Potential for Successful Ecological 

Remediation, Restoration, and Monitoring

By Susan E. Finger, Stanley E. Church, and Paul von Guerard

Chapter F of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Animas River Watershed, San Juan County, Colorado

Edited by Stanley E. Church, Paul von Guerard, and Susan E. Finger

Professional Paper 1651

U.S. Department of the Interior

U.S. Geological Survey
Contents

Abstract .....................................................................................................................................................1067

Introduction...............................................................................................................................................1067

Purpose and Scope ........................................................................................................................1069

Remediation Activities in the Animas River Watershed Study Area ...............................................1069

Identifying Sites for Remediation ..........................................................................................................1073

Monitoring Strategies and Tools for Evaluation of Ecological Recovery .......................................1074

Monitoring Success in the Animas River Watershed Study Area ...................................................1075

Summary....................................................................................................................................................1077

References Cited......................................................................................................................................1078

Figure

 1. Map showing locations of sites remediated, Animas River watershed study 

area, 2004 .................................................................................................................................1070

Tables

 1. Summary of remediation projects completed, Animas River watershed study 

area, 2004 .................................................................................................................................1071

 2. Examples of biological components and corresponding parameters that may 

be measured to evaluate progress of ecological recovery .............................................1076
Abstract

Historical mining has adversely affected the water, sediment, and biological resources in the Animas River watershed 

study area. Remediation has been ongoing in the watershed 

since the early 1990s, and monitoring information suggests an 

improvement in water quality at several sites. Because a substantial amount of the metal load to the watershed is derived 

from weathering of rock that has not been disturbed by mining, recovery of the ecosystem to premining conditions is not 

feasible. The recovery goal is, therefore, to improve the overall 

health of the aquatic ecosystem and the surrounding landscape 

and reestablish a viable trout fishery. More than half the high 

priority sites identified by the U.S. Geological Survey have 

been remediated. Remediation has also occurred at 23 sites 

identified by the Animas River Stakeholders Group. Sources 

of dissolved copper, which represents a major ecological 

risk to trout in the river, have been reduced in areas such as 

Mineral Creek. Some recovery of the aquatic community is 

occurring at specific sites. However, copper and several other 

constituents remain near 1994 to 1996 baseline concentrations 

at the A72 gauging station on the Animas River, which best 

reflects the effects of upstream remediation. Additional activities such as rehabilitation and restoration might be appropriate 

to enhance the ecological recovery.

Introduction

Historical mining has resulted in contamination of land, 

water, and biological resources in many parts of the Animas 

River watershed study area. Other chapters in this volume 

have characterized the extent and severity of this contamination (Nash and Fey, Chapter E6; Mast and others, Chapter E7; 

Kimball and others, Chapter E9; Wright, Simon, and others, 

Chapter E10; Leib and others, Chapter E11; Church, Fey, and 

Unruh, Chapter E12; Besser and Brumbaugh, Chapter E18; 

Anderson, Chapter E20). In general, historical mining and 

associated activities in the Animas River watershed study area 

have substantially degraded the water quality and adversely 

altered the aquatic habitat, resulting in severely impaired 

biological communities in a major portion of this complex 

area. In addition, weathering of sulfide minerals in mines 

and in deposits of mine wastes has increased acid drainage 

(Nash and Fey, this volume; Mast and others, this volume). 

A substantial volume of mill tailings was also released into 

the surface streams and has physically and chemically altered 

the substrate, resulting in a loss of productive aquatic and 

riparian habitat. Historically, the only native fish species 

known to occur in the Animas River watershed study area 

was the Colorado River cutthroat trout (Oncorhynchus clarkii 

pleuriticus), although one account suggested that the mottled 

sculpin (Cottus bairdi), a species that occurs commonly in 

downstream reaches, may have occurred in portions of the 

watershed study area. An early account of the area by ichthyologist David Starr Jordan (1891) referred to deep pools full 

of trout in the Animas River canyon. At present, mining activities have degraded stream conditions (Bove and others, this 

volume, Chapter E3), and little to no aquatic life occurs in the 

upper Animas River, the entire length of Cement and Mineral 

Creeks, and several smaller tributaries. South Fork Mineral 

Creek and several tributaries of the upper Animas River, which 

drain basins that provide substantial acid-neutralizing capacity, 

support populations of brook trout and a even few cutthroat 

trout. The Animas River between Maggie Gulch and Cement 

Creek in Silverton supports brook trout and a substantial invertebrate community, suggesting that water and habitat quality in this reach is improving. The Animas River watershed 

study area is a highly complex system whose complexity is 

increased by more than 5,300 inactive mine, mill, and prospect 

sites (Church, Mast, and others, this volume, Chapter E5). 

Planning for the ecological recovery of this system requires an 

understanding of premining baseline conditions as well as the 

hydrological processes, the geological and geochemical characteristics, and the biological limitations of this watershed. 

Although the scope of the scientific investigations contained 

in this volume will not be feasible for all basins containing mining-affected sites, the many parameters measured in 

these studies can be used to develop models that will guide 

the outcome of remedial and restoration activities in other 

watersheds.

Chapter F

Potential for Successful Ecological Remediation, 

Restoration, and Monitoring

By Susan E. Finger, Stanley E. Church, and Paul von Guerard
Remediation, reclamation, rehabilitation, and restoration 

are all terms referring to activities that attempt to alter and 

improve the biological and physical conditions at a degraded 

site. These terms are closely linked, but they refer to distinct 

phases in the process of ecological recovery. Because of the 

high cost associated with reparation of ecologically impaired 

areas, an understanding of these processes and how they 

may complement each other is critical to success. Practiced 

independently, these activities will lead to different endpoints 

in ecological succession, and it is thus important to clearly 

delineate goals and objectives for watershed recovery during 

the initial project planning process.

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 surrounding landscape. Remediation can also involve the reduction or elimination of metal and acid loading from draining mines. The actual 

cleanup activities can result in ecological injury and should be 

addressed early in the planning process, because some remedial actions may preclude successful ecological restoration. 

