United States Department of Agriculture

Forest 

Service 

Southwestern 

Region

MB-R3-05-6D

December 2013

Final Environmental 

Impact Statement for 

the Rosemont Copper 

Project

A Proposed Mining Operation 

Coronado National Forest 

Pima County, Arizona

Volume 2
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Printed on recycled paper – December 2013 
Environmental Impact Statement for the 

Rosemont Copper Project

Coronado National Forest

Pima County, Arizona

Lead Agency: U.S. Department of Agriculture Forest Service

Cooperating Agencies: Bureau of Land Management, National Park Service, Saguaro 

National Park, Smithsonian Astrophysical Observatory – Fred 

Lawrence Whipple Observatory, U.S. Army Corps of Engineers, 

U.S. Department of the Air Force Davis-Monthan Air Force Base 

162nd Fighter Airwing, Arizona Department of Environmental 

Quality, Arizona Department of Mines and Mineral Resources, 

Arizona Department of Transportation, Arizona Department of Water 

Resources, Arizona Game and Fish Department, Arizona Geological 

Survey, Arizona State Land Department, Arizona State Mine 

Inspector, Arizona State Parks, Pima County, City of Tucson, Town 

of Sahuarita

Responsible Official: Jim Upchurch, Coronado National Forest, Forest Supervisor

300 W. Congress St.

Tucson, AZ 85701

For Information Contact: Bev Everson, Interdisciplinary Team Leader

300 W. Congress St.

Tucson, AZ 85701

(520) 388-8300

Abstract: This final environmental impact statement (FEIS) documents the analysis of six 

alternatives (including a “no action” alternative) that was developed for the Rosemont Copper Project 

analysis. Alternative 4 – Barrel Alternative is the U.S. Forest Service preferred alternative. 

The Notice of Intent to prepare this document was published in the Federal Register on March 13, 

2008. The public comment period was subsequently extended with a Notice of Intent that was 

published in the Federal Register on April 29, 2008. The draft environmental impact statement 

(DEIS) was released for public comment with a Notice of Availability (NOA) on October 19, 2011. 

The NOA was later revised to update meeting information and published on December 6, 2011. 

Subsequently, the comment period was extended with a Notice of Extension published in the Federal 

Register on January 27, 2012.

The Rosemont Copper Project proposes to mine copper and associated minerals on the Nogales 

Ranger District of the Coronado National Forest. The proposed activities include an amendment to 

the 1986 “Coronado National Forest Land and Resource Management Plan.” 

Final Environmental Impact Statement for the Rosemont Copper Project i

Acronyms and Abbreviations

Documents

forest plan “Coronado National Forest Land and Resource Management Plan,” 

as amended (U.S. Forest Service 1986)

preliminary MPO preliminary mine plan of operations (WestLand Resources Inc. 2007)

Other abbreviations

°F degrees Fahrenheit

ΔE color difference index

AAC Arizona Administrative Code

ACC Arizona Corporation Commission

ADEQ Arizona Department of Environmental Quality

ADOT Arizona Department of Transportation

ADWR Arizona Department of Water Resources

AGFD Arizona Game and Fish Department

AGS Arizona Geological Survey

ARS Arizona Revised Statutes

ASLD Arizona State Land Department

Augusta Resource Augusta Resource Corporation

AUM animal unit month

BLM Bureau of Land Management

CAA Clean Air Act

CAFÉ corporate average fuel economy

CD compact disc

CaCO3 calcium carbonate

CEC Certificate of Environmental Compatibility

Census U.S. Census

CEQ Council on Environmental Quality

Final Environmental Impact Statement for the Rosemont Copper Project iii
Acronyms and Abbreviations

CFR Code of Federal Regulations

CH4 methane

CO carbon monoxide

CO2 carbon dioxide

CWA Clean Water Act

dB decibel

dBA A-weighted decibel

DEIS draft environmental impact statement

EIS environmental impact statement

EPA U.S. Environmental Protection Agency

ESA Endangered Species Act

FEIS final environmental impact statement

Forest Service U.S. Forest Service

FSH Forest Service Handbook

FSM Forest Service Manual

g the acceleration due to gravity equaling 32 feet per second squared

GIS geographic information system

GPS global positioning system

HPTP historic properties treatment plan

Hz hertz

I- interstate

ID team interdisciplinary team

IMPLAN Impact Analysis for Planning

iv Final Environmental Impact Statement for the Rosemont Copper Project
Acronyms and Abbreviations

kHz kilohertz

kV kilovolt

lb/mile pound per mile

LED light emitting diode

m3

/m2 cubic meter(s) per square meter

mg/L milligram(s) per liter

μg/m3 microgram(s) per cubic meter

MOA memorandum of agreement

MOU memorandum of understanding

mpg mile(s) per gallon

MPO mine plan of operations

MSHA Mine Safety and Health Administration

MW megawatt(s)

NAAQS national ambient air quality standards

NAGPRA Native American Graves Protection and Repatriation Act

NEPA National Environmental Policy Act

NFS National Forest System

NFSR National Forest System road

N2O nitrous oxide

NO2 nitrogen dioxide

NOx nitrogen oxides

NRHP National Register of Historic Places

O3 ozone

Pb lead

PM2.5 particulate matter less than or equal to 2.5 microns in diameter

Final Environmental Impact Statement for the Rosemont Copper Project v
Acronyms and Abbreviations

PM10 particulate matter less than or equal to 10 microns in diameter

REMI Regional Economic Models Incorporated

ROD record of decision

Rosemont Copper Rosemont Copper Company

Rosemont Copper Project EIS Rosemont Copper Project Environmental Impact Statement

ROW right-of-way

SHPO State Historic Preservation Office

SO2 sulfur dioxide

SR State Route

TCP traditional cultural property

TEP Tucson Electric Power Company

the Coronado Coronado National Forest (the agency)

USACE U.S. Army Corps of Engineers

U.S.C. United States Code

USFWS U.S. Fish and Wildlife Service

USGS U.S. Geological Survey

VOC volatile organic compound

WUS waters of the United States

vi Final Environmental Impact Statement for the Rosemont Copper Project
Contents

Volume 1

Chapter 1. Purpose of and Need for Action ...........................................................1

Introduction ........................................................................................................................................ 1

Changes from the Draft Environmental Impact Statement................................................................. 3

Document Structure............................................................................................................................ 3

Volume 1....................................................................................................................................................... 3

Volume 2....................................................................................................................................................... 4

Volume 3....................................................................................................................................................... 4

Volume 4....................................................................................................................................................... 4

Volume 5....................................................................................................................................................... 5

Appendix .................................................................................................................................................. 5

Volume 6....................................................................................................................................................... 5

Appendix, Continued................................................................................................................................ 5

Background......................................................................................................................................... 6

Purpose of and Need for Action ......................................................................................................... 6

Proposed Action in Brief.................................................................................................................... 8

Connected Actions........................................................................................................................................ 8

Electrical Transmission Line .................................................................................................................... 8

Water Supply Pipeline .............................................................................................................................. 9

Electrical Distribution Line....................................................................................................................... 9

Arizona National Scenic Trail Reroute..................................................................................................... 9

State Route 83 Highway Maintenance and Improvements....................................................................... 9

Decision Framework........................................................................................................................... 9

Forest Service.............................................................................................................................................. 10

U.S. Army Corps of Engineers ................................................................................................................... 11

Arizona Corporation Commission .............................................................................................................. 12

Tribal Consultation........................................................................................................................... 12

Public Involvement........................................................................................................................... 13

Scoping ....................................................................................................................................................... 13

Public Review of the Draft Environmental Impact Statement .................................................................... 14

Issues ................................................................................................................................................ 15

Issue 1: Impact on Land Stability and Soil Productivity............................................................................. 15

Issue 1 Factors for Alternative Comparison ........................................................................................... 15

Issue 2: Impact on Air Quality.................................................................................................................... 15

Issue 2 Factors for Alternative Comparison ........................................................................................... 16

Issue 3: Impact on Water Resources........................................................................................................... 16

Issue 3A: East Side Groundwater Availability ....................................................................................... 16

Issue 3B: West Side Groundwater Availability ...................................................................................... 17

Issue 3C: Groundwater Quality .............................................................................................................. 17

Issue 3D: Surface Water Availability ..................................................................................................... 17

Issue 3E: Surface Water Quality............................................................................................................. 18

Issue 4: Impact on Seeps, Springs, and Riparian Vegetation ...................................................................... 18

Issue 4 Factors for Alternative Comparison ........................................................................................... 18

Issue 5: Impact on Plants and Animals ....................................................................................................... 19

Issue 5A: Vegetation............................................................................................................................... 19

Issue 5A Factor for Alternative Comparison .......................................................................................... 19

Final Environmental Impact Statement for the Rosemont Copper Project vii
Contents

Issue 5B: Habitat Loss............................................................................................................................ 19

Issue 5C: Nonnative Species................................................................................................................... 19

Issue 5C Factor for Alternative Comparison .......................................................................................... 19

Issue 5D: Wildlife Movement................................................................................................................. 20

Issue 5E: Special Status Species............................................................................................................. 20

Issue 5F: Animal Behavior ..................................................................................................................... 20

Issue 6: Impact on Cultural Resources........................................................................................................ 20

Issue 6A: Impacts on Historic Properties................................................................................................ 21

Issue 6B: Disturbance of Human Remains............................................................................................. 21

Issue 6C: Sacred Sites............................................................................................................................. 21

Issue 6D: Traditional Resource Collecting Areas................................................................................... 22

Issue 7: Impact on Visual Resources........................................................................................................... 22

Issue 7 Factors for Alternative Comparison ........................................................................................... 22

Issue 8: Impact on Dark Skies and Astronomy ........................................................................................... 22

Issue 8 Factor for Alternative Comparison............................................................................................. 23

Issue 9: Impact on Recreation..................................................................................................................... 23

Issue 9 Factors for Alternative Comparison ........................................................................................... 23

Issue 10: Impact on Public Health and Safety............................................................................................. 23

Issue 10 Factors for Alternative Comparison.......................................................................................... 23

Issue 11: Impacts on Social and Economic Resources................................................................................ 24

Issue 11A: Regional Socioeconomics..................................................................................................... 24

Issue 11B: Rural Landscapes.................................................................................................................. 24

Issue 12: Impact on Transportation/Access ................................................................................................ 24

Issue 12 Factors for Alternative Comparison.......................................................................................... 24

Chapter 2. Alternatives, Including the Proposed Action.....................................25

Introduction ...................................................................................................................................... 25

Changes from the Draft Environmental Impact Statement............................................................... 25

Alternatives Considered in Detail..................................................................................................... 27

Removal of Heap Leach Facility from Barrel Alternative .......................................................................... 28

Applicability of Heap Leach Facility Removal to Other Alternatives........................................................ 30

General Overview of Mining Operations.................................................................................................... 30

Mine Facilities and Activities................................................................................................................. 31

Ancillary Facilities and Activities .......................................................................................................... 39

Interim Management................................................................................................................................... 53

Typical Short-Term Interim Management .............................................................................................. 53

Typical Long-Term Interim Management .............................................................................................. 54

Reclamation and Closure ........................................................................................................................ 54

Permits and Authorizations..................................................................................................................... 56

Detailed Description of Alternatives........................................................................................................... 61

Alternative 1 – No Action....................................................................................................................... 61

Action Alternatives................................................................................................................................. 63

Mitigation and Monitoring.......................................................................................................................... 93

Mitigation and Monitoring – Reporting and Evaluation......................................................................... 95

Postclosure Monitoring........................................................................................................................... 97

Financial Assurance .................................................................................................................................... 97

Alternatives Considered but Eliminated from Detailed Study ....................................................... 100

Mining Other Locations............................................................................................................................ 101

Mining Methods........................................................................................................................................ 101

Shafts, Adits, and Other Underground Methods................................................................................... 101

Reducing Pit Size.................................................................................................................................. 101

viii Final Environmental Impact Statement for the Rosemont Copper Project
Contents

In Situ Leaching.................................................................................................................................... 102

High-Temperature/High-Pressure Leaching ......................................................................................... 103

Traditional Slurry Tailings.................................................................................................................... 103

Transporting Tailings by Slurry Pipeline to Scholefield Canyon ......................................................... 103

Configuring the Pit to Allow “Continuous” Backfill............................................................................ 104

Complete Backfill or Partial Backfill of the Pit.................................................................................... 104

Reconfiguring or Relocating the Waste Rock and Tailings Facilities ................................................. 106

Modifying the Life of the Mine ................................................................................................................ 107

Change in Scheduled Hours of Operation................................................................................................. 107

Twelve-Hour Operation with the Same Production Planned for a 24-Hour Operation 

and Same Mine Life.............................................................................................................................. 107

Twelve-Hour Operation with Half the Production Planned for a 24-Hour Operation 

and Double the Mine Life..................................................................................................................... 108

Suspending Operations During High-Wind Events .................................................................................. 109

Water Supply ............................................................................................................................................ 110

Transportation........................................................................................................................................... 111

Natural Gas Pipeline ................................................................................................................................. 112

Land Exchange or Purchase of the Rosemont Copper Project Area by the Forest Service...................... 112

Downsize Electrical Transmission Line.................................................................................................... 113

Bury Electrical Transmission Line............................................................................................................ 114

Forest Plan Consistency.................................................................................................................. 114

Proposed Forest Plan Amendment............................................................................................................ 117

Management Area 16 – Rosemont Mining Area .................................................................................. 117

Finding of Significance......................................................................................................................... 120

Forest Plan Revision ................................................................................................................................. 120

Alternatives Impact Summary ........................................................................................................ 120

Volume 2

Chapter 3. Affected Environment and Environmental Consequences ............139

Introduction .................................................................................................................................... 139

Geology, Minerals, and Paleontology ............................................................................................ 144

Introduction............................................................................................................................................... 144

Changes from the Draft Environmental Impact Statement ................................................................... 144

Issues, Cause and Effect Relationships of Concern.............................................................................. 144

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 145

Summary of Effects by Issue Factor by Alternative ............................................................................. 145

Affected Environment............................................................................................................................... 147

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 147

Existing Conditions .............................................................................................................................. 153

Environmental Consequences................................................................................................................... 172

Direct and Indirect Effects of Each Alternative.................................................................................... 172

Cumulative Effects ............................................................................................................................... 176

Mitigation Effectiveness....................................................................................................................... 177

Effects of Amending the Coronado Forest Plan ................................................................................... 177

Soils and Revegetation ................................................................................................................... 178

Introduction............................................................................................................................................... 178

Changes from the Draft Environmental Impact Statement ................................................................... 178

Issues, Cause and Effect Relationships of Concern.............................................................................. 179

Final Environmental Impact Statement for the Rosemont Copper Project ix
Contents

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 179

Summary of Effects by Issue Factor by Alternative ............................................................................. 182

Affected Environment............................................................................................................................... 185

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 185

Existing Conditions .............................................................................................................................. 187

Environmental Consequences................................................................................................................... 192

Direct and Indirect Effects of Each Alternative.................................................................................... 192

Cumulative Effects ............................................................................................................................... 213

Mitigation Effectiveness....................................................................................................................... 214

Air Quality and Climate Change .................................................................................................... 217

Introduction............................................................................................................................................... 217

Changes from the Draft Environmental Impact Statement ................................................................... 217

Issues, Cause and Effect Relationships of Concern.............................................................................. 219

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 220

Summary of Effects by Issue Factor by Alternative ............................................................................. 229

Affected Environment............................................................................................................................... 229

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 229

Existing Conditions .............................................................................................................................. 229

Environmental Consequences................................................................................................................... 248

Direct and Indirect Effects of Each Alternative.................................................................................... 248

Cumulative Effects ............................................................................................................................... 280

Mitigation Effectiveness....................................................................................................................... 283

Effects of Amending the Coronado Forest Plan ................................................................................... 287

Groundwater Quantity .................................................................................................................... 288

Introduction............................................................................................................................................... 288

Changes from the Draft Environmental Impact Statement ................................................................... 288

Issues, Cause and Effect Relationships of Concern.............................................................................. 291

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 293

Summary of Effects by Issue Factor by Alternative ............................................................................. 316

Affected Environment............................................................................................................................... 318

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 318

Existing Conditions................................................................................................................................... 320

Mine Water Supply (Upper Santa Cruz Subbasin) ............................................................................... 320

Mine Site (Davidson Canyon/Cienega Basin) ...................................................................................... 325

Environmental Consequences................................................................................................................... 328

Direct and Indirect Effects of Each Alternative.................................................................................... 328

Cumulative Effects ............................................................................................................................... 355

Mitigation Effectiveness....................................................................................................................... 357

Effects of Amending the Coronado Forest Plan ................................................................................... 362

Groundwater Quality and Geochemistry........................................................................................ 362

Introduction............................................................................................................................................... 362

Changes from the Draft Environmental Impact Statement ....................................................................... 362

Issues, Cause and Effect Relationships of Concern.............................................................................. 364

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 365

Summary of Effects by Issue Factor by Alternative ............................................................................. 369

Affected Environment............................................................................................................................... 370

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 370

Existing Conditions .............................................................................................................................. 373

Environmental Consequences................................................................................................................... 376

Direct and Indirect Effects of Each Alternative.................................................................................... 376

Proposed Action and Action Alternatives............................................................................................. 394

Cumulative Effects ............................................................................................................................... 394

Mitigation Effectiveness....................................................................................................................... 395

x Final Environmental Impact Statement for the Rosemont Copper Project
Contents

Effects of Amending the Coronado Forest Plan ................................................................................... 398

Surface Water Quantity .................................................................................................................. 398

Introduction............................................................................................................................................... 398

Changes from the Draft Environmental Impact Statement ................................................................... 400

Issues, Cause and Effect Relationships of Concern.............................................................................. 401

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 401

Summary of Effects by Issue Factor by Alternative ............................................................................. 403

Affected Environment............................................................................................................................... 406

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 406

Existing Conditions .............................................................................................................................. 408

Environmental Consequences................................................................................................................... 423

Direct and Indirect Effects of Each Alternative.................................................................................... 423

Cumulative Effects ............................................................................................................................... 437

Mitigation Effectiveness....................................................................................................................... 439

Effects of Amending the Coronado Forest Plan ................................................................................... 443

Surface Water Quality .................................................................................................................... 443

Introduction............................................................................................................................................... 443

Changes from the Draft Environmental Impact Statement ................................................................... 444

Issues, Cause and Effect Relationships of Concern.............................................................................. 444

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 446

Summary of Effects by Issue Factor by Alternative ............................................................................. 447

Affected Environment............................................................................................................................... 448

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 448

Existing Conditions .............................................................................................................................. 451

Environmental Consequences................................................................................................................... 454

Direct and Indirect Effects of Each Alternative.................................................................................... 454

Cumulative Effects ............................................................................................................................... 479

Mitigation Effectiveness....................................................................................................................... 480

Effects of Amending the Coronado Forest Plan ................................................................................... 484

Seeps, Springs, and Riparian Areas................................................................................................ 485

Introduction............................................................................................................................................... 485

Changes from the Draft Environmental Impact Statement ................................................................... 485

Issues, Cause and Effect Relationships of Concern.............................................................................. 487

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 488

Summary of Effects by Issue Factor by Alternative ............................................................................. 506

Affected Environment............................................................................................................................... 506

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 506

Existing Conditions .............................................................................................................................. 512

Environmental Consequences................................................................................................................... 523

Direct and Indirect Effects of Each Alternative.................................................................................... 523

Cumulative Effects ............................................................................................................................... 564

Mitigation Effectiveness....................................................................................................................... 566

Effects of Amending the Coronado Forest Plan ................................................................................... 569

Biological Resources...................................................................................................................... 570

Introduction............................................................................................................................................... 570

Changes from the Draft Environmental Impact Statement ................................................................... 570

Issues, Cause and Effect Relationships of Concern.............................................................................. 571

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 573

Summary of Effects by Issue Factor by Alternative ............................................................................. 582

Affected Environment............................................................................................................................... 582

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 582

Existing Conditions .............................................................................................................................. 590

Final Environmental Impact Statement for the Rosemont Copper Project xi
Contents

Volume 3

Chapter 3. Affected Environment and Environmental Consequences ............653

Biological Resources...................................................................................................................... 653

Environmental Consequences................................................................................................................... 653

Direct and Indirect Effects of Each Alternative.................................................................................... 653

Cumulative Effects ............................................................................................................................... 711

Mitigation Effectiveness....................................................................................................................... 713

Effects of Amending the Coronado Forest Plan ................................................................................... 723

Landownership and Boundary Management.................................................................................. 725

Introduction............................................................................................................................................... 725

Changes from the Draft Environmental Impact Statement ................................................................... 725

Issues, Cause and Effect Relationships of Concern.............................................................................. 726

Affected Environment............................................................................................................................... 726

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 726

Existing Conditions .............................................................................................................................. 726

Environmental Consequences................................................................................................................... 729

Direct and Indirect Effects of Each Alternative.................................................................................... 729

Cumulative Effects ............................................................................................................................... 729

Mitigation Effectiveness....................................................................................................................... 730

Effects of Amending the Coronado Forest Plan ................................................................................... 731

Livestock Grazing........................................................................................................................... 732

Introduction............................................................................................................................................... 732

Changes from the Draft Environmental Impact Statement ................................................................... 734

Issues, Cause and Effect Relationships of Concern.............................................................................. 734

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 735

Summary of Effects by Issue Factor by Alternative ............................................................................. 736

Affected Environment............................................................................................................................... 737

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 737

Environmental Consequences................................................................................................................... 740

Direct and Indirect Effects of Each Alternative.................................................................................... 740

Cumulative Effects ............................................................................................................................... 748

Mitigation Effectiveness....................................................................................................................... 748

Effects of Amending the Coronado Forest Plan ................................................................................... 750

Dark Skies ...................................................................................................................................... 751

Introduction............................................................................................................................................... 751

Changes from the Draft Environmental Impact Statement ................................................................... 751

Issues, Cause and Effect Relationships of Concern.............................................................................. 752

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 752

Summary of Effects by Issue Factor by Alternative ............................................................................. 755

Affected Environment............................................................................................................................... 758

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 758

Existing Conditions .............................................................................................................................. 758

Environmental Consequences................................................................................................................... 759

Direct and Indirect Effects of Each Alternative.................................................................................... 759

Direct and Indirect Effects of Each Alternative.................................................................................... 760

Cumulative Effects ............................................................................................................................... 764

Mitigation Effectiveness....................................................................................................................... 765

Effects of Amending the Coronado Forest Plan ................................................................................... 767

xii Final Environmental Impact Statement for the Rosemont Copper Project
Contents

Visual Resources ............................................................................................................................ 767

Introduction............................................................................................................................................... 767

Changes from the Draft Environmental Impact Statement ................................................................... 767

Issues, Cause and Effect Relationships of Concern.............................................................................. 767

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 768

Affected Environment............................................................................................................................... 781

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 781

Coronado Forest Plan............................................................................................................................ 782

Other Scenery Management Plans and Guidance ................................................................................. 782

Existing Conditions and Landscape Character ..................................................................................... 786

Existing Scenic Integrity....................................................................................................................... 789

Environmental Consequences................................................................................................................... 797

Direct and Indirect Effects of Each Alternative.................................................................................... 797

Comparison of Alternatives.................................................................................................................. 824

Cumulative Effects ............................................................................................................................... 824

Potential State-Wide Impacts to the Arizona National Scenic Trail..................................................... 827

Mitigation Effectiveness....................................................................................................................... 829

Mitigation Measures............................................................................................................................. 829

Effects of Amending the Coronado Forest Plan ................................................................................... 832

Recreation and Wilderness............................................................................................................. 833

Introduction............................................................................................................................................... 833

Changes from the Draft Environmental Impact Statement ................................................................... 833

Issues, Cause and Effect Relationships of Concern.............................................................................. 834

Summary of Effects by Issue Factor by Alternative ............................................................................. 834

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 836

Affected Environment............................................................................................................................... 839

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 839

Existing Conditions .............................................................................................................................. 841

Environmental Consequences................................................................................................................... 851

Direct and Indirect Effects of Each Alternative.................................................................................... 851

Cumulative Effects ............................................................................................................................... 869

Mitigation Effectiveness....................................................................................................................... 871

Effects of Amending the Coronado Forest Plan ................................................................................... 873

Hazardous Materials....................................................................................................................... 875

Introduction............................................................................................................................................... 875

Changes from the Draft Environmental Impact Statement ................................................................... 875

Issues, Cause and Effect Relationships of Concern.............................................................................. 875

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 876

Summary of Effects by Issue Factor by Alternative ............................................................................. 878

Affected Environment............................................................................................................................... 880

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 880

Existing Conditions .............................................................................................................................. 882

Environmental Consequences................................................................................................................... 883

Direct and Indirect Effects of Each Alternative.................................................................................... 883

Cumulative Effects ............................................................................................................................... 905

Mitigation Effectiveness....................................................................................................................... 905

Effects of Amending the Coronado Forest Plan ................................................................................... 906

Fuels and Fire Management ........................................................................................................... 906

Introduction............................................................................................................................................... 906

Changes from the Draft Environmental Impact Statement ................................................................... 906

Issues, Cause and Effect Relationships of Concern.............................................................................. 907

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 907

Final Environmental Impact Statement for the Rosemont Copper Project xiii
Contents

Summary of Effects by Issue Factor by Alternative ............................................................................. 909

Affected Environment............................................................................................................................... 909

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 909

General Management Direction for Fuels and Fire Management on the Coronado National Forest... 910

Existing Conditions .............................................................................................................................. 911

Environmental Consequences................................................................................................................... 914

Direct and Indirect Effects of Each Alternative.................................................................................... 914

Cumulative Effects ............................................................................................................................... 918

Mitigation Effectiveness....................................................................................................................... 919

Effects of Amending the Coronado Forest Plan ................................................................................... 920

Transportation/Access.................................................................................................................... 921

Introduction............................................................................................................................................... 921

Changes from the Draft Environmental Impact Statement ................................................................... 922

Issues, Cause and Effect Relationships of Concern.............................................................................. 923

Issue 12: Impact on Transportation/Access .............................................................................................. 923

Issue 12 Factors for Alternative Comparison........................................................................................ 923

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 925

Summary of Effects by Issue Factor by Alternative ............................................................................. 927

Affected Environment............................................................................................................................... 927

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 927

Existing Conditions .............................................................................................................................. 929

Environmental Consequences................................................................................................................... 940

Direct and Indirect Effects of Each Alternative.................................................................................... 940

Cumulative Effects ............................................................................................................................... 954

Mitigation Effectiveness....................................................................................................................... 955

Effects of Amending the Coronado Forest Plan ................................................................................... 957

Noise............................................................................................................................................... 958

Introduction............................................................................................................................................... 958

Changes from the Draft Environmental Impact Statement ................................................................... 958

Issues, Cause and Effect Relationships of Concern.............................................................................. 959

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 959

Summary of Effects by Issue Factor by Alternative ............................................................................. 969

Affected Environment............................................................................................................................... 970

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 970

Existing Conditions .............................................................................................................................. 972

Environmental Consequences................................................................................................................... 981

Direct and Indirect Effects of Each Alternative.................................................................................... 981

Cumulative Effects ............................................................................................................................... 987

Mitigation Effectiveness....................................................................................................................... 988

Public Health and Safety ................................................................................................................ 989

Introduction............................................................................................................................................... 989

Changes from the Draft Environmental Impact Statement ................................................................... 989

Issues, Cause and Effect Relationships of Concern.............................................................................. 990

Analysis Methodology, Assumptions, Uncertain and Unknown Information ..................................... 991

Summary of Effects by Issue Factor by Alternative ............................................................................. 993

Affected Environment............................................................................................................................... 993

Relevant Laws, Regulations, Policies, and Plans.................................................................................. 993

Existing Conditions .............................................................................................................................. 993

Environmental Consequences................................................................................................................. 1000

Direct and Indirect Effects of Each Alternative.................................................................................. 1000

Cumulative Effects ............................................................................................................................. 1010

Mitigation Effectiveness..................................................................................................................... 1011

xiv Final Environmental Impact Statement for the Rosemont Copper Project
Contents

Effects of Amending the Coronado Forest Plan ................................................................................. 1014

Cultural Resources........................................................................................................................ 1014

Introduction............................................................................................................................................. 1014

Changes from the Draft Environmental Impact Statement ................................................................. 1015

Issues, Cause and Effect Relationships of Concern............................................................................ 1016

Analysis Methodology, Assumptions, Uncertain and Unknown Information ....................................... 1018

Analysis Area – Direct and Indirect Effects ....................................................................................... 1018

Analysis Area – Cumulative Effects................................................................................................... 1018

Analysis Methodology........................................................................................................................ 1018

Uncertain and Unknown Information ................................................................................................. 1021

Summary of Effects by Issue Factor by Alternative ........................................................................... 1021

Affected Environment............................................................................................................................. 1022

Relevant Laws, Regulations, Policies, and Plans................................................................................ 1022

Tribal Consultation for the Rosemont Copper Project........................................................................ 1026

Existing Conditions ............................................................................................................................ 1028

Environmental Consequences................................................................................................................. 1035

Direct and Indirect Effects of Each Alternative.................................................................................. 1035

Cumulative Effects ............................................................................................................................. 1044

Mitigation Effectiveness..................................................................................................................... 1049

Socioeconomics and Environmental Justice................................................................................. 1053

Introduction............................................................................................................................................. 1053

Changes from the Draft Environmental Impact Statement ................................................................. 1053

Issues, Cause and Effect Relationships of Concern............................................................................ 1054

Issue 11: Impacts on Social and Economic Resources ....................................................................... 1054

Analysis Methodology, Assumptions, Uncertain and Unknown Information ................................... 1055

Summary of Effects by Issue Factor by Alternative ........................................................................... 1058

Affected Environment............................................................................................................................. 1063

Relevant Laws, Regulations, Policies, and Plans................................................................................ 1063

Existing Conditions ............................................................................................................................ 1063

Population and Demographics............................................................................................................ 1063

Housing............................................................................................................................................... 1067

Property Values .................................................................................................................................. 1068

Employment........................................................................................................................................ 1070

Income Characteristics........................................................................................................................ 1075

Quality of Life Conditions.................................................................................................................. 1089

Environmental Justice......................................................................................................................... 1092

Environmental Consequences................................................................................................................. 1097

Direct and Indirect Effects of Each Alternative.................................................................................. 1097

Cumulative Effects ............................................................................................................................. 1125

Mitigation Effectiveness for Socioeconomics .................................................................................... 1128

Mitigation Effectiveness for Environmental Justice ........................................................................... 1130

Required Disclosures.................................................................................................................... 1131

Short-Term Uses and Long-Term Productivity....................................................................................... 1131

Geology, Minerals, and Paleontology................................................................................................. 1132

Soils and Revegetation........................................................................................................................ 1132

Air Quality and Climate Change......................................................................................................... 1132

Groundwater Quantity ........................................................................................................................ 1132

Surface Water Quantity ...................................................................................................................... 1133

Seeps, Springs, and Riparian Areas.................................................................................................... 1133

Biological Resources.......................................................................................................................... 1133

Dark Skies........................................................................................................................................... 1133

Visual Resources ................................................................................................................................ 1133

Final Environmental Impact Statement for the Rosemont Copper Project xv
Contents

Recreation and Wilderness ................................................................................................................. 1133

Transportation/Access ........................................................................................................................ 1134

Cultural Resources.............................................................................................................................. 1134

Socioeconomics and Environmental Justice ....................................................................................... 1134

Unavoidable Adverse Effects.................................................................................................................. 1134

Air Quality and Climate Change......................................................................................................... 1134

Soils and Revegetation........................................................................................................................ 1134

Groundwater Quantity ........................................................................................................................ 1135

Surface Water Quantity ...................................................................................................................... 1135

Seeps, Springs, and Riparian Areas.................................................................................................... 1135

Biological Resources.......................................................................................................................... 1135

Livestock Grazing............................................................................................................................... 1135

Dark Skies........................................................................................................................................... 1135

Visual Resources ................................................................................................................................ 1136

Recreation and Wilderness ................................................................................................................. 1136

Hazardous Materials........................................................................................................................... 1136

Fuels and Fire Management................................................................................................................ 1136

Transportation/Access ........................................................................................................................ 1136

Noise................................................................................................................................................... 1136

Public Health and Safety..................................................................................................................... 1136

Cultural Resources.............................................................................................................................. 1136

Socioeconomics and Environmental Justice ....................................................................................... 1137

Irreversible and Irretrievable Commitments of Resources..................................................................... 1137

Geology, Minerals, and Paleontology................................................................................................. 1137

Air Quality and Climate Change......................................................................................................... 1137

Soils and Revegetation........................................................................................................................ 1138

Groundwater Quantity ........................................................................................................................ 1138

Groundwater Quality and Geochemistry ............................................................................................ 1138

Surface Water Quantity ...................................................................................................................... 1138

Surface Water Quality ........................................................................................................................ 1139

Seeps, Springs, and Riparian Areas.................................................................................................... 1139

Biological Resources.......................................................................................................................... 1139

Livestock Grazing............................................................................................................................... 1140

Dark Skies........................................................................................................................................... 1140

Visual Resources ................................................................................................................................ 1140

Recreation and Wilderness ................................................................................................................. 1140

Hazardous Materials........................................................................................................................... 1141

Fire and Fuels Management................................................................................................................ 1141

Transportation/Access ........................................................................................................................ 1141

Noise................................................................................................................................................... 1142

Public Health and Safety..................................................................................................................... 1142

Cultural Resources.............................................................................................................................. 1142

Socioeconomics and Environmental Justice ....................................................................................... 1142

Cumulative Effects.................................................................................................................................. 1142

Other Required Disclosures.................................................................................................................... 1142

Consultation Under the Endangered Species Act ............................................................................... 1143

Consultation Under the National Historic Preservation Act ............................................................... 1143

Conflicts with Regional, State, and Local Plans, Policies, and Controls........................................... 1143

xvi Final Environmental Impact Statement for the Rosemont Copper Project
Contents

Volume 4

Chapter 4. Consulted Parties ............................................................................1153

Introduction .................................................................................................................................. 1153

Tribal Consultation....................................................................................................................... 1153

Government .................................................................................................................................. 1153

Federal .................................................................................................................................................... 1153

State ........................................................................................................................................................ 1154

County..................................................................................................................................................... 1154

Local ....................................................................................................................................................... 1154

Organizations................................................................................................................................ 1155

Commenters on the DEIS............................................................................................................. 1156

Organizations that Commented on the DEIS .......................................................................................... 1156

Organizations.......................................................................................................................................... 1158

Individuals............................................................................................................................................... 1160

Additional Individuals.................................................................................................................. 1309

Chapter 5. List of Preparers ..............................................................................1319

Forest Service ............................................................................................................................... 1319

SWCA Environmental Consultants.............................................................................................. 1321

Other Assisting Consultants ......................................................................................................... 1323

Glossary..............................................................................................................1325

Literature Cited...................................................................................................1347

Index....................................................................................................................1423

Volume 5

Appendix

A. U.S. Army Corps of Engineers’ Section 404(b)(1) Alternatives Analysis 

B. Mitigation and Monitoring Plan (includes U.S. Army Corps of Engineers’ Habitat Mitigation 

Plan)

C. Visual Simulations (on CD)

D. Memorandum of Agreement (prepared under Section 106 of the National Historic Preservation 

Act)

E. Tribal Consultation

Final Environmental Impact Statement for the Rosemont Copper Project xvii
Contents

Volume 6

Appendix, Continued

F. U.S. Fish and Wildlife Service Biological Opinion 

G. Summary of Response to Comments on the DEIS (comments and responses on CD)

List of Figures

Volume 1

Figure 1. Project location and Barrel Alternative footprint ....................................................................2

Figure 2. Sulfide ore processing; general schematic ............................................................................34

Figure 3. Oxide ore processing, general schematic ..............................................................................35

Figure 4. Typical transmission and pipeline easement (Tucson Electric Power Company 2011)........40

Figure 5. Approved utility alignment for the Rosemont Copper Project..............................................42

Figure 6. Process water schematic........................................................................................................44

Figure 7. Arizona National Scenic Trail relocations.............................................................................52

Figure 8. Alternative 1 – No Action .....................................................................................................62

Figure 9. Alternative 2 – Proposed Action footprint.............................................................................65

Figure 10. Layout of plant facilities under the proposed action ...........................................................68

Figure 11. Stormwater control concept under the proposed action ......................................................70

Figure 12. Road changes under the proposed action ............................................................................71

Figure 13. Alternative 3 – Phased Tailings Alternative footprint .........................................................73

Figure 14. Phased Tailings Alternative plant site .................................................................................75

Figure 15. Phased Tailings Alternative stormwater control concept ....................................................77

Figure 16. Road changes under the Phased Tailings Alternative..........................................................79

Figure 17. Alternative 4 – Barrel Alternative footprint ........................................................................81

Figure 18. Barrel Alternative plant site ................................................................................................83

Figure 19. Barrel Alternative stormwater concept................................................................................85

Figure 20. Road changes under the Barrel and Barrel Trail Alternatives.............................................86

Figure 21. Alternative 5 – Barrel Trail Alternative footprint................................................................88

Figure 22. Barrel Trail Alternative stormwater control concept (flowthrough drains not shown) .......89

Figure 23. Alternative 6 – Scholefield-McCleary Alternative footprint...............................................91

Figure 24. Road changes under the Scholefield-McCleary Alternative ...............................................92

Figure 25. Basic Forest Service bonding process as supported by regulations and guidance ..............98

Figure 26. Designated management areas, Coronado National Forest...............................................116

Figure 27. Proposed Coronado National Forest Management Area 16 – Rosemont Mining Area.....119

xviii Final Environmental Impact Statement for the Rosemont Copper Project
Contents

Volume 2

Figure 28. Analysis area for geology, minerals, and paleontology.....................................................146

Figure 29. General geology of the project area. Adapted from Tetra Tech (2007b), 

Johnson and Ferguson (2007), and Drewes (1972a)............................................................157

Figure 30. Geological cross section of the project area. Adapted from Tetra Tech (2007b), 

Johnson and Ferguson (2007), and Drewes (1972a)............................................................159

Figure 31. Analysis area for soils .......................................................................................................181

Figure 32. Reclamation area: revegetation types year 5.....................................................................197

Figure 33. Reclamation area: revegetation types year 10...................................................................198

Figure 34. Reclamation area: revegetation types year 15...................................................................199

Figure 35. Reclamation area: revegetation types year 22...................................................................200

Figure 36. Phasing of concurrent reclamation activities for preferred alternative .............................206

Figure 37. Surface treatments for revegetation for preferred alternative ...........................................208

Figure 38. Analysis area and nonattainment and maintenance areas for air.......................................221

Figure 39. Distribution of winds (percent) at the project site.............................................................237

Figure 40. Pima County monitoring sites (Pima County Department of Environmental 

Quality 2009c) .....................................................................................................................241

Figure 41. Visibility at Saguaro National Park East ...........................................................................247

Figure 42. Locations of Class I areas .................................................................................................258

Figure 43. Analysis area for groundwater quantity ............................................................................289

Figure 44. Tucson Active Management Area .....................................................................................303

Figure 45. Groundwater levels in the Cienega Basin .........................................................................308

Figure 46. Comparison of sources of recharge and withdrawal sinks in mine water supply

analysis area in the Upper Santa Cruz Subbasin..................................................................323

Figure 47. Groundwater levels in the Upper Santa Cruz Subbasin in 2004 and 2005 .......................324

Figure 48. Subsidence in the Sahuarita and Green Valley areas, Pima County, 

February 2009 through January 2010. Adapted from ADWR (2010)..................................326

Figure 49. Geographic area of impact from mine water supply pumping after 20 years of 

pumping during the active mining phase (Errol L. Montgomery and Associates 

Inc. 2009a) ...........................................................................................................................331

Figure 50. Regional water-level drawdown after 20 years of active mining, including 

mine supply pumping...........................................................................................................332

Figure 51. Regional water-level drawdown after 20 years without mine supply pumping ................333

Figure 52. Regional water-level elevations after 20 years of active mining, including mine 

supply pumping....................................................................................................................334

Figure 53. Regional water-level elevations after 20 years without mine supply pumping.................335

Figure 54. Water-level drawdown in the vicinity of the mine at the end of active mining.................341

Figure 55. Water-level drawdown in the vicinity of the mine 20 years after active mining...............342

Figure 56. Water-level drawdown in the vicinity of the mine 50 years after active mining...............343

Figure 57. Water-level drawdown in the vicinity of the mine 150 years after active mining.............344

Figure 58. Water-level drawdown in the vicinity of the mine 1,000 years after active mining..........345

Figure 59. Range of water-level drawdown 1,000 years after active mining based on 

sensitivity analyses...............................................................................................................351

Figure 60. Analysis area for groundwater quality ..............................................................................366

Final Environmental Impact Statement for the Rosemont Copper Project xix
Contents

Figure 61. Analysis area for surface water quantity ...........................................................................399

Figure 62. Outstanding Arizona Waters and stock tanks....................................................................411

Figure 63. Analysis area for cumulative effects – surface water quantity ..........................................438

Figure 64. Analysis area for surface water quality .............................................................................445

Figure 65. Potentially jurisdictional waters within the project area ...................................................452

Figure 66. Analysis area for seeps, springs, and riparian areas..........................................................489

Figure 67. Stream reaches of concern ................................................................................................490

Figure 68. Overview of Pima County mapped riparian habitat..........................................................494

Figure 69. Seeps and springs within the analysis area........................................................................513

Figure 70. Depth of water in Upper Cienega Creek for period of record, 2001 to 2013....................531

Figure 71. Analysis area for biological resources...............................................................................574

Figure 72. Stock tanks within the analysis area..................................................................................592

Figure 73. Mine adits and shafts within the analysis area (WestLand Resources Inc. 2009d)...........593

Figure 74. Talus slopes, rocky outcrops, and rocky canyon bottoms and locations of 

collections of talussnails within the analysis area (Schmalzel and Archer 2010)................594

Figure 75. Vegetation types within the analysis area (Brown 1994; Pima County 2013) ..................596

Figure 76. Wildlife linkages relative to the analysis area (Arizona Game and Fish 

Department 2012e; Beier et al. 2008; Beier et al. 2006a; The Arizona Wildlife 

Linkages Workgroup 2006)..................................................................................................606

Volume 3

Figure 77. Mineral survey fractions ...................................................................................................728

Figure 78. Grazing allotments and the Barrel Alternative..................................................................733

Figure 79. Analysis area for dark skies...............................................................................................753

Figure 80. Analysis area for visual resources.....................................................................................769

Figure 81. Coronado National Forest scenic integrity objectives.......................................................772

Figure 82. Analysis viewpoints ..........................................................................................................774

Figure 83. Road and trail concern levels............................................................................................776

Figure 84. A project area landscape....................................................................................................787

Figure 85. Viewpoint 3 in relation to Arizona National Scenic Trail reroute alternatives..................794

Figure 86. Barrel Alternative regional visibility.. ...............................................................................805

Figure 87. Visual simulation of the Scholefield-McCleary Alternative as seen from viewpoint 2 ....806

Figure 88. Visual simulation of the Barrel Alternative (with revegetation over the span of 

20 years) as seen from viewpoint 2......................................................................................807

Figure 89. Analysis area for recreation and wilderness resources......................................................838

Figure 90. Recreation Opportunity Spectrum and proposed action....................................................842

Figure 91. Recreation sites .................................................................................................................847

Figure 92. Recreation Opportunity Spectrum with Phased Tailings Alternative................................861

Figure 93. Recreation Opportunity Spectrum with Barrel Alternative...............................................863

Figure 94. Recreation Opportunity Spectrum with Barrel Trail Alternative ......................................866

Figure 95. Recreation Opportunity Spectrum with Scholefield-McCleary Alternative .....................868

Figure 96. Analysis area for hazardous materials...............................................................................877

Figure 97. Hazardous materials storage—proposed action ................................................................892

xx Final Environmental Impact Statement for the Rosemont Copper Project
Contents

Figure 98. Hazardous materials storage—Barrel Alternative.............................................................893

Figure 99. Analysis area for fire and fuels management ....................................................................908

Figure 100. Fire occurrence within Rosemont Copper claim boundary on NFS land, 

1988 to 2009 ........................................................................................................................912

Figure 101. Original transportation/access analysis area ...................................................................924

Figure 102. Transportation/access expanded analysis area ................................................................926

Figure 103. County and State roads....................................................................................................931

Figure 104. Coronado National Forest roads......................................................................................933

Figure 105. Access roads....................................................................................................................950

Figure 106. Analysis area and locations of noise receptors (Tetra Tech 2009e).................................960

Figure 107. Ambient noise monitoring locations (Tetra Tech 2009e) ................................................974

Figure 108. Analysis area for public health and safety.......................................................................992

Figure 109. Analysis area for direct and indirect effects on cultural resources................................1019

Figure 110. Analysis area for cumulative effects on cultural resources ...........................................1020

Figure 111. Analysis area for socioeconomics..................................................................................1057

List of Tables

Volume 1

Table 1. Landownership or management of the utility corridor ...........................................................41

Table 2. Large-truck trip per weekday data (years 1 and 20 of operations phase) ...............................50

Table 3. Permits and authorizations that may be applicable to the proposed 

Rosemont Copper Mine .........................................................................................................56

Table 4. Differences among action alternatives evaluated....................................................................63

Table 5. Mine life and anticipated production schedule for the proposed action alternative, 

Rosemont Copper Project ......................................................................................................66

Table 6. Mine life and anticipated production schedule for the Phased Tailings Alternative...............74

Table 7. Mine life and anticipated production schedule for the Barrel Alternative..............................82

Table 8. Coronado National Forest Plan consistency considerations.................................................115

Table 9. Management prescriptions for Coronado National Forest Management Area 16................117

Table 10. Reduction in existing management areas............................................................................120

Table 11. Alternatives comparison table: disturbance elements.........................................................121

Table 12. Alternatives impact summary .............................................................................................123

Volume 2

Table 13. Summary of effects.............................................................................................................147

Table 14. Summarized geology, age, potential paleontological content, and paleontological 

sensitivity of the project area using the Potential Fossil Yield Classification system..........169

Table 15. Amount of rock removed by formation ..............................................................................173

Table 16. Summary of proposed surface disturbance in acres for each alternative by Potential 

Fossil Yield Classification ranking ......................................................................................174

Final Environmental Impact Statement for the Rosemont Copper Project xxi
Contents

Table 17. Soil characteristics in the analysis area...............................................................................182

Table 18. Summary of effects.............................................................................................................183

Table 19. Summary of the potential plant community and soil conditions based on the general 

ecosystem survey .................................................................................................................189

Table 20. Rangeland conditions from the 1950s through 2010 ..........................................................189

Table 21. Watershed condition classification within the analysis area ...............................................191

Table 22. Desired vegetation condition over time ..............................................................................196

Table 23. Species expected to be present............................................................................................202

Table 24. Reclamation phasing over active mining phase for preferred alternative...........................205

Table 25. Soil productivity based on ecological site descriptions (in pounds per acre).....................210

Table 26. Direct soil productivity loss and soil salvage volumes by alternative ................................212

Table 27. Summary of expected changes to sediment delivery under alternatives ............................213

Table 28. Summary of effects.............................................................................................................230

Table 29. Air quality laws, ordinances, regulations, and standards....................................................233

Table 30. Summary of average monthly precipitation (in inches) from various sources ...................235

Table 31. Summary of average monthly temperatures (°F) from various sources .............................236

Table 32. Average monthly pan evaporation for nearby stations and the project area (inches)..........238

Table 33. National Ambient Air Quality Standards............................................................................239

Table 34. Pima County monitoring data, 2008 through 2012, Maximum Recorded 

Concentration of Criteria Pollutant (Monitoring Station Shown in Parentheses)................242

Table 35. Pima County 2008 emissions inventory (tons per year).....................................................248

Table 36. Premining fugitive dust emissions associated with surface disturbances in 

tons per year.........................................................................................................................252

Table 37. Premining tailpipe emissions for worker and equipment shipment trips in 

tons per year – all alternatives..............................................................................................252

Table 38. Active mining tailpipe emissions from worker and equipment shipment trips in 

tons per year – proposed action, Phased Tailings, Barrel Trail, and ScholefieldMcCleary Alternatives.........................................................................................................253

Table 39. Active mining tailpipe emissions from worker and equipment shipment trips 

in tons per year – Barrel Alternative ....................................................................................254

Table 40. Premining fugitive dust emissions from paved surfaces in tons per year – 

all alternatives......................................................................................................................254

Table 41. Active mining fugitive dust emissions from paved surfaces in tons per year.....................255

Table 42. Maximum annual point and fugitive source emissions within the perimeter fence 

under the action alternatives in tons per year.......................................................................256

Table 43. Comparison of Pima County emissions and premining emissions under the action 

alternatives (in tons per year)...............................................................................................257

Table 44. Comparison of Pima County emissions and active mining emissions under the action 

alternatives (in tons per year)...............................................................................................257

Table 45. Maximum modeled and ambient emission concentrations at the perimeter fence for 

proposed action and action alternatives...............................................................................261

Table 46. Maximum modeled and ambient emission concentrations at Saguaro National 

Park East boundary for action alternatives ..........................................................................265

Table 47. Maximum modeled and ambient emission concentrations at Class I areas for all action 

alternatives...........................................................................................................................269

xxii Final Environmental Impact Statement for the Rosemont Copper Project
Contents

Table 48. VISCREEN level 1 modeling of visibility impacts at Saguaro National Park East 

Class I area...........................................................................................................................271

Table 49. VISCREEN level 2 modeling of visibility impacts at Saguaro National Park East 

Class I area...........................................................................................................................272

Table 50. CALPUFF modeling of visibility impacts at other Class I areas........................................274

Table 51. CALPUFF modeling of deposition impacts for each Class I area......................................277

Table 52. Summary of nitrogen deposition impacts for selected Class I areas...................................279

Table 53. Summary of effects.............................................................................................................316

Table 54. Summary of the Federal, State, and local regulatory requirements applicable 

to the project with respect to groundwater quantity.............................................................318

Table 55. Estimate of water balance for the Davidson Canyon/Cienega Basin..................................327

Table 56. Modeled groundwater-level drawdown for selected wells.................................................329

Table 57. Modeled and historic rates of water-level change for selected wells..................................336

Table 58. Number of registered wells potentially impacted near mine water supply pumping..........337

Table 59. Modeled groundwater-level drawdown for selected public supply, municipal, 

or government wells.............................................................................................................337

Table 60. Modeled groundwater drawdown resulting from mine pit at end of active mining............346

Table 61. Modeled groundwater drawdown resulting from mine pit 20 years after mine closure .....347

Table 62. Modeled groundwater drawdown resulting from mine pit 50 years after mine closure .....347

Table 63. Modeled groundwater drawdown resulting from mine pit 150 years after mine closure ...348

Table 64. Modeled groundwater drawdown resulting from mine pit 1,000 years after mine 

closure..................................................................................................................................349

Table 65. Predicted time to first modeled impacts (years after start of active mining), 

including range of sensitivity analysis.................................................................................352

Table 66. Number of registered wells potentially impacted near mine pit .........................................353

Table 67. Comparison of equilibrium loss of water availability by pit lake.......................................353

Table 68. Summary of effects.............................................................................................................369

Table 69. Summary of the Federal, State, and local regulatory requirements applicable 

to the project with respect to groundwater quality...............................................................370

Table 70. Number of geochemical tests conducted on Rosemont Copper waste rock samples .........375

Table 71. Expected water quality from tailings facility......................................................................380

Table 72. Expected water quality from waste rock seepage ...............................................................381

Table 73. Expected water quality from heap leach seepage ...............................................................382

Table 74. Water balance of the mine pit lake 200 years after mine closure........................................387

Table 75. Results of geochemical modeling for mine pit lake at 200 years .......................................388

Table 76. Summary of effects.............................................................................................................404

Table 77. Summary of the Federal, State, and local regulatory requirements applicable 

to the project with respect to surface water resources..........................................................406

Table 78. Summary of past wildfires larger than 10 acres..................................................................409

Table 79. Summary of primary watersheds within the project area ...................................................409

Table 80. Annual peak flows in Barrel Canyon at SR 83 bridge, 1962 to 1976 .................................412

Table 81. Annual mean stream flows in Cienega Creek below the confluence with Davidson 

Canyon, 1994 to 2010..........................................................................................................413

Table 82. Surface water flow at Cienega Creek near Sonoita, Arizona..............................................415

Final Environmental Impact Statement for the Rosemont Copper Project xxiii
Contents

Table 83. Surface water flow at Cienega Creek near Pantano, Arizona ...........................................416

Table 84. Surface water flow at Pantano Wash near Vail, Arizona ...................................................417

Table 85. Surface water flow at Davidson Canyon Wash near Vail, Arizona ...................................419

Table 86. Summary of onsite surface water rights associated with the project area...........................420

Table 87. Summary of offsite surface water rights within the area of groundwater drawdown.........421

Table 88. Summary of stock tanks associated with the project area...................................................422

Table 89. Direct impacts to stock tanks by alternative .......................................................................428

Table 90. Impacts to surface runoff by alternative .............................................................................429

Table 91. Indirect impacts to downstream stock tanks.......................................................................431

Table 92. Summary of expected changes to postclosure stormwater flow under the 

proposed action ....................................................................................................................433

Table 93. Summary of expected changes to postclosure stormwater flow under 

Phased Tailings Alternative..................................................................................................434

Table 94. Summary of expected changes to postclosure stormwater flow under 

Barrel Alternative.................................................................................................................435

Table 95. Summary of expected changes to postclosure stormwater flow under 

Barrel Trail Alternative ........................................................................................................436

Table 96. Summary of expected changes to postclosure stormwater flow under 

Scholefield-McCleary Alternative .......................................................................................436

Table 97. Summary of effects.............................................................................................................447

Table 98. Summary of the Federal, State, and local regulatory requirements applicable 

to the project with respect to surface water resources..........................................................448

Table 99. Summary of preliminary jurisdictional waters delineation within project area and 

utility corridor......................................................................................................................453

Table 100. Summary of Davidson Canyon existing base flow water quality.....................................455

Table 101. Summary of Lower Cienega Creek existing base flow water quality...............................457

Table 102. Results of baseline stormwater quality samples in Barrel Canyon...................................459

Table 103. Summary of impacts under each action alternative on potential WUS and the 

presence/absence of special aquatic sites.............................................................................463

Table 104. Summary of postmine average annual sediment delivery to the USGS gaging 

station for each alternative ...................................................................................................467

Table 105. Predicted stormwater runoff water quality (in mg/L) and applicable surface water

standards in Barrel Canyon..................................................................................................475

Table 106. Stream reaches of concern ................................................................................................491

Table 107. Relationships between selected riparian vegetative characteristics and selected 

hydrologic characteristics based on San Pedro study ..........................................................497

Table 108. Summary of effects...........................................................................................................507

Table 109. Seeps, springs, and other water features within the analysis area.....................................514

Table 110. Riparian affected environment..........................................................................................520

Table 111. Potential to affect Outstanding Arizona Water in Davidson Canyon and Lower 

Cienega Creek......................................................................................................................548

Table 112. Summary of screening analysis to identify potential problem constituents in 

mine runoff...........................................................................................................................550

Table 113. Potential to affect Outstanding Arizona Water in Upper Cienega Creek ..........................554

xxiv Final Environmental Impact Statement for the Rosemont Copper Project
Contents

Table 114. Estimated impacts to springs and seeps as a result of proposed action.............................556

Table 115. Summary of special status plant and animal species that are specifically addressed 

in this FEIS ..........................................................................................................................579

Table 116. Summary of effects...........................................................................................................583

Table 117. Vegetation type by landowner (acres) within analysis area ..............................................595

Table 118. Information regarding intermountain animal movement corridors in and near 

the analysis area ...................................................................................................................602

Volume 3

Table 119. Anticipated impacts to biophysical features resulting from each action 

alternative and connected actions ........................................................................................660

Table 120. Anticipated impacts to seeps, springs, and stock tanks resulting from each action 

alternative and connected actions ........................................................................................663

Table 121. Range of direct impacts to vegetation type by landownership (acres lost or altered) 

from all action alternatives and connected actions ..............................................................665

Table 122. Direct impacts to vegetation type (acres lost or altered) resulting from each action 

alternative and connected actions ........................................................................................666

Table 123. Potential direct impacts (acres lost or altered) to special status plant and animal 

species’ habitat resulting from each action alternative and connected actions in the 

project area...........................................................................................................................673

Table 124. Direct impacts (acres and percent lost by unit and total) to jaguar proposed critical 

habitat resulting from each action alternative and connected actions..................................694

Table 125. Direct impacts (acres and percent of total lost or modified) to the Santa Rita 

Mountains Important Bird Area resulting from each action alternative and 

connected actions.................................................................................................................698

Table 126. Direct impacts (acres and percent of total within analysis area lost or modified) 

to Pima County’s Conservation Lands System lands associated with the 

“Sonoran Desert Conservation Plan” resulting from each action alternative 

and connected actions..........................................................................................................699

Table 127. Direct impacts (lost or modified) by the proposed action to animal movement 

corridors within the analysis area.........................................................................................701

Table 128. Direct impacts (lost or modified) by the Phased Tailings Alternative to animal 

movement corridors within the analysis area.......................................................................703

Table 129. Direct impacts (lost or modified) by the Barrel Alternative to animal movement 

corridors within the analysis area.........................................................................................705

Table 130. Direct impacts (lost or modified) by the Barrel Trail Alternative to animal 

movement corridors within the analysis area.......................................................................707

Table 131. Direct impacts (lost or modified) by the Scholefield-McCleary Alternative to 

animal movement corridors within the analysis area...........................................................709

Table 132. Summary of effects...........................................................................................................736

Table 133. Summary of current grazing activities within project area ...............................................738

Table 134. Rangeland conditions from the 1950s through 2010 ........................................................739

Table 135. Potential loss of grazing during premining and active mining phases under 

proposed action ....................................................................................................................741

Table 136. Stock ponds and springs lost under proposed action ........................................................742

Final Environmental Impact Statement for the Rosemont Copper Project xxv
Contents

Table 137. Potential loss of grazing during premining and active mining phases under 

Phased Tailings Alternative..................................................................................................745

Table 138. Potential loss of grazing during premining and active mining phases under 

Barrel Alternative.................................................................................................................746

Table 139. Additional stock ponds lost under Barrel Alternative .......................................................746

Table 140. Potential loss of grazing during premining and active mining phases under 

Barrel Trail Alternative ........................................................................................................747

Table 141. Potential loss of grazing during premining and active mining phases under 

Scholefield-McCleary Alternative .......................................................................................747

Table 142. Additional springs lost under Scholefield-McCleary Alternative .....................................748

Table 143. Summary of effects...........................................................................................................756

Table 144. Comparison of light source locations and outputs............................................................761

Table 145. Comparison of light sources of towns and cities in southern Arizona..............................761

Table 146. Comparison of Scenery Management System and Visual Management System 

objectives.............................................................................................................................770

Table 147. Magnitude and degrees of effects.....................................................................................779

Table 148. Summary of effects...........................................................................................................780

Table 149. Sensitive viewsheds..........................................................................................................790

Table 150. Santa Rita Ecosystem Management Area and regional visibility impacts by 

alternative.............................................................................................................................821

Table 151. Visibility impacts to SR 83 and Box Canyon Road, by alternative .................................822

Table 152. Summary of effects...........................................................................................................835

Table 153. Recreation Opportunity Spectrum classifications within the Santa Rita Ecosystem 

Management Unit.................................................................................................................843

Table 154. Semiprimitive motorized setting indicators*....................................................................854

Table 155. Summary of effects...........................................................................................................878

Table 156. Permits, laws, and regulatory codes related to facilities that produce, transport, 

store, or dispose of toxic or hazardous materials in Arizona ...............................................881

Table 157. Summary of potentially hazardous materials and their anticipated quantities..................884

Table 158. List of analytical reagents.................................................................................................888

Table 159. Estimated frequency of shipments of hazardous materials to the project area .................890

Table 160. Potential environmental hazards and potential receptors..................................................900

Table 161. Summary of effects...........................................................................................................909

Table 162. Permits, laws, and regulatory codes related to fuels and fire management in Arizona.....910

Table 163. Human related activities affecting fuel load or fire risk ...................................................915

Table 164. Summary of effects...........................................................................................................928

Table 165. SR 83 annual average daily traffic volume, 2006 to 2011................................................934

Table 166. Study segments................................................................................................................935

Table 167. Level of service criteria ....................................................................................................938

Table 168. Existing level of service – roadway segments.............................................................938

Table 169. Weekday mine related traffic ............................................................................................942

Table 170. Weekend mine related traffic ............................................................................................942

Table 171. Copper concentrate and copper cathode truck trips..........................................................946

Table 172. 2012 level of service – roadway segments – active mining phase year 1 ...............947

xxvi Final Environmental Impact Statement for the Rosemont Copper Project
Contents

Table 173. MPO, Phased Tailings, Barrel Trail, and Scholefield-McCleary Alternatives 

traffic volume – active mining phase year 1 ........................................................................952

Table 174. Barrel Alternative traffic volume – active mining phase year 1 .......................................952

Table 175. Roads decommissioned and lost to motorized use by action alternative..........................953

Table 176. Typical dBA levels............................................................................................................962

Table 177. Site acceptability standards...............................................................................................965

Table 178. Peak overpressure (airblast) levels ...................................................................................965

Table 179. Maximum peak particle velocity ......................................................................................966

Table 180. Federal Highway Administration Noise Abatement Criteria ............................................966

Table 181. Occupational Safety and Health Administration permissible noise exposures.................967

Table 182. Summary of effects...........................................................................................................969

Table 183. Summary of noise levels at project area monitoring sites (dBA) .....................................975

Table 184. Summary of noise levels at active copper mine (in dBA) ................................................978

Table 185. Noise impacts expected to occur during premining phase................................................982

Table 186. Noise impacts expected to occur during final reclamation and closure phase..................983

Table 187. Impacts from airborne and ground vibrations...................................................................984

Table 188. Noise impacts expected to occur during operational phase under proposed action..........984

Table 189. Noise impacts expected to occur during operational phase under Barrel Alternative ......985

Table 190. Noise impacts expected to occur during operational phase under Barrel Trail

Alternative ...........................................................................................................................986

Table 191. Noise impacts expected to occur during operational phase under ScholefieldMcCleary Alternative...........................................................................................................987

Table 192. Summary of effects...........................................................................................................994

Table 193. Baseline traffic counts for SR 83....................................................................................1000

Table 194. Traffic volume – premining phase year 1 .......................................................................1003

Table 195. Proposed action, Phased Tailings, Barrel Trail, and Scholefield Alternatives –

traffic volume active mining phase year 1 .........................................................................1004

Table 196. Barrel Alternative – traffic volume active mining phase year 1 .....................................1004

Table 197. Estimated frequency of shipments of hazardous materials*...........................................1008

Table 198. Summary of effects.........................................................................................................1021

Table 199. Chronology of the Rosemont area ..................................................................................1028

Table 200. Archaeological investigations conducted for the Rosemont Copper Mine survey .........1031

Table 201. Direct impacts to historic properties...............................................................................1037

Table 202. Indirect impacts to historic properties.............................................................................1039

Table 203. Direct and indirect impacts to human remains ...............................................................1040

Table 204. Resource collection areas excluded by alternative .........................................................1043

Table 205. Summary of effects.........................................................................................................1059

Table 206. Comparative historical and projected populations for the analysis area and the 

United States......................................................................................................................1065

Table 207. Selected age, household, and housing characteristics, 2010...........................................1066

Table 208. Number of owner-occupied housing units and median property values for the 

analysis area .......................................................................................................................1068

Table 209. Summary of property values within 10 miles of the project area ...................................1069

Final Environmental Impact Statement for the Rosemont Copper Project xxvii
Contents

Table 210. Labor force summary, 2000 and 2011 ............................................................................1070

Table 211. Major employers by county, 2008...................................................................................1070

Table 212. Employment by industry, 2001 and 2010 .......................................................................1073

Table 213. Current role of the Coronado National Forest’s recreation related contributions 

to the area economy (employment and labor income).......................................................1075

Table 214. Personal and household income characteristics, 2010....................................................1076

Table 215. Industry output in 2008 for Pima County—top 20 industries in county.........................1077

Table 216. Industry output in 2008 for Santa Cruz County—top 20 industries in county ...............1078

Table 217. Industry output in 2008 for Cochise County—top 20 industries in county ....................1079

Table 218. Primary and secondary property tax levies in 2011........................................................1081

Table 219. Transaction privilege and severance tax distribution to counties ...................................1082

Table 220. Shannon-Weaver Diversity Index for each county in the analysis area.........................1083

Table 221. Off-highway-vehicle expenditures in the analysis area and in Arizona, 2002................1084

Table 222. Hunting and fishing expenditures in the analysis area and in Arizona, 2001 .................1085

Table 223. National tourism impact ratios........................................................................................1085

Table 224. Tourism related sectors for three-county area: Industry output using Minnesota 

IMPLAN Group and adjusted using tourism impact ratios ...............................................1086

Table 225. Nature-based travel.........................................................................................................1087

Table 226. Estimated annual economic impact of the Whipple Observatory in Arizona 

(dollars in millions)............................................................................................................1089

Table 227. ADOT programmed funding for SR 83 improvements, 2001 to 2010 ...........................1090

Table 228. Minority populations in the analysis area, 2010 .............................................................1094

Table 229. Poverty and low income statistics for the analysis area, 2010........................................1096

Table 230. Projected impact on property values within 5 miles of proposed mine ..........................1107

Table 231. Projected effects on annual property tax revenues within 5 miles of proposed mine.....1108

Table 232. Annual direct impacts to tourism in the Patagonia Census County Division ................. 1111

Table 233. Direct impacts to nature-based tourism, greater Tucson area .........................................1113

Table 234. Secondary effects of reduction in nature-based tourism, greater Tucson area................1113

Table 235. Potential impacts to net migration in Santa Cruz County by alternative ........................1120

Table 236. Projected population increase, 2010 to 2035 ..................................................................1121

Table 237. Induced effects of changes in net migration in Santa Cruz County................................1121

Table 238. Potential environmental justice impacts common to all action alternatives...................1123

xxviii Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and 

Environmental Consequences

Introduction

This chapter describes the natural and human environment that may be affected by the proposed 

action and its alternatives. It also discloses the direct, indirect, and cumulative impacts of the 

proposed action and alternatives. The analysis disclosed for each resource section in this chapter 

considers the effects of the proposed project as well as the effects on the proposed amendment to the 

“Coronado National Forest Land and Resource Management Plan” (forest plan) (U.S. Forest Service

1986) (see the “Forest Plan Consistency” section in chapter 2). Environmental resources were 

grouped into three categories—Physical Environment, Biological Resources, and Social 

Environment—for effects analysis. Further, the text for each resource area within a category was 

divided into three subsections: “Introduction,” “Affected Environment,” and “Environmental 

Consequences.”

Each “Introduction” section informs the reader of changes that have been made since the draft 

environmental impact statement (DEIS) was released for public review in September 2011. It also 

defines both the temporal bounds and the spatial area of analysis specific to each resource and 

reiterates issues and cause/effect relationships of concern that were expressed during the public 

scoping process (see the “Issues” section in chapter 1) and public review of the DEIS. Resources not 

directly linked to a specific issue or cause/effect relationship (e.g., “Geology, Minerals, and 

Paleontology”) must still be evaluated as part of the National Environmental Policy Act (NEPA) 

review to accomplish full public disclosure of potential impacts. Bounds and issues help focus the 

effects analysis on an area of potential effects and influence the methods used to quantify impacts, 

including unit(s) of measure (e.g., acres, miles, cubic tons). Finally, each “Introduction” section 

describes the methodology, assumptions, unknown and/or uncertain information, and data used in the 

analysis. 

Each “Affected Environment” section begins by identifying laws, regulations, and policies that 

regulate and/or guide management of the resource. The existing conditions for the resource are then 

described qualitatively and/or quantitatively, depending on the analysis factors and measures 

identified in issue statements at the end of chapter 1 and on information available to the Coronado 

National Forest (the Coronado) interdisciplinary team (ID team). Descriptions of existing conditions 

are sometimes grouped into subcategories for clarity. 

Past and present actions that may have contributed to or are currently affecting existing conditions are 

briefly identified in each “Affected Environment” section. For example, historic (past) mining 

activities in the area of potential effects for the Rosemont Copper Project are described in the 

“Geology, Minerals, and Paleontology” resource section, as well as in other resource sections where 

past mining activities have had legacy effects on the existing condition of a resource (e.g., “Water”). 

Present actions that contribute effects on the existing condition of a resource are also discussed as the 

basis for characterizing potential effects of activities proposed by the action alternatives. For 

example, current traffic statistics for State Route (SR) 83 characterize the existing conditions, which 

then provide a baseline against which specialists can assess the type and scale of potential effects 

from mine related traffic on SR 83.

The “Environmental Consequences” section discloses the direct, indirect, and cumulative effects of 

each proposed alternative on each resource, beginning with the no action alternative. As discussed in 

chapter 2, no action for the Rosemont Copper Project means that the mine plan of operations (MPO) 

Final Environmental Impact Statement for the Rosemont Copper Project 139
Chapter 3. Affected Environment and Environmental Consequences

would not be approved and that Rosemont Copper Company (Rosemont Copper) would not be 

authorized to use National Forest System (NFS) lands for any portion of the proposed project.

The impacts of implementing the action alternatives are addressed next, beginning with a discussion 

of effects that are common to all action alternatives and followed by disclosure of effects expected 

from individual alternatives.

Please note that the term “Santa Rita Ecosystem Management Area” is used in a number of resource 

sections in this chapter to refer to the geographical area composed of NFS lands and private 

inholdings that encompasses the Santa Rita Mountains. 

Council on Environmental Quality (CEQ) regulations define a cumulative impact as one that 

“results from the incremental impact of the action when added to other past, present, and reasonably 

foreseeable actions regardless of what agency (federal or nonfederal) or person undertakes such other 

actions. Cumulative impacts can result from individually minor but collectively significant actions 

taking place over a period of time” (40 Code of Federal Regulations (CFR) 1508.7).

As stated above, past and present actions that contribute to the existing condition of the affected 

environment in the project area are discussed under the “Affected Environment” heading. To estimate 

the potential for and significance of cumulative impacts, the effects of each alternative must be 

considered in conjunction with those of “reasonably foreseeable” actions that have the same temporal 

and spatial bounds as the alternatives. Reasonably foreseeable actions are those that are likely to 

occur in the future and do not include those that are speculative. In order to determine which future 

activities are likely to occur, the Coronado ID team convened to create a list of reasonably 

foreseeable actions with input from all resource specialists. 

Specific projects listed by the ID team as reasonably foreseeable actions must be sufficiently defined 

with respect to the nature of the actions and their location relative to the proposed action and 

alternatives to facilitate consideration of their potential impacts. Information such as this may 

originate in an application for a permit, formal consideration of authorization of an activity by a 

Federal, State, or local agency, or approval of action by a legislative body (e.g., City Council, County 

Commission, or Congress). Projects that are not developed to this extent are considered speculative 

and are not “reasonably foreseeable.” Therefore, it is not appropriate to include them in a cumulative 

effects analysis. Certain actions within the spatial and temporal bounds of the Rosemont Copper 

Project that were considered to be speculative include the future mining by Rosemont Copper of 

other mineral deposits in the area, specifically the Peach-Elgin, Copper World, and Broadtop 

deposits. Currently, no proposals for development of these projects have been submitted to the 

Coronado or other land management agency. 

Those actions determined by the ID team to be reasonably foreseeable and sufficiently defined for 

analysis of their contribution to cumulative effects, when considered with the effects of the Rosemont 

Copper Project, are as follows:

• The U.S. Forest Service (Forest Service) is proposing landscape-level fire management and 

fuels reduction projects in two areas of the Coronado National Forest. Both projects would 

include an amendment to the forest plan, to establish less restrictive visual quality objectives 

in the project area.

◦ The Catalina-Rincon FireScape Project, proposed on the Santa Catalina Ranger District 

and adjacent lands in Pima, Pinal, and Cochise Counties, Arizona. Proposed activities 

140 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

include vegetation hand thinning, mechanical treatments, firewood harvesting, 

application of prescribed fire, and selective use of herbicides. Annual treatment of 

approximately 50,000 acres is proposed. 

◦ The Chiricahua FireScape Project is proposed for the Chiricahua, Dragoon, and Dos 

Cabezas Mountains. The Forest Service, National Park Service, Bureau of Land 

Management (BLM), and U.S. Fish and Wildlife Service (USFWS) propose to implement 

fuels reduction activities on approximately 500,000 acres in southeastern Arizona. 

Activities could include thinning, piling by hand or machine, chipping, lopping and 

scattering, pruning, mastication, grubbing, firewood harvest, and use of prescribed fire.

• The Nogales Ranger District proposes to remove hazardous fuels on 2,500 acres in Hog and 

Gardner Canyons on the Nogales Ranger District.

• The Santa Catalina Ranger District proposes to reduce hazardous fuels by using thinning, 

mechanical treatments, and prescribed fire on approximately 150 acres. The Loma Linda 

Hazardous Fuels Reduction Project would be located south of Summerhaven, Arizona.

• The Forest Service proposes to approve two MPOs for the Moore and Moore No. 4 Placer 

Mine and the Dice No. 8 Placer Mine, both located 2 miles southwest of 

Washington/Duquesne, Arizona. Actions for each project would include trenching and 

washing of excavated material in a 1- to 2-acre area for a maximum of 1 year.

• The Forest Service proposes to approve an MPO for Javelina Minerals Exploration for 

mineral exploration drilling of eight holes in an area located approximately 3 miles southeast

of Patagonia, Arizona. Activities would occur for a maximum of 1 year.

• The Forest Service proposes to approve an MPO to OZ Exploration Proprietary Ltd. for 

mineral exploration drilling in the East Paymaster and Guajolote Flats areas in the Patagonia 

Mountains. Activities would occur for a maximum of 1 year.

• The BLM proposes to approve an MPO to expand the Andrada Mine limestone quarry in the 

Davidson Canyon drainage system north and northeast of the Santa Rita Mountains. 

The Andrada Mine is located approximately 4 miles from the Tucson, Arizona, city limits 

and 1 mile from the Vail, Arizona, city limits.

• The Forest Service proposes to approve an MPO for minerals exploration drilling on the 

Helix Margarita property for a maximum of 1 year. This property is located near Arivaca in 

Santa Cruz County, Arizona, about 75 miles south of Tucson, Arizona.

• The Forest Service proposes to approve an MPO for Arizona Minerals Inc. for proposed 

minerals exploration (referred to as Hermosa minerals exploration) on the Sierra Vista 

Ranger District, approximately 6 miles southeast of Patagonia, Arizona. The proposal 

involves drilling for core samples and water monitoring wells. Drilling would occur for a 

maximum of 2 years, with monitoring to continue for up to 10 years.

• The Forest Service proposes to approve an MPO for Regal Resources for minerals

exploration drilling of five holes to obtain evidence of mineralization over a 2-acre area for a 

maximum of 1 year. The Patagonia/Sunnyside minerals exploration project is located near 

Nogales, Arizona, about 45 miles south of Tucson, Arizona. 

• In late 2009, Freeport-McMoRan bought 8,900 acres of the long-closed Twin Buttes Mine 

site, near Sahuarita. Required permits for reopening the mine have not been issued to date, 

but it is reasonable to assume that this mine could be reopened at some point in the future.

• The former Oracle Ridge Mine, located on private property within the Santa Catalina Ranger 

District, is an inactive, small-scale underground copper mine in the permitting and detail 

Final Environmental Impact Statement for the Rosemont Copper Project 141
Chapter 3. Affected Environment and Environmental Consequences

design stage for resuming operations. The proposed mine operation would use the same 

surface footprint as previous operations to the extent possible.

• The Forest Service proposes to issue a special use permit to Oracle Ridge Mining, LLC, 

authorizing the use of forest roads, a parking area, and a utility corridor during operation of 

the existing Oracle Ridge Mine, which is located on private land on the Santa Catalina 

Ranger District.

• The Santa Catalina District proposes to authorize drilling to explore for minerals

approximately 10 miles southeast of Summerhaven, Arizona. The Korn Kob Minerals

Exploration CE project involves short-term (1 year or less) mineral, energy, or geophysical 

investigations and their incidental support activities, which may require cross-country travel 

by vehicles and equipment, construction of less than 1 mile of low-standard road, or use and 

minor repair of existing roads.

• In May 2010, a lease was granted to Charles Seel for mining purposes for 240 acres of

Arizona State Trust Land Department (ASLD) State Trust land (from State land 

commissioner) in Section 29, Township 17 South, Range 17 East, adjacent to CalPortland 

leases in Davidson Canyon. There are no known plans to explore for or develop mineral 

resources on this lease in the foreseeable future. 

• The BLM proposes to approve a decision for programmatic aquatic special status species 

reintroductions at Las Cienegas National Conservation Area. The purpose of this project is to 

conserve imperiled aquatic species through the establishment of new populations in 

strategically located livestock and wildlife watering ponds. The project would include:

species translocations for federally listed Chiricahua leopard frog, desert pupfish, Gila 

topminnow, and Gila chub; release of Mexican gartersnakes into stock ponds and modified 

storage tanks; release of Sonora mud turtles into stock ponds from sources in the Cienega and 

O’Donnell Creek basins; planting of Huachuca water umbel at suitable pond locations; and 

protection of native leopard frog, fish, and reptile populations from invasive species.

Activities would occur over a 10-year period.

• The BLM and Arizona Game and Fish Department (AGFD) are proposing reintroduction of 

beaver into Cienega Creek at Las Cienegas National Conservation Area. The timing of this 

potential action has not yet been determined.

• The Community Water Company of Green Valley is proposing delivery and recharge of 

groundwater with water from the Central Arizona Project in the Green Valley area.

• The Farmers Investment Company is proposing the extension of Central Arizona Project 

water into actively farmed pecan groves and activation of a groundwater savings facility near 

Sahuarita.

• Pima County may propose specific actions related to its “Sonoran Desert Conservation Plan,”

including acquisition of archaeological and historical sites and traditional use sites for 

conservation and heritage education purposes, tours, monitoring, and other uses of sites by 

Pima County staff and others. Specific sites or actions are not currently known.

• The Forest Service proposes to add, decommission, close, or change designation of roads in 

the NFS road (NFSR) database and prohibit off-road motorized travel for dispersed camping 

in certain areas on the Nogales Ranger District.

• The Sierra Vista and Santa Catalina Ranger Districts are proposing to make changes to their 

District motorized travel systems. Actions could include additions to the NFSR database, 

decommissioning, change in maintenance level, and other actions to meet administrative and 

user needs.

142 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

• The Forest Service is proposing to reauthorize the grazing permit for the Gardner allotment,

located 5 miles north of Sonoita.

• Development of the Farmers Investment Company property within the Town of Sahuarita’s 

jurisdiction over the next 40 to 50+ years for residential and commercial mixed use is 

proposed, along with the enhancement of more than 12 miles of the Santa Cruz River in both 

the town of Sahuarita and Pima County.

• Rancho Sahuarita is a proposed 3,048-acre planned community located within the Town of 

Sahuarita’s jurisdiction adjacent to the northwestern portions of the Sahuarita Farms 

property. The plan allows for 11,680 residential dwelling units, or 3.8 residents per acre. 

The plan also includes about 1,000 acres of mixed-use and/or other non-residential land uses.

• Quail Creek is a proposed 1,700-acre master-planned retirement community located northeast 

of Sahuarita Farms’ southernmost specific plan parcel. The community is within the Town of 

Sahuarita’s jurisdiction and is entitled for approximately 5,000 housing units and a limited 

amount of non-residential uses adjacent to Old Nogales Highway.

• Madera Highlands is a proposed 920-acre community located within the Town of Sahuarita’s 

jurisdiction. The plan allows for approximately 3,500 units, or approximately 3.8 residents 

per acre. It is located adjacent to the eastern boundary of Sahuarita Farms’ southernmost 

development parcel.

• Tucson Electric Power Company (TEP) proposes two expansions of 138-kilovolt (kV) power 

transmission lines that may be within one or more Rosemont Copper Project analysis areas. 

The first would involve the Vail substation–Cienega substation–Spanish Trail substation. 

It would use the existing Vail–Fort Huachuca/Vail–Spanish Trail 138-kV corridor between 

Vail substation and seven spans east of Wentworth Road and then would involve 

construction of a new double-circuit 138-kV line northeast for approximately 2 miles to 

TEP’s proposed Cienega site. The second expansion project would involve the South 

substation–Hartt substation–Green Valley substation. It would tap into the existing South–

Green Valley 138-kV circuit and drop into a new station adjacent to the right-of-way (ROW) 

located approximately 1 mile south of Old Nogales Highway and Duval Mine Road.

• The BLM is preparing an EIS for the Southline Transmission Line Project, proposed to be 

built in southern New Mexico and Arizona. Southline Transmission, LLC, proposes to 

construct, operate, and maintain a high-voltage power line in two segments totaling 

approximately 360 miles. The first segment would be a new double-circuit 345-kV line from 

a substation in Afton, New Mexico (south of Las Cruces), to a substation in Apache, Arizona 

(south of Willcox). This 225-mile segment would provide up to 1,500 megawatts of capacity. 

The second segment would be an upgrading and rebuilding of about 130 miles of existing 

transmission lines between the Apache substation and the Saguaro substation northwest of 

Tucson. It would provide capacity for an additional 1,000 megawatts of electricity. The line 

would cross Federal lands managed by the BLM and other agencies. 

It also would cross State and private lands. 

• Demand for groundwater in the Sahuarita area is expected to increase by 200 percent by the 

year 2030. 

Final Environmental Impact Statement for the Rosemont Copper Project 143
Chapter 3. Affected Environment and Environmental Consequences

Geology, Minerals, and Paleontology

Introduction

This section presents the geology, minerals, and paleontology resources that could be encountered 

within the project area. The objective of the analysis is to evaluate the potential impacts on these 

resources that could result from the construction or operation of the proposed action or its 

alternatives.

Changes from the Draft Environmental Impact Statement

In response to public and agency comments, the Forest Service further explored possible impacts to 

cave resources. This resource section now provides more details on applicable laws and the 

possibility of impacts and further describes known cave resources that are part of the existing 

conditions (see the “Cave Resource Laws,” “Cave Resources and Karst Landforms,” and “Caves” 

parts of this resource section). This resource section was also reorganized for readability and 

consistency.

Issues, Cause and Effect Relationships of Concern

Even though impacts on geology, minerals, paleontology, and caves were not identified as major 

issues during the public scoping process, the following section addresses the alternatives’ impacts on

these resources in order to provide a full impact analysis, as well as to provide background 

information that is used in the analysis of impacts to other resources, such as groundwater. Other 

aspects of the project that are analyzed in this section include the following:

• Amount of rock removed by formation (tons)

• Potential loss of paleontological resources (moderate to high class/sensitive acres disturbed)

• Qualitative assessment of geotechnical and seismic stability of pit

• Qualitative assessment of potential for disturbance of cave resources 

Other matters that were considered include the following:

• Subsidence. The potential for subsidence to occur is linked primarily to groundwater

withdrawal. Therefore, this issue is analyzed in detail in the “Groundwater Quantity”

resource section in chapter 3.

• Loss of locatable mineral resources due to burial by waste rock and tailings. Impacts to 

locatable mineral resources, such as restriction of access to minerals due to burial by waste 

materials, could potentially be a loss to Rosemont Copper, which has laid claim to all such 

bedrock minerals within the project footprint and the surrounding area. However, 

development of potential ore deposits on most of the claims has not occurred, and no 

proposal to further explore or recover the potential resources has been made at this time.

• Legal authority for locatable minerals operations on NFS land relative to ownership and 

validity of mining claims. Regulatory authority to conduct locatable minerals operations on

NFS lands is found in CFR 228 Subpart A, allowing for activities that are reasonably 

incidental to mining, whether or not the operator has active mining claims in the area, and 

including processing and disposal of locatable minerals.

144 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Analysis Methodology, Assumptions, 

Uncertain and Unknown Information 

The analysis area for geology, minerals, paleontology, and caves coincides with the analysis area used 

for the groundwater analysis. This is because of the implications of groundwater impacts and possible 

geological and cave connections (figure 28). Available data from published and unpublished 

literature, government reports from sources such as the Arizona Department of Water Resources

(ADWR) and U.S. Geological Survey (USGS), and available geotechnical studies were used as 

baseline data for this analysis. Numerous scientific publications were consulted to provide baseline

geological, paleontological, and cave data.

Geological mapping conducted by USGS and additional information provided by Rosemont Copper 

(Ferguson 2009; Ferguson et al. 2009; Johnson and Ferguson 2007; Tetra Tech 2007c, 2009c) were

consulted to identify the geological units that occur within the project area. The analysis regarding the 

amount of rock removed and the geotechnical and seismic stability was conducted based on 

numerous reports provided and generated by Rosemont Copper and their consultants. The Arizona 

Geological Survey (AGS) reviewed 2007 and 2009 geotechnical reports by Tetra Tech and “did not 

find any deficiencies, gaps, or errors in any of the sections that our geologic staff reviewed” (Arizona 

Geological Survey 2010). Since these reports, there have been some updates to the pit design based 

on updated drilling results (Nicholas et al. 2012; Pratt and Nicholas 2009).

Occurrences of paleontological and cave resources are closely tied to the geological units in which 

they are contained. The probability of finding paleontological and cave resources can be broadly 

predicted from the geological units present at or near the surface. The paleontological sensitivity 

of each geological unit within the project area was evaluated using the Potential Fossil Yield 

Classification system (Bureau of Land Management 2007). The Potential Fossil Yield Classification 

system was originally developed in 1996 by the Forest Service’s Paleontology Center of Excellence 

and the Region 2 Paleontology Initiative. Modifications have been made by the BLM in subsequent 

years. The Potential Fossil Yield Classification version used for this analysis was recently approved

as policy by the BLM and is widely recognized and used by Federal agencies. A museum records 

search of previously recorded paleontological localities in the project vicinity was performed by the 

Arizona Museum of Natural History for the purposes of determining whether there are any known 

fossil localities within or near the project area.

Because analysis of cave resources requires focused knowledge, experts were consulted for their 

professional opinion in this area (Hoag, Peachey et al. 2012). Also, after a number of cooperating 

agencies expressed interest in this area, a meeting was held to exchange ideas and expertise in order 

to inform the analysis and the decision maker (Garrett 2012a).

Summary of Effects by Issue Factor by Alternative

Table 13 presents the summary comparison of impacts from each alternative.

Final Environmental Impact Statement for the Rosemont Copper Project 145
Chapter 3. Affected Environment and Environmental Consequences

Figure 28. Analysis area for geology, minerals, and paleontology

146 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 13. Summary of effects

Issue Factor No Action Proposed 

Action

Phased 

Tailings Barrel Barrel Trail

ScholefieldMcCleary

Other Effects

Considered

Amount of rock

removed (tons)

None 1.83

billion*

1.85

billion†

1.91

billion‡

1.85

billion

1.85

billion

Potential loss of 

paleontological 

resources (moderate to 

high potential 

class/sensitive acres 

disturbed)

No effect 

from 

proposed 

mine

2,876 2,904 3,202 3,541 2,449

Qualitative assessment 

of geotechnical and 

seismic stability of pit

Not 

applicable

Failure is 

unlikely because 

of the design 

criteria for 

expected seismic 

activity

Same as 

proposed 

action

Same as 

proposed 

action

Same as 

proposed 

action

Same as 

proposed 

action

Qualitative assessment 

of potential for 

disturbance of cave 

resources

No effect 

from 

proposed 

mine

No disturbance 

to known caves; 

geological 

formations have 

low potential for 

caves; therefore, 

it is unlikely that 

unknown 

resources would 

be impacted

Same as 

proposed 

action

Same as 

proposed 

action

Same as 

proposed 

action

Same as 

proposed 

action

* Source: Huss (2007).

† Source: Huss (2009).

‡ Source: M3 Engineering and Technology Corporation (2012).

Affected Environment

Relevant Laws, Regulations, Policies, and Plans

Metals and other locatable mineral resources on Forest Service lands are managed in accordance with 

the Mining and Minerals Policy Act of 1970, which states that the Federal Government should “foster 

and encourage private enterprise in the development of economically sound and stable industries, and 

in the orderly and economic development of domestic resources to help assure satisfaction of 

industrial, security, and environmental needs.” Administration of locatable mineral resources on NFS 

lands follows direction in regulations at 36 CFR 228 Subpart A. The regulations describe what 

information is required for a proposal to explore for, develop, and recover locatable minerals; how 

impacts to resources from a proposed operation will be scoped, assessed, and mitigated; and how 

reclamation will be bonded and completed during the operation at the conclusion of activity.

The regulations apply to locatable minerals activity, whether or not the operator has active or valid 

mining claims.

Mining Laws

Forest Service direction for management of locatable minerals also follows the Multiple Use Mining 

Act of 1955 and the General Mining Law of 1872, as amended. The Multiple Use Mining Act of 1955 

Final Environmental Impact Statement for the Rosemont Copper Project 147
Chapter 3. Affected Environment and Environmental Consequences

removed common varieties of minerals, such as sand and gravel, clay, building stone, and cinders,

from the category of locatable minerals and provided for multiple uses of the lands and surface 

resources on mining claims. 

The General Mining Law of 1872 (mining law) (30 United States Code (U.S.C.) 22–54) authorizes 

citizens to stake or “locate” mining claims on Federal lands in order to acquire exclusive mineral 

rights. The mining law consists of five basic elements: discovery of a valuable mineral, location of 

mining claims, recordation of claims, maintenance (performance of annual requirements on claims), 

and patenting of a claim, with possible transfer of the surface estate to the claimant. Conditions and 

requirements for these elements are detailed in BLM regulations (43 CFR Chapter 2).

Mineral Discovery

There is no Federal statutory definition of what constitutes a valuable mineral deposit; however,

several judicial and administrative rulings or declarations on the subject have been made.

The prudent man rule was first defined in Castle v. Womble, 19 Land Decision 455 (1894), in which 

the Secretary of the Interior held that “where minerals have been found and the evidence is of such a 

character that a person of ordinary prudence would be justified in the further expenditure of his labor 

and means, with a reasonable prospect of success, in developing a valuable mine, the requirements of 

the statute have been met.” This definition was approved by the U.S. Supreme Court in 1905. 

The marketability test is supplemental to the prudent man rule and considers deposit economics and 

market entry. The claimant is required to show a reasonable prospect of making a profit from the sale 

of minerals from a claim or a group of contiguous claims. Meeting the above “discovery” 

requirements is the key test for determining whether a mining claim is valid for mineral patent 

applications, or whether there are valid existing rights in the event of a segregation or withdrawal of 

the lands from the mining law.

Claim Location and Mineral Discovery

Mining claim location and demonstration of mineral discovery are not required for approval of 

locatable minerals operations subject to Forest Service regulations at 36 CFR 228 Subpart A. 

However, these topics are discussed here because of public concern relative to the validity of mining 

claims in the project area.

Under the mining law, the public lands are free and open to exploration, acquisition, and purchase. 

The mining claimant may enter the land and locate mining claims to cover the ground of interest for 

minerals or for mineral processing and recovery and waste disposal. Mining claims may be located 

prior to a discovery if the ground is of interest, and as long as the claimant actively holds and works 

the ground, seeking a discovery, the claimant is protected by the doctrine of pedis possessio. This 

judicial doctrine protects the claimant against rival claimants having no better right to the land and 

allows them peaceful adverse possession of the land pending discovery. The mining law grants to the 

successful claimant (one who has a discovery of a valuable mineral deposit) an equitable title to the 

minerals discovered, which is a fully protected property right under the U.S. Constitution.

Mining claims may be located only by citizens of the United States, persons who have declared an 

intention to become citizens, and corporations organized under any State law. Mining claims may 

only be located on Federal lands open to mineral entry under the mining laws and only for mineral 

commodities considered to be locatable. Locatable minerals include metallic minerals, certain 

unusual nonmetallic minerals, and minerals that are of an uncommon variety, with unique or special 

properties. 

148 Final Environmental Impact Statement for the Rosemont Copper Project
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There are four main types of mining claims: lode, placer, tunnel, and mill site. Lode claims are 

located on indurated bedrock, whereas placer claims are located on loosely consolidated materials, 

such as mineral bearing sands and gravels, or on layered bedrock. Tunnel claims are linear in nature 

and resemble a right-of-way (ROW), intended to allow for access to ore bodies held under other 

mining claims. Mill site claims are located for processing of minerals and for disposal of waste. 

There is no Federal statutory definition of what constitutes a valuable mineral deposit; however, 

several judicial and administrative rulings or declarations on the subject have been made. The prudent 

man rule was first defined in Castle v. Womble, 19 Land Decision 455 (1894), in which the Secretary 

of the Interior held that “where minerals have been found and the evidence is of such a character that 

a person of ordinary prudence would be justified in the further expenditure of his labor and means, 

with a reasonable prospect of success, in developing a valuable mine, the requirements of the statute 

have been met.” This definition was approved by the U.S. Supreme Court in 1905. The marketability 

test is supplemental to the prudent man rule and considers deposit economics and market entry. 

The claimant is required to show a reasonable prospect of making a profit from the sale of minerals 

from a claim or a group of contiguous claims. Meeting the above “discovery” requirements is the key 

test for determining whether a mining claim is valid for mineral patent applications, or whether there 

are valid existing rights in the event of a segregation or withdrawal of the lands from the mining law.

Claim Patent Requirements

It is not necessary to have a patent in order to remove minerals from a mining claim. In fact, it is not 

even necessary to have a mining claim to explore for, process, and recover locatable minerals from 

Forest Service lands if the land is open to mineral entry. However, a patent in most cases gives the 

claim owner title to the surface estate in addition to his or her rights to the locatable minerals. 

In order to obtain patent, the claimant must have performed at least $500 worth of development work 

per claim; must have had a mineral survey and plat prepared at the claimant’s expense; must show 

that he or she holds possessory rights by chain of title documents; must publish a notice for potential 

adverse claimants to assert his or her claims; and must demonstrate discovery of a valuable mineral 

deposit within the meaning of the mining law. Demonstrating discovery typically involves extensive 

mineral exploration and feasibility analysis of the mineral resources.

It should be noted that on October 1, 1994, Congress imposed a moratorium on spending 

appropriated funds for the acceptance or processing of mineral patent applications that had not yet 

received First Half Final Certificate or were not in Washington, D.C., for Secretarial review of First 

Half Final Certificate on or before September 30, 1994. Until the moratorium is lifted, the BLM will 

not accept or consider new patent applications.

Surface Management Regulations

Regardless of the rights inherent in patented or unpatented claims, mine operators must comply with 

Federal surface management regulations. Until the 1960s, there were no Federal or State statutes or 

regulations governing hardrock mining. This began to change, however, with the enactment of 

Federal statutes, including the Wilderness Act, NEPA, Clean Water Act (CWA), Clean Air Act (CAA), 

and Endangered Species Act (ESA). These statutes did not target hardrock mining, but mine 

operations were subject to their provisions. State environmental protection laws, including some 

mining-specific laws, also began to emerge during this period.

Surface use regulations at 36 CFR 228 Subpart A, governing mining operations on lands managed by 

the Forest Service, were promulgated in 1974. Additionally, operators are required to comply with all 

Final Environmental Impact Statement for the Rosemont Copper Project 149
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other Federal, State, and local laws and regulations, and in the State of Arizona, operators must file a 

reclamation plan with the State Mine Inspector’s office for mining activities on associated private 

lands.

Paleontological Resource Laws

Fossils are classified as nonrenewable scientific resources and are protected by various laws, 

ordinances, regulations, and standards across the country. Professional standards for the assessment 

and mitigation of adverse impacts on paleontological resources have been established by the Society 

of Vertebrate Paleontology (1995; 1996). Federal protections for scientifically significant 

paleontological resources apply to projects if any construction or other related project impacts occur 

on federally owned or managed lands, involve the crossing of State lines, or are federally funded. 

Federal protections apply to scientifically significant paleontological resources on federally owned or 

administered lands within the project area. Pertinent Federal laws, ordinances, regulations, and 

standards are summarized in the following sections. 

Paleontological Resources Preservation Act

In March 2009, the Paleontological Resources Preservation Act was enacted as a result of the passage 

of the Omnibus Public Lands Management Act of 2009, Public Law 111-011, Title VI, Subtitle D,

“Paleontological Resources Preservation.” Under the Paleontological Resources Preservation Act, 

fossils from Federal lands are Federal property that must be preserved and protected using scientific 

principles and expertise. The Paleontological Resources Preservation Act provides the following:

• Uniform definitions for “paleontological resources” and “casual collecting;”

• Uniform minimum requirements for paleontological resource-use permit issuance (terms, 

conditions, and qualifications of applicants);

• Uniform criminal and civil penalties for illegal sale and transport, theft, and vandalism of 

fossils from Federal lands; and

• Uniform requirements for curation of Federal fossils in approved repositories.

The Paleontological Resources Preservation Act applies only to lands administered by the U.S. 

Department of the Interior (except tribal lands) and the NFS. Implementing regulations for this 

legislation are currently under development. 

Federal Land Policy and Management Act 

Neither the Federal Land Policy and Management Act of 1976 (43 U.S.C. 1712(c), 1732(b)) nor 

the Federal Land Policy and Management Act of 1962 (30 U.S.C. 611, Subpart 3631.0, et seq.)

specifically refer to fossils. However, “significant fossils” are understood and recognized in policy as 

scientific resources. Permits that authorize the collection of significant fossils for scientific purposes 

are issued under the authority of the Federal Land Policy and Management Act. 

American Antiquities Act of 1906 (6 U.S.C. 431–433)

The act establishes a penalty for disturbing or excavating any historic or prehistoric ruin or 

monument or object of antiquity on Federal lands as a maximum fine of $500 or 90 days in jail. 

The American Antiquities Act is pertinent to paleontological resources because “objects of antiquity” 

include fossils.

150 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

National Historic Preservation Act of 1966

The act (Public Law 89 665; 16 U.S.C. 470 et seq.) provides for the survey, recovery, and 

preservation of significant paleontological data when such data may be destroyed or lost as a result of 

a Federal, federally licensed, or federally funded project.

Title 43 Code of Federal Regulations

Under 43 CFR 8365.1–5, the collection of scientific resources, including vertebrate fossils, is 

prohibited without a permit. Except where prohibited, individuals are also authorized to collect some 

invertebrate and plant fossils for their personal use. The use of fossils found on Federal lands for 

commercial purposes is also prohibited. 

Cave Resource Laws

Caves are classified as nonrenewable scientific resources and are protected by various laws, 

ordinances, regulations, and standards across the country. Federal protections for scientifically 

significant cave resources apply to projects if any construction or other related project impacts occur 

on federally owned or managed lands, involve the crossing of State lines, or are federally funded. 

Federal protections apply to scientifically significant cave resources on federally owned or 

administered lands within the project area. Pertinent Federal laws, ordinances, regulations, and 

standards are summarized in the following sections. 

Federal Cave Resources Protection Act of 1988

The Federal Cave Resources Protection Act was enacted to secure, protect, and preserve significant 

caves on Federal lands. This law directs the Secretaries of the Interior and Agriculture to prepare and 

periodically update a list of significant caves for lands under their jurisdiction. This information is 

confidential but can be released upon a written request by Federal or State Government agencies or 

educational/research institutions. This law prohibits knowingly destroying, disturbing, defacing, 

marring, altering, removing, or harming any significant cave or altering the free movement of any 

animal or plant life into or out of any significant cave on Federal lands.

The Organic Administration Act of 1897

Regulations issued under the act (16 U.S.C. 551) authorize protection of cave resources from theft 

and destruction (36 CFR 261.9a, 9b, 9g, and 9h). Under 36 CFR 294.1, classification is authorized for 

special interest areas that are managed for recreation use substantially in their natural condition. 

Special closures are authorized under 36 CFR 261.53 to protect threatened cave resources.

Cave Resource Regulations

Forest Service Manual 2882 –

Geologic Resources Program Management

This direction states that the Forest Service must secure, protect, and preserve significant caves for 

the perpetual use, enjoyment, and benefit of all people and to foster increased cooperation and 

exchange of information with those who use caves for scientific, educational, or recreational purposes 

(U.S. Forest Service 2008f). This policy is to protect and maintain caves and cave ecosystems in 

accordance with Federal law and develop volunteer management agreements with the scientific 

community or recreational caving groups to assist with cave protection. The policy is to not make 

available to the public the locations of significant caves except in response to a qualified written 

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request or when it is determined that the disclosure would not create a risk of harm, theft, or 

destruction of cave resources (U.S. Forest Service 2008e).

Forest Service Manual 2356 – Cave Management

The objective of this direction is to provide cave related recreational, cultural, educational, and 

scientific study opportunities that serve public needs and to balance surface resource management 

and cave use with the protection of cave values. The policy is to manage caves as a nonrenewable 

resource to maintain their geological, scenic, educational, cultural, biological, hydrologic, 

paleontological, and recreational values; classify caves containing outstanding values as geological 

or historical areas (U.S. Forest Service 1990a); emphasize wild cave management with few or no 

facilities to facilitate use; develop management prescriptions for caves of significant value; 

coordinate surface and cave resource management activities; protect threatened, endangered, 

proposed, and sensitive species in accordance with the ESA (16 U.S.C. 1531) and Forest Service

Manual (FSM) 2670 (U.S. Forest Service 2005a); protect cultural sites and deposits in accordance 

with FSM 2361.03 (U.S. Forest Service 2008c); and develop and foster communications, 

cooperation, and volunteerism with interested publics, Federal agencies, State agencies, and local 

governments. 

Coronado National Forest Land 

and Resource Management Plan

Under the management direction of the “Coronado National Forest Land and Resource Management 

Plan,” as amended (forest plan) (U.S. Forest Service 1986:9), the following goal is set forth: 

“Preserve and protect caves for their unique environmental, biological, geological, hydrological, 

archaeological, paleontological, cultural and recreational values.” No other mention of 

paleontological resources is identified in the forest plan. 

Management direction is similarly limited with respect to mineral resources, as follows:

• To the extent possible, avoid construction of roads across sensitive soils and scenic lands. 

Prohibit the construction of roads across mountain meadows.

• Mining and leasing activities will be allowed within the framework of applicable laws and 

regulations, including environmental laws and regulations designed to mitigate the impacts of 

mining activities. Emphasis should be on gaining cooperation and control through the use of 

operating plans and bonds for rehabilitation to protect and restore surface resources.

Direction for cave management was added to the forest plan in January 1992 through amendment 6, 

which added and modified management direction for cave and cultural resources. One goal of the 

forest plan is to preserve and protect caves for their unique environmental, biological, geological, 

hydrologic, archaeological, paleontological, cultural, and recreational values. The following standards 

and guidelines from the forest plan are pertinent to the Rosemont Copper Project:

• Surface disturbing land management decisions will include consideration of potential impacts 

to delicate cave ecosystems.

• Measures for protection of caves will be incorporated into project planning. These may 

include avoidance of the alteration of cave entrances; limitation of management activities 

within an area draining into a cave if they may affect the cave ecosystem; avoidance of 

diversion of surface drainage into caves; and limitation of public access if required to prevent 

damage to cave resources or if there are safety hazards.

152 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

• Identified bat roosts will be managed as a sensitive resource and for the enhancement of 

populations. Protection measures may include seasonal closures, education, and gating. 

Management of roosts will include consultation with State and Federal wildlife agencies.

• Access for exploration and development of locatable mineral resources will be analyzed in 

response to a proposed MPO. 

• Those areas needed to protect caves from mining activities will be withdrawn from mineral 

entry.

Existing Conditions

Physiography

Arizona is divided into three geographic provinces; this division is based on distinct geological and 

geographic characteristics. The three provinces were first reported by Fenneman (1931:274, 326, 328, 

381) and were more recently described by Titley and Zürcher (2008:275–276). The provinces are the 

Colorado Plateau, Transition Zone, and Basin and Range. The transitions between these provinces 

typically are gradational, both physiographically and geologically, although the transition from the 

Colorado Plateau of northern Arizona to the Transition Zone of central Arizona is a relatively 

pronounced change from high plateaus of relatively flat-lying Paleozoic through Cenozoic strata and 

volcanic flows to abrupt mountains and valleys of Proterozoic and younger rocks. The Transition 

Zone of central Arizona gradationally changes to the mountains and valleys of the Basin and Range 

of central, southern, and western Arizona, a region that contains sedimentary, igneous, and 

metamorphic rocks ranging in age from Proterozoic through Cenozoic.

The Basin and Range province of southern Arizona has been further divided into the Mexican 

Highlands and Sonoran Desert subprovinces. The Mexican Highlands area comprises southeastern 

Arizona and southwestern New Mexico. The topography there is characterized by average elevations 

and physiographic relief that are greater than those of the Sonoran Desert subprovince to the west 

(Hayes 1969:35). The Sonoran Desert subprovince is distinguished by extensive, largely undissected 

valleys separated by intermittent mountain ranges that cover less than one-fourth of the region (Hayes 

1969:35, 36, 43, 440).

The project area is in the eastern part of the Sonoran Desert subprovince (Arizona Geological Society 

2007:26), near the boundary with the Mexican Highlands, on the eastern slope of the Santa Rita 

Mountains, a range that separates the Cienega Basin to the east from the Santa Cruz Basin to the 

west. Elevations in the project area range from 4,600 to nearly 6,300 feet above mean sea level. Slope 

angles vary from less than 3 percent in drainage bottoms to more than 100 percent on the rock faces 

of some mountain fronts.

Regional Geology

The oldest, or “basement,” rocks in Arizona are Proterozoic in age. These units are overlain by thick 

sequences (as much as 1.2 to 2.4 miles) of Paleozoic-, Mesozoic-, and Cenozoic-age (Phanerozoic) 

sedimentary and volcanic rocks. Titley (1995:7) describes the regional Phanerozoic cover as 

“consisting of Paleozoic [continental] platform strata and a variable thickness of Mesozoic clastic and 

volcanic rocks.” The Paleozoic-Mesozoic transition was a period of uplift and erosion. Mesozoic 

igneous stocks intruded into the Proterozoic through Mesozoic-age formations. Cenozoic dikes and 

volcanic rocks crosscut older formations throughout Arizona.

Final Environmental Impact Statement for the Rosemont Copper Project 153
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Three important periods of tectonic activity affected the modern landscape of southern Arizona, 

including the Rosemont area, as follows: (1) the Laramide Orogeny (mountain-building event), 

approximately 80 million to 45 million years ago; (2) the mid-Tertiary Orogeny, approximately 

25 million to 16 million years ago; and (3) the Basin and Range Orogeny, which lasted until about 

5 million years ago (Armstrong and Ward 1991:13.209 to 13.210). The Laramide Orogeny was a time 

of regional volcanic and intrusive activity, with complex folding and thrust faulting. Large, 

disseminated copper deposits in central and southern Arizona were emplaced with the intrusion of 

granitic rocks during the Laramide Orogeny. Tertiary extension of the crust produced high-angle 

faulting that characterized the Basin and Range orogenic phase. The crustal extension was 

accompanied by volcanism. The steeply dipping, mountain range bounding faults formed the valleys 

and mountains of the Basin and Range province seen today. Although major tectonic activity ceased 

in this region about 5 million years ago (Menges and Pearthree 1989:675), deposition and erosion of 

landforms, as well as limited earthquake and fault activity, continue to the present time. The largest 

magnitude earthquake of Quaternary age in the region occurred along the 32-mile-long Santa Rita 

fault, located on the western flank of the Santa Rita Mountains. This earthquake was estimated by the 

AGS (Pearthree and Calvo 1987:1) to have been of magnitude 6.4 to 7.3 and to have occurred 

between 60,000 and 100,000 years ago. In southeastern Arizona, Late Quaternary faults such as the 

Santa Rita fault are reported by Pearthree and Calvo (1987:1) to have extremely long repeat intervals 

between displacement events and reactivation of faulting after a period of inactivity.

Mineralization episodes are spatially and temporally diverse across Arizona. Titley and Zürcher 

(2008:275) consider the following mineralizing episodes to be the most important: Paleoproterozoic 

(approximately 2,500 million to 1,600 million years ago), Jurassic (201 million to 145 million years 

ago), Late Cretaceous to Early Tertiary (Laramide, approximately 80 million to 45 million years ago), 

and Middle to Late Tertiary. Laramide porphyry deposits in the region extend from Bagdad and 

Mineral Park in northwestern Arizona southeastward to Cananea in Sonora, Mexico. This regional 

cluster of deposits is part of the larger, extensive belt of porphyry copper deposits that is traced 

through the Cordillera of North and South America. The Rosemont deposit is one of more than 35 

significant porphyry copper deposits formed in southeastern Arizona and adjacent areas during 

Laramide time.

Rosemont Deposit Geology

The Rosemont deposit is located in the Helvetia and Rosemont mining districts in the northern Santa 

Rita Mountains. Adjacent mining districts include the Empire, Greaterville, Old Baldy, and Pima 

districts. Farther south, in the Patagonia Mountains, are the Harshaw and Patagonia districts. The first 

significant study of mineral deposits and geology of the region is by Schrader (1915:78). That 

investigation is a detailed analysis of the presence of gold, silver, copper, lead, zinc, tungsten, and 

molybdenum in fissure veins and replacement or contact-metamorphic deposits, and it contains a 

detailed geological map of the area. Starting in the 1950s, work in the area began to describe larger, 

disseminated deposits such as the Rosemont ore deposit through an extensive drilling program. 

The Rosemont ore deposit was identified as a major porphyry copper deposit in 1963. Drilling 

continued sporadically over the next four decades, culminating in the most recent drilling programs, 

conducted by Augusta Resource Corporation (Augusta Resource) and Rosemont Copper from 2005 

through 2011 (Rose 2008:26–27).

A geological map showing the rock formations of the project area is shown in figure 29. Figure 30

depicts an east-west geological cross section and shows the surface and subsurface rock formations in 

the area of the proposed open pit and dry-stack tailings. The geology of the Rosemont area is 

154 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

described at regional and local scales by Schrader (1915:44), Drewes (1971:C1; 1972a:4–6; 1972b:

1–2), Hardy (1997:44–71), Ferguson (2009), Ferguson et al. (2001:6–29), Ferguson et al. (2009), and 

Johnson and Ferguson (2007). Geological mapping for the area is ongoing and is constantly being 

revised. Not all units discussed in this section are represented in figures 29 and 30. In particular, 

several units important to paleontological investigations and discussed later in this section were not 

mapped at the scale shown in figures 29 and 30.

The Rosemont area contains a sequence of Proterozoic intrusive rocks overlain by Paleozoic 

carbonate rocks, quartz sandstone, siltstone, Mesozoic sedimentary and igneous rocks, and Cenozoic 

basin-fill formations and igneous rocks. The bedrock units are crosscut by andesite dikes and quartz

monzonite dikes and stocks; mafic lava flows are found in selected basin-fill units. The stratigraphic 

sequence that hosts the Rosemont deposit includes, from oldest to youngest, the Bolsa Quartzite and 

Abrigo Limestone (both of Cambrian age); Devonian Martin Formation; Mississippian Escabrosa 

Limestone; Pennsylvanian Horquilla Limestone; Earp Formation (Pennsylvanian to Permian age); 

Colina Limestone, Epitaph Formation, and Scherrer Formation (all of Permian age); Upper 

Jurassic/Lower Cretaceous Glance Conglomerate; and Lower Cretaceous Willow Canyon Formation. 

The Horquilla Limestone is the most significant host rock, accounting for almost one-half of the 

sulfide mineralization. Significant mineralization also occurs in the Earp Formation and Colina 

Limestone, and minor mineralization occurs in the other Paleozoic units. The Mesozoic host rocks are 

the Willow Canyon Formation and the Glance Conglomerate, which are predominantly arkosic 

siltstone, sandstone, and conglomerate. The Willow Canyon Formation also includes mafic or 

andesitic flows, which host minor mineralization.

Mesozoic sedimentary rocks consist of continental and shallow marine conglomerate, sandstone, and 

siltstone units that overlie the older units. Some volcanic (andesitic) rocks are interbedded with the 

Mesozoic sedimentary sequence. A Lower Cretaceous andesite flow ranging in width from a few tens 

of feet to several hundred feet wide overlies siltstone of the Lower Cretaceous Willow Canyon 

Formation. Shale and laminated mudstone of the Lower Cretaceous Apache Canyon Formation and 

Upper Cretaceous Mt. Fagan Rhyolite and Rhyolite megabreccia (ash-flow tuff) overlie the Willow 

Canyon Formation.

Cenozoic rock units include consolidated and unconsolidated (loose) conglomerate, colluvium, talus 

debris, and alluvium. Conglomerates are composed of clay- to boulder-sized grains eroded from older 

rocks that are at the surface at the time at which the conglomerate is deposited. The Gila 

Conglomerate ranges in age from Pliocene to Miocene (Johnson and Ferguson 2007), and the 

thickness varies locally. This unit contains a wide range of clasts, ranging from granitic rocks, 

quartzite, carbonate, argillite, and rhyolite. The matrix contains calcite and is notably alkaline, similar 

to contemporary soils in the adjacent basins.

Igneous rocks in the Santa Rita Mountains are of Proterozoic, Jurassic, and Late Cretaceous/Early 

Tertiary (Laramide Orogeny) age. Proterozoic granitic rocks are on the crest of the Santa Rita 

Mountains and down the western slope in the Rosemont-Helvetia area. Mapped rock types include 

granite, quartz diorite, quartz monzonite, and associated aplite. Small Laramide intrusions (stocks) of 

quartz monzonite and quartz latite occur in the project area, and larger stocks of similar composition 

occur to the north at Broadtop Butte and west in the Helvetia area.

The copper sulfide bearing materials in potentially economic concentrations consist primarily of 

Horquilla Limestone (50 percent), Colina Limestone (40 percent), quartz monzonite porphyry 

Final Environmental Impact Statement for the Rosemont Copper Project 155
Chapter 3. Affected Environment and Environmental Consequences

(5 percent), and the Earp Formation (5 percent) (Vector Arizona 2006:table 2). The copper oxide 

bearing host rocks in potentially economic concentrations consist primarily of Willow Canyon arkose 

(50 percent), quartz monzonite porphyry (15 percent), and quartz latite porphyry and andesite 

(35 percent). 

Mineralization occurs primarily in the form of copper sulfide minerals—principally copper sulfides 

like chalcopyrite, chalcocite, and bornite—and also molybdenite, which is a molybdenum sulfide 

mineral. These minerals occur as veinlets and disseminations in the Paleozoic, garnet-diopside skarn 

and associated marble and hornfels. The sulfide minerals are accompanied by quartz, amphibole, 

serpentine, and chlorite alteration. Silver is minor but economically important. Silver mineralization 

is associated with the primary copper mineralization in the Paleozoic rocks. Trace amounts of gold 

are anticipated to be recovered; however, recovery rates are not expected to be significant. Copper 

oxide mineralization results from weathering of the primary copper sulfide minerals. The oxide 

mineralization occurs in the upper part of the ore deposit. Copper oxide mineralization primarily 

includes copper bearing limonite, chrysocolla, tenorite, malachite, and azurite. Minor amounts of 

enriched chalcocite and associated native copper mineralization are found in and beneath the oxide 

mineralization.

Descriptions of the principal units found in the Rosemont deposit area and the approximate 

thicknesses of the units are presented below and are based on information compiled by Johnson and 

Ferguson (2007) and on descriptions of Rosemont drill core (Arizona Geological Society 2007:

39–41).

Cenozoic Era 

Quaternary Period

Younger Alluvium (Holocene–Late Pleistocene, 0–10 feet): Alluvium deposited in streams 

and washes that are actively being incised, generally less than 10 feet deep, locally vegetated.

Colluvium and Talus (Holocene–Late Pleistocene, variable, unmeasured thickness): 

Unconsolidated deposits and debris consisting of subangular to angular pebbles, cobbles, 

and boulders derived from upslope units.

Older Alluvium (Late Pleistocene, 13–40 feet): Weakly consolidated gravel terraces 

consisting of medium- to thick-bedded, sandy, pebble-cobble gravel with rare boulders, 

derived from upslope or upstream units. Granitoid clasts are absent in the upper Pleistocene 

terrace gravels, so this is an important diagnostic characteristic of the Gila Conglomerate.

The deposits are generally incised between 13 and 40 feet, locally forming cliffs and ledges 

as much as 10 feet high.

Tertiary Period (including units spanning Late Cretaceous–Early Tertiary age)

Gila Conglomerate (Pliocene–Miocene, >655 feet): Light brown, medium- to thick-bedded, 

conglomerate, pebbly sandstone, and sandstone with a calcareous matrix. The clasts are 

subangular to rounded and consist of granitic rocks, quartzite, limestone, argillite, and 

rhyolite ash-flow tuff. The abundance of clasts varies, depending on the composition of 

nearby upslope areas.

156 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 29. General geology of the project area. Adapted from Tetra Tech (2007b), Johnson and Ferguson (2007), and Drewes (1972a).

Final Environmental Impact Statement for the Rosemont Copper Project 157

Chapter 3. Affected Environment and Environmental Consequences Figure 30. Geological cross section of the project area. Adapted from Tetra Tech (2007b), Johnson and Ferguson (2007), and Drewes (1972a).

Final Environmental Impact Statement for the Rosemont Copper Project 159
Chapter 3. Affected Environment and Environmental Consequences

Skarn (Paleogene–Upper Cretaceous, >655 feet): Metasomatic alteration (influx of 

hydrothermal solutions rich in silica, aluminum, iron, and magnesium) and replacement of 

carbonate units, producing calc-silicate rocks and hornfels in association with sulfide and 

oxide copper mineralization. Skarn contains gangue minerals characterized by intense ironoxide and local clay alteration; it is synonymous with the term tactite. 

Quartz-feldspar porphyry (Paleogene–Upper Cretaceous, unmeasured thickness): Light

gray to pink felsic porphyry dikes and stocks containing 8 to 15 percent phenocrysts of quartz 

and as much as 25 percent feldspar and 1 to 2 percent biotite.

Andesite porphyry (Paleogene–Upper Cretaceous, unmeasured thickness): Strongly 

altered, fragmental, fine-grained plagioclase porphyritic andesite or intrusive porphyry. 

Elliptical outcrops are located along the margin of the Mount Fagan caldera. 

Cretaceous Period

Mount Fagan Rhyolite (Upper Cretaceous, at least 5,000 feet): Rhyolite ash-flow tuff 

containing 20 to 35 percent phenocrysts (1 to 4 millimeters) of K-feldspar, plagioclase, 

quartz, and biotite. The unit is typically strongly welded but is also poorly welded in many 

areas, particularly in the vicinity of megabreccia blocks and megabreccia avalanche breccias 

contained within it. Two U-Pb zircon ages of 73 million years have been obtained recently 

from the rhyolite just northeast of the Rosemont area (Ferguson 2011).

Mount Fagan Rhyolite megabreccia (Upper Cretaceous): Blocks and avalance breccia 

blocks contained within the Mount Fagan Rhyolite. Blocks, ranging in size from 1 to 1,000 

meters, consist mostly of fractured blocks of the Bisbee Group, Fort Crittenden Formation, 

and andesite lava. Some blocks have been confused for intact stratigraphic sections of 

Tertiary conglomerate, but contact relationships show this to be incorrect (Ferguson 2009). 

Blocks of Fort Crittenden Formation conglomerate within the Mount Fagan Rhyolite east of 

SR 83 in the Empire Mountains and in the 73-million-year-old Cat Mountain Rhyolite of the 

Tucson Mountains (which is probably correlative to the Mount Fagan Rhyolite) have both 

yielded Upper Cretaceous hadrosaur skeletons.

Fort Crittenden Formation (Upper Cretaceous, 0–1,000 feet thick): Pebble-cobble-sparse 

boulder conglomerate, pebbly sandstone, and lesser siltstone and mudstone. Clasts are mostly 

derived from the underlying Bisbee Group but also locally include abundant volcanic. 

Mudstone-rich parts of the formation have recently yielded dinosaur fossils in the Cienega 

Basin near an ash layer that has recently yielded a U-Pb zircon date of 69 million years 

(Ferguson 2011).

Andesite lava (Upper Cretaceous, 0–800 feet): Andesite lava containing less than 

15 percent phenocrysts (<3 millimeters) of plagioclase and lesser altered mafics (probably 

olivine and pyroxene).

Turney Ranch Formation (Lower Cretaceous, 3,280 feet): Alternating layers of sandstone 

and mudstone that range from 16 to 160 feet thick and typically are reddish in color 

(Ferguson 2009; Ferguson et al. 2001:11). The sandstone commonly is cross stratified, 

and the sandstone units generally are fractured (Ferguson et al. 2009:27).

Shellenberger Formation, lower part (Lower Cretaceous, 1,000 feet): Arkosic sandstone 

and mudstone capped by the Mural limestone. The limestone, less than 20 feet thick, is a 

160 Final Environmental Impact Statement for the Rosemont Copper Project
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distinctive oyster packstone that defines the top of this unit. Sandstone is fine- to mediumgrained, arkosic to lithic, and argillaceous. The sandstone is medium bedded with diffuse, 

low-angle cross-strata. Mudstone intervals include abundant siltstone, and pure shale or 

claystone is rare.

Shellenberger Formation, upper part (Lower Cretaceous, 1,500 feet): Arkosic sandstone, 

mudstone, and rare pebbly sandstone. Sandstone is thin- to thick-bedded, typically massive or 

weakly plane-bedded or cross-stratified and argillaceous, arkosic. Sandstone also occurs in 

fairly thick, ripple-laminated beds. Mudstone, making up slightly more than one-half of the 

formation, is almost exclusively dark olive green. The unit includes a distinctive type of 

massive, fine- to medium-grained, spotted argillaceous sandstone. The spots, making up as 

much as 30 percent, are diffuse, are evenly spaced, and range in size from 0.5 to 2 

millimeters. The lower part includes locally abundant, irregular carbonate nodules that 

weather out of mudstone units. Mudstone is mostly silty, with relatively sparse pure shale or 

claystone intervals.

Bisbee Group—

Apache Canyon Formation (Lower Cretaceous, 1,000–2,000 feet): Arkosic sandstone, 

mudstone, limestone, and rare pebbly sandstone. The Apache Canyon is dominated by 

mudstone and arkosic-lithic sandstone. It is distinguished by its signature lithology: dark, 

typically laminated, nonfossiliferous, fetid, micritic limestone. The limestone, making up as 

much as 50 percent of the formation, occurs in thin- to medium-bedded, rarely thick-bedded 

sequences of amalgamated laminated to thin-laminated black limestone interleaved with dark 

mudstone and shale. Rare, thin- to medium-bedded massive recrystallized limestone is also 

present. Sandstone occurs in thin- to thick-bedded units that display bed-scale cross 

stratification, but also, and more commonly, graded beds, either massive or plane bedded 

stratified. Ripple-laminated sequences are common in individual thin beds and laminae and 

as gradational tops to the graded beds. The mudstone, which dominates the formation, occurs 

in sets that range up to 35 feet thick. The mudstone is also mostly shale or claystone with 

sparse thin-bedded to laminated siltstone.

Willow Canyon Formation (Lower Cretaceous, 7,200 feet): A succession of medium- to 

coarse-grained, feldspathic sandstone (typically arkosic arenite) and argillaceous sandstone 

with some vuggy, silty mudstone. A distinctive interval of volcaniclastic pebble-cobble 

conglomerate is present near the middle of the unit, below a sequence of mafic lava flows. 

The conglomerate contains as much as 70 percent mafic and intermediate-composition, 

porphyritic, igneous clasts, including clasts of chert and quartzose sandstone. Sandstone 

throughout the formation is cross stratified to plane bedded, typically medium to thick 

bedded. Weak to moderate propylitic alteration has been identified in the Willow Canyon 

Formation in the Rosemont area.

Mafic lava (Lower Cretaceous, 32–328 feet): A series of mafic lava flows within the 

Willow Canyon Formation and the Glance Conglomerate. The flows are calcite and quartz 

and typically very fine grained (Johnson and Ferguson 2007). 

Glance Conglomerate (Upper Jurassic and/or Lower Cretaceous, 0–980 feet): Massive to 

very thick-bedded, clast-supported conglomerate containing pebbles, cobbles, and local 

boulders that reflect the composition of underlying Proterozoic through Permian rocks. 

Final Environmental Impact Statement for the Rosemont Copper Project 161
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The basal contact is an angular unconformity. Within the Rosemont area, the Glance is a 

clast-supported limestone conglomerate recrystallized to fine- to medium-grained marble.

Glance Conglomerate clastic dike (Upper Jurassic and/or Lower Cretaceous): Clastsupported conglomerate composed of pebbles and cobbles of quartz sandstone and granitoid 

rock (Johnson and Ferguson 2007).

Paleozoic Era

Permian Period

Naco Group—

Rain Valley Formation (Permian, 330 feet): Gray, medium- to thick-bedded limestone, 

intercalated with subordinate thin-bedded to laminated, locally ripple-laminated, fine-grained 

sandstone and siltstone. The unit is generally present in the Santa Rita Mountains but is not 

found locally.

Concha Limestone (Permian, 660–820 feet): Light to medium gray, medium- to thickbedded, massive to planar-laminated, amalgamated, cherty limestone. Chert nodules 

characteristically are wispy and poorly formed. Locally dolomitic, the limestone mostly is 

micritic but includes skeletal wackestone and possible packstone, which locally contain 

spiculite beds and brachiopod fragments.

Scherrer Formation (Permian, 1,080–1,610 feet): Generally light gray to pink, finegrained, massive, quartzose sandstone with rare laminations. The upper portion locally is 

differentiated as a transitional interval consisting of cream-colored, medium-bedded, 

dolomicrite with poorly preserved siltstone and argillaceous carbonate rocks.

Epitaph Formation (Permian, 820–1,280 feet): A mixed siliciclastic-carbonate unit. 

The siliciclastic units are purple to reddish, thin- to medium-bedded siltstone and silty 

mudstone, and fine-grained, laminated sandstone. These units commonly are metamorphosed 

to light, orange-pink or greenish hornfels. The carbonate units are light gray to pink micritic 

carbonates.

Colina Limestone (Permian, 165–540 feet): A light gray to white, medium- to thickbedded, amalgamated, commonly dolomitic, micritic carbonate and skeletal wackestone.

Earp Formation (Permian–Pennsylvanian, 490–660 feet): A mixed siliciclastic-carbonate 

consisting of light, reddish brown to light green, thin- to medium-bedded, planar-laminated 

siltstone, silty mudstone, and very fine-grained sandstone that is intercalated with light gray 

to pinkish gray, thick-bedded, micritic limestone and skeletal wackestone. The siliciclastic 

components commonly are metamorphosed to light green or orange-pink hornfels.

Pennsylvanian Period

Naco Group—

Horquilla Limestone (Pennsylvanian, 660–980 feet): Light gray, thin- to thick-bedded, 

cherty limestone with interbeds of dark gray to green silty mudstone and shale that becomes

more abundant higher in the section.

162 Final Environmental Impact Statement for the Rosemont Copper Project
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Mississippian Period

Escabrosa Limestone–Martin Formation undifferentiated (Mississippian–Devonian, 

230–560 feet): Light gray, medium- to thick-bedded, amalgamated, massive, locally cherty, 

recrystallized limestone. Massive dolostone or dolomitic limestone locally is present in the 

lower section. Although an unconformity is present between the Martin Formation and the 

Escabrosa Limestone, these units are not preserved well enough in this area to distinguish 

between them.

Cambrian Period

Abrigo Formation (Cambrian, 330–660 feet): Thin- to medium-bedded limestone with 

laminae. The lower part contains intercalated fine-grained, parallel-laminated to ripplelaminated, fine-grained sandstone, siltstone, silty mudstone, and shale. Locally, the unit has 

partly been metamorphosed to light pinkish gray to greenish yellow, calc-silicate hornfels that 

form resistant outcrops with recessive, thin beds, lenses, and laminations.

Bolsa Quartzite (Cambrian, 260–570 feet): Light gray, medium- to fine-grained, thick- to 

medium-bedded, quartzose sandstone that forms cliffs and ledges. The lower part is cross 

stratified, commonly coarse grained, and locally feldspathic, with composition apparently 

ranging from quartz arenite to subarkosic arenite. Pebbly to granular beds occur near the base 

of the unit, which unconformably overlies granitic basement. The upper part of the Bolsa 

Quartzite is medium gray, fine-grained, and commonly bioturbated with Planolites and 

Skolithos ichnofossils (traces of ocean-bottom burrows) and includes as much as 30 percent

siltstone and shale near the gradational contact with the overlying Abrigo Formation.

Proterozoic Era

Quartz Monzonite (Early or Middle Proterozoic, unmeasured thickness): Mediumgrained, quartz monzonite granite with 15 to 20 percent altered dark minerals (Johnson and 

Ferguson 2007).

Folding and faulting occurred in several intervals of geological time. Most host rocks at Rosemont 

dip steeply (approximately 55 to 65 degrees) to the east. The principal faults in the area include the 

nearly horizontal Flat fault and the younger north-striking Backbone fault system. The Flat fault 

places mostly Mesozoic sedimentary rocks over the older Paleozoic units. The postmineral Backbone 

fault system defines the western boundary of the ore deposit and separates the mineralized, Paleozoic 

limestone units on the east from the Proterozoic granodiorite and lower Paleozoic quartzite on the 

west. No evidence exists in the deposit area of recent fault activity that cross cuts Quaternary or 

Holocene talus, colluvium, alluvial fan, or terrace gravels; these alluvial formations typically mask 

the underlying, older fault contacts where faults are present (Ferguson et al. 2009). 

The Rosemont deposit primarily is a garnet-diopside skarn of the type that formed in Paleozoic 

sedimentary rocks of Cambrian, Devonian, Mississippian, Pennsylvanian, and Permian age elsewhere 

in Arizona and the western United States. The deposit formed in response to emplacement of quartz 

latite to quartz monzonite stocks approximately 56 million years ago during the Laramide Orogeny. 

Marble was formed from the more pure carbonate rock types, while the more siliceous, silty rocks 

were altered to hornfels.

The Flat fault separates the upper, weakly mineralized oxide zone from the underlying, strongly 

mineralized, sulfide zone. Oxidized and supergene copper mineralization above the Flat fault appear 

to be well developed in the Mesozoic-age andesitic rocks (Huss 2009:27–28).

Final Environmental Impact Statement for the Rosemont Copper Project 163
Chapter 3. Affected Environment and Environmental Consequences

Mineralization from the Laramide Orogeny is typically associated with intrusions of granite-like 

rocks, although it also occurs less frequently in adjacent, older sedimentary rocks. Unlike most 

other porphyry copper deposits in the area, the Rosemont mineralization occurred primarily in 

metamorphosed limestone (skarn) and other sedimentary rocks, rather than in a granitic or related 

intrusive rock. Most of the oxide mineralization occurs in the Mesozoic sedimentary and volcanic 

rocks.

Mineral Exploration and Mining History

Southeastern Arizona is a major copper-producing area. A roughly triangular area from northeast of 

Phoenix, east to Safford, and south to Bisbee contains a number of active and closed porphyry copper 

mines that have operated (or had operated, if closed) since the early 1900s. Ten mines are currently 

active in this area: the Quadra Carlota operation; the Freeport-McMoRan Miami, Safford, Morenci, 

and Sierrita operations; the BHP Billiton Miami and Pinto Valley operations; and the ASARCO Ray, 

Silver Bell, and Mission operations. The ASARCO Mission Mine is approximately 20 miles west of 

Rosemont and shares common geological and mineralization characteristics.

Mineral exploration in the Santa Rita Mountains dates from the mid-1800s, and by 1880, small 

underground mines and smelters had been established in the area. The Helvetia and Rosemont mining 

districts, located on the west and east flanks, respectively, of the northern Santa Rita Mountains, were 

established in 1880. By the time most production had ceased in 1951, the area had produced 

approximately 227,300 tons of ore containing 17.3 million pounds of copper, 1.1 million pounds of 

zinc, and 181,000 ounces of silver. The locations of known historic mine workings in relation to the 

proposed Rosemont facilities are illustrated in figure 28.

Although most production ceased in 1951, the Narragansett Mine, which produced copper, silver, 

zinc, lead, gold mineralization, continued to operate until 1961. More than 90,000 tons of ore

materials averaging more than 4 percent copper and 0.5 ounce of silver per ton were produced from 

this mine (Mindat 2010a). Mineral exploration continued in the northern Santa Rita Mountains to the 

present, with most exploration targeting much larger, more disseminated ore deposits than those that 

were mined historically.

Banner Mining Company, which had acquired most of the claims in the area by the late 1950s, drilled 

the discovery hole into the Rosemont deposit. Anaconda Mining Company acquired the property in 

1963 and carried out an extensive exploration program that identified Rosemont as a major porphyry 

copper deposit. In 1973, Anaconda joined with AMAX, forming the ANAMAX partnership. 

The partnership lasted until 1986, when Anaconda was dissolved, at which time the Rosemont and 

Peach-Elgin properties were sold to a real estate company. ASARCO purchased the property in 1988, 

began engineering studies on the Rosemont property, and drilled 12 diamond drill holes. In 2004, 

ASARCO sold the entire property to real estate interests. Augusta Resource acquired the Rosemont 

property in 2005, continued delineation of the Rosemont deposit through sampling and drilling, and 

submitted a preliminary MPO (WestLand Resources Inc. 2007a) in 2007 to the Forest Service.

Other Mining Activity

There is no significant metal mining in the immediate vicinity of the proposed project or in the 

Cienega Basin to the east of the Santa Rita Mountains. Major metal mining activity, primarily copper 

and molybdenum, with lesser amounts of gold and silver, has occurred since the mid-1950s 

approximately 20 miles northwest of the project site in the Santa Cruz Basin. Three major porphyry 

164 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

copper/molybdenum operations are located on the east side of the Sierrita Mountains (on the west 

side of the Santa Cruz Basin), near the communities of Green Valley and Sahuarita. These include the 

Sierrita and Mission Mines, which are active, and the currently closed Twin Buttes Mine. The San 

Xavier Mine, a smaller operation associated with the Mission Mine, is inactive. Exploration of other 

metal prospects occurs in the area when market conditions provide incentives.

The area also has produced limestone for industrial purposes, including high-grade calcium carbonate 

suitable for cement manufacturing and pharmaceutical use. The Imerys limestone quarry, located on 

the Coronado National Forest on the northwest side of the Santa Rita Mountains, is an active open-pit

mine that occupies about 22 acres. Limestone mined from the quarry (calcium carbonate) is used for 

landscaping, calcium supplements, paper filler and coating, paint and drywall filler, and various other 

products. The operation produces more than 217,000 tons of material per year. Mineralization has 

been reported as “contact metamorphism deposit of the Escabrosa Limestone altered to marble” 

(Mindat 2010b).

A new operation that would expand an existing limestone quarry has been proposed approximately 

6 miles northeast of the Rosemont Copper Mine in the Davidson Canyon drainage. A second quarry is 

proposed on the east side of Davidson Wash. The quarry expansion and new quarry by CalPortland 

Cement are under review by Federal and State agencies. 

The Andrada Marble Quarry (W.R. Henderson Arizona Properties) is located in Vail and is an active 

marble quarry currently operating on private land. The operator has a pending MPO filed with the 

BLM to mine Federal minerals on adjacent State Trust lands.

Rosemont Claim History

According to the 2007 preliminary MPO, the core of the project area consists of 132 patented lode 

claims totaling 1,968 acres. Surrounding the patented lode claims is a contiguous group of 850 

unpatented lode mining claims totaling approximately 12,000 acres. Rosemont Copper also owns 911 

acres of private fee land in the area. Most of the unpatented claims were staked on Federal land now 

administered by the Coronado, and a limited number of claims in the northwestern portion of the 

property are on Federal land administered by the BLM. 

The first patented Rosemont claims date from 1898 and predate Arizona Statehood and the 

designation of the Coronado National Forest by the U.S. Congress. The most recent claims were 

patented in the 1990s. All private land and unpatented mining claims described above are owned 

and/or controlled by Augusta Resource.

Waste and Ore Classification

Waste rock is typically defined as rock material overlying an ore deposit or within a mine plan that is 

below the cutoff grade required for economic extraction and processing. The waste rock is removed 

to access the ore materials and requires disposal in an overburden pile or waste rock disposal facility. 

Cutoff grades may decrease or increase throughout the mine life due to fluctuations in capital and 

operating costs, processing recovery effectiveness and efficiencies, commodity prices, or other 

reasons. A statement by Augusta Resource (2012), based on the 2012 “NI 43-101 Technical Report 

for the Rosemont Copper Project, Updated Feasibility Study,” reports that sulfide waste material at 

Rosemont falls below a grade of 0.15 percent total copper. Oxide waste is reported to be material 

with a grade below 0.10 percent total copper and below 0.30 percent for mixed sulfide/oxide material.

Final Environmental Impact Statement for the Rosemont Copper Project 165
Chapter 3. Affected Environment and Environmental Consequences

The percentages of rock types forming potential waste materials at Rosemont are tabulated below in 

the “Impacts Common to All Action Alternatives” subsection. The percentage of waste relative to ore

has decreased in recent years, as additional mineralized material has been delineated through drilling, 

geological mapping, and other mineral exploration and development activities. More than one-half of 

the waste materials consist of weathered (oxidized) and fresh (unoxidized) arkose and other oxidized 

units in the Willow Canyon Formation. Andesite and various Paleozoic formations constitute the 

remaining waste rock materials. 

Ore is defined as the portion of a mineral deposit that can be economically extracted and processed 

for the metals of interest it contains. The Rosemont ore deposit contains copper, molybdenum, silver, 

and gold mineralization primarily in Paleozoic limestone units that were metamorphosed to skarn by 

intrusion of the Laramide quartz monzonite porphyry stocks. Extensive drilling has identified 

mineralization to a depth of at least 2,000 feet below the surface (Huss 2009:27). The degree 

(concentration) of mineralization diminishes to the south; it appears to extend northward amid 

complex faulting and eastward beneath an increasingly thick Mesozoic cover, as observed in drill 

cores.

Geotechnical

Site Geotechnical Environment

Rosemont Copper has completed site-wide geotechnical investigations (Tetra Tech 2007b, 2009c, 

2009d), the findings of which would be incorporated into the design of the project infrastructure. 

The project area is generally characterized by two surficial conditions: (1) bedrock at or near the 

surface with a thin mantle of soil (except where it is thicker in drainage bottoms); and (2) bedrock 

covered with Cenozoic alluvial deposits, including the Gila Conglomerate (Tetra Tech 2009c).

The structural setting at Rosemont is complex. A north-striking, steep, easterly tilted section of

Paleozoic marine sediments appears to be overlain with Glance Conglomerate and Willow Canyon 

Formation within the upper plate of an east-dipping, low-angle fault zone. The structural setting has 

been further complicated by several major north-trending, steeply east-dipping normal faults, which 

downdrop the stratigraphic section to the east, as well as numerous northeast- and northwest-trending

high-angle structural zones (Tetra Tech 2007b).

Along the ridge and east side of the Santa Rita Mountains is the area of highest fault density in the 

project area. Here, the Paleozoic rock units that outcrop are heavily faulted and fractured, with dips 

generally between 60 and 90 degrees. The density of faulting and fracturing decreases with distance 

from the east of the ridge. Mesozoic rocks of the Bisbee Group outcropping east of the Paleozoic 

units tend to be less faulted and fractured and are less steeply dipping than the Paleozoic units, with 

dips generally between 30 and 60 degrees (Montgomery and Associates Inc. 2010).

There are two notable faults that are frequently noted in any discussion of the faulting within the 

project area. The high-angle faulted zone in the Paleozoic units along the Santa Rita Mountains is 

referred to as the “Backbone fault” (Montgomery and Associates Inc. 2010). The Backbone fault is a 

complex structural assemblage of thrust faults, high-angle normal faults, and tear faults that forms the 

western edge of the east-dipping block of Paleozoic sediments, which include the Rosemont copper 

deposit (Anzalone 1995). The faults dip in an easterly direction at variable angles up to 90 degrees. 

The low-angle fault between the Willow Canyon Formation and the underlying Paleozoic units is 

identified as the “Flat fault.” The Flat fault, which is at the base of the Willow Canyon Formation in 

166 Final Environmental Impact Statement for the Rosemont Copper Project
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the proposed pit area, originated as a large displacement normal fault. Subsequent tilting of the strata 

in the area rotated this fault to a low angle, giving it the appearance of a low-angle thrust fault. 

The fault is present on the surface at the contact between the Willow Canyon and the Paleozoic units. 

The fault dips in an easterly direction at variable angles up to about 20 degrees (Montgomery and 

Associates Inc. 2010).

Earthquakes (Seismicity)

Historic earthquake activity in Arizona has been documented by DuBois et al. (1982), Pearthree and 

Calvo (1987:1), and Stover and Coffman (1993:62), while Quaternary faulting in the State has been 

mapped and reported by Menges and Pearthree (1983:18–33; 1989:649, 659, 666–669, 672–675), 

Pearthree and Calvo (1987:97–99, 107–114), and Pearthree et al. (1983:1–8, 12–30, 37–52).

The most notable seismic event felt in Arizona occurred in 1887 in Bavispe, Mexico, approximately 

110 miles southeast of the project site. Ground shaking was felt as far north as Albuquerque, New 

Mexico. Structural damage from the earthquake was recorded in the Tucson area, including damage 

to the courtyard wall at the San Xavier Mission, southwest of town. The USGS estimated the 

magnitude of this earthquake at 7.4 (Stover and Coffman 1993:62). The largest earthquake to occur 

within Arizona in historic times happened on July 21, 1959, along the Arizona–Utah border. 

The USGS reported the magnitude of that earthquake as 5.6. The magnitude of the earthquake that 

formed the Quaternary-age Santa Rita fault on the western flanks of the Santa Rita Mountains is 

estimated to have been between 6.4 and 7.3 (Pearthree and Calvo 1987:1). The maximum earthquake 

recorded by the USGS in the immediate project area was magnitude 4.5.

Although no earthquake in recorded history has caused deaths or injuries in Arizona, potentially 

active faults in the Basin and Range province and the Transition Zone can occasionally generate 

significant earthquakes of moderate intensity, with a possibility of serious damage over a wide area. 

Tetra Tech (2007b) completed a regional seismological assessment for the project, and the results 

indicate that five faults within an approximately 60-mile radius of the project site have been active in 

historic times and that an additional 22 faults within a 125-mile target radius have been active in 

historic times. All of the potentially active faults in the Phoenix and Tucson areas have low slip rates 

and long intervals between ruptures and have had little historic activity. Because of this, the AGS

places these areas in the low to moderate hazard category.

Concerns were raised during public comment about the possibility of creating a manmade seismic 

event through activities at the mine, either groundwater pumping or recharge, or the removal and 

placement of more than 1 billion tons of material. Manmade seismic events do occur; this is 

sometimes termed “induced seismicity.” Mining, oil or gas extraction, geothermal energy 

development, hydraulic fracturing, groundwater pumping, and water reservoirs have all been known 

to create small seismic events. Several studies have reviewed the occurrence, magnitude, and risk of 

such activities (U.S. Geological Survey 2013b).

The largest induced events in the United States have resulted from oil and gas extraction activities; 

the largest recorded earthquake magnitude was 6.5. Very small, typically nondamaging seismic events 

caused by mining activities like blasting are considered routine and are tracked by the USGS. 

Nonroutine induced seismic events caused by mining activities have also been analyzed by the 

USGS. In the period from 1973 to 2000, the largest recorded induced seismic event attributed to 

mining had an earthquake magnitude of 5.3 (U.S. Geological Survey 2013b). Seismic design of the 

waste rock and tailings facilities is based on peak ground acceleration, rather than magnitude. 

In general, however, the background earthquake used for the seismic design of the waste rock facility 

Final Environmental Impact Statement for the Rosemont Copper Project 167
Chapter 3. Affected Environment and Environmental Consequences

was 6.5 (Mohseni 2010; Tetra Tech 2007b), and for tailings facilities, it was 7.1 (AMEC Earth and 

Environmental Inc. 2009b). A historical analysis of induced seismic events indicates that it is unlikely 

that an induced seismic event, whether from mining or other human activities, would produce an 

earthquake of greater magnitude than the natural earthquake risks already considered in design of the 

facility.

Arizona Department of Environmental Quality (ADEQ) regulations (2004) require the development 

of two seismic design values for incorporation in mine facility design. Seismic design values are 

expressed as peak ground acceleration at the site relative to the earth’s gravity.

• Maximum Probable Earthquake – Earthquake with an 80 percent probability of not being 

exceeded in 100 years or the largest historical earthquake, whichever is greater. This design 

value is to be used for structures with a relatively short design life (e.g., 10 years) and 

minimum potential threat to human life or environment. At the project area, these facilities 

include the heap leach pads, nonjurisdictional ponds, and other short-lived facilities.

• Maximum Credible Earthquake – The maximum earthquake that appears possible under the 

presently known tectonic framework. This design value is to be used where human life is 

potentially threatened. This value would be used in the design of the waste rock facility and 

the dry-stack tailings facility.

Tetra Tech (2007b) completed a regional seismological assessment, with the following findings 

relative to the project area:

• The peak ground acceleration for a maximum probable earthquake for an earthquake with 

an 80 percent probability of not being exceeded in 100 years is 0.045 g (where g is the 

acceleration due to gravity equaling 32 feet per second squared).

• The peak ground acceleration for a maximum probable earthquake for the largest historical 

earthquake (Bavispe, Mexico, 1887) is 0.036 g. Therefore, the maximum probable 

earthquake seismic design value for the project area is a peak ground acceleration of 0.045 g, 

which is the greater of the two values.

• The peak ground acceleration for the maximum credible earthquake for the Santa Rita fault

zone located 6.9 miles from the project site is 0.328 g. This fault zone is Quaternary in age 

and has a length of 32.3 miles. The value of 0.328 g was therefore selected as the relevant 

maximum credible earthquake seismic design value for the project area.

While seismic design is based on peak ground acceleration, not magnitude, in general the waste rock

facility was designed to a 6.5 magnitude background earthquake, and the tailings facility was 

designed to a 7.1 magnitude earthquake.

Subsidence

Land subsidence is the lowering of the land surface resulting from changes that take place 

underground. The most common causes of land subsidence from human activity are: (1) pumping 

groundwater, oil, and gas from underground reservoirs; and (2) collapse of an underground mine. 

A common cause of subsidence from natural causes is dissolution of limestone by groundwater, 

which results in sinkholes, caves, and other karst features. Assessment of geological hazards in the 

project area indicates that there is little risk of subsidence from historic mining operations or karst 

features (Tetra Tech 2007c:16). Land subsidence associated with groundwater withdrawal is 

described in the “Groundwater Quantity” resource section in chapter 3.

168 Final Environmental Impact Statement for the Rosemont Copper Project
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Paleontology

Paleontological resources, or fossils, are the remains, imprints, or traces of once-living organisms 

preserved in rocks and sediments. These include mineralized, partially mineralized, or unmineralized 

bones and teeth, soft tissues, shells, wood, leaf impressions, footprints, burrows, and microscopic 

remains. The project area contains geological units (formations and members thereof) that are known 

in other areas of southern Arizona to contain scientifically significant paleontological resources. 

Fossil bearing sedimentary rocks in southeastern Arizona contain an array of various ages and types 

of vertebrate, invertebrate, and plant fossils. Mesozoic rock units near the project area have yielded 

marine invertebrates, as well as dinosaurs and other terrestrial vertebrates. Fossils have also been 

identified in Neogene surficial sedimentary deposits such as the Gila Conglomerate, as well as in 

unnamed Pliocene and Pleistocene lacustrine and alluvial deposits close to the project area.

The sedimentary bedrock geological formations and overlying surficial sedimentary deposits that 

occur within the perimeter fence of the project area are listed in table 14. It should be noted that the 

geological data analyzed were derived from published mapping by Johnson and Ferguson (2007), 

Ferguson et al. (2009), and Ferguson (2009). The paleontological sensitivity of each geological unit 

within the project area was ranked according to the Potential Fossil Yield Classification (Bureau of 

Land Management 2007). The Potential Fossil Yield Classification designations were assigned by the 

authors of the “Paleontological Resource Survey Report” (DeBusk et al. 2011), based on the results 

of the literature and records reviews and subsequent field survey. The Forest Service concurs with 

these classifications. 

Table 14. Summarized geology, age, potential paleontological content, and 

paleontological sensitivity of the project area using the Potential Fossil Yield 

Classification system

Geological Unit Map 

Symbol Age Typical Fossils

Potential 

Fossil Yield 

Classification

Disturbed areas d Holocene No in situ fossils in deposits of 

Holocene age

Class 2 (Low)

Younger surficial 

sedimentary 

deposits

Qy2, Qa, 

Qtc, Qyc

Holocene No in situ fossils in deposits of 

Holocene age

Class 2 (Low)

Older surficial 

sedimentary 

deposits

Qoa, Qi3, 

Qi2

Late Pleistocene–

Holocene

Vertebrates, invertebrates, and 

plants

Class 3a 

(Moderate)

Gila Conglomerate Tc Pliocene–Miocene Mammals, freshwater 

invertebrates, microfossils, and 

petrified wood

Class 3b 

(Unknown)

Megabreccia, 

Mesobreccia

Krz, Kra Upper Cretaceous Hadrosaur found in Empire 

Mountains in megabreccia 

block of Fort Crittenden 

Formation

Class 3b 

(Unknown)

Fort Crittenden 

Formation

Kfc Upper Cretaceous Dinosaurs, fish, amphibians,

and reptiles

Class 3a 

(Moderate)

Bisbee Group

Turney Ranch 

Formation

Kt Lower Cretaceous Dinosaurs, turtles, fish, 

invertebrates, and plants

Class 3a 

(Moderate)

Final Environmental Impact Statement for the Rosemont Copper Project 169
Chapter 3. Affected Environment and Environmental Consequences

Geological Unit Map 

Symbol Age Typical Fossils

Potential 

Fossil Yield 

Classification

Apache Canyon 

Formation

Ka Lower Cretaceous Possible terrestrial vertebrates 

in some facies

Class 3b 

(Unknown)

Shellenberger 

Canyon 

Formation

Ks Lower Cretaceous Dinosaurs, turtles, reptiles, 

fish, invertebrates, 

crocodilians, and petrified 

wood

Class 3a 

(Moderate)

Willow Canyon 

Formation

Kw Lower Cretaceous None reported Class 2 (Low)

Glance 

Conglomerate

Kjg Upper Jurassic–Lower 

Cretaceous

Sparse marine invertebrates in 

limestone clasts

Class 3a 

(Moderate)

Naco Group

Rain Valley 

Formation

Pr Permian Locally common marine 

invertebrates

Class 3a 

(Moderate)

Concha 

Limestone

Pch Permian Locally common marine 

invertebrates

Class 3a 

(Moderate)

Scherrer 

Formation

Permian Sparse marine invertebrates Class 3a 

(Moderate)

Epitaph 

Formation

Pe Permian Marine invertebrates Class 3a 

(Moderate)

Colina Limestone Pc Permian Sparse marine invertebrates Class 3a 

(Moderate)

Earp Formation PPe Pennsylvanian–Permian Diverse marine invertebrates Class 3a 

(Moderate)

Horquilla 

Limestone

Pennsylvanian Chaetitid corals locally 

abundant

Class 3a 

(Moderate)

Escabrosa 

Limestone

MDu Mississippian–Devonian Marine invertebrates and 

uncommon vertebrates

Class 3a 

(Moderate)

Martin Formation Dm Mississippian–Devonian Marine vertebrates (mostly 

placoderms), conodonts, and 

diverse invertebrates 

Class 3a 

(Moderate)

Abrigo Formation Ca Cambrian None reported Class 1 

(Very low)

Bolsa Quartzite Cb Cambrian Ichnofossils (Planolites) Class 2 (Low)

Previously recorded fossil localities occur approximately 3 miles away in the Gardner 

Canyon Formation and approximately 1 mile away in the Shellenberger Canyon Formation. 

The Shellenberger Canyon Formation has yielded fossil remains from dinosaur, crocodile, and turtle, 

as well as bivalves. A fossil locality in the Fort Crittenden Formation in the southeastern Santa Rita 

Mountains has also produced dinosaurs, crocodiles, a few different types of turtles, and invertebrates. 

At least one Late Pleistocene fossil locality has also been reported within a few miles of the project 

area. That site has produced camel, mastodon, horse, bison, and other mammals (Huckell 1980; U.S. 

Forest Service 2011c). Numerous invertebrate fossil localities have been found in the Escabrosa 

Limestone, Epitaph Formation, Scherrer Formation, Concha Limestone, and Rain Valley Formation

within the project area and to the north, northwest, and southwest. No significant fossil localities were 

discovered within the proposed perimeter fence boundary during the paleontological resources field 

surveys conducted in March 2011. 

170 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Cave Resources and Karst Landforms

Known Cave Resources

Moderately extensive cave systems are common in southern Arizona, particularly in the Paleozoic 

limestone formations that occur in the region. Two caves of commercial and scientific importance are 

Kartchner Caverns State Park near Benson and Colossal Cave Mountain Park near Tucson. Kartchner 

Caverns is a wet cave and a developed State park that is located within the limestone hills at the base 

of the Whetstone Mountains (Hill 1999). The park is approximately 23 miles due east of the project 

area. Colossal Cave, publicly owned but located in a privately owned park, is a dry cave in the 

Rincon Mountains approximately 17 miles north-northeast of the project area. This cave formed in a 

structurally complex block of deformed limestone—notably the Escabrosa Limestone (Peachey 

2000). No known caves are located within the immediate project area. 

Two caves, Cave of the Bells and Onyx Cave, both wet caves, are in the eastern slopes of the Santa 

Rita Mountains. Cave of the Bells is in Sawmill Canyon, approximately 7 miles south of the project 

area. The cave is about 0.25 mile long. It has many passages and 60-foot-tall vertical passageways 

that are developed in a complex stratigraphic sequence of Permian carbonate units, including the 

Colina Limestone, Epitaph Formation, and Concha Limestone. Onyx Cave is approximately 8 miles 

south of the Rosemont site and was designated by the National Park Service in 1974 as a National 

Natural Landmark. It has extensive passages, including about 3,000 feet of main passages and an 

additional 1,500 feet in side passages. The cave is about 0.5 mile long. The cave has a series of 

passageways and rooms that intersect primarily the Permian Rain Valley Formation and possibly also 

the Colina Limestone. The cave has exceptional speleothem development, including large slab or disk 

formation, large shields, abundant helectities, rim stone, flowstone, segmented pillars, and 

uncommonly long, slender soda straws.

The Glove Mine (Cave), a natural fissure or cave feature formed in Pennsylvanian Horquilla 

Limestone, is located approximately 16 miles south-southwest of the Rosemont project area on 

the western flanks of the Santa Rita Mountains. The cave is privately owned and was mined 

intermittently from 1922 through 1972 for copper, lead, and molybdenum mineralization. 

The mineralization was deposited in steeply dipping, coalescing pipes formed along faults and fault

intersections in favorable limestone; there is no skarn mineralization at the Glove Mine (Cave). 

The cave is designated as “dry” and is situated above the water table. Olson (1966) reported that 

meteoric water was the source of water that percolated through open fractures during high seasonal 

rainfall.

Agua Caliente Caves are so noted for multiple entrances and loops in the Permian Concha Limestone,

but the “caves” are actually a single network/fissure cave system. This cave is privately owned and 

gated and is located 15 miles south-southwest of the Rosemont project area on the western flanks of 

the Santa Rita Mountains in Santa Cruz County north of Glove Mine (Cave). The cave is above the 

water table and is designated as “dry,” but meteoric water can enter the cave through fractures during 

locally heavy rainfall events.

The term “wet” versus “dry” cave is a relative term that lacks any formal definition. The term is 

useful for describing relative cave conditions found in the same general regional environment but 

does not imply any particular characteristics and does not correlate with caves in other parts of the 

country. Most caves in southeastern Arizona are seasonally wet to some degree, but the quantity of 

water is relatively limited, dissipates quickly, is sensitive to drought conditions, and does not typically 

Final Environmental Impact Statement for the Rosemont Copper Project 171
Chapter 3. Affected Environment and Environmental Consequences

occur in a free-flowing stream. Wet caves and the presence of “living” (i.e., actively growing) 

speleothems is a common association made by the public but is not always accurate. 

Unknown Caves and Karst Potential

A number of public and agency comments were received regarding the potential existence of 

unknown cave or karst systems. In response to these comments, the Coronado contracted cave and 

karst experts to explore the potential for these features in the Santa Rita Mountains and the Rosemont 

project area in particular. 

Karst landforms are those with distinctive characteristics or relief and drainage arising primarily from 

dissolution of rock or soils by natural waters. The term applies to the dissolution of rock by flowing 

groundwater (Hoag, Peachey et al. 2012). Basically, the features of karst landforms and/or 

topography supply water to caves. While it is common for the term “karst” to generally be used to 

refer to cave formations, it is important to define the term strictly here because it implies that certain 

features and conditions are present. Although the karst topography and subsurface drainage were 

created in Late Mississippian time in the Escabrosa Limestone, active karst topography is not present 

today in southern Arizona. SRK states, “The definitional features of karst topography, with respect to 

supplying water to caves, are not present in southeastern Arizona” (Hoag, Peachey et al. 2012).

There are caves caused by nonkarst processes when one of three processes happens. Oxidation 

subsidence caves are formed when sulfide minerals are oxidized after exposure to meteoric water and 

oxygen. Through the oxidation, there is shrinkage that creates a kind of underground dome that 

may shift geologically and create surface cracks that weather with exposure and create a cave. 

Hydrothermal dissolution caves form by the rising thermal fluids’ interaction, mixing and cooling 

with certain rock formations. Hypogenic dissolution caves are caused by aggressive dissolution that 

begins far below the surface by acidic reactions, such as the oxidation of sulfides, that become 

aggressive again once they are exposed to meteoric waters close to the surface (Hoag, Peachey et al. 

2012).

Hypogenic dissolution created both the Onyx and Aqua Caliente Caves, described below, in the Santa 

Rita Mountains. Rosemont Copper has stated that no indication of caves or open spaces was found in 

the project drill cores and that the calc-silication that occurred during the hydrothermal mineralization 

event significantly changed the original limestone rock composition, making them unlikely hosts for 

subsequent cave formation (Cornoyer 2011a).

Environmental Consequences

Direct and Indirect Effects of Each Alternative

No Action Alternative

Under the no action alternative, no new impacts on geology, minerals, paleontology, or cave

resources would occur. Because the ore deposit would remain without development, there would 

likely be further characterization and/or exploration holes drilled within the project area once the ore 

deposit changed ownership or was decided to be developed. Neither climate change nor increasing 

population trends are expected to have any impacts on geology or paleontology resources. As noted 

previously, most caves in southeastern Arizona are seasonally wet to some degree. Continuing 

drought in the region would result in less moisture available to caves, which could impact cave 

resources, as could recreation pressures from increasing population. 

172 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Impacts Common to All Action Alternatives

Impacts to geology and mineral resources are the same for all action alternatives, other than those 

described for specific alternatives later in this section. 

Impacts to geology and mineral resources are associated with the excavation and relocation of 

geological materials from the mine pit and are related to mineral processing and mine waste disposal. 

In addition, there is a potential land subsidence impact related to the mine water supply withdrawal in 

the Santa Cruz Valley (see the “Groundwater Quantity” resource section in chapter 3). All impacts are 

common to all action alternatives. 

The mining operation would excavate and relocate approximately 1.8 billion to 1.9 billion tons of 

geological material, described in table 15.

Table 15. Amount of rock removed by formation

Rock Type/Formation Ore Removed 

(kilotons)

Waste Removed 

(kilotons)

Total Removed 

(kilotons)

Oxide – QMP/QLP 0 24,280 24,280

Oxide – Andesite 0 95,887 95,887

Oxide – Arkose 0 521,426 521,426

Oxide – Other 0 0 0

Sulfide – QMP/QLP 17,612 0 17,612

Sulfide – Abrigo 16,554 100,512 117,066

Sulfide – Concha 2,159 31,204 33,363

Sulfide – Epitath 72,730 29,610 102,340

Sulfide – Colina 98,542 12,194 110,736

Sulfide – Earp 111,704 22,629 134,333

Sulfide – Horquilla 281,334 68,251 349,585

Sulfide – Escabrosa 22,325 21,767 44,092

Sulfide – Other 44,246 152,095 196,341

Overburden 0 7,053 7,053

Tertiary Gravels 0 156,547 156,547

Total 667,206 1,243,455 1,910,661

Source: M3 Engineering and Technology Corporation (2012). 

Note: This table reflects rock removed under the Barrel Alternative, which removes the greatest amount of rock, based on 

the pit design. This level of detail was not provided in previous feasibility studies.

Slippage or ground movement may occur inside the Rosemont Copper Project open pit on individual 

benches or portions of benches and would vary over time during pit expansion; this type of 

subsidence is typically limited to the confines of the pit. The potential for slippage and the intensity 

of the potential slippage depend on the type and competency of the rock remaining in the pit walls 

after excavation, the angle or slope of intersecting fault structures, and the location above natural or 

human-made voids. Slope stability management would be addressed by the pit slope and catch-bench 

designs, dewatering programs to depressurize the pit walls, and routine monitoring programs. A slope 

stability analysis by Pratt et al. (2007:1–2) showed that depressurization by dewatering would be 

required primarily in the east wall (Willow Canyon Formation), south wall (Gila Conglomerate), and 

northwest wall (Bolsa Quartzite). Seismic hazards are considered low to moderate; because of 

appropriate project design criteria used for the tailings and waste rock facilities, seismic impacts to 

operations are not expected (AMEC Earth and Environmental Inc. 2009b; Mohseni 2010; Tetra Tech 

2007b). 

Final Environmental Impact Statement for the Rosemont Copper Project 173
Chapter 3. Affected Environment and Environmental Consequences

Paleontology

For this project, the area within the perimeter fence for the proposed action and each action 

alternative was analyzed for potential effects on paleontological resources. A paleontological field 

survey was conducted by Forest Service and SWCA Environmental Consultants paleontologists of 

the areas with exposures of paleontologically sensitive geological units (Potential Fossil Yield 

Classification Classes 3 through 5), as determined by desktop analysis. The results of the field survey 

were used to further refine the paleontological resource sensitivity of geological units specific to the 

project area. 

The results of this refinement showed that no geological units within the project area are considered 

to have a Potential Fossil Yield Classification ranking of Class 4 (high) or Class 5 (very high) 

sensitivity. Therefore, conditional paleontological surface clearance is recommended; monitoring

ahead of ground disturbance would be required in some areas to prevent impacts to significant fossils

in geological units that still have a moderate (Class 3b) potential for significant fossils, such as the 

Gila Conglomerate and Cretaceous volcanics. For the impacts analysis of subsurface impacts to 

paleontological resources, the total number of possible disturbance acres within geological units by 

Potential Fossil Yield Classification was calculated for each alternative. These calculations were used 

to estimate indirect and direct effects on paleontological resources as a result of project related 

surface-disturbing activities. Table 16 summarizes these calculations for each of the action 

alternatives.

Table 16. Summary of proposed surface disturbance in acres for each alternative by 

Potential Fossil Yield Classification ranking 

Potential Fossil Yield 

Classification Ranking

Proposed 

Action

Phased 

Tailings Barrel Barrel Trail

ScholefieldMcCleary

Class 1 (Very low) 1,237 1,127 700 837 2,362

Class 2 (Low) 277 278 328 313 242

Class 3a (Moderate) 388 389 440 408 389

Class 3b (Unknown) 2,488 2,515 2,762 3,133 2,060

Class 4 (High) 0 0 0 0 0

Class 5 (Very High) 0 0 0 0 0

Subtotal Classes 3–5/ Sensitive Acres 2,876 2,904 3,201.86 3,541 2,449

Total Acres 4,391 4,310 4,229.30 4,690 5,054

Caves

The two closest known caves to the project area are the Cave of the Bells and Onyx Cave, located 

about 7 to 8 miles away. Oxygen isotope analyses were conducted on a stalagmite from Cave of the 

Bells and indicated that over the past 75,000 years, the water entering the cave has been meteoric in 

nature (Spencer n.d. [2012]). All other known caves in the area also have meteoric source water. 

Therefore, any possible groundwater withdrawal from the area would not affect known caves, and 

surface water impacts that would result from the project would be far removed from these known 

caves. 

There has been extensive exploration and work conducted in the project area, both historically and 

recently, without cave discovery. In decades of field visits and searches by local specialists and 

recreationalists, no caves have been uncovered. Drilling density is currently about 1 drill hole every 

250 feet, which allows for an understanding of what is beneath the proposed facility area. The drilling 

174 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

has not uncovered any caves, and the original limestone geological units have metamorphosed into 

marble and skarn, which are resistant to nonkarst dissolution. SRK concludes, “In SRK’s professional 

opinion, the existence of caves has been assessed to the best extent possible at the current time” 

(Hoag, Peachey et al. 2012). A review of available information by the Coronado’s consulting 

geologists and cave specialists indicated that no impacts are expected to any unknown caves.

Proposed Action

Under the proposed action, a maximum total of 5,602 disturbed acres within the project area as 

defined for this analysis (see assumptions) is proposed for disturbance. Of these, 2,876 acres have 

moderate or unknown paleontological sensitivity (see table 16). Of all the alternatives, the proposed 

action has the third highest potential for disturbance of paleontologically sensitive acreage and 

potential adverse effects on scientifically significant paleontological resources.

Phased Tailings Alternative

Under the Phased Tailings Alternative, a maximum total of 5,471 disturbed acres within the project 

area as defined for this analysis (see assumptions) is proposed for disturbance. Of these, 2,904 acres 

have moderate or unknown paleontological sensitivity (see table 16). Of all the alternatives, the 

Phased Tailings Alternative has the second lowest potential for disturbance of paleontologically 

sensitive acreage and potential adverse effects on scientifically significant paleontological resources.

Barrel Alternative

Because this alternative does not use the oxide ore process, some of what would otherwise be 

characterized as oxide ore would be disposed of as part of the waste rock; therefore, the actual 

tonnage of waste rock versus ore and tailings would increase. The overall volume would not 

change—only the constituent percentages. This design difference would not lead to any additional 

effects regarding stability or seismic activity. 

Under the Barrel Alternative, a maximum total of 5,421 disturbed acres within the project area as 

defined for this analysis (see assumptions) is proposed for disturbance. Of these, 3,202 acres have 

moderate or unknown paleontological sensitivity (see table 16). Of all the alternatives, the Barrel 

Alternative has the lowest potential for disturbance of paleontologically sensitive acreage and 

potential adverse effects on scientifically significant paleontological resources.

Barrel Trail Alternative

Under the Barrel Trail Alternative, a maximum total of 5,878 disturbed acres within the project area 

as defined for this analysis (see assumptions) is proposed for disturbance. Of these, 3,541 acres have 

moderate or unknown paleontological sensitivity (see table 16). Of all the alternatives, the Barrel 

Trail Alternative has the second highest potential for disturbance of paleontologically sensitive 

acreage and potential adverse effects on scientifically significant paleontological resources.

Scholefield-McCleary Alternative

Under the Scholefield-McCleary Alternative, a maximum total of 6,187 disturbed acres within the 

project area as defined for this analysis (see assumptions) is proposed for disturbance. Of these, 2,449

acres have moderate or unknown paleontological sensitivity (see table 16). Of all the alternatives, the 

Final Environmental Impact Statement for the Rosemont Copper Project 175
Chapter 3. Affected Environment and Environmental Consequences

Scholefield-McCleary Alternative has the highest potential for disturbance of paleontologically 

sensitive acreage and potential adverse effects on scientifically significant paleontological resources.

Cumulative Effects

As outlined in the introduction to chapter 3, cumulative impacts of past and present actions are 

identified and analyzed in the “Affected Environment” part of each resource section, including for 

“Geology, Minerals, and Paleontology.” This cumulative effects discussion addresses the cumulative 

impacts of the action alternatives and any applicable reasonably foreseeable actions as identified on 

the Coronado ID team’s list of reasonably foreseeable future actions, provided in the introduction to 

chapter 3. 

No impacts to geology, minerals, or cave resources are expected from the proposed action or any of 

the action alternatives. Therefore, foreseeable actions would not contribute to cumulative impacts for 

those resources. 

The following reasonably foreseeable actions from that list were determined to contribute to a 

cumulative impact to paleontological resources:

• The BLM proposes to approve an MPO to expand the Andrada Mine limestone quarry in the 

Davidson Canyon drainage system north and northeast of the Santa Rita Mountains. 

The Andrada Mine is located approximately 4 miles from the Tucson, Arizona, city limits 

and 1 mile from the Vail, Arizona, city limits. This expansion has the potential to impact 

paleontological resources should they exist in the areas proposed for disturbance. 

• In late 2009, Freeport-McMoRan bought 8,900 acres of the long-closed Twin Buttes Mine 

site, near Sahuarita. Required permits for reopening the mine have not been issued to date, 

but it is reasonable to assume that this mine could be reopened at some point in the future.

Activities associated with reopening and operating this mine have the potential to impact 

paleontological resources through ground disturbance.

• The residential and commercial development of the Farmers Investment Company property 

within the jurisdiction of the Town of Sahuarita could have an impact. Much of this land has 

been actively managed for agriculture for many decades; however, the potential for 

development activities to impact paleontological resources still exists.

• Expansion of Rancho Sahuarita, Quail Creek, and Madera Highlands subdivisions could have 

an impact. Ground-disturbing activities associated with these subdivision expansions have 

the potential to further impact paleontological resources.

Ground-disturbing activities associated with these projects have the potential to disturb

paleontologically significant geological formations within the area. When combined with the risk of 

disturbance to paleontological resources from the action alternatives, the cumulative effect would be 

an increased risk of disturbance to and potential loss of paleontological resources.

Climate Change

No effects from expected climate change are anticipated for geological or paleontological resources.

As noted previously, most caves in southeastern Arizona are seasonally wet to some degree. Changes 

in precipitation patterns and temperature caused by climate change would result in less moisture 

available to caves, which could impact cave resources.

176 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Mitigation Effectiveness

Mitigation and Monitoring – Forest Service

• Upon discovery of paleontological resources, suspension of operations pending Forest 

Service review (FS-GMP-01). Upon discovery of significant paleontological resources, 

Rosemont Copper would suspend work at that site and the site would be investigated by the 

appropriate personnel before work resumes. The designated Forest Service representative 

would promptly coordinate the investigation with appropriate Forest Service or other 

specialist. Significant fossils may be recovered.

• Upon discovery of a cave or sinkhole, suspension of operations pending Forest Service

review (FS-GMP-02). Upon indication or discovery of a cave or sinkhole, Rosemont Copper 

would suspend work at that site and contact the designated Forest Service representative to 

investigate the discovery before work is reinitiated. The designated Forest Service 

representative would promptly coordinate the investigation with appropriate agency resource 

specialists. Any natural void in rock that is large enough for a human to enter constitutes a 

cave. Any collapse feature in or over carbonate rock constitutes a sinkhole.

Conclusion of Mitigation Effectiveness

Neither of the mitigation measures would be effective in avoiding or reducing impacts to caves or 

paleontological resources should they be encountered during project implementation. These 

mitigation measures would require disturbance to halt while resource professionals examined, 

recorded, and potentially salvaged items from the disturbed area (in the case of paleontological 

resources). However, the resources in their original settings would likely be heavily impacted, 

regardless of these mitigation measures.

Effects of Amending the Coronado Forest Plan

The effects to geology, minerals and paleontology resources from amending the Coronado Forest 

Plan are described under “Direct and Indirect Effects” above. The amendment would remove the 

following current management area standards and guidelines related to minerals management:

MA 4:

1. Common materials for personal or commercial use will require a permit.

2. Attempt to locate borrow areas in places that would enhance resources or facilities.

The proposed amendment would establish the following standards and guidelines for management 

area 16 related to minerals management:

1. To the extent possible, avoid construction of permanent roads across Federal lands unless 

needed for future access.

2. Mineral exploration and extraction activities will be allowed within the framework of 

applicable laws and regulations, including environmental laws and regulations designed to 

mitigate the impacts of mining activities. Emphasis will be on gaining cooperation and 

control through the use of operating plans and bonds for reclamation to protect and restore 

NFS surface resources, where practicable.

As noted in the analysis of direct, indirect and cumulative effects, this amendment would allow 

mineral development within management area 16. Permitted removal of common material would be 

Final Environmental Impact Statement for the Rosemont Copper Project 177
Chapter 3. Affected Environment and Environmental Consequences

allowed so long as it is within the framework of applicable laws and regulations. Borrow pits would 

likely be associated with approved mine plans of operation, which would dictate their location. 

The current forest plan does not contain management area standards and guidelines pertaining to 

geological, paleontological, or cave resources for management areas 1, 4, or 7A. 

Soils and Revegetation

Introduction

This section discusses soils and soil productivity in the project area and in the analysis area, as well 

as revegetation potential as it relates to mine reclamation. Soil consists of the mineral and organic 

matter on the surface that supports vegetation and stores moisture. Soils are defined by their specific 

physical, chemical, and biological characteristics. Soil productivity is the ability of a given soil to 

support plant growth under natural conditions.

Changes from the Draft Environmental Impact Statement

Public concerns regarding the “Soils” resource section of the DEIS were related primarily to the 

analysis of revegetation potential, in particular a general disbelief in the predicted success of 

revegetation activities. While the Coronado has expertise in managing vegetation and found the DEIS 

predictions to be reasonable, it was also recognized after reviewing public comments that making 

such predictions in the environmental impact statement (EIS) document may be premature. 

The ultimate outcome of revegetation efforts depends entirely on the selected techniques, adaptive 

management approaches, and success criteria, which would only be fully identified in the final 

reclamation and closure plan submitted with the final MPO. Expected revegetation success has been 

approached in the final environmental impact statement (FEIS) in the following way, which differs 

from the DEIS. First, the reclamation techniques and revegetation concepts currently proposed by 

Rosemont Copper are disclosed, including soil salvage techniques and stockpile locations, surface 

preparation and treatment, and seed application techniques (see the “Revegetation Techniques 

Proposed by Rosemont Copper” part of this resource section). Second, the available greenhouse 

studies and onsite reclamation test plot results are reviewed to provide pertinent information about the 

demonstrated outcome of revegetation attempts (see the “Assessment of Revegetation Potential of 

Waste Rock and Tailings Facilities” part of this resource section). Finally, the Coronado’s purpose 

and goals of revegetation are discussed (see the “Desired Condition” and “Revegetation Success 

Criteria” parts of this resource section). 

Species-specific predictions of revegetation success over time have been removed from the FEIS, 

since there was inadequate information available to support those predictions. Predictions of 

revegetation success and monitoring requirements will be addressed in a final revegetation plan, to be 

approved by the Coronado prior to approval of the final MPO. However, general information on 

desired conditions for vegetation has been included in the “Environmental Consequences” part of this 

resource section. This information is intended to disclose the best professional judgment of Coronado 

specialists regarding the expected outcome of revegetation activities (see the “Desired Condition” and 

“Revegetation Success Criteria” parts of this resource section). 

Further detail concerning the phasing and timing of concurrent reclamation has been obtained from 

Rosemont Copper, and this information is presented in the FEIS (see the “Revegetation Techniques 

Proposed by Rosemont Copper” part of this resource section).

178 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Disturbance acreage has been updated in the FEIS. Impacts on soil resources are related directly to 

areas of surface disturbance. For the DEIS, any area contained within the perimeter fence was 

considered disturbed. This has been refined for the FEIS; areas of disturbance largely lie within the 

security fence, along the primary access road and utility maintenance road and the utility corridor. 

The area between the perimeter and security fences would not be disturbed, other than discrete 

locations for facilities like groundwater test wells and the compliance check dam, which are included 

in the accounting of disturbance (see the “Soil Productivity Directly Lost to Mine Activities” part of 

this resource section).

Issues, Cause and Effect Relationships of Concern

One significant issue was identified during scoping concerning soils and soil productivity. Mine 

activities that disturb the soil and remove vegetation can cause erosion, loss of the ability of soil to 

sustain vegetation, and the movement of sediment into surface waters.

Issue 1: Impact on Land Stability and Soil Productivity

Ground disturbance from clearing vegetation, grading, and stockpiling soils has the potential to

accelerate erosion and reduce soil productivity. The tailings and waste rock facilities could be 

unstable over time, and reclamation may not adequately result in a stable, revegetated landscape.

The geochemical composition of tailings and waste rock facilities may not support native vegetation. 

Soils are nonrenewable resources. Damage, disturbance, and removal of the soil resource may result 

in a loss of soil productivity, physical structure, and ecological function across the proposed mine site 

and across downgradient lands. The mining area could potentially act as a barrier to sourcing and 

supporting natural downslope transportation of geological material, water, and nutrients through 

alluvial, eolian, and fluvial processes. 

Issue 1 Factors for Alternative Comparison

1. Qualitative assessment of long-term stability of tailings and waste rock facilities, including 

expected results of reclamation

2. Acres and quantitative level of disturbance leading to lost soil productivity

3. Qualitative assessment of the potential for revegetation of tailings and waste rock facilities

4. Qualitative evaluation of alteration of soil productivity and soil development

5. Tons per year of sediment delivery to Davidson Canyon, Cienega Creek, or other streams 

and washes, compared with background sediment loading

Analysis Methodology, Assumptions, 

Uncertain and Unknown Information 

Temporally, any potential impacts on soils would occur during the construction, active mining, and 

final reclamation and closure phases. However, soil is a nonrenewable resource, and the loss of soils 

within the project area is considered to be permanent unless reclamation occurs that places salvaged 

soil in these areas and results in successful revegetation to criteria established by the Coronado. 

Because of the need for reclamation to be completed and successful, the temporal bounds of analysis

for soils encompasses the postclosure phase, as well. 

Final Environmental Impact Statement for the Rosemont Copper Project 179
Chapter 3. Affected Environment and Environmental Consequences

The spatial area of analysis for soils encompasses the project area (i.e., mine process facilities, fuel 

storage tanks, processing fluid pipelines, tailings facility, and waste rock facility), access roads, and 

utility corridor. The analysis area for soils is depicted in figure 31, and the soil types shown in figure 

31 are described in table 17. This is the appropriate area for analyzing direct and indirect impacts to 

soils, as it contains all soil-disturbing activities associated with the action alternatives. The reroute of 

the Arizona National Scenic Trail was not included in the analysis area for soils; the level of ground 

disturbance expected from use of the trail is similar to that experienced from the casual recreational 

use that already occurs in the area. Further, any vegetation clearing activities for either the trail or the 

trailheads is likely to affect no more than 10 to 20 acres, which represents less than one hundredth of 

1 percent of the watershed area for Upper Cienega Creek, which receives most of the runoff from the 

area in which the trail reroute is located.

Soils of the Coronado National Forest were identified using the National Resources Conservation 

Service (2010b) Web Soil Survey. In addition, site-specific soil profile surveys were conducted by 

Tetra Tech in March 2007 and August 2010 to assess the potential for soils to support reclamation and 

revegetation (Tetra Tech 2010i).

Qualitative assessments of long-term stability for waste rock and the character of risks to stability 

through time are based on stability analysis by Tetra Tech (2010f); for tailings, the qualitative 

assessments are based on stability analysis by AMEC Earth and Environmental (2009b).

The area and quantitative level of disturbance leading to lost soil productivity are measured by the 

footprint of surface-disturbing mine activities. The qualitative evaluation of alteration of soil

productivity and soil development is analyzed by assessing the potential for revegetation and 

potential for erosion after revegetation occurs. Sediment delivery to Davidson Canyon and Cienega 

Creek from the watershed as a whole under each alternative was estimated by Zeller (2012; 2010a; 

2010b); sediment volume was converted to tonnage using a bulk density of 1.5 grams per cubic 

centimeter. Expected changes in sediment delivery and total suspended solid concentrations were 

modeled using the Pacific Southwest Interagency Committee (1968) method for sediment yield 

analysis. This analysis specifically modeled changes in sediment delivery at the point at which SR 83 

crosses Barrel Canyon. Sediment delivery to other streams and washes was not analyzed. In 

particular, sediment delivery to Upper Cienega Creek was not analyzed, as there is no significant 

surface disturbance within this watershed. Analysis of sediment delivery is included in this section as 

an indication of how erosion might change in the watershed; effects on the geomorphology of 

Davidson Canyon and Cienega Creek from delivery of this sediment downstream are more fully 

analyzed in the “Surface Water Quality” resource section in chapter 3.

The draft stormwater pollution prevention plan has been made available for the mine (Rosemont 

Copper Company 2013). This is a living document that will constantly change throughout the mine 

life to adapt to changing conditions. In addition, the plan will be reviewed by ADEQ prior to 

construction and will likely be modified at that time. The plan was reviewed for details of 

stabilization measures or sediment control measures to be implemented on soil salvage piles and 

reclaimed slopes to minimize erosion. At this time, the details contained in the plan are minimal and 

do not provide sufficient information to include in this section.

180 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 31. Analysis area for soils

Final Environmental Impact Statement for the Rosemont Copper Project 181
Chapter 3. Affected Environment and Environmental Consequences

Table 17. Soil characteristics in the analysis area

Map 

Unit 

Symbol

Map Unit Name Soil Type Acres Erosion

Potential

Percent 

Analysis 

Area*

Number 

of Site 

Locations 

on Map

McF Mabray-Chiricahua-Rock outcrop 

association, steep

Cobbly sandy 

loam and very 

gravelly loam

2,753 Severe 21% 4

LgF Lampshire-Graham-Rock outcrop 

association, steep

Very cobbly 

loam

1,926 Severe 15% 3

HaF Hathaway gravelly sandy loam, 

20 to 50% slopes

Gravelly sandy 

loam

1,584 Moderate 12% 2

LcF Lampshire-Chiricahua association, 

steep

Very cobbly 

loam

1,513 Severe 11% 3

CoE Chiricahua cobbly sandy loam, 

10 to 45% slopes

Cobbly sandy 

loam

1,279 Moderate 10% 2

BhD Bernardino-Hathaway association, 

rolling

Gravelly clay 

loam

910 Slight 7% 2

FrF Faraway-Rock outcrop complex, 

30 to 60% slopes

Very cobbly fine 

sandy loam

836 Severe 6% 2

TrF Tortugas-Rock outcrop complex, 

25 to 60% slopes

Very cobbly 

loam

414 Severe 3% 3

WgE White House gravelly loam, 

10 to 35% slopes

Gravelly loam 406 Moderate 3% 3

CtB Comoro soils, 0 to 5% slopes Gravelly sandy 

loam

386 Slight 3% 4

HhE2 Hathaway soils, 1 to 40% slopes, 

eroded

Gravelly sandy 

loam

267 Moderate 2% 1

An Anthony soils Sandy loam 205 Slight 2% 3

CmE Castro very gravelly sandy loam, 

10 to 40% slopes

Very gravelly 

sandy loam

153 Moderate 1% 1

CgE Caralampi gravelly sandy loam, 

10 to 40% slopes

Gravelly sandy 

loam

132 Moderate 1% 3

Rn Rock outcrop-Lithic Haplustolls 

association

Not applicable 128 Not Rated 1% 4

SoB Sonoita gravelly sandy loam, 

1 to 8% slopes

Gravelly sandy 

loam

106 Slight <1% 6

BgF Barkerville-Gaddes association, 

steep

Cobbly sandy 

loam

95 Severe <1% 1

Subtotal – Area with Slight 

Erosion Potential

1,607 12%

Subtotal – Area with Moderate 

Erosion Potential

3,821 29%

Subtotal – Area with Severe 

Erosion Potential

7,537 58%

Total – Analysis Area 13,287 100%

Source: Natural Resources Conservation Service (2010b). 

