred to Smith and others 

(2000) for the basic magnetic anomaly and apparent resistivity flightline data and grids that would permit these types of 

analyses. The following text discusses the various geophysical 

image files that can be found in the /bldr_cd/gis_db/geosci/ 

geophys/geotiff directory.

Images relating to the magnetic anomaly data include a 

reduced-to-pole magnetic anomaly map, a high-pass magnetic anomaly map, and an image of a model that illustrates 

estimates of magnetic susceptibility and volume percent 

magnetite. Except at the north magnetic pole, magnetic 

anomalies are distorted in shape and positioned off their 

causative sources. In order to correct for the distortion and 

dislocation of magnetic anomalies in the study area, a reduction-to-pole operation was applied to the magnetic anomaly 

field to produce the reduced-to-pole magnetic anomaly image 

(rtp_mag.tif). To emphasize magnetic anomalies caused by 

lateral variations in magnetic properties of rocks from surface 

elevations to approximate depths of 200 m, a filter was applied 

to the reduced-to-pole data to create the high-pass magnetic 

anomaly image (rtp_mag_hipass.tif). From these data, models 

of magnetic susceptibilities and corresponding values for percent magnetite were calculated (mag_magnetite.tif).

Images that portray apparent resistivity of rocks as 

measured from the airborne geophysical survey are provided 

on the CD-ROM. The images represent electrical resistivity 

of rocks at three frequencies resulting in different depths of 

penetration. The image produced using the highest frequency 

(56,000 Hz) shows resistivities of rocks at depths from the topographic surface to a few meters to 10 m. The mid-frequency 

(7,200 Hz) image (res7200.tif) maps electrical resistivities of 

rocks from the surface to depths of approximately 30 m. The 

lowest frequency (900 Hz) image (res900.tif) maps resistivities 

of rocks at depths to approximately 60 m.

For nearly all the Cretaceous- and Tertiary-age volcanic 

and plutonic rocks exposed in the Boulder River watershed, 

increased amounts of acid-consuming calcic and mafic minerals are associated with increased levels of the mineral magnetite. Magnetite is the main source for magnetic anomalies 

and, in part, resistivity anomalies. McCafferty and others (this 

volume) have converted the magnetic and apparent resistivity 

anomaly data to maps of volume percent magnetite to infer 

places in the watershed with low acid-neutralizing potential. 

Estimates for volume percent magnetite calculated from the 

900-Hz apparent resistivity data are shown in the image file 

em_magnetite.tif. Volume percent magnetite estimates modeled from the magnetic anomaly data are given in the 

mag_magnetite.tif file. Low values in both geophysical magnetite models have been combined to produce an integrated 

product that represents locations of rocks with little to no acidneutralizing potential (gp_low_ANP.tif).

Remote Sensing Data

The remote sensing section includes three vector files 

and five raster files. The first vector file represents linear 

features (lin_f.eOO and lin_f.shp) that were mapped from 

remote sensing base images. They are assumed to represent 

the spatial distribution, spatial frequency, and orientation 

of faults, joints, and fractures associated with structurally 

controlled ground-water flow. The second vector file is a wet 

soil coverage (wetsoil.eOO and wetsoil.shp). This coverage 

shows areas of saturated soils that are associated with shallow 

ground water. The third file illustrates wetlands (wetland.eOO 

and wetland, shp) that are defined as areas that have soils with 

perennial or seasonal high water tables. The vector files are 

provided in Arclnfo export format in the /bldr_cd/gis_db/ 

geosci/remosens/eOO directory, and in ESRI shapefile format in the /bldr_cd/gis_db/geosci/remosens/shape directory. 

See Chapter D9 in this volume (McDougal and others) for a 

detailed description of these files.