Successful remedial actions result from risk-management decisions based on cost-benefit analysis that evaluates the potential 

outcome of several alternatives. These alternatives range from 

a simple “no action” alternative to a much more costly and 

complicated one such as complete removal of contaminated 

material. Performance measures for successful remediation 

might include:

• Major sources of contamination in the watershed 

have been reduced or eliminated

• Trace-element concentrations in water no longer 

exceed acute or chronic criteria for aquatic life

• Trace-element concentrations in streambed sediment 

no longer exceed sediment-quality guidelines

• Stream banks have been stabilized and erosion has 

been minimized, or

• Flood-plain revegetation has reduced or eliminated 

the transport of contaminated sediment, mine waste, 

or mill tailings downstream.

Reclamation is a term commonly used in association 

with mined lands. The main objective of reclamation is the 

stabilization of terrain, improvement in landscape appearance 

and esthetics, and the return of land to what might regionally 

be defined as a useful purpose. Revegetation is usually a component of reclamation, but revegetation commonly includes 

establishing only a few species for the main purpose of site 

stabilization to reduce erosion and runoff, rather than restoring 

ecological value.

Rehabilitation is most similar to restoration in that rehabilitation planning uses preexisting ecological conditions as 

models or references. Rehabilitation seeks to recreate ecosystem processes, productivity, or services, but does not emphasize the establishment of preexisting species composition and 

diversity. Specifically, rehabilitation does not attempt to return 

the landscape to its prior baseline state or, in this case, does 

not attempt to reestablish premining ecosystems. As is true of 

the Animas River watershed study area, restoration may be 

impossible in many mining-affected areas of the West, because 

of anthropogenic and natural factors that may limit ecological 

recovery. However, if remediation, reclamation, and rehabilitation are ecologically based, they will lead to more timely and 

ecologically functional restoration.

Restoration is the process of returning an ecosystem to 

a close approximation of its historical or premining condition 

prior to physical or chemical disturbance (National Research 

Council, 1992). Therefore, premining conditions are the 

ideal starting point. Although an injured ecosystem may 

never return to conditions identical to those in the past, it can 

recover to conditions that are functionally equivalent to those 

of the previous environment. The underlying goal of restoration is ecological recovery. This goal must be realistic given 

the geologic, hydrologic, and biologic characteristics of the 

ecosystem. Therefore, in an area affected by historical mining, 

an understanding of premining conditions in the watershed is 

required. In the Animas River watershed study area, weathering and release of metals from hydrothermally altered, 

unmined areas (Bove and others, this volume) limited the 

biological community in some areas. Such complexity caused 

by geology and hydrology must be understood in any restoration effort. 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 actions as 

creation of viable fisheries habitat, restocking a stream with 

fish, reintroduction of aquatic invertebrates and terrestrial 

species, or revegetation of the flood plain to compensate for 

ecological losses. Performance measures for successful restoration might include:

• Self-sustaining populations of fish occur throughout 

the watershed

• Colonies of nesting birds are successfully reproducing, 

or

• A healthy riparian corridor is present.

Both restoration and rehabilitation can produce a system with 

a high degree of ecological integrity.

Monitoring is a critically important but an often undervalued and underutilized tool for determining the success 

of remedial measures and evaluation of ecological recovery. 

Adequate and appropriate monitoring procedures are the most 

direct measure of the success of remedial strategies and the 

1068 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Ecological Remediation, Restoration, and Monitoring 1069

resulting rates of recovery for populations, communities, or 

ecosystems. However, monitoring rarely receives the attention 

and funding necessary for development and implementation 

of a successful restoration plan. Kondolf and Micheli (1995) 

indicate that despite increased commitment to stream restoration, post-restoration monitoring has generally been neglected. 

Monitoring plans need not be exhaustive or complex. However, they must be designed to address specific objectives and 

applied over the entirety of the project in a consistent manner. 

They will not only offer a measure of success for the project, 

but they will also provide information useful in predicting 

restoration outcomes at other sites.

Purpose and Scope

In this chapter, we describe the factors that influence successful ecological restoration and recovery of the 

aquatic community in the Animas River watershed study 

area. Successful restoration is a result of 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. Although the desire of 

land-management agencies may be for ecological recovery to 

a preexisting baseline or premining condition, this may not be 

economically attainable or feasible. Remediation or removal 

of the contaminated materials and reduction of the amount 

of contamination in the stream may result in a measurable 

improvement of water quality. However, the biological community may need additional changes before it can respond. 

Numerous factors must be considered before the restoration 

alternative with the highest probability of success can be 

identified. The success of any restoration effort can be best 

documented through 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 remediation and 

restoration efforts.

Remediation Activities in the Animas 

River Watershed Study Area

More than 30 years ago, the Colorado Division of 

Wildlife attempted to replenish the fisheries in the Animas 

River by stocking rainbow trout, brook trout, and brown trout 

in the watershed. Observational data suggest that neither 

rainbow nor brown trout were able to reproduce upstream 

from the Animas River canyon reach, but brook trout, which 

are more tolerant of low pH and toxic metal exposure than the 

other species, have persisted. Brook trout is the predominant 

fish species in the Animas River watershed study area, despite 

no documented stocking of this species since 1985. By the 

early 1990s, interest in reducing the environmental effects of 

the many inactive mines and prospects in the Animas River 

watershed study area began. In 1991–1992, a preliminary 

water-quality sampling of the major streams in the Animas 

River watershed study area was coordinated by the Colorado 

Department of Health and Environment. The Colorado 

Division of Mines and Geology, the USDA Forest Service, 

and the Bureau of Land Management (BLM) inventoried and 

ranked inactive mines in the study area (Wright, Simon, and 

others, this volume).

The Animas River Stakeholders Group (ARSG) and 

Federal land-management agencies began planning for 

cleanup activities in the mid-1990s. Sunnyside Gold, Inc., 

implemented a number of remediation activities in the watershed study area as a condition for terminating its discharge 

permit at the American tunnel (site # 96, fig. 1). Sunnyside 

Gold, Inc., has completed numerous remediation projects, 

including removal of tailings deposits in the upper Animas 

River between Eureka and Howardsville, removal of mine 

dumps at the Longfellow mine (site # 77) and Koehler tunnel 

(site # 75), construction of hydrologic controls to prevent 

surface runoff from flowing overland through dump and tailings piles, and the plugging of the numerous portals and adits 

(fig. 1; table 1). Most of this remediation work on Sunnyside 

properties was completed by 1996. Remediation activities 

by BLM include mine drainage collection and diversion at 

Joe and Johns mine (site # 87), acid-mine drainage collection 

and hydrologic controls at the Lark mine (site # 86), acid-mine 

drainage collection and passive wetland treatment at the Forest 

Queen mine (site # 195), hydrologic controls and capping of 

the mine dump at the May Day mine (site # 181), acid-mine 

drainage collection and removal of waste rock at the Bonner 

mine (site # 172), and the removal of tailings from the Animas 

River flood plain at the Lackawanna Mill site (site # 287). 