* Excludes soils representing less than 0.5% of analysis area.

Summary of Effects by Issue Factor by Alternative

Table 18 presents the summary comparison of impacts from each alternative.

182 Final Environmental Impact Statement for the Rosemont Copper Project
Final Environmental Impact Statement for the Rosemont Copper Project 183

Table 18. Summary of effects

Issue Factor No Action Proposed 

Action Phased Tailings Barrel Barrel Trail 

Issue 1.1: Qualitative assessment of 

long-term stability of tailings and 

waste rock facilities, including 

expected results of reclamation

None Modeling 

indicates that 

waste rock and 

tailings would be 

more stable than 

required by 

regulations

Same as for 

proposed action

Same as for 

proposed action

Same as for 

proposed action

Issue 1.2: Acres and quantitative level 

of disturbance leading to lost soil

productivity

No changes from 

the proposed mine. 

Disturbance from 

grazing, recreation

use, and fire 

activity would 

continue. 

Recreation use and 

fire activity would 

increase with 

population and 

climate change.

5,612 5,481 5,431 5,888 

Issue 1.3: Qualitative assessment of 

the potential for revegetation of 

tailings and waste rock facilities

None Onsite test plots 

and greenhouse 

studies indicate 

that revegetation 

can produce a 

vegetation volume 

that is similar to 

historic climax 

conditions under 

proper 

management

Same as for 

proposed action

Same as for 

proposed action

Same as for 

proposed action
184 Final Environmental Impact Statement for the Rosemont Copper Project

Issue Factor No Action Proposed 

Action Phased Tailings Barrel Barrel Trail 

Issue 1.4: Qualitative evaluation of 

alteration of soil productivity and soil 

development

None Soil productivity 

would be 

reclaimed 

following 

placement of soil

or soil/rock cover 

and revegetation, 

with the exception 

of 955 acres of 

mine pit

Same as for 

proposed action

Same as for 

proposed action

Same as for 

proposed action

Issue 1.5: Tons per year of sediment

delivery to Davidson Canyon, 

Cienega Creek, or other streams and 

washes, compared with background 

sediment loading

32,600 16,000 16,500 22,170 20,300 
Chapter 3. Affected Environment and Environmental Consequences

Affected Environment

Relevant Laws, Regulations, Policies, and Plans

NFS soil resources are defined, protected, and maintained under the Organic Administration Act of 

1897, Bankhead-Jones Farm Tenant Act of 1937, Multiple-Use Sustained-Yield Act of 1960, Forest 

and Rangeland Renewable Resources Planning Act of 1974, and National Forest Management Policy 

Act of 1976. 

Soil resources and reclamation are managed in accordance with the following guidelines:

• FSM 2550, “Soil Management” (U.S. Forest Service 2010b), and R3 Technical Guidance 

(U.S. Forest Service 2013b);

• FSM 2840, “Reclamation” (U.S. Forest Service 1990b);

• FSM 2070, “Vegetation Ecology” (U.S. Forest Service 2008b);

• FSM 1940, “Inventory, Monitoring, and Assessment Activities” (U.S. Forest Service 2009b);

• U.S. Department of Agriculture “Soil Survey Manual” (U.S. Department of Agriculture Soil 

Survey Division Staff 1993);

• Title 27 Arizona Revised Statutes (ARS) Chapter 1, Article 4;

• Forest Service General Technical Report W0-68, “Terrestrial Ecological Unit Inventory 

Technical Guide: Landscape and Lane Unit Scales” (Winthers et al. 2005);

• FS-1006, “Native Plant Materials Policy: A Strategic Framework” (U.S. Forest Service

2012d);

• Comprehensive Environmental Response, Compensation, and Liability Act, which 

establishes prohibitions and requirements concerning closed and abandoned hazardous waste 

sites and provides for liability of persons responsible for releases of hazardous waste at these 

sites;

• Arizona Administrative Code (AAC) R18-7-201, “Arizona Soil Remediation Levels:” Soil 

remediation levels would be applied to determine the extent to which reclamation must 

mitigate any known soil contamination during mine closure; soil remediation levels are also 

applicable in the event of contamination or spills that occur during active mine life; and 

• AAC R18-9-A209, “Aquifer Protection Permit Closure Requirements:” Investigation and 

characterization of potential soil contamination is a component of closure and contingency 

plans required under the Arizona Aquifer Protection Permit process.

Forest Service Guidance

General Management Direction for 

Soils on the Coronado National Forest

Federal policy for soil management requires the Forest Service, in accordance with FSM 2550, to do 

the following: promote and sustain biological and hydrological function, manage ecosystems to 

maintain or improve soil quality, and use soil properties to assess the condition and potential effects 

on soil while planning and implementing projects (U.S. Forest Service 2010b). Soils are managed by 

the Forest Service in accordance with direction contained in the forest plan (U.S. Forest Service 

1986), in recognition of the fact that soil productivity affects the quality and quantity of water that 

originates in the watersheds of the Coronado National Forest and provides water to southern Arizona 

and New Mexico. Management activities are directed to protect or enhance watershed conditions in 

recognition of the connection between hydrologic function and soil productivity. Under management 

Final Environmental Impact Statement for the Rosemont Copper Project 185
Chapter 3. Affected Environment and Environmental Consequences

directives in the forest plan, best management practices “will be used to minimize the time of 

recovery to a satisfactory erosion level, minimize soil productivity loss, improve water quality and 

minimize channel damage” (U.S. Forest Service 1986:38). Further, the forest plan states that 

management plans, including those for mineral extraction, should carefully consider activities that 

affect sensitive soils and riparian areas to minimize soil damage (U.S. Forest Service 1986:38–40). 

The Forest Service’s reclamation objectives and management policies for lands disturbed by mineral 

extraction and associated activities are outlined in FSM 2840. The Forest Service manages 

reclamation efforts in order to reduce the environmental impacts of mineral extraction and ensure that 

disturbed lands are returned to a use that is consistent with long-term forest land and resource 

management plans. According to FSM 2840, the following policies are to be implemented to achieve 

the Forest Service’s reclamation objectives:

1. Reclamation shall be an integral part of plans of operation that propose surface disturbance.

2. All lands disturbed by mineral activities shall be reclaimed to a condition that is consistent 

with forest land and resource management plans, including applicable State air and water 

quality requirements.

3. All reclamation requirements included in a plan of operations shall include measurable 

performance standards. Reclamation requirements shall be those that are reasonable, 

practicable, and necessary to attain standards.

4. Reclamation shall be undertaken in a timely fashion and occur sequentially with ongoing 

mineral activities.

5. Reclamation bonds, sureties, or other financial guarantees shall ordinarily be required for all 

mineral activities that require a plan of operations; dollar amounts of such guarantees shall be 

sufficient to cover the full cost of reclamation.

6. To the extent practicable, reclaimed NFS land shall be free of long-term maintenance 

requirements.

Additional Forest Service objectives and management policies for disturbed lands are also addressed 

in FSM 2070:

1. The Forest and Rangeland Renewable Resource Planning Act of 1974, as amended by the 

National Forest Management Act of 1976 (Section 6, codified at 16 U.S.C. §1600(g)), 

provides for diversity of plant and animal communities based on the suitability and capability 

of the specific land areas in order to meet overall multiple-use objectives and within the 

multiple-use objectives of a land management plan. The act also requires, where appropriate, 

to the degree practicable, to preserve the diversity of tree species similar to that existing in 

the region controlled by the plan.

2. Section 515 of the Surface Mining Control and Reclamation Act of 1977 (30 U.S.C. 1201, 

1201 (note), 1236, 1272, 1305), as amended, directs the establishment on the mine areas, and 

all other lands affected, of a diverse, effective and permanent vegetative cover of the same 

seasonal variety native to the areas of land to be affected and capable of self-regeneration and 

plant succession at least equal in extent of cover to the natural vegetation on the area, except 

that introduced species may be used in the revegetation process where desirable and 

necessary to achieve the approved postmining land use plan.

186 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

State Requirements

Reclamation is also managed under the Arizona Mined Land Reclamation Act, which provides a 

mechanism for requiring the reclamation of mined lands to a safe, stable condition. 

Title 27 ARS Chapter 1, Article 4, specifies the requirements for new mines to submit a reclamation

plan to the Arizona State Mine Inspector. The State Mine Inspector is responsible for reclamation on 

private property. Two criteria contained in the statute specifically involve soils and soil productivity:

• Section 27-971(B)(9) requires that the plan include information on proposed reclamation

measures that would be taken to address erosion control and stability; and

• Section 27-974 specifies that prior to disturbance, soil shall be conserved unless otherwise it 

is unable to be conserved or it is unnecessary to do so.

Investigation and characterization of potential soil contamination is contained under the Arizona 

Aquifer Protection Permit regulations. The aquifer protection permit was issued to Rosemont Copper 

on April 3, 2012. Under these regulations, a closure plan is required that includes the following:

• A site investigation plan that includes a summary of relevant site studies already conducted 

and a proposed scope of work for any additional site investigation necessary to identify the 

following: the lateral and vertical extent of contamination in soils and groundwater, using 

applicable standards; the approximate quantity and chemical, biological, and physical 

characteristics of each waste, contaminated water, or contaminated soil proposed for removal 

from the facility; the approximate quantity and chemical, biological, and physical 

characteristics of each waste, contaminated water, or contaminated soil that would remain at 

the facility; and information regarding site conditions related to pollutant fate and transport 

that may influence the scope of sampling necessary to characterize the site for closure.

• A closure design that identifies the following: the method used, if any, to treat any material 

remaining at the facility; the method used to control the discharge of pollutants from the 

facility; any limitation on future land or water uses created as a result of the facility’s 

operations or closure activities; and the methods used to secure the facility.

Existing Conditions

Soil Occurrence and Characteristics

The project area is in the Basin and Range physiographic province of southeastern Arizona. 

The range of soil characteristics that occur in the project area includes mixed variations of sandy 

loam, cobbly loam, and gravelly loams on gentle to steep slopes, along with valley bottoms with rock 

outcrops on side slopes. 

Surface water and soils transported from the project area flow into various drainages, which then flow 

first into Davidson Canyon and eventually into Cienega Creek. Table 17, above, describes each of the 

soil units represented in figure 31. 

Existing Soil Disturbance

Existing Mineral Related Disturbance

Mineral related disturbance from previous mineral exploration and extraction is evident in the area, 

as described in the “Geology, Minerals, and Paleontology” resource section of chapter 3. Historic 

mining activity began in the mid-1800s. By the 1880s, the production of mines in the Rosemont and 

Final Environmental Impact Statement for the Rosemont Copper Project 187
Chapter 3. Affected Environment and Environmental Consequences

Helvetia mining districts supported the construction and operation of two smelters, one on each side 

of the Santa Rita Mountains. Mine dumps, road ballast, and slag deposits from historic mining 

operations are visible, but not a dominant feature in the landscape. A slag deposit in the SW 1⁄4 of 

Section 29 (Township 18 South, Range 16 East) is visible from NFSR 4058. Downslope of the 

Naragansett Mine works are heavily vegetated dumps. Mining production in the project area ceased 

in 1951. 

Rosemont Copper recently conducted exploratory drilling in the project area to ascertain the location, 

distribution, and geological configuration of the mineral deposits within its mineral claim area. Since 

2005, Rosemont Copper has drilled 87 boreholes. The most recent drilling occurred in 2011 and 

2012, when 12 boreholes were drilled. These areas of disturbance include well pads, typically 

measuring 30 by 60 feet, and access roads. In total, 266 locations have been drilled to investigate the 

ore body.

The University of Arizona’s School of Natural Resources and the Environment, in conjunction with 

Rosemont Copper, is currently conducting an onsite revegetation program on privately owned land to 

determine which reclaimable soils and overburden within the proposed project area are conducive to 

vegetation growth, using slopes and materials similar to the proposed reclaimed waste rock and 

tailings facilities. Existing vegetation and topsoil were removed from the test site area and replaced 

with a variety of soil materials and treatment covers to test revegetation success. The cumulative total 

of the test plots’ disturbance area is approximately 8 acres, located on private land.

Existing Grazing Related Disturbance

The majority of NFS land surrounding the project area is currently under permit for livestock grazing. 

The Rosemont Copper property is part of an existing ranching facility. Currently, Rosemont Copper 

holds term grazing permits on four allotments: Rosemont, Thurber, Greaterville, and DeBaud. 

The four allotments permitted to Rosemont Copper contain a mixture of Federal, State, and private 

lands totaling approximately 22,190 acres, with 19,370 acres of land suitable for livestock grazing.

Cattle grazing disturbs soil by removing protective vegetation and compacting soil surfaces (Shaw et 

al. 1991). The Coronado currently employs a rotational grazing system on all of its allotments as part 

of an adaptive management strategy in order to allow pastures to rest when necessary, which results 

in faster recovery. See the “Livestock Grazing” resource section for more detail.

Existing Recreation Related Disturbance

Existing soil disturbance from recreation related activities is the result of trails, access roads, offhighway-vehicle areas, other developed recreation facilities, and recreation such as camping in 

undeveloped areas as well. Forest roads, routes, and trails in the project area total 285 miles. 

Immediately adjacent to the project area are two off-highway-vehicle staging areas that see 

considerable recreation use. Travel in the project area is restricted to designated routes only; however, 

some unauthorized off-trail motorized use does occur. See the “Recreation and Wilderness” resource 

section for more detail on existing use levels and trends.

Overall Current Condition of Watershed

The erosion potential for the entire watershed is addressed by a combination of the erosion potential 

of various soils (see table 17) and the state of vegetation on the watershed. There are two vegetative 

conditions to consider: the historic climax plant community and the current conditions. The historic 

climax plant community represents the plant community that existed at the time of European 

immigration and settlement. It is the plant community that was in dynamic equilibrium with its 

188 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

environment and was best adapted to the unique combination of environmental factors associated 

with the site. The historic climax plant community was obtained from the Ecological Site 

Descriptions prepared by the Natural Resources Conservation Service (2006; 2010a). Fehmi (2007)

notes that the Rosemont Copper Mine site is visibly degraded from the historic climax plant 

community, primarily because of the substantial cover of juniper and mesquite present, which 

resulted from historical fire prevention strategies and overgrazing by cattle. Once the canopy cover of 

these species increases to more than 25 percent, site instability and soil erosion can occur.

The “General Ecosystem Survey for the Coronado National Forest” (Shaw et al. 1991:5) further 

compares the current condition of the watershed with the historic climax condition (table 19). 

In general, vegetation basal area currently represents approximately 5 percent of the surface, whereas 

under historic climax conditions, it would represent 15 to 25 percent of the surface. Likewise, bare 

soil would represent 20 to 45 percent of the surface under historic climax conditions, but it currently 

represents 30 to 60 percent of the surface.

Table 19. Summary of the potential plant community and soil conditions based on the 

general ecosystem survey

Landform State Overstory Rock 

Fragments Litter VegetationBasal Area

Bare 

Soil

South-facing slopes Historic climax 15% 50% 5% 20% 25%

South-facing slopes Current 25% 50% 5% 5% 40%

North-facing slopes Historic climax 50% 30% 40% 15% 20%

North-facing slopes Current 50% 30% 40% 5% 30%

Elevated flats Historic climax 15% 30% 5% 25% 45%

Elevated flats Current 25% 30% 5% 5% 60%

Source: Shaw et al. (1991 : Map Units 490.1–490.3).

While describing “current” conditions, the general ecosystem survey is a regional document, and the 

descriptions are both generalized and dated. More recent current rangeland conditions have been 

monitored by the Coronado but are not directly comparable to the historic climax plant community. 

Rangeland monitoring results are shown in table 20. Rangeland monitoring analysis collects 

quantitative data and expresses the results in four categories: poor, fair, good, and excellent. Soil

condition is a qualitative assessment of soil characteristics and is expressed as unsatisfactory, 

impaired, or satisfactory, with “satisfactory” being the highest level obtainable. Rangeland 

monitoring indicates that both vegetation and soil condition have generally improved over time.

Table 20. Rangeland conditions from the 1950s through 2010

Allotment 1950s 

Vegetation

1950s 

Soils

1967 

to 1969

Vegetation

1967 

to 1969

Soils

1995

Vegetation

1995

Soils

2005 

to 2010

Vegetation

2005 

to 2010

Soils

Rosemont – – Fair to 

good

High fair to 

excellent

Fair to 

excellent

– Good to 

excellent

Satisfactory

Greaterville – – Good High fair to 

excellent

Fair to 

excellent

– Fair to 

excellent

Satisfactory

DeBaud – – Fair to 

high fair

Fair to 

good

Fair to 

good

– High fair to 

good

Satisfactory

Thurber Fair to 

good

Fair to 

good

– – Good to 

excellent

– Fair to 

good

Good to 

excellent

Final Environmental Impact Statement for the Rosemont Copper Project 189
Chapter 3. Affected Environment and Environmental Consequences

Allotment 1950s 

Vegetation

1950s 

Soils

1967 

to 1969

Vegetation

1967 

to 1969

Soils

1995

Vegetation

1995

Soils

2005 

to 2010

Vegetation

2005 

to 2010

Soils

Helvetia – – Fair to 

good

Fair to 

good

– – Fair Good

Stone 

Springs

– – Fair Fair – – Poor to 

excellent

Satisfactory

Sources: Biedenbender (2010a; 2010b); Brown (2007); Lockwood (2007; 2010a; 2010b). 

Notes: – = No soils or vegetation conditions were reported for this time period. 

The rating system used to characterize soils in rangeland condition assessments has changed over time. By 2005, the Forest 

Service had adopted soil ratings as described below. Prior to this, ratings were given on a rating scale of “poor” to 

“excellent.” 

The most recent soil rating system is based on the Natural Resources Conservation Service Soil Condition Rating Guide. 

These ratings are defined as follows (U.S. Forest Service 1999:4–5): 

Satisfactory – Indicators signify that soil function is being sustained and soil is functioning properly and normally. 

The ability of soil to maintain resource values and sustain outputs is high.

Impaired – Indicators signify a reduction in soil function. The ability of soil to function properly has been reduced and/or 

there exists an increased vulnerability to degradation.

Unsatisfactory – Indicators signify that loss of soil function has occurred. Degradation of vital soil functions results in the 

inability of soil to maintain resource values, sustain outputs, and recover from impacts.

The Forest Service has recently undertaken a comprehensive and consistent assessment of watershed 

condition on all national forests (U.S. Forest Service 2012h). The Coronado completed the 

assessment in the analysis area in 2011. The assessment includes soils, forest cover, forest health, 

terrestrial invasive species, and rangeland condition, all of which are indicative of soil and vegetation

conditions. Five watersheds were assessed for 12 specific indicators of watershed health in the project 

area. The results of these 12 indicators were then used to assign an overall condition classification. 

These watersheds are more general than those discussed in the “Surface Water Quantity” section; the 

correlation between the two sections is included in the footnotes to table 21. Also, these conditions 

only refer to those portions of the watershed that are on the Coronado National Forest (U.S. Forest 

Service 2012h). These recent watershed conditions are summarized in table 21.

In summary, based on the available surveys, including the General Ecosystem Survey, rangeland

surveys, and the watershed condition assessment, the project area is functioning at a sufficient level to 

support present uses such as livestock grazing. The trends for the condition of vegetation and soils are 

improving.

Soils Suitable for Reclamation

In March 2007 and August 2010, Tetra Tech studied soil profiles from 14 sites that represent the 

characteristic soil types within the project area in order to assess the potential for soils in the project 

area to be salvaged for vegetation growth media for reclamation (Tetra Tech 2007d; 2007f, 2010i).

Salvaging would involve stripping the natural soils from areas to be disturbed by mining and 

stockpiling those soils for later use in reclamation activities. The study analyzed soils for physical and 

chemical properties, including soil acidity and alkalinity, electrical conductivity, sodium adsorption 

ratio, nutrient content, and acid base accounting. Tetra Tech (2010i) concluded that potential soil 

salvage was available in five general areas: north-aspect soils, south-aspect soils, residual benches 

and sideslopes, alluvial terraces, and alluvial washes/fans. The locations of the soils suitable for 

salvaging approximately correspond to the Bernardino-Hathaway association (BhD) and Hathaway 

gravelly sandy loam (HaF), as depicted in figure 29. 

190 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 21. Watershed condition classification within the analysis area

Indicator Box Canyon 

Wash

Davidson 

Canyon*

Sycamore 

Canyon

Fortynine 

Wash–Cienega 

Creek†

Empire 

Gulch

Aquatic biota Fair Fair Fair Fair Good

Riparian/watershed vegetation Fair Fair Fair Fair Fair

Water quality Good Good Good Good Good

Water quantity Fair Fair Good Fair Fair

Aquatic habitat Fair Fair Fair Fair Fair

Roads and trails Fair Fair Fair Fair Fair

Soil Fair Good Fair Good Good

Forest cover Good – – – Good

Forest health Good Good Good Good Good

Terrestrial invasive species Fair Fair Fair Fair Fair

Rangeland vegetation Fair Fair Fair Good Fair

Overall watershed condition 

classification

Functioning –

at risk

Functioning –

at risk

Functioning –

at risk

Functioning –

at risk

Functioning –

at risk

Notes: 

– = The indicator is not applicable to these watersheds.

Explanation of ratings (Potyondy and Geier 2011):

Good – A rating of “good” is the expected indicator value in a watershed with high geomorphic, hydrologic, and biotic 

integrity relative to its natural potential condition, and it suggests that the watershed is functioning properly with respect to 

that indicator.

Fair – A rating of “fair” is the expected indicator value in a watershed with moderate geomorphic, hydrologic, and biotic 

integrity relative to its natural potential condition, and it suggests that the watershed is functioning at risk with respect to 

that indicator.

Poor – A rating of “poor” is the expected indicator value in a watershed with moderate geomorphic, hydrologic, and biotic 

integrity relative to its natural potential condition, and it suggests that the watershed is functioning at unacceptable risk with 

respect to that indicator 

Functioning – at risk – The rating “functioning – at risk” is an overall assessment of the overall state of the watershed, 

based on the combined individual indicator values, and it indicates that the watershed has only moderate geomorphic, 

hydrologic, and biotic integrity relative to its natural potential condition.

* This watershed includes the areas encompassed by the waste rock, tailings, and plant site facilities. This watershed 

corresponds to the following watersheds analyzed in the “Surface Water Quantity” resource section of the EIS: Davidson 

Canyon, Mulberry Canyon, Papago Canyon, Scholefield Canyon, McCleary Canyon, Wasp Canyon, Barrel Canyon, Upper 

Barrel Canyon, and East Canyon.

† This watershed corresponds to the following watersheds analyzed in the “Surface Water Quantity” resource section of the 

EIS: Oak Tree Canyon and North Canyon.

The north-aspect soils available for salvage are sandy loams with an approximate salvage depth of 12 

inches. South-aspect soils available for salvage are sandy loams that have approximately 6 inches of 

suitable soil for salvage, with occasional deeper deposits in pockets. Residual benches and sideslopes 

consist of clays and clay loams; while soils extend deeper in these areas, the salvage depth is 

generally limited to approximately 12 inches. Alluvial terraces generally consist of gravelly loams 

that have a salvage depth of approximately 18 inches. The alluvial washes/fans consist of loamy 

sands and sandy loams located in the bottoms of drainages, and these have the deepest soil salvage 

potential—approximately 18 to 36 inches. 

Estimated Soil Salvage Volumes

The estimated soil salvage areas and volumes in the dry-stack tailings facility, waste rock facility, and 

other disturbed areas of the Rosemont Copper Mine are based on soil texture, organic matter, coarse 

fragments, and nutrient content. The estimated areas and volumes of soil salvage were estimated for 

Final Environmental Impact Statement for the Rosemont Copper Project 191
Chapter 3. Affected Environment and Environmental Consequences

all alternatives in November 2010 (Tetra Tech 2010i) and updated in July 2012 to specifically reflect 

the Barrel Alternative (CDM Smith 2012a). The volume of available soil salvage differs by 

alternative and is discussed in the “Environmental Consequences” part of this resource section. 

Existing Indications of Revegetation Success

Revegetation success has reportedly been observed in the proposed pit area where weathered bedrock 

material has been used for reclamation of exploration sites (Tetra Tech 2007d). The primary physical 

properties limiting salvage include high clay content and high coarse-fragment content. Soils on the 

ridgetops, especially in the northwestern portion of the project area, have high clay concentrations in 

the subsoil that may require special consideration for reclamation planning. High percentages of 

coarse fragments are generally common throughout the project area. The primary chemical property 

limiting salvage is nutrient content. Nutrient content is variable throughout the survey area, according 

to the results of the sampling conducted in 2007 and 2010 (Tetra Tech 2007f).

The completed studies by the University of Arizona School of Natural Resources and the 

Environment provide data from greenhouse and onsite test plots that indicate that revegetation 

success is feasible. These studies are described later in this resource section.

Environmental Consequences

Direct and Indirect Effects of Each Alternative

No Action Alternative

Under the no action alternative, there would be no impact on the existing soil conditions on public 

lands resulting from mine development, other than that involved with the reclamation of any existing 

exploration related or baseline collection disturbances. Impacts on soil resources from recreational 

use, livestock grazing, and fire activity would continue to occur. Levels of soil disturbance from these 

uses could increase as increasing population in southern Arizona results in additional recreational use 

of the area. Levels of livestock grazing on NFS lands are expected to be stable in the future, and 

additional soil disturbance from this use is not expected to occur. Fire activity could increase with 

expected trends from climate change, potentially resulting in increased soil impacts.

Impacts Common to All Action Alternatives

Impacts common to all action alternatives include stability analyses, descriptions of expected 

revegetation techniques, and the assessment of the potential for revegetation to successfully occur. 

Impacts that differ between alternatives include disturbed acreage, sediment delivery, soil salvage 

volumes, and constraints with respect to reclamation. 

Stability of Tailings and Waste Rock Facilities

The overall stability of the tailings and waste rock facilities is critical to reclamation success.

Structurally, the tailings and waste rock facilities must be designed to prevent mass wasting and 

collapse in order to provide a stable surface for vegetation growth. AMEC Earth and Environmental 

(2009b) conducted stability analyses of the dry-stack tailings facility, and Tetra Tech (Mohseni 2010)

conducted stability analyses of the waste rock facility. In both cases, modeling indicated that the 

designed waste rock and tailings facilities are more stable than what is required by regulations, based 

on the planned crest height, bench widths, and slopes. The minimum factor-of-stability values 

required under regulations as best available control technology are 1.0 for seismic failure and 1.3 for 

192 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

static failure. As modeled, the factor-of-stability values for the tailings and waste rock facilities range 

from 1.0 to 1.2 for seismic failure and from 1.9 to 2.3 for static failure.

Liquefaction can occur with the tailings material at moisture content greater than 19 percent, which 

can lead to greater instability. For the dry-stack tailings, the moisture is not expected to exceed 18 

percent, which represents the upper limit for conveyance and trafficability (AMEC Earth and 

Environmental Inc. 2009b; Tetra Tech 2007a). Concerns have been raised that precipitation would 

raise moisture within the dry-stack tailings and lead to slope failure. This would not occur for the 

primary reason that the entire tailings facility is contained within the perimeter waste rock buttress.

In addition, stormwater management plans indicate that stormwater collecting on the top of the 

tailings facility that does not immediately evaporate would be pumped off and used as process water.

Stability of Pit Walls

Pit design includes identifying proper angles for slopes, as well as proper spacing and widths of 

benches. The feasibility of the pit design was initially assessed in 2008 (Pratt et al. 2008).

The resulting recommended slope angles were based on either an overall factor of safety of 1.2, or a 

catch-bench design with an 80 percent reliability of maintaining a minimum catch-bench width. This 

study particularly noted that the northwest wall, above which is located the crest of the Santa Rita 

Mountains, required further study. Cooperating agencies have also raised concerns over the northwest 

wall of the pit and the potential to impact the crest of the Santa Rita Mountains. While the rocks 

present in this area were considered competent (Bolsa Quartzite and Precambrian Granite), there was 

concern about the relation of the pit to the contact between these two rock types and the potential for 

a slope failure along this contact.

Two additional borings (AR-2059 and AR-2060) were subsequently drilled in part to explore this 

contact. The data collected from these and previous drill holes did not show a clear zone of weakness 

or indicate the need to implement pit design modifications to avoid potential stability problems from 

the contact. The pit was further refined during subsequent feasibility studies (Huss 2009; M3 

Engineering and Technology Corporation 2012), with the slope angles on the northwest wall 

remaining similar to the original design.

Additional concerns have been raised about the potential to depressurize parts of the pit through 

dewatering, based on the results of aquifer tests performed at the site, particularly on the south wall 

(Nicholas et al. 2012). This could result in a change in pit slope during operations in this area, 

depending on the actual conditions encountered.

The 2008 analysis summarizes the process typically undertaken in order to assess pit wall stability:

As the mine is expanded and additional geologic data are collected, a better understanding of 

the geology within the deposit will be developed. In the initial stages of mine life, the surface 

exposures of rock are limited and a great number of assumptions must be made, as time and 

budget do not permit an extremely detailed subsurface excavation. Data can be more 

efficiently collected during the excavation of the pit, and as the pit is deepened, invaluable 

operational experience is gained. Thus, slope-angle recommendations become a series of 

successive approximations with ongoing re-evaluation throughout the mine life in 

conjunction with the acquisition of new data and experience. (Pratt et al. 2008:1–6)

In part to address this issue, pit stability monitoring has been required by the Forest Service. Details 

of this monitoring are included in appendix B (see monitoring measure FS-SR-04). If concerns over 

Final Environmental Impact Statement for the Rosemont Copper Project 193
Chapter 3. Affected Environment and Environmental Consequences

pit stability arise due to the results of the pit stability monitoring or for other reasons, the Forest 

Service would assess available data and determine whether specific management actions would be 

taken or whether revisions to the MPO would be required. 

Soil Development and Productivity Lost to Erosion after Reclamation

During the premining and active mining phases, soil loss from the watershed would be reduced by 

using structural and engineered sediment controls, as well as concurrent revegetation, primarily on 

the waste rock perimeter buttresses. Postclosure, reduction of soil loss from the watershed would be 

dependent on structural and engineered sediment controls and on revegetation of the site to prevent 

erosion from occurring. Reduction of the actual erosion of soil from surfaces can only be 

accomplished through revegetation of the site or the use of protective rock cover. Rock cover is 

generally undesirable with respect to recovery of soil productivity.

All in-place natural soils would be lost during premining and active mining phases within the security 

fence, including the plant site, waste rock facility, tailings facility, and the pit area, and along the

primary access road and utility maintenance road. During reclamation, replacement growth media 

would be placed on the site surface and seeded for revegetation. Growth media would be a mix of 

salvaged soils from the site. The growth media are expected to support vegetation but would not 

develop a natural soil profile for many decades after closure of the site. The presence of a natural soil 

profile typically results in higher productivity because of better retention of soil moisture available 

for plants and less risk of loss by erosion. Unlike the mine site, the soils along the pipeline and power 

line routes would be disturbed but not removed. These areas would likely use less complicated 

revegetation techniques, such as hydroseeding and erosion control features, with no need for the 

placement or treatment of salvaged soils as described later in this section for the waste rock and 

tailings facilities. 

Revegetation would only be considered complete when certain reclamation criteria have been met. 

It is the responsibility of the Coronado to determine these success criteria and the responsibility of 

Rosemont Copper to develop methodologies and techniques, including adaptive management, that 

can meet the revegetation criteria. The final reclamation and closure plan would provide further detail 

on the techniques to be employed, as well as monitoring and success criteria required for approval by 

the Coronado. The long-term purpose of undertaking revegetation is to create a self-sustainable 

ecosystem that would promote site stability and repair hydrologic function. Specific goals include 

providing soil stability to prevent erosion by stormwater runoff and wind and providing vegetation

cover that is appropriate to support postmining land uses, in this case wildlife habitat, livestock 

grazing, and recreation. 

Soil Salvage Plans

Detailed plans for soil salvage have been proposed for the preferred alternative (CDM Smith 2012b).

Stockpile locations are specific only to the Barrel Alternative, but the following procedures would be 

used to manage salvaged soil for all action alternatives.

• Soil salvaging in specific areas would not take place until it is necessary to disturb those 

areas for mine activities.

• At soil salvage locations, pits would be dug to verify removal depth of salvage soils.

• Erosion and sediment controls would be installed both upslope and downslope of soil

removal areas. These controls are required under the stormwater pollution prevention plan 

194 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

that would be mandatory under the mine’s Arizona Pollutant Discharge Elimination System 

permit for stormwater. Dust controls would also be implemented.

• Soil would be transported using haul trucks or other equipment to a stockpile location or 

directly to the waste rock and tailings facilities. If possible, transportation would be direct, 

rather than incorporating long-term stockpiles. Stockpiles would be located in four different 

areas over the life of the mine (see CDM Smith 2012b for location maps). 

• Stockpile 1 is located immediately east of the dry-stack tailings facility, with a footprint of 

approximately 18 acres and a capacity of 501,000 cubic yards. This stockpile would be used 

generally through the first 8 years of operations.

• Stockpile 2 is located south of stockpile 1 and would be used for years 8 through 14 of 

operations. Stockpile 2 has a footprint of approximately 39 acres and a capacity of 502,000 

cubic yards.

• Stockpile 3 is located on the top of the waste rock facility and would be used for years 14 

through 22 of operations. Stockpile 3 has a footprint of 22 acres and a capacity of 335,000 

cubic yards.

• Stockpile 4 is also located on the top of the waste rock facility and would be used for years 

14 through 22 of operations and during closure. Stockpile 4 has a footprint of 18 acres and a 

capacity of 283,000 cubic yards.

• Soil stockpiles would be managed to reduce potential erosion, designed to reduce potential 

for compaction to maintain air circulation and drainage, and if anticipated to be in existence 

for at least 1 year, would have vegetative cover using a broadcast seed mix and possibly 

stabilizers like straw mulch with tackifier. 

• No mechanical manipulation of the salvaged soil or creating soil by crushing waste rock has 

been proposed. Soil has not been proposed to be salvaged from any areas that would not 

ultimately be disturbed by the mine operations, and no offsite borrow pits are planned.

Revegetation and Expected Revegetation Success

Desired Condition

The Coronado has determined the general desired vegetation condition for the reclaimed waste rock

and tailings facilities over time. The desired vegetation condition represents what can reasonably be 

expected on disturbed, reclaimed growth medium that would exhibit more xeric soil moisture 

conditions than those found on natural areas. Desired conditions are included in the FEIS as a 

somewhat general, qualitative description of what the reclaimed sites will support following 

revegetation, at different time periods. The desired conditions have been developed through a review

of the Natural Resources Conservation Service Ecological Site Descriptions, test plot data, and 

expertise of Coronado staff and others. 

It should be noted that the desired condition is not the same as reclamation success criteria, which are 

more site specific and quantitative and will be fully described in the revegetation plan currently being 

developed, to be approved with the final MPO. Most importantly, success criteria would be tied to the 

performance of undisturbed areas called reference areas or reference sites. The success criteria would 

be informed by data collection on the final reference sites once they are approved by the Coronado. 

The final revegetation plan will use the process described in the “Adaptive Management Technical 

Guide” developed by the U.S. Department of the Interior (Williams et al. 2009), and further detail is 

shown in the “Revegetation Success Criteria” part of this resource section. Desired vegetation

condition varies across the site, influenced primarily by aspect and soil texture and chemistry. There 

Final Environmental Impact Statement for the Rosemont Copper Project 195
Chapter 3. Affected Environment and Environmental Consequences

are six revegetation site types that are considered for the reclaimed waste rock and tailings facilities, 

as summarized in table 22. The spatial distribution over time of these areas across the site is 

summarized in figures 32 through 35. 

Table 22. Desired vegetation condition over time

Revegetation Site Type Vegetation

Type

Number of 

Species

Percent 

Canopy 

Cover – 5 

Years after 

Planting

Percent 

Canopy 

Cover – 10 

Years after 

Planting

Percent 

Canopy 

Cover – 15 

Years after 

Planting

Percent 

Canopy 

Cover – 20 

Years after 

Planting

East-facing slopes Grasses 5 to 10 10 to 30 10 to 30 10 to 30 10 to 30

Shrubs 3 to 5 1 to 5 1 to 5 1 to 15 1 to 15

West-facing slopes Grasses 5 to 10 10 to 20 10 to 30 10 to 30 10 to 30

Shrubs 3 to 5 1 to 5 1 to 5 1 to 15 1 to 15

Slopes with increased rock 

cover

Grasses 3 to 7 5 to 20 10 to 20 10 to 20 10 to 20

Shrubs 1 to 3 0 to 5 1 to 5 3 to 5 3 to 5

South-facing slopes Grasses 5 to 10 5 to 15 10 to 20 10 to 20 10 to 30

Shrubs 1 to 3 1 to 5 1 to 5 1 to 5 1 to 5

Succulents 1 to 3 1 to 3 1 to 5 1 to 5 1 to 5

North-facing slopes Grasses 5 to 10 10 to 30 10 to 30 15 to 45 15 to 45

Shrubs 3 to 7 (<10 

years after 

planting)

3 to 10 (>10 

years after 

planting)

3 to 10 3 to 10 5 to 10 5 to 15

Trees 1 to 2 0 to 3 1 to 5 1 to 5 2 to 5

Level areas Grasses 5 to 10 10 to 30 10 to 30 15 to 40 15 to 40

Shrubs 3 to 5 1 to 5 1 to 10 1 to 10 1 to 10

Trees 1 to 2 0 to 3 0 to 3 1 to 3 1 to 3

As shown in table 22, while grasses and shrubs would occur across all revegetation site types, trees 

are likely only to consistently occur on north-facing slopes and level areas, and succulents are most 

likely to consistently occur on southern exposures. Note that succulents do not offer significant cover, 

so although the percent cover would not change over time, the density of these plants still would 

increase. Each revegetation site type is described below. Slope aspect influences soil moisture, with 

the greatest amount of soil moisture being retained on the north slopes and the least on south-facing 

slopes. More soil moisture is also retained on flat areas, compared with angled slopes such as on the 

sides of the waste rock and tailings facilities. Elevation also influences plant communities. The waste 

rock and tailings facilities fall roughly from 4,600 to 5,500 feet above mean sea level, with some 

areas extending as high as 5,700 feet above mean sea level.

196 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental ConsequencesFigure 32. Reclamation area: revegetation types year 5

Final Environmental Impact Statement for the Rosemont Copper Project 197
Chapter 3. Affected Environment and Environmental Consequences

Figure 33. Reclamation area: revegetation types year 10

198 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental ConsequencesFigure 34. Reclamation area: revegetation types 

Final Environmental Impact Statement for the Rosemont Copper Project 199
Chapter 3. Affected Environment and Environmental Consequences

Figure 35. Reclamation area: revegetation types year 22

200 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

East-facing slopes— Vegetation would be composed primarily of warm season perennial grasses, 

some forbs, and small shrubs. Small shrubs or sub-shrubs may be present but would not be clearly 

visible from a distance. Trees may be present but would be very widely distributed and would make 

up a small amount of the plant community. Long slope runs may require additional rock cover for soil

stabilization.

West-facing slopes— Vegetation would be composed primarily of warm season perennial grasses, 

some forbs, and small shrubs. Small shrubs or sub-shrubs may be present but would not be clearly 

visible from a distance. Trees may be present, but would be very widely distributed and would make 

up a small amount of the plant community. West-facing aspects would look similar to east-facing 

aspects but may be composed of different species within the same functional groups.

Slopes with increased rock cover— Vegetation would be composed primarily of warm season 

perennial grasses, mixed forbs, and a minor component of small shrubs, compared with east- and 

west-facing slopes. Because of the steepness of these slopes, increased rock cover would be placed 

over the soil cap for erosion protection and increased stability. Species that favor rocky soils would be 

used. These areas are expected to be stable, even with relatively low amounts of vegetation cover; 

they would primarily be on the western side of the facilities and would not be visible from SR 83.

South-facing slopes— Vegetation would be composed primarily of warm season perennial grasses, 

some forbs, and small shrubs. Small shrubs or sub-shrubs may be present but would not be clearly 

visible from a distance. Trees may be present but would be very widely distributed and would make 

up a small amount of the plant community. Palmer agaves would be transplanted in clumps to mimic 

how they appear on undisturbed sites. Other culturally significant plans, such as sotol (Dasylirion 

wheeleri) and beargrass (Nolina microcarpa), may also be planted in clumped distribution on these 

portions of the facility. The greater amount of surface rock and less grass cover in these areas would 

be clearly visible.

North-facing slopes— Vegetation would be composed of warm season perennial grasses and forbs, 

mixed with shrubs and dispersed trees. A higher density of shrubs and trees would establish on these 

slopes, compared with savannas or level-ground grasslands. It would take a number of years for 

shrubs and trees to grow large enough to be visible from a distance. Some species of trees may be 

deciduous, losing their leaves during the winter.

Level areas— Vegetation would be composed primarily of warm season perennial grasses, mixed 

forbs, an increased amount of small shrubs, compared with east- and west-facing slopes, and widely 

dispersed trees. Shrubs and trees would give a savannalike appearance and would be visible from a 

distance once the plant community matures, which would take a number of years.

Plant species— A variety of plant species would be incorporated into the seed mixes used for 

revegetation, informed in part by greenhouse and test plot studies conducted by Rosemont Copper, 

reference area vegetation, the success of previously revegetated areas on the mine site, and the need 

to plant species of cultural importance. This seed mix would be expected to adaptively change over 

time based on the success of different species. In addition, other species not specifically seeded would 

be expected to opportunistically grow, including those that might be in the natural seed bed in the 

salvaged soil. It is important to note that the seed/planting mix and desired conditions do not account 

for mesquite, acacia, mimosa, or one-seed juniper. It is expected that these species would readily 

colonize the reclaimed sites and, therefore, would not be seeded. They are not included in desired 

condition estimates of species richness or canopy cover. Their presence would contribute additional 

Final Environmental Impact Statement for the Rosemont Copper Project 201
Chapter 3. Affected Environment and Environmental Consequences

species richness and cover beyond what is described here. The strategy for salvaging and using soil is 

intended to preserve the biological component within the soil to the extent practicable during the 

mine operations to promote the natural reestablishment of plant species native to the area. This 

strategy includes selectively stripping the upper soil layers and either placing that material directly on 

the reclaimed landform or storing that material in shallow stockpiles for as short a time as possible. 

This approach would be developed more fully in the final MPO.

The species currently proposed for the seed mix are summarized in table 23, along with a list of 

additional species that are being considered for seeding/planting.

Table 23. Species expected to be present

Grasses Forbs Shrubs/

Succulents Trees

Planned 

Seed Mix

Scientific 

Name

Common 

Name

Scientific 

Name

Common 

Name

Scientific 

Name

Common 

Name

Scientific 

Name

Common 

Name

Bouteloua 

curtipendula

Sideoats 

grama

Baileya 

multiradiata

Desert 

marigold

Agave 

palmeri

Palmer’s 

agave

Juniperus 

deppeana

Alligator 

juniper

Eragrostis 

intermedia 

Plains 

lovegrass

Eschscholzia

minutiflora

Mexican gold 

poppy

Atriplex 

canescens

Four-wing 

saltbush

Quercus 

arizonica

White oak

Bouteloua 

gracilis

Blue grama Calliandra

eriophylla

Fairy duster Quercus 

emoryi

Emory oak

Elymus sp. Bottlebrush 

squirreltail

Celtis pallida Desert 

hackberry

Quercus

oblongifolia

Mexican blue 

oak

Digitaria 

californica

Arizona 

cottontop

Cercocarpus 

sp.

Mountain 

mahogany

Hilaria

belangeri

CurlymesquiteDasylirion 

wheeleri

Desert spoon

or sotol

Leptochloa

dubia

Green 

sprangletop

Fouquieria 

splendens 

Ocotillo

Garrya

wrightii

Wright’s 

silktassel

Nolina 

microcarpa

Beargrass

Rhus

trilobata

Skunkbush 

sumac

Rhus virens Evergreen 

sumac

Yucca elata Soaptree 

yucca

Yucca 

schottii

Schott’s 

yucca

Potential 

Additions

Bothriochloa 

barbinodis

Cane 

beardgrass

Dalea Dalea

Bouteloua

hirsuta

Hairy 

grama

Eriogonum

spp.

Buckwheat

Bouteloua

chondrosioides

Sprucetop 

grama

Krameria sp. Range ratany

202 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Grasses Forbs Shrubs/

Succulents Trees

Bouteloua

repens

Slender 

grama

Krascheninni

kovia sp.

Winterfat (on 

calcareous 

soils)

Heteropogon

contortus

Tanglehead Menodora sp. Menodora 

(on 

calcareous 

soils)

Lycurus sp. Wolfstail Parthenium

incanum

Mariola (on 

calcareous 

soils)

Sporobolus

cryptandrus

Sand 

dropseed

Zinnia sp. Zinnia (on 

calcareous 

soils)

Lippia (on 

calcareous 

soils)

Revegetation Success Criteria

In practice, revegetation would only be considered complete when certain reclamation success criteria 

have been met. An adaptive management approach following the “Adaptive Management Technical 

Guide” developed by the U.S. Department of the Interior would be used to make adjustments in 

techniques to reach those criteria if monitoring indicates that the currently proposed methods prove 

ineffective (Williams et al. 2009). In the DEIS, the Coronado made an effort to both establish these 

success criteria and offer predictions regarding the ultimate revegetation success. After consideration 

of public comments, the Coronado determined that both of these efforts were premature, as success 

criteria and predicted success both rely on the final reclamation and closure plan, and in particular on 

the detailed sampling results from selected reference sites. This final reclamation and closure plan 

would be incorporated into the final MPO, which would be prepared after publication of the FEIS and 

ROD. Instead of the approach taken in the DEIS, the following provides a discussion of the goals of 

undertaking revegetation and the expected types of information that would be provided in the final 

reclamation and closure plan.

The purpose of undertaking revegetation is to create a self-sustainable ecosystem that would promote 

site stability and repair hydrologic function. Specific goals include providing soil stability to prevent 

erosion by stormwater runoff and wind, revegetating with native species that are appropriate for the 

site and selected for specific growing conditions (considering slope, aspect, and elevation), 

potentially including species of cultural importance to tribes, and providing vegetation cover that is 

appropriate to support postmining land uses, in this case wildlife habitat, livestock grazing, and 

recreation.

The final reclamation and closure plan would provide further detail on the techniques to be employed, 

as well as monitoring and success criteria for approval by the Coronado. The monitoring plan would 

identify selected reference sites, protocols for tracking survivorship and growth in terms of both 

amount and type of vegetation, and protocols for tracking soil stability and erosion. The final 

reclamation and closure plan would also identify adaptive management strategies to meet these 

success criteria. The adaptive management strategy would be based on quantitative monitoring data 

from reference plots, test plots, previously revegetated areas, and scientific literature. 

Final Environmental Impact Statement for the Rosemont Copper Project 203
Chapter 3. Affected Environment and Environmental Consequences

Reference areas would serve as a standard of comparison to assess whether mined areas have been 

successfully revegetated (Chambers and Brown 1983). Reference areas would be selected as 

representative of ecological site descriptions in the vicinity of the mine and would have soil, slope, 

aspect, and elevation that are similar to the revegetated sites. Selection of reference areas by the 

Coronado is currently ongoing. Rosemont Copper proposed potential reference sites in June 2013 

(Rennick and Antonioli 2013). Data collection has not yet occurred on these potential reference sites. 

Detailed data collection during the appropriate field season will need to be completed prior to 

submittal by Rosemont Copper of the final reclamation and closure plan. The Coronado will make a 

final selection of reference sites after reviewing the collected data. Final reference sites will be fully 

surveyed, and the results will be used to help identify success criteria that will be included in the final 

reclamation and closure plan. Additional survey data could potentially be collected after approval of 

the final MPO and prior to implementation of revegetation efforts to refine goals and success criteria.

Data collection on the reference sites would involve the assessment or measurement of a variety of 

rangeland health attributes, soil data, and vegetation data. The goal of the data collection would be to 

identify undisturbed ecological sites within the immediate project area that represent the ecological 

conditions desired for the ultimate reclaimed facility (Rennick and Antonioli 2013). 

Success criteria for revegetated sites would be expressed as a percent similarity to the reference sites. 

Test plots were established in 2009 by Rosemont Copper, and a number of different grass species 

were seeded. Results helped develop the preliminary seed mix (Lawson 2011), and additional species 

may be seeded/planted to determine their potential for success on revegetated areas. Revegetation 

would be ongoing, with some areas reclaimed as soon as year 1 of the active mining phase. These 

previously revegetated test plots would be monitored like the reference areas, and lessons learned on 

these plots would inform future revegetation efforts in terms of what site preparation techniques, seed 

mixes, or timing of technique results in the best success. Research on restoration of mined lands 

continues to advance our knowledge in this science. Research would be reviewed and incorporated as 

appropriate to the Rosemont Copper revegetation efforts.

Data collected on revegetated sites would be used to determine whether success criteria have been 

met and to indicate whether adjustments to growth medium, soil amendments, seed/plant mix, 

seed/plant application rates, site preparation techniques, and/or additional mitigation measures are 

needed.

Rosemont Copper has proposed draft success criteria for consideration. These may or may not be 

similar to those ultimately selected by the Coronado. Following are the Rosemont Copper proposed 

draft criteria:

Soil/Site Stability— This would be a visual indicator, based on standard techniques for rangeland

health assessment. Reclamation would be considered successful if the rating for the reclaimed area 

were the same class or a higher class, compared with the reference area.

Vegetation Cover— This would be a field measurement based on standard vegetation survey 

techniques, such as line-point intercept. Reclamation would be considered successful if perennial 

plant cover were greater than or equal to 70 percent that of the reference site, with a 90 percent level 

of confidence.

Vegetation Density— This would be a field measurement based on standard vegetation survey 

techniques, such as quadrat surveying. Reclamation would be considered successful if perennial plant 

density were greater than or equal to 70 percent of that of the reference site.

204 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Presence/Absence of Invasive Species and Weedy Species— This would be a visual indicator, as 

well as being based on the results of the vegetation surveys. Reclamation would be considered 

successful if invasive species management criteria were met.

Revegetation Techniques Proposed by Rosemont Copper

For the purposes of evaluating the potential for revegetation to be successful in this FEIS, the 

revegetation techniques proposed by Rosemont Copper are discussed below, along with the results of 

greenhouse studies and onsite reclamation test plots.

Concurrent reclamation would take place over the life of the project, with initial reclamation 

beginning on the lowest levels of the waste rock perimeter buttresses by the end of the first year. 

The proposed acreage of reclamation activities over time is shown in table 24, and the locations of 

these activities are shown in figure 36.

Exact phasing of concurrent reclamation is specific to each alternative. As noted below, the 

Scholefield-McCleary and Barrel Trail Alternatives may have longer delays in implementing 

concurrent reclamation due to logistics, amount of salvage soil, safety considerations, and the need to 

rehandle placed material.

Table 24. Reclamation phasing over active mining phase for preferred alternative

Project Phase

Acres 

Undergoing 

Reclamation

(Federal)

Acres 

Undergoing 

Reclamation

(State)

Acres 

Undergoing 

Reclamation

(Private)

Acres 

Reclaimed 

(Federal)

Acres 

Reclaimed 

(State)

Acres 

Reclaimed 

(Private)

End of year 1 104 0 10 0 0 0

End of year 2 125 10 34 104 0 10

End of year 3 224 10 25 229 10 44

End of year 4 51 7 17 453 20 69

End of year 5 77 5 11 504 27 86

End of year 10 374 5 11 581 32 97

End of year 15 374 2 7 955 37 108

End of year 22 1575 5 184 1329 39 115

Postclosure 0 0 0 3196 44 299

Source: CDM Smith (2012a).

Notes:

Assumes 1 year for completion of active reclamation activities.

Acreage through end of year 22 is for waste rock and tailings facilities; postclosure acreage includes an additional 292 acres 

for the plant site (Federal). An additional 889 acres of possible reclamation associated with the utility corridor and 226 acres 

associated with the primary access road are not included in these totals, as portions of these areas may remain in place and 

therefore may not need reclamation or may be reclaimed early in the process and then remain undisturbed thereafter.

Revegetation would be the responsibility of the mine operator. The description of revegetation 

procedures provided below has been developed by Rosemont Copper. However, the Coronado would 

dictate the criteria that must be met for the revegetation to be considered successful and complete. 

Some changes in revegetation efforts are expected over time as actual revegetation progress is 

monitored for success and methods are modified to achieve the desired results. Appendix B describes 

the monitoring and reporting requirements that would occur (see mitigation measures FS-SR-01 and 

FS-SR-02). Evaluation of monitoring results would determine whether revegetation activities were 

successfully meeting success criteria. If not, revegetation strategies would be reviewed and plans 

developed to improve outcomes and eventually achieve success criteria. The revegetation success 

Final Environmental Impact Statement for the Rosemont Copper Project 205
Chapter 3. Affected Environment and Environmental Consequences

Figure 36. Phasing of concurrent reclamation activities for preferred alternative

206 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

criteria would be determined and specified in the final MPO; success criteria potentially could be 

modified based on subsequent survey efforts prior to implementing revegetation.

Revegetation procedures would differ, depending on whether upland or riparian areas are being 

revegetated. Most of the landform, which consists of the waste rock and tailings facilities, would be 

covered with growth medium and revegetated with upland vegetation. However, there may be limited 

areas along drainages where riparian revegetation would be appropriate. Upland revegetation would 

generally follow these steps: regrading, placement of salvage soils, ripping, transplantation of trees 

and shrubs, seed application, surface treatment such as application of mulch and tackifier, and 

maintenance/monitoring activities.

Regrading— Areas would be regraded to obtain stable, permanent slope conditions as designated in 

the final reclamation plans. Where possible, such as at the plant site, grading would be undertaken 

with the intention of restoring more natural slopes and minimizing erosion. The potential for restoring 

natural slopes is limited with respect to the waste rock and tailings facilities, but such regrading will 

be incorporated to the extent practicable, primarily on top of the facilities. The regrading required for 

the Barrel Trail Alternative would be more extensive than for the other action alternatives and would 

delay revegetation efforts, compared with the other action alternatives.

Soil Salvage and Placement— Soils would be salvaged onsite as described previously in this 

resource section and would be used as surface cover for revegetation. Almost all slopes would receive 

either a cover of soil or a mixture of soil and rock cover, although the Scholefield-McCleary 

Alternative is unlikely to have sufficient salvage soil available for complete coverage. In the most 

recent plans developed for the Barrel Alternative, several steep slopes on the side of the landform 

adjacent to the pit would remain solely rock with no soil cover. Specific surface treatment locations 

for the waste rock and tailings facilities are shown in figure 37. For shorter slope runs between 

benches (less than 300 feet), the surface treatment is likely to consist primarily of soil cover. 

For longer slope runs between benches (more than 300 feet), the soil cover could be limited to the 

upper 300 feet of the slope to prevent erosion. The lower 300 feet may consist of rock or a 

combination of soil and rock. Other configurations may also be considered, such as the use of soil 

islands; these are small areas (probably less than 10 acres) in which soil of greater depth is placed to 

improve species’ diversity and benefit planted trees and shrubs. Where present, the total depth of soil 

cover would vary but is estimated to be approximately 12 inches (CDM Smith 2012b). Mulched 

vegetation material available from site clearance could be used as a soil additive if appropriate.

The strategy for salvaging and using soil is intended to preserve the biological component within the 

soil to the extent practicable during the mine operations to promote the natural reestablishment of 

plant species native to the area. This strategy includes selectively stripping the upper soil layers and 

either placing that material directly on the reclaimed landform or storing that material in shallow 

stockpiles for as short a time as possible. This approach would be developed more fully in the final 

MPO.

Ripping— After placement of salvage soil, the soil surface would be ripped or otherwise 

mechanically manipulated in order to create an optimal seedbed. Ripping and furrowing generally 

would follow contours to minimize erosion. In addition, larger woody material salvaged during 

clearing operations would be placed on the slopes in order to promote soil stability and promote 

microclimates and variation in vegetation.

Final Environmental Impact Statement for the Rosemont Copper Project 207
Chapter 3. Affected Environment and Environmental Consequences

Figure 37. Surface treatments for revegetation for preferred alternative

208 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Seeding and Transplantation— The native seed mix would be agreed upon and approved by the 

Coronado and would be informed by the greenhouse studies, test-plot data, reference sites, and results 

from previously revegetated areas. The seed mix and application techniques could vary, depending on 

slope, aspect, elevation, and underlying growth media. The seed mix may also incorporate native 

plant species that are culturally important to tribes.

Comments from cooperating agencies have questioned the ability of native seed sources to reestablish 

trees across the landform through volunteering, due to the large size of the landform and the distance 

from undisturbed vegetation and native seed sources. A final decision on tree, shrub, and succulent 

species seeding/planting and the required densities and cover has not been made, pending review of 

the reference site data. Plans are to begin testing many of the woody species listed in table 23 in 

greenhouse and test plot locations. Some species such as one seed juniper, mesquite, acacia, and 

mimosa are considered to be somewhat invasive and are expected to colonize the disturbed areas 

from the seed bank within the salvaged soil and from adjacent areas. Other woody species would be 

seeded or planted to ensure similarity to reference site vegetation. Currently, trees are only proposed 

for seeding/planting on north slopes, as these conditions are more mesic and more favorable to their 

success. The plans are to seed/plant a number of shrub/succulent species on south slopes such as

sotol, bear grass, agave, and ocotillo. Tree, shrub, and succulent species will be seeded and planted as 

needed to meet success criteria.

Surface Treatment— Appropriate site preparation may include lightly dragging the area after seed 

application, soil amendments, and/or application of certified weed-free straw mulch with a tackifier. 

Slow-release fertilizer may be incorporated to promote plant growth.

Assessment of Revegetation Potential 

of Waste Rock and Tailings Facilities

Analysis of revegetation potential was approached using a two-part strategy through research 

conducted by Rosemont Copper in conjunction with the University of Arizona. The first part of the 

research focused on the assessment of potential seed mixes for the site, including greenhouse 

testing to identify those seed mixes most likely to thrive in actual material from the site. This 

experimentation used substrate materials that would be similar to the soil salvaged from the site. 

The second part of the research focused on long-term construction and testing of in situ reclamation

plots at the mine site itself.

The revegetation potential of soil on future waste rock and tailings facilities can be both 

quantitatively and qualitatively analyzed, based on the University of Arizona greenhouse results. 

The likely outcome of reclamation efforts was assessed by comparing soil productivity observed in 

the greenhouse experiments with soil productivity under theoretically ideal conditions. Soil

productivity is the amount of vegetation that can be potentially supported by the soil, measured in

pounds of vegetation per acre. The theoretically ideal level of soil productivity is represented by the 

historic climax plant community that existed at the time of European immigration and settlement. 

These conditions would not necessarily be reached during reclamation, but they represent a measure 

for assessing the possible outcome of revegetation techniques explored by Rosemont Copper. These 

historic climax plant communities have been identified for different regions using the Natural 

Resources Conservation Service (2013) Ecological Site Descriptions. Based on the ecological site 

descriptions, acceptable soil productivity for the Rosemont area ranges from roughly 415 to 3,150 

pounds of vegetation per acre, as shown in table 25. 

Final Environmental Impact Statement for the Rosemont Copper Project 209
Chapter 3. Affected Environment and Environmental Consequences

Table 25. Soil productivity based on ecological site descriptions (in pounds per acre)

Ecological Site 

Description* Soil Types Test Plot Material Low Value Representative Value High Value

Granitic hills (12 to 16) McF; LgF; LcF; CoE Glance 525 915 1,545

Limestone hills (12 to 16) McF – 415 810 1,275

Volcanic hills (12 to 16) LgF – 430 860 1,360

Limy slopes (16 to 20) HaF Gila 671 1,290 1,685

Clay loam upland (12 to 16) BhD – 502 865 1,425

Limy slopes (12 to 16) BhD; HhE2 – 555 1,000 1,765

Sandy wash (12 to 16) CtB – 825 1,800 3,150

Loamy slopes (16 to 20) CmE Arkose 763 1,520 2,350

Granitic hills (16 to 20) Rn; BgF – 524 1,240 1,985

Loamy slopes (12 to 16) WgE; CgE Gila 426 905 1,505

Limestone hills (16 to 20) TrF – 576 1,165 1,480

Sandy loam, deep (12 to 16) An – 521 1,005 1,855

Sandy loam upland (12 to 16) SoB – 602 1,066 1,755

Source: Natural Resources Conservation Service (2013).

Note:

– = No test plot material coincides with this ecological site description.

* Numbers in parentheses represent precipitation zone, in inches.

Three material types from the Rosemont area were tested by the University of Arizona to represent 

future waste rock or tailings: Gila, Glance, and Arkose materials. These materials were collected in 

the field and created by mixing the top 3 meters of the existing soil profile. The Gila material was 

collected at a location characterized by the Hathaway gravelly sandy loam soil type (HaF). 

The Glance material was collected at a location characterized by Chiricahua cobbly sandy loam 

(CoE). The Arkose material was collected at a location characterized by Casto very gravelly sandy 

loam (CmE). These soil samples were collected from private land (see figure 31). Based on the 

ecological site descriptions, acceptable soil productivity for the specific soil types used for the 

greenhouse studies ranges from roughly 426 to 2,350 pounds of vegetation per acre, as shown in 

table 25.

Greenhouse results for the recommended seed mix grown in Gila and Glance materials were within 

the acceptable soil productivity range: 1,010 and 1,080 pounds of vegetation per acre, respectively. 

Arkose material, however, showed limited productivity, at 290 pounds of vegetation per acre, which 

suggests that this particular material might have limited revegetation potential. These limitations were 

primarily the result of the generally coarser texture of the material and its inability to retain water. 

The researchers concluded that mixing it with the other soil types—as would be expected during 

mining—would likely improve its performance.

The University of Arizona greenhouse studies represent potential results under ideal conditions:

adequate water, stable growth media, minimal slopes, and thorough and even seed coverage. While 

these studies have resulted in selection of a seed mix with the best likelihood of establishing 

vegetation, they do not represent expected conditions found in nature, nor is this likely to be the final 

seed mix approved by the Coronado in the final MPO. Actual revegetation potential is likely to be 

less successful and variable overall. Some areas likely would match the results indicated by the 

greenhouse studies; other areas may experience much less revegetation or may not successfully 

210 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

revegetate at all. Such factors as drought conditions, slope instability, aggressive exotic vegetation 

(such as Lehmann lovegrass (Eragrostis lehmanniana)), poor growth media, and incomplete or 

patchy seed coverage could reduce revegetation success and would be addressed in an adaptive 

management approach to continually refine revegetation objectives based on quantifiable data from 

reference areas, test plots, and previously revegetated sites.

To better address natural conditions, Rosemont Copper conducted experiments with onsite 

reclamation test plots. Initial establishment of the plots took place in 2009 (Lawson 2011). Plots were 

designed to replicate conditions similar to those that would be experienced on the waste rock

perimeter buttresses around the tailings and waste rock facilities, with respect to slope (3:1), aspect 

(east facing), and elevation (4,600 to 5,400 feet above mean sea level). Similar to the greenhouse 

studies, soil cover at the sites consisted of Gila and Arkose materials at a depth of 12 inches. Fortyeight individual test plots were created to test variables of elevation, soil type, surface roughness, and 

surface treatment (straw mulch, straw mulch mixed with soil, and no mulch). The seed mix selected 

for use on the test plots was based on the results of the University of Arizona greenhouse studies.

It should be noted that the test plots were only conducted on east-facing slopes, whereas particularly 

on south-facing slopes, revegetation efforts may differ substantially due to sun exposure.

The results of the onsite test plots are similar to those of the greenhouse studies. They demonstrate 

that soil productivity can reach the desired range with appropriate treatment under real world 

conditions. Soil productivity or biomass when measured in the cool season ranged from 713 to 2,856 

pounds per acre; when measured in the warm season, it ranged from 17 to 1,438 pounds per acre 

(see table 25 for comparison with theoretical conditions). Vegetation basal cover ranged from 1.7 to 

10.9 percent during the cool season and from 0 to 15.3 percent during the warm season (see table 19 

for comparison with theoretical conditions). The wide range of results reflects the range of the 

experimental variables, with some combinations being unsuccessful and other combinations 

performing much better. The onsite test plots demonstrate that desired conditions can be reached, 

but they also show that care must be taken during revegetation to select the appropriate surface 

preparation and treatment to provide the greatest potential for revegetation success.

The current soil conditions at the site are degraded from historic climax conditions, although they are 

still considered satisfactory. The research conducted by the University of Arizona and Rosemont 

Copper indicates that use of the selected seed mix and appropriate surface treatment could result in 

revegetation of soil on waste rock and tailings facilities that would approximate native vegetative 

conditions. These studies are not a guarantee of revegetation success due to differences in seed mix, 

slope aspect, and potentially different climatic conditions. 

Proposed Action and Action Alternatives

Soil Productivity Directly Lost to Mine Activities

Soil productivity is the capability of a soil to produce and support plant and vegetation biomass. 

The primary impact to soil productivity is the actual loss of topsoil directly where mine activities 

would remove or disturb the soil. This loss of soil productivity would be temporary for many areas, 

provided that salvaged soil is replaced on these areas and revegetation successfully occurs. 

Loss of soil productivity is determined based on the surface area disturbed by mining activities. 

Recovery of soil productivity means that the soil can support an amount and type of vegetation that 

are similar to what it supported before the mine. For the DEIS, any lands within the perimeter fence 

were assumed to be disturbed; it was assumed that these lands would therefore lose soil productivity. 

Final Environmental Impact Statement for the Rosemont Copper Project 211
Chapter 3. Affected Environment and Environmental Consequences

For the FEIS, this assumption has been refined. Lands within the security fence are assumed to be 

disturbed, as are some other areas such as the primary access road and utility maintenance road. 

However, the lands between the perimeter fence and the security fence would largely not be 

disturbed, other than discrete areas such as test wells and the compliance point dam, which have been 

taken into account in the acreage figures. 

According to the preliminary MPO, the proposed action would impact approximately 5,612 acres of 

soils within the project area. Of the 5,612 impacted acres, 4,387 acres would lie within the security 

fence, including 955 acres that would be impacted by the open pit. The remaining 1,225 acres would 

be impacted by the power line, pipeline, primary access road and utility maintenance road, activities 

associated with forest road decommissioning or construction, and the Arizona National Scenic Trail

reroute. The acreage of the other action alternatives varies slightly but is similar, ranging from 5,431 

to 6,197 acres (table 26). The acreage includes areas disturbed by facilities, the power line, pipeline, 

primary access road, utility maintenance road, forest road decommissioning or construction, and the 

Arizona National Scenic Trail reroute.

Table 26. Direct soil productivity loss and soil salvage volumes by 

alternative

Alternative Acres Impacted Soil Salvage Volume

(cubic yards)

No action 0 0

Proposed action 5,612 4,234,000

Phased Tailings 5,481 3,947,000

Barrel 5,431 4,252,000

Barrel Trail 5,888 4,267,000

Scholefield-McCleary 6,197 2,111,000

Note: Soil salvage volume is the total of pit area, plant site, and waste rock and tailings facilities, plus an 

additional 1.4 million cubic yards of opportunistic salvage.

Estimated Soil Salvage Volumes

The volume of soil available for salvage and use for reclamation differs by alternative. Salvage 

volume calculations are based on four components: salvage of soil from the pit area, salvage of soil 

from the plant site area, salvage of soil from the areas occupied by the waste rock and tailings 

facilities, and opportunistic soil salvage. Opportunistic soil salvage encompasses salvage of soil from 

other disturbed areas, or areas where soil might occur in scattered pockets for which volume is not 

able to be calculated. 

The pit area and plant site remain identical between alternatives and account for 268,000 cubic yards 

and 12,000 cubic yards of soil salvage, respectively. Soil salvage from the waste rock and tailings 

areas differs between alternatives and ranges from 431,000 cubic yards (Scholefield-McCleary) to 

2,587,000 cubic yards (Barrel Trail). Opportunistic soil salvage is difficult to estimate but has been 

approximated as 1,400,000 cubic yards (CDM Smith 2012b). The estimated total soil salvage 

volumes by alternative are shown in table 26.

The total amount of salvage material needed for reclamation activities will depend on the final soil

cover requirements, which will be determined in the final reclamation and closure plan. Overall, it 

may be determined that some areas would remain primarily rock cover, such as is shown in figure 31, 

whereas other areas would receive a 12-inch cover of salvaged soil material. Preliminary estimates 

212 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

for the Barrel Alternative indicate that approximately 3,689,000 cubic yards of material would be 

needed to address all areas receiving soil cover (CDM Smith 2012b). Based on these estimates, 

sufficient soil salvage material would be available to meet expected reclamation needs for all 

alternatives except for the Scholefield-McCleary Alternative. 

Sediment Delivery

Sediment enters stormwater through erosion of native soils, tailings facility, and waste rock facility. 

The stormwater management facilities that are part of the action alternatives have been designed to 

maintain total suspended sediment concentrations in stormwater runoff similar to baseline conditions. 

Total suspended sediment concentrations have been analyzed in stormwater flows at the site for about 

a half-dozen flow events that occurred between January 2010 and September 2011. The observed 

concentrations are highly variable, ranging from near zero to more than 44,000 milligrams per liter 

(mg/L). Sediment delivery was modeled to the USGS gaging station in Barrel Canyon at the SR 83 

bridge, the downstream stormwater analysis point for postmining conditions for each alternative 

(Zeller 2010a, 2010b, 2012). The sediment delivery for the baseline conditions (no action) and all the 

action alternatives is summarized in table 27. Note that the analysis of postmine sediment

concentrations was based on modeling, not the field observations.

Table 27. Summary of expected changes to sediment delivery under alternatives

Condition

Contributing 

Watershed

Area 

(square miles)

Average Annual 

Sediment

Delivery 

(acre-feet)

Average Annual 

Sediment

Delivery 

(tons)

Sediment

Concentration 

(parts per 

million)

Percent 

Change 

from 

Baseline

No action 14 16.10 32,600 16,407 –

Proposed action 6.82 7.84 16,000 16,194 −50.9

Phased Tailings 7.06 8.12 16,500 16,210 −49.4

Barrel 11.33 10.88 22,170 13,686 −32.0

Barrel Trail 8.65 9.95 20,300 16,273 −37.7

ScholefieldMcCleary 10.35 11.90 24,200 16,317 −25.8

Based on the sediment modeling, sediment delivery to the downstream watershed is expected to 

decrease from baseline conditions, while suspended sediment concentrations are expected to remain 

relatively unchanged. The primary reason for a decrease in sediment delivery to the downstream 

watershed would be a reduction in contributing watershed size. Contributing watershed size would be 

reduced because diversions and stormwater ponds would cause a decrease in stormwater runoff from 

the mine site, reducing the amount of water running off the watershed and carrying sediment. 

Cumulative Effects

None of the reasonably foreseeable actions as identified on the Coronado ID team’s list of reasonably 

foreseeable future actions, provided in the introduction to chapter 3, fall within the analysis area for 

soils; therefore, these actions are not analyzed for their effect on soil or soil productivity. Trends in 

past and present actions, such as increased recreation from an increasing population, are expected to 

affect areas that have already been impacted; these areas have been analyzed as part of the affected

environment. 

Final Environmental Impact Statement for the Rosemont Copper Project 213
Chapter 3. Affected Environment and Environmental Consequences

Climate Change

Expected climate change conditions could have an effect on the success rate of revegetation and 

therefore on long-term soil stability. Revegetation could become more difficult due to the potential 

for more variable temperatures and precipitation. Some models predict higher temperatures and 

prolonged droughts, whereas other models predict warmer and wetter conditions in the Southwest. 

Initial completion of revegetation would be based on meeting Coronado success criteria, not on a 

specified level of effort. Revegetated sites would be compared with reference sites, and these 

comparisons would be used to monitor the effects of climate change on both disturbed and 

undisturbed sites. This would allow for adjustments in species composition based on the monitoring

results. Therefore, initial revegetation can be assumed to be eventually successful, even if additional 

work must be conducted by Rosemont Copper in order to meet Coronado success criteria. However, 

the effects of climate change could increase the vulnerability of vegetation cover on the site years or 

decades after successful revegetation has been accomplished. Revegetation success would be 

monitored and compared with reference sites. Seed mix, soil preparation, and planting procedures 

could be modified using monitoring results to respond to changing climatic conditions.

Mitigation Effectiveness 

Mitigation and Monitoring – Forest Service

• Growth media salvage and application (FS-SR-01). In order to support reclamation

activities, soil and other growth media would be salvaged, stored, and applied to the surface 

of the perimeter waste rock buttress and waste rock and tailings facilities in order to facilitate 

revegetation.

• Revegetate disturbed areas with native species (FS-SR-02). Reclamation efforts would 

include revegetation of native grasses, forbs, shrubs, and trees on areas disturbed by mining 

and mine related activities. Revegetation would include detecting and treating of invasive 

weed species.

• Concurrent placement of perimeter buttress (FS-SR-03). Placement of the perimeter 

buttress would allow for reclamation activities to take place earlier, concurrent with mine 

operations. 

• Sediment transport monitoring (FS-SR-05). The movement of sediment between the mine 

facility and SR 83 would be monitored to identify areas of scour or aggradation that could be 

caused by changes in sediment load and surface flow.

• Limit ground-disturbing activities between perimeter fence and security fence (FS-CR05). Any additional soil disturbance between the security fence and perimeter fence would be 

limited, which would reduce erosion and loss of soil productivity.

Mitigation and Monitoring – Other Regulatory and Permitting Agencies

• Power line and water line locations (OA-SR-01). The final location of the power line as 

considered by the Arizona Corporation Commission (ACC) is the shortest route, minimizing 

soil disturbance.

• Paving mine roads (OA-AQ-01). Paving of certain roads with the mine is required under the 

air quality permits and would also serve to reduce the potential for erosion of soil from 

disturbed road areas.

214 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

• Tailings would be processed and placed to reduce water content and overall footprint

(OA-GW-05). The use of dry-stack tailings instead of traditional slurry tailings would allow 

for a much smaller footprint for the tailings facility, minimizing soil disturbance.

• Implementation of stormwater pollution prevention plan (OA-SW-02). Required under 

the stormwater permit for the mine, implementation of the stormwater pollution prevention 

plan would include use of structural sediment controls and best management practices

intended to minimize the potential for erosion from the mine site.

Mitigation and Monitoring – Rosemont Copper

• Eliminate future development of private lands on top of waste rock and tailings

(RC-LO-02). Disallowing future soil disturbance on top of the reclaimed waste rock and 

tailings facilities would minimize the potential for future soil disturbance that would reverse 

reclamation and revegetation efforts.

Conclusion of Mitigation Effectiveness

The design of the proposed action and other action alternatives includes a mine footprint that is 

substantially smaller than conventional mines with similar production capacity. This reduced mine 

footprint would avoid surface disturbance of soils and loss of soil productivity from these areas, 

compared with conventional designs. This is attributable to the use of dry-stack tailings technology. 

Also as part of the design, waste rock perimeter buttresses would be built around the dry-stack 

tailings and the waste rock facilities. The waste rock perimeter buttresses would be built early in the 

stages of the mine; once each lift or stage of the waste rock perimeter buttress is complete, concurrent 

reclamation can begin. Concurrent reclamation of the first portions of the waste rock perimeter 

buttresses can occur as early as year 1 of mine operations. Early reclamation would allow salvaged 

soil to be placed back on the surface and soil productivity to be reestablished. 

A mine reclamation plan is required by Forest Service regulations and is subject to approval by the

Arizona State mine inspector and the Coronado. The policy requires that disturbed lands be reclaimed 

to a condition that is consistent with forest land and resource management plans. Revegetation of 

disturbed areas is a key aspect of the reclamation plan. In order to enhance revegetation efforts, 

specifications and goals for the salvage, storage, and reuse of growth media (topsoil) from disturbed 

areas have been developed with the goal of providing sufficient cover on all disturbed areas to be 

reclaimed. Control of noxious and invasive weeds would be critical to success of the revegetation 

efforts. Additional revegetation would take place through the salvage, propagation, and planting of 

agave plants. All of these efforts, if successful at meeting Coronado revegetation objectives, would be 

effective at reestablishing soil cover and vegetation on bare waste rock slopes, which would be 

effective at reducing soil erosion, soil loss, and downstream sedimentation.

With the exception of eliminating future development of the waste rock and tailings facilities, the 

mitigation measures described above are part of the design of the action alternatives and, thus, have 

been incorporated into the analysis of direct and indirect impacts on soil resources. The impacts 

described earlier in this section include these mitigation measures.

Revegetation success is expected to improve over time, as natural vegetation communities slowly 

become reestablished. Any future development of the waste rock and tailings facilities would 

necessarily involve soil disturbance and removal or destruction of vegetation placed during the mine 

reclamation activities. By eliminating the potential for any development in the future, the 

Final Environmental Impact Statement for the Rosemont Copper Project 215
Chapter 3. Affected Environment and Environmental Consequences

revegetation would be allowed to mature, further establish communities similar to the natural 

environment, and continue to help prevent erosion or loss of soil cover.

Effects of Amending the Coronado Forest Plan

The effects on soil resources and revegetation from amending the Coronado forest plan are described 

under “Direct and Indirect Effects” above. The amendment would remove the following current 

management area standards and guidelines related to soil resources and revegetation:

MA 1:

1. Restore to satisfactory watershed condition, on an emergency basis, watersheds or portions of 

watersheds when damaged. Watershed treatment is a low priority in this Management Area.

Water and soil resources improvements may consist of channel stabilization and revegetation 

using native or nonnative species. 

MA 4:

1. Restore damaged watersheds to a satisfactory watershed condition. Watershed treatment is a 

high priority in this Management Area. Watershed maintenance and improvement may 

consist of channel stabilization, activities to increase water infiltration, and revegetation using 

native or non-native species.

2. Manage all programs to eliminate or minimize onsite and downstream water pollution.

3. Provide, to the extent possible, conservation pools and minimum streamflows in authorizing 

or developing water storage impoundments and diversion projects.

MA 7A:

1. Restore damaged watersheds to satisfactory watershed condition. Watershed treatment is a 

high priority in this Management Area. Watershed maintenance and improvement may 

consist of channel stabilization, activities to increase water infiltration, and revegetation using 

native or non-native species.

2. Manage all programs to eliminate or minimize onsite and downstream water pollution.

The proposed amendment would establish the following standard and guideline for management area 

16 related to soil resources and revegetation:

1. Mine reclamation revegetation treatments will be conducted using primarily native species. 

Species will be approved by the Forest Service prior to use.

As noted in the analysis of direct, indirect, and cumulative effects, this amendment would allow 

mineral development within management area 16. Revegetation is a required component of the final 

reclamation and closure plan, which must be reviewed and approved by the Forest Service prior to 

approval of the final MPO.

The current forest plan does not contain management area standards and guidelines specifically 

pertaining to soils for management areas 1, 4, or 7A. 

216 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Air Quality and Climate Change

Introduction

The primary factors that influence regional air quality are the locations of air pollution sources, the 

quantity and chemical characteristics of the pollutants emitted by those sources, the topography of the 

region, and the local meteorological conditions. Potential direct and indirect impacts to air quality 

from the proposed project have been assessed for the premining, active mining, and final reclamation

and closure phases of the project and spatially within the anticipated geographic pollutant dispersion 

range. 

Changes from the Draft Environmental Impact Statement

In a response to public and agency comments and concerns on the DEIS, the analysis for the air 

quality section has been revised. These comments and concerns focused on several key issues, 

including specific technical aspects of the air quality modeling protocols, the exceedances of air 

quality standards by the modeled air quality impacts for the Barrel, Barrel Trail, and ScholefieldMcCleary Alternatives, the lack of discussion regarding hazardous air pollutants (specifically lead 

(Pb)), and the estimation of mobile source emissions associated with worker commuting and offsite 

trucks.

The air quality modeling conducted for the DEIS incorporated AERMOD, CALPUFF, and 

VISCREEN models and numerous rounds of cooperating agency review. However, in response to 

comments from the public and agencies, the Coronado requested additional modeling in order to

ensure results were reasonable for prediction of air quality impacts. These efforts included a 

conference call between the Coronado, Rosemont Copper’s consultant (JBR Environmental 

Consultants, Inc.), and a variety of agencies to discuss concerns with AERMOD and CALPUFF 

modeling protocols. The conference call was held on March 21, 2012, and included the following 

agencies: Forest Service, U.S. Environmental Protection Agency (EPA), Pima County, National Park 

Service, and Smithsonian Institution. Revised modeling protocols were coordinated by the Coronado 

with the EPA and other interested agencies, and direction was provided by the Coronado to Rosemont 

Copper concerning the appropriate modeling assumptions and techniques to use in revising the 

modeling. Revised modeling was provided by Rosemont Copper in December 2012 and January 2013 

(JBR Environmental Consultants Inc. 2012c, 2012d, 2012e, 2013c). For more detail, see the 

“AERMOD Modeling of Compliance with NAAQS at the Perimeter Fenceline for the Action 

Alternatives” part of this resource section.

After receipt of additional modeling submitted to the Coronado, it was determined that the restart 

options in the CALPUFF modeling had not been set to the preferred settings. At the request of the 

Coronado, a sensitivity analysis was developed cooperatively with Rosemont Copper’s consultant to 

determine the relative impact of revising the restart option in CALPUFF. The sensitivity analysis 

consisted of examining one of the months that is likely to have the greatest impact from the potential 

restart issue. Ultimately, the annual Barrel Alternative emissions scenario was remodeled for that 

month (August) of the 2001 meteorological year. While the results of the sensitivity analysis 

indicated a slight increase in the modeled criteria pollutant concentrations as well as the deposition 

and visibility impacts, it was determined by the Coronado that the results did not warrant a full rerun 

of the modeling for the Barrel Alternative (see the “Projected Effects on Deposition of Sulfur and 

Nitrogen on Class I Areas” part of this resource section, as well as table 51). 

Final Environmental Impact Statement for the Rosemont Copper Project 217
Chapter 3. Affected Environment and Environmental Consequences

In addition and at the request of the Coronado, Rosemont Copper’s consultant also provided the 98th 

percentile impact value for modeled visibility impacts, representing the 8th highest value averaged 

over three modeled meteorological years. The delta deciview 98th percentile values were requested in 

order to evaluate the visibility modeling in accordance with the Federal Land Manager Air Quality

Values Work Group guidance (U.S. Forest Service et al. 2010). These 98th percentile values have 

been included in table 50.

Due to the availability of new ambient air monitoring data, table 34 has been updated with new 

station data for the years 2011 and 2012, as well as lead for 2012 at one station. During updating, it 

was noticed that the PM10 value for 2009 needed to be updated to account for the exceptional events 

of that year and subsequently was changed. An error in figure 41 presented visibility data for Saguaro 

National Park West instead of Saguaro National Park East. This error was corrected, and in addition, 

the “Worst 20%” values were added to the figure. In other tables, minor typographical errors were 

discovered and corrected, and values were updated to reflect the revised modeling results. 

In response to comments on the DEIS and that previous modeling indicated that several alternatives, 

including the preferred alternative, would not meet air quality standards, a number of mitigation and 

monitoring measures were added to the project, which are discussed in detail in appendix B and 

under the “Mitigation Effectiveness” part of this section. 

A number of public comments were received on the DEIS regarding the lack of analysis of toxic 

contaminants, especially lead, potentially contained within the fugitive dust. Potential lead emissions

have now been evaluated through modeling (see the “AERMOD Modeling of Compliance with 

NAAQS at the Perimeter Fenceline for the Action Alternatives” part of this resource section). With 

respect to other toxic contaminants, determination of the makeup of particulates is not a standard 

analysis conducted when evaluating particulate emissions. The Federal national ambient air quality

standards (NAAQS) establish maximum concentrations in ambient air for suspended particulate 

matter. These standards were adopted by the EPA to protect public health (primary standards) and 

public welfare against decreased visibility as well as damage to animals, crops, vegetation, and 

buildings (secondary standards) (U.S. Environmental Protection Agency 2012e). These primary 

standards provide public health protection, including protecting the health of “sensitive” populations 

such as asthmatics, children, and the elderly. For the purposes of this analysis, it is presumed that if 

compliance with the NAAQS is achieved for lead, particulate matter less than or equal to 2.5 microns 

in diameter (PM2.5), and particulate matter less than or equal to 10 microns in diameter (PM10), public 

health would be protected from any toxic components within the particulate emissions as 

well. Additional disclosure of the types and amounts of hazardous materials associated with the 

proposed mine is found in the “Hazardous Materials” resource section of chapter 3. Additional 

analysis of the potential for release of hazardous materials, along with potential impacts to public 

health from releases, is found in the “Public Health and Safety” resource section of chapter 3.

Public comments were received concerning the potential effects of bioaccumulation of heavy metals 

from fugitive dust. All soils naturally contain trace levels of metals. The presence of metals in soil is, 

therefore, not indicative of contamination. The concentration of metals in uncontaminated soil is 

primarily related to the geology of the parent material from which the soil was formed. Determination 

of the makeup of particulates is not a standard analysis conducted when evaluating particulate 

emissions. Similar to the discussion above, it is presumed that if compliance with the PM10 and PM2.5

NAAQS is achieved, public health would be protected from the toxic metals compounds within the 

particulate emissions as well. 

218 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

The specific potential for asbestos-containing minerals to occur in the project area is now explicitly 

addressed (see the “Presence of Asbestos-Containing Minerals” part of this resource section).

The air quality impact analysis has been revised to include estimates of criteria pollutant emissions

generated by worker commuter vehicles and equipment/shipment delivery trucks. The Coronado has 

evaluated estimates on the mass emissions of criteria pollutants and greenhouse gas emissions 

resulting from these activities for comparison with that of the Pima County emission inventory total 

(see the “Emission Inventories” part of this resource section).

Hydrometeorology data originally located in the “Surface Water Quality” resource section have been 

incorporated into this resource section (see the “Local and Regional Climate” part of this resource 

section). The meteorological and visibility data presented in the “Affected Environment” part of this 

resource section have been updated with more recent data where available. 

On January 31, 2013, ADEQ issued the “Air Quality Class II Synthetic Minor Permit for the 

Rosemont Project” (Permit No. 55223) (Arizona Department of Environmental Quality 2013a). 

According to ADEQ, the air quality permit will ensure that Rosemont Copper meets all Federal, 

State, and local requirements by operating with enhanced emissions controls. These enhanced 

emission controls, which include paving the 3.1-mile main access road and main plant roads not used 

by haul trucks, using Tier IV engines in six of the haul trucks, the addition of a scrubber to the lime 

systems, and installing seven cartridge dust collectors to replace the originally proposed six less 

efficient wet scrubbers and molybdenum dust collector, would result in a reduction in emissions of 

coarse dust particles by approximately 52 tons per year, fine particulates by 47 tons per year, oxides 

of nitrogen by 70 tons per year, and volatile organic compounds (VOCs) by 6 tons per year, compared 

with emissions in the original Pima County permit application. The revised modeling submitted to 

ADEQ in July 2012 demonstrates compliance with the NAAQS for criteria pollutants, for the 

configuration proposed to ADEQ. This configuration is similar but not identical to the Barrel 

Alternative. Modifications would be requested to the air permit if necessary, depending on the final 

MPO approved by the Coronado. It should be noted that the modeling conducted by ADEQ to 

demonstrate compliance with NAAQS is not the same as that considered in the FEIS. The air 

permitting process typically only includes stationary emission sources, whereas the modeling 

conducted for the FEIS included both stationary and mobile emission sources in order to provide a 

full analysis of potential emissions.

In the DEIS, climate change was addressed solely in this section. While climate change continues to 

be addressed here, every resource section in this chapter now contains a section addressing how 

climate change could affect that particular resource. 

A new issue indicator was added to address the potential for degradation to Class I airsheds.

Issues, Cause and Effect Relationships of Concern

Issue 2: Impact on Air Quality

Changes in air quality that could potentially occur from the mine operation were identified as a 

significant issue. Construction, mining, and reclamation activities at the mine and along 

transportation and utility corridors would increase dust, airborne chemicals, and transportation related 

(mobile) emissions in the affected area. The CAA and other laws, regulations, policies, and plans set 

thresholds for air quality, including Class I airsheds. 

Final Environmental Impact Statement for the Rosemont Copper Project 219
Chapter 3. Affected Environment and Environmental Consequences

The emission of greenhouse gases has been implicated in global climate change, and the policy 

of the Federal Government is to reduce these emissions when possible (Executive Order 13514). 

Greenhouse gases are those in the atmosphere that retain heat. They are natural and keep the earth 

from becoming too cold. The specific gases known as greenhouse gases are carbon dioxide (CO2), 

methane (CH4), nitrous oxide (N2O), and fluorocarbons. CH4, N2O, and fluorinated gases would be 

emitted by the project; however, the anticipated level of emissions of these gases is much smaller 

than the level of CO2 emissions associated with the project.

Issue 2 Factors for Alternative Comparison

1. Particulate emission estimates, compared with background and threshold (PM2.5 and PM10)

2. Greenhouse gas emission estimates, compared with background (tons) during premining, 

active mining, and final reclamation and closure phases

3. VOC and nitrogen oxide (NOx) emissions and emissions rates to air

4. Quantitative assessment of the ability to meet air quality standards

5. Qualitative assessment of the potential for degradation to Class I airsheds

Analysis Methodology, Assumptions, 

Uncertain and Unknown Information 

For both the air quality and greenhouse gas emissions analyses, the temporal bounds of analysis is

defined by the three operational phases of the mine: premining, active mining, and final reclamation 

and closure. The active project life is anticipated to be between 24.5 to 30 years. Mining activities 

exclusively for copper production would begin after 18 to 24 months of initial construction. Activities 

would include mining and processing of ore, the placement of dry-stack tailings in the tailings 

facility, continued construction of perimeter buttresses, and continued placement of waste rock in the 

waste rock facility. Reclamation would be phased during the mine life, with concurrent reclamation

occurring on the outer slopes of the perimeter buttress and waste rock facility as those surfaces are 

completed. Closure and reclamation would take place after cessation of active operations. Postmining 

activities such as monitoring after reclamation and closure are not expected to produce substantial 

emissions and, therefore, are not part of the temporal bounds of analysis. For the analysis of climate

change impacts, the temporal bounds of analysis is defined by the best temporal resolution of existing 

studies on the region, from the present to 2050 and 2100.

The spatial analysis area differs for different modeling approaches. The size of the analysis area for 

air quality can vary, depending on the air quality parameter being analyzed and the sensitivity of the 

impacted receptor(s), and is divided into the “near-field” and “far-field” analysis areas. 

The near-field air quality analysis area is an approximately 691-square-mile area centered on the 

project site that includes the mine operations, residential areas, and public land within Pima and Santa 

Cruz Counties (figure 38). The near-field analysis area is up to 31 miles from the mine. The near-field 

analysis area includes Saguaro National Park East, which is the Class I airshed nearest to the mine. 

Compliance with NAAQS is assessed at the perimeter fenceline for each alternative, which represents 

the point at which the public will be excluded from exposure to air quality associated with the mine. 

The perimeter fence is a physical barrier (see chapter 2 for the full description) within which the 

public would not be allowed except for mine related activities. Meeting NAAQS at the fenceline 

indicates that the air quality in areas of public exposure would comply with national standards 

developed to protect public health.

220 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 38. Analysis area and nonattainment and maintenance areas for air

Final Environmental Impact Statement for the Rosemont Copper Project 221
Chapter 3. Affected Environment and Environmental Consequences

The far-field air quality analysis area analyzes air quality beyond the near-field range of 31 miles and 

includes five additional Class I Airsheds (Saguaro National Park West; Chiricahua National 

Monument; Chiricahua Wilderness; Galiuro Wilderness; Superstition Wilderness).

The analysis area for the effects of climate change on the project area is the Southwest region 

of the United States, as defined by the U.S. Global Change Research Program (Karl et al. 2009).

The contribution of greenhouse gas emissions related to the proposed project is generally limited to 

direct emissions occurring within the project area, although emissions from employees commuting in 

personal vehicles are also included.

The connected actions that are described in chapter 1 include the use of mechanized equipment to 

reroute an electrical transmission line within the project area; construct an electrical distribution, 

water supply line and associated maintenance road within the utility corridor; reroute the Arizona 

National Scenic Trail and construct ancillary facilities; and implement SR 83 highway maintenance 

improvements required by the Arizona Department of Transportation (ADOT) encroachment permit. 

The surface disturbance from these activities has been considered in the description of impacts 

common to all action alternatives for the premining phase, when they would be constructed. None of 

the connected actions are expected to significantly contribute to emissions during the active mining 

phase.

Air Quality Analysis Methodology

Analysis of air quality impacts was conducted using four approaches.

• First, emissions (in tons per year) are calculated and presented for each alternative for the 

premining and active mining phases. These emissions are compared with the current total 

emissions for Pima County.

• Second, an air quality model (AERMOD) has been used to predict the concentrations of 

criteria pollutants, compared with NAAQS at the perimeter fence for each alternative.

• Third, two air quality models (AERMOD and CALPUFF) have been used to predict the 

concentrations of criteria pollutants, compared with NAAQS, at six Class I areas (Saguaro 

National Park East, Saguaro National Park West, Galiuro Wilderness, Chiricahua National 

Park, Chiricahua Wilderness, Superstition Wilderness) and to compare the concentrations of 

pollutants emitted by the mine to allowable Class I increments for those pollutants.

• Fourth, two air quality models (VISCREEN for Saguaro National Park East and CALPUFF 

for the others) have been used to assess changes in visibility at the same six Class I areas. 

In addition, two air quality models (AERMOD for Saguaro National Park East and 

CALPUFF for the others) have been used to assess deposition of sulfur and nitrogen at the 

same six Class I areas.

Emission Inventories

Fugitive Dust from Surface Disturbance

There are numerous ways to estimate fugitive dust emissions from construction activities. However, 

the level of precision depends on the availability and accuracy of project-specific data such as 

silt content of excavated soil, soil moisture content, depth of excavation, wind speed, annual 

precipitation, type of construction equipment used, distance traveled, and the frequency and 

magnitude of water or surfactant application to control dust on unpaved roads and in the excavation 

areas.

222 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Fugitive dust emissions associated with mine development were quantified using a fugitive dust 

emission factor for PM10 available on the California Air Resources Board webpage (California 

Environmental Protection Agency Air Resources Board 2002). The emission factor, 0.19 ton of PM10 

per acre-month, was developed to analyze PM10 emissions generated from average construction 

operations. This emission factor is a derived emission factor based on studies that are representative 

of non-residential construction projects. The worst-case emission factor of 0.42 ton of PM10 per acremonth is assumed 25 percent of the time, while the study average value of 0.11 ton of PM10 was 

assumed the other 75 percent of the time. The derived 0.19-ton PM10 ton per acre-month emission 

factor therefore conservatively represents anticipated emissions from earthmoving construction 

operations anticipated for the Rosemont Copper Project. The 0.19-ton PM10 per acre-month is 

referenced in the EPA National Emission Inventory procedure documents for non-residential 

construction activities (E.H. Pechan and Associates Inc. 2005; U.S. Environmental Protection Agency

2001). These emission factors of emission tons per acre-month are applied to the average acreage 

disturbed during the first year of construction. Specific activities generating dust during the 

premining phase are not specifically analyzed. It is assumed that the acreage impacted would be the 

result of many different construction activities.

PM2.5 emissions from fugitive dust associated with mine development are estimated as a fraction of 

the PM10 emissions. South Coast Air Quality Management District recommends assuming that 21 

percent of PM10 emissions are PM2.5 from mechanical/fugitive emission sources (i.e., construction 

emissions). This PM2.5 ratio is more conservative than the EPA general ratio for construction and 

demolition activities of 0.1 PM2.5 to PM10 (Midwest Research Institute 2006). However, as there is a 

high degree of variability in estimating PM2.5 emissions (the EPA AP-42 estimated ratios of PM2.5 to 

PM10 range from 0.1 for unpaved roads and construction and demolition, to 0.15 for aggregate 

handling and storage piles, industrial wind erosion, and open area wind erosion), PM2.5 emissions for 

fugitive dust sources were conservatively estimated using the South Coast Air Quality Management 

District default ratio (i.e., 21 percent). 

Certain infrequent activities were not included in the emissions inventories. Grading activities that 

may be needed on the utility maintenance road were not included; grading would likely occur less 

than once per year. Similarly, any fugitive dust emissions from stormwater control areas (perimeter 

ditches, stormwater containment ponds) were not included. Although some wind may carry some dust 

from these areas, they would not be disturbed by machinery and they occupy minimal acreage,

compared with the waste rock and tailings facilities.

Tailpipe Emissions

The assumptions used for the number of bus trips, equipment shipments, and worker trips in order to 

calculate tailpipe emissions are the same as described in the “Transportation/Access” resource 

section. The mileage assumptions used are clearly stated with the analysis and are as follows:

26 miles round trip for buses during premining, 80 miles round trip for worker commuting during 

active mining, and 80 miles round trip for equipment shipments. It is recognized that it is not possible 

to know exactly where bus pickups might be for construction workers, where employees would be 

driving from in order either to reach the bus pickups or to drive directly to the mine, from which 

direction the trips might originate, or which roads the trips might use. The mileage assumptions used 

reasonable locations for bus pickups, either near Tucson (for instance, at SR 83 and Interstate (I-) 10) 

or in Sonoita, reasonable distances from worker’s homes in Tucson, Sonoita, or Patagonia to the 

mine, and reasonable routes for equipment/shipment haulage (either from Tucson or Nogales). 

Final Environmental Impact Statement for the Rosemont Copper Project 223
Chapter 3. Affected Environment and Environmental Consequences

On-road motor vehicle emissions for Rosemont Copper employee vehicles and haul trucks were 

calculated using emission factors for on-road gasoline and diesel vehicles obtained from Mobile 6 

emission factors. Mobile 6 is an EPA-approved emission factor model for predicting emission factors 

based on vehicle class. The emission factor in pound per mile (lb/mile) for on-road gasoline 

combustion was based on a CO2 emission factor of 19.4 lb/gallon and an average fuel economy of 

25.5 miles per gallon (mpg). The 25.5-mpg fuel economy assumes a 50/50 mix of passenger vehicles 

to light trucks with fuel economies of 27.5 to 23.5 mpg, respectively, based on the proposed corporate 

average fuel economy (CAFÉ) rule for 2010 (U.S. Environmental Protection Agency 2012d). 

The emission factor in lb/mile for on-road diesel combustion was based on a CO2 emission factor of 

22.2 lb/gallon and an average fuel economy of 6.6 mpg. 

Greenhouse gases such as CH4, N2O, and fluorinated gases would also be emitted; however, the 

anticipated level of emissions of these gases is much smaller than the level of CO2 emissions. When

considering greenhouse gas emissions from the combustion of gasoline or number 2 fuel oil (diesel), 

more than 99.99 percent of those emissions are in the form of CO2; therefore, for this analysis, only 

CO2 emissions are considered. It is recognized that not all greenhouse gases have uniform global 

warming potential. For instance, N2O has a global warming potential of 310 times the potential of 

CO2. However, if the remaining 0.01 percent of emissions were N2O, it would only account for 

approximately 2 percent of the global warming potential, a figure that is insignificant in relation to 

other uncertainties in this analysis.

Fugitive Dust Emissions from Paved Surfaces 

Emissions from vehicle/equipment travel on paved roads were calculated based on emission factors

developed from equations 1 and 2 in AP-42, chapter 13.2.1, “Paved Roads” (U.S. Environmental 

Protection Agency 2011a). Daily and annual construction and operations emissions were quantified 

using the anticipated timeline, type of equipment, quantity of equipment, hours of operation, and 

reasonable assumptions. Mileage assumptions used were identical to those described above.

Point and Fugitive Emissions Associated with Active Mining

The methodology, calculation process rates, determination of emission factors, and application of 

control efficiencies for mine operations are discussed in detail for each emission source within 

“Emission Inventory Information Years 1, 5, 10, 15, and 20, Rosemont Copper Project, Southeastern 

Arizona” (JBR Environmental Consultants Inc. 2011). Emission unit process rates, regulatory 

emission limitations and standards, manufacturer estimates, EPAAP-42 documents, engineering 

experience from other similar projects, and EPA modeling programs were used to estimate the 

emissions of criteria air pollutants from the proposed action and action alternatives. 

These emission rates are based on the following primary assumptions:

• The facility is anticipated to have a projected operating life of between 24.5 to 30 years, with 

peak mining rates of up to 376,000 tons per day of total material (ore and waste);

• Haul trucks would be operated 6,600 hours per year for each haul truck;

• Tier IV emission standards would be used on selected nonroad engines (all except haul trucks 

and the 2,000 horsepower front-end loaders);

• The maximum blasting process rate would be one blast per day; and

• Modeled emissions represent controlled rates with mitigation applied.

224 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

The following additional mitigation measures have been added as described in the “Amendment to: 

Application for a Class II Permit and Emission Inventory Information Rosemont Copper Project 

Southeastern Arizona” (JBR Environmental Consultants Inc. 2012a) and the ADEQ Air Quality Class 

II Synthetic Minor Permit (Arizona Department of Environmental Quality 2013a):

• Use of Tier IV engines on 6 of the 31 planned haul trucks (the 6 haul trucks with Tier IV 

engines would enter service after year 10 of mine operations);

• Paving of the main road entry (3.1 miles) and support vehicle use (nonhaul truck) roads;

• Changes to the lime systems, including process changes such as: elimination of pebble line 

loading directly onto semiautogenous grinding mill feed conveyor, slaking all lime in two 

lime slakers, addition of wet scrubber control device for lime slaking processes; and

• The replacement of six less efficient wet scrubbers and the molybdenum dust collector with 

seven more efficient cartridge filter dust collectors as control devices at various process 

points throughout the facility.

Fugitive particulate matter emissions that result from erosion of the tailings storage areas are 

susceptible to moderate to high wind speeds and wind erosion. Overall, the tailings can be 

characterized as a silt with sand, with an average maximum particle size of 0.419 millimeter and

average 72.6 percent fines (passing the No. 200 sieve). Tailing storage emissions were estimated 

assuming that the annual, daily, and hourly process rates for wind erosion of the tailings storage are 

equal to the maximum area of the land containing the tailings (1,500 acres) and continuous operation 

of the storage area (i.e., 8,760 hours/year, 24 hours/day, 1 hour/hour). Uncontrolled particulate matter, 

PM10, and PM2.5 emissions from the tailings storage were calculated using the methodology and 

equations from EPA’s AP-42, section 13.2.5, “Industrial Wind Erosion,” dated November 2006

(U.S. Environmental Protection Agency 2006). The smallest threshold friction velocity of 0.43 meter 

per second (about 1 mile per hour) was assumed to approximate the tailings. 

Furthermore, based on the hourly data collected at the meteorological station at the Rosemont Copper 

Project site from April 2006 through May 2009, the highest wind speed, 10.70 meters per second

(about 24 miles per hour), for the time period between disturbances was used to estimate the 

uncontrolled emissions from tailings storage. Emissions of particulate matter resulting from wind 

erosion would be mitigated by constructing the perimeter buttress around the tailings facility using waste 

rock. The perimeter buttress would break up the air flow and reduce exposure of tailings facility to windy 

conditions (JBR Environmental Consultants Inc. 2011).

The emissions modeling for active mining was based on the year of maximum expected emissions, 

both the year with the highest projected mining rate and the year with the highest haul truck vehicle 

miles traveled. The exact year modeled differs between alternatives. For the proposed action, Phased 

Tailings Alternative, Barrel Trail Alternative, and Scholefield-McCleary Alternative, year 1 of active 

mining represents the year with the highest projected mining rate, and year 5 of active mining

represents the year with the highest projected haul truck vehicle miles traveled. However, for the 

Barrel Alternative, year 12 of active mining was projected as the year with the highest project haul 

truck travel. Therefore, year 12 of active mining was selected for analysis instead of year 5 of active 

mining for the Barrel Alternative. 

Note that the Phased Tailings Alternative is a variation of the proposed action and does not lead to 

any change in emissions or location of emission sources (JBR Environmental Consultants Inc. 

2012e). Like the proposed action, the Phased Tailings Alternative incorporates a waste rock perimeter 

Final Environmental Impact Statement for the Rosemont Copper Project 225
Chapter 3. Affected Environment and Environmental Consequences

buttress that would completely surround the dry-stack tailings. Furthermore, the heap leach facility 

would be located in the same place as for the other alternatives. Although the construction of the 

tailing phases is reversed from that of the proposed action, at the end of mine life, the final waste rock 

and tailings facility would occupy the same location as the proposed action. Therefore, the Phased 

Tailings Alternative was not modeled, as modeled emissions would be the same as for the proposed 

action.

Near-Field Predictive Modeling Approach

Evaluation of air quality impacts from each alternative within the near-field analysis area was 

conducted using AERMOD, EPA’s regulatory default model for near-field analysis. AERMOD is used 

to model concentrations of criteria pollutants, which are then combined with appropriate background 

concentrations and compared with the NAAQS. Modeling was conducted by Rosemont Copper, with 

model inputs and control parameter options selected in accordance with the protocol established in 

the “User’s Guide for the AMS/EPA Regulatory Model – AERMOD” (U.S. Environmental Protection 

Agency 2004b). A detailed description of the AERMOD modeling approach, including modeling 

assumptions and data availability, is provided in the “AERMOD Modeling Protocol to Assess 

Ambient Air Quality Impacts, April 2012” for the project (JBR Environmental Consultants Inc. 

2012b). The Forest Service provided direction to Rosemont Copper concerning the assumptions and 

methodologies to be used in the AERMOD modeling (Rosemont Copper Company 2012d).

In addition to compliance with NAAQS, the Forest Service also is required to evaluate “air quality

related values” at Class I areas. These air quality related values include deposition of contaminants 

and visibility effects. The EPA VISCREEN screening model was applied to each alternative in order 

to evaluate the effect of the emissions to visibility levels at the Saguaro National Park East Class I

area. VISCREEN is recommended by the EPA to calculate the potential visual impact of a plume of 

specified emissions for specific meteorological conditions at Class I airsheds within 31 miles 

(50 kilometers) of an air pollution source. 

The VISCREEN model is used to calculate concentrations of selected contaminants within an 

elevated plume and predict the movement and dispersal of that plume. The model calculates the 

change in the color difference index and contrast between the plume and the viewing background 

(U.S. Forest Service et al. 2010). The specified emissions used in this analysis are particulate matter, 

NOx, soot, and sulfates. It is important to understand that the meteorological conditions used in this 

analysis represent a worst-case scenario for wind speeds and atmospheric stability. A detailed 

description of the VISCREEN model used for this analysis is provided in “VISCREEN: Revised 

Visibility Impact Analysis at Saguaro East National Park, December 2012” (JBR Environmental 

Consultants Inc. 2012d).

AERMOD was also used to calculate impacts from deposition of nitrogen and sulfur at Saguaro 

National Park East, which is the nearest Class I area (JBR Environmental Consultants Inc. 2013a).

Far-Field Predictive Modeling Approach for Class I Areas

Evaluation of potential effects on air quality related values from the project to more distant Class I 

areas other than Saguaro National Park East was conducted by Rosemont Copper using CALPUFF 

Version 5.8, which is the recommended model for long-range transport applications (40 CFR 51, 

“Revision to the Guidelines on Air Quality Models,” November 2005). 

226 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

The CALPUFF model is used to determine impacts to both visibility and deposition at Class 1 

airsheds that are located in the far-field analysis area (greater than 31 miles (50 kilometers) away 

from the project air pollution source). A detailed description of the CALPUFF modeling approach, 

including modeling assumptions and data availability, is provided in “CALPUFF Modeling Protocol 

to Assess Ambient Air Quality Impacts, December 2012” (JBR Environmental Consultants Inc. 

2012c).The Forest Service provided direction to Rosemont Copper concerning the assumptions and 

methodologies to be used in the CALPUFF modeling (Rosemont Copper Company 2012d).

Presence of Asbestos-Containing Minerals

In 2011, in response to cooperating agency concerns and anecdotal evidence that asbestiform 

minerals, specifically tremolite, had been observed in the Imerys marble quarry, the Coronado 

investigated the potential for asbestos-containing minerals to occur within the project area. Further 

detail was requested and obtained from Rosemont Copper regarding the mineralogy of the ore deposit 

(Cornoyer 2011b).

The term “asbestos” is an industrial term, not a true geological or mineralogical definition. In general, 

asbestos occurs as one of six naturally occurring minerals, including actinolite and tremolite. These 

minerals are very similar, differing only in the amount of iron present, and the continuum of minerals 

is often referred to as tremolite-actinolite. Tremolite-actinolite minerals are common in limestone 

formations that have been metamorphosed by igneous intrusions, which in general is the geological 

setting under which the Rosemont deposit was formed. Only fibrous forms of these minerals are 

considered asbestiform; these minerals more commonly occur in non-asbestos-containing forms, such 

as massive or granular crystalline forms (Harris 2003).

According to Rosemont Copper, tremolite and actinolite were observed in drill cores throughout the 

Rosemont deposit. The presence was locally limited, and the minerals were not observed to have the 

silky fibers or aggregate mats that are typical of the asbestos-containing form of these minerals. 

The minerals were reported as occurring in local disseminations and commonly also as having been 

altered to chlorite, talc, and carbonates (Cornoyer 2011b). Research in 2003 conducted by the AGS

regarding the presence of asbestiform minerals specifically in the Rosemont area came to similar 

conclusions: “[P]rimary references by those who have studied in detail the geology and ore deposits 

of these areas note the presence of actinolite-tremolite but none indicate that it is asbestiform” 

(Harris 2003:9).

While asbestiform minerals may occur in many geological settings, including those of the project 

area, research by the AGS and by observations made directly by Rosemont geologists logging the 

drill cores give no indication that asbestiform minerals are present in the Rosemont deposit itself. 

For the purposes of the air quality analysis, the potential for the presence of airborne asbestos from 

mining activities is handled through analysis of all particulate matter and the ability for the project to 

meet air quality standards for particulate matter.

Climate Change Methodology

Greenhouse gas emission sources included in the climate change analysis consisted of point sources 

and mobile sources for comparison with that of the Pima County emission inventory total. Reports by 

the Intergovernmental Panel on Climate Change (2007) and the U.S. Global Change Research

Program (Karl et al. 2009; U.S. Global Change Research Program 2009) conclude that the climate is 

changing, that the change will accelerate, and that human caused emissions of greenhouse gases 

(in particular, CO2) are the primary cause of accelerated climate change. The primary factors that 

Final Environmental Impact Statement for the Rosemont Copper Project 227
Chapter 3. Affected Environment and Environmental Consequences

influence greenhouse gas emissions from the project are the combustion of fossil fuels in highway

and nonroad vehicles for project construction, operations, and employee commuting, and the 

combustion of fossil fuels in project processing equipment. The primary greenhouse gas emitted by 

these activities is CO2; therefore, the analysis focuses on the emission of this gas. Projected impacts 

of climate change on the project area include changes to regional temperature and precipitation levels 

and patterns; the impacts of these changes on resource values are analyzed separately under each 

individual resource section in this chapter. 

Uncertain and Unknown Information

Although it is possible to quantify a project’s direct effects on greenhouse gas emissions, the actual 

intensity of an individual project’s indirect effects on global climate is uncertain. Uncertainty in 

predicting climate change effects is expected because it is not possible to meaningfully link 

individual project actions to quantitative effects on climatic patterns.

Climate change is a global problem that results from global greenhouse gas emissions. There are 

more sources and actions emitting greenhouse gases (in terms of both absolute numbers and types) 

than are typically encountered when evaluating the emissions of other pollutants. These emissions are 

often categorized as either anthropogenic (human caused) or nonanthropogenic (naturally occurring). 

From a quantitative perspective, there is no single dominating anthropogenic source and fewer 

sources that would even be close to dominating total greenhouse gas emissions. The global climate

change problem is much more the result of numerous and varied sources, each of which might seem 

to make a relatively small addition to global atmospheric greenhouse gas concentrations. Currently,

there are no sites within the study area that are collecting ambient greenhouse gas data. Ambient 

background data that exist are parametrically derived from fossil fuel combustion and other industrial 

sources. For the action alternatives, emissions of criteria air pollutants would cease with closure of 

the project. However, CO2 is long-lived within the atmosphere, and CO2 emissions from the action 

alternatives would continue to incrementally contribute to global climate change. Because global 

climate change results from emitting activities taking place around the world, the indirect effects of 

greenhouse gas emissions from the action alternatives cannot be directly linked to particular regional 

or global effects of climate change.

The action alternatives would result in long-term direct and indirect effects on air quality in the 

project area and nearby Class I areas. One indirect effect of the project would be the air pollutant 

emissions resulting from power generation to meet the electrical power demand of the project. 

The electric utility service provider for the project would be TEP. However, the power consumed by 

the project could come from a wide geographic area (i.e., Western Interconnect), and the manner in 

which this power is generated varies (e.g., fossil fuels, nuclear, solar, wind, hydro power, geothermal, 

etc.), all of which are in the TEP portfolio for energy production. It is estimated the project would 

require 108 to 112 megawatts (MW) (WestLand Resources Inc. 2007a). If the power demand of the 

project were to be supplied solely by a fossil fuel-fired plant(s), there would be an indirect increase in 

criteria pollutant and greenhouse gas emissions. However, the calculation of these indirect impacts 

cannot be made because the type and location of the generation facility or facilities are unknown, the 

quantity of any resulting emissions is unknown, and the Forest Service has no control over how or 

where the energy is created.

228 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

With respect to emissions inventories, some details are not available at this time and would not be 

available until construction occurs. Assumptions were made for missing data, including the location 

from which the vehicles and equipment would be mobilizing and the distance traveled by on-road 

vehicles. 

As noted previously, it is recognized that it is not possible to know exactly where bus pickups might 

be for construction workers, where employees would be driving from to reach the bus pickups or to 

drive directly to the mine, from which direction the trips might originate, or which roads the trips 

might use. The mileage assumptions used reasonable locations for bus pickups, either near Tucson 

(for instance, at SR 83 and I-10) or in Sonoita, reasonable distances from worker’s homes in Tucson, 

Sonoita, or Patagonia to the mine, and reasonable routes for equipment/shipment haulage (either from 

Tucson or Nogales). 

With respect to modeling compliance with NAAQS at the perimeter fence, in several instances there 

is uncertainty due to background concentrations. The background concentrations for 1-hour sulfur 

dioxide (SO2) and for lead were conservatively assumed to be equal to the modeled concentration. 

Further, there was a lengthy process undertaken with cooperating agencies and the EPA to determine 

the most appropriate background concentrations to use for PM10. The Coronado provided guidance to 

Rosemont Copper on this aspect of the modeling (Rosemont Copper Company 2012d). A more 

detailed discussion of the use of background concentrations is presented in the AERMOD report

(JBR Environmental Consultants Inc. 2012e). It should be noted that upon review of the results, the 

Coronado did not fully agree with the rationale presented by Rosemont Copper. The Coronado’s final 

opinion on the use of background concentrations is discussed in the “AERMOD Modeling of 

Compliance with NAAQS at the Perimeter Fence for the Action Alternatives” part of this resource 

section.

Summary of Effects by Issue Factor by Alternative 

Table 28 presents the summary comparison of impacts from each alternative. 

Affected Environment

Relevant Laws, Regulations, Policies, and Plans

Mine operations are subject to a wide range of Federal, State, and local requirements. Many of these 

require permits before the mine operations begin; others may require approvals or consultations, 

mandate the submission of various reports, and/or establish specific prohibitions or performance

based standards. Table 29 provides a summary of air quality laws, regulations, policies, and plans at 

the Federal, State, and local level. 

Existing Conditions 

Air Quality and Climate Change Conditions

Local and Regional Climate

The project area lies in one of the most distinctive regions of Arizona, with a mixture of desert plains, 

lush grasslands, and pine-topped mountains. The proposed project is located in southern Arizona on 

the eastern front of the Santa Rita Mountain range, which is surrounded by arid desert basins.

Final Environmental Impact Statement for the Rosemont Copper Project 229
Table 28. Summary of effects

Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 2.1: 

PM2.5 versus 

background and 

threshold

No change 

resulting from 

the proposed 

mine. Fugitive 

dust and 

emissions

expected to 

increase with 

population.

Premining: 

0.7% increase in 

Pima County 

annual emissions

Active mining:

4× increase versus 

background levels; 

complies with 

NAAQS at 

perimeter fence

Same as for proposed 

action

Same as for proposed 

action

Same as for proposed 

action

Pr

in

C

em

A

6× 

ba

ex

N

fe

Issue 2.1: 

PM10 versus 

background and 

threshold

No change 

resulting from 

the proposed 

mine. Fugitive 

dust and 

emissions

expected to 

increase with 

population.

Premining:

0.7% increase in 

Pima County 

annual emissions

Active mining:

3× increase versus 

background levels; 

exceedance of the 

NAAQS at 

perimeter fence

Same as for proposed 

action

Premining: 

0.7% increase in Pima 

County annual 

emissions

Active mining: 

3× increase versus 

background levels; 

complies with NAAQS

at perimeter fence

Premining:

0.7% increase in Pima 

County annual emissions

Active mining:

4× increase versus 

background levels; 

exceedance of the 

NAAQS at perimeter 

fence

Pr

in

C

em

A

4× 

ba

ex

N

fe

Issue 2.2: Greenhouse 

gas emissions versus 

background

No change 

resulting from 

the proposed 

mine. 

Greenhouse gas 

emissions

expected to 

increase with 

population.

Premining: <0.1% 

increase in Pima 

County CO2

emissions

Active mining:

~1% increase in 

Pima County CO2

emissions

Approximately the 

same as for proposed 

action

Approximately the 

same as for proposed 

action

Approximately the same 

as for proposed action

A

sa

ac

230 Final Environmental Impact Statement for the Rosemont Copper Project
Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 2.3: 

VOC emissions

No change 

resulting from 

the proposed 

mine. 

VOC emissions

expected to 

increase with 

population.

Premining:

Emission rate of 

<1 ton per year

Active mining:

Less than 1% 

increase in Pima 

County VOC 

emissions; emission

rate of about 86 

tons per year

Premining: Emission

rate of <1 ton per year

Active mining: Less 

than 1% increase in 

Pima County VOC 

emissions; emission

rate of about 86 tons 

per year

Premining: Emission

rate of <1 ton per year

Active mining: Less 

than 1% increase in 

Pima County VOC 

emissions; emission

rate of about 82 tons 

per year

Premining: Emission

rate of <1 ton per year

Active mining: Less 

than 1% increase in 

Pima County VOC 

emissions; emission rate 

of about 88 tons per year

Pr

ra

A

th

Pi

em

ra

pe

Issue 2.3: 

NOx emissions

No change 

resulting from 

the proposed 

mine. 

NOx emissions

expected to 

increase with 

population.

Premining: <0.1% 

increase in Pima 

County NOx

emissions Active 

mining: 3.4% 

increase in Pima 

County NOx

emissions; emission

rate of about 1,200 

tons per year 

Same as for proposed 

action

Same as for proposed 

action

Premining: <0.1% 

increase in Pima county 

NOx emissions Active 

mining: 3.6% increase in 

Pima County NOx

emissions; emission rate 

of about 1,250 tons per 

year

Pr

in

co

A

in

C

em

ra

to

Issue 2.4: Meeting of 

air quality standards

No change 

resulting from 

the proposed 

mine. Continued 

monitoring and 

regional 

emission

reduction efforts 

likely to 

maintain 

compliance with 

NAAQS.

Exceedance of 

PM10 NAAQS at 

perimeter fence

Same as for proposed 

action

Complies with all 

NAAQS at perimeter 

fence

Exceedance of PM10

NAAQS at perimeter 

fence. 

Ex

an

pe

Final Environmental Impact Statement for the Rosemont Copper Project 231
Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 2.5: Effects on 

air quality in 

Class I airsheds

No change 

resulting from 

the proposed 

mine. Effects on 

Class I airsheds 

expected to 

increase with 

population.

Emissions do not 

exceed Class I 

increment 

thresholds; may 

contribute to 

degradation of air 

quality related 

values in the 

Saguaro National 

Park East, Saguaro 

National Park West, 

and Galiuro 

Wilderness Area 

Class I airsheds

Same as for proposed 

action

Same as for proposed 

action

Emissions do not exceed 

Class I increment 

thresholds; may 

contribute to degradation 

of air quality related 

values in the Saguaro 

National Park East and 

Galiuro Wilderness Area 

Class I Airsheds

Sa

ac

232 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 29. Air quality laws, ordinances, regulations, and standards

Laws, Ordinances, 

Regulations, and 

Standards

Description Applicability

Federal

Federal New Source 

Review (NSR)/Prevention 

of Significant 

Deterioration (PSD), 

40 CFR 51, subpart I, and 

40 CFR 52.2(1)

The PSD program was developed to prevent 

significant deterioration in the air quality of those 

areas that meet the NAAQS. In general, the 

NSR/PSD rules define a “major source” as any 

source with the potential to emit 250 tons per 

year (tpy) or more of a criteria pollutant.

A more stringent threshold is defined for a 

limited number of “categorical sources,” source 

categories for which the PSD applicability 

threshold is 100 tpy of any criteria pollutant. 

The Rosemont Copper Project is not a 

listed categorical stationary source as 

defined by PSD. Since the facility is a 

noncategorical source, fugitive emissions

are not considered for major-source 

applicability determinations. Thus, the 

potential-to-emit of criteria pollutants (not 

including fugitives) from the facility 

would be below the NSR/PSD majorsource threshold of 250 tpy. However, the 

fugitive emissions have been accounted for 

and analyzed in the modeling analysis 

presented within this section.

New Source Performance 

Standards (NSPS), 

40 CFR 60

The Federal NSPS are technology-based 

standards applicable to new and modified 

stationary sources of regulated air emissions. 

While the NAAQS emphasize air quality in 

general, the NSPS focus on particular sources 

of pollutants. The NSPS program sets uniform 

emission limitations for approximately 70 

industrial source categories or subcategories 

of sources that are designated by size as well as 

by type of process.

The crushers, screens, conveyor belt 

transfer points, storage bins, and truck 

unloading are affected facilities located in 

a metallic mineral processing plant as 

defined in NSPS Subpart LL; therefore,

NSP Standards are applicable and have 

conditions in the air permit to meet these 

standards.

NAAQS, 40 CFR 50 The establishment of the NAAQS set maximum 

concentrations in ambient air for Pb, NOx, SO2, 

CO, suspended PM10, and ozone.

Determination of whether Rosemont 

Copper complies with the CAA, including 

NAAQS, is the responsibility of the 

permitting agency, in this case ADEQ. The 

Coronado has used meeting of NAAQS at 

the perimeter fenceline as an indicator that 

NFS surface resources would not be 

unduly impacted by project emissions.

National Emission

Standards for Hazardous

Air Pollutants (NESHAP), 

40 CFR 61 and 63

NESHAP rules address health concerns that are 

considered too localized to be included under the 

scope of NAAQS. In general, NESHAP 

regulations apply to affected sources that are 

located at (or are themselves) major sources of 

hazardous air pollutant (HAP) emissions, as 

defined in 40 CFR 63.2. That is, any stationary 

source that emits or has the potential to emit 

(considering controls in the aggregate) 10 tpy or 

more of any single HAP or 25 tpy or more of any 

combination of HAPs.

Based on the estimated, maximum 

potential emissions for the proposed mine 

operation, the Rosemont Copper Project 

would not be a “major HAP source.”

However, applicable NESHAPs pertaining 

to the boiler, emergency engine, and 

storage tanks would apply.

Acid Rain Program 

Emission Monitoring,

40 CFR 72 and 75

The EPA established a program to control 

emissions that contribute to the formation of acid 

rain. The overall goal of the Acid Rain Program 

is to achieve significant environmental and 

public health benefits through reductions in 

emissions of SO2 and NOx, the primary causes of 

acid rain. The acid rain regulations are applicable 

to “affected units” as defined in the regulations.

Mine operations are not regulated under 

the Acid Rain Program. Based on the 

estimated maximum potential emissions

for the proposed mine operation, the 

Rosemont Copper Project would not be a 

major source of SO2 emissions; therefore, 

these regulations are not applicable.

Final Environmental Impact Statement for the Rosemont Copper Project 233
Chapter 3. Affected Environment and Environmental Consequences

Laws, Ordinances, 

Regulations, and 

Standards

Description Applicability

Regional Haze Rule, 

40 CFR 51

The Regional Haze Rule addresses visibility 

impairment in national parks and wilderness

(Class I) areas. Under PSD requirements, a new 

source of criteria pollutant and air toxics 

emissions must analyze its impacts to Class I 

areas, including visibility and regional haze.

Determination of whether Rosemont 

Copper complies with the CAA, including 

visibility impacts, is the responsibility of 

the permitting agency, in this case ADEQ.

However, as a Federal land manager, the 

Coronado has a responsibility to analyze 

impacts of the project on air quality related 

values, including visibility and deposition.

Compliance Assurance 

Monitoring Program, 

40 CFR 64 

The Federal regulations implementing 

compliance-assurance monitoring apply to major 

sources that must obtain a Title V operating 

permit pursuant to 40 CFR 70. 

The compliance-assurance monitoring rules are 

primarily aimed at emission units that are 

individually above major source thresholds and 

that use control devices in order to comply with 

an emission limitation (40 CFR 64.2). 

The proposed mine is not a major source 

of criteria pollutants; consequently, the 

facility would not be subject to 

compliance-assurance monitoring

requirements.

Accidental Release 

Prevention Program/Risk 

Management Plans, 

40 CFR 68 

The Accidental Release Prevention Program 

applies to facilities that may store quantities of 

toxic or flammable chemicals above listed 

thresholds. The requirements include process 

hazards analyses, implementation of work 

practices to prevent releases, and development of 

site-specific risk management plans. 

Based on its process and design, the 

proposed mine would not store onsite 

quantities of listed chemicals above the 

thresholds listed in 40 CFR 68; therefore, 

this program would not be applicable to 

the facility.

Stratospheric Ozone

Protection Regulations, 

40 CFR 82, subpart F 

Under Title VI of the CAA, the EPA is 

responsible for programs that protect the 

stratospheric ozone layer.

Processes at the planned mine would not 

involve the use of chlorofluorocarbon 

compounds. Therefore, these operations 

would not be subject to chlorofluorocarbon

related regulations.

General Conformity 

Analysis, 40 CFR 51, 

subpart W, and 40 CFR 93 

States and local authorities have the 

responsibility for bringing their regions into 

compliance with NAAQS or more stringent 

standards they may adopt. State implementation 

plans (SIPs) are EPA-approved plans that set 

forth the pollution control requirements 

applicable to the various sources addressed by 

each SIP. Federal actions must be evaluated for 

conformity to the local SIP if the project:

(1) is located within an EPA-designated 

nonattainment or maintenance area; (2) would 

result in emissions above major-source threshold 

quantities of a criteria pollutants;

(3) is not a listed exempt action; and (4) has not 

been accounted for in an EPA-approved SIP. 

The project site is in attainment for all 

criteria pollutants, but the greater Tucson 

area contains a PM10 nonattainment area 

and a CO maintenance area. Under ADEQ

requirements, the project also does not 

exceed major source thresholds. The 

Coronado has analyzed the project for 

effects on NFS surface resources, not 

conformity. The Coronado has used 

meeting of NAAQS at the perimeter 

fenceline as an indicator that NFS surface 

resources would not be unduly impacted 

by project emissions.

234 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Laws, Ordinances, 

Regulations, and 

Standards

Description Applicability

Arizona

49 ARS; 18 AAC The policies, regulations, and responsibilities of 

the ADEQ, including State and County air 

pollution control measures, are defined in 

49 ARS and 18 AAC. 

The State of Arizona has the primary 

authority in the State for air pollution 

control and abatement and is responsible 

for administration of the CAA under EPA

Region IX.

The State of Arizona has exerted 

jurisdiction over the air permit for the 

Rosemont Copper Project. Point-source 

emissions of criteria pollutants from the 

facility would be less than the Title V 

source threshold of 100 tpy. Consequently, 

the facility would operate under a Class II 

permit issued by the ADEQ.

Local

Pima County Code 17 Pima County Code 17.12 requires a fugitive dust 

activity permit for any person conducting land

stripping, earthmoving, blasting, trenching, or

road construction.

Pima County Code 17.16 requires compliance

with visible emissions standards for any single

emission point, multiple emission point, or

fugitive emissions source.

Pima County has indicated that activities 

involving roads not directly within the 

mine, as well as activities within the utility 

corridor, would be required to obtain 

permits and meet standards described 

under Title 17 of the Pima County Code.

Because of the physiography of this region, which consists of wide basins surrounded by mountain 

ranges, significant variation in the precipitation pattern occurs over short distances and varies by 

season and with elevation. Precipitation data are available for the project area from a variety of 

sources and periods, as shown in table 30, including a monitoring station that was installed within the 

project area near the center of the proposed open pit.

Table 30. Summary of average monthly precipitation (in inches) from various sources

Month

Sellers*

(1931 to 

1970)

Helvetia†

(1916 to 

1950)

Canelo 1 

NW†

(1981 to 

2010)

Santa Rita 

Experimental 

Range†

(1981 to 2010)

Rosemont 

Mine Site‡

(2006 to 

2008)

Rosemont 

Mine Site§

(2009 to 

2011)

January – 1.58 1.52 1.90 0.59 2.47

February – 1.72 1.14 1.55 0.79 1.85

March – 1.14 1.03 1.38 0.45 0.72

April – 0.52 0.58 0.78 0.45 0.46

May – 0.28 0.25 0.39 0.51 0.38

June – 0.67 0.63 0.38 0.98 0.35

July – 4.05 4.32 5.16 5.51 2.18

August – 4.15 4.03 4.44 3.74 1.54

September – 2.19 1.77 2.32 1.62 1.49

October – 0.68 1.18 1.59 0.24 0.21

November – 1.22 0.88 1.05 1.11 0.07

December – 1.52 1.53 2.03 1.16 0.91

Final Environmental Impact Statement for the Rosemont Copper Project 235
Chapter 3. Affected Environment and Environmental Consequences

Month

Sellers*

(1931 to 

1970)

Helvetia†

(1916 to 

1950)

Canelo 1 

NW†

(1981 to 

2010)

Santa Rita 

Experimental 

Range†

(1981 to 2010)

Rosemont 

Mine Site‡

(2006 to 

2008)

Rosemont 

Mine Site§

(2009 to 

2011)

Annual Total 

Precipitation 16 19.73 18.86 22.97 17.12 12.61

Average Annual Snowfall – 7.7 5.2 3.9 – –

Note:

– = No data available.

* University of Arizona (Hargis and Harshbarger n.d. [1977]).

† Western Regional Climate Center (2009; 2013a; 2013b; 2013c).

‡ Carrasco (2009).

§ Data provided by Rosemont Copper.

The climate is semiarid. The average annual precipitation ranges from 13 to 23 inches, with roughly

60 percent occurring as a result of convective storms during the summer monsoon season (July 

through October) and the remaining occurring as a result of frontal storms during the winter season 

(November through March). May and June are typically the driest months. Winter precipitation falls 

partly as snow between November and April, averaging less than 8 inches of snowfall with little 

lasting accumulated depth.

Monthly average temperature data are available from the onsite weather station and from several of 

the same stations for which precipitation data are available, as summarized in table 31.

Table 31. Summary of average monthly temperatures (°F) from various sources

Station*

Month

Helvetia(1916 to 1950)Average MaximumHelvetia(1916 to 1950)Average MinimumCanelo 1 NW(1971 to 2000)Average MaximumCanelo 1 NW(1971 to 2000)Average MinimumSanta Rita Experimental Range(1971 to 2000)Average MaximumSanta Rita Experimental Range(1971 to 2000)Average MinimumRosemont Mine Site†(2006 to 2010)Average MaximumRosemont Mine Site†(2006 to 2010)Average Minimum

January 57.93 35.85 57.90 26.10 60.40 37.50 63.8 26.6

February 61.14 38.25 61.50 28.20 64.30 39.70 68.9 25.3

March 66.42 42.43 66.10 31.70 68.60 43.20 76.5 29.0

April 74.83 49.40 73.70 36.70 76.00 48.30 77.0 35.2

May 82.88 55.97 81.80 43.40 83.80 55.80 85.9 43.8

June 92.12 64.41 90.40 52.40 93.30 64.60 92.5 56.8

July 91.27 67.63 88.30 59.80 92.00 66.80 91.9 60.7

August 87.93 65.82 85.50 58.40 89.10 65.20 88.5 61.1

September 86.49 63.45 83.80 52.70 86.50 62.30 85.2 54.4

October 78.27 54.45 76.50 41.90 78.60 54.50 83.0 37.4

November 67.80 43.60 65.90 31.80 67.70 42.80 77.4 31.3

December 60.55 38.26 58.20 26.70 60.70 37.50 69.4 22.8

* Western Regional Climate Center (2009).

† Data provided by Rosemont Copper.

236 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

At the monitoring station installed within the project area, the average maximum monthly 

temperature ranges from 64 degrees Fahrenheit (°F) in January to 93 °F in June. Elsewhere, the 

average maximum monthly temperature ranges from a low of approximately 59 °F in January to a 

high of approximately 92 °F in June. Temperature inversions can occur throughout the year but are 

most intense in the winter, trapping pollutants in a cold air layer near the surface until the air is heated 

and able to rise and mix with other air layers. During colder winter mornings, vehicular pollutant 

concentrations increase in the area because of stagnant air conditions, especially in areas of heavy 

vehicle congestion.

Winds predominantly flow from the west to the east, corresponding to the slope of the terrain from 

the higher mountain elevations to the west and the lower canyon elevations to the east. Figure 39 

shows the distribution of wind direction and wind speed at the project area during 2008. Hot, humid, 

and windy conditions during the summer monsoon period contribute to naturally occurring 

windblown dust in the region, although dust storms may be exacerbated by land disturbances that 

destroy soil crusts and/or result in the removal of vegetation. 

Figure 39. Distribution of winds (percent) at the project site

Final Environmental Impact Statement for the Rosemont Copper Project 237
Chapter 3. Affected Environment and Environmental Consequences

Evaporation

Evaporation pan data do not exist for the same stations that were used for the precipitation and 

temperature data. However, evaporation pan measurements were added to the onsite weather station 

in June 2008, and evaporation pan data are available from other weather stations in southern Arizona. 

Nearby stations with pan evaporation data include Tucson, University of Arizona, with more than 100 

years of data, and Nogales 6 N, with more than 50 years of data. The closest station is in Nogales.

In addition to the limited onsite evaporation pan measurements, estimates of pan evaporation rates 

have been determined for the project area based on the 50 years of continuous data for both 

precipitation and evaporation measurements recorded at the nearby Nogales weather station (Carrasco 

2009). The projected project area pan evaporation rates range from a low of 2.89 inches per month in 

August to a high of 10.75 inches in June, with an estimated annual evaporation rate of 71.52 inches 

(table 32). 

Table 32. Average monthly pan evaporation for nearby stations and the project area 

(inches)

Month

Tucson, 

University of 

Arizona 

(1894 to 2007)*

Nogales 6 N 

(1952 to 

2007)*

Rosemont 

Copper Project 

(2008)*

Rosemont 

Copper 

Project 

(2009 to 

2011)

†

Estimated Pan 

Evaporation

Rosemont 

Copper Project 

Area

January 3.25 3.59 – 2.38 4.13

February 4.57 4.46 – 3.46 4.28

March 6.95 7.01 – 6.09 7.11

April 9.88 9.35 – 3.74 8.50

May 12.87 11.91 – 3.19 10.38

June 14.91 13.31 – 4.57 10.75

July 13.17 10.00 4.77 – 4.93

August 11.65 8.28 2.92 3.98 2.89

September 10.35 8.06 4.11 5.33 4.40

October 7.81 7.17 2.32 4.11 6.15

November 4.73 4.49 2.20 3.65 4.11

December 3.37 3.57 2.22 2.91 3.89

Annual Total 

Pan Evaporation 103.51 91.20 – – 71.52

Note:

– = No data available.

* Carrasco (2009).

† Data provided by Rosemont Copper (2012f).

Local and Regional Air Quality

National Ambient Air Quality Standards

As directed by the Federal CAA, the EPA has established NAAQS for seven “criteria” pollutants 

(table 33). These standards were adopted by the EPA to protect public health (primary standards) and 

public welfare against decreased visibility as well as damage to animals, crops, vegetation, and 

buildings (secondary standards). The seven pollutants are carbon monoxide (CO), nitrogen dioxide

(NO2), ozone (O3), inhalable particulate matter (PM10), fine particulate matter (PM2.5), SO2, and lead. 

238 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

States and other delegated entities are required to adopt standards that are at least as stringent as the 

NAAQS. The Arizona Ambient Air Quality Standards and Pima County Ambient Standards are 

identical to the NAAQS (40 CFR 50.4–50.16; 18 AAC Chapter 2, Article 2, Sections 201–206: Pima 

County Code Title 17 Chapter 17.08). The Pima County Department of Environmental Quality has 

original jurisdiction pursuant to State law and receives delegated authority from the EPA to 

implement and enforce applicable Federal air quality standards in Pima County. 

Table 33. National Ambient Air Quality Standards

Pollutant Averaging Time

Primary Standards

micrograms per cubic meter (μg/m3) 

(parts per million (ppm))

Secondary Standards

μg/m3 (ppm)

CO 1-hour 40 (35)c No standard

CO 8-hour 10 (9) No standard

NO2 1-hour 189 (0.100) No standard

NO2 Annual 100 (0.053) 100 (0.053)

O3 1-houra (0.12) (0.12)

O3 8-hour (0.075) (0.075)

PM10 24-hour 150 150

PM10 Annualb 50 50

PM2.5 24-hour 35d 35e

PM2.5 Annual 12h 15

SO2 3-hour No standard 1300 (0.5)

SO2 1-hour 195 (0.075)f No standard

Pb Rolling 3-month average 0.15g 0.15g

Source: 40 CFR 50.

a 1-hour standard revoked in Arizona on June 15, 2005.

b Annual standard revoked effective December 18, 2006.

c Milligrams per cubic meter (ppm).

d New 24-hour standard effective December 18, 2006.

e New 24-hour standard effective December 18, 2006.

f New standard effective June 2, 2010.

g New standard effective January 12, 2009.

h The primary standard changed on December 14, 2012, from 15 μg/m3 to 12 μg/m3

.

Rosemont Copper had previously submitted an application for air permit to Pima County, which was 

subsequently denied. That process resulted in a lawsuit between Rosemont Copper and Pima County. 

It was ruled by Arizona Superior Court that Pima County’s decision to deny the permit was “arbitrary 

and capricious.” An application was instead submitted by Rosemont Copper to the ADEQ. ADEQ 

responded: “Due to the confusion and uncertainty caused by the inappropriate denial of the Rosemont 

permit, to ensure that duplicative installation air quality permits are not required of the facility, and 

pursuant to ARS 49-402 (b) and R9-3-1101 of the Arizona SIP, ADEQ is hereby asserting complete 

air quality jurisdiction, effective immediately, over the Rosemont Copper Project” (Arizona 

Department of Environmental Quality 2012a). Therefore, ADEQ is now the jurisdictional authority 

responsible for issuing and monitoring Rosemont Copper’s air permit.

Final Environmental Impact Statement for the Rosemont Copper Project 239
Chapter 3. Affected Environment and Environmental Consequences

Clean Air Act Attainment Status

Based on NAAQS, the CAA requires that States classify air basins (or portions thereof) as either 

attainment or nonattainment with respect to the criteria pollutants. A particular geographic region may 

be designated an attainment area for some pollutants and a nonattainment area for others. The project 

is within the Pima Intrastate Air Quality Control Region and is classified as “attainment” (better than 

national standards) or nonclassifiable/attainment for total suspended particulates, PM10, CO, SO2, 

NO2, and O3 (40 CFR 81.303). Regionally, the Tucson area contains a PM10 nonattainment area and a 

CO maintenance area; the remaining criteria pollutants are in attainment (see figure 38). 

The air quality in Tucson and surrounding areas is generally within compliance; criteria pollutant

levels are normally below the Federal and State health standards. However, the Tucson region does 

contain an area for which PM10 levels exceed the NAAQS (a “nonattainment area”); it also 

contains an area for which CO levels exceeded health standards in the past but for which, 

through management of area emissions, the levels have been reduced to meet existing standards 

(a “maintenance area”). Sources of pollution in the region include on-road, nonroad, area, and point 

sources. On-road sources include cars, trucks, buses, motorcycles, and any other motorized road 

vehicle. Nonroad sources include construction and mining equipment, lawn equipment, and any other 

motorized nonroad equipment. Area sources include residential fireplaces, woodstoves, or unpaved 

lots. Point sources include power plants, cement plants, mining operations, and any other emission

source with a single point of pollution release.

The major pollutants in the Tucson region are CO, particulate matter, and O3. Mobile sources are the 

largest emission source in the region and are the largest contributor to levels of CO and NOx, one of 

the precursors to the formation of O3. Area and point sources are the largest contributors to levels of 

particulate matter.

Recent Air Quality Monitoring Data and 

National Ambient Air Quality Standards Exceedances 

The Pima County Department of Environmental Quality and ADEQ maintain a network of air 

quality monitoring sites throughout Pima County. The locations of the Pima County Department of 

Environmental Quality monitoring sites are presented in figure 40. The assessment of existing criteria 

pollutants levels in the area is based on data collected and reported by the Pima County Department 

of Environmental Quality in 2008, 2009, and 2010 (Pima County Department of Environmental 

Quality 2009a, 2009b, 2011). Monitoring results are provided in table 34.

Carbon Monoxide 

CO is formed from the combustion of carbon based products. Of the criteria pollutants, CO is one of 

the most commonly occurring pollutants in Pima County. Motor vehicles are the primary source of 

CO in the Tucson area; total emissions of CO per vehicle-mile traveled exceed all other pollutants 

combined. In 2008, the Pima County Department of Environmental Quality established six CO

monitoring sites; none of these sites reported an exceedance of either the 1- or 8-hour standard during 

the monitoring period 2008 through 2010.

240 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 40. Pima County monitoring sites (Pima County Department of Environmental 

Quality 2009c)

Final Environmental Impact Statement for the Rosemont Copper Project 241
Table 34. Pima County monitoring data, 2008 through 2012, Maximum Recorded Concentration of Crite

(Monitoring Station Shown in Parentheses)

Year

CO

hour - Max Concentration 1

35 parts per million (ppm)CO

hour - Max Concentration 8

9 ppm

3 O

hour - Max Concentration 1

0.12 ppm

3 O

- 4th Highest Concentration 8

hour0.075 ppm

10 PM

hour - Max Concentration 24

micrograms per cubic 150 

meter (μg/m3

)

2.5 PM

hour - Max Concentration 24

35 μg/m3

2.5 PM

Arithmetic Annual Mean15 μg/m3

2 NO

hour - Max Concentration 1

0.100 ppm

2 NO

Arithmetic Annual Mean0.053 ppm

2 SO

hour - Max Concentration 3

0.5 ppmSO

2008 2.9 

(22nd/ 

Alvernon)

1.9 

(Cherry/ 

Glenn)

0.090 

(Saguaro 

National 

Park)

0.074 

(Saguaro 

National 

Park East)

146* 

(South 

Tucson)

28.2 

(Geronimo)

7.64 

(Coachline)

0.054 

(22nd/ 

Craycroft)

0.0134 

(22nd/ 

Craycroft)

0.014 

(22nd/ 

Craycroft)

(

Cr

2009 2.3 

(22nd/ 

Alvernon)

1.3 

(Cherry/ 

Glenn)

0.084 

(Tangerine)

0.068 

(Tangerine)

127* 

(South 

Tucson)

31 

(Geronimo)

8.2 

(Geronimo)

0.050 

(22nd/ 

Craycroft)

0.012 

(22nd/ 

Craycroft)

0.005 

(22nd/ 

Craycroft)

(

Cr

2010 2.8 

(Golf Links 

and Kolb)

1.4 

(Golf Links 

and Kolb)

0.082 

(Children’s 

Park)

0.069 

(Fairgroun

ds)

79 

(South 

Tucson)

29 

(Geronimo)

9.5 

(Geronimo)

0.0637 

(22nd/ 

Craycroft)

0.0116 

(22nd/ 

Craycroft)

0.007 

(22nd/ 

Craycroft)

(

Cr

2011 3.1

(22nd/ 

Alvernon)

1.8

(22nd/ 

Alvernon)

0.098

(Saguaro 

National 

Park)

0.075 

(Saguaro 

National 

Park)

119

(South 

Tucson)

33.7

(Coachline)

9.5

(Geronimo)

0.050

(22nd/ 

Craycroft)

0.0280

(22nd/ 

Craycroft)

0.005

(Children’s 

Park)

(Ch

2012 1.9

(22nd/ 

Craycroft)

1.3

(22nd/ 

Alvernon)

0.081

(Saguaro 

National 

Park)

0.071

(Saguaro 

National 

Park)

107

(Prince 

Road)

27.7

(Geronimo)

9.3

(Geronimo)

0.052

(22nd/ 

Craycroft)

0.0284

(Children’s 

Park)

0.004

(Children’s 

Park)

(Ch

Number of 

Stations

6 6 9 9 9 6 6 2 2 2 

Notes:

Max = Maximum; ppm = Parts per million parts of air, by volume; μg/m3 = Micrograms per cubic meter of air.

* The PM10 values for South Tucson in 2008 and 2009 represent the second and third highest concentrations, respectively, measured at those locatio

values are awaiting approval for an EPA designation as natural events because of high winds.

242 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Nitrogen Dioxide 

NO2 is a gas that forms primarily when fuel is burned at high temperatures; common sources include 

vehicle exhaust or industry/power plant emissions. NO2 is a precursor to O3 and can contribute to 

haze and visibility reduction. Ambient concentrations of NO2 are well below the standard in the 

Tucson metropolitan area. In 2008, the Pima County Department of Environmental Quality

established two sites for the measurement of ambient concentrations of NO2. There has been no 

exceedance or violation of the NAAQS for NO2 during the monitoring period 2008 through 2010.

Ozone

Stratospheric O3 occurs naturally, but O3 can also be formed at ground level from the reaction of 

VOCs and NOx in the presence of heat and sunlight. In 2008, the Pima County Department of 

Environmental Quality operated nine O3 monitoring sites. Maximum concentrations of O3 were

moderate to high, but no site had an exceedance of the 8-hour standard. The average 8-hour level 

across all O3 monitoring stations was 0.068 parts per million, or 91 percent of the NAAQS. 

The Saguaro National Park East monitoring site recorded the highest O3 levels, with the 8-hour level 

reaching 0.074 part per million, or 99 percent of the allowable level under the NAAQS.

Particulate Matter

Particulate matter occurs from a wide range of activities, such as construction, agriculture, industrial 

processes, vehicular travel, and fugitive dust. Particulate matter pollution is made up of a number of 

components, including acids (such as nitrates and sulfates), organic chemicals, metals, and soil or 

dust particles. Particulate matter can cause adverse health and environmental effects, including 

visibility reduction, environmental damage, and aesthetic damage.

The EPA is concerned about particles that are 10 micrometers or 2.5 micrometers (PM10 and PM2.5) in 

diameter or smaller because those are the particles that generally pass through the throat and nose and 

enter the lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health 

effects. Numerous scientific studies have linked particulate matter pollution exposure to a variety of 

problems, including the following: 

• Increased respiratory symptoms, such as irritation of the airways, coughing, or difficulty 

breathing; 

• Decreased lung function;

• Aggravated asthma;

• Development of chronic bronchitis;

• Irregular heartbeat;

• Nonfatal heart attacks; and

• Premature death in people with heart or lung disease.

People with heart or lung diseases, children, and older adults are the most likely to be affected by 

particulate matter pollution exposure. However, even if a person is healthy, that person may 

experience temporary symptoms from exposure to elevated levels of particulate matter pollution.

Fine particles (PM2.5) are the major cause of reduced visibility (haze) in parts of the United States, 

including many national parks and wilderness areas. 

Particles can be transported over long distances by wind and then deposited on the ground or in water. 

The effects of this deposition include the following: making lakes and streams acidic, changing the 

Final Environmental Impact Statement for the Rosemont Copper Project 243
Chapter 3. Affected Environment and Environmental Consequences

nutrient balance in coastal waters and large river basins, depleting the nutrients in soil, damaging 

sensitive forests and farm crops, and affecting the diversity of ecosystems. Particulate matter

pollution can also stain and damage stone and other materials, including culturally important objects 

such as statues and monuments.

Nine monitoring sites for PM10 were established by the Pima County Department of Environmental 

Quality in 2008. Across all monitoring sites, there were three exceedances of NAAQS. At Santa Clara 

Station on October 27, 2008, the station recorded a value of 173 micrograms per cubic meter (μg/m3

). 

On July 22, 2009, the South Tucson and Orange Grove Stations recorded high values of 270 and 184 

μg/m3

. The exceedances are awaiting approval from the EPA for designation as natural events

because of high winds. Therefore, the second highest recorded value of 2008 and the third highest 

recorded value of 2009 are presented in table 34 for PM10. 

The Pima County Department of Environmental Quality established six monitoring sites for PM2.5 in 

eastern Pima County in 2008. There was no exceedance or violation of the NAAQS for PM2.5 in 2008 

and none since monitoring began in 1999. 

Sulfur Dioxide 

SO2 exists as a gas associated with the burning of high-sulfur coal, oil, or diesel fuel. It can combine 

with water and oxygen to form sulfuric acid (acid rain), a highly corrosive chemical. Ambient 

concentrations of SO2 are extremely low in the Tucson metropolitan area because of the lack of major 

sources. One Pima County Department of Environmental Quality site monitored ambient 

concentrations of SO2 since 2008; there was no exceedance or violation of the NAAQS during the 

monitoring period 2008 through 2012.

Lead 

Monitoring for lead, a toxic metal, by the Pima County Department of Environmental Quality began 

in 1975 and was discontinued in 1997; lead concentrations were extremely low, and Pima County has 

no major sources of lead. On October 15, 2008, the EPA strengthened the national lead standard. As a 

result of the revised standard, Pima County is required to begin area monitoring at the Children’s 

Park location. Since monitoring began in January 2012, the 24-hour maximum concentration of lead 

was 0.005 μg/m3 in 2012, well below the NAAQS standard of 0.15 μg/m3 as a 3-month rolling 

average.

Air Toxics

Hazardous air pollutants, also known as air toxics, are those pollutants that have been shown to cause 

or possibly cause cancer in humans or may cause adverse environmental and ecological effects.

In 2001, the EPA developed a national network for monitoring ambient levels of air toxics. There is 

one National-Scale Air Toxics Assessment monitoring site operated by the ADEQ in Phoenix; no 

monitoring sites are located in or near the project area. Based on the latest 2002 assessment, resident 

cancer, neurological, and respiratory risks from hazardous air pollutants in the project area are 

estimated to be low (average total risk is 21 in 1 million). Approximately 89 percent of hazardous air 

pollutants in Pima County originate from background sources; mobile sources account for the 

majority of remaining hazardous air pollutant emissions. Primary hazardous air pollutants for the 

county include benzene, carbon tetrachloride, acetaldehyde, and 1,4-dichlorobenzene. 

244 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Proximity to Class I and II Areas 

In addition to the NAAQS, national air quality standards exist for the prevention of significant 

deterioration. The prevention of significant deterioration requirements provide maximum allowable 

increases in pollutant concentrations for areas that are already in compliance with the NAAQS 

(i.e., attainment or management areas). Under the prevention of significant deterioration, a Class I 

area is one in which only a small amount of new pollution is allowed. These areas include national 

parks, wilderness areas, monuments, and other areas of special national and cultural significance that 

have been designated as Class I airsheds by congressional action. The closest Class I area to the 

project area is Saguaro National Park East and West, at approximately 27 and 41 miles, respectively, 

from the project area. The Galiuro Wilderness is approximately 59 miles from the project area. 

Chiricahua National Monument and the Chiricahua Wilderness are about 87 to 90 miles away from 

the project area. The Superstition Wilderness is about 122 miles away from the project area. As part 

of the NEPA process, Class I areas within the air quality study area of a proposed project must be 

evaluated with regard to the potential impact and impairment concerns of the project on air quality 

related values such as visibility, flora/fauna, water quality, soils, odor, and any other resources 

specified by the Federal land manager to ensure compliance with FSM 2580.1 (2d); FSM 2580.2; and 

42 U.S.C. 7475(d)(2)(B) and (C) (U.S. Forest Service et al. 2010).

The project area is located within a Class II airshed and, as such, is required to be in compliance with 

Class II allowable increases in pollutant concentrations. Other portions of the Nogales Ranger 

District, including the Mount Wrightson Wilderness, are also within a Class II airshed. Class II areas 

include all other clean air regions other than Class I areas and allow moderate pollution increases. 

Allowable prevention of significant deterioration increments (“increments”) currently exist for four 

criteria pollutants: SO2, NO2, PM2.5, and PM10. 

Fugitive emissions are not included in the determination of potential to emit unless a source is listed 

in 1 of 28 source categories enumerated under 40 CFR 52.21 (b)(1)(iii). ADEQ issued a minor source 

air construction permit on January 31, 2013, because the majority of emissions from the Rosemont

Copper Mine operation would classified as fugitive. Under AAC, Title 18, Chapter 2, Section 319, 

review of increments is not explicitly required for minor source air construction permits.

Under 40 CFR 52.21 (b)(20)(vii), fugitive emissions are treated in the same manner as other 

nonfugitive emissions and would be included in a full increment analysis. Therefore, for purposes of 

NEPA, the Class I and Class II increment levels are for all emissions from the Rosemont Copper 

Mine Project are included in the FEIS to disclose potential impacts, but this should not be construed 

as an increment analysis, as would be required for major source permits under AAC 18.2. 

Implementation of increment analysis is the responsibility of the permitting agency, in this case 

ADEQ.

Visibility

Visibility is the degree to which the atmosphere is transparent to visible light. It is an important 

air quality related value, particularly in scenic and recreational areas. Scenic vistas in most U.S. 

parklands can be diminished by haze that reduces contrast, dilutes colors, and reduces the distinctness 

or visibility of distant landscape features. Visibility degradation in national park lands and forests is a 

consequence of broader, regional-scale visibility impairment from visibility-reducing particles and 

their precursors, which are often carried long distances to these remote locations.

Final Environmental Impact Statement for the Rosemont Copper Project 245
Chapter 3. Affected Environment and Environmental Consequences

Sulfates, nitrates, organic matter, elemental carbon (soot), nitrogen compounds, soil dust, and their 

interaction with water cause most anthropogenic visibility impairment. The causes and severity of 

visibility impairment vary over time and space, depending on meteorological conditions, sunlight, 

and the size and proximity of emission sources.

Visibility protection requirements are included in prevention of significant deterioration regulations 

requiring protection of air quality related values for Class I areas. The CAA, Title I, Part C, states,

“Congress declares as a national goal the prevention of any future, and the remedying of any existing, 

impairment of visibility in mandatory Class I federal areas which impairment results from manmade 

air pollution.” More specifically, Congress expressed the national desire to preserve the ability to see 

long distances, entire panoramas, and specific features associated with the statutory Class I areas.

In July 1999, the EPA published the Regional Haze Rule to address visibility impairment in Class I 

areas. The goal of the Regional Haze Rule is to restore the visibility in these Class I areas to natural 

conditions. The 1999 Regional Haze Rule requires States to submit implementation plans that 

establish long-term goals for restoring visibility to natural conditions. Plans submitted by States must 

ensure no visibility degradation to Class 1 areas on the top 20 percent least impaired (cleanest) days 

and visibility improvement in Class 1 areas on the top 20 percent most impaired (haziest) days.

The EPA Regional Haze Rule specifies that modeling must be conducted to demonstrate reasonable 

progress toward the goal of achieving natural visibility in each Class I area.

Visibility conditions are commonly quantified in deciviews, a measure of visibility based on light

extinction because of haze. The lower the deciview level, the better the visibility. Figure 41 shows

recent visibility levels for the total average annual deciviews, average deciviews on the top 20 percent 

clearest days, and average deciviews on the bottom 20 percent worst visibility days at Saguaro 

National Park East (Interagency Monitoring of Protected Visual Environments 2012). Monitored data

for the whole of Saguaro National Park (East and West) from 1997 to 2001 indicated an average of 

13.7 deciviews on the 20 percent worst days (“Preliminary 2018 Reasonable Progress Visibility 

Target Values for 309(g) and 308 of the Federal Regional Haze Rule” (Morris and Moore 2003)).

Deposition

Another air quality related value of concern is the atmospheric deposition of pollutants. Atmospheric 

deposition of pollutants, particularly sulfur and nitrogen, is a concern due to the potential for 

acidification of lakes and streams, as well as the potential to affect the ecosystem by changes in 

nutrient cycling, encouragement of invasive species, and reduction in biodiversity. Deposition can 

occur both in both dry and wet phases. Deposition of sulfur or nitrogen is most commonly measured 

in kilograms per hectare per year. Existing deposition values have been modeled for the entirety of 

the United States (SWCA Environmental Consultants 2013a), including the three nearest Class I 

areas: Saguaro National Park West, Saguaro National Park East, and the Galiuro Wilderness.

Saguaro National Park East

Current total nitrogen deposition within the boundaries of Saguaro National Park East is estimated as 

ranging from 4.1 to 4.7 kilograms per hectare per year. Current total sulfur deposition within the 

boundaries of Saguaro National Park East is estimated as ranging from 1.4 to 1.8 kilograms per 

hectare per year.

246 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 41. Visibility at Saguaro National Park East

Saguaro National Park West

Current total nitrogen deposition within the boundaries of Saguaro National Park West is estimated 

as ranging from 3.4 to 4.4 kilograms per hectare per year. Current total sulfur deposition within the 

boundaries of Saguaro National Park West is estimated as ranging from 0.5 to 0.7 kilogram per 

hectare per year.

Galiuro Wilderness

Current total nitrogen deposition within the boundaries of the Galiuro Wilderness is estimated as 

ranging from 3.7 to 4.8 kilograms per hectare per year. Current total sulfur deposition within the 

boundaries of the Galiuro Wilderness is estimated as ranging from 1.4 to 1.8 kilograms per hectare 

per year.

Pima County Emission Inventory

Data from the EPA’s 2008 National Emissions Inventory (U.S. Environmental Protection Agency 

2012a) can be used to illustrate air pollutant emission levels from various point, area and fugitive 

source categories for the Tucson region. These data are divided into various source categories:

• Point sources: stationary sources that emit a significant amount of pollution into the air, such 

as power plants, industrial processes, fossil fuel combustion equipment, and large 

manufacturing facilities.

0

2

4

6

8

10

12

14

16

18

20

2002 2003 2004 2005 2006 2007 2008 2009 2010

Deciviews

Mean

Best 20%

Worst 20%

Final Environmental Impact Statement for the Rosemont Copper Project 247
Chapter 3. Affected Environment and Environmental Consequences

• Area sources: sources that consist of smaller residential and commercial combustion outputs, 

manufacturing processes not vented to stacks, dust from earthmoving, landscaping, fires, and 

windblown dust.

• Nonroad equipment: sources that consist of exhaust emissions from construction, mining and 

agricultural equipment, and vehicles that do not travel on highways.

• On-road vehicles and road dust: sources that consist of exhaust emissions and fugitive dust 

associated with vehicles traveling on roads (paved and unpaved). 

• Miscellaneous sources: biogenic emissions from plants, including crops, indigenous 

vegetation, and landscaping, agricultural activities, and vehicle refueling activities.

Table 35 summarizes the various emissions sources in Pima County. On-road vehicle emissions 

contribute the largest portion of gaseous pollutants to total county air pollutant emissions. Area 

sources contribute the largest portion of particulate pollutants to total county particulate emissions.

Table 35. Pima County 2008 emissions inventory (tons per year)

Emissions Source Type NOx CO SO2 PM10 PM2.5 VOCs CO2

On-road vehicles 22,883 132,700 375 1,225 917 11,766 5,858,045

Nonroad equipment 6,047 49,214 127 492 441 4,257 502,422

Industrial processes 2,087 3,490 6 13,002 1,822 123 –

Electricity generation 2,127 152 2,884 163 144 22 –

Fossil fuel combustion 1,506 719 1,360 522 171 51 –

Fires 176 8,194 69 833 718 1,437 93,965

Residential wood combustion 126 7,416 21 1,073 1,072 1,323 –

Waste disposal 12 35 8 11 8 200 –

Miscellaneous 4 153 0 11,962 2,587 4,767 –

Road dust NA NA NA 10,739 1,557 NA NA

Solvent use NA NA NA NA NA 9,573 NA

Total 34,967 202,074 4,850 40,021 9,437 33,519 17,426,666*

Source: EPA (2012a). 

Notes:

– = No data available.

NA = Not applicable.

* EPA’s National Emissions Inventory does not include CO2 emissions for all emission source types. Data are from 

Regional Greenhouse Gas Inventory, Pima Association of Governments, November 2008, encompassing the eastern Pima 

County area, which consists of a rectangular area, with the north line stopping at the Pima County line, the south line 

stopping at the southern edge of Sahuarita, the east line stopping at Vail, and the west line stopping at Three Points.

Environmental Consequences

Direct and Indirect Effects of Each Alternative

No Action Alternative

Under the no action alternative, impacts to air quality from mining and associated activities would not 

occur. Existing and ongoing impacts to air quality from fugitive dust and vehicle emissions are 

expected to increase over time with continued population growth in southern Arizona. However, it is 

expected that monitoring and remedial actions by Pima County and ADEQ would be effective in 

keeping these gradual changes within NAAQS.

248 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Impacts Common to All Action Alternatives

The five action alternatives (proposed action, Phased Tailings, Barrel, Barrel Trail, and ScholefieldMcCleary) would involve constructing, operating, reclaiming, and closing an open-pit mine for the 

recovery of copper ore. Reclamation would be phased during the mine life, with concurrent 

reclamation occurring on the outer slopes of the perimeter buttress and waste rock facility as those 

surfaces are completed. The projected active mine life would be approximately between 24.5 to 30

years, including premining, active mining, and closure and final reclamation. 

Construction, mining, and reclamation activities at the mine and along transportation and utility 

corridors may increase fugitive dust, airborne chemicals, and vehicular emissions in the project area 

and lead to a change in air quality in Class I and Class II airsheds. During construction of the project, 

temporary and localized increases in atmospheric concentrations of NO2, CO, SO2, VOCs, PM2.5, and 

PM10 would result from exhaust emissions of workers’ vehicles, heavy construction vehicles, diesel 

generators, and other machinery and equipment. Increased emissions of fugitive dust would also 

result from clearing, excavation, and grading activities associated with mine, transportation, and 

utility corridor construction.

Mine operations would result in emissions of criteria and hazardous air pollutants. Mobile sources 

(worker and plant/facility vehicles) would provide an ongoing source of emissions for the life of the 

project. The project may also lead to decreased visibility and increased haze in the region, caused by 

increased particulate matter and other criteria pollutant emissions. Mine operations would also result 

in emissions of CO2, a greenhouse gas linked to global warming and climate change.

Premining Phase

Activities included in the premining phase are the construction of access roads, installation of power 

lines, site preparation for the fixed facilities, delivery of materials and equipment to the mine, and 

other construction vehicle activity. Sources of air pollutant emissions during these activities include 

both particulate matter emissions and fuel-combustion emissions. As described in chapter 2, 

construction and preproduction activities at the mine pit would occur for 18 to 24 months prior to the 

startup of the mine and ore processing operations. The following sources of emissions are calculated 

and analyzed for the premining phase.

• Criteria air pollutant and greenhouse gas tailpipe emissions from construction worker 

vehicles and equipment/shipment delivery associated with the development of the mine site; 

• Fugitive dust emissions (PM10 and PM2.5) from construction and worker commuting vehicles 

traveling on paved roads; and 

• Fugitive dust emissions (PM10 and PM2.5) from earthmoving activities. 

Active Mining Phase

The action alternatives share the following components:

• Heavy equipment mining operations, including drilling, blasting, loading, and hauling of ore

and rock; 

• Major processing operations, including crushing, grinding, flotation, leaching, and solvent 

extraction;

• Tailings and waste rock placement and storage;

Final Environmental Impact Statement for the Rosemont Copper Project 249
Chapter 3. Affected Environment and Environmental Consequences

• Secondary processing operations, including the use of fuel burning equipment, reagent 

systems, storage tanks, an analytical laboratory, crud treatment and recovery, and onsite 

mobile vehicles;

• Shipment to market for copper cathodes and copper, molybdenum, and silver concentrates, as 

well as delivery of equipment and materials; and

• Vehicle travel by employees to and from the project site.

The above components would result in the direct emissions of all criteria pollutants, as well as VOCs, 

sulfuric acid, greenhouse gases, and several regulated hazardous air pollutants from the exhaust 

emissions of vehicles, heavy equipment, and other fuel burning equipment. In addition, fugitive 

dust emissions would result from vehicular traffic on unpaved surfaces, processing equipment 

(e.g., pebble crusher area scrubber, copper concentrate scrubber 1 and 2, molybdenum concentrate 

dryer, various pieces of laboratory equipment), and the dry-stack tailings facility. However, ore haul 

truck travel represents more than 70 percent of total particulate related emissions. NOx and VOC 

emissions from the exhaust emissions of vehicles, heavy equipment, and other fuel-burning 

equipment would lead to the formation of ground-level O3. The following sources of emissions are 

calculated and analyzed for the active mining phase:

• Criteria air pollutant and greenhouse gas tailpipe emissions from worker vehicles and 

equipment/shipment delivery associated with the operation and reclamation of the mine; 

• Fugitive dust emissions (PM10 and PM2.5) from equipment and worker commuting vehicles

traveling on paved roads; and

• Point and fugitive emissions associated with the mining equipment, material handling 

sources, storage piles, and fuel storage tanks. 

Mine Closure and Reclamation

Mine reclamation activities would be concurrent with the mine operations, using a phased approach, 

would begin as early as year 1 of active mining, and would continue through the active mining phase 

as well as during the closure and final reclamation phase of the mine. Reclamation activities would

include removal of unneeded buildings, roads, and other facilities; removal of the water supply

pipeline and electrical supply line and associated facilities; revegetation of disturbed areas (e.g., mill 

site, plant, access roads requiring closure), regrading and revegetation of the waste rock and tailings 

facilities, and removal of the perimeter and security fences. Phasing of reclamation activities is 

described in the “Soils and Revegetation” resource section. Of a total of approximately 3,600 acres to 

be reclaimed in the project area, about 1,500 acres will have already been concurrently reclaimed by 

the end of the active mining phase. Final reclamation activities could temporarily disturb roughly 

2,100 acres. An additional 900 acres associated with the utility corridor and 226 acres associated with 

the primary access road could also potentially be disturbed for final reclamation activities. Compared 

with the approximately 5,400 acres being disturbed during the premining phase, emissions for final 

reclamation and closure activities would be substantially less than during premining and active 

mining; for this reason the reclamation and closure phase has not been explicitly modeled for air 

quality impacts.

Proposed Action and Action Alternatives

This section analyzes impacts to air quality from the proposed action and action alternatives. 

It presents the emissions associated with each alternative for both the premining and active mining 

phases and assesses the ability of the alternatives to comply with NAAQS at the perimeter fenceline 

250 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

and at Class I areas, and impacts to the air quality related values of visibility and deposition. This 

section includes the results of four different analyses:

• Emission inventories for each alternative:

◦ Premining emissions, which consists of three components: fugitive dust from all surface 

disturbances both inside and outside the perimeter fence, tailpipe emissions outside the 

perimeter fence, and fugitive emissions from driving on paved roads outside the 

perimeter fence. These are compared with total emissions from Pima County.

◦ Active mining emissions, which consists of three components: tailpipe emissions outside 

the perimeter fence, fugitive emissions from driving on paved roads outside the perimeter 

fence, and point and fugitive emissions within the perimeter fence from mining and 

processing. These are compared with total emissions from Pima County.

• Compliance with NAAQS for each alternative:

◦ Compliance as measured at the perimeter fence; this includes modeled emissions from 

within the perimeter fence combined with appropriate background concentrations.

◦ Compliance as measured at six Class I airsheds; this includes modeled emissions from 

within the perimeter fence, combined with appropriate background concentrations.

• Impacts to air quality related values, for each alternative:

◦ Visibility as measured at six Class I areas. As discussed in the methodology section, note 

that because it is located within the near field analysis area, Saguaro National Park East 

uses a different modeling technique for visibility (VISCREEN), compared with the 

modeling technique (CALPUFF) used for the other five Class I areas, which are located 

within the far-field analysis area. 

◦ Deposition as modeled at six Class I areas. As discussed in the methodology section, note 

that because it is located within the near-field analysis area, Saguaro National Park East 

uses a different modeling technique for deposition (AERMOD), compared with the 

modeling technique (CALPUFF) used for the other five Class I areas, which are located 

within the far-field analysis area.

• Projected effects on climate change, for each alternative.

Emission Inventories

Emission inventories have been prepared for the premining phase and the active mining phase. 

The types of emissions analyzed include fugitive dust emissions (i.e., PM10 and PM2.5) from surface 

disturbance during premining activities, emissions of criteria air pollutants and greenhouse gas 

emissions from worker vehicles and equipment deliveries during premining and active mining, 

fugitive dust emissions (i.e., PM10 and PM2.5) from travel on paved surfaces during premining and 

active mining, and emissions from point and fugitive sources associated with active mining.

Surface Disturbance Emissions – Premining Phase

During construction of the mine infrastructure, fugitive dust emissions associated with surface 

disturbances (e.g., excavating, grading, construction, and other earthmoving activities) would be 

generated. Fugitive dust emissions were quantified for each alternative operating scenario using an 

estimate of the number of acres disturbed during the first year of the premining phase and reasonable 

assumptions. The estimate of disturbed acreage was taken from the most recent reclamation and 

closure plan, which was prepared specifically for the Barrel Alternative, and has been assumed to be 

approximately equivalent between alternatives for the initial construction activities. The resulting 

Final Environmental Impact Statement for the Rosemont Copper Project 251
Chapter 3. Affected Environment and Environmental Consequences

potential emission estimates for fugitive dust resulting from surface disturbance during the first year 

of construction are summarized in table 36.

Table 36. Premining fugitive dust emissions associated with surface disturbances in 

tons per year Alternative

Estimated Area Disturbed During Construction Period (acres)*Average Monthly Disturbance During Construction Period (acres/month)PM10 EmissionFactor (tons/acre-month)†PM10 Emissions,Total (tons/month)PM10 Emissions,Total (tons/year)PM2.5 Emissions,Total (tons/year)

‡

Proposed action 

(preliminary MPO) 2,697 123 0.19 23.4 280.4 58.9

Phased Tailings 2,697 123 0.19 23.4 280.4 58.9

Barrel 2,697 123 0.19 23.4 280.4 58.9

Barrel Trail 2,697 123 0.19 23.4 280.4 58.9

Scholefield-McCleary 2,697 123 0.19 23.4 280.4 58.9

* The area disturbed during construction has been estimated based on the most recent reclamation and closure plan. Monthly 

disturbance is calculated by averaging over the 22-month construction period (CDM Smith 2012a:table 13-1).

† The California Air Resources Board document states that the emission factor is for site preparation work, which may 

include scraping, grading, loading, digging, compacting, light-duty vehicle travel, and other operations (California 

Environmental Protection Agency Air Resources Board 2003). The construction emission factor is assumed to include the 

effects of typical control measures such as routine watering. A dust control effectiveness of 50% is assumed from these 

measures, which is based on the estimated control effectiveness of watering; based on the dust control plan included in the 

air quality permit issued by ADEQ, Rosemont Copper would likely meet a 90% dust control efficiency.

‡ Based on South Coast Air Quality Management District derived default values for mechanical dust generating sources 

(e.g., construction), the PM2.5 fraction of PM10 is 21%. 

Vehicle/Equipment Tailpipe Emissions –

Premining and Active Mining Phases 

During premining and active mining operations, on-highway vehicles would generate gaseous 

exhaust emissions. Tables 37, 38, and 39 summarize both the emission estimates for criteria and 

greenhouse gas pollutants for both the premining and active mining phases of the mine. There is no 

discernible difference between alternatives for premining tailpipe emissions (see table 37). However, 

due to the removal of oxide ore processing, tailpipe emissions differ between the Barrel Alternative 

(see table 39) and the other action alternatives (see table 38). 

Table 37. Premining tailpipe emissions for worker and equipment shipment trips in 

tons per year – all alternatives

Activity Quantity (trips 

per day or year) NOX SO2 CO PM / PM10 / PM2.5* VOCs CO2

†

Weekday

Bus trips 37 0.2 <0.01 0.2 0.02 0.1 422

Equipment / 

Shipment trips 50 8.5 0.02 2.1 0.24 0.5 1,754

Subtotal – 8.7 0.02 2.4 0.27 0.6 2,176

252 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Activity Quantity (trips 

per day or year) NOX SO2 CO PM / PM10 / PM2.5* VOCs CO2

†

Weekend

Bus trips 28 0.1 <0.01 0.1 0.01 <0.01 128

Equipment / 

Shipment trips 25 1.7 <0.01 0.4 0.05 0.1 351

Subtotal NA 1.8 <0.01 0.5 0.06 0.1 478

Annual

Heavy load 

truck trips 1,000 0.7 <0.01 0.2 0.02 <0.01 135

Total NA 11.1 0.02 3.0 0.34 0.8 2,789

Notes: Bus trips were estimated using a round-trip mileage of 26 miles. Equipment/shipment and heavy load truck trips were 

estimated using a round-trip mileage of 80 miles. This mileage is an approximation, as both the bus trips and 

equipment/shipment and heavy load truck trips could come either from the north or south of the mine site.

Emission factors for on-road gasoline and diesel vehicles were obtained from EPA (2003).

NA = Not applicable.

* For on-road equipment, particulate matter emission factor was used to calculate PM10 and PM2.5 emissions.

† Emission factors in lb/mile for on-road gasoline combustion were based on a CO2 emission factor of 19.4 lb/gallon and 

assuming an average fuel economy of 25.5 mpg. Emission factors in lb/mile for on-road diesel combustion were based on a 

CO2 emission factor of 22.2 lb/gallon and assuming an average fuel economy of 6.6 mpg.

Table 38. Active mining tailpipe emissions from worker and equipment shipment 

trips in tons per year – proposed action, Phased Tailings, Barrel Trail, and 

Scholefield-McCleary Alternatives

Activity

Quantity 

(trips per 

day)

NOX SO2 CO PM / PM10 / 

PM2.5* VOCs CO2

†

Weekday

Worker-trips 284 3.6 0.04 62.2 0.16 4.7 2,253

Equipment / 

Shipment trips 88 1.5 0.01 1.6 0.17 0.9 3,087

Subtotal NA 5.1 0.06 63.8 0.33 5.6 5,340

Weekend

Worker-trips 244 1.2 0.02 21.4 0.06 1.6 774

Equipment / 

Shipment trips 74 0.5 <0.01 0.5 0.06 0.3 1,038

Subtotal NA 1.8 0.02 21.9 0.11 1.9 1,813

Total NA 6.9 0.07 85.7 0.44 7.5 7,153

Notes: Equipment/shipment trips and worker trips were estimated using a round-trip mileage of 80 miles. This mileage is an 

approximation, as both the worker trips and equipment/shipment trips could come either from the north or south of the mine site.

Emission factors for on-road gasoline and diesel vehicles were obtained from EPA (2003).

NA = Not applicable.

* For on-road equipment, particulate matter emission factor was used to calculate PM10 and PM2.5 emissions.

† Emission factors in lb/mile for on-road gasoline combustion were based on a CO2 emission factor of 19.4 lb/gallon and 

assuming an average fuel economy of 25.5 mpg. Emission factors in lb/mile for on-road diesel combustion were based on a 

CO2 emission factor of 22.2 lb/gallon and assuming an average fuel economy of 6.6 mpg.

Final Environmental Impact Statement for the Rosemont Copper Project 253
Chapter 3. Affected Environment and Environmental Consequences

Table 39. Active mining tailpipe emissions from worker and equipment shipment trips 

in tons per year – Barrel Alternative

Activity

Quantity 

(trips per 

day)

NOX SO2 CO PM / PM10 / 

PM2.5* VOCs CO2

†

Weekday

Worker-trips 311 3.9 0.05 68.1 0.18 5.1 2,467

Equipment / 

Shipment trips 69 1.2 0.01 1.2 0.13 0.7 2,420

Subtotal NA 5.2 0.06 69.4 0.31 5.8 4,888

Weekend

Worker-trips 266 1.3 0.02 23.3 0.06 1.7 844

Equipment / 

Shipment trips 55 0.4 <0.01 0.4 0.04 0.2 772

Subtotal NA 1.7 0.02 23.7 0.10 2.0 1,616

Total NA 6.9 0.08 93.1 0.41 7.8 6,504

Notes: Equipment/shipment trips and worker trips were estimated using a round-trip mileage of 80 miles. This mileage is an 

approximation, as both the worker trips and equipment/shipment trips could come either from the north or south of the mine

site.

Emission factors for on-road gasoline and diesel vehicles were obtained from EPA (2003).

NA = Not applicable.

* For on-road equipment, particulate matter emission factor was used to calculate PM10 and PM2.5 emissions.

† Emission factors in lb/mile for on-road gasoline combustion were based on a CO2 emission factor of 19.4 lb/gallon and 

assuming an average fuel economy of 25.5 mpg. Emission factors in lb/mile for on-road diesel combustion were based on a 

CO2 emission factor of 22.2 lb/gallon and assuming an average fuel economy of 6.6 mpg.

Vehicle/Equipment Travel over Paved Surfaces –

Premining and Active Mining

During the premining and active mining, fugitive dust emissions would be generated from vehicles 

and equipment traveling over the paved surfaces to and from the mine. Tables 40 and 41 summarize 

these fugitive dust emissions during the premining and active mining phases of the mine. There is no 

discernible difference between alternatives for premining paved surface emissions (see table 40). 

However, due to the removal of oxide ore processing, the number of trips differs between the Barrel 

Alternative and the other action alternatives, both of which are described in table 41. 

Table 40. Premining fugitive dust emissions from paved surfaces in tons per year –

all alternatives

Activity Quantity 

(trips per day or year) PM10 PM2.5

Weekday

Bus trips 37 0.7 0.2

Equipment / Shipment trips 50 5.5 1.4

Subtotal NA 6.2 1.5

Weekend

Bus trips 28 0.2 <0.01

Equipment / Shipment trips 25 1.1 0.3

Subtotal NA 1.3 0.3

254 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Activity Quantity 

(trips per day or year) PM10 PM2.5

Annual

Heavy load truck trips 1,000 0.4 0.1

Total NA 7.9 1.9

Notes: Bus trips were estimated using a round-trip mileage of 26 miles. Equipment/shipment and heavy load truck trips 

were estimated using a round-trip mileage of 80 miles. This mileage is an approximation, as both the bus trips and 

equipment/shipment and heavy load truck trips could come either from the north or south of the mine site.

Emission factor was calculated using equations 1 and 2 in chapter 13.2.1 “Paved Roads,” from EPA (2011a). (Note: There 

may be situations in which low silt loading and/or low average weight would yield calculated negative emissions from 

equation 1. If this occurs, the emissions calculated from equation 1 should be set to zero.)

NA = Not applicable.

Table 41. Active mining fugitive dust emissions from paved surfaces in tons per year

Proposed Action,

Phased Tailings, 

Barrel Trail, and 

ScholefieldMcCleary 

Alternatives

Barrel 

Alternative 

Activity Quantity (trips 

per day) PM10 PM2.5

Quantity (trips 

per day) PM10 PM2.5

Weekday

Worker-trips 284 3.0 0.7 311 3.3 0.8

Equipment / 

Shipment trips 88 4.8 1.2 69 3.8 0.9

Subtotal NA 7.8 1.9 NA 7.0 1.7

Weekend

Worker-trips 244 1.0 0.3 266 1.1 0.3

Equipment / 

Shipment trips 74 1.6 0.4 55 1.2 0.3

Subtotal NA 2.6 0.6 NA 2.3 0.6

Total NA 10.4 2.6 NA 9.3 2.3

Notes: Equipment/shipment trips and worker trips were estimated using a round-trip mileage of 80 miles. This mileage is an 

approximation, as both the worker trips and equipment/shipment trips could come either from the north or south of the mine site.

Emission factor was calculated using equations 1 and 2 in chapter 13.2.1, “Paved Roads,” from EPA (2011a). (Note: There 

may be situations where low silt loading and/or low average weight would yield calculated negative emissions from 

equation 1. If this occurs, the emissions calculated from equation 1 should be set to zero.)

NA = Not applicable.

Point and Fugitive Emissions Associated with Active Mining

The point and fugitive emissions within the perimeter fence associated with active mining and 

processing of ore vary by alternative, due to the different distances needed to transport ore and 

tailings, the different locations and configurations for waste rock and tailings, and differences in 

processing associated with the removal of oxide ore processing from the Barrel Alternative. These 

emissions are summarized in table 42.