The five raster files included in the remote sensing section show the linear features in terms of spatial frequency 

(frequency.tif), number of intersections (intersect.tif), and 

total length within a grid cell (length.tif). The contour maps 

represent zones of least occurrence of linear features, shortest 

linear features, and least number of intersections with cooler 

colors, and zones of higher occurrence, greater length, and
Digital Databases for the Boulder River Watershed 515

greater occurrence of intersections with warm colors. Two 

derivative maps have been produced from these images. The 

first is a combination of the spatial frequency and the length of 

the mapped linear features (frequency_length.tif). The second 

is a combination of the spatial frequency of the linear features 

and the number of the linear feature intersections (frequency_ 

intersect.tif). These five files are provided in the GeoTIFF 

format. See Chapter D9 (McDougal and others) in this volume 

for a detailed description of the files. The files can be found in 

the /bldr_cd/gis_db/geosci/remosens/geotiff directory.

The geologic maps and the geochemical, biological, 

geophysical, and remote sensing data are listed in table 4, and 

are available on the CD-ROM in the /bldr_cd/gis_db/geosci 

directory.

Relational Database

The Boulder River watershed relational database was 

constructed to be used as a tool for data synthesis and analysis, 

and as an archive of data collected during the Boulder River 

watershed study. It includes data collected by U.S. Geological 

Survey biologists, geologists, and hydrologists within or 

adjacent to the Boulder River watershed during the period 

1995 to 20001 . It is a tabular relational database containing 

field measurements made at point locations, and laboratory 

analyses of samples collected at point locations. Qualityassurance data are not included; information on field and 

laboratory quality-assurance practices is located in individual 

chapters in this report or in previously published reports. A 

Geographic Information System (GIS) representation of the 

database is discussed elsewhere in this chapter.

Contents of Database

The Boulder River watershed relational database contains 

data contributed by eight U.S. Geological Survey scientists or 

teams (table 5). These data sets comprise all of the available 

data collected as part of the project. Data were collected at 

479 sites (fig. 3). Twenty-four media types were sampled, 

including 1,038 water samples, 1,094 earth material samples, 

and 79 biological material samples. Water media sampled 

included surface water (streams), ground water (well water), 

and springs. Earth media sampled included soils, bedrock, and 

various types of sediment. Biological media sampled included 

biofilm, fish tissue, invertebrate tissue, and tree tissue. The 

database contains 67,366 results, which are quantitative, qualitative, or descriptive measurements; the database contains 

776 defined measurement types (parameters).

'Forty-eight analyses of bedrock samples collected during 1952-54 also are 

included in the database.

Database Structure

Because of the scope and complexity of data collected as 

part of the Boulder River watershed study, a relational database structure was designed for data storage. Data are grouped 

into logical units (tables), and relationships are defined to link 

the tables. This structure provides efficient storage of information (that is, the information need not be repeated), and also 

provides for built-in data-verification checks; for example, a 

result cannot exist without corresponding site, sample, and 

parameter information. The relational database structure also 

is powerful and efficient for retrieving subsets of data to meet 

user requirements.

The primary tables in the Boulder River watershed relational database (directory rel_db on the accompanying 

CD-ROM) are the FieldSites, Sample, Result, and Parameter 

tables (fig. 4). The FieldSites table contains information 

about each of the 479 sites in the database. A SiteNumber 

uniquely identifies each site. Sites that are considered colocated for purposes of spatial analysis are assigned the same 

AMLIAnalysisID. A ProjectCode for each site indicates 

what project and scientist established the site. The attribute 

PPSiteLabel contains the label which is used for a field site 

on figures or diagrams elsewhere in this Professional Paper. 

These labels are not always exactly the same as the field sites' 

SiteNumber. Additional characteristics in the FieldSites table 

include locational coordinates, SiteComment, and a Stream 

designation which indicates if a site is located on a stream, and 

if so, which one.

The Sample table contains information about material 

collected at each site, such as the date and time of collection, 

and the type of material (sample media) collected at the site. 

Media type should be carefully noted when data are analyzed, 

so that data of different types are not mistakenly equated; for 

example, the database contains analyses for arsenic in fish 

livers and in fish gills, organs which might have different characteristics relative to the bioaccumulation of metals. Optional 

characteristics in the Sample table include SamplePreparation, 

SampleComment, and CollectionMethod.

The Result table contains measurements made at sites. 