Other remediation work has been done by the San Juan 

Resource and Conservation District, Silver Wing Mining 

Company, Gold King mine, Office of Surface Mining, Salem 

Minerals, and Mining Remedial Recovery (William Simon, 

Animas River Stakeholders Group, written commun., 2005; 

Robert H. Robinson, Bureau of Land Management, written 

commun., 2005).

Remediation work that has been completed in the Animas 

River watershed study area through 2004 is summarized in 

figure 1 and table 1. Of the more than 5,300 mine, mill, and 

prospect sites, information in this volume suggests that about 

80 sites are responsible for 90 percent of the metal loads to 

surface water. Of the 39 priority sites identified by Nash and 

Fey (this volume), 9 (23 percent) have been remediated. Of the 

61 high-priority sites identified by the ARSG, 14 (23 percent) 

have been remediated. The ARSG is actively working with 

Federal, State, and local funding sources to remediate these 

sites and reduce the metal loading in surface water in the 

watershed study area.
Howardsville

Gladstone

Eureka

Chattanooga

Animas

Forks

Silverton

107 48' 107 32'

37 

25'

37 

46'

107 40' o o o

o

o

'

0

0

1

2

3

4

5 MILES

6 8 KILOMETERS

Mineral Cre ek

Animas River

Cem ent C reek

An

mi as

River

Mines

Watershed study area

 boundary

EXPLANATION

South Fork

Mill tailings

Remediation done with

Private funds

Public and private funds

Public funds

Mayflower

Mill

Sunnyside

mine

Sunnyside

Flotation 

Mill

286

510

509

508

507

234

181

195

164

161

113

116 125

57

49

96

95

111

31

83

82

86

87

148

147

120

84

80

79

75

76

77

172

141

13

A72

A68

CC48

M34

A72 Gauging station

SA

Animas River

watershed 

study area

C O L O R A D O

Durango

Figure 1. Locations of sites remediated in the Animas River watershed study area through October 2004 (data from table 1, 

William Simon, ARSG, written commun., 2004). Sites designated by sources of funding for remediation work (private, public, or both). 

Numbers are AMLI_MINE_ID site numbers in the Animas River watershed database (Church, Mast, and others, this volume, Chapter E5; 

Sole and others, this volume, Chapter G). SA, San Antonio mine (table 1).

1070 Environmental Effects of Historical Mining, Animas River Watershed, Colorado

52'
Ecological Remediation, Restoration, and Monitoring 1071

Table 1. Summary of remediation projects completed, Animas River watershed study area, 2004.

[San Juan R. C. & D., San Juan County Resource and Conservation District; ARSG, Animas River Stakeholders Group; U.S. OSM, U.S. Department of the 

Interior, Office of Surface Mining; U.S. BLM, U.S. Department of the Interior, Bureau of Land Management; U.S. FS, U.S. Department of Agriculture (USDA) 

Forest Service; mine site locations from Church, Mast, and others, this volume; mill site locations from Jones, this volume, Chapter C; yd3

, cubic yards of 

material; data provided by William Simon, Animas River Stakeholders Group, written commun., 2004, and by Robert H. Robinson, BLM, written commun., 

2005. Site numbers are AML_MINE_ID numbers in the Animas River watershed database]

Project 

sponsor

Project 

site

Location

(fig. 1)

Type of 

remediation

Date project

completed

Improvement

(actual or anticipated)

Private funds

Sunnyside 

Gold, Inc.

Lead Carbonate 

Mill. 

Gladstone, South Fork 

Cement Creek, site # 95.

Removal of 27,000 yd3

 of mill 

tailings from stream bank.

1991 Reduce loading of metals to Cement 

Creek and erosion transport of mill 

tailings. 

Sunnyside 

Gold, Inc.

Mayflower Mill Mayflower Mill tailings, 

sites # 507–509.

Re-contour inactive mill tailings 

ponds and cap; 625,000 yd3

 of mill 

tailings and overburden moved. 

1992 Mined land remediation—reduce loading of metals to Animas River and 

erosion transport of mill tailings.

Sunnyside 

Gold, Inc.

Lake Emma

Sunnyside Basin

Sunnyside mine collapse, 

site # 116.

Fill mine subsidence at Lake Emma, 

remove 240,000 yd3

 mine waste 

and re-contour. 

1993 Mined land remediation and reduce 

loading of metals to Animas River.

Sunnyside 

Gold, Inc.

American tunnel 

waste dump.

Gladstone, on bank of 

South Fork Cement 

Creek, site # 96.

Remove 90,000 yd3 waste dump and 

underlying historical mill tailings.

1995 Mined land remediation and reduce 

loading of metals to Cement Creek 

and erosion transport of mill 

tailings. 

Sunnyside 

Gold, Inc.

Sunnyside Eureka 

Mill, tailings at 

town site.

On banks and in flood 

plain of Animas 

River, downstream 

of site # 164. 

Remove 112,000 yd3

 of mill tailings 1996 Reduce loading of metals to Animas 

River and erosion transport of mill 

tailings. 

Sunnyside 

Gold, Inc.

Sunnyside mine 

hydraulic seal 

project.

Sunnyside mine, sites 

# 116, # 120, # 96.

Bulkheads placed in Sunnyside mine 

to restore hydrologic regime to 

approximate premining hydrology 

and eliminate drainage from adits. 

1997 Place mine workings under water to 

reduce oxidation, restore groundwater movement around mine 

workings and eliminate need for 

perpetual water treatment.

Sunnyside 

Gold, Inc.

American tunnel American tunnel at 

Gladstone, site # 96. 

Divert and treat Cement Creek, 

fill Sunnyside mine pool to 

mitigate any short-term impacts 

of remediation projects. 

8/1996 to 

12/1999

Reduce loading to Animas River to 

offset any short-term impacts of 

remediation of other sites.

Sunnyside 

Gold, Inc.

Mayflower Mill 

tailings, Boulder 

Creek. 

Mill tailings at site # 509, 

flood plain of Boulder 

Creek. 