Final Environmental Impact Statement for the Rosemont Copper Project 255
Chapter 3. Affected Environment and Environmental Consequences

Table 42. Maximum annual point and fugitive source emissions within the perimeter 

fence under the action alternatives in tons per year

Alternative Pollutant 

PM10

Pollutant 

PM2.5

Pollutant 

SO2

Pollutant 

NOX

Pollutant 

CO

Pollutant 

Pb

Proposed action 943.2 138.9 20.6 1,194.8 1,476.8 0.39

Phased Tailings 943.2 138.9 20.6 1,194.8 1,476.8 0.39

Barrel 1,037.7 147.8 20.5 1,190.2 1,475.1 0.43

Barrel Trail 1,003.1 145.3 20.6 1,243.1 1,524.9 0.42

ScholefieldMcCleary 1,109.8 157.2 20.6 1,355.8 1,637.2 0.46

Source: JBR Environmental Consultants, Inc. (2013d).

Notes: 

Values shown represent either years 1, 5, or 12 (Barrel Alternative only), whichever represents the greatest emissions.

Note that the Barrel Alternative does not include solvent extraction/electrowinning operation, due to removal of heap leach 

facility and oxide ore processing.

Comparison of Premining and Active 

Mining Emissions to Countywide Emissions

Projected emissions from the project can be compared with countywide emissions for Pima County.

These comparisons are made in table 43 for premining emissions and table 44 for active mining 

emissions. The premining emissions shown in table 43 are the sum of the emissions already described 

for fugitive dust from surface disturbance (see table 36), tailpipe emissions for travel to and from the 

mine site by workers and for equipment shipments (see table 37), and fugitive dust emissions for 

travel on paved roads to and from the mine site (see table 40). The active mining emissions shown in 

table 44 are the sum of the emissions already described for tailpipe emissions for travel to and from 

the mine site by workers and for equipment shipments (see tables 38 and 39), fugitive dust emissions 

for travel on paved roads to and from the mine site (see table 41), and point and fugitive source 

emissions from active mining activities within the perimeter fence (see table 42).

Projected Compliance with the National Ambient Air Quality Standards 

Based on the emissions results, modeling work was conducted to examine the effects of projected 

emissions compliance with NAAQS at the perimeter fence and at Class I areas. Figure 42 shows the 

locations of the modeled values for evaluating impacts to Class I areas.

Ambient air impact analyses were performed to evaluate whether the action alternatives would 

comply with the NAAQS. An AERMOD modeling report titled “Rosemont Copper Project

AERMOD Modeling Report to Assess Ambient Air Quality Impacts” (JBR Environmental 

Consultants Inc. 2012e) evaluated the potential impacts to the NAAQS of the action alternatives at 

the project area boundary (i.e., the perimeter fence) and at the boundary of the nearest Class I area, 

the Saguaro National Park East. The potential impacts to the NAAQS of the action alternatives to five 

additional Class I areas (Saguaro National Park West, Galiuro Wilderness, Chiricahua National 

Monument, Chiricahua Wilderness, and Superstition Wilderness) were analyzed using a CALPUFF 

modeling report titled “Rosemont Copper Company Revised CALPUFF Modeling Report to Assess 

Impacts in Class I Areas” (JBR Environmental Consultants Inc. 2013c). CALPUFF is applicable to 

the far-field analysis area, unlike AERMOD, which is applicable to the near-field analysis area. 

The modeling results for the action alternatives are discussed below.

256 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 43. Comparison of Pima County emissions and premining emissions under the 

action alternatives (in tons per year)

NOx CO SO2 PM10 PM2.5 VOCs CO2

Pima County* 34,967 202,074 4,850 40,021 9,437 33,519 17,426,666†

Proposed action 11.1 3.0 0.02 291.14 61.84 0.8 2,789

Percent Additional <0.1% <0.1% <0.1% 0.7% 0.7% <0.1% <0.1%

Phased Tailings 11.1 3.0 0.02 291.14 61.84 0.8 2,789

Percent Additional <0.1% <0.1% <0.1% 0.7% 0.7% <0.1% <0.1%

Barrel 11.1 3.0 0.02 290.04 61.54 0.8 2,789

Percent Additional <0.1% <0.1% <0.1% 0.7% 0.7% <0.1% <0.1%

Barrel Trail 11.1 3.0 0.02 291.14 61.84 0.8 2,789

Percent Additional <0.1% <0.1% <0.1% 0.7% 0.7% <0.1% <0.1%

Scholefield-McCleary 11.1 3.0 0.02 291.14 61.84 0.8 2,789

Percent Additional <0.1% <0.1% <0.1% 0.7% 0.7% <0.1% <0.1%

Note: Values represent the sum of fugitive dust emissions from ground disturbance (see table 36), tailpipe emissions (see 

table 37), and fugitive dust emissions from paved surfaces (see table 40).

* EPA (2012a). 

† EPA’s National Emissions Inventory does not include CO2 emissions for all emission source types. Data are from 

Regional Greenhouse Gas Inventory, Pima Association of Governments, November 2008, encompassing the eastern Pima 

County area, which consists of a rectangular area, with the north line stopping at the Pima County line, the south line 

stopping at the southern edge of Sahuarita, the east line stopping at Vail, and the west line stopping at Three Points.

Table 44. Comparison of Pima County emissions and active mining emissions under 

the action alternatives (in tons per year)

NOx CO SO2 PM10 PM2.5 VOCs CO2

Pima County* 34,967 202,074 4,850 40,021 9,437 33,519 17,426,666†

Proposed action 1,202 1,563 21 954 142 86 182,393

Percent Additional 3.4% 0.8% 0.4% 2.4% 1.5% 0.3% 1.0%

Phased Tailings 1,202 1,563 21 954 142 86 182,393

Percent Additional 3.4% 0.8% 0.4% 2.4% 1.5% 0.3% 1.0%

Barrel 1,197 1,568 21 1,047 151 82 177,162

Percent Additional 3.4% 0.8% 0.4% 2.6% 1.6% 0.2% 1.0%

Barrel Trail 1,250 1,611 21 1,014 148 88 191,597

Percent Additional 3.6% 0.8% 0.4% 2.5% 1.6% 0.3% 1.1%

Scholefield-McCleary 1,363 1,723 21 1,121 160 94 213,073

Percent Additional 3.9% 0.9% 0.4% 2.8% 1.7% 0.3% 1.2%

Note: Values represent the sum of tailpipe emissions (see tables 38 and 39), fugitive dust from paved surfaces (see table 41), 

and point and fugitive source emissions associated with active mining within the perimeter fence (see table 42).

* EPA (2012a). 

† EPA’s National Emissions Inventory does not include CO2 emissions for all emission source types. Data are from 

Regional Greenhouse Gas Inventory, Pima Association of Governments, November 2008, encompassing the eastern Pima 

County area, which consists of a rectangular area, with the north line stopping at the Pima County line, the south line 

stopping at the southern edge of Sahuarita, the east line stopping at Vail, and the west line stopping at Three Points.

Final Environmental Impact Statement for the Rosemont Copper Project 257
Chapter 3. Affected Environment and Environmental Consequences

Figure 42. Locations of Class I areas

258 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

AERMOD Modeling of Compliance with NAAQS

at the Perimeter Fence for the Action Alternatives

The following criteria pollutants were modeled using AERMOD: PM10, PM2.5, NO2, CO, SO2, and 

Pb. Because the project area is located in a rural area without air quality monitoring stations nearby, 

background concentrations of NO2, CO, and SO2 (with the exception of 1-hour SO2) were assumed to 

be at levels recommended by the ADEQ for use in rural areas. Project area monitoring was conducted 

from April 2006 to May 2009 to obtain background PM10 concentrations, while PM2.5 background 

concentrations were obtained from the nearest air quality monitoring station in Tucson, Arizona. 

Because of the lack of availability of data, the background concentrations for 1-hour SO2 and for lead

were conservatively assumed to be equal to the modeled concentration. A more detailed discussion of 

the use of background concentrations is presented in the AERMOD report (JBR Environmental 

Consultants Inc. 2012e).

Based on numerous rounds of cooperator reviews, additional modeling was conducted in order to 

ensure that results were reasonable for prediction of air quality impacts. This included the use of two 

separate PM10 background concentrations to anticipate the maximum ambient concentration

(“ambient concentration” is the addition of modeled concentration and background concentration) 

from the action alternatives. Based on the JBR review of the PM10 concentration data collected 

from the onsite monitoring station and the large differences between the highest measured value 

(71.3 μg/m3

) and the second highest value (40.3 μg/m3), a statistical analysis was conducted on all 

data to determine their probability of occurrence. This analysis is provided within appendix C of the 

AERMOD report for the project (JBR Environmental Consultants Inc. 2012e). 

The statistical analysis indicates that the probability of occurrence of the concentration of 71.3 μg/m3

is 5.9 × 10−11. This low probability indicates that the concentration of 71.3 μg/m3

is an outlier to 

the distribution and should not be included while determining the background concentration. 

Additionally, Pima County comments to ADEQ during the Rosemont Copper permitting process 

indicate that a regional dust storm was the source of the outlier data point (Pima County Department 

of Environmental Quality 2012). As an event that would not be likely to recur, Rosemont Copper 

argued that the high data point likely represents an “exceptional event,” as defined under 40 CFR Part 

50, Subchapter 50.1(j-l), and 50.14, and, as such, should not be considered for the purpose of 

demonstration of compliance with the NAAQS. The EPA, in consultation with Rosemont Copper, 

suggested that the next highest value recorded, 40.3 μg/m3

, could be used as a replacement value for 

the outlier. Therefore, the 24-hour background PM10 concentration was based on the average of 40.3, 

40.3, and 31.6 μg/m3

, which equals 37.4 μg/m3. Using the PM10 outlier value of 71.3 μg/m3 to 

calculate the 24-hour background PM10 concentration results in a background value of 47.7 μg/m3

(JBR Environmental Consultants Inc. 2012e). Both values (37.4 and 47.7 μg/m3

) were modeled and 

are included in the data presented in this section for the purposes of comparison. 

Upon review, the Forest Service found that using the lower background value was not supported.

Therefore, while both background values (37.4 and 47.7 μg/m3

) were modeled, only the background 

value of 47.7 μg/m3 is used in predicting compliance with NAAQS at the perimeter fenceline.

Similar to PM10 concentrations, modeling for 1-hour NO2 was conducted under two scenarios in order 

to provide a comparison of modeling assumptions. In the first scenario, sources of NO2 emissions are 

analyzed using an NO2 to NOx ratio of 0.1, while under the second scenario an NO2 to NOx ratio of 

0.05 was used for emission sources (JBR Environmental Consultants Inc. 2012e). In-stack NO2/NOx

data are readily available for industrial point sources. However, there is minimal in-stack data 

available for mobile sources since mobile source emissions are typically measured after mixing with 

Final Environmental Impact Statement for the Rosemont Copper Project 259
Chapter 3. Affected Environment and Environmental Consequences

ambient air. Documentation from Rosemont Copper and Caterpillar, Inc., identifies a range of NO2

from 0.05 to 0.15 of the engine-out NOx emissions as being typical. However, oxidation catalysts and 

diesel particulate filters can increase the ratio of engine-out NO2 (Hockridge 2011). Furthermore, 

in-stack NO2/NOx ratio must be representative of exhaust gases before leaving the stack and before 

any mixing or oxidation by ambient air has occurred. Since the model’s in-stack parameter requires 

measurements that are representative of NOx emissions before they leave the stack, data derived from 

EPA test procedures are inappropriate for model input for mobile sources such as ore haul trucks. 

Therefore, an NO2 to NOx ratio of 0.05 was analyzed for mobile sources (the majority of the proposed 

sources) and internal combustion engines. However, for purposes of comparison, an NO2 to NOx ratio 

of 0.1 for mobile sources and internal combustion engines was also analyzed and results included. 

Because of the lack of data for the use of a lower NO2 to NOx ratio for blasting emissions, an NO2 to 

NOx ratio of 0.5 was used for blasting emission sources. 

Compliance with NAAQS is determined by adding the modeled concentration of criteria pollutants 

with the background concentration of criteria pollutants. The background concentrations, modeled 

concentrations, and projected maximum ambient concentrations (background concentration plus 

modeled concentration) of criteria pollutants for the proposed action and each of the alternative 

actions are presented in table 45.

The NAAQS for criteria pollutants also involve specific time intervals: 1-hour, 8-hour, 24-hour, 

3-month rolling average, or annual. Due to the revocation of the annual PM10 standard since the DEIS 

was issued, annual PM10 was no longer evaluated in the modeling.

The following discussion pertains to the modeled impacts at the perimeter fence for the proposed 

action and each of the alternatives. As noted, the Coronado has determined that several key 

assumptions selected by Rosemont Copper to model air quality impacts are appropriate and has based 

conclusions in the FEIS on these values. Specifically, an NO2 to NOx ratio of 0.05 was considered 

appropriate, and a background PM10 concentration of 47.7 μg/m3 was considered appropriate. 

Modeling using variations of these assumptions was also conducted for comparison, specifically an 

NO2 to NOx ratio of 0.1 and a background PM10 concentration of 37.4 μg/m3

. These alternative 

modeling results are provided for comparison (shown by the shaded cells in table 45) but are not 

considered the most appropriate assumptions and therefore are not used to draw conclusions about 

compliance with NAAQS for this analysis. As shown in table 45, these alternative assumptions result 

in the inability to meet NAAQS at the perimeter fence for any of the alternatives. 

In addition, the modeled impacts were compared with Class II increment levels. Increment levels for 

Class II areas are threshold levels intended to prevent the air quality in clean areas from deteriorating 

to the level set by the NAAQS. The modeled concentrations shown in table 45 include both stationary 

and mobile emission sources. As noted previously, Class II increment levels are provided for 

disclosure only. Determination of whether Rosemont Copper’s emissions represent a violation of 

applicable air quality laws and regulations is solely under the regulatory authority of ADEQ as the 

agency issuing the permit. At this time, ADEQ has not required an increment analysis on the 

Rosemont Copper Project.

260 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 45. Maximum modeled and ambient emission concentrations at the perimeter fence for proposed action and action alternatives

Modeled 

Concentration

μg/m3)

Maximum 

Ambient 

Concentration

(μg/m3) 

Type of 

Emission

Averaging 

Period

Year of Active 

Mining 

Evaluatedk

Background 

Concentration

(μg/m3)

Proposed 

Action / 

Phased 

Tailings

Barrel 

Alternative

Barrel Trail

Alternative

ScholefieldMcCleary 

Alternative

Proposed 

Action / 

Phased 

Tailings

Barrel 

Alternative

Barrel Trail

Alternative

ScholefieldMcCleary 

Alternative

PSD Class II 

Increment

(μg/m3)

NAAQS

(μg/m3)

CO 1-houra Year 1 582.0 1,501.5 1,010.0 1,429.7 5,251.6 2,083.5 1,592.0 2,011.7 5,833.6 NA 40,000

Year 5 or 12 582.0 1,338.2 814.4 1,122.9 5,225.4 1,920.2 1,396.4 1,704.9 5,807.4

8-houra Year 1 582.0 639.0 311.7 383.5 1,543.7 ,1221.0 893.7 965.5 2,125.7 NA 10,000

Year 5 or 12 582.0 609.7 295.3 323.9 1522.7 1191.7 877.3 905.9 2104.7

NO2 1-hourb,g Year 1 24.5 145.4 130.2 141.6 151.9 169.9 154.7 166.1 176.4 NA 188.6

Year 5 or 12 24.5 133.4 123.4 135.0 146.5 157.9 147.9 159.5 171.0

1-hourb,h Year 1 24.5 206.7 170.0 188.9 219.0 231.2 194.5 213.4 243.5

Year 5 or 12 24.5 175.3 149.4 172.3 199.5 199.8 173.9 196.8 224.0

Annual Year 1 4.0 22.4 19.5 24.5 30.8 26.4 23.5 28.5 34.8 25 100

Year 5 or 12 4.0 21.8 19.0 22.6 29.9 25.8 23.0 26.6 33.9

PM10 24-hourc,i Year 1 37.4 103.1 92.9 113.8 143.7 140.5 130.3 151.2 181.1 30 150

Year 5 or 12 37.4 100.0 101.1 130.5 164.4 137.4 138.5 167.9 201.8

24-hourc,j Year 1 47.7 103.1 92.9 113.8 143.7 150.8 140.6 161.5 191.4

Year 5 or 12 47.7 100.0 101.1 130.5 164.4 147.7 148.8 178.2 212.1

PM2.5 24-hourd Year 1 7.2 19.8 18.5 18.6 34.9 27.0 25.7 25.8 42.1 9 35

Year 5 or 12 7.2 20.0 16.5 21.0 36.4 27.2 23.7 28.2 43.6

Annual Year 1 3.1 3.8 3.4 4.2 5.2 6.9 6.5 7.3 8.3 4 12m

Year 5 or 12 3.1 3.2 2.9 4.1 5.2 6.3 6.0 7.2 8.3

SO2 1-houre Year 1 –l 22.0 11.8 13.2 62.7 44.0 23.7 26.5 125.4 NA 195

Year 5 or 12 –l 21.9 11.8 12.2 62.6 43.8 23.5 24.4 125.3

3-hourf Year 1 43.0 19.6 10.1 9.9 44.8 62.6 53.1 52.9 87.8 512 1,300

Year 5 or 12 43.0 19.5 10.5 9.9 44.7 62.5 53.5 52.9 87.7

24-hourf Year 1 17.0 6.0 3.6 3.6 15.6 23.0 20.6 20.6 32.6 91 365

Year 5 or 12 17.0 6.0 3.8 3.6 15.6 23.0 20.8 20.6 32.6

Annual Year 1 3.0 0.3 0.1 0.1 0.3 3.3 3.1 3.1 3.3 20 80

Year 5 or 12 3.0 0.2 0.1 0.1 0.3 3.2 3.1 3.1 3.3

Pb 3-Month Rolling 

Average

Year 1 –l 0.026 0.024 0.027 0.033 0.05 0.05 0.1 0.07 NA 0.15

Year 5 or 12 –l 0.024 0.021 0.029 0.039 0.05 0.04 0.06 0.08

Notes: Bolded values are values that exceed the NAAQS. Shaded cells represent two modeling scenarios run only for comparison purposes, but use assumptions other than those approved by the Coronado and are not used to draw conclusions about impacts. 

NA = Not applicable. PSD = Prevention of significant deterioration.

a Represents the 2nd highest concentration.

b Represents the 98th percentile concentration over a 3-year period. 

c Represents the 4th highest concentration over a 3-year period.

d Represents the average of the highest 24-hour concentrations over a 3-year period.

e Represents the 99th percentile concentration over a 3-year period.

f Represents the highest 2nd highest concentration. 

g NO2/NOx ratio of 5% was used for tailpipe and internal combustion engine emissions.

h NO2/NOx ratio of 10% was used for tailpipe and internal combustion engine emissions.

i PM10 background concentration was calculated by replacing the outlier value of 71.3 μg/m3 with 40.3 μg/m3

.

j PM10 background concentration includes the outlier value of 71.3 μg/m3

. 

k Year 5 of active mining is evaluated for each scenario except for the Barrel Alternative, which is evaluated at year 12 of active mining.

l Background concentration was set equal to the highest modeled impact due to the lack of available appropriate data.

m The primary standard changed on December 14, 2012, from 15 μg/m3 to 12 μg/m3

; the modeling reports for the project report the old standard.

Final Environmental Impact Statement for the Rosemont Copper Project 261

Chapter 3. Affected Environment and Environmental Consequences

As shown, SO2 impacts were modeled to be less than the Class II increment levels for all action 

alternatives. Therefore, significant deterioration is not expected to occur, as the amount of new SO2

pollution does not exceed the applicable prevention of significant deterioration increments. However, 

exceedances of the annual NO2, 24-hour PM10, 24-hour PM2.5, and annual PM2.5 Class II increment 

values were observed under certain scenarios. Impacts specific to the proposed action and the various 

alternatives are discussed in further detail below. 

Impacts Specific to the Proposed Action and Phased Tailings Alternative

Under the selected assumptions (i.e., NO2 to NOx ratio of 0.05 and PM10 background concentration of 

47.7 μg/m3

), modeling estimated increases up to four times current levels of pollutant concentrations 

for PM2.5, CO, NOx, and lead at the perimeter fence.

Using the selected assumptions, the maximum predicted ambient concentrations for PM10 (24-hour) 

are above the corresponding NAAQS at the perimeter fence. Therefore, the proposed action and 

Phased Tailings Alternative would not be protective of NFS surface resources beyond the perimeter 

fenceline. Minor changes in stacking and hauling would likely allow these alternatives to comply 

with NAAQS, similar to the Barrel Alternative below, if determined to be appropriate by the Forest 

Supervisor. As modeled, however, these alternatives would not meet NAAQS.

Impacts Specific to the Barrel Alternative

Under the selected assumptions, modeling of the Barrel Alternative indicates increases up to two 

times the current levels of pollutant concentrations for PM10, PM2.5, CO, NOx, and lead at the 

perimeter fence. However, NAAQS would be met for all criteria pollutants at the perimeter fence.

Impacts Specific to the Barrel Trail Alternative

Modeling indicates increases up to four times current levels of pollutant concentrations for PM2.5, 

CO, NOx, and lead at the perimeter fence. The modeled impacts for this alternative indicate elevated 

impacts on SR 83, which runs in close proximity to the perimeter fence on the east side of the project. 

This elevated impact is attributable to the proximity of the haul roads and waste rock facility to the 

process area boundary on the east side. Using the selected assumptions, the maximum predicted 

ambient concentrations for PM10 (24-hour) are above the corresponding NAAQS at the perimeter 

fence; therefore, this alternative would not be protective of NFS surface resources beyond the 

perimeter fenceline. 

While it is theoretically feasible to relocate the perimeter fence for the Barrel Trail Alternative to a 

location where NAAQS would be met, that would require moving the fence onto private land or 

encompassing SR 83 within the perimeter fence, which could allow exposure by the general public to 

air quality exceeding NAAQS. The Coronado determined that it was not appropriate to adjust the 

perimeter fencelines in the case of the Barrel Trail Alternative in an effort to meet NAAQS.

Impacts Specific to the Scholefield-McCleary Alternative

Modeling indicates increases up to six times the current levels of pollutant concentrations for CO, 

NOx, and lead at the perimeter fence. The highest modeled impacts for this alternative are attributable 

to the proximity of the haul roads and waste rock facility adjacent to the process area boundary on the 

southeast side. Using the selected assumptions, the maximum predicted ambient concentrations for 

PM10 (24-hour) and PM2.5 (24-hour) are above the corresponding NAAQS at the perimeter fence; 

therefore, this alternative would not be protective of NFS surface resources beyond the perimeter 

fenceline.

Final Environmental Impact Statement for the Rosemont Copper Project 263
Chapter 3. Affected Environment and Environmental Consequences

As with the Barrel Trail Alternative, while it is theoretically feasible to relocate the perimeter fence 

for Scholefield-McCleary Alternative to a location where NAAQS would be met, it would require 

moving the fence onto private land or encompassing SR 83 within the perimeter fence, which could 

allow exposure by the general public to air quality exceeding NAAQS. The Coronado determined that 

it was not appropriate to adjust the perimeter fencelines in the case of the Scholefield McCleary 

Alternative in an effort to meet NAAQS.

Potential to Contribute to PM10 Nonattainment Status

Comments from cooperating agencies suggested that the potential for the mine to contribute to 

nonattainment for PM10 status should be analyzed in some manner. Current maximum PM10

concentrations observed in the Tucson area are summarized in table 34 and range from 79 to 146 

μg/m3

. Concentrations of PM10 resulting from the mine have not been modeled at these specific 

points. However, concentrations modeled at the boundary of Saguaro National Park East have been 

and can be used as a rough approximation of concentrations some distance from the mine. PM10

concentrations at the boundary of Saguaro National Park East range from 1.9 to 3.7 μg/m3

, depending 

on the alternative (table 46). For the Barrel Alternative, which is the only alternative that meets 

NAAQS at the fenceline, the modeled PM10 concentrations at Saguaro National Park East range from 

2.2 to 2.8 μg/m3

. The NAAQS for PM10 is 150 μg/m3. 

A simple calculation suggests that the contribution from the Rosemont Copper Mine would not 

trigger nonattainment status. Like any emission source large or small, the Rosemont Copper Project 

would contribute to regional air quality, and emissions from the Rosemont Copper Mine would 

slightly increase the risk for nonattainment. It would not be appropriate to state, however, that 

Rosemont Copper would be responsible for or cause nonattainment should it happen, as current levels 

observed in at least one monitoring station are already close to the NAAQS. 

AERMOD Modeling of Compliance with NAAQS

at Saguaro National Park East for the Action Alternatives

NAAQS maintenance at the nearest Class I area, Saguaro National Park East, was also examined. 

Additionally, wind conditions are more likely to direct pollutant emissions to this Class I area, 

compared with the other Class I areas (JBR Environmental Consultants Inc. 2012e). Criteria 

pollutants analyzed in the JBR modeling exercise were PM10, PM2.5, NO2, CO, SO2, and lead. 

Background concentrations were obtained from the air quality monitoring station located at the 

Saguaro National Park East for PM10 and PM2.5. Rural area background concentrations of NO2, CO, 

and SO2 (with the exception of 1-hour SO2) were used. Also as with the modeling done at the project 

area, background concentrations for 1-hour SO2 and for lead were conservatively assumed to be equal 

to the modeled concentration due to the unavailability of data. A more detailed discussion of the use 

of background concentrations is presented in the AERMOD report (JBR Environmental Consultants 

Inc. 2012e). 

The background concentrations, modeled concentrations, and projected maximum ambient 

concentrations (background concentration plus modeled concentration) of criteria pollutants for the 

impact of the proposed action and each of the alternative actions on the Saguaro National Park East 

are presented in table 46.

264 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 46. Maximum modeled and ambient emission concentrations at Saguaro National Park East boundary for action alternatives

Modeled

Concentration

(μg/m3)

Maximum 

Ambient 

Concentration

(μg/m3)

Type of 

Emission

Averaging 

Period

Year of Active 

Mining Evaluatedk

Background 

Concentration

(μg/m3)

Proposed 

Action / 

Phased 

Tailings

Barrel 

Alternative

Barrel Trail

Alternative

ScholefieldMcCleary 

Alternative

Proposed 

Action / 

Phased 

Tailings

Barrel 

Alternative

Barrel Trail

Alternative

ScholefieldMcCleary 

Alternative

PSD Class I 

Increment

(μg/m3)

NAAQS

(μg/m3)

CO 1-houra Year 1 582.0 115.2 90.1 96.1 130.6 697.2 672.1 678.1 712.6 NA 40,000

Year 5 or 12 582.0 121.2 99.2 106.6 130.1 703.2 681.2 688.6 712.1

8-houra Year 1 582.0 16.9 15.9 15.4 22.2 598.9 597.9 597.4 604.2 NA 10,000

Year 5 or 12 582.0 19.7 14.0 17.4 21.3 601.7 596.0 599.4 603.3

NO2 1-hourb,g Year 1 24.5 61.3 56.9 55.8 77.4 85.8 81.4 80.3 101.9 NA 188.6

Year 5 or 12 24.5 69.4 61.5 63.0 78.0 93.9 86.0 87.5 102.5

1-hourb,h Year 1 24.5 62.3 56.9 55.8 79.2 86.8 81.4 80.3 103.7

Year 5 or 12 24.5 69.4 61.5 63.3 81.5 93.9 86.0 87.8 106.0

Annual Year 1 4.0 0.41 0.4 0.4 0.5 4.4 4.4 4.4 4.5 2.5 100

Year 5 or 12 4.0 0.4 0.4 0.4 0.5 4.4 4.4 4.4 4.5

PM10 24-hourc,i Year 1 47.6 2.05 2.2 1.9 2.7 49.7 49.8 49.5 50.3 8.0 150

Year 5 or 12 47.6 2.8 2.8 2.6 3.7 50.4 50.4 50.2 51.3

PM2.5 24-hourd Year 1 9.0 0.35 0.4 0.4 0.5 9.4 9.4 9.4 9.5 2.0 35

Year 5 or 12 9.0 0.4 0.5 0.5 0.6 9.4 9.5 9.5 9.6

Annual Year 1 4.2 0.02 0.02 0.02 0.02 4.2 4.2 4.2 4.2 1.0 12l

Year 5 or 12 4.2 0.02 0.02 0.02 0.03 4.2 4.2 4.2 4.2

SO2 1-houre Year 1 –k 0.28 0.2 0.2 0.2 0.6 0.4 0.4 0.4 NA 195

Year 5 or 12 –k 0.3 0.2 0.2 0.2 0.6 0.5 0.5 0.4

3-hourf Year 1 43.0 0.14 0.1 0.1 0.1 43.1 43.1 43.1 43.1 25.0 1,300

Year 5 or 12 43.0 0.2 0.1 0.1 0.1 43.2 43.1 43.1 43.1

24-hourf Year 1 17.0 0.03 0.02 0.02 0.02 17.0 17.0 17.0 17.0 5.0 365

Year 5 or 12 17.0 0.03 0.02 0.023 0.02 17.0 17.0 17.0 17.0

Annual Year 1 3.0 8.7E-04 8.3E-04 8.4E-04 8.6E-04 3.0 3.0 3.0 3.0 2.0 80

Year 5 or 12 3.0 8.1E-04 7.5E-04 8.1E-04 8.4E-04 3.0 3.0 3.0 3.0

Pb 3-Month 

Rolling Average Year 1 –k 2.5E-04 2.7E-04 2.6E-04 3.2E-04 5.0E-04 5.4E-04 5.2E-04 6.4E-04 NA 0.15

Year 5 or 12 –k 3.0E-04 3.3E-04 3.2E-04 4.4E-04 6.0E-04 6.6E-04 6.4E-04 8.8E-04

Notes: Shaded cells represent scenarios run only for comparison purposes, but use assumptions other than those approved by the Coronado and are not used to draw conclusions about impact. NA = Not available. PSD = Prevention of significant deterioration.

a Represents the 2nd highest concentration.

bRepresents the 98th percentile concentration over a 3-year period. 

c Represents the 4th highest concentration over a 3-year period.

d Represents the average of the highest 24-hr concentrations over a 3-year period.

e Represents the 99th percentile concentration over a 3-year period.

fRepresents the highest 2nd highest concentration. 

g NO2/NOx ratio of 5% was used for tailpipe and internal combustion engine emissions.

h NO2/NOx ratio of 10% was used for tailpipe and internal combustion engine emissions.

i PM10 background concentration includes the outlier value of 71.3 μg/m3

.

j Year 5 of active mining is evaluated for each scenario except for the Barrel Alternative, which is evaluated at year 12 of active mining.

k Background concentration was set equal to the highest modeled impact as a result of the lack of available appropriate data.

l The primary standard changed on December 14, 2012, from 15 μg/m3 to 12 μg/m3; the modeling reports for the project report the old standard.

Final Environmental Impact Statement for the Rosemont Copper Project 265

Chapter 3. Affected Environment and Environmental Consequences

As shown in table 46, the modeled impacts were compared with Class I increment levels. Increment 

levels for Class I areas are threshold levels intended to prevent the air quality in clean areas from 

deteriorating to the level set by the NAAQS. As with the Class II increment levels, Class I increment 

levels are provided for disclosure only. Determination of whether Rosemont Copper’s emissions

represent a violation of applicable air quality laws and regulations is solely under the regulatory 

authority of ADEQ as the agency issuing the permit. At this time, ADEQ has not required an 

increment analysis on the Rosemont Copper Project.

As shown, criteria pollutants were modeled to be less than the Class I increment levels for all action 

alternatives. Therefore, significant deterioration is not expected to occur as the amount of new 

pollution does not exceed the applicable prevention of significant deterioration increments. 

Furthermore, as presented in table 46, the NAAQS would be maintained at Saguaro National Park 

East for all criteria pollutants for all action alternatives.

As with the modeling conducted at the perimeter fence, one additional modeling analysis for 

comparison purposes only was conducted (shaded cells in table 46), using an NO2 to NOx ratio of 0.1 

for mobiles sources and internal combustion engines (JBR Environmental Consultants Inc. 2012e). 

This modeling analysis also resulted in maintenance of NAAQS at Saguaro National Park East for all 

criteria pollutants for all action alternatives. Modeling indicates that NAAQS for criteria pollutants 

are met at Saguaro National Park East for all alternatives. 

CALPUFF Modeling for Compliance with NAAQS

at other Class I areas for the Action Alternatives

Additional Class I areas were analyzed for possible degradation of NAAQS using CALPUFF as a farfield model. The following additional Class I areas (with their direction and distance from the center 

of the park to the project area noted parenthetically) were analyzed for criteria pollutants: 

• Saguaro National Park West (66 kilometers northwest); 

• Galiuro Wilderness (95 kilometers northeast); 

• Chiricahua National Monument (140 kilometers east); 

• Chiricahua Wilderness (145 kilometers east); and 

• Superstition Wilderness (195 kilometers northwest). 

Regionally representative background concentrations for each criteria pollutant were selected for the 

Class I areas analyzed. As with the AERMOD modeling, the 2 years representing the highest 

anticipated emissions were selected for modeling criteria pollutant emissions from the mine. 

The results are summarized in table 47. 

The modeled impacts were compared with Class I increment levels. Increment levels for Class I areas 

are threshold levels intended to prevent the air quality in clean areas from deteriorating to the level 

set by the NAAQS. As shown, criteria pollutants were modeled to be less than the Class I increment 

levels for all action alternatives. Therefore, significant deterioration is not expected to occur, as the 

amount of new pollution does not exceed the applicable prevention of significant deterioration 

increments. Furthermore, as presented in table 47, the NAAQS would be maintained at each of the 

Class I areas analyzed for all criteria pollutants for the action alternatives.

Final Environmental Impact Statement for the Rosemont Copper Project 267
Chapter 3. Affected Environment and Environmental Consequences

CALPUFF, AERMOD, and VISCREEN Modeling for Projected 

Impacts to Air Quality Related Values at Class I Areas

Modeling work was also conducted to examine the effects of projected emissions on air quality

related values of visibility and deposition in Class I areas and on compliance with the EPA Regional 

Haze Rule regarding visibility in Class I areas. Figure 42 shows the locations of the modeled values 

for evaluating impacts to Class I areas.

The regulation of air pollution sources has been statutorily delegated to the EPA to administer either 

directly or through the devolved authority granted to States, tribes, or local agencies. However, public 

lands, such as Federal Class I areas, should be analyzed by the Federal land manager in charge of 

such lands, regardless of whether or not the air pollution source is within or outside such public land, 

for possible detrimental impacts to those lands from air pollution sources to various air quality related 

values such as visibility impairment, O3 effects on vegetation, and effects of pollutant deposition on 

soils and surface waters (U.S. Forest Service et al. 2010). To this end, the action alternatives have 

been examined for the impacts they could have on visibility and sulfate and nitrate deposition using 

the various screening criteria that have been developed to quantify the impact that an air pollution 

source could have to Class I areas near the project area. 

The following Class I areas (with their direction and distance from the center of the park to the 

project area noted parenthetically) were analyzed for visibility and/or pollutant deposition: 

• Saguaro National Park East (44 kilometers north); 

• Saguaro National Park West (66 kilometers northwest); 

• Galiuro Wilderness (95 kilometers northeast); 

• Chiricahua National Monument (140 kilometers east) 

• Chiricahua Wilderness (145 kilometers east); and 

• Superstition Wilderness (195 kilometers northwest). 

The action alternatives’ potential to impact air quality related values at Saguaro National Park was 

modeled using VISCREEN for visibility and AERMOD for deposition, which are the appropriate 

models for near-field analysis. Visibility and pollutant deposition to the five other Class I areas were 

modeled in the far-field analysis using CALPUFF.

Projected Effects on Visibility in Class I Areas

A level 1 screening analysis was performed in VISCREEN to assess the action alternatives’ impact on 

visibility in Saguaro National Park East. The VISCREEN model is used for near-field analysis of 

visibility impacts to Class I airsheds that are within 31 miles of an air pollution source. The model 

calculates the change in the color difference index and contrast between the plume and the viewing 

background that result from an elevated plume emanating from a point source. Each alternative is 

modeled under four different scenarios that use different azimuth viewing angles (i.e., the plume is 

backlit or fore-lit by the sun) and different elevations (i.e., the plume is in contrast against the sky or 

against the ground).

268 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 47. Maximum modeled and ambient emission concentrations at Class I areas for all action alternatives

Modeled Impact 

Concentration

(μg/m3)

Cumulative 

Impact 

Concentration

(μg/m3)

Type of 

Emission

Averaging 

Period

Background 

Concentration

(μg/m3)

Proposed Action

/ Phased Tailings

Barrel 

Alternative

Barrel Trail

Alternative

ScholefieldMcCleary 

Alternative

Proposed Action / 

Phased Tailings

Barrel 

Alternative

Barrel Trail

Alternative

ScholefieldMcCleary 

Alternative

Class I Increment 

(μg/m3)

NAAQS

(μg/m3)

Saguaro 

National Park 

West

NOx 1-houra,f 24.5 4.84 5.26 4.86 5.97 29.34 29.76 29.36 30.47 NA 188

Annual 4.0 0.11 0.63 0.12 0.13 4.11 4.63 4.12 4.13 2.5 100

SOx 1-hourb 17.2 0.40 0.40 0.40 0.40 17.60 17.60 17.60 17.60 NA 195

3-hourc 43.0 0.18 0.18 0.18 0.18 43.18 43.18 43.18 43.18 25.0 1,300

24-hourc 14.0 0.04 0.04 0.04 0.04 14.04 14.04 14.04 14.04 5.0 365

Annual 3.0 6.40E-04 5.34E-04 5.47E-04 2.96E-02 3.00 3.00 3.00 3.03 2.0 80

PM2.5 24-hourd 11.4 0.15 0.14 0.12 0.14 11.55 11.54 11.52 11.54 2.0 35

Annual 5.1 0.02 0.02 0.02 0.02 5.12 5.12 5.12 5.12 1.0 12

PM10 24-houre 47.6 0.60 0.55 0.65 0.80 48.20 48.15 48.25 48.40 8.0 150

Chiricahua 

National 

Monument

NOx 1-houra,f 24.5 15.19 9.14 10.54 10.64 39.69 33.64 35.04 35.14 NA 188

Annual 4.0 0.01 4.63E-03 4.94E-03 5.45E-03 4.01 4.00 4.00 4.01 2.5 100

SOx 1-hourb 17.2 0.18 0.18 0.18 0.18 17.38 17.38 17.38 17.38 NA 195

3-hourc 43.0 0.08 0.07 0.08 0.08 43.08 43.07 43.08 43.08 25.0 1,300

24-hourc 14.0 0.01 0.01 0.01 0.01 14.01 14.01 14.01 14.01 5.0 365

Annual 3.0 2.83E-04 2.63E-04 2.27E-03 2.75E-04 3.00 3.00 3.00 3.00 2.0 80

PM2.5 24-hourd 11.4 0.21 0.09 0.15 0.14 11.61 11.49 11.55 11.54 2.0 35

Annual 5.1 2.23E-03 2.15E-03 2.27E-03 2.24E-03 5.10 5.10 5.10 5.10 1.0 12

PM10 24-houre 47.6 1.11 0.46 0.79 0.74 48.71 48.06 48.39 48.34 8.0 150

Chiricahua 

Wilderness

Area

NOx 1-houra,f 24.5 7.83 6.49 5.50 5.95 32.33 30.99 30.00 30.45 NA 188

Annual 4.0 4.92E-03 3.81E-03 3.63E-03 4.17E-03 4.00 4.00 4.00 4.00 2.5 100

SOx 1-hourb 17.2 0.14 0.25 0.14 0.14 17.34 17.45 17.34 17.34 NA 195

3-hourc 43.0 0.04 0.17 0.04 0.04 43.04 43.17 43.04 43.04 25.0 1,300

24-hourc 14.0 0.01 0.04 0.01 0.01 14.01 14.04 14.01 14.01 5.0 365

Annual 3.0 2.34E-04 2.27E-04 2.27E-04 2.27E-04 3.00 3.00 3.00 3.00 2.0 80

PM2.5 24-hourd 11.4 0.12 0.06 0.09 0.08 11.52 11.46 11.49 11.48 2.0 35

Annual 5.1 1.68E-03 1.76E-03 1.70E-03 1.72E-03 5.10 5.10 5.10 5.10 1.0 12

PM10 24-houre 47.6 0.63 1.98 0.42 0.41 48.23 49.58 48.02 48.01 8.0 150

Final Environmental Impact Statement for the Rosemont Copper Project 269
Chapter 3. Affected Environment and Environmental Consequences

Modeled Impact 

Concentration

(μg/m3)

Cumulative 

Impact 

Concentration

(μg/m3)

Type of 

Emission

Averaging 

Period

Background 

Concentration

(μg/m3)

Proposed Action

/ Phased Tailings

Barrel 

Alternative

Barrel Trail

Alternative

ScholefieldMcCleary 

Alternative

Proposed Action / 

Phased Tailings

Barrel 

Alternative

Barrel Trail

Alternative

ScholefieldMcCleary 

Alternative

Class I Increment 

(μg/m3)

NAAQS

(μg/m3)

Galiuro 

Wilderness

Area

NOx 1-houra,f 24.5 56.96 64.37 54.20 58.18 81.46 88.87 78.70 82.68 NA 188

Annual 4.0 0.04 0.03 0.03 0.03 4.04 4.03 4.03 4.03 2.5 100

SOx 1-hourb 17.2 0.42 0.41 0.42 0.42 17.62 17.61 17.62 17.62 NA 195

3-hourc 43.0 0.22 0.21 0.22 0.22 43.22 43.21 43.22 43.22 25.0 1,300

24-hourc 14.0 0.03 0.03 0.03 0.03 14.03 14.03 14.03 14.03 5.0 365

Annual 3.0 4.70E-04 2.59E-02 4.35E-04 4.36E-04 3.00 3.03 3.00 3.00 2.0 80

PM2.5 24-hourd 11.4 0.75 0.44 0.63 0.54 12.15 11.84 12.03 11.94 2.0 35

Annual 5.1 9.35E-03 8.16E-03 8.34E-03 8.11E-03 5.11 5.11 5.11 5.11 1.0 12

PM10 24-houre 47.6 4.79 2.73 3.93 3.42 52.39 50.33 51.53 51.02 8.0 150

Superstition 

Wilderness

Area

NOx 1-houra,f 24.5 1.35 1.99 1.65 1.83 25.85 26.49 26.15 26.33 NA 188

Annual 4.0 1.78E-03 1.62E-03 1.71E-03 0.49 4.00 4.00 4.00 4.49 2.5 100

SOx 1-hourb 17.2 0.03 0.03 0.03 0.03 17.23 17.23 17.23 17.23 NA 195

3-hourc 43.0 0.01 0.01 0.01 0.01 43.01 43.01 43.01 43.01 25.0 1,300

24-hourc 14.0 3.41E-03 3.42E-03 3.40E-03 3.39E-03 14.00 14.00 14.00 14.00 5.0 365

Annual 3.0 5.69E-05 5.06E-05 5.13E-05 5.16E-05 3.00 3.00 3.00 3.00 2.0 80

PM2.5 24-hourd 11.4 0.03 0.02 0.03 0.03 11.43 11.42 11.43 11.43 2.0 35

Annual 5.1 1.06E-03 1.07E-03 1.06E-03 1.14E-03 5.10 5.10 5.10 5.10 1.0 12

PM10 24-houre 47.6 0.15 0.12 0.15 0.15 47.75 47.72 47.75 47.75 8.0 150

Note: NA = Not available. 

a Represents the 98th percentile concentration over a 3-year period. 

b Represents the 99th percentile concentration over a 3-year period.

c Represents the highest 2nd highest concentration. 

d Represents the average of the highest 24-hour concentrations over a 3-year period.

e Represents the 4th highest concentration over a 3-year period.

f An NO2/NOx ratio of 5% was used for tailpipe and internal combustion engine emissions

.

270 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

A level 1 screening analysis assesses visibility under the worst-case air quality impact from a source 

using the worst-case meteorological conditions (wind speed of 1 meter per second, which is about 2

to 3 miles per hour, and atmospheric stability class “F”). The “worst-case” meteorological conditions 

analyzed are not necessarily representative of the site but are representative of the worst possible 

meteorological conditions that could occur at any location. The results of the level 1 screening 

analysis performed to assess the impact to visibility at Saguaro National Park East from the action 

alternatives are shown in table 48. 

Table 48. VISCREEN level 1 modeling of visibility impacts at Saguaro National Park 

East Class I area

Color Difference Contrast Contrast

Background Theta

(o)

Azi 

(o)

Distance 

(km)

Alpha 

(o) Criteria Plume Criteria Plume

Proposed 

Action / 

Phased 

Tailings 

Alternative / 

Barrel 

Alternative

Sky 10 141 46.5 28 2.0 1.726 0.05 −0.024

Sky 140 141 46.5 28 2.0 2.388* 0.05 −0.078*

Terrain 10 84 34.3 84 2.0 4.883* 0.05 0.035

Terrain 140 84 34.3 84 2.0 0.634 0.05 0.007

Barrel Trail

Alternative

Sky 10 141 46.5 28 2.0 1.779 0.05 −0.026

Sky 140 141 46.5 28 2.0 2.431* 0.05 −0.079*

Terrain 10 84 34.3 84 2.0 4.899* 0.05 −0.035

Terrain 140 84 34.3 84 2.0 0.644 0.05 0.007

ScholefieldMcCleary 

Alternative

Sky 10 141 46.5 28 2.0 1.904 0.05 −0.029

Sky 140 141 46.5 28 2.0 2.529* 0.05 −0.082*

Terrain 10 84 34.3 84 2.0 4.936* 0.05 0.035

Terrain 140 84 34.3 84 2.0 0.668 0.05 0.008

* Indicates that screening criteria are exceeded.

The results of the level 1 screening analysis indicate that viewers at Saguaro National Park East could

notice a change to the color and contrast of background views (sky and terrain) through the plume at 

various angles during worst-case scenario wind speeds and atmospheric stability conditions for all the 

action alternatives. However, as discussed in the VISCREEN modeling report, the default “worstcase” meteorological conditions analyzed in the level 1 screening analysis are not representative of 

actual site-specific meteorological conditions. The report notes that actual meteorological data 

gathered by the National Weather Service for the Tucson airport station indicated that there were no 

hours for which the worst-case meteorological conditions (1 meter per second wind speed and 

atmospheric stability class “F”) applied for 2002 (JBR Environmental Consultants Inc. 2012d).

Final Environmental Impact Statement for the Rosemont Copper Project 271
Chapter 3. Affected Environment and Environmental Consequences

A level 2 screening analysis was therefore performed to better analyze impacts using the actual worstcase meteorological conditions as recorded from the National Weather Service Tucson airport site for 

the year 2002. The actual worst-case conditions identified from this site were 2 meters per second 

(about 4 to 5 miles per hour) wind speeds and atmospheric stability class “F.” These conditions 

appear for about 303 hours during the entire year, which translates to approximately 3.4 percent of the 

hours per year (JBR Environmental Consultants Inc. 2012d). Table 49 presents the results of the level 

2 visibility screening analysis performed for Saguaro National Park East.

Table 49. VISCREEN level 2 modeling of visibility impacts at Saguaro National Park 

East Class I area

Color Difference Contrast Contrast

Background Theta 

(o)

Azi 

(o)

Distance 

(km)

Alpha 

(o) Criteria Plume Criteria Plume

Proposed 

Action / 

Phased 

Tailings 

Alternative / 

Barrel 

Alternative

Sky 10 141 46.5 28 2.0 0.946 0.05 −0.013

Sky 140 141 46.5 28 2.0 1.3 0.05 −0.043

Terrain 10 84 34.3 84 2.0 2.527* 0.05 0.017

Terrain 140 84 34.3 84 2.0 0.315 0.05 0.004

Barrel Trail

Alternative

Sky 10 141 46.5 28 2.0 0.975 0.05 −0.014

Sky 140 141 46.5 28 2.0 1.324 0.05 −0.044

Terrain 10 84 34.3 84 2.0 2.535* 0.05 0.017

Terrain 140 84 34.3 84 2.0 0.321 0.05 0.004

ScholefieldMcCleary 

Alternative

Sky 10 141 46.5 28 2.0 1.044 0.05 −0.016

Sky 140 141 46.5 28 2.0 1.378 0.05 −0.046

Terrain 10 84 34.3 84 2.0 2.554* 0.05 0.018

Terrain 140 84 34.3 84 2.0 0.333 0.05 0.004

* Indicates that screening criteria are exceeded.

The level 2 screening analysis for Saguaro National Park East shows a reduced impact to visibility 

from the action alternatives. The results indicate that project impacts to view contrast and sky 

visibility would be below viewer threshold levels for three out of four scenarios. However, the results 

do indicate that viewers at Saguaro National Park East could still notice terrain background color 

changes at certain viewer angles during certain times of day. A level 2 screening analysis is still a 

conservative screening tool representing site-specific worst-case meteorological conditions. 

Furthermore, as discussed in the VISCREEN report, “almost all of the emissions from the 

Rosemont Project are emitted from volume sources . . . dispersed across many acres of land area.” 

The VISCREEN model, however, must treat “emissions from a myriad of sources . . . as if they were 

emitted from a single stack” (JBR Environmental Consultants Inc. 2012d). Therefore, in addition to 

272 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

assessing the impact to visibility under the most conservative meteorological conditions, the 

emissions from the action alternatives are also conservatively represented by the model.

The far-field CALPUFF model was used to determine visibility impacts to the other five Class 1 

airsheds because they are more than 31 miles (50 kilometers) away from the project area. It is 

important to note that the EPA allows the use of the CALPUFF model for distances as far as 186 

miles (300 kilometers), which is considered the limit for a far-field air quality impact analysis. 

The days above 0.5 deciview, days above 1.0 deciview, the 98th percentile impact, and the maximum 

deciview impact values are shown in table 50 (JBR Environmental Consultants Inc. 2013c). 

Use of the 98th percentile value does not give undue weight to the extreme tail of the distribution 

of visibility data values. Using the 98th percentile value would exclude approximately 7 days 

(98 percent of 365 days) per year from modeling consideration. In determining the 98th percentile

value, the eighth highest value for each modeled meteorological year was averaged and reported. 

The “Federal Land Managers’ Air Quality Related Values Workgroup (FLAG) Phase I Report –

Revised” (U.S. Forest Service et al. 2010) uses this approach to minimize the chance that visibility 

impacts might be caused by unusual meteorology or conservative assumptions in the model, allowing 

for 7 days per year to be above the threshold before additional review of impacts is required.

The EPA has stated (40 CFR 51) that a delta deciview level of 0.5 or more is considered to contribute 

to visibility impairment and that a delta deciview level of 1.0 or more is considered to cause visibility 

impairment. According to these metrics, all of the action alternatives could contribute to noticeable 

visibility impairment at each of the Class I areas analyzed. A summary of visibility impacts for each 

Class I area by action alternative is provided below.

Proposed Action and Phased Tailings Alternative

The modeling indicates that the proposed action and Phased Tailings Alternative could cause 

visibility impairment (>1.0 deciview) at Saguaro National Park West for 10 days out of the year and 

at Galiuro Wilderness for 9 days out of the year. The results also indicate that the proposed action and 

the Phased Tailings Alternative could contribute to visibility impairment (>0.5 deciview) at Saguaro 

National Park West for 31 days out of the year, at Chiricahua National Monument for 2 days out of 

the year, at Chiricahua Wilderness for 1 day out of the year, at the Galiuro Wilderness for 18 days out 

of the year, and at the Superstition Wilderness for 1 day out of the year. 

The 98th percentile deciview impact for the proposed action and Phased Tailings Alternative ranged 

from 1.23 deciview (Galiuro Wilderness – year 1) to 0.05 deciview (Superstition Wilderness –

year 5). At their highest modeled impact, these alternatives could change visibility by 2.39 deciviews 

at Saguaro National Park West and by 7.71 deciviews at the Galiuro Wilderness. 

Barrel Alternative

The Barrel Alternative could cause visibility impairment (>1.0 deciview) at Saguaro National Park 

West for 4 days out of the year and at Galiuro Wilderness for 7 days out of the year; it could 

contribute to visibility impairment (>0.5 deciview) at Saguaro National Park West for 14 days out of 

the year and at the Galiuro Wilderness for 16 days out of the year. The 98th percentile deciview 

impact for the Barrel Alternative ranged from 0.76 deciview (Galiuro Wilderness – year 5) to 0.06 

deciview (Superstition Wilderness – year 1).

At its highest modeled impact, the Barrel Alternative could change visibility by 4.21 deciviews at 

Saguaro National Park West and by 3.47 deciviews at the Galiuro Wilderness. 

Final Environmental Impact Statement for the Rosemont Copper Project 273
Table 50. CALPUFF modeling of visibility impacts at other Class I areas

Emissions

for Year 1 

of Active 

Mining

Emissions

for Year 5 or 

12 of Active 

Mining*

Criteria

Proposed 

Action / 

Phased 

Tailings

Barrel 

Alternative

Barrel Trail

Alternative

ScholefieldMcCleary 

Alternative

Proposed 

Action / 

Phased 

Tailings

Barrel 

Alternative

Barrel T

Alterna

Saguaro National Park West

Days above 0.5 deciview (dv) 31 14 11 15 6 7 7 

Days above 1.0 dv 10 4 0 1 1 0 0 

98th percentile dv impact 1.10 0.71 0.53 0.58 0.49 0.49 0.48 

Maximum dv impact 2.39 4.21 0.866 1.02 1.24 0.935 0.874 

Chiricahua Wilderness Area

Days above 0.5 dv 0 0 0 0 1 0 0 

Days above 1.0 dv 0 0 0 0 0 0 0 

98th percentile dv impact 0.26 0.19 0.19 0.20 0.26 0.25 0.22 

Maximum dv impact 0.461 0.234 0.221 0.239 0.666 0.348 0.299 

Chiricahua National Monument

Days above 0.5 dv 2 0 0 1 1 0 1 

Days above 1.0 dv 0 0 0 0 0 0 0 

98th percentile dv impact 0.12 0.10 0.09 0.11 0.11 0.14 0.10 

Maximum dv impact 0.673 0.327 0.398 0.418 0.902 0.426 0.828 

Galiuro Wilderness Area

Days above 0.5 dv 16 9 8 9 18 16 14 

Days above 1.0 dv 9 3 2 2 7 7 6 

98th percentile dv impact 1.23 0.61 0.50 0.58 0.90 0.76 0.77 

Maximum dv impact 7.71 2.58 2.32 2.44 3.50 3.47 3.12 

Superstition Wilderness Area

Days above 0.5 dv 1 0 0 0 0 0 0 

Days above 1.0 dv 0 0 0 0 0 0 0 

98th percentile dv impact 0.11 0.06 0.06 0.06 0.05 0.06 0.05 

Maximum dv impact 0.606 0.329 0.270 0.307 0.279 0.278 0.254 

Note: Bold represents exceedance of 1.0 dv threshold.

*Year 5 of active mining is evaluated for each scenario except for the Barrel Alternative, which is evaluated at year 12 of active mining.

274 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Barrel Trail Alternative

The Barrel Trail Alternative could cause visibility impairment (>1.0 deciview) at the Galiuro 

Wilderness for 6 days out of the year and could contribute to visibility impairment (>0.5 deciview) at 

Saguaro National Park West for 11 days out of the year, at Chiricahua National Monument for 1 day

out of the year, and at the Galiuro Wilderness for 14 days out of the year. The 98th percentile 

deciview impact for the Barrel Trail Alternative ranged from 0.77 deciview (Galiuro Wilderness) to 

0.05 deciview (Superstition Wilderness). At the highest modeled impact, the Barrel Trail Alternative

could change visibility by 3.12 deciviews at the Galiuro Wilderness. 

Scholefield-McCleary Alternative

The Scholefield-McCleary Alternative could cause visibility impairment (>1.0 deciview) at Saguaro 

National Park West for 1 day out of the year and at the Galiuro Wilderness for 5 days out of the year. 

In addition, the modeling indicates that the Scholefield-McCleary Alternative could contribute to 

visibility impairment (>0.5 deciview) at Saguaro National Park West for 16 days out of the year, at 

Chiricahua National Monument for 1 day out of the year, and at the Galiuro Wilderness for 13 days 

out of the year. The 98th percentile deciview impact for the Scholefield-McCleary Alternative ranged 

from 0.75 deciview (Galiuro Wilderness) to 0.06 deciview (Superstition Wilderness). At the highest 

modeled impact, the Scholefield-McCleary Alternative could change visibility by 1.10 deciviews at 

Saguaro National Park West and by 3.02 deciviews at the Galiuro Wilderness. 

Projected Effects on Deposition of 

Sulfates and Nitrates on Class I Areas

Based on the CALPUFF model output files, predicted deposition impacts for sulfates and nitrates, 

resulting from SO2 and NOX emitted by the proposed project, were calculated for the far-field Class I 

areas. Predicted deposition impacts for Saguaro National Park East (the only near-field Class I areas 

were calculated using AERMOD. Table 51 summarizes the maximum predicted deposition rates for 

these chemical species. Deposition was calculated to include both dry and wet deposition flux and the 

total deposition impacts at each Class I area. These values are compared with the deposition analysis 

threshold for the western United States (0.005 kilograms per hectare per year). The modeling results 

indicate that the maximum annual average deposition for sulfur from the project is very limited for all 

Class I areas and is below the threshold levels that indicate an adverse impact may exist. However, 

the modeling results do indicate that the maximum annual average deposition for nitrogen from the 

project exceeds the deposition analysis threshold in Saguaro National Park East, Saguaro National 

Park West, and the Galiuro Wilderness for all action alternatives. As indicated by the “Federal Land 

Managers’ Air Quality Related Values Work Group (FLAG) – Phase I Report – Revised” (U.S. Forest 

Service et al. 2010), the deposition analysis threshold is not necessarily an adverse impact threshold. 

The deposition analysis threshold is the additional amount of deposition that triggers a management 

concern and indicates that a source should be looked at in more detail, not necessarily the amount that 

constitutes an adverse impact to the environment.

When the deposition analysis threshold is exceeded by the model predictions for a specific project, as 

it is at these three Class I areas, the next step is to examine whether ecosystems in these Class I areas 

are sensitive to and potentially affected by deposition. Research indicates that responses to nitrogen 

deposition includes alteration of species composition, specifically an increase in biomass of exotic 

species and decreases in native species. This in turn can result in management consequences, 

Final Environmental Impact Statement for the Rosemont Copper Project 275
Chapter 3. Affected Environment and Environmental Consequences

including increases in vegetation cover, leading to increased fire-carrying capacity, which can alter 

fire frequency in the ecosystems that are not adapted to frequent wildfires. Deposition also has an 

effect on biotic soil crusts (which consist of bacteria, green algae, microfungi, and lichens) and 

mycorrhizal fungi, which are key aspects of soil productivity in desert environments. Nitrogen 

deposition can alter the diversity, abundance, and functioning of mycorrhizal fungi, cause shifts in 

lichen communities, and cause alteration of biotic crusts (Allen and Geiser 2011:134; Fenn and Allen 

2011:171).

The point at which changes due to nitrogen deposition begin to have harmful effects is called the 

critical load, which is also measured in kilograms of nitrogen deposition per hectare per year. Critical 

loads are estimated based on previous research and the estimates have varying reliability. Critical 

loads have been estimated for portions of the ecoregions in question for both lichens and herbaceous 

plants and shrubs. The critical load for lichens—the level at which harmful changes could occur—

is estimated as 3.0 kilograms of nitrogen deposition per hectare per year. The critical load for 

herbaceous plants and shrubs—the level at which harmful changes could occur—is estimated from 

3.0 to 8.4 kilograms of nitrogen deposition per hectare per year (Allen and Geiser 2011:139; Fenn and 

Allen 2011). The National Park Service uses the most protective critical load threshold for 

herbaceous plants, shrubs, and lichens, which is 3 kilograms per hectare per year.

Table 52 summarizes the modeled incremental nitrogen deposition from the Rosemont Copper 

Project, the existing nitrogen deposition that has been modeled for these areas, and the estimated 

critical loads for these ecoregions.

Effect of Visibility and Deposition Impacts on Saguaro National Park

Based on the research shown in table 52, the National Park Service believes that desert and semiarid 

ecosystems in the area, such as those found in Saguaro National Park, may be impacted by current 

levels of nitrogen deposition. The effects described in this section were prepared in conjunction with 

the National Park Service.

Consisting of two districts and up to six distinctive biotic communities, Saguaro National Park 

exhibits a vast array of biodiversity. Recently, the park has documented up to 1,044 different species 

within its boundaries, more than 400 of which, mostly invertebrate animals and nonvascular plants, 

were previously unknown in the park. At least one documented species of bryophyte is currently 

believed to be new to science (National Park Service 2012).

The critical load values described above were developed to protect these diverse, sensitive ecosystem 

components from the harmful effects of nitrogen deposition. As shown in table 52, current nitrogen 

deposition levels are exceeding these minimum critical load values, indicating that herbaceous plants, 

shrubs, lichens, and mycorrhizal fungi communities in Saguaro National Park and the surrounding 

region may be at risk for decreases in biodiversity and shifts in species composition. 

276 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 51. CALPUFF modeling of deposition impacts for each Class I area

Modeled 

Deposition for 

Year 1 of Active 

Mining 

(kilogram per 

hectare per year 

(kg/ha/yr))

Modeled 

Deposition for 

Year 5 or 12 of 

Active Miningd

(kg/ha/yr)

Pollutant Class I Area Proposed Action / 

Phased Tailings Barrel Alternative Barrel TrailAlternative

ScholefieldMcCleary 

Alternative

Proposed Action / 

Phased Tailings

Barrel 

Alternative

Barrel Trail

Alternative

ScholefieldMcCleary 

Alternative

Class I Deposition 

Analysis 

Thresholds

(kg/ha/yr)

Sulfur Saguaro National Park Easta 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.0005 0.005

Saguaro National Park West 0.0014 0.0007 0.0005 0.0005 0.0005 0.0004 0.0004 0.0004

Chiricahua Wilderness Area 0.0002 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001

Chiricahua National Monument 0.0002 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001 0.0001

Galiuro Wilderness Area 0.0010 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002

Superstition Wilderness Area 0.0004 0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001 <0.0001

Nitrogen Saguaro National Park Eastc 0.0518 0.0523 0.0554 0.0627 0.0507 0.0494 0.0540 0.0611 0.005

Saguaro National Park West 0.0188b 0.0186 0.0182 0.0204 0.0161 0.0153 0.0147 0.0189

Chiricahua Wilderness Area 0.0019 0.0017 0.0016 0.0017 0.0019 0.0017 0.0015 0.0018

Chiricahua National Monument 0.0021 0.0017 0.0016 0.0017 0.0022 0.0019 0.0017 0.0019

Galiuro Wilderness Area 0.0069 0.0064 0.0055 0.0063 0.0089 0.0067 0.0060 0.0070

Superstition Wilderness Area 0.0017b 0.0012 0.0013 0.0015 0.0014 0.0013 0.0012 0.0015

Source (except for footnotes a, b, and c): JBR Environmental Consultants Inc.(2012c).

Notes:

Bolded values are values that exceed deposition threshold of 0.005 kg/ha/yr.

a Gaseous deposition of sulfur at Saguaro National Park East was provided in a memorandum titled “AERMOD Gaseous Deposition Results at Saguaro NP East” from JBR Environmental Consultants, Inc. (2013a), dated April 19, 2013.

b Modeled deposition for year 1 of the proposed action/Phased Tailings Alternative for sulfur and nitrogen in Saguaro National Park West and Superstition Wilderness was provided in a memorandum titled “CALPUFF Far-Field Analysis, Revised Impact Tables” from JBR Environmental 

Consultants, Inc. (2013b), dated March 26, 2013.

c Gaseous deposition of nitrogen at Saguaro National Park East was remodeled by the Forest Service after the receipt of the April 19, 2013, memo from JBR Environmental Consultants Inc., and was provided in a memorandum titled “Revised Nitrogen Deposition Modeling for Saguaro East 

National Park,” dated June 11, 2013 (U.S. Forest Service 2013a).

d Year 5 of active mining is evaluated for each scenario except for the Barrel Alternative, which is evaluated at year 12 of active mining.

Final Environmental Impact Statement for the Rosemont Copper Project 277

Chapter 3. Affected Environment and Environmental Consequences

Table 52. Summary of nitrogen deposition impacts for selected Class I areas

Class I Area

Existing Total 

Nitrogen 

Deposition 

(kilogram per 

hectare per year 

(kg/ha/yr))*

Range of 

Incremental 

Nitrogen 

Deposition from 

Rosemont Copper 

Project – All 

Alternatives 

(kg/ha/yr)

Estimated Critical 

Load – Lichens 

(kg/ha/yr)†

Estimated Critical 

Load – Vegetation

Response 

(kg/ha/yr)†

Saguaro National 

Park East 4.1 to 4.7 0.0494 – 0.0627 3.0 3.0 to 8.4

Saguaro National 

Park West 3.4 to 4.4 0.0147 to 0.0204 3.0 3.0 to 8.4

Galiuro Wilderness 3.7 to 4.8 0.0055 to 0.0089 3.0 3.0 to 8.4

* SWCA Environmental Consultants (2013a).

† Allen and Geiser (2011:139); Fenn and Allen (2011). Note that the National Park Service uses the most protective critical 

load threshold for herbaceous plants, shrubs, and lichens, which is 3 kg/ha/yr.

Research indicates that elevated nitrogen deposition favors the invasion of exotic grasses, such as 

buffelgrass (Lyons et al. 2013), which outcompetes native species and increases fine fuel loading in 

arid areas, ultimately increasing fire frequency beyond what these ecosystems were historically 

adapted to (Rao et al. 2010). Many National Park Service sites in this area also contain cultural 

resources that could also be at risk if fire frequency increases. Buffelgrass and the ensuing threat of 

fire are a major concern for Saguaro National Park. There is an estimated 2,000 acres of buffelgrass 

in the park, and buffelgrass is spreading at a rate of up to 35 percent annually. Many scientists believe 

that if this buffelgrass expansion continues, local extinctions of the iconic saguaros and many other 

native species may occur, changing the Sonoran Desert, its wildlife, and Saguaro National Park 

forever (National Park Service 2011). Saguaro National Park has undertaken extensive efforts to 

control and manage buffelgrass invasions and has seen some success. Increased nitrogen deposition 

may undermine these efforts and exacerbate this significant issue. 

Because current estimates indicate that the area is likely at or exceeding nitrogen critical load values,

the National Park Service has expressed significant concern over the additional nitrogen deposition 

predicted to occur in Saguaro National Park from the Rosemont Copper Mine. Nitrogen deposition 

from the Rosemont Copper Mine alone under all action alternatives may exceed the deposition 

analysis threshold by a factor of 3 to 12, depending on the alternative and year of operations. 

The National Park Service has concluded that increases of this magnitude would significantly 

contribute to an adverse environmental effect in Saguaro National Park. 

With respect to visibility, impacts of the magnitude described in this section are a significant concern 

to the National Park Service in general, and are of particular concern in this circumstance considering 

that Saguaro National Park will not meet the regional haze goals under the ADEQ proposed regional 

haze state implementation plan. Regional modeling completed for the regional haze process 

demonstrates that visibility on the 20 percent best visibility days at Saguaro National Park will 

degrade in the future. The goal of the regional haze program is to improve visibility on the 20 percent 

worst days and prevent degradation on the 20 percent best days. Visibility impacts from the 

Rosemont Copper Mine may impede progress toward the national visibility goal.

Final Environmental Impact Statement for the Rosemont Copper Project 279
Chapter 3. Affected Environment and Environmental Consequences

Projected Effects on Climate Change

The CO2 emissions are summarized earlier in this resource section in tables 43 and 44. For the 

proposed action, the premining phase would result in emissions of about 2,800 tons per year. For the 

proposed action, active mining within the perimeter fence would result in emissions averaging about 

175,000 tons per year CO2. An additional 7,200 tons per year CO2 during the active mining phase are 

estimated to be emitted as a result of worker commuter vehicle and equipment/shipment truck traffic. 

Therefore, the average CO2 emissions would equate to approximately 182,000 tons per year CO2 for 

the proposed action during the active mining phase. According to the EPA, the average emissions per 

person in the United States are 20,750 pounds per year (U.S. Environmental Protection Agency

2012c). Therefore, the average CO2 emissions from the proposed action during the active mining 

phase are roughly equivalent to the emissions from approximately 17,500 people in the United States.

Pima County greenhouse gas emissions in 2007 were 17,426,666 tons CO2, so the action alternatives 

would increase emissions of CO2 within the county by approximately 1 percent. Because climate

change results from the cumulative past and present greenhouse gas emissions around the globe, 

emissions from the action alternatives cannot be said to cause any particular effect of climate change.

Cumulative Effects

As outlined in the chapter 3 introduction, cumulative impacts of past and present actions are 

identified and analyzed in the “Affected Environment” part of each resource section, including for 

“Air Quality and Climate Change.” This cumulative effects discussion addresses the cumulative 

impacts of the action alternatives and any applicable reasonably foreseeable actions as identified on 

the Coronado ID team’s list of reasonably foreseeable future actions, provided in the chapter 3 

introduction. Impacts from ongoing and past emission sources to air quality are already accounted for 

in the discussion of background air quality. The following reasonably foreseeable future actions from 

that list were determined to contribute to a cumulative impact to air quality:

• The Forest Service is proposing landscape-level fire management and fuels reduction projects 

in two areas of the Coronado National Forest. 

◦ The Catalina-Rincon FireScape Project, proposed on the Santa Catalina Ranger District 

and adjacent lands in Pima, Pinal, and Cochise Counties, Arizona. Proposed activities 

include vegetation hand thinning, mechanical treatments, firewood harvesting, 

application of prescribed fire, and selective use of herbicides. Annual treatment of 

approximately 50,000 acres is proposed.

◦ The Chiricahua FireScape Project is proposed for the Chiricahua, Dragoon, and Dos 

Cabezas Mountains. The Forest Service, National Park Service, BLM, and USFWS

propose to implement fuels reduction activities on approximately 500,000 acres in 

southeastern Arizona. Activities could include thinning, piling by hand or machine, 

chipping, lopping and scattering, pruning, mastication, grubbing, firewood harvest, and 

use of prescribed fire.

• The Nogales Ranger District proposes to remove hazardous fuels on 2,500 acres in Hog and 

Gardner Canyons on the Nogales Ranger District.

• The Santa Catalina Ranger District proposes to reduce hazardous fuels by using thinning, 

mechanical treatments, and prescribed fire on approximately 150 acres. The Loma Linda 

Hazardous Fuels Reduction Project would be located south of Summerhaven, Arizona.

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• The Forest Service proposes to approve two MPOs for the Moore and Moore No. 4 Placer 

Mine and the Dice No. 8 Placer Mine, both located 2 miles southwest of Washington/

Duquesne, Arizona. Actions for each project would include trenching and washing of 

excavated material in a 1- to 2-acre area for a maximum of 1 year.

• The Forest Service proposes to approve an MPO for Javelina Minerals Exploration for 

mineral exploration drilling of eight holes in an area located approximately 3 miles southeast 

of Patagonia, Arizona. Activities would occur for a maximum of 1 year.

• The Forest Service proposes to approve an MPO to OZ Exploration Proprietary Ltd. for 

mineral exploration drilling in the East Paymaster and Guajolote Flats areas in the Patagonia 

Mountains. Activities would occur for a maximum of 1 year.

• The Santa Catalina District proposes to authorize drilling to explore for minerals

approximately 10 miles southeast of Summerhaven, Arizona. The Korn Kob Minerals

Exploration CE project involves short-term (1 year or less) mineral, energy, or geophysical 

investigations and their incidental support activities, which may require cross-country travel 

by vehicles and equipment, construction of less than 1 mile of low-standard road, or use and 

minor repair of existing roads.

• The BLM proposes to approve an MPO to expand the Andrada Mine limestone quarry in the 

Davidson Canyon drainage system north and northeast of the Santa Rita Mountains. 

The Andrada Mine is located approximately 4 miles from the Tucson, Arizona, city limits 

and 1 mile from the Vail, Arizona, city limits.

• In late 2009, Freeport-McMoRan bought 8,900 acres of the long-closed Twin Buttes Mine 

site, near Sahuarita. Required permits for reopening the mine have not been issued to date, 

but it is reasonable to assume that this mine could be reopened at some point in the future.

• The former Oracle Ridge Mine, located on private property within the Santa Catalina Ranger 

District, is an inactive, small-scale underground copper mine in the permitting and detail 

design stage for resuming operations. The proposed mine operation would use the same 

surface footprint as previous operations to the extent possible. 

• The Forest Service proposes to issue a special use permit to Oracle Ridge Mining, LLC, 

authorizing the use of forest roads, a parking area, and a utility corridor during operation of 

the existing Oracle Ridge Mine, which is located on private land on the Santa Catalina 

Ranger District.

• The Forest Service proposes to approve an MPO for minerals exploration drilling on the 

Helix Margarita property for a maximum of 1 year. This property is located near Arivaca in 

Santa Cruz County, Arizona, about 75 miles south of Tucson, Arizona.

• The Forest Service proposes to approve an MPO for Arizona Minerals Inc. for proposed 

minerals exploration (referred to as Hermosa minerals exploration) on the Sierra Vista 

Ranger District, approximately 6 miles southeast of Patagonia, Arizona. The proposal 

involves drilling for core samples and water monitoring wells. Drilling would occur for a 

maximum of 2 years, with monitoring to continue for up to 10 years.

• The Forest Service proposes to approve an MPO for Regal Resources for minerals

exploration drilling of five holes to obtain evidence of mineralization over a 2-acre area for a 

maximum of 1 year. The Patagonia/Sunnyside minerals exploration project is located near 

Nogales, Arizona, about 45 miles south of Tucson, Arizona.

• Potential individual developments are proposed within the Sahuarita area, including 

development of the Farmers Investment Company property (known as Sahuarita Farms), the 

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Chapter 3. Affected Environment and Environmental Consequences

Rancho Sahuarita development, the Quail Creek development, and the Madera Highlands 

development.

• The Forest Service proposes to add, decommission, close, or change designation of roads in 

the NFSR database and prohibit off-road motorized travel for dispersed camping in certain 

areas on the Nogales Ranger District.

• The Sierra Vista and Santa Catalina Ranger Districts are proposing to make changes to their 

District motorized travel systems. Actions could include additions to the NFSR database, 

decommissioning, change in maintenance level, and other actions to meet administrative and 

user needs.

Sufficient data are not currently available to quantify potential air pollutant emission sources from the 

foreseeable actions listed above. Therefore, cumulative impacts from the proposed Rosemont Copper 

Project and the foreseeable actions are addressed qualitatively. These reasonably foreseeable actions

could further degrade air quality in ways similar to the action alternatives, through emissions from 

surface disturbance, tailpipe and fugitive dust emissions from mobile sources, and point-source 

emissions from industrial activities. 

The listed exploration projects are short term, use motorized equipment, and disturb small amounts of 

ground. While they would contribute greenhouse gases and dust, overall emissions would be 

relatively small, compared with other development activities.

The developments are commercial and residential developments that would disturb areas that are 

currently vegetated, potentially increasing dust production. Use of mechanized equipment would 

produce greenhouse gases. Population increases would lead to increased greenhouse gases and 

emissions from motorized sources.

The potential mining operations in Davidson Canyon, as well as the Twin Buttes mine, would require 

air permits from either ADEQ or Pima County and would contribute air pollutants similar to those 

from other mining operations, including Rosemont Copper.

Fuel thinning projects typically can include prescribed burning as well as burning of slash piles.

These activities would contribute to degradation of air quality for short periods of time due to smoke 

emissions. State and Federal agencies typically coordinate such events with the local air quality 

regulators and only burn when conditions allow for good smoke dispersion. If modeling predicts 

weather conditions that would result in conditions where air quality standards would be exceeded, the 

land management agencies typically wait to carry out burning projects until more favorable 

conditions exist.

The closure of roads would tend to reduce dust emissions from traffic and recreation activities, while 

addition of new roads would tend to increase dust emissions. 

Cumulatively, these foreseeable actions could combine with predicted impacts from the Rosemont 

Copper Project action alternatives to potentially result in the following: 

• Further additions to the total emissions within Pima County, which cumulatively could lead 

to an exceedance of the PM10 and O3 NAAQS in the Tucson and Saguaro National Park East 

areas and to the risk of “nonattainment” designation of these areas for PM10 and/or O3;

• Further increases to concentrations of other air pollutants in the Tucson and Saguaro National 

Park areas; and

282 Final Environmental Impact Statement for the Rosemont Copper Project
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• Further degradation of visibility in the Saguaro National Park area.

Climate Change

In addition, the effects of climate change on the project area are also considered a cumulative effect, 

as they result from the cumulative emissions of greenhouse gases across the globe.

Current research (Southwestern Region Climate Change and Forest Planning Work Group 2010)

suggests that climate change will have several effects on the project area and throughout southeast 

Arizona. Temperature levels in the Southwest are anticipated to rise as a result of global climate 

change. By the end of the 21st century, temperatures could rise by 5 °F to 8 °F. Overall precipitation 

levels in the Southwest are anticipated to fall by as much as 10 percent as a result of global climate 

change. The effects of these changes on the project are expected to be an increased risk of drought 

and wildfire.

All projected effects of climate change on the project area, including temperature, precipitation, 

drought, wildfire, and flooding effects, are anticipated under all alternatives (including the no action 

alternative). All alternatives except the no action alternative would be net contributors of greenhouse 

gas emissions, but these emissions cannot be tied to the climate change effects described above.

Mitigation Effectiveness 

Mitigation associated with air quality would be accomplished through facility design and permit 

requirement and includes control measures for site-specific point, mobile, and fugitive sources.

Unless noted otherwise, these mitigation measures would apply to all action alternatives.

Mitigation and Monitoring – Forest Service

• Growth media salvage and application (FS-SR-01). In order to support reclamation

activities, soil and other growth media would be salvaged, stored, and applied to the surface 

of the perimeter waste rock buttress and waste rock and tailings facilities in order to facilitate 

revegetation and minimize bare ground subject to wind erosion.

• Revegetation of disturbed areas with native species (FS-SR-02). Reclamation efforts 

would include revegetation of native grasses, forbs, shrubs, and trees on areas disturbed by 

mining and mine related activities and minimize bare ground subject to wind erosion. 

Revegetation would include detection and treatment of invasive weed species.

• Concurrent placement of perimeter buttress (FS-SR-03). Placement of the perimeter 

buttress allows for reclamation activities to take place earlier, concurrent with mine 

operations, minimizing bare ground subject to wind erosion.

• Limiting ground-disturbing activities between perimeter fence and security fence

(FS-CR-05). Any additional soil disturbance between the security fence and perimeter fence 

would be limited, thus reducing dust emissions.

Mitigation and Monitoring – Other Regulatory and Permitting Agencies

• Processing and placement of tailings to reduce water content and overall footprint

(OA-GW-05). The use of dry-stack tailings instead of traditional slurry tailings would allow

for a much smaller footprint for the tailings facility, minimizing soil disturbance. The 

characteristics of placing material other than in a slurry is also expected to minimize the 

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Chapter 3. Affected Environment and Environmental Consequences

accumulation of fine-grained sediments on top of the tailings, which would minimize the 

potential for wind erosion.

• Paving of mine roads (OA-AQ-01). Paving of certain roads within the mine is required 

under the air quality permits and would also serve to reduce the potential for erosion of soil

from disturbed road areas.

• Dust control for unpaved roads (OA-AQ-02). This mitigation contains a number of actions 

that are designed to control at least 90 percent of PM10 emissions from the unpaved road 

network. These actions include application and reapplication of chemical dust suppressant 

and watering as needed.

• Dust control for open areas and storage piles (OA-AQ-03). This mitigation contains a 

number of actions that are designed to control fugitive dust emissions from open areas and 

storage stockpiles. These activities include application and reapplication of chemical dust 

suppressant and water. Open areas and storage piles that are not actively used would be 

controlled by applying sufficient chemical dust suppressant and/or water to develop and 

maintain a visible crust. Other means such as use of an adhesive soil stabilizer, paving 

covering, landscaping, detouring, or other acceptable means of dust control may be used.

• Control of particulate emissions from lime slaking process (OA-AQ-04). This mitigation

includes the refinement of the design of the lime slaking system, including the addition of a 

lime slaker scrubber.

• Control of particulate emissions from major metallic mineral processing operations

(OA-AQ-05). This mitigation includes the installation, operation, and maintenance of 

cartridge dust filters and other measures to control particulate matter emissions from major 

metallic mineral processing operations.

• Use of covers on mix tanks and settlers to reduce emissions of VOCs (OA-AQ-06). This 

mitigation involves the installation of covers on specific facilities that could otherwise result 

in VOC emissions.

• Use of drip emitters on heap leach pad to reduce emissions (OA-AQ-07). This mitigation

applies to all alternatives except the Barrel Alternative and involves the installation and use 

of drip emitters to apply solution to the heap leach to minimize airborne aerosols. 

• Reduction in air emissions from diesel engines associated with stationary equipment

(OA-AQ-08). This mitigation requires the use of low-sulfur diesel for all stationary 

equipment.

• Reduction in air emissions from diesel engines associated with mobile sources

(OA-AQ-09). This mitigation requires the use of newer engine designs on haulage equipment 

and on select mobile sources. This includes the use of Tier 4 EPA compliant equipment for 

emission standards on selected nonroad engines (all except haul trucks and the 2,000 

horsepower front-end loaders); the use of Tier 2 diesel engines for haul trucks; and the use of 

Tier 4 engines for large haulage trucks and support equipment purchased after 2014. It should 

be noted that EPA standards have been changing based on what is technologically available 

and on equipment production schedules. Rosemont Copper would purchase equipment that 

meets EPA standards; the dates may change based on EPA requirements.

• Air pollution control requirements for electrowinning process (OA-AQ-10). This 

mitigation applies to all alternatives except the Barrel Alternative and requires several actions 

and methods to control potential emissions in the electrowinning process, including 

installation and use of scrubbers to control sulfuric acid emissions; dilution of sulfuric acid 

and use of drip system to minimize mist emissions; installation, use, and maintenance of 

284 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

covers to control acid emissions; and use of foam, dispersion/poly balls, surfactants, or other 

effective means of controlling sulfuric acid emissions. 

• Opacity monitoring (OA-AQ-11). This monitoring is required under the air quality permits 

and describes emission limitations and established monitoring, reporting, and recordkeeping 

requirements regarding opacity.

Mitigation and Monitoring – Rosemont Copper

• Limit travel on utility maintenance road (RC-TA-03). This mitigation requires that travel 

on the utility maintenance road be limited to necessary travel only for maintenance activities 

and limits road maintenance to only that necessary for operations.

• Transporting employees in natural gas powered buses to reduce NOx emissions

(RC-AQ-01). This mitigation implements a carpooling plan in which the majority of 

employees will be transported to and from the mine site in company owned or leased buses 

that are powered by natural gas.

Conclusion of Mitigation Effectiveness

The above mitigation measures are required either under the air quality permit or as a design feature 

of the facility. Much greater detail on the exact requirements is contained in the air quality permit 

itself. Mitigation effectiveness has been analyzed below for point sources, mobile sources, and 

fugitive emissions.

Point Sources

Point-source pollution control equipment would be used on all process equipment with significant 

emissions potential (under Pima County Code 17.04.304(A)(212), “significant” means in terms of the 

potential of a source to emit more than 15 tons per year of PM10). 

• Water sprays would be used to control dust emissions at the primary crusher dump pocket, 

while cartridge filter dust collectors would be used in the following areas and on the 

following emission units: primary crushing building, crushed-ore stockpile building and 

tunnels, reclaim tunnel, pebble crusher, copper concentrate area (two dust collectors), and the 

molybdenum dust collector/electrostatic precipitator. Chutes would be required at conveyorto-conveyor transfer points to further minimize drop point emissions. This measure would 

reduce emissions and potential impacts to air quality.

• The coarse ore stockpile and concentrate loadout areas would be contained within the 

enclosed stockpile building. The enclosed building would include a four-walled structure, 

covered by a roof, and access to the interior controlled by a movable door or flexible strip 

curtains. This measure would reduce emissions and potential impacts to air quality.

• The coarse ore stockpile dome pertains to all action alternatives except the proposed action 

and would reduce dust generation and potential impacts to air quality.

• To avoid aerosol losses to the wind, emitters (similar to drip irrigation) would be used to 

apply acid leaching solution to the heap. This applies to all action alternatives except the 

Barrel Alternative. This measure would reduce emissions and potential impacts to air quality. 

Processes with low emissions potential would be controlled via containment (i.e., water 

sprays or physical enclosures), such as the use of water sprays to control particulate

emissions resulting from the unloading of concentrate ore to the primary crusher dump 

hopper. This measure would reduce emissions and potential impacts to air quality.

Final Environmental Impact Statement for the Rosemont Copper Project 285
Chapter 3. Affected Environment and Environmental Consequences

• Other point-source emission mitigation measures would include the use covers to control 

VOC and hazardous air pollutant emissions resulting from the mix tanks and settlers used in 

the solvent extraction system, the use of low-sulfur diesel fuel onsite for all stationary 

equipment to mitigate SO2 emissions, and compliance with materials safety data sheet 

specified procedures to reduce the impacts of chemical releases into the atmosphere. This 

measure would reduce emissions and potential impacts to air quality.

Mobile Sources

Project mobile source emissions (tailpipe emissions) would be mitigated through the use of newer 

engine designs in project vehicles, which are subject to stricter Federal regulation and result in lower 

emissions.

• The use of Tier 4 diesel engines on selected nonroad engines (all except haul trucks and the 

2,000 horsepower front-end loaders) would be required. With the exception of six haul 

trucks, the use of Tier 2 diesel engines would be required for haul trucks prior to 2014; six of 

the haul trucks purchased before 2014 and all other haul trucks purchased after 2014 would 

require diesel engines meeting Tier 4 standards. Rosemont Copper would ensure that 

construction equipment is properly maintained at all times, does not unnecessarily idle, and is 

tuned to manufacturers’ specifications. This measure would reduce emissions and potential 

impacts to air quality.

• Mobile source emissions would be further reduced by requiring a delivery schedule for 

project truck traffic to minimize idling time on SR 83 during peak traffic hours. Additionally, 

the primary access road would be placed so that it avoids traffic impacts on local routes and 

with the intersection arranged to provide through-traffic patterns using turn lanes for all 

action alternatives. This measure would reduce emissions and potential impacts to air quality.

Fugitive Sources

• The primary access road and small vehicle plant facility roads would be paved to reduce 

fugitive dust emissions. This measure would reduce emissions and potential impacts to air 

quality.

• Dust control mitigation measures would be used on access, haul, service, and maintenance 

roads during the construction, operation, and closure of the mine. Mine haul roads would be 

constructed using material excavated within the open pit, which may be crushed and screened 

to produce a smooth surface. Haul truck speeds would not exceed 35 miles per hour and 

would usually be less than 25 miles per hour on ramp gradients of 10 percent or more. Dust 

would be suppressed by wetting the road surface using a fleet of appropriately sized water 

trucks with up to 30,000-gallon tank capacities. The roads at the project site would be 

watered sufficiently to achieve at least 90 percent control efficiency of particulate matter

(PM2.5 and PM10). Physical or chemical dust control agents, organic or inorganic binders, 

and/or stabilizing polymers would also be used as appropriate for additional dust mitigation.

This measure would reduce emissions and potential impacts to air quality.

• The project would use a variety of operational and engineering controls for controlling 

fugitive dust associated with the tailings. At least 180 days prior to the start of deposition of 

dry tailings, Rosemont Copper would need to submit a dry tailings management plan for 

approval by the director of ADEQ and would be required to comply with the plan. These dust 

control measures would likely consist of the following controls, as stated in the preliminary 

MPO (WestLand Resources Inc. 2007a):

286 Final Environmental Impact Statement for the Rosemont Copper Project
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◦ Buttresses constructed of waste rock material would be used to break up air flow and 

reduce exposure of large areas of tailings to windy conditions;

◦ The moisture content of the tailings would be sufficient to ensure that dust is not 

generated on the conveyor belts or during the stacking operations;

◦ Tailings would be stacked using a tripper arrangement on mobile conveyors. This method 

would allow placement of the tailings in an irregular shape to break up air flow patterns. 

The tripper would also reduce the need for wheeled vehicles to drive across the tailings;

◦ Materials from the grinders would be such that 80 percent of the material would pass 150 

mesh (0.0041 inch), rather than the conventional tailings size of 80 percent passing 250 

to 325 mesh (0.0025 to 0.0017 inch). The larger size of the material would reduce the 

likelihood of the tailings’ becoming airborne; and

◦ Application of a binder material (such as Enviro Tac) to the surface of the tailings, 

agglomeration chemical to lines within the conveyor system to make larger overall grain 

size in the placed tailings, or the use of water to suppress dust emissions.

• Additionally, the following dust control measures for the mineral tailings are required under 

the air quality permit:

◦ Method 9 opacity monitoring twice daily;

◦ Physical inspection of tailings for “easily erodible areas” at least once daily when winds 

speeds are at or above 15 miles per hour, or gusts are at or above 20 miles per hour; and

◦ Annual effectiveness review of the tailings management plan.

All dust control measures would reduce emissions and potential impacts to air quality.

Other

The air quality permit requires the installation and operation of continuous ambient monitors of PM10

and onsite meteorological data beginning at least 90 days prior to the start of mine operations. 

A protocol and monitoring plan would be required to be submitted within 180 days of the issuance of 

the air quality permit.

At the time of publication of the DEIS, the air quality modeling did not incorporate many of these 

mitigation measures, and as a result, none of the alternatives were modeled to meet NAAQS at the 

perimeter fence. These mitigation measures have been developed both through coordination with the 

Coronado, as well as through the air quality permitting process, and are expected to be effective in 

reducing potential air quality impacts. Revised modeling indicated that the Barrel Alternative would 

meet NAAQS at the perimeter fence. There has been a reduction in emissions of coarse dust particles 

by approximately 47 tons and of fine particulates by 43 tons, compared with the original Pima 

County air quality permit application submitted by Rosemont Copper.

The voluntary carpooling plan is estimated to offset or reduce NOx emissions by approximately 1,200 

pounds per year.

Effects of Amending the Coronado Forest Plan

The effects on air quality and climate change from amending the Coronado forest plan are described 

under “Direct and Indirect Effects” above. The current forest plan does not contain management area 

standards and guidelines specifically pertaining to air quality or climate change for management areas 

1, 4, or 7A, nor would there be specific standards for new management area 16. 

Final Environmental Impact Statement for the Rosemont Copper Project 287
Chapter 3. Affected Environment and Environmental Consequences

However, new management area 16 does contain a standard and guideline under “Minerals

Management” that states,

Mineral exploration and extraction activities will be allowed within the framework of 

applicable laws and regulations, including environmental laws and regulations designed to 

mitigate the impacts of mining activities. Emphasis will be on gaining cooperation and 

control through the use of operating plans and bonds for reclamation to protect and restore 

NFS surface resources, where practicable.

Approval of the forest plan amendment would allow actions that would impact air quality in the area. 

Four of the action alternatives considered would not meet NAAQs and therefore would not be 

protective of NFS surface resources beyond the perimeter fenceline (proposed action and Phased 

Tailings, Barrel Trail, and Scholefield-McCleary Alternatives). These alternatives cannot be selected 

for implementation in their current state. The remaining alternative (Barrel Alternative) would meet 

NAAQS and therefore be protective of NFS surface resources beyond the perimeter fenceline. 

Ultimately, if an action alternative is selected, it would be protective of NFS surface resources and 

thereby comply with this standard for management area 16 regarding air quality.

A description of the effects of climate change is included in each resource section in this chapter of 

the FEIS.

Groundwater Quantity

Introduction

The proposed mine involves potential impacts to groundwater quantity in two groundwater basins 

(figure 43). The mine water supply is proposed to be pumped from wells located on private land in 

the Santa Cruz Valley near the town of Sahuarita in the Upper Santa Cruz Subbasin of the Tucson 

Active Management Area. The mine pit and mine facilities would be located in the Davidson Canyon 

drainage east of the Santa Rita Mountains, which is adjacent to the Cienega Creek Basin. In addition 

to the active removal of groundwater from the mine pit during active mining, the presence of the 

mine pit would have a long-term impact on groundwater hydrology in the vicinity of the mine even 

after final reclamation and closure.

Changes from the Draft Environmental Impact Statement

Concerns raised during public comment on the DEIS primarily focused on several key issues, 

including specific technical aspects of the groundwater modeling, the possibility that the overall 

hydrogeologic framework of the area had been misinterpreted, and the ability of the models to assess 

impacts on springs and waters such as Davidson Canyon, Cienega Creek, and Empire Gulch.

One common theme in the public comments received on the DEIS involved the organization of the 

document. It was pointed out that the discussion of seeps, springs, and riparian areas was spread 

throughout the groundwater, surface water, and biological resource sections, making it difficult to 

understand potential impacts. To address this concern, the analysis of impacts on riparian areas and 

springs has been moved from the “Groundwater Quantity” resource section to the new “Seeps, 

Springs, and Riparian Areas” resource section.

288 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 43. Analysis area for groundwater quantity

Final Environmental Impact Statement for the Rosemont Copper Project 289
Chapter 3. Affected Environment and Environmental Consequences

The groundwater modeling approach described in the DEIS was extensive, incorporating multiple 

models and independent peer review. However, in response to public comments as well as concerns 

from cooperating agencies and Forest Service specialists, the Coronado undertook additional 

technical investigations in order to ensure that the models were reasonable with respect to their

prediction of impacts. These investigations included the following: posing specific technical 

questions to Coronado contractors (Ugorets, Cope, and Sieber 2012); convening a panel of experts to 

discuss various groundwater issues directly and in person with Federal cooperating agencies, Forest 

Service resource specialists and the Forest Service decision maker (Garrett 2012h); and requesting 

and assessing additional information on groundwater boundary conditions from Rosemont Copper 

(Rosemont Copper Company 2012g; Ugorets, Cope, and Sieber 2012). A final groundwater panel 

meeting was held in October 2012 that consisted of Coronado-contracted groundwater modeling 

specialists, Forest Service resource specialists, the Forest Service decision maker, Rosemont 

Copper’s groundwater modelers, and Federal cooperating agencies (Garrett 2012g). The purpose of 

this meeting was specifically to review additional sensitivity analyses conducted by Rosemont 

Copper concerning boundary conditions and more generally to determine whether the models are 

appropriate for use for the FEIS.

Overall, the Forest Service specialists, their contracted experts, and the Forest Service decision maker

found that the models used in the FEIS are valid, reasonable, and acceptable for predicting impacts 

related to this project. However, a common opinion among experts is that the site-specific 

groundwater models—or any groundwater models—do not have the ability to predict impacts on

distant waters such as Cienega Creek, Davidson Canyon, and Gardner Canyon, where these impacts 

are the result of small groundwater changes (in some cases, less than 1 foot of drawdown) at remote 

periods in the future (hundreds or even thousands of years from now). Therefore, while the results of 

the models are still presented for these distant waters and long time periods, the uncertainty involved 

is more explicitly described by giving a range of impacts based on the results of the model sensitivity 

analysis (see tables 60 through 64 and figure 59 in the “Predicted Change in Groundwater Levels as a 

Result of the Mine Pit” part of this resource section).

Another concern expressed by cooperating agencies was the need for more detail on the magnitude 

and timing of impacts on various water sources (residences, springs, and streams). The Coronado

requested and received more detail on the timing of impacts, and these results are presented in the 

FEIS (see table 65 in the “Predicted Change in Groundwater Levels as a Result of the Mine Pit” part 

of this resource section).

A series of comments was made concerning the overall hydrogeologic framework of the area, most 

notably the possibility that a relatively direct hydrologic connection exists between the proposed 

mine pit and distant waters such as Cienega Creek. In the comments, this connection was variously 

hypothesized as being either related to faults or fractures not discovered or modeled or as being 

related to karst features in Cretaceous-age sedimentary rocks that underlie the Cienega Basin. In order 

to further investigate this question, the Coronado asked their consulting geological experts to prepare 

an analysis that answered specific questions. The Coronado then conducted two meetings with 

experts from cooperating agencies to discuss this issue. This investigation is fully detailed in the 

“Geology, Minerals, and Paleontology” resource section. With respect to the groundwater analysis, 

the Coronado determined that the hydrogeologic framework that forms the basis for the models is 

reasonable and supported by available evidence and that no evidence suggests that a regionally 

connected karst system exists that would form a direct connection between the open mine pit and 

distant waters such as Cienega Creek.

290 Final Environmental Impact Statement for the Rosemont Copper Project
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Another major concern raised during public comment was the absence of predicted impacts to 

individual wells. As noted in the DEIS, for most wells, there is a lack of the information that would 

be required to predict impacts. Several commenters refuted this statement, pointing out available 

databases and data sources. The Coronado is aware of these data sources, had reviewed them for the 

DEIS, and had found (and still finds) that the information available for most wells remains 

insufficient for assessing impacts to individual wells (see the “Analysis Methodology, Assumptions, 

Uncertain and Unknown Information” part of this section). However, additional details have been 

added about the progression of impacts to all wells over time and space, to give a better picture of 

potential impacts that could occur to individual wells (see table 58 in the “Predicted Change in 

Groundwater Levels and Geographic Area of Impact” part of this resource section, and table 66 in the 

“Effect on Well Owners” part of this resource section). Commenters also raised the issue of impacts 

to water resources relied upon by colonias. A colonia is a rural community located in the border 

region of Arizona that generally lacks potable water supply, adequate sewage systems, and decent, 

safe, and sanitary housing. There are four colonias identified within the general area of pumping, 

including one identified as “Sahuarita Town” that encompasses most of the Town of Sahuarita.

The impacts to the water supply of residents within colonias would be identical to those described for 

individual well owners in general. 

The specific concern raised with colonias is the general lack of financial resources to respond to a 

disruption in their water supply. The economic impacts from the potential disruption of water supply, 

as well as an analysis of environmental justice impacts, is included in the “Socioeconomics and 

Environmental Justice” resource section in this chapter.

Additional mitigation measures have been incorporated into the document and assessed for 

effectiveness at reducing impacts (see the “Mitigation Effectiveness” part of this resource section, as 

well as appendix B).

Monitoring has been incorporated into the mitigation and monitoring plan (see appendix B) in order 

to address uncertainty associated with groundwater modeling (see the “Mitigation Effectiveness” and 

“Monitoring Intended to Assess Groundwater Modeling” parts of this resource section).

Issues, Cause and Effect Relationships of Concern

Cause and Effect Relationships

Pumping of mine supply water in the Upper Santa Cruz Subbasin would remove water from the 

regional aquifer and would lower groundwater levels, which could cause reduced groundwater 

availability to existing wells and water users. In the Davidson Canyon/Cienega Basin, development 

of the mine pit would intercept groundwater from fractures in rock formations in the immediate 

vicinity of the mine, as well as from the adjacent basin fill. Together, the fractured rock and basin fill 

form the regional aquifer of that groundwater basin (see figure 43). During active mining, water from 

the mine pit would be actively pumped, which would cause drawdown in the regional aquifer. This 

drawdown would cause impacts on wells, springs, streams, and riparian areas. After final reclamation

and closure, a mine pit lake would form that would lose water through evaporation. The water lost to 

evaporation would be partially offset by groundwater flowing into the mine pit lake, perpetuating the 

aquifer drawdown caused by the mine pit dewatering. 

Final Environmental Impact Statement for the Rosemont Copper Project 291
Chapter 3. Affected Environment and Environmental Consequences

Identified Significant Issues

Several significant issues were identified with respect to groundwater resources, as discussed in 

chapter 1. Issues 3A and 3B relate directly to groundwater availability. Groundwater also is related to 

Issue 3D, Surface Water Availability, for the effect groundwater drawdown can have on surface water, 

riparian areas, and springs. This topic is now covered in the new “Seeps, Springs, and Riparian

Areas” section of the FEIS. 

Issue 3: Impact on Water Resources

This group of issues relates to the effects during premining, active mining, final reclamation and 

closure, and postmining phases on the quality and quantity of water for beneficial uses, wells, and 

stock watering. 

Issue 3A: East Side Groundwater Availability

The proposed open-pit mine may reduce groundwater availability to private and public wells in the 

vicinity of the open pit. Household water availability could potentially be reduced. 

Issue 3A Factors for Alternative Comparison

1. Direction and feet of change in water table level, including annual average, range, and rate, 

compared with background 

2. Impairment of mountain-front groundwater recharge function

3. Geographic extent in which water resources may be impacted

4. Duration of the effect (in years)

5. Comparison of mine pit water loss by evaporation with overall basin water balance

6. Potential reduction in subsurface groundwater outflow from Davidson Canyon to Cienega 

Creek

7. Approximate number of wells within the geographic extent of the impact

Issue 3B: West Side Groundwater Availability

Water needed to run the mine facility could reduce groundwater availability to private and public 

wells in the Santa Cruz Valley, specifically the communities of Sahuarita and Green Valley, Arizona. 

Household water availability could potentially be reduced. 

Issue 3B Factors for Alternative Comparison

1. Water needed for operations from the Santa Cruz Valley and comparison with other water 

uses and basin water balance, measured in acre-feet

2. Direction and feet of change in water table level, including annual average and range and 

rate, compared with background

3. Geographic extent in which water resources may be impacted

4. Duration of the effect (in years)

5. Potential for subsidence to occur as a result of groundwater withdrawal

6. Approximate number of wells within the geographic extent of the impact

292 Final Environmental Impact Statement for the Rosemont Copper Project
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Analysis Methodology, Assumptions, 

Uncertain and Unknown Information 

Temporal Bounds of Analysis and Analysis Area 

The temporal bounds of analysis for the mine water supply well field in the Upper Santa Cruz 

Subbasin has been selected to extend to 140 years after initiation of pumping in order to allow the 

cone of depression that would result from 20 years of groundwater pumping to stabilize. While 20 

years represents the maximum amount of drawdown in the vicinity of the Rosemont Copper water 

supply wells, the lateral extent of the cone of depression would continue to expand after pumping 

stopped. The temporal bounds of analysis for the area in the Davidson Canyon/Cienega Basin extends 

to 1,000 years after completion of mining. Specific snapshots of groundwater conditions for the 

analysis area are considered at the end of active mining and 20, 50, 150, and 1,000 years after final 

reclamation and closure. It is recognized that predicting conditions 1,000 years in the future is 

speculative at best, as is discussed in greater detail later in this section; however, this long time frame

was selected in order to allow the bedrock aquifer impacted by the mine pit to come close to 

equilibrium. The analysis area shown in figure 43 was selected to encompass all areas within which 

groundwater could be affected by either the mining water supply well field near Sahuarita or the mine 

pit; the analysis area encompasses the areas included in the groundwater models conducted for the 

analysis (approximately 1,060 square miles). 

The connected actions that are described in chapter 2 include the use of mechanized equipment to 

reroute an electrical transmission line within the project area; construct an electrical distribution line, 

water supply line and associated maintenance road within the utility corridor; reroute the Arizona 

National Scenic Trail and construct ancillary facilities; and implement SR 83 highway maintenance 

improvements required by the ADOT encroachment permit. These activities have been considered in 

the description of impacts common to all action alternatives for the premining phase, when they 

would be constructed; and for the final reclamation and closure phase, when the water line and 

electrical distribution line would be removed. 

Methodology for Impacts Analysis

The measurement factors for the issues are based on expected changes in the groundwater flow 

regime, including groundwater levels, flow direction, and recharge. In order to determine the 

predicted impacts on groundwater levels in the Upper Santa Cruz Subbasin, results from a

groundwater flow model were used. In order to determine the predicted impacts on groundwater

levels in the Davidson Canyon/Cienega Basin, results from three other groundwater flow models 

were used to provide a range of possible impacts. The groundwater models used in this analysis are 

discussed later in this methodology section.

As previously mentioned, the Coronado reviewed available data sources and determined that 

insufficient information was available to assess impacts on individual wells. In order to fully predict 

the impacts to an individual well, the following information is needed: well depth, perforated interval, 

current water level, pump setting, and the response by water levels to pumping conditions. Of these 

characteristics, well depth and perforated interval are commonly available through public databases. 

However, current water level, pump settings, and pumping water levels are rarely reported or 

regularly updated. More importantly, the groundwater models are built to predict impacts in the 

regional aquifer; for many individual wells, the connection to this aquifer is not known, as these wells 

often intersect small pockets of alluvium or localized fracture systems. The geological information 

needed to assess this connection for an individual well is largely unavailable, although driller logs are 

Final Environmental Impact Statement for the Rosemont Copper Project 293
Chapter 3. Affected Environment and Environmental Consequences

available for some wells detailing the hydrologic units encountered during drilling. The Coronado

remains unable to assess impacts to individual wells; therefore, the analysis essentially remains as it 

was presented in the DEIS, although it is presented with greater details of the progression of potential 

impacts in space and time.

Thresholds of Concern

The threshold of concern with respect to impacts to water wells in the Santa Cruz Valley is a drop in 

water levels greater than 10 feet over any period. Note that under Arizona water laws, there is no 

regulatory mechanism that prescribes such a threshold. However, the 10-foot threshold is commonly 

used in other nonapplicable Arizona regulatory programs, such as well spacing requirements (AAC 

R12-15-1302), although the well spacing program only considers drawdown over the first 5 years of 

pumping.

In the DEIS, the 5-foot contour of the expected decrease in groundwater levels was used as the 

threshold for assessing impacts to wells and springs. Several public comments suggested that this 

drawdown was too large to use as a threshold for wells and springs and that it should be 1 foot, or 

even 0 feet. The Coronado considered the reasonableness of the selected 5-foot drawdown threshold 

(Garrett 2012h; Ugorets, Cope, and Hoag 2012). There are two primary reasons for selecting this 

threshold: the predictive accuracy of the models used, and the natural variability of groundwater 

levels. 

The models used to predict impacts to groundwater availability have a level of uncertainty that must 

be considered when interpreting the model results. While the models can mathematically predict 

groundwater drawdown to thousandths of a foot, in reality this level or refinement is meaningless. 

The models were designed for the purpose of predicting the inflow of groundwater to the mine pit

and the general drawdown that would occur in the regional aquifer; however, the farther the 

predictions are in terms of distance from the mine pit and the farther out in time the predictions occur, 

the less certain they become. The groundwater modeling experts contracted by the Coronado 

determined that the reasonable limit of certainty of the groundwater models is the 5- to 10-foot 

drawdown contour (Ugorets, Cope, and Hoag 2012). Within this contour, the groundwater models 

would be able to reasonably predict changes to wells, springs, and streams. Changes below this 

threshold are beyond the capabilities of the models to accurately predict. 

Public comments correctly indicated that impacts to springs and intermittent or perennial stream

reaches could occur as a result of very small changes in groundwater level. This suggests that 

although these small levels of drawdown are beyond our ability to predict with numerical models, 

they could still cause impacts that need to be disclosed in this FEIS. However, the 5-foot threshold is 

also pertinent for a second reason, which is the natural seasonal variability of groundwater. Available 

data suggest that groundwater levels in the area naturally vary from year to year and from season to 

season. In a well in lower Davidson Canyon, groundwater levels have been observed to fluctuate by 

more than 10 feet in a single year (Pima Association of Governments Watershed Planning 2005). 

Two stock wells along Empire Gulch have been monitored by the ADWR for three to four decades, 

and the results show that water levels have varied between 4 and 5 feet. Similar stock wells along 

Cienega Creek show variation between 3 and 5 feet (SWCA Environmental Consultants 2012c). 

Two wells immediately adjacent to lower Cienega Creek were monitored between 2007 and 2009 by 

the Pima Association of Governments and exhibited a fluctuation in water level of up to 5 feet 

seasonally (Pima Association of Governments 2010b). Montgomery and Associates conducted a 

similar analysis on a much greater number of wells located throughout the basin (not just near 

294 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

streams) and found that the average short-term fluctuation in groundwater levels was 7.1 feet and that 

the long-term fluctuation in groundwater levels was 19.7 feet (Davis 2010).

While drawdown of less than 5 feet could cause impacts to springs and surface waters, natural 

variability in groundwater levels is already causing changes of this magnitude in the vicinity of 

sensitive surface waters in the analysis area. This makes identification of drawdown that could be due 

to the mine dewatering impractical in the field because there is no reliable method for separating out 

ongoing seasonal or annual variation from impacts from the mine. Given this natural variability, as 

well as the limitations of the model to predict impacts below this level, the 5-foot drawdown contour 

was determined to be the appropriate threshold for predicting impacts to groundwater levels in the 

FEIS. It should be noted that the limitations of the models for analyzing impacts to perennial stream

flow and riparian areas is explored further in the “Seeps, Springs, and Riparian Areas” section of 

chapter 3.

Overview of Modeling Process

The methodology for determining impacts to groundwater for Issues 3A and 3B involves developing 

numerical groundwater flow models to predict the effect of the proposed mine water supply pumping 

on the groundwater system in the Upper Santa Cruz Subbasin and to predict the effect of dewatering 

of the mine pit on the groundwater system in Davidson Canyon/Cienega Basin. 

Groundwater flow models are tools that attempt to mathematically simulate a real world groundwater

system. All models begin by analyzing and incorporating any available geological and hydrologic 

data that have been observed in the field, such as water level measurements, aquifer test results, and 

the results of geological mapping and drilling. Using these data as a starting point, modelers then 

make a series of assumptions about how the groundwater system operates and choose appropriate 

techniques for simulating the real world system mathematically. Although there is no single way to 

construct a groundwater flow model, there is an accepted process for constructing these models 

(American Society for Testing and Materials 2006). 

Groundwater flow models are sophisticated tools, but they are only an approximation of reality, 

and the modeler has to constantly assess whether the model results are accurate and realistic. 

The modeling process is meant to ensure that this assessment occurs in a systematic and objective 

way. Three primary methods are built into the standard modeling process to ensure the accuracy of 

the model:

• Calibration. Calibration is the process through which various model parameters are 

systematically changed, within reasonable bounds, in order to get the model results to match 

real-world conditions (the calibration target). In groundwater flow modeling, the calibration 

target often consists of historic measured water levels or water-level trends. 

• Sensitivity Analysis. Sensitivity analysis is a systematic evaluation of which model 

parameters have the largest effect on the model results and an evaluation of how uncertainty 

about each parameter will affect the accuracy and reliability of the model.

• Verification. Verification is a step beyond calibration that is desirable but is not always able 

to be performed. In verification, once a model is believed to be calibrated to best match the 

calibration target, the model is then compared with a completely different set of known realworld conditions. This comparison ensures that the model is flexible, simulates the real-world 

environment under many conditions, and has not been “hard wired” to match the calibration 

target. 

Final Environmental Impact Statement for the Rosemont Copper Project 295
Chapter 3. Affected Environment and Environmental Consequences

Conducting both calibration and verification requires having two entirely separate targets. Aside from 

historic water levels that were used for calibration, no other targets suitable for verification were 

available; therefore, verification was not conducted for any of the models discussed below. Lack of 

verification is not considered a fatal flaw to a model and does not suggest that the models are not 

accurate or usable. Rather, “a calibrated but unverified model may still be used to perform predictive 

simulations when coupled with a careful sensitivity analysis” (American Society for Testing and 

Materials 2006).

A fourth step in the modeling process, known as validation, takes place in the future. During this 

process, the past predictions of the model are compared with conditions measured in the field to 

determine whether the model accurately estimated future impacts. 

Validation of predictive modeling is not specifically called for in the aquifer protection permit, but the 

Coronado is requiring that Rosemont Copper continually update one of the groundwater flow models 

and refine predictions of groundwater changes based on the continued collection of groundwater 

levels in the future (see monitoring measure FS-BR-27 in appendix B).

Scientific Uncertainty and Professional Disagreement

In the case of the proposed project, the Coronado recognized that groundwater flow models were the 

only tools that could reasonably be used to assess future impacts from the proposed project. Because 

of their critical importance, two additional steps were intentionally built into the modeling process. 

• A system for independent peer review of the models was implemented. Under this system, 

modeling reports contracted by Rosemont Copper (from Errol L. Montgomery and

Associates and Tetra Tech) were reviewed independently by consultants selected by the 

Coronado and recognized as being experts in the field of groundwater modeling (MWH and

SRK Consulting). These consultants prepared itemized critiques of the modeling reports, 

including the assumptions made, interpretation of data, and modeling techniques used. Faceto-face meetings were conducted, allowing the modeling experts from different consultants to 

come to consensus on various points of contention. Based on the peer review, revised models 

were prepared as described later in this section. Additional peer review and criticism were

also provided by Forest Service specialists and several cooperating agencies, including BLM, 

EPA, and USGS. 

• The original model for the mine site groundwater system was constructed by Errol L. 

Montgomery and Associates. Rosemont Copper recognized early in the process that the 

ultimate accuracy of the modeling depends strongly on the geological and hydrologic 

assumptions made in the model. To balance possible subjectivity in the selection of 

assumptions, Rosemont Copper commissioned Tetra Tech to prepare a second, independent 

groundwater flow model of the mine site. The only original connection between the models 

was the underlying hydrologic data used as a basis for the models and the desire to model 

identical areas; other than this, the interpretation of these data and the design and operation of 

the models were conducted independently of one another. 

The original intent of conducting a peer review process (initiated in early 2009) was to build 

consensus from cooperating agencies, technical experts, and the project proponent in order to identify 

the most accurate and appropriate methods of conducting groundwater flow modeling. As expressed 

in public comments and as has become clear from meetings and correspondence with cooperating 

agencies that have taken place since the issuance of the DEIS, disagreement remains among 

296 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

professionals about several aspects of the groundwater models and the scientific uncertainty 

associated with the selected modeling techniques. 

The burden on the Coronado when faced with such professional disagreement and scientific 

uncertainty has been established by both regulation and NEPA case law. Regulations dictate that the 

FEIS shall respond to comments, that the Coronado shall discuss at appropriate points in the FEIS

any opposing view that was not adequately discussed in the DEIS, and that the FEIS shall indicate the 

Coronado’s response to the issues raised (40 CFR 1502.9(b)). Case law has further elaborated on this 

and indicates that the Coronado must acknowledge and respond to comments by outside parties that 

raise significant scientific uncertainties and that offer reasonable support that such uncertainties exist. 

However, the Coronado does not have the burden to anticipate questions that are not necessary to its 

analysis or to respond to uncertainties that are not reasonably supported by any scientific authority.

1

In light of the realization that despite the peer review process differences of opinion remain, the 

Coronado implemented a process that was intended to achieve four specific goals:

1. Determine whether the qualified professionals contracted by the Coronado for their specific 

groundwater modeling expertise are of the professional opinion that the models used are 

appropriate and acceptable for predicting impacts to groundwater systems;

2. Clearly identify any analysis areas where the Coronado specialists or the modeling experts 

contracted by the Coronado believe the models may not be sufficient;

3. Investigate issues raised during public comment; and

4. Achieve consensus or ensure that alternative viewpoints are clearly articulated and are 

available to the Forest Supervisor for consideration in determining analysis methodology.

In order to conduct this process, specific actions taken by the Coronado following issuance of the 

DEIS include the following:

• The Coronado requested written expert opinions on specific questions compiled by Forest 

Service specialists and cooperators and through public comments (Hoag, Bird et al. 2012; 

Hoag, Peachey et al. 2012; Hoag, Sieber et al. 2012; Kline et al. 2012; Ugorets, Cope, and 

Hoag 2012; Ugorets, Cope, and Sieber 2012). Note that these questions may or may not have 

been previously addressed during the peer review process; the intention of these additional 

requests was to obtain concise and direct expert opinions on specific topics, whether new or 

not.

• The Coronado requested additional information from Rosemont Copper and Pima County to 

help address aspects of the modeling questioned during public comment (U.S. Forest Service

2011e, 2012a, 2012c, 2012e, 2012f).

• The Coronado conducted a conference call with their contracted groundwater experts (SRK 

Consulting) and Coronado and Forest Service national specialists in order to discuss findings 

related to specific questions compiled by the Coronado (Garrett 2012d). The Forest 

Supervisor participated in this conference call.

• The Coronado conducted an expert panel meeting on May 3, 2012, in order to bring 

specialists face to face to discuss outstanding groundwater modeling and geochemical issues, 

including impacts to Outstanding Arizona Waters of Davidson Canyon and Cienega Creek. 

1 Lands Council v. McNair, No. 07-350000EB, 9th Cir. 2009.

Final Environmental Impact Statement for the Rosemont Copper Project 297

 
Chapter 3. Affected Environment and Environmental Consequences

This included experts contracted by the Coronado (SRK Consulting and Golder Associates), 

Coronado and Forest Service national specialists, and representatives from Federal agencies, 

including the USGS, BLM, and EPA. The Deputy Forest Supervisor represented the 

responsible official at this meeting in order to gain an understanding of the various 

viewpoints expressed (Garrett 2012h).

• The Coronado conducted a meeting on June 28, 2012, in order to discuss potential data 

sources and techniques that could be applied to analyzing groundwater impacts on riparian 

resources. In addition to Forest Service specialists, the meeting attendees included the EPA, 

BLM, Pima County, USGS, AGFD, and ADEQ (Garrett 2012b).

• The Coronado conducted field visits with specialists from Arizona State Parks on May 15, 

2012, and July 18, 2012, in order to discuss issues related to caves, regional hydrology, and 

the potential for karst systems to impact the project. The Forest Supervisor and forest 

hydrologist both participated in these field visits.

• The Coronado hosted a meeting on July 24, 2012, that included Arizona State Parks, Pima 

County, AGS, EPA, Coronado and national specialists, and the geological experts contracted 

by the Coronado (Garrett 2012a). The purpose of the meeting was to discuss the potential for 

existing caves to be impacted by the project, the potential for unknown caves to be located 

during project excavations, and, with respect to groundwater modeling, the potential for 

regional connectivity via faults, fractures, or karst systems to occur and whether the regional 

hydrologic framework used for the groundwater modeling was adequate and sufficient. 

The Forest Supervisor participated in this meeting.

• The Coronado hosted a meeting on October 18, 2012, that included Coronado contracted 

groundwater modeling specialists, Coronado resource specialists and decision makers, 

Rosemont Copper’s groundwater modelers, and Federal cooperating agencies (Garrett 

2012g). The purpose of this meeting was specifically to review additional sensitivity analyses 

conducted by Rosemont Copper concerning boundary conditions and more generally to 

determine whether the models are appropriate for use for the FEIS. The Forest Supervisor 

participated in this meeting.

After conducting the peer review process and the above steps to investigate alternative points of view, 

the Coronado delineated three issues that remain fundamental points of disagreement. These are 

discussed below. 

Misunderstanding of Regional Hydrogeologic Framework

Various parties have indicated the possibility that the modelers have fundamentally misunderstood the 

hydrogeologic framework, with the result that impacts from groundwater drawdown on distant water 

sources (especially Cienega Creek) are, therefore, greatly underestimated. There are three general 

arguments that have arisen related to this issue.

The first argument suggests that the depth of the mine pit and the dewatering of the pit during active 

mine operations could result in the dewatering of vast surrounding areas of the aquifer, particularly 

beneath the Sonoita Plain. In essence, this argument suggests that any area that has groundwater

levels that are higher than the pit bottom could ultimately lose groundwater to the pit. 

The second argument suggests that there are faults or fracture systems that are not accounted for in 

the groundwater modeling and that unmapped or unknown fault/fracture systems could lead to direct 

impacts, even at long distances, on distant water sources. A similar argument suggests the existence 

of an extensive regional interconnected aquifer unit, described as being a carbonate unit with karst298 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

like cave features that allow rapid movement of groundwater, which is unlike the geology mapped 

and modeled for the site.

The third argument suggests that the groundwater levels and hydraulic conductivities selected for the 

model are misinterpreted or inappropriate.

These alternative viewpoints were considered by the Coronado, and the issues raised were 

investigated through the process previously described. The Coronado found that these concerns are 

not substantiated by available data and do not rise to a level to suggest that the modeling assumptions 

and modeling techniques used in this analysis are inappropriate. The first argument arises from an 

oversimplification of a complex hydrogeologic system. The assumption that groundwater would 

automatically drain away to a lower elevation may be correct in close proximity with no hydrologic 

complications, but it cannot be applied regionally as it ignores real world data. Specifically, it ignores 

the geology between the mine pit and distant waters that has been verified through drilling and 

seismic investigation; actual groundwater elevations and flow patterns as measured in the field since 

the 1940s; the conductivity of various hydrologic units as established by aquifer testing throughout 

the basin; and, most of all, it ignores the element of time. The groundwater flow models are tools that 

are able to take all of these complexities into account and are the most appropriate tools to apply to 

the analysis.

The second and third arguments represent differences in interpretation of available hydrologic and 

geological data. The Coronado found that the existing models already take into account known 

regional faults and fracture zones, that they were modeled appropriately as areas of higher 

conductivity, and that the points raised to the contrary were not sufficient to demonstrate the 

existence of significant faults that had not been considered. The potential for a regional connected 

carbonate aquifer was found to be extremely unlikely, given the evidence from extensive geological 

mapping and data collection conducted at the site, the lack of hydrologic data to support such a 

supposition, and the well-established geological history of large-scale faulting and structural changes 

in southern Arizona. 

Inappropriate Model Boundary Conditions

Since early in the modeling process, there have been disagreements about the boundary conditions 

used for the models, in particular the western boundary of the model. Under most circumstances, the 

preference for modelers is to choose model boundaries that are associated with an obvious physical 

hydrogeologic feature, like a mountain range or a lake. In the regional sense, these can make for 

greatly simplified model boundary conditions. For instance, in much of southern Arizona, it can be 

assumed that, compared with the alluvial basins, groundwater flow through mountain areas is 

negligible; therefore, mountain ranges become convenient no-flow boundaries for modelers. 

In the case of this project, such simplifications are complicated because the project is actually located 

within the hardrock mountains, and the pit is located within feet of the basin boundary formed by the 

crest of the Santa Rita Mountains. The typical regional modeling approach assumes that no 

groundwater flow occurs in these areas. However, this is clearly not the case in the Rosemont area, 

based on the wells drilled and aquifer testing conducted.

To address this, both modelers commissioned by Rosemont Copper placed artificial boundaries some 

distance west of the mountain front. Such artificial boundaries are a valid modeling technique. 

However, they make it more difficult to assess how those artificial boundaries are affecting the 

model, and it is incumbent on the modelers to properly document the effects of the artificial 

Final Environmental Impact Statement for the Rosemont Copper Project 299
Chapter 3. Affected Environment and Environmental Consequences

boundaries. Arguments that were generally raised about these artificial western model boundaries 

suggested that the model water balance could be artificially distorted by these boundaries and that 

therefore the impacts of groundwater loss from the pit are underestimated or incorrectly estimated. 

At the request of the Coronado, additional sensitivity analyses were conducted by Rosemont 

Copper’s modelers with the specific goal of quantifying the possible distortions the selected boundary 

conditions could have on the groundwater models. These results were discussed and reviewed in the 

October 18, 2012, meeting.

As a whole, it was found that the artificial boundary conditions—and particularly the western 

boundary—did have a quantifiable effect on the model results, but this effect was highly dependent 

on time. The western boundary allows water to flow from east to west, out of the model domain. 

At no time does groundwater ever flow into the modeled area from this boundary; however, as the 

cone of depression expands and encounters the artificial western boundary (about 150 years after 

mine closure), the amount of water flowing out of the modeled area is reduced. When this reduction 

in boundary outflow becomes a substantial percentage of the groundwater entering the pit, it has the 

potential to offset water that otherwise would have to come from elsewhere in the model. Roughly 

speaking, effects from the boundaries remained minimal until about 300 years after closure of the 

mine. After this time, the change in flow from the artificial boundaries becomes a larger and larger 

percentage of the groundwater entering the pit, which in turn could cause a reduction in modeled 

impacts elsewhere in the model domain.

The quantifiable effect of the model boundaries on predicted drawdown in the aquifer was evaluated 

by conducting a modeling run in which the groundwater flows out of the model boundaries were 

fixed and not allowed to change. This in itself is not a realistic situation, but it allows the effect of the 

boundaries to be isolated and quantified. Rosemont Copper’s groundwater modelers presented the 

results of these runs, and it was found that the changes in water levels at sensitive riparian areas, 

while quantifiable, did not materially change the conclusions of the FEIS. For instance, the modeled 

drawdown after 1,000 years at Empire Gulch increased from about 3.3 feet to 3.5 feet for one model, 

and from about 6 feet to 7.5 feet for another model. Similarly, the modeled drawdown at Cienega 

Creek remained unchanged for one model at less than 0.1 feet, and increased from about 0.5 to 0.7 

feet for another model (Garrett 2012g). It was generally concluded by the Forest Service specialists, 

the Forest Service consulting groundwater modeling experts, Rosemont Copper’s modeling experts, 

and the Forest Service decision maker that although the artificial boundaries indeed have an 

undesirable effect on modeling results after several hundred years, the actual change before then is 

well within the uncertainty of the modeling and does not affect the overall modeling conclusions. 

Further, the Coronado considered an additional model provided by Pima County as an alternative 

viewpoint to show a range of impacts (the Dr. Myers model); this model used the more traditional 

boundary condition located along the ridgeline of the Santa Rita Mountains. It was concluded that the 

models prepared are the most appropriate tools for predicting impacts in the FEIS, provided that their 

associated uncertainty is fully disclosed.

A final point was agreed upon while reviewing the model boundaries. It was agreed that even at a 

point 1,000 years after final reclamation and closure of the mine, the models do not yet predict that 

equilibrium conditions have been reached and therefore do not reflect the ultimate impact that could 

occur to the aquifer. In reality, it was recognized by all parties that any modeling 1,000 years in the 

future is extremely speculative, and a steady-state modeling run exceeding 1,000 years in duration 

would be equally speculative. However, considering a steady-state scenario does provide an 

indication of the total amount of water that could be lost from the hydrologic system. Under a steadystate condition, there is no change in groundwater storage in the aquifer and, therefore, any 

300 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

groundwater entering the mine pit must come from another source of water besides storage. In the 

model domain, this could be the capture of recharge that otherwise would find its way to springs or 

flowing streams, reduction in the amount of water lost to flowing streams, or most likely, reduction in 

the amount of water lost to evapotranspiration from riparian areas. The amount of groundwater lost to 

the pit from evapotranspiration under a steady-state condition, as disclosed later in this resource 

section, likely ranges from 170 to 370 acre-feet. This represents the ultimate amount of water no 

longer available to streams, springs, or riparian areas once the model comes to equilibrium, all else 

being equal.

One final concern with the western boundary is the inability to predict groundwater drawdown 

beyond (west of) the boundary. In an ideal situation, the model boundary would be located far from 

any stresses (such as the mine pit), and therefore drawdown caused by those stresses would be 

unlikely to ever reach the boundary. In the case of the Rosemont Copper groundwater models, 

however, based on the geology and water levels of the basin, the modelers determined the appropriate 

location of the western model boundary and in doing so placed the western model boundary close 

enough that drawdown indeed reaches and is truncated at the western model boundary. This does not 

affect the analysis because there are no critical areas that would be affected beyond the western 

boundary: the known springs on the west side of the Santa Rita Mountains fall within the model 

domain, with no identified springs located beyond the boundary; the primary concentration of 

residential wells associated with Corona de Tucson lies within the boundary; and there are no 

sensitive riparian areas that rely on regional groundwater located within several miles of the model 

boundary (SWCA Environmental Consultants 2013m). It is recognized that because of the nearness 

of the western boundary, the propagation of impacts into the groundwater basin west of the Santa Rita 

Mountains is not able to be analyzed with these groundwater models; however, it is believed that no 

critical areas that would be affected by groundwater drawdown have been excluded.

Need for Additional Hydrogeologic Investigation

Suggestions were made through public comment and cooperating agencies that the hydrogeologic 

investigations conducted were not extensive enough throughout the Cienega Creek basin, or that 

geophysical techniques existed that would allow for discovery or delineation of karst, fracture, or 

fault features on the site. The Coronado requested information on these geophysical techniques from 

Arizona State Parks, the USGS, and the Coronado’s expert consultants. After consideration of this 

information, the Coronado found that these methods would not provide any additional understanding 

of the local or regional hydrogeologic framework. Further, the Coronado determined that the general 

belief that the modeling was limited solely to data collected near the mine site is unfounded. 

The geological data used by the modelers incorporated well and borehole data not only near the mine 

pit but throughout the Cienega Creek basin. Aquifer test data were used not only for wells near the 

proposed mine pit but also along upper and lower Cienega Creek and Davidson Canyon. Similarly, 

groundwater levels were widely available throughout the basin, dating even from the 1940s, and were 

sufficient to determine regional flow gradients and flow direction (Hoag, Peachey et al. 2012). 

A large body of documentation has been produced regarding the groundwater modeling process. 

For the purposes of analyzing groundwater impacts in this FEIS, the full range of modeling work has 

been considered, not just a single report or model. For the mine site groundwater system, results from 

both independent models as well as a third model commissioned by Pima County have been used in 

order to offer a range of possible impacts. Any limitations in the modeling that may affect the impacts 

are clearly assessed and stated.

Final Environmental Impact Statement for the Rosemont Copper Project 301
Chapter 3. Affected Environment and Environmental Consequences

Monitoring Intended to Assess Groundwater Modeling

In consideration of uncertainty associated with predicting long-term impact of any hydrologic system 

and the limitations identified in the groundwater models, three monitoring components have been 

incorporated into the mitigation and monitoring plan (see appendix B for full details). These 

monitoring components are intended to provide a database from which periodic assessment of model 

predictions can be undertaken and management strategies adapted if necessary. The monitoring 

includes:

• Monitoring to determine impacts from pit dewatering on downstream sites in Barrel 

and Davidson Canyons (FS-BR-22). Monitoring would be conducted of surface water, 

alluvial groundwater, and deeper groundwater at sites in Barrel and Davidson Canyons.

Several locations have already been installed and are being actively monitored, whereas 

others would require access from landowners.

• Spring, seep, and constructed/enhanced waters monitoring (FS-SSR-02). A suite of 

selected seeps and springs has been monitored for baseline conditions since 2007 and would 

be monitored to identify any impacts that may occur due to dewatering of the regional aquifer

in the vicinity of the mine pit. Specific seeps and springs included in this monitoring are 

listed in appendix B.

• Periodic validation and rerun of groundwater model throughout life of mine (FS-BR27). This measure would involve basic data collection of water levels, meteorological data, 

and water balance components, which would allow for the predictions of groundwater 

impacts to be revised based on actual hydrologic observations. Specific wells to be monitored 

are listed in appendix B.

Summary of Models Used

Mine Water Supply in Upper Santa Cruz Subbasin

Montgomery Mine Water Supply Model

The impacts to groundwater levels associated with the mine water supply well field near Sahuarita 

are predicted using a groundwater flow model constructed by Errol L. Montgomery and Associates 

(2009a; 2010), referred to hereafter as the Montgomery Mine Water Supply model. The proposed 

location for the mine water supply wells in the Santa Cruz Valley is within the Upper Santa Cruz 

Subbasin, which is a groundwater subbasin within the Tucson Active Management Area. The Tucson 

Active Management Area is an administrative area that was created under the Arizona Groundwater

Management Act of 1980; within the Tucson Active Management Area, groundwater resources are 

intensively managed by the ADWR. As part of the basin management, the ADWR has developed and 

maintains a groundwater model for the Tucson Active Management Area that covers 3,250 square 

miles (Mason and Bota 2006). 

The Tucson Active Management Area model was calibrated by the ADWR to match two datasets: 

water levels representing predevelopment conditions in 1940, and changing water levels between 

1941 and 1999. The model was then able to be used by the ADWR to predict future conditions from 

2000 through 2024. The model is executed using the computer code MODFLOW 2000. Tucson 

Active Management Area boundaries and geographic features are shown in figure 44. 

The Montgomery Mine Water Supply model is a modification of the Tucson Active Management 

Area model. The modifications made to the Tucson Active Management Area model primarily consist 

of refinements in the immediate vicinity of the mine water supply, based on the availability of more 

302 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 44. Tucson Active Management Area

Final Environmental Impact Statement for the Rosemont Copper Project 303
Chapter 3. Affected Environment and Environmental Consequences

recent site-specific data. Modifications include changes in cell size, aquifer parameters, layer 

thickness, groundwater demands, and recharge. 

This type of refinement of an existing model is a standard accepted practice for using a regional-scale 

model to analyze impacts from a specific project (Leake and Claar 1999). Use of the Tucson Active 

Management Area model as the basis for the mine water supply pumping prediction allows the 

predictive model to benefit from the long-term, area-wide data contained in the Tucson Active 

Management Area model. As such, the Montgomery Mine Water Supply model uses information 

recorded over the 66-year period from 1940 through 2006 as the basis for predicting groundwater

behavior for a 20-year period of pumping. The predictive model incorporates the groundwater

stresses, pumping withdrawals, and groundwater recharge facilities currently on file with the ADWR. 

The pumping withdrawal for the proposed project is then added into the model in order to predict the 

additional drawdown from the proposed project. 

The Montgomery Mine Water Supply model was calibrated based on observed water-level trends in 

various wells in the vicinity of the proposed well field from the period from 1981 through 2005. 

Status of Model and Peer Review

Independent peer review of the Montgomery Mine Water Supply model (Errol L. Montgomery and 

Associates Inc. 2009a) was conducted by MWH (Haws and Leeson 2010) to identify deficiencies in 

approach and execution of the modeling. A revised Montgomery Mine Water Supply model was

prepared (Errol L. Montgomery and Associates Inc. 2010) and was reviewed again by MWH to

identify whether deficiencies had been addressed (Haws and Leeson 2011). MWH concluded the 

following:

• “After reviewing the Report Addendum and Additional Discussion memorandum, it is 

MWH’s opinion that the groundwater flow model developed by M&A meets industry 

standards for groundwater flow models and is adequate for predicting potential groundwater 

level changes caused by Rosemont mine supply pumping” (Haws and Leeson 2011:1).

MWH also identified several areas requiring additional documentation, which was subsequently 

provided (Barter and Whittier 2011a, 2011b).

Calibration of Model

A transient calibration analysis was completed (Barter and Odom 2011). Because of large seasonal 

fluctuations in groundwater levels in the Sahuarita area that are largely the result of agricultural 

pumping, the calibration was conducted on groundwater-level trends, rather than on individual 

groundwater-level measurements. Statistical assessment of the calibration was calculated using 

individual water-level measurements corrected for the offset observed in the water-level trends. 

The peer review process concluded that this technique was sufficient to demonstrate calibration 

(Haws and Leeson 2011). The calibration results were as follows: 

• The residual mean of the transient calibration was 20.7 feet. The residual mean is the average 

of the residuals. A residual is the difference between an observed calibration target water 

level and a modeled water level at the same location. The residual mean for the model 

calibration is positive, which indicates a model bias toward overpredicting regional 

groundwater level declines.

304 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

• The absolute residual mean of the transient calibration was 21.66 feet. The absolute residual 

mean is the average of the absolute values of the residuals and represents the magnitude of 

differences seen between observed and modeled water levels.

• The residual mean square error is 25.26 feet. One widely used standard for assessing the 

success of the calibration is the residual mean square error divided by the range of observed 

values; values below 10 percent are generally considered to be acceptably calibrated. 

The residual mean square error divided by the range of observed values was 10.6 percent.

• The calibration success (as measured by the residual mean square error divided by the range 

of observed values) slightly exceeds the typical cutoff for acceptability of 10 percent. This 

appears to be the result of the difficulties in finding acceptable calibration targets in the 

immediate vicinity of the project because of large seasonal fluctuations in groundwater

levels. With respect to use of the model in the FEIS, the calibration is considered acceptable 

on the strength of MWH’s final conclusions, subject to the limitations described in the next 

section. 

Potential Limitations and Current Usability of Model

The Mine Water Supply model developed by Montgomery and Associates (2009a; 2010) has been 

used in order to analyze impacts in this FEIS, recognizing the following limitations:

• The calibration is considered acceptable by the peer reviewers (Haws and Leeson 2011).

However, Montgomery and Associates (Barter and Odom 2011) provides one caution about 

the model results: “In this evaluation results indicate the model is showing a small bias to 

overpredict regional groundwater level decline during the calibration period. This bias does 

not render the model results invalid, but does indicate a potential that projected drawdown 

from Rosemont pumping could potentially be slightly smaller than simulated.” In practice, 

this reflects a more conservative analysis in the FEIS and is therefore considered acceptable 

for analyzing impacts from pumping.

• Given the model cell size and uncertainties concerning connection of shallow wells to the 

regional aquifer, assessing impacts to local wells is not feasible. Using any large-scale model 

to predict the impacts to individual wells with any certainty is not feasible. Furthermore, an 

inventory of all wells with the necessary information to assess impacts (depth, screened 

interval, pump setting, current water levels) does not exist and would be prohibitively costly 

and time consuming to create (see “Analysis Methodology, Assumptions, Uncertain and 

Unknown Information” part of this section). It is unlikely that any modification to the 

model—or any model—would be able to fully analyze impacts to individual wells. 

The model is still used to assess impacts, with the understanding that impacts to individual 

wells are considered in a qualitative rather than quantitative manner.

Mine Site Models in the Davidson Canyon/Cienega Basin

Unlike for the Santa Cruz Valley, no regional groundwater models have been constructed that include

the project area in the Davidson Canyon/Cienega Basin; all modeling for the project area has been 

conducted specifically because of the proposed project. For the purposes of this FEIS, three models 

are considered.

Also in contrast to the modeling for the mine water supply, the area of the proposed mine pit has not 

benefited from a lengthy period of historical data regarding groundwater levels, groundwater

response to pumping, or the overall knowledge of area-wide hydrologic parameters. In addition, the 

Final Environmental Impact Statement for the Rosemont Copper Project 305
Chapter 3. Affected Environment and Environmental Consequences

geology of the project area is substantially more complex than that of the Santa Cruz Valley. In order 

to balance possible subjectivity when selecting modeling assumptions, two independent groundwater 

flow models were commissioned by Rosemont Copper from Errol L. Montgomery and Associates 

and Tetra Tech to analyze the effect of the proposed mine pit on groundwater in Davidson Canyon 

and the Cienega Basin. (Note that with respect to documentation included in the project record, the 

Tetra Tech model was later revised under the auspices of Engineering Analytics, Inc., and HydroLogic, LLC.) Both models use the same model domain, pump test data, and fundamental geological

data, but each model takes a different approach to developing the model cells and assigning 

geological and hydrologic properties to each cell. Each modeler conducted unique sensitivity and 

calibration computations and reached similar but not identical predictions regarding the response of 

the groundwater system to the stress imposed by the mine pit. 

Outside the two independent models commissioned by Rosemont Copper, Pima County 

commissioned another independent model by Dr. Tom Myers, which was presented to the Coronado 

as an alternative model for analyzing impacts to groundwater. 

Each of these three models is discussed separately below. For the purposes of the impacts analysis in 

this FEIS, the predictive results from all three models were considered in order to develop a range of 

potential impacts, subject to the limitations listed for each model. 

Montgomery Mine Site Model

The impacts to groundwater levels resulting from active pumping of groundwater from the proposed 

mine pit during mine operations, as well as long-term removal of groundwater from the aquifer by 

evaporation from the mine pit lake, are predicted using a groundwater flow model constructed by 

Errol L. Montgomery and Associates (2010), referred to hereafter as the Montgomery Mine Site 

model. 

The framework for the Montgomery Mine Site groundwater model is based in part on a 

hydrogeologic data collection program implemented in 2008, which included well drilling, water

level monitoring, aquifer testing, and water quality sampling. These observed hydrogeologic data 

were incorporated into a groundwater flow model that covers 457 square miles and consists of 

10 layers, with the base of the model at an elevation of 1,000 feet above mean sea level. 

The modeling process for Errol L. Montgomery and Associates consisted of constructing a steadystate model; a steady-state model assumes that the basin being modeled is in equilibrium, with no 

significant changes in water inflow, outflow, or storage over time. The steady-state model was 

constructed and then calibrated to the observed present-day water levels. Once calibrated, the model 

was modified to include the removal of groundwater caused by the proposed mine pit, and the 

resulting changes in groundwater levels are simulated over time (1,022 years in this case). The model 

is executed using the computer code MODFLOW-SURFACT.

Errol L. Montgomery and Associates made several important assumptions in order to construct their 

model:

• Perennial stream reaches are modeled using a stream-aquifer interaction package (STR). 

The vertical hydraulic conductivity of the stream bottoms were set to 100 feet per day. This 

value is larger than typically observed in the field; this allows for a conservative estimate of 

the amount of water lost from streams as a result of groundwater drawdown (i.e., the value 

306 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

used in the model shows that streams lose water more easily to the aquifer if groundwater 

levels decline than is observed in the field).

• Evaporation losses from the mine pit lake are modeled using a lake modeling package 

(LAK2).

• Boundary conditions at the edges of the model domain are a combination of constant-head 

boundaries and general-head boundaries. Constant-head boundaries assume that water levels 

remain constant at the model edges and calculate the amount of water needed to flow in or 

out of the model to maintain those water levels. General-head boundaries allow both water 

levels and groundwater flow to change at the edges of the model. Both constant-head and 

general-head boundaries can allow an unlimited amount of water to enter or leave the model; 

for this reason, it is necessary to consider the modeled groundwater flows through constanthead or general-head boundaries when assessing the validity of a groundwater model.

• Groundwater pumpage not related to mining within the model area was not simulated. 

Groundwater pumpage within the basin was estimated to be between 400 and 500 acre-feet 

per year. This domestic pumping was not included in the model because of the small,

dispersed nature of the pumping and because of the speculative information available about 

the pumping. Furthermore, historic groundwater-level data do not show declining trends in 

the general area of the domestic pumping near Sonoita. Note that even though this domestic 

pumpage was not modeled specifically, it has been analyzed in the FEIS as an ongoing trend.

Although it is recognized that flow with the aquifer occurs almost exclusively through fractures and 

faults, the model treats the aquifer as if it were porous media (similar to the Mine Water Supply

model). This is a standard approach for modeling large, regional fractured bedrock systems, provided 

that the results are analyzed at an appropriate scale. There are other methods for modeling 

groundwater flow in fractured aquifers; however, for the most part, such modeling methods require 

extensive data on either individual fractures or homogeneous fracture zones. Collection of this level 

of data is not feasible for a model of this size (457 square miles), and from a logistical standpoint,

there is a limited ability to determine the hydraulic characteristics of individual faulting and 

fracturing features. Further, the hydraulic characteristics of faulted systems over the analysis area are 

not typically dominated by individual faults. Rather, the hydraulic extensiveness of individual faults 

is typically limited. Instead, on average, the system of finite but connected individual faults and 

fractures behaves in a way that is equivalent to the behavior of a porous medium. Use of an 

equivalent porous media to model fractured flow is widely recognized by specialists as being 

acceptable for analyzing groundwater flow at regional scales, as is modeled here (Ugorets, Cope, and 

Sieber 2012). Such models are less acceptable for analyzing fate and transport over shorter distances, 

as individual fractures play an increasingly important role in contaminant movement.

Three fault zones were modeled: the Davidson Canyon Fault Zone, Backbone Fault Zone, and Flat 

Fault (figure 45).

Status of Model and Peer Review

Independent peer review of the first draft of the Montgomery Mine Site model (Montgomery and 

Associates Inc. 2009) was conducted by SRK Consulting to identify deficiencies in approach and 

execution of the modeling. A revised Montgomery Mine Site model was prepared (Montgomery and 

Associates Inc. 2010) and was reviewed again by SRK Consulting to identify whether deficiencies 

were addressed. SRK Consulting (Ugorets and Cope 2010) concluded the following: 

Final Environmental Impact Statement for the Rosemont Copper Project 307
Chapter 3. Affected Environment and Environmental Consequences

Figure 45. Groundwater levels in the Cienega Basin

308 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

• “The ground water model presented in the revised report addresses the comments and 

recommendations made by SRK in its review of the original report. SRK finds the revised 

model and report to represent hydrogeological conditions that are appropriate to the model 

that was developed and to the data that were available. The predictive model is based on a 

good steady-state calibration and a reasonable transient-state calibration.”

• “Model predictions for both mining and post-mining conditions are reasonable, are based on 

the results of a completed comprehensive analysis, and provide a possible range of potential 

impacts to the ground water system and to surface-water bodies.”

• “The model was conceptualized, constructed, and presented to standard industry practices. 

Though there remain and will always remain uncertainties with a simulation of complex 

natural systems, the revised model is judged to be sufficient in concept and execution such 

that the resulting predictions of impacts are reasonably supported and defended by the 

available data.”

SRK Consulting also noted several deficiencies in documentation that they felt should be reviewed to 

enhance defensibility of the model. Additional information was submitted by Montgomery and 

Associates in May 2011 (Barter and Whittier 2011a; 2011b) and June 2012 (Barter 2012a). 

The additional data, including further sensitivity analyses concerning the model boundaries, were 

evaluated by SRK Consulting, the Coronado, and the USGS during a series of meetings in May 2012 

and October 2012 and found to be sufficient to demonstrate the appropriateness of the model (Garrett 

2012g, 2012h).

Calibration of Model

A calibration was conducted on both the steady-state and transient models. 

• Horizontal hydraulic conductivity, vertical hydraulic conductivity, storage, stream 

parameters, evapotranspiration, and recharge were varied during the calibration.

• Observed groundwater levels were used as calibration targets, including water-level

responses during pump testing of five wells in order to calibrate the transient model.

• The residual mean of the steady-state calibration was 26.2 feet. The residual mean for the 

model calibration is positive, which indicates a model bias toward simulating higher 

groundwater levels than is observed in the field. The absolute residual mean of the steadystate calibration was 58.0 feet. The residual standard deviation is 80.6 feet. The residual 

standard deviation divided by the range of observed values was 2.8 percent; values below 10 

percent are generally considered to be acceptably calibrated.

• Difficulties in calibrating water levels on the west side of the model, nearest the mine pit, 

were identified. This means that the predicted groundwater levels in the immediate vicinity of 

the mine pit should be used with caution. Overall, the difficulties in calibrating the model in 

this area result from the use of a porous media model to model fracture flow conditions. On a 

regional scale, the porous media model is reliable for predicting water-level impacts on seeps, 

springs, and other hydrologic features; however, the model may not fully reflect the 

individual fractures that supply water to those features. This has not affected the overall 

analysis of impacts. The expected changes in water levels in the immediate vicinity of the 

mine pit are very large, and impacts on springs and wells in this area are not in question, even 

if some error exists in the exact predicted amount of water level change.

• The Montgomery Mine Site model steady-state water balance is as follows. Inflows to the 

model area consisted of recharge (6,500 acre-feet per year) and inflow to the Cienega Basin 

Final Environmental Impact Statement for the Rosemont Copper Project 309
Chapter 3. Affected Environment and Environmental Consequences

from general-head and constant-head boundaries (2,509 acre-feet per year). Outflows from 

the model area consisted of evapotranspiration (5,007 acre-feet per year), groundwater

discharge to Cienega Creek (1,715 acre-feet per year), and outflow from general-head and 

constant-head boundaries into the Tucson Basin (2,282 acre-feet per year).

Sensitivity Analysis of Model

A sensitivity analysis was conducted on both the steady-state and transient models. The model 

parameters analyzed during the sensitivity analysis included horizontal and vertical hydraulic

conductivity, hydraulic conductivity of the various fault zones, and recharge. Additional model 

parameters concerning the water balance for the mine pit lake were also analyzed. Montgomery and 

Associates (2010:figures 117–119) concluded the following:

• Overall, Montgomery and Associates found that varying the model parameters by an order of 

magnitude higher or lower did not provide an improvement on the model calibration.

• The greatest changes due to sensitivity analysis occur in the first several hundred years of the 

simulation. Changes in hydraulic conductivity cause drawdown contours to advance or 

recede by up to 3 miles in some directions, particularly along Davidson Canyon.

• However, by 1,000 years, changes in any of the sensitivity parameters do not result in a shift 

in drawdown contours of more than 1 mile.

Potential Limitations and Current Usability of Model

The Montgomery Mine Site model (Montgomery and Associates Inc. 2010) has been used in order to 

analyze impacts in this FEIS, based on the following:

• The calibration has been determined to be within acceptable range. Although it was not 

entirely successful on the west side of the model, errors in predicted water levels at this 

location do not change the overall impact assessment.

• Full peer review and revisions have been completed and have found the model to be 

acceptable (Garrett 2012g; Ugorets and Cope 2010). 

• It is recognized that the record of historic water-level data used as a basis for the model is 

mostly limited to the period since 2008 in the immediate vicinity of the mine. However, 

water levels are available throughout the modeled area, including water levels from as early 

as the 1940s.

• It is recognized that predicting conditions hundreds of years or 1,000 years in the future is 

speculative; however, this long time frame was selected in order to allow the bedrock aquifer

impacted by the mine pit to come close to equilibrium.

• It is recognized that while pumpage in the basin was not able to be quantified and modeled, 

pumpage in the basin is increasing and lack of modeling of this pumpage may affect future 

predictions.

• It is recognized that while much of the Cienega Basin was included in the model domain, the 

purpose of this model was to analyze impacts from dewatering of the mine pit; therefore, the 

model may not be appropriate for use elsewhere in the basin without additional revision.

• The model has been used for the impacts analysis in this FEIS as one out of three models that 

have been prepared for the project area, and it is not presented as the sole prediction of 

impacts. 

310 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Tetra Tech Mine Site Model

The impacts to groundwater levels resulting from active pumping of groundwater from the proposed 

mine pit during active mining, as well as long-term removal of groundwater by evaporation from the 

mine pit lake, are also predicted using a second, independent groundwater flow model constructed by 

Tetra Tech (2010g), referred to hereafter as the Tetra Tech Mine Site model. 

The Tetra Tech Mine Site model covers the same model domain of 457 square miles as the 

Montgomery Mine Site model and relies on the same underlying hydrogeologic data and horizontal 

grid. However, the Tetra Tech model consists of 20 layers, versus 10 layers in the Montgomery Mine 

Site model. The base of the model still lies at an elevation of 1,000 feet below mean sea level, like the 

Montgomery Mine Site model. 

Tetra Tech’s modeling process was similar to that of Errol L. Montgomery and Associates and also 

consisted of constructing a steady-state model and calibration of that model. Tetra Tech then ran two 

additional models over time, based on the steady-state model, in order to simulate the active pumping 

of groundwater from the pit and then the subsequent loss of water to evaporation from the pit lake 

after mine closure. The first transient model covers 22 years of pit dewatering associated with the 

active mining phase of the project. The second transient model covers the next 1,000 years following 

final reclamation and closure of the mine. The model is executed using the computer code 

MODFLOW-SURFACT.

Like Errol L. Montgomery and Associates, Tetra Tech made several important assumptions in order to 

construct their model, as follows: 

• Perennial reaches of Cienega Creek and Davidson Canyon are included in the model. 

The perennial reaches were modeled using a stream flow routing package (SFR1).

The vertical hydraulic conductivity of the stream bottoms was set to 6.6 feet per day. Similar 

to the Montgomery Mine Site model, this value is larger than typically observed in the field; 

this allows for a conservative estimate of the amount of water lost from streams as a result of 

groundwater drawdown (i.e., the value used in the model shows that streams lose water more 

easily to the aquifer if groundwater levels decline than is observed in the field).

• Evaporation losses from the mine pit lake are modeled using a lake modeling package 

(LAK2).

• Boundary conditions at the edges of the model domain are constant-head boundaries. 

General-head boundaries were not used in the model. 

• Tetra Tech also did not model any groundwater pumpage within the model area.

• A possible barrier to groundwater flow from an intrusive dike across Davidson Canyon was 

modeled, as was the Backbone Fault. Davidson Canyon Fault and Flat Fault were not 

explicitly incorporated into the Tetra Tech Mine Site model.

• Although it is recognized that flow within the aquifer occurs almost exclusively through 

fractures and faults, the model also treats the aquifer as if it were porous media, which as 

previously discussed is appropriate, given the regional scale of the model.

Status of Model and Peer Review

Documentation of the Tetra Tech Mine Site model was produced in separate technical memoranda as 

each part of the model was constructed (O'Brien 2010a, 2010b, 2010c, 2010d). Independent peer 

review of each of the Tetra Tech Mine Site model technical memoranda was conducted by SRK 

Final Environmental Impact Statement for the Rosemont Copper Project 311
Chapter 3. Affected Environment and Environmental Consequences

Consulting. A complete Tetra Tech Mine Site model report was produced that incorporated changes 

agreed to during peer review and face-to-face meetings (Tetra Tech 2010g). SRK Consulting 

completed peer review of the complete Tetra Tech Mine Site model report. After making several 

additional recommendations, SRK Consulting (Ugorets 2011) concluded the following:

• “Despite those uncertainties, SRK concludes that the ground water model presented in the 

final version of the report was conceptualized, constructed, and presented to standard 

industry practices. The model addresses the comments and recommendations made by SRK 

in its review of the individual sections of the report. Further, SRK finds that the model 

generally represents hydrogeological conditions that are appropriate to the available data, is 

robust, and well calibrated to the pre-mining steady-state conditions. Model predictions for 

both mining and post-mining conditions are reasonable, are based on the results of 

comprehensive sensitivity analyses, and provide a range of potential impacts to the 

groundwater system and to surface-water bodies.”

As with the Montgomery Mine Site model, SRK Consulting also noted several deficiencies in 

documentation that they felt should be reviewed to enhance defensibility of the model. Additional 

information was submitted in May 2011 (O'Brien and Ridlen 2011a, 2011b) and June 2012 (O'Brien 

2012). 

The additional data, including further sensitivity analyses concerning the model boundaries, were 

evaluated by SRK Consulting, the Coronado, and the USGS during a series of meetings in May 2012 

and October 2012 and eventually found to be sufficient to demonstrate the appropriateness of the 

model (Garrett 2012g, 2012h).

Calibration of Model

A calibration was conducted on the steady-state model. Unlike the Montgomery Mine Site model, no 

transient calibration on the full model was conducted, although several aquifer tests were analyzed 

using a transient calibration technique. 

• Horizontal conductivity, vertical conductivity, recharge, stream bed conductivity, and 

conductivity of a modeled groundwater flow barrier were varied during the calibration.

• Observed groundwater levels were used as calibration targets, and results were given, with 

calibration targets both weighted for reliability and unweighted.

• The residual mean of the calibration was −1.18 (unweighted) and −4.47 feet (weighted). 

The residual mean for the model calibration is slightly negative, which indicates a slight 

model bias toward underpredicting groundwater levels.

• The absolute residual mean of the calibration was 97.61 (unweighted) and 55.05 (weighted).

• The residual standard deviation was 133.12 feet (unweighted) and 90.17 feet (weighted). 

The residual standard deviation divided by the range of observed values was 4.6 

(unweighted) and 3.1 percent (weighted).

• Difficulties in calibrating water levels on the west side of the model, nearest the mine pit, 

were identified. This means that the predicted groundwater levels in the immediate vicinity of 

the mine pit should be used with caution. Overall, the difficulties in calibrating the model in 

this area result from the use of a porous media model to model fracture flow conditions. On a 

regional scale, the porous media model is reliable for predicting water-level impacts, but on 

the scale of seeps, springs, and other hydrologic features, the model may not fully reflect the 

individual fractures that supply water to those features. This has not affected the overall 

312 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

impacts analysis. The expected changes in water levels in the immediate vicinity of the mine 

pit are very large, and impacts to springs and wells in this area are not in question, even if 

some error exists in the exact predicted amount of water level change.

• The Tetra Tech Mine Site model steady-state water balance is as follows. Inflows to the 

model area consisted of recharge (9,900 acre-feet per year) and inflow from constant-head 

boundaries (24,465 acre-feet per year). Outflows from the model area consisted of 

evapotranspiration (5,633 acre-feet per year), stream flow out of the model area from Cienega 

Creek (2,616 acre-feet per year), and outflow from constant-head boundaries (26,116 acrefeet per year).

Sensitivity Analysis of Model

A sensitivity analysis was conducted on both the steady-state and transient models. The model 

parameters analyzed during the sensitivity analysis included horizontal and vertical hydraulic 

conductivity, hydraulic conductivity of the intrusive dike, specific storage, specific yield, and 

recharge. Additional model parameters concerning the water balance for the mine pit lake were also 

analyzed. Tetra Tech concluded the following:

• A range of aquifer storage parameters was analyzed. Aquifer storage parameters had a large 

effect on the extent of drawdown over the first 200 years of modeling. Higher storage values 

resulted in drawdown receding 3 miles toward the mine pit, while lower storage values 

resulted in drawdown advancing an additional 1 mile beyond the mine pit. Higher storage 

values result in a longer time to equilibrium drawdown because more water must be removed

for a given decline in water levels. Lower storage values result in the cone of depression 

reaching equilibrium conditions sooner because there is less water to remove to reach the 

same water level. Either way, the equilibrium extent of the cone of depression should be the 

same.

• Changes in pit lake parameters such as precipitation, evaporation, and pit-wall runoff were

analyzed. Lower evaporation rates resulted in a smaller cone of depression, with the 5-foot 

drawdown contour shifting more than 1 mile closer to the pit, along with increased modeled 

flow in streams.

• A change in the amount of postmining recharge was analyzed. The Tetra Tech Mine Site 

model assumed that recharge would actually increase slightly (about 2 percent), from a 

premining recharge of 9,900 acre-feet per year to a postmining recharge of 10,092 acre-feet 

per year. Because of this difference in approach, Tetra Tech conducted a sensitivity analysis 

by modeling an unchanged recharge after construction of the mine. The reduction in recharge 

resulted in greater modeled reductions in stream flow in Cienega Creek and Davidson 

Canyon, drawdown advancing up to an additional 3 miles beyond the mine pit, and greater 

reduction in evapotranspiration.

• The choice of boundary conditions for the western boundary of the model (constant-head 

boundaries) was analyzed by modeling different kinds of boundary conditions, including 

no-flow and general-head boundaries. Variance in boundary conditions from constant-head to 

general-head did not change the direction of flow out of the model boundary, nor did it 

significantly change the amount of flow or water levels. The no-flow boundary was found to 

cause instability in the model and could not be simulated.

• The intrusive dike was analyzed by varying the hydraulic conductivity by an order of 

magnitude. Results indicated that the intrusive dike may act to reduce propagation of impacts 

down Davidson Canyon. One recommendation by SRK Consulting during their final review 

Final Environmental Impact Statement for the Rosemont Copper Project 313
Chapter 3. Affected Environment and Environmental Consequences

was for additional sensitivity analysis to be conducted, as the simulation of the dike is “less 

than fully supported by the analyses and conclusions” (Ugorets 2011). This sensitivity 

analysis was subsequently conducted and submitted to the Coronado (O'Brien and Ridlen 

2011a). Removal of the dike entirely in the sensitivity analysis resulted in minor changes to 

the propagation of drawdown in Davidson Canyon.

Potential Limitations and Current Usability of Model

The mine site model developed by Tetra Tech (2010g) has been used in order to analyze impacts in 

this FEIS, based on the following:

• The calibration appears to be within acceptable range. Although it was not entirely successful 

on the west side of the model, errors in predicted water levels at this location are not expected 

to change the overall impact assessment.

• Full peer review and revisions have been completed and have found the model to be 

acceptable (Ugorets 2011). 

• The record of historic water level data used as a basis for the model is largely limited to the 

period since 2008 in the immediate vicinity of the mine. However, water levels are available 

throughout the modeled area, including water levels from as early as the 1940s.

• It is recognized that predicting conditions hundreds of years or 1,000 years in the future is 

highly speculative; however, this long time frame was selected in order to allow the bedrock 

aquifer impacted by the mine pit to come close to equilibrium.

• It is recognized that while pumpage in the basin was not able to be quantified and modeled, 

pumpage in the basin is increasing, and lack of modeling of this pumpage could affect future 

predictions.

• It is recognized that while much of the Cienega Basin was included in the model domain, the 

purpose of this model was to analyze impacts from dewatering of the mine pit; therefore, the 

model may not be appropriate for use elsewhere in the basin without additional revision.

• Overall, the peer review process determined that the model predictions are reasonable; 

however, one specific concern remaining with the Tetra Tech Mine Site model was the 

inclusion of the intrusive dike across Davidson Canyon, which acts as a barrier to 

groundwater flow and may therefore underestimate impacts along Davidson Canyon. 

The peer review suggested that additional sensitivity analyses be conducted to analyze the 

impacts of including the intrusive dike. This sensitivity analysis has been conducted. 

• The model has been used for the impact analysis in this FEIS as one out of three models that 

have been prepared for the project area, and it is not presented as the sole prediction of 

impacts. 

The Dr. Myers Mine Site Model

Dr. Tom Myers was contracted by Pima County to conduct an independent modeling effort, referred 

to hereafter as the Dr. Myers Mine Site model, as well as to review modeling conducted by Errol L. 

Montgomery and Associates (Myers 2008, 2010a). The modeling process used by Dr. Myers is 

similar in nature to both the Tetra Tech and Montgomery Mine Site models. First, he calibrated a 

steady-state model. Then, he ran various transient models to simulate stresses associated with actively 

pumping groundwater from the pit and from the loss of water from the formation of the pit lake. 

No transient calibration was conducted. Unlike Errol L. Montgomery and Associates and Tetra Tech, 

Dr. Myers ran the transient model for a period of 7,500 years.

314 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Construction of the Dr. Myers Mine Site model is fundamentally different from the other two models: 

it uses a smaller model area that is more reflective of natural topographic boundaries, and it uses very 

different boundary conditions. Both the Errol L. Montgomery and Associates and Tetra Tech Mine 

Site models extend the model beyond the topographic boundaries and use conditions that allow 

groundwater to flow in and out of the model domain in order to maintain the model water balance. 

Dr. Myers allows no groundwater to flow in and out of the model domain, except where Davidson 

Canyon and Cienega Creek leave the project area. Dr. Myers also specifies drain cells along Cienega 

Creek that model discharge to the creek. The model also differs with respect to how water loss from 

the pit is handled. The model is constructed using the computer code MODFLOW-2000.

It should be noted that although the model domain and approach are different, as with the other 

models, the fundamental output from the model is similar: it predicts water levels in the regional

aquifer.

Status of Model and Peer Review

During public comment, Pima County indicated that the Dr. Myer Mine Site model underwent peer 

review by Stan Leake with the USGS. Further information on the peer review process was requested 

by the Coronado but has not been received. The Dr. Myers Mine Site model has undergone one 

revision (Myers 2010b) from the original version prepared (Myers 2008).

Calibration of Model

A calibration was conducted on the steady-state model. 

• Horizontal conductivity and vertical conductivity appear to have been varied during the 

calibration.

• Observed groundwater levels were used as calibration targets, weighted for reliability.

• The residual mean of the calibration was −13.1 to 37.1 feet, depending on the layer. 

• The absolute residual mean of the calibration was not presented. 

• The residual standard deviation is 39.8 to 64.4 feet. The residual standard deviation divided 

by the range of observed values was not presented, nor is the range of values presented. 

Assuming a similar range of observed values as used by Errol L. Montgomery and 

Associates, the residual standard deviation divided by the range of observed values would be 

1.2 to 2.0 percent.

• Any difficulties with model calibration on the west side of the model were not discussed, nor 

were figures presented to allow for an assessment of this.

• A sensitivity analysis was presented in graphical form.

Potential Limitations and Current Usability of Model

The mine site model developed by Dr. Myers (Myers 2010b) also been used for the impacts analysis 

in this FEIS, recognizing the following limitations:

• The calibration appeared to be within acceptable range, based on data presented and some 

further assumptions.

• While peer review has reportedly been performed on the model, the results and details of the 

peer review were not made available to the Coronado and cannot be assessed. 

Final Environmental Impact Statement for the Rosemont Copper Project 315
Chapter 3. Affected Environment and Environmental Consequences

• The model has been used for the impacts analysis in this FEIS as one out of three models that 

have been prepared for the project area, and it is not presented as the sole prediction of

impacts. 

Summary of Effects by Issue Factor by Alternative

Table 53 presents the summary comparison of impacts from each alternative.

Table 53. Summary of effects

Issue Factor No Action Proposed Action Phased 

Tailings Barrel Barrel Trail

ScholefieldMcCleary

Davidson 

Canyon/ 

Cienega Basin

Issue 3A.1: 

Direction and feet

of change in water 

table level

Issue 3A.3: 

Geographic extent

in which water 

resources may be 

impacted

Potential 

changes owing 

to increased 

basin water use 

and potential 

changes owing 

to climate

change could 

reduce 

groundwater

availability

More than 100-foot 

drawdown near mine pit

within several years; springs

in close proximity to pit 

(Fig Tree, Scholefield, 

Rosemont) experience over

10 feet of drawdown within 

the active mining phase; 

distant surface waters 

(Gardner Canyon, Davidson 

Canyon, Cienega Creek) 

unlikely to experience 

substantial drawdown over 

any time period, with the 

exception of Empire Gulch, 

which could experience 

several feet of drawdown 

beginning 50 years or more 

after closure of the mine; 

residences in Corona de 

Tucson unlikely to 

experience drawdown over 

5 feet; residences along 

Singing Valley Road could 

experience over 10 feet of 

drawdown within 20 years 

of closure of the mine; 

residences along Hilton 

Ranch Road could see up to 

10 feet of drawdown within 

20 years of closure of the 

mine.

Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Issue 3A.2: 

Relative 

impairment of 

mountain-front 

groundwater

recharge function 

None About 35 acre-feet, per 

year, in perpetuity

Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Issue 3A.4: 

Duration of effect 

(in years)

None Perpetuity Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as for 

proposed 

action

316 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Issue Factor No Action Proposed Action Phased 

Tailings Barrel Barrel Trail

ScholefieldMcCleary

Issue 3A.5: 

Comparison of 

mine pit water loss 

by evaporation with 

overall basin water 

balance

None Total dewatering loss 

during active mining of 

13,000 to 18,500 acre-feet; 

annual water loss in 

perpetuity of 170 to 370 

acre-feet, which is 

equivalent to ~3% of basin 

recharge

Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Issue 3A.6: 

Potential reduction 

in subsurface 

groundwater

outflow from 

Davidson Canyon

to Cienega Creek

Potential 

reduction 

owing to 

climate change

Maximum reduction of 

11.7% based on estimated 

surface flow reduction

Maximum 

reduction 

of 11.3% 

based on 

estimated 

surface 

flow 

reduction

Maximum 

reduction 

of 4.4% 

based on 

estimated 

surface 

flow 

reduction

Maximum 

reduction 

of 10.7% 

based on 

estimated 

surface 

flow 

reduction

Maximum 

reduction of 

5.8% based 

on estimated 

surface flow 

reduction

Issue 3A.7: 

Approximate 

number of wells 

within geographic 

extent of impact

None 360 to 370 Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Upper Santa 

Cruz Subbasin

Issue 3B.1: Water 

needed for 

operations from 

Santa Cruz Valley 

and comparison 

with other water 

uses and basin 

water balance, 

measured in acrefeet

None Total water use of 99,600 

acre-feet, with permitted 

water use up to 120,000 

acre-feet. Annual water use 

of 5,400 acre-feet during 

first 8 years represents an 

increase of 6.7% in area 

pumping

Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as for

proposed 

action

Issue 3B.2: 

Direction and feet 

of change in water

table level

Water-level 

declines from 

3.5 to 6.5 feet 

per year in 

vicinity of 

water supply

wells

Additional water-level 

declines from 1.5 to 3.5 feet 

per year due to pumping; 

total drawdown of 90 feet in 

vicinity of wells due to 

pumping 

Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Issue 3B.3: 

Geographic extent

in which water 

resources may be 

impacted 

None 3 to 4 miles from pumping 

center

Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Issue 3B.4: 

Duration of effect 

(in years) 

None 100 to 140 years Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Final Environmental Impact Statement for the Rosemont Copper Project 317
Chapter 3. Affected Environment and Environmental Consequences

Issue Factor No Action Proposed Action Phased 

Tailings Barrel Barrel Trail

ScholefieldMcCleary

Issue 3B.5: 

Potential for 

subsidence to occur 

as a result of 

groundwater

withdrawal

Continue of 

current rate of 

decline 0.7 to 

1.4 inches per 

year

The incremental withdrawal 

for the mine water supply

would contribute to the 

overall groundwater

withdrawal and land 

subsidence in the Sahuarita 

area

Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Issue 3B.6: 

Approximate 

number of wells 

within geographic 

extent of impact

None 500 to 550 Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Affected Environment

Relevant Laws, Regulations, Policies, and Plans

Table 54 lists the applicable laws, regulations, and policies related to the use, protection, and 

management of groundwater resources that would apply to the development and operation of the 

project. These laws, regulations, and policies, collectively referred to as “regulation(s) in the 

following sections,” are outlined in more detail in the following sections. 

Table 54. Summary of the Federal, State, and local regulatory requirements applicable 

to the project with respect to groundwater quantity

Law/Regulation Regulates

Federal

FSMs 2520, 2530, and 2880; and FS-881 and 

FS-990a Technical Guide

Watershed protection and management, water resource management, 

geological resources, groundwater management, and water quality 

management

State

Well permits and well construction standards Drilling and completion of wells or borings

Groundwater rights/water transfer Pumping of groundwater from within an active management area;

transfer of water outside an active management area

Recharge permits (water storage permit) Storage of water in a permitted underground storage facility

Recovery permits Recovery of recharged water through pumping of groundwater

Well Permits/Well Construction Standards 

(Arizona Administrative Code R12-15, Article 8)

All wells drilled within Arizona, as well as borings greater than 100 feet deep, must comply with well 

construction standards, as administered by the ADWR. Authorization is obtained by filing of a Notice 

of Intent with the ADWR. Well construction standards also apply to proper capping and abandonment 

of wells and borings when no longer needed. 

The well field located in the Upper Santa Cruz Subbasin would require ADWR approval prior to 

construction. These permits must be granted, provided that all regulatory requirements are met.

318 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Groundwater Rights/Water Transfer

The water supply for the mine would be withdrawn from wells located within the Tucson Active 

Management Area. As established under the Arizona Groundwater Management Act of 1980, within 

an active management area almost all pumping of groundwater requires some form of groundwater

right or groundwater withdrawal permit (ARS 45-451). In the case of the mine water supply, the 

ADWR has issued a Mineral Extraction and Metallurgical Processing Permit to Rosemont Copper 

(ARS 45-514). The ADWR is required to grant this permit, provided that all conditions under the 

statute are met, including the condition that no other alternative water supplies are available.

The groundwater pumped from the well field within the Tucson Active Management Area would be 

transferred outside the active management area for use at the mine. There are provisions within the 

Groundwater Management Act that restrict the transfer of water from within an active management 

area; however, the code provides for transfer of water pumped under a groundwater withdrawal 

permit, subject to payment of damages (ARS 45-543). 

Groundwater Recharge

Artificial recharge of water to the aquifer requires issuance of a water storage permit by the ADWR. 

This permit allows the holder to recharge water in an existing permitted underground storage facility. 

Contracting for available Central Arizona Project water is a separate process executed through the 

Central Arizona Water Conservation District. Public comments raised the issue that use of Central 

Arizona Project water for recharge could interfere with delivery of Central Arizona Project allotments 

to the Tohono O’odham Nation. The types of Central Arizona Project water available to Rosemont 

Copper for recharge are described more fully in the “Mitigation Effectiveness” part of this resource 

section; however, all types of water that could be used by Rosemont Copper for recharge are subject 

to delivery priority as established by law, and the recharge of such water could not be legally 

approved if it violated existing priority deliveries. 

Southern Arizona Water Rights 

Settlement Act and Associated Legislation

Negotiations to settle Indian water rights associated with portions of Tohono O’odham lands within 

the boundaries of the Tucson Active Management Area have occurred since the Southern Arizona 

Water Rights Settlement Act of 1982 and culminated with portions of the Arizona Water Settlements 

Act of 2007. As part of the settlement of these water rights, restrictions have been codified in Arizona 

law regarding the ability for the State of Arizona to approve nonexempt groundwater wells near the 

Tohono O’odham reservation (ARS 45-2711). Under these statutes, the ADWR in general may not 

approve a well that results in a drawdown of more than 10 feet after 5 years of pumping at the Tohono 

O’odham reservation boundary. When applying for well drilling permits, Rosemont Copper would 

need to provide sufficient demonstration to the ADWR of compliance with these restrictions. 

However, based on modeling conducted to support the FEIS and described in this section, it does not 

appear that the Rosemont Copper water supply would violate these statutory restrictions. Further, the 

groundwater wells already drilled by Rosemont Copper in the Sahuarita area were reviewed and 

approved by the ADWR. 

Forest Service Guidance

FSM 2520 (U.S. Forest Service 1992a) provides guidance for watershed protection and management. 

Specific areas of responsibility include planning, implementing, and monitoring watershed 

Final Environmental Impact Statement for the Rosemont Copper Project 319
Chapter 3. Affected Environment and Environmental Consequences

improvements (including abandoned mine lands); managing riparian areas for long-term 

conservation, productivity, biological diversity, and ecosystem integrity; and managing wetlands and 

flood plains. 

FSM 2530 (U.S. Forest Service 1992b) provides guidance for water resource management. Specific 

areas of responsibility include integrating water resource management with land management plans, 

coordinating with other agencies, conducting water resource investigations and collecting hydrologic 

data, and managing and monitoring water quality. Water quality management and monitoring have 

the specific objective of protecting and improving water quality to allow beneficial uses on NFS land.

FSM 2880 (U.S. Forest Service 2008d) provides direction for analysis of geological resources, hazards, 

and services. With respect to water resources, FSM 2880 provides direction for the inventory and 

analysis of groundwater dependent ecosystems. Guidance for hydrogeologic investigation techniques is

further elaborated in FS-881, “Technical Guide to Ground Water Resource Management” (Glasser et al. 

2007). Guidance for best management practices for managing water quality on NFS lands is detailed in 

FS-990a, “National Best Management Practices for Water Quality Management on National Forest 

System Lands” (U.S. Forest Service 2012i).

Forest Service direction established agency policy and objectives and assigns responsibilities to 

Forest Service personnel for that policy. Forest Service guidance is nonprescriptive in nature. It does 

not provide absolute requirements for managing water quality or water resources but provides general 

objectives to be considered when managing those resources.

Existing Conditions

The proposed project is in two groundwater basins located south of Tucson, Arizona. The mine water 

supply wells are in the Upper Santa Cruz Subbasin of the Tucson groundwater basin, which is located

in the Santa Cruz Valley west of the Santa Rita Mountains. The mine itself is in the Davidson Canyon 

drainage, which is within the administrative boundaries of the Tucson Active Management Area but is 

hydrologically separate. The Davidson Canyon drainage is immediately adjacent to the Cienega 

Basin, which is located east of the Santa Rita Mountains and which for the purposes of the FEIS is 

considered part of the Cienega Basin. It is therefore referred to here as the Davidson Canyon/Cienega 

Basin (see figure 44).

Mine Water Supply (Upper Santa Cruz Subbasin)

The proposed project anticipates using up to 5,400 acre-feet per year of fresh water over the first 

8 years of the active mining phase and 4,700 acre-feet per year after year 9 of the active mining 

phase. Minor pumping is expected to occur during the premining and final reclamation and closure 

phases, as well. The limited groundwater resources at the mine preclude developing the mine water 

supply at that location; therefore, Rosemont Copper has obtained two properties in the Upper Santa 

Cruz Subbasin on which to locate the mine water supply wells. These locations, shown in figure 44, 

are in the Sahuarita Heights area near the intersection of Sahuarita and Santa Rita Roads.

The right to extract and use up to 6,000 acre-feet of groundwater per year from the Tucson Active 

Management Area was granted to Rosemont Copper by the ADWR on January 18, 2008, under 

Mineral Extraction and Metallurgical Processing Groundwater Withdrawal Permit No. 59-

215979.0000. This type of permit is a “shall issue” permit that must be granted unless reliable 

alternative water supplies (uncommitted municipal and industrial Central Arizona Project water, 

320 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

surface water, or effluent) are available at comparable cost at the point where the mine’s wellhead or 

distribution system would otherwise exist (ARS 45-514(A)(2) and (3)).

Total groundwater use by Rosemont Copper from the Upper Santa Cruz Subbasin is expected to be 

99,600 acre-feet and is permitted up to 120,000 acre-feet. Additional process water would be obtained 

through pit dewatering at the mine site, which would reduce the amount needed to be transported to 

the mine site; the dewatering amount is estimated to total 13,000 to 18,500 acre-feet (Montgomery 

and Associates Inc. 2010; Tetra Tech 2010g).

Once transported, process water is expected to be fully consumed; no wastewater discharge is 

expected to be generated at the mine site. Where not directly consumed, most of the water would be 

entrained as pore water in the tailings facility and heap leach pad (except for the Barrel Alternative). 

General Hydrogeologic Framework

The Upper Santa Cruz Subbasin is a broad, north-south trending alluvial valley drained by the Santa 

Cruz River and its tributaries. The Upper Santa Cruz Subbasin is bounded on the east by the Santa 

Rita Mountains and on the west by the Sierrita Mountains. At the deepest points, the Upper Santa 

Cruz Subbasin contains several thousand feet of alluvial materials. The principal hydrologic units in 

the analysis area, in descending order, are as follows: recent alluvium consisting of unconsolidated 

modern stream channel and flood plain sediments; the Fort Lowell Formation of Quaternary age; the 

Tinaja beds of Tertiary age; the Pantano Formation and the Helmet Fanglomerate of Tertiary age; and 

a bedrock complex of Precambrian to Tertiary age.

The recent alluvium comprises stream channel, flood plain alluvium, and terrace deposits that occur

chiefly beneath the channel and flood plain of the Santa Cruz River and tributary washes. Thickness 

of recent alluvium ranges from zero at the contact with older rocks to probably no more than 100 feet. 

The Fort Lowell Formation and Tinaja Beds are collectively referred to as basin-fill deposits. 

Thickness ranges from a few feet at the margins of the basin to more than 1,200 feet, generally 

increasing with distance from the mountain areas. The Fort Lowell Formation and Tinaja beds form

the principal aquifer in most parts of the analysis area. Tertiary age sediments lying below the Tinaja 

beds include the Pantano Formation and the Helmet Fanglomerate. The Pantano Formation is 

generally poorly permeable; however, the Helmet Fanglomerate is the principal aquifer for the 

Mission well field (located west of the Pima Mine Road recharge project). Except where abundantly 

fractured or weathered, the rocks that form the bedrock complex below the Pantano Formation are 

poorly permeable and yield only small quantities of groundwater to wells. In the analysis area, the 

bedrock complex is believed to function as a relatively impermeable basal unit below the regional 

aquifer.

Sources of Recharge

Within the analysis area, groundwater recharge includes natural recharge from infiltration of 

precipitation and surface runoff; incidental recharge from agricultural irrigation and mine tailing 

seepage from the Sierrita mine; and artificial recharge at permitted underground storage facilities, 

including wastewater treatment facilities. 

The principal source of recharge in the area is from infiltration of stream flow along the Santa Cruz 

River channel and tributary washes (estimated to be approximately 12,300 acre-feet per year within

the analysis area). Another important source of natural recharge occurs along the mountain fronts as a 

result of infiltration of runoff originating in the mountain areas near the basin margins (estimated to 

Final Environmental Impact Statement for the Rosemont Copper Project 321
Chapter 3. Affected Environment and Environmental Consequences

be approximately 9,700 acre-feet per year from the Sierrita and Santa Rita Mountains within the 

analysis area). These two sources are the principal components of natural groundwater recharge in the 

analysis area. Incidental recharge from agricultural irrigation primarily comes from irrigation of 

pecan groves by Farmers Investment Company, located along the Santa Cruz River west and south of 

the Rosemont Copper properties (see figure 44), and accounts for about 5,900 acre-feet of recharge

annually. Seepage from mine tailing impoundments at Sierrita accounts for about 7,500 acre-feet of 

recharge annually; the mine tailings at Esperanza and Twin Buttes are no longer considered to be 

discharging. 

Artificial recharge is attributable to four underground storage facilities in the analysis area: Pima 

Mine Road Recharge Project, Robson Ranch Quail Creek, San Xavier Arroyos Project, and Sahuarita 

Wastewater Treatment Plant. Green Valley Wastewater Treatment Plant was historically recharging 

the aquifer and continues to do so; however, a large portion of the effluent from the plant is now 

recharged at Robson Ranch Quail Creek. All four underground storage facilities are currently 

artificially recharging the aquifer; these recharge locations are shown in figure 44. Artificial recharge 

rates reported in 2007 were used for flow modeling and totaled approximately 24,300 acre-feet. Total 

recharge in the analysis area, both natural and artificial, is approximately 60,000 acre-feet per year.

Groundwater Withdrawals

Groundwater withdrawals for agricultural irrigation, mining, public water supplies, domestic uses, 

and recreational uses have resulted in groundwater-level declines in the area. These historic and 

present groundwater withdrawals are one of the principal factors influencing the direction of 

groundwater movement in the area. Based on data published by the ADWR, in 2006 groundwater

withdrawals in the analysis area totaled approximately 82,000 acre-feet. Major water users include 

pecan grove irrigation by Farmers Investment Company (30,000 acre-feet), mining pumping 

associated with the ASARCO Mission and Freeport-McMoRan Sierrita Mines (33,400 acre-feet), 

and pumping by public water providers in the area, including recreational uses such as golf course 

irrigation (18,700 acre-feet). Major water providers include Community Water Company of Green 

Valley, Green Valley Domestic Water Improvement District, Las Quintas Serenas Water Company, 

Farmers Water Company, Rancho Sahuarita Water Company, and Quail Creek Water Company. 

Major sources of recharge and groundwater withdrawal in the analysis area are summarized in figure 

46. Overall, groundwater withdrawals exceed sources of recharge by approximately 22,000 acre-feet 

per year, not including the proposed Rosemont Copper mine water supply pumping. 

Groundwater Levels and Conditions

Overall, groundwater levels in the analysis area have declined as more groundwater has been 

withdrawn from the regional aquifer over the past several decades than has been replenished by 

recharge, although the rate of groundwater-level decline has decreased since 1980, compared with the

rate of decline from the previous four decades. Trends in groundwater-level changes vary by location; 

measured groundwater levels during the past 10 years for wells nearest the Rosemont Copper 

properties are generally declining at a rate of 1 to 2 feet per year. 

Groundwater recharge at Pima Mine Road Recharge Project and natural flood recharge along the 

Santa Cruz River have mitigated or reversed groundwater-level declines in the central and northern 

portions of the Green Valley area. However, relatively larger groundwater-level declines associated 

with pumping in the Green Valley area still exist to the south. 