The characteristic measured is identified using a ParameterCode, a succinct 20-character-length field that can be used as 

a column name in a data report or spreadsheet. Measurements 

consist of a numeric value and an optional ValueRemarkCode, 

which is used to qualify results such as nondetections or 

estimates. Optional characteristics in the Result table include 

AnalyticMethodShortName and LabShortName.

The Parameter table is a lookup table that contains a complete description of each characteristic measured. Although 

the Result table contains a short description of the characteristic measured (ParameterCode), a lengthier description 

is needed owing to the highly specific nature of laboratory 

measurements. For example, the ParameterCode "Ag_ss" 

is shorthand for "Silver, sediment, suspended, ground finer 

than 0.15 millimeters, laboratory, micrograms per gram." 

The Parameter table also includes a ConstituentName field to
516 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

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Table 4. Geologic maps and geochemical, biological, geophysical, and remote sensing data in the Boulder River watershed GIS database.—Continue

Subject Description File name File format(s) 

Water Ribbon 

Maps — Continued

Biological data 

Geophysics

Remote sensing

Ribbon map that shows the concentration of zinc in the water 

recast as hazard quotient values in terms of the ERA water quality standards

Ribbon map that shows the concentration of cadmium + copper 

+ zinc in the water recast as hazard quotient values in terms of 

the ERA water quality standards

Estimated distribution of trout population prior to 1997

56K Hz. resistivity

7200 Hz. resistivity

900 Hz. resistivity

Reduced-to-the-pole magnetic anomaly

Reduced-to-the-pole high pass magnetic anomaly

Volume percent magnetite estimated from 900-Hz resistivity

Volume percent magnetite estimated from the high pass magnetic

anomaly data 

Geophysically-inferred bedrock with low acid-neutralizing

potential

Outline of the geophysical study area boundary

The spatial frequency of mapped linear features

The combined spatial frequency and intersections of mapped

linear features 

The combined spatial frequency and length of mapped linear

features

The number of intersections of mapped linear features 

The length of mapped linear features 

Areas that have soils with perennial or seasonal high water tables

Areas of saturated soils that are associated with linear features 

Linear features that have been delineated from fracture analysis

wat_zn.eOO, 

wat_zn.shp

wat_all.eOO, 

wat_all.shp

fish.eOO, 

fish.shp

res56K.tif

res7200.tif

res900.tif

rtp_mag.tif

rtp_mag_hipass.tif

em_magnetite.tif

mag_magnetite.tif

gp_low_ANP.tif 

gp_poly.eOO, gp_poly.shp

frequency.tif 

frequency_intersect.tif

frequency_length.tif

intersect.tif

length.tif

wetland.eOO, wetland.shp

wetsoil.eOO, 

wetsoil.shp

lin_f.eOO, lin_f.shp

Arclnfo vector coverage

Arclnfo vector coverage

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N

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GeoTiff 

GeoTiff 

GeoTiff 

GeoTiff 

GeoTiff

GeoTiff

GeoTiff

Arclnfo vector coverage

GeoTiff 

GeoTiff

GeoTiff

GeoTiff 

GeoTiff 

Arclnfo vector coverage

Arclnfo vector coverage 

Arclnfo vector coverage

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M

M
518 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

Table 5. Data sources for sample-site data in the Boulder River watershed relational database.

[ Not all data have been published elsewhere in the documents listed in the Reference column. See appropriate chapter in this volume or the accompanying 

CD-ROM for access to all of the data ]

AMU Project 

Component

Characterization of

water-quality

conditions

Uncle Sam Gulch,

Bullion Mine

„ 4 . . .. 4 Media Contact scientist . . sampled

D.A. Nimick Surface

water,

ground

water

B.A. Kimball Surface

water

Number of 

sites

111

168

Number of 

samples

858

172

Number of 

results

14,682

7,186

Reference

Nimick and Cleasby

(2000)

Kimball and others

(this volume)