Remove 5,700 yd3

 of mill tailings 1997 Reduce loading of metals to Animas 

River and erosion transport of mill 

tailings.

Sunnyside 

Gold, Inc.

Ransom mine adit. Eureka town site, 

site # 161.

Bulkhead seal to stop deep mine 

drainage and remediate portal. 

1997 Restore hydrologic regime and reduce 

rate of ore oxidation by placing 

mine workings under water to 

reduce metal loading to Animas 

River. 

Sunnyside 

Gold, Inc.

Gold Prince mine 

waste and mill 

tailings.

Placer Gulch, site # 49. Bulkhead seals to stop deep mine 

drainage, consolidate mine 

waste and mill tailings, removed 

6,000 yd3

 mine waste and construct upland diversions.

1997 Reduce exposure to water to reduce 

metal loading to Animas River.

Sunnyside 

Gold, Inc.

Longfellow-Koehler Headwaters of Mineral 

Creek, Longfellow 

mine, site # 77; Junction 

mine, site # 76; Koehler 

tunnel, site # 75.

Remove Koehler mine-waste dump 

(32,100 yd3

), consolidate Junction 

mine dump and Longfellow mine 

dump and cap, capture adit drainage, construct diversions, conduct 

feasibility study of wetland 

treatment of Koehler tunnel acidic 

drainage. 

1997 Reduce metal loading to Mineral 

Creek and erosion transport of 

mine waste.

Sunnyside 

Gold, Inc.

Pride of the West 

mill tailings.

Howardsville, site # 234. Remove 84,000 yd3

 of mill tailings 1997 Reduce metal loading to Animas 

River and transport of mill tailings 

by erosion.

Sunnyside 

Gold, Inc.

Sunnyside mine Sunnyside mine, 

American tunnel 

treatment, site # 96.

Inject 652 tons of hydrated lime 

into the Sunnyside mine pool to 

provide increased alkalinity and 

reduce oxygen available in mine 

for pyrite oxidation.

1997 Improve initial conditions as water 

table is restored by installing bulkhead to stop acidic mine drainage.
Project 

sponsor

Project 

site

Location

(fig. 1)

Type of 

remediation

Date project

completed

Improvement

(actual or anticipated)

Private funds—Continued

Sunnyside 

Gold, Inc.

Mayflower 

Hydrological 

Control.

Mayflower Mill tailings 

pond #1, site # 507.

Capture and divert three upland 

drainages that provide supply to 

ground water upgradient of mill 

tailings. 

1999 Minimize potential for contact of 

runoff with mill tailings and reduce 

potential for metal loading to 

Animas River. 

Sunnyside 

Gold, Inc.

Mayflower mill 

tailings pond #4. 

Mayflower Mill tailings 

pond #4 drainage modification, site # 510.

Install lined diversion ditch to capture 

surface runoff and prevent infiltration through mill tailings. 

1999 Minimize potential for contact of 

runoff with mill tailings and reduce 

potential for metal loading to 

Animas River.

Sunnyside 

Gold, Inc.

Mayflower mill 

tailings pond #4.

Divert ground water 

upgradient from mill 

tailings pond #4, 

site # 510.

Capture ground water and divert 

around mill tailings impoundment, 

tailings pond #4.

1995,

1999

Minimize potential for contact of 

ground water with mill tailings and 

reduce potential for metal loading 

to Animas River.

Sunnyside 

Gold, Inc.

Power plant 

flats.

Animas River near old 

power plant, east of 

site # 509.

Removed mill tailings to tailings 

pond #4, site # 510.

2003 Reduce metal loading to Animas 

River.

Sunnyside 

Gold, Inc.

Mogul mine 

bulkhead.

Cement Creek, site # 31 Install bulkhead in Mogul mine to 

stop acidic drainage.

2003 Reduce metal loading to Cement 

Creek.

Sunnyside 

Gold, Inc.

Koehler tunnel 

bulkhead.

Koehler tunnel (site # 75) Install bulkhead in Koehler tunnel 

to stop acidic drainage.

2003 Reduce metal loading to Mineral 

Creek.

Sunnyside 

Gold, Inc.

Reactive barrier Animas River flood 

plain below Mayflower 

Mill, mill tailings 

pond #4 (site # 510).

Passive treatment of contaminated 

ground water before entering 

Animas River.

2003 Reduce metal loading to Animas 

River.

Gold King 

Mines, 

Inc.

Gold King mine North Fork Cement Creek, 

site # 111.

Hydrologic controls for workings 

and mine waste.

1998 Reduce metal loading to North Fork 

Cement Creek.

Gold King 

Mines, 

Inc.

Gold King mine North Fork Cement Creek, 

site # 111.

Pipe Gold King adit discharge to 

Gladstone for active treatment 

of acidic drainage.

2002 Reduce metal loading to Cement 

Creek.

Mining 

Remedial 

Recovery.

Sunbank group Placer Gulch, site # 57 Anoxic drain, settling pond, waste 

consolidation, bulkhead.

1995 Raise pH from draining adit, reduce 

metal loading to Animas River from 

adits and mine waste.

Salem 

Minerals.

Mammoth tunnel Cement Creek, site # 148 Settling ponds for mine drainage 1999 Reduce iron load to Cement Creek.

Silver Wing 

Mining 

Co.

Silver Wing mine Animas River, site # 125 Collect acidic mine water, install 

hydrologic controls.

1995 Divert acidic drainage around minewaste dump, reduce metals loading 

to Animas River.

Private and public funds

Silver Wing 

Mining 

Co.

Silver Wing mine Animas River, site # 125 Install anoxic drain, settling pond, 

and bioreactor.

2000 Reduce metal loading to Animas 

River.

San Juan R. 

C. & D., 

ARSG.

Carbon Lake–

Phase I.

Carbon Lake mine, 

Mineral Creek, 

site # 80. 

Removal of 1,900 yd3 of waste rock 

from stream channel.

Phase I– 

1999

Reduce loading of metals, especially 

cadmium, copper, iron, lead, manganese, and zinc, to Mineral Creek.

San Juan R. 

C. & D., 

ARSG.

Carbon Lake—

Phase II. 

Koehler tunnel, 

Mineral Creek, 

site # 75. 

Reduce flows from Koehler tunnel 

by reducing infiltration into 

surface mine workings.