322 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 46. Comparison of sources of recharge and withdrawal sinks in mine water 

supply analysis area in the Upper Santa Cruz Subbasin

The groundwater withdrawals previously described are those associated with large water users; 

additional groundwater is drawn by what are known as “exempt” wells. Exempt wells are typically 

residential or stock wells that must be designed to pump less than 35 gallons per minute and irrigate 

no more than 2 acres. Groundwater use from exempt wells is difficult to track; other than when 

drilled, there are no reporting requirements to the ADWR associated with exempt wells. Groundwater

levels in shallow residential wells located near the western portion of the Rosemont Copper property 

are higher than groundwater levels measured deeper in the aquifer and appear to vary less in response 

to seasonal agricultural pumping than deeper groundwater levels. The average annual groundwater

elevation in the shallow residential wells is approximately 60 feet higher in the area west of the 

Rosemont Copper property, a difference that decreases to a negligible amount east of the Rosemont 

Copper property. 

The variation in water levels likely reflects complex subsurface aquifer units and a dynamic aquifer 

system, and possibly the potential for a perched aquifer system. Patterns of groundwater movement in 

the area are controlled by location and quantity of groundwater recharge and discharge, including 

groundwater pumped from wells, and by aquifer hydraulic properties. Groundwater-level contours 

based on field measurements collected from late 2004 through early 2005 are shown in figure 47. 

The direction of groundwater movement is generally parallel to the Santa Cruz River, from south to 

north. 

In general, groundwater movement west of the river is toward the northeast, and groundwater

movement east of the river is toward the northwest. Groundwater-level contours in the vicinity of the 

two Rosemont Copper properties indicate that groundwater flow gradient is toward the northwest.

Pumping tests were conducted at two Rosemont Copper test wells in 2007. Based on the results of 

pumping tests, the sustainable long-term pumping rates for production wells installed at these two 

locations were estimated to be approximately 1,500 and 500 gallons per minute.

Final Environmental Impact Statement for the Rosemont Copper Project 323
Chapter 3. Affected Environment and Environmental Consequences

Figure 47. Groundwater levels in the Upper Santa Cruz Subbasin in 2004 and 2005

324 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Land Subsidence

Most subsidence in Arizona occurs as a result of pumping groundwater from aquifers, an activity that 

removes support for alluvial particles and allows the material to compact. Historic land subsidence

resulting from groundwater withdrawal has been recorded in the Green Valley area of the Santa Cruz 

Basin (figure 48). Data from 2006 indicate that the groundwater withdrawals by nonexempt well 

owners in the Green Valley area totaled approximately 82,100 acre-feet. That total encompasses

30,000 acre-feet by the Farmers Investment Company for irrigating pecan groves, 33,400 acre-feet by 

the ASARCO Mission and Freeport-McMoRan Sierrita operations, and 18,700 acre-feet for public 

water supply, including golf course irrigation (Errol L. Montgomery and Associates Inc. 2009c). 

During the first 8 years of the active mining phase, Rosemont Copper would use approximately 5,400

acre-feet per year from water supply wells located near Sahuarita; this quantity would diminish to 

approximately 4,700 acre-feet per year for the remaining years of the active mining phase (Errol L. 

Montgomery and Associates Inc. 2009a).

The ADWR publishes annual maps showing land subsidence in the Sahuarita and Green Valley area. 

The most recent map, for the period from February 2009 through January 2010, is shown in figure 

48; the map shows that subsidence of less than 0.2 inch occurred in a broad area north of East

Sahuarita Road (west of I-19) southward to near Whitehouse Canyon Road (Arizona Department of 

Water Resources 2010). Over that period, two limited areas near major supply wells subsided by 0.7

to 1.4 inches. Incremental additional subsidence is expected on an annual basis owing to future 

committed groundwater withdrawals in the area, including groundwater withdrawals associated with 

the mine water supply.

Mine Site (Davidson Canyon/Cienega Basin)

General Hydrogeologic Framework and Conditions

Hydrogeology in the project area, within Davidson Canyon and the Cienega Basin on the east side of 

the Santa Rita Mountains, is fundamentally different from that at the proposed well field in the Santa 

Cruz Valley. Although geology had been well characterized in the area, prior to the proposed project 

limited hydrogeologic information such as well logs, groundwater quality samples, or groundwater 

hydrographs existed for the immediate vicinity of the mine. Beginning in 2008, an intensive 

hydrogeologic investigation was undertaken, including the installation of 30 wells and piezometers 

at 17 locations in the vicinity of the mine. The wells were designed to characterize the near-pit

hydrogeology, monitor groundwater levels at multiple depths, characterize the hydrogeology 

throughout the upper Davidson Canyon watershed, including bedrock and alluvium, and install longterm monitoring wells between 1 and 5 miles away from the proposed mine pit. Monitoring has 

continued in these wells, as well as in springs and seeps, including aquifer testing, water-level and 

flow monitoring, and water quality sampling (Errol L. Montgomery and Associates Inc. 2009b).

Substantial amounts of hydrogeologic information exist elsewhere in the Davidson Canyon/Cienega 

Creek basin away from the immediate mine site, including lithologic logs, groundwater levels dating 

back to the 1940s, and aquifer testing along both upper and lower Cienega Creek and Davidson 

Canyon.

Hydrogeology in the project area is characterized by fractured and faulted Paleozoic age sedimentary 

and Mesozoic age sedimentary and volcanic rocks, bounded on the west by competent Precambrian 

intrusive rocks that form the core of the Santa Rita Mountains and bounded on the southeast by 

unfractured, strongly cemented basin-fill deposits (see figures 29 and 30 in the “Geology, Minerals, 

and Paleontology” resource section). Groundwater in the vicinity of the mine exists in three general 

Final Environmental Impact Statement for the Rosemont Copper Project 325
Chapter 3. Affected Environment and Environmental Consequences

Figure 48. Subsidence in the Sahuarita and Green Valley areas, Pima County, 

February 2009 through January 2010. Adapted from ADWR (2010).

326 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

areas. Limited quantities of groundwater occur in the faults and fractures of the consolidated 

Mesozoic and Paleozoic basement rocks of the Santa Rita Mountains. Moderate quantities of 

groundwater occur in the basin-fill deposits in upper Cienega Basin to the southeast of the project. 

Groundwater also exists in the shallow recent alluvium along the ephemeral wash channels. This 

alluvial groundwater is recharged during substantial storm events and may then infiltrate into 

underlying bedrock fractures, evaporate or be transpired by plants, or move as subsurface flow 

downstream. Groundwater in the alluvial stream deposits is believed to discharge in several springs in 

lower Davidson Canyon (Reach 2 Spring and Escondido Spring), as well as to eventually discharge 

subsurface from Davidson Canyon at the confluence with Cienega Creek (Tetra Tech 2010a). 

The majority of the proposed mine pit would be completed in faulted and fractured bedrock. 

Groundwater in the project area is found in relatively limited quantities in the bedrock complex. 

Regionally in the Cienega Basin, the majority of the groundwater is stored in the basin-fill deposits 

and in the shallow alluvium occurring along the principal surface water drainage channels.

Based on measurements obtained in approximately 70 wells, piezometers, and drill holes during the 

period from 1975 through 2008, the measured groundwater levels in the immediate vicinity of the 

proposed pit ranged from artesian conditions of about 34 feet above to more than 400 feet below land 

surface. Contours of groundwater elevation for the region are shown in figure 45. The direction of 

groundwater movement in the bedrock appears to be strongly influenced by topography, with the 

entire basin generally draining to the north toward Tucson. The general direction of groundwater

movement in the immediate project area is toward the east but transitions with distance to the 

northeast. 

Groundwater enters the basin as recharge originating from precipitation and exits the basin through 

evapotranspiration, groundwater outflow, groundwater pumping, and discharge to surface streams. 

Assumptions for the exact proportion of each component of the water balance differ between the 

three models prepared for the project area, as shown in table 55. It should be noted that the Dr. Myers 

Mine Site model covers a different area from the Tetra Tech Mine Site and Montgomery Mine Site 

models.

Table 55. Estimate of water balance for the Davidson Canyon/Cienega Basin

Component of Steady-State 

Model Water Balance

Montgomery and 

Associates (2010)

Tetra Tech 

(2010g)

Myers 

(2010a)*

Recharge from precipitation (acre-feet) 6,500 9,909 Estimated 7,000

Evapotranspiration (acre-feet) 5,007 4,240 Estimated 1,200

Pumping† (acre-feet) 400 to 500 Not estimated Not estimated

* Model domain differs from Montgomery and Associates and Tetra Tech model domains.

† Value was estimated but not used in the model.

Wells in the project area are primarily used for domestic and stock water uses and have sustainable 

well yields from less than 1 to 3 gallons per minute. Estimates of groundwater use by wells within the 

Davidson Canyon/Cienega Basin are approximately 400 to 500 acre-feet per year; most of this occurs 

in the vicinity of Sonoita-Elgin, while a smaller proportion may occur in the lower part of the 

Cienega Basin, including in the vicinity of the project (Montgomery and Associates Inc. 2010).

Water use by domestic and stock wells has steadily increased in the basin. In 1980, approximately 

630 domestic or stock wells were known to be in the Cienega Basin. By 1990, the number of 

Final Environmental Impact Statement for the Rosemont Copper Project 327
Chapter 3. Affected Environment and Environmental Consequences

domestic and stock wells had increased to more than 1,000, and by 2010, the number of domestic and 

stock wells had increased to more than 1,800 (Arizona Department of Water Resources 2011c). 

Seeps and Springs

Seeps and springs represent an interface between groundwater and surface water systems, as well as 

serving important roles for riparian, biological, and cultural resources. The DEIS analyzed impacts to 

seeps and springs in a variety of resource sections, which ultimately resulted in confusion for the 

reader. For the FEIS, all impacts associated with seeps, springs, and riparian areas have been 

consolidated into a new section titled “Seeps, Springs, and Riparian Areas.” 

Environmental Consequences

Direct and Indirect Effects of Each Alternative

No Action Alternative

Under the no action alternative, groundwater conditions in both the Upper Santa Cruz Subbasin and 

the Davidson Canyon/Cienega Basin will continue to change to reflect existing groundwater uses and 

increased future groundwater uses. Groundwater levels in the Upper Santa Cruz Subbasin will 

continue to decline because of existing groundwater withdrawals, as shown in table 56. These 

groundwater withdrawals will increase further with expected population increases in Pima County, 

although there is also the potential for alternative water sources to be used such as Central Arizona 

Project water to supply these demands. Land subsidence would likely continue to occur in the 

Sahuarita area at the current rate of 0.7 to 1.4 inches per year.

In the Davidson Canyon/Cienega Basin, domestic and stock water use associated with residential 

development has increased with population growth in the Sonoita area and elsewhere. This water use 

is expected to continue to grow as the population increases. These withdrawals have the potential to 

impact springs, seeps, and perennial or intermittent streams such as Cienega Creek. Impacts could 

occur either by direct surface disturbance of the watershed or by changes in groundwater levels

resulting from groundwater withdrawal, not only by municipal wells but also by the combined impact 

from dispersed exempt domestic wells.

Climate change will affect groundwater and surface water resources, as well. For the Southwest, 

expected changes that are occurring and will continue to evolve include an increase in mean annual 

temperature, a more frequent drought cycle, a decrease in winter precipitation, and an increased 

frequency of heavy rains and flooding. These changes will have effects on groundwater levels and on 

springs, seeps, and perennial or intermittent streams, particularly Cienega Creek, Empire Gulch, 

Davidson Canyon, and Gardner Canyon. Effects from climate change will exacerbate the stresses on 

these waters from increased groundwater use for domestic and stock purposes. 

Impacts Common to All Action Alternatives

Impacts to groundwater quantity are associated with the mine water supply pumping in the Upper 

Santa Cruz Subbasin and the drawdown from the mine pit, located east of the Santa Rita Mountains. 

Both the mine water supply pumping and the mine pit are common to all action alternatives. 

Therefore, with respect to groundwater level changes, groundwater availability, and impacts to wells,

the impacts from these activities are common to all action alternatives.

328 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Impacts Resulting from Mine Water Supply 

Pumping in Upper Santa Cruz Subbasin

Predicted Change in Groundwater

Levels and Geographic Area of Impact

The water table in the Upper Santa Cruz Subbasin is in decline as a result of existing municipal, 

residential, agricultural, and mining withdrawals. Results of the mine water supply model (Barter and 

Odom 2011; Errol L. Montgomery and Associates Inc. 2009a, 2010) indicate that additional 

drawdown of the water table would occur as a result of both existing and future public and private 

pumping and the proposed mine water supply withdrawal (see table 56). 

Table 56. Modeled groundwater-level drawdown for selected wells

Well Cadastral Location, 

Name, and Proximity to 

Pumping

Time 

Period

Estimated 

Drawdown 

without Mine 

Water Supply 

Pumping 

(feet)

Estimated 

Drawdown 

with Mine Water 

Supply Pumping 

(feet)

Estimated 

Additional 

Drawdown from 

Mine Water 

Supply Pumping 

(feet)

D-17-14 07DDD (FICO S-12)

Located ~2,000 feet north of 

northern parcel

Year 10

of active 

mining

10 50 40

D-17-14 07DDD (FICO S-12)

Located ~2,000 feet north of 

northern parcel

Year 20

of active 

mining

90 150 60

D-17-14 21ACD

Located immediately adjacent to 

west side of southern parcel

Year 10

of active 

mining

25 60 35

D-17-14 21ACD

Located immediately adjacent to 

west side of southern parcel

Year 20

of active 

mining

70 120 50

D-17-14 17DCC

Located between the two 

parcels, ~3,000 feet south of 

northern parcel and ~7,000 feet 

northwest of southern parcel

Year 10

of active 

mining

15 60 45

D-17-14 17DCC

Located between the two 

parcels, ~3,000 feet south of 

northern parcel and ~7,000 feet 

northwest of southern parcel

Year 20

of active 

mining

80 150 70

D-17-14 04BCB (City of Tucson 

SC-023A)

Located ~2 miles northeast of 

northern parcel

Year 10

of active 

mining

25 35 10

D-17-14 04BCB (City of Tucson 

SC-023A)

Located ~2 miles northeast of 

northern parcel

Year 20

of active 

mining

130 160 30

D-17-14 30BBB (FICO S-33)

Located ~2 miles southwest of 

northern parcel

Year 10

of active 

mining

5 20 15

D-17-14 30BBB (FICO S-33)

Located ~2 miles southwest of 

northern parcel

Year 20

of active 

mining

70 100 30

Final Environmental Impact Statement for the Rosemont Copper Project 329
Chapter 3. Affected Environment and Environmental Consequences

The threshold of significance for impacts to wells was selected as being 10 feet. The geographic area 

within which water supply, domestic, stock, and irrigation wells would be impacted above this 

threshold of significance is shown in figure 49. After 10 years of active mining, this represents an area up 

to 3 miles from the Rosemont well field. After 20 years of active mining, this represents an area up to 4 

miles from the Rosemont well field.

In order to compare the estimated impacts with background changes in water levels, five wells were 

selected that represent a variety of distances and directions from the two Rosemont Copper properties 

on which pumping would occur. Note that these do not represent the only wells in the analysis area. 

These wells have been selected for their record of historic water levels and because they were 

specifically assessed in the Errol L. Montgomery and Associates Inc. (2009a) modeling report. 

Locations of these wells are shown in figure 49. The modeled drawdown in water levels at each well 

without mine water supply pumping and with mine water supply pumping at two points in time 

(10 and 20 years after pumping commences at the start of the active mining phase) is shown in 

table 56.

The contours shown in figure 49 represent the drawdown expected to occur over 20 years of the 

active mining phase that is solely due to the mine water supply pumping; however, significant 

drawdown is expected in the area due to other groundwater pumping. Drawdown expected to occur 

over 20 years of the active mining phase due to both mine water supply pumping and other estimated 

groundwater pumping is shown in figure 50. Drawdown expected to occur over 20 years due solely to 

other groundwater pumping (without the mine water supply pumping) is shown in figure 51.

In addition to drawdown, potential changes in groundwater flow direction are a potential impact from 

mine water supply pumping. Water-level elevation contours, which indicate the direction of 

groundwater flow, after 20 years of active mining are shown in figure 52 (with both mine water 

supply pumping and other groundwater pumping) and figure 53 (without mine water supply pumping, 

only other groundwater pumping). No significant changes in flow direction are expected to occur as a 

result of mine water supply pumping. The gradient of the water table would change slightly, from 8.1 

feet per 1,000 feet without mine water supply pumping, to 9.4 feet per 1,000 feet with mine water 

supply pumping.

Groundwater-level drawdown resulting from pumping for the mine water supply is estimated to be as 

great as 90 feet immediately adjacent to the Rosemont Copper properties and 10 feet or less 

approximately 3 to 4 miles from the Rosemont Copper properties. The area within the 10-foot 

drawdown contour encompasses approximately 42 square miles. The annual drawdown rate with and 

without mine water supply pumping, along with the historic annual drawdown rate for each well, is

shown in table 57. The increased rate of decline would persist for the 20-year expected duration of 

pumping during the active mining phase. When pumping ceases, some recovery of water levels may 

be seen in the immediate vicinity of the Rosemont Copper properties; however, in general, the overall 

drop in water levels caused by the mine supply pumping would not recover unless water levels in the 

regional aquifer began increasing as a whole.

330 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 49. Geographic area of impact from mine water supply pumping after 20 

years of pumping during the active mining phase (Errol L. Montgomery and 

Associates Inc. 2009a)

Final Environmental Impact Statement for the Rosemont Copper Project 331
Chapter 3. Affected Environment and Environmental Consequences

Figure 50. Regional water-level drawdown after 20 years of active mining, including 

mine supply pumping

332 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 51. Regional water-level drawdown after 20 years without mine supply 

pumping

Final Environmental Impact Statement for the Rosemont Copper Project 333
Chapter 3. Affected Environment and Environmental Consequences

Figure 52. Regional water-level elevations after 20 years of active mining, including 

mine supply pumping

334 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 53. Regional water-level elevations after 20 years without mine supply 

pumping

Final Environmental Impact Statement for the Rosemont Copper Project 335
Chapter 3. Affected Environment and Environmental Consequences

The Montgomery Mine Water Supply model was originally conducted only for 20 years of active 

mining, ending when mine water supply pumping ceases (Errol L. Montgomery and Associates Inc. 

2009a, 2010). While this represents the point of maximum drawdown in the immediate vicinity of the 

Rosemont wells, the Forest Service requested that the model be extended until the cone of depression 

stops expanding. The extended modeling concluded that the cone of depression would keep 

expanding until between 100 and 140 years after pumping ceases. During this time, the cone of 

depression would reach approximate equilibrium and stop expanding. The 10-foot drawdown contour 

is projected to expand an additional 1 to 2 miles laterally before it stops expanding, encompassing 

approximately 78 square miles, as shown in figure 49 (Barter and Whittier 2011b).

The values in tables 56 and 57 and in figure 50 represent predicted drawdown. However, a seasonal 

variation of 10 to 100 feet above and below the average annual groundwater level is expected as a 

result of agricultural pumping in the area, although the effect of seasonal agricultural withdrawal may 

decrease if the agricultural land is converted to residential use. 

Table 57. Modeled and historic rates of water-level change for selected wells

Well Cadastral Location, Name, 

and Proximity to Pumping

Without Mine 

Water Supply 

Pumping

Annual Rate 

of Change 

(feet per year)

With Mine 

Water Supply 

Pumping

Annual Rate 

of Change 

(feet per year)

Attributable to 

Mine Water 

Supply 

Pumping

Annual Rate 

of Change 

(feet per year)

Historic 

Annual Rate 

of Change 

(feet per year

(date range))

D-17-14 07DDD (FICO S-12)

Located ~2,000 feet north of northern 

parcel

4.5 7.5 3 1.7 

(1947 to 2005)

D-17-14 21ACD

Located immediately adjacent to west 

side of southern parcel

3.8 6 2.2 1 

(1975 to 2006)

D-17-14 17DCC

Located between the two parcels, 

~3,000 feet south of northern parcel 

and ~7,000 feet northwest of southern 

parcel

4 7.5 3.5 3.2 

(1953 to 1979)

D-17-14 04BCB (City of Tucson SC023A)

Located ~2 miles northeast of northern 

parcel

6.5 8 1.5 1.2 

(1968 to 2007)

D-17-14 30BBB (FICO S-33)

Located ~2 miles southwest of 

northern parcel

3.5 5 1.5 3.5 

(1952 to 2005)

As described in chapter 1, the active mining phase of the project is 20 to 25 years; the groundwater

modeling for the water supply was conducted for only 20 years, which is the life of the current 

extraction permit issued by the ADWR. If mining continued for longer than 20 years, which is a 

likely scenario, then additional water use would occur and there would be additional impacts to 

groundwater levels above and beyond those described by the modeling. However, the rate of change 

or decline in subsequent years after year 20 of active mining would be consistent with those modeled. 

For instance, with respect to the selected wells shown in table 57, if the upper range of the active 

mining phase were reached (25 years), the additional drawdown due to the mine water supply 

pumping would range from 7.5 to 17.5 feet. 

336 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

As shown in table 58, approximately 500 to 550 domestic or other production wells registered with 

the ADWR could be impacted by drawdown in groundwater levels over 10 feet (i.e., are located 

within the 10-foot drawdown contour); approximately 62 percent of these are smaller domestic or 

exempt wells. Note that this is not considered a comprehensive inventory of wells in the area, nor are 

there adequate well construction and operation details to determine whether this drawdown would 

impact individual well performance. Shallow wells in the analysis area are not specifically assessed 

by the model because of their possible disconnect with the regional aquifer and the general lack of 

information about the construction and operation of small domestic supply wells. However, in 

general, similar drawdowns could also occur in shallow wells, although the model is not able to 

predict these specific impacts. 

Table 58. Number of registered wells potentially impacted near mine water supply

pumping

Within the 10-Foot 

Drawdown 

Contour, 140 Years

after Pumping

Within the 10-Foot 

Drawdown 

Contour, 20 Years 

after Pumping

Within the 30-Foot 

Drawdown 

Contour, 20 Years

after Pumping

Within the 50-Foot 

Drawdown 

Contour, 20 Years 

after Pumping

Number of wells 500 to 550 350 to 400 150 to 200 100 to 150

Note: Number of wells excludes exploratory wells, monitor wells, piezometers, test wells, and cathodic protection wells.

It includes domestic wells, stock wells, production wells, and public supply wells.

In addition to the representative wells analyzed in tables 56 and 57, several specific wells associated 

with water companies, municipalities, or other government entities have been assessed. These wells 

are summarized in table 59.

Table 59. Modeled groundwater-level drawdown for selected public supply, municipal, 

or government wells

Cadastral 

Location Well Owner Well Depth (feet)

Expected Drawdown in Regional 

Aquifer from Rosemont Copper 

Pumping after 20 Years (feet)

D-18-13 02BAB Community Water Company of Green Valley 700 <10

D-18-13 02BDD Community Water Company of Green Valley 1,000 <10

D-17-13 26BCC Las Quintas Serenas Water Company 807 20 to 30

D-17-13 26CCD Las Quintas Serenas Water Company 922 20 to 30

D-17-13 25DAB* Pima County 300 20 to 30

D-17-14 08ADD* Pima County Parks and Recreation 500 30 to 40

D-17-13 14CAB* Pima County Solid Waste Management 470** 20 to 30

D-17-13 01CDD Sahuarita Water Company 905 20 to 30

D-17-13 01BAC Sahuarita Water Company 990 20 to 30

D-17-13 01ABB Sahuarita Water Company 982 20 to 30

D-16-13 36CBC Sahuarita Water Company 1,053 <10

D-17-13 11BAA Sahuarita Water Company 1,080 20 to 30

D-17-13 01ACC† Town of Sahuarita 1,135 20 to 30

D-17-14 04BCB City of Tucson 600 20 to 30

D-17-14 02BAA City of Tucson 624 <10

D-16-14 26CCC City of Tucson 700 <10

D-16-14 21DDC City of Tucson 600 <10

D-16-14 21CCB City of Tucson 600 <10

Final Environmental Impact Statement for the Rosemont Copper Project 337
Chapter 3. Affected Environment and Environmental Consequences

Cadastral 

Location Well Owner Well Depth (feet)

Expected Drawdown in Regional 

Aquifer from Rosemont Copper 

Pumping after 20 Years (feet)

D-17-13 26AAB Valle Verde Water 677 20 to 30

D-18-13 02BCC Community Water Company of Green Valley 515 <10

D-17-14 04ACA City of Tucson 602 20 to 30

D-16-14 28CCB City of Tucson 500 <10

D-16-14 21DBB City of Tucson 650 <10

D-16-14 20ACB City of Tucson 535 <10

D-16-14 20ADA City of Tucson 540 <10

D-16-14 20BBB City of Tucson 403 <10

D-17-13 26A Valle Verde Water 507 10 to 20

D-17-13 36CDD* Pima County Wastewater (water supply) 400 10 to 20

D-17-13 36DAC* Pima County Wastewater (monitoring wells) 30 to 60 10 to 20

D-17-13 36CAD* Pima County compliance well at Green Valley 

Water Reclamation Facility 230 10 to 20

D-17-13 36BDD* Pima County compliance well at Green Valley 

Water Reclamation Facility 230 10 to 20

* Pima County provided comments on these specific wells during cooperating agency review of the FEIS. They indicate that 

for the given drawdown shown in the table, pumps in some wells may have to be lowered, but water levels would remain 

within the screened interval of the well. However, they further note that this reduces the useful life of the well and that if 

drawdowns are greater than those modeled due to a longer duration of pumping, some of these wells would need to be 

replaced.

† This well is offered specific protection under a License for Right-of-Way Encroachment agreement executed between 

Rosemont Copper and the Town of Sahuarita on June 24, 2013.

Effect on Overall Groundwater Availability

In addition to impacts to specific wells from groundwater drawdown, there is the potential to affect 

overall groundwater availability within the Upper Santa Cruz Subbasin and within the Tucson Active 

Management Area as a whole. Within the Upper Santa Cruz Basin Subbasin, the 5,400 acre-feet per 

year represents a 6 to 7 percent increase over the current estimated pumpage demand of 82,000 acrefeet; within the entire Tucson Active Management Area, it represents a 2 percent increase over the 

estimated pumpage demand of 252,000 acre-feet. 

Effect on Land Subsidence — Land subsidence associated with groundwater withdrawal in the 

Santa Cruz Valley is expected to continue in association with the degree of pumping in excess of 

recharge. This subsidence is being monitored by the ADWR and currently is occurring in the 

Sahuarita area at a rate of 0.7 to 1.4 inches per year. The incremental withdrawal from the Upper 

Santa Cruz Subbasin for the mine water supply would contribute to the overall groundwater 

withdrawal from the Sahuarita area that has resulted in the land subsidence observed in the area.

Cooperating agencies also raised concerns over land subsidence occurring on the east side of the 

Santa Rita Mountains, near the mine pit itself. The concern is that dewatering of the aquifer due to the 

mine pit may change hydrostatic pressures in the subsurface and result in collapse of karst or cave 

features. The potential for this subsidence near the mine pit was analyzed by Rosemont Copper in 

2007: “Although there are limestone units mapped in the western Project area, there is no visible

evidence of karst terrain. Therefore, subsidence due to karst does not pose a credible risk to

construction operations at the Project site” (Tetra Tech 2007b).

338 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Additional studies contracted by the Coronado in response to public comments on the DEIS 

investigated the potential for karst or cave features to occur in the vicinity of the mine pit. These 

studies reached similar conclusions, finding that the potential for features to exist in the vicinity of 

the mine is low (Hoag, Peachey et al. 2012). Cooperating agency concerns included areas beyond the 

immediate mine site, since a much larger region might experience water-level drawdown due to the 

mine pit. However, the greatest drawdowns and the greatest changes in hydrostatic pressure would be 

experienced in the area considered, and the lack of cave or karst features suggests a relatively low 

chance for subsidence. The Coronado has developed a requirement to monitor for the presence of 

cave or karst features during operations; full details are included in appendix B (see mitigation

measure FS-GMP-02).

Effect on Tohono O’odham Nation – Under the Southern Arizona Water Rights Settlement Act and 

associated legislation, restrictions have been placed on well drilling and pumping with respect to the 

water supply of the Tohono O’odham Nation. Based on modeling conducted to support the FEIS and 

described in this section, it does not appear that impacts from the Rosemont Copper water supply 

pumping would intersect the Nation boundary in a way that would violate these statutory 

restrictions—specifically, a drawdown greater than 10 feet intersecting the boundary of the Nation 

after 5 years of pumping. As shown in figure 49, the 10-foot drawdown contour just touches the 

boundary of the Nation after 20 years of pumping.

Impacts Resulting from the Mine 

in the Davidson Canyon/Cienega Basin

The results of the groundwater modeling in the Davidson Canyon/Cienega Basin indicate that the 

mine pit would create a permanent drawdown of the water table. Groundwater would flow toward the 

mine pit in perpetuity from the time at which the excavation intersects the water table. At first, during 

active mining, groundwater would be pumped directly from the mine pit or from dewatering wells 

next to the mine pit. After final reclamation and closure, the pit is expected to gradually fill with 

groundwater, forming a mine pit lake. The mine pit lake would lose water through evaporation, and 

this water would be perpetually replenished in part by groundwater from the regional aquifer. In this 

way, the mine pit lake is expected to act as a permanent regional hydraulic sink. 

Pumping of the mine pit would draw down the level of groundwater in the regional aquifer, forming 

what is known as a cone of depression (figures 54 through 58). Because the mine pit lake would act 

to remove groundwater in perpetuity from the system, this cone of depression is expected to persist in 

perpetuity. The boundaries of the cone of depression would migrate outward for a very long period of 

time until they eventually reach equilibrium. The various models estimate equilibrium would be 

reached between 700 and 7,000 years after closure of the mine. The cone of depression would stop 

expanding, but the flow of groundwater toward the mine pit would be a permanent feature of the 

regional aquifer. Note that a cone of depression does not indicate a reversal of gradient or a change in 

the direction of groundwater flow. These are two separate concepts. The cone of depression extends 

many miles outward from the mine pit; the area in which groundwater flow is actually reversed is 

relatively close to the pit.

Predicted Change in Groundwater Levels as a Result of the Mine Pit

The temporal bounds of analysis extends to 1,000 years after mine closure. In order to assess the 

progression of impacts, snapshots of groundwater conditions are assessed at the end of active mining 

and at 20, 50, 150, and 1,000 years after final reclamation and closure. The modeled areas of impact, 

as defined by the 5-foot drawdown contours of the Montgomery and Tetra Tech Mine Site models and 

Final Environmental Impact Statement for the Rosemont Copper Project 339
Chapter 3. Affected Environment and Environmental Consequences

the 1-foot drawdown contour of the Dr. Myers model (Dr. Myers did not publish a 5-foot contour), 

are shown for selected time periods in figures 54 through 58. After 1,000 years, the area within the 

5-foot contour encompasses approximately 134 square miles, as shown in figure 58.

Within the analysis area, impacts are further assessed at selected geographic locations, chosen 

because they represent important areas of potential surface water/groundwater interaction throughout 

the Davidson Canyon/Cienega Basin and because they represent a range of distance and direction 

from the mine pit. The selected areas have been refined since the DEIS to include additional points of 

concern. It should be noted that these areas were selected in this section solely as representative 

points to convey a sense of groundwater drawdown to the reader; predicted impacts to individual

springs, seeps, streams, and riparian areas are fully analyzed in the new “Seeps, Springs, and Riparian

Areas” resource section of the FEIS. These selected locations are shown in figures 54 through 58 and 

are listed below:

• Rosemont Spring. This spring is located approximately 0.7 mile southeast of the mine pit and 

was selected to represent groundwater conditions near the pit.

• Reach 2 Spring. This spring is located approximately 12 miles down Davidson Canyon from 

the mine pit and was selected not only to represent a point this distance from the mine pit but 

also because Reach 2 Spring is the point at which a perennial reach of Davidson Canyon 

historically began. In recent years, this reach has been observed to be intermittent rather than 

perennial.

• Upper Empire Gulch springs near Empire Ranch. These springs are located approximately 

3.5 miles east of SR 83 in Empire Gulch.

• Confluence of Davidson Canyon and Cienega Creek. This confluence is located 

approximately 14 miles down Davidson Canyon from the mine pit. 

• Confluence of Gardner Canyon and Cienega Creek. This perennial reach of Cienega Creek is

located approximately 9 miles east-southeast of the mine pit.

• Perennial portion of Cienega Creek. This portion is located approximately 11 miles eastnortheast of the mine pit, near USGS stream gage no. 09484550.

• Intermittent portion of Cienega Creek. This portion is located approximately 14 miles 

northeast of the mine pit, near USGS stream gage no. 09484560.

• Corona de Tucson residential area. This is located approximately 9 miles north of the mine 

pit, within the Santa Cruz Valley, on the other side of Santa Rita Mountains.

• Nearest residences (and likely domestic wells) along Singing Valley Road. These are

approximately 3 miles southeast of mine pit. 

• Nearest residences (and likely domestic wells) along Hilton Ranch Road. These are

approximately 6 miles northeast of mine pit.

• Fig Tree Spring. This spring is located approximately 1.5 miles north of the mine pit. This 

spring has a pocket of mesoriparian vegetation associated with it.

• Scholefield Spring. This spring is located approximately 2.5 miles northeast of the mine pit. 

This spring has a pocket of mesoriparian vegetation associated with it.

• Sycamore Spring. This spring is located approximately 3 miles north of the mine pit.

• Ruelas Spring. This spring is located approximately 1 mile west of the mine pit.

• Helvetia Spring. This spring is located approximately 2.5 miles northwest of the mine pit and 

represents a location where a complex of springs is located on lands managed by the BLM. 

340 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 54. Water-level drawdown in the vicinity of the mine at the end of active 

mining

Final Environmental Impact Statement for the Rosemont Copper Project 341
Chapter 3. Affected Environment and Environmental Consequences

Figure 55. Water-level drawdown in the vicinity of the mine 20 years after active 

mining

342 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 56. Water-level drawdown in the vicinity of the mine 50 years after active 

mining

Final Environmental Impact Statement for the Rosemont Copper Project 343
Chapter 3. Affected Environment and Environmental Consequences

Figure 57. Water-level drawdown in the vicinity of the mine 150 years after active 

mining

344 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 58. Water-level drawdown in the vicinity of the mine 1,000 years after active 

mining

Final Environmental Impact Statement for the Rosemont Copper Project 345
Chapter 3. Affected Environment and Environmental Consequences

As indicated earlier, to the extent possible, all three groundwater flow models were used to assess 

groundwater impacts at these times and locations. The following tables summarize the estimated 

groundwater drawdown in the regional aquifer resulting from the mine pit at the end of active mining 

(table 60; see figure 54), 20 years after mine closure (table 61; see figure 55), 50 years after mine 

closure (table 62; see figure 56), 150 years after mine closure (table 63; see figure 57), and 1,000 

years after mine closure (table 64; see figure 58). Note that the results in tables 60 through 64 

represent the uppermost aquifer at each monitoring point. Drawdown in these tables may differ 

slightly from the contours shown in figures 54 through 58, which reflect drawdown in a consistent 

layer across the modeling domain.

Table 60. Modeled groundwater drawdown resulting from mine pit at end of active 

mining

Location

Predicted Drawdown 

(feet) from 

Montgomery Model 

Predicted Drawdown 

(feet) from 

Tetra Tech Model 

Predicted Drawdown 

(feet) from the 

Dr. Myers Model

Rosemont Spring 80

(20 to 180)

97

(64 to 106)

4.5

Reach 2 Spring <0.1

(<0.1 to 0.1)

<0.1

(<0.1 to 0.6)

Outside model domain

Upper Empire Gulch springs <0.1

(Same)

0.1

(<0.1 to 0.2)

0

Davidson/Cienega Confluence <0.1

(Same)

<0.1

(Same)

Outside model domain

Gardner/Cienega Confluence <0.1

(Same)

<0.1

(Same)

0

Cienega near stream gage no. 

09484550 (perennial reach)

<0.1

(Same)

<0.1

(Same)

0

Cienega near stream gage no. 

09484560 (intermittent reach)

<0.1

(Same)

<0.1

(Same)

0

Corona de Tucson <0.1

(Same)

<0.1

(<0.1 to 4.5)

Outside model domain

Singing Valley Road 

residences

0.5

(0.1 to 1)

7

(1 to 13)

0.1

Hilton Ranch Road residences 1

(0.5 to 2)

0.5

(<0.1 to 2.0)

0

Fig Tree Spring 25

(2 to 70)

25

(5 to 38)

Outside model domain

Scholefield Spring 2

(1 to 3)

14

(2 to 21)

0

Sycamore Spring 2

(1 to 15)

4

(<0.1 to 9)

Outside model domain

Ruelas Spring 1

(1 to 2)

5

(<0.1 to 15)

Outside model domain

Helvetia Spring 1

(1 to 8)

2

(<0.1 to 7)

Outside model domain

Sources: Barter (2012a); O’Brien (2012); Myers (2012).

Notes: Values represent the following model layers: Montgomery (Layer 1), Tetra Tech (Layer 17), Myers (Layer 1).

Results in parentheses represent range of drawdown from sensitivity analysis.

346 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 61. Modeled groundwater drawdown resulting from mine pit 20 years after mine 

closure

Location

Predicted Drawdown 

(feet) from 

Montgomery Model

Predicted Drawdown 

(feet) from

Tetra Tech Model

Predicted Drawdown 

(feet) from the 

Dr. Myers Model

Rosemont Spring 210

(110 to 300)

87

(69 to 95)

11

Reach 2 Spring <0.1

(<0.1 to 0.5)

<0.1

(<0.1 to 1.15)

Outside model domain

Upper Empire Gulch Springs <0.1

(<0.1 to 0.1)

0.2

(<0.1 to 0.5)

0

Davidson/Cienega Confluence <0.1

(Same)

<0.1

(<0.1 to 0.15)

Outside model domain

Gardner/Cienega Confluence <0.1

(Same)

<0.1

(Same)

0

Cienega near stream gage no. 

09484550 (perennial reach) 

<0.1

(Same)

<0.1

(Same)

0

Cienega near stream gage no. 

09484560 (intermittent reach)

<0.1

(Same)

<0.1

(Same)

0

Corona de Tucson <0.1

(<0.1 to 0.5)

0.3

(<0.1 to 5.4)

Outside model domain

Singing Valley Road residences 1

(0.2 to 3)

15

(5 to 26)

0.2

Hilton Ranch Road residences 3

(1 to 6)

1.6

(<0.1 to 3.9)

0.8

Fig Tree Spring 60

(20 to 230)

26

(10 to 30)

Outside model domain

Scholefield Spring 5

(2 to 18)

10

(<0.1 to 14)

0

Sycamore Spring 3

(1 to 50)

8

(1 to 13)

Outside model domain

Ruelas Spring 2

(1 to 5)

20

(1 to 40)

Outside model domain

Helvetia Spring 3

(2 to 40)

9

(1 to 18)

Outside model domain

Sources: Barter (2012a); O’Brien (2012); Myers (2012).

Notes: Values represent the following model layers: Montgomery (Layer 1), Tetra Tech (Layer 17), Myers (Layer 1).

Results in parentheses represent range of drawdown from sensitivity analysis.

Table 62. Modeled groundwater drawdown resulting from mine pit 50 years after mine 

closure

Location

Predicted Drawdown 

(feet) from

Montgomery Model

Predicted Drawdown 

(feet) from 

Tetra Tech Model

Predicted Drawdown 

(feet) from the 

Dr. Myers Model

Rosemont Spring 240

(120 to 330)

90

(75 to 97)

19.5

Reach 2 Spring 0.1

(<0.1 to 1.5)

<0.1

(<0.1 to 1.25)

Outside model domain

Upper Empire Gulch Springs <0.1

(<0.1 to 0.5)

0.5

(<0.1 to 1.8)

0.2

Davidson/Cienega Confluence <0.1

(Same)

<0.1

(<0.1 to 0.2)

Outside model domain

Final Environmental Impact Statement for the Rosemont Copper Project 347
Chapter 3. Affected Environment and Environmental Consequences

Location

Predicted Drawdown 

(feet) from

Montgomery Model

Predicted Drawdown 

(feet) from 

Tetra Tech Model

Predicted Drawdown 

(feet) from the 

Dr. Myers Model

Gardner/Cienega Confluence <0.1

(<0.1 to 0.1)

<0.1

(<0.1 to 0.15)

0

Cienega near stream gage no. 

09484550 (perennial reach)

<0.1

(Same)

<0.1

(<0.1 to 0.15)

0

Cienega near stream gage no. 

09484560 (intermittent reach)

<0.1

(Same)

<0.1

(Same)

0

Corona de Tucson <0.1

(<0.1 to 1)

0.8

(<0.1 to 4.5)

Outside model domain

Singing Valley Road residences 3

(2 to 8)

23

(11 to 32)

0.6

Hilton Ranch Road residences 6

(3 to 10)

2.2

(<0.1 to 4.2)

1.6

Fig Tree Spring 140

(60 to 270)

24

(10 to 27)

Outside model domain

Scholefield Spring 15

(4 to 30)

10

(<0.1 to 14)

0.1

Sycamore Spring 10

(2 to 75)

12

(2 to 15)

Outside model domain

Ruelas Spring 5

(1 to 10)

39

(3 to 63)

Outside model domain

Helvetia Spring 10

(3 to 65)

15

(2 to 26)

Outside model domain

Sources: Barter (2012a); O’Brien (2012); Myers (2012).

Notes: Values represent the following model layers: Montgomery (Layer 1), Tetra Tech (Layer 17), Myers (Layer 1).

Results in parentheses represent range of drawdown from sensitivity analysis.

Table 63. Modeled groundwater drawdown resulting from mine pit 150 years after 

mine closure

Location

Predicted Drawdown 

(feet) from

Montgomery Model

Predicted Drawdown 

(feet) from 

Tetra Tech Model

Predicted Drawdown 

(feet) from the 

Dr. Myers Model

Rosemont Spring 310

(125 to 410)

98

(84 to 102)

42.9

Reach 2 Spring 0.3

(<0.1 to 3.0)

<0.1

(<0.1 to 0.9)

Outside model domain

Upper Empire Gulch Springs 0.3

(0.1 to 1.4)

2.5

(0.5 to 5.0)

0.3

Davidson/Cienega Confluence <0.1

(Same)

<0.1

(<0.1 to 0.2)

Outside model domain

Gardner/Cienega Confluence <0.1

(<0.1 to 0.4)

0.2

(<0.1 to 0.35)

0.1

Cienega near stream gage no. 

09484550 (perennial reach)

<0.1

(Same)

0.25

(<0.1 to 0.35)

0

Cienega near stream gage no. 

09484560 (intermittent reach)

<0.1

(Same)

<0.1

(Same)

0

Corona de Tucson 0.5

(<0.1 to 1.5)

3.5

(0.3 to 5.0)

Outside model domain

348 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Location

Predicted Drawdown 

(feet) from

Montgomery Model

Predicted Drawdown 

(feet) from 

Tetra Tech Model

Predicted Drawdown 

(feet) from the 

Dr. Myers Model

Singing Valley Road residences 14

(8 to 33)

35

(21 to 42)

2.3

Hilton Ranch Road residences 15

(9 to 24)

4.1

(0.5 to 6.6)

3.6

Fig Tree Spring 240

(100 to 280)

27

(15 to 30)

Outside model domain

Scholefield Spring 40

(10 to 60)

14

(3 to 18)

0.6

Sycamore Spring 30

(10 to 95)

16

(5 to 19)

Outside model domain

Ruelas Spring 15

(1 to 30)

75

(26 to 83)

Outside model domain

Helvetia Spring 40

(8 to 80)

27

(8 to 32)

Outside model domain

Sources: Barter (2012a); O’Brien (2012); Myers (2012).

Notes: Values represent the following model layers: Montgomery (Layer 1), Tetra Tech (Layer 17), Myers (Layer 1).

Results in parentheses represent range of drawdown from sensitivity analysis.

Table 64. Modeled groundwater drawdown resulting from mine pit 1,000 years after 

mine closure

Location

Predicted Drawdown 

(feet) from

Montgomery Model

Predicted Drawdown 

(feet) from

Tetra Tech Model

Predicted Drawdown 

(feet) from the 

Dr. Myers Model

Rosemont Spring 420

(134 to 709)

98

(77 to 98)

112.1

Reach 2 Spring 1.0

(<0.1 to 4.0)

0.3

(0.15 to 0.3)

Outside model domain

Upper Empire Gulch Springs 3.3

(2.3 to 5.0)

6.0

(4.4 to 6.0)

4.3

Davidson/Cienega Confluence <0.1

(Same)

0.1

(Same)

Outside model domain

Gardner/Cienega Confluence <0.1

(<0.1 to 0.8)

0.5

(0.3 to 0.5)

2.2

Cienega near stream gage no. 

09484550 (perennial reach)

<0.1

(Same)

0.5

(0.4 to 0.5)

0.2

Cienega near stream gage no. 

09484560 (intermittent reach)

<0.1

(Same)

<0.1

(Same)

0.3

Corona de Tucson 1

(0.1 to 13)

5.9

(3.7 to 5.9)

Outside model domain

Singing Valley Road 

residences

85

(46 to 99)

41

(31 to 41)

13.9

Hilton Ranch Road residences 37

(12 to 67)

6.1

(3.6 to 8.6)

13.2

Fig Tree Spring 294

(99 to 402)

29

(18 to 29)

Outside model domain

Scholefield Spring 78

(17 to 120)

17

(8 to 17)

19.8

Final Environmental Impact Statement for the Rosemont Copper Project 349
Chapter 3. Affected Environment and Environmental Consequences

Location

Predicted Drawdown 

(feet) from

Montgomery Model

Predicted Drawdown 

(feet) from

Tetra Tech Model

Predicted Drawdown 

(feet) from the 

Dr. Myers Model

Sycamore Spring 63

(14 to 113)

19

(12 to 19)

Outside model domain

Ruelas Spring 67

(21 to 113)

74

(62 to 78)

Outside model domain

Helvetia Spring 64

(11 to 129)

30

(23 to 30)

Outside model domain

Sources: Barter (2012a); O’Brien (2012); Myers (2012).

Notes: Values represent the following model layers: Montgomery (Layer 1), Tetra Tech (Layer 17), Myers (Layer 1).

Results in parentheses represent range of drawdown from sensitivity analysis.

The results shown in the figures and tables reflect the modeling scenario determined by the modelers 

to be the best fit for existing data. However, one important aspect of modeling is to conduct 

sensitivity runs in order to assess how reasonable changes in modeling parameters could affect the 

end result. Public comments received on the DEIS suggested the need to better reflect the uncertainty 

associated with groundwater modeling by presenting more details of the reasonable range within 

which predicted impacts could occur. Therefore, one change made to these tables since the DEIS is to 

include the range of impacts from the sensitivity runs where available; these are shown in parentheses 

in each cell of the tables. The range of results to the predicted drawdown after 1,000 years is also 

shown in figure 59.

Based on public comments, there was also a desire to better understand the timing of effects, rather 

than simply relying on a few snapshots in time. Table 65 shows the time at which modeled drawdown 

effects first occur at the various monitoring points in the models.

The impacts resulting from these predicted groundwater-level drawdowns on domestic wells and 

overall groundwater availability are assessed below. Impacts of these predicted groundwater-level 

drawdowns on perennial stream flow, riparian vegetation, and individual springs and seeps are 

assessed in the “Seeps, Springs, and Riparian Areas” resource section.

Effect on Well Owners

The greatest effects on well owners are predicted to occur in the area along Singing Valley Road west 

of SR 83. Modeling indicates that these well owners may eventually see up to 85 feet of water level 

decline, if those wells are connected with the regional aquifer that would be affected by the mine pit. 

In the near term (i.e., during active mining and up to 20 years after mine closure), water level declines 

in this area are modeled to reach up to 15 feet.

Well owners in the area along Hilton Ranch Road east of SR 83 are also predicted to experience 

changes in groundwater levels. Modeling indicates that these well owners may eventually see up to 

37 feet of water level decline, if those wells are connected to the regional aquifer that would be 

affected by the mine pit. In the near term (during active mining and up to 20 years after mine 

closure), water level declines in this area are expected to be 3 feet or less. 

350 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 59. Range of water-level drawdown 1,000 years after active mining based on 

sensitivity analyses

Final Environmental Impact Statement for the Rosemont Copper Project 351
Chapter 3. Affected Environment and Environmental Consequences

Table 65. Predicted time to first modeled impacts (years after start of active mining), 

including range of sensitivity analysis

Location Montgomery Model Tetra Tech Model The Dr. Myers Model

Rosemont Spring 2

(Same)

2

(2 to 3)

By end of active mining

Reach 2 Spring 32 

(14 to Never)

72

(5 to 322)

Outside model domain

Upper Empire Gulch Springs 92

(22 to 172)

19

(4 to 97)

By 50 years after active 

mining

Davidson/Cienega Confluence Never

(Same)

42

(8 to 227)

Outside model domain

Gardner/Cienega Confluence Never

(712 to Never)

42

(22 to 172)

By 150 years after active 

mining

Cienega near stream gage no. 

09484550 (perennial reach)

Never 

(Same)

27

(14 to 172)

By 1,000 years after 

active mining

Cienega near stream gage no. 

09484560 (intermittent reach)

Never

(Same)

522

(72 to 722)

By 1,000 years after 

active mining

Corona de Tucson 102

(42 to 182)

21

(3 to 27)

Outside model domain

Singing Valley Road 

residences

6

(5 to 19)

3

(2 to 8)

By end of active mining

Hilton Ranch Road residences 6

(5 to 17)

7

(3 to 27)

By 20 years after active 

mining

Fig Tree Spring 2

(2 to 7)

3

(2 to 5)

Outside model domain

Scholefield Spring 5

(5 to 15)

4

(2 to 7)

By 50 years after active 

mining

Sycamore Spring 6

(4 to 16)

5

(3 to 15)

Outside model domain

Ruelas Spring 18

(5 to 132)

3

(1 to 22)

Outside model domain

Helvetia Spring 10

(5 to 22)

6

(2 to 27)

Outside model domain

Sources: Barter (2012a); O’Brien (2012); Myers (2012).

Notes: Values represent the following model layers: Montgomery (Layer 1), Tetra Tech (Layer 17), Myers (Layer 1).

Results in parentheses represent range of predicted timing of impacts from sensitivity analysis.

As shown in table 66, approximately 360 to 370 domestic or other production wells registered with 

the ADWR could eventually be impacted by drawdown in groundwater levels over 10 feet (i.e., are 

located within the 10-foot drawdown contour); approximately 95 percent of these are smaller 

domestic, stock, or exempt wells. Note that this is not considered a comprehensive inventory of wells 

in the area, nor are there adequate well construction and operation details to determine whether this 

drawdown would impact individual well performance.

Public comments also raised concerns over the use of groundwater at the Bluejay Mine, which is 

located on the west side of the Santa Rita Mountains. Operations for this mine withdraw groundwater 

from a mine shaft, and reduction in groundwater availability might affect mine operations. In terms of 

impacts, the Bluejay Mine is located near Sycamore Spring, which is described in tables 60 through 

64 and shown in figures 54 through 58. Groundwater levels at the Bluejay Mine are predicted to 

decrease, beginning during active mining, and with drawdown reaching as great as 63 feet.

352 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 66. Number of registered wells potentially impacted near mine pit

Number of Registered 

Wells within 5-Foot 

Drawdown Contour

Number of Registered 

Wells within 10-Foot 

Drawdown Contour

Number of Registered 

Wells within 100-Foot 

Drawdown Contour

At mine closure 80 to 90 40 to 50 <10

20 years after closure 110 to 120 70 to 80 <10

50 years after closure 200 to 210 90 to 100 <10

150 years after closure 240 to 250 140 to 150 <10

1,000 years after closure 360 to 370 180 to 190 <10

Note: Contours based on combination of both Montgomery Mine Site Model (Layer 1) and Tetra Tech Mine Site Model 

(Layer 17). Number of wells excludes exploration wells, monitor wells, piezometers, test wells, and cathodic protection 

wells. It includes domestic wells, stock wells, production wells, and public supply wells.

Effect on Overall Groundwater Availability

The mine pit would be actively pumped or dewatered during the active mining phase and then would

act as a hydraulic sink to the regional aquifer in perpetuity. When equilibrium is reached, the loss of 

water from the aquifer as a result of the pit is estimated to be anywhere from 104 gallons per minute 

(Montgomery and Associates Inc. 2010) to 230 gallons per minute (Tetra Tech 2010g). This amount 

represents the maximum amount of water that would enter the mine pit, eventually evaporate, and be 

lost to the overall aquifer—thereby being unavailable to supply perennial flows, riparian vegetation, 

or groundwater outflow from the basin—and totals approximately 170 to 370 acre-feet per year.

During active mining, the loss of water would be greater. Estimates of the pit dewatering rate range as 

high as 650 gallons per minute (Montgomery and Associates Inc. 2010:figure 106, table 6; Tetra Tech 

2010g:figure 8-3). The total volume of water removed from the aquifer during the entire active mine 

life ranges from about 13,000 acre-feet (Tetra Tech 2010g) to 18,500 acre-feet (Montgomery and 

Associates Inc. 2010).

At equilibrium, the loss of water from the groundwater basin due to the mine pit lake would be

approximately 170 to 370 acre-feet per year; for comparison, this amount would represent a loss 

equivalent to about 3 percent of the current basin recharge, as shown in table 67.

Table 67. Comparison of equilibrium loss of water availability by pit lake

Component of 

Water Balance in 

Davidson 

Canyon/Cienega 

Creek basin

Estimate Under 

Premining 

Conditions 

(acre-feet 

per year)*

Equilibrium 

Water Loss 

from Pit Lake 

(acre-feet 

per year)

Equilibrium 

Water Loss 

as a Percentage 

of Average Water 

Balance 

Component

Source

Recharge from 

Precipitation

6,500 to 9,900 170 to 370 ~3 Montgomery and 

Associates Inc. (2010);

Tetra Tech (2010g); 

Myers (2010b)

Evapotranspiration 1,200 to 5,600 170 to 370 ~8 Montgomery and 

Associates Inc. (2010);

Tetra Tech (2010g); 

Myers (2010b)

Pumpage 400 to 500 170 to 370 ~60 Montgomery and 

Associates Inc. (2010)

* Note that geographic areas differ for various estimates, as detailed in table 55.

Final Environmental Impact Statement for the Rosemont Copper Project 353
Chapter 3. Affected Environment and Environmental Consequences

Public comments also raised concerns about the impact from mining operations on the water supply

for the Tucson metropolitan area as a whole. The primary impact on the metropolitan area water 

supply would be from the mine water supply pumping in the Sahuarita area, which has been 

described earlier in this section. It is unlikely that the groundwater impacts from the mine pit in the 

Davidson Canyon/Cienega Creek basin would have any significant effect on the Tucson metropolitan 

area. Some contribution to Cienega Creek stream flow arises from Davidson Canyon, and the 

potential for reductions to this flow is described later in this section. Beyond this, there is the 

potential that some precipitation on the west side of the Santa Rita Mountains that otherwise would 

infiltrate fractured bedrock and eventually flow westward into the alluvial fill of the Tucson basin 

would instead be captured by the expanding cone of depression from the mine pit and flow back 

toward the mine. The boundary condition sensitivity modeling runs conducted suggest that this 

capture is probably less than 200 acre-feet per year (Barter 2012b; O'Brien 2013). By contrast, the 

entire annual demand in the Tucson Active Management Area is approximately 252,000 acre-feet per 

year.

Effect on Mountain-Front Recharge

Mountain-front recharge is a component of the hydrologic system in which precipitation falling on 

relatively impermeable mountain ranges concentrates into stream channels, which then infiltrates the 

ground and recharges aquifers when it reaches permeable alluvial fans, fracture zones, or basin fill 

deposits. Because the mine pit cuts off part of the mountain front, mountain-front recharge 

capabilities would be affected.

None of the models or studies have estimated the overall amount of mountain-front recharge that

occurs in the basin; therefore, estimates of the effects that the mine would have are difficult to make. 

The best estimate of losses to mountain-front recharge is the amount of precipitation and runoff that 

would be captured by the mine pit and would subsequently evaporate. This water does not recharge 

the aquifer directly and would not flow downstream, where it would recharge. At equilibrium, 

estimates range from 490 acre-feet per year (Montgomery and Associates Inc. 2010:99) to 519 acrefeet per year (Tetra Tech 2010g:79) of precipitation and runoff captured by the mine pit. 

However, mountain-front recharge typically represents only a percentage of the overall precipitation 

in a basin. Studies have variously estimated mountain-front recharge to be equivalent to 0.6 to 26 

percent of precipitation in southwestern basins, with a median estimate of about 7 percent (Wilson 

and Guan n.d. [2004]:7). This would suggest that the precipitation and runoff captured by the mine pit

likely could reduce mountain-front recharge by about 35 acre-feet per year, and perhaps by as much 

as 127 acre-feet per year. This represents a loss of water to the aquifer system that otherwise would be 

available. This effect would occur in perpetuity.

Effect on Groundwater Discharge from Davidson Canyon

Groundwater discharge in the subsurface from Davidson Canyon to the Cienega Creek drainage 

potentially supports downstream flow in Cienega Creek. Although details of this hydrogeologic 

connection are not fully analyzed in any of the modeling reports, they were investigated in a previous 

study (Pima Association of Governments 2003). This study found that 8 to 24 percent of the base 

flow in Cienega Creek was likely derived from the subsurface flow or base flow received from 

Davidson Canyon. These flows help sustain the riparian areas along Lower Cienega Creek. Two 

potential impacts to groundwater discharge could occur: (1) from reductions in flow as a result of

drawdown in the regional aquifer; and (2) from reductions in shallow groundwater moving through 

the alluvial stream sediments, which are recharged from surface storm flows.

354 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

The potential for the reduction of flow in lower Davidson Canyon is more fully discussed in the 

“Seeps, Springs, and Riparian Areas” resource section of this chapter, and the results are summarized 

here. With respect to drawdown in the regional aquifer; the weight of the available evidence suggests 

that it is unlikely that flows in lower Davidson Canyon are connected to the regional aquifer that 

would be impacted by the mine site (Ugorets, Cope, and Hoag 2012). Dr. Myers (2010b) assumed 

that a connection to the regional aquifer exists and estimated the potential reduction in Davidson 

Canyon discharge as a result of drawdown in the regional aquifer to be 6.4 percent. However, 

drawdown at Reach 2 spring in lower Davidson Canyon even after 1,000 years is modeled to be 0.3 

foot or less, and drawdown at the confluence of Davidson Canyon and Cienega Creek is modeled to 

be 0.1 foot or less (see table 64). These levels are beyond the reasonable ability of the models to 

predict impacts and are not suggestive of any likely changes, even assuming that the springs and 

underflow in lower Davidson Canyon are connected to the regional aquifer.

The more likely cause-and-effect scenario would be a potential reduction in ephemeral surface flows 

in Davidson Canyon, which could reduce recharge of the alluvial aquifer system in lower Davidson 

Canyon and therefore reduce subsurface flows or base flow into Cienega Creek. Average annual 

runoff from the proposed mine site is expected to decrease by between 17 and 46 percent, depending 

on the action alternative, compared with baseline runoff in Barrel Canyon at SR 83. Because lower 

Davidson Canyon receives water from a wider watershed than just Barrel Canyon, the reduction in 

lower Davidson Canyon (approximately 12 miles downstream) would be less (Zeller 2011a). 

The reduction can be estimated as roughly 4 to 12 percent, compared with the baseline, depending on

the action alternative, as described more fully in the “Surface Water Quantity” resource section. 

The surface water hydrology of the watershed suggests that this estimate of reduced surface flows in 

lower Davidson Canyon is conservative. The estimates above are based on regression equations in an 

ideal watershed without consideration of channel losses. In reality, flows from the project site would 

need to flow downstream approximately 12 miles in an ephemeral stream channel (desert wash) 

composed of pockets of highly transmissive sediments before those flows would contribute recharge 

to lower Davidson Canyon. Recharge is more likely to derive from closer tributaries, although 

certainly during larger flow events, contribution from Barrel Canyon would occur. See the discussion 

in the “Davidson Canyon Stream Flow” part of the “Seeps, Springs, and Riparian Areas” resource 

section.

Proposed Action and Action Alternatives

The impacts described above apply to the proposed action and all action alternatives. There are no 

substantial differences in impacts that are unique to specific alternatives.

Cumulative Effects

This cumulative effects discussion addresses the cumulative impacts of the action alternatives and 

any applicable reasonably foreseeable actions as identified on the Coronado ID team’s list of 

reasonably foreseeable future actions, provided in the introduction to chapter 3. The following 

reasonably foreseeable actions from that list were determined to contribute to a cumulative impact to 

groundwater quantity:

• The Community Water Company of Green Valley is proposing delivery and recharge of 

groundwater with water from the Central Arizona Project in the Green Valley area.

Final Environmental Impact Statement for the Rosemont Copper Project 355
Chapter 3. Affected Environment and Environmental Consequences

• The Farmers Investment Company is proposing the extension of Central Arizona Project 

water into actively farmed pecan groves and activation of a groundwater savings facility near 

Sahuarita. Demand for groundwater in the Sahuarita area is expected to increase by 200 

percent by the year 2030. Potential individual developments are proposed within the 

Sahuarita area, including development of the Farmers Investment Company property (known 

as Sahuarita Farms), the Rancho Sahuarita development, the Quail Creek development, and 

the Madera Highlands development.

• In late 2009, Freeport-McMoRan bought 8,900 acres of the long-closed Twin Buttes Mine 

site, near Sahuarita. Required permits for reopening the mine have not been issued to date, 

but it is reasonable to assume that this mine could be reopened at some point in the future.

Community Water Company of Green Valley is currently planning potential Central Arizona Project 

water delivery and recharge in the Green Valley area. The amount and location of storage is unknown, 

although Community Water Company currently holds a Central Arizona Project subcontract for 2,858 

acre-feet of water. Environmental documentation necessary to build the pipeline was completed by 

the U.S. Bureau of Reclamation in July 2010; construction of the pipeline was initiated in July 2012.

Green Valley Water Domestic Water Improvement District also holds a Central Arizona Project 

subcontract for 1,900 acre-feet of water, the direct use or recharge of which could be facilitated by 

this same pipeline.

There is a new groundwater savings facility currently permitted by the ADWR that would involve the 

potential extension of Central Arizona Project water use into the Farmers Investment Company 

actively farmed pecan groves located east of Sahuarita. 

Both of these projects create the potential for direct use of surface water or recharge of surface water 

in the Upper Santa Cruz Subbasin, which could offset or supplement groundwater use. This would 

result in possible changes in the overall water balance of the basin and, potentially, changes in water 

levels and direction of water flow. Overall, recharge of surface water would be considered a positive 

benefit for the hydrologic system as it would offset existing and future overdraft of groundwater 

resources. These potential recharge projects were not incorporated into the Montgomery Mine Water 

Supply model and therefore are not quantified as part of the modeling effort. Four other active 

recharge projects were incorporated into the modeling.

By 2030, projected deliveries of groundwater in the Sahuarita area will almost double, and private 

wells will likewise double their groundwater withdrawal. A large part of this projected water use 

would likely come from the four planned developments considered reasonably foreseeable actions, 

which together form an almost contiguous 13,000 acres that would potentially be developed. Another 

major water user could be the Twin Buttes Mine, if reopened.

With respect to the projected increase in water use in the Upper Santa Cruz Subbasin, an additional 

26,000 acre-feet of groundwater use was incorporated into the Montgomery Mine Water Supply 

model and are therefore already largely accounted for in the analysis of direct and indirect effects. 

Specifically, even without mine water supply pumping, groundwater levels in the Upper Santa Cruz 

Subbasin have historically decreased by 1 to 3.5 feet per year and are projected to continue to 

decrease by 3.5 to 6.5 feet per year. Mine water supply pumping over a 20-year period of active 

mining is projected to increase this rate of drawdown to a total decrease of 5 to 8 feet in groundwater 

levels per year. The withdrawal of groundwater for future use, combined with withdrawals from the 

Upper Santa Cruz Subbasin for the mine water supply, would contribute to the overall groundwater 

356 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

withdrawal from the Sahuarita area that has resulted in the land subsidence observed in the area. This 

land subsidence is still active.

Climate Change

Expected climate change conditions would have an effect on the overall water balance of the basin. 

The overall volume of precipitation falling on the basin is expected to decrease, but it is difficult to 

assess how this would actually change the amount of recharge to the aquifer occurring through stream 

channels and off mountain fronts. For instance, while overall annual precipitation may decrease from 

5 to 10 percent, changes in the distribution of that rainfall could result in more or less recharge. Large 

flows are generated typically either by winter storm events, which are predicted to decrease, as well 

as extreme monsoon storm events, for which predictions are largely uncertain. Localized aquifer 

systems can recharge water from either type of event.

In any case, it is likely that the increased temperatures and reduced precipitation will increase the 

vulnerability of springs and riparian systems relying on the groundwater system. The cumulative 

impact to these riparian systems from prolonged droughts, such as that currently ongoing, is more 

fully detailed in the “Seeps, Springs, and Riparian Areas” resource section of this chapter.

Mitigation Effectiveness 

Mitigation and Monitoring – Forest Service

• Growth media salvage and application (FS-SR-01). In order to support reclamation

activities, soil and other growth media would be salvaged, stored, and applied to the surface 

of the perimeter waste rock buttress and waste rock and tailings facilities in order to facilitate 

revegetation.

• Revegetation of disturbed areas with native species (FS-SR-02). Reclamation efforts will 

include revegetation of native grasses, forbs, shrubs, and trees on areas disturbed by mining 

and mine related activities. Revegetation would include detecting and treating invasive weed 

species.

• Concurrent placement of perimeter buttress (FS-SR-03). Placement of the perimeter 

buttress allows reclamation activities to take place earlier, concurrent with mine operations. 

• Location, design, and operation of facilities and structures intended to route 

stormwater around the mine and into downstream drainages (FS-SW-01). Various 

stormwater diversion channels and location of facilities have been designed and located in 

order to maintain flow downstream as much as possible and avoid contact of stormwater with 

processing facilities and ore stockpiles.

• Stormwater diversion for Barrel Alternative designed to route more stormwater into 

downstream drainages postclosure (FS-SW-02). Following publication of the DEIS, the 

Forest Service undertook an effort to apply the concepts of geomorphic reclamation to the 

Barrel Alternative. The result is a design that would route more stormwater into downstream 

drainages postclosure than previous designs.

• Plant site location and design adjustments to reduce impacts to biological resources

(FS-BR-01). The entire plant site is sited and designed to reduce its size and overall footprint 

and to use gravity instead of pumping to move process water where possible. 

• Monitoring to determine impacts from pit dewatering on downstream sites in Barrel

and Davidson Canyons (FS-BR-22). Monitoring would be conducted of surface water, 

Final Environmental Impact Statement for the Rosemont Copper Project 357
Chapter 3. Affected Environment and Environmental Consequences

alluvial groundwater, and deeper groundwater at sites in Barrel and Davidson Canyons.

Several locations have already been installed and are being actively monitored, whereas 

others will require access from landowners.

• Periodic validation and rerun of groundwater model throughout the life of the mine

(FS-BR-27). This measure would involve basic data collection of water levels, 

meteorological data, and water balance components, which would allow for the predictions of 

groundwater impacts to be revised based on actual hydrologic observations. Specific wells to 

be monitored are listed in appendix B.

• Removal of unneeded facilities during closure (FS-VR-02). These facilities include 

buildings, the plant site, some roads, the perimeter and security fence, power supply line, 

piping systems, and water supply pipeline. The plant site would be recontoured and 

revegetated with native vegetation. Building foundations would either be removed or broken 

up and buried. Reclamation and revegetation of this area would minimize erosion and allow

stormwater flow to be returned to the watershed.

Mitigation and Monitoring – Other Regulatory and Permitting Agencies

• Control and recycling of process water (OA-GW-04). This mitigation measure would 

result in overall reduction of fresh water use and avoidance of potentially contaminated 

discharges by containing all process water in lined facilities, to be recycled back into the 

process stream to offset fresh water use.

• Processing and placement of tailings to reduce water content and overall footprint

(OA-GW-05). The use of dry-stack tailings instead of traditional slurry tailings would allow

a much smaller footprint for the tailings facility, minimizing soil disturbance.

• Groundwater quality and aquifer level monitoring required by the aquifer protection 

permit (OA-GW-06). The aquifer protection permit requires the construction and operation 

of point of compliance monitoring wells and institutes groundwater quality monitoring and 

sampling protocols and reporting. These measures would ensure that water quality problems, 

if present, would be identified and monitored.

• Monitoring of quantity of supply water removed from the Santa Cruz Basin (OA-GW07). Under the mineral extraction permit for the water supply wells, the quantity of water 

pumped from the Santa Cruz Basin is monitored and reported annually to the ADWR.

Mitigation and Monitoring – Rosemont Copper

• Providing of protection for individual private residential well owners against the risk 

that mine-associated groundwater drawdown could impact their well (RC-GW-01). This 

mitigation involves implementing a legally binding well owner protection agreement that 

would provide certain protections for potential impacts to individual well owners.

• Recharging of the aquifer in the Tucson Active Management Area to offset pumping of 

mine supply water (RC-GW-02). Rosemont Copper has committed to recharging 105 

percent of water pumped from the Santa Cruz Basin and has already implemented recharge of 

a substantial percentage of this total. 

• Extension of Central Arizona Project pipeline to Green Valley (RC-GW-03). Rosemont 

Copper has funded a 7-mile extension of the Central Arizona Project to deliver Community 

Water Company of Green Valley’s Central Arizona Project allotment and has the potential to 

358 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

use the extra capacity of that pipeline to recharge in the general vicinity of the mine supply 

wells, rather than elsewhere in the Tucson Active Management Area.

Conclusion of Mitigation Effectiveness

Dry-stack tailings use significantly less water than traditional slurry tailings; for instance, Rosemont 

Copper’s expected water use is five to six times less than that used by the Sierrita Mine, located in 

Green Valley. The filtering of tailings also allows that water to be recycled back into the mine 

process, further reducing water needs. These design features are an effective mitigation technique that 

would reduce groundwater use. The location of the plant site outside major drainages and the 

diversions to route stormwater efficiently through or around project facilities and to transport runoff

water to downstream watersheds would be effective at maintaining surface flows and reducing 

impacts to shallow groundwater stored in alluvial sediments in Barrel and Davidson Canyons. 

The redesign of stormwater management for the Barrel Alternative is effective at mitigating 

reductions in surface water flows and would cut these reductions in half, compared with the previous 

stormwater design. Similarly, soil salvage, revegetation of disturbed areas with native vegetation, and 

the ability to conduct concurrent reclamation are effective measures for getting as much stormwater 

as possible to flow downstream during the active mining phase and would reduce impacts to shallow 

groundwater stored in alluvial sediments in Barrel and Davidson Canyons. The removal of unneeded 

facilities during closure would allow more water to move downstream in the postclosure phase.

Rosemont Copper would mitigate the potential effects of mine related pumping on residential water 

supply wells in the Sahuarita Heights neighborhood by entering into an agreement with the Rosemont 

United Sahuarita Well Owners. The agreement, which is currently in place, is a legally binding 

residential well protection plan that has been negotiated and implemented by the United Sahuarita 

Well Owners group and Rosemont Copper. This well protection plan addresses pump inspection, 

pump maintenance, pump replacement, well inspection, well maintenance, and well replacement to 

ensure that residential water wells in the Sahuarita area would remain productive throughout the 

life of minerals production operations. The well owner protection program would be effective at 

mitigating impacts to well owners near the mine water supply pumping, provided that those owners 

have entered into the agreement. A similar program has been offered on the east side of the Santa Rita 

Mountains and is intended to offset any impacts associated with dewatering associated with the mine 

pit; similarly, this program would be effective at mitigating any impacts, provided that those owners 

have entered into the agreement. 

On June 24, 2013, Rosemont Copper entered into a License for Right-of-Way Encroachment 

agreement with the Town of Sahuarita, specifically to allow construction of the water supply pipeline 

within the Town of Sahuarita’s ROW. Among other stipulations, the agreement requires Rosemont 

Copper to mitigate any effects to one Town of Sahuarita production well and three monitoring wells

(Town of Sahuarita and Rosemont Copper Company 2013).

Rosemont Copper would implement regional groundwater mitigation measures within the Tucson 

Active Management Area, specifically the following:

• Use available Central Arizona Project water as a source to conduct recharge within the 

Tucson Active Management Area;

• Recharge would occur as close as possible within the Tucson Active Management Area to the 

Rosemont Copper supply well field in the area of the cone of depression caused by Rosemont 

Copper water withdrawal. In 2007, Rosemont Copper entered into a Letter of Intent with 

Final Environmental Impact Statement for the Rosemont Copper Project 359
Chapter 3. Affected Environment and Environmental Consequences

Community Water Company of Green Valley to fund an extension of the Central Arizona 

Project pipeline into Green Valley area. This pipeline has been designed to allow not only for 

use of Central Arizona Project water by Community Water Company but also to allow 

Rosemont Copper to bring “new” or “wet” water for recharge in the area actually affected by 

mine water supply pumping. Construction of this pipeline began in July 2012.

• To the extent practicable, Central Arizona Project storage credits would be balanced with 

water to be pumped from mine supply well field, with the intent to maintain a surplus 

inventory of storage credits prior to pumping groundwater for mineral extraction use.

• Maintain water storage and use inventory records to show that Central Arizona Project 

recharge credits are balanced against groundwater removed from the Tucson Active 

Management Area.

With respect to the Upper Santa Cruz Subbasin, the mitigation measures are intended to reduce 

drawdown from pumping as much as possible through recharge and then mitigate remaining effects 

through the well owner protection program. The extent to which the recharge would be effective at 

reducing drawdown in the immediate vicinity of the Rosemont Copper pumping is unknown because 

the exact recharge site is as of yet unknown. Through 2009, 45,000 acre-feet of water have been 

recharged by Rosemont Copper at the Pima Mine Road and Avra Valley recharge facilities (Pearce 

2010). The Pima Mine Road facility is located within the Upper Santa Cruz Subbasin approximately 

3 to 4 miles from the mine supply pumping and is within the area expected to be impacted by 

pumping. However, to date, only 600 acre-feet of water has been recharged at the Pima Mine Road 

facility. The remaining 44,400 acre-feet of water has been recharged elsewhere in the Tucson Active 

Management Area, but not within the Upper Santa Cruz Subbasin or near the mine supply pumping 

(Pearce 2010). Wherever future recharge occurs, the Tucson Active Management Area as a whole 

would benefit, but it is unknown whether actual drawdown in the Upper Santa Cruz Subbasin would 

be significantly offset. The presence of the pipeline extension funded by Rosemont Copper would 

allow for the possibility that future recharge can occur in the area of pumping and that the recharge 

credits currently acquired could be traded for recharge of “new” or “wet” water near the site of 

pumping.

As detailed in appendix B, the recharge to be conducted by Rosemont Copper is a voluntary measure. 

On June 24, 2013, Rosemont Copper entered into a License for Right-of-Way Encroachment 

agreement with the Town of Sahuarita. Among other stipulations, the agreement requires Rosemont 

Copper to carry out recharge in the amount of 105 percent of the groundwater withdrawn and requires 

that the recharge be carried out within the area of drawdown (Town of Sahuarita and Rosemont 

Copper Company 2013). For the purposes of the analysis in the FEIS, this mitigation measure is still 

considered voluntary. It is the understanding of the Coronado that the license agreement would not be 

enforced if a different ROW were selected within the town for the water supply pipeline.

To date, Rosemont Copper has purchased and recharged excess Central Arizona Project water. Public 

concern has been raised that with shortages likely on the Colorado River over the next few decades, 

Rosemont Copper would be unable to meet recharge obligations due to the unavailability of excess 

water. Indeed, recent work conducted by the U.S. Bureau of Reclamation confirms that the Colorado 

River Basin faces a range of future imbalances between water supply and water demand, although 

there are many opportunities and actions that could be taken to reduce potential shortages 

(U.S. Bureau of Reclamation 2012).

360 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

However, Arizona water law allows for other contracting mechanisms for obtaining renewable 

sources of water for recharge, and excess Central Arizona Project water is not the only potential 

source of water for recharge. Specifically, long-term recharge credits may be purchased by Rosemont 

Copper that reflect renewable water that has already been recharged. This is one mechanism by which 

holders of a Central Arizona Project allotment, while not allowed to lease water directly to Rosemont 

Copper, could effectively allow use of their water to satisfy recharge obligations elsewhere. 

In addition, some Central Arizona Project subcontractors (namely Indian subcontractors) are legally 

allowed to directly lease their Central Arizona Project water (Myers and Shipman 2012). These 

mechanisms would be effective at fulfilling recharge obligations; however, they would not 

necessarily result in physical recharge near the area of pumping. 

Public concern has also been raised regarding the ability of Rosemont Copper to sell or use their 

accumulated long-term recharge credits to allow additional pumping of groundwater, thus negating 

the effectiveness of recharge as a mitigation measure for groundwater use. Under Arizona water law, 

there is no requirement for Rosemont Copper to recharge water to offset the groundwater extracted 

under their groundwater withdrawal permit. The recharge as proposed is a completely voluntary 

mitigation measure. Therefore, it is accurate to say that having earned long-term storage credits by 

recharging excess Central Arizona Project water, Rosemont Copper would legally be allowed to sell 

them or use them for additional groundwater pumping. However, this is not what Rosemont Copper 

has proposed. Rosemont Copper has proposed that:

• Long-term storage credits would be voluntarily extinguished as needed to offset groundwater

pumping conducted under their groundwater withdrawal permit; or

• The water supply wells would be legally reclassified as recovery wells, which would allow 

long-term storage credits to be “recovered,” rather than needing to voluntarily extinguish the 

credits (WestLand Resources Inc. 2007a). 

Whichever mechanism is used, the intention of conducting the voluntary recharge is to offset the 

groundwater use under the withdrawal permit, not to use the recharge as a legal means to extract 

additional groundwater above and beyond that allowed by the withdrawal permit. 

Cooperating agencies raised concerns that future recharge undertaken by Rosemont Copper could 

harm the operation of existing recharge facilities. The regulatory process of obtaining permits to 

recharge through the ADWR requires that effects of water-level rise due to the recharge be assessed.

This would include the effect on any existing recharge facilities.

The effects of the mitigation elements associated with the facility design have already been 

incorporated into the impacts analysis. The effectiveness of direct recharge in the Upper Santa Cruz 

Subbasin has not been incorporated into the groundwater flow models due to the uncertain nature of 

the location in which water would be recharged in the future.

In addition to the mitigation measures described above, which would effectively avoid, minimize, 

reduce, rectify, or compensate for impacts, a suite of monitoring measures is also being proposed. 

These measures generally would not be effective as mitigation, but rather would provide a means for 

monitoring changes to the hydrologic regime. 

Final Environmental Impact Statement for the Rosemont Copper Project 361
Chapter 3. Affected Environment and Environmental Consequences

Effects of Amending the Coronado Forest Plan

The effects on groundwater quantity from amending the Coronado forest plan are described under 

“Direct and Indirect Effects” above. The current forest plan does not contain management area 

standards and guidelines specifically pertaining to groundwater quantity for management areas 1, 4,

or 7A. 

New management area 16 does contain a standard and guideline under “Watershed and Soil

Maintenance and Improvement” that would apply to both groundwater quantity and quality:

1. To the extent practicable, mining facilities and reclamation should strive to emulate natural 

hydrologic functions.

Approval of the forest plan amendment would allow actions that would result in groundwater

drawdown in both the Upper Santa Cruz Subbasin and Davidson Canyon/Cienega Basin. Mitigation

measures to recharge the Tucson Active Management Area aquifer may offset the impacts to Upper 

Santa Cruz Subbasin a great degree. However, development of the mine pit would result in a 

hydraulic sink that would draw down the regional aquifer in perpetuity. Details are provided earlier in 

this resource section. 

Groundwater Quality and Geochemistry

Introduction

The proposed mine involves potential impacts to groundwater quality in two groundwater basins.

The mine water supply would be pumped from wells located on private land in the Santa Cruz Valley 

near the town of Sahuarita in the Upper Santa Cruz Subbasin of the Tucson Active Management Area.

The mine pit and mine facilities are located in the Davidson Canyon drainage east of the Santa Rita 

Mountains. There are unlikely to be any water quality impacts in the Upper Santa Cruz Subbasin near 

the mine water supply pumping because no discharges of potential contaminants are associated with 

the pumping wells. However, the mine operations proposed in the Davidson Canyon/Cienega Basin 

have the potential to affect groundwater quality as a result of seepage from unlined mine waste rock

and tailings facilities, potential leakage from heap leach processing facilities, and formation of a 

permanent pit lake following mine closure. The pit lake is described in this section because of its 

direct association with groundwater.

Changes from the Draft Environmental Impact Statement

Numerous comments were received concerning the predictions of groundwater quality and 

geochemical modeling disclosed in the DEIS. One of the most widespread comments, including 

comment by the EPA, questioned the prediction that precipitation would not infiltrate the waste rock

or tailings facilities and cause seepage, which could potentially impact groundwater quality. In direct 

response to these concerns, the Coronado requested that additional modeling scenarios be conducted 

by Rosemont Copper for more conservative precipitation conditions. Rosemont Copper responded by 

conducting modeling under seven different reclamation scenarios—including a scenario in which

ponding occurs on the surface of the waste rock and tailings facilities—and under four different 

climatic scenarios. The additional modeling reinforces earlier predictions that, under all scenarios, 

conditions are such that any precipitation infiltrating the waste rock or tailings would quickly 

evaporate, and no additional seepage would result. This more robust analysis is included in the FEIS

(see the “Predicted Seepage Rates” part of this resource section).

362 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Many technical concerns were raised over the analysis of predicted geochemistry in the pit lake. 

A series of specific questions was compiled by the Coronado from public comments, and these 

questions were investigated by the Coronado’s contracted geochemical experts. The results of this 

analysis are described in the FEIS (see the “Impacts from Mine Pit Lake” part of this resource 

section).

There was also a general concern that the geochemical sampling conducted was not adequately 

described in the DEIS and that the underlying types of samples, number of samples, and variety of 

geochemical tests conducted were not summarized. A summary of all geochemical sampling and tests 

conducted is now included in the FEIS (see the “Overview of Geochemical Tests Conducted by 

Rosemont Copper” part of this resource section).

One of the major concerns about the proposed mine operations as described in the DEIS, especially 

as expressed by the EPA, was the operation of the heap leach pad. Concerns were raised about the 

potential for release of pregnant leach solution and the lack of detail for how the heap leach would be 

managed during closure, especially treatment of any residual draindown. Since the publication of the 

DEIS, in response to agency concerns and as a result of logistical issues, the heap leach operation has 

been removed from the Barrel Alternative, which has been identified as the Forest Service preferred 

alternative. The oxide ore that otherwise would have been leached would now be processed through 

the sulfide flotation circuit or become waste rock.

However, the heap leach pad remains a part of the proposal for the other action alternatives. In order 

to address concerns, additional information was requested and received from Rosemont Copper about 

operation of the heap leach pad. Two additional pieces of information were received. First, the aquifer

protection permit has been issued by the ADEQ; therefore, details of the liners, monitoring, and 

collection systems required for the heap leach and other process facilities are available and are better 

described in the FEIS (see the “Ability to Demonstrate Best Available Demonstrated Control 

Technology” part of this resource section). Second, details have been obtained for how Rosemont 

Copper would construct the heap leach treatment systems and how they would retain access to those 

systems for monitoring and sampling after enclosure of the heap leach pad in waste rock (see the 

“Predicted Seepage Rates” part of this resource section).

Concerns were raised that the sulfate plume in the Upper Santa Cruz Subbasin originating from the 

Sierrita mine was inadequately disclosed. The location of this plume and the planned control of the 

plume are now better described (see the “Impacts to Sierrita Sulfate Plume” part of this resource 

section).

Concerns were also raised about the apparent laboratory contamination observed in organic sampling 

from monitoring wells on the site. The Coronado requested a review of this information from their 

consulting geochemical experts, and this analysis has been added to the FEIS (see the “Organic 

Constituents” part of this resource section).

Another concern raised in public comments was the potential for technological enhancement of 

naturally occurring radioactive materials in the dry-stack tailings facility. The Coronado has 

undertaken additional investigations on this topic, and this analysis has been added to the FEIS (see 

the “Potential for Technologically Enhanced Naturally Occurring Radioactive Materials” part of this 

resource section).

Other concerns were raised in public comments about the levels of arsenic expected from seepage

from the tailings facility. The Coronado has undertaken additional investigations to determine 

Final Environmental Impact Statement for the Rosemont Copper Project 363
Chapter 3. Affected Environment and Environmental Consequences

whether the geochemical modeling used is appropriate and acceptable. A further question is the 

appropriate standard with which to compare arsenic concentrations, as there is a discrepancy between 

the arsenic standard set by the EPA for drinking water and the standard set by the State of Arizona for 

protection of groundwater quality. This discrepancy has been further described in the FEIS (see the 

“Appropriate Standards for Comparison of Groundwater Quality” part of this resource section).

Additional mitigation measures have been incorporated into the document and assessed for 

effectiveness at reducing impacts (see “Mitigation Effectiveness” part of this resource section, as well 

as appendix B).

Monitoring has been incorporated into the mitigation and monitoring plan (see appendix B) in order 

to address uncertainty associated with geochemistry, acid rock drainage, and the potential for seepage

from the waste rock facility (see the “Mitigation Effectiveness,” “Monitoring Intended to Assess 

Seepage Predictions,” and “Monitoring Intended to Assess Geochemical Predictions” parts of this 

resource section).

Issues, Cause and Effect Relationships of Concern

Mine operations involve several components that have the potential to affect groundwater. With 

certain geology and rock types, precipitation falling on waste rock and tailing facilities has the 

potential to leach metals from the rock, which could potentially infiltrate the aquifer and impact 

groundwater quality. Hazardous materials used at the mine could be released to the environment, 

which could cause contaminated runoff or directly infiltrate the aquifer. The mine pit lake, because of 

its contact with exposed rock formations, could develop hazardous water quality conditions, which 

could cause impacts to groundwater, birds, and wildlife.

One significant issue was identified with respect to groundwater quality. Issue 3C relates to 

groundwater quality in the Cienega Basin, which may be impacted by the mine operations. The issue, 

with specific factors and units of measure for determining environmental consequences, is listed 

below.

Issue 3C: Groundwater Quality

Construction and operation of the mine pit, waste rock, and leach facilities have the potential to 

exceed Arizona Aquifer Water Quality Standards. The mine pit could result in the creation of a 

permanent pit lake, which has the potential to concentrate dissolved metals and toxins and may lower 

pH levels. Likewise, disposal of waste material in surface facilities such as tailings, waste rock, and 

leaching operations could potentially contribute to degradation of the aquifer.

Issue 3C Factors for Alternative Comparison

1. Ability to meet Arizona Aquifer Water Quality Standards at points of compliance designated 

in the aquifer protection permit 

2. Ability to demonstrate best available demonstrated control technology2

2 Use of best available demonstrated control technology is required by the aquifer protection permit. The purpose is to 

employ engineering controls, processes, operating methods, or other alternatives to reduce discharge of pollutants to the 

greatest degree achievable before they reach the aquifer.

364 Final Environmental Impact Statement for the Rosemont Copper Project

 
Chapter 3. Affected Environment and Environmental Consequences

Other Effects Considered

Even though impacts to water quality in the Upper Santa Cruz Subbasin were not identified as a 

significant issue during the public scoping process, this resource section addresses the alternatives’ 

impacts concerning the possible effect that pumping from the mine water supply well field would 

have on groundwater flow directions and gradients in the Upper Santa Cruz Subbasin. Primarily, this 

resource section addresses the potential for mine water supply pumping to cause migration of known 

areas of groundwater contamination, such as leaking underground storage tanks or the known sulfate 

plume from the Sierrita mine tailings. Of 54 known leaking underground storage tanks identified 

within the general area, all but 2 have been closed. The two open sites are located almost 10 miles 

southwest of Sahuarita (Arizona Department of Environmental Quality 2010). In general, 

groundwater contamination from most leaking underground storage tanks extends only a few hundred 

feet; therefore, further analysis of the effects on these leaking underground storage tanks was not 

conducted. However, potential impacts on the Sierrita sulfate plume from mine water supply pumping 

have been analyzed and are addressed in this section.

Analysis Methodology, Assumptions, 

Uncertain and Unknown Information 

Temporal Bounds of Analysis and Analysis Area

The temporal bounds of analysis near the mine site extends to 1,000 years after final reclamation and 

closure, in order to allow the bedrock aquifer impacted by the mine pit to come close to equilibrium. 

The temporal bounds of analysis near the mine water supply in the Santa Cruz Valley is 140 years 

after pumping ceases, in order to allow the cone of depression resulting from groundwater pumping 

to stabilize. The spatial area of analysis shown in figure 60 matches that for “Groundwater Quantity” 

and was selected to encompass all areas within which groundwater could be affected by either the 

mining water supply well field near Sahuarita or the mine and mine pit; the analysis area 

encompasses the areas included in the groundwater models conducted for the analysis. 

The connected actions that are described in chapter 2 include the use of mechanized equipment to 

reroute an electrical transmission line within the project area; construct an electrical distribution line, 

water supply line, and associated maintenance road within the utility corridor; reroute the Arizona 

National Scenic Trail and construct ancillary facilities; and implement SR 83 highway maintenance 

improvements required by the ADOT encroachment permit. These activities have been considered in 

the description of impacts common to all action alternatives for the premining phase, when they 

would be constructed; and for the final reclamation and closure phase, when the water line and 

electrical distribution line would be removed.

Methodology for Impacts Analysis

The assessment factors include the ability to meet Arizona Aquifer Water Quality Standards at the 

points of compliance designated in the aquifer protection permit and the ability to demonstrate best 

available demonstrated control technology. Best available demonstrated control technology means the 

use of the most applicable and effective techniques available to prevent groundwater contamination.

Final Environmental Impact Statement for the Rosemont Copper Project 365
Chapter 3. Affected Environment and Environmental Consequences

Figure 60. Analysis area for groundwater quality

366 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

In order to assess the ability to meet Arizona Aquifer Water Quality Standards, several specific parts 

of the mine operation were assessed. These include the following:

• Expected water quality of drainage from heap leach facilities;

• Expected water quality from seepage of precipitation through waste rock;

• Expected water quality from water seepage from tailings;

• Expected water quality in the mine pit lake;

• Potential for acid conditions in the mine pit lake; and

• Expected fate and transport of any contaminants reaching groundwater.

The methodology for determining impacts to groundwater quality involves both geochemical and 

groundwater predictive flow modeling to determine the likely effect on groundwater quality 

downgradient of the mine and in the pit lake predicted to form following mine closure. 

The geochemical predictive models account for potential sources from the waste rock, tailings, heap 

leach, and mine pit walls, as well as contributions from natural groundwater, surface runoff, and 

precipitation. Groundwater predictive flow models (Errol L. Montgomery and Associates Inc. 2009a, 

2010; Montgomery and Associates Inc. 2010; Myers 2010a; Tetra Tech 2010g) are discussed in the 

“Groundwater Quantity” section. Several additional technical reports consider the resulting 

geochemistry and potential fate and transport of contaminants. Seepage from waste rock, tailings, and 

heap leach facilities is described in “Infiltration, Seepage, Fate and Transport Modeling Report:

Revision 2” (Tetra Tech 2012a) with additional documentation provided in “Rosemont Facility Fate 

and Transport Modeling Response to Comments: Technical Memorandum” (Hudson and Williamson 

2011). Predictions of the geochemistry of the mine pit lake are described in “Geochemical Pit Lake 

Predictive Model: Revision 1” (Tetra Tech 2010c).

As with the groundwater flow models, these two predictive geochemical modeling reports have 

undergone peer review (Day and Hoag 2011; Sieber 2011; Sieber et al. 2010; Ugorets and Day 2010). 

Revised reports based on peer reviews have been completed. Following public comment on the DEIS, 

the Coronado also commissioned several reports to address various topics concerning geochemistry 

(Hoag, Bird et al. 2012; Hoag, Sieber et al. 2012; Kline et al. 2012).

The impacts of discharge of runoff to surface waters from waste rock and tailings facilities are 

analyzed in the “Surface Water Quality” section of this FEIS.

Several public comments concerned the lack of analysis for specific chemical byproducts of mining 

operations that would be exposed to surface water or groundwater or would be present in seepage

from the tailings facility. Most of the specific byproducts raised during public comment do not have 

specific aquifer water quality standards and therefore were not included in the analyses or modeling 

conducted. However, the lack of modeling does not change the ultimate fate of these compounds, if 

they were present. If these compounds did exist in tailings seepage they would not be discharged to 

the environment but would be contained by the capture zone of the mine pit lake. Geochemical 

modeling was not revised to attempt to incorporate these chemical byproducts. 

However, one concern over chemical byproducts from blasting was analyzed further. The potential 

for nitrogen residue to be present from the use of ammonium nitrate explosives is well established, 

and nitrate, nitrite, and ammonia have regulatory standards that must be met for groundwater and 

surface water. This analysis relies on available literature, estimates of remnant nitrogen residue, and 

potential exposure pathways (see the “Potential for Residue from Ammonium Nitrate Explosives” 

part of this section).

Final Environmental Impact Statement for the Rosemont Copper Project 367
Chapter 3. Affected Environment and Environmental Consequences

One other concern raised was analysis for radon. Ambient groundwater quality samples were not 

tested for radon. Levels of radon in groundwater do not have a numeric water quality standard and,

therefore, were not addressed in this analysis.

Scientific Uncertainty and Professional Disagreement

As with groundwater flow modeling, the geochemical modeling process also involved peer review by 

independent experts (SRK Consulting), as well as comment and review from cooperating agencies. 

Most comments and questions related to the geochemical modeling efforts have been determined by 

the Coronado to have been adequately answered and the geochemical modeling techniques to be 

appropriate. However, one issue remains that is a source of scientific uncertainty and professional 

disagreement.

Rosemont Copper has conducted extensive geochemical analysis of the rock types encountered at the 

site that are representative of the ore body and waste rock. These samples are categorized by 

geological unit (i.e., Arkose, or Horquilla Limestone, Willow Canyon Formation). Within each 

geological unit or formation, however, there is a wide variety of difference in the minerals found, 

referred to as the mineralogy of the unit. Rosemont Copper has not conducted detailed mineralogical 

laboratory analysis of the samples collected. Questions arose as to whether this is appropriate and 

whether this mineralogical analysis is needed to support geochemical modeling. 

The geochemical experts contracted by the Coronado (SRK Consulting) determined that the analysis 

conducted is sufficient to support the modeling (Hoag, Bird et al. 2012). Other specialists believe 

such mineralogical sampling is essential to understanding future geochemical impacts. The forest 

supervisor reviewed the available information and determined that the analysis conducted to date is 

sufficient to support the geochemical modeling relied upon in the FEIS, but also implemented 

requirements for future mineralogical analysis (see monitoring measure FS-GW-03 in appendix B).

Monitoring Intended to Assess Geochemical Predictions

While the geochemical analysis, specifically the potential for acid rock drainage, has been fully 

assessed and the found by the Coronado to be reasonable and valid, in consideration of public 

concerns regarding the uncertainty associated with geochemical modeling, existing waste rock

characterization and interpreting the potential for acid rock drainage, four monitoring components 

have been incorporated into the mitigation and monitoring plan (see appendix B for full details). Two 

of these are required under the aquifer protection permit issued to Rosemont Copper:

• Reduction of the potential for acid generation from tailings and waste rock (OA-GW02). Geochemical testing has indicated that there is adequate neutralization capacity in the 

overall waste rock composition to prevent potential acid generation. However, proper 

placement of the waste rock is necessary to allow this buffering capacity to be effective. This 

mitigation involves requirements for the segregation and encapsulation of potentially acidgenerating waste rock with rock that has buffering capabilities in order to reduce the risk of 

potential acid generation. This is required under the aquifer protection permit issued to 

Rosemont Copper.

• Groundwater quality and aquifer level monitoring required by the aquifer protection 

permit (OA-GW-06). The aquifer protection permit requires the construction and operation 

of point-of-compliance monitoring wells and institutes groundwater quality monitoring and 

sampling protocols and reporting. These measures would ensure that water quality problems, 

if present, would be identified and monitored.

368 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

The Coronado has required two additional monitoring measures in order to ascertain that the 

reactivity of the waste rock pile is fully understood in order to ensure an adequate closure design is 

implemented, and to ensure that changes in groundwater quality are not occurring on forest lands 

beyond the immediate facility. 

• Additional waste rock and tailings characterization (FS-GW-03). During operations, 

additional waste rock characterization tests, above and beyond those required by the aquifer

protection permit, would be required to be conducted on waste rock and tailings. This 

additional analysis includes requirements for humidity cell testing, whole rock chemistry, and 

mineralogical analysis in addition to the acid-base accounting and leachate testing already 

being conducted for the aquifer protection permit.

• Additional water quality monitoring of springs and wells (FS-GW-02). A suite of springs 

and wells, other than the point-of-compliance wells required to be monitored under the 

aquifer protection permit, would be monitored for water quality changes. These monitoring 

locations are situated beyond the perimeter fence of the mine and are intended to provide 

surveillance of any water quality changes that may be triggered by the changes in the 

hydrologic system. Specific springs and wells to be monitored are listed in appendix B.

Summary of Effects by Issue Factor by Alternative

Table 68 presents the summary comparison of impacts from each alternative.

Table 68. Summary of effects

Issue Factor No Action Proposed Action Phased 

Tailings Barrel Barrel Trail

Scholefield

-McCleary

Issue 3C.1: 

Ability to meet 

Arizona Aquifer

Water Quality

Standards at 

points of 

compliance 

designated in the 

aquifer protection 

permit

Concentrations 

of arsenic in 

some ambient 

groundwater

samples 

exceed aquifer

water quality 

standards

Modeled water quality 

for potential seepage

from tailings and waste 

rock meets standards; 

modeled water quality 

from lined heap leach 

exceeds standards for 

cadmium, fluoride, and 

selenium but would not 

be discharged; 

treatment of heap leach 

with an engineered 

biological system meets 

standards; modeled 

water quality in mine 

pit lake exceeds the 

aquifer water quality 

standard for thallium 

and potentially 

ammonia, but the 

standard is not 

applicable to pit lakes.

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action, 

with 

exception 

of heap 

leach, 

which has 

been 

removed 

from 

Barrel

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Final Environmental Impact Statement for the Rosemont Copper Project 369
Chapter 3. Affected Environment and Environmental Consequences

Issue Factor No Action Proposed Action Phased 

Tailings Barrel Barrel Trail

Scholefield

-McCleary

Issue 3C.2: 

Ability to 

demonstrate best 

available 

demonstrated 

control 

technology

None Best available 

demonstrated control 

technology has been 

accepted through the 

aquifer protection 

permit process and has 

been determined to be 

adequate.*

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Other Effects 

Considered

Impact to Sierrita 

sulfate plume

None Minor changes in 

gradient or groundwater

levels as a result of 

mine supply pumping 

would occur in the 

vicinity of the Sierrita 

sulfate plume. Overall 

direction of flow, 

location of plume, and 

effectiveness of control 

are not expected to be 

affected.

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as 

for 

proposed 

action

Same as for

proposed 

action

* As noted in the text, the aquifer protection permit would eventually be revised to reflect whatever mine scenario is 

described in the final MPO. It is assumed that the control technologies for individual discharging facilities would remain the 

same as those in the approved aquifer protection permit.

Affected Environment

Relevant Laws, Regulations, Policies, and Plans

Table 69 lists the applicable laws, regulations, and policies related to the use, protection, and 

management of groundwater resources that would apply to the development and operation of the 

project. These laws, regulations, and policies, which will collectively be referred to in the following 

sections as “regulation(s),” are outlined in more detail in the following sections. 

Table 69. Summary of the Federal, State, and local regulatory requirements applicable 

to the project with respect to groundwater quality

Law/Regulation Regulates

Federal

Safe Drinking Water Act Water quality in public water supply systems; primacy delegated to Pima 

County

FSMs 2520, 2530, and 2880;

and FS-881 and 990a Technical Guide

Watershed protection and management, water resource management, 

geological resources, groundwater management, and water quality 

management

State

Aquifer Protection Permit Discharge of pollutants to surface or aquifer

State Water Quality Standards Allowable water quality limits in surface waters and groundwater

Local

Public Water System New source approval and construction of public water system

370 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Federal

Safe Drinking Water Act (Public Law 93-523)

As mandated by the Safe Drinking Water Act, passed in 1974, the EPA regulates contaminants of 

concern to domestic water supply. Contaminants of concern relevant to domestic water supply are 

defined as those that pose a public health threat or that alter the aesthetic acceptability of the water. 

The EPA regulates these types of contaminants through the development of national primary and 

secondary maximum contaminant levels for finished water. 

In Arizona, the ADEQ administers the Safe Drinking Water Act (AAC R18-4), but the Pima County 

Department of Environmental Quality has the authority to review and approve new construction and 

new source approval for a public water system. The public drinking water system at the mine facility 

would require approval from Pima County Department of Environmental Quality prior to 

construction and operation.

State and Local

Aquifer Protection Permits (Arizona Revised Statutes 49-241)

Any discharge of a pollutant from a facility either directly to an aquifer or to the land surface or the 

vadose zone in such a manner that there is a reasonable probability that the pollutant would reach an 

aquifer requires issuance of an aquifer protection permit by the ADEQ. Unless the discharge is either 

specifically exempted by statute (ARS 49-250), or if the discharge is authorized under one of the 

General Aquifer Protection Permits issued by the ADEQ (AAC R18-9, Article 3), then the discharge 

requires issuance of an individual aquifer protection permit by the agency.

Temporary discharges associated with construction (hydrostatic line testing or well testing) would

likely be covered under existing general aquifer protection permits. The coarse ore stockpile, 

temporary run-of-mine stockpile, and vehicle and equipment wash are covered under general aquifer 

protection permits as well. An individual aquifer protection permit is required for potential discharges 

at the mine associated with various process facilities. In addition, mine tailings and heap leach 

facilities are both considered to be discharging facilities requiring permits (ARS 49-241.B.6 and 

49-241.B.7). 

An individual aquifer protection permit was issued to Rosemont Copper by the ADEQ on April 3, 

2012. The aquifer protection permit determined that the design of the following facilities was 

adequate to meet best available demonstrated control technologies: the dry-stack tailings facility 

(unlined), the process water temporary storage pond (lined), the primary settling basin (lined), the 

raffinate pond (lined), the heap leach pad (lined), the pregnant leach solution pond (lined), the 

stormwater pond (lined), the waste rock storage area (unlined), and the nonmunicipal solid waste 

landfill (lined). It should be noted that the approved aquifer protection permit was not for a mine 

layout identical to the preferred alternative. Following development of the final MPO, the aquifer 

protection permit would need to be amended to reflect the actual facilities to be built. 

State Water Quality Standards 

(Arizona Administrative Code Title 18, Chapter 11)

State regulations dictate numeric water quality standards both for surface waters and for groundwater. 

Numeric Arizona Aquifer Water Quality Standards apply to all groundwater within the State. 

Numeric Surface Water Quality Standards are specific to the use of the water, as well as any special 

designations for surface waters, and there are varying standards for acute and chronic exposure. State 

Final Environmental Impact Statement for the Rosemont Copper Project 371
Chapter 3. Affected Environment and Environmental Consequences

regulations also identify a narrative water quality standard for groundwater. The narrative standard 

states that a discharge shall not cause or contribute to a violation of a water quality standard 

established for a navigable water of the State and that a discharge shall not cause a pollutant to be 

present in an aquifer that impairs existing or reasonably foreseeable future uses of water in an aquifer, 

or at a concentration which endangers human health.

From a regulatory standpoint, the mine pit lake is neither a navigable water subject to surface water

standards nor a discharging facility subject to aquifer water quality standards. However, as a useful 

tool for disclosing and analyzing water quality impacts in the pit lake, both standards are compared 

with the pit lake water quality in this section.

Appropriate Standards for Comparison of Groundwater Quality

Beginning in 2001, the EPA set the maximum contaminant level for arsenic in drinking water systems 

at 0.010 milligram per liter. This authority derives from the Federal Safe Drinking Water Act, which 

is described above. When the Federal maximum contaminant level was lowered to 0.010 milligram 

per liter, public drinking water systems throughout the State of Arizona were faced with also meeting 

this standard. However, the authority under the Safe Drinking Water Act applies only to public 

drinking water systems and does not extend to regulation of groundwater quality in general. 

Jurisdiction over general groundwater quality remains with the State of Arizona and is administered 

through the aquifer protection permit program as described above and through adherence to State 

aquifer water quality standards. Unlike the standard of 0.010 milligram per liter, which is applicable 

to public water systems, the Arizona Numeric Aquifer Water Quality Standard for arsenic remains at 

0.050 milligram per liter. As such, the individual aquifer protection permit issued to Rosemont 

Copper uses the current aquifer standard of 0.050 milligram per liter.

There have been proposals to lower the Arizona Aquifer Water Quality Standard to 0.010 milligram 

per liter, as was acknowledged in the DEIS. However, at present, this action has not been approved by 

the State of Arizona, nor does the arsenic standard appear reasonably likely to decrease in the near 

future as there are no formal proposals to do so. The Coronado has considered public comments that 

arsenic concentrations associated with discharges to groundwater from the mine should be compared 

with the drinking water level of 0.010 milligram per liter but has determined that to do so would be 

inconsistent with applicable State laws and regulations, inconsistent with the issued aquifer protection 

permit, and contrary to the decisions of the pertinent permitting authority, which is the ADEQ. 

Therefore, in the FEIS, arsenic concentrations are compared with the Arizona Aquifer Water Quality 

Standard of 0.050 milligram per liter, as well as with background arsenic levels. As described above, 

in addition to the numeric aquifer water quality standard for arsenic, the State of Arizona narrative 

aquifer water quality standards prohibit a discharge that would cause a pollutant to be present in an 

aquifer that impairs existing or reasonably foreseeable future uses of water in an aquifer. All aquifers

in Arizona are considered drinking water aquifers. Therefore, it is reasonable to assess whether 

predicted arsenic concentrations would impair future use of the aquifer for drinking water. This 

analysis has been conducted in the “Environmental Consequences” part of this resource section.

Forest Service Guidance

Forest Service guidance with respect to water resources is fully described in the “Groundwater

Quantity” resource section in this chapter.

372 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Existing Conditions

Extensive groundwater quality sampling has been conducted over the past few years throughout the 

project area, from existing springs, from wells drilled during the hydrogeologic investigation for the 

proposed project, and from existing wells in the area. Results of this sampling are presented in Errol 

L. Montgomery and Associates (2009b) and Rosemont Copper (2012f), with pertinent results 

included in the following description of conditions and summarized later in this resource section in 

tables 71 through 73. 

Inorganic and Metal Constituents

Groundwater quality in the analysis area is considered acceptable for most uses. Total dissolved

solids in groundwater samples collected from 39 wells and 12 springs ranged from 100 to 1,700 

mg/L, with a median concentration of 360 mg/L. The field pH ranged from about 6.5 to 9.3, with a 

median of about 7.5, and the laboratory pH ranged from about 5.7 to 9.5, with a median of about 8.1. 

Nitrate, a commonly occurring contaminant in groundwater due to agricultural practices, septic tanks, 

and effluent discharge, ranged from below detection limits to 8.4 mg/L with a median of about 0.5 

mg/L, below the Arizona Aquifer Water Quality Standard of 10 mg/L. Fluoride, another naturally 

occurring contaminant, ranged from below detection limits to 3.6 mg/L, with a median of about 0.7 

mg/L, which is below the Arizona Aquifer Water Quality Standard of 4 mg/L. 

Metals with numeric Arizona Aquifer Water Quality Standards include antimony, arsenic, barium, 

beryllium, cadmium, chromium, cyanide, lead, mercury, nickel, selenium, and thallium. With the 

exception of arsenic, none of the groundwater samples exceeded Arizona Aquifer Water Quality 

Standards for these metals. Arsenic is a common naturally occurring metal contaminant in Arizona 

groundwater, and concentrations in project area groundwater samples ranged from below detection 

limits to 0.067 mg/L, which is above the Arizona Aquifer Water Quality Standard of 0.05 mg/L. For 

the most part, however, arsenic in the aquifer is below the arsenic standard. The median concentration 

of arsenic was 0.0032 mg/L, and of the 250 water samples analyzed for arsenic, only 7 exceeded the 

arsenic standard of 0.05 mg/L, all of which were taken from the same Pima County well (D-16-17 

31dcb). Based on these findings, no existing metal contamination of groundwater by past site use, 

including historic mining, is believed to exist in the analysis area.

Organic Constituents

Groundwater samples were collected from 38 wells and 6 springs and analyzed for volatile organic 

compounds and semivolatile organic compounds. There were 104 instances in which an organic 

compound was detected in a groundwater sample by the analytical laboratory. However, 48 of 

these instances were either the result of documented laboratory contamination or of suspected 

contamination of the sample because similar compounds were detected in quality control samples, 

such as the method blank or trip blank. Of the remaining instances, 39 were detected by the 

instrumentation but at methods below the limits considered practical for quantifying chemical 

constituents. 

Only 17 instances were considered to accurately reflect possible contamination. These include eight 

instances where dimethyl ketone (also known as acetone), diethyl phthalate, or 2-butanone was 

measured; these are considered common laboratory contaminants, although they can also be present 

in the environment. Seven instances of toluene were measured in groundwater samples, ranging from 

10 to 141 micrograms per liter. Two instances of benzoic acid were measured in groundwater 

samples, ranging from 65 to 70 micrograms per liter.

Final Environmental Impact Statement for the Rosemont Copper Project 373
Chapter 3. Affected Environment and Environmental Consequences

Toluene is an environmental contaminant commonly identified with contamination from gasoline or 

other fuels. Benzoic acid can be found alone in the environment but is also a potential breakdown 

product of toluene. The wells in which these constituents were found exhibit no pattern and are found 

across the entire project area. The Arizona Aquifer Water Quality Standard for toluene is 1,000 

micrograms per liter, and there is no numeric standard for benzoic acid. 

Public comment variously suggested that the detections described above reflected the presence of 

groundwater contamination in the aquifer, or that the discovery of laboratory contaminants 

invalidated the entire suite of sampling for organic constituents. The Coronado requested a review of 

this information by their contracted geochemical experts (Kline et al. 2012). This review determined 

that the number of detections for organic compounds was not unusual for a multi-year groundwater 

monitoring program such as that conducted by Rosemont Copper. Further, it was determined that the 

results of the remaining analyses, as well as the overall organics sampling program, were valid and 

that an extensive follow-up monitoring program was not necessary.

Radiochemical Constituents

Groundwater samples collected from 38 wells and 6 springs and were analyzed for gross alpha and 

gross beta activity, radium (radium-226 and radium-228), and uranium (total uranium, uranium-234, 

uranium-235, and uranium-238). Adjusted gross alpha activity exceeded the Arizona Aquifer Water 

Quality Standard of 15 picoCuries per liter in one sample from piezometer TTBH-08-08C and in one 

of three samples collected from drill hole P-899. Radium-226 and radium-228 also exceeded the 

Arizona Aquifer Water Quality Standard of 5 picoCuries per liter combined from piezometer TTBH08-08C and drill hole P-899. 

Adjusted gross alpha activity is a measure of the amount of radiation emitted by radioactive elements 

such as uranium or radium. Uranium and radium are both naturally occurring, particularly in bedrock 

aquifers. Radium and gross alpha activity are common naturally occurring contaminants in Arizona 

groundwater.

Overview of Geochemical Tests 

Conducted by Rosemont Copper

A great deal of public concern was raised regarding the types and number of geochemical tests 

conducted by Rosemont Copper and the need to more fully understand the sampling and test work 

that underlie the predictions of the geochemical modeling. 

There are two general categories of geochemical tests undertaken by Rosemont Copper. One category 

of tests is primarily designed to determine the potential for acid rock drainage to occur. A second 

category of tests is designed to determine the chemical constituents and metals that would be 

expected to occur in water contacting waste rock or tailings. The types and number of tests are 

described here; the usage of these tests results to predict impacts is further detailed in the 

“Environmental Consequences” part of this resource section.

The potential for acid rock drainage is assessed through both short- and long-term tests. Static acid 

base accounting is the primary short-term test that was used. In these tests, the acid potential and 

neutralization potential of a rock sample are measured. The difference between neutralization 

potential and acid potential is called net neutralization potential; values of net neutralization potential 

greater than 20 represent minimal or no potential for acid rock drainage. The ratio of neutralization 

potential to acid potential is also a method of assessing the potential for acid rock drainage; a ratio 

374 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

greater than 3 is generally considered to represent minimal or no potential for acid rock drainage. 

A total of 226 static acid base accounting tests was conducted on 15 different rock types, as 

summarized in table 70.

Table 70. Number of geochemical tests conducted on Rosemont Copper waste rock

samples

Rock Type

Tons of 

Material

(thousands)

Percent of 

Material

Acid Base 

Accounting

Synthetic 

Precipitation

Leaching 

Procedure

Meteoric 

Water Mobility 

Procedure

Humidity Cell

Tests and 

Duration

Arkose 546,336 44.38 55 8 8 4 (35 weeks)

Tertiary 141,227 11.47 5 0 0 None tested

Abrigo 113,815 9.24 6 5 0 None tested

Horquilla 87,141 7.08 26 8 2 None tested

Glance 80,841 6.57 4 0 0 None tested

Andesite 49,118 3.99 38 4 6 7 (35 weeks)

Concha 34,107 2.77 6 1 1 None tested

Martin 32,304 2.62 7 4 0 None tested

Earp 29,577 2.40 14 6 0 2 (35 weeks)

Epitaph 27,150 2.21 16 6 0 1 (35 weeks)

Escabrosa 22,859 1.86 10 4 0 None tested

Bolsa 23,447 1.90 13 6 0 2 (25 weeks)

Colina 16,145 1.31 11 4 0 None tested

Quartz 13,047 1.06 9 2 1 None tested

Scherrer 8,542 0.69 0 0 0 None tested

Precambrian 

Granodiorite 4,203 0.34 0 0 0 None tested

Undefined 941 0.08 0 0 0 None tested

Overburden 391 0.03 6 2 2 None tested

Total 1,231,173 100 226 60 20 16

Source: Rosemont Copper (2012a:75). 

For those rocks that are suspected of having potential for acid rock drainage based on static testing, 

kinetic testing is often conducted, such as a humidity cell test. In this case, 16 humidity cell tests were 

conducted on 5 different rock types for which static testing suggested some acid-generating potential. 

Humidity cell testing is conducted over long periods of time in order to measure the rate at which 

acid production could occur. In these tests, waste rock is exposed to humidified oxygenated air and 

rinsed once a week, and the rinse solution is analyzed for acid-generating and chemical constituents. 

Most of the humidity cell tests were run for 35 weeks. Several public comments questioned whether 

the duration of the humidity cell tests was sufficient. The Coronado requested an opinion on this from 

geochemical specialists, and it was determined that as long as stable trends are apparent and the 

results are part of a larger strategy to characterize waste rock, it is acceptable to use kinetic testing as 

short as 20 weeks in duration (Hoag, Bird et al. 2012).

In order to determine the likely chemical constituents that would be expected to dissolve from waste 

rock into stormwater or seepage, a different suite of tests is used. The synthetic precipitation leaching 

procedure is conducted by combining waste rock materials with water in a closed container, agitating 

the solution for 16 to 20 hours, and then analyzing the water for dissolved chemical constituents. 

Rosemont Copper conducted 60 synthetic precipitation leaching tests on 13 waste rock types. 

The meteoric water mobility procedure is similar but only allows one pass, or first flush, of water to 

Final Environmental Impact Statement for the Rosemont Copper Project 375
Chapter 3. Affected Environment and Environmental Consequences

occur. Rosemont Copper conducted 20 meteoric water mobility procedure tests on six waste rock 

types. In addition to these two procedures, the weekly results of the humidity cell tests can also be 

used to assess water quality changes over the long term. 

A variety of comments have been made regarding the sufficiency of the type and number of 

geochemical tests conducted by Rosemont Copper. Following the public comment period, the 

Coronado requested opinions from geochemical specialists on a number of these issues:

• It was determined that the number, type, and distribution of samples were sufficient to 

adequately support the geochemical modeling conducted to date (Hoag, Bird et al. 2012).

• It was determined that the nine samples used to represent the future tailings material were

adequate in number and also were geologically representative of the future tailings material 

(Hoag, Bird et al. 2012).

• Some comments suggested that Rosemont Copper be required to conduct formal, detailed 

mineralogical analysis of waste rock samples. While this type of analysis may be useful for 

providing realistic constraints on model assumptions, it was determined that the mineralogy 

of the deposit was well understood and that detailed work would likely not appreciably 

change the results or conclusions of the geochemical models (Hoag, Bird et al. 2012). This 

issue remains a point of scientific uncertainty and professional disagreement, as previously 

discussed.

• The EPA raised the concern that the synthetic precipitation leaching procedure results may 

underrepresent concentrations in the geochemical models. This issue had been addressed 

through the peer review process of the geochemical modeling and was reevaluated in light of 

public comments. It was determined that the synthetic precipitation leaching procedure data 

were indeed appropriate for use in the geochemical models (Hoag, Sieber et al. 2012).

Environmental Consequences

Direct and Indirect Effects of Each Alternative

No Action Alternative

Under the no action alternative, no impacts to groundwater quality beyond existing ambient 

concentrations would occur. Groundwater quality would continue to meet all existing numeric 

Arizona Aquifer Water Quality Standards, with the exception of arsenic. Over time, population is 

expected to increase in the area, increasing development and water use; however, these activities 

generally do not have the potential to affect groundwater quality.

Impacts Common to All Action Alternatives

All mine facilities potentially impacting groundwater quality are located near the mine pit, which has 

a location common to all alternatives. While the exact location of other facilities such as the waste 

rock, tailings, and heap leach pad may vary to some degree by alternative, the difference in location is 

not relevant to evaluating the general impact on groundwater quality; therefore, with one noted 

exception (the heap leach facility), the potential impact to groundwater quality from these facilities is 

considered common to all alternatives.

376 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Impacts from Seepage from Tailings, 

Waste Rock, and Heap Leach Facilities

The specific individual mine activities and conditions that need to be considered with respect to 

groundwater quality are as follows:

• Expected water quality from water seepage from tailings;

• Expected water quality from seepage of precipitation through waste rock;

• Expected water quality of drainage from heap leach facilities (applicable to all action 

alternatives except the Barrel Alternative); and

• Fate and transport of any contaminants reaching the groundwater.

Predicted Seepage Rates 

Overall, infiltration from precipitation over tailings, waste rock, or the heap leach facilities is 

expected to be negligible. Near surface storage is expected to be such that based on infiltration 

modeling any precipitation that does not immediately run off would remain near the surface and then 

be lost to evaporation or transpiration by vegetation. The modeling techniques used to reach this 

conclusion were questioned during public comment, including by the EPA. In response, the Coronado 

requested that Rosemont Copper conduct more extensive and conservative infiltration modeling. 

Rosemont Copper conducted revised modeling and provided it to the Coronado (Tetra Tech 2012a).

In response to the Coronado’s request for more extensive and conservative modeling, Rosemont 

Copper created additional variations of a series of model parameters in order to provide better 

assurance that infiltration of precipitation was not expected under real world and extreme climatic 

conditions. 

• With respect to climate, five different scenarios were analyzed: average climate conditions 

(which has a little bit of precipitation every day because of averaging), the 24-hour, 100-year 

storm event (which provides analysis of a short-duration and high-intensity event, such as 

observed during the Arizona monsoon season), a multiday storm event (which provides 

analysis of a winter frontal storm that occurs over a longer period of time during cooler 

temperatures), 10 years of actual measured daily data, and 50 years of actual measured daily 

data. 

• With respect to cover scenarios, four different scenarios were analyzed that included no 

reclamation cover, a mixed reclamation cover of sand and gravel, a 1-foot-thick reclamation 

soil cover, and a 3-foot-thick reclamation soil cover. (By design, a 1-foot-thick soil cover is 

expected to be used, as described in the “Soils and Revegetation” resource section.)

• Each of the four cover scenarios were analyzed with and without vegetation present.

• An additional scenario was run with ponding occurring on the benches of the facilities, which 

is a condition that would be expected for the Phased Tailings, Scholefield-McCleary, and 

Barrel Trail Alternatives but not for the proposed action and Barrel Alternative.

Similar to the results described in the DEIS, none of these scenarios resulted in infiltration of 

precipitation into the waste rock, tailings, or heap leach facilities. With the ponding scenarios, several 

of the climatic conditions (24-hour, 100-year and multiday) did result in stormwater infiltrating past 

the surface layer of the waste rock facility, but the end result indicated that the infiltrated water is still 

eventually lost to evaporation. 

Final Environmental Impact Statement for the Rosemont Copper Project 377
Chapter 3. Affected Environment and Environmental Consequences

As no water is incorporated into the waste rock, and as no precipitation infiltrates the facility even 

under extreme climatic and ponding conditions, no seepage is expected from the waste rock facility. 

Seepage from the tailings stack would develop as a result of the loss of the pore water present after 

filtration, as moisture content falls from 18 percent during stacking to a field capacity of 11 percent. 

Seepage from the tailings facility is estimated to rise to 8.4 gallons per minute over the active life of 

the mine. After final reclamation and closure, the seepage rate from the tailings facility would 

steadily decrease and is predicted to reach zero seepage approximately 500 years after closure. This 

seepage does not occur in a single spot but is spread over the approximately 1,000 acres of the 

tailings facility. Public comments requested that this amount of seepage be given some perspective. 

During active mine life, 8.4 gallons per minute of seepage represents roughly 0.01 gallon per minute 

per acre of tailings facility, or slightly less than 14.5 gallons of seepage per acre per day from the 

entire tailings facility. Another way of visualizing the magnitude of seepage is to imagine the depth of 

seepage that would occur over the course of an entire year; in this case, a year’s worth of seepage 

would accumulate to a depth of less than a quarter of an inch over the 1,000 acres of the tailings 

facility. 

Seepage from the lined heap leach facility would be present and collected during the leaching 

process, which is expected to take approximately 6 years. Seepage would also be present and 

collected approximately 3 years after cessation of leaching, at which time the heap leach facility 

would be closed and encapsulated with waste rock. At the time of closure of the heap leach, seepage

from the heap leach facility is estimated to be approximately 10 gallons per minute. Modeling 

indicates that heap leach seepage would decrease to 5 gallons per minute by 5 years after closure and 

to 1 gallon per minute by 45 years after closure and that seepage would cease approximately 115 

years after closure (Tetra Tech 2010e). As previously mentioned, the heap leach facility is included in 

all action alternatives except the Barrel Alternative.

Some comments asked for a more thorough description of exactly how the heap leach pad would be 

closed and encapsulated in waste rock and still allow for monitoring and sampling of residual 

drainage. These details have since been provided by Rosemont Copper (Nelson 2012). After 

encapsulation, any residual drainage from the heap leach pad would flow from the heap leach 

collection system via pipe into a primary treatment basin, which would be located in the position of 

the former pregnant leach solution pond. The old liner for the pregnant leach solution pond would 

have been removed and replaced with a new liner system, and the treatment pond would have been 

filled with crushed limestone as well a mixed carbon source such as manure, straw, or wood chips; 

the exact contents of the primary and secondary treatment basin would be determined based on the 

sampling of the heap leach drainage. After passing through the primary treatment basin, treated 

drainage would flow via pipe to a secondary treatment basin in the location of the former stormwater

pond; the existing stormwater pond liner would stay in place. The secondary treatment basin would 

likely be filled with crushed limestone. After treatment in the secondary basin, drainage would flow 

via pipe to a sump. The sump would be accessible to the surface of the waste rock by a 4- to 6-footdiameter concrete riser pipe. This access would allow drainage to be monitored for quantity and 

sampled for treatment effectiveness. Drainage would discharge from the sump to the ground via an 

open port. If sampling indicates that treatment is ineffective, the sump is equipped with pump 

equipment to evacuate the drainage for further active treatment.

Concerns were raised by cooperating agencies over the apparent unregulated discharge of treated 

heap leach draindown to the aquifer, for those alternatives. To be clear, treated heap leach drainage 

meeting Arizona Aquifer Water Quality Standards would be allowed to flow into and out of the riser 

pipe and infiltrate into the ground. Treated heap leach drainage not meeting Arizona Aquifer Water 

378 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Quality Standards would be pumped out and either treated further or used in the process circuit 

(Nelson 2012).

Encapsulation of a heap leach facility with waste rock is not typical with open-pit mines, as usually 

heap leach activities continue throughout the life of the mine. The nature of the ore at this location 

indicates that heap leach processing is only required for the initial 6 years of active mining. Waste 

rock encapsulation is expected to be beneficial for two reasons: prevention of infiltration of 

precipitation through the heap leach, and provision of large volumes of acid-neutralizing waste rock. 

Public comments raised concerns that the encapsulating waste rock would not be protective of the 

heap leach as was suggested in the DEIS. The Coronado conducted further investigation of this 

question and determined that while the waste rock encapsulation would help prevent infiltration of 

precipitation into the heap, it indeed would not be effective at neutralizing any drainage because of 

the very limited area of contact the drainage has with waste rock lying above and beside the heap 

(Hoag, Sieber et al. 2012). Therefore, the treatment systems described above are the sole method for 

neutralization of any heap leach drainage.

Monitoring Intended to Assess Seepage Predictions

While the Coronado has undertaken analysis that concludes it is unlikely that seepage would occur 

from the waste rock facility due to infiltration of precipitation, in consideration of the public concerns 

raised about this potential, a monitoring component has been incorporated into the mitigation and 

monitoring plan (see appendix B for full details): 

• Monitoring of waste rock for seepage (FS-GW-01). Lysimeters or other collection 

equipment would be placed within the waste rock facility in order to monitor for the presence 

of seepage and allow for analysis of any leachate.

Expected Water Quality

This section describes the modeled water quality expected if seepage were to occur from the tailings, 

waste rock, and heap leach facilities. An overall discussion of the potential for acid rock drainage to 

occur, based on the numerous geochemical characterization tests conducted on materials from the 

site, is included in the “Surface Water Quality” resource section.

Tailings Facility— Geochemical models typically assume a starting liquid solution with a given 

concentration of various inorganic and metal constituents. Next, the movement of this starting 

solution through an unsaturated material such as waste rock or tailings is modeled. As the solution 

passes through the material, changes in geochemistry resulting from dissolution or precipitation of 

minerals are modeled, resulting in a final discharge or seepage solution.

The starting solution for the tailings seepage model was based on nine samples that were physically

leached through simulated tailings in the laboratory. These samples were leached using standard 

leaching procedures typically conducted under laboratory conditions (the synthetic precipitation 

leaching procedure and the meteoric water mobility procedure). The starting solutions were then 

modeled as moving through the tailings facility. The expected seepage water quality for constituents 

with a numeric Arizona Aquifer Water Quality Standard is shown in table 71. The predicted water 

quality for seepage from tailings is not expected to exceed any numeric Arizona Aquifer Water 

Quality Standards (Hudson and Williamson 2011; Tetra Tech 2010e).

Cooperating agencies have raised concerns about the potential for tailings seepage, which is expected 

to occur at a rate of about 8.4 gallons per minute, to migrate downstream as subsurface flow in 

Final Environmental Impact Statement for the Rosemont Copper Project 379
Chapter 3. Affected Environment and Environmental Consequences

shallow alluvial sediments, eventually returning to the surface as a seep or spring. The amount of 

tailings seepage equals about 13 acre-feet per year. This amount is less than 1 percent of the average 

annual runoff in Barrel Canyon. As no seeps or springs occur in the alluvial materials of Barrel 

Canyon upstream of SR 83 under current conditions, the addition of this amount of seepage is 

unlikely to result in new seeps. However, if tailings seepage were to daylight or appear at the surface

downstream, none of the concentrations reported in the tailings seepage would exceed the applicable 

surface water quality standards in Barrel Canyon (see the “Groundwater Quality and Geochemistry” 

resource section for the calculated standards in Barrel Canyon). Discussion of the full list of analytes 

in the tailings seepage (not just those with aquifer water quality standards, shown in table 71) can be 

found in the project record (Hudson and Williamson 2011). 

Table 71. Expected water quality from tailings facility

Constituent

Arizona Aquifer Water 

Quality Standard 

(mg/L)

Predicted Tailings 

Seepage

(mg/L)

Ambient Groundwater

Quality 

(mg/L)*

pH No standard 5.87 8.1

(5.7 to 9.5)

Antimony 0.006 Not present <0.0004

(<0.0004 to 0.0044)

Arsenic 0.05 Not present 0.0032

(<0.0005 to 0.067)

Barium 2 0.017 0.050

(<0.003 to 0.206)

Beryllium 0.004 Not present <0.0001

Cadmium 0.005 Not present <0.0001

(from not detectable to 0.001)

Chromium 0.1 Not present <0.003

(<0.003 to 0.01)

Fluoride 4.0 2.37 0.7

(<0.1 to 3.6)

Lead 0.05 Not present <0.0001

(<0.0001 to 0.0049)

Mercury 0.002 Not present <0.0001

(<0.0001 to 0.0003)

Nickel 0.1 Not present <0.005

(<0.005 to 0.03)

Nitrate and Nitrite (as N) 10 0.001 0.44

(<0.02 to 8.4)

Selenium 0.05 0.006 <0.0001

(<0.0001 to 0.0055)

Thallium 0.002 Not present <0.0001

(<0.0001 to 0.0012)

Note: 

Not present – constituent was either not detected in laboratory leached tailings solution and therefore was not modeled or 

was below laboratory detection limits in the modeled seepage.

* Median result from all well and spring samples, with range shown in parentheses. For samples without detections of 

contaminants above laboratory detection limits, the smallest detection limit is shown. If no range is shown, then all samples

were below laboratory detection limits.

Waste Rock Facility— Under all modeled climatic conditions, seepage is not expected to occur from 

the waste rock facility. However, geochemical modeling was conducted to estimate seepage water 

quality if any infiltration were to occur (Hudson and Williamson 2011; Tetra Tech 2010e).

380 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

The starting solution for the waste rock modeling was based on 13 samples that were physically 

leached through simulated waste rock in the laboratory. Expected water quality from any waste rock 

seepage is shown in table 72 for those modeled constituents with numeric Arizona Aquifer Water 

Quality Standards. None of the constituents predicted in the waste rock seepage exceed current 

Arizona Aquifer Water Quality Standards. 

Table 72. Expected water quality from waste rock seepage

Constituent

Arizona Aquifer Water 

Quality Standard 

(mg/L)

Predicted Waste 

Rock Seepage

(mg/L)

Ambient Groundwater

Quality 

(mg/L)*

pH No standard 7.73 8.1

(5.7 to 9.5)

Antimony 0.006 Not present <0.0004

(<0.0004 to 0.0044)

Arsenic 0.05 0.013 0.0032

(<0.0005 to 0.067)

Barium 2 0.013 0.050

(<0.003 to 0.206)

Beryllium 0.004 Not present <0.0001

Cadmium 0.005 0.0004 <0.0001

(<0.0001 to 0.001)

Chromium 0.1 Not present <0.003

(<0.003 to 0.01)

Fluoride 4.0 1.18 0.7

(<0.1 to 3.6)

Lead 0.05 0.003 <0.0001

(<0.0001 to 0.0049)

Mercury 0.002 Not present <0.0001

(<0.0001 to 0.0003)

Nickel 0.1 Not present <0.005

(<0.005 to 0.03)

Nitrate and Nitrite (as N) 10 0.018 0.44

(<0.02 to 8.4)

Selenium 0.05 0.036 <0.0001

(<0.0001 to 0.0055)

Thallium 0.002 Not present <0.0001

(<0.0001 to 0.0012)

Note:

Not present – constituent was either not detected for the analysis of the waste rock samples and therefore was not modeled 

or was below laboratory detection limits in the modeled seepage.

* Median result from all well and spring samples, with range shown in parentheses. For samples without detections of 

contaminants above laboratory detection limits, the smallest detection limit is shown. If no range is shown, then all samples

were below laboratory detection limits.

Heap Leach Facility (applies to all action alternatives except Barrel Alternative)— The starting 

solution for the heap leach facility seepage model was based on laboratory leach tests and was then 

modeled as moving through two rock types expected to be present in the heap (andesite and quartz 

monzonite porphyry). 

As previously described, following closure and encapsulation of the heap leach facility, the collection 

system would remain in place and would use a passive treatment system in order to neutralize any 

Final Environmental Impact Statement for the Rosemont Copper Project 381
Chapter 3. Affected Environment and Environmental Consequences

remaining potential seepage. Monitoring of the treated drainage via a concrete riser pipe to the 

surface of the waste rock would be possible to ensure that treatment is effective.

Two passive treatment systems have been modeled to demonstrate conceptually that treatment of 

heap leach seepage would be adequate. Each treatment system would consist of two treatment basins. 

The engineered biological system would involve placement of carbon sources in the first basin to 

promote biological treatment, followed by placement of crushed limestone in the second basin to 

control alkalinity. The crushed limestone system would have crushed limestone in both basins. 

The engineered biological system may be modified based on sampling of actual heap leach drainage.

The expected seepage water quality, as well as the water quality using each of the passive treatment 

systems, is summarized in table 73, which shows those modeled constituents with numeric Arizona 

Aquifer Water Quality Standards (Hudson and Williamson 2011). Based on the modeling, seepage 

from the heap leach facility before and after passive treatment with crushed limestone would still 

exceed numeric Arizona Aquifer Water Quality Standards for cadmium, fluoride, and selenium. 

However, the engineered biological system would reduce concentrations of all constituents below 

numeric Arizona Aquifer Water Quality Standards. As noted previously, the actual treatment system 

would be designed based on analysis of actual drainage from the heap leach. Also, the heap leach is 

not contained in the Barrel Alternative.

Table 73. Expected water quality from heap leach seepage

Constituent

Arizona Aquifer

Water Quality

Standard

(mg/L)

Predicted Heap 

Leach Facility 

Seepage

(mg/L)

Seepage through 

Engineered 

Biological System 

(mg/L)

Seepage through 

Crushed 

Limestone 

(mg/L)

pH No standard 3.23 6.31 6.59

Antimony 0.006 Not present Not present Not present

Arsenic 0.05 0.003 0.003 0.002

Barium 2 0.013 0.013 0.011

Beryllium 0.004 Not present Not present Not present

Cadmium 0.005 0.307 0.002 0.305

Chromium 0.1 0.034 0.009 0.034

Fluoride 4.0 5.23 2.64 1.96

Lead 0.05 Not present Not present Not present

Mercury 0.002 Not present Not present Not present

Nickel 0.1 Not present Not present Not present

Nitrate and Nitrite (as N) 10 Not present Not present Not present

Selenium 0.05 0.099 Not present* 0.099

Thallium 0.002 Not present Not present Not present

Notes:

Boldfaced numbers indicate an exceedance of the aquifer water quality standard.

Not present = Constituent was either not detected for the analysis of the leached rock samples and therefore was not 

modeled or was below laboratory detection limits in the modeled seepage.

* Modeled seepage was reported but with an extremely low concentration (7.6 × 10−13 mg/L), effectively not present in the 

solution.

382 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Comparison of Rosemont Deposit with Other Arizona Mines

In general, public comments (including those from the EPA) expressed concern that the geochemical 

modeling may be inaccurate, given real world water quality issues that have arisen at other mines, 

especially porphyry copper deposits in Arizona. The Coronado requested that this issue be further 

investigated by the geochemical experts consulting with the Coronado and be further explored during 

an expert panel meeting with Federal cooperating agencies on May 3, 2012 (Garrett 2012h; Hoag, 

Sieber et al. 2012).

At first glance, the Rosemont deposit seems similar to other copper deposits in Arizona in that it is a 

porphyry copper deposit that contains sulfide mineralization in skarn derived from Paleozoic 

carbonate formations. However, nearly all porphyry copper deposits in Arizona and nearby States 

(Nevada and New Mexico) contain large amounts of mineralized intrusive igneous rock (from 30 to 

100 percent by volume mined). In contrast, these materials in the Rosemont deposit account for only 

6 percent of the total materials to be mined. As a whole, this results in a substantially larger ratio of 

carbonate rocks, which tend to neutralize acid, than is found in other similar deposits. In total, 8 

mines with similar porphyry copper deposits that contain skarn were researched, and 13 additional 

mines with porphyry copper deposits that do not contain skarn were researched. None of these mines 

were found to be a reasonable analog to the Rosemont deposit because of the large amount of 

carbonate rocks in the Rosemont deposit, compared with igneous intrusive rocks in the comparison 

deposits.

In itself, this comparison does not necessarily rule out the potential for water quality problems. 

The site-specific geochemical testing and modeling that have been completed as part of this analysis 

are the appropriate methods for determining that answer. However, the comparison does respond to 

the public perception that the potential for water quality problems at the Rosemont deposit is similar 

to the potential for water quality problems observed at other developed copper deposits in Arizona.

In addition to the dissimilarity of the Rosemont Copper deposit to other copper deposits, the results of 

the various geochemical tests to estimate the potential for acid rock drainage also indicate there is 

little potential for acid generation. Of the static tests conducted, only 5 percent of the rock samples 

(11 out of 226) indicated the potential for acid generation. Based on these results, 16 rock samples 

were selected for further kinetic testing. When the majority of these materials were subjected to longterm humidity cell testing, the leachate pH remained neutral, and the trends in sulfate, iron, and 

acidity provided no indication of sulfide oxidation. One rock type, Bolsa Quartzite, was shown to 

produce net acidity during humidity cell testing as a result of sulfide oxidation. 

As a whole, the percentage of waste rock mined that is potentially acid generating is 10 percent, 

which is a mix of rock with likely acid-generating potential (2 percent) and with uncertain acidgenerating potential (8 percent) (Williamson 2012). The remaining 90 percent is non-acid generating 

or acid neutralizing. As noted previously, guidance from the ADEQ indicates that any net 

neutralization potential greater than 20 indicates the waste rock can be generally considered non-acid 

generating. Calculated net neutralizing potential for waste rock mined per year ranges from 75 to 

more than 500, with a running annual average value of 225 for the projected life of the mine; thus, as 

a whole the waste can generally be considered non-acid generating.

Final Environmental Impact Statement for the Rosemont Copper Project 383
Chapter 3. Affected Environment and Environmental Consequences

Potential for Technologically Enhanced 

Naturally Occurring Radioactive Materials

Public comments raised the potential for the mining process to concentrate naturally occurring 

radioactive materials in the tailings. The Coronado requested further investigation of this issue from 

their contract geochemical experts (Kline et al. 2012). The investigation focused on the ranges of 

uranium typically found in crustal-type rocks, the general concentrations by rock type generally 

found in the Rosemont deposit, the results of radionuclide and whole rock geochemical analysis 

conducted by Rosemont Copper on rock samples, and the solubility of uranium at the pH ranges 

expected to be encountered in the tailings. 

The most common source of radioactive materials is igneous intrusive and metamorphic basement 

rocks; as discussed above, compared with other deposits, these types of rocks are largely absent from 

the Rosemont deposit, although other types of rocks, including those present, typically also have 

lower levels of radioactivity. Geochemical analysis conducted by Rosemont Copper generally 

supported the finding that elevated levels of radioactive materials were not present. Mobility of any 

uranium present in the tailings was expected to be low, based on geochemical testing. Overall, the 

review found that the potential for technological enhancement of naturally occurring radioactive 

materials was adequately investigated and that the mineralized and unmineralized rocks present in the 

Rosemont deposit would not generate detectable concentrations of these materials in the resulting 

tailings (Kline et al. 2012).

Potential for Residue from Ammonium Nitrate Explosives

The potential for the presence of residue from the use of nitrogen-based explosives has been well 

documented in the literature (Ferguson and Leask 1988; Forsyth et al. n.d. [1995]; Morin and Hutt 

2009; Pommen 1983; Revey 1996). The explosive reaction that occurs involving ammonium nitrate 

and fuel oil ideally generates only water, carbon dioxide gas, nitrogen gas, and heat. It is the rapid 

release and expansion of these gases that creates the explosive power of the mixture. However, the 

reaction is seldom completely efficient, and nitrogen can remain as a residue in waste rock and in the 

blast zone. Early literature analyzed explosive use in coal mines in Canada and suggested that 1 to 6 

percent of the total nitrogen could remain as residue (Pommen 1983). The lower end of this range 

(1 percent) is typically associated with the dry use of ammonium nitrate, while the higher end of this 

range (6 percent) is typically associated with the use of a slurry form of ammonium nitrate. The slurry 

form of the explosive is usually used in wet environments; only dry use of ammonium nitrate fuel oil 

explosive is expected to be used by Rosemont Copper. Further studies of these same mines and 

additional mines clarified that the total nitrogen loss depended largely on the form of the explosive 

used and suggested that use of ammonium nitrate-fuel oil under dry conditions has significantly less 

residue, as little as 0.2 percent of the total nitrogen (Ferguson and Leask 1988). Therefore, for the 

purposes of this analysis, in order to calculate the potential nitrogen residue, the range of values 

associated with dry use of ammonium nitrate was used (0.2 to 1 percent).

Approximately 20,100 tons of ammonium nitrate would be used for blasting each year (see the 

“Hazardous Materials” resource section of chapter 3). By weight, ammonium nitrate is approximately 

35 percent nitrogen. The total nitrogen being imported to the site in the form of ammonium nitrate is 

therefore approximately 14 million pounds per year. It can be estimated that 0.2 to 1 percent would 

remain as residue after blasting (based on dry use of ammonium nitrate), or approximately 28,000 to 

140,000 pounds per year (or approximately 588,000 to 2.9 million pounds over the entire active 

mining phase). Residual phases of inorganic nitrogen can include ammonia, ammonium, nitrite, and 

nitrate, depending on the chemical and biological reactions that take place. Of these, ammonia is the 

384 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

most toxic to aquatic organisms, and the toxicity varies depending on both pH and temperature. 

Although reactions can vary greatly due to site-specific conditions, previous studies have estimated 

that approximately 87 percent of nitrogen residue exists as nitrate, 11 percent exists as ammonia, and 

2 percent exists as nitrite (Ferguson and Leask 1988).

The fate and transport of any nitrogen residue to groundwater or surface waters is of concern, as there 

are aquifer and surface water quality standards for nitrate, nitrite, and ammonia. There are two 

general areas in which nitrogen residue could be present within the mine site: within the pit, and 

within the waste rock facility. Within the pit itself, any residue transported by precipitation and 

infiltrating to groundwater would eventually end up in the pit lake that would form after closure. 

Blasting residue was not incorporated into the pit lake geochemical modeling (Tetra Tech 2010c). 

However, estimates suggest that if nitrogen residue were present in the pit, were to persist over the 

entire life of them mine, and were to persist and accumulate in the forming pit lake, concentrations of 

total nitrogen ranging from 6.7 to 33.3 mg/L could occur. This estimate assumes a range of explosive 

residue from 0.2 to 1 percent, assumes that approximately three percent of the total residue would 

remain in the pit rather than the waste rock facility, and that the pit lake would have a volume of 

about 1,000 acre-feet, which is expected to occur by about 20 years following mine closure (SWCA 

Environmental Consultants 2013e). 

The exposure pathway for this residue in the pit lake would be limited to birds or wildlife that could 

readily access the pit lake. As discussed elsewhere in this section, the surface water quality standards 

are not applicable to the pit lake from a regulatory perspective, but can be used to qualitatively assess 

potential impacts to exposed birds or wildlife. In this case, the most restrictive numeric surface water 

standards are for ammonia for warmwater aquatic and wildlife. Depending on temperature, the acute 

standard ranges from 6.95 to 8.4 mg/L, and the chronic standard ranges from 0.773 to 2.43 mg/L. 

Ammonia concentrations in the pit lake could range from 0.74 to 3.7 mg/L (SWCA Environmental 

Consultants 2013e). Under these scenarios, estimates suggest that if chronic exposure occurred there 

could be negative impacts to wildlife and aquatic species due to ammonia levels in the pit lake.

An additional concern is nitrogen residue that would be entrained with the waste rock removed from 

the pit that would then be exposed to surface water runoff. Unlike residue remaining in the pit, any 

impacts from waste rock runoff could potentially leave the mine site and impact downstream waters. 

Stormwater would come into contact with only a small fraction of the waste rock. Most of the waste 

rock slopes would be covered by salvaged soil during reclamation, preventing stormwater from 

contact with residual nitrogen that might be entrained with the waste rock. Stormwater would likely 

only come into direct contact with waste rock in the conveyance channels along the benches, which 

represents a small percentage of the entire waste rock volume, with contact persisting for a relatively 

short amount of time. However, for erosion control some areas of the waste rock facility might have a 

final cover of waste rock, not salvaged soil, and exposure of stormwater to explosive residue could 

occur in these areas. Estimates suggest that concentrations of total nitrogen ranging from 1.4 to 7.2 

mg/L could occur in runoff (SWCA Environmental Consultants 2013e). This estimate assumes that 

approximately 5 percent of the waste rock represents surface or near-surface rock that could come 

into contact with stormwater runoff, and that contact could occur over the entire area of the waste 

rock facility.

There are no applicable surface water quality standards for nitrate, nitrite, or ammonia in the 

ephemeral washes immediately downstream. If infiltration of this runoff occurred, estimates suggest 

that numeric aquifer water quality standards for nitrate (10 mg/L) and nitrite (1 mg/L) would not be 

exceeded (SWCA Environmental Consultants 2013e).

Final Environmental Impact Statement for the Rosemont Copper Project 385
Chapter 3. Affected Environment and Environmental Consequences

Further studies indicate that much of the loss of nitrogen is influenced by handling practices, more so 

than incomplete reactions, with as much as 5 to 15 percent loss experienced through spillage and 

improper handling (Forsyth et al. n.d. [1995]; Revey 1996). For these reasons it is desirable to have a 

robust explosives management program, as studies have found that rigorous explosives management 

programs were able to reduce ammonia concentrations by 50 percent (Revey 1996) (see mitigation

measure FS-HM-01 in appendix B, and the “Mitigation Effectiveness” part of this resource section).

Fate and Transport of Contaminants

Seepage from the tailings facility is expected to occur because of process water that is present during 

stacking, but geochemical modeling indicates that this seepage is not expected to exceed any numeric 

Arizona Aquifer Water Quality Standards. Seepage from the waste rock facility is not expected to 

occur, but in the event that it does, geochemical modeling indicates that it would not exceed any 

numeric Arizona Aquifer Water Quality Standards. Seepage from the heap leach facility in the 

proposed action, Phased Tailings, Barrel Trail, and Scholefield-McCleary Alternatives is expected to 

be treated after completion of active heap processing. Modeling indicates that untreated seepage 

would exceed numeric Arizona Aquifer Water Quality Standards; seepage treated with an engineered 

biological system would meet numeric Arizona Aquifer Water Quality Standards. 

The fate of seepage reaching groundwater, if it occurs, is modeled using the three independent 

groundwater flow models that were conducted for the project area (Montgomery and Associates Inc. 

2010; Myers 2008, 2010a; Tetra Tech 2010g). All three models predict the presence of a cone of 

depression in the groundwater table around the mine pit as a result of active pumping of the mine pit 

during active mining and as a result of evaporation from the mine pit in perpetuity after mine closure. 

The cone of depression that occurs encompasses the area beneath the heap leach facility. By the end 

of active mining, groundwater levels beneath the heap leach facility are predicted to decrease by more 

than 100 feet (see the “Groundwater Quantity” resource section). While the liner and collection 

systems are designed to and fully expected to capture all seepage from the heap leach facility that 

exceeds numeric Arizona Aquifer Water Quality Standards, any seepage that inadvertently infiltrated 

to groundwater would move toward and be contained in the pit lake. 

The cone of depression that results in groundwater flowing toward the pit lake would take time to 

develop during the mine life, and there is a possibility that heap leach seepage, if the containment 

system failed, could move laterally before reaching regional groundwater or migrate offsite before the 

cone of depression expanded to reach the heap leach facility. This scenario was modeled by analyzing 

particle tracks during the active mine life and after final reclamation and closure (Tetra Tech 2010g). 

Based on the modeling, with the exception of seepage from the northern portion of the dry-stack 

tailings facility, the movement of any potential infiltration is still toward the mine pit lake, even 

during active mining while the cone of depression is still developing. 

During the active mine life, groundwater beneath the northern portion of the dry-stack tailings facility 

would continue to move northward and eastward, generally following the Davidson Canyon drainage 

and regional groundwater flow directions. As the mine pit lake develops and groundwater flow 

directions continue to change, seepage would begin to flow westward to the mine pit lake. However, 

as seepage from the dry-stack tailings facility is not expected to exceed any numeric Arizona Aquifer

Water Quality Standard, there would be no water quality impacts from seepage flow away from the 

mine site during active mining operations. 

386 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Impacts from Mine Pit Lake

With respect to the mine pit lake, the following indicators were considered for the impacts analysis:

• Expected water quality in the mine pit lake; and

• Potential for acid conditions to form in mine pit lake.

The geochemistry of the mine pit lake that is predicted to develop after closure of the mine would not 

present a threat to groundwater regionally; as previously described, the pit is expected to capture 

regional groundwater and draw any contaminants toward it. However, the geochemistry of the mine 

pit lake is still potentially a hazard in and of itself. Impacts that would result from the geochemistry 

of the mine pit lake are analyzed in this section.

There are three general concerns with respect to the geochemistry of the pit lake: the potential for an 

acidic lake to form; geochemical reactions with the rock of the pit walls; and, since the pit represents 

a hydraulic sink, the potential for concentration of constituents due to evaporation of water from the 

pit. These parameters were evaluated in a geochemical and water balance model of the mine pit lake 

formation (Tetra Tech 2010c).

Predicted Lake Water Balance

The mine pit lake would be a dynamic system, gradually filling over a period of approximately 700 

years. In that time, the lake elevation would increase by approximately 1,229 feet, rising from 

approximately 3,050 to 4,279 feet above mean sea level. The final pit volume would be 

approximately 95,975 acre-feet, with a surface area of approximately 213 acres (Tetra Tech 2010g).

Geochemical modeling (Tetra Tech 2010c) was based on a time frame of 200 years, at which time the 

pit lake stage would reach 3,962 feet above mean sea level (approximately 75 percent of its ultimate 

depth). The selection of 200 years as the time period to analyze the pit lake water chemistry is based 

on the professional judgment of the geochemistry modelers (SWCA Environmental Consultants 

2013n). The water balance of the lake at that time point is shown in table 74. 

Table 74. Water balance of the mine pit lake 200 years after mine closure

Water Balance Component Annual Volume 

(acre-feet)

Inflows

Direct precipitation on lake surface 229.4

Runoff from mine pit walls 210.9

Groundwater inflow 139.7

Outflows

Groundwater outflow 0

Evaporation 517.1

Increase in Mine Lake Volume 62.9

Predicted Geochemistry

Numerous public comments were received on the geochemical modeling used to predict water quality 

in the pit lake, primarily focused on the inputs, assumptions, and techniques used in the modeling. 

Prior to publication of the DEIS, the modeling itself had undergone a peer review process and was 

found to be acceptable. In response to six specific technical issues brought up during public 

Final Environmental Impact Statement for the Rosemont Copper Project 387
Chapter 3. Affected Environment and Environmental Consequences

comment, the Coronado conducted additional investigations (Hoag, Bird et al. 2012). The review 

found that most of these concerns had been addressed in a reasonable manner or simply could not be 

addressed as suggested in the comments. However, the review found that two of these concerns had 

merit. These issues include: (1) accounting for chemical loading that could occur as precipitation 

percolates through fractures in the pit walls, and (2) the potential for stratification to occur. In both 

cases, however, it was concluded by the Coronado’s consulting geochemical modeling experts that 

while changing the methods of modeling these conditions would have an effect on the results, it was 

unlikely to significantly change the modeling outcome. 

The geochemical model considered the starting chemistry of the various sources of water entering the 

pit lake. The chemistry of the groundwater inflow was assumed to be similar to that of groundwater 

samples obtained throughout the area (Errol L. Montgomery and Associates Inc. 2009b). 

The chemistry of the precipitation was obtained from the nearest national Atmospheric Deposition 

Program station at Organ Pipe National Monument, approximately 200 miles west of the project area. 

The chemistry of the runoff resulting from the interaction of precipitation with the rocks of the mine 

pit walls was based on a variety of tests, including acid base accounting tests, humidity cell tests, and 

laboratory leaching procedures. Only one rock type (Bolsa Quartzite) produced acid-forming 

conditions during humidity cell testing. The results of all three types of tests were considered when 

developing the input chemistry from runoff from mine pit walls. 

Based on these inputs, four different geochemical modeling scenarios were conducted, as shown in 

table 75. Three of these scenarios represented a range (low, average, high) of possible geochemistry 

from interaction of water with the mine pit walls. The fourth scenario was designed to determine 

whether water interacting solely with Bolsa Quartzite, which is expected to be acidic, would be 

neutralized by the water in the mine pit lake. The results of all four modeling scenarios are shown in 

table 75. Numeric Arizona Aquifer Water Quality Standards are included in the table for comparison.

Table 75. Results of geochemical modeling for mine pit lake at 200 years

Constituent

Numeric Arizona 

Aquifer Water 

Quality

Standards

Scenario 1: 

Low 

Geochemical 

Loading

Scenario 2: 

Average 

Geochemical 

Loading

Scenario 3: 

High 

Geochemical 

Loading

Scenario 4: 

Average 

Loading with 

Bolsa 

Quartzite

Aluminum No standard 0.158 0.197 0.260 0.357

Antimony 0.006 0.003 0.003 0.003 0.003

Arsenic 0.05 0.004 0.005 Not present 0.003

Barium 2 Not present Not present 0.009 Not present

Beryllium 0.004 0.001 0.001 0.001 0.001

Bicarbonate No standard 37.3 36.2 37.0 36.0

Cadmium 0.005 0.002 0.002 0.002 0.002

Calcium No standard 89.9 99.8 107.7 100.7

Chloride No standard 9.9 11.1 12.5 11.1

Chromium 0.1 0.004 0.005 0.005 0.005

Copper No standard 0.004 0.004 0.005 0.163

Fluoride 4.0 1.1 1.2 1.4 1.2

Iron No standard Not present Not present Not present Not present

Lead 0.05 0.004 0.015 0.017 0.015

388 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Constituent

Numeric Arizona 

Aquifer Water 

Quality

Standards

Scenario 1: 

Low 

Geochemical 

Loading

Scenario 2: 

Average 

Geochemical 

Loading

Scenario 3: 

High 

Geochemical 

Loading

Scenario 4: 

Average 

Loading with 

Bolsa 

Quartzite

Magnesium No standard 22.7 25.7 30.1 25.6

Manganese No standard 0.229 0.255 0.243 0.254

Mercury 0.002 0.002 0.001 Not present Not present

Molybdenum No standard 0.137 0.150 0.192 0.154

Nickel 0.1 0.005 0.006 0.007 0.010

pH No standard 8.1 8.0 8.0 8.0

Potassium No standard 5.1 5.7 6.3 5.4

Selenium 0.05 0.013 0.014 0.016 0.014

Silver No standard 0.004 0.004 0.005 0.004

Sodium No standard 31.9 35.9 38.6 35.3

Sulfate No standard 330.6 374.1 518.5 375.8

Thallium 0.002 0.005 0.006 0.007 0.006

Total Dissolved 

Solids 527 589 751 590

Uranium 0.005 0.006 0.006 0.006

Zinc 0.745 0.847 0.959 0.862

Notes: 

All results are in mg/L.

Boldfaced numbers indicate an exceedance of the aquifer water quality standard.

Not present = Constituent was not modeled to be present at concentrations above three decimal places.

Potential for Acid Lake Formation— Based on the geochemical modeling, none of the modeled 

scenarios create acidic lake conditions. 

Qualitative Comparison of Pit Lake with Aquifer Water Quality Standards— Under Arizona 

laws, the pit lake is not considered to be a facility discharging to groundwater; therefore, aquifer

water quality standards are not applicable. However, these standards provide a point of comparison 

for the water quality in the pit lake. The geochemistry of the mine pit lake results from the 

contributing inflow water quality, the interaction with mine wall rock, and evaporation. Geochemical 

modeling indicates that thallium exceeds the numeric Arizona Aquifer Water Quality Standards under 

all four scenarios modeled. Thallium has not been observed at these levels in the background ambient 

groundwater samples collected in the project area and therefore is likely elevated due to contact with 

and reaction to the exposed rock.

Qualitative Comparison of Pit Lake with Surface Water Quality Standards— The mine pit lake 

is not a navigable water and is not regulated under surface water quality regulations. However, 

surface water quality standards are specific to wildlife use and are therefore useful solely as a tool for 

assessing the potential impacts to wildlife. The comparisons provided below are based on the acute 

and chronic surface water standards designated for warmwater aquatic species and wildlife. Note that 

some standards change as water hardness changes; a hardness of 355 mg/L (as calcium carbonate 

[CaCO3]) was used to calculate standards for comparison to pit lake water quality (Garrett 2012c). 

Surface water standards have been developed for both acute and chronic exposure. Wildlife groups 

that are most likely to be directly impacted by toxins potentially present in the mine pit lake include 

Final Environmental Impact Statement for the Rosemont Copper Project 389
Chapter 3. Affected Environment and Environmental Consequences

invertebrates (i.e., insects, etc.) and birds. Wildlife most likely to be indirectly impacted includes any 

animals that prey on insects or birds that have come in contact with the water in the mine pit lake. 

Acute exposure by avian species is the most likely scenario to occur, given the depth and isolation of 

the pit lake and general inaccessibility by wildlife. Chronic exposure is unlikely to occur directly, but 

chronic exposure could occur indirectly through predation on insects.

Geochemical modeling indicates that some surface water quality standards for acute exposure to 

warmwater aquatic species and wildlife could be exceeded:

• Copper exceeds the acute surface water standard for two scenarios. Copper has not been 

observed in background ambient groundwater concentrations at these levels.

• Zinc exceeds the acute surface water standard under all four scenarios. The concentrations 

modeled for the pit lake (0.745 to 0.959 mg/L) appear to be largely the result of the 

concentration of zinc naturally occurring in groundwater samples collected from near-pit 

wells (0.694 mg/L). The background concentration also exceeds the acute surface water 

standard for zinc.

Geochemical modeling also indicates that some surface water quality standards for chronic exposure 

to warmwater aquatic species and wildlife could be exceeded:

• Cadmium exceeds the chronic surface water standard under all four scenarios. Cadmium has 

not been observed in background ambient groundwater concentrations at these levels and 

therefore is likely elevated due to contact with and reaction to the exposed rock.

• Copper exceeds the chronic surface water standard under all four scenarios. Copper has not 

been observed in background ambient groundwater concentrations at these levels and 

therefore is likely elevated due to contact with and reaction to the exposed rock.

• Lead exceeds the chronic surface water standard for three scenarios. Lead has not been 

observed in background ambient groundwater concentrations at these levels and therefore is 

likely elevated due to contact with and reaction to the exposed rock.

• Mercury exceeds the chronic surface water standard for at least two scenarios. Mercury has 

not been observed in background ambient groundwater concentrations at these levels and 

therefore is likely elevated due to contact with and reaction to the exposed rock.

• Selenium exceeds the chronic surface water standard under all four scenarios. The 

concentrations modeled for the pit lake (0.013 to 0.016 mg/L) appear to be partially the result 

of the concentration of selenium occurring in groundwater samples collected from near-pit 

wells (0.00212 mg/L), although the modeled concentrations are substantially higher. 

The background concentration also exceeds the chronic surface water standard for selenium.

• Zinc exceeds the chronic surface water standard under all four scenarios. As noted above, 

this appears to be largely the result of the concentration of zinc occurring naturally in 

groundwater samples collected from near-pit wells, which also exceeds the chronic surface 

water standard for zinc.

Potential impacts to biological resources based on these exceedances are analyzed in the “Biological 

Resources” resource section of this chapter.

390 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Impacts to Sierrita Sulfate Plume

The Sierrita open-pit copper mine is located approximately 7 miles southwest of the Rosemont 

Copper Mine water supply wells. The Sierrita mine has been operational since the 1950s, and since 

the 1970s, it has used a slurry method to deposit tailings to the east of the open pit. Over time, 

seepage from the slurry tailings impoundment has infiltrated to groundwater and has migrated 

downgradient, resulting in a plume of groundwater impacted by high sulfate concentrations that 

extends northeast from the tailings facility. In 2006, Sierrita agreed to the ADEQ’s request to conduct 

remedial actions concerning the plume, including pumping to halt migration of the plume and 

replacement of affected water sources.

The extent of the sulfate plume originating from the Sierrita mine tailings has not been fully 

characterized by Sierrita or ADEQ; however, Sierrita intends to conduct mitigation pumping to 

prevent further migration of this plume northward into the Upper Santa Cruz Subbasin. 

The mitigation pumping would be located approximately 5.5 miles south of the Rosemont Copper 

Mine water supply pumping and would extend an additional 5 miles southward from there

(see figures 52 and 53 in the “Groundwater Quantity” resource section). Mitigation pumping is 

expected to commence in 2012 and extend through 2060, extracting about 23,000 acre-feet per year. 

By removing groundwater from the vicinity of the sulfate plume, the mitigation pumping will create a 

cone of depression in the groundwater table. The purpose of this is to control the movement of the 

sulfate plume and prevent any further migration. The mitigation pumping will be offset by reduced 

pumping by Sierrita elsewhere in the basin.

Any change in water levels, gradient, or flow direction has the potential to cause migration of existing 

areas of groundwater contamination. The location of the sulfate plume is beyond the expected range 

of significant drawdown from the Rosemont Copper Mine water supply wells. No change in flow 

direction is expected to occur in the aquifer near the Sierrita plume from the Rosemont Copper Mine 

water supply pumping; the change in gradient is from 8.2 feet per 1,000 feet without mine water 

supply pumping to 9.4 feet per 1,000 feet with water supply pumping (the change in water-level 

contours with and without the mine supply pumping is shown in the “Groundwater Quantity” 

resource section in figures 52 and 53). The approximate 15 percent increase in gradient resulting from 

the Rosemont Copper Mine water supply pumping could cause a change in the rate of movement of 

the Sierrita sulfate plume, but the overall direction of groundwater flow, location of the plume, and 

ability to control the plume are unlikely to be substantially affected. 

Summary of Impact Assessment

The assessment factors identified during scoping include the ability to meet Arizona Aquifer Water 

Quality Standards and the ability to demonstrate best available demonstrated control technology. 

Ability to Meet Arizona Aquifer Water Quality Standards

The ability to meet Arizona Aquifer Water Quality Standards is summarized as follows:

• Potential seepage from dry-stack tailings is expected to meet numeric Arizona Aquifer Water 

Quality Standards.

• Potential seepage from the waste rock facility is expected to meet numeric Arizona Aquifer

Water Quality Standards.

• For the proposed action, Phased Tailings, Barrel Trail, and Scholefield-McCleary 

Alternatives, untreated seepage from the lined heap leach facility could exceed numeric 

Final Environmental Impact Statement for the Rosemont Copper Project 391
Chapter 3. Affected Environment and Environmental Consequences

Arizona Aquifer Water Quality Standards for cadmium, fluoride, and selenium; untreated 

heap leach drainage is not planned to be discharged to the environment. Modeling shows that 

seepage after treatment with an engineered biological system is expected to meet numeric 

Arizona Aquifer Water Quality Standards. 

Narrative water quality standards must also be met. These standards indicate that a discharge shall not 

cause or contribute to a violation of a water quality standard established for a navigable water of the 

state and that a discharge shall not cause a pollutant to be present in an aquifer that impairs existing or 

reasonably foreseeable future uses of water in an aquifer, or in a concentration that endangers human 

health. None of the seepage expected from the tailings, or potentially occurring from the waste rock 

or heap leach, is expected to impact a navigable water, as these discharges would be captured by the 

mine pit lake. 

Existing and reasonably future use of groundwater in the project area (Davidson Canyon watershed) 

is limited to domestic wells. There are not currently any public water systems (as defined by the Safe 

Drinking Water Act) that occur in the vicinity of the project (Arizona Corporation Commission 

2012a; U.S. Environmental Protection Agency 2012f, 2012g). None of the individual domestic wells 

that would occur within the area likely to be affected by tailings or waste rock seepage, as these 

discharges would be captured by the mine pit lake and do not exceed any water quality standards 

applicable to these individual wells that would preclude use for domestic purposes.

Ability to Demonstrate Best Available Demonstrated Control Technology

The ability to demonstrate best available demonstrated control technology at each of the facilities is a 

requirement of the aquifer protection permit issued by the ADEQ on April 3, 2012 (Arizona 

Department of Environmental Quality 2012b) and is summarized as follows:

• Dry-stack tailings facility. The stability of the dry-stack tailings facility was evaluated under 

both static and seismic loading conditions, and the factors of safety meet those required by 

the ADEQ. Waste rock buttresses are built around the facility, and stormwater management 

has been designed to control stormwater and minimize the potential for erosion. 

• Process water temporary storage pond. The process water temporary storage pond is 

actually divided into two cells (the process water pond and the temporary storage pond). 

The process water pond is double-lined, consisting of a bottom sodium bentonite 

geosynthetic clay liner overlaid by a 60-millimeter high-density polyethylene geomembrane 

liner, a leak collection and removal system, and a top 60-millimeter high-density 

polyethylene geomembrane liner. The temporary storage pond is single-lined, consisting 

of a sodium bentonite geosynthetic clay liner and a 60-millimeter geomembrane liner. 

The process water temporary storage pond operates with a 2-foot freeboard, and liners are 

secured in an engineered anchor trench. A slope stability analysis was found to be adequate 

under ADEQ standards. The temporary storage pond would be dry under normal operations, 

and impounded temporary or emergency storage water would be removed within 60 days.

• Primary settling basin. The primary settling basin receives nonfiltered tailings on a shortterm basis and stormwater. The primary settling basin is single-lined, consisting of a sodium 

bentonite geosynthetic clay liner and a 60-millimeter high-density polyethylene 

geomembrane liner, secured in an engineered anchor trench. The primary settling basin 

operates with a 2-foot freeboard. A slope stability analysis was found to be adequate under 

ADEQ standards. Impounded water in the primary settling basin would be removed within 

60 days.

392 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

• Raffinate pond. The raffinate pond stores raffinate before it is pumped to the heap leach pad. 

The raffinate pond is double-lined, consisting of consisting of a bottom sodium bentonite 

geosynthetic clay liner overlain by a 60-millimeter linear low-density polyethylene 

geomembrane liner, a leak collection and removal system, and a top 80-millimeter highdensity polyethylene geomembrane liner. The process water temporary storage pond operates 

with a 3-foot freeboard, and liners are secured in an engineered anchor trench. A slope 

stability analysis was found to be adequate under ADEQ standards. 

• Heap leach pad. The heap leach pad is single-lined, consisting of a sodium bentonite 

geosynthetic clay liner overlaid by a 60-millimeter linear low-density polyethylene 

geomembrane liner, above which is a minimum 3-foot layer of overliner drain fill (crushed 

rock). A network of collection piping within the overliner drain fill would collect and 

transport the pregnant leach solution. Liners are secured in an engineered anchor trench. 

A slope stability analysis was found to be adequate under ADEQ standards. Based on 

comments from the EPA, the Coronado also requested an independent review of the ability of 

the heap leach liner system to withstand the pressure generated by waste rock encapsulation 

(Hoag, Sieber et al. 2012). This analysis found that placement of the waste rock materials is 

within the design criteria for the heap leach facility.

• Pregnant leach solution pond. The pregnant leach solution pond stores solution collected 

from the heap leach pad. The pregnant leach solution pond is double-lined, consisting of a 

bottom sodium bentonite geosynthetic clay liner overlaid by a 60-millimeter linear lowdensity polyethylene geomembrane liner, a leak collection and removal system, and a top 

80-millimeter high-density polyethylene geomembrane liner. The pregnant leach solution 

pond operates with a 3-foot freeboard, and liners are secured in an engineered anchor trench. 

A slope stability analysis was found to be adequate under ADEQ standards. The pregnant 

leach solution pond is designed to provide storage for 8 hours of operational flows plus 24 

hours of draindown flows.

• Stormwater pond. The stormwater pond is located near the heap leach pad and pregnant 

leach solution pond and is designed to receive operational and stormwater overflow from the 

pregnant leach solution pond. The stormwater pond is single-lined, consisting of a sodium 

bentonite geosynthetic clay liner overlaid by a 80-millimeter high-density polyethylene 

geomembrane liner. The stormwater pond operates with a 3-foot freeboard, and liners are 

secured in an engineered anchor trench. A slope stability analysis was found to be adequate 

under ADEQ standards. Impounded water in the stormwater pond would be removed within 

45 days.

• Waste rock facility. The stability of the waste rock facility was evaluated under both static 

and seismic loading conditions, and the factors of safety meet those required by the ADEQ. 

Stormwater management has been designed to control stormwater and minimize the potential 

for erosion. A materials testing program and waste rock segregation plan would be 

implemented to ensure that placement of potentially acid-generating waste rock is not on the 

outer slopes or other areas subject to contact with stormwater.

• Nonmunicipal solid waste landfill. The nonmunicipal solid waste landfill is permitted to 

receive such materials as clean fill, construction and demolition debris, landscape rubble and 

vegetative waste, rubbish, plastic, metal, and glass. It would not receive materials such as any 

waste generated offsite, any municipal solid waste, tires, batteries, septage, asbestoscontaining material, or sewage sludge. The landfill is lined with a 24-inch recompacted clay 

layer and would be overlapped by a 24-inch-thick soil layer. 

Final Environmental Impact Statement for the Rosemont Copper Project 393
Chapter 3. Affected Environment and Environmental Consequences

Certain aspects of the aquifer protection permit may change once the MPO is finalized. For instance, 

if the Barrel Alternative is implemented, the heap leach and underdrains would be at variance with 

the issued permit. The ADEQ has procedures for changes to the aquifer protection permit. Most 

importantly, for these changes to be approved requires demonstration that the best available 

demonstrated control technology remains in place for these facilities. For the purposes of assessing 

impacts in the FEIS, it is reasonable to expect that the individual facilities described above would 

have similar control technologies despite modifications to the permit.

Proposed Action and Action Alternatives

The impacts described above apply to the proposed action and all action alternatives. There are no 

substantial differences in impacts that are unique to specific alternatives.

Cumulative Effects

This cumulative effects discussion addresses the cumulative impacts of the action alternatives and 

any applicable reasonably foreseeable actions as identified on the Coronado ID team’s list of 

reasonably foreseeable future actions, provided in the introduction to chapter 3. The following 

reasonably foreseeable actions from that list were determined to contribute to a cumulative impact to 

groundwater quality and geochemistry:

• The Community Water Company of Green Valley is proposing delivery and recharge of 

groundwater with water from the Central Arizona Project in the Green Valley area.

• The Farmers Investment Company is proposing the extension of Central Arizona Project 

water into actively farmed pecan groves and activation of a groundwater savings facility near 

Sahuarita.

• Demand for groundwater in the Sahuarita area is expected to increase by 200 percent by the 

year 2030. Potential individual developments are proposed within the Sahuarita area, 

including development of the Farmers Investment Company property (known as Sahuarita 

Farms), the Rancho Sahuarita development, the Quail Creek development, and the Madera 

Highlands development.

• In late 2009, Freeport-McMoRan bought 8,900 acres of the long-closed Twin Buttes Mine 

site, near Sahuarita. Required permits for reopening the mine have not been issued to date, 

but it is reasonable to assume that this mine could be reopened at some point in the future.

The potential impacts associated with these activities are similar to those discussed in the 

“Groundwater Quantity” resource section in that they could change the water balance, groundwater

levels, and groundwater flow directions within the Upper Santa Cruz Subbasin. In terms of 

groundwater quality, increased drawdown could potentially cause changes to the direction or rate of 

movement of the Sierrita sulfate plume.

Climate Change

Although climate change is likely to have an effect on the aquifer of the area and may reduce 

groundwater availability and increase depth to water, groundwater quality is generally good 

throughout the basin and does not vary with depth. Climate change is not expected to have an effect 

on the quality of groundwater resources.

394 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Mitigation Effectiveness 

Mitigation and Monitoring – Forest Service

• Monitoring of waste rock for seepage (FS-GW-01). Lysimeters or other collection 

equipment would be placed within the waste rock facility in order to monitor for the presence 

of seepage and allow for analysis of any leachate.

• Location, design and operation of facilities and structures intended to route stormwater

around the mine and into downstream drainages (FS-SW-01). Various stormwater 

diversion channels and location of facilities have been designed and located in order to 

maintain flow downstream as much as possible and avoid contact of stormwater with 

processing facilities and ore stockpiles.

• Monitoring to determine impacts from pit dewatering on downstream sites in Barrel 

and Davidson Canyons (FS-BR-22). Monitoring would be conducted of surface water, 

alluvial groundwater, and deeper groundwater at sites in Barrel and Davidson Canyons.

Several locations have already been installed and are being actively monitored, whereas 

others will require access from landowners.

• Hazardous materials containment and management (FS-HM-01). In order to reduce 

potential human health and environmental risks, hazardous materials and substances will be 

managed and contained within facilities that are designed, constructed, and maintained to 

meet applicable laws and regulations. These facilities will include leak containment and 

recovery systems as required and adequate stormwater management and drainage systems to 

prevent contamination of outside containment areas. An explosives and blasting management 

procedure would be required to be implemented to ensure best management practices are 

applied.

• Additional waste rock and tailings characterization (FS-GW-03). During operations, 

additional waste rock characterization tests, above and beyond those required by the aquifer

protection permit, would be required to be conducted on waste rock and tailings. This 

additional analysis includes requirements for humidity cell testing, whole rock chemistry, and 

mineralogical analysis in addition to the acid-base accounting and leachate testing already 

being conducted for the aquifer protection permit.

• Additional water quality monitoring of springs and wells (FS-GW-02). A suite of springs 

and wells, other than the point-of-compliance wells required to be monitored under the 

aquifer protection permit, would be monitored for water quality changes. These monitoring 

locations are situated beyond the perimeter fence of the mine and are intended to provide 

surveillance of any water quality changes that may be triggered by the changes in the 

hydrologic system. Specific springs and wells to be monitored are listed in appendix B.

• Periodic update and rerunning of pit lake geochemistry model throughout life of mine 

(FS-GW-04). This measure requires that the geochemistry model for the pit lake be rerun 

periodically, using the most recent geological and geochemical information obtained during 

operations. The model would be used to predict potential future water quality and, if 

necessary, inform potential mitigation measures upon closure.

• Monitoring, pumping, and treatment of heap leach drainage (FS-GW-05). This measure 

is applicable to all alternatives but Barrel. This measure requires that any draindown from the 

heap leach be monitored after encapsulation of the heap leach pad in the waste rock facility, 

in order to ascertain the effectiveness of passive treatment. Any drainage that does not meet 

numeric aquifer water quality standards would need to be actively treated prior to discharge.

Final Environmental Impact Statement for the Rosemont Copper Project 395
Chapter 3. Affected Environment and Environmental Consequences

Mitigation and Monitoring – Other Regulatory and Permitting Agencies

• Design and location of the heap leach facility to reduce potential impacts to 

groundwater and surface water quality (OA-GW-01). This measure is applicable to all 

alternatives but Barrel. The heap leach facility has been designed and located to reduce the 

risk of potential contamination of groundwater from seepage. It is designed to collect all 

possible drainage and solution; is located on top of a stable rock location; the liner system is 

designed to meet requirements of the aquifer protection permit; and the facility would be 

encapsulated by waste rock at closure to protect from stormwater infiltration.

• Reduction of the potential for acid generation from tailings and waste rock (OA-GW02). Geochemical testing has indicated that there is adequate neutralization capacity in the 

overall waste rock composition to prevent potential acid generation. However, proper 

placement of the waste rock is necessary to allow this buffering capacity to be effective. This 

mitigation involves requirements for the segregation and encapsulation of potentially acidgenerating waste rock with rock that has buffering capabilities in order to reduce the risk of 

potential acid generation.

• Equipment and methods to keep potentially contaminated water from being released 

into the environment (OA-GW-03). This mitigation measure requires the use of lined 

ponds; retention of all contact stormwater for reuse as process water; and the installation of 

overflow alarms to alert operators of a potential overflow situation. Much of these mitigation 

components are required under the aquifer protection permit or stormwater permit.

• Control and recycling of process water (OA-GW-04). This mitigation measure would 

result in overall reduction of fresh water use and avoidance of potentially contaminated 

discharges by containing all process water in lined facilities, to be recycled back into the 

process stream to offset fresh water use.

• Processing and placement of tailings to reduce water content and overall footprint

(OA-GW-05). The use of dry-stack tailings instead of traditional slurry tailings would allow 

for a much smaller footprint for the tailings facility, minimizing soil disturbance.

• Groundwater quality and aquifer level monitoring required by the aquifer protection 

permit (OA-GW-06). The aquifer protection permit requires the construction and operation 

of point-of-compliance monitoring wells and institutes groundwater quality monitoring and 

sampling protocols and reporting. These measures would ensure that water quality problems, 

if present, would be identified and monitored.

• Well abandonment or capping (OA-GW-08). This mitigation measure requires proper 

abandonment or capping of any unused wells or boreholes, in accordance with ADWR

regulations and guidance.

• Detention and testing of stormwater (OA-SW-01). This mitigation measure requires 

detention and testing of stormwater quality from perimeter waste rock buttress areas for water 

quality testing prior to flowing downstream of the mine site. This also would allow a

reduction of suspended sediment in stormwater flows before flowing downstream.

Conclusion of Mitigation Effectiveness

Use of dry-stack tailings would greatly reduce the potential for seepage to occur from the tailings 

facility, reducing it to a maximum of approximately 8 gallons per minute. While geochemical 

modeling predicts that tailings seepage would not exceed aquifer water quality standards, the 

reduction in seepage would further reduce any risk from tailings seepage.

396 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Under the Arizona Aquifer Protection Permit program, all permitted facilities must use the best 

available demonstrated control technology to minimize or eliminate discharges. To do so, a mine has 

the option of selecting prescriptive control technologies or analyzing site-specific controls. 

Prescriptive control technologies are generally considered to be the more conservative and protective 

approach. Rosemont Copper chose to adopt prescriptive best available demonstrated control 

technologies in their permit application. Permitted facilities include the dry-stack tailings facility 

(unlined), the process water temporary storage pond (lined), the primary settling basin (lined), the 

raffinate pond (lined), the heap leach pad (lined), the pregnant leach solution pond (lined), the 

stormwater pond (lined), the waste rock facility (unlined), and the nonmunicipal solid waste landfill 

(lined). The heap leach facility is further designed to prevent potential discharge of contaminants for 

all alternatives except for the Barrel Alternative. The heap leach facility is designed and situated to 

collect all possible drainage and solution. It is on top of a stable rock location and would be 

encapsulated by waste rock to protect from stormwater infiltration up to the maximum reasoned 

storm event. Additional design features are intended to route stormwater around the mine, thus 

preventing contact with potential contaminants associated with plant site or ore piles, and detain 

stormwater for testing prior to release downstream. These design features would be effective at 

reducing the potential for impacts to groundwater quality at the mine site or in downstream shallow 

alluvial aquifers.

As a whole, the body of waste rock is expected to have little potential for acid rock drainage, as there 

are significant quantities of acid neutralizing rock and relatively little potentially acid-generating 

waste rock. However, proper placement of these two types of waste rock is necessary to take 

advantage of the acid neutralization potential. A waste rock segregation plan has been incorporated 

into the design of the facility and would be informed by continued monitoring and testing of waste 

rock for acid-generating potential as it is developed from the mine and placed into the waste rock 

facility. Proper implementation of the waste rock segregation plan would be effective at reducing the 

potential for impacts to groundwater quality.

Hazardous materials would be managed as required under various permits, including Mine Safety and 

Health Administration (MSHA) requirements and ADEQ requirements for storage and secondary 

containment that would be specified in the stormwater permit. Proper management of hazardous

materials would be effective at reducing the potential for impacts to groundwater quality. In 

particular, proper blasting management procedures would be effective at reducing nitrogen residue 

that could accumulate in the forming pit lake or impact downstream surface water.

Monitoring and treatment of heap leach drainage, if needed, would prevent any potential discharge of 

contaminants to the aquifer, even if this requires active pumping and remediation. Periodically 

rerunning the pit lake model would not be effective at changing water quality in the pit lake or 

preventing impacts to groundwater quality, but it would allow for the best predictions of pit lake 

water quality changes over time, in order to inform future management decisions after closure. Proper 

closure of unused wells or boreholes will limit potential pathways for contaminants to migrate from 

the surface to the aquifer.

These mitigation measures are expected to be effective in avoiding or reducing impacts to 

groundwater quality. The effectiveness of the mitigation measures has been incorporated into the 

analysis and is described in more detail throughout this section.

In addition to the mitigation measures described above, which would effectively avoid, minimize, 

reduce, rectify, or compensate for impacts, a suite of monitoring measures is also proposed or 

Final Environmental Impact Statement for the Rosemont Copper Project 397
Chapter 3. Affected Environment and Environmental Consequences

required under permits. These measures generally would not be effective as mitigation, but rather 

would provide a means for monitoring potential changes to groundwater quality. 

Effects of Amending the Coronado Forest Plan

The effects on groundwater quantity from amending the Coronado forest plan are described under “Direct 

and Indirect Effects” above. The current forest plan does not contain management area standards and 

guidelines specifically pertaining to groundwater quality for management areas 1, 4, or 7A. 

New management area 16 does contain a standard and guideline under “Watershed and Soil

Maintenance and Improvement” that would apply to both groundwater quantity and quality:

1. To the extent practicable, mining facilities and reclamation should strive to emulate natural 

hydrologic functions.

Approval of the forest plan amendment would allow actions that would result in impacts to 

groundwater quality in the Davidson Canyon/Cienega Basin. All action alternatives would meet 

Arizona Aquifer Water Quality Standards at points of compliance designated in the aquifer protection 

permit. Modeled water quality in mine pit lake exceeds the aquifer water quality standard for thallium 

and potentially ammonia, but the standard is not applicable to pit lakes. Details are provided earlier in 

this resource section. 

Surface Water Quantity

Introduction

This section discusses the potential impact to the presence and quantity of surface water resources. 