Chapter in

which data

are 

primarily

used

D5

D6

tributary, and Cataract

Creek metal-loading

study 

Rare earth geochemistry

of acidic waters 

Characterization of

ecosystem health 

Characterization of

stream sediment and

mine wastes

P.L. Verplanck 

A.M. Farag 

D.L. Fey

Surface 

water 

Biota

Biota, rock, 

sediment, 

soil, mine 

wastes

Characterization of 

tailings core

S.E. Church

Chemical and lead D.M. Unruh 

isotope compositions 

of mine wastes and 

premining sediment

Chemical compositions D.L. Fey

of mine wastes 

Rock geochemistry

Sediment, 

soil, mine 

wastes

Biota, sediment

Rock, soil

B.S. Van Gosen Rock

8 8 429 Verplanck and oth- Data not

ers(1999) used

15 67 331 Farag and others D10

(this volume)

95 607 28,226 Fey and Church D4, D8, El

(1998); Fey and 

others (1999); 

Fey, Church, and 

Finney (2000); 

Fey and Church

(1999); Fey,

Desborough, and

Finney (2000) 

1 232 8,768 Church, Unruh, El

and others (this

volume) 

21 186 5,691 Unruh and others D8

(2000)

21 33 941 Desborough and D1,D2, D4

others (1998) 

39 48 1,112 Ruppel(1963); Dl

Becraft and others

(1963)

TOTAL 479 2,211 67,366

group results according to the element or compound type (for 

example, zinc), and a Ppcode field which lists the corresponding measurement code (where available) in the U.S. Geological Survey's National Water Information System and the U.S. 

Environmental Protection Agency's STORET database.

Relationships between these tables are depicted as lines 

in figure 4. The FieldSites table is linked to the Sample table 

by including a common field (Site Number) in both tables; 

therefore a sample cannot exist without a corresponding site in 

the FieldSites table. The symbols "1" and "oo" on the relationship line indicate a one-to-many relationship, that is, a site

may have many samples. Similarly a sample may have many 

results, and a parameter may have many results.

The Boulder River watershed relational database contains 

10 tables in addition to the 4 principal tables. The Qualitative 

Result table includes measurements that are text values 

(as opposed to number values in the Result table). The 

SpatialAnalysisSites table provides site groupings so that data 

may be extracted from sites that are logically co-located for 

analysis purposes. The AnalyticMethod table provides additional information on laboratory techniques used. The LabName table provides additional information about analytical 

laboratories that produced chemical results. The Project table
Digital Databases for the Boulder River Watershed 519

SteNumber

Site-Name

SiteComment

PtoiectCode

PPSiteLabel

AMLIAnalysisID

Latitude

Longitude

UTM_Easting

UTM_Nor thing

Stt earn

SiteNumber

SarripleMarne

SarnpleLocationDescription

SarnpleOate

SampleTime

SampleMediaCode

CollectionMethod

SarnplePreparation

SarnpleComiTient

ResultID

SamplelO

Value

ValuePernarkCode

Parameter Code

AnalyticMethodShor tName

LabShortName

Filter PoreSceValueGjiriments

ParameterCode

Parameter Name 

Ppcode

ConstituentMame 

PoreSire 

Repot tUnits

«

Figure 4. Primary tables in the relational database and the relationships between tables.

provides additional information about projects that provided 

data to the Boulder River watershed relational database. The 

SampleMedia table provides additional information about 

the media types sampled. The LocationMaster table contains 

characteristics for each field site derived by map overlay 

using a GIS system. The MineSites table contains information 

about the mine-related sites located in the study area, and the 

MineSitesAditFlow table contains data about flowing adits 

that exist at certain mine-related sites. The FieldSiteMineSiteAssocs table lists certain field sites that are associated with 

mine-related sites.

A bitmap file (relationship_diagram.bmp), containing 

a complete diagram of the relationships of all the files in the 

Boulder River watershed relational database, exists on the 

accompanying CD-ROM in the /bldr_cd/rel_db directory.

Relational databases can be implemented using a variety 

of proprietary or nonproprietary software packages. The 

Boulder River watershed relational database is provided on the 

CD-ROM attached to this report in a format compatible with 

proprietary software (Microsoft Access 2000) in the /bldr_cd/ 

rel_db/mdb directory, and in a nonproprietary format in the 

/bldr_cd/rel_db/ascii directory. A README.txt file on the 

CD-ROM in /bldr_cd/rel_db provides technical details about

how to use the database in these two formats. A more complete discussion of the creation and content of the database is 

included on the CD-ROM in a Federal Geographic Data Committee-compliant metadata file in /bldr_cd/rel_db/meta.