Phase II– 

2001 

Reduce metals loading to Mineral 

Creek by reducing infiltration of 

water into old mine workings.

San Juan R. 

C. & D., 

ARSG.

Carbon Lake—

Phase III. 

Congress mine, 

Mineral Creek, 

site # 79. 

Complete removal of Congress 

mine-waste dump.

Phase III– 

2003 

Reduce metals loading to Mineral 

Creek by removal of mine wastes 

and beneficiation.

San Juan R. 

C. & D., 

ARSG.

Carbon Lake—

Phase III. 

Carbon Lake, site # 80, 

ditch reclamation.

Diversion ditch, wetlands, and stream 

reclamation, water rights purchased 

and water diverted to Uncompahgre 

River watershed restored to 

Mineral Creek drainage.

Phase III– 

2003 

Reduce metals loading to Mineral 

Creek by removal of mine wastes 

and site beneficiation.

San Juan R. 

C. & D., 

ARSG.

Galena Queen and 

Hercules mines.

Prospect Gulch, sites # 82 

and # 83.

Remove mine waste, install hydrologic controls, add soil amendments, and revegetation.2001 Elimination of surface water leaching 

of toxic metals. Reduce metal loading to Cement Creek.

Table 1. Summary of remediation projects completed, Animas River watershed study area, 2004.—Continued

1072 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Ecological Remediation, Restoration, and Monitoring 1073

Project 

sponsor

Project 

site

Location

(fig. 1)

Type of 

remediation

Date project

completed

Improvement

(actual or anticipated)

Private and public funds—Continued

San Juan R. 

C. & D., 

ARSG.

San Antonio 

Project. 

San Antonio mine Install hydrologic controls, remove 

wastes from stream, consolidate 

wastes and neutralize, revegetation.

2004 Reduce metal loading and acidity to Mineral Creek; stabilize 

site, remove mine wastes, restore 

streambed and riparian habitat.

San Juan R. 

C. & D., 

ARSG.

Handies Peak 

Project.

Lucky Jack mine, site # 13 Hydrologic controls, remove wastes 

from fen, consolidate, neutralize, 

and revegetation; adit and shaft 

closures.

2004 Reduce metal loading and acidity to 

upper Animas River; uncover fen 

and restore.

U.S. BLM 

and Duke 

Energy.

Henrietta mine Prospect Gulch, site # 84 Hydrologic controls and mine waste 

removal.

2004 Reduce metal loading to Cement 

Creek.

Public funds

U.S. OSM Galena Queen mine Prospect Gulch, site # 82 Waste consolidation and hydrologic 

controls.

1998 Reduce surface water leaching of toxic 

metal loading to Cement Creek.

U.S. BLM Joe & Johns mine Prospect Gulch, site # 87 Mine drainage collection and 

diversion.

1999 Collect acidic drainage for later treatment project development, reduce 

metal loading to Cement Creek.

U.S. BLM Lark mine Prospect Gulch, site # 86 Install collection system for acidic 

water, hydrologic controls.

1999 Collect acidic drainage for possible 

treatment, remove surface water 

from site, reduce metal loading 

to Cement Creek.

U.S. BLM Forest Queen mine Animas River near Eureka, 

site # 195.

Install collection system for 

acidic water and passive wetland 

treatment.

1999 Reduce metal loading to Animas 

River.

U.S. BLM May Day mine Cement Creek, site # 181 Hydrologic controls, cap top of 

mine-waste pile.

1999 Reduce surface water leaching 

of toxic metals.

U.S. BLM Lackawanna Mill 

tailings.

Animas River near 

Silverton, site # 286, 

site # 181.

Removal of mill tailings from 

flood plain to May Day dump 

for consolidation and capping.

2000 Reduce metal loading to Animas 

River.

U.S. BLM Elk tunnel Cement Creek, site # 147 Install limestone drain 2003 Reduce metal loading to Cement 

Creek.

USDA

FS.

Bonner mine Middle Fork Mineral 

Creek, site # 172.

Install collection system for acidic 

water and diversion, move waste 

rock from avalanche path.

2000 Reduce metal loading to Mineral 

Creek.

USDA

FS.

Brooklyn mine Mineral Creek, site # 141 Hydrologic controls and minewaste removal.2004 Reduce metal loading to Mineral 

Creek.

Table 1. Summary of remediation projects completed, Animas River watershed study area, 2004.—Continued

Identifying Sites for Remediation

One of the major goals of the Abandoned Mine Lands 

(AML) Initiative was to identify and prioritize contaminated 

sites for remediation that would provide the greatest benefit to 

the ecological recovery of the watershed study area. Because 

fiscal resources are limited, land-management agencies must 

invest their funds where remediation has the highest probability 

of success. The geographic extent of the Animas River watershed study area, the large number of inactive mine, mill, and 

prospect sites, and the complexities of the geology and hydrology of the region increased the challenges of identifying specific cleanup sites that will contribute to the most efficient and 

effective recovery of the aquatic system. In prioritizing sites in 

the Animas River watershed study area, planners must acknowledge that both mined and unmined areas contribute significantly 

to the in-stream load for the major constituents of concern.

Prioritizing mine-site remediation at the watershed scale 

requires an understanding of how multiple sources of acidic, 

metal-rich drainage affect the streams in the watershed and 

how the stream will respond if those sources are reduced or 

removed. Kimball and others (this volume) have demonstrated 

that using a combination of tracer-dilution and synoptic waterquality sampling provides the information on discharge and 

concentration necessary to evaluate mass chemical loading 

both spatially and temporally in an aquatic ecosystem. Massloading studies are also useful when those loads enter the 

environment directly from a specific source such as a tributary 

or when they are released in a diffuse manner through ground 

water. For example, this approach was instrumental in determination of remedial measures for the Mineral Creek basin 

by demonstrating that the Mineral Creek basin was a primary 

source of copper for the Animas River and thus a critical 

target for remediation. Eight sites in Mineral Creek have been 
remediated by removal of mine waste (table 1), and as a result, 

copper concentration and loading were reduced (J.R. Owen, 

written commun., 2005; http://www.waterinfo.org/arsg/). 

Identification and minimizing of this source of copper were 

also important in terms of ecological recovery, as the assessment of surface water-quality effects on aquatic life had demonstrated that dissolved copper posed the greatest risk to brook 

trout, the dominant species of fish in streams (Besser and 

others, this volume, Chapter D). Remediation of the Mineral 

Creek basin also resulted in a reduction in zinc and cadmium 

concentrations.