Surface water resources discussed in this section include washes, creeks, and stock tanks located 

within the analysis area. A detailed analysis of impacts to springs and seeps is provided in the “Seeps, 

Springs, and Riparian Areas” resource section of this chapter.

The analysis for surface water quantity resources considers all alternatives plus all connected actions, 

and the analysis area is based on the following two considerations: (1) the direct modification of the 

topography and alteration of the surface water regime in the project area as a result of mining and the 

development of mine infrastructure; and (2) the indirect effects of mining activities on downgradient 

surface water drainages. Downstream surface water drainages in the analysis area include the 

immediate sub-watersheds, including Barrel Canyon, the portion of Davidson Canyon that receives 

discharge from the project area and is tributary to lower Cienega Creek, and Cienega Creek 

downstream of its confluence with Davidson Canyon to the Pantano Dam (figure 61). While the 

project area itself drains to Davidson Canyon and ultimately Cienega Creek, also included in the 

analysis area for surface water quantity are the utility corridor to the west of the project (including an

urbanized portion of the watershed within the town of Sahuarita that likely drains to storm drains and 

ultimately to the Santa Cruz River) and portions of watersheds to the east of the project (North 

Canyon, Oak Tree Canyon, and Empire Gulch) that are crossed by the Arizona National Scenic Trail

alignment.

The temporal bounds of analysis includes all phases of mine life involving surface disturbance, 

including the premining, active mining, and final reclamation and closure phases of the project. 

Analysis of the reclamation and revegetation of the site to prevent erosion from occurring also 

encompasses the postclosure phase, as discussed in the “Soils and Revegetation” resource section of 

this chapter. 

398 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 61. Analysis area for surface water quantity

Final Environmental Impact Statement for the Rosemont Copper Project 399
Chapter 3. Affected Environment and Environmental Consequences

Changes from the Draft Environmental Impact Statement

Since publication of the DEIS, the most substantial change to the surface water section has been a 

redesign of postclosure stormwater management for the Barrel Alternative (see the “Overview of 

Stormwater Management” part of this resource section). In addition, in response to public comments, 

the modeling approach used for estimating storm flows has been further reviewed (see the “Coronado 

National Forest Review of Surface Water Modeling Techniques” part of this resource section).

Postclosure stormwater management for the Barrel Alternative has been redesigned to address public 

and agency concerns regarding: (1) the storage of stormwater on the top and benches of the tailings 

and waste rock facilities, (2) the use of flowthrough drains beneath the tailings and waste rock 

facilities, and (3) the amount of water being removed in perpetuity from the upper reaches of the 

watershed. An iterative process involving a team of experts working closely with project engineers 

was a critical component in the redesign of the Barrel Alternative (SWCA Environmental Consultants 

2013g). As a result of the redesign efforts, several design concerns were eliminated, and the amount 

of water being removed from the watershed has been improved. The flowthrough drains have been 

eliminated for the Barrel Alternative due to concerns over their long-term maintenance. With regard 

to the amount of water being removed from the upper reaches of the watershed, postclosure 

stormwater retention ponds have been eliminated from the top of the tailings and waste rock facilities. 

Instead, these facilities shed all runoff, which is channeled to drop structures that discharge into 

Barrel Canyon or tributaries. As a result, the amount of runoff removed from the watershed has been 

reduced by half for the Barrel Alternative.

Additional mitigation measures have been incorporated into the document and assessed for 

effectiveness at reducing impacts (see the “Mitigation Effectiveness” part of this resource section, 

as well as appendix B).

Monitoring has been incorporated into the “Mitigation and Monitoring Plan” (see appendix B) in 

order to address uncertainty associated with stormwater modeling (see the “Mitigation Effectiveness” 

and “Monitoring Intended to Assess Stormwater Modeling” parts of this resource section).

In response to public comments, particularly those received from Pima County, the hydrologic 

modeling approach used to estimate storm flows was reviewed for applicability in Pima County, and

the Coronado contracted additional analysis to ensure that the modeling methods used are 

appropriate. Additional modeling sensitivity analyses were conducted, and the modeling approach 

used by Rosemont Copper was compared with other methods and determined to be reasonable.

Other changes from the DEIS include the following:

• The analysis area for indirect and cumulative impacts was expanded to include: (1) the 

watershed in which the electric transmission line and water supply pipeline are located; 

(2) both locations of proposed Arizona National Scenic Trail reroutes; and (3) all road 

construction and decommissioning associated with the proposed project.

• Additional data were analyzed for offsite surface water rights (see the “Indirect Impacts to 

Offsite Surface Water Rights” part of this resource section).

• Additional data were analyzed for offsite stream flows (see the “Stream Flow” part of this 

resource section).

• The effectiveness of new mitigation measures and reclamation plans (including concurrent 

reclamation) was analyzed (see the “Mitigation Effectiveness” part of this resource section).

400 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Issues, Cause and Effect Relationships of Concern

One significant issue was identified concerning surface water quantity.

Issue 3D: Surface Water Availability

Construction and operation of the mine pit, tailings, waste rock, and leach facilities have the potential 

to change surface water discharge to Davidson Canyon and Cienega Creek, portions of which are 

designated an Outstanding Arizona Water by the ADEQ. Additionally, the availability of water for 

stock watering tanks could be reduced. 

Issue 3D Factors for Alternative Comparison

1. Quantitative assessment of water released and available for beneficial uses, measured as 

percent reduction from baseline

4. Number of stock watering tanks that would be unavailable

5. Change in volume, frequency, and magnitude of runoff from the project area

6. Change in recharge of the aquifer by runoff

Analysis Methodology, Assumptions, 

Uncertain and Unknown Information 

The methodology for assessing changes in surface water quantity consists primarily of hydrologic 

modeling of 100-year peak storm flows resulting from design precipitation events (specifically, the 

National Oceanic and Atmospheric Administration Atlas 14 24-hour mean-precipitation value and the 

Natural Resources Conservation Service Type II 24-hour temporal storm distribution) using the U.S. 

Army Corps of Engineers’ (USACE’s) computer program Hydrologic Engineering Center Hydrologic 

Modeling System, Version 3.4. The same modeling is carried out under baseline conditions and for 

each action alternative, with both peak flow and total flow volume being modeled. 

The watershed area considered in this modeling totals 8,960 acres. That area represents the portion of 

the watershed above the USGS stream gage on Barrel Canyon at SR 83. Below this point, the wash 

and any contributing watershed would remain undisturbed under all alternatives. Modeling results 

were then used to evaluate indirect impacts from reduced flows in washes downstream of the stream 

gage on Barrel Canyon. 

In response to public comments regarding concerns over the hydrologic modeling approach chosen, 

modeling methods used for estimating storm flow were revisited. Zeller (2011b) validated the model 

results using the USGS Bulletin 17B statistical analysis and Region 13 Regional Regression 

Equation, and he calibrated the model using local data from two nearby USGS stream gages (Barrel 

Canyon and Davidson Canyon). Zeller determined that the modeling approach used was reasonable. 

Numerous public comments, primarily from Pima County, were received regarding the hydrologic 

modeling for surface flow at the Rosemont site. These comments focused mainly on: (1) the choice of 

the model that was used, and (2) the assumptions behind the model inputs that were used, including 

the curve number3 and precipitation. To address these comments, the Coronado contracted Golder 

3 The “curve number” is one way to describe how a watershed reacts to rainfall. The curve number is a measure of the 

amount of water that will run off the watershed after a storm, rather than infiltrate or evaporate from the watershed. High 

curve numbers mean that more water will run off. For instance, pavement has a curve number value of 98. Lower curve 

numbers mean that more water will remain on the watershed, usually because the water is slowed or captured by vegetation

or soil.

Final Environmental Impact Statement for the Rosemont Copper Project 401

 
Chapter 3. Affected Environment and Environmental Consequences

Associates to run additional surface water model scenarios based in part on the Pima County 

comments; the purpose of this remodeling effort was to evaluate the validity of the model that had 

been used and to analyze the sensitivity of a reasonable range of model inputs. Ultimately, the 

Coronado determined that the modeling as presented by Rosemont Copper is valid and appropriate; 

the additional modeling sensitivity runs conducted inform the possible range of results that could 

occur. Further detail is provided below in the “Coronado National Forest Review of Surface Water 

Modeling Techniques” part of this resource section.

In addition to surface flow modeling, public comments were also received that questioned the design 

parameters used for storage features (i.e., retention basins, process ponds). Through a process of 

iterative peer review by experienced professionals, the Coronado determined that the storage criteria 

used in association with the proposed design of stormwater features were based on regulatory 

guidance and reasonable engineering practices; therefore, the Coronado did not undertake any 

additional modeling with respect to the design of storage features. Notwithstanding, the Coronado did 

request a redesign of the postclosure stormwater management for the Barrel Alternative to address, in 

part, concerns regarding the storage of stormwater on the top and benches of the tailings and waste 

rock facilities.

Volumes for individual stock ponds have not been measured, but reasonable estimates of stock pond 

volumes are available based on available ADWR data. Priority and validity of surface water rights 

affected by the project have not yet been determined by the Superior Court through the General 

Stream Adjudication of the Gila River; therefore, surface water rights could not be fully analyzed but 

were analyzed to the extent possible using available data from the ADWR.

Coronado National Forest Review 

of Surface Water Modeling Techniques

Golder Associates’ new surface water model (hereafter, Golder model) to estimate changes in peak 

flows from pre- to postmining conditions incorporated the PC-Hydro computer software as 

recommended by Pima County Regional Flood Control District (Pima County 2012b). Using the 

prescribed PC-Hydro model, Golder Associates performed a series of sensitivity analysis runs that 

consisted of four scenarios with variations of two model input parameters, rainfall and curve number. 

For the sensitivity analysis, high and low values of precipitation and curve number were input into 

the Golder model. The high precipitation value of 5.35 inches was based on the 24-hour storm depth

derived from methods recommended by Pima County Regional Flood Control District (i.e., the 

National Oceanic and Atmospheric Administration Atlas 14, Upper 90% Confidence Limits). The low 

precipitation value of 4.75 inches was based on the 24-hour storm depth, which was used in the 

Rosemont Copper model. Using the curve number tables recommended by Pima County Regional 

Flood Control District and provided in the PC-Hydro User Guide (Arroyo Engineering LLC 2007),

Golder Associates determined that for existing conditions, the high curve number would be 90 (based 

on 20 percent cover density of mountain brush vegetation), and the low curve number would be 85 

(based on 40 percent cover density of mountain brush vegetation). Based on this guidance, the curve 

numbers for dry-stack tailings and waste rock facility surfaces in postmining conditions were 

assigned values of 90 and 85 based on the range of cover density. In the Rosemont Copper model, 

a curve number of 85 was chosen for both existing and postmining conditions based on the larger 

watershed land use and soil type as well as the anticipated proposed soil type (soil type “C”) to be 

used on mining facility features.

402 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Golder model results show that the curve number is the more sensitive of the two input parameters of 

concern. When the curve number input remains constant and precipitation changes, model results 

change by 4 percentage points for low curve number (13 percent versus 17 percent) and by 2 

percentage points for high curve number (26 percent versus 28 percent). When the precipitation input 

remains constant and the curve number changes, model results change by 13 percentage points for 

low precipitation (13 percent versus 26 percent) and by 11 percentage points for high precipitation 

(17 percent versus 28 percent).

The Golder modeling effort provided one piece of information out of many used by the Coronado to 

assess the surface flow models, sediment transport models, and design storms used for sizing 

stormwater management features. The full list of peer review, sensitivity analyses, and other reviews 

relied upon by the Coronado is summarized in the record (SWCA Environmental Consultants 2013l).

This includes an interactive peer review process conducted by professionals with expertise in the field 

of stormwater management and modeling that took place between August 2010 and June 2011, two 

individual modeling reports describing sensitivity analyses (Chee and Hemmen 2010; Baxter and 

Patterson 2012), and an additional detailed rebuttal of cooperating agency comments (Zeller 2011b).

Based on this information, the Coronado has determined that the surface flow and sediment modeling 

used in the FEIS is reasonable and appropriate to provide an informed analysis, and that the sizing 

and design of stormwater control features are also reasonable and appropriate to provide an informed 

analysis in the FEIS.

The Coronado recognizes that the detailed assumptions used in the models and used to size 

stormwater management features remains a point of professional disagreement with individuals from 

cooperating agencies with specific expertise in this area. Ultimately, it is the responsibility of 

Rosemont Copper to ensure that proper design and implementation of any stormwater features are

done in a safe, professional manner and are consistent with any applicable regulations.

Monitoring Intended to Assess Stormwater Modeling 

In consideration of the concerns raised regarding the stormwater modeling, two monitoring

components have been incorporated into the “Mitigation and Monitoring Plan” (see appendix B for 

full details). The monitoring includes the following:

• Monitoring to determine impacts from pit dewatering on downstream sites in Barrel 

and Davidson Canyons (FS-BR-22). Monitoring would be conducted of surface water, 

alluvial groundwater, and deeper groundwater at sites in Barrel and Davidson Canyons.

Several locations have already been installed and are being actively monitored, whereas 

others would require access from landowners.

• Continued operation and data gathering of USGS flow gage that would provide data for 

surface water flows downstream of the mine site (RC-SW-01). Rosemont Copper would 

annually fund the USGS to operate and maintain the existing flow gage at Barrel Canyon.

Summary of Effects by Issue Factor by Alternative

Table 76 presents the summary comparison of impacts from each alternative.

Final Environmental Impact Statement for the Rosemont Copper Project 403
Table 76. Summary of effects

Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 3D.1: Quantitative assessment of 

water released and available for beneficial 

uses

No change Beneficial uses of 

ephemeral stream

flows primarily related 

to stock tanks; after 

mitigation, negligible 

effect on beneficial 

uses

Same as for 

proposed action

Same as for 

proposed action

Same as for 

proposed action

Issue 3D.4: Number of stock watering 

tanks that would be unavailable

0 11 stock tanks directly 

lost; 

6 stock tanks possibly 

indirectly impacted 

downstream, but 

reduction in flow due 

to mine unlikely to 

affect tanks

11 stock tanks 

directly lost; 6 

stock tanks 

possibly indirectly 

impacted 

downstream, but 

reduction in flow 

due to mine 

unlikely to affect 

tanks

15 stock tanks 

directly lost; 5 

stock tanks 

possibly indirectly 

impacted 

downstream, but 

reduction in flow 

due to mine 

unlikely to affect 

tanks

15 stock tanks 

directly lost; 5 

stock tanks 

possibly indirectly 

impacted 

downstream, but 

reduction in flow 

due to mine 

unlikely to affect 

tanks

Issue 3D.5: Change in volume, 

frequency, and magnitude of runoff from 

the project area

Possible 

reduction 

owing to 

climate

change

Postclosure 45.8% 

reduction in average 

annual volume of 

stormwater flow; 

53.1% reduction in 

100-year, 24-hour 

peak stormwater flow; 

9.7% reduction in 

stormwater flow in 

lower Davidson 

Canyon.

Approximately 30 to 

50% reduction during 

operations.

Postclosure 44.3% 

reduction in 

average annual 

volume of 

stormwater flow; 

49.9% reduction in 

100-year, 24-hour 

peak stormwater 

flow; 11.1% 

reduction in 

stormwater flow in 

lower Davidson 

Canyon 

Approximately

30 to 50% 

reduction during 

operations.

Postclosure 17.2% 

reduction in 

average annual 

volume of 

stormwater flow; 

22% reduction in 

100-year, 24-hour 

peak stormwater 

flow; 4.3% 

reduction in 

stormwater flow in 

lower Davidson 

Canyon 

Approximately

30 to 40% 

reduction during 

operations.

Postclosure 42.0% 

reduction in 

average annual 

volume of 

stormwater flow; 

40.0% reduction 

in 100-year, 24-

hour peak 

stormwater flow; 

10.5% reduction 

in stormwater 

flow in lower 

Davidson Canyon 

Approximately 30

to 50% reduction 

during operations.

404 Final Environmental Impact Statement for the Rosemont Copper Project
Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 3D.6: Change in recharge to the 

aquifer by runoff

Possible 

reduction 

owing to 

climate

change

Reduction in recharge 

to shallow alluvial 

aquifers possible but 

cannot be quantified.

Overall loss of 

mountain-front 

recharge to aquifer

about 35 acre-feet per 

year, in perpetuity.

Reduction in 

recharge to 

shallow alluvial 

aquifers possible

but cannot be 

quantified. Overall 

loss of mountainfront recharge to 

aquifer about 35 

acre-feet per year, 

in perpetuity.

Reduction in 

recharge to shallow 

alluvial aquifers

possible but cannot

be quantified.

Overall loss of 

mountain-front 

recharge to aquifer

about 35 acre-feet

per year, in 

perpetuity.

Reduction in 

recharge to 

shallow alluvial 

aquifers possible

but cannot be 

quantified. Overall 

loss of mountainfront recharge to 

aquifer about 35 

acre-feet per year, 

in perpetuity.

Final Environmental Impact Statement for the Rosemont Copper Project 405
Chapter 3. Affected Environment and Environmental Consequences

Affected Environment

Relevant Laws, Regulations, Policies, and Plans

Table 77 lists the applicable laws, regulations, and policies related to the use, protection, and 

management of surface water quantity resources that would apply to the development and operation 

of the project. These laws, regulations, and policies, which will collectively be referred to in the 

following sections as “regulation(s),” are outlined in more detail in the following sections. 

Table 77. Summary of the Federal, State, and local regulatory requirements applicable 

to the project with respect to surface water resources

Law/Regulation Regulates

Federal

CWA – Section 404 Discharge of dredged or fill material into waters of the U.S.

FSMs 2520, 2530, and 2880; FS-881 and FS990a (Technical Guides)Watershed protection and management, water resource management, 

geological resources, groundwater management, and water quality 

management

State

Dam Safety Permit Jurisdictional dams of certain purpose, height, width, or capacity 

Surface Water Rights Diversion of springs, surface flow, and certain wells

Local

Pima County Floodplain and Erosion Hazard 

Management Ordinance

Regulatory flood plains and riparian habitat designated by Pima 

County

Federal

Clean Water Act Section 404

Section 404 of the CWA regulates the discharge of dredged or fill material into waters of the U.S. 

(WUS). While this has an effect on both surface water quantity and quality, as well as riparian areas, 

for the purposes of this EIS, Section 404 of the CWA is fully discussed in the “Surface Water 

Quality” resource section of chapter 3. 

Forest Service Guidance

FSMs and technical guides provide guidance for watershed protection and management for both 

surface water and groundwater resources. These manuals and technical guides are described in the 

“Groundwater Quantity” resource section.

State

Dam Safety Permit (Arizona Administrative Code R12-15, Article 12)

ADWR regulates the safety of dams within the State of Arizona. Dam safety rules are applicable only 

to certain dams, with exemptions based on purpose, height, and capacity. The compliance dam 

located in the Barrel Canyon drainage would have a capacity of 2 acre-feet. This size dam is 

exempted under AAC R12-15-1203 from jurisdictional requirements set forth by ADWR and would 

not require the agency’s approval prior to construction. 

406 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Surface Water Rights

Water rights within the State of Arizona operate within a bifurcated legal framework in which surface 

water rights are considered completely separate from groundwater rights. Surface water rights are 

assigned under the legal doctrine of prior appropriation or “first in time, first in right” and have a 

priority date based on when the water was first put to beneficial use. But a Federal reserved water 

right (water right associated with an Indian reservation or public lands) has a priority date that goes 

back at least as far as the date on which the lands were set aside. The doctrine of Federal reserved

water rights was first established into law in 1908 when the U.S. Supreme Court ruled to reserve the 

water rights on Indian reservations. Federal reserved water rights are now extended to include all 

federally reserved public lands, such as national forests, national parks or recreation areas, military 

bases, and national wildlife refuges. The priority date of the water right is the date on which the 

public lands were established, and the quantity of reserved water rights is dependent on the specific 

purposes for which the land was reserved.

Historically, the administrative process of claiming or registering a surface water right in Arizona has 

not considered other water rights already claimed on the same water source. Thus, most water sources 

within the State are overappropriated, with multiple claims on the same water. The process of sorting 

through the priority of these conflicting rights is being handled by the Superior Court under the 

Arizona General Stream Adjudication. In addition to surface water sources, withdrawals from certain 

groundwater wells will eventually also be prioritized as surface water rights, depending on their effect 

on surface water sources.

Surface water rights that are located within the analysis area fall under the General Stream 

Adjudication of the Gila River. Currently, the Gila River Adjudication is focusing only on the first 

subwatershed, that of the San Pedro River. No prioritization has yet occurred for surface water rights 

within the Cienega Creek watershed or within the analysis area.

Local

Title 16 Pima County Floodplain and 

Erosion Hazard Management Ordinance (2010-FC5)

The Pima County Regional Flood Control District regulates flooding and erosion hazards on private 

property within unincorporated areas of Pima County through the Floodplain and Erosion Hazard 

Management Ordinance. The goal of the ordinance is twofold. The first goal of the ordinance is to 

ensure that new development within flood plains is safe from flooding and erosion hazards and does 

not adversely impact adjacent property. This is accomplished through implementation of the flood

plain use permit process and conformance with the National Flood Insurance Program, as 

administered by the Federal Emergency Management Agency. The second goal of the ordinance is to 

protect natural resources within flood-prone areas. These riparian areas are recognized by the county 

for their importance in mitigating flood hazards, providing natural erosion control, and promoting 

recharge into underground aquifers. 

In 2001, the Pima County Board of Supervisors adopted the Comprehensive Land System regional 

plan policy (Pima County 2004), which applies the science-based policies and principles of 

conservation developed in the “Sonoran Desert Conservation Plan” (Pima County 2009). Riparian

areas are one of the five elements considered for conservation in the plan. As such, the Pima County 

Board of Supervisors has adopted maps of regulated riparian habitat throughout the county. As part of 

the flood plain use permit process, proposed developments are subject to review for impacts to 

mapped regulated riparian habitat if more than 1⁄3 acre of a property’s regulated riparian habitat is 

Final Environmental Impact Statement for the Rosemont Copper Project 407
Chapter 3. Affected Environment and Environmental Consequences

disturbed. In some instances where disturbed regulated riparian habitat is classified as Hydroriparian, 

Mesoriparian, and/or Important Riparian Area, a mitigation plan needs to be approved by the Pima 

County Board of Supervisors. Refer to the “Required Disclosures” section at the end of chapter 3 for 

more discussion regarding the “Sonoran Desert Conservation Plan.”

The applicability of these ordinances to the Rosemont Copper Mine site has been the subject of 

disagreement. As noted in chapter 2, it is the responsibility of the operator, in this case Rosemont 

Copper, to ensure that its actions comply with applicable Federal, State, and local laws and 

regulations.

Existing Conditions

Regional Hydrologic Setting 

The project lies within the Basin and Range physiographic province, which is characterized by 

northwest-trending mountain ranges separated by broad, thick alluvial basins. The project area lies at 

the border of the Sonoran Desert and Mexican Highland subprovinces of southeastern Arizona and 

southwestern New Mexico (Tetra Tech 2010d). The Sonoran Desert subprovince consists of low 

mountain ranges and broad valleys, while the Mexican Highland subprovince is characterized by 

greater altitudes and local relief, along with dissected basins.

Hydrometeorology

The proposed project is located in an arid desert region where precipitation patterns vary significantly 

over short distances and temperatures vary with elevation. Local hydrometeorology parameters such 

as precipitation, temperature, and evaporation have been monitored in the general vicinity of the 

project area for decades and in the project area itself for several years. A summary of these data is

presented in the “Air Quality and Climate Change” resource section in this chapter.

Surface Water 

Past activities that have affected surface water quantity resources on the Coronado National Forest 

include historic grazing activities and mining. Use of natural resources on public lands for grazing 

livestock and mining dates back to settlement times (Baker Jr. et al. 2004). Historic excessive or

improper livestock grazing practices in the Southwest have resulted in the loss of herbaceous cover 

and litter and an increase in erosion, surface runoff, flooding, and downcutting, although soil and 

vegetation conditions have been improving in the project area over the past few decades. The effects 

of grazing in the project area are discussed in the “Livestock Grazing” and “Soils and Revegetation” 

resource sections in this chapter. Monitoring results by the Coronado have shown that conditions on 

the grazing allotments in the project area are satisfactory. Numerous small-scale and several largescale mining projects have occurred in the past either on or in the vicinity of the project area. 

Past wildfires have also affected surface water quantity resources on the Coronado National Forest. 

After a fire, the loss of vegetation cover and physical changes to the soil surface (i.e., hydrophobic 

soils) increase surface water runoff and erosion potential. The greatest impacts to surface water runoff 

occur in the first years after a fire, gradually decreasing over time as vegetation is reestablished. 

The speed of recovery could take up to decades and depends on factors such as the severity and 

intensity of the fire and the type of vegetation community that was burned. Since 1989, there have 

been nine fires larger than 10 acres that have occurred in the analysis area (table 78). Of the nine

fires, four are greater than 10 percent of the area that is being analyzed; all four have occurred 

since 2005. 

408 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 78. Summary of past wildfires larger than 10 acres

Fire Date Started Acres Affected Area Relative to 

Analysis Area (percent)

Gardner Fire 07/18/89 75 0.5

Fagan Fire 08/08/95 134 0.8

Florida Fire 07/07/05 23,186 142.5

Fagan Fire 04/30/07 533 3.3

Hilton Fire 2/11/12 432 2.7

Mulberry Fire 06/02/08 61 0.4

Melendrez Fire 05/29/09 5,791 35.6

Fish Fire 04/21/09 2,026 12.5

Greaterville Fire 05/02/11 2,331 14.3

Washes and Creeks (Natural Drainages) in Project Area

The project area is located in the foothills on the east side of the Santa Rita Mountains. This area is 

drained by ephemeral watercourses that flow primarily in a northeasterly direction from highelevation ridges on the eastern flank of the Santa Rita Mountains through foothills toward larger 

drainages located at lower elevations on the basin floor. Four major drainages occur in the primary 

area of disturbance: Wasp, McCleary, Scholefield, and Barrel Canyons. Scholefield, Wasp, and 

McCleary Canyons drain to Barrel Canyon, which then joins Davidson Canyon approximately 4 

miles to the east of the project area. Davidson Canyon wash flows northwesterly between the Empire 

and Santa Rita Mountains into Cienega Creek, which eventually becomes Pantano Wash downstream 

of Pantano Dam. The distance from the confluence of Barrel and Davidson Canyons to the outlet of 

Davidson Canyon at Cienega Creek is approximately 14 miles. Drainage from these systems 

eventually reaches the Santa Cruz River north of Tucson. 

Barrel Canyon watershed is the largest of the four major drainages that occur in the primary area of 

disturbance. Two subwatersheds, Upper and Lower Barrel, total more than 2,300 acres and combine 

to make Barrel Canyon proper. Barrel Canyon is the largest of the affected watersheds, extending 

almost 4 miles from its headwaters to its confluence with East Canyon; the average sandy-bottom 

channel width for washes in Barrel Canyon is estimated to be 51 feet. For comparison purposes, 

average wash widths in Wasp, McCleary, and Scholefield Canyons are approximately 38, 29, and 27 

feet, respectively. Table 79 presents details on the four primary watersheds that occur within the 

project area.

Table 79. Summary of primary watersheds within the project area

Watershed Drainage

Size (acres)

Drainage 

Size 

(square 

miles)

Average 

Drainage 

Length 

(feet)

Average 

Wash 

Width 

(feet)

Average 

Slope 

(percent)

Elevation 

Range 

(feet above 

mean sea 

level)

Barrel Canyon* 2,304 3.6 20,581 51 4 5,400 to 4,550

Wasp Canyon 1,408 2.2 9,250 38 14 6,100 to 4,800

McCleary 

Canyon 1,536 2.4 16,635 29 7 5,700 to 4,550

Scholefield 

Canyon 2,048 3.2 11,643 27 12 5,800 to 4,400

* Includes both Upper Barrel and Lower Barrel Canyons.

Final Environmental Impact Statement for the Rosemont Copper Project 409
Chapter 3. Affected Environment and Environmental Consequences

Field reconnaissance was conducted by WestLand Resources Inc. (2010c; 2010e; WestLand 

Resources Inc. 2010f) for the purpose of collecting data on drainage features within the project area. 

The results of their efforts indicate that perennial or nearly perennial surface water within the project 

area is limited to very small pools at spring sites or to stock ponds. Of the drainage features identified 

and recorded for the project area, more than 90 percent (265 out of 288) were identified as being 

ephemeral washes. 

Groundcover varies from desert brush in the steep, rocky terrain of the east half of the project area to 

herbaceous and mountain brush on the west side. Dense xeroriparian vegetation consisting of trees 

and shrubs lines the margins of washes and occurs within flood plain areas, where moisture is stored 

in the alluvium. Riparian vegetation is discussed in detail in the “Seeps, Springs, and Riparian Areas” 

resource section in this chapter.

Stream bed material found within the major drainages consists of unconsolidated sand, gravel, silt, 

and clay. This recent alluvium is 2 to 4 feet thick on the bottom of the major drainages (Tetra Tech 

2007f). Flood plains at the lower elevations of the major washes are not more than 100 feet wide and 

are considerably more restricted in upstream reaches at higher elevations. Figure 61 depicts the major 

drainage basins on the project area, and table 79 summarizes the size and characteristics of the 

watersheds. Perennial or intermittent surface water in the project area occurs only as very small pools 

or stock ponds; all of the washes and drainages are ephemeral. 

Water Resources Downgradient of the Mine 

Surface drainage from the project area leaves via the Barrel Canyon drainage, including Scholefield 

and Papago Canyons, which drain a small portion of the northeastern part of the project area. Barrel 

Canyon connects with the Davidson Canyon drainage east of SR 83, approximately 4 miles 

downstream of the project area. Farther downstream in the watershed (approximately 14 miles), 

Davidson Canyon is tributary to Cienega Creek. Cienega Creek is the main surface water drainage in 

a basin that flows northwest into the Tucson Active Management Area and covers an area measuring 

approximately 605 square miles in southern Arizona (figure 62). Cienega Creek has significant 

reaches (approximately 8 miles) of intermittent or perennial water as it flows through Las Cienegas 

National Conservation Area and in the vicinity of the confluence with Davidson Canyon. Farther 

downstream, Cienega Creek becomes Pantano Wash, which eventually flows into the Santa Cruz 

River on the northwest side of Tucson. Portions of Cienega Creek and a reach of Davidson Canyon 

approximately 11 miles downstream of the project area have been designated an Outstanding Arizona 

Water by the ADEQ (figure 62). Both Cienega Creek and Davidson Canyon are outside any area of 

direct impact from the proposed project but could be indirectly impacted by reductions in stream

flow. A full analysis of impacts to these Outstanding Arizona Waters is included in the “Seeps, 

Springs, and Riparian Areas” resource section in this chapter.

South and east of the project area, Cienega Creek passes through the Las Cienegas National 

Conservation Area. North of the project area, Cienega Creek passes through the Cienega Creek 

Natural Preserve, which stretches from just south of I-10 northwest to Colossal Cave Road. 

The western boundary of the Las Cienegas National Conservation Area is approximately 3 miles from 

the eastern boundary of the project area. Cienega Creek is divided into two sections: the upper 

section, which drains the central valley east of the project area; and the lower section, which flows 

through a narrow valley and becomes Pantano Wash north of the project area (see figure 62). 

Between the confluence with Davidson Canyon and the “Narrows” section, impermeable bedrock 

forces water to the surface, creating stretches of perennial flow. Limited flow data exist for both 

410 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 62. Outstanding Arizona Waters and stock tanks

Final Environmental Impact Statement for the Rosemont Copper Project 411
Chapter 3. Affected Environment and Environmental Consequences

Davidson Canyon and Cienega Creek; data from USGS gage no. 09484550 on upper Cienega Creek 

(approximately 8miles east of the project area) indicate perennial flow at this location for the last 

decade (U.S. Geological Survey 2011). 

The Outstanding Arizona Water portion of Davidson Canyon is identified as a perennial, free-flowing 

reach; however, field visits conducted in January 2010 to investigate spring flow within Davidson 

Canyon found that most of the southern portion of the reach was dry (Tetra Tech 2010a). With the 

exception of small perennial sections, based on data from 1968 through 1975 (Arizona Department of 

Water Resources 2011a), both Davidson Canyon and Lower Cienega Creek are intermittent streams 

that flow for limited portions of the year, with some perennial reaches in Cienega Creek.

Watershed Yield 

Various calculations have been made in previous literature concerning the amount of water leaving 

the area watersheds as runoff. These analyses were made solely on the Barrel and Scholefield Canyon 

watersheds, which form a total watershed area of approximately 9,000 acres. Estimates of flow

leaving these watersheds as runoff range from 900 to 1,500 acre-feet per year (Hargis and 

Harshbarger n.d. [1977]). At existing conditions, the average annual runoff from contributing 

watersheds associated with the project area to the point of concentration (USGS gage no. 09484580) 

is estimated to be 1,407 acre-feet (Krizek 2010c).

Stream Flow

Flow monitoring at seeps and springs and in washes is an ongoing activity in and around the project 

area. Runoff from the drainage areas to the point of concentration in Barrel Canyon at USGS gage no. 

09484580 is typically intermittent and of short duration. Historic peak flow data exist for Barrel 

Canyon from 1962 through 1976, and there are daily stream flow data after January 23, 2009 (U.S. 

Geological Survey 2010). The maximum peak flows in major drainages on the project area are related 

to episodic heavy thunderstorm precipitation during the summer months; all peak flows in Barrel 

Canyon occurred during the months of July through September. Peak flows recorded annually from 

1962 through 1976 at Barrel Canyon range from approximately 150 cubic feet per second to nearly 

2,000 cubic feet per second (table 80). The available 2009 flow data indicate that Barrel Canyon is an 

ephemeral drainage, with only occasional flow. At existing conditions, the 100-year flood peak at the 

point of concentration in Barrel Canyon (USGS gage no. 09484580) is estimated to be 8,072 cubic 

feet per second (Krizek 2010c). 

Table 80. Annual peak flows in Barrel Canyon at SR 83 bridge, 1962 to 1976

Year Date Peak Flow 

Occurred

Peak Stage Height 

(feet)

Peak Flow 

(cubic feet per second)

1962 Unknown 2.54 140

1963 Unknown 2.57 145

1964 September 10, 1964 4.78 879

1965 September 8, 1965 3.64 480

1966 Unknown 2.97 260

1967 September 1967 3.04 323

1968 July 26, 1968 6.15 1,600

1969 July 23, 1969 1.7 <15

1970 July 20, 1970 5.6 1,350

1971 August 1971 6.87 1,900

412 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Year Date Peak Flow 

Occurred

Peak Stage Height 

(feet)

Peak Flow 

(cubic feet per second)

1972 July 1972 2.92 240

1973 Unknown 1.23 <10

1974 September 21, 1974 5.64 1,350

1975 September 13, 1975 4.6 980

1976 August 1976 5.24 1,100

Source: USGS (2010).

Note: Data are from USGS gage no. 09484580.

The Pima Association of Governments has been monitoring stream flow in Cienega Creek Natural 

Preserve downstream of the project area along lower Davidson Canyon since 2005 and along lower 

Cienega Creek since 1993 (Pima Association of Governments 2012b). Monitoring in lower Davidson 

Canyon extends 4.3 miles downstream from a spring south of I-10 (presumably Reach 2 Spring; see 

the “Seeps, Springs, and Riparian Areas” resource section in this chapter) and consists of recording 

the presence/absence of stream flow (also known as “wet/dry mapping”). For this method, the length 

of the channel is walked, the locations of flows are recorded, and the extent of stream flow is mapped 

and measured. Monitoring efforts along lower Cienega Creek begin where it crosses I-10 and 

continue 9 miles downstream to Pantano Dam. Cienega Creek surface water quantity monitoring 

includes wet/dry mapping as well as monthly stream flow volumetric measurements taken manually 

with a flow meter.

The Pima Association of Governments performs wet/dry mapping of Davidson Canyon on a quarterly 

basis. Since monitoring began, September has consistently been the quarter with the longest flowing 

reach; for the 2009 to 2010 monitoring year, it was the only quarter in which flow was observed. 

Along Cienega Creek, a perennial reach occurs just upstream and downstream of its confluence with 

Davidson Canyon. The Pima Association of Governments (2012b) reported that for the 2009 to 2010 

monitoring year, stream flow along this perennial reach ranged from a low of 0.08 cubic feet per 

second in September 2009 to 1.07 cubic feet per second in March 2010. Historically, the annual mean 

stream flow along this perennial reach has declined since 1994 (table 81), and the average total length 

of surface flow in the Cienega Creek Preserve has also decreased over time since 1975.

Table 81. Annual mean stream flows in Cienega 

Creek below the confluence with Davidson 

Canyon, 1994 to 2010

Year Annual Mean Stream Flow 

(cubic feet per second)

1994 1.87

1995 1.31

1996 1.09

1997 1.34

1998 1.15

1999 1.32

2000 1.15

2001 1.72

2002 1.37

2003 0.70

2004 0.65

Final Environmental Impact Statement for the Rosemont Copper Project 413
Chapter 3. Affected Environment and Environmental Consequences

Year Annual Mean Stream Flow 

(cubic feet per second)

2005 0.49

2006 0.72

2007 1.06

2008 0.99

2009 1.16

2010 0.39

Source: Pima Association of Governments (2010).

Note: Data are from Marsh Station stream flow monitoring site.

Available surface flow data from four USGS stream gages located in the vicinity of the project area 

were obtained using the online National Water Information System Web Interface (U.S. Geological

Survey 2013d). The gages are located at:

• Cienega Creek near Sonoita (gage no. 09484550). This gage is located in a perennial section 

of Upper Cienega Creek and is also referenced in the “Groundwater Quantity” resource 

section of this chapter.

• Cienega Creek near Pantano (gage no. 09484560). This gage is located in an intermittent or 

ephemeral part of Lower Cienega Creek, several miles above the confluence with Davidson 

Canyon, and is also referenced in the “Groundwater Quantity” resource section of this 

chapter.

• Pantano Wash near Vail (gage no. 09484600). This gage is located at the confluence of 

Cienega Creek with Pantano Wash, downstream of the confluence with Davidson Canyon, 

at the boundary of the analysis area.

• Davidson Canyon Wash near Vail (gage no. 09484590). This gage is located within the reach 

of lower Davidson Canyon that is designated an Outstanding Arizona Water, between Reach 

2 Spring and the confluence with Cienega Creek.

Data were compiled using the data set containing mean discharge for each month of data collected 

during the period of record for each location. Median, minimum, and maximum of the means were 

then determined by month for each location. A summary of the data is presented in tables 82

through 85.

Cienega Creek near the Sonoita gage has a period of record from 2001 to present. Data indicate that 

this reach of Cienega Creek is perennial. No full months in the period of record were recorded with 

no flow; however, a period of no flow did occur in May and June 2010. This gage is discussed in 

great detail in the “Seeps, Springs, and Riparian Areas” resource section in this chapter. 

The period of record for Cienega Creek near the Pantano gage is February 1968 to September 1975. 

Greater variability is evident in these data, compared with the upstream gage, with the median 

monthly mean ranging from no flow to 4.4 cubic feet per second. The largest flows occur in July and 

August, with the highest in July 1974, when the monthly mean flow was recorded at 53.8 cubic feet 

per second. Flow characteristics suggest that this reach is ephemeral or intermittent. 

The Pantano Wash gage has the longest period of record, from 1959 to present. This is a perennial 

stream reach; the median monthly mean ranges from 0.798 cubic feet per second in October to 18.88 

cubic feet per second in August.

414 Final Environmental Impact Statement for the Rosemont Copper Project
Final Environmental Impact Statement for the Rosemont Copper Project 415

Table 82. Surface water flow at Cienega Creek near Sonoita, Arizona

Monthly Mean Flow (in cubic feet per second), Cienega Creek near Sonoita, Arizona, Gage No. 0948455

Period of Record 2001 to present

Jan Feb Mar Apr May Jun Jul Aug Sep Oct 

2001 – – – – – – – – 0.97 0.89 

2002 1.33 1.51 1.51 1.26 0.69 0.33 0.60 1.28 0.37 0.36 

2003 0.82 0.90 0.93 0.70 0.45 0.22 1.41 2.97 0.46 0.74 

2004 0.94 1.15 1.26 1.04 0.52 0.27 0.90 1.75 0.31 0.45 

2005 0.76 0.80 0.80 0.69 0.40 0.24 0.61 7.76 0.71 0.31 

2006 0.75 0.79 0.79 0.63 0.43 0.23 6.73 15.40 18.10 0.48 

2007 0.84 0.88 0.97 0.70 0.41 0.22 30.10 8.41 1.19 0.42 

2008 0.87 0.94 0.96 0.72 0.42 0.65 32.70 1.97 0.53 0.59 

2009 1.20 1.37 1.29 0.93 0.46 0.30 1.25 0.62 1.01 0.37 

2010 3.34 1.12 1.02 0.74 0.07 0.07 5.72 12.10 0.59 0.45 

2011 0.94 0.98 1.00 0.83 0.53 0.27 0.43 0.39 6.90 0.66 

2012 0.92 0.99 1.04 0.87 0.49 0.25 0.79 0.36 1.32 – 

Median 0.92 0.98 1.0 0.74 0.45 0.25 1.25 1.97 0.84 0.45 

Minimum 0.75 0.79 0.79 0.63 0.07 0.07 0.43 0.36 0.31 0.31 

Maximum 3.34 1.51 1.51 1.26 0.69 0.65 32.70 15.40 18.10 0.89 

Source: USGS (2013d).

Note: 

– = No data available.
Table 83. Surface water flow at Cienega Creek near Pantano, Arizona

Monthly Mean Flow (in cubic feet per second), Cienega Creek near Pantano, Arizona, Gage No. 094845

Period of Record 1968 to 1975

Jan Feb Mar Apr May Jun Jul Aug Sep Oct 

1968 – – 0 0 0 0 16.70 9.45 0 0 

1969 0 0 0 0 0 0 6.15 2.10 1.63 0 

1970 0 0 0 0 0 2.58 4.22 14.60 7.96 0 

1971 0 0 0 0 0 0 3.59 38.90 2.44 1.96 

1972 0 0 0 0 0 0 2.57 1.86 12.60 0.18 

1973 0 7.94 1.33 0 0 0 3.21 0 0 0 

1974 0.02 0 0 0 0 0 53.80 6.35 13.40 0 

1975 0 0 0 0 0 0 0.21 0 6.37 – 

Median 0 0 0 0 0 0 3.91 4.23 4.41 0 

Minimum 0 0 0 0 0 0 0.21 0 0 0 

Maximum 0.019 7.94 1.33 0 0 2.58 53.80 38.90 13.40 1.96 

Source: USGS (2013d).

Note: 

– = No data available.

416 Final Environmental Impact Statement for the Rosemont Copper Project
Final Environmental Impact Statement for the Rosemont Copper Project 417

Table 84. Surface water flow at Pantano Wash near Vail, Arizona

Monthly Mean Flow (in cubic feet per second), Pantano Wash near Vail, Arizona, Gage No. 09484600, 

Period of Record 1959 to 1974 and 1989 to present

Jan Feb Mar Apr May Jun Jul Aug Sep Oct 

1959 – – – – – – – – – 6.50 

1960 17.70 3.17 2.25 1.61 1.55 1.33 4.08 23.10 2.97 3.22 

1961 2.40 1.44 1.60 1.51 1.37 1.01 8.40 47.60 14.80 1.33 

1962 5.15 1.73 1.70 1.31 1.25 1.10 3.43 3.45 9.08 1.18 

1963 1.00 1.04 1.00 0.87 1.00 0.91 9.14 88.60 16.30 1.36 

1964 1.52 1.98 1.36 1.75 1.32 1.18 21.90 15.30 105.00 2.55 

1965 1.82 2.10 2.02 1.65 1.95 1.25 4.51 7.39 10.60 0.42 

1966 2.79 36.30 3.19 2.68 1.46 0.96 13.70 38.70 10.50 2.91 

1967 2.68 3.59 2.56 2.03 1.54 1.80 49.60 14.60 12.80 6.67 

1968 3.25 3.56 6.67 3.31 1.45 1.75 18.60 15.10 1.59 1.14 

1969 2.58 2.79 2.74 2.21 0.96 0.53 3.23 4.15 2.90 0.67 

1970 0.89 1.04 0.86 0.92 1.38 2.57 25.60 19.30 5.18 0.97 

1971 0.90 1.05 1.62 1.05 0.46 0.31 2.86 92.60 11.00 4.62 

1972 1.78 1.56 1.54 1.15 0.74 0.79 3.25 2.36 8.94 1.79 

1973 1.48 14.20 18.20 5.16 1.78 0.44 2.38 0.52 0.16 0.10 

1974 0.10 0.10 0.12 0.32 0.19 0.07 21.80 6.86 11.20 – 

1989 – – – – – – – – – 1.14 

1990 0.81 1.03 2.24 3.81 1.48 3.63 47.20 23.40 7.22 1.51 

1991 2.25 2.58 9.15 4.94 1.84 2.55 1.45 0.96 0.60 0.52 

1992 0.81 1.74 3.70 3.53 1.28 1.00 5.22 7.74 1.20 0.66 

1993 110.90 9.31 5.03 2.36 1.86 1.14 6.39 10.40 2.54 0.93 

1994 1.60 1.70 1.66 1.52 1.41 0.89 0.78 1.54 7.58 0.68 

1995 22.20 11.50 4.97 2.16 1.52 0.97 0.66 2.15 0.94 0.27 
Jan Feb Mar Apr May Jun Jul Aug Sep Oct 

1996 0.52 0.79 0.72 0.61 0.43 0.56 8.32 15.90 14.90 1.34 

1997 1.23 1.02 0.84 0.85 0.38 0.21 0.22 5.88 3.29 0.28 

1998 0.71 75.10 21.20 12.00 1.31 0.89 47.30 26.30 2.26 0.47 

1999 0.74 0.57 0.41 0.57 0.41 0.29 41.10 5.22 5.71 0.62 

2000 0.52 0.44 0.55 0.55 0.24 20.80 1.90 23.70 0.93 45.60 

2001 2.85 2.17 2.48 1.68 1.21 1.00 9.73 18.00 0.96 1.09 

2002 0.78 1.32 1.48 1.58 0.79 0.10 1.12 9.14 6.64 0.37 

2003 0.09 0.34 0.54 0.50 0.36 0.08 12.60 10.50 1.02 2.11 

2004 0.33 0.49 1.20 0.64 2.62 0.75 10.60 13.60 0.65 0.40 

2005 0.28 0.23 0.39 0.46 1.50 0.13 6.58 24.50 7.26 0.40 

2006 0.25 0.13 0.12 0.29 1.42 3.83 82.50 27.00 14.20 0.75 

2007 1.04 0.66 3.51 0.72 0.56 1.80 62.70 48.30 1.86 0.72 

2008 3.78 0.70 0.45 0.42 0.36 1.63 55.60 26.40 1.21 0.77 

2009 1.47 1.29 1.56 0.50 0.27 0.40 0.26 0.28 0.79 0.14 

2010 0.12 2.80 10.30 0.53 0.19 0.09 17.30 14.80 0.13 0.12 

2011 0.21 0.22 0.17 0.18 0.22 0.12 37.30 3.30 19.20 1.01 

2012 0.81 0.51 0.52 0.58 0.44 0.54 3.23 10.5 2.9

–

Median 1.14 1.38 1.61 1.23 1.27 0.94 8.36 14.1 4.24 0.95 

Minimum 0.09 0.10 0.12 0.18 0.19 0.07 0.22 0.28 0.13 0.10 

Maximum 110.90 75.10 21.20 12.00 2.62 20.80 82.50 92.60 105.00 45.60 

Source: USGS (2013d).

Note: – = No data available.

418 Final Environmental Impact Statement for the Rosemont Copper Project
Final Environmental Impact Statement for the Rosemont Copper Project 419

Table 85. Surface water flow at Davidson Canyon Wash near Vail, Arizona

Monthly Mean Flow (in cubic feet per second), Davidson Canyon Wash near Vail, Arizona, Gage No. 09

Period of Record 1968 to 1975

Jan Feb Mar Apr May Jun Jul Aug Sep Oct 

1968 – 0.63 0.63 0.52 0.41 0.32 5.08 6.21 0.80 0.71 

1969 0.74 0.72 0.76 0.52 0.47 0.23 0.32 0.99 0.01 0 

1970 0 0 0 0 0 0 11.10 5.85 0.01 0 

1971 0 0.05 0.21 0.13 0.03 0 0 11.20 2.01 0.002 

1972 0.02 0 0 0 0 0 0 0 4.02 0.003 

1973 0 0 0.008 0 0 0 0 0 0 0 

1974 0 0 0 0 0 0 2.85 1.64 8.02 0.003 

1975 0 0 0 0 0 0 0.51 1.27 1.63 

Median 0 0 0.004 0 0 0 0.41 1.46 1.22 0.002 

Minimum 0 0 0 0 0 0 0 0 0 0 

Maximum 0.74 0.72 0.76 0.52 0.47 0.32 11.10 11.20 8.02 0.71 

Source: USGS (2013d).

Note: 

– = No data available.
Chapter 3. Affected Environment and Environmental Consequences

The period of record for the Davidson Canyon Wash gage is February 1968 to September 1975; this 

gage is no longer in service. The range of mean monthly flow at this location corresponds to the 

monsoon season, with the highest occurring in August (11.2 cubic feet per second) and the lowest 

occurring in June just before summer monsoon season (0.318 cubic feet per second). The data also 

show the temporal variability of flow at this location, with many months of no flow. This reach of 

Davidson Canyon appears to be perennial for some periods of time (such as in 1968) but is more 

properly termed an intermittent stream.

Surface Water Trends

The Pima Association of Governments reports on conditions within the Pima County Natural 

Preserve, which encompasses a large portion of Lower Cienega Creek both above and below the 

confluence with Davidson Canyon. Stream flow monitoring (wet/dry mapping) has occurred since 

1984 (Pima Association of Governments 2012b; Powell 2013). The percentage of Cienega Creek that 

flows in this area is cyclical but has steadily decreased since monitoring began in 1984. Since 1999, 

drought monitoring has been conducted, and measurements in June 2011 indicate that this portion of

Cienega Creek has the least amount of flow yet observed, with only 13 percent of the stream 

exhibiting flowing or standing water. Between 1990 and 2011, surface water discharge in Cienega 

Creek declined by 83 percent, while stream flow extent declined by 88 percent (Powell 2013). 

The exact causes of this multi-decade decline are not entirely clear, as several possible stresses may 

be acting in concert, but the current drought cycle is considered one of the primary reasons. Davidson 

Canyon similarly has exhibited a drying trend. Flow has not been observed in lower Davidson 

Canyon in the past few years, whereas flow was observed historically and cited in the nomination of 

Davidson Canyon as an Outstanding Arizona Water. Observations relating to similar recent trends in 

Barrel Canyon, Empire Gulch, and Gardner Canyon have not been identified.

Surface Water Rights Onsite

Surface water rights within the project area associated with Rosemont Copper include those located 

on deeded land, as well as those located on Coronado National Forest land, as summarized in table 

86. Identified surface water rights filed with the ADWR include diversions from 10 springs

(including Questa, Horse Pasture, McCleary, and Rosemont Springs) and multiple diversions from 6

washes (including Wasp, Barrel, and McCleary Canyons). Priority and validity of these surface water 

rights have not yet been determined through the General Stream Adjudication.

Table 86. Summary of onsite surface water rights associated with the project area

General Location Water Right Number Name of Water Source Cadastral Location

Deeded/Fee Lands 33-93235.2 Questa Spring D-18-16 27dd

Deeded/Fee Lands 33-93236.2 Horse Pasture Spring D-18-16 15aa

Deeded/Fee Lands 33-93277.1 Barrel Canyon D-18-16 29ba

Deeded/Fee Lands 33-93278.1 McCleary Canyon D-18-16 19cc

Deeded/Fee Lands 33-93279.1 Wasp Canyon D-18-16 29cd

Deeded/Fee Lands 33-96516.0 Wasp Canyon D-18-15 36ab

Deeded/Fee Lands 36-25948.1 Rosemont Spring D-18-16 32bc

Deeded/Fee Lands 36-25954 Unnamed Spring D-18-15 23ba

Coronado National Forest 38-93308.1 Unnamed Wash D-18-16 33cc

Coronado National Forest 38-93309.1 Unnamed Wash D-18-16 34bc

Coronado National Forest 38-93310.1 Unnamed Wash D-18-15 25dd

420 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

General Location Water Right Number Name of Water Source Cadastral Location

Coronado National Forest 36-25911 Wasp Canyon D-18-15

D-18-16

Coronado National Forest 36-25912 McCleary Canyon D-18-16

Coronado National Forest 36-25945 McCleary Spring D-18-16 30ab

Coronado National Forest 36-25946 Unnamed Spring D-18-16 30cd

Coronado National Forest 36-25947 Unnamed Spring D-18-16 30cd

Coronado National Forest 36-25950 Unnamed Spring D-18-16 21bc

Coronado National Forest 36-25951 Unnamed Spring D-18-16 29ab

Coronado National Forest 36-25956 Unnamed Spring D-18-16 19cd

Source: Pearce (2007).

Surface Water Rights Offsite

Offsite surface water rights that could be impacted include any surface rights where surface 

water/groundwater exchange occurs, which could include diversions from springs or washes but 

generally not from stock tanks. Table 87 summarizes the surface water rights (excluding stock tanks) 

that are located outside the footprint of the project but still within the influence of groundwater 

drawdown (defined by the 5-foot drawdown contour). Data were obtained from the ADWR Statement 

of Claimant database. Priority and validity of these surface water rights have not yet been determined 

through the General Stream Adjudication.

Table 87. Summary of offsite surface water rights

within the area of groundwater drawdown

Name on Water Right Number of 

Water Rights

Coronado National Forest 80

ASARCO 28

Ocotillo Ranches Inc. 26

BLM 21

ASLD 20

Robinson 17

Bowman 15

Lauderbach 10

Barchas 6

McCain 5

Maldonado 4

Andrada Properties 3

Cote 3

Zeagler 3

Adler 2

Coronado Investments Inc. 2

Stewart Title and Trust No. 1460 2

Arizona Game and Fish Commission 1

Boschert 1

Carbone 1

Final Environmental Impact Statement for the Rosemont Copper Project 421
Chapter 3. Affected Environment and Environmental Consequences

Name on Water Right Number of 

Water Rights

Garrett 1

Harm 1

Hickman 1

Hillman 1

Keim 1

Martin 1

Montgomery 1

Moore 1

Nikrasch 1

Prieve 1

Robinson Cattle LLC 1

Snow 1

Source: ADWR (2005).

The BLM has raised concerns about their Federal reserved water rights, particularly those associated 

with Las Cienegas National Conservation Area. Of the 21 surface water rights identified for BLM, 3

are associated with springs on the west side of the Santa Rita Mountains (Helvetia, Chavez, and 

Zackendorf Springs), 4 are associated with ephemeral tributaries to Cienega Creek (North Canyon, 

Middle Canyon, and Oak Tree Canyon), and 13 are associated with Empire Gulch. The Empire Gulch 

water rights cover the entire reach from the confluence with Cienega Creek upstream to the boundary 

of the Las Cienegas National Conservation Area near SR 83.

Stock Tanks

Ongoing grazing activities and associated stock tank development and maintenance occur on and 

around the project area. Stock tanks associated with the project include those located on deeded land,

on Coronado National Forest land, or downstream in the Davidson Canyon watershed, as summarized 

in table 88. Data were obtained from the Coronado, ADWR Surface Water Rights and Statement of 

Claimant databases, and USGS topographic maps. The water source that feeds these stock ponds 

varies. Most commonly, the stock ponds are constructed earthen berms within drainages that impound 

surface runoff. There are several stock ponds in the project area that are known to be fed by springs

and that have been developed with concrete structures to capture spring flow (WestLand Resources 

Inc. 2010c). 

Table 88. Summary of stock tanks associated with the project area

ID Watershed Water Right 

Number Name of Water Source Cadastral Location

1 Barrel Canyon 38-24457 Barrel Tank‡ D-19-16 06dd

2 Wasp Canyon 38-26056 Upper Barrel Tank† D-18-15 25dc

3 Barrel Canyon 38-57582 Stock Tank* D-19-16 06ab

4 Barrel Canyon 38-40329 North Basin Tank* D-19-16 05bc

5 Barrel Canyon 38-62329 South Basin 4 Tank* D-19-16 06dd

6 Barrel Canyon 38-62339 North Basin Tank 2‡ D-19-16 05bc

7 Upper Barrel Canyon 38-70161 East Dam Header Tank* D-18-16 29ac

8 Upper Barrel Canyon 38-70775 North Dam Header Tank* D-18-16 29ac

422 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

ID Watershed Water Right 

Number Name of Water Source Cadastral Location

9 Barrel Canyon 38-70799 Unnamed Stock Tank* D-19-16 05bc

10 Wasp Canyon 38-70881 Section 25* D-18-15 25dd

11 Davidson Wash 38-63384 4th of July Tank* D17-17 30ab

12 Davidson Wash 38-66914 Unnamed Stock Tank* D17-17 30cd

13 Davidson Wash Not available Unnamed Tank‡ D-17-16 36a

14 Davidson Wash Not available Unnamed Tank‡ D-17-17 07b

15 East Barrel Canyon 38-70879 Section 33 Tank D-18-16 33cc

16 East Barrel Canyon 38-26061 Dirt Tank†‡ D-18-16 33cc

17 East Barrel Canyon 38-49861 Section 33 Tank* D-18-16 33cc

18 Barrel Canyon Coronado 

National Forest

Unnamed Tank‡ D-18-16 32c

19 McCleary Canyon 38-26053 McCleary Tank† D-18-16 30bb

20 McCleary Canyon Asarco Unnamed Stock Pond† D-18-16 19cc

21 Barrel Canyon Not available East Dam Tank‡ D-18-16 28ac

22, 23 Box Canyon Not available Unnamed Tank§ (2 tanks) D-19-15 01da

24 Davidson Canyon Not available Unnamed Tank§ D-18-16 01ab

Note: The “Biological Resources” resource section references two stock tanks by name: Lower Stock Tank and East Dam 

Tank. East Dam Tank (#21) is identified in the table above. It is not clear which tank corresponds to Lower Stock Tank, 

which is located within the area of the mine pit. It likely corresponds to either Upper Barrel Tank (#2) or Section 25 Tank 

(#10).

* Data are from ADWR (2011b) Surface Water Filings database.

† Data are from ADWR (2005) Statement of Claimant database.

‡ Data are from USGS Map/Geographic Names Information System (2013a; 2013c).

§ Data are from Forest Service (2011f).

Aquifer Recharge

One source of aquifer recharge is the infiltration of runoff through coarse alluvial sediments along 

ephemeral stream channels like Barrel Canyon and Davidson Canyon. The amount of water currently 

recharged through alluvial channels typically would require infiltration measurements or repeated 

stream flow measurements at multiple locations. Neither of these techniques have been undertaken on 

Barrel Canyon or Davidson Canyon; therefore, the effect of reductions in runoff on recharge of 

shallow downstream alluvial aquifers cannot be directly quantified.

Environmental Consequences

This section presents only impacts associated with surface water quantity. Impacts to seeps, springs, 

and riparian habitat as well as potential changes in perennial flow status are discussed in the “Seeps, 

Springs, and Riparian Areas” resource section of this chapter.

Direct and Indirect Effects of Each Alternative

Specific impacts analyzed for each alternative include surface water peak flows, average annual 

surface water flow volume, and number of stock tanks both directly and indirectly impacted. Surface 

water flows from the project area were calculated in both cubic feet per second and acre-feet per year 

for the USGS gage located by the SR 83 bridge. 

Final Environmental Impact Statement for the Rosemont Copper Project 423
Chapter 3. Affected Environment and Environmental Consequences

Overview of Stormwater Management

Public comments indicated that the DEIS did not provide an adequate overall picture for stormwater

management. In addition, substantial work has been conducted since the DEIS to redesign stormwater 

management for the preferred alternative to improve downstream water availability. The purpose of 

the following description is to provide a comprehensive comparison between the redesigned Barrel 

Alternative and the stormwater management for the other alternatives.

Redesign of the Barrel Alternative

During public comment, several cooperating agencies, including the EPA and the USACE, expressed 

concerns over postclosure stormwater management as it was described in the DEIS. Primary points of 

concern included the storage of stormwater on the top and benches of the tailings and waste rock

facilities; the amount of water being removed in perpetuity from the upper reaches of the watershed, 

with a resulting serious impact to downstream riparian resources; and the use of flowthrough drains 

beneath the tailings and waste rock facilities. 

In response to these concerns, the Coronado requested that Rosemont Copper undertake a redesign of 

postclosure stormwater management for the Barrel Alternative. As a result, a revised stormwater 

management plan was developed for the Barrel Alternative, and it has been analyzed in the FEIS 

(Tetra Tech 2012b).

Barrel Alternative—Stormwater Management 

during Premining and Active Mining Phases

Stormwater is necessarily handled differently during premining and active mining, compared with 

postclosure. During active mining, certain areas of the mine site are required to be zero discharge 

under the multisector general stormwater permit, which has been obtained by Rosemont Copper 

(coverage was granted to Rosemont Copper by ADEQ on February 7, 2013). These include any areas 

in which stormwater comes into contact with ore stockpiles or processing facilities. Runoff from 

tailings is allowed to be released under the stormwater permit, but Rosemont Copper is choosing not 

to allow this to protect water quality. The maximum loss of runoff to the watershed occurs during the 

first 10 years of active mining when runoff from these areas is retained onsite and recycled as process 

water. During this period, the loss of runoff would vary but is likely to approach a reduction in annual 

average runoff of about 30 to 40 percent, compared with undeveloped baseline conditions (SWCA 

Environmental Consultants 2013f). Stormwater losses during the premining and active mining phases 

would likely be even higher for other alternatives, approximating the postclosure stormwater losses 

described below.

Where possible, diversions have minimized the amount of water required to be retained by routing 

stormwater around these process areas. Specifically, during active mining the runoff from the area 

above the plant site is sent downstream using a permanent diversion channel that directs water into 

upper McCleary Canyon instead of onto the plant site. A similar diversion exists to the west of the pit. 

However, runoff from this area is not able to discharge downstream and is generally retained and 

allowed to infiltrate as recharge into the subsurface in several ponds at the toe of the waste rock

facility. 

The mine design incorporates concurrent reclamation. A perimeter waste rock buttress would be built 

around the waste rock and tailings facilities. As this buttress is completed, the surface would be 

reclaimed and revegetated. Concurrent reclamation means that the revegetation of the waste rock 

buttress would start taking place while active mining is still occurring; in fact, concurrent reclamation 

424 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

would begin to occur by the end of the first year of active mining. As the surface is revegetated and

stabilized, stormwater would begin to be released downstream rather than being retained onsite. 

Therefore, the amount of runoff lost to the watershed would be gradually reduced as areas are closed 

or capped with waste rock and reclaimed. 

A large portion of the waste rock buttresses that surround the tailings facility and the waste rock 

facility itself would be concurrently reclaimed by year 10 of the active mining phase; these areas 

would begin to discharge water downstream as concurrent reclamation is completed. The upper 

benches and tops of the waste rock and tailings facilities would be reclaimed beginning in year 16 of 

the active mining phase but not completely reclaimed until the mine is fully closed.

During active mining, several areas would not discharge downstream. Runoff in the vicinity of the pit

itself would be retained in the pit or, before development of the pit, in stormwater ponds. Runoff from 

the plant site would be retained in stormwater or process ponds and recycled as process water. Runoff 

from tailings facilities, prior to capping and reclamation, would also be retained in various ways and 

would not be allowed to discharge. Tailings runoff would be at times necessarily stored on top of the 

tailings facility during active mining and allowed to evaporate; when there are large volumes of 

ponded water present, the ponded stormwater on the tailings facility can be actively pumped off and 

recycled as process water.

Barrel Alternative—Stormwater Management after Closure

The redesign of stormwater management undertaken for the Barrel Alternative focused primarily on 

postclosure conditions. Previously, postclosure stormwater ponds on the top of the tailings and waste 

rock piles were designed to retain the 1,000-year, 24-hour storm event, and stormwater ponds on the 

benches of the waste rock and tailings were designed to retain the 500-year, 24-hour storm event. 

With the redesign, these ponds have been eliminated. Instead, the waste rock and tailings facilities 

shed all runoff, which is designed to flow laterally along benches until reaching several concrete drop 

structures, at which point the runoff would be discharged either into the natural washes (Barrel 

Canyon or a tributary) or into a diversion channel that would carry runoff along the toe of the waste 

rock and tailings facilities. The diversion channel would then discharge that runoff into the natural 

washes. Adjacent to the waste rock and tailings facilities, the plant site would be regraded and 

reclaimed, and a diversion channel would be constructed to allow discharge of stormwater from the 

plant site into upper McCleary Canyon.

By eliminating the stormwater retention ponds, substantially more postclosure runoff would be 

retained in the watershed. Previously, annual average postclosure runoff from the mine was reduced 

by approximately 34 percent, compared with undeveloped baseline conditions. With the redesign, 

annual average postclosure runoff from the mine is reduced by only 17 percent, compared with 

undeveloped baseline conditions. 

There are still several areas (the mine pit itself and diversions to the west of the mine pit) that would 

not discharge downstream in perpetuity. All precipitation falling within and near the pit would be 

retained in the pit. The diversion channel west of the pit would collect precipitation in stormwater

retention ponds along the southern toe of the waste rock facility and would be allowed to infiltrate as 

aquifer recharge, but it would not be able to flow downstream as surface water due to topography. 

Previously, the stormwater design for the Barrel Alternative also made use of flowthrough drains 

located under the waste rock and tailings facilities. In the redesign, these flowthrough drains were 

removed from the Barrel Alternative because of concerns about long-term maintenance and possible 

Final Environmental Impact Statement for the Rosemont Copper Project 425
Chapter 3. Affected Environment and Environmental Consequences

intermingling of tailings seepage with stormwater. These flowthrough drains would theoretically have 

allowed stormwater from the plant site and west of the pit to continue flowing downstream; in reality, 

that stormwater would have likely infiltrated into and recharged the aquifer rather than continuing as 

surface flow.

Postclosure, all runoff from the closed and reclaimed waste rock and tailings facilities and the plant 

site would be allowed to discharge downstream. Only two general areas of the mine site would not 

discharge runoff downstream. These include the mine pit itself and diversions to the west of the 

mine pit.

Stormwater Management for the Phased Tailings, 

Barrel Trail, and Scholefield-McCleary Alternatives

Stormwater management for the Phased Tailings, Barrel Trail, and Scholefield-McCleary Alternatives 

is similar to that analyzed in the DEIS and similar to the Barrel Alternative before it was redesigned. 

During premining, active mining, and postclosure phases, stormwater would be stored on top of and 

on the benches of the waste rock and tailings facilities and would not be discharged downstream 

except in extreme events. While concurrent reclamation would still occur, it would not facilitate any 

stormwater passing downstream. Runoff from the plant site and the diversion west of the open pit

would also be retained onsite. These three alternatives would all maintain flow from above the plant 

site by diverting it into upper McCleary Canyon during both active mining and postclosure. 

Flowthrough drains are still part of the stormwater management of the Phased Tailings and Barrel 

Trail Alternatives and would allow at least infiltration of retained water from the plant site, if not 

direct surface runoff. The Scholefield-McCleary Alternative has no flowthrough drains. As identified 

in the DEIS, these stormwater management schemes would reduce average annual postclosure runoff 

by approximately 42 percent for the Barrel Trail Alternative, by 44 percent for the Phased Tailings 

Alternative, and by 23 percent for the Scholefield-McCleary Alternative, compared with undeveloped 

baseline conditions.

Stormwater Management for the Proposed Action

The proposed action handles stormwater entirely differently from the other action alternatives. Runoff

under the proposed action would be largely allowed to discharge downstream, similar to the redesign 

of the Barrel Alternative. However, much of the stormwater management relied on a feature known as 

the central drain. Designed as a vertical chimney drain as well as a flowthrough underdrain, the 

central drain was considered problematic because of the potential for discharge of stormwater into the 

tailings and waste rock facilities and the concern that this would result in greater potential for 

seepage. The central drain concept was dropped during the development of the other alternatives.

As identified in the DEIS, the proposed action would reduce average annual postclosure runoff by 

approximately 46 percent, compared with undeveloped baseline conditions.

No Action Alternative

Under baseline conditions (no action), surface water within the project area will continue to consist 

solely of stock tanks or ephemeral flows that occur as the result of precipitation events. The no action 

alternative would result in no further impacts to the quantity of surface water resources. Grazing will 

continue. Stock tanks will continue to be monitored and maintained for use by stock and wildlife. 

The use of surface water for recreation and/or stock watering would likely increase relative to the 

predicted increase in population growth and residential development. Ephemeral washes on the 

426 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

project area will continue to flow in response to precipitation. Climate change will continue over 

time. Anticipated decreases in winter precipitation would decrease the occurrence of ephemeral 

flows, and the anticipated increase in the frequency of heavy rains would create higher peak flows 

with a greater potential for flooding.

Impacts Common to All Action Alternatives

For each action alternative, as mining operations progress over time, ephemeral stormwater flows 

from the project area would change, primarily as a result of the retention of water from certain 

portions of the mine and from changes in surface topography and characteristics from disturbed areas,

such as the pit, operating facilities, and tailings and waste rock facilities.

All of the action alternatives would result in alteration of the natural surface hydrology. Impacts 

related to surface water quantity that are common to all action alternatives include the modification of 

stormwater peak flows, modification to overall runoff volume from the watersheds, and direct loss of 

stock tanks. The direct loss of springs through dewatering or surface disturbance and the direct loss of 

riparian areas are discussed in the “Seeps, Springs, and Riparian Areas” resource section of this 

chapter. Changes in erosion potential that would result from changes in ephemeral flows are assessed 

in the “Surface Water Quality” resource section of this chapter.

Direct impacts to stock tanks and indirect impacts to downstream stock tanks (see figure 62) and 

other beneficial uses would occur under all action alternatives and are discussed below. Postclosure 

stormwater management techniques differ by alternative; therefore, reductions in runoff and peak 

flow are analyzed for each alternative in turn. 

While the analysis area for surface water quantity includes the various connected actions beyond the 

project area, such as the power line, water pipeline, Arizona National Scenic Trail reroute, 

improvements to SR 83, primary access road, and utility maintenance road, disturbance in these areas 

would not result in any retention of surface water flow. While a change in surface characteristics, 

such as loss of vegetation or paving of the road, could change runoff characteristics, this change was 

determined to be relatively minor and similar among all action alternatives.

Proposed Action and Action Alternatives

Direct Loss of Stock Tanks by Surface Disturbance

Stock tanks would be directly lost as a result of surface disturbance under all alternatives except for 

the no action alternative. Based on a review of USGS topographic maps and ADWR database 

(Arizona Department of Water Resources 2011b), expected stock tank losses per action alternative 

range from 8 to 19 and are summarized in table 89. 

The capacity of each individual stock tank has not been measured, but ADWR (2011b) records 

indicate that stock tanks in the project area each use from approximately 0.1 to 6.0 acre-feet of water 

per year. Assuming that all the stock tanks directly impacted by the project area have the capacity to 

hold the maximum 6.0 acre-feet of water per year, the estimated maximum total capacity lost per 

alternative would range from 30 acre-feet per year for the Scholefield-McCleary Alternative to 90

acre-feet per year for the Barrel and Barrel Trail Alternatives. 

Final Environmental Impact Statement for the Rosemont Copper Project 427
Chapter 3. Affected Environment and Environmental Consequences

Table 89. Direct impacts to stock tanks by alternative

Alternative Stock Tanks 

Lost

Names of Stock Tanks

(ID)

Estimated Total Capacity 

Lost per Alternative

(acre-feet per year)

No action 0 Not applicable Not applicable

Proposed action 11 Barrel Tank (1)

Upper Barrel Tank (2)

North Basin Tank (4)

South Basin 4 Tank (5)

North Basin Tank 2 (6)

East Dam Header Tank (7)

North Dam Header Tank (8)

Section 25 (10)

3 Unnamed Tanks (3, 9, 18)

66

Phased Tailings 11 Barrel Tank (1)

Upper Barrel Tank (2)

North Basin Tank (4)

South Basin 4 Tank (5)

North Basin Tank 2 (6)

East Dam Header Tank (7)

North Dam Header Tank (8)

Section 25 (10)

3 Unnamed Tanks (3, 9, 18)

66

Barrel 15 Barrel Tank (1)

Upper Barrel Tank (2)

North Basin Tank (4)

South basin 4 Tank (5)

North Basin Tank 2 (6)

East Dam Header Tank (7)

North Dam Header Tank (8)

Section 25 (10)

Dirt Tank (16)

McCleary Tank (19)

2 Section 33 Tanks (15, 17)

3 Unnamed Tanks (3, 9, 18)

90

Barrel Trail 15 Barrel Tank (1)

Upper Barrel Tank (2)

North Basin Tank (4)

South basin 4 Tank (5)

North Basin Tank 2 (6)

East Dam Header Tank (7)

North Dam Header Tank (8)

Section 25 (10)

Dirt Tank (16)

East Dam Tank (21)

2 Section 33 Tanks (15, 17)

3 Unnamed Tanks (3, 9, 18)

90

Scholefield-McCleary 5 Upper Barrel Tank (2)

Unnamed Tank (3)

East Dam Header Tank (7)

North Dam Header Tank (8)

Section 25 Tank (10)

30

428 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Direct Loss of Stormwater Flows to Downstream Beneficial Uses

Each action alternative incorporates various design features to maintain flow from undisturbed areas 

above the mine operations and to manage stormwater runoff (see chapter 2 and the alternatives 

discussion later in this resource section). Much of the runoff from the proposed action would not be 

retained onsite but instead would be allowed to discharge downstream via a central drain feature 

using a vertical chimney and underdrain. Conversely, runoff from Phased Tailings, Barrel Trail, and 

Scholefield-McCleary Alternatives would be stored on top of and on the benches of the waste rock

and tailings facilities and would not be discharged downstream except in extreme events. For the 

Phased Tailings and Barrel Trail Alternatives, only flowthrough drains would allow infiltration and 

direct runoff of retained water from the plant site. For the Barrel Alternative, stormwater retention 

ponds were eliminated from the benches of the waste rock and tailings facilities. Instead, runoff 

would be shed from these facilities and then routed to wrap around diversion channels and discharge 

into the natural washes. Redesign of the Barrel Alternative stormwater management plan has resulted 

in this alternative’s having the largest area contributing to runoff and thus allowing the largest amount 

of runoff to be retained in the watershed. 

Postclosure stormwater peak flows and volume for all action alternatives were modeled using the 

USACE computer program Hydrologic Engineering Center Hydrologic Modeling System, Version 

3.4 (Chee 2010; Krizek 2010a, 2010b, 2010c, 2010d). Modeling results were validated using the 

USGS Bulletin 17B statistical analysis and Region 13 Regional Regression Equation. The direct 

effects on stormwater peak flows and volume would be proportionate to the drainage area available 

for contributing to runoff for each alternative, which would vary by action alternative (table 90).

Table 90 provides a summary of the alternatives and their impacts on various watersheds during both 

premining/active mining and postclosure; details are presented for each action alternative.

Table 90. Impacts to surface runoff by alternative

Alternative

Contributing 

Drainage Area 

(square miles)

Watersheds

with Major Impacts

Change in Average 

Annual Runoff Volume 

during Premining and 

Active Mining Phases*

Change in Average 

Annual Postclosure 

Runoff Volume

No action 14 Not applicable Not applicable Not applicable

Proposed 

action 6.82 Barrel, McCleary, Wasp Reduced 30 to 50% from baseline

Reduced by 45.8% from 

baseline

Phased 

Tailings 7.06 Barrel, McCleary (delayed 10 years), Wasp

Reduced 30 to 50% from 

baseline

Reduced by 44.3% from 

baseline

Barrel 11.326 Barrel, McCleary, Wasp Reduced 30 to 40% from 

baseline

Reduced by 17.2% from 

baseline

Barrel Trail 7.56 Barrel, McCleary, Wasp Reduced 30 to 50% from 

baseline

Reduced by 42% from 

baseline

ScholefieldMcCleary10.35 Barrel, Wasp, Scholefield Reduced 30 to 50% from 

baseline

Reduced by 22.8% from 

baseline

* Operational changes are approximated based on phasing of acreage removed from watershed during premining and active 

mining phases, as well as being informed by modeled results for postclosure phase.

Farther downstream from the project area, the impact from disturbed areas would attenuate as the 

contributing watershed becomes larger. The average annual runoff for lower Davidson Canyon 

Wash at its confluence with Cienega Creek was modeled for the proposed action using regression 

equations. Model results show that runoff for the proposed action is predicted to be reduced from 514 

acre-feet for existing conditions to 464 acre-feet for postmine conditions, which is slightly less than a 

10 percent reduction once postmine conditions are considered (Zeller 2011a). Runoff estimates at the 

Final Environmental Impact Statement for the Rosemont Copper Project 429
Chapter 3. Affected Environment and Environmental Consequences

confluence of Davidson Canyon Wash and Cienega Creek were not modeled for the remaining action 

alternatives; however, they can be approximated based on the model results for the proposed action

(Tetra Tech 2010a). Stormwater flow in the Davidson Canyon watershed is estimated to be reduced 

by 4.3 percent for the Barrel Alternative; for the remaining action alternatives, stormwater flow in the 

Davidson Canyon watershed is estimated to be reduced by 5.8 to 11.3 percent (SWCA Environmental 

Consultants 2012d).

Cooperating agencies have commented that these estimated reductions in flow to Davidson Canyon 

may be underestimated because the mine site is located at the head of the watershed at a higher 

elevation and because due to orographic effects on precipitation, the relative contribution of water to 

the watershed is greater from these areas. This effect is acknowledged as being likely. However, 

Barrel Canyon is only one drainage that arises off of the Santa Rita Mountains and supplies Davidson 

Canyon. McCleary Canyon, Scholefield Canyon, Papago Canyon, and Mulberry Canyon also would 

experience similar orographic effects and (depending on the alternative) would still supply water to 

Davidson Canyon. The east side of Davidson Canyon receives drainage from the Empire Mountains.

Although these are not as high in elevation as the Santa Rita Mountains (rising to an approximate 

elevation of about 5,000 feet above mean sea level rather than 6,000 feet above mean sea level), they 

would likely still have an orographic effect. While it is acknowledged that Barrel Canyon receives 

higher precipitation due to its location, it is by no means the only part of the Davidson Canyon 

watershed that does, and the estimates provided are still valid approximations, albeit with some 

uncertainty. 

With respect to modification of stormwater peak flows and volume, reductions in runoff are primarily 

important because they indirectly impact the water availability for downstream use. Ephemeral flows, 

such as those found throughout the project area, are of importance: (1) to downstream user surface 

water rights; (2) for sustaining riparian vegetation; (3) for livestock and wildlife; (4) in some cases to 

supply spring flow; and (5) for groundwater recharge in the channel. This section addresses the 

downstream users; indirect impacts from reduced stormwater flow to wildlife are discussed in the 

“Biological Resources” resource section of this chapter. Indirect impacts to livestock are discussed in 

the “Livestock Grazing” resource section of this chapter. Indirect impacts to riparian vegetation and 

springs, including several springs in Davidson Canyon (Reach 2 Spring, Escondido Spring) believed 

to rely on ephemeral flows stored in shallow alluvial sediments, are discussed in the “Seeps, Springs, 

and Riparian Areas” resource section of this chapter.

Indirect Impacts to Offsite Surface Water Rights

With respect to downstream users, because of the flashy nature of ephemeral flows, in-channel 

storage such as a reservoir or stock tank would be required in order to use any significant amount of 

ephemeral flow. No reservoirs are located within the analysis area; however, there are stock tanks 

located on the downstream channels that would be impacted under all action alternatives. 

Modification of stormwater peak flows and volume is also important for erosion potential and threat 

to property and human health and safety. 

An offsite surface water right can be indirectly impacted by the project in one of two ways: (1) by a 

reduction in stormwater runoff in the channel if the water right is located in the main stem of 

Davidson Canyon; or (2) in a situation in which the surface water right has surface water/

groundwater exchange such as at a spring or perennial reach of a stream. Based on the expected 

minimal reductions in storm flow by the time it exits Davidson Canyon (4.3 to 11.3 percent), surface 

water rights beyond Davidson Canyon are unlikely to be impacted by changes in surface water 

hydrology in the project area. For the most part, in-channel surface water rights consist of stock 

430 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

tanks, which are discussed separately below. Other than stock tanks, there are an additional 262 

offsite surface water rights (see table 87) within the area of groundwater drawdown that could 

possibly be indirectly impacted by the project. Of these, 47 percent of the surface water right holders 

are public agencies: the Coronado, BLM (water rights primarily associated with the Las Cienegas 

National Conservation Area), ASLD, and AGFD. Other offsite water rights holders include mines, 

cattle companies, and individuals. 

Some water sources would be impacted, as described in the “Seeps, Springs, and Riparian Areas” 

resource section of this chapter. Whether surface water rights associated with these water sources 

would be impacted is not possible to determine from a regulatory standpoint; both priority and 

validity of these surface water rights have not yet been determined through the General Stream 

Adjudication of the Gila River.

While the regulatory status of BLM’s water rights is not definite, the physical impact to the water 

sources has been analyzed (see the “Seeps, Springs, and Riparian Areas” resource section of this 

chapter). The following physical impacts are likely to affect the BLM water rights:

• Helvetia, Chavez, and Zackendorf Springs are highly likely to be impacted if their source of 

water arises from the regional aquifer. Drawdown of several feet is modeled to occur by the 

end of the active mining phase, gradually increasing to more than 60 feet after 1,000 years.

Helvetia Spring is believed to derive water from the regional aquifer; the source of water for 

Chavez and Zackendorf Springs is less certain. These levels of drawdown would almost 

certainly affect or eliminate flow in Helvetia Spring and possibly Chavez and Zackendorf 

Springs.

• Water rights associated with ephemeral tributaries to Cienega Creek are not likely to be 

impacted by drawdown in the regional aquifer.

• Stream flow in Empire Gulch is expected to be impacted, although impacts are highly 

uncertain. Modeling scenarios differ on the time frame for when changes in stream flow 

would occur in Empire Gulch. Some modeling scenarios suggest that Empire Gulch would 

begin to transition from a perennial stream to an intermittent or ephemeral stream by 50 years 

after mine closure, whereas others suggest these changes would happen later. However, all 

modeling scenarios agree that by 1,000 years after mine closure, Empire Gulch would 

transition from a perennial stream to an ephemeral stream. Water rights along Empire Gulch 

would likely be impacted by these changes. 

Indirect Impacts to Downstream Stock Tanks 

Based on the ADWR surface water filing database (Arizona Department of Water Resources 2011b), 

all surface water filings in Davidson Canyon downstream of the project area are stock tanks. 

Downstream stock tanks would be indirectly impacted under all action alternatives as a result of a 

reduction in ephemeral storm flows from the project area. The stock tanks impacted are shown in 

table 91.

Table 91. Indirect impacts to downstream stock tanks

Alternative Watershed ID Name of 

Water Source

Cadastral 

Location Landowner

Proposed action and 

Phased Tailings

Barrel Canyon 21 East Dam Tank D-18-16 28ac Forest Service

Scholefield-McCleary Barrel Canyon 18 Unnamed tank D-18-16 32c Private

Final Environmental Impact Statement for the Rosemont Copper Project 431
Chapter 3. Affected Environment and Environmental Consequences

Alternative Watershed ID Name of 

Water Source

Cadastral 

Location Landowner

All action alternatives Davidson Canyon 14 Unnamed tank D-17-17 07b Private

All action alternatives Davidson Canyon 13 Unnamed tank D-17-16 36a ASLD

All action alternatives Davidson Canyon 11 4th of July Tank D-17-17 03ab ASLD

All action alternatives Davidson Canyon 24 Unnamed tank D-18-16 01ab Private

All action alternatives Davidson Canyon 12 Unnamed stock tank D-17-17 03cd ASLD

All action alternatives would indirectly impact five downstream stock tanks in Davidson Canyon. 

Three of the action alternatives (proposed action, Phased Tailings, and Scholefield-McCleary) would

indirectly impact one additional downstream stock tank in Barrel Canyon. 

Surface water in stock tanks is collected both by the direct input of precipitation into the tank and by 

runoff from the upstream drainage. Given the high spatial variability of precipitation in this region, 

surface water runoff contributing to a stock tank could come from just a portion of the upstream 

drainage or could come from the entire drainage. The capacity of each individual stock tank that 

would be indirectly impacted is not known; however, ADWR (Arizona Department of Water 

Resources 2011b) records indicate that stock tanks indirectly impacted downstream of the project 

area each use approximately 0.1 to 14.6 acre-feet of water per year. Assuming that all stock tanks 

indirectly impacted by the project have the capacity to hold 14.6 acre-feet per year, an estimate of 

total capacity lost is 73 acre-feet per year for two action alternatives (Barrel and Barrel Trail) and 

87.6 acre-feet per year for the remaining three action alternatives (proposed action, Phased Tailings, 

and Scholefield-McCleary). 

The proposed action would indirectly impact a total of six downstream stock tanks. Considering that 

the average annual runoff of storm flow from the proposed action is 762 acre-feet (table 92), and 

assuming that all runoff would be from the entire upstream drainage, it would take a small portion of 

the total flow (approximately 11.5 percent) to fill all of the impacted stock tanks. The Barrel 

Alternative would indirectly impact five downstream stock tanks, and it would take 6.3 percent of the 

average annual runoff to fill all downstream stock tanks to capacity. For the remaining action 

alternatives, the requirement of total flow to fill the impacted stock tanks would be 7.8 to 11.2 

percent. 

Because flow volumes from each action alternative would be more than sufficient to fill downstream 

stock tanks that would be indirectly impacted by any action alternative, and because there is a high 

likelihood that these stock tanks could be filled from more localized precipitation instead of runoff

from the project area, this impact to downstream users is considered insignificant.

Indirect Impacts to Aquifer Recharge

As previously noted, the amount of water currently recharged through alluvial channels typically 

would require infiltration measurements or repeated stream flow measurements at multiple locations.

Neither of these techniques have been undertaken on Barrel Canyon or Davidson Canyon; therefore,

the effect of reductions in runoff on recharge of shallow downstream alluvial aquifers cannot be 

directly quantified.

However, infiltration into alluvial stream channels is one of the mechanisms through which mountain 

front recharge occurs. Rough estimates of losses of mountain-front recharge to the aquifer indicate 

that as a whole it likely could be reduced by about 35 acre-feet per year, and perhaps by as much as 

127 acre-feet per year (see the “Effect on Mountain-Front Recharge” part of the “Groundwater

432 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Quantity” resource section). At least a portion of this reduction in recharge would likely represent a 

reduction in infiltration of stormwater in the uppermost ephemeral washes in the watershed, such as 

in Barrel Canyon.

Proposed Action

The proposed action would have a total of 4,387 acres within the security fenceline. The majority of 

disturbance would occur in Barrel, Wasp, McCleary, and Scholefield Canyons. Surface water

management facilities include stormwater basins and diversions around the facility to convey storm 

events that occur in undisturbed areas upgradient of the pit, operating facilities, waste rock, and 

tailings facilities. These diversion structures would place the water into a central drain intended to 

provide hydraulic connection between the upgradient side of the project area and the downgradient 

side; therefore, runoff from any watershed area located upgradient of the proposed action is expected 

to arrive at the USGS gaging station (Krizek 2010c). Permanent diversion structures are designed to 

carry at least the 100-year, 24-hour storm event; and drainage features to transfer stormwater from the 

top of the dry-stack tailings are designed to carry the 500-year, 24-hour storm (Krizek 2010c; Tetra 

Tech 2007e, 2010h).

Table 92 summarizes the modeled watershed yield from baseline conditions and under the proposed 

action.

Table 92. Summary of expected changes to postclosure stormwater flow under the 

proposed action

Condition

Discharge 

Area 

(square miles)

100-Year, 

24-Hour 

Peak Flows 

(cubic feet 

per second)

Average 

Annual 

Volumes 

(acre-feet)

Change in 

Postclosure

100-Year, 

24-Hour Peak 

Flows (percent)

Percent Change 

in Postclosure

Average Annual 

Volumes 

(percent)

Baseline* 14 8,072 1,407 Not applicable Not applicable

Proposed action* 6.82 3,785 762 −53.1 −45.8

Source: Krizek (2010c).

* At point of concentration: USGS gage no. 09484580.

Phased Tailings Alternative

The Phased Tailings Alternative would have a total of 4,308 acres within the security fenceline. This

alternative allows the tailings to be stored in two separate phases, effectively isolating the tailings 

footprint to an area of Barrel Canyon and leaving McCleary Canyon open for a period of 

approximately 10 years after the start of active mining. 

Stormwater controls include basins and diversions around the facility to convey storm events that 

occur upgradient of the pit, operating facilities, waste rock facility, and tailings facility. Surface water

drainage channels would be placed every 100 feet of vertical rise on the outer slopes of the dry-stack 

tailings and waste rock facilities. Stormwater would flow to stilling pools/drop-structures, natural 

ground, or stormwater basins. Drop structures located on the east side of the dry-stack tailings facility 

would drain to Barrel Canyon. Other diversion structures would place the water into a retention pond; 

therefore, runoff from any watershed located upgradient of the Phased Tailings Alternative is not 

expected to arrive at the USGS gaging station (Krizek 2010a). Permanent diversion structures would 

be designed to carry at least the 100-year, 24-hour storm event; the top of the dry-stack tailings and 

Final Environmental Impact Statement for the Rosemont Copper Project 433
Chapter 3. Affected Environment and Environmental Consequences

stormwater control basins in the waste rock facility are expected to contain storm flows up to the 500-

year, 24-hour storm event. 

Table 93 summarizes the modeled watershed yield from baseline conditions and under the Phased 

Tailings Alternative.

Table 93. Summary of expected changes to postclosure stormwater flow under 

Phased Tailings Alternative

Condition

Discharge 

Area 

(square miles)

100-Year,

24-Hour 

Peak Flows 

(cubic feet 

per second)

Average 

Annual 

Volumes 

(acre-feet)

Change in 

Postclosure

100-Year, 

24-Hour Peak 

Flows 

(percent)

Percent

Change in 

Postclosure

Average 

Annual 

Volumes

Baseline* 14 8,072 1,407 Not applicable Not applicable

Phased Tailings* 7.06 4,044 784 −49.9 −44.3

Source: Krizek (2010a).

* At point of concentration: USGS gage no. 09484580.

Barrel Alternative

The Barrel Alternative has a total of 4,228 acres within the security fenceline. Stormwater

management features have been redesigned for this alternative and now include stormwater diversion 

features that allow for more surface water runoff to the watershed after closure. Further, there would 

be no flowthrough drains beneath the tailings and waste rock facilities and no storage of stormwater 

on their tops or benches postclosure.

During premining and active mining and as required by stormwater discharge permits, no stormwater

that comes into contact with ore stockpiles, tailings, or processing facilities would be allowed to 

discharge offsite. Operational stormwater storage is designed for the 500-year, 24-hour storm (Tetra 

Tech 2012b). Runoff from the area above the plant site would be maintained using a permanent 

diversion channel to direct water into upper McCleary Canyon instead of onto the plant site. Water 

from the diversion channel would pass under the primary access road through culverts designed to 

carry the 100-year, 24-hour rainfall event; larger flows would pass over the road. A similar diversion 

west of the pit would direct runoff to several retention ponds at the toe of the waste rock facility, 

where it would be allowed to infiltrate. 

The maximum loss of runoff to the watershed would occur during the first 10 years of active mining,

when runoff from these areas would be retained onsite and recycled as process water; during this 

period, the loss of runoff to the watershed would vary but is likely to approach a reduction in annual 

average runoff of about 30 to 40 percent, compared with undeveloped baseline conditions. Because 

reclamation would occur concurrently during active mining, the amount of runoff to the watershed 

would gradually be increased as areas are closed or capped with waste rock and reclaimed. By year 

10 of active mining, portions of the waste rock buttresses that surround the tailings facility and the 

waste rock facility itself would be reclaimed, and by year 16 of active mining reclamation would 

begin on the upper benches and tops of the waste rock and tailings facilities.

Postclosure, all runoff from the closed and reclaimed waste rock and tailings facilities and the plant 

site would be allowed to discharge downstream. Only two general areas of the mine site would not 

discharge runoff downstream: the mine pit itself and diversions to the west of the mine pit. The tops 

of the waste rock and tailings facilities would be graded to discharge stormwater to the lower 

434 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

benches, flowing laterally along the benches until reaching several concrete drop structures, at which 

point the runoff would either be discharged into natural washes (Barrel Canyon or a tributary) or 

discharged into a diversion channel along the toe of the waste rock and tailings facilities and then 

discharged into natural washes. Channels and drop structures are designed to carry the 1,000-year, 

24-hour peak flow. 

Table 94 summarizes the modeled watershed yield from baseline conditions and under the Barrel 

Alternative conditions.

Table 94. Summary of expected changes to postclosure stormwater flow under Barrel 

Alternative

Condition

Discharge 

Area 

(square 

miles)

100-Year, 

24-Hour 

Peak Flows 

(cubic feet 

per second)

Average 

Annual 

Volumes 

(acre-feet)

Change in 

Postclosure

100-Year, 

24-Hour Peak 

Flows (percent)

Percent Change 

in Postclosure

Average Annual 

Volumes

Baseline* 14 8,072 1,404 Not applicable Not applicable

Barrel 

Alternative*

11.326 6,293 1,162 −22.0 −17.2

Source: Krizek (2010b).

* At point of concentration: USGS gage no. 09484580. 

Barrel Trail Alternative

The Barrel Trail Alternative would have a total of 4,688 acres within the security fenceline. Under 

this alternative, the dry-stack tailings and waste rock would be confined to Barrel Canyon and an 

unnamed tributary of Barrel Canyon. The majority of disturbance for this alternative would occur in 

Barrel, Wasp, McCleary, and Scholefield Canyons. 

Stormwater controls for this alternative include basins and diversions around the facility to convey 

storm events upgradient of the pit, operating facilities, waste rock facility, and tailings facility. 

The largest stormwater control feature associated with this alternative is the new Barrel Canyon 

drainage. Its alignment runs between the dry-stack tailings facility and the waste rock facility. This 

drainage feature would be stepped, with sloping channel segments and stilling pools, and the channel 

would be designed to convey stormwater runoff from the reclaimed surface. The south side of the 

waste rock facility would retain runoff detention basins for the 500-year, 24-hour event. Volumes 

exceeding that would be routed down the waste rock slopes to sediment basins. The east side of the 

waste rock facility would have a ridge running adjacent to SR 83 that would serve as a drainage 

divide for the benches. Stormwater on the east side of the ridge would eventually flow to Barrel 

Canyon. Stormwater controls associated with the dry-stack tailings facility would consist of drainage 

benches and drop structures; pooling on top surfaces of the facility would be limited. Stormwater 

runoff from the pit diversion channel south of the open pit is expected to be retained between the toe 

of the waste rock facility and an adjacent natural ridge and would not drain to the USGS gaging 

station (Chee 2010). 

Table 95 summarizes the modeled watershed yield from baseline conditions and under the Barrel 

Trail Alternative.

Final Environmental Impact Statement for the Rosemont Copper Project 435
Chapter 3. Affected Environment and Environmental Consequences

Table 95. Summary of expected changes to postclosure stormwater flow under Barrel 

Trail Alternative

Condition

Discharge 

Area 

(square miles)

100-Year, 

24-Hour 

Peak Flows 

(cubic feet 

per second)

Average 

Annual 

Volumes 

(acre-feet)

Change in 

Postclosure

100-Year, 

24-Hour Peak 

Flows (percent)

Percent Change 

in Postclosure

Average Annual 

Volumes 

Baseline* 14 8,072 1,407 Not applicable Not applicable

Barrel Trail

Alternative*

7.56 4,845 816 −40.0 −42.0

Source: Chee (2010).

* At point of concentration: USGS gage no. 09484580. 

Scholefield-McCleary Alternative

The Scholefield-McCleary Alternative would have a total of 5,045 acres within the security fenceline. 

For this alternative, the dry-stack tailings would be located entirely within Scholefield Canyon, and 

waste rock would be located outside canyon bottoms within McCleary Canyon and between Wasp 

and Barrel Canyons. The majority of disturbance for this alternative would occur in the four major 

drainages (Barrel, Wasp, McCleary, and Scholefield Canyons). Stormwater controls for this 

alternative include basins and diversions around the facility to convey storm events upgradient of the 

pit, operating facilities, waste rock facility, and tailings facility. Surface water drainage benches 

would be placed every 100 feet of vertical rise on the outer slopes of the dry-stack tailings and waste 

rock facilities. Stormwater would flow to stilling pools/drop structures or to natural ground. A portion 

of the diversion channel would route stormwater runoff around the plant site area to Barrel Canyon 

Wash, which would eventually drain to Barrel Canyon. Stormwater from drainage benches and pit 

diversion would drain to Barrel Canyon as well. Stormwater from other runoff from any watershed 

located upgradient of the Scholefield-McCleary Alternative is not expected to arrive at the USGS gaging 

station (Krizek 2010d). Permanent diversion structures would be designed to carry at least the 100-year, 

24-hour storm event; the top of the dry-stack tailings and stormwater control basins in the waste rock 

facility are expected to contain storm flows up to the 500-year, 24-hour storm event. 

Table 96 summarizes the modeled watershed yield from baseline conditions and under the

Scholefield-McCleary Alternative.

Table 96. Summary of expected changes to postclosure stormwater flow under 

Scholefield-McCleary Alternative

Condition

Discharge 

Area 

(square miles)

100-Year, 

24-Hour 

Peak Flows 

(cubic feet 

per second)

Average Annual 

Volumes 

(acre-feet)

Change in 

Postclosure

100-Year, 

24-Hour Peak 

Flows (percent)

Percent Change 

in Postclosure

Average Annual 

Volumes

Baseline* 14 8,072 1,407 Not applicable Not applicable

ScholefieldMcCleary 

Alternative*

10.35 5,689 1,086 −29.5 −22.8

Source: Krizek (2010d).

* At point of concentration: USGS gage no. 09484580. 

436 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Cumulative Effects

As outlined in the chapter 3 introduction, cumulative impacts of past and present actions are 

identified and analyzed in the “Affected Environment” part of each resource section, including for 

“Surface Water Quantity.” This cumulative effects discussion addresses the cumulative impacts of the 

action alternatives and any applicable reasonably foreseeable actions as identified on the Coronado 

ID team’s list of reasonably foreseeable future actions, provided in the introduction to chapter 3.

The analysis area for cumulative effects on surface water quantity includes all the sub-watersheds in 

the vicinity of the project and the watersheds of Davidson, Box, and Sycamore Canyons (figure 63). 

The following reasonably foreseeable actions from that list were determined to contribute to a 

cumulative impact to surface water quantity:

• The BLM proposes to approve an MPO to expand the Andrada Mine limestone quarry in 

the Davidson Canyon drainage system north and northeast of the Santa Rita Mountains. 

The Andrada Mine is located approximately 4 miles from the Tucson, Arizona, city limits 

and 1 mile from the Vail, Arizona, city limits.

• In May 2010, a lease was granted to Charles Seel for mining purposes for 240 acres of ASLD

State Trust land (from State land commissioner) in Section 29, Township 17 South, Range 17 

East, adjacent to CalPortland leases in Davidson Canyon. There are no known plans to 

explore for or develop mineral resources on this lease in the foreseeable future.

• The Forest Service proposes to add, decommission, close, or change designation of roads in 

the NFSR database and prohibit off-road motorized travel for dispersed camping in certain 

areas on the Nogales Ranger District.

Cumulatively, road construction near or on the Coronado National Forest, along with the construction 

of the Rosemont Copper Project, would have long-term, adverse impacts on surface water quantity, 

whereas road decommissioning or prohibiting off-road motorized travel would have long-term, 

favorable impacts on surface water quantity. Favorable impacts, however, would likely be partially 

offset by the addition of new roads in the area, including the new road segments proposed as part of 

the Rosemont Copper Project. Expansion of the limestone quarries in lower Davidson Canyon could 

further reduce surface water quantity beyond the reductions expected under the action alternatives, 

depending on surface water management plans for those facilities. However, because the area is 

relatively small, compared with the watershed, and would be required by the ASLD to be reclaimed 

after the mine is closed, the additional impacts to surface water quantity would be minimal and 

localized. 

Climate Change

As discussed earlier in this chapter, climate change in the desert Southwest is predicted to bring about 

higher mean annual temperatures over the next 100 years, along with less winter precipitation, an 

increase in extreme rainstorms and flooding, and longer periods of drought. The extent to which these 

predictions will occur is uncertain, and the overall difference in the amount of annual precipitation is 

impossible to accurately quantify. However, in general, predicted changes in weather patterns could 

have an effect on the quantity of stormwater that is stored at the surface and available for beneficial 

use. 

Final Environmental Impact Statement for the Rosemont Copper Project 437
Chapter 3. Affected Environment and Environmental Consequences

Figure 63. Analysis area for cumulative effects – surface water quantity

438 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Winter storms typically are frontal systems that produce gentle rainfall over a wide spatial extent, 

allowing for more of the precipitation to be stored at the surface. A decrease in winter rainfall would

mean a decrease in the volume of surface water flow and resulting surface storage. In contrast, an 

increase in more extreme rainstorms would create higher volumes of surface flow passing through the 

ephemeral channels in a shorter period of time, thus limiting the occurrences of low, steady flows that 

would be more conducive to surface storage. With regard to higher temperatures and longer periods 

of drought, ephemeral surface water would be more likely to evaporate and dry up at a faster rate.

Mitigation Effectiveness 

Mitigation and Monitoring – Forest Service

• Growth media salvage and application (FS-SR-01). In order to support reclamation

activities, soil and other growth media would be salvaged, stored, and applied to the surface 

of the perimeter waste rock buttress and waste rock and tailings facilities in order to facilitate 

revegetation.

• Revegetation of disturbed areas with native species (FS-SR-02). Reclamation efforts 

would include revegetation of native grasses, forbs, shrubs, and trees on areas disturbed by 

mining and mine related activities. Revegetation would include detecting and treating of 

invasive weed species.

• Concurrent placement of perimeter buttress (FS-SR-03). Placement of the perimeter 

buttress would allow reclamation activities to take place earlier, concurrent with mine 

operations. 

• Location, design, and operation of facilities and structures intended to route 

stormwater around the mine and into downstream drainages (FS-SW-01). Various 

stormwater diversion channels and location of facilities have been designed and located in 

order to maintain flow downstream as much as possible and avoid contact of stormwater with 

processing facilities and ore stockpiles.

• Stormwater diversion for Barrel Alternative designed to route more stormwater into 

downstream drainages postclosure (FS-SW-02). Following publication of the DEIS, the 

Coronado undertook an effort to apply the concepts of geomorphic reclamation to the Barrel 

Alternative. The result is a design that would route more stormwater into downstream 

drainages postclosure than previous designs.

• Purchasing of water rights to be used for mitigating for impacts in the Cienega Creek

watershed (FS-SSR-01). This mitigation measure involves a suite of actions that involve 

purchasing, severing, and transferring existing senior water rights on Lower Cienega Creek. 

The water rights would be transferred to appropriate entities to become in-stream flow rights 

on Lower and Upper Cienega Creek. Additional actions could include the discharge of water 

below Pantano Dam, which potentially could enhance and support riparian areas, and 

retirement of a groundwater pumping well near to Lower Cienega Creek.

• Spring, seep, and constructed/enhanced waters monitoring (FS-SSR-02). A suite of 

selected seeps and springs has been monitored for baseline conditions since 2007 and would 

be monitored to identify any impacts that may occur due to dewatering of the regional aquifer

in the vicinity of the mine pit. Specific seeps and springs included in this monitoring are 

listed in appendix B.

• Recordation of a restrictive easement on private land parcels in Davidson Canyon to 

mitigate for impacts for loss of habitat for listed species (FS-BR-21). Rosemont Copper 

Final Environmental Impact Statement for the Rosemont Copper Project 439
Chapter 3. Affected Environment and Environmental Consequences

would record restrictive covenants to preclude real estate development and similar land use

activities. Managed grazing, cultural, and some low-impact public use (hiking, bird watching, 

minor forms of hunting) would be allowed in some locations. These lands total 383 acres and 

include portions of ephemeral wash, riparian habitat in Davidson Canyon, Barrel Canyon, 

and Mulberry Canyon, upland buffer habitat adjacent to riparian areas, and three springs.

• Plant site location and design adjustments to reduce impacts to biological resources

(FS-BR-01). The entire plant site is sited and designed to reduce its size and overall footprint

and to use gravity instead of pumping to move process water where possible. 

• Construction, management, and maintenance of water features to reduce potential 

impacts to wildlife and livestock from reduced flow in seeps, springs, surface water, and 

groundwater (FS-BR-05). Up to 30 water features, including stock ponds, would be 

enhanced and managed for sustainability of surface water. These waters would be constructed 

or managed if needed based on impacts observed in the field. While considered primarily

mitigation for impacts to biological resources, this would also mitigate effects on surface 

water resources and riparian resources.

• Recordation of a restrictive easement on the private Sonoita Creek Ranch parcel to 

mitigate for impacts to species listed as threatened or endangered (FS-BR-08). Rosemont 

Copper would record a restrictive covenant on the 1,200-acre Sonoita Creek Ranch parcel

and the accompanying 590 acre-feet of certified water rights. The parcel includes open water, 

forested wetland and riparian habitat, upland habitat adjacent to riparian habitat, seasonal 

ponds, semi-desert grassland, and ephemeral drainages. In the event that restoration is 

required to mitigate impacts to waters of the U.S., Rosemont would utilize the existing 

infrastructure and the naturally occurring water from Monkey Spring (that currently irrigates 

the agricultural fields) to create riparian and/or wetland habitat within the 115-acre fields.

Otherwise water available after the needs of the existing ponds would be discharged onto the 

floodplain terrace of Sonoita Creek, which is currently an agricultural field, in order to 

facilitate the passive restoration of riparian habitat.

• Establishment of the Cienega Creek Watershed Conservation Fund, to be used for 

future mitigation to in the Cienega Creek watershed (FS-BR-16). Rosemont Copper 

would establish an endowment and provide $2,000,000 of funding. This fund would 

essentially be established as a resource to help restore the watershed to a functioning 

ecosystem and as a mechanism to promote adaptive management and allow flexibility in 

mitigation to achieve desired outcomes in light of future uncertainties.

• Monitoring to determine impacts from pit dewatering on downstream sites in Barrel 

and Davidson Canyons (FS-BR-22). Monitoring would be conducted of surface water, 

alluvial groundwater, and deeper groundwater at sites in Barrel and Davidson Canyons.

Several locations have already been installed and are being actively monitored, whereas 

others would require access from landowners.

• Periodic validation and rerun of groundwater model throughout life of mine (FS-BR27). This measure would involve basic data collection of water levels, meteorological data, 

and water balance components, which would allow the predictions of groundwater impacts to 

be revised based on actual hydrologic observations. Specific wells to be monitored are listed 

in appendix B.

• Removal of unneeded facilities during closure (FS-VR-02). These facilities include 

buildings, the plant site, some roads, the perimeter and security fence, power supply line, 

piping systems, and water supply pipeline. The plant site would be recontoured and 

440 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

revegetated with native vegetation. Building foundations would either be removed or broken 

up and buried. Reclamation and revegetation of this area would minimize erosion and allow

stormwater flow to be returned to the watershed.

Mitigation and Monitoring – Other Regulatory and Permitting Agencies

• Power line and waterline locations (OA-SR-01). The final location of the power line as 

considered by the ACC was the shortest route, minimizing soil disturbance.

• Paving of mine roads (OA-AQ-01). Paving of certain roads with the mine is required under 

the air quality permits and would also serve to reduce the potential for erosion of soil from 

disturbed road areas.

• Processing and placement of tailings to reduce water content and overall footprint

(OA-GW-05). The use of dry-stack tailings instead of traditional slurry tailings would allow 

for a much smaller footprint for the tailings facility, minimizing soil disturbance.

• Implementation of stormwater pollution prevention plan (OA-SW-02). Required under 

the stormwater permit for the mine, implementation of the stormwater pollution prevention 

plan would include use of structural sediment controls and best management practices

intended to minimize the potential for erosion from the mine site.

Mitigation and Monitoring – Rosemont Copper

• Continued operation and data gathering of USGS flow gage that would provide data for 

surface water flows downstream of the mine site (RC-SW-01). Rosemont Copper would 

annually fund the USGS to operate and maintain the existing flow gage at Barrel Canyon.

Conclusion of Mitigation Effectiveness

Most of the mitigation measures listed above are associated with design features. Some of the design 

features would reduce the overall footprint of structures or create large stormwater diversions that 

would directly route stormwater around operations, which in turn would reduce the impact to surface 

water quantity by allowing more surface water to flow downstream. Other types of design features 

such as those associated with road paving or revegetation of disturbed areas would also improve 

surface water quantity by allowing more water to flow downstream as soon as possible during the 

active mining phase. Removal of unneeded facilities during closure would allow these areas to be 

revegetated and allow surface water to flow downstream postclosure. These mitigation measures are 

effective at minimizing reductions to surface water quantity within the analysis area.

The most effective mitigation involves the redesign of the Barrel Alternative, where eliminating 

retention ponds and using wraparound storm diversions to discharge flow into the natural channels 

successfully improves the postclosure runoff by reducing it from 34 to 17 percent. Concurrent 

reclamation would allow water to be released downstream as quickly as possible during the active 

mine life.

Best management practices associated with implementation of the stormwater pollution prevention 

plan, required under the stormwater permit for the mine, would effectively maintain the flow of 

surface water in existing drainages. Power lines would be constructed aboveground, and power poles 

are not expected to be placed in washes. Access roads would be constructed in a manner that allows 

stormwater to pass through culverts or dip crossings. Where feasible, once construction is complete, 

washes would be restored to preconstruction contours. Water pipelines would be buried underground. 

Final Environmental Impact Statement for the Rosemont Copper Project 441
Chapter 3. Affected Environment and Environmental Consequences

When pipelines cross a wash or are in the vicinity of a wash, construction would be such that they do 

not impede surface water flow.

Rosemont Copper has committed to replacement of water features (WestLand Resources Inc. 2012h)

and has identified improvements to existing stock tanks and the establishment of new stock tanks 

with surface water sources for livestock and wildlife. Rosemont Copper would establish a long-term 

management/maintenance fund for the proposed improvements and additions to water sources, which 

are proposed to be placed throughout the surrounding landscape, encompassing more than 28 square 

miles in the Santa Rita and Sierrita Mountains. Proposed improvements to existing tanks would 

involve renovations such as removal of sediments to increase the tank volume and soil compaction in 

the tank basin or installation of impervious liners to decrease infiltration. New stock tanks would 

include water source features such as ground-level tanks and wildlife guzzlers, which would replace 

surface water resources lost. However, none would be located in the area of analysis for surface 

waters, and therefore they would be ineffective at mitigating the loss of surface water quantity within 

the analysis area. Yet, these water features may be effective at mitigating other resources, such as 

water sources for livestock grazing (see the “Livestock Grazing” resource section), wildlife habitat

(see the “Biological Resources” resource section), and riparian habitat (see the “Seeps, Springs, and 

Riparian Areas” resource section) and would be effective at providing new surface waters outside the 

analysis area.

A restrictive covenant would be recorded on 383 acres downstream of the project area in lower 

Davidson Canyon. This would at least partially mitigate impacts to surface water quantity by 

protecting approximately 8,000 feet of ephemeral wash in Davidson, Barrel, and Mulberry Canyons 

and restricting land use to low-impact uses such as hiking, bird watching, and managed grazing.

Recordation of a similar restrictive covenant associated with Sonoita Creek Ranch would be at least 

partially effective at mitigating impacts to surface waters but would be outside the area of analysis for 

surface waters. It should also be noted that sufficiency of the mitigation on the Davidson Canyon 

parcels or Sonoita Creek Ranch to offset impacts to jurisdictional WUS has yet to be determined by 

the USACE.

The purchase of senior surface water rights on Cienega Creek and conversion of these water rights

into in-stream flow rights would be effective at providing legal protection to Cienega Creek that 

would help mitigate for any potential impacts to surface water. Cooperating agencies have raised 

concerns that the sever-and-transfer process that must be undertaken through the ADWR is not 

guaranteed to be successful and allows for challenges to any transfer of surface water rights. If the 

water rights transfer were not approved, this mitigation would not be protective of Cienega Creek.

While it is outside the analysis area for surface waters, discharge of water below Pantano Dam if it 

occurred would also be effective at creating or maintaining surface waters in the region, although it 

should be noted that sufficiency of the mitigation to offset impacts to jurisdictional WUS has yet to 

be determined by the USACE.

The effectiveness of the Cienega Creek conservation fund would depend on the nature of the projects 

funded, but in general projects would be expected to be beneficial to surface waters within the area.

In addition to the mitigation measures described above, which would effectively avoid, minimize, 

reduce, rectify, or mitigate for impacts, a suite of monitoring measures is also proposed or required 

under permits. These measures generally would not be effective as mitigation but rather would 

provide a means for monitoring potential changes to surface waters within the analysis area. 

442 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Effects of Amending the Coronado Forest Plan

The effects on surface water quantity from amending the Coronado forest plan are described under 

“Direct and Indirect Effects” above. The amendment would remove the following current 

management area standards and guidelines related to surface water quantity:

MA 1:

1. Restore to satisfactory watershed condition, on an emergency basis, watersheds or portions of 

watersheds when damaged. Watershed treatment is a low priority in this Management Area.

Water and soil resources improvements may consist of channel stabilization and revegetation 

using native or nonnative species.

MA 4:

1. Restore damaged watersheds to a satisfactory watershed condition. Watershed treatment is a 

high priority in this Management Area. Watershed maintenance and improvement may 

consist of channel stabilization, activities to increase water infiltration, and revegetation using 

native or non-native species.

2. Manage all programs to eliminate or minimize onsite and downstream water pollution.

3. Provide, to the extent possible, conservation pools and minimum streamflows in authorizing 

or developing water storage impoundments and diversion projects.

MA 7A

1. Restore damaged watersheds to satisfactory watershed condition. Watershed treatment is a 

high priority in this Management Area. Watershed maintenance and improvement may 

consist of channel stabilization and revegetation using native or non-native species.

2. Manage all programs to eliminate or minimize onsite and downstream water pollution.

New management area 16 contains a standard and guideline under “Watershed and Soil Maintenance 

and Improvement” that would apply to both groundwater quantity and quality:

1. To the extent practicable, mining facilities and reclamation should strive to emulate natural 

hydrologic functions.

Approval of the forest plan amendment would allow actions that would result in impacts to surface 

water quantity. Development of the mine pit and placement of waste rock and tailings would 

permanently decrease surface water flows in downstream drainages. Drawdown in the aquifer from 

the hydraulic sink created by the pit lake could reduce stream flow in some areas. Refer to the 

description of direct, indirect, and cumulative effects presented earlier in this section for further 

information.

Surface Water Quality

Introduction

This section discusses the potential impacts to the quality of existing surface water resources in the 

analysis area. Surface water resources are the same as those listed for “Surface Water Quantity.”

Final Environmental Impact Statement for the Rosemont Copper Project 443
Chapter 3. Affected Environment and Environmental Consequences

The analysis for surface water quality considers the alternatives plus all connected actions, and the 

analysis area is based on the same considerations as those listed for “Surface Water Quantity.” 

The analysis area is depicted in figure 64.

Changes from the Draft Environmental Impact Statement

In response to public comment regarding changes in downstream geomorphology and aggradation 

and scour, an independent qualitative analysis of the geomorphology of Barrel Canyon was 

performed. The sediment yield analysis is now based on the evaluation of two assessments: the 

sediment yield model and a new geomorphology analysis (see the “Sediment Yield and Changes in 

Geomorphology” part of this resource section).

A more robust analysis of predicted stormwater quality runoff from the waste rock facility has been 

completed. Existing stormwater quality data for the analysis area were updated and used for the 

analysis. Comments from cooperating agencies, including EPA and ADEQ, have helped refine this 

analysis (see the “Potential for Acid Rock Drainage,” “Potential for Other Contaminants in Runoff,” 

and “Potential for Meeting Narrative Surface Water Quality Standards” parts of this resource section).

Additional mitigation measures have been incorporated into the document and assessed for 

effectiveness at reducing impacts (see the “Mitigation Effectiveness” part of this resource section, 

as well as appendix B).

Monitoring has been incorporated into the mitigation and monitoring plan (see appendix B) in order 

to address uncertainty associated with analysis of geomorphological changes and acid rock drainage

(see the “Mitigation Effectiveness,” “Monitoring Intended to Assess Potential Geomorphological 

Impacts,” and “Monitoring Intended to Assess Potential Acid Rock Drainage” parts of this resource 

section).

Issues, Cause and Effect Relationships of Concern

One significant issue was identified concerning surface water quality.

Issue 3E: Surface Water Quality

Construction and operation of tailings, waste rock, and leach facilities have the potential to result in 

sediment or other pollutants reaching surface water and degrading water quality, leading to a loss of 

beneficial uses. If sediment enters streams, turbidity will increase, and State water quality standards

could be exceeded. Downstream segments of Davidson Canyon and Cienega Creek are Outstanding 

Arizona Waters (Tier 3), which are given the highest level of antidegradation protection. 

As outstanding resource waters under the ARS, Tier 3 waters must be maintained and protected, 

with no degradation in water quality allowed.

Issue 3E Factors for Alternative Comparison

1. Ability to meet Arizona Surface Water Quality Standards

2. Change in geomorphology and characteristics of downstream channels

3. Acres and locations that may be affected by surface water quality impacts and the duration 

(in years) of those impacts

4. Acres of potentially jurisdictional WUS impacted

444 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 64. Analysis area for surface water quality

Final Environmental Impact Statement for the Rosemont Copper Project 445
Chapter 3. Affected Environment and Environmental Consequences

Analysis Methodology, Assumptions, 

Uncertain and Unknown Information 

The methodology for assessing changes in surface water quality consists of four components: (1) the 

potential for acid rock drainage; (2) expected changes in sediment yield; (3) potential for other 

contaminants; and (4) dredged or fill material into WUS under the CWA. All analyses presented are 

based on resource reports prepared by professionals with expertise in the field. 

The potential for acid rock drainage impacts on surface water quality is assessed using geochemical 

test results from 226 samples collected in the project area. Composite acid base accounting 

techniques were performed on the various rock types using static testing for preliminary screening.

Based on the results of static testing, additional kinetic testing (humidity cell tests) and leaching 

procedures were performed to investigate acid generating potential. These data were used to 

characterize the quality of stormwater runoff from the waste rock.

Expected changes in sediment yield (specifically, total suspended solid concentrations) from the 

project area to the USGS stream gage in Lower Barrel Canyon were modeled using the 1968 Pacific 

Southwest Inter-Agency Committee method (Pacific Southwest Inter-Agency Committee 1968). 

The potential for downstream scour or aggradation caused by changes to upstream sediment yield is 

assessed qualitatively, based on two independent analyses and field observations performed by 

Golder Associates and WestLand Resources Inc. (Patterson and Annandale 2012; Rosemont Copper 

Company 2012a). These studies were used in conjunction with the sediment yield modeling to 

analyze impacts on surface water quality. The Coronado investigated the use of sediment transport 

models (such as HEC-6) and determined that given the type of system that exists in Barrel Canyon 

(Patterson and Annandale 2012) and the difficulty of applying sediment transport models to 

ephemeral systems (Duan et al. 2008; Ruff et al. 1986), running these models would not further 

inform the decision. The draft stormwater pollution prevention plan prepared by Rosemont Copper 

was also reviewed to gain an understanding of expected stormwater controls and stormwater 

sampling points (Rosemont Copper 2013). This document has yet to be reviewed by ADEQ and is 

expected to be modified based on their review, as well as being frequently updated during operations.

The potential for contaminants other than sediment to enter natural drainage ways is assessed using 

geochemical test results to predict water quality of stormwater coming into contact with waste rock.

To better represent the assorted rock types present at the project area, a weighted average of the test 

results is used proportionate to the percentage of rock type present. These are then compared with the 

surface water quality standards specific to the beneficial uses on Barrel Canyon, as well as existing

surface water quality data for the project area. Baseline stormwater samples were collected in 2009, 

2010, and 2011 from Barrel Canyon and its tributaries in order to document baseline surface water 

quality conditions. Available existing water quality data for Davidson Canyon and Cienega Creek

have been summarized as well, although these samples represent base flow instead of stormwater 

runoff.

The fourth component consists of the amount of dredged or fill material within WUS as regulated 

under Section 404 of the CWA. Washes, wetlands, and stock ponds in the project area, the utility 

maintenance road, the power line, and the water supply pipeline were surveyed using field methods 

developed by the USACE (2008a; 2008b). A preliminary jurisdictional waters determination based on 

the surveys was submitted to the USACE on May 29, 2009, with additional information provided on 

July 31, 2009, January 5, 2010, and March 1, 2010. The USACE approved the preliminary 

jurisdictional delineation in November 2010. Two addenda were subsequently submitted to the 

USACE on March 13 and 15, 2012 (WestLand Resources Inc. 2012a; 2012b). Impacts to potentially 

446 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

jurisdictional WUS are summarized in the “U.S. Army Corps of Engineers’ Section 404(b)(1) 

Alternatives Analysis,” included as an appendix to the FEIS. The 404(b)1 alternatives analysis, as 

approved by the USACE, was used by the Coronado to quantitatively assess direct and indirect 

impacts to potentially jurisdictional WUS (i.e., acres of jurisdictional WUS impacted). The Coronado 

has relied on the USACE authority to regulate activities under Section 404 of the CWA to determine 

what constitutes direct and indirect impacts to WUS. Impacts to riparian habitat/vegetation resulting 

from the potential reduction in spring flow or stream flow are addressed in the “Seeps, Springs, and 

Riparian Areas” resource section of this chapter.

The connected actions described in chapter 2 (relocation of electric transmission line; construction 

and eventual removal of the electrical distribution line, water supply pipeline, and associated features; 

rerouting of the Arizona National Scenic Trail; and SR 83 highway maintenance and improvements) 

have all been considered for their potential contribution to direct and indirect impacts. The impacts 

described include these actions, in addition to the activities associated with each of the action 

alternatives.

Summary of Effects by Issue Factor by Alternative

Table 97 presents the summary comparison of impacts from each alternative.

Table 97. Summary of effects

Issue Factor No Action Proposed Action Phased 

Tailings Barrel Barrel Trail

ScholefieldMcCleary

Issue 3E.1: Ability 

to meet Arizona 

Surface Water 

Quality Standards

Current runoff

does not meet 

Arizona 

Surface Water 

Quality

Standards for 

total silver, 

arsenic, 

copper, lead, 

selenium, 

thallium, and 

dissolved 

copper

Runoff from waste rock

is predicted to meet 

Arizona Surface Water 

Quality Standards for all 

constituents except 

dissolved silver; risk of 

exceedance is mitigated 

by waste rock 

segregation techniques 

and suggests that 

dissolved silver would 

likely be below standards 

as well

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as for

proposed 

action

Issue 3E.2: Change 

in geomorphology 

and characteristics of 

downstream 

channels

No changes 

from 

proposed 

mine. 

Changing 

watershed or 

climatic 

conditions 

could alter 

stream 

channels.

Sediment load would 

decrease, but sediment

concentrations would 

remain the same, 

compared with baseline;

analysis indicates that no 

changes in 

geomorphology 

(scour/aggradation) are 

expected in Barrel 

Canyon or Davidson 

Canyon owing to change 

in sediment load

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Final Environmental Impact Statement for the Rosemont Copper Project 447
Chapter 3. Affected Environment and Environmental Consequences

Issue Factor No Action Proposed Action Phased 

Tailings Barrel Barrel Trail

ScholefieldMcCleary

Issue 3E.3: Acres 

and locations that 

may be affected by 

surface water quality 

impacts and duration 

(in years) of those 

impacts

None Runoff would affect 2.5 

miles of Barrel Canyon 

(23 acres), and 14 miles 

of Davidson Canyon 

(234 acres); potential for 

effect is greatest during 

active mine life (20 to 25 

years), gradually 

reducing as reclamation

occurs

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Same as 

for 

proposed 

action

Same as for 

proposed 

action

Issue 3E.4: Acres of 

potentially 

jurisdictional WUS

impacted

0 79.4 79 68.4 84.1 48.9

Affected Environment

Relevant Laws, Regulations, Policies, and Plans

Table 98 lists the applicable laws, regulations, and policies related to the use, protection, and 

management of surface water quality that would apply to the development and operation of the 

project. These laws, regulations, and policies, which will collectively be referred to in the following 

sections as “regulation(s),” are outlined in more detail in the following sections. 

Table 98. Summary of the Federal, State, and local regulatory requirements applicable 

to the project with respect to surface water resources

Law or Regulation Regulates

Federal

CWA – Section 404 Discharge of dredged or fill material into WUS

CWA – Section 303 Surface water quality; implemented by the State of Arizona

Executive Order 11988 – Floodplain

Management Occupancy and modification of flood plains

Executive Order 11990 – Wetlands Destruction, loss, or degradation of wetlands

FSMs 2520, 2530, and 2880; FS-881 and 

FS-990a (Technical Guides)

Watershed protection and management, water resource management, 

geological resources, groundwater management, and water quality 

management

State

CWA – Section 401 State Water Quality

Certification Surface water quality; implemented by the State of Arizona

CWA – Section 402 Arizona Pollutant 

Discharge Elimination System

Surface water quality from point sources, including stormwater;

primacy given to State of Arizona

Federal

Clean Water Act (33 United States Code 1251–1376)

The CWA and the Water Quality Act of 1987 form the major Federal legislation governing water 

quality. The objective of the CWA is “to restore and maintain the chemical, physical, and biological 

integrity of the nation’s waters.” 

Important sections of the CWA are as follows.

448 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Clean Water Act Section 401

Section 401 (Water Quality Certification) requires an applicant for any Federal permit who proposes 

an activity that may result in a discharge to WUS to obtain from the appropriate State certification 

that the discharge will not result in a violation of State surface water quality standards. ARS 49-

202(B)–(H) outline the State’s water quality certification procedures for any Federal permit or license 

that involves a discharge to WUS. The ADEQ may certify, deny, or waive water quality certification. 

No Federal permit or action may be approved if the State denies certification.

Clean Water Act Section 402 / Arizona Pollutant Discharge Elimination System 

(Arizona Revised Statutes 49-255.01)

Section 402 of the CWA establishes the National Pollutant Discharge Elimination System, a 

permitting system for the discharge of any pollutant (except for dredged or fill material) into WUS. 

Since 2002, the ADEQ has had primacy over Section 402 through implementation of the Arizona 

Pollutant Discharge Elimination System. The Arizona Pollutant Discharge Elimination System 

program regulates discharge of pollutants into WUS. Historically, the ADEQ has considered virtually 

all waterways in Arizona, including dry washes, to fall under the jurisdiction of the Arizona Pollutant 

Discharge Elimination System program and gives special consideration to those that have been 

designated Outstanding Arizona Waters.

The Arizona Pollutant Discharge Elimination System program regulates point sources of discharge. 

The most common source regulated is stormwater runoff from construction activities and industrial 

sites. Coverage under the Arizona Pollutant Discharge Elimination System may be obtained either 

through issuance of an Individual Permit or a General Permit by the ADEQ (AAC R18-9-C901). 

There are five general permits that historically have been issued: de minimis discharges, stormwater 

runoff from construction activities (the construction general permit), stormwater runoff from 

concentrated animal feeding operations, stormwater runoff from industrial sites (the multisector 

general permit), and discharge of stormwater from municipal stormwater systems. 

A new multisector general permit for stormwater discharges associated with industrial 

activity/mineral industry was approved by ADEQ on December 20, 2010. Rosemont Copper applied 

for coverage under the multisector general permit, and coverage was issued by ADEQ on February 7, 

2013. This mining multisector general permit specifically applies to stormwater runoff from industrial 

activities related to metal mining, including tailings, waste rock, haul roads, milling, and ancillary 

facilities. A key condition for using the general permit is that stormwater runoff may not mix with 

mine drainage or process water. Stormwater discharges can be covered under the mining multisector 

general permit if the applicant meets the permit’s eligibility criteria and complies with the permit’s 

substantive requirements, including best management practices, stabilization measures, good 

housekeeping measures, sediment controls, inspection requirements, and record-keeping 

requirements. Additionally, the mining general permit requires monitoring for several parameters, 

many of which are hardness dependent, that are specific to copper mining operations. 

Multiple surface water permits may be required for this project. Minor temporary discharges, such as 

pipeline hydrostatic testing or well testing, may be covered as de minimis discharge. Linear 

construction activities, including road building, utility line construction, and other ground disturbance 

performed off the mining facility site and greater than 1 acre in size, may require separate coverage

under the construction general permit if not covered under the mining multisector general permit. 

In addition, ADEQ may determine, upon review of the stormwater pollution prevention plan or 

Final Environmental Impact Statement for the Rosemont Copper Project 449
Chapter 3. Affected Environment and Environmental Consequences

additional information, that an individual permit is required for the project instead of the mining 

multisector general permit.

Clean Water Act Section 404

Section 404 establishes a permit program for the discharge of dredged or fill material into WUS, 

including wetlands. This permit program is jointly administered by the USACE and EPA. 

Consultation with the USFWS and State Historic Preservation Officer may also be required before 

issuance of a permit to ensure compliance with the ESA and National Historic Preservation Act. 

The immediate regulatory decision regarding which activities fall under Section 404 of the CWA lies 

with the USACE Los Angeles District, and Section 404 permitting is discretionary on the part of the 

USACE. In general, there are three methods for obtaining a permit under Section 404: authorization 

under a nationwide permit, authorization under a regional general permit, and issuance of an 

individual permit. For all aspects of the proposed project, including road and utility line crossings of 

WUS, an individual permit would be required. The decision regarding which activities are 

jurisdictional has been made by the USACE. 

Clean Water Act Section 303

The ADEQ has developed surface water quality standards, including narrative limitations, to define 

water quality goals for Arizona’s streams and lakes and provide the basis for controlling discharge of 

pollutants to surface waters. Beneficial uses for water bodies are identified in State water quality 

standards (18 AAC Chapter 11, Article 1) and must be achieved and maintained as required under the 

CWA. Beneficial uses can include support of aquatic life, fish consumption, public water supply, and 

irrigation. The 303(d) list, as required by Section 303(d) of the CWA, is a list of water bodies that 

have a designated beneficial use that is impaired by one or more pollutants. Water bodies included on 

this list are referred to as “impaired waters.” The State must take appropriate action to improve 

impaired water bodies by establishing total maximum daily loads and reducing or eliminating 

pollutant discharges. No impaired waters exist within the analysis area.

Executive Orders

Executive Order 11988 (May 24, 1977) directs each Federal agency to take action to avoid the longand short-term adverse impacts associated with the occupancy and modification of flood plains. 

Agencies are required to avoid direct or indirect support of flood plain development whenever there 

is a practicable alternative. The footprint of the mine is not within any mapped 100-year flood plain 

areas. 

Executive Order 11990 (May 24, 1977) directs Federal agencies to minimize the destruction, loss, or 

degradation of wetlands and to preserve and enhance the natural and beneficial value of wetlands in 

carrying out programs that affect land use.

Forest Service Guidance

FSMs that provide guidance for watershed protection and management are discussed in the 

“Groundwater Quantity” resource section of this chapter. 

450 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

State

Arizona Water Quality Standards 

(Title 18 Arizona Administrative Code Chapter 11)

State regulations dictate numeric water quality standards both for surface waters and for groundwater. 

Numeric surface water quality standards apply to all naturally occurring surface water on nontribal 

lands within the State, while aquifer water quality standards apply to all groundwater within the State. 

Numeric surface water quality standards are specific to the use of the water, as well as any special 

designations for surface waters, and there are varying standards for acute and chronic exposure. 

State regulations also identify a narrative water quality standard for surface water. The narrative 

standards state that surface water shall not contain pollutants in amounts that: (1) settle to form 

bottom deposits that inhibit the growth of aquatic life; (2) cause objectionable odor; (3) cause offtaste or odor in drinking water; (4) cause off-flavor in aquatic organisms; (5) are toxic to humans, 

plants, animals, or other organisms; (6) cause growth of algae that inhibit the growth of other aquatic 

life or impair recreational use; (7) cause a violation of an aquifer water quality standard; or (8) change 

the color of the surface water. Further, narrative water quality standards state that surface water shall 

not contain: a pollutant such as oil or grease that floats or causes a film; a discharge of suspended 

solids that interfere with downstream treatment plants; or solid waste such as refuse, rubbish or trash. 

The narrative water quality standards also state that a wadeable, perennial stream shall support and 

maintain organism richness comparable to that of a stream with reference conditions in Arizona.

Existing Conditions

Waters of the United States

Past activities on the Coronado National Forest that have impacted WUS include historic grazing 

activities, mining, fires, and recreation and off-highway-vehicle usage. Current watershed conditions 

within the analysis area are generally satisfactory, although several subwatersheds have been 

degraded, as discussed in detail in the “Soils and Revegetation” resource section in this chapter. 

Many of the named and unnamed ephemeral drainages on the project area have been determined to be 

potentially jurisdictional WUS by the USACE. WestLand Resources Inc. (2010e; 2010f) submitted to 

the USACE a preliminary jurisdictional delineation to map and estimate the total acreage of 

potentially jurisdictional drainages in the project area and associated utility corridor (figure 65). 

The preliminary jurisdictional delineation was approved by the USACE on November 1, 2010. Two 

addenda to the preliminary jurisdictional delineation were subsequently filed with the USACE on 

March 13 and 15, 2012, for additional areas along the power line and water pipeline (WestLand 

Resources Inc. 2012a; 2012b). The WestLand Resources Inc. delineation estimates that there is a total 

of approximately 125 acres of WUS within the areas surveyed by WestLand Resources Inc., which 

generally correspond to the project area and the utility corridor. The potentially jurisdictional areas 

include the ephemeral drainages associated with Barrel, Scholefield, Wasp, McCleary, Mulberry, and 

Papago Canyons, as well as numerous small, unnamed, ephemeral tributary drainages that flow into 

these canyons. Table 99 provides a list of drainages and the total acreage of potentially jurisdictional 

WUS within the project area, including the utility corridor. 

Final Environmental Impact Statement for the Rosemont Copper Project 451
Chapter 3. Affected Environment and Environmental Consequences

Figure 65. Potentially jurisdictional waters within the project area

452 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 99. Summary of preliminary jurisdictional waters delineation within project area 

and utility corridor

Project Component Area of Analysis

(acres)

Potential WUS

(acres) Identified Features

Mine site 

(WestLand Resources Inc. 2010e)

9,136 101.6 154 ephemeral drainages

10 stock tanks

2 concrete dams

7 springs

1 leaking wellhead

1 wetland (Scholefield Spring)

Water line 

(WestLand Resources Inc. 2010f)

1,158 21.58 95 ephemeral drainages

Addendum to Santa Rita Road utility line 

(WestLand Resources Inc. 2012a)

38 0.98 5 ephemeral drainages

Addendum to Santa Rita Road utility line 

(WestLand Resources Inc. 2012b)

49.7 0.801 49 ephemeral drainages

Surface Water Quality

Stormwater sampling has been conducted by Rosemont Copper in Barrel Canyon and its tributaries 

since 2009, and the samples have been analyzed for water quality. In addition, some surface water

quality data exist for Davidson Canyon downstream near its confluence with Cienega Creek, as well 

as within Cienega Creek. However, these samples appear to represent base flow, not stormwater

runoff. None of the drainages within the analysis area have been designated by the ADEQ as impaired 

or as having other water quality concerns. A portion of Davidson Canyon has been designated an 

Outstanding Arizona Water by the ADEQ, as have portions of Cienega Creek; these areas are fully 

analyzed in the “Seeps, Springs, and Riparian Areas” resource section of this chapter.

Six water quality samples were collected from two locations in lower Davidson Canyon by Pima 

Association of Governments Watershed Planning (2005) between 2002 and 2003. These data were 

provided in the nomination to classify Davidson Canyon as a Unique Water. Rosemont Copper also 

collected water samples in lower Davidson Canyon in 2008 and 2010. Two additional water quality 

samples have been collected more recently by ADEQ in 2012. All Davidson Canyon data are 

summarized below in table 100. Sample locations roughly correspond to two springs presented in 

the “Seeps, Springs, and Riparian Areas” resource section: Reach 2 Spring (“Davidson 1”) and 

Escondido Spring (“Davidson 2”). The sample collected by Rosemont Copper titled “Reach 2 

Davidson Canyon” and the “Davidson Canyon at OAW Spring Source” location sampled by ADEQ

correspond to the “Davidson 1” location sampled by the Pima Association of Governments. Based on 

review of available stream flow and meteorological data, these samples appear to represent base flow 

conditions, not stormwater runoff (SWCA Environmental Consultants 2013k).

Designated uses in the Outstanding Arizona Water section of Davidson Canyon include Aquatic and 

Wildlife (ephemeral), Agricultural Livestock Watering, Fish Consumption, Full Body Contact, Partial 

Body Contact, and Aquatic Wildlife (warm water) (Arizona Department of Environmental Quality

2009). Pima Association of Governments Watershed Planning (2005) found that of the parameters 

that were tested, none exceeded surface water quality standards and that Davidson Canyon had a 

lower concentration of total dissolved solids and most major constituents than Cienega Creek.

Rosemont Copper collected two samples in 2008 farther downstream in Lower Cienega Creek (table 

101) (Rosemont Copper Company 2012f). Four additional water samples have been collected more 

Final Environmental Impact Statement for the Rosemont Copper Project 453
Chapter 3. Affected Environment and Environmental Consequences

recently by ADEQ in 2012 and 2013 (Arizona Department of Environmental Quality 2013b). This 

reach of Cienega Creek is an Outstanding Arizona Water, and beneficial uses in this section include

Agricultural Livestock Watering, Fish Consumption, Full Body Contact, and Aquatic Wildlife (warm 

water). The designated uses in this reach are the same as in Davidson Canyon, and surface water

quality standards are met for every parameter that has a standard except for pH reading on June 24, 

2008. The value is slightly less than the range of values set for the surface water standard for 

livestock watering, which indicates that the water is slightly acidic. Additional water quality data at 

multiple locations on Cienega Creek have been collected from 1987 to 1998 (Arizona Department of 

Environmental Quality 2013b), but are not presented in table 101. Based on review of available 

stream flow and meteorological data, these samples appear to represent base flow conditions, not 

stormwater runoff (SWCA Environmental Consultants 2013k).

Baseline stormwater quality samples were collected in Barrel Canyon near the compliance point dam 

at a station referred to as RP2 (in 2009) and PSW5 (in 2010 and 2011) (Rosemont Copper Company 

2012f). Sampling results are presented in table 102. In all, Rosemont Copper has collected 

stormwater samples from 8 locations on 15 different dates. In addition to samples at RP2 and PSW5, 

the entire range of sampling results from all stormwater samples collected in Barrel Canyon and its 

tributaries is also summarized in table 102. As indicated by the bold numbers in the table, the surface 

water quality standards applicable to Barrel Canyon (the acute standard for aquatic and wildlife

ephemeral, and the standard for partial body contact) has been exceeded in at least some stormwater 

samples in Barrel Canyon and its tributaries for total silver, total arsenic, total and dissolved copper, 

total lead, total selenium, and total thallium. Concentrations of total suspended solids were measured 

for four of the samples near the compliance point dam and range from 4,000 to 33,800 mg/L.

Environmental Consequences

Direct and Indirect Effects of Each Alternative

No Action Alternative

Under baseline conditions (no action), surface water within the analysis area consists of stock tanks, 

ephemeral flows that occur as the result of precipitation events, as well as springs or seeps. Under the 

no action alternative, the Coronado has an ongoing responsibility for managing water resources on 

NFS lands under guidance summarized in the “Relevant Laws, Regulations, Policies, and Plans” part 

of this section; the 1986 forest plan, as amended (U.S. Forest Service 1986); and the ESA. The no 

action alternative would not change the Forest Service’s responsibility for managing water resources 

and would result in no further impacts to the quality of surface water resources. Grazing would 

continue in accordance with the approved forest plan and allotment management plans. Ephemeral 

washes in the analysis area would continue to flow in response to precipitation, and the sediment

yield would continue at the current rate. Climate change would continue over time; anticipated 

decreases in winter precipitation could decrease the occurrence of ephemeral flows and thus the 

delivery of sediment downstream. Conversely, the anticipated increase in heavy rains would create 

higher peak flows with a greater capacity to carry sediment downstream.

Population growth is expected to continue, and recreation within the area is expected to increase. This 

could result in greater ground disturbance and impacts to surface water quality. Decreases in surface 

water quantity due to increased allocation and use could also affect surface water quality.

Based on analysis of existing stormwater samples, applicable surface water quality standards would 

likely continue to be exceeded at times in Barrel Canyon under the no action alternative.

454 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 100. Summary of Davidson Canyon existing base flow water quality 

Parameter

Numeric Surface 

Water Quality

Standard*

6/4/2002 

Davidson 1†

(mg/L)

6/4/2002 

Davidson 2†

(mg/L)

8/2/2002 

Davidson 1†

(mg/L)

10/3/2002 

Davidson 2†

(mg/L)

1/3/2003 

Davidson 2†

(mg/L)

5/8/2003 

Davidson 1†

(mg/L)

4/20/2010 

Reach 2 

Davidson 

Canyon‡

(mg/L)

9/24/2010 

Reach 2 

Davidson 

Canyon‡

(mg/L)

10/22/2008 

Lower 

Davidson 

Canyon‡

(mg/L)

9/10/2012

Davidson 

Canyon –

At OAW

Spring Source

(mg/L)§

11/20/2012

Davidson 

Canyon –

At OAW

Spring Source

(mg/L)§

Alkalinity as Bicarbonate (HCO3) No standard 366 354 305 305 415 402 410 324 332 – –

Alkalinity as CaCO3 No standard 300 290 250 250 340 330 – – – – –

Aluminum No standard <2.0 D <2.0 D <2.0 D <2.0 D <2.0 D <2.0 D 0.23 <0.100 <0.03 <0.2 T –

Antimony 0.030 – 0.088D

0.640 – 0.747T

– – – – – – <0.00200 <0.0020 0.0012 <0.003 T

<0.003D

<0.003 T

<0.003 D

Arsenic 0.150 – 0.340 D

0.030 – 0.200 T

<0.005 D <0.005 D <0.005 D <0.005 D <0.005 D <0.005 D 0.0062 0.00407 0.0028 0.0023 T

0.002 D

<0.003 T

<0.003 D

Barium 98 T – – – – – – 0.348 0.16760 0.158 0.12 T –

Beryllium 0.084 – 1.867 T – – – – – – <0.0005 <0.00050 <0.0001 <0.001 T <0.001 T

Bicarbonate (HCO3) No standard – – – – – – 500 395 366 – –

Cadmium 0.00147 – 0.03023 D

0.050 – 0.700 T

– – – – – – <0.0020¶ <0.00200¶ <0.0001 <0.001 T

<0.001 D

<0.001 T

<0.001 D

Calcium No standard 81 D 93 D 87 D 98 D 96 D 99 D 130 88.6 101 98 T 100 T

Carbonate (CO3) No standard – – – – – – <20 <20.0 19.2 <6.0 T <6.0 T

Chloride No standard 17 19 15 15 15 15 13 7.14 36.3 4.4 T 4.5 T

Chromium 0.23067 – 1.773 D

75 – 1,400 T

– – – – – – <0.0050 <0.00500 <0.01 <0.01 T <0.01 T

Copper 0.02928 – 0.04962 D

0.5 – 1.3 T

– – – – – – 0.0030 0.00200 <0.01 <0.01 T

<0.01 D

<0.01 T

<0.01 D

Field Conductivity (μS) No standard 726.6 794.1 723.3 793 791.3 778.3 1,016 606 696 610 700

Field pH No standard 7.93 7.57 7.88 7.45 7.51 7.39 7.8 7.00 7.82 7.82 7.42

Field Temperature (C) No standard 20.4 23.3 28 19.8 17.6 17.8 19.1 22.6 22.0 23.9 20.4

Fluoride 140 0.48 0.52 0.48 0.48 0.64 0.47 <0.50 0.597 0.8 0.62 T 0.51 T

Hardness as Calcium Carbonate 

(CaCO3)

No standard 300 290 250 250 340 330 440 – 359 320 340

Lab Conductivity (μS) No standard 740 790 600 780 760 770 910 663 727 – –

Lab pH No standard 7.6 7.1 7.7 7.3 7.3 7.2 7.8 7.77 8.5 – –

Total Dissolved Solids No standard 420 390 550 470 520 340 620 462 860 410 440

Lead 0.01099 – 0.28085 D

0.015 – 0.1 T

– – – – – – <0.0020 <0.00200 <0.0001 <0.001 T

<0.001 D

<0.001 T

<0.001 D

Magnesium No standard 21 D 23 D 20 D 23 D 24 D 25 D 26 16.5 25.9 18 T 18 T

Manganese 130.667 T – – – – – – 1.63 0.18130 0.032 0.058 T 0.057 T

Mercury 0.00001 – 0.0024 D

0.010 – 0.280 T

– – – – – – <0.00002¶ <0.00020§ <0.0002¶ <0.0002¶ T

<0.0002¶ D

<0.0002¶ T

<0.0002¶ D

Nickel 0.16804 – 1.513 D

0.511 – 28 T

– – – – – – <0.0050 <0.00500 <0.01 <0.01 T

<0.01 D

–

Nitrate as N 3,733 <1.0 <1.0 <1.0 <1.0 <1.0 <1.0 – – – – –

Nitrate/Nitrite as N No standard – – – – – – 0.25 <0.200 0.81 0.30 T <0.1 T

Final Environmental Impact Statement for the Rosemont Copper Project 455
Chapter 3. Affected Environment and Environmental Consequences

Parameter

Numeric Surface 

Water Quality

Standard*

6/4/2002 

Davidson 1†

(mg/L)

6/4/2002 

Davidson 2†

(mg/L)

8/2/2002 

Davidson 1†

(mg/L)

10/3/2002 

Davidson 2†

(mg/L)

1/3/2003 

Davidson 2†

(mg/L)

5/8/2003 

Davidson 1†

(mg/L)

4/20/2010 

Reach 2 

Davidson 

Canyon‡

(mg/L)

9/24/2010 

Reach 2 

Davidson 

Canyon‡

(mg/L)

10/22/2008 

Lower 

Davidson 

Canyon‡

(mg/L)

9/10/2012

Davidson 

Canyon –

At OAW

Spring Source

(mg/L)§

11/20/2012

Davidson 

Canyon –

At OAW

Spring Source

(mg/L)§

Potassium No standard <5.0 D <5.0 D <5.0 D <5.0 D <5.0 D <5.0 D 3.7 2.84 3.5 2.1 T 2.2 T

Selenium 0.002 – 4.667 T – – – – – – <0.0020 <0.00200 0.0022 <0.002 T <0.001 T

Silicon Dioxide (SiO2) No standard 26 25 29 34 31 28 – – – – –

Silver 0.03491 D

4.667 – 8 T

– – – – – – <0.0050 <0.005 <0.01 <0.01 T

<0.01 D

–

Sodium No standard 48 D 45 D 50 D 43 D 49 D 44 D 40 36.1 51.4 25 T 25 T

Sulfate (SO4) No standard 79 100 91 92 90 84 96 52.7 327 46 T 43 T

Thallium 0.150 – 0.700 D

0.001 – 0.075 T

– – – – – – <0.0005 <0.00050 <0.0001 <0.001 T

<0.001 D

–

Uranium 2.8 T – – – – – – 0.0061 0.00596 0.0067 – –

Zinc 0.3793 D

5.106 – 25 T

– – – – – – <0.050 <0.050 <0.01 <0.05 T

<0.05 D

<0.05 T

<0.05 D

Notes: 

– = The sample was not analyzed for this parameter.

Bold indicates an exceedance of surface water quality standard.

Chromium assumed for purposes of analysis to be Chromium III.

D – Dissolved.

T – Total.

“Davidson 1” is located south of I-10 near the unnamed spring at 31° 59′ 00′′/ 110° 38′ 46′′ (known as Reach 2 Spring in this EIS). “Reach 2 Davidson Canyon” and “Davidson Canyon – At OAW Spring Source” also correspond to this location.

“Davidson 2” is located near the confluence with Cienega Creek near the unnamed spring at 32° 00′ 54′′/110° 38′ 54′′ (known as “Escondido Spring” in this EIS).

Location of “Lower Davidson Canyon” sample is not known.

* Applicable surface water standards include Agriculture-Livestock Watering, Fish Consumption, Full Body Contact, Aquatic and Wildlife-Warmwater-Acute, Aquatic and Wildlife-Warmwater-Chronic. Range of standards shown. Hardness for all surface water standards assumed to be 400 

mg/L.

† Pima Association of Governments (2005).

‡ Rosemont Copper (2012f). Total alkalinity assumed to be measured as HCO3. Not known whether metal concentrations reflect total or dissolved.

§ ADEQ (2013b).

¶ Indicates that the detection limit was above the surface water quality standard for at least one use.

456 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 101. Summary of Lower Cienega Creek existing base flow water quality

Parameter Numeric Surface 

Water Quality Standard*

6/24/08

Lower Cienega Creek

(mg/L)

†

10/22/08

Lower Cienega Creek

(mg/L)†

9/10/12

Cienega Creek

at Marsh Station Road 

(mg/L)‡

11/20/12

Cienega Creek

at Marsh Station Road 

(mg/L)‡

2/27/13

Cienega Creek

at Marsh Station Road 

(mg/L)‡

4/18/13

Cienega Creek

at Marsh Station road 

(mg/L)‡

Alkalinity as Bicarbonate (HCO3) No standard 275 278 – – – –

Aluminum No standard <0.03 <0.03 – – <0.2 T –

Antimony 0.030 – 0.088D

0.640 – 0.747T

0.0005 <0.0004 <0.003 T

<0.003 D

<0.003 T

<0.003 D

<0.003 T

<0.003 D

<0.003 T

<0.003 D

Arsenic 0.150 – 0.340 D

0.030 – 0.200 T

0.0035 0.0030 0.0037 T

0.0035 D

0.0023 T

0.0031 D

<0.003 T

<0.003 D

<0.003 T

<0.003 D

Barium 98 T 0.054 0.060 – – 0.085 T –

Beryllium 0.084 – 1.867 T <0.0001 <0.0001 <0.001 T <0.001 T <0.001 T <0.001 T

Bicarbonate (HCO3) No standard 323 315 300 T 300 T – –

Cadmium 0.00147 – 0.03023 D

0.050 – 0.700 T

<0.0001 <0.0001 <0.0001 T

<0.0001 D

<0.0001 T

<0.0001 D

<0.0001 T

<0.0001 D

<0.0001 T

<0.0001 D

Calcium No standard 186 148 170 T 130 T 170 T 160 T

Carbonate (CO3) No standard 6 12 <6.0 T <6.0 T – –

Chloride No standard 12.2 9.9 11 T 7.7 T 9.6 T 10 T

Chromium 0.23067 – 1.773 D

75 – 1,400 T

<0.01 <0.02 <0.01 T <0.01 T <0.01 T <0.01 T

Copper 0.02928 – 0.04962 D

0.5 – 1.3 T

<0.01 <0.02 <0.01 T

<0.01 D

<0.01 T

<0.01 D

<0.01 T

<0.01 D

<0.01 T

<0.01 D

Field Conductivity (μS) No standard 1,100 1,092 1,200 1,000 1,200 1,200

Field pH No standard 6.23 6.86 7.75 7.62 7.97 7.66

Field Temperature C No standard 25 22.3 24.2 17.9 15.0 18.0

Fluoride 140 0.6 0.6 0.56 T 0.56 T 0.49 T 0.57 T

Hardness as Calcium Carbonate (CaCO3) No standard 671 537 600 470 590 580

Lab Conductivity (μS) No standard 1,400 1,160 – – – –

Lab pH No standard 8.3 8.5 – – – –

Total Dissolved Solids No standard 1,050 840 860 740 860 930

Lead 0.01099 – 0.28085 D

0.015 – 0.1 T

<0.0001 <0.0001 <0.001 T

<0.001 D

<0.001 T

<0.001 D

<0.001 T

<0.001 D

<0.001 T

<0.001 D

Magnesium No standard 50.1 40.7 43 T 33 T 44 T 43 T

Manganese 130.667 T 0.017 0.09 0.15 T 0.02 T <0.01 T <0.01 T

Mercury 0.00001 – 0.0024 D

0.010 – 0.280 T

<0.0002§ <0.0002§ <0.0002§ T

<0.0002§ D

<0.0002§ T

<0.0002§ D

<0.0002§ T

<0.0002§ D

<0.0002§ T

<0.0002§ D

Nickel 0.16804 – 1.513 D

0.511 – 28 T

<0.01 <0.01 – – <0.01 T

<0.01 D

–

Nitrate/Nitrite as N No standard 0.03 0.68 0.28 T 0.34 T <0.10 T <0.10 T

Potassium No standard 4.8 4.5 5.1 T 4.0 T 4.7 T 4.4 T

Selenium 0.002 – 4.667 T <0.0001 0.0001 <0.002 T <0.001 T <0.003§ T <0.002 T

Silver 0.03491 D

4.667 – 8 T

– <0.02 – – <0.01 T

<0.01 D

–

Final Environmental Impact Statement for the Rosemont Copper Project 457
Chapter 3. Affected Environment and Environmental Consequences

Parameter Numeric Surface 

Water Quality Standard*

6/24/08

Lower Cienega Creek

(mg/L)

†

10/22/08

Lower Cienega Creek

(mg/L)†

9/10/12

Cienega Creek

at Marsh Station Road 

(mg/L)‡

11/20/12

Cienega Creek

at Marsh Station Road 

(mg/L)‡

2/27/13

Cienega Creek

at Marsh Station Road 

(mg/L)‡

4/18/13

Cienega Creek

at Marsh Station road 

(mg/L)‡

Sodium No standard 71.5 65.0 65 T 54 T 67 T 66 T

Sulfate (SO4) No standard 486 365 400 T 270 T 370 T 400 T

Thallium 0.150 – 0.700 D

0.001 – 0.075 T

<0.0001 <0.0001 – – <0.001 D –

Uranium 2.8 T 0.0074 0.0054 – – – –

Zinc 0.3793 D

5.106 – 25 T

<0.01 0.01 <0.05 T

<0.05 D

<0.05 T

<0.05 D

<0.05 T

<0.05 D

<0.05 T

<0.05 D

Notes:

Additional water quality samples were also collected on Cienega Creek between 1987 and 1998 and reported in Arizona Department of Environmental Quality (2013b); these samples are not included in this table

– = Sample was not analyzed for this parameter.

D – Dissolved.

T – Total.

“Lower Cienega Creek” sample location is below confluence with Davidson Canyon, but exact location is unknown.

* Applicable surface water standards include Agriculture-Livestock Watering, Fish Consumption, Full Body Contact, Aquatic and Wildlife-Warmwater-Acute, Aquatic and Wildlife-Warmwater-Chronic. Range of standards shown. Hardness for all surface water standards assumed to be 400 

mg/L.

† Rosemont Copper (2012f). Not known whether metal concentrations reflect total or dissolved.

‡ ADEQ (2013b).

§ Indicates that the detection limit was above the surface water quality standard for at least one use.

458 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 102. Results of baseline stormwater quality samples in Barrel Canyon

7/1/2009 7/21/2009 9/6/2009 1/22/2010 8/11/2010 8/3/2011 9/11/2011

Parameter

Numeric Surface 

Water Quality

Standard*

(mg/L)

RP2 

(mg/L)

RP2

(mg/L)

RP2

(mg/L)

PSW5

(mg/L)

PSW5

(mg/L)

PSW5

(mg/L)

PSW5

(mg/L)

Range of results 

for all samples in 

Barrel Canyon 

and tributaries 

(mg/L)

Aluminum (dissolved) No standard <0.10 0.19 <0.10 <0.10 <0.10 <0.10 <0.20 ND–3.7

(0.02–2)

Aluminum (total) No standard 120 400 370 84 65 377 379 ND–400

(0.2–1)

Antimony (dissolved) No standard <0.0020 <0.025 – <0.025 <0.0020 <0.0250 <0.0200 ND

(0.002–0.1)

Antimony (total) 0.747 <0.200 <0.25 <0.25 <0.025 <0.0020 <0.0250 – ND–19.1

(0.002–0.25)

Arsenic (dissolved) 0.44 0.0100 0.029 <0.010 <0.010 <0.010 <0.0100 <0.0100 ND–0.029

(0.01–0.1)

Arsenic 

(total)

0.28 <0.300† 0.45 0.34 0.11 0.037 0.263 0.459 ND–0.459

(0.01–0.3)

Barium (dissolved) No standard 0.0468 0.062 0.032 0.024 0.078 0.031 0.0413 ND–0.316

(0.01–1)

Barium (total) 98 7.49 3.0 3.8 0.93 1.2 3.72 5.63 ND–7.49

(0.1–1)

Beryllium (dissolved) No standard <0.0005 <0.0020 <0.0020 <0.0020 <0.0020 <0.00200 <0.00400 ND

(0.0005–0.1)

Beryllium (total) 1.867 0.0552 0.030 0.027 0.0071 0.005 0.0262 0.0333 ND–0.0552

(0.002–0.05)

Boron (dissolved) No standard <0.10 <0.10 <0.10 <0.10 <0.10 <0.100 <0.500 ND–0.19

(0.05–1)

Boron (total) 186.667 0.010 <1.0 <1.0 <0.10 <0.100 <0.100 0.164 ND–0.578

(0.05–1)

Cadmium (dissolved) 0.08761 <0.0020 <0.0030 <0.0030 <0.0030 <0.0030 <0.00300 <0.00500 ND

(0.002–0.05)

Cadmium (total) 0.7 <0.200 0.053 0.039 0.011 <0.0030 0.0184 0.0398 ND–0.053

(0.003–0.3)

Calcium (dissolved) No standard 34 33 27 25 – – 25.6 ND–63

(4)

Calcium (total) No standard 1,000 620 640 150 110 452 1,880 7.1–1880

Calculated Hardness as 

CaCO3

No standard 2,836 2,616 2,420 568 385 1,843 5,446 –

Chromium (dissolved) 5.95 (CrIII)

0.034 (CrVI)

<0.0050 <0.010 <0.010 <0.010 <0.010 <0.0100 <0.0100 ND

(0.005–0.1)

Chromium (total) 1400 (CrIII)

2.8 (CrVI)

<0.500 1.2 0.26 0.02 0.031 0.223 0.253 ND–1.2

(0.01–0.5)

Copper (dissolved) 0.08588 0.0497 0.032 0.022 0.038 0.012 0.0218 0.0252 ND–0.152

(0.01–0.1)

Copper (total) 1.3 8.53 29 9.1 2.4 0.58 7.94 9.88 ND–29

(0.01–0.1)

Final Environmental Impact Statement for the Rosemont Copper Project 459
Chapter 3. Affected Environment and Environmental Consequences

7/1/2009 7/21/2009 9/6/2009 1/22/2010 8/11/2010 8/3/2011 9/11/2011

Parameter

Numeric Surface 

Water Quality

Standard*

(mg/L)

RP2 

(mg/L)

RP2

(mg/L)

RP2

(mg/L)

PSW5

(mg/L)

PSW5

(mg/L)

PSW5

(mg/L)

PSW5

(mg/L)

Range of results 

for all samples in 

Barrel Canyon 

and tributaries 

(mg/L)

Fluoride (dissolved) No standard – <0.50 <0.50 <0.50 <0.50 – – ND

(0.5)

Fluoride (total) 140 – <0.50 <0.50 <0.50 <0.50 <0.050 <0.50 ND–0.17

(0.05–0.5)

Lead (dissolved) 0.59271 <0.0020 <0.010 <0.010 <0.010 <0.010 <0.0100 <0.0100 ND–0.0748

(0.002–0.15)

Lead (total) 0.015 4.64 6.5 3.8 0.52 0.2 2.52 2.19 ND–6.5

(0.01–0.1)

Manganese (dissolved) No standard 0.265 1.3 <0.010 <0.010 <0.010 0.0151 <0.0200 ND–3.2

(0.01–0.1)

Manganese (total) 130.667 39.3 29 24 5.4 3.3 18.5 23.2 ND–39.3

(0.02–0.1)

Magnesium (dissolved) No standard 2.2 2.6 1.8 1.8 1.1 1.42 1.65 ND–7.6

(0.01–10)

Magnesium (total) No standard 82 260 200 47 27 174 182 ND–260

(10)

Mercury (dissolved) 0.005 <0.0002 – – <0.0002 <0.0002 <0.000100 <0.000100 ND

(0–0.002)

Mercury (total) 0.28 <0.0020 – – <0.0002 0.0004 0.0014 0.00176 ND–0.00176

(0.0001–0.01)

Molybdenum (dissolved) No standard 0.0129 0.023 <0.010 <0.010 <0.010 <0.010 0.0151 ND–0.095

(0.01–0.1)

Molybdenum (total) No standard <0.05 <0.10 <0.010 <0.010 <0.010 <0.010 0.0229 ND–0.0229

(0.01–0.1)

Nickel (dissolved) 13.436 <0.0050 <0.010 <0.010 <0.010 <0.010 <0.0100 <0.0100 ND–4.84

(0.005–0.1)

Nickel (total) 28 <0.500 0.56 0.29 19 0.04 0.264 0.275 ND–19

(0.01–0.5)

Nitrate-Nitrite 

(as N)

233.333 (NO2)

3733.333 (NO3)

– – 1.3 4.6 0.75 0.674 0.801 ND–8.3

(0.1–1)

Selenium (dissolved) 4.667 <0.0020 <0.025 <0.025 <0.025 <0.0020 <0.0250 <0.0300 ND

(0.002–0.1)

Selenium (total) 0.033 <0.200‡ <0.25† <0.25† <0.025† <0.0020 <0.0250 – ND–19.1

(0.002–0.25)

Silver (dissolved) 0.04962 <0.0010 <0.0050 <0.0020 <0.0050 <0.0050 <0.00500 <0.0200 ND–0.0341

(0.001–0.05)

Silver (total) 4.667 <0.100 <0.050 <0.0200 <0.0050 <0.0050 0.0103 43.8 ND–43.8

(0.005–0.1)

Sulfate (dissolved) No standard – 3.5 <3.0 8.7 <3.0 – – ND–13

(3)

Sulfate (total) No standard – 3.6 <3.0 9 <3.0 2.13 3.89 ND–42

(3–5)

460 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

7/1/2009 7/21/2009 9/6/2009 1/22/2010 8/11/2010 8/3/2011 9/11/2011

Parameter

Numeric Surface 

Water Quality

Standard*

(mg/L)

RP2 

(mg/L)

RP2

(mg/L)

RP2

(mg/L)

PSW5

(mg/L)

PSW5

(mg/L)

PSW5

(mg/L)

PSW5

(mg/L)

Range of results 

for all samples in 

Barrel Canyon 

and tributaries 

(mg/L)

Thallium (dissolved) No standard <0.0005 <0.050 <0.0010 <0.050 <0.0005 <0.0500 <0.0200 ND–0.0099

(0.0005–0.1)

Thallium (total) 0.075 <0.0500 <0.50† 0.0123 <0.050 0.0007 <0.0500 <0.0200 ND–0.181

(0.0005–0.5)

Zinc (dissolved) 3.599 <0.050 <0.050 <0.050 <0.050 <0.050 <0.0500 <0.0300 ND

(0.03–0.5)

Zinc (total) 280 3.6 17 9.9 0.18 0.61 6.28 6.33 ND–17

(0.003–0.5)

Total Suspended Solids No standard – – – 4,800 11,000 33,800 12,500 ND–44800

(10)

Total Dissolved Solids No standard – 140 200 140 120 153 356 ND–436

(10)

Specific Conductance at 25 °C No standard – 210 – 180 170 229 172 99–870

Source: Rosemont Copper (2012f).

Notes: 

PSW5 and RP2 are the samples in Barrel Canyon closest to the future compliance point dam. Note that samples on 9/4/09 and 7/21/11 were not included both for space and for completeness.

Range of results shown is for all stormwater samples collected in Barrel Canyon and its tributaries, which includes samples from 8 locations on 15 different dates. These include sample locations in Barrel Canyon at Rosemont Junction, in Upper Barrel Canyon above the future compliance 

point dam, and at the confluence with McCleary, Scholefield, and Wasp Canyons.

– = Sample was not analyzed for this parameter.

ND – Not detected, with range of laboratory detection limits shown in parentheses.

Bold indicates an exceedance of surface water quality standard.

* Range of numeric surface water quality standard shown for Aquatic and Wildlife-Ephemeral-Acute use and Partial Body Contact use; for standards that vary with hardness, the range shown is based on hardness of 400 mg/L as CaCO3.

† Indicates that the detection limit was above the surface water quality standard.

Final Environmental Impact Statement for the Rosemont Copper Project 461

Chapter 3. Affected Environment and Environmental Consequences

Impacts Common to All Action Alternatives

All of the alternatives, with the exception of the no action alternative, would result in surface water

quality impacts to some degree. Direct impacts related to surface water quality that are common to all 

action alternatives include potential impacts from acid rock drainage, impacts from erosion and 

sedimentation, and impacts from other contaminants associated with industrial operations. Indirect 

impacts to surface water quality under each action alternative include potential changes in 

downstream geomorphology caused by changes in sediment yield. Although disturbed acreage varies 

slightly for each action alternative, there are no substantial differences in the type or magnitude of 

impacts on the watershed as a whole. Note, however, that there are several tables included in this 

section that describe the quantitative differences in impacts among all action alternatives. These 

tables are included in this section because, for the most part, the quantitative differences in impacts 

are minor and thus result in the same effects on the resource. These quantitative differences in 

impacts are not repeated in each action alternative’s subsection; rather, the reader is referred back to 

these tables in this section. The following impacts apply to all action alternatives.

Surface Disturbance of Potentially 

Jurisdictional Waters of the United States

WUS support riparian areas and provide natural erosion and sediment control across the watershed. 

They have the capacity to carry or reduce pollutants and nutrients; thus, their loss can indirectly affect 

surface water quality. Table 103 summarizes the direct impacts on potential WUS and the 

presence/absence of special aquatic sites for each alternative. Special aquatic sites, as defined in 40 

CFR 230.3(q-1), include sanctuaries, refuges, wetlands, mud flats, vegetated shallows, coral reefs, 

and riffle and pool complexes. One special aquatic site was identified within the project area and 

consists of wetlands associated with the Scholefield springs. The indirect impacts shown in table 103 

represent effects on WUS downstream of the mine site and outside of the mine footprint. These 

indirect impacts are due to a reduction in stormwater flows. Comments received from cooperating 

agencies, and EPA in particular, suggest that indirect effects on WUS would be greater than those 

listed in table 103. The Coronado has relied on the authority of the USACE to regulate activities 

under Section 404 of the CWA to determine the extent of indirect impacts to WUS.

Table 103. Summary of impacts under each action alternative on potential WUS and 

the presence/absence of special aquatic sites 

Impact to Potential WUS

(acres lost)

Proposed 

Action

Phased 

Tailings Barrel Barrel Trail ScholefieldMcCleary 

Mine operations and pit

Direct 

Indirect

Total

42.5

36.9

79.4

41.8

37.2

79

40.0

28.4

68.4

50.0

34.1

84.1

26.2

22.7

48.9

Direct impacts from 

transmission line

0.25 temporary

0.05 permanent

Same as for 

proposed 

action

Same as for 

proposed 

action

Same as for 

proposed 

action

Same as for 

proposed 

action

Direct impacts from water line 

and utility maintenance road

0.85 temporary*

0.2 permanent

Same as for 

proposed 

action

Same as for 

proposed 

action

Same as for 

proposed 

action

Same as for 

proposed 

action

Special aquatic sites (number) 0 0 0 0 1

Source: USACE Section 404(b)(1) Alternatives Analysis (see appendix A).

* These numbers reflect the maximum impacts that would occur from the use of a standard trenching alternative at wash 

crossings. Though not planned, the use of jack-and-bore technology could reduce impacts to WUS.

Final Environmental Impact Statement for the Rosemont Copper Project 463
Chapter 3. Affected Environment and Environmental Consequences

Most of the impacts to WUS associated with the mine operations and the pit (i.e., the project area) 

would be permanent and extend throughout the premining, active mining, final reclamation and 

closure, and postclosure phases. These impacts include complete excavation of washes in the area of 

the pit and complete filling of washes in the areas of the plant site, waste rock facility, and tailings 

facility. Impacts to WUS associated with the utility corridor would primarily be limited to the 

premining phase and would include temporary excavation for pipeline placement, as well as 

permanent road crossings. The utility maintenance road, water supply pipeline, and electrical 

transmission line would be co-located within the same corridor in most places in order to minimize 

impacts to WUS. In general, impacts from linear features would have a small footprint in washes and 

would be temporary in nature, occurring only during construction, and would then be revegetated or 

otherwise stabilized following construction. Unlike the mine operations, linear construction does not 

tend to concentrate disturbance on a single stream channel like Barrel Canyon, and disturbance would

be short lived rather than permanent. 

Disturbances from the pipeline and transmission line are expected to be relatively small (estimated to 

total 0.10 acre) and to be mitigated by best management practices for construction (i.e., structural 

erosion control techniques such as silt fences and straw bales, along with soil stabilization measures). 

The water line would be buried underneath potential WUS, and permanent impacts would result from 

the construction of road crossings and bank stabilization; specifications for burial have not been 

determined at this time. Power lines would be constructed aboveground with an unpaved associated

access road, and no transmission poles would be constructed in washes. The only permanent impact 

to a wash would occur at culverted road crossings and at no more than three utility poles in the 

steeper portions of the alignment through the Santa Rita Mountains. Where feasible, the potential 

WUS would be restored to preconstruction contours following construction of the transmission line 

and access road. Culverted road crossings would be designed with proper erosion control and energy 

dissipation measures; specifications for road crossings have not been determined at this time. 

Effective detention upstream of culverts would be designed so that they have the positive effect of 

reducing erosive peak flow and extending flow durations to promote better flow regimes, increase 

recharge, and generally improve habitat. Implementation of these erosion controls and the stormwater

best management practices required under the stormwater pollution prevention plan would further 

prevent the potential for erosion during and after construction. The acreage shown in table 103 

represents the maximum impact using standard trenching. Use of alternative technologies such as 

jack-and-bore would be evaluated for use during construction and may reduce impacts further.

All disturbed areas except the utility maintenance road would be hydroseeded with native grasses and 

completely stabilized following the premining phase (see the “Soils and Revegetation” resource 

section in this chapter). 

Sediment Yield and Changes in Geomorphology

Potential indirect effects on surface water quality include changes in downstream sediment yield from 

the baseline caused by the loss of WUS and riparian areas and changes in downstream 

geomorphology caused by changes in sediment yield.

WUS and vegetation associated with riparian habitat offer natural erosion control across the 

landscape. Dredging and filling these streams, along with clearing vegetation in the project area, 

would directly affect sediment yield generated from the project area. Changes in sediment yield are of 

concern for several reasons: (1) there would be a loss of soil from the project area; (2) movement of 

that soil into stream channels can affect water quality by increasing total suspended sediment in 

surface water flows; and (3) changes in sediment yield can result in geomorphological changes to 

464 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

downstream washes, causing problems with soil scour or aggradation. The impacts to soil loss from 

the project area are discussed in detail in the “Soils and Revegetation” resource section in this 

chapter. The impact of the movement of soil from the project area is analyzed in this resource section 

and is based on sediment modeling performed by Tetra Tech (Zeller 2010a, 2010b, 2012). Impacts to 

the geomorphology of downstream washes are also discussed in this resource section.

One of the major functions of a stream is to transport sediment. Ephemeral channels such as those 

found in the project area have a cyclical pattern of infill and erosion. In this pattern, sediment 

movement usually occurs as pulses associated with flash thunderstorm flows that push large amounts 

of coarse sediment through the system (Levick et al. 2008). Long-term stream sedimentation behavior 

is based on the equilibrium between erosion and deposition of sediment delivered to the system. 

When that delivery system is disrupted or altered, changes to stream aggradation (the rising of the 

grade of a stream bed) and scour (the erosive removal of sediment from a stream bed) can occur until 

the system reaches equilibrium once again. 

Sediments in ephemeral channels are usually deep, consisting mostly of sand and gravels. While 

sediment-laden runoff is not desirable, a decrease in sediment production in headwaters could cause 

narrowing of channels as sediment-starved waters cut into channel deposits left by larger flows. This 

downcutting can ultimately increase the gradient of the channel and would be likely to result in the 

formation of discontinuous gullies as gradient adjustments shift farther and farther downstream. 

Additionally, as channels become narrower and alluvial bed material is removed, out-of-bank flows 

become reduced, and formerly rich flood plain areas can become hydrologically disconnected. This 

disrupts water, sediment, and nutrient enrichment of these areas (Levick et al. 2008). 

In response to public comment, the Coronado contracted an independent geomorphic assessment of 

Barrel Canyon to determine the current geomorphic condition of the drainage and qualitatively assess 

the potential that geomorphic changes could occur with the development of the project (Patterson and 

Annandale 2012). Based on field observations, Patterson and Annandale (2012) determined that: 

(1) Barrel Canyon is a sediment-transport limited system; and (2) there are two grade controls 

between the project area and the confluence of Barrel and Davidson Canyons. 

• A sediment-transport limited system means that there is more sediment in the system than the 

flowing water can transport during normal or even flood-flow conditions; this is common in 

ephemeral streams due to the flashy nature of flows. Flashy flows emanating from large 

precipitation events pick up sediment in a pulse of water and then deposit it quickly as flows 

recede, forming a poorly sorted loose layer in the streambed. The bed materials observed in 

Barrel Canyon consist of a thick layer of unconsolidated sands, gravels, and cobbles, typical 

of sediment-transport limited systems. Other evidence of a sediment-transport limited system 

observed in the field includes angular particles, localized erosion that does not propagate 

upstream, and deposited materials on top of bedrock and under the SR 83 bridge. 

• Grade control in a system limits the extent of any potential change in a system gradient. 

Two grade control structures occur in Barrel Canyon downstream of the proposed project: 

one is manmade (the bridge at SR 83), and one is natural (the occurrence of bedrock within 

the streambed upstream of its confluence with Davidson Canyon).

Patterson and Annandale (2012) concluded that, based on three geophysical variables (sediment

availability, channel geometry, and water flow), the proposed mine would not have a significant 

impact to the geomorphology of Barrel and Davidson Canyons. First, this conclusion is supported by 

the fact that the availability of loose sediment on the surface of the catchment surrounding Barrel and 

Final Environmental Impact Statement for the Rosemont Copper Project 465
Chapter 3. Affected Environment and Environmental Consequences

Davidson Canyons would continue to supply sediment to the streams, regardless of the presence of 

the project. Thus, the amount of sediment supplied is greater than what the flowing water can carry in 

the transport limited nature of the system. With respect to the Outstanding Arizona Waters in lower 

Davidson Canyon, the area affected by the proposed mine is relatively small (13 percent), compared 

with the entire catchment upstream of the Outstanding Arizona Waters. Any changes in sediment load 

would not significantly impact the fluvial geomorphology of the stream system; moreover, the 

estimated impact of total change in flow and sediment load in lower Davidson Canyon (roughly 4 

percent) would be within the normal variation of an ephemeral fluvial system.

Second, the presence of a bedrock grade control structure would prevent streambed degradation, and 

the sediment transport capacity of flowing water would be maintained, regardless of the presence of 

the proposed project. In a fluvial system, grade controls limit the extent of erosion both upstream and 

downstream. 

Third, water flow is a factor. Given the spatial variability of storms in this region, precipitation does 

not often fall evenly over the entire Davidson Canyon watershed. Spatially variable precipitation 

would result in water flow (and the transport of sediment) from various locations throughout the 

watershed at different points in time. The nature of storm variability and the nature of the transportlimited system would remain relatively unchanged, regardless of the presence of the mine. Therefore, 

it is reasonable to expect that the system could remain largely unchanged even with mine disturbance 

upstream, particularly in the lower reaches of Davidson Canyon near the Outstanding Arizona Waters, 

located approximately 12 miles downstream from the mine itself. 

A second independent analysis of geomorphological changes was made by Rosemont Copper 

(2012a). Field investigations into the channel morphology of Davidson Canyon conducted by Tetra 

Tech (2010a) indicated that the system currently is either in equilibrium with respect to sediment load 

or that the sediment supply to the head reaches of the canyon is slightly greater than the transport 

capacity of the wash. This excess transport capacity would tend to modify, at least to some degree, 

the tendency for scour that would occur as a result of reductions in sediment yield.

Sediment delivery was modeled to the USGS gaging station in Lower Barrel Canyon Wash, the 

downstream stormwater control point for postmining conditions for each alternative (Zeller 2010a, 

2010b, 2012). Sediment from the project area would enter stormwater flows through erosion of native 

soils and waste rock; the tailings area would be protected from erosion by waste rock buttresses. 

Stormwater management facilities onsite have been designed to maintain total suspended sediment

concentrations in stormwater runoff similar to baseline conditions. The prediction of future sediment 

loads under each alternative uses standard erosion modeling techniques that consider soil, vegetation, 

and rainfall characteristics but that do not require baseline sediment loads to be known. The lack of 

samples of baseline sediment load in stormwater in the project area does not affect the analysis. 

Further, sediment transport modeling (such as HEC-6) was not conducted; the Coronado determined 

that applying such models to an ephemeral system (Duan et al. 2008; Ruff et al. 1986) would not 

further inform the analysis. Sediment yield for the baseline condition (no action alternative) and all 

action alternatives is summarized in table 104.

A comparison of the results of each action alternative with baseline conditions indicates that sediment

delivery to the USGS gaging station would be reduced to varying degrees for each alternative. This 

reduction would primarily be the direct result of the reduction in the contributing watershed area. 

466 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 104. Summary of postmine average annual sediment delivery to the USGS 

gaging station for each alternative 

Condition

Contributing 

Watershed

Area

(square miles)

Average 

Annual 

Sediment

Delivery*

(acre-feet)

Sediment

Concentration*

(parts per 

million)

Percent

Change in 

Annual 

Sediment

Delivery from 

Baseline

Percent 

Change in 

Sediment

Concentration 

from Baseline

No action –

as modeled

14 16.0 16,407 – –

No action –

as sampled

– – 4,800 – 33,800 – –

Proposed action 6.82 7.84 16,194 −51.3 −1.3%

Phased Tailings 7.06 8.12 16,210 −49.6 −1.2%

Barrel 11.33 10.88 13,686 −32.4 −16.5%

Barrel Trail 8.65 9.95 16,273 −38.2 −0.8%

ScholefieldMcCleary10.35 11.90 16,317 −26.1 −0.5%

Sources: Zeller (2012; 2010a; 2010b).

* Based on sediment delivery to the USGS gaging station in Lower Barrel Canyon.

Based on Tetra Tech (Zeller 2010a, 2010b, 2012) baseline sediment delivery modeling, the average 

amount of sediment expected from the types of watersheds found within the project area is 1.15 acrefeet of sediment per year per square mile of watershed. The estimated decrease in sediment yield 

from disturbed areas upstream of the USGS gaging station ranges from approximately 26 to 51 

percent, depending on the action alternative. This decrease in sediment yield would primarily be the 

result of the changes in the contributing watershed area, which would be caused by capture from 

mine facilities. 

All action alternatives would result in a reduction in sediment yield from the Barrel Canyon 

watershed. Overall sediment concentrations would not change substantially (approximately 13,600 to 

16,300 mg/L) and would remain within the range observed in stormwater samples collected from 

Barrel Canyon (up to 33,000 mg/L). The redesigned stormwater management for the Barrel 

Alternative would reduce the sediment concentration more than the other alternatives; with respect to 

total suspended sediment concentrations, this reduction in sediment yield would be beneficial in 

maintaining the water quality of ephemeral storm flows. No change in the geomorphology of the 

channel is expected to occur as a result of this change in sediment yield for any alternatives. 

Monitoring Intended to Assess Potential Geomorphological Impacts

In consideration of the uncertainty associated with predicting geomorphological changes, a 

monitoring components have been incorporated into the mitigation and monitoring plan 

(see appendix B for full details). The monitoring includes:

• Sediment transport monitoring (FS-SR-05). The movement of sediment between the mine 

facility and SR 83 would be monitored to identify areas of scour or aggradation that could be 

caused by changes in sediment load and surface flow.

Location and Duration of Surface Water Quality Impacts

The reach of Barrel Canyon that could be affected is approximately 2.5 miles long, from the USGS 

gaging station to the confluence with Davidson Canyon. The bridge at SR 83, just downstream of the 

Final Environmental Impact Statement for the Rosemont Copper Project 467
Chapter 3. Affected Environment and Environmental Consequences

gaging station, has been identified as a point of concern for potential changes in geomorphology of 

the channel, scour in particular. This reach of Barrel Canyon represents approximately 23 acres of 

stream channel that could be impacted by the reduction in sediment load. However, according to 

Patterson and Annandale (2012), the presence of sediment on bedrock near the bridge indicates the 

abundant availability of sediment in the system, and the bridge serves as a grade control that limits 

the erosion capacity of the stream. The reach of Davidson Canyon that could potentially be affected is 

approximately 14 miles long, from the confluence with Barrel Canyon to the confluence with 

Cienega Creek. This reach of Davidson Canyon represents approximately 234 acres of stream 

channel that could be impacted by the reduction in sediment load. The duration of these impacts 

would be throughout the active mine life, gradually reducing as areas are revegetated and 

reclaimed. A lesser level of impact would be expected to occur in perpetuity. While some ephemeral 

stream flow and sediment yield would be expected to return to Barrel and Davidson Canyons 

postclosure because of the gradual reduction in active stormwater control, the mine pit would always 

act to capture precipitation, and hydrologic conditions would not be expected to return to premine 

levels. The analyses conducted indicate that these impacts would not occur downgradient of the 

natural bedrock control into the lower reaches of Davidson Canyon. The bedrock control is located in 

Barrel Canyon upstream of its confluence with Davidson Canyon; it is made of erosion-resistant 

bedrock and would continue to control the stream gradient for an extremely long time (Patterson and 

Annandale 2012; Rosemont Copper Company 2012a).