Data may be extracted from the Boulder River watershed relational database to meet specific user needs. Within 

relational database software packages, queries may be constructed and saved to retrieve data using user-defined criteria; 

the Microsoft Access version of the Boulder River watershed 

relational database on the CD-ROM contains several example 

queries. Suppose a scientist wishes to examine downstream 

patterns of zinc concentrations in water along the mainstem 

of Cataract Creek during August 1997. To extract the necessary data from the database, a series of linked queries is 

constructed. The initial query is used to select the database 

fields of interest and to place conditions on retrieving the data. 

For the Zinc Synoptic data, the user would like a table that 

includes the site name, the instantaneous water discharge, the 

zinc concentration and the distance of the sampling point from 

the starting point on the stream. The query qselZnSynopticData (fig. 5) selects the fields of interest.

The query combines data from three tables, the FieldSites 

table (which contains the SiteName and Stream), the Sample

g? qseIZnSynopticData: Select Query ""^^^••^^^^^••^^^^^^^^^^^^•^•HIIBI

Latitude "*1 

Lorxjirude 

UTM_Eastmg 

LITM_Nofthinc _ 

Stream jj

1 00

SampleTrne •*•[ 

SarnpleMediaC 

CollectionHett . 

SamplePrepar _ j 

SampleCommfjJ

T 00

Value jj 

ValueRemark' 

ParameterCoc 1 

AnalyticMethc — 

LabShortWarnfjJ

±u

Field: q.liJUi'iU ~ 

Table: FieldSites

1. Stream

FieldSites

Sort:

Show: 0 0

Criteria: "Cat at act Creek" 

or:

fl

———————————————————————————————————————————————————— j

SampleDate ParameterCode Pesult: [Result MValuePernarKode] & [Pesult] '[Value —

Sample Pesult —

0 B 0

#81 1 3/ 1 '?97# "Zn_w_f " Ot "Qmstant" Or "SegDist"

Figure 5. Graphical view of the qseIZnSynopticData query.
520 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

table (which contains the SampleDate), and the Result table 

(which contains result information). Conditions are placed on 

this query so that only data with a Stream of "Cataract Creek" 

are selected, only samples taken on 8/13/97 are selected, and 

only results for water discharge, zinc concentration, and downstream distance are selected. This query also constructs the 

Result value as a concatenation of the numerical result along 

with any remark code. The graphical view of the query shown 

in figure 5 is translated into a Structured Query Language 

(SQL) statement as follows:

SELECT FieldSites.SiteName, FieldSites.Stream, 

Sample.SampleDate, ResultParameterCode, [Result]! 

[ValueRemarkCode] & [Result]![Value] AS Result 

FROM (FieldSites INNER JOIN Sample ON 

FieldSites.SiteNumber = Sample.SiteNumber) INNER 

JOIN Result ON Sample.SamplelD = ResultSamplelD 

WHERE (((FieldSites.Stream)="Cataract Creek") AND 

((Sample.SampleDate)=#8/13/1997#) AND ((Result. 

ParameterCode)="Zn_w_f" Or (Result.ParameterCode)= 

"Qinstant" Or (Result.ParameterCode)="SegDist"));

The second query in this example (qselZnSynopticData_ 

Crosstab) is a crosstab query which pivots the results of interest so that they appear as columns rather than rows. The third 

query (qmakZnSynopticResults) makes a new table containing 

the results sorted by downstream distance. A portion of this 

table is shown in figure 6.

Data Viewer Software

Two freeware GIS data viewer software packages are 

provided on the accompanying CD-ROM These products are 

GIS data explorers. The purpose of the data viewer software 

is to give the user the capabilities to perform elementary GIS 

analysis on the digital data. The vector coverages and raster 

images provided on the CD-ROM are useful for illustrating the 

processes and dynamics, in terms of mine drainage, that occur 

in the watershed.