Reactive transport models developed during the AML 

Initiative provide an approach to anticipate changes that 

could occur in the water column following implementation of remedial measures. These models not only predict 

the change at a specific site, but also can assess potential 

downstream effects on loading. Evaluation of different 

remedial alternatives using these reactive-transport models 

can influence decisions prior to implementation of expensive 

engineering solutions. Information on tracer-dilution discharge and synoptic sampling from the Mineral Creek basin 

described previously was used to evaluate two water-treatment 

alternatives (Runkel and Kimball, 2002). Option 1 simulated 

conditions where only ferric (not ferrous) iron was removed. 

Option 2 evaluated total removal of iron. The model indicated 

that both options increased pH and reduced total and dissolved 

concentrations of aluminum, arsenic, copper, and ferrous 

and ferric iron. Dissolved lead concentrations were reduced 

by 18 percent in option 1. Lead and iron were removed in 

option 2. However, the model for option 2 indicates that the 

removal of all iron will ultimately result in increased loading 

of lead in Mineral Creek because downstream lead sources 

will not be attenuated by sorption to iron colloids. In addition, 

the model indicated that zinc concentrations would not be 

reduced by either option. Given the long-term costs of operating a water-treatment facility, these predictive models provide 

an extremely important tool for cost-benefit analysis in the 

decision-making process.

In prioritizing sites, scientists and land-use managers 

must also consider the biological community that is dependent on the habitat for survival. Using a risk-based approach, 

Besser and others (this volume) categorized areas in the 

watershed as low risk, moderate risk, high risk, and severe 

risk. Focusing on remedial measures for stream improvement in regions of moderate to high risk offers an optimum 

potential for measurable biological response. Besser and 

others (this volume) and Anderson (this volume) both offer 

biologically based indices to rank or assess the environmental 

impact of mining. Indices such as these that measure injury 

to the biological resources also provide a means to gauge 

recovery after remedial or restoration options have been 

implemented.

Monitoring Strategies and Tools 

for Evaluation of Ecological Recovery

Monitoring is an essential tool for evaluation of the success of remediation and restoration efforts and assessment of 

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: used to evaluate project 

implementation and ecological effectiveness

• Trend assessment: includes an extended sampling plan 

to identify changes across spatial and temporal scales

• Risk assessment: used to identify hazard sources, causal 

relationships, and resource injury within an ecosystem

• Baseline characterization: used to quantify ecological 

conditions prior to an actual disturbance. It may also 

be used to collect information at a reference site to estimate premining baseline conditions for a comparable 

disturbed habitat.

The type and extent of monitoring necessary will depend 

on specific management objectives (Kondolf, 1995). In the 

case of a historical mining area, the strategy most appropriate 

for evaluation of the success of remediation and restoration 

would be performance evaluation. The three components of 

performance evaluation include:

• Implementation monitoring

• Effectiveness monitoring

• Validation monitoring.

Implementation monitoring addresses the question: 

“Were the remediation and restoration measures done correctly?” Exploring this relatively simple 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 be sensitive enough to 

detect changing conditions and have statistical validity. This 

level of monitoring is more time consuming than implementation monitoring. However, if monitoring data indicate that 

goals are not being met, problems can be evaluated in a timely 

manner, and adjustments can be made to the remediation and 

restoration designs.

Validation monitoring addresses the question: “Are the 

underlying assumptions used in the remediation and restoration designs and the cause-effect relations correct?” This is 

1074 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Ecological Remediation, Restoration, and Monitoring 1075

the most costly level of monitoring and 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 specific scientific expertise to design and implement.

Monitoring involves the 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, 

in this section, we present a refined list of the types of monitoring variables that are 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 environmental conditions, and therefore, understanding the 

effect of remediation and restoration activities on biota is often 

the most important part of monitoring. Physical and chemical 

variables that may significantly affect the quality of aquatic 

habitat include temperature, turbidity, dissolved oxygen, pH, 

alkalinity/acidity, hardness, nutrients, streamflow, 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 trace-element concentrations in water, streambed sediment, 

and biota that during the assessment phase of the project have 

been identified as being impaired. For the chemical analysis 

of water, measurement of the fraction (total recoverable or 

dissolved) that relates specifically to national or State waterquality 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. In the 

Animas River watershed study area, this will not be possible 

in several stream reaches because of naturally acidic metalrich conditions or limited suitable physical habitat. Recovery 

following remediation may be achieved more efficiently by 

changes that would increase the quality of the substrate for the 

benthic community, expand and enhance the aquatic habitat 

to increase the reproductive success of trout, or alter physical 

conditions to provide expanded overwintering habitat for adult 

trout (Milhous, this volume, chapter E21). Successful recovery 

can only be documented through measurement of biological endpoints (table 2). Selection of biological measurements 

is generally determined by the response of the predominant 

species needed to achieve the restoration goals. For example, 

in the Animas River watershed study area, both the ARSG 

and 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, predominantly 

of brook trout, survival and health of individual fish (Karr, 

1981; Farag and others, 2004), trace-element concentrations 

in biofilm and invertebrates, and indices of health of the 

aquatic invertebrate community (Klemm and others, 1990; 

Pflakin and others, 1989). In addition, avian species such as 

the white-tailed ptarmigan, which occurs near Silverton, may 

also provide a means to evaluate ecosystem recovery. Larison 

and others (2000) correlated renal damage in ptarmigan with 

dietary exposure to cadmium and suggested that consumption of cadmium-contaminated willow (Salix spp.) from the 

Silverton area created potentially life threatening conditions 

for older ptarmigan. Monitoring the population status of these 

birds and evaluating the concentration of cadmium and the 

overall health of the kidney offers a means to assess watershed 

recovery. Given that the pathway of exposure appears to be 

through consumption of willow, monitoring the concentration 

of cadmium in willow leaf buds and in recently grown shoots 

and stems provides an indication of changes in the birds’ food 

source that might occur following remediation of the habitat.

