Mine expansion 2000 TPD, application to amend operating permit no. 00118 : draft environmental assessment

196 Pages·1991·13.4 MB·English

by  United States. Forest Service

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HELENA, MONTANA 59620
Mine Expansion 2000 TPD
Application to Amend Operating Permit No. 00118
DRAFT ENVIRONMENTAL ASSESSMENT
December 1991
I ft i f i
1
Prepared by
Montana Department of State Lands
Montana Department of Health and Environmental Sciences
and the U.S. Forest Service
MONTANASTATE LIBRARY
S622.3424L3Mettd1991c.1
Mineexpansion2000TPD,applicationto
3 0864 00075843 6
Stillwater Mining Company
Nye, Montana
Mine Expansion 2000 TPD
Application to Amend Operating Permit No. 00118
DRAFT ENVIRONMENTAL ASSESSMENT
December 1991
Prepared by
Montana Department of State Lands
Montana Department of Health and Environmental Sciences
and the U.S. Forest Service
TABLE OF CONTENTS
CHAPTER INTRODUCTION
1 - 1
1.1 Project Location and Background 1
1.2 Brief Summary ofthe Proposed Action 3
1.3 Purpose and Need for Action 3
1.4 Land Status 4
1.5 Agency Roles and Responsibilities 5
1.5.1 Department of State Lands 5
1.5.2 U.S. Forest Service 6
1.5.3 Other Federal Agencies 7
1.5.4 Other State Agencies ' 7
1.6 The NEPA/MEPA Process 9
1.7 Issues and Concerns 10
1.8 Issue Statements 12
,
1.8.1 Tailing Impoundment 12
1.8.2 Socio-Economics/Traffic 13
1.8.3 Wildlife 14
1.8.4 Surface and Groundwater Resources 14
1.8.5 Wetlands/Flood Plains 15
CHAPTER 2 - SUMMARY OF PROPOSALS, ALTERNATIVES, AND OTHER
DEVELOPMENTS
16
2.0 Introduction 16
2.1 Development of Alternatives * 16
2.2 Alternative 1 - No Action 17
2.3 Alternative 2 - Company's Proposal 17
2.3.1 Mining Plans and Methods 17
2.3.2 Explosives 19
2.3.3 Production 19
2.3.4 Ore Processing 19
2.3.5 Tailing Disposal Facility - Impoundment 20
2.3.6 Waste Rock 20
2.3.7 Mine Water Use and Management 20
2.3.7.1 Potable Water 21
2.3.7.2 Stillwater River Water 21
2.3.7.3 Adit Water 21
2.3.7.4 Project Water Management 23
2.3.8 Energy Consumption and Source 23
i
2.3.9 Roads 23
2.3.10 Equipment 23
2.3.11 Surface Support Facilities 24
2.3.12 Mine Utilities 25
2.3.13 Security and Public Safety 25
2.3.14 Sewage Disposal 26
2.3.15 Solid Waste 26
2.3.16 Fire Protection 26
2.3.17 Personnel 27
2.3.18 Project Closure and Reclamation 27
2.3.18.1 Tailings Impoundment 28
2.3.18.2 Grading 28
2.3.18.3 Embankment Stabilization 31
2.3.18.4 Dust Control 31
2.3.18.5 Waste Rock Storage 31
2.3.18.6 SoD Handling 32
2.3.18.7 Revegetation 36
2.3.18.8 Surface Facilities 36
2.3.18.9 Mine Working 36
2.3.18.1 Facility Removal 36
2.3.18.11 Mine Drainage 37
2.3.18.12 Estimated Reclamation Units and Costs 37
•
2.3.19 Water Resources Monitoring Plan 37
2.3.20 Petition for Modification of Quality ofAmbient Waters 39
2.4 Alternative 3 - Modifications Concerning Tailings Impoundments 41
2.4.1 Introduction 41
2.4.2 Lvision-Makers* Selection 41
2.4.3a No Action - 3a 41
2.4.3b Company's Proposal - 3b 41
2.4.3c Partial Approval - 3c 43
2.4.3d Modified Impoundment - 3d 43
2.5 Alternative 4 - Water Treatment 43
2.5.1 No Action -4a 44
2.5.2 Company's Proposal - 4b 45
2.5.3 Advanced Water Treatments - 4c 45
2.6 Proposed Action with Modifications - Alternative 5 46
2.6.1 Water Resources 46
2.6.2 Tailing Impoundment Reclamation/Revegetation 49
2.6.3 Waste Rock 50
2.6.4 Soils 50
ii
2.6.5 Wildlife 51
2.6.6 Aesthetics 51
2.6.7 Traffic 51
2.7 Other Related Development Activities 51
2.7.1 Projects ofConcern Evaluated (CNF) 53
2.7.2 Projects ofConcern Evaluated (GNF) 56
2.7.3 Projects of Concern Not Evaluated 58
CHAPTER AFFECTED ENVIRONMENT
3 - 59
3.0 Introduction 59
3.1 Geology 59
3.1.1 Geotechnical 60
3.2 Water Resources 61
3.2.1 Surface Water 61
3.2.2 Groundwater 65
3.2.3 Adit Water 69
3.3 Soils 74
3.4 Wildlife and Fisheries 76
3.4.1 Vegetation Types 76
3.4.2 Local Wildlife Species of Concern 77
3.4.3 Threatened, Endangered, and Sensitive Species 79
3.4.4 Fisheries 80
3.5 Air Quality and Climate 81
3.5.1 Air Quality 81
3.5.2 Climatology and Meteorology 82
3.6 Land Uses 83
3.6.1 Recreation 83
3.6.2 Wilderness 83
3.6.3 Beartooth Ranch Operation 83
3.6.4 Land Uses Outside the National Forest 83
3.7 Aesthetics 84
3.7.1 Visuals 84
3.7.2 Noise 85
3.8 Socioeconomics/Traffic 85
3.8.1 Population 86
3.8.2 Labor Force 87
.