• ZnSynopticResults : Table ^^•^^•^•••^^^^^^^^^^^^^^^^HEilESI

>

Re

SiteName j Discharge Zinc Concentration

CC-150 4 13 <10 

CC-850 4.27 <10

CC-1370 4 38 <10

CC-I610 445 <10

CC-1690 4 59 <10

CC-2490 455 '<10

CC-3450 6 <10

CC-3850 6 14 <10

CC-4660 6.43 33

Cataract Creek below Hoodoo Creek 6 53 53

CC-5940 6 6 47

CC-6800 6.67 36

CC-7900 6.74 35

CC-8700 6.81 45

CC-9220 6 99 45

CC-10380 724 47

CC-11055 7.59 42

CC-12115 791 56

CC-13255 816 57

CC-14055 8.33 52

CC- 14855 8.44 60

CC- 15655 855 56

CC- 16845 8.83 58

CC-17645 9.22 53

CC-18545 9.53 30

CC- 19245 9.75 30

Cataract Creek above Uncle Sam Gulch 9.57 ^31

Cataract Creek below Uncle Sam Gulch 1151 470

CC-20730 11.69 460

CC-21130 11.86 457 

CC-21715 1193 422

cord: M I . < j j 2 * IH l>*| of 46

Distance j^_

150 

» 850

1370

1610

1690

2490

3450

3850

4660

4940

5940

6800 -J

7900

8700

9220

10380

11055

I 12115

13255

I 14055

14855

15655

16845

17645

18545

19245; '

19700

20050

20730

21130 

21715 jj

Figure 6. The reformatted results of the qseIZnSynopticData query.
Digital Databases for the Boulder River Watershed 521

The two data viewer software packages are ArcExplorer 

2.0 and MapSheets Express 1.3. ArcExplorer 2.0 was written 

by Environmental Systems Research Institute, Inc. MapSheets 

Express was written by ERDAS, Inc.

Using these two products, the spatial data can be displayed, queried, and overlaid to produce map output. MapSheets Express enables the user to generate maps that can be 

imported into PowerPoint presentations. In addition, Word 

and WordPerfect documents can be output from MapSheets 

Express.

The two software packages have some important differences. ArcExplorer is better at handling vector files than 

raster files. Raster images can be displayed in ArcExplorer, 

but one cannot query the images. The raster images can only be 

displayed one at a time as a background for vector files. Basically, this image is a static backdrop with no inherent analysis 

properties.

In contrast, MapSheets Express has more functionality for 

raster images than ArcExplorer provides. The user is able to 

query pixels of the raster images. The attributes of these pixels 

are accessible in the data tables for user output. In addition, 

MapSheets Express allows the user to control the transparency of the images, which allows several raster images to be 

displayed on top of one another. In summary, for vector data 

work, ArcExplorer is a more effective tool, and for raster data 

work, MapSheets Express is better.

The two packages have similar platform requirements. 

ArcExplorer 2.0 requires a PC with Windows 98/2000/NT/XP 

operating systems. It requires Internet Explorer 4.0 for the 

internet capabilities of the software. MapSheets Express 1.3 

requires Windows 95 or Windows NT version 4.0 operating 

system or later. Both ArcExplorer 2.0 and MapSheets Express 

1.3 need 16 MB RAM and an IBM/PC or compatible system 

with 486-class processor or better.

bldr cd

Boulder River Watershed CD-ROM

The directory structure for the data and information 

contained on the Boulder River watershed CD-ROM is shown 

in figure 7.

The rel_db directory contains the relational database 

version of the sample-site data collected for the study, and 

the mine-related site inventory compiled for the study. The 

directory itself contains a README.txt file which describes 

the contents of the directory, and a bitmap file (relationship_diagram.bmp) which is a diagram of all the tables in the 

relational database, and the relationships between them. The 

mdb subdirectory contains the Microsoft Access version of 

the relational database (BoulderAMLI.mdb), the ascii subdirectory contains relational database tables in the form of flat, 

ASCII files, and the meta subdirectory contains metadata for 

the relational database.

The gis_db directory contains three subdirectories 

(basecart, sitedata, and geosci), each of which contains different types of data in formats suitable for use in Geographic 

Information Systems. The basecart subdirectory contains 

base cartographic data used as reference for the other data. 