Potential for Acid Rock Drainage

Acid rock drainage is a natural process that takes place as mineralized rock surface areas are oxidized 

when they are exposed to weathering and when the resulting stormwater runoff, or drainage, from the 

rock becomes acidic. As the drainage becomes more acidic, it has an increased capacity to leach out 

other elements, particularly metals, from the rock. This can result in polluted runoff, which can 

impact the quality of surrounding surface water bodies. Acid rock drainage occurs naturally in the 

environment at a very slow pace, but mining activities accelerate the process by exposing a large 

amount of rock to weathering in a short amount of time. Additionally, mine-processed rock and 

fractured waste rock have an increased amount of exposed surface area that can come into contact 

with water and oxygen.

Alkalinity in mine runoff water primarily comes from dissolved carbonate. When mine water has a 

pH greater than 4.5, it is said to be alkaline and has the capacity to neutralize acid. However, it is the 

net alkalinity (alkalinity greater than acidity) or net acidity (acidity greater than alkalinity) of the 

water that determines whether the mine rock contains enough alkalinity to neutralize the mineral 

acidity before it is eventually used up and comes to equilibrium (Metesh et al. 1998).

At the Rosemont Copper Mine, the ore is contained primarily within limestone and skarn 

(metamorphosed limestone) rocks, with minor amounts in quartz monzonite porphyry (igneous), 

andesite (volcanic), and arkose (sandstone) rocks. Waste rock would also be composed of these same 

rock types. Geological materials at the project area were characterized using a variety of geochemical 

analyses; see the “Groundwater Quality and Geochemistry” resource section for a full summary of all 

tests conducted.

In general, the total sulfide content of host rock at the project area is low, less than 3 percent. 

Although sulfide mineralization is present at the project area, acid-neutralizing limestone (calcium 

carbonate) is abundant (Tetra Tech 2010b, 2010c). Additionally, topsoil samples were collected and 

analyzed for their acid-generating potential (Tetra Tech 2010e). In these static tests, 11 percent of the 

topsoil samples (2 out of 19) and 5 percent of the rock samples (11 out of 226) indicated the potential 

468 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

for acid generation. Static testing is generally considered a preliminary screening analysis, with more 

reliable kinetic testing conducted if there are indications that there may be acid-generating potential. 

Sixteen rock samples were selected for further kinetic testing. When the majority of these materials 

were subjected to long-term humidity cell testing, the leachate pH remained neutral, and the trends in 

sulfate, iron, and acidity provided no indication of sulfide oxidation. One rock type, Bolsa Quartzite, 

was shown to produce net acidity during humidity cell testing as a result of sulfide oxidation.

At the conclusion of the proposed project, final reclamation of the project area would include 

reclamation and closure of the facilities and final regrading and revegetation of the “Rosemont 

Ridge” landform. The landform would consist of waste rock from the open pit, a closed heap leach 

facility (except under the Barrel Alternative), and a closed dry-stack tailings facility; these facilities 

would all be buttressed and capped with inert or acid-neutralizing waste rock. Direct precipitation and 

runoff from the landform have the potential to generate acid rock drainage because sulfide minerals, 

such as those proposed to be mined, have the potential to generate sulfuric acid when exposed to 

water and air. Based on the overall abundance of potential acid-neutralizing rock types, as defined by 

geochemical sampling and testing, it is believed that the naturally occurring lime content of the orebearing and waste rock material would neutralize any sulfuric acid produced in the processed ore 

(tailings) or waste rock and that the generation of acid rock drainage is unlikely (Tetra Tech 2010b). 

Because the tailings and heap leach facilities, as well as any waste rock with potentially acidgenerating material, would be buttressed and capped with inert or acid-neutralizing rock, the potential 

for acid rock drainage is considered low. Note that independent peer review of the Rosemont Copper 

expert reports concurred with this conclusion (Ugorets and Day 2010; Hoag, Bird and Day 2012; 

Hoag, Sieber and Rasmussen 2012). 

Rosemont Copper has calculated predictions of the tonnages of each rock type by year that would be 

encountered as mining progresses and has calculated the percentage of rock that has been 

characterized as either non-potentially acid generating or potentially acid generating (Williamson 

2012). The percentage of total potentially acid-generating waste mined relative to the total waste 

mined is predicted for each year beginning in year 1 of active mining and continuing to year 21 of 

active mining. In any given year, the percent of potentially acid-generating waste mined averages 9 

percent a year, with the highest amount, 16 percent, being predicted for year 4 of active mining.

Also calculated was the weighted average net neutralization potential for waste rock by year during 

active mining. The net neutralization potential is the difference between the acid neutralization 

potential and the acid-generating potential expressed as tons of calcium carbonate equivalent per 

kilotons of sample. In accordance with ADEQ (2004) best available demonstrated control technology

guidance, if the net neutralization potential is less than −20, it can be considered acid generating; 

between −20 and +20, the waste has the potential to form acid, and when the net neutralization 

potential is above +20, the waste can be generally considered non-acid generating. Calculated net 

neutralizing potential for waste rock mined per year ranges from 75 to more than 500, with a running 

annual average value of 225 for the projected life of the mine. Thus, the waste rock as a whole can 

generally be considered non-acid generating.

Encapsulation of rock believed to have acid rock drainage potential and continual testing of waste 

rock for acid rock drainage potential are design elements of the proposed action and all action 

alternatives that would mitigate potential acid rock drainage. The waste rock would be managed 

during mining by monitoring potentially acid-generating and non-acid-generating materials and 

placing materials in designated areas. Modeling results show that Bolsa Quartzite was the only nonore rock type that indicated a net capacity to generate acidic drainage (Tetra Tech 2010b, 2010c).

Final Environmental Impact Statement for the Rosemont Copper Project 469
Chapter 3. Affected Environment and Environmental Consequences

Under the requirements of the aquifer protection permit, potentially acid-generating waste rock would 

not be used for construction of the perimeter buttresses, tailings starter buttresses, drains, or channel 

grading fills but instead would be placed in the interior of waste rock facility and would be 

encapsulated by the acid-neutralizing and non-acid-generating waste materials (Tetra Tech 2009a). 

Inert or acid-neutralizing waste rock shall be used to build haul roads and buttresses around waste 

rock and tailings facilities to provide a buffer zone that would isolate potentially acid-generating 

materials from water infiltration and discharge. 

The above design is intended to eliminate or reduce the potential for any acid rock drainage; proper 

implementation of this design and placement of waste rock and tailings is critical. The methodology 

for stacking and placing waste rock and tailings was submitted to the ADEQ as part of the aquifer

protection permit application (Krizek 2011). The aquifer protection permit was issued to Rosemont 

Copper on April 3, 2012.

Routine inspections of the waste rock facility would be performed from the time construction begins 

and would continue after significant rainfall events for the term of the ADEQ Aquifer Protection 

Permit. Inspections would include a visual assessment of the integrity of the waste rock facility. 

Additionally, monitoring at the compliance point dam or sediment control structures located 

downgradient of the waste rock facility shall serve as a final control point where water would be 

temporarily detained for testing as required under the stormwater permit. 

The compliance point dam, as detailed in the following section, would be the final sediment pond 

located at the outlet of Barrel Canyon. The location for the compliance point dam was chosen because 

it is the downgradient edge of the collective drainages associated with project activities. It is here that 

final water quality testing for contaminants of concern (as required by the stormwater permit) would 

be performed prior to release into the natural channel (Tetra Tech 2009a). 

Because inert or acid-neutralizing waste rock would be used to build buttresses around waste rock 

and tailings facilities to provide acid buffering, there is little potential for acid rock drainage. Proper 

implementation of the waste rock stack design and routine inspections of the waste rock facility are 

components of the ADEQ Aquifer Protection Permit. Modeling and geochemical analysis indicate 

that acid rock drainage is unlikely to occur. However, if acid rock drainage were to occur, it would be 

identified early during the planned testing of stormwater under the stormwater permit.

The acid base accounting tests on composite samples (Tetra Tech 2010b), subsequent kinetic testing 

(Tetra Tech 2010c), assessment of the ability of the waste rock to control acid rock drainage, and

implementation of the measures required under the aquifer protection permit indicate that there is a 

low probability for impacts to surface water quality to occur from acid rock drainage (Tetra Tech 

2010c).

In June 2012, further refinements to the Barrel Alternative resulted in removal of the heap leach 

facility. As a result, some ore that otherwise would have been piled in the lined heap leach facility 

would be placed in the unlined waste rock facility. The Coronado requested that Rosemont Copper 

revise the percentages of potentially acid-generating waste rock due to this change, as well as the 

overall calculation of neutralization potential. Revised calculations indicate minor changes in 

percentage and timing of placing waste rock but nothing that changes the overall conclusions. For the 

refined Barrel Alternative without the heap leach facility, in any given year the percentage of 

potentially acid-generating waste mined that is likely to produce acid drainage averages 10 percent a 

year, with the highest amount, 16 percent, still being predicted for year 4 of active mining. Similarly, 

470 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

calculated net neutralizing potential for waste rock mined per year still ranges from 75 to more than 

500, with a running annual average value of 225 for the projected life of the mine (Rosemont Copper 

Company 2012e). 

Monitoring Intended to Assess Potential Acid Rock Drainage

In consideration of public concerns regarding the uncertainty associated with interpreting the 

potential for acid rock drainage, three monitoring components have been incorporated into the 

“Mitigation and Monitoring Plan” (see appendix B for full details). Two of these are required under 

the permits that have been issued to Rosemont Copper:

• Reduction of the potential for acid generation from tailings and waste rock (OA-GW02). Geochemical testing has indicated that there is adequate neutralization capacity in the 

overall waste rock composition to prevent potential acid generation. However, proper 

placement of the waste rock is necessary to allow this buffering capacity to be effective. This 

mitigation involves requirements for the segregation and encapsulation of potentially acidgenerating waste rock with rock that has buffering capabilities in order to reduce the risk of 

potential acid generation. This is required under the aquifer protection permit issued to 

Rosemont Copper. In comments, the ADEQ confirmed that any synthetic precipitation 

leachate procedure testing performed that indicates concentrations of metals above aquifer 

water quality standards would require segregation of that waste rock.

• Detention and testing of stormwater (OA-SW-01). This mitigation measure requires 

detention and testing of stormwater quality from perimeter waste rock buttress areas for water 

quality testing prior to flowing downstream of the mine site. This would also allow for a 

reduction in suspended sediment in stormwater flows before flowing downstream. This is 

required under the stormwater permit issued to Rosemont Copper.

The Coronado has required an additional monitoring measure in order to ascertain that the reactivity 

of the waste rock pile is fully understood in order to ensure an adequate closure design is 

implemented. 

• Additional waste rock and tailings characterization (FS-GW-03). During operations, 

additional waste rock characterization tests, above and beyond those required by the aquifer

protection permit, would be required to be conducted on waste rock and tailings. This 

additional analysis includes requirements for humidity cell testing, whole rock chemistry, and 

mineralogical analysis in addition to the acid-base accounting and leachate testing already 

being conducted for the aquifer protection permit.

Potential for Other Contaminants in Runoff

Regardless of the acid generation potential of the waste rock, other naturally occurring contaminants 

could potentially occur in surface water when waste rock comes into contact with stormwater. 

The heap leach and dry-stack facilities would not be exposed to surface runoff, nor would the plant 

site or processing facilities. Precipitation falling on these areas during operations would be fully 

contained and not released downstream, and postclosure, the heap leach (except for the Barrel 

Alternative) and dry-stack tailings facility would be capped with waste rock. However, during 

operations and postclosure, the waste rock facility would be exposed to surface runoff that leaves the 

project area and could have the potential to impact downstream surface water quality. Therefore, it is 

appropriate to analyze the potential water quality resulting from contact between precipitation and the 

waste rock. 

Final Environmental Impact Statement for the Rosemont Copper Project 471
Chapter 3. Affected Environment and Environmental Consequences

Public comments raised the concern for elevation of nitrogen concentrations in groundwater and 

surface water due to the residue from the use of ammonium nitrate on site. This potential is analyzed 

in the “Groundwater Quality and Geochemistry” resource section of chapter 3 and is not reiterated 

here, although applicable to surface water quality.

A prediction of water quality from precipitation contacting waste rock can be based on the results of 

leachate testing—specifically, tests conducted using the synthetic precipitation leaching procedure.

This testing was conducted by Rosemont Copper in order to support the aquifer protection permit 

process; see the “Groundwater Quality and Geochemistry” resource section for a full summary of all 

tests conducted. A total of 67 of these tests was conducted on a variety of core samples that represent 

the major waste rock types to occur in the waste rock facility. The prediction of runoff water quality 

was made by averaging the sample results by waste rock type and then calculating a weighted 

average based on the percentage of each waste rock type to be present in the waste rock facility (table 

105). Full details of the assumptions used in this analysis and detailed discussion of the uncertainties 

involved can be found in the project record (SWCA Environmental Consultants 2013k).

Barrel Canyon has applicable surface water quality standards: the acute standard for Aquatic and

Wildlife-Ephemeral, and the Partial Body Contact standard. Predicted water quality for runoff from 

waste rock does not exceed any applicable water quality standards in Barrel Canyon, with the 

exception of dissolved silver. The predicted concentration of dissolved silver in stormwater runoff 

from the waste rock facility is 0.0025 mg/L, compared with the surface water quality standard of 

0.00081 mg/L.

A total of 18 stormwater samples has been collected from Barrel Canyon and its tributaries and 

analyzed for dissolved silver (see table 102). For 16 of these samples, the laboratory detection 

limits are greater than the surface water quality standard; therefore, it is not possible to use these 

samples to assess the current ability of existing stormwater to meet surface water quality standards.

The remaining two samples of existing stormwater quality in Barrel Canyon and its tributaries exceed 

the surface water quality standard for dissolved silver under existing conditions.

There are two mitigation measures that make this estimate of water quality a conservative prediction 

(SWCA Environmental Consultants 2013k). The most important is the requirement for Rosemont 

Copper to continually characterize waste rock during operations and segregate any waste rock that 

shows acid generation potential or potential to cause water quality problems. This testing is required 

under the Arizona Aquifer Protection Permit (Krizek 2011). Rosemont Copper is prohibited by the 

permit from placing problematic waste rock on the perimeter buttresses or in water conveyance 

channels. The prediction of runoff water quality assumes the ability of all waste rock types to interact 

equally with stormwater; in reality, those waste rock types that are most likely to contribute to water 

quality problems, including dissolved silver, would not have an opportunity to contact stormwater.

In addition, during operations and postclosure, stormwater would not be allowed to flow off of any 

areas of the waste rock facility until reclamation has been completed. During reclamation, a cover of 

growth media derived from onsite soils would be placed over the waste rock. For most of the waste 

rock facility, stormwater would be in contact with this soil, not with waste rock. However, some 

contact between stormwater and waste rock is still likely to occur in the stormwater conveyance 

channels, which would likely not have any soil cover. Geochemical tests have been conducted on soil 

samples as well as waste rock (see table 105). Predicted water quality for runoff from soil also

exceeds water quality standards in Barrel Canyon for dissolved silver, as well as total lead and 

dissolved mercury. 

472 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Concerns have also been raised for the potential for seepage from the tailings facility to enter the 

aquifer and “daylight” or return to the surface in Barrel Canyon downstream of the mine. The impacts 

of and potential for this occurrence are analyzed in the “Groundwater Quality and Geochemistry” 

resource section. Similar geochemical tests (i.e., synthetic precipitation leaching procedure) for 

tailings samples have been included in table 105 for comparison. Predicted water quality in the event 

tailings seepage were to appear in Barrel Canyon exceeds applicable surface water quality standards 

for dissolved silver, dissolved cadmium, total and dissolved lead, dissolved mercury, and total 

selenium.

The three predictions of water quality shown in table 105 represent a range of possible outcomes for 

runoff in Barrel Canyon, each with different probabilities of occurring. It is known for certain that 

stormwater would contact both soils and waste rock in some manner. The most likely scenario would 

involve stormwater contacting both soil cover (on the slopes of the waste rock facility) and waste 

rock (in the conveyance channels of the waste rock facility). The percentage contribution from each 

source is not possible to easily predict, nor is it possible to predict the beneficial effects of waste rock 

segregation. Dissolved silver is the only constituent that would be likely to exceed surface water

standards under any waste rock/soil mixing scenario. As noted, dissolved silver already exceeds 

surface water standards in existing runoff in Barrel Canyon. Tailings seepage would have more 

problematic constituents if it occurred, but as analyzed in the “Groundwater Quality and 

Geochemistry” resource section, the probability of tailings “daylighting” in Barrel Canyon is low.

Requirements for Control of Water Quality under Stormwater Permit

Discharge of stormwater that would exceed the surface water quality standard for any contaminant, 

including dissolved silver, lead, and mercury, in Barrel Canyon is prohibited under Rosemont 

Copper’s stormwater permit. All discharges to WUS, including stormwater discharges from mining 

operations, require permitting under Section 402 of the CWA. In Arizona, Section 402 is administered 

by the ADEQ through the Arizona Pollutant Discharge Elimination System program. Rosemont 

Copper was issued authorization to discharge stormwater under the Arizona Pollutant Discharge 

Elimination System Mining Multi-Sector General Permit by ADEQ on February 4, 2013. Rosemont 

Copper is required to maintain coverage under this permit (or other applicable Arizona Pollutant 

Discharge Elimination System permit) until the site has been released from applicable State or 

Federal reclamation requirements.

The permit requires Rosemont Copper to select, design, install, and implement control measures 

(including best management practices), as appropriate, to ensure the discharge meets applicable water 

quality standards. The permit does not dictate the specific control measures that must be 

implemented; Rosemont Copper is able to modify control measures as needed, provided that 

stormwater discharges meet standards.

In order to determine whether water quality standards are met, the permit requires water quality 

monitoring of stormwater discharges at any outfall locations (i.e., where the facility discharges into a 

WUS, including dry washes). Analyses must be conducted for pH, hardness, and metals (antimony, 

arsenic, beryllium, cadmium, copper, iron, lead, mercury, nickel, selenium, silver, zinc), as shown in 

table 105. If at any time the Rosemont Copper becomes aware, or ADEQ determines, that the 

facility’s discharge causes or contributes to an exceedance of an applicable water quality standard, 

then Rosemont Copper is required to take corrective action, document the corrective actions, and 

report the corrective actions to ADEQ. This may include corrective actions even for constituents that 

are naturally elevated in stormwater runoff.

Final Environmental Impact Statement for the Rosemont Copper Project 473
Chapter 3. Affected Environment and Environmental Consequences

It should be noted that although coverage under the Multi-Sector General Permit has been issued by 

ADEQ, ADEQ has yet to conduct a review of the stormwater pollution prevention plan (Rosemont 

Copper Company 2013). It is under ADEQ’s jurisdiction to determine whether or not the planned 

stormwater controls contained in the stormwater pollution prevention plan would be protective of 

water quality in downstream waters. Upon review of the plan, ADEQ may require additional 

stormwater controls or may require coverage under a different stormwater permitting program.

Potential for Meeting Narrative Surface Water Quality Standards

As described earlier, narrative surface water quality standards have been established by the State of 

Arizona in addition to numeric standards. With regard to narrative surface water quality standards, 

water quality described in table 105 is not expected to contain oil or grease; is not expected to be 

toxic to humans, animals, plants, or other organisms; and is not expected to discolor or create an 

off-taste or odor. The potential to meet narrative standards for taste and odor can be assessed by 

comparing surface water quality data in table 105 with the EPA Secondary Drinking Water Standards. 

The EPA secondary standards are not applicable to surface runoff in any way, but they are useful for 

assessing impacts to taste and odor and other aesthetic concerns. These nonmandatory standards were 

established for 15 constituents that could cause offensive taste, odor, color, corrosivity, foaming, or 

staining in drinking water. These constituents do not present a risk to human health, and the EPA 

Secondary Drinking Water Standards are not enforceable. Rather, they are guidelines for suggested 

maximum contaminant levels that have been set with the aesthetic quality of water in mind 

(U.S. Environmental Protection Agency 2012h).

Based on the analysis results presented in table 105, current secondary maximum contaminant levels 

are not exceeded for chloride, copper, fluoride, iron, manganese, silver, sulfate, total dissolved solids, 

or zinc. The predicted concentration of aluminum in stormwater runoff (0.2050 mg/L) exceeds the 

secondary maximum contaminant level (0.05 to 0.20 mg/L). Elevated aluminum levels can cause 

discoloration of water. Aluminum levels as high as 400 mg/L have been observed in stormwater 

samples collected from Barrel Canyon and its tributaries; in fact, 36 of 38 existing stormwater 

samples exceeded the secondary maximum contaminant level for aluminum.

Sediment Control Measures

Application to ADEQ for coverage under the General Permit for Stormwater Discharges requires the 

following: (1) analytical monitoring of stormwater discharges for parameters specific to the coppermining sector; and (2) development of a stormwater pollution prevention plan to outline best 

management practices that would be used to minimize the discharge of pollutants in stormwater from 

the site. The stormwater pollution prevention plan for the project identifies the stormwater outfalls, 

control measures, monitoring schedule, and analytical parameters that would be monitored as part of 

the project (Rosemont Copper Company 2013).

Every action alternative proposes to employ methods during the premining and active mining phases 

to control sediment loading off the mine site; the methods vary by alternative but generally have the 

same objectives and effectiveness. For the Barrel Alternative, sediment structures would be installed 

throughout the mine site to temporarily capture stormwater for the purpose of reducing total 

suspended solids in stormwater runoff. These basins would be unlined and sized according to the 

upstream disturbed catchment area. They would be designed out of porous waste rock and serve as 

temporary structures where stormwater velocities would be slowed to allow for settling sediments

before the stormwater seeps through the rock fill and progresses downstream. 

474 Final Environmental Impact Statement for the Rosemont Copper Project
Final Environmental Impact Statement for the Rosemont Copper Project 475

Table 105. Predicted stormwater runoff water quality (in mg/L) and applicable surface water standards 

Canyon

Predicted Runoff

Water Quality from 

Waste Rock

(mg/L)

Predicted Runoff

Water Quality from 

Soil Cover 

(mg/L)

Predicted Tailings 

Seepage Water 

Quality

(mg/L)

Surface Water 

Standard for

Partial Body 

Contact 

(mg/L)

Surface Water 

Standard for

Aquatic and Wildlife

Ephemeral – Acute 

(mg/L)*

Aluminum (total)† 0.2050 0.4870 0.0800 No standard No standard 

Antimony (total) 0.0100 0.0052 0.0100 0.747 No standard 

Arsenic (dissolved) 0.0130 0.0335 0.1687 No standard 0.44 

Arsenic (total) 0.0130 0.0335 0.1687 0.28 No standard 

Barium (total) 0.0071 0.0047 1.6680 98 No standard 

Beryllium (total) 0.0010 0.0010 0.0010 1.867 No standard 

Boron (total) Not sampled Not sampled Not sampled 186.667 No standard 

Cadmium (total) 0.0010 0.0010 0.0840 0.7 No standard 

Cadmium 

(dissolved)

0.0010 0.0010 0.0840 No standard 0.01049 

Calcium (total) 16.42 6.6 10.9 No standard No standard 

Chloride (total)† 0.9634 0.5357 0.3950 No standard No standard 

Copper (total)† 0.0085 0.0067 0.0050 1.3 No standard 

Copper (dissolved) 0.0085 0.0067 0.0050 No standard No standard 

Fluoride (total)† 0.3316 0.2063 1.27 140 No standard 

Iron (total)† 0.1638 0.2433 0.0300 No standard No standard 
Predicted Runoff

Water Quality from 

Waste Rock

(mg/L)

Predicted Runoff

Water Quality from 

Soil Cover 

(mg/L)

Predicted Tailings 

Seepage Water 

Quality

(mg/L)

Surface Water 

Standard for

Partial Body 

Contact 

(mg/L)

Surface Water 

Standard for

Aquatic and Wildlife

Ephemeral – Acute 

(mg/L)*

Lead (total) 0.0048 0.0151 0.1692 0.015 No standard 

Lead (dissolved) 0.0048 0.0151 0.1692 No standard 0.05657 

Manganese (total)† 1.064 0.0161 0.0020 130.667 No standard 

Magnesium (total) 0.0069 0.8167 0.2000 No standard No standard 

Mercury (total) 0.0002 0.0101 0.2000 0.28 No standard 

Mercury 

(dissolved)

0.0002 0.0101 0.2000 No standard 0.005 

Molybdenum 

(total)

0.0405 0.0117 0.0750 No standard No standard 

Molybdenum

(dissolved)

0.0405 0.0117 0.0750 No standard No standard 

Nickel (total) 0.0050 0.0050 0.0050 28 No standard 

Nickel (dissolved) 0.0050 0.0050 0.0050 No standard 2.116 

Nitrate + Nitrite 0.0310 Not sampled 0.0400 233.333 (NO2)

3733.333 (NO3)

No standard 

Potassium (total) 2.933 1.503 0.7400 No standard No standard 

Selenium (total) 0.0200 0.0200 0.0967 4.667 0.033 

Silver (total)† 0.0025 0.0025 0.0025 4.667 No standard 

Silver (dissolved) 0.0025 0.0025 0.0025 No standard 0.00081 

Sodium (total) 4.167 6.1 2.395 No standard No standard 

476 Final Environmental Impact Statement for the Rosemont Copper Project
Final Environmental Impact Statement for the Rosemont Copper Project 477

Predicted Runoff

Water Quality from 

Waste Rock

(mg/L)

Predicted Runoff

Water Quality from 

Soil Cover 

(mg/L)

Predicted Tailings 

Seepage Water 

Quality

(mg/L)

Surface Water 

Standard for

Partial Body 

Contact 

(mg/L)

Surface Water 

Standard for

Aquatic and Wildlife

Ephemeral – Acute 

(mg/L)*

Sulfate (SO4) 

(total)†

33.13 1.98 13.475 No standard No standard 

Total dissolved 

solids†

78.41 Not sampled 39.5 No standard No standard 

Thallium (total) 0.0082 0.0028 0.0075 0.075 No standard 

Uranium (total) 0.0022 0.0034 Not sampled 2.8 No standard 

Zinc (total) † 0.0058 0.0066 0.0050 280 No standard 

Zinc (dissolved) 0.0058 0.0066 0.0050 No standard 0.565 

Source: SWCA Environmental Consultants (2013k).

Notes:

Predicted values for dissolved and total concentrations are the same, based on synthetic precipitation leaching procedure results (see SWCA Environ

(2013k) for discussion).

Shading indicates that the constituent is required to be sampled for under the stormwater permit.

Bold indicates a predicted exceedance of the designated surface water quality standards.

Range of results shown is for all stormwater samples collected in Barrel Canyon and its tributaries, which includes samples from 8 locations on 15 d

ND – Not detected, with range of laboratory detection limits shown in parentheses.

* This constituent is subject to surface water quality standards for this designated use based on dissolved concentrations. The ADEQ has developed 

constituent, and the standards vary, depending on the designated use and measured hardness of the water taken during the sample (see appendix A (

Dissolved standards are based on a calculated hardness of 45 mg/L CaCO3, which is based on a weighted average calcium concentration of 16.42 m

average magnesium concentration of 1.06 mg/L.

† A secondary drinking water standard maximum contaminant level has been established for these constituents. 
Chapter 3. Affected Environment and Environmental Consequences

The sediment structures would be located based on topography, and as the mining operation 

progresses some structures may be abandoned and others constructed downstream. Additionally, two 

permanent sediment control structures, one in the Barrel Canyon drainage and one in Trail Creek 

drainage, would be placed just downstream of the wraparound diversion channels at the toe of the 

slope.

For the remaining action alternatives, the primary stormwater control feature includes sediment

basins located on top of tailings and waste rock benches. For the Phased Tailings and Barrel Trail

Alternatives, flowthrough underdrains designed to carry stormwater offsite would incorporate starter 

embankments designed to filter sediment before it enters the drain and protective geotextile liners in 

the drain to filter out sediment before stormwater is released in the natural channel. The Phased 

Tailings and Barrel Trail Alternatives would also incorporate a geomembrane covering for the 

underdrains to prevent comingling of stormwater and tailings seepage.

A small dam, referred to as the compliance point dam, has been designed for temporary impoundment 

at the lower end of the Barrel Canyon drainage before stormwater is slowly released into the natural 

drainage. This dam would be built under all alternatives, but for the Barrel Alternative there would be 

two such dams, one on each drainage, receiving discharge from the waste rock and tailings facilities. 

This rock dam would be approximately 6 feet tall and has been designed as a porous, flowthrough 

sediment pond with a relatively small capacity of 2 acre-feet. It would be constructed during the 

premining phase using inert or acid-neutralizing waste rock and would provide the last point of 

detention in the series of stormwater controls and a point for surface water flows to be monitored and 

tested; the Arizona Pollutant Discharge Elimination System permitting program has chemical 

and sediment content monitoring requirements for any stormwater that is discharged offsite. 

The compliance point dam would be constructed as an unlined embankment, and normally, the area 

behind the embankment would be empty. Water would be temporarily impounded behind the dam 

during storm events and then would be slowly released downstream through the porous rock-fill 

embankment. The design of the compliance point dam is such that large flows are expected to overtop 

and occasionally destroy the dam. If the dam were damaged by a storm event, it would be repaired 

and rebuilt as necessary. Because the compliance point dam would be constructed of inert rock, has a 

small capacity, would be rebuilt, and is not considered a dam under the jurisdiction of dam safety 

regulations, any possible effects of the dam’s being destroyed are considered insignificant. Depending 

on reclamation success of the facility slopes, the compliance point dam would be evaluated and 

removed during the final reclamation and closure phase under the CWA permitting program in place 

at that time.

Cooperating agencies have commented on the potential for unregulated discharge of stormwater that 

has been in contact with ore bodies and mine processing facilities in the event that the compliance 

point dam is overtopped and destroyed, which could happen with some frequency. This concern is 

based on a misunderstanding of the purpose of the compliance point dam. The stormwater reaching 

the compliance point dam is not halted or permanently retained by the dam in any way and will flow 

downstream in any case. The dam allows for some settling of sediment, detains stormwater 

temporarily, and allows for a convenient location to collect stormwater samples. The dam does not, 

however, prevent stormwater from flowing downstream.

In addition, the stormwater reaching the dam would not at any time have contacted tailings, ore

stockpiles, or processing facilities. Stormwater from those areas is completely retained onsite in 

various stormwater ponds and is not allowed to discharge downstream under any scenario.

Stormwater reaching the compliance point dam has only been in contact with waste rock, either 

478 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

flowing off of the perimeter buttress, the waste rock facility, or, once closed, the waste rock cap over 

the tailings facility.

Conclusions of Ability to Meet Surface Water Quality Standards

Based on available information, the following conclusions can be drawn from the analysis regarding 

the ability of surface water quality to meet both numeric and narrative water quality standards:

• Geochemical testing conducted for waste rock characterization indicates that the potential for 

acid rock drainage to occur is low.

• Applicable surface water standards have been exceeded in at least some stormwater samples 

in Barrel Canyon and its tributaries for total silver, total arsenic, total and dissolved copper, 

total lead, total selenium, and total thallium. 

• Predictions of runoff water quality from the tailings and waste rock facilities from all action 

alternatives is not expected to degrade the existing surface water quality in the analysis area, 

when consideration is given to mitigation measures. Predicted concentrations of dissolved 

silver exceed surface water standards; concentrations of dissolved silver currently exceed 

standards in some stormwater samples collected from Barrel Canyon and its tributaries. 

• Mitigation measures include the required segregation of problematic waste rock under the 

aquifer protection permit, and the placement of growth media on top of waste rock.

• Under the stormwater permit, discharge of stormwater containing concentrations of any 

constituents above surface water quality standards in Barrel Canyon would be prohibited. 

Rosemont Copper would be required to implement control measures to reduce concentrations 

if occurring. 

• Narrative standards are predicted to be met, with the exception of aluminum, which is already 

present in most of the existing stormwater samples collected from Barrel Canyon and its 

tributaries.

• Permit requirements would also prohibit any discharges that occur to surface waters in Barrel 

Canyon from causing or contributing to a decrease in the existing water quality of the 

downstream Outstanding Arizona Waters in Davidson Canyon (AAC R-18-11-101). Potential 

impacts to the Outstanding Arizona Waters are analyzed in the “Seeps, Springs, and Riparian

Areas” resource section of this chapter.

• Because the action alternatives are designed to contain stormwater contacting processing 

facilities, tailings, or ore onsite and because monitoring protocols would be put in place at the 

point of compliance, the potential for other contaminants to enter surface water is considered 

low. 

Proposed Action and Action Alternatives 

With the exception of the varying amount of impacts associated with each alternative as listed in 

tables 103 and 104, there are no further impacts solely specific to a particular action alternative.

Cumulative Effects

The analysis area for cumulative effects on surface water quality is identical to that described in the 

“Surface Water Quantity” resource section, as are the reasonably foreseeable actions that could 

contribute to a cumulative impact to surface water quality. 

Final Environmental Impact Statement for the Rosemont Copper Project 479
Chapter 3. Affected Environment and Environmental Consequences

The reasonably foreseeable actions discussed in the “Surface Water Quantity” resource section all 

have not only the potential to change the amount of surface water flows in the analysis area but would 

represent additional disturbance that could increase erosion in the analysis area, which would impact 

surface water quality. As a whole, these changes are unlikely to be significant when assessed in the 

context of the watershed as a whole. 

Climate Change

With regard to surface water quality, the climate change feature of concern is the predicted increase in 

extreme rainstorms and flooding across the desert Southwest. This predicted change in weather 

patterns could have an effect on the quality of stormwater runoff. An increase in more extreme 

rainstorms and flooding would create higher volumes of surface flow passing through the ephemeral 

channels in a shorter period of time. This would increase the potential for erosion and sediment-laden 

flows. The deposition and aggradation of sediment associated with extreme flooding would affect 

channel geomorphology and increase the potential for channel downcutting.

Mitigation Effectiveness 

Mitigation and Monitoring – Forest Service

• Growth media salvage and application (FS-SR-01). In order to support reclamation

activities, soil and other growth media would be salvaged, stored, and applied to the surface 

of the perimeter waste rock buttress and waste rock and tailings facilities in order to facilitate 

revegetation.

• Revegetation of disturbed areas with native species (FS-SR-02). Reclamation efforts 

would include revegetation of native grasses, forbs, shrubs, and trees on areas disturbed by 

mining and mine related activities. Revegetation would include detection and treatment of 

invasive weed species.

• Concurrent placement of perimeter buttress (FS-SR-03). Placement of the perimeter 

buttress allows reclamation activities to take place earlier, concurrent with mine operations. 

• Sediment transport monitoring (FS-SR-05). The movement of sediment between the mine 

facility and SR 83 would be monitored to identify areas of scour or aggradation that could be 

caused by changes in sediment load and surface flow.

• Additional waste rock and tailings characterization (FS-GW-03). During operations, 

additional waste rock characterization tests, above and beyond those required by the aquifer

protection permit, would be required to be conducted on waste rock and tailings. This 

additional analysis includes requirements for humidity cell testing, whole rock chemistry, and 

mineralogical analysis in addition to the acid-base accounting and leachate testing already 

being conducted for the aquifer protection permit.

• Periodic update and rerunning of pit lake geochemistry model throughout life of mine 

(FS-GW-04). This measure requires that the geochemistry model for the pit lake be rerun 

periodically, utilizing the most recent geologic and geochemical information obtained during 

operations. The model would be used to predict potential future water quality and if 

necessary, inform potential mitigation measures upon closure.

• Location, design, and operation of facilities and structures intended to route 

stormwater around the mine and into downstream drainages (FS-SW-01). Stormwater is 

not allowed to contact mine processing facilities or waste rock, but is routed around 

480 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

operations instead. This reduces the potential for exposure of stormwater to potential 

contaminants.

• Recordation of a restrictive easement on private land parcels in Davidson Canyon to 

mitigate for loss of habitat for listed species (FS-BR-21). Rosemont Copper would record 

restrictive covenants to preclude real estate development and similar land use activities.

Managed grazing, cultural, and some low impact public use (hiking, bird watching, minor 

forms of hunting) would be allowed in some locations. These lands total 383 acres and 

include portions of ephemeral wash, riparian habitat in Davidson Canyon, Barrel Canyon, 

and Mulberry Canyon, upland buffer habitat adjacent to riparian areas, and 3 springs.

• Plant site location and design adjustments to reduce impacts to biological resources

(FS-BR-01). The entire plant site is sited and designed to reduce its size and overall footprint

and to use gravity instead of pumping to move process water where possible. 

• Establishment of the Cienega Creek Watershed Conservation Fund, to be used for 

future mitigation to in the Cienega Creek watershed (FS-BR-16). Rosemont Copper 

would establish an endowment and provide $2,000,000 of funding. This fund would 

essentially be established as a resource to help restore the watershed to a functioning 

ecosystem and as a mechanism to promote adaptive management and allow flexibility in 

mitigation to achieve desired outcomes in light of future uncertainties.

• Monitoring to determine impacts from pit dewatering on downstream sites in Barrel 

and Davidson Canyons (FS-BR-22). Monitoring would be conducted of surface water, 

alluvial groundwater, and deeper groundwater at sites in Barrel and Davidson Canyons.

Several locations have already been installed and are being actively monitored, whereas 

others would require access from landowners.

• Monitoring of water quality in potential Chiricahua leopard frog habitat (FS-BR-28).

This measure would require a revolving sampling schedule to monitor water quality in 

potential habitat locations, which might include new or enhanced surface waters.

• Removal of unneeded facilities during closure (FS-VR-02). These facilities include 

buildings, the plant site, some roads, the perimeter and security fence, power supply line, 

piping systems, and water supply pipeline. The plant site would be recontoured and 

revegetated with native vegetation. Building foundations would either be removed or broken 

up and buried. Reclamation and revegetation of this area would minimize erosion and allow 

stormwater flow to be returned to the watershed.

• Hazardous materials containment and management (FS-HM-01). In order to reduce 

potential human health and environmental risks, hazardous materials and substances would

be managed and contained within facilities that are designed, constructed, and maintained to 

meet applicable laws and regulations. These facilities would include leak containment and 

recovery systems as required and adequate stormwater management and drainage systems to 

prevent contamination of outside containment areas. An explosives and blasting management 

procedure would be required to be implemented to ensure that best management practices are 

applied.

• Limiting ground-disturbing activities between perimeter fence and security fence

(FS-CR-05). Any additional soil disturbance between the security fence and perimeter fence 

would be limited.

Final Environmental Impact Statement for the Rosemont Copper Project 481
Chapter 3. Affected Environment and Environmental Consequences

Mitigation and Monitoring – Other Regulatory and Permitting Agencies

• Power line and water line locations (OA-SR-01). The final location of the power line as 

considered by the ACC was the shortest route, minimizing soil disturbance.

• Paving of mine roads (OA-AQ-01). Paving of certain roads with the mine is required under 

the air quality permits and would also serve to reduce the potential for erosion of soil from 

disturbed road areas.

• Design and location of the heap leach facility to reduce potential impacts to 

groundwater and surface water quality (OA-GW-01). The heap leach facility has been 

designed and located to reduce the risk of potential contamination of groundwater from 

seepage. It is designed to collect all possible drainage and solution; it is located on top of a 

stable rock location; the liner system is designed to meet requirements of the aquifer

protection permit; and the facility would be encapsulated by waste rock at closure to protect it 

from stormwater infiltration.

• Reduction of the potential for acid generation from tailings and waste rock (OA-GW02). Geochemical testing has indicated that there is adequate neutralization capacity in the 

overall waste rock composition to prevent potential acid generation. However, proper 

placement of the waste rock is necessary to allow this buffering capacity to be effective. This 

mitigation involves requirements for the segregation and encapsulation of potentially acidgenerating waste rock with rock that has buffering capabilities in order to reduce the risk of 

potential acid generation.

• Equipment and methods to keep potentially contaminated water from being released 

into the environment (OA-GW-03). This mitigation measure requires the use of lined 

ponds; retention of all contact stormwater for reuse as process water; and the installation of 

overflow alarms to alert operators of a potential overflow situation. Many of these mitigation 

components are required under the aquifer protection permit or stormwater permit.

• Control and recycling of process water (OA-GW-04). This mitigation measure would 

result in an overall reduction in fresh water use and avoidance of potentially contaminated 

discharges by containing all process water in lined facilities, to be recycled back into the 

process stream to offset fresh water use.

• Processing and placement of tailings to reduce water content and overall footprint

(OA-GW-05). The use of dry-stack tailings instead of traditional slurry tailings would allow 

for a much smaller footprint for the tailings facility, minimizing soil disturbance.

• Detention and testing of stormwater (OA-SW-01). This mitigation measure requires 

detention and testing of stormwater quality from perimeter waste rock buttress areas for water 

quality testing prior to flowing downstream of the mine site. This would also allow for a 

reduction in suspended sediment in stormwater flows before flowing downstream.

• Implementation of stormwater pollution prevention plan (OA-SW-02). Required under 

the stormwater permit for the mine, implementation of the stormwater pollution prevention 

plan would include use of structural sediment controls and best management practices

intended to minimize the potential for erosion from the mine site.

Mitigation and Monitoring – Rosemont Copper

• Elimination of future development of private lands on top of waste rock and tailings

(RC-LO-02). Disallowing future soil disturbance on top of the reclaimed waste rock and 

482 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

tailings facilities would minimize the potential for future soil disturbance that would reverse 

reclamation and revegetation efforts.

Conclusion of Mitigation Effectiveness

Many of the above mitigation measures are either design features or permit requirements, and their 

effectiveness has been analyzed as direct and indirect effects. Several design features would minimize 

the amount of surface disturbance and therefore would minimize the potential for erosion that would 

affect surface water quality. Concurrent reclamation and the removal of unneeded facilities during 

closure would effectively reduce the effects of erosion from the project area through successful 

revegetation. Limiting ground-disturbing activities between the perimeter fence and the security fence 

would reduce the potential for impacts to surface water quality from erosion.

Under the Arizona Aquifer Protection Permit program, all permitted facilities must use the best 

available demonstrated control technology to minimize or eliminate discharges. To do so, a mine has 

the option of selecting prescriptive control technologies or analyzing site-specific controls. 

Prescriptive control technologies are generally considered to be the more conservative and protective 

approach. Rosemont Copper chose to adopt prescriptive best available demonstrated control

technologies in their permit application. Permitted facilities include the dry-stack tailings facility 

(unlined), the process water temporary storage pond (lined), the primary settling basin (lined), the 

raffinate pond (lined), the heap leach pad (lined), the pregnant leach solution pond (lined), the 

stormwater pond (lined), the waste rock facility (unlined), and the nonmunicipal solid waste landfill 

(lined). 

The heap leach facility is further designed to prevent potential discharge of contaminants, for all 

alternatives except for the Barrel Alternative. The heap leach facility is designed and situated to 

collect all possible drainage and solution. It is on top of a stable rock location and would be 

encapsulated by waste rock to protect from stormwater infiltration up to the maximum reasoned 

storm event. Additional design features are intended to route stormwater around the mine, thus 

preventing contact with potential contaminants associated with plant site or ore stockpiles, and for 

detaining stormwater for testing prior to release downstream. These design features would be 

effective at reducing the potential for impacts to surface water quality at the mine site or downstream.

As a whole, the body of waste rock is expected to have little potential for acid rock drainage, as there 

are significant quantities of acid-neutralizing rock and relatively little potentially acid-generating 

waste rock. However, proper placement of these two types of waste rock is necessary to take 

advantage of the acid neutralization potential. A waste rock segregation plan has been incorporated 

into the design of the facility and would be informed by continued monitoring and testing of waste 

rock for acid-generating potential as it is developed from the mine and placed into the waste rock 

facility. Proper implementation of the waste rock segregation plan would be effective at reducing the 

potential for impacts to surface water quality.

Periodically rerunning the pit lake model would not be effective at changing water quality in the pit 

lake or preventing impacts to groundwater quality, but it would allow for the best predictions of pit 

lake water quality changes over time, in order to inform future management decisions after closure.

Monitoring of potential water sources considered as potential habitat for Chiricahua leopard frogs 

would ensure that any changes in water quality that could potentially occur through a variety of 

mechanisms (airborne dust, groundwater inflow, surface water runoff) would be identified and 

incorporated into management decisions.

Final Environmental Impact Statement for the Rosemont Copper Project 483
Chapter 3. Affected Environment and Environmental Consequences

Hazardous materials would be managed as required under various permits, including MSHA 

requirements and ADEQ requirements for storage and secondary containment that would be specified 

in the stormwater pollution prevention plan required under the stormwater permit. Proper 

management of hazardous materials would be effective at reducing the potential for impacts to 

surface water quality. In particular, proper blasting management procedures would be effective at 

reducing nitrogen residue that could accumulate in the forming pit lake or impact downstream surface 

water.

Mitigation measures and best management practices associated with implementation of the 

stormwater pollution prevention plan are intended to reduce the potential for surface water quality 

impacts from improper use, storage, or disposal of petroleum products and other chemicals. 

Implementation of these best management practices as well as structural erosion controls would also 

reduce the potential for surface water quality impacts from sediment. 

A restrictive covenant would be recorded on 383 acres downstream of the project area in lower 

Davidson Canyon that would preclude real estate development and restrict grazing. This would 

effectively mitigate impacts to surface water quality by protecting upland buffer habitat adjacent to 

washes and restricting land use to low-impact uses such as hiking, bird watching, and managed 

grazing. It should also be noted that sufficiency of the mitigation on the Davidson Canyon parcels or 

Sonoita Creek Ranch to offset impacts to jurisdictional WUS has yet to be determined by the 

USACE.

The effectiveness of the Cienega Creek conservation fund would depend on the nature of the projects 

funded, but in general projects would be expected to be beneficial to surface waters within the area.

In addition to the mitigation measures described above, which would effectively mitigate for impacts, 

a suite of monitoring measures is also proposed or required under permits. These measures generally 

would not be effective as mitigation but rather would provide a means for monitoring potential 

changes to surface waters within the analysis area. 

Effects of Amending the Coronado Forest Plan

The effects on surface water quality from amending the Coronado forest plan are described under 

“Direct and Indirect Effects” above. The amendment would remove the following current 

management area standards and guidelines related to surface water quality:

MA 1:

1. Restore to satisfactory watershed condition, on an emergency basis, watersheds or portions of 

watersheds when damaged. Watershed treatment is a low priority in this Management Area.

Water and soil resources improvements may consist of channel stabilization and revegetation 

using native or nonnative species.

MA 4:

1. Restore damaged watersheds to a satisfactory watershed condition. Watershed treatment is a 

high priority in this Management Area. Watershed maintenance and improvement may 

consist of channel stabilization, activities to increase water infiltration, and revegetation using 

native or non-native species.

2. Manage all programs to eliminate or minimize onsite and downstream water pollution.

484 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

3. Provide, to the extent possible, conservation pools and minimum streamflows in authorizing 

or developing water storage impoundments and diversion projects.

MA 7A

1. Restore damaged watersheds to satisfactory watershed condition. Watershed treatment is a 

high priority in this Management Area. Watershed maintenance and improvement may 

consist of channel stabilization and revegetation using native or non-native species.

2. Manage all programs to eliminate or minimize onsite and downstream water pollution.

New management area 16 contains a standard and guideline under “Watershed and Soil Maintenance 

and Improvement” that would apply to both groundwater quantity and quality:

1. To the extent practicable, mining facilities and reclamation should strive to emulate natural 

hydrologic functions.

Approval of the forest plan amendment would allow actions that would result in impacts to surface 

water quality. With all of the action alternatives, there is a potential for elevated dissolved silver 

levels in runoff from waste rock; sediment loads would decrease downstream; and jurisdictional 

WUS would be directly impacted. Refer to the description of direct, indirect, and cumulative effects 

presented earlier in this section for further information.

Seeps, Springs, and Riparian Areas

Introduction

One widespread public comment received on the DEIS concerned the organization of the document 

because the discussion of riparian areas was addressed in multiple resource sections, including the 

four water resource sections and the “Biological Resources” resource section. For the FEIS, the 

analysis of impacts to riparian areas has been consolidated into this new section, along with analysis 

of impacts to seeps and springs, as well as perennial waters.

As used in this document, the word “riparian” is used to describe plant communities associated with 

natural washes, rivers, ponds, and springs; this definition encompasses a wide spectrum of vegetation

types, from wetland areas that might be found along Cienega Creek to the dry washes found on much 

of the proposed mine site itself. In general, reference in this EIS to “riparian areas” includes not only 

the riparian vegetation itself (xeroriparian, mesoriparian, or hydroriparian) but any related water 

sources and the aquatic habitat they represent.

Changes from the Draft Environmental Impact Statement

Three different sources of riparian mapping available for the analysis area were discussed in the 

DEIS, along with the limitations and characteristics of each mapping source. Public comments 

questioned the rationale behind the mapping selection used in the DEIS, particularly the perceived 

dismissal of Pima County mapping efforts. Comments also indicated that, while the Pima County 

mapping was admittedly more expansive than other mapping sources, the county’s mapping efforts 

focus on habitat corridors, which is a valuable characteristic to consider when addressing riparian 

areas. The Coronado convened a meeting of cooperating agencies (Garrett 2012e) to discuss riparian 

mapping needs and reconsider riparian mapping data sources. The Pima County riparian mapping 

Final Environmental Impact Statement for the Rosemont Copper Project 485
Chapter 3. Affected Environment and Environmental Consequences

was subsequently selected for use in the FEIS (see the “Riparian Mapping” part of this resource 

section). This differs from the riparian mapping used in the DEIS.

Several comments, including those from the EPA, stated that the analysis of impacts to both riparian 

areas and springs was too narrowly focused, assessing only the acres of impacts to riparian areas and 

the numbers of springs impacted, without fully investigating the physical and biological effects that 

would be observed. The FEIS supplements the previous measures with an analysis of expected 

impacts to the function of these springs, seeps, and riparian areas in terms of vegetation type and 

health (see the “Riparian Condition Assessment” part of this resource section). The approaches used 

were further refined based on comments from the EPA on preliminary versions of the FEIS.

Regarding seeps and springs, information from additional field investigations conducted since the 

publication of the DEIS has allowed the seeps and springs inventory to be revised. This has reduced 

the uncertainty associated with the analysis of expected impacts to seeps and springs (see “Seeps and 

Springs” under the “Existing Conditions” part of this resource section).

Many commenters, including the EPA and other cooperating agencies, found the analysis of 

Outstanding Arizona Waters (located in lower Davidson Canyon and along Cienega Creek) to be 

deficient in the DEIS. A more complete impacts analysis, focusing on criteria specified by regulation 

as well as the original nomination criteria for those Outstanding Arizona Waters, is included in the 

FEIS (see the “Outstanding Arizona Waters Analysis” and “Effect on Outstanding Arizona Waters” 

parts of this resource section).

Some commenters identified areas of intermittent stream channel that were not analyzed, particularly 

in Sycamore Canyon (north of the mine site), Sycamore Canyon (a different canyon south of the mine 

site), Box Canyon, and Mulberry Canyon. These areas have been analyzed, but as individual spring

locations instead of intermittent reaches (SWCA Environmental Consultants 2013m). The FEIS has 

been changed to specify that some intermittent channels would be affected along with these springs.

Some comments suggested that the analysis of riparian resources or springs in the Upper Santa Cruz 

Subbasin, where the mine water supply would be withdrawn, was deficient. The regional water table 

in this area has historically been high enough to be hydraulically connected to such features but at 

present is more than 100 feet below the ground surface along the Santa Cruz River and in the vicinity 

of the pumping wells, and it does not support any riparian or spring resources. Given the amount of 

groundwater withdrawal from this aquifer for domestic, agricultural, industrial, and commercial uses 

and given the projections for population growth in the future, it is unlikely that the water table will 

recover to the point that it would support riparian or spring resources. Therefore, analysis of riparian 

resources or springs in the Upper Santa Cruz Subbasin remains absent from the FEIS, although it 

should be noted that some springs analyzed in this section that occur in the Santa Rita Mountains near 

the mine site are technically within the Upper Santa Cruz Subbasin. Effects on these springs due to 

mine pit losses are analyzed in full.

Additional mitigation measures have been incorporated into the document and assessed for 

effectiveness at reducing impacts (see the “Mitigation Effectiveness” part of this resource section, as 

well as appendix B).

Monitoring has been incorporated into the “Mitigation and Monitoring Plan” (see appendix B) in 

order to address uncertainty associated with analysis of seeps, springs, perennial waters, and 

Outstanding Arizona Waters (see the “Mitigation Effectiveness,” “Monitoring Intended to Assess 

Potential Impacts to Stream Flow,” “Monitoring Intended to Assess Potential Impacts to Outstanding 

486 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Arizona Waters,” and “Monitoring Intended to Assess Potential Impacts to Seeps and Springs” parts 

of this resource section).

Issues, Cause and Effect Relationships of Concern

One significant issue was identified that specifically concerns seeps, springs, and riparian areas 

(Issue 4). In addition, portions of another significant issue (Issue 3D) pertain to effects on perennial 

waters and Outstanding Arizona Waters, both of which are addressed in this section.

Issue 3D: Surface Water Availability

Construction and operation of the mine pit, tailings, waste rock, and leach facilities have the potential 

to change surface water discharge to Davidson Canyon and Cienega Creek, portions of which are 

designated an Outstanding Arizona Water by the ADEQ. Additionally, the availability of water for 

stock watering tanks could be reduced. 

Issue 3D Factors for Alternative Comparison

1. Number of stream miles changed from intermittent/perennial flow status to ephemeral flow 

status as a result of the project 

2. Quantitative assessment of potential lowering of the water table/reduced groundwater flow to 

Davidson Canyon and Cienega Creek that results in permanent changes in flow patterns and 

that may affect their Outstanding Arizona Water4 designations and current designated uses

Issue 4: Impact on Seeps, Springs, and Riparian Areas

Potential impacts on seeps, springs, and associated riparian vegetation could result from the alteration 

of surface and subsurface hydrology because of the pit and other operations. Potential impacts could 

include reduced or eliminated flow to seeps and springs and loss of, or change in, the function of 

riparian areas.

Issue 4 Factors for Alternative Comparison

1. Acres of riparian areas disturbed, by vegetation classification 

2. Number of seeps and springs degraded or lost

3. Change in the function of riparian areas

4. Qualitative assessment of ability to meet legal and regulatory requirements for riparian 

areas

5

4 The State of Arizona has the sole authority to make a determination about whether or not the proposed project would 

violate State water quality regulations by degrading Outstanding Arizona Waters. The person seeking authorization for a 

regulated discharge to a tributary to, or upstream of, an Outstanding Arizona Water (in this case Rosemont Copper) has the 

responsibility to demonstrate to the State of Arizona that the regulated discharge will not degrade existing water quality in 

the downstream Outstanding Arizona Water. This demonstration by Rosemont Copper, and determination by the State of 

Arizona, has not yet been completed. Independent of this determination, the potential for degradation of Outstanding 

Arizona Waters was raised by the public as an issue of importance, and therefore the Forest Service has the responsibility 

under NEPA to take a “hard look” at the potential for degradation. The analysis in this FEIS uses criteria developed by the 

Forest Service to assess this potential using available information; however, the State of Arizona would make their own 

determination using their own regulatory criteria and the information available to them at the time, which could differ from 

that used by the Forest Service.

5 This analysis reflects the criteria developed and analyzed by the Forest Service, which will differ from those used by the 

State of Arizona to make their determination of the ability of the proposed project to meet regulatory requirements.

Final Environmental Impact Statement for the Rosemont Copper Project 487

 
Chapter 3. Affected Environment and Environmental Consequences

Analysis Methodology, Assumptions, 

Uncertain and Unknown Information 

Analysis Area

The analysis area includes all areas within which seeps, springs, riparian vegetation, perennial stream

flow, or Outstanding Arizona Waters may be impacted (figure 66). The southern boundary of the 

analysis area runs along the Pima/Santa Cruz County line, which generally represents both the 

farthest southern extent of modeled groundwater drawdown and the southern extent of available 

riparian mapping. The eastern and northern boundaries extend far enough to encompass all 

hydroriparian and mesoriparian areas along Cienega Creek, extending downstream past the Davidson 

Canyon confluence to the Pantano dam. It should be noted that the biological opinion authored by the 

USFWS makes reference to Mattie Canyon, which is not within the analysis area for the “Seeps, 

Springs, and Riparian Areas” resource section of this chapter. Mattie Canyon is located east of 

Cienega Creek, very near USGS gage no. 09484550, and is generally beyond the area for which the 

groundwater models estimate impacts (see the “Groundwater Quantity” resource section of this 

chapter). Potential impacts to Mattie Canyon would be expected to be similar to those for Upper 

Cienega Creek, as described in this resource section.

The western boundary of the analysis area follows the western extent of modeled groundwater

drawdown. As noted in the “Groundwater Quantity” resource section in this chapter, drawdown 

would be expected to extend beyond the western boundary several hundred years after closure of the 

mine. No seeps, springs, hydroriparian areas, mesoriparian areas, or perennial flows were identified 

beyond the boundary that would be affected by the inability to fully analyze drawdown beyond the 

model boundary (SWCA Environmental Consultants 2013m). The analysis area also incorporates the 

utility line corridor to the west, as some xeroriparian areas would be impacted by surface disturbance 

in this area.

The temporal analysis period extends up to 1,000 years in the future, which represents the length of 

time over which groundwater levels are expected to come into equilibrium.

For analysis of impacts on stream flow and riparian vegetation, the analysis area has been categorized 

into the following reaches, as shown in figure 67 and summarized in table 106.

Information on these reaches is available from various sources, including site visits in 2012 along 

Upper and Lower Cienega Creek (WestLand Resources Inc. 2012m), site visits over numerous years 

along Lower Cienega Creek (Pima Association of Governments 2010b, 2012a; Powell 2013), and site 

visits in 2010 and 2011 along Davidson Canyon (Tetra Tech 2010a; WestLand Resources Inc. 2011g).

Seeps and Springs

An inventory of springs was compiled from multiple data sources within the analysis area. Data 

sources included detailed springs inventories conducted for the project in the immediate vicinity of 

the mine site (Errol L. Montgomery and Associates Inc. 2009b; Tetra Tech 2010a; WestLand 

Resources Inc. 2007b), springs identified from ADWR water rights data (Pearce 2007), springs 

identified on USGS 1:24,000-scale topographic maps, and several springs requested to be added by 

the BLM. However, comments on the DEIS pointed out that uncertainty remained regarding the 

location and condition of many of these springs. To reduce this uncertainty, in 2011 and 2012 

WestLand Resources Inc. conducted field surveys of 104 springs identified within the analysis area, 

including all springs analyzed in the DEIS (WestLand Resources Inc. 2012j). The results of these 

field surveys have been incorporated into the springs inventory. 

488 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 66. Analysis area for seeps, springs, and riparian areas

Final Environmental Impact Statement for the Rosemont Copper Project 489
Chapter 3. Affected Environment and Environmental Consequences

Figure 67. Stream reaches of concern

490 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Table 106. Stream reaches of concern

Reach General Location Description of Flow Regime* Special Status

Cienega Creek 1 From headwaters to confluence 

with Gardner Canyon

Spatially intermittent; based on comments 

received from EPA, indications are that 

some part of the reach above Gardner 

Canyon exhibits characteristics of perennial 

flow

None 

Cienega Creek 2 From confluence of Gardner 

Canyon to the Narrows

Spatially intermittent; some perennial 

reaches; contains USGS gage no. 09484550

(titled “Cienega Creek, near Sonoita”); this 

gage has been operational since 2001

Outstanding 

Arizona Water

Cienega Creek 3 The Narrows Spatially intermittent; some perennial 

reaches

Outstanding 

Arizona Water

Cienega Creek 4 From the Narrows to confluence 

with Davidson Canyon

Spatially intermittent; some perennial 

reaches; contains USGS gage no. 09484560

(titled “Cienega Creek, near Pantano”); this 

gage was operational between 1968 and 

1975

Outstanding 

Arizona Water

Cienega Creek 5 From confluence with Davidson 

Canyon to Pantano Dam

Spatially intermittent; some perennial 

reaches

Outstanding 

Arizona Water

Gardner Canyon 1 Upper Gardner Canyon Ephemeral None

Gardner Canyon 2 Lower Gardner Canyon Based on comments received from BLM,

approximately 1 mile above the confluence 

with Cienega Creek, it is perennial

None

Empire Gulch From headwaters to confluence 

with Cienega Creek

Spatially intermittent; some perennial 

reaches; perennial reaches extend 

approximately 3 miles upstream from 

confluence with Cienega Creek

None

Davidson Canyon 1 From headwaters to confluence 

with Barrel Canyon

Ephemeral None

Davidson Canyon 2 From Barrel Canyon to Davidson 

Spring

Ephemeral None

Davidson Canyon 3 From Davidson Spring to Reach 

2 Spring

Ephemeral None

Davidson Canyon 4 From Reach 2 Spring to 

confluence with Cienega Creek

Has been intermittent or perennial in the 

past; recently has been intermittent;

contains USGS gage no. 09484590 (titled 

“Davidson Canyon Wash, near Vail’). This 

gage was operational between 1968 and 

1975.

Outstanding 

Arizona Water

Barrel Canyon 1 From mine site to SR 83 Ephemeral; contains USGS gage no. 

09484580 (titled “Barrel Canyon, near 

Sonoita”). This gage has been operational 

since 2009.

None

Barrel Canyon 2 From SR 83 to confluence with 

Davidson Canyon

Ephemeral None

* Ephemeral stream: In a typical year, an ephemeral stream has flowing water only during, and for a short duration after, 

precipitation events. Ephemeral stream beds are located above the water table year-round. Groundwater is not a source of 

water for the stream. Runoff from rainfall is the primary source of water for stream flow.

Intermittent stream: An intermittent stream has flowing water during certain times of the year, when groundwater provides 

water for stream flow. During dry periods, intermittent streams may not have flowing water. Runoff from rainfall is a 

supplemental source of water for stream flow.

Perennial stream: During a typical year, a perennial stream has flowing water year-round. The water table is located above 

the streambed for most of the year. Groundwater is the primary source of water for stream flow. Runoff from rainfall is a 

supplemental source of water for stream flow.

Final Environmental Impact Statement for the Rosemont Copper Project 491
Chapter 3. Affected Environment and Environmental Consequences

Springs occur when groundwater discharges to the ground surface. Flow from seeps and springs in 

the Rosemont, Davidson Canyon, and Cienega Creek areas can be attributed to the following: 

(1) discharge of shallow subsurface fracture flow that is directly dependent on storm and runoff

events and that may or may not be in direct hydraulic connection with the regional groundwater flow

system; (2) discharge of groundwater via fractures that intersect land surface and that are in 

connection with the regional groundwater flow system; (3) discharge from the recent stream channel 

alluvium or other shallow aquifer, where it is forced to flow to land surface at bedrock constrictions; 

and/or (4) discharge of groundwater along low-permeability fault zones that force groundwater to 

flow to the land surface. 

For many of the seeps and springs considered for this analysis, the exact source of groundwater is 

unknown. The source of water is important to predicting impacts to springs. Springs hydraulically 

connected to the regional aquifer are likely to be impacted by groundwater drawdown associated with 

the mine pit. Springs that receive water from local fractures or that are located in ephemeral stream

channels may or may not be impacted, even when they are in close proximity to the pit. Many springs 

may have a mix of regional and local water sources. For springs and seeps, the following qualitative 

thresholds were established to reflect this uncertainty and are used in this analysis:

• High – The predicted changes in hydrology due to the mine would impact resource function, 

and the source of water can either be estimated with high certainty to be connected with the 

regional aquifer, or impacts would occur no matter what the source of water. 

• Possible – Reduction in flow could occur, given predicted changes in hydrology as a result of

the mine, but uncertainty exists regarding the source of the water. Springs that have not been 

physically located in the field are assumed to exist, and impacts are considered possible. 

• Unlikely – Predicted changes in hydrology as a result of the mine are small enough that they 

are unlikely to cause a reduction in flow, regardless of the source of water, or the source of 

the water is local and unlikely to be affected by aquifer drawdown associated with the pit.

Springs that fall beyond the modeled 5-foot drawdown contour are considered unlikely to be 

impacted.

With respect to determining the likely source of water for springs and seeps, several lines of evidence 

have been considered. These are as follows:

• Multiple and repeated observations of flow or presence of water occurring over several years 

and different seasons are considered adequate to determine whether a spring is perennial (and

therefore likely connected to the regional aquifer) or local. Twenty-three springs have been 

monitored to this extent; 10 of these were found to be perennial springs likely tied to the 

regional aquifer.

• One or two repeated observations of flow or presence of water were not considered adequate 

evidence to determine the likely source of water for a spring. Most springs fall in this 

category. Most of these visits occurred during summer 2011 or 2012; many springs visited 

exhibited no flow or presence of water but were only visited during periods with high 

evapotranspiration, which could reduce spring flow.

• Comparison of spring elevation with the elevation of the regional aquifer was not considered 

adequate evidence to determine the likely source of water for a spring. This comparison 

would assume that the water level elevation in the regional aquifer is known with great 

certainty. Great detail about the water level elevation is known in the immediate vicinity of 

the mine pit but is necessarily extrapolated elsewhere between fewer data points. Given the 

492 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

relative complexity of the regional aquifer, this comparison was not considered adequate to 

determine spring source.

• Isotopic data, where available, were considered adequate evidence to determine the likely 

source of water for a spring (Tetra Tech 2010a). For the springs in lower Davidson Canyon, 

isotopic evidence suggests a strong influence of summer precipitation, which would indicate

a local source rather than the regional aquifer. Other springs sampled (Deering, MC-1, MC-2, 

Rosemont, Ruelas, Sycamore) have mixed results that suggest a variety of water sources 

from both the regional aquifer and more localized sources. Only Questa Spring exhibited a 

signature that suggests a strong regional source of water.

• Inorganic water quality and temperature can also be used to determine the source of springs. 

Comparison with other water quality data was not considered adequate evidence to determine 

the likely source of water for a spring, primarily due to the lack of extensive background 

sampling with which to make comparisons.

In summary, the FEIS analysis has made use of available data where the data have been deemed 

sufficient to determine the source of water for individual springs. Only long-term field observations 

over several years or seasons have provided this level of evidence. For springs without such evidence, 

springs are assumed to have the potential to be impacted, which is consistent with Forest Service

policy.

Riparian Areas

Riparian Mapping

Similar to the DEIS, three sources of riparian mapping are available for the area of analysis: Pima 

County, the Forest Service, and WestLand Resources Inc. (the latter conducted on behalf of Rosemont 

Copper). Each source represents different techniques, definitions, and geographic coverage. 

The DEIS used a combination of these mapping sources, primarily relying on mapping by WestLand 

Resources Inc. for the mine site and on Pima County mapping to define hydroriparian and 

mesoriparian areas elsewhere along major stream corridors.

The Coronado has considered both public comments and input from cooperating agencies and has 

decided to use the Pima County riparian mapping source in the FEIS. The Forest Service coverage is 

too limited in geographic extent and largely ignores xeroriparian areas. The Pima County mapping is 

largely based on remote photographic analysis and generally encompasses a wider swath along 

washes than that conducted by WestLand Resources Inc., which is based in part on field surveys. 

However, the underlying purpose of the Pima County riparian mapping is to identify corridors of 

overall wildlife habitat, whereas the site-specific mapping by WestLand Resources Inc. focused on 

identifying the extent of specific vegetation species. Determining the presence of wider habitat 

corridors and their impact to biological resources is one of the primary purposes of analyzing impacts 

to riparian vegetation in the first place, whether that vegetation lies along dry washes or flowing 

streams, and this largely informed the Coronado’s decision to select the Pima County mapping. 

Use of the Pima County mapping offers three benefits: an appropriate focus on habitat corridors, 

consistency across the area of analysis, and extensive geographic coverage. The Pima County 

mapping used for the EIS is shown in figure 68.

It is recognized that when compared with onsite surveys such as those conducted by WestLand 

Resources Inc., discrepancies arise, and the Pima County mapping may in places overestimate the 

acreage of riparian species impacted WestLand Resources Inc. (2010c) noted that Pima County 

Final Environmental Impact Statement for the Rosemont Copper Project 493
Chapter 3. Affected Environment and Environmental Consequences

Figure 68. Overview of Pima County mapped riparian habitat

494 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

mapping overestimated riparian resources 86 percent of the time in 43 riparian area widths measured 

in Barrel and Scholefield Canyons. These differences in acreage were determined by the Coronado to 

be acceptable, given the different criteria used by Pima County. However, in several reaches of Barrel 

and Davidson Canyons, discrepancies were also evident concerning the overall species types 

indicated by Pima County mapping and those observed in the field by WestLand Resources Inc. 

In these cases, acreages have not been changed, but the overall type of habitat has been reinterpreted 

from that used by Pima County. Each of these instances is discussed in the “Affected Environment” 

part of this resource section.

Johnson et al. (1984) presented a riparian classification system that focuses on relative abundance and 

species composition within riparian zones. The riparian mapping of Pima County and of WestLand 

Resources Inc. is based on this system.

“Hydroriparian” habitats are generally associated with perennial watercourses and/or springs. Plant 

communities are dominated by obligate or preferential wetland plant species such as willow and 

cottonwood. The cottonwood/willow forest is a typical example of this habitat type.

“Mesoriparian” habitats are generally associated with perennial or intermittent watercourses or 

shallow groundwater. Plant communities may be dominated by species that are also found in drier 

habitats (e.g., mesquite), but they may contain some preferential riparian plant species such as ash or 

netleaf hackberry. Mesquite bosques and the sycamore-ash association are characteristic of this 

habitat type. 

“Xeroriparian” habitats are generally associated with an ephemeral water supply. These communities 

typically contain plant species also found in upland habitats; however, these plants are typically larger 

and/or occur at higher densities than adjacent uplands. Xeroriparian habitat is further divided into 

four subclasses to reflect the amount of vegetation present. 

The Pima County Regional Flood Control District’s “Regulated Riparian Habitat Mitigation

Standards and Implementation Guidelines” (Pima County Regional Flood Control District 2011)

defines the xeroriparian subcategories as follows:

Xeroriparian A – The most dense xeroriparian subcategory: total vegetative volume greater 

than 0.856 cubic meters per square meter (m3

/m2).

Xeroriparian B – Moderately dense xeroriparian subcategory: total vegetative volume less 

than or equal to 0.856 m3

/m2 and greater than 0.675 m3/m2.

Xeroriparian C – Less dense xeroriparian subcategory: total vegetative volume less than or 

equal to 0.675 m3

/m2 and greater than 0.500 m3/m2.

Xeroriparian D – Less to sparse plant density xeroriparian subcategory that provides 

hydrologic connectivity to other riparian habitat areas: total vegetative volume less than or 

equal to 0.500 m3

/m2.

USFWS National Wetlands Inventory maps were not relied on for mapping of riparian areas because 

they do not show all wetlands and do not map riparian areas unless they happen to be mapped 

wetlands. These maps were derived from aerial photointerpretation with varying limitations due to 

scale, photo quality, inventory techniques, and other factors. Consequently, the maps tend to show 

only wetlands that are readily photointerpreted, taking into consideration photo and map scale. Some 

Final Environmental Impact Statement for the Rosemont Copper Project 495
Chapter 3. Affected Environment and Environmental Consequences

wetland types were conspicuous and readily mapped, whereas drier wetlands and forested wetlands 

are more difficult to photointerpret, and larger ones were often missed. Often, the photography was 

captured during a dry year, making wetland identification equally difficult. The Coronado determined 

that the Pima County mapping was inclusive of many wetland areas and selected not to use the 

National Wetlands Inventory maps.

The BLM has also conducted wetland inventories within the Las Cienegas National Conservation 

Area and has identified more than 30 perennial or seasonal wetlands. Most of these occur on the 

Cienega Creek flood plain immediately upstream and downstream of the confluence with Empire 

Gulch, including named wetland complexes such as Cieneguita Wetland, Spring Water Wetland, and 

Cinco Ponds Wetland. Another complex, the Cold Spring Wetland, occurs upstream of the Mattie 

Canyon confluence on Cienega Creek. These wetland complexes all occur within the hydroriparian 

habitat mapped by Pima County along Cienega Creek (see figure 68). Impacts to these wetland 

complexes are not analyzed individually but are assumed to be part of the analysis of impacts to 

stream flow and riparian vegetation. 

It should be noted that these wetlands may or may not be considered jurisdictional under Section 404 

of the CWA. Potentially jurisdictional wetlands under Section 404 must meet specific criteria with

regard to hydrology, hydrophytic vegetation, and hydric soils. The analysis undertaken by the 

Coronado in this resource section is geared toward the physical impacts that may occur to these 

wetland areas in order to disclose potential impacts as required under NEPA. This is independent of 

the potential for these wetlands to be jurisdictional under Section 404. The analysis of impacts to 

WUS considered jurisdictional by the USACE is summarized in the “Surface Water Quality” resource 

section of this FEIS and is contained in the 404(b)1 Alternatives Analysis in appendix A of this FEIS.

Cooperating agencies identified several areas of intermittent stream that they believed were not 

reflected in the analysis. In fact, these areas were included but were analyzed as individual spring

locations instead of as linear intermittent stream reaches. These include Sycamore Canyon (north of 

the mine site), Sycamore Canyon (a different canyon south of the mine site), Mulberry Canyon, and 

Box Canyon. The resources associated with these areas are already fully assessed through the springs

and seeps analysis. The analysis indicates which springs correspond to these intermittent streams.

Riparian Condition Assessment

The Coronado met with cooperating agencies (Garrett 2012e) to discuss available techniques, collect 

additional data from these cooperating agencies, and select an approach for conducting an impact 

analysis of riparian vegetation.

Numerous techniques were brought to the attention of the Coronado. The ADEQ shared their 

techniques for Stream Ecosystem Monitoring (Arizona Department of Environmental Quality 2012c). 

Several agencies identified rapid assessment techniques used throughout the West (Stacey et al. 

2006). The Ecological Site Description process used by the Natural Resources Conservation Service 

was suggested and investigated by the Coronado (Natural Resources Conservation Service 2011).

Pima County provided numerous references to local riparian mapping and assessment efforts. 

Numerous sources in literature were identified that describe the response to or reliance on

groundwater levels by various riparian tree species (e.g., cottonwood, willow, tamarisk, mesquite). 

All of these sources were evaluated by the Coronado for use in the riparian analysis (SWCA 

Environmental Consultants 2012f). In addition, initial riparian assessments were further refined based 

on comments from EPA that were received on preliminary versions of the FEIS.

496 Final Environmental Impact Statement for the Rosemont Copper Project
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Selected Data Sources

The decision to use the approach to the riparian assessment addressed in this section was informed 

primarily by an analogous study conducted on the San Pedro River in southeastern Arizona, titled 

“Hydrologic Requirements of and Consumptive Ground-Water Use by Riparian Vegetation along the 

San Pedro River, Arizona” (Leenhouts et al. 2006). This study was published by the USGS, with 

cooperation by numerous other cooperating agencies, including the BLM, ADWR, and EPA. The San 

Pedro River provides a pertinent analog for the project area, particularly for Cienega Creek and 

Davidson Canyon. Not only is the San Pedro River geographically close (approximately 20 miles 

eastward, in the next adjacent valley), but it shares similar elevations (roughly 4,500 to 3,500 feet 

above mean sea level) and climatology (approximately 12 to 20 inches of rain per year). The San 

Pedro River also encompasses a wide variety of hydrologic conditions, and, like Cienega Creek, it 

represents a riparian corridor passing through an alluvial valley with a strong dependence on 

groundwater resources.

The San Pedro study analyzes the statistical correlation between riparian habitat characteristics and 

hydrologic and geographic characteristics. Riparian habitat in the San Pedro study differentiated 

12 vegetation types. Characteristics of these vegetation types are compared with hydrologic and 

geographic characteristics such as stream flow persistence, depth to groundwater, groundwater 

fluctuations, stream flood power, elevation, and flood plain width. The importance of the statistical 

correlations from the San Pedro study is not necessarily in the exact statistical or numerical 

relationship, but rather in whether a relationship may exist that is statistically significant, as shown in 

table 107. For this analysis, these 12 vegetation types have been classified as either 

hydroriparian/mesoriparian or xeroriparian. In reality, there is a great deal of overlap between these 

species, and they may occur in a variety of environments with varying degrees of success.

Table 107. Relationships between selected riparian vegetative characteristics and 

selected hydrologic characteristics based on San Pedro study

Riparian Vegetation

Characteristic

General Category Specific 

Parameter

Stream Flow

Permanence

(i.e., perennial 

vs. intermittent)

Depth to 

Groundwater

Flood Stream 

Power 

(i.e., runoff)

Hydroriparian and Mesoriparian 

Vegetation Types

Hydromesic pioneer trees (Fremont 

cottonwood/Goodding’s

willow/Arizona sycamore)

Basal area Perennial flows 

correlate to greater 

basal area

None Greater flood 

power correlates 

to greater basal 

area

Stem density Perennial flows 

correlate to greater 

stem density for 

Goodding’s willow

Deeper 

groundwater

correlates to less 

stem density

None

Mesic pioneer trees (tamarisk, tree 

tobacco, desert willow)

Basal area Perennial flows 

correlate to less 

basal area

None None

Stem density Perennial flows 

correlate to less stem

density

None None

Final Environmental Impact Statement for the Rosemont Copper Project 497
Chapter 3. Affected Environment and Environmental Consequences

Riparian Vegetation

Characteristic

General Category Specific 

Parameter

Stream Flow

Permanence

(i.e., perennial 

vs. intermittent)

Depth to 

Groundwater

Flood Stream 

Power 

(i.e., runoff)

Mesic competitor trees (netleaf 

hackberry, velvet mesquite, velvet ash, 

Arizona walnut)

Basal area Perennial flows 

correlate to greater 

basal area

None None

Hydromesic pioneer shrubs 

(seepwillow)

Cover None None None

Hydric herbaceous perennials (bulrush, 

cattail)

Cover Perennial flows 

correlate to greater 

cover

Deeper 

groundwater

correlates to less 

cover

None

Mesic herbaceous perennials (sacaton 

grass, other grasses)

Cover Perennial flows 

correlate to less 

cover

Deeper 

groundwater

correlates to less 

cover

None

Hydric annuals (rabbitsfoot grass, 

knotweeds)

Cover Perennial flows 

correlate to greater 

cover

Deeper 

groundwater

correlates to less 

cover

Greater flood 

power correlates 

to greater cover

Mesic annuals (sweetclover) Cover None, due to mixed 

results

Deeper 

groundwater

correlates to less 

cover

Greater flood 

power correlates 

to greater cover

Xeroriparian Vegetation Types

Xeric pioneer shrubs (rabbitbrush, 

burrobrush)

Cover None None None

Xeric competitor shrubs/small trees 

(fourwing saltbush, littleleaf sumac, 

catclaw acacia)

Cover Perennial flows 

correlate to less 

cover

Deeper 

groundwater

correlates to

greater cover

None

Xeric annuals (copper leaf, morning 

glory)

Cover None None None

Xeric perennials (grama, Lehmann’s 

lovegrass)

Cover None None Greater flood 

power correlates 

to greater cover

Source: Leenhouts et al. (2006).

Notes:

Relationships shown in this table are only those with statistical significance as reported in Leenhouts et al. (2006).

Competitor: Plants that compete for limited resources such as water or nutrients, resulting in lowered fecundity, growth, or 

survival of one or more other species.

Hydric: Plants that are intolerant of drought stress and that grow in areas saturated with water.

Mesic: Plants that require intermediate amounts of water and that grow in habitats that are neither excessively wet nor dry.

None: Indicates that no correlation of statistical significance was identified in the San Pedro study.

Pioneer: Plants that are adapted for life in frequently disturbed environments and that occupy areas that were recently 

disturbed (such as areas cleared by a flood or fire).

Xeric: Plants that grow in dry habitats and that are adapted to survive on limited water.

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Additional findings from available literature on the relationship between water availability and flow 

regimes and plant community response were further researched. The hydrologic/vegetative 

relationships from those studies are described below (SWCA Environmental Consultants 2012f).

• Researchers at the San Pedro Riparian National Conservation Area concluded that if stream

flow became more intermittent and depth to the alluvial groundwater table increased, 

herbaceous species such as bulrush and rushes would decline in abundance, and streamsidezone species composition would shift toward species such as Bermudagrass. Across the flood 

plain, cottonwood/willow recruitment rates would decrease and mortality rates would 

increase; cottonwood/willow forests could give way to tamarisk shrublands (Leenhouts et al. 

2006).

• Other researchers found that along the semiarid San Pedro River, hydrophytic species,

including cottonwood and willow, dominated at wetter sites, whereas at drier sites, plant 

communities became dominated by mesophytic species, including saltcedar. Dry sites had 

increased areal coverage of shrublands and decreased woodland coverage, as well as a 

decrease in maximum canopy height, total vegetation volume, and upper canopy vegetation 

volume. Increasing flood disturbance and site water availability led to increased species 

richness within cottonwood and willow patches (Lite 2004).

• Changes to flood pulses can be expected to result in changes in vegetation composition and 

structure, wherein alterations to flow may result in a shift in community structure and an 

eventual loss of biodiversity (Capon 2003).

• Riparian forest communities formerly dominated by Fremont cottonwood and Goodding’s 

willow exhibited vegetative community shifts away from cottonwood/willow following

depressed flood plain water tables and changes to duration, intensity, and frequency of 

flooding (Busch and Smith 1995).

• Maximum canopy height and upper stratum vegetation volume decrease as site water 

availability declines. Sites with deeper water tables and more intermittent flows had less 

woodland areal coverage and more shrublands (Lite and Stromberg 2005).

• Semiarid plant communities are adapted to short, regular periods of drought; however, when 

groundwater levels are artificially lowered, there is a fundamental shift in ecosystem function 

from one buffered from drought by stable groundwater conditions to one sensitive to small 

changes in precipitation. Elmore et al. (2003) documented a linear decline in native 

phreatophytic cover followed by an increase in exotic species in some areas when 

groundwater was pumped down; in the remaining areas, cover was suppressed.

• Horton and Clark (2001) found that decline of native riparian forests downstream of water 

diversions is often the result of a lack of successful regeneration of native species. Higher 

drought tolerance allowed tamarisk seedlings to persist in dry soils where willow seedlings 

died.

• Most researchers agreed that dense, multiage forests declined in abundance and age-class 

diversity where water availability was less. Cottonwood/willow forests gave way to tamarisk 

stands as site-average groundwater depths across the flood plain deepened. Conditions were

too dry at intermittent-dry stream flow regime sites to allow for establishment of cottonwood 

and willow seedlings. Tamarisk abundance increased at dry sites, likely due, in part, to 

reduced competitive interactions with cottonwood and willow trees(Leenhouts et al. 2006).

Similarly, Scott et al. studied sustained cottonwood response to water table decline following 

in-channel sand mining along an ephemeral sandbed stream. Cottonwood demonstrated a 

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Chapter 3. Affected Environment and Environmental Consequences

threshold response to water table declines in medium alluvial sands and sustained 88 percent

mortality over a 3-year period (Scott et al. 1999). 

Summary of Riparian Vegetation/Hydrologic Relationships

The San Pedro study, as well as other literature cited, was used as a guide for identifying potential 

cause-and-effect relationships between hydrologic changes and vegetation changes. The following 

summarizes the relationships used to conduct the analysis of changes to riparian vegetation in the 

FEIS:

• Hydromesic and mesic trees and shrubs are more common in the presence of perennial 

stream flow (Fremont cottonwood, Goodding’s willow, Arizona sycamore, tamarisk, tree 

tobacco, desert willow, netleaf hackberry, velvet mesquite, velvet ash, Arizona walnut). 

Hydromesic trees (Fremont cottonwood, Goodding’s willow, Arizona sycamore) also show 

sensitivity to groundwater declines, including mortality. Declines in groundwater and a 

resulting transition from perennial to intermittent stream flow would decrease recruitment of 

cottonwood/willow, increase mortality rates, decrease canopy height and vegetation volume, 

and encourage transition of cottonwood/willow forest to deeper-rooted tamarisk. Similar to 

cottonwood and willow, tamarisk (also known as saltcedar) thrives in the presence of 

abundant groundwater, but it can also extend its roots much deeper than cottonwood or 

willow as the water table drops. 

• With respect to surface flow, increasing flood disturbance encourages species richness within 

cottonwood and willow patches. Various plant types (hydric annuals, mesic annuals, and 

xeric perennials) also exhibit greater cover with increased flood disturbance. Declines in 

surface flow would decrease species richness and cover.

• Hydric and mesic herbaceous perennials (bulrush, cattail, sacaton grass, and other grasses) 

and hydric and mesic annuals (rabbitsfoot grass, knotweeds, sweetclover) show greater cover 

in the presence of perennial stream flow and are also sensitive to groundwater declines. 

Declines in groundwater and a resulting transition from perennial to intermittent stream flow 

would lead to mortality and declines in abundance of these plants.

• Xeric annuals, perennials, and small shrubs generally show no or slight correlation with 

perennial flow or sensitivity to groundwater declines.

Comments from cooperating agencies on preliminary versions of the FEIS questioned the lack of 

analysis of riparian processes, including dissipation of energy, cycling of nutrients, removal of 

elements and compounds, retention of particulates, export of organic carbon, and maintenance of 

animal communities. All of these are acknowledged as important functions of riparian areas, and it is 

acknowledged that these functions would be lost if riparian areas were impacted. However, for the 

purposes of analysis in the FEIS, impacts to these functions would result from loss of or reduction in 

health of riparian habitat. Where the FEIS concludes that riparian habitat would be impacted in some 

manner, there would be a corresponding reduction in the effectiveness of the riparian processes 

described above, but these riparian processes are not analyzed individually.

Changes in riparian vegetation would also have indirect effects. Reduction in the health of riparian 

vegetation can increase susceptibility to pests and allow for establishment of invasive species, 

particularly tamarisk. These in turn can result in increased fuel loads and fire risk, which also 

increases the risk to nearby healthy riparian areas. Reduction in the health of riparian vegetation can 

also impact surface flow characteristics like retention and removal of sediment and dissipation of 

flood flows. The biotic community can be indirectly impacted by changes in nutrient cycling, change 

500 Final Environmental Impact Statement for the Rosemont Copper Project
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in habitat or vegetation cover, and resulting changes in prey base. Changes to the biotic community 

are addressed in the “Biological Resources” section of this FEIS.

It should also be noted that the assessment of riparian vegetation in this section is meant to provide an 

analysis of the riparian corridor as a whole. It is understood that certain species or individuals could 

be more sensitive to hydrologic changes. Specific impacts to special status species are analyzed in 

more detail in the “Biological Resources” section of this FEIS.

Important Riparian Areas

Important Riparian Areas, as defined by Pima County, are those regulated riparian habitats that have 

the highest value and can include any of the various classifications of regulated habitat type. They 

provide critical watershed and water resource management function and landscape linkages and are 

valued for their higher water availability, vegetation density, connectivity factors, and biological 

productivity, compared with adjacent uplands (Pima County Regional Flood Control District 2010). 

A total of 494 acres of Important Riparian Areas is located within the project area, including much of 

Barrel Canyon and its tributaries. An Important Riparian Area is a regulatory distinction but does not 

factor into the assessment of physical riparian impacts in the FEIS.

Perennial Stream Flow

Effects on perennial stream flow are addressed primarily through groundwater modeling. Quantitative 

assessments have been used. For the most part, however, the threshold of accuracy for the available 

models (about 5 feet) renders the analysis of groundwater drawdown on distant surface waters highly 

uncertain. The conclusion of groundwater experts consulted by the Coronado is that such small 

drawdowns are beyond the ability of these groundwater models, or any groundwater model, to 

accurately predict (see the “Groundwater Quantity” resource section in chapter 3). While the analysis 

of perennial stream flow contained in the “Seeps, Springs, and Riparian Areas” resource section is 

quantitative, it reflects predicted impacts from relatively small amounts of groundwater drawdown, 

often fractions of a foot, that are occurring decades, hundreds, or even 1,000 years in the future. It is 

important to understand that the detailed predictions contained in this section are meant to inform the 

decision and to show what could potentially happen if the model predictions were to occur as 

modeled; however, this does not change the overall uncertainty.

Accuracy of the groundwater models is discussed fully in the “Groundwater Quantity” resource 

section of chapter 3. While there are limitations to the groundwater models, the Coronado reviewed 

available options and determined that the groundwater models remain the most appropriate tool for 

estimating potential impacts to surface waters (Ugorets, Cope, and Hoag 2012). The uncertainties 

involved that lend context to these quantitative estimates are discussed in detail in the “Effect on 

Perennial Stream flow” part of this resource section.

Based on comments from cooperating and regulatory agencies on several preliminary versions of the 

FEIS, the methods of assessing impacts to both riparian habitat and perennial stream flow were 

revised. The revised approach reflects the uncertainty related to the groundwater models by assuming 

that a range of groundwater drawdown could occur and then assessing the resulting impacts to both 

perennial stream flow and riparian habitat if those drawdowns were to occur. This does not alleviate 

the uncertainties involved, but it permits a more quantitative and probabilistic assessment of impacts 

to stream flow and riparian areas, if drawdowns were to occur as predicted. Each assessment of 

perennial stream flow and riparian habitat includes these categories: Lowest Estimate; Estimate 

Based on Best-Fit Models; Highest Estimate. The lowest estimate is based on the smallest drawdown 

Final Environmental Impact Statement for the Rosemont Copper Project 501
Chapter 3. Affected Environment and Environmental Consequences

observed in any of the sensitivity analyses from the three groundwater models (see the “Predicted 

Change in Groundwater Levels as a Result of the Mine Pit” part of the “Groundwater Quantity”

resource section). The highest estimate is based on the highest drawdown observed in any of the 

sensitivity analyses from the three groundwater models.

When conducting modeling sensitivity analyses, ranges of values for different input parameters are 

modeled in various combinations. Only reasonable values are selected for inclusion in the range of 

possible values. Thus, any of the sensitivity analyses can be considered to be reasonable outcomes of 

the modeling. However, while reasonable, the sensitivity analyses are not all equally probable to 

occur. Model calibration typically results in only one modeling run that is considered to best fit the

available real-world hydrologic data (i.e., groundwater levels). These best-fit modeling runs are those 

that are described and relied upon in the “Groundwater Quantity” resource section of chapter 3. For 

assessing impacts to stream flow, the “estimate based on best-fit models” represents the best 

calibrated modeling run from each of the Tetra Tech, Montgomery, and Dr. Myers models. 

Actual impacts to stream flow would depend on the specific channel geometry, hydraulic connection 

with the regional aquifer, and riparian vegetation characteristics. Forest Service policy in the absence 

of specific data showing otherwise is to assume that water sources are hydraulically connected with 

groundwater. It has been assumed that Cienega Creek, Empire Gulch, and Gardner Canyon are 

hydraulically connected with the regional aquifer and that base flow derives solely from this source.

In reality, base flow is likely to include both contributions from regional groundwater and storage of 

storm flows in local shallow alluvial aquifers. The relationship between aquifer water levels and 

stream flow is not linear, but for the purposes of this analysis it is assumed that a drawdown in the 

regional aquifer would be reflected by a similar change in the depth of flow in the stream.

Channel geometry and flow characteristics are highly variable along a channel, even within short 

distances. This is evident from the high longitudinal variability exhibited during annual stream 

presence/absence monitoring conducted within the Pima County Cienega Creek Natural Preserve, 

which takes place on Cienega Creek Reaches 4 and 5 (see the “Climate Change” and “Effect on 

Perennial Stream Flow” parts of this resource section). There is very little detailed channel geometry 

or flow information anywhere on Upper Cienega Creek, Empire Gulch, or Gardner Canyon, with the 

exception of one USGS stream gage on Upper Cienega Creek (gage no. 09484550, Cienega Creek 

near Sonoita). This stream gage has high-quality stream flow, stage, and depth of water measurements 

for the period of record from 2001 through 2013. This was a period of persistent and severe drought. 

These stream gage data allow for detailed analysis of how water levels in the stream react to drought 

and react seasonally at or near the stream gage.

For the purposes of analyzing impacts to Upper Cienega Creek, Empire Gulch, and Gardner Canyon, 

the predicted modeled drawdowns are superimposed on the actual period of record (2001 through 

2013) from the Cienega Creek stream gage. The Cienega Creek stream gage represents only one data 

point for understanding stream flow changes; however, it was assumed to be representative of Upper 

Cienega Creek, Empire Gulch, and Gardner Canyon for the purposes of this analysis. While this 

approach makes use of all available information, the projection may not provide an accurate depiction 

of likely outcomes of groundwater drawdown on surface flow and habitat at all locations on Upper 

Cienega Creek, Empire Gulch, and Gardner Canyon.

Once drawdowns are superimposed, two metrics are calculated: the probability or average number of 

days per year the stream would be dry, and the probability of average number of days per year the 

stream would experience extremely low-flow conditions (defined as depths of water less than 0.2 foot

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for the purposes of this analysis). For Upper Cienega Creek, additional corrections are made to 

account for potential loss of contributing surface flow from Empire Gulch and Gardner Canyon. 

Drawdown changes of less than 0.1 foot are assumed to result in no impact; this is the smallest 

increment of drawdown reported from the model sensitivity analyses. Details of the analysis 

methodology, including detailed calculations of impacts, are contained in the project record 

(SWCA Environmental Consultants 2013o).

Time Frames for Impacts

As described in the “Groundwater Quantity” resource section, groundwater impacts from pit

dewatering were modeled for extremely long periods of time, up to 1,000 years or more, in order to 

allow the aquifer to come to equilibrium. Uncertainty of modeling results increases with time. For the 

purposes of analysis of perennial stream flow, seeps and springs, and riparian habitat, it was useful to 

consider two different time frames: near term and long term. 

Near-term impacts are defined as those occurring during the active mine life and up to 50 years after 

final reclamation and closure. Long-term impacts are defined as those that occur beyond 50 years 

after final reclamation and closure and up to 1,000 years after final reclamation and closure. 

Near-term impacts have a higher level of certainty. Long-term impacts are less certain or even 

speculative, not only because the uncertainty of the model results increases with time but because the 

cumulative effects from other future actions and climate change are difficult to predict during these 

long time frames.

Once groundwater begins to be removed from the aquifer by the mine, either by pumping and 

dewatering during active mining, or through evaporation from the pit lake after closure, groundwater 

drawdown in the aquifer proceeds steadily over time, eventually reaching equilibrium when no 

further drawdown occurs. The various models estimate equilibrium would be reached between 700 

and 7,000 years after closure of the mine. For ease of assessing impacts in this section and the 

“Groundwater Quantity” resource section, several specific points in time were selected for analysis: 

50 years after closure, 150 years after closure, and 1,000 years after closure. The analysis does not 

imply that impacts from groundwater drawdown would occur only at these specific times, but rather 

that impacts would develop steadily over time before reaching the levels predicted at these specific 

times. 

Outstanding Arizona Waters Analysis

The analysis of potential impacts to Outstanding Arizona Waters focuses on three generalized 

reaches: Lower Davidson Canyon (Reach 4 in figure 67), Lower Cienega Creek (Reaches 4 and 5 in 

figure 67), and Upper Cienega Creek (Reaches 1, 2, and 3 in figure 67). 

The State of Arizona has the sole authority to make a determination about whether or not the 

proposed project would violate State water quality regulations by degrading Outstanding Arizona 

Waters. The person seeking authorization for a regulated discharge to a tributary to, or upstream of, 

an Outstanding Arizona Water (in this case Rosemont Copper) has the responsibility to demonstrate 

to the State of Arizona that the regulated discharge will not degrade existing water quality in the 

downstream Outstanding Arizona Water. This demonstration by Rosemont Copper, and determination 

by the State of Arizona, has not yet been completed. Independent of this determination, the potential 

for degradation of Outstanding Arizona Waters was raised by the public as an issue of importance, 

and therefore the Forest Service has the responsibility under NEPA to take a “hard look” at the 

Final Environmental Impact Statement for the Rosemont Copper Project 503
Chapter 3. Affected Environment and Environmental Consequences

potential for degradation. Regulatory requirements associated with Outstanding Arizona Waters relate 

primarily to antidegradation of water quality, and the State of Arizona will make a determination 

based on the applicable regulatory criteria, using the information available to them at the time of their 

assessment. For the analysis contained in this FEIS, the Coronado developed a series of criteria that 

are different from those that would be used by the State of Arizona. These criteria developed by the 

Coronado are based not only on regulatory requirements, but also on the reasons that these waters 

were originally nominated as Outstanding Arizona Waters. 

The original nominations for Davidson Canyon and Cienega Creek were reviewed for the 

characteristics that make these waters unique (Fonseca et al. 1990; Pima Association of Governments 

Watershed Planning 2005). In general, the following characteristics were identified as justification for 

nomination: presence of perennial waters; free-flowing condition; good water quality; exceptional 

recreational or ecological significance, including bird watching, geology, aesthetics, educational use, 

and use as a wildlife corridor; association with threatened and endangered species, with water quality 

and quantity being essential to the maintenance and propagation of these species; and for Lower 

Davidson Canyon, the contribution to stream flow in Lower Cienega Creek through surface or 

subsurface flow.

For the analysis of Outstanding Arizona Waters undertaken by the Coronado, the potential of the 

proposed mine to affect the following characteristics has been analyzed using these criteria, which 

were developed solely by the Coronado and are informed both by regulatory requirements and the 

nomination criteria:

• Change in the presence of perennial spring or stream flow. For Lower Davidson Canyon and 

Upper and Lower Cienega Creek, the expected groundwater drawdown associated with the 

mine pit could have the potential to affect spring or stream flow. For Lower Davidson 

Canyon and the portion of Lower Cienega Creek downstream of the confluence with 

Davidson Canyon, the mine site also has the potential to affect stormwater runoff volume.

• Change in groundwater quality. For all three reaches, there is the potential to directly affect 

groundwater quality.

• Change in surface water quality. For Upper Cienega Creek, changes in stream flow due to 

groundwater drawdown have the potential to indirectly affect aspects of water quality such as 

temperature and the ability of the stream to receive contaminants (natural or man-made) 

without harmful effects on the aquatic system. This ability is known as “assimilative 

capacity.” For Lower Davidson Canyon and the portion of Lower Cienega Creek downstream 

of the confluence with Davidson Canyon, there is the potential to directly affect surface water 

quality through stormwater runoff. This includes the ability to meet regulatory standards for 

antidegradation of existing water quality and regulatory standards for bottom deposits and 

biological integrity for wadeable, perennial streams. These regulatory standards are discussed 

later in this section.

• Change in riparian vegetation. For all three reaches, there is the potential to indirectly affect 

riparian vegetation as a result of changes in either groundwater levels or surface water flow.

• Change in geomorphology. Changes in the surface flow regime could indirectly affect Lower 

Davidson Canyon and the portion of Lower Cienega Creek downstream of the confluence 

with Davidson Canyon.

• Change in contributions of subflow from Lower Davidson Canyon into Lower Cienega 

Creek.

504 Final Environmental Impact Statement for the Rosemont Copper Project
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The analysis of potential impacts to Outstanding Arizona Waters necessarily draws on analyses 

conducted in numerous other resource sections of this EIS. These analyses are summarized but not 

repeated in their entirety: analyses of groundwater quality and surface water quality are contained in 

those resource sections, with the exception of potential water quality degradation due to loss of 

stream flow, which is analyzed elsewhere in this “Seeps, Springs, and Riparian Areas” resource 

section; analysis of geomorphology is contained in the “Surface Water Quality” resource section; 

analysis of subflow into Cienega Creek is contained in the “Groundwater Quantity” resource section; 

and analysis of perennial flows and riparian vegetation is detailed elsewhere in this “Seeps, Springs, 

and Riparian Areas” resource section. 

Scientific Uncertainty and Professional Disagreement

Beginning with the DEIS, and with several preliminary versions of the FEIS, the analysis 

methodology and conclusions with respect to potential impacts to perennial streams and riparian 

areas have been reviewed and commented on by cooperating agencies. Significant disagreement 

about the severity of impacts that could occur to perennial and intermittent streams has arisen, 

notably from EPA, BLM, and Pima County. In general, this disagreement has centered on two factors: 

the application of the groundwater models to predict impacts on distant perennial and intermittent

streams, and the consideration of exacerbating factors like drought, climate change, and seasonality.

The analysis of potential impacts to stream flow in this section has been refined in an attempt to 

remove subjectivity and address uncertainty. However, due to the limited accuracy of the 

groundwater models outside the 5-foot drawdown contour, significant uncertainty remains. 

The analysis has two components. First, the impact of predicted drawdown from the mine is 

compared with existing baseline conditions in the perennial streams of interest; these existing 

baseline conditions are represented by actual water-level measurements collected on Cienega Creek

over a 12-year period (2001 through 2013) and extrapolated from this single site to the rest of Upper 

Cienega Creek, Empire Gulch, and Gardner Canyon, for the purposes of this analysis only. 

The inherent uncertainty in the modeling has been represented by presenting a range of results (low, 

best fit, high) as previously described.

The second part of the analysis takes into account that there are other exacerbating trends or factors 

that could increase the severity or probability of impacts. Several of these were identified by EPA

(Leidy 2013):

• Ten federally listed endangered and threatened plant and animal species, several of which are 

obligate aquatic, survive within the Rosemont Copper Project impact and assessment areas. 

By definition, these species populations are already at risk of local extinction, extirpation, or 

further population declines under current environmental conditions. 

• The long-term trend in surface flows in Lower Cienega Creek is one of continuing decline 

due to several factors, which may include increasing domestic groundwater pumping and 

persistent natural drought. One consequence of declining ground and surface water

availability is a continuing long-term, decreasing trend in the length of available wetted 

stream channel along Lower Cienega Creek. 

• In response to decreased ground and surface water availability, Pima County has documented 

changes in the species composition of riparian communities from hydro- and mesoriparian 

communities to more xeric plant communities. Such changes signal that the system may be 

Final Environmental Impact Statement for the Rosemont Copper Project 505
Chapter 3. Affected Environment and Environmental Consequences

close to an ecological tipping point wherein there will be large-scale, landscape-level changes 

from wetter toward drier-end riparian communities. 

• Climate models predict a trend of increasing temperatures, decreasing precipitation, and 

increased periods of prolonged drought in the arid American Southwest. This will lead to less 

available surface and ground water for use by species dependent on these resources.

These exacerbating factors are incorporated in three places in this document. The assessment of 

impacts under the no action alternative takes into account ongoing trends, including the current 

drought and observed reductions in surface water availability. The “Climate Change” part of this 

resource section (and other resource sections) addresses predicted changes in temperature and 

precipitation. The “Effect on Perennial Stream Flow” part of this resource section consolidates and 

discusses how these exacerbating factors could change the predictions under existing baseline

conditions.

Summary of Effects by Issue Factor by Alternative

Table 108 presents the summary comparison of impacts from each alternative.

Affected Environment

Relevant Laws, Regulations, Policies, and Plans

Relevant laws, regulations, policies, and plans applicable to riparian habitat are discussed in the 

“Surface Water Quantity” and “Surface Water Quality” resource sections of this chapter.

Outstanding Arizona Waters

Outstanding Arizona Waters are classified by the Director of the ADEQ and are specifically identified 

by rule (AAC R18-11-112). The primary consideration given to Outstanding Arizona Waters consists 

of special protections against degradation, known as the Tier 3 Anti-Degradation criteria (AAC R18-

11-107D and R18-11-107.01C; 40 CFR 131,12(a)(3)).

Tier 3 Anti-Degradation criteria include several specific requirements:

• New or expanded point-source discharges cannot be made directly to an Outstanding Arizona 

Water;

• Water quality of a discharge to a tributary of, or upstream of, an Outstanding Arizona Water

shall not degrade existing water quality in the Outstanding Arizona Water; and

• A discharge regulated under Section 404 of the CWA that may affect existing water quality 

of an Outstanding Arizona Water requires a water quality certification from the ADEQ. 

In addition, while not specific to Outstanding Arizona Waters, there are also regulatory requirements 

specific to wadeable, perennial streams (AAC R18-11-108.01 and R-18-11-108.02). Regulations 

require that a wadeable, perennial stream shall support and maintain a community of organisms 

having a taxa richness, species composition, tolerance, and functional organization comparable to that 

of a stream with reference conditions in Arizona. Regulations also have specific requirements for 

bottom deposits, primarily limiting the percentage of fine sediments, especially in riffle habitats.

506 Final Environmental Impact Statement for the Rosemont Copper Project
Final Environmental Impact Statement for the Rosemont Copper Project 507

Table 108. Summary of effects

Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 3D.2: 

Number of stream 

miles changed from 

intermittent/perenni

al flow status to 

ephemeral flow 

status as a result of 

the project

None predicted;

increased 

population growth 

and climate change

could have a 

continued impact 

on perennial waters 

similar to trends 

currently observed

Empire Gulch, about 3 miles impacted 

Low estimate: No or minor changes up to 150 

years after closure; ephemeral by 1,000 years 

after closure

Best-fit models: Mixed results showing 

intermittent or ephemeral by 150 years after 

closure; all models indicate ephemeral by 

1,000 years after closure

High estimate: Ephemeral by 50 years after 

closure

Cienega Creek, about 20 miles impacted

Low estimate: No or minor changes 

predicted.

Best-fit models: Mixed results, with one 

model showing no or minor changes through 

1,000 years, one model showing intermittent 

conditions by 1,000 years, and one model 

showing intermittent conditions by 150 years 

and ephemeral conditions by 1,000 years

High estimate: Minor change predicted up to 

50 years after closure; intermittent by 150 

years after closure; ephemeral by 1,000 years 

after closure

Davidson Canyon: No change predicted

Gardner Canyon, about 1 mile impacted 

Low estimate: No change predicted

Best-fit models: No or minor changes 

predicted up to 150 years after closure. Mixed 

results at 1,000 years, ranging from no 

change to ephemeral.

High estimate: Minor changes predicted up to 

50 years after closure; intermittent by 150 

years after closure; ephemeral by 1,000 years 

after closure

Intermittent streams: Some intermittent 

streams associated with springs in Sycamore 

Canyon (north), Sycamore Canyon (south), 

Box Canyon, and Mulberry Canyon may be 

impacted

Same as for 

proposed action

Same as for 

proposed action

Same as for 

proposed action
Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 3D.3: 

Quantitative 

assessment of 

potential lowering 

of the water 

table/reduced 

groundwater flow 

to Davidson 

Canyon and 

Cienega Creek that 

results in 

permanent changes 

in flow patterns and 

that may affect 

their Outstanding 

Arizona Water*

designations and 

current designated 

uses

None predicted; 

increased 

population growth 

and climate change

could have a 

continued impact 

on perennial waters 

similar to trends 

currently observed

Upper Cienega Creek: Up to 50 years after 

closure of the mine, most modeling scenarios 

show no predicted effects 

At 150 years after closure, some modeling 

scenarios show no or minor changes in flow, 

and some modeling scenarios show that there 

may be transition from perennial to 

intermittent flow, and increased duration of 

extremely low-flow conditions

At 1,000 years after closure, modeling 

scenarios are mixed, showing a range of 

outcomes, including minor changes in flow, 

transition from perennial to intermittent flow, 

and transition from perennial to ephemeral 

flow. All modeling scenarios show increased 

duration of extremely low-flow conditions.

Davidson Canyon and Lower Cienega 

Creek: None predicted; reduction in surface 

runoff could change recharge to shallow 

alluvial aquifer; distance downstream makes 

impacts highly uncertain. Some water quality 

constituents potentially elevated in runoff, but 

potential is reduced by waste rock segregation 

procedures.

Same as for 

proposed action

Same as for 

proposed action

Same as for 

proposed action

508 Final Environmental Impact Statement for the Rosemont Copper Project
Final Environmental Impact Statement for the Rosemont Copper Project 509

Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 4.1: Acres of 

riparian areas 

disturbed, by 

vegetation

classification 

None predicted; 

increased 

population growth 

and climate change

could have a 

continued impact 

on perennial waters 

similar to trends 

currently observed

Pima County Mapped Riparian Habitat

directly disturbed = 686 acres

Barrel Canyon = 162 acres of xeroriparian 

habitat expected to be indirectly impacted 

with high certainty

Empire Gulch = 407 acres of hydroriparian 

habitat could be indirectly impacted

Davidson Canyon (Reach 2) = 502 acres of 

xeroriparian habitat expected to be indirectly 

impacted with moderate certainty 

No riparian habitat is expected to be 

indirectly impacted along Cienega Creek, 

Gardner Canyon, or lower Davidson Canyon

An additional 14 riparian areas associated 

with springs would be directly or indirectly 

disturbed with high certainty; and an 

additional 35 riparian areas associated with 

springs may be indirectly disturbed but with 

less certainty

Pima County 

Mapped Riparian

Habitat directly 

disturbed = 

649 acres 

Indirect impacts to 

Barrel Canyon, 

Empire Gulch, 

Davidson Canyon, 

and Cienega Creek

are the same as for 

proposed action

Riparian impacts 

associated with 

springs are the same 

as for proposed 

action

Pima County 

Mapped Riparian

Habitat directly 

disturbed = 

588 acres

Indirect impacts 

to Barrel 

Canyon, Empire 

Gulch, Davidson 

Canyon, and 

Cienega Creek

are the same as 

for proposed 

action

An additional 13 

riparian areas

associated with 

springs would be 

directly or 

indirectly 

disturbed with 

high certainty; 

and an additional 

36 riparian areas 

associated with 

springs may be 

indirectly 

disturbed but 

with lower 

certainty

Pima County 

Mapped Riparia

Habitat directly 

disturbed = 

633 acres

Indirect impacts 

to Barrel 

Canyon, Empire 

Gulch, Davidso

Canyon, and 

Cienega Creek

are the same as 

for proposed 

action

Riparian impact

associated with 

springs are the 

same as for 

Barrel 

Alternative
Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 4.2: Number 

of seeps and 

springs degraded or 

lost

None predicted; 

increased 

population growth 

and climate change

could have a 

continued impact 

on perennial waters 

similar to trends 

currently observed

Seven springs directly lost due to surface 

disturbance;

10 springs highly likely to be indirectly 

impacted due to drawdown;

59 springs may be indirectly impacted due to 

drawdown, but water source is unknown;

19 springs unlikely to be impacted

Eight springs

directly lost due to 

surface disturbance;

nine springs highly 

likely to be 

indirectly impacted 

due to drawdown;

59 springs may be 

indirectly impacted 

due to drawdown, 

but water source is 

unknown;

19 springs unlikely 

to be impacted

Five springs

directly lost due 

to surface 

disturbance;

11 springs highly 

likely to be 

indirectly 

impacted due to 

drawdown;

60 springs may 

be indirectly 

impacted due to 

drawdown, but 

water source is 

unknown;

19 springs

unlikely to be 

impacted

Same as for 

Barrel 

Alternative

Issue 4.3: Change 

in the function of 

riparian areas

None predicted; 

increased 

population growth 

and climate change

could have a 

continued impact 

on perennial waters 

similar to trends 

currently observed

Hydroriparian habitat along Empire Gulch 

would transition to mesoriparian or 

xeroriparian

Pockets of mesoriparian habitat along 

Davidson Canyon (Reach 2) could transition 

to mesoriparian or xeroriparian with moderate 

certainty

Xeroriparian habitat in lower Barrel Canyon 

highly certain to experience reduced vitality, 

extensiveness, and health and to transition to 

lesser quality habitat

Along Upper Cienega Creek, widespread 

transition from hydroriparian to xeroriparian 

habitat is unlikely, but contraction of 

hydroriparian habitat could occur with 

conversion at the transitional margins

Same as for 

proposed action

Same as for 

proposed action

Same as for 

proposed action

510 Final Environmental Impact Statement for the Rosemont Copper Project
Final Environmental Impact Statement for the Rosemont Copper Project 511

Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 4.4: 

Qualitative 

assessment of 

ability to meet legal 

and regulatory 

requirements for 

riparian areas

†

Increased 

population growth 

and climate change

could have a 

continued impact 

on perennial waters 

similar to trends 

currently observed

Upper Cienega Creek: Six criteria assessed 

for impacts to Outstanding Arizona Waters. 

Few changes predicted up to 50 years after 

closure, but some risk in changes of flow and 

frequency of low-flow conditions in the longterm (see Issue 3D.3). Low-flow conditions 

could affect biological characteristics under 

wadeable, perennial standards. 

Davidson Canyon and Lower Cienega 

Creek: Seven criteria assessed for impacts to 

Outstanding Arizona Waters. Full analysis of 

ability to meet water quality requirements 

Davidson Canyon is not possible, but 

screening analysis suggests that some 

constituents may be elevated in stormwater. 

This potential is reduced by several safety 

factors, including waste rock segregation 

requirements. Otherwise, no predicted 

changes that would affect Outstanding 

Arizona Waters or biological characteristics 

protected under wadeable, perennial 

standards. Geomorphological changes 

unlikely to affect bottom deposit 

characteristics protected under wadeable, 

perennial standards.

Same as for 

proposed action

Same as for 

proposed action

Same as for 

proposed action

* The State of Arizona has the sole authority to make a determination about whether or not the proposed project would violate State water quality re

Outstanding Arizona Waters. The person seeking authorization for a regulated discharge to a tributary to, or upstream of, an Outstanding Arizona W

Rosemont Copper) has the responsibility to demonstrate to the State of Arizona that the regulated discharge will not degrade existing water quality i

Outstanding Arizona Water. This demonstration by Rosemont Copper, and determination by the State of Arizona, has not yet been completed. Indep

determination, the potential for degradation of Outstanding Arizona Waters was raised by the public as an issue of importance, and therefore the For

responsibility under NEPA to take a “hard look” at the potential for degradation. The analysis in this FEIS uses criteria developed by the Forest Serv

potential using available information; however, the State of Arizona would make their own determination using their own regulatory criteria and the 

to them at the time, which could differ from that used by the Forest Service.

† This analysis reflects the criteria developed and analyzed by the Forest Service, which will differ from those used by the State of Arizona to make 

the ability of the proposed project to meet regulatory requirements.
Chapter 3. Affected Environment and Environmental Consequences

With respect to the Outstanding Arizona Water in Davidson Canyon, degradation of existing water 

quality is prohibited. With respect to the Outstanding Arizona Water in Upper and Lower Cienega 

Creek, both anti-degradation and wadeable, perennial standards would need to be met.

The State of Arizona has the sole authority to make a determination about whether or not the 

proposed project would violate State water quality regulations by degrading Outstanding Arizona 

Waters. The person seeking authorization for a regulated discharge to a tributary to, or upstream of, 

an Outstanding Arizona Water (in this case Rosemont Copper) has the responsibility to demonstrate 

to the State of Arizona that the regulated discharge will not degrade existing water quality in the 

downstream Outstanding Arizona Water. This demonstration by Rosemont Copper, and determination 

by the State of Arizona, has not yet been completed. Independent of this determination, the potential 

for degradation of Outstanding Arizona Waters was raised by the public as an issue of importance, 

and therefore the Forest Service has the responsibility under NEPA to take a “hard look” at the 

potential for degradation. The analysis in this FEIS uses criteria developed by the Forest Service to 

assess this potential using available information; however, the State of Arizona would make their own 

determination using their own regulatory criteria and the information available to them at the time, 

which could differ from that used by the Forest Service.

Existing Conditions 

Seeps and Springs

As previously discussed, to reduce uncertainty in the springs inventory, in 2011 and 2012 WestLand 

Resources Inc. conducted field surveys of 104 springs identified within the analysis area, including 

all springs analyzed in the DEIS (WestLand Resources Inc. 2012j). Field data collected included 

survey data, photo documentation, coordinates, elevation, presence of surface water, presence of 

riparian vegetation, presence of stock watering infrastructure, and description of field efforts. 

The results of these efforts highlight the uncertainty associated with the springs inventory:

• WestLand Resources Inc. could not survey 22 of the 104 springs because of access 

constraints; they were either in extremely remote locations or on private property. For the 

purposes of this analysis, all 22 of these unsurveyed springs remain in the inventory of 

springs to be considered. They are assumed to exist in functional condition in the location 

noted. 

• The existence of 24 out of the 104 springs could not be verified in the field because the 

springs could not be located. However, because of field observations (evidence of water 

staining, tufa deposits, historic stock watering infrastructure, or remnants of more dense 

vegetation in the vicinity of the presumed spring location), not all of these springs were 

eliminated from the analysis in the FEIS. It was determined that 16 of these springs are 

likely intermittent in nature, and these were kept in the springs inventory for analysis.

The remaining eight springs were assumed to be transient seeps or to reflect a recording error 

and were removed from the inventory.

• In all, 95 springs remain in the springs inventory analyzed in this section (figure 69). Detailed 

seeps and springs observation data obtained during the period 2006 through 2012 are shown 

in table 109 where available.

512 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 69. Seeps and springs within the analysis area

Final Environmental Impact Statement for the Rosemont Copper Project 513
Chapter 3. Affected Environment and Environmental Consequences

Table 109. Seeps, springs, and other water features within the analysis area

ID

Spring

(Cadastral 

Location)

Elevation 

(feet)

Observed Flow Rate 

and Characteristics* Data Source

1 Barrel Spring

[D-18-16 14cab]

4,278 Spring observed from 2007 to 

2011; long periods with no flow; 

observed flow up to 1 cubic foot 

per second

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

Company (2012f); WestLand 

Resources Inc. (2007b; 2012j)

2 Basin Spring

[D-19-15 11bab]

5,018 Evidence of water not observed 

(summer 2011); riparian vegetation

present

USGS (2013c); WestLand Resources 

Inc. (2011k)

3 Batamout Spring

[D-18-16 8ba]

5,044 Evidence of water not observed 

(summer 2011); riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2011k)

4 Bee Spring

[D-18-16 31bb]

5,129 Improved. Small seep, <1 gallon 

per minute (summer 2011); riparian 

vegetation present

ADWR (2005); WestLand Resources 

Inc. (2011k)

5 Big Spring

[D-18-16 18caa]

4,653 No flow but some evidence of 

water observed; no riparian 

vegetation present (summer 2011)

USGS (2013a); WestLand Resources 

Inc. (2011k)

6 Bobo Spring

[D-17-17 21d]

3,980 Unknown; spring not located or 

observed

USGS (2013a)

7 Bootlegger Spring

[D-17-18 31cc]

4,101 Unknown; spring not located or 

observed

USGS (2013c)

8 Bowman Spring

[D-19-15 13ac]

5,156 Improved; no riparian vegetation

present (summer 2011)

USGS (2013c); WestLand Resources 

Inc. (2011k)

9 Box Canyon Spring -

Stock Drinker No. 1

[D-19-15 12ba]

4,885 Spring improved, water 

intermittently present; riparian 

vegetation present

ADWR (2005); WestLand Resources 

Inc. (2011k; 2012j)

10 Box Canyon Spring -

Stock Drinker No. 2

[D-19-15 12ba]

4,890 Spring improved, water 

intermittently present; riparian 

vegetation present

WestLand Resources Inc. (2012j)

11 California Mine Spring

[D-17-17 19db]

3,849 Unknown; spring not located or 

observed

USGS (2013c); WestLand Resources 

Inc. (2012j)

12 Chavez Spring

[D-18-15 14dbb]

4,407 Water present (summer 2011); 

riparian vegetation present

WestLand Resources Inc. (2012j)

13 Cold Water Spring

[D-18-17 23dbc]

4,240 Unknown; spring not located or 

observed

ADWR (2005)

14 Cow Spring

[D-17-16 19dca]

4,108 Unknown; spring not located or 

observed

ADWR (2005)

15 Crucero Spring No. 1

[D-18-16 9cbd]

4,800 No water present (summer 2011); 

riparian vegetation present

WestLand Resources Inc. (2012j)

16 Crucero Spring No. 2

[D-18-16 9cbd]

4,751 Spring observed from 2008 to 

2011; long periods without flow; 

flow observed up to 1.6 gallons per 

minute; no riparian vegetation

present

Rosemont Copper Company (2012f); 

WestLand Resources Inc. (2012j)

17 Dam Spring

[D-17-16 32aac]

4,351 Unknown; spring not located or 

observed

ADWR (2005)

18 Davidson Spring

[D-17-17 19ac]

3,891 Unknown; spring not located or 

observed

Tetra Tech (2010a)

19 Deering Spring

[D-19-15 1dbd]

5,277 Spring observed from 2008 to 

2011; consistent flow observed up 

to 1.59 gallons per minute; riparian 

vegetation present

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

Company (2012f); WestLand 

Resources Inc. (2012j)

514 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

ID

Spring

(Cadastral 

Location)

Elevation 

(feet)

Observed Flow Rate 

and Characteristics* Data Source

20 Diesler Spring

[D-18-15 24cc]

4,830 No water present (summer 2012); 

riparian vegetation present

ADWR (2005); WestLand Resources 

Inc. (2012j)

21 Escondido Spring

[D-16-17 30a]

3,341 Spring observed from 2010 to 

2011; consistently dry; reports of 

perennial flow in channel 

historically

Pima Association of Governments 

Watershed Planning (2005); 

Rosemont Copper Company (2012f);

Tetra Tech (2010a); WestLand 

Resources Inc. (2012j)

22 Feliz Spring

[D-18-15 35ba]

5,121 Damp, with possible evidence of 

water (summer 2011); riparian 

vegetation present

ADWR (2005); WestLand Resources 

Inc. (2012j)

23 Fence Spring

[D-17-15 35bdb]

3,676 Unknown; spring not located or 

observed

ADWR (2005)

24 Fig Tree Spring

[D-18-16 19abb]

5,068 Spring observed from 2008 to 

2011; consistent presence of water 

with minor dry periods; supports 

wetland area of approximately 0.5 

acre

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

Company (2012f); WestLand 

Resources Inc. (2010c; 2012j)

25 Heiter Spring

[D-18-15 1ddb]

4,151 Evidence of water not observed 

(summer 2011); riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2011k)

26 Helvetia Spring

[D-18-15 14dba]

4,570 Spring observed from 2009 to 

2011; consistent flow observed up 

to 3.7 gallons per minute; riparian 

vegetation present

Rosemont Copper (2012f); 

WestLand Resources Inc. (2012j)

27 Hilton Spring

[D-17-17 32caa]

4,255 Unknown; spring not located or 

observed

ADWR (2005)

28 Horse Pasture Spring

[D-18-16 15aa]

4,333 Evidence of water not observed 

(summer 2011); riparian vegetation

present

Pearce (2007); WestLand Resources 

Inc. (2011k)

29 HQ Water Spring

[D-18-16 16cd]

4,614 Evidence of water not observed 

(summer 2011); riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2011k; 2012j)

30 Indian Spring

[D-17-15 36cbc]

3,990 Unknown; spring not located or 

observed

ADWR (2005)

31 La Cholla Spring

[D-18-16 5cba]

5,169 Improved; flow observed (fall 

2011); riparian vegetation present

ADWR (2005); WestLand Resources 

Inc. (2012j)

32 Little Indian Spring

[D-17-15 36cbc]

3,990 Unknown; spring not located or 

observed

ADWR (2005)

33 Locust Spring

[D-19-15 1bdb]

5,468 Spring observed from 2008 to 

2011; mostly dry with occasional 

flowing water; no riparian 

vegetation present

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

(2012f); WestLand Resources Inc.

(2012j)

34 Lower Mulberry Spring

[D-18-16 9dbb]

4,679 Spring observed from 2008 to 

2011; consistent presence of water; 

riparian vegetation present

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

(2012f)

35 McCleary Dam

[D-18-16 29bda]

4,761 Spring observed from 2008 to 

2011; consistent flow observed up 

to 8 gallons per minute; riparian 

vegetation present

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

(2012f); WestLand Resources Inc.

(2012j)

Final Environmental Impact Statement for the Rosemont Copper Project 515
Chapter 3. Affected Environment and Environmental Consequences

ID

Spring

(Cadastral 

Location)

Elevation 

(feet)

Observed Flow Rate 

and Characteristics* Data Source

36 McCleary No. 1

[D-18-16 30abc]

4,987 Spring observed from 2006 to 

2011; long periods with no flow; 

flow observed up to 1 gallon per 

minute; no riparian vegetation

present

Errol L. Montgomery and Associates 

Inc. (2009b); Pearce (2007); 

Rosemont Copper (2012f);

WestLand Resources Inc. (2007b; 

2012j)

37 McCleary No. 2 

[D-18-16 19cdd]

5,085 Spring observed from 2006 to 

2011; consistent presence of water; 

riparian vegetation present

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

(2012f); WestLand Resources Inc. 

(2007b; 2012j)

38 Mescal Spring

[D-17-17 21a]

4,014 Unknown; spring not located or 

observed

USGS (2013a)

39 Mesquite Flat Spring

[D-18-16 7aaa]

4,709 Presence of water observed (fall 

2011); riparian vegetation present

USGS (2013c); WestLand Resources 

Inc. (2012j)

40 Mine Water Spring

[D-19-15 24dc]

5,401 Improved; evidence of water not 

observed and no riparian vegetation

present (summer 2011)

ADWR (2005); WestLand Resources 

Inc. (2011k)

41 Mudhole Spring

[D-18-16 17bb]

4,715 No flow; ground moist; some 

riparian vegetation present (summer 

2011)

ADWR (2005); WestLand Resources 

Inc. (2011k)

42 Mueller Spring

[D-18-16 29cc]

4,838 Improved; evidence of water not 

observed and no riparian vegetation

present (summer 2011)

ADWR (2005); WestLand Resources 

Inc. (2011k; 2012j)

43 Mulberry Canyon

[D-18-16 16a]

4,511 Wetted area in channel; riparian 

vegetation present (summer 2012)

WestLand Resources Inc. (2012j)

44 Mulberry Spring

[D-18-16 9abc]

4,927 Spring observed from 2008 to 

2011; consistent presence of water; 

riparian vegetation present

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

(2012f)

45 Oak Spring

[D-18-16 17bbc]

4,881 Standing pool; riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2011k)

46 Ojo Blanco Spring

[D-18-16 5cd]

5,012 Improved; riparian vegetation

present; presence of water observed 

(summer 2011)

USGS (2013a); WestLand Resources 

Inc. (2011k)

47 Ophir Gulch Well

[D-19-15 24dd]

5,321 Water about 1 to 1.5 meters below 

ground level (summer 2012)

WestLand Resources Inc. (2012j)

48 Paja Verde Spring

[D-19-15 23ca]

5,546 Evidence of water not observed and 

no riparian vegetation present 

(summer 2011)

USGS (2013a)

49 Papago Spring (No. 2)

[D-18-16 16bba]

4,800 Spring observed from 2008 to 

2011; long periods without flow; 

flow observed up to 3.57 gallons 

per minute; no riparian vegetation

present

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

(2012f); WestLand Resources Inc. 

(2012j)

50 Peligro Adit

[D-18-15 24dcc]

5,010 Spring observed from 2008 to 

2011; consistent flow observed but 

has been dry since 2010; no 

riparian vegetation present

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

(2012f); WestLand Resources Inc. 

(2012j)

51 Proctor Box Spring

[D-19-15 12bc]

4,841 Evidence of water not observed 

(summer 2011); riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2011k; 2012j)

516 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

ID

Spring

(Cadastral 

Location)

Elevation 

(feet)

Observed Flow Rate 

and Characteristics* Data Source

52 Questa Spring

[D-18-16 27ddd]

4,604 Small pond present; spring

observed from 2007 to 2011; 

consistent flow observed up to 0.3 

gallon per minute; no riparian 

vegetation present

Errol L. Montgomery and Associates 

Inc. (2009b); Pearce (2007); 

Rosemont Copper (2012f); 

WestLand Resources Inc. (2007b; 

2012j)

53 Rock Spring

[D-18-16 6ddd]

5,074 Evidence of water not observed 

(summer 2011); riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2012j)

54 Rockhouse Spring

[D-18-17 10cda]

4,490 Unknown; spring not located or 

observed

ADWR (2005)

55 Rosemont Spring

[D-18-16 32bbc]

4,922 Spring observed from 2007 to 

2011; consistent flow observed up 

to 0.79 gallon per minute; riparian 

vegetation present

Errol L. Montgomery and Associates 

Inc. (2009b); Pearce (2007); 

Rosemont Copper (2012f); 

WestLand Resources Inc. (2007b; 

2012j)

56 Ruelas Spring

[D-18-15 35bdc]

5,029 Spring observed from 2008 to 

2011; consistently dry with 

occasional dampness; riparian 

vegetation present

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

(2012f); WestLand Resources Inc. 

(2012j)

57 Ruelas Spring Number 

Two and Three

[D-18-15 26aa]

4,827 No flow, but presence of water 

observed (summer 2012); no 

riparian vegetation present

USGS (2013a); WestLand Resources 

Inc. (2012j)

58 Rust Spring

[D-18-15 1acb]

4,212 Unknown; spring not located or 

observed

ADWR (2005)

59 Sanford Spring

[D-18-17 15daa]

4,322 Unknown; spring not located or 

observed

ADWR (2005)

60 Scholefield No. 1 

Spring

[D-18-16 16ccc]

4,747 Spring observed from 2007 to 

2011; consistently dry; wetland 

area present (0.3 acre)

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

(2012f); WestLand Resources Inc. 

(2007b; 2010c; 2012j)

61 Scholefield No. 2 

Spring

[D-18-16 17adb]

4,883 Spring observed from 2007 to 

2011; long periods without flow; 

flow observed up to 1.3 gallons per 

minute; no riparian vegetation

present

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

(2012f); WestLand Resources Inc. 

(2007b)

62 Scholefield No. 3 

Spring

[D18-16 17caa]

5,117 Most recent observations show 

flow <1 gallon per minute; ground 

moist; no riparian vegetation

present

WestLand Resources Inc. (2007b; 

2011k; 2012j)

63 Shamrod Spring

[D-18-15 14bcd]

4,122 Evidence of water not observed 

(summer 2011); riparian vegetation

present

WestLand Resources Inc. (2012j)

64 Siphon Spring

[D-17-16 31cda]

4,535 Unknown; spring not located or 

observed

ADWR (2005); WestLand Resources 

Inc. (2012j)

65 Soldier Spring

[D-18-15 25bb]

4,848 Evidence of water not observed and 

no riparian vegetation present 

(summer 2012)

ADWR (2005); WestLand Resources 

Inc. (2012j)

66 SS-2 (Casita Spring)

[D-18-15 13aab]

4,470 Spring observed for 6 months in 

2008; no flow or evidence of flow 

observed; no riparian vegetation

present

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

(2012f); WestLand Resources Inc. 

(2012j)

Final Environmental Impact Statement for the Rosemont Copper Project 517
Chapter 3. Affected Environment and Environmental Consequences

ID

Spring

(Cadastral 

Location)

Elevation 

(feet)

Observed Flow Rate 

and Characteristics* Data Source

67 SW

[D-19-15 1bbb]

5,540 Spring observed from 2008 to 

2011; mostly dry with occasional 

dampness; riparian vegetation

present

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

(2012f); WestLand Resources Inc. 

(2012j)

68 Sycamore Spring

[D-18-15 12dba]

4,211 Spring observed from 2008 to 

2011; consistent flow or standing 

water in sump; flow observed up to 

1.3 gallons per minute; riparian 

vegetation present

Errol L. Montgomery and Associates 

Inc. (2009b); Rosemont Copper 

(2012f); WestLand Resources Inc. 

(2012j)

69 Tree Spring

[D-18-16 8acc]

4,915 No water present (summer 2011) 

but some evidence of past presence 

of water; some riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2012j)

70 Tub Spring

[D-18-16 6dd]

4,837 Presence of water observed 

(summer 2011); riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2012j)

71 Tunnel Spring

[D-17-16 32cb]

4,436 Unknown; spring not located or 

observed

USGS (2013c)

72 Tunnel Spring # 2

[D-17-16 31bbd]

4,039 Unknown; spring not located or 

observed

ADWR (2005)

73 Unnamed Spring

(South of Deering 

Spring)

[D-19-15 1d]

5,236 Evidence of water not observed 

(summer 2012); riparian vegetation

present

WestLand Resources Inc. (2012j)

74 Unnamed Spring (in 

Box Canyon)

[D-19-15 11a]

4,772 Pool of water and riparian 

vegetation observed (2011 and 

2012)

WestLand Resources Inc. (2012j)

75 Reach 2 Spring

[D-17-17 6bd]

3,518 Spring observed from 2010 to 

2011; mostly dry with occasional 

flow or standing water; reports of 

perennial flow in channel 

historically; riparian vegetation

present

Pima Association of Governments 

Watershed Planning (2005); 

Rosemont Copper (2012f); Tetra 

Tech (2010a); WestLand Resources 

Inc. (2012j)

76 Unnamed Spring

(in South Sycamore 

Canyon)

[D-19-15 01c]

5,072 Pool of water and riparian 

vegetation observed (2011 and 

2012)

WestLand Resources Inc. (2012j)

77 Unnamed Spring

No. 1

[D-18-15 23ba]

4,413 Unknown; spring not located or 

observed

Pearce (2007)

78 Unnamed Spring

No. 12

[D-18-17 6ac]

4,398 Unknown; spring not located or 

observed

USGS (2013c)

79 Unnamed Spring

No. 13

[D-18-15 34aa]

4,830 Presence of water observed 

(summer 2011); no riparian 

vegetation present

ADWR (2005); WestLand Resources 

Inc. (2012j)

80 Unnamed Spring

No. 14

[D-18-16 21bc]

4,637 Evidence of water not observed 

(summer 2011); riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2011k; 2012j)

81 Unnamed Spring

No. 16

[D-17-15 36cc]

4,138 Unknown; spring not located or 

observed

ADWR (2005)

518 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

ID

Spring

(Cadastral 

Location)

Elevation 

(feet)

Observed Flow Rate 

and Characteristics* Data Source

82 Unnamed Spring

No. 17

[D-18-16 8ac]

4,993 Evidence of water not observed 

(summer 2011); riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2012j)

83 Unnamed Spring

No. 18

[D-18-15 13ac]

4,657 Evidence of water not observed 

(summer 2011); riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2012j)

84 Unnamed Spring

No. 2

[D-18-16 30cd]

5,152 Standing pool; no riparian 

vegetation present

Pearce (2007); WestLand Resources 

Inc. (2011k; 2012j)

85 Unnamed Spring

No. 20

D-17-16 31cd]

4,526 Unknown; spring not located or 

observed

ADWR (2005)

86 Unnamed Spring

No. 21

[D-18-16 6dc]

4,805 Evidence of water not observed 

(summer 2011); riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2012j)

87 Unnamed Spring

No. 22

[D-18-16 7da]

4,552 Evidence of water not observed 

(summer 2011); riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2011k)

88 Unnamed Spring

No. 24

[D-18-16 8ca]

4,759 Evidence of water not observed 

(summer 2011); riparian vegetation

present

ADWR (2005); WestLand Resources 

Inc. (2011k)

89 Unnamed Spring

No. 3

[D-18-16 30cd]

5,101 Presence of water observed (spring

2012); no riparian vegetation

present

Pearce (2007); WestLand Resources 

Inc. (2012j)

90 Unnamed Spring

No. 4

[D-18-16 26bc]

4,536 Presence of water observed 

(summer 2011); riparian vegetation

present

Pearce (2007); WestLand Resources 

Inc. (2011k)

91 Unnamed Spring

No. 5

[D-18-16 29ab]

4,810 Presence of water observed (spring

2012); riparian vegetation present

Pearce (2007); WestLand Resources 

Inc. (2011k; 2012j)

92 Unnamed Spring

No. 7

[D-17-17 28b]

4,167 Unknown; spring not located or 

observed

USGS (2013c)

93 Upper Empire Gulch 

Spring

[D-19-17 18aad]

4,610 Presence of water observed (spring

2012); riparian vegetation present

WestLand Resources Inc. (2012j)

94 Water Develop Spring

[D-18-16 17ab]

4,846 Improved; standing pool; riparian 

vegetation present (summer 2011)

ADWR (2005); WestLand Resources 

Inc. (2011k)

95 Zackendorf Spring

[D-18-15 14ada]

4,539 Flow observed in summer 2011, 

spring 2012, and summer 2012; 

riparian vegetation present

WestLand Resources Inc. (2012j)

* Flow rate as observed in 2008 and 2009 by WestLand Resources Inc., Montgomery and Associates, or Tetra Tech, or in 

2011 and 2012 by WestLand Resources Inc. (2012j).

Little historical information has been consistently collected from these springs with respect to flow 

quantity, frequency, or water quality; data are limited primarily to observations and sampling in 1975 

and again from 2006 through 2012. Little can be said about the long-term seasonal variation in these 

springs; however, in the discharge measurements collected, all the springs exhibited very low rates of 

discharge. None of the springs in the vicinity of the project area are particularly large; most have flow 

of less than 1 gallon per minute. Based on the monitoring period, the following springs appear likely 

to have perennial flow and therefore are likely tied to the regional aquifer: Rosemont, Helvetia, 

Final Environmental Impact Statement for the Rosemont Copper Project 519
Chapter 3. Affected Environment and Environmental Consequences

Sycamore, Questa, Deering, Lower Mulberry, Mulberry, Fig Tree, McCleary Dam, and McCleary 

No. 2. Isotopic water quality samples are generally mixed, with the exception of those for Questa 

Spring, which appears to have a signature that strongly suggests a regional water source. However, 

the isotopic signatures do not rule out contribution from the regional aquifer for any of the other 

springs listed. Several of the seeps and springs in the analysis area have been developed in the past 

for stock use, and all of the springs are assumed to be being used for stock and wildlife watering as 

well as for recreational purposes. 

Riparian Areas

Riparian areas mapped by Pima County within the analysis area are summarized in table 110. 

As noted previously, it was determined that several reaches varied from the Pima County 

classification. These are explicitly noted in table 110; specific evidence and rationale are discussed 

below.

Table 110. Riparian affected environment

Reach Acres of 

Riparian Habitat

Pima County Riparian

Habitat Classification Species Types Present

Cienega Creek 1 695.13 Hydroriparian Cottonwood and Goodding’s willow*

Cienega Creek 1 364.69 Xeroriparian B Large mesquites and scrub mesquites with 

scattered cottonwoods*

Cienega Creek 2 2,086.96 Hydroriparian Mature cottonwood and Goodding’s 

willow*

Cienega Creek 2 323.98 Xeroriparian B Mesquite and soapberry†‡

Cienega Creek 2 65.58 Xeroriparian C Mesquite and soapberry†‡

Cienega Creek 3 382.27 Hydroriparian Mature cottonwood and Goodding’s 

willow with young velvet ash*

Cienega Creek 3 35.88 Xeroriparian B Mesquite and netleaf hackberry*

Cienega Creek 3 126.96 Xeroriparian C Mesquite with desert broom and 

burrobrush*

Cienega Creek 3 0.78 Xeroriparian D Mesquite and soapberry†‡

Cienega Creek 4 11.15 Xeroriparian A Mature mesquite and netleaf hackberry*

Cienega Creek 4 179.52 Xeroriparian B Mesquites with burrobrush*

Cienega Creek 4 656.81 Xeroriparian C Less dense mesquites with burrobrush*

Cienega Creek 4 38.58 Xeroriparian D Mesquite and soapberry†‡

Cienega Creek 4 2138.93 Hydroriparian Mature cottonwoods and ash with some 

Goodding’s and seep willow*

Cienega Creek 5 4.86 Xeroriparian A Mesquite*

Cienega Creek 5 21.75 Xeroriparian B Mesquites with burrobrush*

Cienega Creek 5 168.15 Xeroriparian C Less dense mesquites with desert broom 

and burrobrush*

Cienega Creek 5 49.91 Xeroriparian D Mesquite and soapberry†‡

Cienega Creek 5 463.95 Hydroriparian Cottonwood and willow gallery forest*

Gardner Canyon 1 356.44 Xeroriparian B Mesquite and soapberry†‡

Gardner Canyon 1 1.28 Xeroriparian C Mesquite and soapberry†‡

Gardner Canyon 1 346.55 Hydroriparian Cottonwood, willow, seepwillow, 

sycamore, and hackberry†

Gardner Canyon 2 129.29 Xeroriparian B Mesquite and soapberry†‡

Gardner Canyon 2 121.51 Hydroriparian Cottonwood, willow, seepwillow, 

sycamore, and hackberry†

Empire Gulch 86.00 Xeroriparian A Mesquite and soapberry†‡

520 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Reach Acres of 

Riparian Habitat

Pima County Riparian

Habitat Classification Species Types Present

Empire Gulch 631.39 Xeroriparian B Mesquite and soapberry†‡

Empire Gulch 127.90 Xeroriparian C Mesquite and soapberry†‡

Empire Gulch 407.46 Hydroriparian Large cottonwood willow gallery*

Davidson Canyon 1 84.03 Xeroriparian B Acacia, desert willow, ironwood, 

paloverde, mesquite, soapberry†

Davidson Canyon 1 99.20 Hydroriparian§ Large ash trees*

Davidson Canyon 2 355.61 Xeroriparian B Mesquites and hackberry*

Davidson Canyon 2 31.23 Xeroriparian C Small mesquites and desert willow*

Davidson Canyon 2 33.95 Xeroriparian D Acacia and desert broom*

Davidson Canyon 2 570.38 Hydroriparian§ Seep willow, Arizona walnut, and 

cottonwood*

Davidson Canyon 3 0.50 Xeroriparian B Juniper*

Davidson Canyon 3 28.93 Xeroriparian C Mesquite and hackberry*

Davidson Canyon 3 26.21 Xeroriparian D Desert broom and acacia*

Davidson Canyon 3 71.05 Hydroriparian§ Willows, ash, and tamarisk*

Davidson Canyon 4 5.71 Xeroriparian A Large mesquite and hackberry*

Davidson Canyon 4 5.05 Xeroriparian B Mesquite*

Davidson Canyon 4 50.42 Xeroriparian C Small mesquite and juniper*

Davidson Canyon 4 3.27 Xeroriparian D Desert broom and acacia*

Davidson Canyon 4 174.78 Hydroriparian Willows, ash, tamarisk, and cottonwood*

Barrel Canyon 1 192.54 Hydroriparian§ Large mesquites, oak, juniper, desert 

willow, and sumac*

Barrel Canyon 1 21.74 Xeroriparian B Small mesquites, juniper, and hackberry*

Barrel Canyon 2 12.39 Hydroriparian§ Seep willow*

Total Hydroriparian 7,940.51 NA NA

Total Xeroriparian A 107.72 NA NA

Total Xeroriparian B 2,575.69 NA NA

Total Xeroriparian C 1,637.06 NA NA

Total Xeroriparian D 152.7 NA NA

Note:

NA = Not applicable.

* From actual field observations (WestLand Resources Inc. 2010c, 2012j, 2012m).

† From generic Pima County habitat type descriptions (Pima County Regional Flood Control District 2011). 

‡ Vegetation descriptions based on input from BLM.

§ The Pima County habitat designation does not match field descriptions of species types; for purposes of analysis, these 

areas are considered xeroriparian/mesoriparian instead of hydroriparian.

Riparian Field Descriptions and 

Variance from Pima County Mapping

The Pima County mapping was supplemented with field descriptions from other sources. Three 

project-specific riparian studies were reviewed that each cover narrowly defined specific study areas. 

Below is a list of the project-specific riparian studies and a brief summary of each:

• “Onsite Riparian Habitat Assessment, Rosemont Project,” April 2010 (WestLand Resources 

Inc. 2010c). This onsite riparian habitat assessment was performed based on normalized 

difference vegetation index display values developed from satellite imagery for the project 

area, supplemented with field observations. Five different classes of riparian habitat, ranging 

from xeroriparian to hydroriparian, were delineated. 

Final Environmental Impact Statement for the Rosemont Copper Project 521
Chapter 3. Affected Environment and Environmental Consequences

• “Offsite Riparian Habitat Analysis and Mapping,” August 17, 2010 (WestLand Resources 

Inc. 2011g). The study area for this report consists of upper Barrel Canyon from just north of 

SR 83 downstream to its confluence with Davidson Canyon and from Davidson Canyon to its 

confluence with Cienega Creek. This offsite riparian habitat assessment was performed based 

on normalized difference vegetation index display values from satellite imagery verified by 

field measurements at 70 locations within the study area.

• “Trip Report for Cienega Creek Site Visit Conducted on October 26–28, 2011, and 

November 3, 2011” (WestLand Resources Inc. 2012m). The study area for this report 

consists of Cienega Creek downstream of its intersection with I-10 to the Pantano Dam. Field 

observations were recorded and photodocumentation provided. Recorded field parameters 

include vegetation type, dominant species, approximate density, presence of stream flow, and 

presence of fish.

Much of the Pima County riparian mapping along Cienega Creek matches field descriptions of 

riparian vegetation species reasonably well. However, field descriptions for several reaches 

downstream of the proposed mine site in Barrel Canyon and Davidson Canyon do not match well 

with Pima County mapping. The downstream reaches of Barrel Canyon are identified by Pima 

County as having 226 acres of riparian habitat, of which 90 percent is mapped as “hydroriparian” 

(see table 110). Hydroriparian habitat is typified by obligate or preferential wetland plant species, 

such as willow and cottonwood, and is generally associated with perennial water. Neither cottonwood 

nor willows were identified in field surveys in Barrel Canyon; seepwillow can also define 

hydroriparian habitat but was identified at less than 11 percent of sampled points (WestLand 

Resources Inc. 2010c). In addition, neither perennial nor intermittent water occurs within Barrel 

Canyon. Barrel Canyon is therefore analyzed in the FEIS as xeroriparian with pockets of 

mesoriparian habitat and not as hydroriparian habitat.

Of the 1,540 acres of riparian habitat mapped in the Davidson Canyon reaches, 915 acres (60 percent) 

are classified as hydroriparian by Pima County. Davidson Canyon has been classified in field surveys 

as largely xeroriparian or mesoriparian, although with individual cottonwood and willows and 

pockets of higher quality habitat, particularly in the lower reaches (WestLand Resources Inc. 2011g). 

Only one part of Davidson Canyon has been considered in the past to have perennial flows, which is 

the lower reach (Davidson Reach 4). For the purposes of the FEIS analysis, Reach 4 of Davidson 

Canyon is considered hydroriparian; however, Reaches 1 through 3 of Davidson Canyon are analyzed 

as xeroriparian with pockets of mesoriparian habitat.

Surface Flow

Historical surface water flow data for Barrel Canyon, Davidson Canyon, and Cienega Creek are 

presented in the “Surface Water Quantity” resource section in this chapter. Surface flow 

characteristics are summarized by reach in table 106. As noted in the table, some perennial flow has 

occurred in four of the drainages: in lower Davidson Canyon (Reach 2 Spring to the confluence with 

Cienega Creek), Cienega Creek (from confluence with Gardner Canyon to Pantano Wash), Empire 

Gulch, and approximately 1 mile of Gardner Canyon above the confluence with Cienega Creek.

Several intermittent stream channels may exist in the area and these intermittent channels overlap 

springs that are analyzed and are believed to represent the same physical feature (i.e., a wetted area 

along an otherwise ephemeral channel). Intermittent reaches may exist in Sycamore Canyon (north of 

the mine site), Sycamore Canyon (a different canyon south of the mine site), Mulberry Canyon, and 

522 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Box Canyon. These intermittent reaches are analyzed in the same manner as the spring locations in 

these same areas.

Outstanding Arizona Waters 

A portion of Davidson Canyon has been designated an Outstanding Arizona Water by the ADEQ after 

being nominated in 2005 by Pima County. The designated reach begins approximately 12 river miles 

downstream of its confluence with Barrel Canyon and extends 3.2 miles to its confluence with 

Cienega Creek. This reach begins approximately where perennial and intermittent stream flow

begins, which is associated with discharge from the Reach 2 Spring.

All of Cienega Creek has also been designated an Outstanding Arizona Water by the ADEQ after 

being nominated in 1990 by Pima County. The designated reach begins at the confluence of Gardner 

Canyon and extends 28.3 miles to Pantano Dam. 

The Outstanding Arizona Water designation ensures that existing surface water quality will be 

maintained and protected for the designated use of the surface water; existing surface water quality 

for base flow in Davidson Canyon and Lower Cienega Creek is discussed in the “Surface Water 

Quality” resource section. The locations of Outstanding Arizona Waters in Davidson Canyon and 

Cienega Creek are shown in figure 65 in the “Surface Water Quality” resource section.

Environmental Consequences

Direct and Indirect Effects of Each Alternative

No Action Alternative

Under baseline conditions (no action), seeps, springs, and riparian areas within the analysis area 

would not be impacted by mine activities but would still likely undergo changes from current 

conditions, uses, and trends. The use of riparian areas for recreation would likely increase relative to 

the predicted increase in population growth and residential development. Use for stock watering 

could change, depending on changes in livestock management. 

Ephemeral washes in the analysis area will continue to flow in response to precipitation, supporting 

xeroriparian zones. However, current trends show the impact that prolonged drought can have on 

spring and stream flow, and these changes could persist or worsen, exacerbated by climate change

(see the “Climate Change” part of this resource section). Changes in vegetation type from 

hydroriparian or mesoriparian to xeroriparian, or from shallow rooted phreatophytic vegetation like 

cottonwood/willow to deeper rooted vegetation like tamarisk or mesquite could occur as conditions 

become drier.

Impacts Common to All Action Alternatives

Impacts common to all action alternatives include effects on perennial flows, indirect effects on 

riparian areas and vegetation, and effects on Outstanding Arizona Waters. The effects on seeps and 

springs vary between alternatives owing to different footprints of ground disturbance, as do direct 

effects on riparian vegetation owing to surface disturbance.

The terms “near term” and “long term” are used extensively in the following discussion. As noted 

earlier, near-term impacts are defined as those occurring during the active mine life and up to 50 

years after final reclamation and closure. Long-term impacts are defined as those that occur more 

Final Environmental Impact Statement for the Rosemont Copper Project 523
Chapter 3. Affected Environment and Environmental Consequences

than 50 years after final reclamation and closure and up to 1,000 years after final reclamation and 

closure. Near-term impacts have a higher level of certainty. Long-term impacts are less certain or 

even speculative, not only because the uncertainty of the model results increases with time but 

because the cumulative effects from other future actions and climate change are entirely 

unpredictable during these long time frames.

Effect on Perennial Stream Flow

As shown in table 106, there are several intermittent or perennial stream sections within the analysis 

area for which impacts from groundwater level changes are a concern:

• Portions of Empire Gulch from Empire Ranch approximately 3 miles to the confluence with 

Cienega Creek;

• Cienega Creek near the confluence with Gardner Canyon and near stream gage no. 09484550

(Cienega Creek Reaches 2 and 3);

• Portions of Cienega Creek just upstream and downstream of the Davidson Canyon 

confluence (Cienega Creek Reaches 4 and 5); 

• Portions of Gardner Canyon approximately 1 mile upstream of the confluence with Cienega 

Creek (Gardner Canyon Reach 2); and

• Portions of Davidson Canyon from Reach 2 Spring to the confluence with Cienega Creek

(Davidson Canyon Reach 4).

As with springs, changes to perennial flows in streams are highly dependent on the geological

conditions that bring about those perennial flows in the first place. Perennial flow can result from 

discharge of water from the regional aquifer into the streambed as a result of the intersection of 

fracture zones or upwelling from regional groundwater flow encountering a flow barrier. Perennial 

flow can also result from discharge of shallow groundwater that is stored and moving subsurface in 

alluvial stream sediments, and that is forced to the surface by geological conditions, such as bedrock 

constrictions of the stream channel. In the case of this shallow alluvial groundwater, changes in 

ephemeral surface flows are more likely to impact perennial flows than changes in regional 

groundwater levels.

Uncertainty, Trends, and Exacerbating Factors

Analysis of potential impacts to perennial streams from drawdown of groundwater in the regional 

aquifer has been refined since the DEIS by the Coronado in response to comments by the public, 

cooperating agencies, and EPA. The analysis contained in this section makes use of the best available 

science, data, and tools to quantify the increased risk of negative outcomes in Empire Gulch, Cienega 

Creek, and Gardner Canyon to the extent possible. Negative outcomes include both risk of drying as 

well as risk of extremely low-flow conditions occurring, which can negatively affect water and 

habitat quality and the organisms that depend on these resources. The intent of this analysis is to 

disclose the full range of possible effects on perennial stream flow, using quantification and 

probability based on the best available science, data, and tools while also informing these results with 

qualitative discussion of trends and exacerbating factors occurring in the watershed.

While the analysis contained in this section is quantitative, it reflects predicted impacts from 

relatively small amounts of groundwater drawdown, often fractions of a foot, that are occurring 

decades, hundreds, or even a thousand years in the future. The conclusion of groundwater experts 

consulted by the Coronado is that such small drawdowns are beyond the ability of these groundwater 

524 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

models, or any groundwater model, to accurately predict (see the “Groundwater Quantity” resource 

section in chapter 3). It is important to understand that the detailed predictions contained in this 

section are meant to inform the decision and to show what could potentially happen if the model 

predictions were to occur as modeled; however, this does not change the overall uncertainty.

There are other trends and exacerbating factors occurring in the watershed that add to the uncertainty 

of predicting impacts to perennial streams. These are discussed elsewhere in the document (see the 

“No Action” and “Climate Change” parts of this resource section), but it is important to reiterate them 

here as well to help inform the impact predictions contained in this section. These factors include 

climate change, current stress and downward trends observed on Lower Cienega Creek, and increases 

in groundwater pumpage within the Cienega Creek basin. While these factors add to the overall 

uncertainty, they provide general trends that can also inform the decision.

Climate Change and Recent Trends

Climate change in the desert Southwest is predicted to bring about higher mean annual temperatures 

over the next 100 years, along with less winter precipitation, an increase in extreme rainstorms and 

flooding, and longer periods of drought. The impact these changing climate conditions would have on 

perennial streams like Cienega Creek is not simple to predict. A great deal will depend on how and 

where rainfall occurs (i.e., summer monsoons versus winter frontal storms) and on the ultimate 

source of water for perennial streams. Several good summaries of the variability of expected climate 

change are available (Overpeck et al. 2012). Models consistently suggest rising temperatures, but 

effects on precipitation, and especially seasonal timing of precipitation, are less consistent. Climate 

models differ in the amount of reduction expected to be experienced during summer and winter storm 

events (Overpeck et al. 2012). The reaction of riparian vegetation to changing climate conditions will 

also have its own influence on water availability in riparian areas. These changes are difficult to 

predict on a site-specific basis. For instance, as noted elsewhere in this section, spring water samples 

analyzed for isotopes suggest that some springs (in lower Davidson Canyon) are strongly influenced 

by summer precipitation, whereas others are more influenced by winter precipitation. However, while 

site-specific predictions are difficult, there is general agreement that temperatures will rise and 

overall water availability is likely to decrease due to climate trends.

Local drought and recent fluctuations in climate should not automatically be considered indicative 

of long-term climate change; there have always been drought cycles in the desert Southwest, 

interspersed with abnormally wet conditions. Climate change would not interrupt this cycle but is 

predicted to exacerbate drought and cause overall changes in the length and frequency of drought 

periods. The Cienega Creek basin, like the rest of Arizona, is currently in the midst of a multi-decadal 

drought that began, by most counts, in the late 1990s and, with the exception of a few wet years, has 

yet to be alleviated. While the ongoing drought may or may not be the result of long-term climate 

change, the trends observed because of the drought are useful as examples of the long-term effects 

that would result from climate change.

Pima County has recently documented many of the long-term changes observed on the Cienega 

Creek Natural Preserve between 1990 and 2011 (Powell 2013), located along what is usually referred 

to as Lower Cienega Creek (Cienega Creek Reaches 4 and 5, as shown in figure 67). Measurements 

of drought severity indicate that drought conditions have roughly been ongoing in the Cienega Creek 

basin since 1996. Over this period, Lower Cienega Creek has seen noticeable reductions in both the 

amount of stream flow, the geographic length of stream flow, and the average depth to groundwater.

Causes for these changes are likely varied, but persistent drought is one of the leading stressors. 

Final Environmental Impact Statement for the Rosemont Copper Project 525
Chapter 3. Affected Environment and Environmental Consequences

Two other trends concerning Cienega Creek are also pertinent. When reviewing these, it is important 

to understand the distinction between Lower Cienega Creek and Upper Cienega Creek. Upper 

Cienega Creek is generally considered to extend from the headwaters downstream to an area known 

as the “Narrows,” which is located about 7 to 8 miles upstream of I-10 (Cienega Creek Reaches 1, 2, 

and 3, as shown in figure 67). Upper Cienega Creek generally flows through basin fill alluvium, with 

some limited pockets of younger alluvium. The basin fill alluvium is generally assumed to be part of 

the regional aquifer, which would be impacted by drawdown from the mine or other aquifer 

dewatering. Upper Cienega Creek flows through the Las Cienegas National Conservation Area and 

includes the tributaries of Gardner Canyon, Mattie Canyon, and Empire Gulch. 

Lower Cienega Creek, located below the Narrows, generally is characterized by flow through 

younger alluvium. There are likely still hydraulic connections between the younger alluvium and the 

regional aquifer, but ephemeral storm flows are also important to replenish the shallow alluvium 

along Lower Cienega Creek. Lower Cienega Creek largely flows through Pima County’s Cienega 

Creek Natural Preserve, eventually terminating at Pantano Dam, several miles below the confluence 

with Davidson Canyon.

The hydrologic monitoring in Cienega Creek Natural Preserve and the documentation of downward 

trends in stream flow are pertinent to Lower Cienega Creek. Two similar sources of data farther 

upstream on Upper Cienega Creek include a stream gage operated by the USGS (no. 09484550;

Cienega Creek near Sonoita) and reported monitoring of wetted stream length within the Las 

Cienegas National Conservation Area. Neither source shows a similar downward trend. Stream flow 

and water levels are available from the USGS stream gage from 2001 through 2013; these data are 

key to the analysis of potential impacts from the mine discussed later in this section (see figure 70).

While Upper Cienega Creek experienced one very dry month in May/June 2010 when flow ceased, 

overall there has not been a major downward trend in winter or summer base flow similar to that 

observed in Lower Cienega Creek during the same period (Powell 2013:figure 12).

In addition, it has been reported by Pima County that stream flow conditions have been monitored 

within BLM Las Cienegas National Conservation Area like they have been monitored within the 

Pima County Cienega Creek Natural Preserve. These data have not been made available for analysis 

by the Coronado. The results are interpreted and reported by Pima County (Powell 2013). According 

to Pima County interpretation of these data, flow extent on Upper Cienega Creek decreased between 

1990 and 2012 but also actually increased during the period 2006 through 2011, opposite the trend on 

Lower Cienega Creek (Powell 2013:figure 32).

These differences in response to drought conditions likely reflect differences in hydrologic 

connection with the regional aquifer and sources of groundwater supporting perennial stream flow.

Groundwater Use and Pumpage in Cienega Basin

As discussed in the “Groundwater Quantity” resource section, wells in the project area are primarily 

used for domestic and stock water uses and have sustainable well yields from less than 1 to 3 gallons 

per minute. Estimates of groundwater use by wells within the Davidson Canyon/Cienega Basin are 

approximately 400 to 500 acre-feet per year. Most of this occurs in the vicinity of Sonoita-Elgin, 

while a smaller proportion may occur in the lower part of the Cienega Basin (Montgomery and 

Associates Inc. 2010).

Water use by domestic and stock wells has steadily increased in the basin. In 1980, approximately 

630 domestic or stock wells were known to be in the Cienega Basin. By 1990, the number of 

526 Final Environmental Impact Statement for the Rosemont Copper Project
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domestic and stock wells had increased to more than 1,000, and by 2010, the number of domestic and 

stock wells had increased to more than 1,800 (Arizona Department of Water Resources 2011c). Many 

of these wells are considered to be exempt wells, which typically use less than 35 gallons per minute. 

Taken in combination, however, water use by these wells can be substantial. In addition to this, the 

Cienega Basin is located outside any active management area. Pumping within active management 

areas is regulated by the ADWR and is subject to issuance of groundwater rights. Because it is 

outside an active management area, even larger industrial, commercial, or municipal wells in the 

Cienega Basin can be drilled and pumped with little requirement, other than that the groundwater be 

put to beneficial use. 

Many stock and domestic wells may not intersect the regional aquifer but rely on smaller, isolated 

pockets of alluvium or perched units not hydraulically connected with the regional system. Any 

individual well, unless directly adjacent to Cienega Creek, would have a negligible direct effect on 

stream flow. However, taken as a whole, the total amount of water withdrawn from wells within the 

Cienega Basin has to come from either aquifer storage or some other part of the basin water balance.

Either option has the potential to cumulatively remove enough water from the aquifer to eventually 

affect perennial stream flow. 

This potential is described in recent projections in the Cienega Creek basin, comparing population

growth to stream flow depletion (Marshall et al. 2010). This work suggests that on Lower Cienega 

Creek, most demand projection scenarios indicate that by 2050 groundwater demand would exceed 

the base flow of Lower Cienega Creek. The same is not true for Upper Cienega Creek. Depending on 

specific water conservation scenarios, groundwater demand would remain the same or increase but 

would not exceed base flow. These types of comparisons of groundwater demand with base flow are 

not indications of direct impact but rather of the potential for increasing groundwater pumpage to 

occupy a larger and larger portion of the basin water balance. These comparisons also highlight the 

different conditions experienced by Upper and Lower Cienega Creek.

Surface Water Allocation

Arizona has a bifurcated water law system, which means that groundwater and surface water

allocations are handled differently. While there are few restrictions on groundwater pumping within 

the Cienega Basin, there are significant restrictions on the allocation and use of surface waters. 

All surface water use in Arizona requires a valid surface water right. Certificated water rights are 

those that have been perfected, and those surface water rights are superior to all other surface water 

rights with a later priority date but junior to all rights with an earlier (older) priority date. On Cienega 

Creek, several downstream certificated water rights are currently diverted at Pantano Dam and have 

priority dates senior to all other surface water rights on Cienega Creek. The presence of these senior 

certificated water rights effectively prevents further allocation of water along Cienega Creek; 

therefore, surface water use is unlikely to continue to grow in the way that groundwater pumpage 

increases over time. The senior certificated water rights are also those that are to be severed and 

transferred to serve as instream flow rights on Upper Cienega Creek (see mitigation measure

FS-SSR-01 in Appendix B).

Overall Effect on Predictions

The purpose of this discussion preceding the analysis of effects on perennial stream flow is to 

highlight that in addition to the uncertainty contained in the analysis itself, there are other 

exacerbating factors in the watershed or groundwater basin that are likely to shift the underlying 

baseline conditions and therefore add another layer of uncertainty. In all cases discussed above, while 

Final Environmental Impact Statement for the Rosemont Copper Project 527
Chapter 3. Affected Environment and Environmental Consequences

specific effects may vary widely (for instance between Lower Cienega Creek and Upper Cienega 

Creek), the overall trend is negative. Climate change is likely to reduce water availability throughout 

the desert Southwest, although exactly how this would manifest is not predictable on a site-specific 

basis. Upper Cienega Creek may be somewhat shielded from drastic responses to drought, while 

Lower Cienega Creek reacts more quickly and negatively, but this very stability may mean that there 

is a greater reliance of Upper Cienega Creek on the regional aquifer and therefore a greater risk that 

any drawdown occurring in the aquifer due to the mine would have negative effects. Increased 

population growth and associated pumpage in the basin, while it is not clear exactly where it would 

occur or how much would occur, would become an increasing component of the available water 

balance. In the long term, these effects would likely spread throughout the basin.

If these current trends continue, there is little doubt that the desert Southwest, the greater Tucson area, 

and the Cienega Creek basin will experience severe water shortages at some unknown point in the 

future. Should such a situation occur, evaporation from the Rosemont Copper mine pit lake would be 

one of many factors in groundwater drawdown and related surface water effects in the Cienega Creek 

basin.

Predicted Effects on Empire Gulch Stream Flow

Portions of Empire Gulch are perennial or intermittent downstream of Empire Ranch and the nearby 

springs (titled Upper Empire Gulch springs in table 109). No surface disturbance from mining 

facilities is located within the Empire Gulch watershed; therefore, in assessing potential changes 

to stream flow, only the possible contribution of flow from the regional groundwater system is 

considered. An estimated 3 miles of Empire Gulch could be affected by hydrologic changes; this 

represents the reach of Empire Gulch roughly from the Upper Empire Gulch springs to the 

confluence with Cienega Creek.

All three groundwater flow models predict changes in groundwater levels in the vicinity of the Upper 

Empire Gulch springs (Montgomery and Associates Inc. 2010; Myers 2008; Tetra Tech 2010g). In all 

cases, the groundwater drawdown modeled to occur to Empire Gulch is less than that near the mine 

site but larger than that experienced along Cienega Creek, as shown in tables 59 through 64 of the 

“Groundwater Quantity” resource section of this chapter. 

Level of Uncertainty for Empire Gulch

The levels of drawdown assessed for the near term in Empire Gulch are beyond the ability of the 

models to accurately predict and have a high level of uncertainty. Some of the levels of drawdown 

assessed for the long term in Empire Gulch are within the ability of the models to accurately predict 

and therefore have higher reliability. The long time frames and distance involved add a high level of 

uncertainty. Qualitatively, the trends for all three models suggest that drawdown could eventually 

occur; the impacts of that drawdown on stream flow could reasonably lie anywhere within the range 

of estimates provided. In addition, very little flow or channel data exist for Empire Gulch, and the 

applicability of the USGS stream gage data to represent Empire Gulch is highly uncertain. The stream 

gage data are more likely to be reasonable toward the confluence of Empire Gulch with Cienega 

Creek. Portions of Empire Gulch farther upstream are likely more sensitive and would experience 

greater impacts.

While the analysis contained in this section is quantitative, it reflects predicted impacts from 

relatively small amounts of groundwater drawdown, often fractions of a foot, that are occurring 

decades, hundreds, or even 1,000 years in the future. The conclusion of groundwater experts 

528 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

consulted by the Coronado is that such small drawdowns are beyond the ability of these groundwater 

models, or any groundwater model, to accurately predict (see the “Groundwater Quantity” resource 

section in chapter 3). It is important to understand that the detailed predictions contained in this 

section are meant to inform the decision and to show what could potentially happen if the model 

predictions were to occur as modeled; however, this does not change the overall uncertainty.

Analysis of impacts to BLM Federal reserved water rights associated with Empire Gulch is included 

in the “Indirect Impacts to Offsite Water Rights” part of the “Surface Water Quantity” resource 

section of this chapter. Water rights along Empire Gulch would likely be impacted by the changes 

described.

Near-Term Impacts

Existing Baseline Conditions— Under existing baseline conditions, dry conditions occur an average 

of 3 days per year (0.7 percent of the time), and dry or extremely low flow conditions (defined for 

this analysis as flow less than 0.2 foot) occur an average of 4 days per year (1.0 percent of the time).

Lowest Estimate— The lowest estimated drawdown at Empire Gulch 50 years after closure is less 

than 0.l foot. If occurring, in general this amount of drawdown is unlikely to result in any noticeable 

loss of surface flow in Empire Gulch.

Estimate Based on Best-Fit Models— Based on the best-fit models, the estimated drawdowns at 

Empire Gulch 50 years after closure for the three models are less than 0.1 foot (Montgomery), 

0.2 foot (Myers), and 0.5 foot (Tetra Tech). A drawdown of 0.2 foot would increase the risk of dry 

conditions occurring to 4 days per year (1.0 percent) and would increase the risk of dry or extremely 

low-flow conditions occurring to 146 days per year (40.1 percent). A drawdown of 0.5 foot would 

increase the risk of dry conditions occurring to 283 days per year (77.5 percent) and would increase 

the risk of dry or extremely low-flow conditions occurring to 352 days per year (96.3 percent). 

Highest Estimate— The highest estimated drawdown at Empire Gulch 50 years after closure is 1.8 

feet (Tetra Tech). A drawdown of 1.8 feet would increase the risk of dry conditions occurring to 361 

days per year (98.9 percent) and would increase the risk of dry or extremely low-flow conditions 

occurring to 362 days per year (99.1 percent).

Long-Term Impacts

Lowest Estimate— The lowest estimated drawdown at Empire Gulch 150 years after closure is 0.l 

foot (Montgomery). If occurring, in general this amount of drawdown is unlikely to result in any 

noticeable loss of surface flow in Empire Gulch. The lowest estimated drawdown at Empire Gulch 

1,000 years after closure is 2.3 feet (Montgomery). A drawdown of 2.3 feet would increase the risk of 

dry conditions occurring to 363 days per year (99.4 percent) and would increase the risk of dry or 

extremely low-flow conditions occurring to 363 days per year (99.5 percent).

Estimate Based on Best-Fit Models— Based on the best-fit models, the estimated drawdowns at 

Empire Gulch 150 years after closure for the three models are 0.3 foot (Montgomery and Myers) and 

2.5 feet (Tetra Tech). A drawdown of 0.3 foot would increase the risk of dry conditions occurring to 

32 days per year (8.8 percent) and would increase the risk of dry or extremely low-flow conditions 

occurring to 283 days per year (77.5 percent). A drawdown of 2.5 feet would increase the risk of dry 

conditions occurring to 363 days per year (99.5 percent) and would increase the risk of dry or 

extremely low-flow conditions occurring to 364 days per year (99.6 percent). The estimate 

drawdowns at Empire Gulch 1,000 years after closure for the three models are 3.3 feet 

Final Environmental Impact Statement for the Rosemont Copper Project 529
Chapter 3. Affected Environment and Environmental Consequences

(Montgomery), 4.3 feet (Myers), and 6.0 feet (Tetra Tech). These drawdowns would increase the risk 

of dry conditions occurring to 364 to 365 days per year (99.7 to 100 percent).

Highest Estimate— The highest estimated drawdown at Empire Gulch 150 years after closure is 5.0 

feet (Tetra Tech). The highest estimated drawdown at Empire Gulch 1,000 years after closure is 6.0 

feet (Tetra Tech). Either of these drawdowns would increase the risk of dry conditions occurring to 

365 days per year (100 percent).

Predicted Effects on Upper Cienega Creek Stream Flow

With respect to Upper Cienega Creek (Cienega Creek Reaches 1, 2, and 3, as shown in figure 67), 

no surface disturbance from mining facilities is located within the Upper Cienega Creek watershed 

upstream of the confluence with Davidson Canyon. Any contribution to perennial flows resulting 

from stormwater stored in shallow alluvial stream sediments would not be affected. Therefore, in 

assessing the potential changes to stream flow in Upper Cienega Creek, only the possible contribution 

to stream flow from the regional groundwater system is considered.

All three groundwater flow models predict changes in groundwater levels along Upper Cienega 

Creek (Montgomery and Associates Inc. 2010; Myers 2008; Tetra Tech 2010g). In all cases, the 

groundwater drawdown modeled to occur along Cienega Creek is less than that near the mine site, 

as shown in tables 59 through 64 of the “Groundwater Quantity” resource section of this chapter. 

Upper Cienega Creek also receives surface water flow from Empire Gulch, and the potential for 

reduction in Empire Gulch stream flow could therefore also result in reductions in Upper Cienega 

Creek’s stream flow as well. The percent contribution of Empire Gulch to Upper Cienega Creek has 

not been determined by fieldwork, but estimates of reductions have been incorporated into the 

analysis (SWCA Environmental Consultants 2013j). 

Level of Uncertainty for Upper Cienega Creek

The levels of drawdown assessed for the near term and long term in Upper Cienega Creek are beyond 

the ability of the models to accurately predict and have a high level of uncertainty. The long time 

frames and distance involved add a high level of uncertainty. Qualitatively, the trends for all three 

models suggest that drawdown could eventually occur; the impacts of that drawdown on stream flow

could reasonably lie anywhere within the range of estimates provided.

Public and cooperator comments suggest that small changes in groundwater level or flow, even if 

dwarfed by the natural background variability, have an additive effect that could impact riparian 

vegetation or aquatic species during times of drought or even seasonally. This possibility was 

disclosed in the DEIS and remains valid. Since the impact analysis makes use of the entire period 

of record on Upper Cienega Creek from 2001 to 2013, it incorporates these critical times of year. 

The daily depths of water for the USGS stream gage on Cienega Creek near Sonoita are shown in 

figure 70 for the period 2001 to 2013. Seasonally, the lowest mean monthly stream flows tend to 

occur in May and June. The lowest observed depth of water during this period was zero (June 2010), 

when the stream actually went dry for a period of 1 month. Clearly, a small change in stream flow

could result in loss of surface flow during these drought periods. 

530 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 70. Depth of water in Upper Cienega Creek for period of record, 2001 to 2013

While the analysis contained in this section is quantitative, it reflects predicted impacts from 

relatively small amounts of groundwater drawdown, often fractions of a foot, that are occurring 

decades, hundreds, or even 1,000 years in the future. The conclusion of groundwater experts 

consulted by the Coronado is that such small drawdowns are beyond the ability of these 

groundwatermodels, or any groundwater model, to accurately predict (see the “Groundwater

Quantity” resource section in chapter 3). It is important to understand that the detailed predictions 

contained in this section are meant to inform the decision and to show what could potentially happen 

if the model predictions were to occur as modeled; however, this does not change the overall 

uncertainty.

Near-Term Impacts

Existing Baseline Conditions— Under existing baseline conditions, dry conditions occur an average 

of 3 days per year (0.7 percent of the time), and dry or extremely low-flow conditions (defined for 

this analysis as flow less than 0.2 foot) occur an average of 4 days per year (1.0 percent of the time).

Lowest Estimate— The lowest estimated drawdown at Cienega Creek 50 years after closure is less 

than 0.l foot (for both the Montgomery and Tetra Tech models). If occurring, in general this amount 

of drawdown is unlikely to result in any noticeable loss of surface flow in Cienega Creek.

Final Environmental Impact Statement for the Rosemont Copper Project 531
Chapter 3. Affected Environment and Environmental Consequences

Estimate Based on Best-Fit Models— Based on the best-fit models, estimated drawdown at Cienega 

Creek 50 years after closure is less than 0.1 foot (for all three models). If occurring, in general this 

amount of drawdown is unlikely to result in any noticeable loss of surface flow in Cienega Creek. 

Highest Estimate— The highest estimated drawdown at Cienega Creek 50 years after closure is 0.15 

foot (Tetra Tech), but loss of contributing stream flow from Empire Gulch would increase this to 0.20 

foot. A drawdown of 0.2 foot would increase the risk of dry conditions occurring to 4 days per year 

(1.0 percent) and would increase the risk of dry or extremely low-flow conditions occurring to 141 

days per year (40.6 percent).

Long-Term Impacts

Lowest Estimate— The lowest estimated drawdown at Cienega Creek 150 years after closure is less 

than 0.l foot (for both the Montgomery and Tetra Tech models). If occurring, in general this amount 

of drawdown is unlikely to result in any noticeable loss of surface flow in Cienega Creek. The lowest 

estimated drawdown at Cienega Creek 1,000 years after closure is still less than 0.1 foot 

(Montgomery), but loss of contributing stream flow from Empire Gulch would increase this to 0.15 

foot. A drawdown of 0.15 foot would increase the risk of dry conditions occurring to 3 days per year 

(0.9 percent) and would increase the risk of dry or extremely low-flow conditions occurring to 88 

days per year (24.2 percent).

Estimate Based on Best-Fit Models— Based on the best-fit models, the estimated drawdowns along 

Cienega Creek 150 years after closure for the three models are less than 0.1 foot (Montgomery and 

Myers), and 0.25 foot (Tetra Tech); however, loss of contributing stream flow from Empire Gulch 

would increase these drawdowns to 0.15 foot and 0.3 foot, respectively. A drawdown of 0.15 foot 

would increase the risk of dry conditions occurring to 3 days per year (0.9 percent) and would 

increase the risk of dry or extremely low-flow conditions occurring to 88 days per year (24.2 

percent). A drawdown of 0.3 foot would increase the risk of dry conditions occurring to 32 days per 

year (8.8 percent) and would increase the risk of dry or extremely low-flow conditions occurring to 

283 days per year (77.5 percent). The estimated drawdowns along Cienega Creek 1,000 years after 

closure for the three models are less than 0.l foot (Montgomery), 0.2 foot (Myers), and 0.5 foot (Tetra 

Tech); however, loss of contributing stream flow from both Empire Gulch and Gardner Canyon 

would increase these drawdowns to 0.15 foot, 0.38 foot, and 0.68 foot, respectively. A drawdown of 

0.15 foot would increase the risk of dry conditions occurring to 3 days per year (0.9 percent) and 

would increase the risk of dry or extremely low-flow conditions occurring to 88 days per year 

(24.2 percent). A drawdown of 0.38 feet would increase the risk of dry conditions occurring to 125 

days per year (34.1 percent) and would increase the risk of dry or extremely low-flow conditions 

occurring to 339 days per year (92.8 percent). A drawdown of 0.68 foot would increase the risk of dry 

conditions occurring to 351 days per year (96.2 percent) and would increase the risk of dry or 

extremely low-flow conditions occurring to 354 days per year (96.9 percent).

Highest Estimate— The highest estimated drawdown along Cienega Creek 150 years after closure is 

0.35 foot (Tetra Tech), but loss of contributing stream flow from both Empire Gulch and Gardner 

Canyon would increase this to 0.53 foot. A drawdown of 0.53 foot would increase the risk of dry 

conditions occurring to 313 days per year (85.7 percent) and would increase the risk of dry or 

extremely low-flow conditions occurring to 352 days per year (96.5 percent). The highest estimated 

drawdown along Cienega Creek 1,000 years after closure is 0.5 foot (Tetra Tech), but loss of 

contributing stream flow from both Empire Gulch and Gardner Canyon would increase this to 0.68 

foot. A drawdown of 0.68 foot would increase the risk of dry conditions occurring to 351 days per 

532 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

year (96.2 percent) and would increase the risk of dry or extremely low-flow conditions occurring to 

354 days per year (96.9 percent).

Predicted Effects on Gardner Canyon Stream Flow

With respect to Gardner Canyon (Gardner Canyon Reach 2, as shown in figure 67), no surface 

disturbance from mining facilities would be located within the Upper Cienega Creek watershed 

upstream of the confluence with Davidson Canyon. Any contribution to perennial flows resulting 

from stormwater stored in shallow alluvial stream sediments would not be affected. Therefore, in 

assessing the potential changes to stream flow in Gardner Canyon, only the possible contribution to 

stream flow from the regional groundwater system is considered.

Groundwater drawdown modeled to occur at the confluence of Gardner Canyon and Cienega Creek is 

shown in tables 59 through 64 of the “Groundwater Quantity” resource section of this chapter. 

Level of Uncertainty for Gardner Canyon

The levels of drawdown assessed for the near term and long term in Gardner Canyon are beyond the 

ability of the models to accurately predict and have a high level of uncertainty. The long time frames 

and distance involved add a high level of uncertainty. Qualitatively, the trends for all three models 

suggest that drawdown could eventually occur; the impacts of that drawdown on stream flow could 

reasonably lie anywhere within the range of estimates provided. In addition, no flow or channel data 

exist for Gardner Canyon, and the applicability of the USGS stream gage data to represent Gardner 

Canyon is highly uncertain. The stream gage data are more likely to be reasonable toward the 

confluence of Gardner Canyon with Cienega Creek. Portions of Gardner Canyon farther upstream are 

likely more sensitive and would experience greater impacts.

While the analysis contained in this section is quantitative, it reflects predicted impacts from 

relatively small amounts of groundwater drawdown, often fractions of a foot, that are occurring 

decades, hundreds, or even 1,000 years in the future. The conclusion of groundwater experts 

consulted by the Coronado is that such small drawdowns are beyond the ability of these groundwater 

models, or any groundwater model, to accurately predict (see the “Groundwater Quantity” resource 

section in chapter 3). It is important to understand that the detailed predictions contained in this 

section are meant to inform the decision and to show what could potentially happen if the model 

predictions were to occur as modeled; however, this does not change the overall uncertainty.

Near-Term Impacts

Existing Baseline Conditions— Under existing baseline conditions, dry conditions occur an average 

of 3 days per year (0.7 percent of the time), and dry or extremely low-flow conditions (defined for 

this analysis as flow less than 0.2 foot) occur an average of 4 days per year (1.0 percent of the time).

Lowest Estimate— The lowest estimated drawdown at Gardner Canyon 50 years after closure is less 

than 0.l foot (for all three models). If occurring, in general this amount of drawdown is unlikely to 

result in any noticeable loss of surface flow in Gardner Canyon.

Estimate Based on Best-Fit Models— Based on the best-fit models, the estimated drawdown at 

Gardner Canyon 50 years after closure is less than 0.1 foot (for all three models). If occurring, in 

general this amount of drawdown is unlikely to result in any noticeable loss of surface flow in 

Gardner Canyon.

Final Environmental Impact Statement for the Rosemont Copper Project 533
Chapter 3. Affected Environment and Environmental Consequences

Highest Estimate— The highest estimated drawdown at Gardner Canyon 50 years after closure is 

0.15 foot (Tetra Tech). A drawdown of 0.15 foot would increase the risk of dry conditions occurring 

to 3 days per year (0.9 percent) and would increase the risk of dry or extremely low-flow conditions 

occurring to 88 days per year (24.2 percent).

Long-Term Impacts

Lowest Estimate— The lowest estimated drawdown at Gardner Canyon 150 years after closure is 

less than 0.l foot (for the Montgomery model). If occurring, in general this amount of drawdown is 

unlikely to result in any noticeable loss of surface flow in Gardner Canyon. The lowest estimated 

drawdown at Gardner Canyon 1,000 years after closure is still less than 0.1 foot (Montgomery). 

If occurring, in general this amount of drawdown is unlikely to result in any noticeable loss of surface 

flow in Gardner Canyon. 

Estimate Based on Best-Fit Models— Based on the best-fit models, the estimated drawdowns at 

Gardner Canyon 150 years after closure are less than 0.1 foot (Montgomery), 0.1 foot (Myers), and 

0.2 foot (Tetra Tech). A drawdown of 0.2 foot would increase the risk of dry conditions occurring to 4 

days per year (1.0 percent) and would increase the risk of dry or extremely low-flow conditions 

occurring to 146 days per year (40.1 percent). The estimated drawdowns at Gardner Canyon 1,000 

years after closure are less than 0.1 foot (Montgomery), 0.5 foot (Tetra Tech), and 2.2 feet (Myers). 

A drawdown of 0.5 foot would increase the risk of dry conditions occurring to 283 days per year 

(77.5 percent) and would increase the risk of dry or extremely low-flow conditions occurring to 352 

days per year (96.3 percent). A drawdown of 2.2 feet would increase the risk of dry conditions or 

extremely low-flow conditions occurring to 363 days per year (99.4 percent).