Monitoring Success in the Animas 

River Watershed Study Area

Monitoring provides the information required to determine the changes in water and sediment quality and improvement in or deterioration of the status and health of the ecological community. Initial awareness of the impaired fisheries in 

the Animas River was documented through surveys conducted 

by Federal and State agencies in the 1960s and 1970s. In 

the reach of the Animas River upstream of Silverton, only 

one trout was recovered in an electrofishing survey in 1968 

(U.S. Department of the Interior, unpub. data, 1968). Beginning 

in 1973, twenty years of fish stocking by the Colorado Division 

of Wildlife provided no evidence of reproductive success in 

rainbow or brown trout. Only brook trout were successful. 

More recent surveys of fish and benthic macroinvertebrates 

(Peter Butler, Robert Owen, and William Simon, Unpublished 

report to Colorado Water Quality Control Commission, 2001; 

Anderson, this volume; Besser and Brumbaugh, this volume; 

Milhous, this volume) indicate that, although many parts of the 

study area remain adversely affected by water and habitat quality, some trout populations may show signs of recovery following site-specific remedial activities. South Fork Mineral Creek 

and several tributaries of the upper Animas River support brook 

and cutthroat trout. Brook trout also occur in the Animas River 

between Maggie Gulch and the confluence with Cement Creek. 

However, mining effects and continued drainage of naturally 

acidic water from hydrothermally altered areas in the headwaters (Bove and others, this volume) have resulted in little to no 

aquatic life in the Animas River upstream of Eureka and in the 

entire reach of both Mineral and Cement Creeks even prior to 

mining.
Water-quality monitoring has provided important insights 

into the effects of remedial measures. J.R. Owen (written 

commun., 2005; http://www.waterinfo.org/arsg/) has assessed 

progress towards meeting water-quality goals (established 

for the watershed study area by the Colorado Water Quality 

Control Commission) using water-quality data collected at the 

gauges from 1994 to 2004. During that 10-year period, waterquality samples were collected approximately at monthly 

intervals. A stream-flow regression model was used to account 

for changes in constituent concentrations with seasonal flow 

(Leib and others, 2003). The period between 1994 and 1996, 

prior to remediation in the watershed study area (table 1), 

provided baseline concentrations for this analysis. Changes 

in aluminum, cadmium, copper, zinc, manganese, and sulfate 

concentrations were measured at four USGS gauging stations 

in the watershed (A68, A72, CC48, and M34; fig. 1). To summarize the effects of remediation:

In the Mineral Creek basin, eight sites have undergone 

remediation (table 1), which has resulted in decreased concentrations of all constituents except manganese and iron. Iron 

remained near the baseline concentration, and the manganese 

concentration appears to experience a site-specific increase.

In the Cement Creek basin, remediation occurred at 

15 sites in the basin (table 1). Concentrations of aluminum, 

cadmium, manganese, and copper dropped markedly following initial water treatment at the Gladstone portal on Cement 

Creek, but metal concentrations have fluctuated around the 

baseline values since 1999, when water treatment was discontinued by Sunnyside Gold, Inc., at the American tunnel 

(site # 96). Sulfate concentrations dropped substantially after 

final installation of the plugs eliminated acid mine drainage 

from the American tunnel.

The upper Animas River basin was the major contributor 

of dissolved manganese and zinc loads in the Animas River. 

Sunnyside Gold, Inc., has completed major long-term remediation projects at multiple sites on their properties (table 1). 

Although manganese concentrations have remained elevated, 

zinc concentrations have decreased to baseline values. Cadmium concentrations have remained generally above baseline 

values.

The Animas River downstream of Silverton at the gauge 

(A72, fig. 1) integrates the effects of all upstream remediation efforts. It also is the point of compliance established by 

the Colorado Water Quality Control Commission for instream 

Table 2. Examples of biological components and corresponding parameters that may be measured 

to evaluate progress of ecological recovery.

Biological component Parameter

Primary productivity Periphyton or biofilm density

Aquatic macrophytes species and density

Concentration of trace elements

Aquatic invertebrate community Species composition

Numbers of individuals

Diversity

Biomass

Concentration of trace elements

Fish community Species composition

Age class distribution

Fish health assessment

Population density

Concentration of trace elements 

In-stream exposure experiments

Riparian wildlife/terrestrial community 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

Riparian vegetation Species composition

Condition

Successional changes

Soil toxicity assessment

1076 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Ecological Remediation, Restoration, and Monitoring 1077

concentrations of aluminum, cadmium, copper, iron, manganese, and zinc. At this location, cadmium and sulfate concentrations have fluctuated around the baseline values, whereas 

copper concentrations were below baseline values until 2004 

when concentrations increased, probably related to increases 

in the load from Cement Creek. Manganese concentrations 

continue to be higher than baseline values observed before 

remediation began, probably because of the large amount of 

manganese in the mill tailings and stream gravel from sites 

(Vincent and Elliott, this volume, Chapter E22; Church, Fey, 

and Unruh, this volume) remediated on the upper Animas 

River (table 1).

Although some sites show measurable improvement, 

recovery is not dramatic. However, encouraging signs, such 

as the reoccurrence of benthic invertebrates in Mineral Creek 

downstream of the confluence with South Fork Mineral Creek, 

have been observed (William Simon, ARSG, written commun., 2005). Continued monitoring is essential to follow these 

long-term changes and relate them to biological improvement. 

Monitoring should include chemical, physical, and biological measures to evaluate the magnitude of change that occurs 

following remedial actions and to allow for the estimation of 

recovery rates so that lessons learned can be applied to other 

watersheds.

Summary

Historical mining practices have resulted in the degradation of fisheries and their supporting habitat in the Animas 

River watershed study area. Both mined and unmined areas 

contribute to the contamination. Many activities, including remediation, reclamation, rehabilitation, and restoration, are available for watershed recovery. At this point, the 

major activity in the Animas River watershed study area has 

been remediation (fig. 1). Although only half of the very 

high priority sites on Federal lands identified by Nash and 

Fey (this volume) and by Kimball and others (this volume) 

have been addressed, and 23 percent of sites identified by 

the Animas River Stakeholders Group, Bureau of Land 

Management, USDA Forest Service, and the U.S. Geological 

Survey have been remediated through various engineering 

options (table 1), some improvement in water quality has been 

demonstrated by the water-quality data analysis. Individual 

sites have responded to the remediation work done, as evidenced by the improved water chemistry at individual sites 

(William Simon, ARSG, written commun., 2005). Remediation work conducted by the Federal agencies, the ARSG, 