The basecart subdirectory itself contains a README.txt file 

describing the base cartographic data. Below this subdirectory, the eOO subdirectory contains Arclnfo export files of 

base cartographic data stored as Arclnfo coverages. The 

shape subdirectory contains ESRI shapefiles and .dbf files of 

the data contained in the Arclnfo coverages. The elev subdirectory contains a compressed tar file, which when uncompressed creates an Arclnfo workspace containing an elevation 

grid, and slope, aspect and shaded relief grids derived from 

the elevation grid. The elev subdirectory also includes TIFF 

image file representations of the elevation data, and TIFF

rel._db gis.

1

1 

db viewer

1

i 1

meta mdb ascii ArcExplorer MapSheetsJExpress

1 1

basecart sitedata geosci

1

sta eOO

H 1 1 1

shape elev drg meta eOO

1

1 1

shape dbf

1 1 

meta aep_project geo

1

ogy geochem geo

h rh H

3hys remc

1 i

. 1 >sens biologic

H Hh

eOO shape pdf eOO shape eOO shape geotiff eOO shape geotiff

Figure 7. Directory tree structure for the Boulder River watershed CD-ROM.

eOO shape
522 Environmental Effects of Historical Mining, Boulder River Watershed, Montana

images of legends for the elevation data image files. The meta 

subdirectory contains metadata for the data in the eOO, shape, 

and elev subdirectories. The drg subdirectory contains U.S. 

Geological Survey Digital Raster Graphic (DRG) image files 

for the eight 7.5-minute quadrangles which contain the majority of the data in the Boulder River watershed study.

The second subdirectory under the gis_db directory, 

the sitedata subdirectory, contains the sample-site and minerelated site data from the relational database, but in formats 

directly compatible with Geographic Information Systems. 

A README.txt file at the sitedata level provides descriptive 

information about the data stored beneath it. The eOO subdirectory contains the site data as Arclnfo export files of coverages 

and Arclnfo export files of INFO files. The shape subdirectory 

contains three site data layers (field sites, analysis sites, and 

mine-related sites) as ESRI shapefiles. The dbf subdirectory 

contains 11 tables which contain information about the sites, 

and data collected at the sites. These tables are in the form of 

.dbf files. The meta subdirectory contains metadata about the 

data in the eOO, shape, and dbf subdirectories.

The third subdirectory under the gis_db directory, the 

geosci subdirectory, contains geoscientific and hydrologic 

data sets, as well as a sample ArcExplorer project file. A 

README.txt file in the geosci subdirectory lists the contents 

of the directory. There are seven subdirectories: geology, 

geochem (geochemistry), geophys (geophysics), remosens 

(remote sensing), biologic, meta (metadata), and aep_project 

(ArcExplorer project file). The meta subdirectory contains 

metadata about all of the interpretive geoscientific data. In 

each of the data subdirectories, an eOO subdirectory contains 

data as Arclnfo export files of coverages, a shape subdirectory contains data as shape files, and a geotiff subdirectory 

(if one exists) contains data in the GeoTIFF format. The pdf 

subdirectory under the geology directory contains the geology 

map of Chapter Dl in a PDF format. It also contains a PDF of 

a fence diagram showing correlation of Quaternary deposits 

in Buckeye meadow, in the Basin Creek drainage, which is a 

second plate discussed in Chapter Dl. A PDF of the complete 

topographic base also is included in this directory.

The viewer directory contains two data viewer software 

packages. The directory itself contains a README.txt file 

which summarizes the directory's contents. There are two subdirectories: ArcExplorer and MapSheets_Express. The ArcExplorer subdirectory contains a file (ae2setup.exe) which is an 

executable file that allows one to install the ArcExplorer 2.0 

data viewer software. The ArcExplorer.pdf file, created when 

the ae2setup.exe file is run, is a User Guide for ArcExplorer 

which includes a tutorial. Similarly, the MapSheets_Express 

subdirectory contains an executable file (mxsetup.exe) that 

allows one to install the MapSheets Express 1.3 data viewer 

software. The Readme.txt file, created when the mxsetup.exe 

file is run, provides various types of information about the 

MapSheets Express program.