Highest Estimate— The highest estimated drawdown at Gardner Canyon 150 years after closure is 

0.4 foot (Montgomery). A drawdown of 0.4 foot would increase the risk of dry conditions occurring 

to 146 days per year (40.1 percent) and would increase the risk of dry or extremely low-flow 

conditions occurring to 349 days per year (95.5 percent). The highest estimated drawdown at Gardner 

Canyon by 1,000 years after closure is 2.2 feet. A drawdown of 2.2 feet would increase the risk of dry 

conditions or extremely low-flow conditions occurring to 363 days per year (99.4 percent).

Predicted Effect on Davidson Canyon Stream Flow

Potential impacts to stream flow in lower Davidson Canyon (Davidson Canyon Reach 4, as shown in 

figure 67) are handled in two separate ways. The available evidence suggests that the stream flow and 

springs arising in lower Davidson Canyon derive their water from a localized source, specifically 

storm flow stored in shallow alluvial stream sediments. Impacts have been analyzed assuming this 

source of water for lower Davidson Canyon. However, there is uncertainty with this interpretation.

Therefore, impacts to Davidson Canyon are also analyzed under the assumption that the stream flow 

and springs arising in lower Davidson Canyon are connected to the regional aquifer, which would be 

impacted by the mine pit.

Potential Impacts Based on a Shallow Alluvial Source

A detailed hydrogeologic analysis of Davidson Canyon was conducted by Tetra Tech (2010a)

specifically to assess potential impacts to stream flow and springs within Davidson Canyon. Rather 

than using modeling, this study focused on assessing observed field data in order to determine likely 

impacts to perennial stream flow in lower Davidson Canyon (Tetra Tech 2010a). Based on water 

quality data, geological mapping and reconnaissance, observed groundwater levels, and observed 

flow data, Tetra Tech (2010a) drew several conclusions about the source of surface flow that begins 

534 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

at Reach 2 Spring and persists intermittently to the confluence of Cienega Creek. The Tetra Tech 

(2010a) report concludes that it is likely that Reach 2 Spring (as well as Escondido Spring, which is 

closer to the confluence with Cienega Creek) derives its water from ephemeral storm flows stored in 

the shallow alluvial stream sediments, which are then forced to the surface by bedrock constrictions 

of the stream channel, and that these springs are not likely connected to the regional aquifer that 

would be impacted by the mine pit. 

These conclusions are based on several lines of evidence. Geological conditions were observed that 

would be conducive to forcing shallow alluvial water to the surface in the locations of Reach 2 and 

Escondido Springs. In addition, isotope signatures of water from Reach 2 Spring and Escondido 

Spring both reflect the influence of summer precipitation, in contrast to wells in the regional aquifer, 

which reflect the influence of winter precipitation. Finally, this stretch of Davidson Canyon has 

actually been dry during the past few years, rather than being supported by perennial flow, as would 

be expected from a more constant regional groundwater source. 

After publication of the DEIS, the Coronado undertook further investigation of impacts to 

Outstanding Arizona Waters, including those of Davidson Canyon, and specifically tasked SRK 

Consulting to review and weigh the evidence and determine the most likely source of water for flow 

in Davidson Canyon (Garrett 2012h; Ugorets, Cope, and Hoag 2012). SRK Consulting concluded that

while some of the available evidence was anecdotal and less than certain, the available information 

suggests that there is no connection between the Davidson Canyon springs and the regional aquifer. 

Primary lines of evidence for this conclusion included observed groundwater levels in a well located 

in lower Davidson Canyon and completed in bedrock, observations of Reach 2 Spring during 

sequential field visits, and isotopic signatures of the spring water (Ugorets, Cope, and Hoag 2012).

These studies suggest that drawdown in the regional groundwater is unlikely to affect the springs in 

lower Davidson Canyon. Conversely, these studies also suggest that reductions in surface flow have 

the potential to reduce recharge to the shallow alluvial aquifer in lower Davidson Canyon and thereby 

impact Reach 2 and Escondido Spring and potential base flow between those springs and Cienega 

Creek. Unlike for Upper Cienega Creek, the proposed surface disturbance by the mine within the 

headwaters of the Davidson Canyon watershed would reduce surface water flows.

Modeling of changes in ephemeral surface runoff as a result of the mine activities has been conducted 

(Krizek 2010a, 2010b, 2010c, 2010d; Zeller 2012). Runoff in Barrel Canyon (at SR 83) would

decrease by approximately 17 to 46 percent, depending on the alternative, as a result of capture of 

runoff by mine facilities. This change in stream flow would decrease with distance downstream 

(Zeller 2011a). Estimated reductions in surface flow in lower Davidson Canyon (approximately 12 

miles downstream) range from 4.3 to 11.5 percent (SWCA Environmental Consultants 2012d).

The surface water hydrology of the watershed suggests that modeling of reduced surface flows in 

lower Davidson Canyon is likely overestimated. Specifically, the estimates above are based on 

regression equations in an ideal watershed without consideration of channel losses. In reality, in order 

to recharge the stream aquifer in lower Davidson Canyon, storm flows from Barrel Canyon need to 

travel downstream approximately 12 miles in an ephemeral stream channel (desert wash) composed 

of pockets of highly transmissive sediments. Multiple studies have estimated stream losses in 

ephemeral stream channels, with a range between 0.3 acre-foot and more than 17,000 acre-feet of 

water lost per mile of ephemeral channel (Cataldo et al. 2004). Qualitatively, given the travel distance 

from Barrel Canyon, the recharge in lower Davidson Canyon is more likely to derive from closer 

Final Environmental Impact Statement for the Rosemont Copper Project 535
Chapter 3. Affected Environment and Environmental Consequences

tributaries, although certainly during larger flow events, contribution from Barrel Canyon could 

occur.

In summary, the weight of the available evidence suggests that lower Davidson Canyon is not 

hydraulically connected to the regional aquifer that would be impacted by the pit dewatering. 

Changes in surface flow and, therefore, to the recharge to shallow alluvial aquifers are possible as a 

result of disturbance by the mine and the removal of portions of the watershed upstream. The effect of 

the reduction in surface flow is estimated and could reduce storm flows by 4.3 to 11.5 percent, 

depending on alternative, but this effect on recharge is likely to be overestimated, with the 

contribution being less owing to the distance downstream of the project area and substantial channel 

losses. Predictions of loss of recharge to the shallow alluvial aquifer have a high level of uncertainty 

because of the nature of the channels and the relatively great distance between the impacts from the 

proposed mine and lower Davidson Canyon.

Comments from cooperating agencies have suggested that the distance between the mine site and 

lower Davidson Canyon is not pertinent, as any losses to the shallow alluvial aquifer in Barrel 

Canyon and Davidson Canyon would eventually flow into lower Davidson Canyon anyway as 

subflow in the shallow alluvial aquifer. This is not a realistic scenario based on the actual 

characteristics of the channel. There are substantial stretches of stream channel with rock present at 

the surface and no alluvium at all (Patterson and Annandale 2012). The stream channel along Barrel 

Canyon and Davidson Canyon is not a continuous thread of alluvium, but rather linear pockets of 

alluvium separated by reaches with little or no alluvial material. This is a common occurrence in 

southern Arizona.

The fate of stormwater infiltrating into these pockets of alluvium would be varied. Some of the 

stormwater would be stored as soil moisture in the channel or channel banks and would not infiltrate 

to any shallow water table. Some of the stormwater would be used by riparian vegetation, either 

drawing directly from a shallow water table (typical with hydroriparian vegetation like cottonwoods 

or willows) or from stored soil moisture (typical with xeroriparian vegetation). This stormwater 

would be transpired and lost to the watershed, although for a beneficial use. Some stormwater would 

infiltrate through alluvial materials and fractures in the bedrock, recharging the regional aquifer. It is 

also likely that the regional aquifer could contribute water to shallow alluvial materials in the same 

manner. Some stormwater would flow subsurface downstream and be forced to the surface by 

constrictions in the stream channel; indeed, this is likely the case for Barrel Spring in Barrel Canyon 

and for Reach 2 and Escondido Springs in lower Davidson Canyon.

The studies cited in the section (Cataldo et al. 2004) have not been used to try to quantify the 

stormwater losses. This would not be appropriate, given that these studies are not all applicable to the 

geology along Barrel Canyon and Davidson Canyon and that the uncertainty and range of results is so 

great. These studies are cited solely as an indication that stormwater losses in ephemeral channels are 

a physical reality and can be substantial. The effect on surface flows in lower Davidson Canyon, 

assuming no transmission losses at all, ranges from 4.3 to 11.5 percent. This effect should be 

considered a maximum possible loss to shallow alluvial aquifers in lower Davidson Canyon, with 

actual losses likely to be much lower.

Potential Impacts Based on a Regional Source

If the assumption that the springs in lower Davidson Canyon are not connected to the regional aquifer

is incorrect, an assessment similar to that conducted for Upper Cienega Creek, Empire Gulch, and 

Gardner Canyon can be used to assess potential impacts to Davidson Canyon.

536 Final Environmental Impact Statement for the Rosemont Copper Project
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Level of Uncertainty for Davidson Canyon—The levels of drawdown assessed for both the near 

term and long term in Davidson Canyon are beyond the ability of the models to accurately predict 

and have a high level of uncertainty. The long time frames and distance involved also add a high level 

of uncertainty. Qualitatively, the trends for the models suggest that drawdown could eventually occur; 

the impacts of that drawdown on stream flow could reasonably lie anywhere within the range of 

estimates provided, if the springs in lower Davidson Canyon are in connection with the regional 

aquifer.

While the analysis contained in this section is quantitative, it reflects predicted impacts from 

relatively small amounts of groundwater drawdown, often fractions of a foot, that are occurring 

decades, hundreds, or even 1,000 years in the future. The conclusion of groundwater experts 

consulted by the Coronado is that such small drawdowns are beyond the ability of these groundwater 

models, or any groundwater model, to accurately predict (see the “Groundwater Quantity” resource 

section in chapter 3). It is important to understand that the detailed predictions contained in this 

section are meant to inform the decision and to show what could potentially happen if the model 

predictions were to occur as modeled; however, this does not change the overall uncertainty.

Near-Term Impacts—

Lowest Estimate – The lowest estimated drawdown at Reach 2 Spring in Davidson Canyon 50 

years after closure is less than 0.l foot (for both the Montgomery and Tetra Tech models). If 

occurring, in general this amount of drawdown is unlikely to result in any noticeable loss of 

surface flow in Davidson Canyon.

Estimate Based on Best-Fit Models – Based on the best-fit models, the estimated drawdowns at 

Reach 2 Spring 50 years after closure are 0.1 foot or less (for both the Montgomery and Tetra 

Tech models). If occurring, in general this amount of drawdown is unlikely to result in any 

noticeable loss of surface flow in Davidson Canyon.

Highest Estimate – The highest estimated drawdown at Reach 2 Spring 50 years after closure is 

1.5 foot (Montgomery). If occurring and if Reach 2 Spring is in connection with the regional 

aquifer, in general this amount of drawdown would likely cause widespread absence of surface 

flow for large portions of the year.

Long-Term Impacts—

Lowest Estimate – The lowest estimated drawdown at Reach 2 Spring up to 1,000 years after 

closure is less than 0.l foot (Montgomery). If occurring, in general this amount of drawdown is 

unlikely to result in any noticeable loss of surface flow in Davidson Canyon. 

Estimate Based on Best-Fit Models – Based on the best-fit models, the estimated drawdowns at 

Reach 2 Spring 150 years after closure are less than 0.1 foot (Tetra Tech) and 0.3 foot 

(Montgomery). If occurring and if Reach 2 Spring is in connection with the regional aquifer, in 

general this amount of drawdown would noticeably reduce stream flows but would not result in 

widespread absence of flow. This amount of drawdown would potentially cause a reduction in the 

length of wet sections or even drying of some sections. Based on the best-fit models, the 

estimated drawdowns at Reach 2 Spring 1,000 years after closure are 0.3 foot (Tetra Tech) and 

1.0 feet (Montgomery). If occurring and if Reach 2 Spring is in connection with the regional 

aquifer, in general this amount of drawdown would likely cause widespread absence of surface 

flow for large portions of the year.

Final Environmental Impact Statement for the Rosemont Copper Project 537
Chapter 3. Affected Environment and Environmental Consequences

Highest Estimate – The highest estimated drawdown at Reach 2 Spring 150 years after closure is 

3.0 feet, reaching 4.0 feet 1,000 years after closure (Montgomery). If occurring and if Reach 2 

Spring is in connection with the regional aquifer, in general this amount of drawdown would 

likely cause widespread absence of surface flow for large portions of the year.

Predicted Effects on Lower Cienega Creek Perennial Stream Flow

The potential for reduction of perennial stream flow on Lower Cienega Creek (Cienega Creek 

Reaches 4 and 5, as shown in figure 67) would be driven by two factors. Reduction of contribution 

from Davidson Canyon could affect Reach 5, and reduction of contribution from Upper Cienega 

Creek could affect Reaches 4 and 5.

Based on the analysis of Davidson Canyon presented above, the same conclusions would apply to 

Lower Cienega Creek below the confluence with Davidson Canyon. Effects on Cienega Creek due to 

surface flow reduction would be minimal (see the “Effect on Groundwater Discharge from Davidson 

Canyon” part of the “Groundwater Quantity” resource section of this chapter).

The difference in hydrology between Upper Cienega Creek and Lower Cienega Creek makes it 

difficult to determine how changes in Upper Cienega Creek would propagate downstream. There is a 

geographic disconnect between the typically perennial sections of Upper Cienega Creek and Lower 

Cienega Creek. Over the past decade, Lower Cienega Creek has experienced negative stream flow 

trends due in great part to the ongoing drought. However, over this same time period, Upper Cienega 

Creek has exhibited relatively little change in summer or winter base flow. This does not indicate that 

Upper Cienega Creek is not an important contributor to flow to Lower Cienega Creek; rather, it 

suggests that Lower Cienega Creek also relies on other sources of water that are more sensitive to 

drought.

For predicting impacts, the most conservative approach is to assume that any changes on Upper 

Cienega Creek driven by groundwater drawdown would propagate to Lower Cienega Creek as well, 

and that similar changes in perennial stream flow would be experienced downstream as well as 

upstream.

Summary of Impacts to Stream flow

To summarize impacts to stream flow, it is useful to translate the increase in risk of drying to the 

definitions of perennial, intermittent, and ephemeral streams. A perennial stream exhibits flow in 

response to groundwater most of the year, although dry spells do occur, as happened in June 2010 on 

Upper Cienega Creek. Slight increases in risk of drying, for instance from an average of 3 days per 

year to 4 days per year, would not shift the stream from perennial to intermittent. However, increases 

in the risk of drying that suggest dry spells would occur with regularity instead of infrequently could 

shift the stream from perennial to intermittent. For the purposes of this analysis, an increase in risk of 

drying to anything more than 30 days per year suggests that dry spells would occur regularly, likely 

during low summer flows in May and June and therefore would shift the stream from perennial to 

intermittent. Ephemeral streams flow only in response to storms, which occur approximately 15 days 

per year; therefore, an increase in risk of drying that extends longer than about 350 days per year 

would be considered to shift the stream from perennial or intermittent to ephemeral. As noted earlier, 

drawdown happens steadily over time, and impacts would be present at times other than the time 

frames of 50, 150, and 1,000 years after closure.

538 Final Environmental Impact Statement for the Rosemont Copper Project
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• For Empire Gulch, the lowest estimates of drawdown would not change the perennial nature 

of the stream up to 150 years after closure, but the stream would be ephemeral by 1,000 years 

after closure.

• For Empire Gulch, estimates of drawdown for best-fit models are mixed. Two of the best-fit 

models indicate that the stream would shift from perennial to intermittent by150 years after 

closure. One of the best-fit models indicates that the stream would be intermittent by 50 years 

after closure and ephemeral by 150 years after closure. All three best-fit models indicate that 

the stream would be ephemeral by 1,000 years after closure.

• For Empire Gulch, the highest estimates of drawdown indicate a change from perennial to 

ephemeral stream by 50 years after closure.

• For Upper Cienega Creek, the lowest estimates of drawdown would not change the perennial 

nature of the stream, even up to 1,000 years after closure.

• For Upper Cienega Creek, estimates of drawdown for best-fit models are mixed. One best-fit 

model indicates that the perennial nature of the stream would not change even up to 1,000 

years after closure. One best-fit model indicates the stream would remain perennial up 

through 150 years after closure but would gradually become intermittent by 1,000 years after 

closure. The third best-fit model indicates the stream would remain perennial up through 50 

years after closure, would gradually become intermittent by 150 years after closure with dry 

periods averaging 1 month per year, and would become ephemeral by 1,000 years after 

closure.

• For Upper Cienega Creek, the highest estimates of drawdown would not change the perennial 

nature of the stream up through 50 years after closure, but the stream would gradually 

become intermittent by 150 years after closure and would become ephemeral by 1,000 years 

after closure.

• For Lower Cienega Creek, the same impacts experienced on Upper Cienega Creek are 

assumed to propagate downstream and be experienced on Lower Cienega Creek as well.

• For Gardner Canyon, the lowest estimates of drawdown would not change the perennial 

nature of the stream, even up to 1,000 years after closure.

• For Gardner Canyon, estimates of drawdown for best-fit models would not change the 

perennial nature of the stream up through 150 years after closure. At 1,000 years after 

closure, results are mixed, with one model indicating a perennial stream, one model 

indicating an intermittent stream, and one model indicating an ephemeral stream.

• For Gardner Canyon, the highest estimates of drawdown would not change the perennial 

nature of the stream up through 50 years after closure. The stream would gradually become 

intermittent by 150 years after closure, and by 1,000 years after closure, the stream would be 

ephemeral.

• The weight of the available evidence suggests that lower Davidson Canyon is not 

hydraulically connected to the regional aquifer that would be impacted by the pit dewatering. 

Changes in surface flow and, therefore, to the recharge to shallow alluvial aquifers are 

possible as a result of disturbance and the removal of portions of the watershed upstream by 

mining activities. There would be an estimated reduction in surface flow of 4.3 to 11.5 

percent, depending on the alternative, but a similar effect on recharge is likely to be 

overpredicted because of the distance downstream of the project area and the high channel 

transmission losses. 

Final Environmental Impact Statement for the Rosemont Copper Project 539
Chapter 3. Affected Environment and Environmental Consequences

Indirect Effect on Water Quality due to Stream Flow Depletion

As noted, the risk of drying (i.e., shifting the nature of flow from perennial to intermittent or 

ephemeral) is only one of the negative outcomes that can occur from impact of drawdown along 

Upper Cienega Creek, Empire Gulch, and Gardner Canyon. Extremely low-flow conditions can also 

have an effect, primarily due to potential changes in water quality.

Under existing conditions, Upper Cienega Creek seasonally experiences depths of flow as low as 

about 0.3 foot in May and June. As the amount of flow in the stream decreases, water temperatures 

can increase, dissolved oxygen can become depleted, nutrient loads can become more concentrated, 

and the assimilative capacity of the stream can be reduced. The exact amount of change in water 

quality cannot be easily quantified, but down to depths of 0.3 foot, the water quality would remain 

within the seasonal variation experienced under existing conditions.

The risk of extremely low-flow conditions (defined for this analysis as 0.2 foot or less) has been 

quantified. While the analysis contained in this section is quantitative, it reflects predicted impacts 

from relatively small amounts of groundwater drawdown, often fractions of a foot, that are occurring 

decades, hundreds, or even 1,000 years in the future. The conclusion of groundwater experts 

consulted by the Coronado is that such small drawdowns are beyond the ability of these groundwater 

models, or any groundwater model, to accurately predict (see the “Groundwater Quantity” resource 

section in chapter 3). It is important to understand that the detailed predictions contained in this 

section are meant to inform the decision and to show what could potentially happen if the model 

predictions were to occur as modeled; however, this does not change the overall uncertainty.

Under these conditions, water quality would continue to deteriorate and would reach levels not 

typically experienced in the stream. Note that the impacts described below do not include any periods 

when the stream has been predicted to be ephemeral (see “Effects on Perennial Stream flow” part of 

this resource section).

• For Empire Gulch, the lowest estimates of drawdown indicate that the risk of extremely lowflow conditions and degraded water quality occurring does not change.

• For Empire Gulch, estimates of drawdown for best-fit models mostly indicate a substantial 

increase in the risk of extremely low-flow conditions and degraded water quality starting as 

early as 50 years after closure, increasing from an average of 4 days per year to at least 146 

days per year, although one model indicates no changes at 50 years after closure. By 150 

years after closure, substantial portions of the year (283 days per year) would be experiencing 

low-flow conditions and degraded water quality.

• For Upper Cienega Creek, the lowest estimates of drawdown indicate that the risk of 

extremely low-flow conditions and degraded water quality occurring does not change up to 

150 years after closure. At 1,000 years after closure, the risk increases somewhat from an 

average of 4 days per year under existing conditions to 88 days per year. These days would 

occur seasonally during the summer.

• For Upper Cienega Creek, estimates of drawdown for best-fit models indicate that the risk of 

extremely low-flow conditions and degraded water quality occurring does not change up to 

50 years after closure. At 150 years after closure, the risk increases from an average of 4 days 

per year under existing conditions to anywhere from 88 to 283 days per year. At 1,000 years 

after closure, the risk increases to anywhere from 88 days to nearly the whole year (339 

days).

540 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

• For Upper Cienega Creek, the highest estimates of drawdown indicate a substantial increase 

in the risk of extremely low-flow conditions and degraded water quality starting as early as 

50 years after closure, increasing from an average of 4 days per year to 146 days per year, 

and eventually to nearly the whole year (352 days) by 150 years after closure.

• For Gardner Canyon, the lowest estimates of drawdown indicate that the risk of extremely 

low-flow conditions and degraded water quality occurring does not change.

• For Gardner Canyon, estimates of drawdown for best-fit models indicate that the risk of 

extremely low-flow conditions and degraded water quality occurring does not change up to 

50 years after closure. At 150 years after closure results are mixed, indicating anywhere from 

no change in risk up to an increase to146 days of extremely low-flow conditions and 

degraded water quality. At 1,000 years after closure results remain mixed, indicating 

anywhere from no change in risk up to nearly the whole year (352 days).

• For Gardner Canyon, the highest estimates of drawdown indicate an increase in the risk of 

extremely low-flow conditions and degraded water quality starting as early as 50 years after 

closure, increasing from an average of 4 days per year to 88 days per year, and eventually to 

nearly the whole year (349 days) by 150 years after closure.

Indirect Effect on Riparian Vegetation

The direct disturbance of xeroriparian vegetation present in onsite washes varies by alternative and is 

presented by alternative later in this section. This section addresses the indirect effects on riparian 

vegetation beyond the surface disturbance within the project area, owing either to changes in 

stormwater runoff or to changes in groundwater levels. The analysis contained in this section depends 

on the quantitative assessment provided earlier in this chapter. That assessment was based on 

predicted impacts from relatively small amounts of groundwater drawdown, often fractions of 

a foot, that are occurring decades, hundreds, or even 1,000 years in the future. The conclusion of 

groundwater experts consulted by the Coronado is that such small drawdowns are beyond the ability 

of these groundwater models, or any groundwater model, to accurately predict (see the “Groundwater

Quantity” resource section in chapter 3). It is important to understand that the detailed predictions 

contained in this section are meant to inform the decision and to show what could potentially happen 

if the model predictions were to occur as modeled; however, this does not change the overall 

uncertainty.

Predicted Effect on Riparian Vegetation in Empire Gulch

Hydroriparian habitat is present. An estimated 407 acres has been mapped as hydroriparian habitat 

and may be affected. Xeroriparian habitat is also present but is unlikely to be affected.

Lowest Estimate

In the near term, the lower estimates of groundwater drawdown (0.1 foot) would not be likely to 

result in any changes to riparian vegetation or impacts to aquatic vegetation. In the long term, the 

lower estimates of groundwater drawdown (2.3 feet) would be unlikely to cause widespread mortality 

or transition from hydroriparian to xeroriparian habitat since many of these species can still access 

water several feet below ground surface. However, cottonwood/willow forest would experience stress 

due to deeper groundwater availability, including a decrease in canopy height and vegetation volume.

While total conversion from a hydroriparian to a xeroriparian corridor is unlikely, there is likely to be 

contraction of the hydroriparian area, with conversion occurring at the transitional margins of the 

habitat. Herbaceous perennials (bulrush, cattail, grasses) and annuals would experience mortality and 

Final Environmental Impact Statement for the Rosemont Copper Project 541
Chapter 3. Affected Environment and Environmental Consequences

reduced abundance. In the long term, wetland complexes within the hydroriparian zone would likely 

experience drying and mortality of obligate wetland plants, and aquatic vegetation would experience 

widespread mortality.

Estimate Based on Best-Fit Models

In the near term, the estimates of groundwater drawdown based on the best-fit models (0.2 foot) 

would not be likely to result in any changes to riparian vegetation. In the long term, the estimates of 

groundwater drawdown based on the best-fit models (4.3 feet) would contribute to mortality and a 

transition from hydroriparian to xeroriparian habitat. Cottonwood/willow forest would experience 

increased mortality rates and a decrease in canopy height and vegetation volume, and the transition 

from cottonwood/willow forest to deeper rooted tamarisk or mesquite would be encouraged.

Herbaceous perennials (bulrush, cattail, grasses) and annuals would experience mortality and reduced 

abundance. In the long term, wetland complexes within the hydroriparian zone would likely 

experience drying and mortality of obligate wetland plants, and aquatic vegetation would experience 

widespread mortality.

Highest Estimate

In the near term, the higher estimate of groundwater drawdown (1.8 feet) would be unlikely to cause 

widespread mortality or transition from hydroriparian to xeroriparian habitat, but cottonwood/willow 

forest would experience stress due to deeper groundwater availability, including a decrease in canopy 

height and vegetation volume. While total conversion from a hydroriparian to a xeroriparian corridor 

is unlikely, there is likely to be contraction of the hydroriparian area, with conversion occurring at the 

transitional margins of the habitat. Herbaceous perennials (bulrush, cattail, grasses) and annuals 

would experience mortality and reduced abundance. In the long term, the higher estimate of 

groundwater drawdown (6.0 feet) would contribute to mortality and a transition from hydroriparian to 

xeroriparian habitat. Cottonwood/willow forest would experience increased mortality rates and a 

decrease in canopy height and vegetation volume, and the transition from cottonwood/willow forest 

to deeper rooted tamarisk or mesquite would be encouraged. Herbaceous perennials (bulrush, cattail, 

grasses) and annuals would experience mortality and reduced abundance. In the near term and long

term, wetland complexes within the hydroriparian zone would likely experience drying and mortality 

of obligate wetland plants, and aquatic vegetation would experience widespread mortality.

Predicted Effect on Riparian Vegetation in Cienega Creek (Reaches 1 through 5)

Lowest Estimate

The lower estimates of groundwater drawdown (less than 0.1 foot) would not be likely to result in 

any changes to riparian vegetation, even up through 1,000 years after mine closure.

Estimate Based on Best-Fit Models

The estimates of groundwater drawdown based on the best-fit models (up to 0.5 foot) would not be 

likely to result in any changes to riparian vegetation, even up through 1,000 years after mine closure.

Highest Estimate 

The higher estimate of groundwater drawdown (up to 0.8 foot) would not be likely to result in 

widespread changes to riparian vegetation, even up through 1,000 years after mine closure. However, 

while total conversion from a hydroriparian to a xeroriparian corridor is unlikely, there is likely to be 

contraction of the hydroriparian area, with conversion occurring at the transitional margins of the 

habitat.

542 Final Environmental Impact Statement for the Rosemont Copper Project
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Predicted Effect on Riparian Vegetation in Gardner Canyon (Reaches 1 and 2)

Lowest Estimate 

The lower estimates of groundwater drawdown (less than 0.1 foot) would not be likely to result in 

any changes to riparian vegetation, even up through 1,000 years after mine closure.

Estimates Based on Best-Fit Models

The estimates of groundwater drawdown based on best-fit models (up to 0.5 foot) would not be likely 

to result in any changes to riparian vegetation, even up through 1,000 years after mine closure.

Highest Estimate 

The higher estimate of groundwater drawdown (up to 0.8 foot) would not be likely to result in 

widespread changes to riparian vegetation, even up through 1,000 years after mine closure. However, 

while total conversion from a hydroriparian to a xeroriparian corridor is unlikely, there is likely to be 

contraction of the hydroriparian area, with conversion occurring at the transitional margins of the 

habitat.

Predicted Effect on Riparian Vegetation in Davidson Canyon (Reach 1)

Predicted Hydrologic Changes

This reach of Davidson Canyon is upstream of the confluence with Barrel Canyon. No changes in 

surface flow are expected to occur.

Drawdown in the regional aquifer is predicted to range from 10 to 100 feet in this location; however, 

this reach of Davidson Canyon is primarily xeroriparian, with pockets of mesoriparian vegetation. 

Some of this vegetation may rely on groundwater but would most likely be relying on shallow 

alluvial groundwater, as there are no indications of perennial or intermittent flow in this reach and no 

extensive hydroriparian or mesoriparian galleries. No change would be expected to occur with 

shallow alluvial groundwater.

Expected Effects on Riparian Vegetation

No areas of riparian vegetation associated with this reach of Davidson Canyon would be expected to 

be impacted based on the hydrologic changes described above.

Predicted Effect on Riparian Vegetation in Davidson Canyon (Reach 2)

Predicted Hydrologic Changes

As with Reach 1 of Davidson Canyon, drawdown in the regional aquifer is predicted (ranging from 5 

to 10 feet). However, there are no indications of connection of this reach to regional groundwater. 

On the other hand, changes in surface flow can be estimated to occur along this reach and would 

range from 13.1 to 34.8 percent (SWCA Environmental Consultants 2012d). This reach is close 

enough to the mine disturbance in Barrel Canyon that this prediction has a relatively high level of 

certainty. This change in surface flow may reduce the amount of stormwater recharging the shallow 

alluvial aquifer and therefore the amount available for riparian habitat.

Expected Effects on Riparian Vegetation

This reach of Davidson Canyon is characterized as xeroriparian habitat with pockets of mesoriparian 

habitat; these pockets of mesoriparian habitat may be supported by shallow alluvial groundwater.

Pockets of mesoriparian habitat may experience reduced recruitment, increased mortality rates, 

Final Environmental Impact Statement for the Rosemont Copper Project 543
Chapter 3. Affected Environment and Environmental Consequences

decreased canopy height and vegetation volume, and potentially a transition to deeper rooted species 

such as tamarisk or mesquite. An estimated 502 acres has been mapped by Pima County as 

hydroriparian habitat along this reach (although reinterpreted for this analysis as xeroriparian with 

pockets of mesoriparian) and may be affected. The acreage that may be affected (502 acres) is less 

than that shown for Davidson Canyon Reach 2 in table 110 (570 acres), as some of the riparian areas 

along adjoining tributaries are unlikely to be affected by reductions in surface flow.

The major xeroriparian species present are adapted to cyclical climatic conditions and do not rely on 

groundwater. Effects on this xeroriparian habitat, from less water availability and reduced flood 

disturbance, could vary greatly, from reduced vegetation volume to mortality of individuals; however,

a complete loss of xeroriparian habitat is unlikely. 

Predicted Effect on Riparian Vegetation in Davidson Canyon (Reaches 3 and 4)

Predicted Hydrologic Changes

While historically some perennial or intermittent stream flow has occurred in Reach 4 of Davidson 

Canyon, as analyzed earlier in this section, the water sources in lower Davidson Canyon are unlikely 

to be connected with the regional aquifer or to experience changes owing to drawdown in that 

aquifer.

Changes in surface flow can be estimated to occur along these reaches and would range from 4.3 to 

11.5 percent (SWCA Environmental Consultants 2012d); these changes theoretically could affect 

recharge to the shallow alluvial aquifer. However, these reaches are a great distance downstream, and 

as previously discussed, given the travel distance from Barrel Canyon, the recharge in lower 

Davidson Canyon is more likely to derive from closer tributaries, although certainly during larger 

flow events contribution from Barrel Canyon could occur. The effect on recharge is likely to be 

overestimated, with the contribution being less owing to the distance downstream of the project area

and substantial channel losses. Predictions of losses to recharge to the shallow alluvial aquifer and 

therefore loss of water available to support riparian vegetation have a high level of uncertainty.

Expected Effects on Riparian Vegetation

Reach 3 of Davidson Canyon consists of xeroriparian habitat with pockets of mesoriparian habitat

that may be supported by shallow alluvial groundwater. The major xeroriparian species present are 

adapted to cyclical climatic conditions and do not rely on groundwater. Effects on this xeroriparian 

habitat from less water availability and reduced flood disturbance are unlikely, given the expected 

reduction in flow. 

Pockets of mesoriparian habitat are similarly unlikely to experience effects, given the unlikely effects 

on recharge of the alluvial aquifer.

Reach 4 of Davidson Canyon has been classified as hydroriparian habitat. Similarly, this habitat is 

unlikely to experience effects, given the unlikely effects on recharge of the alluvial aquifer.

Predicted Effect on Riparian Vegetation in Barrel Canyon (Reaches 1 and 2)

Predicted Hydrologic Changes

Drawdown in the regional aquifer is predicted to range from 10 to 100 feet in this location; however, 

this reach of Barrel Canyon is primarily xeroriparian, with pockets of mesoriparian vegetation. Some 

of this vegetation may rely on regional groundwater but is most likely relying on shallow alluvial 

544 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

groundwater, as there are no indications of perennial or intermittent flow in this reach and no 

extensive hydroriparian or mesoriparian galleries. 

The primary hydrologic changes along Barrel Canyon would be the result of a reduction in surface 

runoff, which with high certainty would range from 17.2 to 45.8 percent. Even for the Barrel 

Alternative, for which stormwater management was redesigned to maximize downstream flow, this 

percentage only reflects the postclosure reduction in flow, and greater effects would be felt generally 

in the first 10 years of the mine life (up to a 30 to 40 percent reduction) before concurrent reclamation

is established that allows more water to flow to the downstream watershed. The reduction in runoff 

would persist in the long term, even after final reclamation and closure, as some portions of the 

watershed would be permanently cut off. 

Expected Effects on Riparian Vegetation

These reaches of Barrel Canyon are considered xeroriparian habitat with pockets of mesoriparian 

habitat. The primary concern is not the reduction in recharge of a shallow alluvial aquifer, as the 

major xeroriparian and mesoriparian species present are adapted to cyclical climatic conditions and 

do not rely on groundwater. Instead, the decrease in overall water availability in general would result 

in changes in riparian vegetation. These changes are difficult to quantify. Unlike hydroriparian 

species and the extensive studies on the San Pedro River and elsewhere, changes in xeroriparian 

vegetation as a result of water availability have not been greatly studied. In general, water availability 

does not necessarily change the species makeup of xeroriparian habitat but reduces the overall 

vitality, extensiveness, and health. These effects are quite easy to observe; overall water availability is 

the sole difference between the four classes of xeroriparian habitat defined and mapped by Pima 

County. 

Effects on this xeroriparian habitat from less water availability and reduced flood disturbance could 

vary greatly, from reduced vegetation volume to mortality of individuals. A complete loss of 

xeroriparian habitat is unlikely, but a transition from high quality xeroriparian habitat to lesser quality 

xeroriparian habitat is highly likely in these reaches of Barrel Canyon. A total of 162 acres of riparian 

habitat has been mapped along these reaches that may be affected. The acreage that may be affected 

(162 acres) is less than that shown for Barrel Canyon Reaches 1 and 2 in table 110 (205 acres), as 

some of the riparian areas along adjoining tributaries are unlikely to be affected by reductions in 

surface flow.

Monitoring Intended to Assess Potential Stream Flow Impacts

In consideration of the uncertainty associated with predicting long-term impact to stream flow, three 

monitoring components have been incorporated into the “Mitigation and Monitoring Plan” (see 

appendix B for full details). The monitoring includes:

• Monitoring to determine impacts from pit dewatering on downstream sites in Barrel 

and Davidson Canyons (FS-BR-22). Monitoring would be conducted of surface water, 

alluvial groundwater, and deeper groundwater at sites in Barrel and Davidson Canyons. 

Several locations have already been installed and are being actively monitored, whereas 

others would require access from landowners.

• Periodic validation and rerun of groundwater model throughout life of mine (FS-BR27). This measure would involve basic data collection of water levels, meteorological data, 

and water balance components, which would allow for the predictions of groundwater 

Final Environmental Impact Statement for the Rosemont Copper Project 545
Chapter 3. Affected Environment and Environmental Consequences

impacts to be revised based on actual hydrologic observations. Specific wells to be monitored 

are listed in appendix B.

• Continued operation and data gathering of USGS flow gage that would provide data for 

surface water flows downstream of the mine site (RC-SW-01). Rosemont Copper would 

annually fund the USGS to operate and maintain the existing flow gage at Barrel Canyon.

Contextual Discussion of Effects on Empire Gulch and Cienega Creek

Empire Gulch

The potential impacts to Empire Gulch discussed above describe the changes to the natural 

environment, specifically changes that would occur in the type of vegetation and habitat in Empire 

Gulch, and the potential transition of the stream from perennial to ephemeral. Those impacts would 

also have more widespread effects on the human environment in Empire Gulch.

The historic Empire Ranch has been a working cattle ranch since the 1860s, and in 1976, it was listed 

in the National Register of Historic Places (NRHP). In the 1980s, public support developed to 

preserve the ranch and its natural resources in their pristine condition, which culminated in 1988 with 

a series of land exchanges that placed the property into public ownership under the administration of 

the BLM. Located in the heart of Empire Gulch and the Las Cienegas National Conservation Area, 

Empire Ranch is still a draw for the historic importance of the ranch itself and the natural beauty of 

the area. Ranching continues, as well as recreation activities, public events, and ongoing efforts to 

preserve and enhance the natural resources in this area. In 1997, the Empire Ranch Foundation was 

established as a private nonprofit organization to work with the BLM to develop private support to 

preserve the ranch buildings and enhance the educational and recreational opportunities it offers to 

the general public.

There is great uncertainty with the predictions regarding how much, where, and how fast groundwater

drawdown might occur from dewatering associated with the mine pit. Based on the best available 

science as described in this resource section, impacts to Empire Gulch are more certain to occur than 

those to other perennial streams, and most scenarios indicate that effects would be seen within 50 

years of closure of the mine. These effects would gradually increase over time, likely affecting flow 

at the springs in Empire Gulch, stream flow within the Empire Gulch channel, and the riparian gallery 

present along the channel. Due to the Forest Service’s jurisdictional limitation that mitigation

measures can be required only on NFS surface resources, no mitigation measures are proposed that 

would directly offset the impacts predicted to occur along Empire Gulch (see the “Mitigation and 

Monitoring” part of chapter 2, and appendix B for further detail).

These changes over time would not affect the historic nature of Empire Ranch, the ranch buildings, or 

likely even the continuing ranching operations. However, the eventual absence of free-flowing water, 

the loss of large trees, and the transition into a drier desert wash like that farther upstream would 

cause a substantial change to the character of Empire Ranch and the natural setting that is currently 

enjoyed at the ranch. This would represent a loss of some of the characteristics for which Empire 

Ranch was preserved and protected.

Cienega Creek

Cienega Creek extends from its headwaters near Sonoita approximately 36 miles downstream, 

flowing through both the Las Cienegas National Conservation Area and the Cienega Creek Natural 

Preserve. Throughout much of this length, Cienega Creek exhibits perennial or intermittent stream

546 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

flow, and an extensive gallery of cottonwood and willow is supported along the Creek. In addition, 

the flood plain of Cienega Creek contains the remnants of once-extensive cienegas, or areas of 

shallow groundwater and wetland complexes.

Cienega Creek is noted for both scenic beauty and ecological significance. It forms an important 

connection for wildlife movement between sky islands in southern Arizona. It is one of the few 

remaining examples of a desert riparian community, exhibiting a high level of plant diversity in a 

relatively small geographic area. Pima County notes that the habitat along Cienega Creek supports 

more than 280 native species of mammals, birds, reptiles, amphibians, fish, and insects that either 

reside in or frequent the preserve and provides habitat for neotropical migratory birds, which 

seasonally use the area for nesting. The presence of perennial stream flow supports native frog and 

fish populations, including threatened and endangered species.

The ecological, recreation, and cultural importance of Cienega Creek is tied irrevocably to its 

hydrology. Cienega Creek is valuable because it is a perennial riparian corridor. Predictions of impact 

to Cienega Creek are less certain than those for Empire Gulch and encompass a wide range of 

possibilities, from no impact at all, to extensive dewatering and drying. The timing is also uncertain, 

with possible changes occurring many decades or hundreds of years in the future. Changes in the 

hydrology severe enough to cause dewatering of Cienega Creek are one possible outcome of the 

mine, and the likelihood of mine effects becoming severe enough to dewater Cienega Creek also 

increases with climate change and increased groundwater demand within the basin. If these severe 

effects were to occur, much of the value of Cienega Creek for recreation, wildlife habitat, scenic 

beauty, and cultural importance would be lost.

Effect on Outstanding Arizona Waters

Seven criteria were developed by the Coronado for the purposes of the FEIS and are assessed to 

analyze potential impacts to Outstanding Arizona Waters: changes in perennial stream flow; change

in groundwater quality; change in surface water quality and ability to meet wadeable, perennial 

standards; change in riparian vegetation; change in geomorphology; and change in subflow. These are 

summarized in table 111 for the Outstanding Arizona Water reaches of lower Davidson Canyon and 

lower Cienega Creek and in table 113 for the Outstanding Arizona Water reaches of Upper Cienega 

Creek. This analysis reflects the criteria developed and analyzed by the Coronado, which will differ 

from those used by the State of Arizona to make their determination of the ability of the proposed 

project to meet regulatory requirements.

Davidson Canyon and Lower Cienega Creek

Potential impacts to each of the seven assessment criteria for Outstanding Arizona Waters are 

summarized in table 111 for Davidson Canyon and Lower Cienega Creek (below the confluence with 

Davidson Canyon). Each assessment criterion is also further described below.

Ability to Meet Antidegradation Standards

Predicted water quality for stormwater runoff in Barrel Canyon is discussed in the “Surface Water 

Quality” resource section, as are all known existing water quality data for Davidson Canyon, Lower 

Cienega Creek, and Barrel Canyon. 

Final Environmental Impact Statement for the Rosemont Copper Project 547
Chapter 3. Affected Environment and Environmental Consequences

Table 111. Potential to affect Outstanding Arizona Water in Davidson Canyon and 

Lower Cienega Creek

Criteria EIS Resource Section 

that Contains Analysis Summary of Impacts

Perennial Stream Flow Seeps, Springs, and Riparian Areas Possible 4.3 to 11.5% reduction in recharge of alluvial 

aquifer from surface flow; impacts muted by distance 

flow has to travel from site to downstream; prediction 

has high level of uncertainty. Perennial flow in lower 

Davidson Canyon is not occurring at present and has 

not occurred for several years; unlikely to be affected 

by changes in recharge; no impacts predicted.

Groundwater Quality Groundwater Quality and 

Geochemistry

Seepage does not exceed any aquifer water quality 

standards; no impacts predicted.

Surface Water Quality Surface Water Quality and Seeps, 

Springs, and Riparian Areas

Predicted runoff water quality from waste rock and 

soil cover meets surface water quality standards in 

Barrel Canyon, or standards are already exceeded.

Full analysis of antidegradation standards and 

compliance with surface water standards in the 

Outstanding Arizona Water reaches of Davidson 

Canyon and Cienega Creek is under the jurisdiction of 

ADEQ and has not yet been conducted. However, 

screening analysis developed by the Coronado 

suggests that molybdenum and sulfate may be 

elevated in mine stormwater runoff but are likely to 

be reduced in part by several mitigations, including 

waste rock segregation requirements (discussed in 

detail below, see table 112).

Riparian Vegetation Seeps, Springs, and Riparian Areas Based on the expected changes in runoff (from 4.3 to 

11.5% reduction), no changes in riparian vegetation

expected.

Geomorphology Surface Water Quality Sediment loads in system would change, but 

geomorphology of stream channel is unlikely to 

change; scour/aggradation changes to Outstanding 

Arizona Water highly unlikely.

Subflow (for Lower Cienega 

Creek)

Groundwater Quantity Contribution of Davidson Canyon subflow to Cienega 

Creek estimated at 8 to 24%; possible 4.3 to 11.5%

reduction in recharge of Davidson Canyon alluvial 

aquifer from surface flow; impacts muted by distance 

flow has to travel from site to downstream; therefore,

prediction has high level of uncertainty. 

Cumulatively, possible reduction in flow in Lower 

Cienega Creek owing to reduction in subflow from 

Davidson Canyon is minimal.

Ability to Meet AntiDegradation Standards and 

Wadeable, Perennial 

Standards

Seeps, Springs, and Riparian

Areas; Surface Water Quality

Discussed in detail below.

Direct comparison of predicted water quality from waste rock runoff (see “Surface Water Quality” 

resource section) to the existing water quality in Davidson Canyon and Lower Cienega Creek is 

problematic and not appropriate, given that the Outstanding Arizona Water portion of Davidson 

Canyon is more than 12 miles downstream in the watershed and the contribution from the mine 

site would represent only a portion of the runoff reaching the Outstanding Arizona Water. More 

importantly, there are no known stormwater samples available for either Davidson Canyon or Lower 

548 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Cienega Creek. All known water quality samples, including those contained in the “Surface Water 

Quality” resource section, are for base flow, not storm flow. 

Because there are no known stormwater samples from anywhere within the Davidson Canyon 

watershed, except those collected by Rosemont Copper in Barrel Canyon, it is impossible to conduct 

a full analysis of whether the mine would degrade water quality in the Outstanding Arizona Water

segments of Davidson Canyon and Lower Cienega Creek. Not only does this prevent comparison of 

predicted stormwater quality with existing stormwater quality in these Outstanding Arizona Water 

reaches, but because Arizona surface water standards change based on water hardness, it also 

prevents even a comparison of predicted stormwater quality with surface water quality standards in 

the Outstanding Arizona Water reaches. Furthermore, based on discussions with ADEQ on 

preliminary drafts of the FEIS, it was made clear to the Coronado that the responsibility and 

jurisdiction for assessing whether the mine meets antidegradation criteria lie with ADEQ. The person 

seeking authorization for a regulated discharge to a tributary to, or upstream of, an Outstanding 

Arizona Water (in this case Rosemont Copper) has the responsibility to demonstrate to the State of 

Arizona that the regulated discharge will not degrade existing water quality in the downstream 

Outstanding Arizona Water. This demonstration by Rosemont Copper, and determination by the State 

of Arizona, has not yet been completed. Independent of this determination, the potential for 

degradation of Outstanding Arizona Waters was raised by the public as an issue of importance and 

therefore the Forest Service has the responsibility under NEPA to take a “hard look” at the potential 

for degradation. The Coronado determined that a screening-level analysis could be conducted with 

available data to identify potential constituents that could be elevated by the runoff from the waste

rock facility. 

Results from the screening analysis are summarized in table 112 and described more fully in the 

record (SWCA Environmental Consultants 2013k). Two scenarios are assessed, corresponding to the 

two scenarios assessed in the “Surface Water Quality” resource section: runoff from waste rock, and 

runoff from soil cover. Based on the screening analysis, concentrations of most constituents actually 

are predicted to decrease under postmine conditions. Concentrations of several other constituents are 

suggested to increase, including total and dissolved fluoride, dissolved aluminum, dissolved 

selenium, and dissolved sodium. These increases are less than 10 percent and may not be considered 

significant, given the relatively great uncertainty associated with this analysis. The screening analysis 

for runoff from waste rock indicates that two constituents may be elevated in mine runoff at levels 

that suggest they could present antidegradation problems: total and dissolved molybdenum, and total 

and dissolved sulfate. The screening analysis for runoff from soil cover suggests that molybdenum 

and sulfate would not be elevated but that dissolved arsenic, dissolved iron, and dissolved sodium 

could present antidegradation problems. In addition, dissolved and total mercury is substantially 

higher. Most waste rock samples contained mercury concentrations below detection limits (74 out of 

78 samples collected), but these detection limits are higher than surface water standards and therefore 

are not able to be incorporated into this part of the analysis. Many or even all of these unusable 

samples could have very low mercury concentrations. The usable samples include one sample with a

very high concentration of mercury (0.03 mg/L). Because of the small number of usable samples, this 

single sample has a large influence on the predictions. However, it appears to be a legitimate sample, 

and it still indicates a potential for degradation from stormwater interacting with soil cover. 

The actual runoff water quality would be predicted to be a mix of the waste rock and soil cover 

estimates.

Final Environmental Impact Statement for the Rosemont Copper Project 549
Table 112. Summary of screening analysis to identify potential problem constituents in mine runoff

Average of 

Existing Water 

Quality in 

Barrel Canyon 

and 

Tributaries 

(mg/L)

Predicted 

Runoff Water 

Quality from 

Waste Rock

(mg/L)

Predicted 

Runoff Water 

Quality from 

Soil Cover 

(mg/L)

Premine 

Prediction of 

Watershed

Water Quality

(mg/L)*

Postmine 

Prediction of 

Watershed

Water Quality

using Waste 

Rock Runoff

(mg/L)†

Percent 

Difference 

between Preand Postmine 

Watershed

Water Quality‡

Postmine 

Prediction 

Watershed

Water Qual

using Soi

Cover Runo

(mg/L)†

Aluminum 

(dissolved)

0.4248 0.2050 0.4870 0.4248 0.3918 −8% 0.4341 

Aluminum (total) 87.14 0.2050 0.4870 87.14 74.10 −15% 74.14 

Antimony 

(dissolved)

0.0240 0.0100 0.0052 0.0240 0.0219 −9% 0.0212 

Antimony (total) 0.0436 0.0100 0.0052 0.0436 0.0386 −12% 0.0379 

Arsenic (dissolved) 0.0161 0.0130 0.0335 0.0161 0.0157 −3% 0.0187 

Arsenic (total) 0.1123 0.0130 0.0335 0.1123 0.0974 −13% 0.1005 

Barium (dissolved) 0.0783 0.0071 0.0047 0.0783 0.0676 −14% 0.0672 

Barium (total) 1.1623 0.0071 0.0047 1.1623 0.9890 −15% 0.9886 

Beryllium 

(dissolved)

0.0084 0.0010 0.0010 0.0084 0.0072 −13% 0.0072 

Beryllium (total) 0.0123 0.0010 0.0010 0.0123 0.0106 −14% 0.0106 

Cadmium 

(dissolved)

0.0058 0.0010 0.0010 0.0058 0.0051 −12% 0.0051 

Cadmium (total) 0.0238 0.0010 0.0010 0.0238 0.0204 −14% 0.0204 

Calcium (dissolved) 25.24 16.42 6.6 25.24 23.92 −5% 22.44 

Calcium (total) 214.9 16.42 6.6 214.9 185.1 −14% 183.7 

Chloride (dissolved) 2.804 0.9630 0.5357 2.804 2.528 −10% 2.463 

Chloride (total) 5.679 0.9630 0.5357 5.679 4.972 −12% 4.907 

Chromium 

(dissolved)

0.0136 0.0030 0.0030 0.0136 0.0120 −12% 0.0120 

Chromium (total) 0.1105 0.0030 0.0030 0.1105 0.0944 −15% 0.0944 

Copper (dissolved) 0.0331 0.0085 0.0067 0.0331 0.0294 −11% 0.0291 

550 Final Environmental Impact Statement for the Rosemont Copper Project
Final Environmental Impact Statement for the Rosemont Copper Project 551

Average of 

Existing Water 

Quality in 

Barrel Canyon 

and 

Tributaries 

(mg/L)

Predicted 

Runoff Water 

Quality from 

Waste Rock

(mg/L)

Predicted 

Runoff Water 

Quality from 

Soil Cover 

(mg/L)

Premine 

Prediction of 

Watershed

Water Quality

(mg/L)*

Postmine 

Prediction of 

Watershed

Water Quality

using Waste 

Rock Runoff

(mg/L)†

Percent 

Difference 

between Preand Postmine 

Watershed

Water Quality‡

Postmine 

Prediction 

Watershed

Water Qual

using Soi

Cover Runo

(mg/L)†

Copper (total) 2.947 0.0085 0.0067 2.947 2.507 −15% 2.506 

Fluoride (dissolved) 0.2500 0.3316 0.2063 0.2500 0.2622 5% 0.2434 

Fluoride (total) 0.2163 0.3316 0.2063 0.2163 0.2336 8% 0.2148 

Iron (dissolved) 0.1418 0.1638 0.2433 0.1418 0.1451 2% 0.1570 

Iron (total) 102.7 0.1638 0.2433 102.7 87.3 −15% 87.33 

Lead (dissolved) 0.0235 0.0048 0.0151 0.0235 0.0207 −12% 0.0222 

Lead (total) 0.8837 0.0048 0.0151 0.8837 0.7519 −15% 0.7534 

Magnesium 

(dissolved)

1.990 1.064 0.8167 1.990 1.851 −7% 1.814 

Magnesium (total) 47.89 1.064 0.8167 47.89 40.86 −15% 40.83 

Manganese 

(dissolved)

0.3406 0.0069 0.1610 0.3406 0.2905 −15% 0.3136 

Manganese (total) 6.131 0.0069 0.1610 6.131 5.212 −15% 5.235 

Mercury (dissolved) 0.0001 0.0002 0.0101 0.0001 0.0002 9% 0.0016 

Mercury (total) 0.0007 0.0002 0.0101 0.0007 0.0006 −10% 0.0021 

Molybdenum 

(dissolved)

0.0172 0.0405 0.0117 0.0172 0.0207 20% 0.0164 

Molybdenum (total) 0.0178 0.0405 0.0117 0.0178 0.0212 19% 0.0169 

Nickel (dissolved) 0.2966 0.0050 0.0050 0.2966 0.2529 −15% 0.2529 

Nickel (total) 0.6783 0.0050 0.0050 0.6783 0.5773 −15% 0.5772 

Nitrate + Nitrite 

(total, as N)

1.704 0.031 Not sampled 1.704 1.453 −15% Not sample

Potassium 

(dissolved)

4.795 2.934 1.503 4.795 4.515 −6% 4.301 

Potassium (total) 28.46 2.934 1.503 28.46 24.63 −13% 24.42 
Average of 

Existing Water 

Quality in 

Barrel Canyon 

and 

Tributaries 

(mg/L)

Predicted 

Runoff Water 

Quality from 

Waste Rock

(mg/L)

Predicted 

Runoff Water 

Quality from 

Soil Cover 

(mg/L)

Premine 

Prediction of 

Watershed

Water Quality

(mg/L)*

Postmine 

Prediction of 

Watershed

Water Quality

using Waste 

Rock Runoff

(mg/L)†

Percent 

Difference 

between Preand Postmine 

Watershed

Water Quality‡

Postmine 

Prediction 

Watershed

Water Qual

using Soi

Cover Runo

(mg/L)†

Selenium 

(dissolved)

0.0140 0.0200 0.0200 0.0140 0.0149 6% 0.0149 

Selenium (total) 0.9864 0.0200 0.0200 0.9864 0.8414 −15% 0.8414 

Silver (dissolved) 0.0090 0.0025 0.0025 0.0090 0.0080 −11% 0.0080 

Silver (total) 2.714 0.0025 0.0025 2.714 2.307 −15% 2.307 

Sodium (dissolved) 2.518 4.167 6.1 2.518 2.765 10% 3.055 

Sodium (total) 7.008 4.167 6.1 7.008 6.582 −6% 6.872 

Sulfate (dissolved) 4.475 33.126 1.98 4.475 8.773 96% 4.101 

Sulfate (total) 7.793 33.126 1.98 7.793 11.593 49% 6.921 

Thallium

(dissolved)

0.0136 0.0082 0.0028 0.0136 0.0128 −6% 0.0120 

Thallium (total) 0.0328 0.0082 0.0028 0.0328 0.0291 −11% 0.0283 

Total Dissolved 

Solids

194.68 78.41 Not sampled 194.68 177.24 −9% Not sample

Zinc (dissolved) 0.0697 0.0058 0.0066 0.0697 0.0601 −14% 0.0602 

Zinc (total) 2.202 0.0058 0.0066 2.202 1.873 −15% 1.873 

Notes: 

Bold numbers indicate that the screening analysis suggests a significant increase in postmine concentrations (greater than a 10 percent change).

* No stormwater quality samples have been identified anywhere within the Davidson Canyon watershed, except for those samples collected by Ros

Canyon and its tributaries. Therefore, the premine watershed water quality can only be estimated by using these water quality samples.

† Postmine water quality is estimated by using a weighted average, with 15% contribution from the predicted runoff from the waste rock or soil cov

contribution from the existing water quality in Barrel Canyon, which is assumed to be representative of the watershed as a whole for lack of other st

‡ Negative numbers indicate water quality is improved from existing conditions; positive numbers indicate water quality is degraded from existing 

552 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

As noted in the “Surface Water Quality” resource section, there are several mitigations that suggest 

this is a conservative estimate. These include the requirement for operational testing and segregation 

of waste rock that may have the potential for acid generation or that may be problematic with respect 

to water quality, along with the placement of a cover of growth media over much of the waste rock 

facility. The screening analysis presented assumes that all stormwater runoff has the opportunity to 

interact with waste rock and that no waste rock has been segregated.

The Forest Service does not have the responsibility or jurisdiction to determine whether or not the 

mine would degrade water quality or violate water quality standards in the Outstanding Arizona 

Water reaches; this determination responsibility lies with ADEQ. However, the Forest Service does 

have the responsibility to assess and disclose potential resource impacts; the purpose of the screening 

analysis is intended to assess the potential to impact water quality beyond Barrel Canyon.

The “Groundwater Quality and Geochemistry” resource section also analyzes the potential for 

tailings seepage to daylight in Barrel Canyon. As noted in that section, the amount of seepage is 

equivalent to about 13 acre-feet per year, which is less than 1 percent of the average annual runoff.

As a total of the entire watershed being analyzed under the screening analysis, the volume of tailings 

seepage is incredibly small, about 1 part in 1,000. The same screening analysis was conducted that 

incorporated tailings seepage into storm flows, but the results did not change from the scenarios 

already considered and shown in table 112.

Ability to Meet Wadeable, Perennial Stream Standards

Lower Cienega Creek currently meets the regulatory definition of a wadeable, perennial stream. 

As such, regulatory requirements specific to biological integrity (taxa richness, species composition,

tolerance, and functional organization comparable to that of a stream with reference conditions in 

Arizona) and bottom deposits would need to be met. With the exception of water quality described 

above, changes predicted in Lower Davidson Canyon and Lower Cienega Creek are limited to 4.3 to 

11.5 percent reduction in ephemeral storm flow. Biological communities in Lower Cienega Creek 

would be sensitive to changes in base flow but are unlikely to be affected by changes in ephemeral 

storm flow. It was also concluded that this level of change in stormwater availability is unlikely to 

substantially change the amount of subflow from Davidson Canyon to Cienega Creek. Based on the 

analyses conducted, no expected effects from the proposed mine would have the potential to change 

biological integrity along any portion of Lower Cienega Creek. Analysis of geomorphological 

changes indicates that changes in sedimentation, aggradation, or scour are unlikely to occur due to the 

hydrologic changes imposed by the mine and therefore are unlikely to affect either biological 

integrity or surface deposits. The water quality screening analysis suggests that some constituents 

may be elevated in mine runoff, but because of the lack of stormwater samples in Lower Davidson 

Canyon or Lower Cienega Creek, this screening analysis is unable to predict water quality changes in 

these Outstanding Arizona Water reaches.

Summary of Expected Effects on Outstanding Arizona Waters

The analysis of effects on Outstanding Arizona Waters is based on criteria developed solely by the 

Coronado that were designed to include both regulatory requirements as well as the original reasons 

for nominating these areas as Outstanding Arizona Waters. The State of Arizona has yet to make a 

determination on whether regulatory standards would be met.

In summary, the only potential effect on the Outstanding Arizona Waters in Lower Davidson Canyon 

and Lower Cienega Creek would be the result of a decrease in runoff that would occur because 

Final Environmental Impact Statement for the Rosemont Copper Project 553
Chapter 3. Affected Environment and Environmental Consequences

portions of the Davidson Canyon watershed would be cut off in perpetuity by the mine site. This 

reduction in ephemeral flow is estimated to be 4.3 to 11.5 percent in lower Davidson Canyon. 

The reduction in surface flow itself would likely have no impact to riparian vegetation or water 

quality; it could represent a reduction in recharge to the shallow alluvial aquifer and subflow from 

Davidson Canyon to Cienega Creek. The distance downstream of the project area (12 miles) that 

flows have to travel before reaching lower Davidson Canyon gives the predicted effect a high level of 

uncertainty, as recharge in lower Davidson Canyon is more likely to occur either from very large 

storm events or from more localized runoff events. A screening analysis suggests that several 

constituents may be elevated due to runoff from the waste rock, although this possibility is reduced

by several safety factors built into operation of the mine (see table 112).

Upper Cienega Creek

Potential impacts to each of the six assessment criteria for Outstanding Arizona Waters are 

summarized in table 113 for Upper Cienega Creek. Each assessment criterion is also further described 

below.

Table 113. Potential to affect Outstanding Arizona Water in Upper Cienega Creek

Criteria EIS Resource Section 

that Contains Analysis Summary of Impacts

Perennial Stream Flow Seeps, Springs, and Riparian

Areas

Results are mixed. Up to 150 years after closure, 

most estimates indicate no change in perennial nature 

of stream, with some possibility of shifting to 

intermittent. Up to 1,000 years after closure, several 

estimates indicate no change in perennial nature of 

stream, and several estimates indicate a shift to 

intermittent flow or conversion to an ephemeral 

stream.

Groundwater Quality Groundwater Quality and 

Geochemistry

Seepage does not exceed any aquifer water quality 

standards; no impacts predicted.

Surface Water Quality Surface Water Quality No change in surface runoff to Upper Cienega Creek. 

In the near term, up to 50 years after closure, no 

increased risk of degraded water quality caused by 

extremely low-flow conditions. Up to 150 years after 

closure, results are mixed. Most estimates indicate 

some increased risk of low-flow conditions 

increasing, anywhere from seasonally during the 

summer to nearly the entire year.

Riparian Vegetation Seeps, Springs, and Riparian

Areas

Most estimates indicate that there is unlikely to be 

any change in riparian vegetation, even up to 1,000 

years after closure. The highest estimates of 

groundwater drawdown indicate that while there may 

not be widespread changes from hydroriparian to 

xeroriparian vegetation, there is likely to be a 

contraction of the hydroriparian area, with conversion 

occurring at the transitional margins.

Geomorphology Surface Water Quality No change in surface runoff to Upper Cienega Creek.

Ability to Meet Wadeable, 

Perennial Standards

Seeps, Springs, and Riparian

Areas; Surface Water Quality

Discussed in detail below.

Ability to Meet Wadeable, Perennial Stream Standards

Upper Cienega Creek currently meets the regulatory definition of a wadeable, perennial stream. 

As such, regulatory requirements specific to biological integrity (taxa richness, species composition, 

554 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

tolerance, and functional organization comparable to that of a stream with reference conditions in 

Arizona) and bottom deposits would need to be met. The potential for reductions in stream flow 

would potentially drive water quality changes as well, as discussed earlier in this section. Results of 

the models are mixed. By 50 years after closure, only one modeling scenario out of five suggests that

there would be an increase in the risk of low-flow conditions occurring. By 150 years after closure, 

four out of five modeling scenarios suggest that there would be an increase in the risk of low-flow 

conditions occurring. By 1,000 years after closure, all modeling scenarios agree that there would 

some level of increase in the risk of low-flow conditions.

These low-flow conditions would increase water temperature, increase nutrient loads, and decrease 

the assimilative capacity of the stream. Changes in these characteristics would have an effect on the 

aquatic biota and the characteristics of biological integrity listed above.

Summary of Expected Effects on Outstanding Arizona Waters

The analysis of effects on Outstanding Arizona Waters is based on criteria developed solely by the

Coronado that were designed to include both regulatory requirements as well as the original reasons 

for nominating these areas as Outstanding Arizona Waters. The State of Arizona has yet to make a 

determination on whether regulatory standards would be met.

Predictions with the most certainty are during the near term, up to 50 years after closure of the mine, 

during which there are few predicted effects on the Outstanding Arizona Water along Upper Cienega 

Creek from the headwaters to the confluence with Davidson Canyon. Over the long term (up to 1,000 

years after closure), the risk increases, although predictions are mixed. Some modeling scenarios 

suggest that there would be no or little change in flow conditions, and some modeling scenarios 

suggest that the stream could shift from perennial flow to intermittent flow, or even completely 

transition to ephemeral flow. At the same time, the frequency of low-flow conditions that could 

degrade water quality would increase. Changes in either the nature of flow or the frequency of lowflow conditions could affect this Outstanding Arizona Water. Predictions of these conditions 

occurring are highly uncertain due to limitations in the accuracy of the models and the long time 

frames involved.

Monitoring Intended to Assess Potential Impacts to Outstanding Arizona Waters

In addition to the three monitoring requirements described previously associated with stream flow 

impacts, two other monitoring measures have been incorporated into the “Mitigation and Monitoring

Plan” to address uncertainty associated with impacts to Outstanding Arizona Waters (see appendix B 

for full details). The additional monitoring includes:

• Sediment transport monitoring (FS-SR-05). The movement of sediment between the mine 

facility and SR 83 would be monitored to identify areas of scour or aggradation that could be 

caused by changes in sediment load and surface flow.

• Detention and testing of stormwater (OA-SW-01). This mitigation measure requires 

detention and testing of stormwater quality from perimeter waste rock buttress areas for water 

quality testing prior to flowing downstream of the mine site. This would also allow for a 

reduction in suspended sediment in stormwater flows before flowing downstream.

Final Environmental Impact Statement for the Rosemont Copper Project 555
Chapter 3. Affected Environment and Environmental Consequences

Proposed Action

Effect on Seeps and Springs

The estimated impacts to seeps and springs, along with the rationale for this assessment, are

presented in table 114. Direct impacts refer to springs that are within the footprint of an action 

alternative and would be disturbed, covered, or otherwise removed and would no longer function as a 

natural spring. Indirect impacts refer to springs that would not be physically disturbed but that may 

experience changes in hydrology as a result of groundwater level declines. Refer to the 

“Methodology” part of this resource section for more information on how spring impacts were 

estimated.

Table 114. Estimated impacts to springs and seeps as a result of proposed action

ID Spring Type of 

Impact Rationale Riparian Impacts

1 Barrel Spring Unlikely Flow observations indicate large 

periods with no flow and suggest a 

likely local, ephemeral source

None

2 Basin Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Deergrass, willows, false indigo 

present upstream of spring; unlikely to 

be affected

3 Batamout Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Netleaf hackberry, soapberry present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

4 Bee Spring Direct Inside footprint of disturbance Oaks present; xeroriparian/ 

mesoriparian habitat would be lost

5 Big Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Soapberry present; xeroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

6 Bobo Spring Unlikely Outside bounds of analysis; beyond 

5-foot groundwater drawdown 

contour

None

7 Bootlegger 

Spring

Unlikely Outside bounds of analysis; beyond 

5-foot groundwater drawdown 

contour

None

8 Bowman Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

9 Box Canyon 

Spring – Stock 

Drinker No. 1

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Ash, oak, netleaf hackberry, grapevine, 

poison ivy, evergreen sumac, 

Goodding’s willow, mesquite, juniper 

present; hydroriparian/mesoriparian 

habitat may be lost or experience 

reduced vitality

10 Box Canyon 

Spring – Stock 

Drinker No. 2

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Ash, oak, netleaf hackberry, grapevine, 

poison ivy, evergreen sumac, 

Goodding’s willow, mesquite, juniper 

present; hydroriparian/mesoriparian 

habitat may be lost or experience 

reduced vitality

11 California Mine 

Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

12 Chavez Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Giant sedge, walnut, ash, grapevine, 

maidenhair fern present; hydroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

556 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

ID Spring Type of 

Impact Rationale Riparian Impacts

13 Cold Water 

Spring

Unlikely Outside bounds of analysis; beyond 

5-foot groundwater drawdown 

contour

None

14 Cow Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

15 Crucero Spring

No. 1

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Oaks, junipers, hackberry, indigo, 

deergrass, willows present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

16 Crucero Spring

No. 2

Unlikely Flow observations indicate large 

periods with no flow and suggest a 

likely local, ephemeral source

None

17 Dam Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

18 Davidson Spring Unlikely Source of flow is likely from Empire 

Mountains and disconnected from 

Davidson Canyon (Tetra Tech 

2010a)

None

19 Deering Spring Highly likely; 

Indirect

Inside 5-foot groundwater drawdown 

contour; flow observations indicate 

consistent water presence and 

suggest a regional source of water

Giant sedge, deergrass, oak, juniper, fig 

present; xeroriparian/mesoriparian 

habitat would be lost or would

experience reduced vitality

20 Diesler Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Oak, cottonwood, willow present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

21 Escondido 

Spring

Unlikely See Outstanding Arizona Water

section for analysis 

None

22 Feliz Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Oaks present; xeroriparian/

mesoriparian habitat may be lost

23 Fence Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

24 Fig Tree Spring Highly likely; 

Indirect

Inside 5-foot groundwater drawdown 

contour; flow observations indicate 

consistent water presence and 

suggest a regional source of water

Giant sedge, oak, fig, milkweed 

present; xeroriparian/mesoriparian 

habitat would be lost or would

experience reduced vitality

25 Heiter Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Netleaf hackberry present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

26 Helvetia Spring Highly likely; 

Indirect

Inside 5-foot groundwater drawdown 

contour; flow observations indicate 

consistent water presence and 

suggest a regional source of water

Ash, willow, buckthorn, evergreen 

sumac, grapevine, giant sedge present; 

hydroriparian/mesoriparian habitat

would be lost or would experience 

reduced vitality

27 Hilton Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Unknown

28 Horse Pasture 

Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Mesquite, netleaf hackberry, juniper, 

walnut, grapevine present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

29 HQ Water 

Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Cottonwood, willow present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

30 Indian Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

Final Environmental Impact Statement for the Rosemont Copper Project 557
Chapter 3. Affected Environment and Environmental Consequences

ID Spring Type of 

Impact Rationale Riparian Impacts

31 La Cholla 

Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Oak, willow, hackberry present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

32 Little Indian 

Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

33 Locust Spring Unlikely Flow observations indicate large 

periods with no flow and suggest a 

likely local, ephemeral source

None

34 Lower Mulberry 

Spring

Highly likely; 

Indirect

Inside 5-foot groundwater drawdown 

contour; flow observations indicate 

consistent water presence and 

suggest a regional source of water

Juniper, soapberry, hackberry, seep 

willow present; xeroriparian/

mesoriparian habitat would be lost or 

would experience reduced vitality

35 McCleary Dam Direct Inside footprint of disturbance Oak, juniper present; xeroriparian/

mesoriparian habitat would be lost

36 McCleary 

No. 1

Unlikely Flow observations indicate large 

periods with no flow and suggest a 

likely local, ephemeral source

None

37 McCleary 

No. 2 

Highly likely; 

Indirect

Inside 5-foot groundwater drawdown 

contour; flow observations indicate 

consistent water presence and 

suggest a regional source of water

Oak, sumac present; xeroriparian/

mesoriparian habitat would be lost

38 Mescal Spring Unlikely Outside bounds of analysis; beyond 

5-foot groundwater drawdown 

contour

None

39 Mesquite Flat 

Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Hackberry, soapberry, seep willow, 

grapevine present; hydroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

40 Mine Water 

Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

41 Mudhole Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Giant sedge, Goodding’s willow, 

deergrass present; hydroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

42 Mueller Spring Direct Inside footprint of disturbance None

43 Mulberry 

Canyon 

Highly likely; 

Indirect

Inside 5-foot groundwater drawdown 

contour; flow observations indicate 

consistent water presence and 

suggest a regional source of water

Juniper, seep willow, rabbitsfoot grass, 

giant sedge present; xeroriparian/

mesoriparian habitat would be lost or 

would experience reduced vitality

44 Mulberry Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Juniper, hackberry present; 

xeroriparian/mesoriparian habitat may

be lost or experience reduced vitality

45 Oak Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

False indigo bush, deergrass present; 

xeroriparian habitat may be lost or 

experience reduced vitality

46 Ojo Blanco 

Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Willow, deergrass, poison ivy present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

47 Ophir Gulch 

Well

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Madrean evergreen woodland present; 

xeroriparian/mesoriparian habitat may

be lost or experience reduced vitality

48 Paja Verde 

Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

558 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

ID Spring Type of 

Impact Rationale Riparian Impacts

49 Papago Spring

(No. 2)

Unlikely Flow observations indicate large 

periods with no flow and suggest a 

likely local, ephemeral source

None

50 Peligro Adit Unlikely Flow observations indicate large 

periods with no flow and suggest a 

likely local, ephemeral source

None

51 Proctor Box 

Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Ash, oak, netleaf hackberry, grapevine, 

poison ivy, evergreen sumac, 

Goodding’s willow, mesquite, juniper, 

wait-a-minute bush present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

52 Questa Spring Highly likely; 

Indirect

Inside 5-foot groundwater drawdown 

contour; flow observations indicate 

consistent water presence and 

suggest a regional source of water

None 

53 Rock Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Deergrass present; xeroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

54 Rockhouse 

Spring

Unlikely Outside bounds of analysis; beyond 

5-foot groundwater drawdown 

contour

None

55 Rosemont 

Spring

Direct Inside footprint of disturbance Willow, juniper, false indigo, deergrass 

present; hydroriparian/mesoriparian 

habitat would be lost

56 Ruelas Spring Highly likely; 

Indirect

Flow observations indicate large 

periods with no flow and suggest a 

likely local, ephemeral source; 

however, proximity to pit likely to 

affect local flow

Willow, hackberry present; 

hydroriparian/mesoriparian habitat

would be lost or would experience 

reduced vitality

57 Ruelas Spring

Number Two 

and Three

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

58 Rust Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

59 Sanford Spring Unlikely Outside bounds of analysis; beyond 

5-foot groundwater drawdown 

contour

None

60 Scholefield 

No. 1 Spring

Unlikely Flow observations indicate large 

periods with no flow and suggest a 

likely local, ephemeral source

None

61 Scholefield 

No. 2 Spring

Unlikely Flow observations indicate large 

periods with no flow and suggest a

likely local, ephemeral source

None

62 Scholefield 

No. 3 Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

63 Shamrod Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Hackberry, sumac, buckthorn, 

grapevine present; hydroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

64 Siphon Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

Final Environmental Impact Statement for the Rosemont Copper Project 559
Chapter 3. Affected Environment and Environmental Consequences

ID Spring Type of 

Impact Rationale Riparian Impacts

65 Soldier Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

66 SS-2 (Casita 

Spring)

Unlikely Flow observations indicate large 

periods with no flow and suggest a 

likely local, ephemeral source

None

67 SW Highly likely; 

Indirect

Flow observations indicate large 

periods with no flow and suggest a 

likely local, ephemeral source; 

however, proximity to pit likely to 

affect local flow

Oak, pinyon pine, false indigo, 

silktassel, juniper; xeroriparian/

mesoriparian habitat would be lost or 

would experience reduced vitality

68 Sycamore 

Spring

Highly likely; 

Indirect

Inside 5-foot groundwater drawdown 

contour; flow observations indicate 

consistent water presence and 

suggest a regional source of water

Sycamore, ash, walnut, hackberry, 

cottonwood, willow, giant sedge; 

hydroriparian/mesoriparian habitat

would be lost or would experience 

reduced vitality

69 Tree Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Cottonwood, soapberry, deergrass 

present; hydroriparian/mesoriparian 

habitat may be lost or experience 

reduced vitality

70 Tub Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Hackberry, oak present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

71 Tunnel Spring Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

72 Tunnel Spring # 

2

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

73 Unnamed Spring

(South of 

Deering Spring)

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Willow, juniper, silk tassel, smooth 

sumac, locust, deergrass present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

74 Unnamed Spring

(in Box Canyon)

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Willow present; hydroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

75 Unnamed Spring

(Reach 2)

Unlikely See “Outstanding Arizona Waters” 

part of this resource section for 

analysis

None

76 Unnamed Spring

(in South 

Sycamore 

Canyon)

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Sycamore, ash, willow, cottonwood, 

deergrass, horsetail, false indigo, 

poison ivy present; hydroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

77 Unnamed Spring

No. 1

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

78 Unnamed Spring

No. 12

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

79 Unnamed Spring

No. 13

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

80 Unnamed Spring

No. 14

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Mesquite present; xeroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

81 Unnamed Spring

No. 16

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

560 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

ID Spring Type of 

Impact Rationale Riparian Impacts

82 Unnamed Spring

No. 17

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Ash, deergrass present; hydroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

83 Unnamed Spring

No. 18

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Ash, walnut present; hydroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

84 Unnamed Spring

No. 2

Direct Inside footprint of disturbance None

85 Unnamed Spring

No. 20

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

None 

86 Unnamed Spring

No. 21

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Mesquite, soapberry, hackberry, 

catclaw, desert cotton present; 

xeroriparian/mesoriparian habitat may

be lost or experience reduced vitality

87 Unnamed Spring

No. 22

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Deergrass present; xeroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

88 Unnamed Spring

No. 24

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Cottonwood, soapberry present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

89 Unnamed Spring

No. 3

Direct Inside footprint of disturbance None

90 Unnamed Spring

No. 4

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Ash present; hydroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

91 Unnamed Spring

No. 5

Direct Inside footprint of disturbance Deergrass present; xeroriparian/

mesoriparian habitat would be lost or 

experience reduced vitality

92 Unnamed Spring

No. 7

Unlikely Outside bounds of analysis; beyond 

5-foot groundwater drawdown 

contour

None

93 Upper Empire 

Gulch Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Cottonwood, willow present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

94 Water Develop 

Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Oak, netleaf hackberry, locust, 

grapevine present; hydroriparian/

mesoriparian habitat may be lost or 

experience reduced vitality

95 Zackendorf 

Spring

Possible; Indirect Inside 5-foot groundwater drawdown 

contour; source of water unknown

Cottonwood, willow, evergreen sumac, 

oak, mountain mahogany, cattails, giant 

sedge, maidenhair fern present; 

hydroriparian/mesoriparian habitat may

be lost or experience reduced vitality

Notes:

High: The predicted changes in hydrology owing to the mine would impact resource function, and the source of water can 

either be estimated with high certainty to be in connection with the regional aquifer or impacts would occur no matter what 

the source of water. 

Possible: Reduction in flow could occur as a result of predicted changes in hydrology owing to the mine, but uncertainty 

exists regarding the source of the water. 

Unlikely: Predicted changes in hydrology owing to the mine are small enough that they are unlikely to cause a reduction in 

flow, regardless of the source of water, or the source of the water is local and unlikely to be affected by drawdown 

associated with the pit. 

Final Environmental Impact Statement for the Rosemont Copper Project 561
Chapter 3. Affected Environment and Environmental Consequences

Of the 95 seeps or springs listed in table 114, 17 are expected to be impacted with high certainty, 

either directly by surface disturbance (7 of the 17 springs) or indirectly by reduction in flow severe 

enough to impact their function as a resource owing to predicted drawdown in the regional aquifer or 

their proximity to the pit (10 of the 17 springs). An additional 59 springs possibly could be impacted 

by reductions in groundwater levels; these springs lie within the area predicted to see at least 5 feet in 

groundwater drawdown but have an indeterminate source of water. Another 19 springs are unlikely to 

be impacted, either because field observations indicate they are fed by local and ephemeral sources or 

because of their distance from the mine pit.

Local areas of riparian habitat are associated with 49 of the springs that would or possibly would be 

indirectly impacted by the loss of water from these springs, based on field observations of species 

types present at these springs. These local riparian zones include the following: 10 areas of 

xeroriparian/mesoriparian habitat that would be impacted with high certainty; eight areas of 

xeroriparian/mesoriparian habitat that may be impacted with low certainty; four areas of 

hydroriparian/mesoriparian habitat that would be impacted with high certainty; and 27 areas of 

hydroriparian/mesoriparian habitat that may be impacted with low certainty.

The proposed action would also directly disturb 686 acres of xeroriparian habitat associated with 

onsite washes. These are the riparian areas mapped by Pima County that fall within the security fence 

or other areas of ground disturbance.

Any intermittent stream segments in Sycamore Canyon (north of the mine site) not accounted for as 

individual springs would experience similar impacts as those described for Sycamore Spring

(ID No. 68) and Unnamed Spring No. 18 (ID No. 83).

Any intermittent stream segments in Sycamore Canyon (a different canyon south of the mine site) not 

accounted for as individual springs would experience similar impacts as those described for SW 

(ID No. 67) and Unnamed Spring in South Sycamore Canyon (ID No. 76).

Any intermittent stream segments in Mulberry Canyon not accounted for as individual springs would 

experience similar impacts as those described for Mulberry Canyon (ID No. 43).

Any intermittent stream segments in Box Canyon not accounted for as individual springs would 

experience similar impacts as those described for Box Canyon Spring-Stock Drinker Nos. 1 and 2 

(ID Nos. 9 and 10), Unnamed Spring in Box Canyon (ID No. 74), and Basin Spring (ID No. 2).

Analysis of impacts to BLM Federal reserved water rights associated with Helvetia, Zackendorf, and 

Chavez Springs is included in the “Indirect Impacts to Offsite Water Rights” part of the “Surface 

Water Quantity” resource section of this chapter. Water rights associated with these three springs are 

likely to be affected by the described impacts. Helvetia is believed to derive water from the regional 

aquifer and therefore there is a high likelihood of impacting the BLM water right. The source of 

water for Chavez and Zackendorf Springs is not clear, but if their source of water is also derived from 

the regional aquifer, impacts to these water rights would also occur.

Phased Tailings Alternative

The estimated impacts to springs and seeps for the Phased Tailings Alternative are identical to those 

for the proposed action, with the exception that McCleary No. 2 would be directly impacted rather 

than indirectly impacted. The same riparian areas associated with these springs would or could be 

562 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

impacted. The Phased Tailings Alternative would also directly disturb 649 acres of xeroriparian 

habitat associated with onsite washes.

Barrel Alternative

The Barrel Alternative would directly impact two fewer springs than the proposed action: McCleary 

Dam and Unnamed Spring No. 5. Instead of being directly impacted, these springs would be 

indirectly impacted. 

• McCleary Dam would have a high likelihood of indirect impacts because observations 

indicate consistent water presence and suggest a regional source of water and because it has 

hydroriparian/mesoriparian habitat associated with it that would be lost or that would 

experience reduced vitality. 

• Unnamed Spring No. 5 would have a possible likelihood of indirect impacts because the 

water source is uncertain and because it has xeroriparian/mesoriparian habitat associated with 

it that may be lost or that may experience reduced vitality.

The Barrel Alternative would also directly disturb 588 acres of xeroriparian habitat associated with 

onsite washes.

Barrel Trail Alternative

The estimated impacts to springs and seeps for the Barrel Trail Alternative are identical to those for 

the Barrel Alternative. The same riparian areas associated with these springs would or could be 

impacted. The Barrel Trail Alternative would also directly disturb 633 acres of xeroriparian habitat

associated with onsite washes.

Scholefield-McCleary Alternative

The Scholefield-McCleary Alternative would directly impact seven more springs than the proposed 

action: HQ Water Spring; McCleary No. 2; Scholefield Nos. 1, 2, and 3; Unnamed Spring No. 14; and 

Water Development Spring. 

• McCleary No. 2 was previously considered to be indirectly impacted with a high likelihood.

• Scholefield No. 1 and Scholefield No. 2 were previously considered unlikely to have indirect 

impacts. Scholefield No. 1 and Scholefield No. 2 have hydroriparian/mesoriparian habitat

associated with them that would be lost.

• HQ Water Spring, Unnamed Spring No. 14, Scholefield No. 3, and Water Development 

Spring were previously considered to have a possible likelihood of indirect impacts. HQ 

Water Spring and Water Development Spring have hydroriparian/mesoriparian habitat

associated with them that would be lost. Unnamed Spring No. 14 has xeroriparian/ 

mesoriparian habitat associated with it that would be lost.

In addition, Mueller Spring would not be directly impacted under the Scholefield-McCleary 

Alternative. This spring would still be considered to have a possible likelihood of indirect impacts.

The Scholefield-McCleary Alternative would also directly disturb 631 acres of xeroriparian habitat

associated with onsite washes.

Final Environmental Impact Statement for the Rosemont Copper Project 563
Chapter 3. Affected Environment and Environmental Consequences

Monitoring Intended to Assess Potential Impacts to Seeps and Springs

One additional monitoring measure has been incorporated into the mitigation and monitoring plan to 

address uncertainty associated with impacts to seeps and springs (see appendix B for full details). 

The additional monitoring includes:

• Spring, seep, and constructed/enhanced waters monitoring (FS-SSR-02). A suite of 

selected seeps and springs has been monitored for baseline conditions since 2007 and would 

be monitored to identify any impacts that may occur due to dewatering of the regional aquifer

in the vicinity of the mine pit. Specific seeps and springs included in this monitoring are 

listed in appendix B.

Cumulative Effects

The analysis area for cumulative effects on seeps, springs, and riparian areas is the same as that used 

for the direct and indirect effects on these resources. It includes the immediate Rosemont area, all of 

Davidson Canyon, and portions of Cienega and Santa Cruz Basins (see figure 66). The analysis area 

extends east 0.5 mile beyond Cienega Creek; west and south to the approximate modeled 5-foot 

groundwater drawdown contour; and north to the Pantano Dam. This cumulative effects discussion 

addresses the cumulative impacts of the action alternatives and any applicable reasonably foreseeable 

actions as identified on the Coronado ID team’s list of reasonably foreseeable future actions, provided 

in the introduction to chapter 3. The following reasonably foreseeable actions from that list were 

determined to contribute to a cumulative impact to seeps, springs, and riparian areas:

• The BLM and AGFD are proposing reintroduction of beaver into Cienega Creek at Las 

Cienegas National Conservation Area. The timing of this potential action has not yet been 

determined.

• The Forest Service is proposing to reauthorize the grazing permit for the Gardner allotment, 

located 5 miles north of Sonoita.

• The BLM proposes to approve an MPO to expand the Andrada Mine limestone quarry in the 

Davidson Canyon drainage system north and northeast of the Santa Rita Mountains. 

The Andrada Mine is located approximately 4 miles from the Tucson, Arizona, city limits 

and 1 mile from the Vail, Arizona, city limits.

• The Forest Service proposes to add, decommission, close, or change designation of roads in 

the NFSR database and prohibit off-road motorized travel for dispersed camping in certain 

areas on the Nogales Ranger District.

• The Nogales Ranger District proposes to remove hazardous fuels on 2,500 acres in Hog and 

Gardner Canyons on the Nogales Ranger District.

• Development of the Farmers Investment Company property within the Town of Sahuarita’s 

jurisdiction over the next 40 to 50+ years for residential and commercial mixed use is 

proposed, along with the enhancement of more than 12 miles of the Santa Cruz River in both 

the town of Sahuarita and Pima County.

• In May 2010, a lease was granted to Charles Seel for mining purposes for 240 acres of ASLD

State Trust land (from State land commissioner) in Section 29, Township 17 South, Range 17 

East, adjacent to CalPortland leases in Davidson Canyon. There are no known plans to 

explore for or develop mineral resources on this lease in the foreseeable future.

564 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

As part of changes to the Nogales District Motorized Travel System, the Coronado proposes to add, 

decommission, close, and/or change road designations, which could include prohibiting off-road 

motorized travel for dispersed camping in certain areas. These activities could change the 

characteristics of the watershed. Closing roads or prohibiting off-road motorized travel to dispersed 

camping areas could have the potential to reduce stormwater runoff from an area. Changes in 

stormwater runoff could affect the availability of water for seeps, springs, and riparian areas.

The Gardner allotment is located 5 miles northwest of Sonoita, and the Coronado is proposing to 

reauthorize the grazing permit on 10,271 acres. This reauthorization is for issuance of a new 10-year 

term grazing permit that would allow for an increase in animal unit months (AUMs) and would 

change the Gardner allotment from seasonal use to year-long use. An adaptive management approach 

is being proposed for the allotment, and several range improvements are being considered to help 

better distribute livestock. Continued grazing and increases in AUMs would likely result in increased

livestock use of surface water. Changes in grazing management practices could change existing 

characteristics of the watershed and stormwater runoff, thus affecting the availability of water for 

seeps, springs, and riparian areas.

Hazardous fuels in Hog and Gardner Canyons are proposed to be removed from more than 2,500 

acres of Coronado National Forest land. These activities would be expected to disturb vegetation and 

change the characteristics of the watershed involved. The use of best management practices would

minimize the potential these activities have to impact seeps, springs, and riparian areas.

Expansion or construction of limestone quarries within the Davidson Canyon drainage has the 

potential to both directly impact riparian resources as well as to change the hydrologic flow regime. 

In conjunction with the changes in flow described above for the Rosemont Copper Project, there 

could be a greater combined effect on xeroriparian vegetation along Davidson Canyon from 

additional surface water loss.

Enhancement of the Santa Cruz River near Sahuarita would have a beneficial impact on riparian 

resources. However, these changes are geographically separate from any impacts to riparian resources 

that would or potentially could occur due to the Rosemont Copper Project. These enhancements are 

envisioned as part of master-planned communities and would be undertaken by whatever entity is 

constructing these communities after appropriate permitting.

Reintroduction of beaver along Cienega Creek would be expected to have a beneficial impact to 

riparian resources by slowing and ponding runoff and increasing water availability, and it would have 

a detrimental impact from use and falling of larger vegetation and trees. Overall, the intention of 

beaver reintroduction is to have a beneficial impact on Cienega Creek. Cumulatively, this would 

potentially offset any impact that could occur due to dewatering of the regional aquifer; however, 

cooperating agencies have commented that the benefits of this action have not been determined and 

are in dispute.

Climate Change

As discussed earlier in this chapter, climate change in the desert Southwest is predicted to bring about 

higher mean annual temperatures over the next 100 years, along with less winter precipitation, an 

increase in extreme rainstorms and flooding, and longer periods of drought. The extent to which these 

predictions will occur is uncertain, and the overall difference in the amount of annual precipitation is 

impossible to accurately quantify. However, predicted changes in weather patterns could have an 

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effect on the quantity of stormwater and groundwater available for use by riparian vegetation. 

Increased temperatures and reduced precipitation will increase the vulnerability of springs and 

riparian systems relying on the groundwater system, whether regional or local. 

The cumulative impact to these riparian systems from prolonged droughts can presently be observed 

from the decade-long drought that is currently ongoing. The Pima Association of Governments 

reports on conditions within the Pima County Natural Preserve, which encompasses a large portion of 

Lower Cienega Creek both above and below the confluence with Davidson Canyon (Cienega Creek 

Reaches 4 and 5). Stream flow monitoring (wet/dry mapping) has occurred since 1984 (Pima 

Association of Governments 2012a; Powell 2013). The percentage of Cienega Creek flowing in this 

area is cyclical but has steadily decreased since monitoring began in 1984. Since 1999, drought 

monitoring has been conducted, and measurements in June 2011 indicate that this portion of Cienega 

Creek has the least percentage flowing yet observed. Only 13 percent of the stream exhibits flowing 

or standing water, compared with the wettest year (2001), in which 49 percent of the stream exhibited 

flowing or standing water, and more normal years, in which roughly 30 percent of the stream 

exhibited flowing or standing water. Between 1990 and 2011, surface water discharge in Cienega 

Creek declined by 83 percent, while stream flow extent declined by 88 percent (Powell 2013). 

The exact causes of this multidecade decline are not entirely clear, as several possible stresses may be 

acting in concert, but the current drought cycle is considered one of the primary reasons. 

The patterns seen in southern Arizona in the past few decades, and particularly on Cienega Creek, 

provide a template for what long-term climate change could look like. Prolonged droughts brought on 

by climate change could result in similar shifts from perennial to intermittent flow along upper 

Cienega Creek and Empire Gulch. This would increase the sensitivity of these areas to any drawdown 

in groundwater due to the mine pit, increasing the overall impact to stream flow, wetland complexes, 

and hydroriparian habitat.

Mitigation Effectiveness 

Measures that would mitigate impacts to seeps, springs, and riparian areas include design features, 

and mitigation measures proposed that would be required either in the biological opinion or the CWA

Section 404 permit. See appendix B for the full “Mitigation and Monitoring Plan.”

Mitigation and Monitoring – Forest Service

• Growth media salvage and application (FS-SR-01). In order to support reclamation

activities, soil and other growth media would be salvaged, stored, and applied to the surface 

of the perimeter waste rock buttress and waste rock and tailings facilities in order to facilitate 

revegetation. This allows as much stormwater as possible to move downstream to support 

riparian vegetation.

• Revegetation of disturbed areas with native species (FS-SR-02). Reclamation efforts 

would include revegetation of native grasses, forbs, shrubs, and trees on areas disturbed by 

mining and mine related activities. Revegetation would include detection and treatment of 

invasive weed species. This allows as much stormwater as possible to move downstream to 

support riparian vegetation.

• Concurrent placement of perimeter buttress (FS-SR-03). Placement of the perimeter 

buttress would allow reclamation activities to take place earlier, concurrent with mine 

operations. This allows as much stormwater as possible to move downstream to support 

riparian vegetation.

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• Location, design, and operation of facilities and structures intended to route 

stormwater around the mine and into downstream drainages (FS-SW-01). Various 

stormwater diversion channels and location of facilities have been designed and located in 

order to maintain flow downstream as much as possible and avoid contact of stormwater with 

processing facilities and ore stockpiles. This allows as much stormwater as possible to move 

downstream to support riparian vegetation.

• Stormwater diversion for Barrel Alternative designed to route more stormwater into 

downstream drainages postclosure (FS-SW-02). Following publication of the DEIS, the 

Coronado undertook an effort to apply the concepts of geomorphic reclamation to the Barrel 

Alternative. The result is a design that would route more stormwater into downstream 

drainages postclosure than previous designs.

• Purchasing of water rights, to be used for mitigating impacts in the Cienega Creek

watershed (FS-SSR-01). This mitigation measure includes a suite of actions that involve 

purchasing, severing, and transferring existing senior water rights on Lower Cienega Creek. 

The water rights would be transferred to appropriate entities to become in-stream flow rights 

on Lower and Upper Cienega Creek. Additional actions could include the discharge of water 

below Pantano Dam potentially could enhance and support riparian areas, along with 

retirement of a groundwater pumping well near to Lower Cienega Creek.

• Spring, seep, and constructed/enhanced waters monitoring (FS-SSR-02). A suite of 

selected seeps and springs has been monitored for baseline conditions since 2007 and would 

be monitored to identify any impacts that may occur due to dewatering of the regional aquifer

in the vicinity of the mine pit. Specific seeps and springs included in this monitoring are 

listed in appendix B.

• Recordation of a restrictive easement on private land parcels in Davidson Canyon to 

potentially mitigate for loss of habitat for listed species (FS-BR-21). Rosemont Copper 

would record restrictive covenants to preclude real estate development and similar land use

activities. Managed grazing, cultural, and some low impact public use (hiking, bird watching, 

minor forms of hunting) would be allowed in some locations. These lands total 383 acres and 

include portions of ephemeral wash, riparian habitat in Davidson Canyon, Barrel Canyon, 

and Mulberry Canyon, upland buffer habitat adjacent to riparian areas and three springs.

• Plant site location and design adjustments to reduce impacts to biological resources

(FS-BR-01). The entire plant site is sited and designed to reduce its size and overall footprint 

and to use gravity instead of pumping to move process water where possible. This reduces 

the amount of xeroriparian vegetation impacted, particularly in McCleary Canyon

• Construction, management, and maintenance of water features to reduce potential 

impacts to wildlife and livestock from reduced flow in seeps, springs, surface water, and 

groundwater (FS-BR-05). Up to 30 water features, including stock ponds, would be 

enhanced and managed for sustainability of surface water. These waters would be constructed 

or managed if needed based on impacts observed in the field. While considered primarily for 

mitigation for impacts to biological resources, it would also mitigate effects on surface water 

resources and riparian resources.

• Recordation of a restrictive easement on the private Sonoita Creek Ranch parcel to 

mitigate for impacts to species listed as threatened or endangered (FS-BR-08). Rosemont 

Copper would record a restrictive covenant on the 1,200-acre Sonoita Creek Ranch parcel 

and the accompanying 590 acre-feet of certified water rights. The parcel includes open water, 

forested wetland and riparian habitat, upland habitat adjacent to riparian habitat, seasonal 

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ponds, semi-desert grassland, and ephemeral drainages. In the event that restoration is 

required to mitigate impacts to WUS, Rosemont Copper would use the existing infrastructure 

and the naturally occurring water from Monkey Spring (that currently irrigates the 

agricultural fields) to create riparian and/or wetland habitat within the 115-acre fields. 

Otherwise water available after the needs of the existing ponds would be discharged onto the 

floodplain terrace of Sonoita Creek, which is currently an agricultural field, in order to 

facilitate the passive restoration of riparian habitat.

• Establishment of the Cienega Creek Watershed Conservation Fund, to be used for 

future mitigation to in the Cienega Creek watershed (FS-BR-16). Rosemont Copper 

would establish an endowment and provide $2,000,000 of funding. This fund would 

essentially be established as a resource to help restore the watershed to a functional 

ecosystem and a mechanism to promote adaptive management and allow flexibility in 

mitigation to achieve desired outcomes in light of future uncertainties.

• Monitoring to determine impacts from pit dewatering on downstream sites in Barrel 

and Davidson Canyons (FS-BR-22). Monitoring would be conducted of surface water, 

alluvial groundwater, and deeper groundwater at sites in Barrel and Davidson Canyons. 

Several locations have already been installed and are being actively monitored, whereas 

others would require access from landowners. 

• Periodic validation and rerun of groundwater model throughout life of mine 

(FS-BR-27). This measure would involve basic data collection of water levels, 

meteorological data, and water balance components, which would allow for the predictions of 

groundwater impacts to be revised based on actual hydrologic observations. Specific wells to 

be monitored are listed in appendix B.

Conclusion of Mitigation Effectiveness

Most of the mitigation measures listed above are associated with design features or permit 

requirements. Some of the design features would reduce the overall footprint of structures or create 

large stormwater diversions that would directly route stormwater around operations, which in turn 

would reduce the impact to downstream riparian resources by allowing for more surface water to 

flow downstream. Other types of design features such as those associated with revegetation of 

disturbed areas would also reduce impacts to riparian resources by allowing water to be discharged 

from reclaimed areas as soon as possible during the active mining phase. Removal of unneeded 

facilities during closure would allow these areas to be revegetated and allow surface water to flow 

downstream postclosure. These mitigation measures would be effective at minimizing reductions to 

surface water quantity within the analysis area to the extent possible. However, these improvements 

in surface flow have been taken into account in the direct and indirect effects analysis, and impacts to 

downstream riparian resources are still expected.

The lands proposed for conservation within Davidson Canyon would be effective at avoiding future 

impacts to xeroriparian resources located along Davidson Canyon by establishing conservation 

easements limiting certain types of land use. The lands proposed for conservation at Sonoita Creek 

Ranch would be at least partially effective at mitigating riparian resources by preserving and possibly 

creating new riparian habitat; however, it should be noted that these lands are not located within the 

analysis area or within the Davidson Canyon/Cienega Creek watershed. It should also be noted that 

sufficiency of the mitigation on the Davidson Canyon parcels or Sonoita Creek Ranch to offset 

impacts to jurisdictional WUS has yet to be determined by the USACE.

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The severance and transfer of water rights on Cienega Creek would not necessarily provide any new 

or “wet” water in either Lower or Upper Cienega Creek; however, by creating a senior instream flow 

right where none currently exists, this mitigation measure would provide significant legal protection 

against future water use that might take water from Cienega Creek, and it would remove legal 

obstacles to conducting restoration or management activities along Cienega Creek. Cooperating 

agencies have raised concerns that the sever-and-transfer process that must be undertaken through the 

ADWR is not guaranteed to be successful and allows for challenges to any transfer of surface water

rights. If the water right transfer were not approved, this mitigation would not be protective of 

Cienega Creek. The exact effects of projects conducted under the conservation fund cannot be known 

at this time, but these projects would be presumed to be beneficial to riparian resources in some 

manner, as this is the purpose of the conservation funds. It should also be noted that sufficiency of the 

mitigation activities on Cienega Creek to offset impacts to jurisdictional WUS, either from transfer of 

water rights or implementation of conservation funds, has yet to be determined by the USACE.

If successful, the new riparian habitat that would be created downstream of Pantano Dam would 

replace hydroriparian habitat if any is lost, although these lands are located just outside the analysis 

area. However there is uncertainty associated with the hydrogeologic characteristics of the stream 

channel downstream of Pantano Dam. While release of water to the stream channel or uplands would 

certainly help create and maintain riparian habitat, the recharge of water to the aquifer may not cause 

the water table to rise shallow enough to support hydroriparian habitat. This depends on the depth to 

bedrock and other subsurface characteristics of the aquifer immediately downstream of Pantano Dam. 

It should also be noted that sufficiency of the mitigation proposed at Pantano Dam and in the stream 

channel downstream to offset impacts to jurisdictional WUS has yet to be determined by the USACE.

The creation, enhancement, or replacement of water sources is likely to support additional riparian 

habitat. The exact location and nature of the habitat that would be supported is not known at this time.

These measures generally would not be effective as mitigation but rather would provide a means for 

monitoring potential changes to surface waters and riparian resources within the analysis area.

Monitoring of groundwater and surface water conditions and periodically rerunning the groundwater 

model would help inform future decisions. This would include providing input for consideration on 

implementation of mitigation measures such as under FS-BR-16 and FS-BR-05, developing closure 

strategies, and providing information to support adaptive management of the mine.

Effects of Amending the Coronado Forest Plan

The effects on seeps, springs, and riparian areas from amending the Coronado forest plan are 

described under “Direct and Indirect Effects” above. The current forest plan does not contain 

management area standards and guidelines specifically pertaining to seeps, springs, and riparian 

vegetation for management areas 1, 4, or 7A. 

New management area 16 contains a standard and guideline under “Watershed and Soil Maintenance 

and Improvement” that would apply to seeps, springs, and riparian areas:

1. To the extent practicable, mining facilities and reclamation should strive to emulate natural 

hydrologic functions.

Approval of the forest plan amendment would allow actions that would result in impacts to seeps, 

springs, and riparian vegetation as described in the “Direct and Indirect Effects” portion of this 

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Chapter 3. Affected Environment and Environmental Consequences

section, including the direct and indirect loss of some springs and the loss and conversion of riparian 

areas.

Biological Resources

Introduction

This section discusses the affected environment and environmental consequences of the proposed 

action and alternatives to biological resources. Biological resources include plant and animal 

populations, as well as other biological and physical resources that provide habitat within the analysis 

area. The scope of analysis encompasses potential impacts from the proposed project and action 

alternatives, taking into consideration both the geographic extent (spatial analysis) and duration of 

impacts (temporal analysis). This section emphasizes potential effects of the project on “special status 

species,” which includes federally listed threatened, endangered, and sensitive species (Forest Service

and BLM), as well as some migratory birds and Forest Service management indicator species. Special 

status species are emphasized because of presumed rarity, conservation concerns, or legal mandates.

Not all species considered by the Forest Service in the NEPA analysis are presented in detail in the 

FEIS; the analysis for many species can be found in reports in the project record, as discussed in the 

“Analysis Methodology” part of this section.

Changes from the Draft Environmental Impact Statement

Several changes were made in response to public and agency comments on the DEIS and cooperating 

agency comments on the Preliminary Administrative Review Draft FEIS and to reflect refinement of 

the action alternatives and connected actions. Below is a bulleted list highlighting these changes:

• Analysis of connected actions was added, including modification of an electrical transmission 

line, rerouting of the Arizona National Scenic Trail, and highway maintenance and 

improvements to SR 83 (addressed throughout the “Affected Environment” and 

“Environmental Consequences” parts of this resource section where applicable);

• Minor changes were made to the “Issues, Cause and Effect Relationships of Concern” part of 

this section;

• “Issue 4: Impact on Seeps, Springs, and Riparian Vegetation,” associated “Factors for 

Alternative Comparison,” and most of the associated discussions for seeps, springs, and 

riparian areas were moved to the “Seeps, Springs, and Riparian Areas” resource section of 

chapter 3;

• The “Analysis Methodology, Assumptions, Uncertain and Unknown Information” part of this 

resource section was expanded upon and clarified, including: 

◦ Sources used for analysis when species-specific survey data were not available; and

◦ A more thorough description of potential for occurrence of species in the analysis area 

and hence which species are analyzed.

• Information in the “Sonoran Desert Conservation Plan” and associated “Multi-species 

Conservation Plan” parts of this section was updated;

• The summary table of special status plant and animal species (table 115) was revised:

◦ Species that were retained for analysis of impacts for the proposed project were added to 

the list to reflect: 

• The addition of connected actions; and

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• Additional documented occurrences. 

◦ The status of several species within this table was updated;

◦ Columns were added to indicate whether species that are analyzed in the FEIS have been 

documented within the analysis area and/or project area; and

◦ Species were reorganized in order by scientific name.

• The summary of effects table was updated (table 116);

• The “Relevant Laws, Regulations, Policies, and Plans” part of the section was updated and 

additional information added;

• More details about past and existing disturbances in the analysis area has been provided 

(see the “Affected Environment” part of this resource section);

• Information in the “Affected Environment” and “Environmental Consequences” parts of this 

resource section has been updated for the following:

◦ “Biophysical Features;”

◦ “Vegetation Communities;”

◦ “Habitat Fragmentation and Animal Movement Corridors;”

◦ “Special Status Species:”

• “Special Status Species” has been reorganized and species added by scientific name 

to match order in table 115; and 

• For “Special Status Species,” a quantitative analysis has been conducted using 

geographic information system (GIS) to estimate the acreage of possible habitat for 

special status species within the analysis area and the expected direct impacts to 

possible habitat for these species.

◦ “Migratory Birds,” including the “Santa Rita Mountains Important Bird Area” and 

“Important Overwintering Areas.”

• Sections in the “Environmental Consequences” part of this resource section have been added 

that describe impacts from dust and air pollutants, noise and vibration, artificial night 

lighting, and increased traffic volumes on SR 83 and other roads;

• The “Environmental Consequences” part of this resource section has been revised for all 

action alternatives, including the addition of tables that compare the direct impacts for all 

action alternatives; 

• The list of reasonably foreseeable actions that could contribute to cumulative impacts of the 

proposed project was updated (see the “Cumulative Effects” part of this section);

• A section on the potential impacts of climate change has been included (see the “Cumulative 

Effects” part of this section); and

• The “Mitigation Effectiveness” part of this resource section has been updated.

Issues, Cause and Effect Relationships of Concern

Issue 5: Impact on Plants and Animals

This group of issues focuses on the effects on plant and animal populations and habitats. Many 

aspects of the mine operations have the potential to affect individuals, populations, and habitat for 

plants and animals, including special status species. This issue includes the potential for impacts on 

wildlife as a result of landscape alteration, and as a result of light, noise, vibration, traffic, and other 

disturbance from the proposed mine operations.

Final Environmental Impact Statement for the Rosemont Copper Project 571
Chapter 3. Affected Environment and Environmental Consequences

Issue 5A: Vegetation

The pit, plant, tailings and waste rock facilities, road and utility corridors, and other facilities have the 

potential to permanently change vegetation, and reclamation may not restore vegetation to preproject 

conditions. 

Issue 5A Factor for Alternative Comparison

1. Acres of terrestrial vegetation permanently lost or altered, by vegetation type

Issue 5B: Habitat Loss

The mine and ancillary facilities could result in a loss or alteration of habitat for numerous plant and 

animal species. Potential impacts could impact upland and riparian habitat and fragmentation of 

riparian habitat and corridors, including Cienega Creek.

Issue 5B Factors for Alternative Comparison

1. Acres by type of terrestrial and aquatic habitat lost, altered, or indirectly impacted

2. Qualitative assessment of impacts on aquatic habitats and surface water that supports wildlife

and plants such as stock tanks, seeps, and springs

3. Qualitative assessment of how changes in the function of riparian areas could impact wildlife

habitat

Issue 5C: Nonnative Species

The mine and its operations have the potential to create conditions conducive to the introduction, 

establishment, and/or spread of nonnative species, which may out-compete native plants and animals. 

Forest Service and other Federal, State, and local laws, regulations, policies, and plans contain 

management direction for invasive plants. 

Issue 5C Factor for Alternative Comparison

1. Acres of disturbance that could create conditions conducive for invasive species

Issue 5D: Wildlife Movement

The mine and its operations could potentially modify and/or fragment wildlife habitats and/or reduce 

connectivity between habitats. Increased traffic could correspondingly increase wildlife mortality and 

injury. 

Issue 5D Factors for Alternative Comparison

1. Qualitative assessment of the change in movement corridors and connectivity between 

wildlife habitats

2. Qualitative assessment of mortality of various animal species resulting from increased 

volume of traffic related to mine operations 

Issue 5E: Special Status Species

The mine and its operations have the potential to impact habitat for special status species (see the 

“Analysis Methodology, Assumptions, Uncertain and Unknown Information” part of this section for a 

description of special status species). 

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Issue 5E Factors for Alternative Comparison

1. Acres of habitat disturbed for each special status species, including impacts to designated and 

proposed critical habitat

2. Potential to affect the population viability of any species

Issue 5F: Animal Behavior

Mine construction, closure and operations, including drilling and blasting, may result in noise and 

vibration, which could impact animal behavior and result in negative impacts on wildlife. Nocturnal 

and other animals may be adversely affected by the light glow in night skies. 

Issue 5F Factors for Alternative Comparison

1. Acres of habitat impacted from noise, vibration, and light

2. Qualitative assessment of effects on wildlife behavior from noise, vibration, and light

Analysis Methodology, Assumptions, 

Uncertain and Unknown Information 

The analysis area for biological resources is defined as the project area (i.e., the area that is composed 

of the open pit, waste rock facility, tailings facility, heap leach facility,6 plant site and ancillary 

facilities, fenced area around the mine (perimeter fence), and mine primary access road), including 

roads that would be decommissioned and constructed, plus a larger surrounding area that may 

experience direct or indirect temporal and spatial impacts from the proposed project. Temporally, the 

potential onsite and offsite impacts resulting from the proposed project encompass all the activities 

associated with premining (18 to 24 months), active mining (20 to 25 years), final reclamation and 

closure (3 years), and postclosure (indefinite). The analysis area includes: (1) areas outside the mine 

footprint that may be affected by vibration and noise, dust and air pollutants, artificial night lighting, 

road decommissionings, and other mining activities; (2) all areas for which mining activity may affect 

groundwater and surface water; and (3) other areas primarily outside the footprint that are related to 

mining activity, such as construction of an electrical transmission line and a water supply pipeline 

(and associated utility maintenance road); modification of an electrical distribution line; rerouting the 

Arizona National Scenic Trail; and highway maintenance and improvements to SR 83 (i.e., connected 

actions). 

The analysis area, which was delineated to consider the impacts of vibration and noise, dust and air 

pollutants, artificial night lighting, increased traffic on SR 83 and other roads, groundwater

drawdown, and surface water alteration, totals approximately 146,163 acres (figure 71). The analysis 

area is located primarily in Pima County but also encompasses a small portion of Santa Cruz County; 

65,289 acres within the analysis area is on lands administered by the Forest Service and BLM, and

the remaining 80,874 acres within the analysis area is on ASLD State Trust land and private land. 

A large portion of the BLM acreage in the analysis area includes the Las Cienegas National 

Conservation Area, primarily as a result of concerns regarding potential groundwater drawdown 

impacts within Cienega Creek and Empire Gulch. The Las Cienegas National Conservation Area is 

managed by the BLM, includes wetlands administered by the BLM, and provides aquatic and riparian 

habitat. Within the privately owned land is approximately 4,317 acres of lands administered by Pima 

County, including approximately one-half of the 4,000-acre Cienega Creek Natural Preserve, which 

occurs along lower Cienega Creek and lower Davidson Canyon. The Cienega Creek Natural Preserve 

6 This applies to all action alternatives except the Barrel Alternative.

Final Environmental Impact Statement for the Rosemont Copper Project 573

 
Chapter 3. Affected Environment and Environmental Consequences

Figure 71. Analysis area for biological resources

574 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

is owned by Pima County Regional Flood Control District and jointly managed by Pima County 

Regional Flood Control District and Pima County Natural Resources, Parks and Recreation

Department. The Cienega Creek Natural Preserve was established to protect natural resources 

(i.e., stretches of perennial flow surrounded by stands of cottonwood, willow, and mesquite trees) and 

cultural resources. 

The analysis area includes vegetation communities, surface water drainages, and onsite physical and 

topographic features (e.g., mountains, caves and mine adits/shafts, seeps and springs, stock tanks, 

rocky outcrops, etc.) that may be directly or indirectly impacted by the project. The analysis area also 

includes the indirect downgradient impacts on the surface water and groundwater environments that 

would result from the onsite diversion and impoundment of surface water;

7 the impacts on springs

and seeps outside the project area;8 and the impacts of vibration,9 noise,

10 dust and air pollutants,11

artificial night lighting,12 and increased traffic volumes on SR 83 and other roads13 resulting from the 

construction and operations of the mine and the connected actions. Therefore, the analysis area 

includes the following: (1) drainages that receive surface water discharge from the mine site, 

including Barrel Canyon and Davidson Canyon Wash past its confluence with Cienega Creek to 

Pantano Dam; (2) springs and seeps within the area of projected groundwater drawdown associated 

with the mine pit, including Empire Gulch and Cienega Creek, which contain wetlands administered 

by the BLM; and (3) areas adjacent to the mine site and transportation and utility corridors (including 

the primary and utility maintenance road locations) that may be impacted by vibration and noise, dust

and air pollutants, and artificial night lighting. Disruption of surface water flow would result from the 

capture of runoff in the pit and stormwater diversions and are only expected to occur along the Barrel 

Canyon drainage and through Davidson Canyon to its confluence with Cienega Creek. The temporal 

analysis period includes 24 hours per day of vibration, noise, dust, and light for the premining (18 to 

14 months), active mining (20 to 25 years), final reclamation and closure phases (3 years); an 

unknown period of time for habitat alteration and revegetation; and up to 1,000 years after closure of 

the mine for the potential for groundwater drawdown and potential changes to riparian habitat.

Analysis of special status plants and animals discussed in this FEIS and its supporting documents 

began with a review of the legal requirements for disclosure of effects. Special status species include 

those afforded protection (or are petitioned/proposed for listing) under the ESA, Forest Service and 

BLM sensitive species, forest-specific management indicator species, migratory birds of conservation 

7 The analysis area is partially defined by a combination of the extent of the Montgomery and Associates Inc. (2010) and

Tetra Tech (2010g) 5-foot drawdown contours of the 1,000-year models, as well as downstream surface waters. See the 

“Groundwater Quantity,” “Surface Water Quantity,” and “Surface Water Quality” sections. 8 Ibid.

9 Vibration from daily blasting are expected to be felt 1 to 2 miles from the project area (see the “Noise” resource section). 10 The analysis area is partially defined by 50 A-weighted decibel (dBA) surface blasting and 55 dBA traffic noise contours, 

an area that is approximately 54,336 acres (Tetra Tech 2009e). Note that it has been determined that weighting systems 

developed for humans (i.e., dBA) are not necessarily appropriate for wildlife species; however, weighting is species 

specific, and received sound levels depend on many factors (e.g., distance from source to receiver, source emission strength, 

source directivity, atmospheric attenuation, terrain, ground cover, weather, and frequency energy) (Pater et al. 2009). See 

the “Noise” and “Transportation/Access” resource sections. 11 Impacts from dust and air pollutants to plants and wildlife could occur within the fenceline of each action alternative, 

where exceedances of primary and secondary NAAQS are modeled to occur (see the “Air Quality and Climate Change” 

resource section). 12 The analysis area is partially defined by the results of the Dark Sky Partners LLC’s (2012) analysis on the night sky and 

includes the three observation locations that will receive the greatest amount of impacts from increased light resulting from 

the proposed project (see the “Dark Skies” resource section). 13 The analysis area is partially defined by the analysis area in the “Transportation/Access” resource section.

Final Environmental Impact Statement for the Rosemont Copper Project 575

 
Chapter 3. Affected Environment and Environmental Consequences

concern,14 AGFD’s Species of Greatest Conservation Need and Species of Economic and 

Recreational Importance, and Pima County’s “Sonoran Desert Conservation Plan”/“Multi-species 

Conservation Plan” covered species. The Forest Service is required to address effects of the proposed 

project on certain species, and the species lists that were generated are the result of reviewing the 

regulatory requirements of the ESA, National Forest Management Act, FSM 2670 (U.S. Forest 

Service 2005a), Migratory Bird Treaty Act, Bald and Golden Eagle Protection Act, Executive 

Order 13443, and Executive Order 13186. Because of the large scale of this project and the 

multijurisdictional nature of land and resource management, and because the agency is required to 

consider downstream effects on special status species from upslope sources, regardless of 

landownership or management agency, the Forest Service also included analysis of special status 

species from the BLM, AGFD, and Pima County that occur in the analysis area. These species are 

addressed in the biologists’ report (SWCA Environmental Consultants 2013c) and biological 

evaluation (SWCA Environmental Consultants 2013b).

The special status species analyzed for this project include the following: (1) the 35 species listed by 

the USFWS as either threatened, endangered, proposed threatened, proposed endangered, candidate, 

or petitioned for listing species for Pima and Santa Cruz Counties (U.S. Fish and Wildlife Service

2013f, 2013g); (2) the 86 animal species and 76 plant species identified as sensitive by the Regional 

Forester for the Southwestern Region of the Forest Service (U.S. Forest Service 2007d);

15 (3) the 33 

species identified as sensitive by the BLM for the Tucson Field Office (Bureau of Land Management 

2005); (4) the 33 species and 1 group identified as management indicator species for the Coronado 

National Forest (U.S. Forest Service 2011b); (5) the 105 species listed as either National Partners in 

Flight priority bird species or migratory nongame birds of management concern in the United States

(Partners in Flight 2006; U.S. Fish and Wildlife Service 2008f); (6) the 531 species listed by the 

AGFD as Species of Greatest Conservation Need; (7) the 13 species listed by the AGFD as Species of 

Economic and Recreational Importance; and (8) the 44 covered species for which Pima County is 

seeking Section 10 ESA permit coverage. In all, approximately 700 species were considered for 

further analysis (SWCA Environmental Consultants 2013c). This section of the EIS is a synthesis that 

tiers to several supporting documents that address effects on special status species. Only some of 

these approximately 700 species are being specifically addressed in this FEIS; the following 

paragraphs provide explanations regarding which species are addressed in this FEIS.

The aforementioned lists of species were analyzed in a series of documents: “Biologists’ Report on 

the Affected Environment and Identification of Species for Disclosure of Effects, Rosemont Copper 

Mine Project, Pima County, Arizona” (“biologists’ report”) (SWCA Environmental Consultants 

2013c), biological evaluation (SWCA Environmental Consultants 2013b), management indicator 

species report (SWCA Environmental Consultants 2013h), migratory bird analysis (SWCA 

Environmental Consultants 2013i), and biological assessment (SWCA Environmental Consultants 

2012b; 2012g; U.S. Forest Service and SWCA Environmental Consultants 2013). Although these 

reports were largely written by SWCA Environmental Consultants, they were reviewed and approved 

by the Coronado. The biologists’ report was the first in the series of supporting documents (SWCA 

Environmental Consultants 2013c), and it laid the groundwork to identify which of the approximately 

700 species being considered should be included in further analysis to meet regulatory requirements. 

14 The category “migratory birds of conservation concern” includes species listed as either National Partners in Flight 

priority bird species or migratory nongame birds of management concern in the United States.

15 The Regional Forester’s Sensitive Species List was recently updated (September 2013); however, this FEIS is considered 

an ongoing action, so it does not need to consider impacts to applicable sensitive species on this list. 

576 Final Environmental Impact Statement for the Rosemont Copper Project

 
Chapter 3. Affected Environment and Environmental Consequences

The report included a literature review and considered species distribution, habitat use, abundance, 

and natural history as a basis for screening or retaining species for further analysis. 

Within the biologists’ report, the potential for occurrence of the species in the analysis area was based 

on the following: (1) documented records; (2) site-specific field surveys; (3) existing information on 

distribution; and (4) qualitative comparisons of the habitat requirements of each species with 

vegetation communities or landscape features (e.g., elevation and aspect, water needs, geology, etc.) 

within the analysis area. The analyses in these reports relied on extensive literature reviews, museum 

specimens, past survey efforts, the AGFD’s Arizona Heritage Geographic Information System 

(2012d), and online locality information such as the AGFD’s Heritage Data Management System,

16

USFWS’s Arizona Ecological Services website,17 Southwest Environmental Information Network,18

Sky Island Alliance’s Madrean Archipelago Biodiversity Assessment Project,

19 and eBird.20 A total of 

152 special status species and one management indicator species group was carried forward from the 

biologists’ report (SWCA Environmental Consultants 2013c) for further analysis in the following 

resource reports.

Any species listed as threatened, endangered, proposed threatened, proposed endangered, candidate, 

or petitioned for listing within Pima County (U.S. Fish and Wildlife Service 2013f) and Santa Cruz 

County (U.S. Fish and Wildlife Service 2013g) were screened in table 2 of the biologists’ report, and 

those deemed to potentially occur in areas to be impacted by the proposed project were carried 

through for detailed analysis within the biological evaluation (SWCA Environmental Consultants 

2013b) and the biological assessment (SWCA Environmental Consultants 2012b). The biological 

assessment was prepared (based on the preferred alternative, the Barrel Alternative) and submitted to 

the USFWS in June 2012, and two supplemental biological assessments were submitted to the 

USFWS in October 2012 (SWCA Environmental Consultants 2012g) and February 2013 (U.S. Forest 

Service and SWCA Environmental Consultants 2013). 

Any species listed as sensitive by the Forest Service (2007e) or BLM (2005) were screened in table 3 

of the biologists’ report, and those deemed to potentially occur in areas to be impacted by the 

proposed project were carried through for detailed analysis within the biological evaluation (SWCA 

Environmental Consultants 2013b). Additional Forest Service sensitive species potentially impacted 

by the rerouting of the Arizona National Scenic Trail to the east side of SR 83 (Barrel, Barrel Trail, 

and Scholefield-McCleary Alternatives) were analyzed in a separate biological evaluation (WestLand 

Resources Inc. 2013a). 

Any species or groups listed as management indicator species by the Forest Service (U.S. Forest 

Service 2011b) were screened in table 4 of the biologists’ report, and those deemed to potentially 

occur in areas to be impacted by the proposed project were carried through for detailed evaluation 

16 Abstracts and distribution maps for many Arizona plants and animals are available at: 

http://www.azgfd.gov/w_c/edits/species_concern.shtml. 17 General species information and range/distribution information is available at: 

http://www.fws.gov/southwest/es/arizona/Docs_Species.htm. 18 A suite of data access technologies and a distributed network of departments, museums, and agencies that provide 

environmental information about floral species in Arizona and beyond is available at: 

http://swbiodiversity.org/seinet/index.php. 19 Access to a growing collection of specimen records and observations of historic and recent faunal records in the 

southwestern U.S. and northwestern Mexico’s Madrean Sky Island region (Sonora, Arizona, Chihuahua, and New Mexico)

is available at: http://www.madrean.org/maba/symbfauna/. 20 Interactive range and point maps by species or subspecies can be explored here: http://ebird.org/content/ebird/.

Final Environmental Impact Statement for the Rosemont Copper Project 577

 
Chapter 3. Affected Environment and Environmental Consequences

within the management indicator species report (SWCA Environmental Consultants 2013h). Any 

migratory bird species on either the National Partners in Flight priority bird species or migratory 

nongame birds of management concern in the United States lists were screened in table 5 of the 

biologists’ report, and those deemed to potentially occur in areas to be impacted by the proposed 

project were carried through for detailed evaluation within the migratory bird analysis (SWCA 

Environmental Consultants 2013i). The Species of Greatest Conservation Need or Species of 

Economic and Recreational Importance as listed by the AGFD in “Arizona’s State Wildlife Action 

Plan: 2013–2022” (Arizona Game and Fish Department 2012a) and the covered species for which 

Pima County is seeking Section 10 permit coverage (Pima County 2010; 2012f) were evaluated in 

tables 6 and 7 of the biologists’ report, respectively (SWCA Environmental Consultants 2013c).

In an effort to use best available science, literature about local distribution of most plants and 

animals, although somewhat limited, was used for the analyses in this FEIS (e.g., ANAMAX surveys 

(Davis and Callahan n.d. [1977])). In addition, WestLand Resources Inc. and their subcontractors 

conducted surveys in the analysis area to better understand presence/absence or local distribution of 

certain special-status species in the project area: select Forest Service sensitive plants (WestLand 

Resources Inc. 2010d; 2011i); Coleman’s coral-root (WestLand Resources Inc. 2010b; 2012g, 

2012k); Pima pineapple cactus (WestLand Resources Inc. 2009e; 2009f; 2010d; 2011c; 2011d); 

Chiricahua leopard frogs (WestLand Resources Inc. 2009a; 2009b; 2011h; 2011l); select bats

(Buecher and Sidner 2013; Buecher et al. 2012; Buecher et al. 2010, 2011; WestLand Resources Inc. 

2009d; 2011j); and talussnails (Schmalzel and Archer 2010; WestLand Resources Inc. 2009g).

The surveys focused on areas of highest potential for direct impact from the project, mostly around 

the proposed footprint. More detailed discussions of each species and important features such as 

springs, seeps, stock ponds, and tanks (potential habitat for Chiricahua leopard frog); mine shafts, 

mine adits, and natural caves (potential bat habitats); and talus slopes (potential habitat for talussnails 

and some reptiles and amphibians) are included in the supporting biology documents for this project.

Environmental surveys also were conducted in the Rosemont area in the 1970s based on ANAMAX’s 

preliminary mining plans for the area (Davis and Callahan n.d. [1977]). No new bird surveys in the 

project or analysis areas were conducted for the purposes of this project. Based on extensive literature 

reviews, past and recent survey efforts, the AGFD’s Arizona Heritage Geographic Information 

System (2012d), and online locality information used in the screening process in the biologists’ 

report, a total of 53 federally protected special-status plant and animal species (i.e., threatened, 

endangered, proposed threatened, proposed endangered, candidate, or petitioned for listing species 

under the ESA, and Forest Service and/or BLM sensitive species) was documented as occurring 

within the project and/or analysis area (table 115).21 Forest Service sensitive species are only included 

if they are known to occur on NFS lands; similarly, BLM sensitive species are only included if they 

are known to occur on BLM lands. Special status species with habitat but no documented occurrence 

records within the analysis area are addressed in the aforementioned resource reports. Columns in 

table 115 include listing status by agency and whether or not there are records from the analysis 

and/or project areas (note that the project area is within the analysis area). Special status species listed 

in table 115 have narratives in both the “Affected Environment” and “Environmental Consequences” 

parts of this resource section. Bats are discussed under a single “Sensitive Bats” heading. 

21 Included in this total is one species, the Santa Rita talussnail (Sonorella walkeri walkeri) (formerly Rosemont talussnail 

(S. rosemontensis). This species is also included in table 115 and the analysis in the FEIS because it was considered for 

analysis in the DEIS as a species that was a candidate for listing under the ESA, but the USFWS determined the species was 

not taxonomically valid.

578 Final Environmental Impact Statement for the Rosemont Copper Project

 
Chapter 3. Affected Environment and Environmental Consequences

Golden eagles, migratory birds, management indicator species, AGFD Species of Greatest 

Conservation Need or Species of Economic and Recreational Importance, and Pima County covered 

species are not shown in the table unless they are also on other lists; however, discussions of these 

groups are included in both the “Affected Environment” and “Environmental Consequences” parts of 

this resource section, and they are discussed in more detail in the biologists’ report (SWCA 

Environmental Consultants 2013c), the migratory bird analysis (SWCA Environmental Consultants 

2013i), and the management indicator species report (SWCA Environmental Consultants 2013h).

Table 115. Summary of special status plant and animal species that are specifically addressed 

in this FEIS 

Scientific Name Common Name

USFW

S

Forest ServiceBLMStateCountyAnalysis AreaProject Area

Plants

Amoreuxia gonzalezii Santa Rita yellowshow S HS X X

Carex ultra Arizona (=Cochise) 

giant sedge

S S X X

Coryphantha scheeri 

var. robustispina

Pima pineapple cactus E HS CS X

Erigeron arisolius Arid throne fleabane S X

Graptopetalum 

bartramii 

Bartram stonecrop PL S S SR X

Heterotheca rutteri Huachuca golden aster S S X

Hexalectris colemanii Coleman’s coral-root PL S S SR X X

Lilaeopsis 

schaffneriana var. 

recurva

Huachuca water umbel E, DCH* HS CS X

Lilium parryi Lemon lily S X X

Manihot davisiae Arizona manihot S X X

Muhlenbergia elongata 

(= M. xerophila) 

Sycamore Canyon 

(Weeping) muhly

S X

Muhlenbergia palmeri 

(= M. dubioides)

Southwestern (Box 

Canyon) muhly

S X

Pectis imberbis Beardless chinchweed PL S X X

Samolus vagans Chiricahua mountain 

brookweed

S X

Stevia lemmonnii Lemmon’s stevia S X X

Tragia laciniata Sonoran noseburn S X X

Amphibians

Lithobates 

chiricahuensis 

Chiricahua leopard 

frog

T, DCH SGCN CS X X

Lithobates yavapaiensis Lowland leopard frog S SGCN CS X

Reptiles

Aspidoscelis 

stictogramma 

Giant spotted whiptail S S SGCN CS X X

Gopherus morafkai Sonoran desert tortoise C S S SGCN CS X

Senticolis triaspis Green ratsnake S SGCN X X

Final Environmental Impact Statement for the Rosemont Copper Project 579
Chapter 3. Affected Environment and Environmental Consequences

Scientific Name Common Name

USFW

S

Forest ServiceBLMStateCountyAnalysis AreaProject Area

Thamnophis eques 

megalops

Northern Mexican 

gartersnake

PT, PCH S S SGCN CS X

Birds

Ammodramus 

savannarum ammolegus

Arizona grasshopper 

sparrow

S SGCN X

Buteo nitida maximus Northern gray hawk S X

Buteogallus 

anthracinus

Common black-hawk S SGCN X

Camptostoma imberbe Northern beardlesstyrannuletS, 

MIS

X X

Coccyzus americanus 

occidentalis 

Western yellow-billed 

cuckoo

C S S SGCN CS X X

Cynanthus latirostris Broad-billed 

hummingbird

S SGCN X X

Empidonax traillii 

extimus

Southwestern willow 

flycatcher

E, DCH SGCN CS X

Megascops trichopsis Whiskered screechowlS SGCN X

Passerina versicolor Varied bunting S SGCN X X

Pipilo [=Melozone] 

aberti

Abert’s towhee S SGCN CS X

Strix occidentalis lucida Mexican spotted owl T, DCH SGCN X

Fishes

Agosia chrysogaster Longfin dace S S SGCN CS X

Gila intermedia Gila chub E, DCH MIS SGCN CS X

Poeciliopsis 

occidentalis 

occidentalis

Gila topminnow E MIS SGCN CS X

Invertebrates

Sonorella 

magdalenensis

Sonoran talussnail PL CS X X

Sonorella walkeri 

walkeri (formerly S. 

rosemontensis)

Santa Rita talussnail 

(formerly Rosemont 

talussnail; see text)

S X X

Mammals†

Baiomys taylori ater Northern pygmy 

mouse

S X X

Choeronycteris 

mexicana 

Mexican long-tongued 

bat

S SGCN CS X X

Corynorhinus 

townsendii pallescens

Pale Townsend’s bigeared batS SGCN CS X X

Lasiurus blossevillii Western red bat S SGCN CS X

Leopardus pardalis Ocelot E SGCN

Leptonycteris curasoae 

yerbabuenae 

Lesser long-nosed bat E SGCN CS X X

580 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Scientific Name Common Name

USFW

S

Forest ServiceBLMStateCountyAnalysis AreaProject Area

Mephitis macroura 

milleri

Hooded skunk S X

Myotis thysanodes Fringed myotis S X X

Myotis velifer Cave myotis S SGCN X X

Nasua narica White-nosed coati S X X

Nyctinomops 

femorosaccus

Pocketed free-tailed 

bat

S S SGCN X X

Panthera onca Jaguar E, PCH SGCN X X

Reithrodontomys 

fulvescens

Fulvous harvest mouse S SGCN X X

Reithrodontomys 

montanus

Plains harvest mouse S SGCN X X

Sigmodon ochrognathus Yellow-nosed cotton 

rat

S SGCN X X

Note: Other special status species that occur in or near the project or analysis area were analyzed in one or more of the 

supporting biological documents and are included cumulatively in sections of this FEIS but not addressed specifically 

(see text for explanation).

Status Key:

USFWS (U.S. Department of the Interior)

C – Candidate. Plant and animal taxa considered for possible addition to the List of Endangered and Threatened Species. 

These are taxa for which the USFWS has on file sufficient information on biological vulnerability and threat(s) to support 

issuance of a proposal to list, but issuance of a proposed rule is currently precluded at present by higher priority listing 

actions.

DCH – Designated Critical Habitat. For listed species, this consists of: the specific areas within the geographical area 

occupied by the species, on which are found those physical or biological features that are essential to the conservation of the 

species and which may require special management considerations or protection; and specific areas outside the geographical 

area occupied by the species that are essential for the conservation of the species.

E – Endangered. Any species that is in danger of extinction throughout all or a significant portion of its range.

PCH – Proposed Critical Habitat. Habitat proposed in the Federal Register to be designated as critical habitat, or habitat

proposed to be added to an existing critical habitat designation, for any listed or proposed species.

PL – Petitioned for Listing. A formal request suggesting that a species, with supporting biological data, be listed under the 

ESA. 

PT – Proposed Threatened. Any species that is proposed in the Federal Register to be listed as threatened under the ESA.

T – Threatened. Any species that is likely to become an endangered species within the foreseeable future throughout all or a 

significant portion of its range.

Forest Service (U.S. Department of Agriculture, Southwestern Region)

MIS – Management Indicator Species. Species managed by the Forest Service because of the following: (1) their population

changes are believed to indicate the effects of management activities; (2) they are monitored during forest plan 

implementation in order to assess the effects of management activities on their populations and the populations of other 

species with similar habitat needs which they may represent; and (3) their population trends would be monitored, in 

cooperation with State fish and wildlife agencies to the extent practicable, and relationships to habitat changes determined. 

S – Sensitive. Those taxa occurring on national forests in Arizona that are identified as sensitive by the Regional Forester 

for the Southwestern Region of the Forest Service (U.S. Forest Service 2007d).

BLM (U.S. Department of the Interior)

S – Sensitive. Those taxa occurring on BLM field office lands in Arizona that are considered sensitive “that require special 

management consideration to avoid potential future listing under the ESA” (Bureau of Land Management 2008a).

State (Arizona Native Plant Law, Arizona Department of Agriculture)

HS – Highly Safeguarded. No collection allowed.

SR – Salvage Restricted. Collection only with permit.

Final Environmental Impact Statement for the Rosemont Copper Project 581
Chapter 3. Affected Environment and Environmental Consequences

State (Species of Greatest Conservation Need in Arizona, AGFD)

SGCN – Species of Greatest Conservation Need in Arizona. Those species that were identified as most in need of 

conservation actions in Arizona (Arizona Game and Fish Department 2012a).

County (Covered Species, Pima County “Sonoran Desert Conservation Plan”)

CS – Covered Species. The “Multi-species Conservation Plan,” which is part of the “Sonoran Desert Conservation Plan,”

identifies 44 species that are proposed for coverage under the forthcoming Section 10 permit.

Analysis Area and/or Project Area

X – Confirmed records

* Designated critical habitat for this species does not occur within the analysis area.

† With the exception of the lesser long-nosed bat, all sensitive bat species are discussed together after the other special 

status mammal species in both the “Affected Environment” and “Environmental Consequences” parts of this resource 

section.

For many species listed in 115, recent surveys have not been conducted for the purposes of the 

project, and recent information regarding the presence or absence of these species within the project 

and analysis areas was incomplete or unavailable. As part of the impact analyses for these species, a

quantitative analysis using GIS was conducted to estimate the acreage of possible habitat for these 

special status species within the analysis area and the expected direct impacts to possible habitat for 

these species (see the “Special Status Species” and “Impacts to Special Status Species” parts of this 

resource section for more details).

Summary of Effects by Issue Factor by Alternative

Table 116 provides a comparison of the impacts for each issue measure by alternative.

Affected Environment

Relevant Laws, Regulations, Policies, and Plans

Numerous environmental laws, regulations, policies, and one plan guide and influence the analysis as 

outlined below. As noted in the “Permits and Authorizations” section in chapter 2, Rosemont Copper 

is responsible for ensuring that its actions comply with applicable Federal, State, and local laws and 

regulations.

Federal

Endangered Species Act

The Endangered Species Act of 1973, as amended, requires Federal agencies (e.g., Forest Service and 

USACE) to use their authority to conserve endangered and threatened species. Section 7(a)(2) of the 

act requires Federal agencies to consult with the USFWS and/or the U.S. National Oceanic and 

Atmospheric Administration Fisheries Service to ensure that the actions they authorize, fund, or 

conduct are not likely to jeopardize the continued existence of any listed species or modify 

designated critical habitat of such species. The Forest Service requested the initiation of Section 7 

formal consultation with the USFWS in June 2012 with the submittal of a biological assessment 

because it has been determined that the proposed project may affect listed species, as well as 

designated critical habitat (SWCA Environmental Consultants 2012b). Due to requests for additional 

information from the USFWS or new information that necessitated the need for updates, two 

supplemental biological assessments were submitted—one in October 2012 (SWCA Environmental 

Consultants 2012g), and one in February 2013 (U.S. Forest Service and SWCA Environmental 

Consultants 2013).

582 Final Environmental Impact Statement for the Rosemont Copper Project
Table 116. Summary of effects

Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 5A.1: Acres 

of terrestrial

vegetation

permanently lost or 

altered, by 

vegetation type*

No change 

from the 

proposed 

mine

5,612 acres permanently lost or 

altered; see table 122 for 

breakdown by vegetation type 

5,481 acres 

permanently lost or 

altered; see table 122 

for breakdown by 

vegetation type 

5,431 acres 

permanently lost or 

altered; see table 122 

for breakdown by 

vegetation type 

5,888 acres 

permanently lost or 

altered; see table 122 

for breakdown by 

vegetation type 

6,

pe

al

fo

ve

Issue 5B.1: Acres 

by type of 

terrestrial and 

aquatic habitat lost, 

altered, or 

indirectly impacted 

No change 

from the 

proposed 

mine

Refer to table 108 (in “Seeps, 

Springs, and Riparian Areas” 

resource section) and table 123 

for detailed information 

regarding these impacts

Same as for proposed 

action

Same as for proposed 

action

Same as for proposed 

action

Sa

ac

Issue 5B.2: 

Qualitative 

assessment of 

impacts on aquatic 

habitats and 

surface water that 

supports wildlife

and plants such as 

stock tanks, seeps, 

and springs

No change 

from the 

proposed 

mine, but 

increased 

population

growth and 

climate

change could 

have an 

impact

Hydroriparian habitat in Empire 

Gulch could be impacted, 

including transition from 

perennial to intermittent or 

ephemeral stream flow, mortality 

of individual species, reduced 

vegetation volume, and possibly 

transition to mesoriparian or 

xeroriparian habitat. Impacts to 

hydroriparian habitat along 

Cienega Creek and Davidson 

Canyon are possible but not the 

most likely scenario. Aquatic 

and riparian habitat associated 

with 7 springs would be lost due 

to direct surface disturbance; 10 

springs are highly likely to be 

indirectly impacted due to 

groundwater drawdown and 

would likely cease functioning 

as viable habitat; and 59 springs 

may be indirectly impacted due 

to drawdown, but their water 

source is unknown.

Direct loss of habitat associated 

with 11 stock tanks.

Same as for proposed 

action, except direct 

disturbance of 8 

springs, highly likely 

indirect impacts to 9 

springs, possible 

indirect impacts to 59 

springs.

Same as for proposed 

action, except direct 

disturbance of 5 

springs, highly likely 

indirect impacts to 11 

springs, possible 

indirect impacts to 60 

springs, and direct 

loss of 15 stock 

tanks.

Same as for Barrel 

Alternative

Sa

ac

di

sp

in

sp

im

an

st

Final Environmental Impact Statement for the Rosemont Copper Project 583
Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 5B.3: 

Qualitative 

assessment of how 

changes in the 

function of riparian 

areas could impact 

wildlife habitat†

No change 

from the 

proposed 

mine

Changes in cover, foraging 

efficiency and success, 

reproductive success, growth 

rates of young, and predatorprey relationships. 

Same as for proposed 

action

Same as for proposed 

action

Same as for proposed 

action

Sa

ac

Issue 5C.1: Acres 

of disturbance that 

could create 

conditions 

conducive for 

invasive species 

No change 

from the 

proposed 

mine

5,612 acres disturbed in the 

project area; an additional 162 

acres of xeroriparian habitat in 

Barrel Canyon, 502 acres of 

xeroriparian habitat in Davidson 

Canyon, and 407 acres of 

hydroriparian habitat in Empire 

Gulch could be indirectly 

impacted by reduced surface 

water flows and groundwater

drawdown resulting conditions 

conducive to invasive species

5,481 acres disturbed 

in the project area; an 

additional 162 acres of 

xeroriparian habitat in 

Barrel Canyon, 502 

acres of xeroriparian 

habitat in Davidson 

Canyon, and 407 acres 

of hydroriparian 

habitat in Empire 

Gulch could be 

indirectly impacted by 

reduced surface water

flows and groundwater

drawdown resulting 

conditions conducive 

to invasive species

5,431 acres disturbed 

in the project area; an 

additional 162 acres 

of xeroriparian 

habitat in Barrel 

Canyon, 502 acres of 

xeroriparian habitat 

in Davidson Canyon, 

and 407 acres of 

hydroriparian habitat 

in Empire Gulch

could be indirectly 

impacted by reduced 

surface water flows 

and groundwater

drawdown resulting 

conditions conducive 

to invasive species

5,888 acres disturbed 

in the project area; an 

additional 162 acres 

of xeroriparian 

habitat in Barrel 

Canyon, 502 acres of 

xeroriparian habitat 

in Davidson Canyon, 

and 407 acres of 

hydroriparian habitat 

in Empire Gulch

could be indirectly 

impacted by reduced 

surface water flows 

and groundwater

drawdown resulting 

conditions conducive 

to invasive species

6,

in 

ad

xe

B

ac

ha

C

of 

ha

G

in

re

flo

dr

co

to 

Issue 5D.1: 

Qualitative 

assessment of the 

change in 

movement 

corridors and 

connectivity 

between wildlife

habitats

No change 

from the 

proposed 

mine

Increase movement habitat

fragmentation and disrupt 

dispersal and migration patterns 

of species using five animal 

movement corridors; restore 

small amount of three movement 

corridors due to 

decommissioning of roads 

Same as for proposed 

action

Increase movement 

habitat fragmentation

and disrupt dispersal 

and migration 

patterns of species 

using six animal 

movement corridors; 

restore small amount 

of three movement 

corridors due to 

decommissioning of 

roads

Same as for Barrel 

Alternative

In

ha

an

an

of 

an

co

am

m

du

de

ro

584 Final Environmental Impact Statement for the Rosemont Copper Project
Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 5D.2: 

Qualitative 

assessment of 

mortality of 

various animal 

species resulting 

from increased 

volume of traffic 

related to mine 

operations 

No change 

from the 

proposed 

mine

Animal mortality would likely 

increase for some species types 

but could decrease for other 

species types (depending on 

local wildlife populations and 

natural histories of species 

encountering roads) during mine 

construction and active mine 

operations

Same as for proposed 

action

Same as for proposed 

action

Same as for proposed 

action

Sa

ac

Issue 5E.1: Acres 

of habitat disturbed 

for each special 

status species, 

including impacts 

to designated and 

proposed critical 

habitat

No change 

from the 

proposed 

mine

5,612 acres lost or converted; 

refer to table 123 for detailed 

information regarding these 

impacts; refer to species’ 

narratives in “Environmental 

Consequences” section for 

discussions of impacts to 

designated or proposed critical 

habitat

5,481 acres lost or 

converted; refer to 

table 123 for detailed 

information regarding 

these impacts; refer to 

species’ narratives in 

“Environmental 

Consequences” section 

for discussions of 

impacts to designated 

or proposed critical 

habitat

5,431 acres lost or 

converted; refer to 

table 123 for detailed 

information regarding 

these impacts; refer 

to species’ narratives 

in “Environmental 

Consequences”

section for 

discussions of 

impacts to designated 

or proposed critical 

habitat

5,888 acres lost or 

converted; refer to 

table 123 for detailed 

information regarding 

these impacts; refer 

to species’ narratives 

in “Environmental 

Consequences”

section for 

discussions of 

impacts to designated 

or proposed critical

habitat

6,

co

ta

in

th

sp

“E

C

fo

im

or 

ha

Issue 5E.2: 

Potential to affect 

the population

viability of any 

species

No change 

from the 

proposed 

mine

Individuals may be impacted, 

but loss of population viability is 

not likely

Same as for proposed 

action

Same as for proposed 

action

Same as for proposed 

action

Sa

ac

Issue 5F.1: Acres 

of habitat impacted 

from noise,

vibration, and light

No change 

from the 

proposed 

mine

Up to 146,163 acres‡ impacted Same as for proposed 

action

Same as for proposed 

action

Same as for proposed 

action

Sa

ac

Final Environmental Impact Statement for the Rosemont Copper Project 585
Issue Factor No Action Proposed Action Phased Tailings Barrel Barrel Trail 

Issue 5F.2: 

Qualitative 

assessment of 

effects on wildlife

behavior from 

noise, vibration, 

and light

No change 

from the 

proposed 

mine

Changes in habitat use, timing of 

activity patterns, inter- and intraspecific communication, 

foraging efficiency and success, 

reproductive success, and 

predator-prey relationships

Same as for proposed 

action

Same as for proposed 

action

Same as for proposed 

action

Sa

ac

* See table 121 for breakdown of impacts to vegetation type by landownership.

† Riparian area disturbance refers to acreage potentially affected indirectly by groundwater drawdown or reduction in surface flows. Direct impacts 

disturbance are analyzed in the “Surface Water Quality” section.

‡ See table 117 for acreages of vegetation community by landownership within the analysis area.

586 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Migratory Bird Treaty Act

The Migratory Bird Treaty Act of 1918, as amended (16 U.S.C. 703–711) provides Federal 

protection to all migratory birds, including nests and eggs. Under this act, it is unlawful to take, kill, 

or possess migratory birds. There are no specific provisions or permit requirements for nonpurposeful 

take; indeed, the intent of the act is to protect migratory birds from purposeful take and regulate take 

where warranted. The Southwestern Regional Office of the Forest Service recommends analyzing the 

impacts as follows: (1) on species of concern listed by National Partners in Flight; (2) on important 

bird areas; and (3) on important overwintering areas, as discussed in a 2008 memorandum of 

understanding between the Forest Service and the USFWS (U.S. Forest Service 2008i).

Executive Order 13186

Issued on January 11, 2001, this executive order states that a memorandum of understanding (MOU) 

between the Forest Service and USFWS was needed to establish conservation goals, mitigative 

measures, and accountability for ground-disturbing activities. The resulting MOU states that the 

Forest Service shall “consider approaches, to the extent practicable, for identifying and minimizing 

take that is incidental to otherwise lawful activities . . . giving due consideration to key wintering 

areas, migration routes, and stopovers” (U.S. Forest Service 2008i).

Executive Order 13186 requires Federal agencies (Section 3(9)) to “identify where unintentional take 

reasonably attributable to agency actions is having, or is likely to have, a measurable negative effect 

of migratory bird populations, focusing first on species of concern, priority habitats, and key risk 

factors.” “Unintentional take” is defined (Section 2(c)) as “take that results from, but is not the 

purpose of, the activity in question.” “Take” is defined (50 CFR 10.12) as to “pursue, hunt, shoot, 

wound, kill, trap, capture, or collect, or attempt to pursue, hunt, shoot, wound, kill, trap, capture, or 

collect.” Note that this law refers only to take, not habitat loss or conversion.

Note that the term “population” may have different connotations, but birds, in particular, are longrange migrants, so for our purposes, a population is considered a range-wide entity, rather than being 

composed of discrete subpopulations, as is often true with smaller, less-mobile organisms. Not only 

do most birds in the project area have long-distance migration patterns, but nesting localities can 

change from one year to the next. For example, a migratory species that winters in Central America 

may nest in different mountain ranges in the United States in subsequent years, depending on 

environmental factors at the time, including the influence of a changing climate. Even wintering birds 

may have short-distance migration variability between valleys and montane habitats.

Executive Order 13443

Issued on August 16, 2007, this executive order is titled “Facilitation of Hunting Heritage and 

Wildlife Conservation.” It has a State and Federal nexus, because (as in this mining proposal) the 

Federal Government may manage public lands, but the State has regulatory authority over managing 

animal populations (Federal ESA or National Forest Management Act requirements notwithstanding). 

In Section 2 of the order, the role of Federal activities are outlined, and it is noted that the Federal 

Government must work cooperatively with the States. As indicated by the title of this order, the 

emphasis is on hunting and conservation, and the Federal Government is required to address its 

activities on these natural resource components. 

These requirements are met in one of the supporting biological documents, the “Biologists’ Report” 

(SWCA Environmental Consultants 2013c), which discloses effects (Section 2a) to Species of 

Final Environmental Impact Statement for the Rosemont Copper Project 587
Chapter 3. Affected Environment and Environmental Consequences

Economic and Recreational Importance (i.e., game species) and Species of Greatest Conservation 

Need, as identified by AGFD, in the “State Wildlife Action Plan” (Section 2f ).

The Bald and Golden Eagle Protection Act

This law (16 U.S.C. 668–668c) was enacted in 1940 and amended several times. The USFWS

recently (September 11, 2009) announced a final rule on two new permit regulations that would allow 

for the nonpurposeful “take” of eagles and eagle nests under this act (50 CFR 13 and 22). Take is 

defined as “pursue, shoot, shoot at, poison, wound, kill, capture, trap, collect, molest or disturb.”

Disturb is defined as “to agitate or bother a bald or golden eagle to a degree that causes, or is likely to 

cause, based on the best scientific information available, (1) injury to an eagle, (2) a decrease in its 

productivity, by substantially interfering with normal breeding, feeding, or sheltering behavior, or 

(3) nest abandonment, by substantially interfering with normal breeding, feeding, or sheltering 

behavior.”

National Forest Management Act

Under this 1976 act, the Secretary of Agriculture “provides for diversity of plant and animal 

communities based on the suitability and capability of the specific land area in order to meet overall 

multiple-use objectives.” In addition to federally listed species (see section on ESA, above), this law 

has regulatory implementation requirements for “management indicator species” and “sensitive 

species” that appear as directives in the FSM.

Management Indicator Species

The role of management indicator species in national forest planning is described in the 1982 

implementing regulations for the National Forest Management Act (36 CFR 219.19(a)(1)). FSM 

2620.5 defines management indicator species as “plant and animal species, communities or special 

habitats selected for emphasis in planning, and which are monitored during forest plan 

implementation in order to assess the effects of management activities on their populations and the 

populations of other species with similar habitat needs which they may represent” (U.S. Forest 

Service 1991:6). These regulations require that certain vertebrate and/or invertebrate species present 

in the area be identified as management indicator species within the planning area (Coronado 

National Forest) and that these species be monitored, as “their population changes are believed to 

indicate the effects of management activities” (36 CFR 219.19(a)(1)).

Forest Service Sensitive Species

As described in FSM 2670.12 (U.S. Forest Service 2005a), the Forest Service will do the following: 

(1) manage “habitats for all existing native and desired nonnative plants, fish, and wildlife species in 

order to maintain at least viable populations of such species;” and (2) avoid actions that “may cause a 

species to become threatened or endangered.”

Bureau of Land Management Sensitive Species

BLM Manual 6840 (Bureau of Land Management 2008a) defines BLM sensitive species as those 

“species that require special management consideration to avoid potential future listing under the 

ESA and that have been identified in accordance with procedures set forth in this manual.”

588 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Executive Order 13112

On February 3, 1999, the President signed Executive Order 13112, which directed Federal agencies to 

prevent introduction of invasive species, control populations, monitor populations, and provide for 

restoration of native species, among other requirements.

State

Arizona Native Plant Law

This law applies to all lands within the State of Arizona (ARS 3-901 to 3-916). State protected native 

plants cannot be legally possessed, taken, or transported from any lands without a permit from the 

Arizona Department of Agriculture; permission of the landowner is also required. Landowners have 

the right to destroy or remove plants growing on their land, but they are required to notify the Arizona 

Department of Agriculture 20 to 60 days prior to the destruction of any protected native plants. 

The law does not apply to: (1) existing canals, laterals, ditches, electrical transmission and 

distribution facilities, ROWs and other facilities, structures or equipment owned, operated, used, or 

otherwise possessed by public service corporations and special districts established under ARS 48;

and (2) normal and routine maintenance of improvements that may cause the incidental or 

unavoidable destruction of native plants. A list of protected plants is provided on the Arizona 

Department of Agriculture Web site (Arizona Department of Agriculture 2005). 

Invasive Plant Species

The State of Arizona has laws addressing the control and eradication of noxious and invasive weeds 

and identifying specific species that fall under noxious weed definitions (AAC R3-4-244 and 245). 

The Arizona Department of Agriculture is responsible for implementing State laws pertaining to 

noxious and invasive weeds. 

Game and Fish

ARS Title 17 specifies State regulations regarding fish and game species, including management on 

State lands, hunting, and take of individuals. ARS 17-102 states that wildlife, both resident and 

migratory, native or introduced, found in this state (with certain exceptions) are property of the State 

and may be taken at such times, in such places, in such manner, and with such devices as provided by 

law or rule of the commission. The AGFD provided comments on the Preliminary Administrative 

Review Draft FEIS to the Coronado that ARS 17-236(A) states that it is unlawful to take or injure any 

bird or harass any bird upon its nest, or remove the nests or eggs of any bird, except as may occur in 

normal horticultural and agricultural practices and except as authorized by commission order.

County

Sonoran Desert Conservation Plan/Multi-species Conservation Plan

Pima County submitted a “Multi-species Conservation Plan” (Pima County 2012e) to the USFWS on 

December 7, 2012, at which time the USFWS opened a 90-day comment period for the DEIS at Pima 

County’s request for an ESA incidental take permit associated with the draft Pima County “Multispecies Conservation Plan” (U.S. Fish and Wildlife Service 2012b). The “Multi-species Conservation 

Plan” (a form of a habitat conservation plan for many species) and the associated incidental take 

permit (i.e., Section 10 permit) could provide Pima County and some specific activities of the private 

sector with a more comprehensive way to comply with the ESA. The permit area would include 

(Pima County 2012d:4): 

Final Environmental Impact Statement for the Rosemont Copper Project 589
Chapter 3. Affected Environment and Environmental Consequences

1) Only those lands under the Pima County Board of Supervisor’s legal authority—

principally private, unincorporated lands over which the Board has some regulatory 

authority—and those lands managed by Pima County for mitigation purposes; 2) all Countyowned lands; 3) lands where Pima County constructs and maintains infrastructure on lands 

owned by another jurisdiction; 4) certain Arizona State Trust lands and Bureau of Land 

Management (BLM) lands that could be disposed to the private sector during the term of the 

permit; and 5) a subset of Arizona State Trust lands on which Pima County holds a grazing 

lease, including some lands outside of Pima County.

The “Multi-species Conservation Plan” is part of the larger “Sonoran Desert Conservation Plan” 

(Pima County 2012e), which is Pima County’s plan to balance conservation and protection of cultural 

and natural resources while maintaining an economically vigorous and financially responsible 

community. As part of the Incidental Take permit, Pima County would agree to implement avoidance 

and minimization conservation measures (e.g., the Maeveen Marie Behan Conservation Lands 

System) and mitigation for impacts of the covered activities (e.g., Pima County has acquired more 

than 71,000 acres of fee-owned lands and more than 130,000 acres of leased lands). Of the five 

elements of the plan, the four that are most relevant to biological resources in the analysis area are 

Critical Habitat and Biological Corridors, Riparian Restoration, Mountain Parks, and Ranch 

Conservation. The “Multi-species Conservation Plan” identifies 44 covered species for the 

forthcoming Section 10 permit and includes 4 plants, 7 mammals, 8 birds, 5 fish, 2 amphibians, 6

reptiles, and 12 invertebrates (Pima County 2012e). Seven species currently are federally listed as 

threatened or endangered, and an additional five species are candidate or have been petitioned for 

listing under the ESA. 

Existing Conditions

This section discusses the existing disturbances and biological resources in the analysis area. The first 

section describes existing disturbances. Next, biophysical and biological information that is important 

in understanding habitats in the analysis area is discussed. Finally, the plant and animal species that 

may occur in the analysis area are presented.

Past, Present, and Existing Disturbances

Past and present actions are reflected in the existing condition of the analysis area. Previous mineral 

exploration and production activities scattered throughout the analysis area have resulted in numerous 

landscape disturbances, such as mine prospects and adits, mine related access roads, and geotechnical 

drilling sites, that potentially contribute to current light levels in the night sky and fugitive dust. 

Additional anthropogenic disturbances have resulted from livestock grazing and all-terrain vehicle

use. Past wildfires have also affected biological resources in the analysis area: since 1989 there have 

been 27 fires larger than 10 acres, totaling approximately 49,321 acres. Fires kill vegetation and 

wildlife to a varying degree, depending on the severity and intensity of the fire, and the recovery can 

take up to decades, depending on the pre-fire vegetation community and the severity and intensity of 

the fire. Further, within and adjacent to the analysis area, there are numerous wells in the Sonoita area 

that support residential and ranching uses and contribute to groundwater drawdown in the analysis 

area. 

590 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Biophysical Features

The analysis area ranges in elevation from approximately 2,721 to 6,635 feet above mean sea level. 

The topography is dominated by rolling to steep hills, drainages, and canyons. The Santa Rita 

Mountain range includes numerous drainages that contain riparian habitat. Barrel Canyon is the 

principal drainage system within the project area (see figure 1). Wasp, McCleary, and Scholefield 

Canyons discharge to Barrel Canyon, which discharges to Davidson Canyon and then to Cienega 

Creek in the northern portion of the analysis area. Empire Gulch and Gardner Canyon discharge into 

upper Cienega Creek in the southeastern portion of the analysis area (see figure 71). The northwest

side of the analysis area is drained by a series of unnamed headwater tributaries of Sycamore Canyon. 

Box Canyon is the major drainage system within the southwestern portion of the analysis area, west 

of the main ridgeline. There are 95 springs and seeps (see figure 69 and table 109 in the “Seeps, 

Springs, and Riparian Areas” resource section) and 148 stock tanks in the analysis area (figure 72). 

Thirty-one springs support some level of hydroriparian/mesoriparian habitat, and an additional 18 

springs support some level of xeroriparian/mesoriparian habitat. 

Two springs in the analysis area were identified as being associated with wetlands: Scholefield 

Spring, located on a tributary to Scholefield Canyon; and Fig Tree Spring, a developed spring near 

the head of a minor unnamed tributary to Sycamore Canyon (WestLand Resources Inc. 2010c). 

The aforementioned water sources provide habitat for aquatic plant and animal species within the 

analysis area. A comprehensive list of springs identified in the analysis area is provided in table 109

in the “Seeps, Springs, and Riparian Areas” resource section of this chapter, and a list of stock tanks 

in the project area is given in table 88 in the “Surface Water Quantity” resource section. Refer to the 

“Groundwater Quantity,” “Groundwater Quality and Geochemistry,” “Surface Water Quantity,” 

“Surface Water Quality,” and “Seeps, Springs, and Riparian Areas” resource sections for discussion 

of the affected environment and water resources. 

Previous mining activity has resulted in a number of mine adits and shafts within and adjacent to the 

analysis area (figure 73); of the 85 mine adits and shafts that were examined in the analysis area, 

41 are documented as providing roosting habitat for bats. For a more detailed evaluation of these 

features, see WestLand Resources Inc. (2009c; 2009d; 2011j); Buecher and Sidner (2013); Buecher et 

al. (2010); Buecher et al. (2011); and Buecher et al. (2012). There are numerous talus slopes and rock 

outcrops present on the steeper portions of the analysis area (approximately 29 acres have been 

mapped in the analysis area in and near the project area) (figure 74); talus slopes and rock outcrops 

provide habitat for talussnails and other special status species. For a more detailed evaluation of these 

features, see WestLand Resources Inc. (2009g).

Vegetation Communities

When McLaughlin and Van Asdall (n.d. [1977]) sampled the vegetation in the project area in the 

early 1970s, 416 plant species in 256 genera in 75 families were found. When McLaughlin and 

Bowers (1990) conducted vegetation surveys in the northern Santa Rita Mountains in 1986 and 1987 

(in an approximately 64,250-acre area mostly within the analysis area), 628 native plant species in 

370 genera in 89 families were collected.

Final Environmental Impact Statement for the Rosemont Copper Project 591
Chapter 3. Affected Environment and Environmental Consequences

Figure 72. Stock tanks within the analysis area

592 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Figure 73. Mine adits and shafts within the analysis area (WestLand Resources Inc. 

2009d)

Final Environmental Impact Statement for the Rosemont Copper Project 593
Chapter 3. Affected Environment and Environmental Consequences

Figure 74. Talus slopes, rocky outcrops, and rocky canyon bottoms and locations of 

collections of talussnails within the analysis area (Schmalzel and Archer 2010)

594 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Uplands

The analysis area contains three upland vegetation communities: semidesert grassland, Madrean 

evergreen woodland, and Chihuahuan desertscrub (Brown 1994), shown in figure 75. There is a total 

of approximately 124,053 acres of upland vegetation in the analysis area (see table 117). Semidesert

grassland, characterized by open grasslands with widely scattered shrubs and cacti, generally covers

the lower elevations of the analysis area. Madrean evergreen woodland mostly covers the higher 

elevations of the analysis area, generally in the western and southern areas, and is characterized by 

open woodlands or savanna, consisting of trees interspersed with grasses and forbs. Chihuahuan 

desertscrub is dominated by creosotebush on plains, low hills, and valleys on the uplands surrounding 

middle Cienega Creek.

Table 117. Vegetation type by landowner (acres) within analysis area

Vegetation Type Forest Service BLM ASLD State 

Trust Lands Private Total

Semidesert grassland 16,415 16,740 44,297 17,346 94,797

Madrean evergreen 

woodland 22,155 927 2,007 2,180 27,269

Chihuahuan desertscrub 0 79 1,751 146 1,976

Sonoran desertscrub 0 0 1* 11 11

Hydroriparian 911 2,778 1,489 2,147 7,325

Xeroriparian A 41 86 0* 18 145

Xeroriparian B 1,815 1,977 2,268 1,059 7,118

Xeroriparian C 739 625 4,803 1,178 7,345

Xeroriparian D 0* 1 147 26 174

Total 42,077 23,212 56,764 24,110 146,163

Note: Because of rounding, the total may not equal the sum of the individual numbers.

* Less than 1 acre occurs within the analysis area. 

Semidesert Grassland

There is a total of approximately 94,797 acres of the semidesert grassland vegetation community in

the analysis area (see table 117). In the semidesert grassland vegetation type, composition, and 

density vary with geographic location, precipitation, and topography. Some areas within this 

vegetation community are nearly barren, with an abundance of sand, rock, gravel, scree, or talus, 

while other areas have sparse to dense vegetation cover that includes succulent species, grasses, 

shrubs, scattered trees, and some herbaceous cover (Brown 1994; U.S. Forest Service 2009d). Within 

the analysis area, semidesert grassland is characterized by grasses interspersed with a variety of low

growing trees, shrubs, and cacti, including whitethorn acacia (Acacia constricta), catclaw acacia 

(A. greggii), prickly-pear cactus (Opuntia spp.), cholla (Cylindropuntia spp.), soaptree yucca (Yucca 

elata), beargrass (Nolina microcarpa), desert spoon (Dasylirion wheeleri), and agave (principally 

Agave schottii and A. palmeri). Native grass species include black grama (Bouteloua eriopoda), blue 

grama (B. gracilis), sideoats grama (B. curtipendula), hairy grama (B. hirsuta), buffalo grass 

(B. dactyloides), plains lovegrass (Eragrostis intermedia), little bluestem (Schizachyrium cirratum), 

plains bristlegrass (Setaria machrostachya), fluffgrass (Dasyochloa pulchella), burrograss 

(Scleropogon brevifolius), and slim tridens (Tridens muticus). The nonnative Lehmann lovegrass 

(E. lehmanniana) is one of the more abundant nonnative grass species in the analysis area. 

Final Environmental Impact Statement for the Rosemont Copper Project 595
Chapter 3. Affected Environment and Environmental Consequences

Figure 75. Vegetation types within the analysis area (Brown 1994; Pima County 2013)

596 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Madrean Evergreen Woodland

There is a total of approximately 27,269 acres of the Madrean evergreen woodland vegetation

community mapped within the analysis area (see table 117). The Madrean evergreen woodland 

vegetation community occurs on foothills, canyons, bajadas, and plateaus between the semidesert 

grasslands and pine forests (Brown 1994; U.S. Forest Service 2009d). However, in the analysis area, 

virtually all of the Madrean evergreen woodland (sensu Brown (1994)) is the lower end, more 

appropriately termed Madrean encinal (oak) woodland, as opposed to the upper end, usually termed 

Madrean pine/oak woodland, and trees indicative of the Madrean pine/oak woodland are absent 

(McLaughlin and Van Asdall n.d. [1977]). This community is dominated by evergreen oaks, and in 

the analysis area, common oak species include Emory oak (Quercus emoryi), Mexican blue oak 

(Q. oblongifolia), Arizona white oak (Q. arizonica), and silverleaf oak (Q. hypoleucoides). Other tree 

species present are alligator bark juniper (Juniperus deppeana), one-seed juniper (J. monosperma), 

velvet mesquite (Prosopis velutina), and Mexican pinyon (Pinus cembroides). All of the shrub and 

warm-season grass species and other ground cover listed in the semidesert grassland section can also 

be found in areas dominated by the Madrean evergreen woodland vegetation community.

Chihuahuan Desertscrub

There is a total of approximately 1,976 acres of the Chihuahuan desertscrub vegetation community in

the analysis area (see table 117) (Brown 1994). Chihuahuan desertscrub is limited to uplands in the 

vicinity of Cienega Creek within the analysis area. The analysis area is within the Mexican Highlands 

Ecoregion; the Chihuahuan Desert influences this ecoregion, and McLaughlin and Van Asdall 

(n.d. [1977]) noted that Chihuahuan desertscrub vegetation components are present in the mine site 

area. Other vegetation in this community includes very large yucca (Yucca spp.), which grow among 

grasses (mostly Bouteloua spp.) or scattered shrubs (e.g., desert zinnia (Zinnia acerosa) and condalia 

(Condalia sp.)), agave (Agave spp.), ocotillo (Fouquieria splendens), jatropha (Jatropha sp.), and 

scattered cacti.

Sonoran Desertscrub

There is a total of approximately 11 acres of the Sonoran desertscrub vegetation community in the

northwestern portion of the analysis area in (see table 117) (Brown 1994). Locally, Sonoran 

desertscrub is also present in lower Davidson Canyon, lower Cienega Creek, although it is not 

mapped there; however, the Sonoran Desertscrub biotic elements are often ecotonal with the other 

upland habitat types. The conspicuous vegetation of the Arizona Upland subdivision of the Sonoran 

Desert includes saguaro, palo verdes, creosotebush, and numerous species of cacti, such as chain fruit 

cholla (Opuntia fulgida) and Engelmann prickly pear (O. phaeocantha var. phaeocantha). 

Riparian

The word “riparian” is used to describe plant communities associated with natural washes, rivers, 

ponds, and springs. Riparian plant associations occur along a continuum of available soil moisture, 

and regulatory agencies and researchers have consequently developed numerous and varied 

definitions of riparian (WestLand Resources Inc. 2010c). Some definitions relate directly to the nature 

of the water supply (e.g., perennial streams only); others relate to the condition and nature of the 

habitats associated with the watercourse (e.g., vegetation location, density, and composition), and still 

others use definitions that incorporate varied combinations of these factors (WestLand Resources Inc. 

2010c). Riparian ecosystems provide habitat for approximately one-third of the plant species in 

western North America, and approximately 60 percent of vertebrate species and 70 percent of 

threatened and endangered species in the arid Southwest are riparian obligates (Poff et al. 2011). 

Final Environmental Impact Statement for the Rosemont Copper Project 597
Chapter 3. Affected Environment and Environmental Consequences

These ecosystems provide essential ecological functions and are unique because species diversity, 

density, and productivity are high in these areas.

There is a total of approximately 22,107 acres of riparian vegetation in the analysis area (see figure

75, table 117). These vegetation communities are present in drainages within the analysis area and 

along downstream portions of Box, McCleary, Sycamore, Scholefield, Wasp, Barrel, Davidson, and 

Gardner Canyons; Empire Gulch; and Cienega Creek. In addition to the riparian vegetation listed 

below as occurring in riparian areas in the analysis area, Emory oak, Mexican blue oak, and Arizona 

white oak are common in Box, McCleary, Sycamore, Scholefield, Wasp, and Barrel Canyons. While 

many springs support some individuals of species considered to indicate hydroriparian habitat, only 

two springs had large mappable areas of hydroriparian vegetation: Scholefield No. 1 spring supports 

about 0.3 acre of wetland, and Fig Tree spring supports about 0.5 acre of riparian habitat, with a very 

limited wetland area. These water sources provide habitat for aquatic species within the analysis area. 

Pima County’s riparian mapping source is used for this project, and the following riparian habitat 

types are mapped within the analysis area (Pima County 2013).

Hydroriparian

Hydroriparian habitats are generally associated with perennial watercourses and/or springs. Plant 

communities are dominated by obligate or preferential wetland plant species such as Goodding’s 

willow (Salix gooddingii) and Fremont cottonwood (Populus fremontii) and also include velvet ash 

(Fraxinus velutina), seep willow (Baccharis salicifolia), Arizona walnut (Juglans major), tamarisk 

(Tamarisk spp.), and mesquite. The cottonwood/willow forest is a typical example of this habitat type. 

The following drainages and associated riparian habitat contain stretches that are mapped as 

hydroriparian: Cienega Creek, Gardner Canyon, Empire Gulch, Davidson Canyon, and Barrel 

Canyon.22 Approximately 7,325 acres of hydroriparian habitat are located within the analysis area.

Aquatic vegetation that is unique to the springs and seeps is present within the analysis area. 

Vegetation at these springs and seeps includes obligate wetland plants (i.e., almost always occur 

under natural conditions in wetlands) such as seep monkey flower (Mimulus guttatus) and water 

speedwell (Veronica anagallis-aquatica), along with facultative wetland plants (i.e., usually occur in 

wetlands, but occasionally found in nonwetlands) such as smooth horsetail (Equisetum laevigatum) 

and Arizona giant sedge (Carex spissa var. ultra) (which is likely a facultative wetland plant). Other 

riparian plant species documented at springs and seeps in the analysis area include sycamore 

(Plantanus wrightii), willow (Salix spp.), netleaf hackberry (Celtis reticulata), and deergrass 

(Muhlenbergia rigens). Within the analysis area, moist soil or surface water (both lentic and lotic 

systems) and associated aquatic vegetation are known to occur at the several springs (e.g., Deering, 

Upper Empire Gulch, Fig Tree, Mudhole, Oak, Ojo Blanco, Rosemont, Scholefield No. 1, Sycamore, 

and Water Develop) (WestLand Resources Inc. 2011k) (see the “Seeps, Springs, and Riparian Areas” 

resource section for details). 

In addition, the BLM provided comments on the Preliminary Administrative Review Draft FEIS to 

the Coronado that Las Cienegas National Conservation Area is well known for its wetlands. The 

Cienega Basin within the Las Cienegas National Conservation Area has more than 30 jurisdictional 

wetlands that cover tens of acres and are both perennial and seasonal (e.g., Cieneguita Wetland, 

Spring Water Wetland, Cinco Ponds Wetland, and Cold Spring Wetland). Areas of aquatic habitats

22 Mapping in Barrel Canyon does not match field descriptions. Pima County riparian mapping indicates that Barrel Canyon 

is hydroriparian; it was reassigned as xeroriparian with pockets of mesoriparian. See the “Seeps, Springs, and Riparian

Areas” resource section of this chapter for further detail.

598 Final Environmental Impact Statement for the Rosemont Copper Project

 
Chapter 3. Affected Environment and Environmental Consequences

and wetlands are too small to map; therefore, they do not appear in figure 75. These wetland areas all 

occur within the hydroriparian habitat mapped by Pima County along Cienega Creek.

Xeroriparian

Xeroriparian habitats are generally associated with an ephemeral water supply. These communities 

typically contain plant species also found in upland habitats; however, these plants are typically larger 

and/or occur at higher densities than adjacent uplands. Approximately 14,782 acres of xeroriparian

habitat are located within the analysis area. Xeroriparian habitat is further divided into four 

subclasses to reflect the amount of vegetation present. Pima County Regional Flood Control District’s 

Regulated Riparian Habitat Mitigation Standards and Implementation Guidelines (Pima County 

Department of Transportation and Flood Control District 2001; Pima County Regional Flood Control 

District 2011) define the xeroriparian subcategories as follows:

• Xeroriparian A: The most dense xeroriparian subcategory with a total vegetative volume 

greater than 0.856 m3

/m2. Xeroriparian A habitat is present in stretches of Cienega Creek, 

Empire Gulch, and Davidson Canyon where vegetation consists of mesquite and netleaf 

hackberry. Approximately 145 acres of xeroriparian A habitat is located within the analysis

area. 

• Xeroriparian B: Moderately dense xeroriparian subcategory with a total vegetative volume 

less than or equal to 0.856 m3

/m2 and greater than 0.675 m3/m2. Xeroriparian B habitat is 

present in stretches of Cienega Creek, Gardner Canyon, Empire Gulch, Davidson Canyon, 

and Barrel Canyon where vegetation consists of mesquite, scattered cottonwood, netleaf 

hackberry, burrobrush (Hymenoclea monogrya), juniper (Juniperus sp.), and acacia (Acacia

sp.). Approximately 7,118 acres of xeroriparian B habitat is located within the analysis area. 

• Xeroriparian C: Less dense xeroriparian subcategory with a total vegetative volume less than 

or equal to 0.675 m3

/m2 and greater than 0.500 m3/m2. Xeroriparian C habitat is present in 

stretches of Cienega Creek, Gardner Canyon, Empire Gulch, and Davidson Canyon where 

vegetation consists of mesquite, desert broom (Baccharis sarothroides), burrobush, desert 

willow (Chilopsis linearis), hackberry (Celtis sp.), and juniper. Approximately 7,345 acres of

xeroriparian C habitat is located within the analysis area. 

• Xeroriparian D: Less to sparse plant density xeroriparian subcategory that provides 

hydrologic connectivity to other riparian habitat areas with a total vegetative volume less than 

or equal to 0.500 m3

/m2. Xeroriparian D habitat is present in stretches of Cienega Creek and 

Davidson Canyon where vegetation consists of acacia and desert broom. Approximately 174

acres of xeroriparian D habitat is located within the analysis area. 

Important Riparian Areas

Important Riparian Areas, as defined by Pima County, are those Regulated Riparian Habitats having 

the highest value and can include any of the various classifications of regulated habitat type listed 

above. They provide critical watershed and water resource management function and landscape 

linkages and are valued for their higher water availability, vegetation density, connectivity factors, 

and biological productivity, compared with adjacent uplands (Pima County Department of 

Transportation and Flood Control District 2001; Pima County Regional Flood Control District 2011). 

An Important Riparian Area is a regulatory distinction but does not factor into the functional 

assessment of riparian impacts. Approximately 14,519 acres of Important Riparian Areas is located

within the analysis area, including much of Barrel Canyon and its tributaries. 

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Nonnative Plant Species

Surveys for nonnative plant species have not been conducted within the analysis area for the purposes 

of this project. Lehmann lovegrass, however, has been noted on Forest Service lands in the analysis 

area (McLaughlin and Van Asdall n.d. [1977]), and buffelgrass (Pennisetum ciliare) has been 

documented near the far northwest end of the proposed utility corridor (WestLand Resources Inc. 

2012d).

Habitat Fragmentation and Animal Movement Corridors

As the human population increases and development continues throughout the State, intact blocks of 

habitat and animal movement corridors within and among those habitat blocks are diminishing. 

In order to address the potential impacts to resident species and maintain biodiversity of native 

species, this has become a key topic in resource management planning in Arizona (and globally) in 

recent years. The general reduction in available space for organisms compromises many aspects of 

their life and natural history needs, including foraging, reproduction, gene flow, dispersal, and 

migration; ultimately, habitat loss or alteration results in the decrease in biodiversity. Most species of 

animals are not completely migratory (and no plants are), as most establish home ranges and 

territories within suitable habitat. However, it is usually essential that organisms are also able to move 

between and among suitable habitat to meet their life history requirements and ensure healthy 

populations (lest they reach a genetic or evolutionary bottleneck). Migration movements can be daily, 

seasonal, or annual, as with animals that move to or from breeding sites or areas with abundant food 

resources (e.g., neotropical migratory birds or animals that move upslope to breed). 

Dispersal is different from migration because organisms permanently move away from their place of 

birth to become established elsewhere. This contributes to a healthy gene pool, which ensures 

persistence of the species (Brown and Gibson 1983; Hudson 1991; Krebs 1994; Zug 1993). Dispersal

abilities differ among organisms. For example, small terrestrial species typically have poor dispersal 

abilities, whereas large, volant (flying), and aquatic species usually have good dispersal abilities. 

Volant species—such as birds, bats, and flying insects—are decidedly more mobile than terrestrial 

species and plants. It is essential for large mammals that also have expansive home range sizes to 

move large distances in order to find additional resources and breeding opportunities. For plants, 

individuals do not have the ability to move themselves; therefore, dispersal is usually dependent on 

wind or an animal transport, and dispersal events typically occur during their seed stage. Thus, 

dispersal events for species are dependent on their life history patterns and can vary in distance and 

timing.

At the local level, the project and montane portion of the action areas is in the northern Santa Rita 

Mountains. With the possible exception of the Madera Canyon recreational and residential area to the 

south, the Santa Rita Mountains represent a fairly large, intact block of montane habitat for native 

species. The only paved roads within the Coronado National Forest boundary are the Madera Canyon 

and Mount Hopkins access roads. All other roads are smaller dirt or gravel roads that receive only 

moderate use. These smaller roads do not contribute to significant fragmentation within the northern 

Santa Rita Mountains. In support of this contention, it is believed that all large, native mammals that 

historically occurred within the Santa Rita Mountains still occur there, except for species that were 

intentionally extirpated (grizzly bear, gray wolf). Although jaguars were historically persecuted, they 

have been increasing in numbers in southeastern Arizona (albeit in very small numbers, represented 

thus far by dispersing males) since provided protection by the ESA. Currently, there is a presumed 

resident male jaguar in the action area (U.S. Forest Service and SWCA Environmental Consultants 

2013). Thus, this large block of intact montane habitat provides for the life history requirements of 

600 Final Environmental Impact Statement for the Rosemont Copper Project
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resident plants and animals. The northern Santa Rita Mountains, north of Box Canyon Road, are 

completely intact, except for some dirt roads and inholdings associated with mining activity. 

The vegetation community is dominated by native species, with more than 400 plant species 

(according to the botanical surveys by McLaughlin and Van Asdall (n.d. [1977]); however, recently,

Lehmann lovegrass, a nonnative species, has increased in relative abundance.

Within the Santa Rita Mountains there are various avenues for animal movement, depending on the 

species. For the aforementioned jaguar, this species is known to use Madrean montane (grassland and 

woodland) topography at the northern end of its range, so the spine of the mountains north and south 

of Box Canyon Road is both habitat and movement corridor for that species. Other special status 

species that use the upper slopes include green ratsnake and talussnails. Other species may move 

along canyon bottoms and drainages, including Wasp, McCleary, Davidson, Barrel, and Box 

Canyons. Many species of animals use the topographic features of drainages or riparian trees as 

habitat and/or movement corridors. For example, neotropical migratory birds often nest in and move 

among the larger trees associated with xeroriparian habitat (washes) because the edge of washes is the 

zone where trees grow larger and more structurally complex than in upland situations. The utility of 

drainages to movement or gene flow is not limited to animals. For example, Coleman’s coral-root is a 

rare, specialized plant that is associated with drainages, so it is logical that it probably has most gene 

flow capabilities along drainages, more so than adjacent uplands (especially because it reproduces 

vegetatively more often than through flowering and long-range pollen/seed dispersal). 

At the landscape level, the analysis area is part of southeastern Arizona’s “Sky Island” mountains 

(referred to collectively as the “Madrean Archipelago”), and the intervening valleys. The Madrean 

Archipelago is characterized by small, disjunct mountains separated by more arid valleys of desert 

and grassland. The mountain environments are isolated from one another by the valleys, which 

generally act as barriers to gene flow between populations of many montane species (Shepard and 

Burbrink 2008). Montane species that are specialized, have low physiological tolerance, and low 

mobility tend to be isolated from other mountains by the valleys. Examples include talussnails, 

montane rodents, and montane rattlesnakes. However, some species are able to cross the valleys 

during migration or dispersal events if they are not so limited. Species that can cross between 

mountain ranges include medium sized to large mammals, foothill species (which tolerate the valleymontane interface), leopard frogs (within moisture constraints, such as rainfall and surface-water 

sources), bats, birds, and some elevation generalists. 

For species that can cross valleys to access adjacent mountains, or are generalized to a variety of 

grassland communities or elevations, identification of the remaining, fairly intact, intermountain 

corridors has received much attention. This is due, in part, to the fact that valleys are targeted for 

development (e.g., roads, agricultural lands, subdivisions, golf courses) more so than the mountains. 

There is also concern that some of the wide-ranging species will be isolated between mountains, 

thereby inhibiting gene flow and recolonization of mountain ranges by currently extirpated species. 