Sunnyside Gold, Inc., and other private parties has addressed 

water-quality issues caused by acid drainage and runoff 

from some of the largest contaminated sites in the watershed 

study area. Because a substantial amount of the metal load in 

the surface drainages is derived simply from weathering of 

hydrothermally altered rock that has not been disturbed by 

mining (Kimball and others, this volume; Wirt and others, this 

volume, Chapter E17), recovery of the watershed to premining 

conditions may not be an attainable goal; that is, it is simply 

not possible to remove all of the metal loading contributed 

by historical mining. Steady improvement in water quality 

should continue as dynamic equilibrium is reestablished following remediation activities. Some recovery of aquatic life 

in designated stream reaches is already occurring. The ability 

of an ecosystem to support a viable fishery depends not only 

on water quality, but also on availability of an uncontaminated 

food source and suitable habitat. Removal of major sources of 

contamination in the watershed will provide improved conditions for survival and reduce the potential for fish to encounter 

acutely toxic conditions. However, chronic water or dietary 

exposure of trout may persist in areas with residual contamination and may delay the recovery of the benthic community as 

well. Sublethal effects resulting from chronic exposure can be 

documented through the measurement of the same biological 

endpoints that were used to evaluate the adverse ecological 

effects prior to remediation. These parameters should include 

measurement of dissolved-metal concentrations (aluminum, 

cadmium, copper, zinc, and sulfate), benthic community surveys, periodic in-stream larval fish exposure studies, and fish 

health and population surveys. Monitoring sites should remain 

consistent with past sites with the potential addition of sites 

near newly remediated areas.

At this point, recovery in the Animas River watershed 

study area has been predominated by remedial measures. 

Future planning may include ecological restoration alternatives that will enhance the recovery of the biological community. The Society for Ecological Restoration (2004) has 

defined nine attributes that “provide a basis for determining 

when restoration has been accomplished.” Some attributes 

can be easily measured, whereas others can only be assessed 

indirectly and may require “research efforts that exceed the 

capabilities and funds of most restoration projects.” However, 

these nine attributes provide a means to evaluate progress of 

ecological recovery following remediation, reclamation, rehabilitation, and restoration of a site.1

1. The restored ecosystem contains a characteristic assemblage of the species that occur in the reference ecosystem 

and provide appropriate community structure.

2. The restored ecosystem consists of indigenous species to 

the greatest practical extent. In restored cultural ecosystems, allowances can be made for exotic domesticated 

species and for non-invasive ruderal and segetal species that presumably co-evolved with them. Ruderals 

are plants that colonize disturbed sites, whereas segetals 

typically grow intermixed with crop species.

1

Material in quote marks, and the nine attributes, are quoted with the 

acquiescence of Society for Ecological Restoration International.
3. All functional groups necessary for the continued 

development and (or) stability of the restored ecosystem 

are represented or, if they are not, the missing groups 

have the potential to colonize by natural means.

4. The physical environment of the restored ecosystem is 

capable of sustaining reproducing populations of the 

species necessary for its continued stability or development along the desired trajectory.

5. The restored ecosystem apparently functions normally 

for its ecological stage of development, and signs of 

dysfunction are absent.

6. The restored ecosystem is suitably integrated into 

a larger ecological matrix or landscape, with which 

it interacts through abiotic and biotic flows and 

exchanges.

7. Potential threats to the health and integrity of the 

restored ecosystem from the surrounding landscape 

have been eliminated or reduced as much as possible.

8. The restored ecosystem is sufficiently resilient to 

endure the normal periodic stress events in the local 

environment that serve to maintain the integrity of 

the ecosystem.

9. The restored ecosystem is self-sustaining to the same 

degree as its reference ecosystem, and has the potential 

to persist indefinitely under existing environmental conditions.***As in any intact ecosystem, the 

species composition and other attributes of a restored 

ecosystem may evolve as environmental conditions 

change.

The severity of the injury to the ecological community 

and the complexities of the Animas River watershed study 

area make ecological recovery a distant goal. Although 

source reduction will improve water quality so that the 

aquatic community no longer encounters acutely toxic exposures, biological recovery may still be limited by the availability of suitable habitat for spawning and overwintering of trout 

or by the chronic exposure of individual organisms through 

water, sediment, and diet. As funds remain limited for remediation and additional restoration options, reduction of the 

sources of contaminants is a positive step toward improving 

the environmental conditions in the Animas River watershed 

study area. Continued monitoring of water, sediment, and 

biological resources will provide the information necessary to determine if recovery is proceeding in an acceptable 

time frame or whether additional remediation or restoration 

measures are required. If monitoring data indicate that goals 

are not being met, adjustments can be made to the remediation 

and restoration designs.

References Cited

Farag, A.M., Nimick, D.A., Kimball, B.A., Church, S.E., 

Skaar, Don, Brumbaugh, W.G., McConnell, Elizabeth, 

and Hogstrand, Christer, 2004, Aquatic health and exposure 

pathways of trace elements, Chapter D10 in Nimick, D.A., 

Church, S.E., and Finger, S.E., eds., Integrated investigations of environmental effects of historical mining in the 

Basin and Boulder mining districts, Boulder River watershed, Jefferson County, Montana: U.S. Geological Survey 

Professional Paper 1652, p. 369–400.

Jordan, D.S., 1891, Report of explorations in Colorado and 

Utah during the summer of 1889, with an account of the 

fishes found in each of the river basins examined: Bulletin 

of the U.S. Fish Commission, v. 9, p. 1–40.

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 

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EPA/600/4–90–030: Cincinnati, Ohio, U.S. Environmental 

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Kondolf, G.M., 1995, Five elements for effective evaluation of 

stream restoration: Restoration Ecology, v. 3, p. 133–136.

Kondolf, G.M., and Micheli, E.R., 1995, Evaluating stream restoration projects: Environmental Management, v. 19, p. 1–15.

Larison, J.R., Likens, G.E., Fitzpatrick, J.W., and Crock, J.G., 

2000, Cadmium toxicity among wildlife in the Colorado 

Rocky Mountains: Nature, v. 406, 181–183.

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loading in the upper Animas River basin, southwestern 

Colorado: U.S. Geological Survey Water-Resources Investigations Report 02–4230, 43 p.

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: Washington, 

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Runkel, R.L., and Kimball, B.A., 2002, Evaluating remedial 

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1078 Environmental Effects of Historical Mining, Animas River Watershed, Colorado