3.8.3 Personal Income 89
3.8.4 Structure ofthe Local Economy 90
3.8.5 Housing ' 93
3.8.6 Community Services and Facilities 94
• •
HI
3.8.7 Attitudes, Beliefs, and Values 96
3.8.8 Property Tax Base 97
3.8.9 Mine Access Corridors and Use Patterns 98
3.9 Cultural Resources • 100
CHAPTER 4 - ENVIRONMENTAL CONSEQUENCES 101
4.0 Introduction 101
4.1 Tailing Impoundment Construction and Operation 101
4.1.1 Environmental Consequences ofImpounded Tailing 103
4.1.2 Geotechnical Issues and Environmental Consequences Common to All
Potential Impoundment Actions 103
4.1.3 Geotechnical Issues and Environmental Consequences that are Unique
to the Tailing Impoundment Alternatives Being Evaluated 106
4.1.3a Tailing Impoundment Alternative 3a, No Action 107
4.1.3b Tailing Impoundment Alternative 3b, Company Proposal 108
4.1.3c Tailing Impoundment Alternative 3c, Partial Approval 109
—
4.1.3d Alternative 3d Modified Tailing Impoundment 110
4.2 Water Resources Ill
4.2.1 Hydrologic Consequences ofthe Alternatives Being Considered Ill
4.2.2 Water Quality 114
4.2.2a Alternative 4a - No Action 118
4.2.2b Alternative 4b - Company's Proposal 122
—
4.2.2c Alternative 4c Advanced Treatment 130
—
4.2.3 Alternative 3 Tailing Impoundments 131
—
4.2.4 Alternative 5 Company Proposal with Modifications 131
4.2.5 Cumulative Impacts ......... 132
4.3 Soils and Tailing Impoundment Reciamation/Revegetation 132
4.3.1 Soil Salvage Review 133
. ,
4.3.1.1 Alternative 3a No Action 135
4.3.1.2 Alternative 3b Company's Proposal 136
4.3.1.3 Alternative 3c Partial Approval 136
4.3.1.4 Alternative 3d Modified Impoundment 136
—
4.3.1.5 Proposed Action with McKHficatk-as Alternative 5 137
4.3.2 Cumulative Soil Impacts 138
4.4 Wildlife 138
4.4.1 Alternative 1 No Action 139
4.4.2 Alternative 2 Company's Pror>osal 140
4.4.3 Alternatives 3a Tailing Impoundment No Action and 3c Tailing
W
Impoundment Partial Approval
4.4.4 Alternative 3d Modified Tailing Impoundment 142
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4.4.5 Alternatives 4a, b, and c Water Treatment 143
—
4.4.6 Proposed Action with Modifications Alternative 5 144
4.5 Air Quality 145
4.5.1 No Action 145
4.5.2 Company's Proposal 145
4.5.3 All Alternatives 145
4.6 Land Uses 146
4.6.1 No Action 146
4.6.2 Company's Proposal 147
4.6.3 Other Alternatives 147
4.6.4 Recreation 148
4.7 Aesthetics - Introduction 149
4.7.1 No Action 149
4.7.2 Company's Proposal 149
4.7.3 Tailing Impoundment Alternatives 150
4.7.4 Water Treatment Alternatives 150
4.7.5 Mitigated Company's Proposal 150
4.8 Socioeconomics/Traffic 150
4.8.1 No Action 150
4.8.1.1 Socioeconomics 150
4.8.2 Company's Proposal 151
4.8.2.1 Socioeconomics 151
4.8.3 Other Alternatives 156
4.8.4 Traffic 156
4.9 Commitment of Resources 160
4.9.1 Irreversible and Irretrievable Impacts 160
4.9.2 Other Impacts Cannot be Totally Mitigated 160
CHAPTER 5 - COMPARISON OF ALTERNATIVES 163
5.0 Summary and Comparison ofAlternatives 163
—
5.1 Alternative 1 No-Action 163
—
5.2 Alternative 2 Company's Proposal 166
—
5.3 Alternative 3 Tailings Impoundment 168
5.4 Alternative 4 - Water Resources 169
5.5 Alternative 5 - Proposed Action with Modifications 170
5.6 Conclusions 172