During the development of the 2006 “Arizona’s Wildlife Linkages Assessment” (The Arizona 

Wildlife Linkages Workgroup 2006), the Pima County 2009 “Sonoran Desert Conservation Plan”

(Pima County 2009), and the “2012 Pima County Wildlife Connectivity Assessment: Report on 

Stakeholder Input” (Arizona Game and Fish Department 2012e), numerous intermountain wildlife

movement corridors have been identified as important to the conservation of species and their 

populations. 

When these corridors or linkages were developed, it was assumed that montane (including foothill) 

source and destination habitats (“refugia”) would remain intact because they are largely on public 

Final Environmental Impact Statement for the Rosemont Copper Project 601
Chapter 3. Affected Environment and Environmental Consequences

lands that would not likely be developed. The source and destination habitats are the large blocks of 

intact montane lands, including the Santa Rita Mountains. Figure 76 clearly shows that these linkages 

are mostly intermountain, connecting the Santa Rita Mountains with the Whetstone, Sierrita, Empire, 

Rincon (hence Santa Catalina), and Patagonia Mountains. Not shown in figure 76 are the intramountain corridors mentioned above (e.g., mountain spine, drainages, and “stepping stone” surface 

waters and other specialized habitat features); this is why there are no corridors shown in the Santa 

Rita Mountains themselves.

These animal intermountain and valley-centric movement corridors were modeled to refine the best 

biological corridor for a small subset of species used in the particular analyses. Table 118 contains the 

details of these corridors within the vicinity of the proposed action (i.e., in and adjacent to the 

analysis area), and figure 76 depicts their geographic placement in the analysis area and surrounding 

region.

Table 118. Information regarding intermountain animal movement corridors in and near the 

analysis area

Animal 

Movement 

Corridor Name

Source Connection 

Details

Size and 

Landownership* Focal Species Threats and Barriers

Linkage 94, 

Rincon-Santa 

Rita-Whetstone 

Linkage

Beier (2006a); the 

Arizona Wildlife

Linkages 

Workgroup 

(2006); AGFD

(2012e)

Provides a roughly 

north-south 

linkage between 

the habitat blocks 

in the Rincon 

Mountains, Santa 

Rita Mountains, 

and the Whetstone 

Mountains; 

includes 6 

stands/corridors

85,304 acres total; 

39,108 acres 

(45.8%) in analysis 

area; total area 

includes mostly

State Trust land but 

also private, BLM,

and national forest 

land; 99.5% is 

natural vegetation,

and 0.5% is 

developed land

12 mammals, 9 

reptiles and 

amphibians, 1 

bird, and 2 fish

Existing roads, 

such as 

I-10 and SR 83; 

the Southern 

Pacific Railroad; 

and border 

security/illegal 

immigration issues

Linkage 92, San 

Xavier-SierritaSanta Rita Linkage

The Arizona 

Wildlife Linkages 

Workgroup (2006)

Provides a roughly 

northwestsoutheast wide 

block linkage 

between the San 

Xavier 

Reservation, the 

Sierrita 

Mountains, and 

the Santa Rita 

Mountains. Note 

that this linkage 

has not been 

refined, i.e., 

modeled yet; thus,

the details are not 

as specific as for 

the others.

176,900 acres total; 

6,286 acres (3.5%) 

in analysis area; 

total area includes 

mostly State Trust 

and private land, 

along with some

BLM land. Note that 

this linkage has not 

been refined, i.e., 

modeled, yet; thus,

the details are not as 

specific as for the 

others.

6 mammals, 2 

reptiles and 

amphibians, and 

1 bird

Existing roads, 

such as 

I-19; Central 

Arizona Project 

canal; the 

Southern Pacific 

Railroad; 

urbanization; and 

border 

security/illegal 

immigration issues

602 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Animal 

Movement 

Corridor Name

Source Connection 

Details

Size and 

Landownership* Focal Species Threats and Barriers

Linkage 93, Santa 

Rita-Tumacacori 

Linkage

Beier (2006b); the 

Arizona Wildlife

Linkages 

Workgroup 

(2006); AGFD

(2012e)

Provides a roughly 

east-west linkage 

between the 

habitat blocks in 

the Santa Rita 

Mountains and the 

TumacacoriAtascosa-Pajarito 

Mountain 

Complex; includes 

4 stands/corridors

98,243 acres total; 

2,571 acres (2.6%) 

in analysis area; 

total area includes 

mostly private, with

some State Trust and

BLM land; 98% is 

natural vegetation,

and 2% is developed 

land

11 mammals, 8 

reptiles and 

amphibians, 1 

bird, and 2 fish

Existing roads, 

such as 

I-19; the Southern 

Pacific Railroad; 

urban 

development along 

I-19; and border 

security/illegal 

immigration issues

Linkage 95, Santa 

Rita-Empire 

Complex

The Arizona 

Wildlife Linkages 

Workgroup (2006)

Provides a roughly 

north-south 

linkage between 

the habitat blocks 

in the Santa Rita 

Mountains and the 

Empire 

Mountains; also 

includes east-west 

crossings of SR 83

20,876 acres total; 

12,068 acres 

(57.8%) in analysis 

area; total area 

includes mostly

private land, but also 

national forest,

BLM, and State 

Trust land. Note that 

this linkage has not 

been refined, i.e., 

modeled, yet; thus,

the details are not as 

specific as for the 

others.

9 mammals, 2 

reptiles, 2 bird, 

and 1 fish

Existing roads, 

such as 

SR 83; 

urbanization; and 

border 

security/illegal 

immigration issues

Linkage 96, 

Patagonia–Santa 

Rita Linkage

Beier (2008); the 

Arizona Wildlife

Linkages 

Workgroup 

(2006); AGFD

(2012e)

Provides a roughly 

southeastnorthwest linkage 

between the 

habitat blocks in 

the Santa Rita 

Mountains and the 

Patagonia 

Mountains; 

includes 3 

stands/corridors

25,150 acres total; 0 

acres (0%) in 

analysis area; total 

area includes mostly

private and national 

forest land, and the 

remaining is either 

State Trust or local 

or State parks; 97% 

is natural vegetation,

0.9% is aquatic, and 

0.3% is agricultural 

land

9 mammals, 3 

reptiles and 

amphibians, 6 

birds, and 4 fish

Existing roads, 

such as SRs 82 

and 83; private 

land; expanding 

urban 

development; and 

border 

security/illegal 

immigration issues

Landscape 

Movement Area 

31: Santa Cruz 

River to Santa Rita 

Experimental 

Range

AGFD (2012e) Santa Cruz River 

Riparian

Movement Area –

Santa Rita 

Experimental 

Range/Coronado 

National Forest 

Wildland Block

3,801 acres total; 16 

acres (0.4%) in 

analysis area; State 

Trust and private 

land

None listed. High-density 

residential 

development; 

high-traffic gravel 

road (Old Nogales 

Highway); railroad

Landscape 

Movement Area 

32: Canoa Ranch 

to Santa Rita 

Experimental 

Range

AGFD (2012e) Canoa Ranch –

Santa Rita 

Experimental 

Range/Coronado 

National Forest 

Wildland Block

3,446 acres total; 0 

acres (0%) in 

analysis area; State 

Trust and private 

land

None listed. Low-density 

residential 

development

Final Environmental Impact Statement for the Rosemont Copper Project 603
Chapter 3. Affected Environment and Environmental Consequences

Animal 

Movement 

Corridor Name

Source Connection 

Details

Size and 

Landownership* Focal Species Threats and Barriers

Riparian

Movement Area 

22: Lee Moore 

Wash Flow 

Corridors

AGFD (2012e) Santa Rita 

Experimental 

Range/Coronado 

National Forest 

Wildland Block –

Santa Cruz River 

Riparian Area

35,749 acres total; 

838 acres (2.4%) in 

analysis area; 

University of 

Arizona (Santa Rita 

Experimental 

Range), BLM, State 

Trust, and private 

land

None listed. High-density 

residential 

development; lowdensity residential 

development; 

paved road (I-10 

bypass); power 

line; solar energy 

development

Riparian

Movement Area 

23: Davidson 

Canyon

AGFD (2012e) Extends Linkage 

#94, Rincon-Santa 

Rita-Whetstone 

Linkage Design

4,614 acres total; 

4,560 acres (98.8%) 

in analysis area; 

State Trust and 

private land

Birds 

(migratory); 

Chiricahua 

leopard frog; 

deer (general); 

Gila monster; 

bobcat; 

mountain lion; 

black bear

High-traffic gravel 

road; industrial/

commercial 

development; 

mining 

(gravel/limestone); 

off-highwayvehicle use

Riparian

Movement Area 

24: Madera 

Canyon

AGFD (2012e) Santa Rita 

Experimental 

Range/Coronado 

National Forest 

Wildland Block –

Santa Cruz River 

Riparian

Movement Area

10,231 acres total; 0 

acres (0%) in 

analysis area; 

national forest, 

private, and State 

Trust land

Birds 

(migratory); 

mammals 

(general)

Low-density 

residential 

development

Riparian

Movement Area 

25: Empire 

Gulch/Oak Tree 

Canyon

AGFD (2012e) Santa Rita 

Experimental 

Range/Coronado 

National Forest 

Wildland Block –

Linkage #94, 

Rincon-Santa 

Rita-Whetstone 

Linkage Design

11,000 acres total; 

11,000 acres (100%) 

in analysis area; 

NFS, BLM, State 

Trust, and private 

land

Birds 

(migratory); 

black bear; coati; 

mountain lion; 

mule deer; 

raptors; whitetailed 

Deer

Agriculture 

(grazing); border 

activities; exotic 

species 

(Lehmann’s 

lovegrass); highdensity residential 

development; lowdensity residential 

development; 

mining (proposed 

Rosemont Copper 

Mine); offhighway-vehicle 

use; solar energy 

development; 

wind energy 

development

604 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

Animal 

Movement 

Corridor Name

Source Connection 

Details

Size and 

Landownership* Focal Species Threats and Barriers

Riparian

Movement Area 

26: Gardner 

Canyon

AGFD (2012e) Harcuvar 

Mountains – Black 

Mountains

5,800 acres total; 

1,320 acres (22.8%) 

in analysis area; 

NFS, BLM, private, 

and State Trust land

American 

pronghorn; birds 

(migratory); 

black bear; 

Chiricahua 

leopard frog; 

coati; mule deer; 

raptors; whitetailed deer

Agriculture 

(grazing); border 

activities; exotic 

species 

(Lehmann’s 

lovegrass); highdensity residential 

development; 

high-traffic gravel 

road (Gardner 

Canyon Road); 

low-density 

residential 

development; 

mining; offhighway-vehicle 

use; paved road 

(SR 286); solar 

energy 

development; 

wind energy 

development

Note: See figure 76.

* Acreage calculations were based on the animal movement corridor shapefiles available online and provided by the 

researchers, e.g., AGFD. Then, the animal movement corridors were overlaid with the project and analysis areas and 

calculations were conducted.

Special Status Species

This section identifies 16 special status plant and 37 special status animal species in table 115 that 

have been documented as occurring23 within the project or analysis areas. Of the 16 special status 

plant species, 2 are federally listed, 3 are petitioned for listing (under the ESA), and14 are Forest 

Service and/or BLM sensitive species. Of the 35 special status animal species, 8 are federally listed, 

1 is proposed threatened, 2 are candidates for Federal listing,1 is petitioned for listing, and 28 are 

Forest Service and/or BLM sensitive species. A quantitative analysis using GIS was conducted to 

estimate the acreage of possible habitat for special status species within the analysis area. For each 

species,24 information about habitat needs in terms of vegetation types (Brown 1994; Pima County 

2013), elevation and aspect (U.S. Geological Survey 2013c), water needs (see “Seeps, Springs, and 

Riparian Areas” and “Surface Water Quantity” resource sections of chapter 3), and geology (only 

used for talussnail habitat analysis (Schmalzel and Archer 2010)) (as described in each species’ 

narratives in this section), was used to conduct a quantitative assessment of special status species’

habitat in the analysis area. Estimated possible habitat for special status plant and animal species 

within the analysis area also is included in each species’ narratives. For many species, however, the 

estimated possible habitat may be smaller than estimated because the amount of possible microhabitat 

23 Or their proposed or designated critical habitat occurs in the project or analysis area. 

24 Analyses of habitat for threatened and endangered species protected under the ESA within the analysis area were not 

conducted because the analyses of impacts to these species will be determined through the Section 7 consultation process.

Final Environmental Impact Statement for the Rosemont Copper Project 605

 
Chapter 3. Affected Environment and Environmental Consequences

Figure 76. Wildlife linkages relative to the analysis area (Arizona Game and Fish 

Department 2012e; Beier et al. 2008; Beier et al. 2006a; The Arizona Wildlife 

Linkages Workgroup 2006)

606 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

could encompass a much smaller area (e.g., species that occur on rocky outcrops because this was not 

information that was available for the entire analysis area for use in the GIS analysis).25

Plants

Santa Rita yellowshow (Amoreuxia gonzalezii). This Forest Service sensitive species grows at 

elevations ranging from 4,200 to 4,600 feet above mean sea level, typically on open, full sun on 

south- and southwest-facing slopes of limestone outcrops and fine granitic soil (Arizona Game and 

Fish Department 2011b). This species is known only from northern Mexico and extending north into 

southern Arizona. This species is only known from four populations in northern Mexico (NatureServe 

2011a), three sites within the Santa Rita Mountains, two sites in the Baboquivari Mountains, and two 

sites in the Rincon Mountains in Arizona (Arizona Game and Fish Department 2011b; Southwest 

Environmental Information Network 2011d; U.S. Forest Service 2007e; WestLand Resources Inc. 

2012l). Threats to this species include development, grazing, mining, habitat degradation, rarity, and 

competition with introduced exotic grasses (e.g., buffelgrass, Lehmann’s lovegrass) (Arizona Game 

and Fish Department 2011b). The USFWS published a partial 90-day finding that determined there 

was enough information on this species to warrant a 12-month status review (U.S. Fish and Wildlife 

Service 2009). However, after review of the best scientific and commercial information available, the 

USFWS found that listing this species is not warranted at this time (U.S. Fish and Wildlife Service 

2011b).

The three locations in the Santa Rita Mountains in Santa Cruz County are more than 10 miles 

southwest of the analysis area (Southwest Environmental Information Network 2011d). This species 

was observed in the project area during mid-1970s vegetation surveys by the University of Arizona 

(McLaughlin and Van Asdall n.d. [1977]), and it has been observed in the past near Rosemont 

Junction (Jenkins 2010). A survey targeting this species was recently conducted, and it was not 

recorded within the project area (WestLand Resources Inc. 2011i). GIS analysis indicates that there is 

an estimated 7,215 acres of possible habitat for this species within the analysis area; this includes all 

areas at elevations ranging from 4,200 to 4,600 feet above mean sea level, on south- and southwestfacing slopes.

Arizona giant sedge (Carex ultra). This plant is a Forest Service and BLM sensitive species. 

Arizona giant sedge is an herbaceous perennial that occurs on moist soil near perennially wet springs

and streams in riparian woodland or oak-pinyon woodland at elevations ranging from 2,040 to 6,000 

feet in southeastern Arizona in Pima, Cochise, Pinal, Graham, Santa Cruz, and Yavapai Counties, 

extreme southwest New Mexico (Hidalgo County), and Sonora and Cahila, Mexico (Arizona Game 

and Fish Department 2000b). This plant is listed as sensitive by the Forest Service because it grows in 

saturated soil near perennial seeps, streams, and springs, areas that could be heavily impacted by 

grazing if not properly managed (U.S. Forest Service 2007e), and the small populations of this plant 

that are typically observed are vulnerable to local disturbance of aquatic habitat (Arizona Game and 

Fish Department 2000b).

This plant species was not observed within an approximately 25-square-mile area referred to as the 

Rosemont area during mid-1970s vegetation surveys by the University of Arizona (McLaughlin and 

Van Asdall n.d. [1977]). This plant species was observed, however, in the northern Santa Rita 

25 Although Pima County has conducted a GIS analysis that produced models for several special status species’ habitat as 

part of the “Sonoran Desert Conservation Plan,” for purposes of consistency these GIS models were not used for the 

analyses in this EIS because Pima County has not conducted a GIS analysis for all special status species’ habitat included in 

this EIS.

Final Environmental Impact Statement for the Rosemont Copper Project 607

 
Chapter 3. Affected Environment and Environmental Consequences

Mountains within the analysis area during vegetation surveys in 1986 and 1987 (McLaughlin and 

Bowers 1990). More recently, this species was observed in the project area at Scholefield Spring

during wetland delineations conducted by WestLand Resources Inc. (2010b) and has been 

documented along lower (Arizona Game and Fish Department 2012d) and upper Cienega Creek

(Bureau of Land Management 2012) within the analysis area. Additional surveys of seeps and springs

in 2011 and 2012 near the project area detected this species at nine additional locations within the 

analysis area (WestLand Resources Inc. 2012j). Although a species-specific survey targeting Arizona 

giant sedge was not conducted, the range of the species is within the analysis area, and there are 

several documented occurrences within the analysis area. GIS analysis indicates that there is an 

estimated 1,099 acres of possible habitat for this species within the analysis area; this includes all 

areas at elevations ranging from 2,040 to 6,000 feet above mean sea level and within a 100-foot 

radius of all stock tanks, seeps, springs, and intermittent or perennial stream reaches. 

Pima pineapple cactus (Coryphantha scheeri var. robustispina). Pima pineapple cactus was listed 

as an endangered species on September 23, 1993 (U.S. Fish and Wildlife Service 1993a), without

critical habitat. Residential and commercial developments are the greatest threats to Pima pineapple 

cactus and its habitat; other threats include habitat loss and fragmentation, competition with 

nonnative species, loss of the existing seed bank, grazing, illegal plant collection, prescribed fire, 

mining, and inadequate regulatory mechanisms (U.S. Fish and Wildlife Service 1993a; 2007c; 

2008b). The effects of climate change (i.e., decreased precipitation and water resources) are a threat 

to many species, including the Pima pineapple cactus. 

In general, Pima pineapple cactus is found in vegetation communities characterized as either Sonoran 

desertscrub (Arizona Upland subdivision) or semidesert grassland, or a combination of the two, and it 

is often associated with the following shrub species: desert zinnia (Zinnia sp.), snakeweed 

(Gutierrezia sarothrae), burroweed (Isocoma tenuisecta), and buckwheat (Eriogonum spp.) 

(U.S. Fish and Wildlife Service 2007c). Within its relatively limited range, Pima pineapple cactus 

generally grows on slopes less than 10 percent and along the tops (upland areas) of alluvial bajadas 

within a range of soil types and depths at elevations between 2,360 and 4,000 feet above mean sea 

level (U.S. Fish and Wildlife Service 2007c; 2008b).

Pima pineapple cactus occurs in southeast Arizona and northern Sonora, Mexico (U.S. Fish and 

Wildlife Service 2007c). A recent Pima pineapple cactus population estimate of 100,000 to 150,000 

was submitted to the USFWS as part of the 5-year review effort for the species. In Arizona, Pima 

pineapple cactus is found south of Tucson, in Pima and Santa Cruz Counties, distributed at very low 

densities throughout the Altar and Santa Cruz Valleys between the Baboquivari Mountains to the west 

and the Santa Rita Mountains to the east. This species is not known or expected to occur within the 

project area but is found within the analysis area at lower elevations west of the mine site, where the 

water and transmission lines and utility maintenance road are proposed, and northeast of the Santa 

Rita Mountains and northwest of the Empire Mountains (Arizona Game and Fish Department 2012d). 

Surveys following guidelines provided by USFWS (Roller 1996) were conducted in 2008 and 2009, 

and 58 living Pima pineapple cacti have been found within the utility corridor (WestLand Resources 

Inc. 2009e, 2010d). 

Arid throne fleabane (Erigeron arisolius). In southeastern Arizona, this Forest Service sensitive 

species has been observed in Pima, Cochise, and Santa Cruz Counties and typically occurs on moist,

rocky soils in grassy openings or roadsides within semidesert grasslands and Madrean evergreen 

(oak, encinal) woodlands at elevations ranging from 4,265 to 5,650 feet above mean sea level in 

Arizona and Sonora, Mexico, and possibly southwestern New Mexico (Arizona Game and Fish 

608 Final Environmental Impact Statement for the Rosemont Copper Project
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Department 2001b). It is listed as sensitive by the Southwestern Region of the Forest Service because 

of its infrequent occurrence; it is found at scattered localities in extreme southeastern Arizona and is 

susceptible to loss through grazing since it typically occurs in grassy areas, which are favorite feeding 

sites for livestock (Arizona Game and Fish Department 2001b; U.S. Forest Service 2007e). 

Arid throne fleabane was not documented as part of the flora of the Rosemont area during surveys in 

the 1970s (McLaughlin and Van Asdall n.d. [1977]). There have been seven collections of this species 

in the Santa Rita Mountains, all outside the project area (Arizona Game and Fish Department 2012d; 

Southwest Environmental Information Network 2011a): three records near Empire Gulch and one 

record along SR 83 that are all apparently within the analysis area, one record along Box Canyon 

Road (near the boundary of the analysis area), one record in Gardner Canyon (approximately 0.5 mile 

south of the analysis area), and one near Smith Canyon (approximately 1.5 miles south of the analysis 

area). Although a species-specific survey targeting arid throne fleabane was not conducted, and arid 

throne fleabane was not observed during various surveys of the analysis area by WestLand Resources 

Inc., the range of the species is within the analysis area, and there are specimen records within the 

analysis area. GIS analysis indicates that there is an estimated 81,006 acres of possible habitat for this 

species within the analysis area; this includes all areas at elevations ranging from 4,265 to 5,650 feet 

above mean sea level, within semidesert grassland and Madrean evergreen woodland vegetation

types.

Bartram stonecrop (Graptopetalum bartramii). This Forest Service and BLM sensitive species has 

been petitioned for listing under the ESA (Center for Biological Diversity 2010b). The petition 

presented substantial scientific or commercial information indicating that listing this species may be 

warranted; therefore, a 12-month review of the status of this species was initiated in August 2012 to 

determine whether listing Bartram stonecrop is warranted (U.S. Fish and Wildlife Service 2012c).

This species is only known from 12 small, widely scattered populations in Cochise, Pima, and Santa 

Cruz Counties within the Baboquivari, Dragoon, Chiricahua, Mule, Patagonia, Rincon, Santa Rita, 

and Tumacacori Mountains in Arizona and one location within Chihuahua, Mexico (Arizona Game 

and Fish Department 2001c). Bartram stonecrop occurs in the Madrean evergreen woodland on 

ledges or slopes of steep-walled canyons at elevations ranging from 3,650 to 6,700 feet above mean 

sea level. It typically occurs in cracks within rocky outcrops in shrub live oak/grassland communities 

alongside spikemoss, liverworts, lichens, and ferns on the sides of rugged canyons along arroyos, and 

where there is usually heavy litter cover and shade where moisture drips from rocks. As with many 

plant species in this region, possible threats to this species may include (Center for Biological 

Diversity 2010b; U.S. Fish and Wildlife Service 2012c): mining, livestock grazing, recreation, road 

construction and maintenance, border patrol activities, exotic plant invasion and control, inadequacy 

of existing regulatory mechanisms, small population size, stochastic events, drought, climate change, 

and collection.

Bartram stonecrop was not observed in the Rosemont area during vegetation surveys conducted in the 

mid-1970s by the University of Arizona (McLaughlin and Van Asdall n.d. [1977]). This plant species 

was observed, however, in the northern Santa Rita Mountains within the analysis area during 

vegetation surveys in 1986 and 1987 (McLaughlin and Bowers 1990). This species was not observed 

during a 2010 survey for this species within and immediately surrounding the project area (WestLand 

Resources Inc. 2010a). This species was documented as occurring in two locations within the analysis 

area but outside the project area: one in the Empire Mountains near the Old Sonoita Highway

junction with SR 83, and the other in lower Gardner Canyon (Southwest Environmental Information 

Network 2011c). There have been two additional collections of this species taken in the Santa Rita

Mountains (Southwest Environmental Information Network 2011c): one record at Sweetwater Spring

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(approximately 2 miles southwest of the analysis area), and one record at Madera Canyon 

(approximately 5.5 miles west-southwest of the analysis area). GIS analysis indicates that there is an 

estimated 42,788 acres of possible habitat for this species within the analysis area; this includes all 

areas at elevations ranging from 3,650 to 6,700 feet above mean sea level, within riparian habitats

and Madrean evergreen woodland vegetation types. The area with suitable microhabitat (i.e., rocky 

outcrop), however, is likely much smaller.

Huachuca golden aster (Heterotheca rutteri). This Forest Service and BLM sensitive species occurs 

in level, open grasslands and oak savannas at elevations between 3,560 and 6,500 feet (Arizona Game 

and Fish Department 2001d). Huachuca golden aster is known from only 11 populations scattered 

across 3 counties in Arizona (Cochise, Pima, and Santa Cruz), and from limited areas within Sonora, 

Mexico (Arizona Game and Fish Department 2001d), and in the San Rafael, Empire, San Pedro, and 

Altar Valleys (Arizona Rare Plant Committee n.d. [2000]). Threats are not well documented and the 

species’ limited distribution is not well understood, but this species is likely vulnerable to disturbance 

of grassland habitat (Arizona Game and Fish Department 2001d).

A species-specific survey targeting arid throne fleabane was not conducted, but this species was not 

observed in the Rosemont area during vegetation surveys conducted in the mid-1970s by the 

University of Arizona (McLaughlin and Van Asdall n.d. [1977]) or during various surveys of the 

analysis area by WestLand Resources Inc. However, the range of the species is within the analysis 

area, and there are specimen records within the analysis area (Arizona Game and Fish Department

2012d). GIS analysis indicates that there is an estimated 119,607 acres of possible habitat for this 

species within the analysis area; this includes all areas at elevations ranging from 3,560 to 6,500 feet 

above mean sea level, within semidesert grassland and Madrean evergreen woodland vegetation

types. The area with suitable microhabitat (i.e., open grassy areas), however, is likely much smaller.

Coleman’s coral-root (Hexalectris colemanii). This Forest Service and BLM sensitive species has 

been petitioned for listing under the ESA (Center for Biological Diversity 2010a). Coleman’s coralroot is a xeroriparian obligate that grows along the slopes of intermittent drainages where large oaks 

(Quercus spp.), particularly white oaks (Quercus arizonica),26 and other tree species provide shade or 

dappled sunlight and leaf litter between 4,315 and 5,739 feet above mean sea level (Baker 2003; 

Catling 2004; Coleman 2002:98–101; WestLand Resources Inc. 2012e). This orchid has an obligate 

symbiotic relationship involving trees (presumably oaks) and mycorrhizal fungi. The known 

distribution of Coleman’s coral-root, prior to 2012,was limited to McCleary Canyon and some small 

tributaries; a tributary of Wasp Canyon, Pima County; Sawmill Canyon (this area is variously referred 

to as Sawmill, Cave Creek, and Gardner Canyon because of its proximity to all of these drainages), 

Santa Cruz County; and the west side of Cochise Stronghold in the Dragoon Mountains, Cochise 

County (Baker 2003; Catling 2004; WestLand Resources Inc. 2010b). It has also been reported from 

the Baboquivari Mountains, Pima County (Arizona Game and Fish Department 2004a; Catling 2004), 

but the current status of this population is unknown. Threats to the species include impacts from 

mining, grazing, recreation, border activity, development, collection, disease, predation, inadequacy 

of existing regulatory mechanisms, and other natural or anthropogenic factors (Center for Biological 

Diversity 2010a).

Numerous canyons in the Santa Rita Mountains and across southeastern Arizona were surveyed for 

this species in 2010, for the purposes of this project (WestLand Resources Inc. 2010b). This species 

was observed in or near the project area in Wasp Canyon (a cluster of 4 inflorescences), and 120

26 Hybridization of oak species is common so this also may have included Q. grisea and Q. oblongifolia.

610 Final Environmental Impact Statement for the Rosemont Copper Project

 
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inflorescences were documented in McCleary Canyon. This species was also observed in two other 

locations outside the analysis area: approximately 25 inflorescences were observed in Sawmill 

Canyon in the Santa Rita Mountains (approximately 0.5 to 0.75 mile south of the analysis area), and

approximately 140 inflorescences were observed in West Stronghold Canyon in the Dragoon 

Mountains (approximately 30 miles east of the analysis area). When these same areas were 

resurveyed in 2011 (WestLand Resources Inc. 2012g) the following were observed: six inflorescences 

in upper McCleary Canyon, six inflorescences in Sawmill Canyon, and one inflorescence in West 

Stronghold Canyon. The lower numbers observed in 2011 than 2010 (13 vs. 289) are likely owing to 

drought from December 2010 to March 2011, several coldest days on record in winter 2010/2011, and 

normal variations in inflorescence production. 

Surveys in 2012 at all previously known locations for this species,27 sites where Arizona crested 

coral-root (Hexalectis arizonica) were found in 2010, and in other mountain ranges and canyons 

throughout southeastern Arizona and southwestern New Mexico resulted in (WestLand Resources 

Inc. 2012k): observations of 1 inflorescence in Wasp Canyon, 50 in McCleary Canyon, 23 in Sawmill 

Canyon, 31 in West Stronghold Canyon; the discovery of the species in 2 new mountain ranges 

(Peloncillo and Whetstone Mountains) and in 6 additional canyons (7 inflorescences in Cottonwood 

Creek, 1 inflorescence in Dry, 29 inflorescences in French Joe, 4 inflorescences in Middlemarch, 2 

inflorescences in Miller Spring, and 1 inflorescence in South Fork of Skeleton); and occurrences of 

this species at a higher elevation, 5,739 feet, than previously reported. This species is now known 

from 5 mountain ranges and 10 canyons. 

The surveys by WestLand Resources Inc. (2012k) were the most intensive targeted search for this 

species ever documented. Although there have been 2 additional sky islands and 6 canyons added to 

the known range of the species, the search and occurrence records in this report suggest the species is 

quite rare. The distribution is not known to extend beyond the southern sky islands of southeastern 

Arizona. It is nearly endemic to the Coronado National Forest (south of I-10) and its inholdings 

(10 of 11 known localities (91 percent)). During this search of likely potential habitat, it was only 

found in 6.2 percent of the locations searched (11 of 178), which included all historic localities. The 

number of individual inflorescences found during the surveys totaled 138, and 37 percent of these 

were in the proposed project area. It should be noted that there is probably a bias toward individuals 

known in the Rosemont area because the area has been extensively surveyed. It is reasonable to 

assume it likely occurs in additional populations, but as currently known (i.e., the best available 

science), it is very limited in distribution and occurs in small numbers in a small portion of seemingly 

potential habitat.

GIS analysis indicates that there is an estimated 37,042 acres that includes possible habitat (habitat 

and microhabitat requirements are imprecisely known, as it seems absent from most seemingly likely 

habitat (WestLand Resources Inc. 2012k)) for this species within the analysis area. This includes all 

areas at elevations ranging from 4,315 to 5,739 feet above mean sea level within riparian habitats and 

Madrean evergreen woodland vegetation types. The area with suitable microhabitat (i.e., along the 

slopes of intermittent drainages where large oaks and other tree species provide shade or dappled 

sunlight and leaf litter), however, is likely much smaller.

Huachuca water umbel (Lilaeopsis schaffneriana var. recurva). The Huachuca water umbel was 

listed as an endangered species on January 6, 1997 (U.S. Fish and Wildlife Service 1997a). Critical 

habitat was designated on July 12, 1999 (U.S. Fish and Wildlife Service 1999). Critical habitat for 

27 With the exception of Baboquivari Canyon in the Baboquivari Mountains because it was not accessible.

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Huachuca water umbel includes seven units in Yavapai, Pinal, Graham, and Greenlee Counties in 

Arizona and in Catron, Grant, and Hidalgo Counties, New Mexico (U.S. Fish and Wildlife Service 

1999). There is no designated critical habitat for this species within the analysis area. Habitats for 

Huachuca water umbel are threatened by growing water demands and associated diversions and 

impoundments, livestock grazing (which contributes to the degradation of watersheds resulting in 

destructive flooding), introduction of invasive nonnative plant species, and sand and gravel mining 

(Arizona Game and Fish Department 2003b; U.S. Fish and Wildlife Service 2008a). The effects of 

climate change (i.e., decreased precipitation and water resources and increased evapotranspiration) 

are a threat to many species (Lenart 2007), including the Huachuca water umbel. 

The Huachuca water umbel is an herbaceous, semiaquatic to occasionally fully aquatic, perennial 

plant requiring perennial water, gentle stream gradients, and mild winters; it occurs in cienegas or 

marshy wetlands at elevations ranging from approximately 2,000 to 6,000 feet above mean sea level 

within Sonoran desertscrub, grassland or oak woodland, and conifer forest vegetation communities 

(Arizona Game and Fish Department 2003b; U.S. Fish and Wildlife Service 1999). Plants can be 

found in unshaded or shaded sites in shallow water, saturated soil near seeps, or in springs and 

streams where it grows in submerged sand, mud, and/or silt in water depths ranging from 2 to 16 

inches. 

The currently known range of Huachuca water umbel includes southeastern Arizona in Santa Cruz, 

Cochise, and Pima Counties (Arizona Game and Fish Department 2003b) and adjacent Sonora, 

Mexico (U.S. Fish and Wildlife Service 1999). It has been documented at 28 sites within this range 

(Pima County 2001). Prior to 2001, the only known extant sites in Pima County were at Empire 

Gulch in the Las Cienegas National Conservation Area (Pima County 2001). In 2001, two new

populations were discovered in Pima County: one at the Cienega Creek Natural Preserve and one at 

Bingham Cienega. There are no known occurrences of this species within the project area, and 

although surveys for this species have not been conducted within the analysis area for the purposes of 

the proposed project, habitat for this species may occur at seeps and springs within the project area. 

In addition to the known site at Empire Gulch in the Las Cienegas National Conservation Area, this 

species has been found in other locations within the analysis area from near the confluence of 

Cienega Creek and Davidson Canyon (Pima County 2001) south to the confluence of Cienega Creek 

with Gardner Canyon in Las Cienegas National Conservation Area (Arizona Game and Fish 

Department 2012d). During a wet/dry mapping survey of Cienega Creek, this species was 

documented in 61 locations in the reach from Mattie Canyon downstream to The Narrows (Simms 

and Anderson 2011). The BLM provided comments on the Preliminary Administrative Review Draft 

FEIS to the Coronado and stated that individuals of this species were recently transplanted to 

Cieneguita Wetland in lower Empire Gulch. 

Lemon lily (Lilium parryi). This Forest Service sensitive plant species is the only true lily in Arizona 

(Arizona Rare Plant Committee n.d. [2000]). It is a large, herbaceous perennial that typically occurs 

in mesic, shady canyon bottoms along perennial streams or adjacent hillside springs on sandy, 

saturated, highly organic soils at elevations ranging between 4,840 and 7,800 feet (Arizona Game and 

Fish Department 2001e). It typically occurs in Petran montane conifer forest dominated by ponderosa 

pine (Pinus ponderosa), Douglas-fir (Pseudotsuga menziesii), true firs (Abies spp.), bigtooth maple 

(Acer grandidentatum), and silverleaf oak (Quercus hypoleucoides). This species is currently rare in 

Arizona and is known only from the Chiricahua (East Turkey Creek), Santa Rita (Florida and Madera 

Canyons, and Rosemont Springs), and Huachuca Mountains (six different locations) in Cochise, 

Pima, and Santa Cruz Counties in Arizona; it is also known to occur in four counties in southern 

California south into Mexico. This species is potentially threatened by horticultural collecting, 

612 Final Environmental Impact Statement for the Rosemont Copper Project
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grazing and trampling, browsing, boring insects, forest fires, high-intensity flooding and downcutting, 

water diversions, and anything else that potentially dewaters perennial streams, such as mining.

A species-specific survey targeting lemon lily was not conducted, but this species was not observed in 

the Rosemont area during vegetation surveys conducted in the mid-1970s by the University of 

Arizona (McLaughlin and Van Asdall n.d. [1977]) or during various surveys of the analysis area by 

WestLand Resources Inc. The range of the species is within the analysis area, however, and this 

species historically occurred at Rosemont Springs before being extirpated, apparently as a result of 

mining activity there in the early 1900s (Arizona Game and Fish Department 2001e). GIS analysis 

indicates that there is an estimated 119 acres of possible habitat for this species within the analysis 

area; this includes all areas at elevations ranging from 4,840 to 7,800 feet above mean sea level and 

within a 100-foot radius of all stock tanks, seeps, springs, and intermittent or perennial stream

reaches.

Arizona manihot (Manihot davisiae). This plant is a Forest Service sensitive species. In Arizona, 

this extremely rare perennial herb typically occurs in grassy, herbaceous open areas on south-facing 

limestone slopes at elevations ranging from 3,500 to 4,785 feet above mean sea level in the 

Baboquivari, Santa Catalina, and Santa Rita Mountains (Arizona Rare Plant Committee n.d. [2000]). 

Only 11 specimens of Arizona manihot have been collected in the United States, and the main threat 

to the species is grazing (U.S. Forest Service 2007e). 

Arizona manihot was not observed within an approximately 25-square-mile area referred to as the 

Rosemont area during mid-1970s vegetation surveys by the University of Arizona (McLaughlin and 

Van Asdall n.d. [1977]). There have been two collections of this species taken in the Santa Rita 

Mountains outside the analysis area (Southwest Environmental Information Network 2011b): one 

south of Agua Caliente Canyon (approximately 10 miles southwest of the analysis area), and one in 

Florida Canyon (approximately 3.5 miles west of the analysis area). A 2011 survey resulted in the 

discovery a small population of this species near lower McCleary Canyon within the project area 

(at approximately 4,785 feet above mean sea level, nearly 800 feet higher than the previously known 

range), and two small populations were found at another location in the Santa Rita Mountains 

approximately 10 to 11 miles southwest of the analysis area (WestLand Resources Inc. 2011i, 2012l). 

Additionally, two individuals were found in separate locations in the Rincon Mountains, a mountain 

range from which it had not been known to occur. GIS analysis indicates that there is an estimated 

31,313 acres of possible habitat for this species within the analysis area; this includes all areas at 

elevations ranging from 3,500 to 4,785 feet above mean sea level, within semidesert grassland and 

Madrean evergreen woodland vegetation communities on south-facing slopes (i.e., aspects from east 

to west). The area with suitable microhabitat (i.e., grassy, herbaceous open areas on limestone 

slopes), however, is likely much smaller.

Sycamore Canyon (Weeping) muhly (Muhlenbergia elongata [=M. xerophila]). This plant is a 

Forest Service sensitive species. Weeping (or Sycamore Canyon) muhly is a perennial herbaceous 

grass that typically occurs in pockets of soil in crevices of cliffs, rocks, and bedrock in seeps and in 

wet soil adjacent to bedrock streambeds within riparian communities of Madrean evergreen woodland 

and the transition zone between the Arizona Upland subdivision of Sonoran desertscrub and 

semidesert grassland at elevations ranging between 3,250 and 6,000 feet (Arizona Game and Fish 

Department 2000c; U.S. Forest Service 2007e). This species is only known from southern Arizona in

the Santa Rita, Santa Catalina, Rincon, Tumacacori, and Baboquivari Mountains in Pima County; and 

Sycamore Canyon of the Pajarito Mountains in Santa Cruz County (Arizona Game and Fish 

Department 2000c). This plant is listed as sensitive by the Forest Service because it is rare, having 

Final Environmental Impact Statement for the Rosemont Copper Project 613
Chapter 3. Affected Environment and Environmental Consequences

been collected at only 10 different localities in Arizona, and it is palatable to ungulates that graze in 

canyon bottoms (Arizona Game and Fish Department 2000c; U.S. Forest Service 2007e). 

This species was not observed in the Rosemont area during vegetation surveys conducted in the mid1970s by the University of Arizona (McLaughlin and Van Asdall n.d. [1977]). This plant species was 

observed, however, in the northern Santa Rita Mountains within the analysis area during vegetation 

surveys in 1986 and 1987 (McLaughlin and Bowers 1990). This species has been documented as 

occurring at one location in Box Canyon, either within or within approximately 3 miles to the west of 

the analysis area (Arizona Game and Fish Department 2012d; Southwest Environmental Information 

Network 2011f). Although species-specific surveys targeting weeping muhly were not conducted, the 

range of the species is within the analysis area, and there is one specimen recorded either within or 

near the analysis area. GIS analysis indicates that there is an estimated 21,949 acres of possible 

habitat for this species within the analysis area; this includes all areas at elevations ranging from 

3,250 to 6,000 feet above mean sea level within riparian habitats. The area with suitable microhabitat 

(i.e., pockets of soil in crevices of cliffs, rocks, and bedrock in seeps and in wet soil), however, is 

likely much smaller.

Southwestern (Box Canyon) muhly (Muhlenbergia palmeri [=M. dubioides]). This Forest Service

sensitive species is rare, having been collected at only seven different localities in Arizona, and it is 

palatable to ungulates (U.S. Forest Service 2007e). Known threats to this species are grazing and 

associated erosion and scouring (Arizona Game and Fish Department 2000c). Box Canyon muhly is 

known only from southeastern Arizona and Sonora, Mexico. In Arizona, this species is known from 

the Huachuca Mountains and Canelo Hills in Cochise County; the Santa Rita, Santa Catalina, and 

Baboquivari Mountains in Pima County; and Sycamore Canyon of the Pajarito Mountains in Santa 

Cruz County (Arizona Game and Fish Department 2000c). This plant grows on rocky slopes in 

canyons and along stream courses, often on cliffs, at elevations ranging from 2,750 to 6,000 feet

above mean sea level. 

This species was not observed in the project area during mid-1970s vegetation surveys by the 

University of Arizona (McLaughlin and Van Asdall n.d. [1977]). This plant species was observed, 

however, in the northern Santa Rita Mountains within the analysis area during vegetation surveys in 

1986 and 1987 (McLaughlin and Bowers 1990). It was not observed during surveys in 2010 and 2011 

targeting this species within the project area (WestLand Resources Inc. 2010a; 2012l). This species 

has been collected in numerous locations within or adjacent to the analysis area (Arizona Game and 

Fish Department 2012d; Southwest Environmental Information Network 2011f, 2013a, 2013c): six 

locations in or near Box Canyon (within the analysis area) and two locations along Box Canyon Road

(approximately 0.25 mile west of the analysis area). Although species-specific surveys targeting 

southwestern muhly were not conducted, the range of the species is within the analysis area, and there 

are specimen records within the analysis area. GIS analysis indicates that there is an estimated 22,110

acres of possible habitat for this species within the analysis area; this includes all areas at elevations 

ranging from 2,750 to 6,000 feet above mean sea level, within riparian habitats. The area with 

suitable microhabitat (i.e., rocky slopes in canyons or on cliffs), however, is likely much smaller.

Beardless chinchweed (Pectis imberbis). This Forest Service sensitive species has been petitioned 

for listing under the ESA (Center for Biological Diversity 2010b). The petition presented substantial 

scientific or commercial information indicating that listing this species may be warranted; therefore, 

a 12-month review of the status of this species was initiated in August 2012 to determine whether 

listing beardless chinchweed is warranted (U.S. Fish and Wildlife Service 2012c). This plant species

is only currently known from 13 small, scattered populations in southern Arizona in Cochise, Pima, 

614 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

and Santa Cruz Counties within the Atascosa, Huachuca, Patagonia, and Santa Rita Mountains and 

Canelo Hills and in western Chihuahua and eastern Sonora, Mexico (Arizona Game and Fish 

Department 2003c). Beardless chinchweed occurs in open grassland and oak-grassland habitat on 

south-facing slopes at elevations typically ranging from 3,600 to 6,475 feet above mean sea level 

rangewide: from 4,000 to 5,500 feet above mean sea level in Arizona and from 2,951 to 4,492 feet 

above mean sea level in Mexico. It may also occur on road cuts, arroyo cuts, and unstable rocky 

slopes, where there is little competition for sunlight (U.S. Fish and Wildlife Service 2012a). The main 

known threats to this species are grazing and road maintenance (Arizona Game and Fish Department 

2003c).

This species was not observed in the Rosemont area during vegetation surveys conducted in the mid1970s by the University of Arizona (McLaughlin and Van Asdall n.d. [1977]). In 1988, this species 

was documented in the analysis area in Sycamore Canyon (south of the project area) (Arizona Game 

and Fish Department 2012d). Surveys targeting this species were conducted within the major 

drainages in the project area in 2010 and 2011, and nine individuals of this species were observed in 

upper McCleary Canyon within the corridor of the proposed utility maintenance road for all action 

alternatives over Lopez Pass(WestLand Resources Inc. 2010a, 2012l); no additional individuals were 

observed in the 2011 survey. The actual number of plants present is not known because this species 

produces ramets from underground rhizomes. GIS analysis indicates that there is an estimated 38,097

acres of possible habitat for this species within the analysis area; this includes all areas at elevations 

ranging from 3,600 to 6,475 feet above mean sea level, within semidesert grassland and Madrean 

evergreen woodland vegetation types and on south-facing slopes (i.e., aspects from southwest to 

southeast). The area with suitable microhabitat (i.e., areas where there is little competition for 

sunlight), however, is likely much smaller.

Chiricahua mountain brookweed (Samolus vagans). This Forest Service sensitive species is 

typically found in moist, sandy soil around springs, seeps, moist-wet meadows, and in and along 

streams at elevations ranging between 4,000 and 7,200 feet (U.S. Forest Service 2007e). This plant is 

listed as sensitive by the Forest Service because of its limited distribution and habitat, which is 

threatened by any activity that might dry up or degrade wetlands, including water diversions, 

recreation, scouring or flooding events, and grazing. Chiricahua Mountain brookweed is known only 

from Cochise, Pima, and Santa Cruz Counties in Arizona. Although this plant is most abundant in the 

Huachuca Mountains, the Chiricahua Mountain brookweed occurs in other mountain ranges in

Cochise, Pima, and Santa Cruz Counties; it also occurs in northern Mexico. 

This species was not observed in the Rosemont area during vegetation surveys conducted in the mid1970s by the University of Arizona (McLaughlin and Van Asdall n.d. [1977]). There have been two 

collections of this species taken in the Santa Rita Mountains (Southwest Environmental Information 

Network 2013b): one record from within the analysis area west of the project area and one record 

from Florida Canyon (approximately 2.5 miles west-southwest of the analysis area). Although a 

species-specific survey targeting Chiricahua Mountain brookweed was not conducted, the range of 

the species is within the analysis area, and there is a specimen record within the analysis area. GIS 

analysis indicates that there is an estimated 593 acres of possible habitat for this species within the 

analysis area; this includes all areas at elevations ranging from 4,000 to 7,200 feet above mean sea 

level and within a 100-foot radius of all stock tanks, seeps, springs, and intermittent or perennial 

stream reaches. 

Lemmon’s stevia (Stevia lemmonnii). This Forest Service sensitive species is a low, erect perennial 

shrub typically grows on rocky canyon slopes, ravines, and streambeds in oak and pine-oak 

Final Environmental Impact Statement for the Rosemont Copper Project 615
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woodlands at elevations between approximately 3,000 and 4,900 feet (Arizona Game and Fish 

Department 2004c). Lemmon’s stevia is known only from Pima and Santa Cruz Counties in Arizona 

and from Sonora to Durango, Mexico. The threats to this species are not well documented but this 

species is likely threatened by anything that causes groundwater drawdown or surface water

reduction, as well as by recreation and grazing. 

This species was not observed in the Rosemont area during vegetation surveys conducted in the mid1970s by the University of Arizona (McLaughlin and Van Asdall n.d. [1977]). This plant species was 

observed, however, in the northern Santa Rita Mountains within the analysis area during vegetation 

surveys in 1986 and 1987 (McLaughlin and Bowers 1990). There have been three collections of this 

species taken in the Santa Rita Mountains, according to SEINet: one record from lower Box Canyon 

within 1 mile west of the analysis area and two historic records (1906 and 1915) from Rosemont 

(Barrel and Davidson Canyons) within the analysis area. Although a species-specific survey targeting 

Lemmon’s stevia was not conducted, the range of the species is within the analysis area, and there are 

specimen records within the analysis area. GIS analysis indicates that there is an estimated 721 acres 

of possible habitat for this species within the analysis area; this includes all areas at elevations 

ranging from 3,000 to 4,900 feet above mean sea level, within riparian habitats within Madrean 

evergreen woodland vegetation community. The area with suitable microhabitat (i.e., rocky canyon 

slopes), however, is likely much smaller.

Sonoran noseburn (Tragia laciniata). This Forest Service sensitive species typically occurs on 

rocky, granitic soils in open woodlands along streams and canyon bottoms and on shaded hillsides in 

oak and mixed-conifer woodland at elevations ranging from 3,500 to 5,680 feet; it may also grow on 

limestone soils and coarse sand (Arizona Game and Fish Department 2004d; U.S. Forest Service

2007e). Sonoran noseburn has limited occurrence and grows at scattered locations that are subject to 

numerous threats, including grazing, mining, road building, and recreation (U.S. Forest Service 

2007e). This species is known from the Huachuca Mountains in Cochise County; the Santa Rita 

Mountains in Pima County; and the Canelo Hills (O’Donnell Canyon) and Atascosa (Sycamore 

Canyon), Pajarito, Patagonia, and Santa Rita Mountains in Santa Cruz County in southeastern 

Arizona (Arizona Game and Fish Department 2004d). It also occurs in eastern Sonora to Chihuahua, 

Mexico, and perhaps into New Mexico. 

This species was not observed in the project area during vegetation surveys conducted in the mid1970s by the University of Arizona (McLaughlin and Van Asdall n.d. [1977]). This plant species was 

observed, however, in the northern Santa Rita Mountains within the analysis area during vegetation 

surveys in 1986 and 1987 (McLaughlin and Bowers 1990). There have been two collections of this 

species in oak woodland within the analysis area: one from near upper McCleary Canyon and one 

from Gardner Canyon near Cienega Creek (Southwest Environmental Information Network 2011e), 

and another in 1986 in Scholefield Canyon (Arizona Game and Fish Department 2012d). There have 

been two additional collections of this species in the Santa Rita Mountains outside the analysis area 

within Big Casa Blanca Canyon (approximately 10 miles south of the analysis area) (Southwest 

Environmental Information Network 2011e). Although a species-specific survey targeting Sonoran 

noseburn was not conducted, the range of the species is within the analysis area, and there are 

specimen records within the analysis area. GIS analysis indicates that there is an estimated 20,888

acres of possible habitat for this species within the analysis area; this includes all areas at elevations 

ranging from 3,500 to 5,680 feet above mean sea level, within riparian habitats. The area with 

suitable microhabitat (i.e., in canyon bottoms or on shaded hillsides), however, is likely much smaller.

616 Final Environmental Impact Statement for the Rosemont Copper Project
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Amphibians

Chiricahua leopard frog (Lithobates chiricahuensis). The Chiricahua leopard frog was listed as a 

threatened species on June 13, 2002 (U.S. Fish and Wildlife Service 2002a), without critical habitat. 

On March 20, 2012, the USFWS designated critical habitat for the Chiricahua leopard frog (U.S. Fish 

and Wildlife Service 2012f). The designated critical habitat totals approximately 11,467 acres in 

Apache, Cochise, Gila, Graham, Greenlee, Pima, Santa Cruz, and Yavapai Counties, Arizona; and 

Catron, Hidalgo, Grant, Sierra, and Socorro Counties, New Mexico. Designated critical habitat is 

present in the analysis area: two critical habitat map units (Unit 8, Eastern Slope of the Santa Rita 

Mountains, and Unit 9, Las Cienegas National Conservation Area) occur entirely within the analysis

area. Unit 8 consists of five tanks, and approximately 186 acres, 5.22 drainage miles, and 1,311 feet 

overland. Unit 9 consists of approximately 1,550 acres and 6.24 drainage miles.

Primary constituent elements identified as essential to the conservation of the Chiricahua leopard frog

in areas occupied at the time of listing of designated critical habitat are as follows (U.S. Fish and 

Wildlife Service 2012f: 16343): (1) aquatic breeding habitat and immediately adjacent uplands with:

(a) standing bodies of fresh water; (b) emergent and/or submerged vegetation, root masses, undercut 

banks, fractured rock substrates, or some combination thereof; (c) no or few nonnative predators; 

(d) absence of chytridiomycosis; and (e) upland habitats that provide opportunities for foraging and 

basking that are immediately adjacent to or surrounding breeding aquatic and riparian habitat; and 

(2) dispersal and nonbreeding habitat, consisting of areas with ephemeral (present for only a short 

time), intermittent, or perennial water that are generally not suitable for breeding, and associated 

upland or riparian habitat that provides corridors (overland movement or along wetted drainages) for 

frogs among breeding sites in a metapopulation: (a) that are not more than 1 mile overland, 3 miles 

along ephemeral or intermittent drainages, 5 miles along perennial drainages, or some combination 

thereof, not to exceed 5 miles; (b) in overland and nonwetted corridors, that provide some vegetation 

cover or structural features for shelter, forage, and protection from predators; and in wetted corridors, 

that provide some ephemeral, intermittent, or perennial aquatic habitat; and (c) that are free of 

barriers that block movement by Chiricahua leopard frogs that are 50 acres or more in size; whose

highways that do not include frog fencing and culverts; and that are free of walls, major dams, or 

other structures that physically block movement. With the exception of impoundments, livestock 

tanks, and other constructed waters, critical habitat does not include manmade structures (such as 

buildings, aqueducts, runways, roads, and other paved areas) and the land on which they are located 

that exist within the legal boundaries. All the primary constituent elements are present within the 

analysis area.

A recovery plan for Chiricahua leopard frog was completed in 2007 (U.S. Fish and Wildlife Service

2007b). The analysis area overlaps a portion of Recovery Unit 2 (Santa Rita-Huachuca-Ajos/Bavispe) 

as designated by the “Chiricahua Leopard Frog Recovery Plan,” which includes two management 

areas: the Santa Rita Management Area (number 5) and the Empire Cienega Management Area 

(number 4). The area west of the steep, north-south ridge that includes Gunsight Pass and Weigles 

Butte and continues south to the southwest corner of the analysis area is in the Santa Rita 

Management Area. The remainder of the analysis area is in the Empire Cienega Management Area. 

The most important threats to the Chiricahua leopard frog are predation by nonnative species and 

disease (U.S. Fish and Wildlife Service 2011d). Numerous studies indicate that waters supporting 

introduced vertebrate predators (e.g., American bullfrogs [Lithobates catesbeiana], crayfish

[Orconectes virilis or Procambarus clarkia], and fish in the family Centrarchidae [Micropterus spp., 

Lepomis spp.]) often lack Chiricahua leopard frogs (U.S. Fish and Wildlife Service 2008d). Recent 

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evidence suggests a chytridiomycete skin fungus, Batrachochytrium dendrobatidis (Bd), is 

responsible for global declines of frogs, toads, and salamanders. Other threats to this species include 

mining, including mining related contaminants; drought and associated limited surface water; floods; 

degradation and loss of habitat as a result of water diversions and groundwater pumping and poor 

livestock management; altered fire regimes as a result of fire suppression; urban and agricultural 

development; road construction; and other human activities, including environmental contamination 

(U.S. Fish and Wildlife Service 2008d; 2011d; 2012f). Also considered important is the disruption of 

metapopulation dynamics, resulting from small populations, which increases the chance of inbreeding 

depression, loss of genetic diversity, extirpation, or extinction. The effects of climate change

(i.e., decreased precipitation and water resources and increased evapotranspiration) are a threat to 

many species (Lenart 2007), including the Chiricahua leopard frog. 

The Chiricahua leopard frog was historically an inhabitant of a variety of aquatic habitats, including 

cienegas, pools, livestock tanks, lakes, reservoirs, streams, and rivers at elevations of 3,281 to 8,890 

feet (U.S. Fish and Wildlife Service 2007b). This species is now often restricted to springs, livestock 

tanks, ponds, and streams in the upper portions of watersheds where nonnative predators 

(e.g., sportfishes, bullfrogs, crayfish, or barred tiger salamanders [Ambystoma mavortium 

mavortium]) either have not yet invaded or been introduced, or where the numbers of nonnative 

predators are few and habitats are complex, which allow Chiricahua leopard frogs to coexist with 

these species. The life history of the Chiricahua leopard frog is a complex life cycle, consisting of 

eggs and larvae that are entirely aquatic and adults that are primarily aquatic but also may be 

terrestrial at times (U.S. Fish and Wildlife Service 2007b; 2011a). This species has the ability to 

disperse among habitats; this dispersal ability allows the species to colonize habitat from a nearby 

extant population of frogs (U.S. Fish and Wildlife Service 2008d; 2011d). Current evidence suggests 

that dispersal of Chiricahua leopard frogs can be up to 1 mile overland, 3 miles within intermittent 

drainages, and 5 miles within perennial drainages. Dispersal of this species and, thus, fluctuation of 

site occupancy, is largely thought to occur during the summer monsoon. Ranid site occupancy is 

known to fluctuate, particularly at stock tanks and other small aquatic systems where water 

availability changes. 

The Chiricahua leopard frog is found in central and southeastern Arizona; west-central and 

southwestern New Mexico; and in Mexico, in northern Sonora and the Sierra Madre Occidental of 

Chihuahua (U.S. Fish and Wildlife Service 2008d; 2011d; WestLand Resources Inc. 2011a). 

The Chiricahua leopard frog apparently has disappeared from more than 75 percent of its historical 

localities; the species has been extirpated from about 80 to 85 percent of its historical localities in 

Arizona and New Mexico (U.S. Fish and Wildlife Service 2008c, 2008d).

Chiricahua leopard frog surveys within the analysis area were conducted in 2008, 2009, 2010, and 

2011 (WestLand Resources Inc. 2009a, 2009b, 2011a, 2011b). Prior to these surveys, in August and 

September 2006, reconnaissance of 15 sites in the analysis area known to support or suspected of 

supporting surface water was conducted, and no frogs were detected (WestLand Resources Inc. 

2009a). Chiricahua leopard frogs were documented in two locations (Lower Stock Tank and East 

Dam) in the project area in 2008 but have not been detected there since, despite annual surveys.

Chiricahua leopard frogs were documented as occurring in 18 locations within the analysis area, and 

the 3 nearest occurrences of this species to the project area (0.2 to 0.3 mile) occurred in 2008.

Chiricahua leopard frogs have been documented in four locations within the analysis area in areas 

that are fed by groundwater; the remaining documented locations are fed by stormwater flows.

Chiricahua leopard frogs are known to occur in seven locations within the analysis area in designated 

critical habitat: five within Unit 8 and two within Unit 9 (Rorabaugh 2010; Rosen 2010; Rosen and 

618 Final Environmental Impact Statement for the Rosemont Copper Project
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Caldwell 2004; U.S. Fish and Wildlife Service 2012f; WestLand Resources Inc. 2009b). However, 

it should be noted that metapopulations are fluid (i.e., they experience dynamic contractions and 

expansions of occupied sites), so the number of locations is subject to change annually, especially due 

to precipitation variation and survival factors (e.g., Bd outbreaks). In very wet years, if disease and 

predation are not at high levels, frogs can occur in many potential locations, while in dry years and 

during disease outbreaks, the metapopulation is contracted into fewer occupied sites.

During sampling efforts at four locations on the Las Cienegas National Conservation Area between 

2002 and 2010, evidence of this species breeding was documented (i.e., larval individuals were 

noted) only at the Empire Gulch Spring site between 2002 and 2010; however, a few individual 

Chiricahua leopard frogs were noted at each site sometime during the 9-year study (Rosen 2010). 

Most recently, in April 2012, the AGFD conducted Chiricahua leopard frog surveys at 13 sites in the 

Santa Rita management area (within and outside the analysis area); Chiricahua leopard frogs were 

detected at 8 sites and were documented breeding at 3 of those sites (Akins 2012). Six of the eight 

detection sites are within the analysis area, and all sites had been recently documented as having 

Chiricahua leopard frogs, with the exception of one location.

Lowland leopard frog (Lithobates yavapaiensis). This Forest Service sensitive species is generally 

restricted to permanent waters located below elevations of 3,000 feet, within small to medium-sized 

streams, small springs, stock ponds, and occasionally in large rivers; however, populations occur in 

aquatic systems with surrounding desertscrub, semidesert grassland, or evergreen woodland at 

elevations of 800 to up to 5,500 feet (Sredl et al. 1997). Lowland leopard frogs breed in a variety of 

natural and human-made aquatic systems (Scott Jr. and Jennings 1985; Sredl and Saylor 1998). Adult 

lowland leopard frogs feed on arthropods and other invertebrates (Arizona Game and Fish 

Department 2006c). Tadpoles are herbivorous, feeding on algae, organic debris, plant tissue, and 

minute organisms in the water (Arizona Game and Fish Department 2006c; Rorabaugh 2008). 

This species is known from Arizona, California, New Mexico, and Mexico. In Arizona, the lowland 

leopard frog is currently distributed throughout the western, central, and southeastern portions of the 

State, south of the Mogollon Rim, and along the Colorado River near Yuma (Arizona Game and Fish 

Department 2006c). Within Pima County, the lowland leopard frog is currently found in the Tanque 

Verde, Pantano, Rincon, Santa Cruz, and Cienega Creek watersheds. In southeastern Arizona, the 

lowland leopard frog typically occurs in a wide variety of human-made and natural permanent and 

semipermanent aquatic systems in Sonoran desertscrub, semidesert grassland, and oak and oak-pine 

woodland at elevations ranging from 480 to 8,200 feet (Arizona Game and Fish Department 2006c).

The greatest threats to this species are habitat alteration and fragmentation, especially as a result of 

the introduction of nonnative predatory and competitive fishes, crayfishes, and frogs (mainly 

American bullfrogs), damming, draining, diversion of water, Bd, water pollution, and heavy grazing.

Although a species-specific survey targeting lowland leopard frogs was not conducted, this species 

was confirmed along lower Davidson Canyon near its confluence with Cienega Creek in 2008 and 

2009 (WestLand Resources Inc. 2009a; 2011l), along upper Davidson Canyon in 2009, and in lower 

and middle Cienega Creek in 2009 and 2010 (WestLand Resources Inc. 2009b; 2011l) while 

conducting Chiricahua leopard frog surveys. They were also observed in numerous tanks in the lower 

elevations of the analysis area in 2010 and 2011, including Blacktail Tank, located a couple miles 

northeast of the project area (WestLand Resources Inc. 2011l). “Rana pipiens” (= L. yavapaiensis

and/or L. chiricahuensis) was observed in the project area during surveys conducted by Lowe and 

Johnson (n.d. [1977]); it is likely most or all detections in the vicinity of the project area were 

Chiricahua leopard frogs, based on habitat affinities and distributional patterns of extant populations. 

Final Environmental Impact Statement for the Rosemont Copper Project 619
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GIS analysis indicates that there is an estimated 1,097 acres of possible habitat for this species within 

the analysis area; however, within this area, the area of suitable water resources (especially for 

breeding) is much smaller than the upland habitat; this includes all areas at elevations ranging from 

480 to 8,200 feet above mean sea level and within a 100-foot radius of all stock tanks, seeps, springs, 

and intermittent or perennial stream reaches.

Reptiles

Giant spotted whiptail (Aspidoscelis stictogramma). This reptile is a Forest Service and BLM

sensitive species. Until recently, it was considered a subspecies of the canyon spotted whiptail, 

A. burti stictogramma, but was found to be a distinct species (Committee on Standard English and 

Scientific Names 2012; Walker and Cordes 2011), as adopted by Committee on Standard English and 

Scientific Names (2012). The giant spotted whiptail is only known from Cochise, Pima, Graham, 

Pinal, and Santa Cruz Counties in Arizona; Hidalgo County, New Mexico; and Sonora, Mexico. This 

lizard is known to occupy the Santa Rita, Santa Catalina, Rincon, Perilla, Santa Teresa, Whetstone, 

Galiuro, Baboquivari, and Pajarito Mountains (Arizona Game and Fish Department 2001a). This 

species inhabits dense shrubby vegetation and open areas of bunchgrass, often among rocks, 

especially near permanent and intermittent streams in mountain canyons, arroyos, and mesas in arid 

and semiarid regions, entering lowland desert along stream courses, in riparian habitat, at elevations 

(in the United States) ranging from about 2,350 feet to 4,800 feet (Arizona Game and Fish 

Department 2001a; Stebbins 2003). This species feeds primarily on insects and spiders (Arizona 

Game and Fish Department 2001a). The greatest threat to this lizard includes anything that threatens 

meso- and xeroriparian habitat, including desiccation of valley bottoms and changes in vegetation;

hence, it is likely to be threatened by climate change (drought) and possibly competition from the

tiger whiptail, A. tigris (Lazaroff et al. 2006).

The giant spotted whiptail was observed in the Rosemont area during surveys conducted by Lowe 

and Johnson (n.d. [1977]) and was referred to as follows: “Common. Occurs throughout the 

Rosemont area. Tends to be a riparian species at lower elevations in the desert grassland, as well 

as more abundant in rocky canyons throughout the site.” The giant spotted whiptail has been 

documented in Wasp Canyon, Cienega Creek, Davidson Canyon, and Empire Gulch (Arizona Game 

and Fish Department 2012d). This species was observed at two locations in lower Davidson Canyon 

in 2001 and at 36 locations in Las Cienegas National Conservation Area from Cinco Ponds and 

Empire Gulch downstream (Cienega Creek) to The Narrows in 2002 and 2003 (Rosen and Caldwell 

2004). A species-specific survey targeting giant spotted whiptail was not conducted, but it is well 

represented, albeit with a spottily distribution, within the project and analysis area. GIS analysis 

indicates that there is an estimated 18,396 acres of possible habitat for this species within the analysis 

area; this includes all areas at elevations ranging from 2,350 to 4,800 feet above mean sea level and 

within all riparian habitats.

Sonoran desert tortoise (Gopherus morafkai). This reptile is a candidate for listing under the ESA

and is a Forest Service and BLM sensitive species. Until recently, this taxon was considered a distinct 

population segment of the more widespread species “desert tortoise” (Committee on Standard English 

and Scientific Names 2012; Murphy et al. 2011). The Sonoran desert tortoise is found in the Arizona 

Upland and Lower Colorado River subdivisions of the Sonoran Desert, desert grassland, and ecotonal 

areas that consist of Sonoran desertscrub with elements of Mojave desertscrub and juniper woodland, 

interior chaparral, and desert grassland at elevations ranging from 510 to 5,300 feet above mean sea 

level (Arizona Game and Fish Department 2010b; Averill-Murray and Klug 2000). This tortoise eats 

a variety of annual and perennial grasses, forbs, and succulents (Arizona Game and Fish Department 

620 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

2010b). This species is known only from southeastern Arizona and Mexico and is currently known to 

occupy Cochise, Gila, Pima, Santa Cruz, Pinal, Graham, La Paz, Mohave, Maricopa, Yuma, and 

Yavapai Counties within Arizona (Averill-Murray and Klug 2000; Committee on Standard English 

and Scientific Names 2012; NatureServe 2011b).

Sonoran desert tortoises were not observed in the project area during surveys conducted by Lowe and 

Johnson (n.d. [1977]). Surveys have not been conducted for Sonoran desert tortoise within the 

analysis area for the purposes of this project; however, the species has been documented in the 

Empire Mountains west of Cienega Creek and east of Davidson Canyon near Cienega Creek (Arizona 

Game and Fish Department 2012d), and this species may occur in portions of the analysis area, such 

as within the area proposed for utility corridors, because habitat is present and these areas are within 

the known range of the species. GIS analysis indicates that there is an estimated 92,406 acres of 

possible habitat for this species within the analysis area; this includes all areas at elevations ranging 

from 510 to 5,300 feet above mean sea level, within Sonoran desertscrub, semidesert grassland, and

Chihuahuan desertscrub vegetation types. The most suitable habitat for this species, however, is 

largely within the lower elevations of the analysis area to the east and north around Cienega Creek, to 

the north around Davidson Canyon (Arizona Game and Fish Department 2010b), and to the west and 

north of the project area in Sonoran desertscrub.

Green ratsnake (Senticolis triaspis). This reptile is a Forest Service sensitive species. The green 

ratsnake is primarily an inhabitant of Madrean evergreen woodland and the upper reaches of 

adjoining semidesert grassland communities in the Baboquivari, Pajarito, Atascosa, Santa Rita, 

Empire, Patagonia, Chiricahua, Swisshelm, Pedregosa, and Peloncillo Mountains of southeastern 

Arizona and southwestern New Mexico at elevations ranging from about 3,600 to 8,000 feet 

(Brennan and Holycross 2006) and in Chihuahua, Sinaloa, and Sonora, Mexico (Madrean 

Archipelago Biodiversity Assessment 2013). In southeastern Arizona, it is usually associated with 

xeroriparian or hydroriparian habitat, especially in rocky canyons (e.g., Radke and Malcom (2005; 

2009)). This snake feeds on small mammals, lizards, birds, and bats (Brennan 2008). There are no 

major threats known for this species (NatureServe 2011c).

Although this species was not observed in the Rosemont area during surveys conducted by Lowe and 

Johnson (n.d. [1977]), an individual was observed in the project area near the proposed utility 

maintenance road during bat surveys (Buecher and Sidner 2013). It has also been documented as 

inhabiting the analysis area within and between the Santa Rita and Empire Mountains (Arizona Game 

and Fish Department 2012d). No species-specific surveys targeting green ratsnake have been 

conducted in the project area, but this is an uncommon, secretive species for which survey would be 

difficult to conduct. This species is reputedly relatively common in Box Canyon (Jones 2013). GIS 

analysis indicates that there is an estimated 14,939 acres of possible habitat for this species within the 

analysis area; this includes all areas at elevations ranging from 3,600 to 8,000 feet above mean sea 

level, within semidesert grassland and Madrean evergreen woodland vegetation types and all riparian 

habitats. The area with suitable microhabitat (i.e., rocky areas such as the talus slopes in and near the 

ridgetop in the project area and rocky washes such as upper McCleary Canyon), however, is likely 

much smaller. 

Northern Mexican gartersnake (Thamnophis eques megalops). This reptile is a candidate for 

listing under the ESA and is a Forest Service and BLM sensitive species. On July 10, 2013, the 

USFWS proposed to list northern Mexican gartersnake as threatened (U.S. Fish and Wildlife Service

2013e) and concurrently proposed to designate critical habitat (U.S. Fish and Wildlife Service 2013e). 

A portion of the Cienega Creek Subbasin Unit of proposed critical habitat for the northern Mexican 

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Chapter 3. Affected Environment and Environmental Consequences

gartersnake is located within the analysis area. The Cienega Creek Subbasin Unit is located of the 

Santa Rita Mountains, north of the Canelo Hills, and west of the Whetstone Mountains, in Pima and 

Santa Cruz Counties. There is a total of 50,393 acres of proposed critical habitat in this unit that 

contains springs, seeps, streams, stock tanks, and terrestrial space within the Las Cienegas National 

Conservation Area and Cienega Creek Natural Preserve, and there is 7.1 stream miles of Cienega 

Creek (1,113 acres) that occurs outside these landownership areas. These areas are considered to be 

currently occupied by the species. Approximately 22,831 acres (including the 7.1 stream miles of 

Cienega Creek outside Las Cienegas National Conservation Area and Cienega Creek Natural 

Preserve) of proposed critical habitat is located within the analysis area. There is no proposed critical 

habitat for the northern Mexican gartersnake within the project area.

Primary constituent elements (i.e., physical or biological features) essential to the conservation of

northern Mexican gartersnakes in areas occupied at the time of listing have been identified and 

include (U.S. Fish and Wildlife Service 2013e:41555): 

(1) Aquatic or riparian habitat that includes: (a) Perennial or spatially intermittent streams of 

low to moderate gradient that possess appropriate amounts of inchannel pools, off-channel 

pools, or backwater habitat, and that possess a natural, unregulated flow regime that allows 

for periodic flooding or, if flows are modified or regulated, a flow regime that allows for 

adequate river functions, such as flows capable of processing sediment loads; or (b) Lentic 

wetlands such as livestock tanks, springs, and cienegas; and (c) Shoreline habitat with 

adequate organic and inorganic structural complexity to allow for thermoregulation, 

gestation, shelter, protection from predators, and foraging opportunities (e.g., boulders, rocks, 

organic debris such as downed trees or logs, debris jams, small mammal burrows, or leaf 

litter); and (d) Aquatic habitat with characteristics that support a native amphibian prey base, 

such as salinities less than 5 parts per thousand, pH greater than or equal to 5.6, and 

pollutants absent or minimally present at levels that do not affect survival of any age class of 

the northern Mexican gartersnake or the maintenance of prey populations. (2) Adequate 

terrestrial space (600 feet lateral extent to either side of bankfull stage) adjacent to designated 

stream systems with sufficient structural characteristics to support life-history functions such 

as gestation, (extended inactivity). (3) A prey base consisting of viable populations of native 

amphibian and native fish species. (4) An absence of nonnative fish species of the families 

Centrarchidae and Ictaluridae, bullfrogs (Lithobates catesbeianus), and/or crayfish 

(Orconectes virilis, Procambarus clarki, etc.), or occurrence of these nonnative species at 

low enough levels such that recruitment of northern Mexican gartersnakes and maintenance 

of viable native fish or soft-rayed, nonnative fish populations (prey) is still occurring.

The northern Mexican gartersnake is restricted to riparian areas, except when dispersing, conducting 

overland foraging movements, or brumating, and occurs at elevations usually ranging from 3,000 to 

5,000 feet but may occur at elevations ranging from 130 to 8,497 feet (Arizona Game and Fish 

Department 2012g; U.S. Fish and Wildlife Service 2013e). An important component of northern 

Mexican gartersnake habitat is a stable supply of native prey, and general habitat types, including:

(1) source-area wetlands (ponds and cienegas); (2) large, lowland river riparian woodlands and 

forests; and (3) upland streamside gallery forests. This gartersnake forages along the banks of water 

bodies, feeding primarily on native fish and adult and larval native ranid frogs, and may also 

supplement its diet with earthworms and vertebrates, such as lizards, small rodents, salamanders, and 

treefrogs and on nonnative bullfrogs and/or bullfrog tadpoles where they co-occur (U.S. Fish and 

Wildlife Service 2013e). The northern Mexican gartersnake historically occurred in Mexico, New 

622 Final Environmental Impact Statement for the Rosemont Copper Project
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Mexico, and every county in Arizona and now occurs in only eight perennial or intermittent stream

reaches and wetlands in Arizona (Arizona Game and Fish Department 2012g; U.S. Fish and Wildlife 

Service 2013e). Current threats to the northern Mexican gartersnake include destruction and

modification of its habitat, predation from nonnative bullfrogs, and reductions in its native prey base 

(U.S. Fish and Wildlife Service 2008g).

There is no suitable habitat, or known occurrences of this species, within the project area, and surveys 

for this species have not been conducted within the analysis area for the purposes of the proposed 

project. The northern Mexican gartersnake has been documented as occurring in Cienega Creek, 

Davidson Canyon, and the Whetstone and Empire Mountains (Arizona Game and Fish Department

2012d). This species was discovered in Davidson Canyon in 2001 (Rosen and Caldwell 2004), and a

significant survey effort for northern Mexican gartersnakes was conducted at the Las Cienegas 

National Conservation Area (Cienega Creek and Empire Cienega) from 2002 to 2008 (U.S. Fish and 

Wildlife Service 2008g). During the 2002 and 2003 field seasons, 53 northern Mexican gartersnakes 

were observed along upper Cienega Creek (Rosen and Caldwell 2004). Rosen and Caldwell (Rosen 

and Caldwell 2004: 21) considered the species to be ‘‘widely distributed, though perhaps reduced in 

abundance’’ in this area. In 2007, survey efforts were concentrated along approximately 2 miles of 

upper Cienega Creek, and only one juvenile northern Mexican gartersnake was observed (Servoss et 

al. 2007). Fish surveys also were conducted at Las Cienegas National Conservation Area in 2008, and 

no northern Mexican gartersnakes were caught or observed (U.S. Fish and Wildlife Service 2008g).

GIS analysis indicates that there is an estimated 1,045 acres of possible habitat for this species within 

the analysis area; this includes all areas at elevations ranging from 3,000 to 5,000 feet above mean 

sea level and within a 100-foot radius of all stock tanks, seeps, springs, and intermittent or perennial 

stream reaches.

Birds

Arizona grasshopper sparrow (Ammodramus savannarum ammolegus). This Forest Service

sensitive species prefers large expanses of relatively tall grass for nesting, and in Arizona, occupies

grasslands that often include scattered low, woody shrubs like mesquite and mimosa (Corman and 

Wise-Gervais 2005). The Arizona grasshopper sparrow is known only from Arizona and New 

Mexico, and in Arizona, this species occurs in Cochise, Pima, and Santa Cruz Counties at elevations 

between 4,140 and 4,900 feet (Arizona Game and Fish Department 2010a). This bird species has 

been detected in the grasslands of the San Bernardino, Babocomari, San Rafael, and Sulphur Springs

Valleys, extreme upper San Pedro River drainage southeast of Sierra Vista, Sonoita Plains north to the 

upper Cienega Creek drainage, and Buenos Aires National Wildlife Refuge in the Altar Valley

(Corman and Wise-Gervais 2005). Nests are placed on the ground at the base of a grass tuft, forb, or 

shrub. This sparrow is omnivorous: its diet consists of mostly insects in summer and grass and weed 

seeds in winter (Arizona Game and Fish Department 2010a). The primary reasons for grasshopper 

sparrow declines in North America are grassland loss, fragmentation, and degradation. The greatest 

threats to this species are cattle grazing, shrub invasion of grasslands, and development.

Although this species was not observed in the Rosemont area during surveys (using transect methods) 

conducted by Russell et al. (n.d. [1977]), the range of the species is within the analysis area, this 

species was collected near the southeast edge of the analysis area in 1969 (Arizona Game and Fish 

Department 2012d), and there have been recent observations (1982 to 2012) of this species in Box 

Canyon, along Greaterville Road, and on Las Cienegas National Conservation Area in the analysis 

area (eBird 2013g). GIS analysis indicates that there is an estimated 88,626 acres of possible habitat

for this species within the analysis area; this includes all areas at elevations ranging from 4,140 to 

Final Environmental Impact Statement for the Rosemont Copper Project 623
Chapter 3. Affected Environment and Environmental Consequences

4,900 feet above mean sea level, within the semidesert grassland vegetation type. The area with 

suitable microhabitat (i.e., areas with scattered low, woody shrubs), however, is likely much smaller.

Northern gray hawk (Buteo nitida maximus). This Forest Service sensitive species typically occurs 

in strands of Sonoran riparian deciduous forest and woodlands, and to a lesser degree Madrean 

evergreen woodland (Glinski 1998). It is typically observed in riparian woodlands with large trees 

(especially cottonwoods) close to mesquite forests with substantial populations of lizards (especially 

of the Sceloporus genus) and small mammals to prey on (Arizona Game and Fish Department 2000a)

at elevations of 1,950 to 5,000 feet above mean sea level (Corman and Wise-Gervais 2005).

The northern gray hawk occurs in southern Arizona, southern Texas, southern New Mexico, and 

Mexico south through Central America and into South America. This species occurs in Cochise, Gila, 

Graham, Pima, Pinal, and Santa Cruz Counties within Arizona. The greatest threats to this species are 

the alteration or elimination of riparian and mesquite bosque habitat (Arizona Game and Fish 

Department 2000a). 

This species was not observed in the Rosemont area during surveys conducted by Russell et al. 

(n.d. [1977]). Although a species-specific survey targeting northern gray hawks was not conducted, 

the range of the species is within the analysis area, and this species has been observed in the analysis 

area in Box and Gardner Canyons, Empire Gulch, and Cienega Creek (eBird 2013h). GIS analysis 

indicates that there is an estimated 6,940 acres of possible habitat for this species within the analysis 

area; this includes all areas at elevations ranging from 1,950 to 5,000 feet above mean sea level, 

within all hydroriparian habitats.

Common black-hawk (Buteogallus anthracinus). This bird species is a Forest Service sensitive 

species. Habitat for common black-hawks includes perennial systems characterized by mature 

riparian gallery forests, with cottonwoods and willows and/or sycamores dominating the overstory 

(Arizona Game and Fish Department 2005). This species occurs from northern South America and 

Guyana, to Central America, throughout Mexico, to the southwestern United States, including 

Arizona, southwest New Mexico, western Texas, and southern Utah. The breeding range is along 

remote streams draining the Mogollon Rim (central Arizona), the big Sandy and Virgin River 

drainages (northwestern Arizona), and the upper Gila River drainages (eastern Arizona). Recorded 

locations in Arizona have been at elevations from 1,750 to 7,080 feet. The common black-hawk is a 

medium-sized to large hawk that breeds in Arizona from March to October and occasionally stays for 

the winter. This obligate riparian nester (cottonwood and sycamore trees are preferred) preys upon 

crustaceans, amphibians, fish, reptiles, and occasionally mammals and insects. Threats to this species 

include anything that alters or eliminates riparian habitat (e.g., clearing vegetation, water diversion, 

diking and damming, and lowering of the water table by underground pumping); this species is also

vulnerable to disturbance and contamination of riparian prey species. 

Surveys have not been conducted for common black-hawk within the analysis area for the purposes 

of this project, and this species was not observed in the Rosemont area during surveys (using transect 

methods) conducted by Russell et al. (n.d. [1977]); however, in 2012 a breeding pair was documented 

in Mulberry Canyon (in the northeastern portion of the analysis area) in spring, and this species has 

been observed, and is likely nesting, in Box Canyon (eBird 2013e; Jones 2012) and near Cienega 

Creek (eBird 2013e). GIS analysis indicates that there is an estimated 7,331 acres of possible habitat

for this species within the analysis area; this includes all areas at elevations ranging from 1,750 to 

7,080 feet above mean sea level, within hydroriparian habitats.

624 Final Environmental Impact Statement for the Rosemont Copper Project
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Northern beardless-tyrannulet (Camptostoma imberbe). This Forest Service sensitive species

inhabits relatively open riparian woodland and heavily wooded dry washes in southeastern Arizona 

primarily from lowland riparian woodlands with Fremont cottonwood and Goodding’s willow stands

but also at fairly regularly in intermittent foothill drainages and dry washes with stands of tall netleaf 

hackberry at elevations from 1,920 to 4,600 feet (Corman and Wise-Gervais 2005). They were found 

nesting along the San Pedro River and its tributaries, Arivaca Creek, Sonoita Creek, upper Santa Cruz 

River, and in wooded foothill drainages of the Baboquivari, Atascosa, Santa Rita, and Santa Catalina 

Mountains. The northern beardless-tyrannulet occurs in Arizona, New Mexico, Texas, and throughout 

large portions of Mexico and south into Central America. This species occurs in Cochise, Graham, 

Pima, Pinal, and Santa Cruz Counties within Arizona. This flycatcher feeds primarily on insects and 

also may eat berries and seeds (Ehrlich et al. 1988). Threats to this species are not well documented 

but would likely include anything that alters or eliminates (e.g., vegetation removal, changes in 

surface water and groundwater, and climate change) the riparian habitat this species inhabits. 

Although a recent species-specific survey targeting northern beardless-tyrannulets was not conducted, 

habitat is present in the analysis area, the range of the species is within the analysis area, this species 

was observed in lower Barrel Canyon in the Rosemont area during surveys (using transect methods) 

conducted by Russell et al. (n.d. [1977]), and there have been recent observations (1996 to 2012) of 

this species in Box Canyon, on Las Cienegas National Conservation Area, and near Cienega Creek in 

the analysis area (eBird 2013i). GIS analysis indicates that there is an estimated 16,430 acres of 

possible habitat for this species within the analysis area; this includes all areas at elevations ranging 

from 1,920 to 4,600 feet above mean sea level, within riparian habitats.

Western yellow-billed cuckoo (Coccyzus americanus occidentalis). This bird is a candidate for 

listing under the ESA and is a Forest Service and BLM sensitive species. Western yellow-billed 

cuckoo has been found in mature Sonoran riparian deciduous forest, cottonwood-willow series, and 

Sonoran riparian scrub within well-developed mesquite bosques or areas of gallery forest found along 

the flood plains of stream and riverbanks in the southwestern United States at elevations less than 

6,600 feet above mean sea level (Arizona Game and Fish Department 2011c; Corman and WiseGervais 2005). The Western Distinct Population Segment (i.e., the subspecies, which is not always 

recognized as taxonomically valid) nests west of the Rocky Mountains in the United States (in all 

counties in Arizona) south to southern Baja California, Mexico, and winters in South America to 

central Argentina and Uruguay (Arizona Game and Fish Department 2011c). Potential migration 

habitat includes areas of Sonoran riparian deciduous forest, cottonwood-willow series, and Sonoran 

riparian scrub that are less well developed than breeding habitat. In southeastern Arizona, western 

yellow-billed cuckoo typically prefers streamside cottonwood, willow groves, and larger mesquite 

bosques (Arizona Game and Fish Department 2002a, 2011c; Corman and Wise-Gervais 2005). This 

bird feeds primarily on hairy caterpillars but also on bird eggs, frogs, lizards, ants, beetles, wasps, 

flies, berries and fruit (Arizona Game and Fish Department 2011c). The loss, degradation, and 

fragmentation of riparian habitat have been identified as the primary causes of western yellow-billed 

cuckoo declines in the western United States (U.S. Fish and Wildlife Service 2001b). The effects of 

climate change (i.e., decreased precipitation and water resources) are a threat to many species, 

including the western yellow-billed cuckoo.

Surveys for this species have not been conducted within the analysis area for the purposes of the 

proposed project; however, this species was observed within Barrel Canyon in the project area 

during surveys (using transect methods) in 1975, but not 1976, conducted by Davis and Callahan 

(n.d. [1977]:167–194). In 1999, a minimum of three yellow-billed cuckoos were detected calling 

along lower Cienega Creek at the “Davidson Canyon confluence” (Corman 2009). Western yellowFinal Environmental Impact Statement for the Rosemont Copper Project 625
Chapter 3. Affected Environment and Environmental Consequences

billed cuckoos have been observed in Box Canyon in the analysis area every year in the summer 

since 2003 (Sebesta 2012); this species likely breeds here because it has been observed in the 

summer. This species is known to occur in Empire Gulch and throughout upper Cienega Creek 

(Bureau of Land Management 2012; eBird 2013l; Institute for Bird Populations 2006). At least seven 

western yellow-billed cuckoos were documented in upper Cienega Creek (along the reach between 

Road 901A and the confluence with Gardner Canyon) on June 18, 2010 (Bureau of Land 

Management 2012). 

In addition, at least three individuals were documented at Empire Gulch during 2010: individuals

were heard and listed as “probable breeder-song” from June through August, and the species was 

listed as “breeder” for the 2010 year for the Empire Gulch Monitoring Avian Productivity and 

Survivorship station. Individuals were observed in 2011 in June, and individuals were heard and 

listed as “probable breeder-song” from June through August for the station. Additionally, one afterhatch-year individual was caught at the station in July 2011, and western yellow-billed cuckoos were 

listed as “breeder” for the 2011 year for the station. Finally, one male was documented downstream of 

The Narrows on Cienega Creek while at an Arizona Bird Conservation Initiative riparian bird survey 

plot on August 8, 2011. GIS analysis indicates that there is an estimated 22,110 acres of possible 

habitat for this species within the analysis area; this includes all areas at elevations below 6,000 feet 

above mean sea level, within riparian habitats.

Broad-billed hummingbird (Cynanthus latirostris). This Forest Service sensitive species occurs 

most frequently in or near broadleaf riparian woodlands in Arizona, usually in drainages dominated 

by Arizona sycamore or Fremont cottonwood, or in mesquite bosques and heavily wooded washes 

that contain large velvet mesquites and netleaf hackberries, at elevations ranging from 1,700 to 5,800 

feet (Corman and Wise-Gervais 2005). The primary food source of this hummingbird is nectar, 

but it also eats insects and spiders (Ehrlich et al. 1988). The broad-billed hummingbird occurs in 

southeastern Arizona (in Pinal, Cochise, Pima, and Santa Cruz Counties), southwestern New Mexico, 

western Texas, and Mexico. The center of abundance in Arizona is from the western slope of the 

Baboquivari Mountains, east to Patagonia, and north to the foothill drainages of the Santa Catalina 

Mountains. Threats to this species are not well documented but would likely include anything that 

alters or eliminates (e.g., vegetation removal, changes in surface water and groundwater, and climate

change) the riparian habitat this species inhabits.

Surveys targeting hummingbirds have not been conducted within the analysis for the purpose of this 

project. This species was not observed in the Rosemont area during surveys (using transect methods) 

conducted by Russell et al. (n.d. [1977]). Habitat is present in the analysis area, and the range of the 

species is within the analysis area. There have been recent (2002 to 2011) observations of this species 

in the analysis area in Box Canyon and near Cienega Creek (eBird 2013d). GIS analysis indicates that 

there is an estimated 22,109 acres of possible habitat for this species within the analysis area; this 

includes all areas at elevations ranging from 1,700 to 5,800 feet above mean sea level, within riparian 

habitats.

Southwestern willow flycatcher (Empidonax traillii extimus). The southwestern willow flycatcher 

was listed as endangered, without critical habitat, on February 27, 1995 (U.S. Fish and Wildlife 

Service 1995a). Critical habitat was later designated on July 22, 1997 (U.S. Fish and Wildlife Service 

1997b), and the lateral extent of the designation was later clarified (U.S. Fish and Wildlife Service 

1997c). In 2001, the USFWS set aside critical habitat in Arizona, California, and New Mexico, then 

redesignated it on October 19, 2005 (U.S. Fish and Wildlife Service 2005b). A total of 737 river miles 

to the lateral extent of the 100-year flood plain (totaling approximately 120,824 acres) across various 

626 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

counties in southern California, Arizona, New Mexico, southern Nevada, and southern Utah was 

included in the final critical habitat designation (U.S. Fish and Wildlife Service 2005b). A final 

recovery plan was released for the southwestern willow flycatcher, and it identified seven recovery 

units, defined based on large watershed and hydrologic units, within seven states (U.S. Fish and 

Wildlife Service 2002b). Within each recovery unit, management units were delineated based on 

watershed or major drainage boundaries. The analysis area is located within the Gila recovery unit 

and the Santa Cruz management unit. On August 15, 2011, the USFWS proposed to revise designated 

critical habitat for the southwestern willow flycatcher to a total of approximately 2,090 stream miles 

(U.S. Fish and Wildlife Service 2011c), and on January 3, 2013, a total of 1,227 stream miles was 

designated critical habitat for this species. Within the analysis area, an 11.1-mile segment of Cienega 

Creek and two segments of Empire Gulch (an isolated 0.3-mile upper segment of Empire Gulch and a 

second 0.8-mile lower segment of Empire Gulch that connects to Cienega Creek) were designated 

critical habitat (U.S. Fish and Wildlife Service 2013c). Although this area was not known to be 

occupied at the time of listing (1991 to 1994), territories have been detected here (1991 to 2010). 

Primary constituent elements in critical habitat for southwestern willow flycatcher are as follows 

(U.S. Fish and Wildlife Service 2005b; 2011c; 2013c): riparian habitat in a dynamic successional 

riverine environment (for nesting, foraging, migration, dispersal, and shelter) with trees and shrubs 

(e.g., willow species, box elder, tamarisk, Russian olive, cottonwood, etc.); dense riparian vegetation

with thickets of trees and shrubs and with thickets; areas of dense riparian foliage; sites for nesting 

that contain a dense tree and/or shrub canopy; dense patches of riparian forests that are interspersed 

with small openings of open water or marsh, or shorter/sparser vegetation that creates a mosaic that is 

not uniformly dense; and a variety of insect prey populations found within or adjacent to riparian 

flood plains or moist environments.

The current threats and reasons for the decline of the southwestern willow flycatcher are numerous, 

complex, and interrelated and are as follows (in approximate order of their significance) (U.S. Fish 

and Wildlife Service 2002b): habitat loss and modification involving water management and land use

practices (i.e., dams and reservoirs, diversions and groundwater pumping, channelization and bank 

stabilization, phreatophyte control, livestock grazing, recreation, fire, agricultural development, 

urbanization); changes in abundance of other species (i.e., exotic species, including brood parasitism 

by the brown-headed cowbird (Molothrus ater)); vulnerability of small populations and demographic 

and genetic effects; and migration and winter range stresses. The effects of climate change

(i.e., increased mean annual temperature, decreased precipitation, and increased evapotranspiration) 

are a threat to many species (Lenart 2007), including the southwestern willow flycatcher. 

The southwestern willow flycatcher breeds in dense riparian habitats where surface water is present 

or where soil moisture is high enough to maintain the appropriate vegetation characteristics (Sogge et 

al. 2010). These habitats primarily contain willow species (Salix spp.), including coyote willow 

(S. exigua) and Goodding’s willow, but typically also contain boxelder (Acer negundo), tamarisk, 

Russian olive (Elaeagnus angustifolia), live oak (Quercus agrifolia), buttonbush (Cephalanthus sp.), 

cottonwood (Populus spp.), alder (Alnus spp.), blackberry (Rubus ursinus), and stinging nettle 

(Urtica spp.) (Sogge et al. 2010; Sogge et al. 1997). Based on the diversity of plant species and 

complexity of habitat structure, four basic habitat types are described for southwestern willow 

flycatcher: monotypic willow, monotypic exotic, native broadleaf dominated, and mixed native/exotic 

(Sogge et al. 1997). Flycatcher territories and nests are typically in the vicinity of open water, 

cienegas, marshy seeps, or saturated soil, sometimes even in areas where nesting substrates are in 

standing water (Sogge et al. 2010). However, hydrologic conditions at a particular site can vary 

Final Environmental Impact Statement for the Rosemont Copper Project 627
Chapter 3. Affected Environment and Environmental Consequences

considerably in Arizona within and between years, and at some locations, particularly during drier 

years, water or saturated soil is only present early in the breeding season (i.e., May and part of June). 

The breeding range of the southwestern willow flycatcher includes southern California, Arizona, New 

Mexico, southwestern Colorado, western Texas, and extreme southern portions of Nevada and Utah, 

although recent breeding records from western Texas are lacking (Sogge et al. 2010; Unitt 1987).

Records of probable breeding southwestern willow flycatchers in Mexico are restricted to extreme 

northern Baja California and Sonora. All willow flycatcher subspecies winter in the subtropical and 

tropical regions of southern Mexico, Central America, and northern South America, but the 

southwestern willow flycatcher appears to be largely restricted to the center of the winter range in the 

vicinity of Costa Rica. The rangewide population of the southwestern willow flycatcher has been 

estimated to be between 500 and 1,000 pairs (Durst et al. 2008; Unitt 1987). Although population 

numbers have increased since the southwestern willow flycatcher was listed, after nearly a decade of 

intensive surveys, the current numbers barely exceed the upper limit of the 1987 estimate. About 57

percent of the 1,299 territories currently estimated throughout the range of the subspecies are located 

along five major rivers (Gila, Rio Grande, Colorado, Santa Ana, and San Pedro). 

The steepest decline in the population level of E. t. extimus has likely occurred in Arizona (Unitt 

1987). Historical records for Arizona indicate that the former range of the southwestern willow 

flycatcher included portions of all major river systems (Colorado, Salt, Verde, Gila, Santa Cruz, and 

San Pedro) and major tributaries. In 2005, 483 territories were known from 47 sites (English et al. 

2006), and in 2006, there were 351 flycatcher territories known from 39 sites (Graber et al. 2007). 

The distribution of flycatchers throughout the State has changed little; since listing, the majority of 

known territories in Arizona have been at two locations: Roosevelt Lake and the San Pedro/Gila 

River confluence. Consequently, population stability in Arizona is believed to be largely dependent 

on these two large populations, and catastrophic events at either location could greatly change the 

status and long-term survival of the southwestern willow flycatcher.

There is no typical habitat, or known occurrences of this species, within the project area, and surveys 

for this species have not been conducted within the analysis area for the purposes of the proposed 

project. A southwestern willow flycatcher habitat inventory in Las Cienegas National Conservation 

Area in 2000 identified 4 stream miles of habitat and 9.5 miles of potential habitat for the species 

(Bodner and Simms 2008). Between 1993 and 2006, the AGFD conducted southwestern willow 

flycatcher distribution and abundance surveys along five reaches of Cienega Creek (from the 

confluence with Gardner Canyon to Coldwater) (Ellis et al. 2008). The only reach of Cienega Creek 

in which resident southwestern willow flycatchers were documented was the uppermost reach, where 

a pair and nest were located in 2001 (within the proposed critical habitat area). A willow flycatcher 

(Empidonax traillii) was documented at the Empire Gulch Monitoring Avian Productivity and 

Survivorship station in July 2006 (Institute for Bird Populations 2006), and in 2011, willow 

flycatchers were documented at the Empire Gulch Monitoring Avian Productivity and Survivorship

station (Bureau of Land Management 2012). 

Whiskered screech-owl (Megascops trichopsis). This Forest Service sensitive species is closely 

associated with habitats that contain dense stands of Madrean evergreen oaks (Corman and WiseGervais 2005). In general, this owl prefers higher elevations and denser forests and woodlands than 

western screech-owls. Whiskered screech-owls are nonmigratory, with calling beginning in late 

February, and nests are most commonly located in Arizona sycamore trees in many southeastern 

Arizona mountain canyons. This owl’s diet mainly consists of large insects and other arthropods 

(Ehrlich et al. 1988). The whiskered screech-owl occurs in southern Arizona, southern New Mexico, 

628 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

and south through Mexico and into Central America and occurs in Cochise, Pima, and Santa Cruz 

Counties in Arizona. This owl is considered locally common to abundant at elevations ranging 

primarily from 5,000 to 7,600 feet in the Baboquivari Mountains in the west, north to the Santa 

Catalina Mountains, and east to the Chiricahua Mountains. Threats to this species are not well 

documented but are likely similar to the threats to the Mexican spotted owl (i.e., timber harvesting,

catastrophic wildfire, recreation, grazing, mining, development and associated noise, and climate

change). 

This species was not observed in the Rosemont area during surveys (using transect methods) 

conducted by Russell et al. (n.d. [1977]). Although a species-specific survey targeting whiskered 

screech-owls was not conducted, the range of the species is within the analysis area, and there are 

specimen records within the analysis area (eBird 2013k). GIS analysis indicates that there is an 

estimated 19,775 acres of possible habitat for this species within the analysis area; this includes all 

areas at elevations ranging from 5,000 to 7,600 feet above mean sea level, within the Madrean 

evergreen woodland vegetation type and all riparian habitats. The area with suitable microhabitat 

(i.e., dense stands of Madrean evergreen oaks or mountain canyons with sycamore trees), however, 

is likely much smaller.

Varied bunting (Passerina versicolor). This Forest Service sensitive species typically inhabits 

brushy arid slopes, canyon, and dry washes in Arizona, with the majority occurring along drainage 

edges containing mesquite and netleaf hackberry at elevations ranging from 1,350 to 5,100 feet 

(Corman and Wise-Gervais 2005). Nests in Arizona are often constructed in velvet mesquite, desert 

hackberry (Celtis ehrenbergiana), catclaw acacia, and graythorn. This species likely eats mostly 

insects and also seeds (Ehrlich et al. 1988). The varied bunting occurs in southern Arizona, southern 

Texas, southern New Mexico, and south through Mexico and into Central America. This species 

occurs in Cochise, Pima, and Santa Cruz Counties within Arizona and is most abundant on the lower 

slopes of the Santa Rita Mountains, south to Patagonia and Nogales, and west along the Mexican 

border to the slopes of the Baboquivari Mountains. Threats to this species are not well documented

but would likely include anything that alters or eliminates (e.g., vegetation removal, changes in 

surface water and groundwater, and climate change) the riparian habitat this species inhabits.

No recent bird surveys have been conducted within the analysis area for the purpose of this project, 

but this species was observed in the Rosemont area during surveys (using transect methods) 

conducted by Russell et al. (Russell et al. n.d. [1977]). There have been recent (1996 to 2012) 

observations of this species in the analysis area near Box Canyon, Empire Gulch, Davidson Canyon, 

and Cienega Creek (eBird 2013j). GIS analysis indicates that there is an estimated 5,554 acres of 

possible habitat for this species within the analysis area; this includes all areas at elevations ranging 

from 1,350 to 5,100 feet above mean sea level, within xeroriparian habitat.

Abert’s towhee (Pipilo [=Melozone] aberti). This Forest Service sensitive species occurs in 

southeastern California, southern Nevada, southwestern Utah, central Arizona, southwestern New 

Mexico, and northern Sonora, Mexico, and nests at elevations ranging from 80 to 4,900 feet above 

mean sea level (Corman and Wise-Gervais 2005; Pima County 2012f). In Arizona, the towhee can be 

found along rivers, streams, and washes in mesquite bosques and cottonwood-willow associations 

with an understory of dense brushy, shrubs within the Lower Sonoran zone. Abert’s towhees eat 

primarily seeds but also feed on insects (Ehrlich et al. 1988). Threats to this species are not well 

documented but would likely include anything that alters or eliminates (e.g., vegetation removal, 

changes in surface water and groundwater, and climate change) the riparian habitat this species 

inhabits.

Final Environmental Impact Statement for the Rosemont Copper Project 629
Chapter 3. Affected Environment and Environmental Consequences

This species was not detected in the Rosemont area during surveys (using transect methods) 

conducted by Russell et al. (n.d. [1977]). Although recent surveys have not been conducted for 

Abert’s towhee, its range is mapped as occurring within the analysis area (Corman and Wise-Gervais 

2005; National Audubon Society 2012 ), and there have been recent (2003 to 2012) observations of 

this species in the analysis area near Box Canyon, Empire Gulch, and Cienega Creek (eBird 2013a).

GIS analysis indicates that there is an estimated 19,256 acres of possible habitat for this species 

within the analysis area; this includes all areas at elevations ranging from 80 to 4,900 feet above 

mean sea level, within all riparian habitats.

Mexican spotted owl (Strix occidentalis lucida). The Mexican spotted owl was listed as a threatened 

species on March 16, 1993 (U.S. Fish and Wildlife Service 1993b), without critical habitat. 

The Mexican Spotted Owl Recovery Team produced the “Mexican Spotted Owl Recovery Plan” in 

1995 (U.S. Fish and Wildlife Service 1995c) and a “First Revision of the Final Recovery Plan for the 

Mexican Spotted Owl” (U.S. Fish and Wildlife Service 2012g). The USFWS designated critical 

habitat for Mexican spotted owl, effective September 30, 2004 (U.S. Fish and Wildlife Service 2004),

and approximately 8.6 million acres of critical habitat for Mexican spotted owl was designated in 

Arizona, Colorado, New Mexico, and Utah, mostly on Federal lands. Within this area, critical habitat 

is limited to areas that meet the definition of protected and restricted habitat, as described in the 

recovery plan, and includes all known owl sites and all areas within mixed-conifer or pine-oak habitat 

with slopes greater than 40 percent where timber harvest has not occurred in the past 20 years. 

Restricted habitat includes mixed-conifer forest, pine-oak forest, and riparian areas outside protected 

habitat. The proposed project is located within the Basin and Range West Ecological Management 

Unit (as identified in the final recovery plan) (U.S. Fish and Wildlife Service 2012g), and the analysis

area overlaps approximately 430 acres of the far northeast corner of critical habitat Unit BR-W-12 in 

Santa Cruz and Pima Counties (U.S. Fish and Wildlife Service 2004). 

The primary constituent elements for Mexican spotted owl critical habitat were determined from 

studies of their habitat requirements and information provided in the recovery plan (U.S. Fish and 

Wildlife Service 2012g). Since owl habitat can include both canyon and forested areas, primary 

constituent elements were identified in both areas (U.S. Fish and Wildlife Service 2004: 53211).

A summary of the primary constituent elements related to forest structure include a range of tree 

species, including mixed conifer, pine-oak, and riparian forest types, composed of different tree sizes 

reflecting different ages of trees; shade canopy created by the tree branches; and large, dead trees 

(snags). Primary constituent elements related to the maintenance of adequate prey species include 

high volumes of fallen trees and other woody debris; a wide range of tree and plant species, including 

hardwoods; and adequate levels of residual plant cover to maintain fruits and seeds and allow plant 

regeneration. Primary constituent elements related to canyon habitat include one or more of the 

following: presence of water; clumps or stringers of mixed-conifer, pine-oak, pinyon-juniper, and/or 

riparian vegetation; canyon wall containing crevices, ledges, or caves; and high percentage of ground 

litter and woody debris. 

The two primary reasons for the original listing of the Mexican spotted owl in 1993 were historical 

alteration of habitat as the result of timber-management practices and the threat of these practices 

continuing, as evidenced in existing national forest plans; the danger of stand-replacing fire was also 

cited (U.S. Fish and Wildlife Service 1995c). In 1995, the Mexican Spotted Owl Recovery Team 

perceived limited threats overall to spotted owls in the Basin and Range West Recovery Unit as the 

result of human activities but considered the primary threats to spotted owls within this recovery unit

to be catastrophic wildfire, recreation, and grazing. Since the release of the recovery plan, threats to

Mexican spotted owl populations in the United States have transitioned from commercial-based 

630 Final Environmental Impact Statement for the Rosemont Copper Project
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timber harvest to the risk of stand-replacing wildfire (U.S. Fish and Wildlife Service 2012g). Other

potential threats to Mexican spotted owl habitat include domestic and wild ungulate grazing, 

recreation, fuels reduction treatments, resource extraction (e.g., timber, oil, gas, metals, and nonmetals), urban or rural development (U.S. Fish and Wildlife Service 1995c; 2008i) , and associated 

noise (Delaney et al. 1999). The effects of climate change (i.e., decreased precipitation and water 

resources) are a threat to many species (Lenart 2007), including the Mexican spotted owl. 

The Mexican spotted owl occurs in disjunct localities on isolated mountain systems and canyons 

within mature mixed-conifer, pine-oak, and riparian forests (U.S. Fish and Wildlife Service 1995c; 

2004). Mature mixed-conifer forests occupied by Mexican spotted owls are mostly composed of 

Douglas-fir (Psuedotsuga menziesii), white fir (Abies concolor), limber pine (Pinus flexilis), and/or 

blue spruce (Picea pungens); pine-oak forests are mostly composed of ponderosa pine (Pinus

ponderosa) and Gambel oak (Quercus gambelii); and riparian forests are dominated by various 

species of broadleaf deciduous trees and shrubs. This species is usually found in areas with some type 

of water source (i.e., perennial streams, creeks, springs, ephemeral water, small pools from runoff, 

reservoir emissions, etc.). Mexican spotted owls typically select areas providing vertical structure and 

high plant species richness that contain a number of large trees of different types. Nests are typically 

observed in either mixed-conifer or Douglas-fir habitat, and roost and nest trees are typically the 

oldest and largest within stands (Ganey and Balda 1989; Ganey and Balda 1994; Seamans and 

Gutierrez 1995; U.S. Fish and Wildlife Service 2012g). Owl foraging habitat includes a wide variety 

of forest conditions, canyon bottoms, cliff faces, tops of canyon rims, and riparian areas, and this 

species generally uses a wider variety of forest conditions (mixed conifers, pine-oak, ponderosa pine, 

pinyon-juniper) for foraging than for nesting/roosting (U.S. Fish and Wildlife Service 1995c; 2004).

The range of the Mexican spotted owl extends from the southern Rocky Mountains in Colorado and 

the Colorado Plateau in southern Utah southward through Arizona, New Mexico, and far western 

Texas, through the Sierra Madre Occidental and Oriental, to the mountains at the south end of the 

Mexican Plateau (U.S. Fish and Wildlife Service 2008i). Mexican spotted owls are widely but 

patchily distributed in Arizona, being found in all but the arid southwestern portion of the State; 

known from the Colorado Plateau in northern Arizona, the Basin and Range Mountains of the 

southeastern part of the State, and the transition zone between these provinces in central and eastcentral Arizona (Ganey and Balda 1989; U.S. Fish and Wildlife Service 1993b). The largest 

concentration of Mexican spotted owls in Arizona occurs in the central and east-central forests along 

the Mogollon Rim, in the White Mountains, and on the volcanic peaks near Flagstaff. In southern 

Arizona, Mexican spotted owls have been found in the Atascosa (Pajarito), Santa Rita, Santa 

Catalina, Patagonia, Whetstone, Galiuro, Huachuca, Chiricahua, Pinaleño, Superstition, Sierra Ancha, 

Mazatzal, and Bradshaw Mountains. 

The project area does not contain typical Mexican spotted owl habitat of mixed conifers, pine-oak, 

ponderosa pine, and pinyon-juniper required for foraging and nesting/roosting. There are no known 

occurrences of this species within the project area, and surveys for this species have not been 

conducted within the analysis area for the purposes of the proposed project. However, the Coronado 

compiled information on Mexican spotted owl protected activity center locations in the northern 

Santa Rita Mountains, and there are no documented Mexican spotted owl records or protected

activity centers within the analysis area. The closest is the Ramanote Canyon Protected Activity 

Center, which is located approximately 0.7 mile to the west-southwest. 

Final Environmental Impact Statement for the Rosemont Copper Project 631
Chapter 3. Affected Environment and Environmental Consequences

Fishes

Longfin Dace (Agosia chrysogaster). This fish is a Forest Service and BLM sensitive species. 

The longfin dace can range from intermittent, hot, low-desert streams (desertscrub) to clear, cool 

brooks at higher elevations (up to the lower end of conifer woodlands), generally below 4,900 feet, 

but they have been recorded up to 6,700 feet (Arizona Game and Fish Department 2006a). This fish 

tends to occupy relatively small or medium-sized streams with sandy or gravelly bottoms and eddies 

or pools near overhanging banks or other cover. Their diet can be highly variable among populations 

in different areas. They are omnivorous and opportunistic, feeding primarily on detritus during the 

daylight when resources are abundant, but they may also feed on various aquatic invertebrates, 

zooplankton, and algae, depending on availability. The longfin dace occurs in aquatic habitats within 

Arizona, New Mexico, Utah, Nevada, and Mexico and occurs in nearly every county within Arizona 

(NatureServe 2010). The greatest threats to this fish are any activities that alter the flow or quality of 

water, and the presence of invasive species (Arizona Game and Fish Department 2006a). Primary 

threats to this species include human activities that alter the quality or flow of water (e.g., flood 

control, groundwater pumping, and irrigation practices) and nonnative species (e.g., red shiner

(Cyprinella lutrensis), crayfish, etc.).

This species was not observed in the Rosemont area during surveys conducted by Lowe and Johnson 

(n.d. [1977]). There is no habitat, or known occurrences of this species, within the project area, and 

surveys for this species have not been conducted within the analysis area for the purposes of the 

proposed project. The longfin dace has been documented as occurring in the analysis area in Cienega 

Creek and Empire Gulch (Arizona Game and Fish Department 2012d). As part of an ongoing 

program established by the U.S. Bureau of Reclamation, fish monitoring was conducted from 2007 

through 2010 in the analysis area in at two locations in lower Cienega Creek upstream of the 

confluence with Davidson Canyon, and 501 longfin dace were taken in 2007; 591 in 2008; 882 in 

2009; and 635 in 2010 (Kesner and Marsh 2010; Marsh and Kesner 2011). In November 2012, the 

AGFD documented a total of 111 individuals of this species at two locations in lower Cienega Creek

near the confluence with Davidson Canyon (Timmons and Upton 2013). GIS analysis indicates that 

there is an estimated 955 acres of possible habitat for this species within the analysis area; this 

includes all areas at elevations below 4,900 feet above mean sea level and within a 100-foot radius of 

all intermittent or perennial stream reaches (i.e., reaches of Cienega Creek, Empire Gulch, and 

Davidson Canyon). The area with suitable microhabitat (i.e., actual areas of intermittent or perennial 

streams), however, is likely much smaller.

Gila chub (Gila intermedia). The Gila chub was listed as endangered with critical habitat on 

November 2, 2005 (U.S. Fish and Wildlife Service 2005c). Critical habitat for Gila chub includes 

seven river units encompassing approximately 160 miles in Grant County, New Mexico, and Yavapai, 

Gila, Greenlee, Graham, Cochise, Pima, Santa Cruz, and Pinal Counties in Arizona. Critical habitat

for this species occurs along Cienega Creek within the analysis area within the Lower Santa Cruz 

River watershed (Area 5). Approximately 6 miles (475 acres) of this area of critical habitat occurs 

within the analysis area in lower Cienega Creek between I-10 and the confluence with Davidson 

Canyon. Another 11.6 miles (844 acres) of critical habitat occurs within the analysis area in upper 

Cienega Creek and Empire Gulch on BLM lands within the Las Cienegas National Conservation 

Area. 

The primary constituent elements of critical habitat include the following habitat components 

(U.S. Fish and Wildlife Service 2005c): perennial pools, areas of higher velocity between pools, and 

areas of shallow water among plants or eddies; water temperatures for spawning ranging from 62.6 °F

632 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

to 75.2 °F, and seasonally appropriate temperatures for all life stages; water quality with reduced 

levels of contaminants, including excessive levels of sediments, and adequate levels of pH, dissolved 

oxygen, and conductivity; food base consisting of invertebrates and aquatic plants; sufficient cover;

and a healthy, intact riparian vegetation community; habitat devoid of nonnative aquatic species or 

habitat in which detrimental nonnatives are kept at a level that allows Gila chub to continue to 

survive and reproduce; and streams that maintain a natural flow pattern, including periodic flooding. 

Both Cienega Creek and Empire Gulch contain one or more primary constituent elements: perennial

pools, the necessary vegetation that provides cover, and adequate water quality.

The primary threats to Gila chub include predation by, and competition with, nonindigenous 

organisms, including fish in the family Centrarchidae; other fish species, bullfrogs, and crayfish; and 

habitat degradation from surface water diversions and groundwater pumping and withdrawals 

(U.S. Fish and Wildlife Service 2005c). Secondary threats include habitat alteration resulting from 

numerous human-caused factors, such as improperly managed livestock grazing, wildfire, agriculture, 

mining, road building, residential development, and recreation. The effects of climate change

(i.e., decreased precipitation and water resources and increased evapotranspiration) are a threat to 

many species (Lenart 2007), including the Gila chub. 

In Arizona, the Gila chub is normally found at elevations ranging between 2,720 and 5,420 feet above 

mean sea level in the smaller headwater streams, cienegas, and springs or marshes of the Gila River 

Basin; they commonly inhabit pools but can also use a diversity of habitats, including small artificial 

impoundments such as human-made ponds (Arizona Game and Fish Department 2002b; U.S. Fish 

and Wildlife Service 2005c). Adults have typically been collected from deep pools with heavily 

vegetated margins and undercut banks, while juveniles have been collected from riffles, pools, and 

undercut banks of runs. In larger stream systems, they commonly use heavily vegetated backwaters 

for cover and feeding. 

Historically, Gila chub were recorded from numerous rivers, streams, and spring-fed tributaries 

throughout the Gila River Basin in southwestern New Mexico, central and southeastern Arizona, and 

northern Sonora, Mexico (U.S. Fish and Wildlife Service 2008e). Currently, the Gila chub is 

restricted to small, isolated populations scattered throughout its historical range, and it has been 

eliminated from approximately 85 to 90 percent of formerly occupied habitat (U.S. Fish and Wildlife

Service 2005c). Of 47 known populations, 29 are considered occupied and all are considered small, 

isolated, and subject to some form of threat (e.g., nonnative species are present in 27 of the 

populations). Historically, the range of the Gila chub covered more than one-quarter of southeastern 

Arizona. Currently in Arizona, the Gila chub is only found in a few waters in Yavapai, Pima, Santa 

Cruz, Graham, Cochise, Gila, and Greenlee Counties. Establishment of new populations of Gila chub 

has been attempted in six sites in Arizona; five sites remain extant.

There is no habitat, or known occurrences of this species, within the project area, and surveys for this 

species have not been conducted within the analysis area for the purposes of the proposed project. 

Gila chub have been reported in 2002, 2009, and 2010 in lower Cienega Creek (from the Cienega 

Creek Natural Preserve, owned and managed by Pima County) (Marsh and Kesner 2010, 2011; 

Reinthal 2009) and in 1985 to 1995, 2001, 2005, 2007, and 2008 within the Las Cienegas National 

Conservation Area (Ehret and Simms n.d. [2009]; Simms 2009; U.S. Fish and Wildlife Service

2005a, 2005c; Weedman et al. 1996); both of these reaches of Cienega Creek are located within the 

analysis area. AGFD conducted surveys in November 2012 at two locations in lower Cienega Creek

near the confluence with Davidson Canyon; however, no individuals of this species were documented 

(Timmons and Upton 2013).

Final Environmental Impact Statement for the Rosemont Copper Project 633
Chapter 3. Affected Environment and Environmental Consequences

Gila topminnow (Poeciliopsis occidentalis occidentalis). Gila topminnow was listed as endangered 

in 1967 without critical habitat (U.S. Fish and Wildlife Service 1967). A recovery plan for Gila 

topminnow was prepared in 1982 (U.S. Fish and Wildlife Service 1984) and revised in 1998 

(Weedman 1998). No recovery units or management areas were developed as part of the recovery 

plan. The primary threats to Gila topminnow populations are habitat destruction and introduction of 

nonnative species (U.S. Fish and Wildlife Service 1998, 2008j; Weedman 1998). The effects of 

climate change (i.e., decreased precipitation and water resources) are a threat to many species (Lenart 

2007), including the Gila topminnow. 

The habitat requirements of Gila topminnows are broad; although preferring shallow, warm, fairly 

quiet waters, they also are easily acclimated to a much wider range of conditions, including both 

lentic and lotic habitats with moderate currents (U.S. Fish and Wildlife Service 1998; 2008j). Gila 

topminnows formerly occupied headwater springs, vegetated margins, and backwater areas of 

intermittent and perennial streams and rivers (Arizona Game and Fish Department 2001f), appearing 

to prefer shallow warm water in a moderate current with dense aquatic vegetation and algae mats. 

Gila topminnows can withstand water temperatures from near freezing to 90 °F to 100 °F and can live 

in a fairly wide range of water chemistries (e.g., pH, dissolved oxygen, and salinities). Gila 

topminnows are omnivorous, likely using a broad spectrum of foods such as detritus and amphipod 

crustaceans but also feed on aquatic insect larvae, especially mosquitoes, when abundant.

Historically, the Gila topminnow was abundant in the Gila River drainage in New Mexico, Arizona, 

and Mexico and was one of the most common fishes of the Colorado River basin, particularly in the 

Santa Cruz system (Arizona Game and Fish Department 2001f; U.S. Fish and Wildlife Service

2008j). Presently, only 11 of the 15 recent natural Gila topminnow populations are considered extant, 

and only 4 do not contain nonindigenous fish and can, therefore, be considered currently secure from 

nonindigenous fish threats. There have been at least 175 wild sites stocked with Gila topminnow; 

however, topminnows persist at only 18 of these locations, including 1 site that is outside the 

historical range and 4 sites containing nonindigenous fish species. 

In Arizona, the Gila topminnow historically was found in most perennial springs, streams, and 

vegetated margins of rivers in the Gila River drainage in Yavapai, Gila, Pinal, Maricopa, Graham, 

Greenlee, Cochise, Pima, Santa Cruz, and Yuma Counties (Arizona Game and Fish Department

2001f). Currently, disjunct populations are present in 9 to 11 natural locations, 22 to 24 reintroduced 

locations within the Gila River drainage, and 1 location in the Bill Williams River drainage (Yerba 

Mansa). Of these locations, 15 are springs, and the remainder consists of creeks and washes. There is 

no habitat, or known occurrences of this species, within the project area, and surveys for this species 

have not been conducted within the analysis area for the purposes of the proposed project. 

Gila topminnows have been reported from the Las Cienegas National Conservation Area and from the 

Cienega Creek Natural Preserve (lower Cienega Creek) within the analysis area in 1985 to 1995 and 

2005 to 2010 (Arizona Game and Fish Department 2012d; Ehret and Simms n.d. [2009]; Simms 

2009; U.S. Fish and Wildlife Service 2005a; Weedman et al. 1996). Gila topminnows are found in 

more than 8 miles of Cienega Creek, and no nonnative fish are present within this stretch, 

representing the largest natural topminnow habitat known within the species’ entire range (U.S. Fish 

and Wildlife Service 1998). Topminnows within Cienega Creek have experienced statistically 

significant declines since 1989; however, the species has remained present in most of the sampling 

stations from 1989 through 2005 (Bodner et al. 2007). Gila topminnows were reintroduced into 

Empire Gulch in 2001 (U.S. Fish and Wildlife Service 2001a) but are currently rare in this location 

(U.S. Fish and Wildlife Service 2006). In November 2012, AGFD documented a total of 116 

634 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

individuals of this species at two locations in lower Cienega Creek near the confluence with 

Davidson Canyon (Timmons and Upton 2013). Lower Davidson Canyon Creek within the analysis 

area (from the confluence with Cienega Creek up to the location where a head cut forms a barrier to 

upstream movement) may provide additional habitat for this species during high-water events.

Invertebrates

Sonoran talussnail (Sonorella magdalenensis). This species was petitioned for listing under the 

ESA (Center for Biological Diversity 2010c) and is also identified as a covered species in Pima 

County’s “Multi-species Conservation Plan.” In July 2012, the USFWS (2012d) announced that the 

species may warrant Federal protection under the ESA but does not anticipate the full status review 

until after 2016 due to commitments of a legal settlement. This talussnail occurs on rockslides and 

talus slopes (volcanic rock and limestone) at elevations ranging from 2,750 to 6,000 feet above mean 

sea level in Pima County (Roskruge, Tucson, Santa Rita, and Cerro Colorado Mountains and 

Tumamoc Hill) and Santa Cruz County (San Cayetano and Tumacacori Mountains) within Arizona

and as far south as the Sierra Pajaritos in Sonora, Mexico (Arizona Game and Fish Department 2008). 

This snail is probably omnivorous, feeding primarily on plant material and also microorganisms 

associated with live and decaying vegetation. The Sonoran talussnail is threatened by anything that 

destroys or disturbs talus slopes, increases interstitial sedimentation, or changes moisture conditions, 

including hard rock mining and invasive plants (U.S. Fish and Wildlife Service 2012i).

During the mid-1970s ANAMAX studies, Miller (n.d. [1977]) carried out field surveys for land snails

in the general area of the Rosemont deposit, and only six species of mollusks were found in the 

project area, including S. magdalenensis. Miller noted that S. magdalenensis has a relatively limited 

range, but it is relatively common in its range. WestLand Resources Inc. (2009g) analyzed the 

talussnail specimens they collected in 2008 and 2009 in the vicinity of the proposed mine site in order 

to determine which taxon (taxa) is present. They concluded that they likely had collected specimens 

of both S. rosemontensis (=S. walkeri walkeri) and S. magdalenensis. Both types were found, often 

together, on both sides of the ridgeline in rockslides and on talus slopes within the project area, and 

habitat is present within the larger analysis area. There is an estimated 28 acres of possible habitat for 

this species within the analysis area.28

Santa Rita talussnail (Sonorella walkeri walkeri = Rosemont talussnail [S. rosemontensis]).

During initial project planning, a land snail referred to as the Rosemont talussnail (S. rosemontensis) 

was found on both sides of the ridgeline in rock slides and on talus slopes within the project area and 

was believed to be endemic to the vicinity of the project area (i.e., northern Santa Rita Mountains, 

north of Box Canyon). However, a recent examination of shell and reproductive anatomy of snails 

from the Santa Rita Mountains resulted in the conclusion that snails previously referred to as 

S. rosemontensis are synonymous with S. walkeri walkeri (Hoffman et al. 2012) and it was not, 

therefore, a taxonomically valid species. The Santa Rita talussnail, S. w. walkeri, is known from the 

Santa Rita and Atascosa Mountains in Arizona (the entire range within the United States) and Sonora 

(Bequaert and Miller 1973). Sonorella walkeri is not considered to be a Forest Service or BLM

sensitive species, nor is it one of the talussnails listed as a Pima County priority vulnerable species. 

Unlike reports by Miller (n.d. [1977]) and WestLand (2009g), the Hoffman et al. (2012) paper was 

published in a peer-reviewed scientific journal. Further, it was written by landsnail experts and used 

sound, tested science to evaluate the validity of the species. For the purposes of this project, S. 

28 The analysis of habitat for talussnails was based on the acreages of talus slopes delineated for surveys conducted in 2008 

and 2009 (Schmalzel and Archer 2010) but may not accurately represent the actual amount of talussnail habitat within the 

analysis area.

Final Environmental Impact Statement for the Rosemont Copper Project 635

 
Chapter 3. Affected Environment and Environmental Consequences

rosemontensis is considered to be a junior synonym of S. walkeri. After a review of the best available 

scientific information, in March 2013, the USFWS determined that listing the Rosemont talussnail as 

an endangered or threatened species was not warranted, and the species was, therefore, removed from 

the candidate list (U.S. Fish and Wildlife Service 2013a).

Mammals

Northern pygmy mouse (Baiomys taylori ater). This Forest Service sensitive species is the smallest 

rodent in North America (Eshelman and Cameron 1987). This species requires well developed, warm 

grassland habitat with a sufficient riparian component (U.S. Forest Service 2007d), is considered to 

be an indicator of southern arid grasslands, and is typically found in sycamore, cottonwood, and 

rabbitbrush riparian habitats (Biota Information System of New Mexico (BISON-M) 2008d). This 

mouse eats primarily stems and fruits of prickly pear, but it also eats seeds, leaves, and berries of 

other plants and may even prey on insects, snails, and small snakes (Eshelman and Cameron 1987). 

The northern pygmy mouse occurs in Arizona, New Mexico, Texas, Louisiana, and Mexico.

In Arizona, this species has been found in Cochise, Pima, Navajo, and Santa Cruz Counties in the 

plains and desert grassland vegetative community and is thought to be extirpated from Graham 

County (Hoffmeister 1986). This species is considered critically imperiled in Arizona and New 

Mexico because of its highly restricted, localized distribution and sensitivity to degradation of 

grassland habitat (U.S. Forest Service 2007d). 

Although a recent species-specific survey targeting northern pygmy mouse was not conducted, this 

species was observed in the Rosemont area during surveys conducted by Roth (n.d. [1977]), was 

more common than all other species in patches of dense grass and weeds, and was also found in 

dense vegetation along roadsides. GIS analysis indicates that there is an estimated 22,129 acres of 

possible habitat for this species within the analysis area; this includes all elevations within all riparian 

habitats. The area with suitable microhabitat (i.e., well-developed, warm grassland habitat with a 

sufficient riparian component in sycamore, cottonwood, and rabbitbrush riparian habitats), however, 

is likely much smaller.

Ocelot (Leopardus pardalis). The ocelot was listed as an endangered species in the U.S. portion of its 

range on July 21, 1982 (U.S. Fish and Wildlife Service 1982), without critical habitat. Recovery of 

the ocelot was originally addressed in “Listed Cats of Texas and Arizona Recovery Plan” (U.S. Fish 

and Wildlife Service 1990a), and an updated draft recovery plan has since been released (U.S. Fish 

and Wildlife Service 2010b). No recovery units or management areas were developed as part of the 

1990 recovery plan (U.S. Fish and Wildlife Service 1990b), and although the updated draft recovery 

plan identified two management units that cover the entire subspecies Leopardus pardalis sonoriensis

and L. p. albescens (U.S. Fish and Wildlife Service 2010b), it mostly focuses on ocelots and ocelot

habitat in Texas. 

When the ocelot was originally listed in 1982, commercial exploitation and illegal hunting were listed 

as significant threats to the species (U.S. Fish and Wildlife Service 1982). Current threats to the 

species include habitat conversion, fragmentation, and loss: human population growth and 

development continue throughout the ocelot’s range, and habitat has been converted to agriculture, 

rangelands, or urban land uses (U.S. Fish and Wildlife Service 2010b). Connectivity among ocelot

populations or colonization of new habitats is also being compromised by continued highway

construction (also causing increased road mortality) and issues associated with border barrier 

development and patrolling the boundary between the United States and Mexico. Other threats to 

ocelots generally include hunting (legal and illegal) and predator control (U.S. Fish and Wildlife 

Service 2008d). Similar to jaguars, large-scale, open-pit mines likely have the potential to threaten 

636 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

habitat of ocelots in southeastern Arizona (McCain and Childs 2008), and the effects of climate

change (i.e., decreased precipitation and water resources) are a threat to many species (Lenart 2007),

including the ocelot. 

Rangewide, ocelots occur primarily within subtropical thorn forest, thornscrub, and dense, brushy 

thickets at elevations below 8,000 feet above mean sea level or in other dense vegetation (>75 percent

canopy cover) with suitable amounts of prey (i.e., rabbits, rodents, birds, and lizards) in tropical 

rainforest, pine forest, gallery forest, riparian forest, semideciduous forest, and dry tropical forest, to 

savanna, shrublands, and marshlands (U.S. Fish and Wildlife Service 2010b). Ocelots are known to 

use semidesert grassland and Madrean evergreen woodland (present in the analysis area) in Arizona 

and Sonora and Sinaloan thornscrub in Sonora (Brown and López-González 2001; Gutiérrez-García 

et al. 2012; Sky Island Alliance and Sonoran Joint Venture 2011). This species’ diet primarily consists 

of rodents but includes a wide variety of small vertebrates and large invertebrates, such as mammals, 

birds, reptiles, amphibians, fish, and insects (Arizona Game and Fish Department 2010c). Ocelots 

hunt both on the ground and in trees, sometimes even catching birds perched in trees. Male ocelots 

tend to travel more than females, and home ranges for both sexes are significantly larger during 

winter than summer.

Historically, ocelots are believed to have ranged over much of Texas, southeastern Arizona, the west 

and east coasts of Mexico, and Central and South America, with individuals found as far south as 

northern Argentina (U.S. Fish and Wildlife Service 2012h). Currently, individuals are still found in 

southern Texas, Arizona, Mexico, and South and Central America; however, population estimates 

throughout the range of the ocelot are unavailable (U.S. Fish and Wildlife Service 1990b). Ocelot

populations appear to be rebounding in parts of its range, where large forests and sufficient prey are 

available, despite the presence of human development, possibly because of a decrease in hunting 

since the end of the 1980s (U.S. Fish and Wildlife Service 2010b). 

Prior to 2009 (from between 1887 and the 1980s), there were eight records of ocelots occurring in 

Arizona, of which three were confirmed (Brown and López-González 2001; U.S. Fish and Wildlife 

Service 2010b). Of these three records, two occurred in Cochise County (west side of Dragoon 

Mountains in 1927 and Pat Scott Peak in the Huachuca Mountains in 1964), and one occurred in 

Camp Verde in Yavapai County in 1932. There were no confirmed accounts of ocelots in Arizona 

between 1964 and 2009, but the number of sightings of this species in Arizona has been on the rise 

since 2009. Six confirmed reports of ocelots have been received in Arizona since 2009 (Arizona 

Game and Fish Department 2010c, 2011d, 2011e, 2012f; U.S. Fish and Wildlife Service et al. 2012):

one from Gila County (in April 2010, an ocelot was found dead along SR 60 between Superior and 

Globe) and five from Cochise County (photographs in November 2009, February and May 2011, and 

fall 2012 in the Huachuca Mountains, and February 2012). Based on spot-pattern recognition from 

photographs, there are at least two individual ocelots that have recently been photographed in 

Huachuca Mountains (U.S. Fish and Wildlife Service 2012h, 2013f). Although there are no 

documented occurrences of ocelots breeding in Arizona, images of a mother ocelot and her kitten 

traveling together along a remote canyon in El Aribabi (on a privately owned ranch in northern 

Sonora, located just 30 miles south of the international border) were recently released (Sky Island 

Alliance and Sonoran Joint Venture 2011).

There are no confirmed recent sightings of ocelot in the Santa Rita Mountains, and there are no recent 

or historic unconfirmed or confirmed records of ocelots in the analysis area. However, surveys for 

this species have not been conducted within the analysis area for the purposes of the proposed 

project, and without surveys, there is no evidence that ocelots do or do not occur in the analysis area. 

Final Environmental Impact Statement for the Rosemont Copper Project 637
Chapter 3. Affected Environment and Environmental Consequences

Although a species-specific survey targeting ocelots was not conducted, habitat is present in the 

analysis area, and the analysis area is within the historic range of the species. The project and analysis

areas are located near biologically best corridors for the jaguar (and hence likely the ocelot, due to 

their similar habitat requirements and historical and current ranges) and at the apex of two wildlife

linkages (strands 5 and 6) that connect the Santa Rita and Whetstone Mountains, near the south end 

of a wildlife linkage (strand 1) that connects the Santa Rita and Rincon Mountains (Beier et al. 

2006a), and near the west end of a wildlife linkage (strand B) that connects the Santa Rita and 

Patagonia Mountains (Beier et al. 2008).

Lesser long-nosed bat (Leptonycteris curasoae yerbabuenae). The lesser long-nosed bat was listed 

as endangered in 1988 without critical habitat (U.S. Fish and Wildlife Service 1988). A recovery plan 

was completed in 1997 (U.S. Fish and Wildlife Service 1997e). No recovery units or management 

areas were developed as part of the 1997 recovery plan; however, the plan states that the lesser longnosed bat will be considered for downlisting to threatened once three major maternity roosts and two 

postmaternity roosts in the United States and three maternity roosts in Mexico have remained stable 

or increased in size for at least 5 years, following the approval of the recovery team. Following a 

5-year review of the status of lesser long-nosed bat, the USFWS determined that while lesser longnosed bat populations do not currently meet the definition of “endangered,” the protection afforded 

by the ESA is warranted because of the continued vulnerabilities of key roost sites (U.S. Fish and 

Wildlife Service 2007a). The USFWS recently (September 9, 2013) proposed to downlist the species 

to “threatened” based on the analysis and recommendations contained in the aforementioned 5-year 

review, which indicates the species may be more abundant than was known at the time of listing 

(U.S. Fish and Wildlife Service 2013b). The primary threats to the lesser long-nosed bat are roost site 

loss or disturbance and impacts to forage availability. Other threats that have contributed to the 

current endangered status of the species include roost disturbance and deterioration, border activities, 

recreation, vandalism, fire, vampire-bat control, mine closures, and forage availability. The effects of 

climate change (i.e., decreased precipitation and water resources) are a threat to many species (Lenart 

2007), including the lesser long-nosed bat.

In the United States, lesser long-nosed bat habitat includes semidesert grasslands and shrublands up 

to the oak transition zone (U.S. Fish and Wildlife Service 1997e). Lesser long-nosed bats roost in 

caves and abandoned mines and tunnels (U.S. Fish and Wildlife Service 1988). Lesser long-nosed 

bats are known to “roost-switch,” possibly in response to forage availability, which makes the small 

number of known roosts potentially significant to the population (U.S. Fish and Wildlife Service 

2007a). A colony of bats may move among several roost sites, and they may require multiple roost 

sites to meet their foraging and reproductive needs (Cole and Wilson 2006). The lack of, or presence 

of few, lesser long-nosed bats at a roost at one time does not indicate that bat numbers have declined 

or mean that the roost site is insignificant, or vice versa (U.S. Fish and Wildlife Service 2007a).

A suitable day roost, typically a cave or mine, is probably the most important habitat requirement; 

however, potentially suitable roosts must be within reasonable foraging distances of sufficient 

amounts of required foods (the nectar and pollen of paniculate agave flowers and the nectar, pollen, 

and fruit produced by columnar cacti). In Arizona, four species of paniculate agaves, Palmer’s agave 

(Agave palmeri), Parry’s agave (A. parryi), desert agave (A. deserti), and amole (A. schotti), and two 

columnar cacti, saguaro cactus and organ pipe cactus (Stenocereus thurberi), provide the main food 

sources for this nectivorous bat. Cactus flowers and fruits are available during the spring and early 

summer, whereas blooming agaves are primarily available during mid- to late summer (typically from 

July through early October). 

638 Final Environmental Impact Statement for the Rosemont Copper Project
Chapter 3. Affected Environment and Environmental Consequences

The lesser long-nosed bat is found from southern Arizona and extreme southwestern New Mexico, 

through western Mexico, and south to El Salvador (U.S. Fish and Wildlife Service 1997e). There

were 17 known major lesser long-nosed bat roost sites in Arizona and Mexico in the early 1990s and 

12 major maternity roost sites. Based on surveys conducted in 1992 and 1993, it was estimated that 

more than 200,000 bats occupied 16 of the 17 sites and that the maternity roosts are occupied by 

more than 150,000 bats. In southern Arizona, lesser long-nosed bat roosts have been found from the 

Picacho Mountains (Pinal County) southwest to the Agua Dulce Mountains (Pima County), southeast 

to the Chiricahua Mountains (Cochise County), and south to the international boundary (U.S. Fish 

and Wildlife Service 2008d). Individuals have also been observed near the Pinaleño Mountains 

(Graham County) and as far north as Phoenix and Glendale (Maricopa County) and from far 

southwestern New Mexico in the Animas and Peloncillo Mountains (Hidalgo County) (U.S. Fish and 

Wildlife Service 1997e). There are three known lesser long-nosed bat maternity roosts and 

approximately 40 total lesser long-nosed bat roosts in Arizona (U.S. Fish and Wildlife Service 

2007a). Known lesser long-nosed bat maternity roosts are all more than 75 miles from the proposed 

project area; however, known major postmaternity roosts, including Patagonia Bat Cave and State of 

Texas, are within about 40 miles of the proposed project area, and several small postmaternity roosts 

are closer. 

Palmer’s agave surveys in the vicinity of the project area and proposed utility corridor were 

conducted, and a regional analysis of Palmer’s agave numbers also was undertaken in 2008 to better 

understand the significance of the agave population on the Rosemont Copper property (WestLand 

Resources Inc. 2009c, 2011e). The mean density of Palmer’s agave densities in the project area was 

approximately 56.7 plants per acre, and the number of agaves in the entire project area was estimated 

to be between approximately 196,268 and 306,209. The mean density of successful flowering stems 

in the project area reported by WestLand Resources Inc. was 1.18 per acre; in comparison, the mean 

density of successful flowering stems on regional plots was 1.14 per acre, and the range of flowering 

stems was estimated to be between 3,951 and 7,187 within the project area. Within the proposed 

utility corridor, 371 agave locations were recorded in 2009, and many of the agave locations included 

more than 1 plant. A total of 53 Palmer’s agaves in 37 locations was recorded during the 2011 survey

(WestLand Resources Inc. 2011e).

Bat surveys of the proposed project area and vicinity were conducted in 2008 (WestLand Resources 

Inc. 2009d), 2009 (Buecher et al. 2010), 2010 (Buecher et al. 2011), 2011 (Buecher et al. 2012), and 

2012 (Buecher and Sidner 2013). Methods included active and passive ultrasonic acoustic sampling 

at flowering agaves, infrared photography and observations of flowering agaves, and surveys of 

potential roost sites. In 2008, 143 potential bat roost sites (i.e., caves, mine shafts, and adits) were 

evaluated within the analysis area and surrounding region (WestLand Resources Inc. 2009d). Of these 

143 sites, 59 were within the proposed project area, and 16 were near the proposed project area. 

Lesser long-nosed bats were documented foraging regularly on agaves in the proposed project area 

from late August to mid-September based on the results of acoustic and infrared surveys. Lesser longnosed bat calls were recorded at 23 of the 27 Palmer’s agave sites, and night vision equipment 

detected frequent lesser long-nosed bat visits to flowering Palmer’s agaves. 

Lesser long-nosed bats were documented roosting at three sites within the analysis area between 2008

and 2011: at Site 9/Chicago Mine in 2008, 2009, and 2011,

29 Site R-2 2008, 2009, 2011, and 2012,30

and the Helena Mine complex in 2008, 2009, 2010, 2011, and 2012. One of these sites (Site 

29 This site was not surveyed in 2010.

30 This site was not surveyed in 2010.

Final Environmental Impact Statement for the Rosemont Copper Project 639

 
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9/Chicago Mine) is within the proposed project area and is located within the proposed mine pit; site 

R-2 is immediately adjacent to the southwestern portion of the project area; and the Helena Mine 

complex is approximately 1 mile north-northeast of the project area. Additionally, the BLM

conducted surveys on their lands near Helvetia late in 2010, and lesser long-nosed bat individuals 

were observed roosting in abandoned mine land features (Hughes 2011). Surveys in the analysis area 

indicate that the project area is located in the postmaternity dispersal region for lesser long-nosed bat 

(maternity colonies in southwestern Arizona disband in July and August), and there are numerous 

Palmer’s agaves and at least three active roosts within the analysis area. Lesser long-nosed bats 

forage and occupy roosts in the area beginning at least in early August and, based on results at the 

Helena Mine complex, continuing into October. The large number of this species present at the 

Helena Mine complex in 2009, 2011, and 2012 indicates that this site could be a roost complex of 

regional importance to lesser long-nosed bats.

Hooded skunk (Mephitis macroura milleri). This Forest Service sensitive species occurs in Arizona, 

New Mexico, Texas, and south through Mexico and into Central America; it occurs in most of the 

counties within Arizona (Hoffmeister 1986). The hooded skunk is primarily insectivorous and, in 

Arizona, is typically found in sycamore, cottonwood, and rabbitbrush riparian habitats in the 

southeast quarter of the State, extending northward as far as Camp Verde and northern Greenlee 

County (Biota Information System of New Mexico 2008e; Hoffmeister 1986). Hooded skunks seem 

to prefer rocky slopes, bases of cliffs, or rocky sides of arroyos at intermediate elevations above the 

deserts but not in the highest mountains (Hoffmeister 1986). This skunk species primarily eats 

insects, fruits, small vertebrates, and bird eggs (Hwang and Lariviére 2001). The hooded skunk is 

listed as sensitive by the Forest Service because of its restricted distribution, conversion of lowelevation riparian habitats to urban and agricultural lands, and indeterminate amount of trapping and 

poisoning (U.S. Forest Service 2007e).

This species was not detected during surveys of the area that occurred during the mid-1970s 

(Roth n.d. [1977]), and although a recent species-specific survey targeting hooded skunk was not 

conducted, habitat exists in the analysis area, the analysis area is within their known range, and this 

species was observed within the analysis area during surveys for sensitive bats (Buecher and Sidner 

2013). GIS analysis indicates that there is an estimated 22,129 acres of possible habitat for this 

species within the analysis area; this includes all elevations within all riparian habitats. The area with 

suitable microhabitat (i.e., rocky slopes, bases of cliffs, or rocky sides of arroyos), however, is likely 

much smaller.

White-nosed coati (Nasua narica). This Forest Service sensitive species occurs in Arizona, New 

Mexico, Texas, and south through Mexico and Central America into the far northwestern portion of 

South America and in over nearly the entire south half of Arizona. White-nosed coatis primarily occur 

in mixed conifer forest, coniferous and mixed woodlands, and juniper savanna; they are also 

commonly observed in montane scrub, Chihuahuan desertscrub, closed basin scrub, plains-mesa 

grassland, and desert grassland (Biota Information System of New Mexico 2008a). White-nosed 

coatis in Arizona inhabit woodlands consisting primarily of oaks, sycamores, and walnuts. They are 

also found in canyons that contain a mixture of oaks and pines, shrubby woodland, or grassland and 

shrubs in the lower canyons of the southeastern mountains (Hoffmeister 1986). They are usually 

found near streams or creeks or some source of water, probably living in natural retreats such as rock 

crevices, cavities among tree roots, and caves or mines (Biota Information System of New Mexico 

2008a; Hoffmeister 1986). Coatis are quite omnivorous when necessary, feeding on what is available; 

they feed extensively on soil-inhabiting invertebrates, lizards, snakes, carrion, rodents, nuts and fruits 

of native trees, prickly pear, and yucca (Hoffmeister 1986). Threats to this species are not well 

640 Final Environmental Impact Statement for the Rosemont Copper Project
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documented; however, it is listed as sensitive by the Forest Service because of its restricted 

distribution (endemic to southeastern Arizona and extreme southwest corner of New Mexico), 

indiscriminant killing, predator control, and riparian habitat degradation (U.S. Forest Service 2007d).

Although a recent species-specific survey targeting white-nosed coati was not conducted, habitat

exists in the analysis area, and the analysis area is within their known range. This species was 

detected during surveys of the area that occurred during the mid-1970s (Roth n.d. [1977]) and has 

been observed in the project area during site visits by SWCA Environmental Consultants biologists 

and archaeologists and is known to frequent washes in the analysis area. GIS analysis indicates that 

there is an estimated 22,129 acres of possible habitat for this species within the analysis area; this 

includes all elevations within all riparian habitats. The area with suitable microhabitat (i.e., near 

streams or creeks or some source of water, probably living in natural retreats such as rock crevices, 

cavities among tree roots, and caves or mines), however, is likely much smaller.

Jaguar (Panthera onca). The jaguar was listed as an endangered species in the U.S. portion of the 

species’ range on July 22, 1997 (U.S. Fish and Wildlife Service 1997d), without critical habitat, and 

the non-U.S. population was listed as endangered in 1972 (U.S. Fish and Wildlife Service 2000). In 

2010, the USFWS announced that designation of critical habitat is of the jaguar was prudent (U.S. 

Fish and Wildlife Service 2010a). Therefore, the USFWS, together with the Jaguar Recovery Team, 

developed a recovery outline, with scientific population and habitat analyses for jaguars that was

considered in the preparation of a critical habitat proposal for the species in the northern portion of 

their range (Jaguar Recovery Team and U.S. Fish and Wildlife Service 2012).

On August 20, 2012, the USFWS proposed to designate critical habitat for the jaguar (U.S. Fish and 

Wildlife Service 2012e). The proposed critical habitat would total approximately 838,232 acres in six 

units in Pima, Santa Cruz, and Cochise Counties, Arizona, and Hidalgo County, New Mexico. 

Two units (53,713 acres) of critical habitat are proposed in the analysis area: 34,084 acres in Unit 

3 – Patagonia and 19,629 acres in Unit 4 – Whetstone (subunit 4b – Whetstone-Santa Rita). On July 

1, 2013, the USFWS announced revisions to proposed critical habitat for the jaguar (U.S. Fish and 

Wildlife Service 2013d). The revised critical habitat would total approximately 858,137 acres in the 

same units, counties, and states as previously, with two units overlapping the analysis area: 366,615

acres in Unit 3 – Patagonia and 12,710 acres in Unit 4 – Whetstone (subunit 4b – Whetstone-Santa 

Rita). A total of 59,492 acres of critical habitat is proposed in the analysis area: 53,498 acres in 

Unit 3 – Patagonia and 5,994 acres in Unit 4 – Whetstone (subunit 4b – Whetstone-Santa Rita).

The Whetstone Unit has three subunits: subunit 4a is a “habitat” unit, whereas subunits 4b and 4c are 

“connector” subunits. Habitat units and subunits are those that provide for jaguar recovery by having 

all primary constituent elements, whereas connector subunits provide general habitat connectivity 

between units, subunits, and Mexico (where source populations exist). 

The primary constituent elements of the revised proposed critical habitat specific to jaguars are 

expansive open spaces in the southwestern United States of at least 38.6 square miles in size that: 

provide connectivity to Mexico; contain adequate levels of native prey species; include surface water

sources available within 12.4 miles of each other; contain 1 to 50 percent canopy cover within 

Madrean evergreen woodland or semidesert grassland vegetation communities; are characterized by 

rugged terrain; are characterized by minimal to no human population density, no major roads, or no 

stable nighttime lighting over any 0.4-square-mile area; and are below 6,562 feet in elevation 

(U.S. Fish and Wildlife Service 2013d). All of the primary constituent elements within the boundaries 

of the proposed critical habitat for jaguar are considered to be present in the project area, except the 

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eastern portion, which lacks only the topographic primary constituent element of rugged terrain 

(SWCA Environmental Consultants 2012g).

Habitat destruction and modification and the illegal killing of jaguars are the two most significant 

threats to the jaguar (Jaguar Recovery Team and U.S. Fish and Wildlife Service 2012). Other current 

threats identified include the development of infrastructure projects (e.g., pedestrian fences, etc.) 

along the U.S.-Mexico border, which could impede the movements of jaguars (U.S. Fish and Wildlife

Service 2008h). The international border is semipermeable, however, with some areas (particularly in 

the mountains) that allow large-bodied animals to cross. Recent droughts have resulted in habitat loss, 

fragmentation, and degradation. Additionally, large-scale, open-pit mines have been identified as 

having the potential to threaten known core habitat of jaguars in southeastern Arizona (McCain and 

Childs 2008). The effects of climate change (i.e., decreased precipitation and water resources) are a 

threat to many species (Lenart 2007), including the jaguar. 

Jaguars are known from a variety of vegetation communities in North and South America. Rangewide, jaguars are mostly found in tropical and subtropical zones (U.S. Fish and Wildlife Service

2008h). In the southwestern United States, the more open, dry habitat has been suggested as being 

marginal in terms of water, cover, and prey densities (Rabinowitz 1999), although there was 

historically a larger and naturally breeding population (Brown and López-González 2001). Jaguar

populations in northwestern Mexico and the southwestern United States occur in arid areas, 

especially thornscrub, mesquite grassland, Madrean oak woodland, and pine-oak woodland 

communities (Boydston and López-González 2005; McCain and Childs 2008). Based on 25 historical 

(from 1902 to 2001) reliable and spatially accurate jaguar sighting records in Arizona, the majority of 

jaguars were observed in scrub grasslands and Madrean evergreen forests, all were within 6.2 miles 

of a water source, and most occurred in moderately rugged to extremely rugged terrain (Hatten et al. 

2005). Additionally, river valleys and other drainage features likely “provide travel corridors for 

jaguars, along with higher prey densities, cooler air, and denser vegetation than surrounding habitats” 

(Jaguar Recovery Team and U.S. Fish and Wildlife Service 2012). 

As part of the process of developing a recovery outline for jaguars in the northern portion of their 

range and in the preparation of a critical habitat proposal for the species, habitat suitability criteria for 

the jaguar has been developed, and a map was produced delineating potential jaguar habitat 

(approximately 6.5 million acres) in Arizona and New Mexico (Hatten et al. 2003). Hatten et al. 

(2003) estimated that 21 to 30 percent of Arizona (23,940 to 34,200 square miles) is possible jaguar

habitat; however, the species currently occurs on an occasional basis in only a small portion of this 

area. Jaguars have relatively large home ranges and appear to select relatively intact habitats away 

from human settlements (U.S. Fish and Wildlife Service 2008h). Jaguar home ranges are highly 

variable and depend on topography, available prey, and population dynamics. No home range studies 

using standard radio-telemetry techniques have been conducted for jaguars in the southwestern 

United States, but based on the use of camera traps in south-central Arizona, one male jaguar was 

reported as having a minimum observed “range” of 525 square miles (McCain and Childs 2008); 

however, female jaguar scat was used at some camera traps at various times, and the potential 

influence of this on the observed range of this male is unknown (Jaguar Recovery Team and U.S. Fish 

and Wildlife Service 2012).

Jaguars historically ranged from the southern United States (California, Arizona, New Mexico, Texas, 

and possibly Louisiana) to southern Argentina (Arizona Game and Fish Department 2004b; U.S. Fish 

and Wildlife Service 2008h). Currently, they range from the southwestern United States (Arizona and 

New Mexico) to northern Argentina; the southwestern United States lies at the extreme northern limit 

642 Final Environmental Impact Statement for the Rosemont Copper Project
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of the jaguar’s range. More than 60 jaguars are reported as having been killed in Arizona and New 

Mexico between 1900 and 2000. Sightings in the United States in the late 20th century to the present 

have occurred mainly along the U.S.-Mexico border. Three records of a female with kittens have been 

documented in the United States, although none since 1910, and no females have been confirmed in 

the United States since 1963. In northwestern and western Mexico, jaguars occur in Colima, Jalisco, 

Nayarit, Sinaloa, Chihuahua, and Sonora to the border with the United States (Jaguar Recovery Team 

and U.S. Fish and Wildlife Service 2012). Breeding populations currently occur in Jalisco, Nayarit, 

Sinaloa, and Sonora, with the most northern recently documented breeding population of jaguars 

occurring in Sonora approximately 130 miles south of the U.S.-Mexico border (Brown and LópezGonzález 2001). Since 2009, two jaguars have been documented at Rancho El Aribabi, Sonora, and 

one jaguar has been documented in the Sierra Los Ajos, both of which are approximately 30 miles 

south of the U.S. border near Naco, Mexico. 

Historically (i.e., prior to 1965), jaguars were reported at numerous locations in Arizona, as far north 

as the Grand Canyon; however, all Arizona records since 1965 have been in the southern portion of 

the State (Arizona Game and Fish Department 2011d; Brown and López-González 2001; Jaguar 

Recovery Team and U.S. Fish and Wildlife Service 2012; U.S. Fish and Wildlife Service 2008h).

Between 1965 and 1986, only three jaguars were documented (and all were killed) in Arizona. 

No jaguars were reported in Arizona for 10 years between 1986 and 1996, but the number of 

sightings of this species in the southwestern United States has been on the rise since 1996. Five, 

possibly six, individual jaguars were documented in the United States between 1996 and 2011: 

two in New Mexico and three or four in Arizona. There are several records of jaguars from southern 

Arizona, three of which are known from the Santa Rita Mountains (Helvetia in 1917, base of Mount 

Baldy in 1918, and Greaterville in 1919), and one of which is from the Empire Mountains (1961) 

within the analysis area (Arizona Game and Fish Department 2011d; Brown and López-González 

2001; Jaguar Recovery Team and U.S. Fish and Wildlife Service 2012; U.S. Fish and Wildlife Service 

2008h). The last historic confirmed sighting of a jaguar in the analysis area was in 1961.

Before 2011, the nearest known recent sighting of a jaguar to the analysis area was in the Baboquivari 

and Pajarito/Atascosa Mountains in 2009 (Arizona Game and Fish Department 2009): the

easternmost portion of the range of this individual was located approximately 20 miles southwest of 

the analysis area (WestLand Resources Inc. 2011f). In 2011, there were two jaguar sightings in 

southeastern Arizona. In June 2011, an unconfirmed sighting (Arizona Game and Fish Department

Class II-7) of a jaguar was reported in the Santa Rita Mountains in Santa Cruz County (Gardner 

2011): this sighting was approximately 13 miles south of the project area and 8 miles south of the 

analysis area. On November 19, 2011, a confirmed sighting of an adult male jaguar occurred when he 

was treed by a mountain lion hunter and his dogs in a canyon in the Whetstone Mountains in Cochise 

County, approximately 25 miles east of the project area and 10 miles east of the analysis area 

(Arizona Game and Fish Department 2011d; Jaguar Recovery Team and U.S. Fish and Wildlife 

Service 2012). The 2011 locality within the Santa Rita Mountains was relatively close to the proposed 

project and the analysis area, and both this and the confirmed individual in the Whetstone Mountains 

were in proposed critical habitat. 

From fall 2012 through spring 2013, there were several confirmed sightings of what appears to be a 

single jaguar in the Santa Rita Mountains. The first record was from an image on a hunter’s trail

camera, was within proposed critical habitat and within the analysis area (i.e., north of Box Canyon 

and south of I-10), and provided the first unequivocal evidence of jaguar occurrence in recent years in 

the analysis area (and Santa Rita Mountains) (U.S. Fish and Wildlife Service 2012e). The remaining 

sightings consist of several photos from different cameras of one male jaguar in different areas of the 

Final Environmental Impact Statement for the Rosemont Copper Project 643
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analysis area and within proposed critical habitat for this species (SWCA Environmental Consultants 

2012g; U.S. Fish and Wildlife Service 2012e; U.S. Forest Service and SWCA Environmental 

Consultants 2013). Based on this individual’s unique spot pattern, this male has been identified as the 

same jaguar in the Whetstone Mountains photographed by the hunter in the fall of 2011. This 

individual was also photographed in 2012 in the southern Santa Rita Mountains, in the general

vicinity of the unconfirmed 2011 sighting. This provides evidence that a jaguar is traveling between 

the Whetstone and Santa Rita Mountain ranges.

Surveys for this species have not been conducted within the analysis area for the purposes of the 

proposed project. However, habitat is present in the analysis area, the analysis area is within the 

historic range of the species, and there have been several recent (2011 to 2013) sightings of at least 

one jaguar within and near the analysis area. The U.S. Forest Service and SWCA Environmental 

Consultants (2013) state that the numerous photographs spanning 3 years suggest that this is a 

resident jaguar in the areas where the animal was photographed. This animal ranges at least from the 

northern Whetstone Mountains and through the northern and southern Santa Rita Mountains. 

The project and analysis areas have been identified as being located near biologically best corridors 

for the jaguar and at the apex of two wildlife linkages (strands 5 and 6) that connect the Santa Rita 

and Whetstone Mountains, near the south end of a wildlife linkage (strand 1) that connects the Santa 

Rita and Rincon Mountains (Beier et al. 2006a), and near the west end of a wildlife linkage (strand B) 

that connects the Santa Rita and Patagonia Mountains (Beier et al. 2008).

Fulvous harvest mouse (Reithrodontomys fulvescens). This Forest Service sensitive species is a 

strictly nocturnal reddish brown harvest mouse that is found on grassy or weedy slopes and alluvial 

fans, usually with shrubs, mesquites, pinions, scattered oaks, or other deciduous trees and in arid 

inland valleys in southeastern Arizona in Cochise, Pima, and Santa Cruz Counties (Biota Information 

System of New Mexico (BISON-M) 2008b; Enature 2007; Hoffmeister 1986). This mouse species 

feeds on invertebrates, seeds, and other plant parts; diet may vary by season (Spencer and Cameron 

1982). The fulvous harvest mouse occurs in Arizona, New Mexico, Texas, Oklahoma, Kansas, 

Missouri, Arkansas, Louisiana, Mississippi, and south through Mexico into Central America 

(U.S. Forest Service 2007d). In southeastern Arizona, this species historically occurred in Cochise, 

Pima, and Santa Cruz Counties but is currently thought to be possibly extirpated from each of these 

counties (Biota Information System of New Mexico (BISON-M) 2008b; Enature 2007; Hoffmeister 

1986; U.S. Forest Service 2007d). This species is listed as sensitive by the Forest Service because it is 

highly sensitive to degradation of mesic, dense grassland habitat and has limited distribution 

(U.S. Forest Service 2007d). Threats to this species are not well documented. 

Although a recent species-specific survey targeting fulvous harvest mouse was not conducted, the 

analysis area occurs within the historic range of the species, and although it was referred to as being 

relatively uncommon in the project area, individuals were detected in small patches of sheltered 

grassland during surveys of the area that occurred during the mid-1970s (Roth n.d. [1977]). 

GIS analysis indicates that there is an estimated 124,043 acres of possible habitat for this species 

within the analysis area; this includes all elevations, within the Chihuahuan desertscrub, semidesert 

grassland, and Madrean evergreen woodland vegetation types. The area with suitable microhabitat 

(i.e., on grassy or weedy slopes and alluvial fans, usually with shrubs or trees), however, is likely 

much smaller.

Plains harvest mouse (Reithrodontomys montanus). This Forest Service sensitive species is a small 

mouse with a long tail (Biota Information System of New Mexico (BISON-M) 2008c; Hoffmeister 

1986; U.S. Forest Service 2007d). The plains harvest mouse is restricted to grassland habitats, both 

644 Final Environmental Impact Statement for the Rosemont Copper Project
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short- and mid-grass prairies, often nesting under stones in pastures dominated by weedy species and 

prickly pear cactus in areas with plenty of seed to eat. This mouse species is both insectivorous and 

herbivorous (Wilkins 1986). The plains harvest mouse occurs in Arizona, New Mexico, Texas, 

Oklahoma, Colorado, Kansas, Nebraska, North Dakota, South Dakota, Missouri, Arkansas, and south 

into Mexico. In Arizona, this species occurs in Chino, Skull, and Verde Valleys, Santa Rosa Wash,

and the southeast corner of Arizona, including the Sulphur Springs and San Pedro Valleys, in 

Cochise, Graham, Greenlee, Pinal, Pima, Yavapai, and Santa Cruz Counties within Arizona but is 

currently thought to possibly be extirpated from Pinal County. In Arizona, this species prefers xeric 

conditions, where water accumulates infrequently, often where there is mesquite, creosotebush, and 

grass, usually in desertscrub or chaparral (Hoffmeister 1986). This species is listed as sensitive by the 

Forest Service because of its patchy and discontinuous distribution and because much of its habitat

has been lost as a result of urbanization and agriculture, but other threats to this species are not well 

documented (U.S. Forest Service 2007d). 

Although a recent species-specific survey targeting plains harvest mouse was not conducted, the 

analysis area occurs within the range of the species, and individuals were detected in in the Oak Tree 

Canyon area during surveys of the project area that occurred during the mid-1970s (Roth n.d. [1977]). 

GIS analysis indicates that there is an estimated 96,785 acres of possible habitat for this species

within the analysis area; this includes all elevations within the Sonoran desertscrub, Chihuahuan 

desertscrub, and semidesert grassland vegetation types. The area with suitable microhabitat (i.e., near 

stones in pastures dominated by weedy species and prickly pear cactus in areas with plenty of seed to 

eat), however, is likely much smaller.

Yellow-nosed cotton rat (Sigmodon ochrognathus). This Forest Service sensitive species occurs in 

Arizona, southwestern New Mexico, Texas, and Mexico (Arizona Game and Fish Department 2003d; 

U.S. Forest Service 2007d). This species occurs in Cochise, Graham, Pima, and Santa Cruz Counties 

within Arizona, although it is possibly extirpated from Graham County. In southeastern Arizona, the 

range of the yellow-nosed cotton rat is mostly bordered by the Baboquivari, Santa Rita, and Santa 

Catalina Mountains to the northwest, the Galiuro Mountains to the north, and the Chiricahua 

Mountains to the east. This species typically inhabits grassy, dry, rocky slopes (often up to 40 

degrees) in or near the oak woodland belt, along with mountain meadows within ponderosa pine and 

Douglas-fir forests, at elevations ranging from 3,000 to 8,500 feet. This rodent mostly feeds on 

grasses (especially Bouteloua gracilis) but occasionally feeds on prickly pear fruits where present, 

which probably provide necessary moisture. The grasses are typically sparse and scattered in clumps 

with dense cover of beargrass, agave, or yucca dispersed through the grass, providing sufficient 

refuges and nest sites. Some of the grasses usually present are blue grama, side-oats grama, three-awn 

(Aristida spp.), muhly (Muhlenbergia spp.), tangle-head (Heteropogon spp.), and gumweed 

(Grindelia spp.). Yellow-nosed cotton rats are known to tolerate more xeric conditions than any other 

Sigmodon (Hoffmeister 1986). This species is threatened by the destruction, elimination, or 

degradation of native perennial grassland habitats as a result of grazing, altered fire regimes, 

urbanization, or other factors (Arizona Game and Fish Department 2003d).

Although a recent survey targeting rodents was not conducted, the analysis area occurs within the 

range of the species, and the species was observed at several widely scattered localities within the 

Rosemont area during surveys conducted by Roth (n.d. [1977]). GIS analysis indicates that there is an 

estimated 123,813 acres of possible habitat for this species within the analysis area; this includes 

elevations ranging from 3,000 to 8,500 feet within the Chihuahuan desertscrub, semidesert grassland, 

and Madrean evergreen woodland vegetation types. The area with suitable microhabitat (i.e., grassy, 

Final Environmental Impact Statement for the Rosemont Copper Project 645
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dry, rocky slopes in or near the oak woodland belt and mountain meadows), however, is likely much 

smaller.

Forest Service and BLM sensitive bat species. For the purposes of this project, 165 potential 

underground roost sites were evaluated, and surveys for cave/underground mine-roosting bat species 

were conducted within the analysis area, mostly within or adjacent to the project area, from 2008 to 

2012 (Arizona Game and Fish Department 2012d; Buecher and Sidner 2013; Buecher et al. 2012; 

Buecher et al. 2010, 2011; Roth n.d. [1977]; WestLand Resources Inc. 2009d). There were no surveys 

conducted specifically for this project for species that are not cave/mine dwellers. The following 

Forest Service and BLM sensitive bat species have been observed within the analysis area, habitat 

exists in the analysis area, and the analysis area is within their known ranges (Arizona Game and Fish 

Department 2012d; Buecher and Sidner 2013; Buecher et al. 2012; Buecher et al. 2010, 2011; Roth 

n.d. [1977]; WestLand Resources Inc. 2009d): Mexican long-tongued bat (Choeronycteris mexicana), 

pale Townsend’s big-eared bat (Corynorhinus townsendii pallescens), western red bat (Lasiurus 

blossevillii), fringed myotis (Myotis thysanodes), cave myotis (Myotis velifer), and pocketed freetailed bat (Nyctinomops femorosaccus). The bats observed in the analysis area were foraging on plant 

or insect resources and/or using mines and adits for day, night, and/or maternity roosts. 

The Mexican long-tongued bat typically occurs in mesic areas within canyons of mixed oak-conifer 

forests or semidesert grasslands at elevations ranging from 2,540 to 7,320 feet (Arizona Game and 

Fish Department 2006b). These bats typically feed on nectar and pollen (especially from paniculate 

agaves), preferring to roost in the dimly lit areas often near the entrance of caves and abandoned 

mines, also sometimes found in shallow caves or rock shelters. The main threat to the Mexican longtongued bat is the loss of food supplies (nectar and pollen of agave and columnar cactus) caused by 

development, ranching practices, harvesting, or any activities that disturb agave and/or columnar 

cactus populations. GIS analysis indicates that there is an estimated 22,110 acres of possible habitat

for Mexican long-tongued bats within the analysis area; this includes all areas at elevations ranging 

from 2,540 to 7,320 feet above mean sea level, within all riparian habitats.

In Arizona, summer day roosts for the pale Townsend’s big-eared bat include caves and mines in 

areas of desertscrub, oak woodland, oak-pine woodland, pinyon-juniper woodland, and coniferous 

forest; the species prefers to hang from open ceilings at roost sites and to not use cracks or crevices 

(Arizona Game and Fish Department 2003a). Night roosts are often in abandoned buildings. 

In winter, these bats hibernate in cold caves, lava tubes, and mines. In Arizona, hibernation sites are 

mostly in upland and mountainous areas, from the vicinity of the Grand Canyon to the southeastern 

part of the State. This bat has been found from 550 to 7,520 feet above mean sea level; however, most 

records are from above 3,000 feet above mean sea level (Hinman and Snow 2003). The primary prey

of this bat species is small moths, but they also eat other insects (Arizona Game and Fish Department 

2003a). The main documented threats to this species are human disturbance at major maternity roosts, 

mining, closure and sealing of abandoned mines, vandalism at maternity and hibernation sites, loss of 

foraging habitat, and possibly exposure to pesticides (Arizona Game and Fish Department 2003a).

GIS analysis indicates that there is an estimated 29,245 acres of possible habitat for pale Townsend’s 

big-eared bats within the analysis area; this includes all areas at elevations ranging from 550 to 7,520 

feet above mean sea level, within Chihuahuan desertscrub and Madrean evergreen woodland 

vegetation communities.

The western red bat is typically found in riparian and other wooded areas of broad-leaf deciduous 

riparian forests and woodlands at elevations ranging from 1,900 to 7,200 feet (Arizona Game and 

Fish Department 2011f). Summer roost sites are typically in tree foliage, sometimes in leafy shrubs or 

646 Final Environmental Impact Statement for the Rosemont Copper Project
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herbs and often in trees of fruit orchards. This species may also roost in saguaro boots and 

occasionally in cave-like situations, although they have generally been observed to avoid caves and 

buildings during both summer and winter (Arizona Game and Fish Department 2011f; Hinman and 

Snow 2003). Winter and day roost sites are also typically in the dense foliage of trees, the hanging bat 

resembling a dead leaf. Moths seem to be an important prey source for red bats, but they also take 

flies, bugs, beetles, cicadas, ground-dwelling crickets, and hymenopterans (Arizona Game and Fish 

Department 2011f). This species primarily roosts in cottonwood trees, and the bats’ notable decline in 

abundance is suspected to be attributable to the loss of cottonwood habitat in North America. GIS 

analysis indicates that there is an estimated 34,594 acres of possible habitat for western red bats 

within the analysis area; this includes all areas at elevations ranging from 1,900 to 7,200 feet above 

mean sea level, within the Madrean evergreen woodland vegetation community and hydroriparian 

habitat.

The fringed myotis occurs throughout most of Arizona, except for the extreme northeast and 

southwest corners, where it is found primarily in mid-elevation habitats ranging from deserts and 

grasslands to woodlands at elevations ranging from 4,000 to 8,437 feet above mean sea level

(Arizona Game and Fish Department 2011g). This insectivorous bat seems to occupy the lowest 

elevational range of all the long-eared myotis species and is most frequently captured in oak-pinyon 

woodlands and other open, coniferous, mid-elevation forests; day and night roosts have been found in 

caves, in mine tunnels, in large snags, under exfoliating bark, and in buildings. This bat is mostly 

threatened by human disturbance of roost sites, especially maternity colonies, through recreational 

caving and mine exploration, but this species is also threatened by the closure of abandoned mines, 

mining at historic sites, toxic material impoundments, pesticide spraying, vegetation conversion, 

livestock grazing, timber harvest, destruction of buildings and bridges used as roosts, and the 

disturbance or destruction of water sources and riparian habitat. GIS analysis indicates that there is an 

estimated 112,389 acres of possible habitat for fringed myotis within the analysis area; this includes

all areas at elevations ranging from 4,000 to 8,437 feet above mean sea level, within all vegetation 

communities and all riparian habitats.

The cave myotis inhabits desertscrub communities that contain creosote, brittlebush, paloverde, and 

cacti, sometimes found in pine-oak communities; it also roosts in caves, tunnels, mine shafts, under 

bridges, and in buildings within a few miles of water (Arizona Game and Fish Department 2002c). 

This species forages in xeroriparian natural communities, typically preferring to forage for insects 

flying over tinajas, springs, and other developed water sources. These bats occur mostly between 300 

and 5,000 feet: this species is typically found in the lower elevations during summer and migrates to 

locations above 6,000 feet above mean sea level in the winter to hibernate. This bat is mostly 

threatened by habitat loss resulting from development and is highly susceptible at roosting sites, 

particularly maternity sites, because of the congregation of large numbers in one place but is also 

threatened by recreational caving, mine closures, and the loss of foraging habitat in riparian zones. 

GIS analysis indicates that the entire analysis area (146,163 acres) likely serves as habitat to the cave

myotis.

In Arizona, the pocketed free-tailed bat has been found in arid lower elevations within a variety of 

plant associations, including desert scrub and pine-oak forest, usually around high cliffs and rugged 

rock outcrops at elevations from 190 to 7,520 feet (Arizona Game and Fish Department 2011h). This 

insectivorous bat typically roosts in rock crevices during the day and may also use human built 

structures, requiring large surfaces of open water nearby for drinking (Arizona Game and Fish 

Department 2011h; U.S. Forest Service 2007d). This species is considered rare overall in the United 

States, and imperiled in Arizona because of its limited distribution and restricted range (U.S. Forest 

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Chapter 3. Affected Environment and Environmental Consequences

Service 2007d). This bat species is threatened by disturbance to or destruction of roost sites and 

pesticides (Arizona Game and Fish Department 2011h). GIS analysis indicates that the entire analysis 

area (146,163 acres) likely serves as habitat to the pocketed free-tailed bat.

Three bat species—pale Townsend’s big-eared bats, fringed myotis, and cave myotis—were detected 

during surveys that occurred in or near the project area during the mid-1970s (Roth n.d. [1977]).

In 1989, a western red bat was documented in Empire Gulch, east of SR 83 (Arizona Game and Fish 

Department 2012d). In 2006, surveys of adits and mines detected Mexican long-tongued bats at two 

sites and cave myotis at one site within the project area. Surveys of adits and mines in 2008 detected

bats (or evidence of bats) at 20 sites within the analysis area, 12 of which were in or immediately 

adjacent to the project area. Acoustic surveys in 2007 and 2008 in the analysis area detected five of 

the aforementioned bat species (cave myotis, fringed myotis, Mexican long-tongued bat, pale 

Townsend’s big-eared bat, and pocketed free-tailed bat) within the analysis area and some within the 

project area (WestLand Resources Inc. 2009d). Surveys of adits and mines in 2008 detected Mexican 

long-tongued bats at 14 sites, cave myotis at 5 sites, fringed myotis at 2 sites, pale Townsend’s bigeared bat at 3 sites, insectivorous bat evidence (e.g., guano) at 9 other sites, and nectivorous bat 

evidence at 3 other sites within the analysis area. Surveys of adits and mines in 2009 detected bats 

(or evidence of bats) at 29 sites within the analysis area, 24 of which were in or immediately adjacent 

to the project area (Buecher et al. 2010). Bat species detected in 2009 included Mexican long-tongued 

bats at 10 sites, cave myotis at 6 sites, fringed myotis at 1 site, pale Townsend’s big-eared bat at 1 

site, insectivorous bat evidence at 8 other sites, and nectivorous bat evidence at 3 other sites within 

the analysis area. 

In 2010, surveys were conducted at fewer adits and mines than in previous year, and bats (or evidence 

of bats) were detected at five sites within the analysis area, four of which were in or immediately 

adjacent to the project area (Buecher et al. 2011). Bat species detected in 2010 included Mexican 

long-tongued bats at two sites, cave myotis at one site, fringed myotis at one site, pale Townsend’s 

big-eared bat at two sites, insectivorous bat evidence at one site, and nectivorous bat evidence at one 

site within the analysis area. Surveys of adits and mines in 2011 detected bats (or evidence of bats) at 

28 sites within the analysis area, 24 of which were in or immediately adjacent to the project area 

(Buecher et al. 2012). Bat species detected in 2011 included Mexican long-tongued bats at 17 sites, 

cave myotis at 2 sites, fringed myotis at 3 sites, pale Townsend’s big-eared bat at 5 sites, 

insectivorous bat evidence at 3 sites, and nectivorous bat evidence at 3 sites within the analysis area.

Surveys of adits and mines in 2012 detected bats (or evidence of bats) at 16 sites within the analysis 

area, most of which were in or immediately adjacent to the project area (Buecher and Sidner 2013). 

Bat species detected in 2012 included Mexican long-tongued bat at four sites, pale Townsend’s bigeared bat at two sites, fringed myotis at five sites, and cave myotis at six sites.

Migratory Birds

Migratory bird species considered for this project were selected from the latest version of the online 

“Migratory Nongame Birds of Management Concern in the United States” (U.S. Fish and Wildlife 

Service 1995b) and the national Partners in Flight list of priority bird species for Mexican Highlands 

Ecoregion (Partners in Flight 2006) (see tables 3 and 4 of the migratory bird analysis) (SWCA 

Environmental Consultants 2013i). For the analysis of impacts to migratory birds, the Southwestern 

Region of the Forest Service has direction to look at impacts to the species on these lists, Partners in 

Flight priority habitats, important bird areas, and important overwintering areas. The migratory bird 

analysis also discusses impacts to bald and golden eagles (i.e., provisions of the Bald and Golden 

Eagle Protection Act).

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Bald and Golden Eagles

There is no evidence that bald eagles occur in the analysis area, and there are no significant bodies of 

water that would sustain a nesting pair or provide foraging habitat. There are several documented 

records of golden eagles (eBird 2013f; Russell et al. n.d. [1977]), including pairs, occurring in the 

analysis area, and foraging habitat is present. There are no known breeding sites within the project or 

analysis area, but targeted surveys have not been conducted. It is possible that golden eagles could be 

nesting within the analysis area but likely outside the project area, particularly in areas with rocky 

ridges, on trees (e.g., large oaks or junipers), or on power line poles.

Santa Rita Mountains Important Bird Area

Important bird areas are sites that provide essential habitat for one or more species of bird (National 

Audubon Society 2010), but those in Arizona can provide habitat for hundreds of species. Important 

bird areas include sites for breeding, wintering, and/or migrating birds; they are usually discrete sites 

that stand out from the surrounding landscape and may include public and/or private lands. The Santa 

Rita Mountains Important Bird Area, encompassing 138,760 acres, contains a number of species of 

conservation status in the Sierra Madre bird community, which extends far south into central Mexico. 

The analysis area encompasses approximately 42,107 acres of Forest Service lands within the Santa 

Rita Mountains Important Bird Area (this important bird area is defined as including all Forest 

Service lands on the Santa Rita Mountains). Further, the Santa Rita Mountains Important Bird Area is 

located within the Mexican monsoon region, an area where western North American land birds stop 

and undergo molt July to October (primarily in grassland and riparian areas) before continuing their 

migration south to wintering grounds in the Neotropics (Chambers et al. 2011; Pyle et al. 2009).

A total of 287 bird species has been observed in the Santa Rita Mountains Important Bird Area

(eBird 2013b), including numerous special status species recognized by the Forest Service (Federal 

threatened or endangered, State of Arizona wildlife of special concern, Forest Service sensitive, etc.). 

These species include some of those noted in tables 2 and 3 of the migratory bird analysis (SWCA 

Environmental Consultants 2013i): northern goshawk (Accipiter gentilis), northern gray hawk, 

Mexican spotted owl, whiskered screech-owl, Montezuma quail (Cyrtonyx montezumae), elegant 

trogon (Trogon elegans), Arizona woodpecker (Picoides arizonae), violet-crowned hummingbird

(Amazilia violiceps), Lucifer hummingbird (Calothorax lucifer), Costa’s hummingbird (Calypte 

costae), buff-breasted flycatcher (Empidonax fulvifrons), varied bunting, golden eagle, American 

peregrine falcon (Falco peregrinus anatum), elf owl (Micrathene whitneyi), northern beardlesstyrannulet, greater pewee (Contopus pertinax), gray flycatcher (Empidonax wrightii), Bell’s vireo

(Vireo bellii), bridled titmouse (Baeolophus wollweberi), Virginia’s warbler (Oreothlypis virginiae), 

MacGillivray’s warbler (Geothlypis tolmiei), Lucy’s warbler (Oreothlypis luciae), black-throated gray 

warbler (Setophaga nigrescens), Grace’s warbler (Setophaga graciae), red-faced warbler (Cardellina 

rubrifrons), Cassin’s sparrow (Peucaea cassinii), Botteri’s sparrow (Peucaea botterii), and buffcollared nightjar (Antrostomus ridgwayi). Some of these species are known to occur in the analysis 

area, or the analysis area contains possible habitat for these species; thus, these species are 

subsequently evaluated in greater detail within either the biologists’ report or migratory bird analysis

(SWCA Environmental Consultants 2013c, 2013i).

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Important Overwintering Areas

The analysis area provides important overwintering habitat for a variety of bird species, as does 

nearly all of southeastern Arizona. Grasslands, woodlands, and riparian areas (including Las Cienegas 

National Conservation Area) have among the highest biodiversity of wintering terrestrial species in 

the United States, along with southern California and southern Texas (see SWCA Environmental 

Consultants (2013i) for a review). Russell et al. (n.d. [1977]) recorded 45 overwintering bird species 

on their four transects (other species were opportunistically observed outside survey transects), 

conducted between January 26 and February 10, 1976, when migratory movements were expected to 

be lowest; this is, therefore, a conservative estimate of the number of species that may use the 

habitats outside this narrow window. Their results confirm a high diversity of overwintering species, 

including short-range migratory species, long-range migratory species, and resident species. 

Overwintering bird species that occur in the Rosemont area (Russell et al. n.d. [1977]) include

(but are not limited to) at least 5 raptors (in addition to golden eagles), 4 woodpeckers, 3 corvids, 

3 wrens, and at least 12 species of sparrows. Additionally, approximately 180 species of birds have 

been documented within the Santa Rita Mountains Important Bird Area during the months of 

December, January, and February from 1900 to 2013 (eBird 2013c).

Coronado National Forest Management Indicator Species

Thirty-three management indicator species in eight indicator groups were identified in appendix G of 

the “Coronado National Forest Land and Resource Management Plan” (U.S. Forest Service 1986), as 

amended. The EIS for the plan explains why these 33 species were chosen as management indicator 

species. Drawing on the plan, all 33 management indicator species identified for the Coronado 

National Forest were initially considered for project analysis. Following are the 11 management 

indicator species and one management indicator species group (primary and secondary cavity nesters) 

with the potential to occur in the analysis area on Forest Service lands because Madrean evergreen 

woodland and semidesert grassland vegetation types and riparian vegetation types occur in the 

analysis area on NFS lands (see table 117): American peregrine falcon, Arizona ridge-nosed 

rattlesnake (Crotalus willardi willardi), Bell’s vireo, Baird’s sparrow (Ammodramus bairdii), black 

bear (Ursus americanus), Gould’s turkey (Meleagris gallopavo mexicana), (northern) gray hawk 

(Buteo plagiatus maximus [=B. nitida]), Montezuma quail, northern beardless-tyrannulet, primary 

and secondary cavity nesters, western barking frog (Craugastor augusti cactorum), and white-tailed 

deer (Odocoileus virginianus). Assessing the impacts of the proposed project on these species’ 

populations, which represent populations of other species with similar habitat needs but that are not 

designated as special status species covered by environmental laws, regulations, policies, or plans, 

allows for an assessment of the impacts on the populations of other species with similar habitat needs.

A more detailed analysis of these species is provided in the supporting management indicator species

report (SWCA Environmental Consultants 2013h) for this project. 

Species of Greatest Conservation Need and Species of Economic and Recreational Importance 

All 531 species listed by the AGFD as Species of Greatest Conservation Need and all 13 species 

listed by the AGFD as Species of Economic and Recreational Importance were included in the 

biologists’ report (SWCA Environmental Consultants 2013c), and of those, 29 Species of Greatest 

Conservation Need are analyzed in this FEIS (see table 115). An analysis of these species is provided 

in the supporting biologists’ report (SWCA Environmental Consultants 2013c).

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Sonoran Desert Conservation Plan/Multi-species Conservation Plan

All 44 species proposed for coverage under the forthcoming “Multi-species Conservation Plan (Pima 

County 2012e) were included in the biologists’ report (SWCA Environmental Consultants 2013c), 

and of those, 18 covered species are analyzed in this FEIS (see table 115). The Conservation Lands 

System within the “Sonoran Desert Conservation Plan” categorizes and identifies locations of priority 

biological resources within Pima County and provides policy guidelines for the conservation of these 

resources. There is approximately 145,130 acres of Conservation Lands System lands in the analysis 

area, including 14,535 acres of Important Riparian Areas, 86,795 acres of Biological Core Areas, and 

43,800 acres of Multiple Use Management Areas (Pima County 2012c). 

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