An ArcExplorer project file (boulder_aml.aep, located 

in the /bldr_cd/gis_db/geosci/aep_project directory on the 

CD-ROM) is available as an example of how to use the

ArcExplorer software to display and use the data on the CDROM. The data files have been organized, and their attributes 

have been displayed, in the legend defined in the project file.

References Cited

Becraft, G.E., Pinckney, D.M., and Rosenblum, Sam, 1963, 

Geology and mineral deposits of the Jefferson City quadrangle, Jefferson, and Lewis and Clark Counties, Montana: 

U.S. Geological Survey Professional Paper 428, 101 p.

Desborough, G.A., Briggs, PH., and Mazza, N., 1998, Chemical and mineralogical characteristics and acid-neutralizing 

potential of fresh and altered rocks and soils of the Boulder 

River headwaters in Basin and Cataract Creeks of northern 

Jefferson Co., Montana: U.S. Geological Survey Open-File 

Report 98-0040, 21 p.

Fey, D.L., and Church, S.E., 1998, Analytical results for 

42 fluvial tailings cores and 7 stream sediment samples 

from High Ore Creek, northern Jefferson County, Montana: 

U.S. Geological Survey Open-File Report 98-0215, 49 p.

Fey, D.L., and Church, S.E., 1999, Analytical results for 

35 mine-waste tailings cores and six bed sediment samples, 

and an estimate of the volume of contaminated materials at 

Buckeye meadow on upper Basin Creek, northern Jefferson 

County, Montana: U.S. Geological Survey Open-File Report 

99-0537, 59 p.

Fey, D.L., Church, S.E., and Finney, C.J., 2000, Analytical results for the Bullion Mine and Crystal Mine waste 

samples and bed sediments from a small tributary to Jack 

Creek and from Uncle Sam Gulch, Boulder River watershed, Montana: U.S. Geological Survey Open-File Report 

00-0031,71 p.

Fey, D.L., Desborough, G.A., and Finney, C.J., 2000, Analytical results for total-digestions, EPA-1312 leach, and net 

acid production for twenty-three abandoned metal-mining 

related wastes in the Boulder River watershed, northern 

Jefferson County, Montana: U.S. Geological Survey OpenFile Report 00-0114, 17 p.

Fey, D.L., Unruh, D.M., and Church, S.E., 1999, Chemical 

data and lead isotopic compositions in stream-sediment 

samples from the Boulder River watershed, Jefferson 

County, Montana: U.S. Geological Survey Open-File Report 

99-0575, 147 p.

Nimick, D.A., and Cleasby, T.E., 2000, Water-quality data for 

streams in the Boulder River Abandoned Mine Lands Initiative study area: U.S. Geological Survey Open-File Report 

00-0099, 70 p.
Digital Databases for the Boulder River Watershed 523

Ruppel, E.T., 1963, Geology of the Basin quadrangle, Jefferson, Lewis and Clark, and Powell Counties, Montana: U.S. 

Geological Survey Bulletin 1151, 121 p.

Smith, B.D., Labson, V.F., and Hill, Pat, 2000, Airborne 

geophysical survey in the Boulder River watershed, Jefferson and Lewis and Clark counties, Montana: U.S. Geological Survey Open-File Report 00-240, one CD-ROM.

Unruh, D.M., Fey, D.L., and Church, S.E., 2000, Chemical 

data and lead isotopic compositions of geochemical baseline 

samples from streambed sediments and smelter slag, lead 

isotopic compositions in fluvial tailings, and dendrochronology results from the Boulder River watershed, Jefferson 

County, Montana: U.S. Geological Survey Open-File Report 

00-0038, 14 p.

Verplanck, P.L., Nordstrom, O.K., and Taylor, H.E., 1999, 

Overview of rare earth element investigations in acid waters 

of U.S. Geological Survey abandoned mine land watersheds: U.S. Geological Survey Water-Resources Investigations Report 99-4018, p. 83-92.

GlO U-S- GOVERNMENT PRINTING OFFICE 2005-774-303