LIST OF PREPARERS 179
v
LIST OF TABLES
m
Table 2.3-1 Proposed Personnel Requirements by Shift 27
Table 2.3-2 Summary ofVolume ofSoil in Existing Stockpiles 35
—
Table 2.3-3 Water Resources Monitoring Plan 1990 Operational Monitoring Stillwater
Mining Company 38
Table 2.3-4 Requested Change in Water Quality Limits (1) 40
Table 2.4-1 Tailing Impoundment Alternatives 42
Table 2.5-1 Comparison of Conventional and Advanced Water Treatment Options 47
Table 3.2-1 Surface Water Quality Data for Stillwater River (SMC-1A, 2 and 10), Nye
Creek (SMC-7) and Mountain View Creek (SMC-6) 64
Table 3.2-2 Groundwater Quality Data - Selected West Side Monitoring Wells 67
Table 3.2-3 Groundwater Quality Data - East Side Monitoring Wells 69
Table 3.2-4 Water Quality Stillwater Valley Ranch Monitoring Well 70
Table 3.2-5 West Side Adit (SMC-3), East Side Adit (SMC-9) and Tailing Impoundment
(SMC-4) Water Quality Data 72
Table 3.2-6 Composite Adit Water Quality and Applicable Water Quality Standards 73
Table 3.3-1 Soil Mapping Units Rated for Suitability as Source ofTopsoil Material 75
Table 3.3-2 Soil Replacement Volumes 76
Table 3.5-1 Summary ofthe PM-10 Suspended Particulate Data January, 1990 - December,
1990 81
Table 3.8-1 Labor Force Statistics for Stillwater County 89
Table 3.8-2 1989 Personal Income by Major Component 90
Table 3.8-3 1989 Labor Income by Major Industry Stillwater County and Montana 91
Table 3.8-4 Covered Employment and Wages In Stillwater County Montana-1989 92
Table 3.8-5 Farm Statistics - 1982 and 1987 . . „ 93
Table 3.8-6 Enrollment in Stillwater County Schools March 31, 1991 96
Table 3.8-7 Average Daily Traffic: FAS 419, FAS 420, FAP 78 99
Table 3.8-8 Residence Area for Stillwater Mining Company Employees (3/31/91) 100
Table 4.2-1 Summary of Effluent Limits^ in SMC Surtax Water Discharge Permit 118
Table 4 2-2 Projected Surface Water Quality from Direct Discharge for Alternative 4a 119
Table 4.2-3 Projected Groundwater Quality from Discharge to SVP Percolation Ponds for
Alternative 4a 120
Table 4.2-4 Projected Surface Water Quality Changes from Discharge ofAdit Water to SVR
Percolation Ponds 121
Table 4.2-5 Application Rate in Pounds per Acre at SMC and EPA Recommended
Cumulative Limits for Agricultural Croplands 122
,
Table 4.2-6 Projected Surface Water Quality from Direct Discharge Under Instream Values
Requested in Petition 123
Table 4.2-7 Projected Groundwater Quality from Discharge to SVR Percolation Ponds 124
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Table 4.2-8 Projected Surface Water Quality from Discharge of Adit Water to SVR
Percolation Ponds 124
Table 4.2-9 Application Rate in Pounds Per Acre Under Alternative 4b and Percent Increase
Relative to No Action 125
Table 4.3-1 Alternative 3a. Soil Loss Calculations for a 50 percent (2:1) slope with an
embankment height of 141 feet. Final reclamation success assuming 50
percent canopy cover, 50 percent rock fragments on the surface, and total
ground cover of60 percent 135
Table 4.5-1 Total Particulate Emissions - Worst-Case Annual Period 146
Table 4.8-1. Projected Mine-Related Vehicle Traffic per Day 157
Table 5.0-1 Summary ofAlternatives 164
VII