INTERIM RECORD OF DECISION
FOR
BONITA PEAK MINING DISTRICT SUPERFUND SITE
OPERABLE UNIT 1
SAN JUAN COUNTY, COLORADO
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INTERIM RECORD OF DECISION
BONITA PEAK MINING DISTRICT SUPERFUND SITE
OPERABLE UNIT 1
SAN JUAN COUNTY, COLORADO
The U.S. Environmental Protection Agency (EPA), with the concurrence of the Colorado
Department of Public Health and Environment (CDPHE), presents this interim record of decision
(IROD) for Operable Unit (OU) 1 of the Bonita Peak Mining District Superfund Site (Site) in San
Juan County, Colorado. The IROD is based on the administrative record for OU1, including the
preliminary remedial investigation (RI) and focused feasibility study (FFS), the proposed plan, the
public comments received, and EPA responses. The IROD presents a brief summary of the Site
characterization, past response actions, actual and potential risks to human health and the
environment, and the selected interim remedy. EPA followed the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA), as amended by the Superfund
Amendments and Reauthorization Act of 1986, the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP), and EPA guidance (EPA 1999) in preparing the IROD. The
three purposes of the IROD are to:
1. Certify that the remedy selection process was carried out in accordance with the
requirements of CERCLA, 42 United States Code (U.S.C.) § 9601 et seq., as amended,
and, to the extent practicable, the NCP;
2. Outline the components and remediation requirements of the selected interim remedy;
and
3. Provide the public with a consolidated source of information about the history,
characteristics, and risk posed by the conditions at OU1, as well as a summary of the
cleanup alternatives considered, their evaluation, the rationale behind the selected interim
remedy, and the agencies' consideration of, and responses to, the comments received.
The IROD is organized in three distinct parts:
1. Part 1 (Declaration) functions as an abstract and data certification sheet for the key
information in the IROD and includes the formal authorizing signature page for the
IROD.
2. Part 2 (Decision Summary) provides an overview of the characteristics of OU1,
alternatives evaluated, and the analysis of those options. It also identifies the selected
interim remedy and explains how the remedy fulfills statutory and regulatory
requirements.
3. Part 3 (Responsiveness Summary) serves the dual purpose of presenting stakeholder
concerns about OU1 and preferences regarding the remedial alternatives, and explaining
how those concerns were addressed and how the preferences were factored into the
remedy selection process.
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DECLARATION
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DECLARATION
SITE NAME AND LOCATION
The Bonita Peak Mining District Superfund Site (Site) (Superfund Enterprise Management
System [SEMS] #CON000802497) is centered in southwestern Colorado in San Juan County.
Within the Site, there are three main drainages (Mineral Creek, Cement Creek, and Upper
Animas River), which flow into the Animas River at Silverton, Colorado. The three main
drainages within the Site contain over 400 abandoned or inactive mines, where large- to small-
scale mining operations occurred. The Site listing on the National Priorities List identifies 48
mining-related sources. The 48 mining-related sources were identified as sources or potential
sources for contaminated media affecting the three main drainages. In addition, two dispersed
campsites have been identified that contain contaminated media.
The Site is currently organized into three operable units (OUs):
• OU1: Site-wide - OU1 encompasses the entire Bonita Peak Mining District Superfund
Site.
• OU2: Mayflower - OU2 includes the Mayflower Tailing Ponds No. 1, No. 2, No. 3, and
No. 4 and the Mayflower Mill and Tailings Study Area.
• OU3: Bonita Peak Groundwater System - OU3 generally includes the saturated and
unsaturated workings of the Sunnyside Mine, associated drainage and haulage tunnels,
nearby mines not known to be connected to the Sunnyside Mine by workings (e.g. Red &
Bonita Mine and Gold King Mine), and the surrounding geographic area that may be
hydraulically connected or influenced by current and/or historical releases from or
management of these mines.
EPA is taking an adaptive management approach to the Site, and data and observations from the
initial characterization identified 26 mining-related sources (including two dispersed campsites)
with contaminant migration issues that could be initially addressed through interim remedial
actions (IRAs) while the Site-wide remedial investigation (RI) is ongoing. Due to minor
modifications from the focused feasibility study, as described in Section 12 of the decision
summary (Part 2), the selected interim remedy applies to 23 mining-related sources. Each of the
23 mining-related sources (including the two dispersed campsites) identified within this interim
record of decision (IROD) are part of OU1.
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected interim remedy for OU1. The remedy selected in
this IROD was chosen in accordance with the Comprehensive Environmental Response,
Compensation and Liability Act (CERCLA) of 1980, as amended by the Superfund Amendments
and Reauthorization Act of 1986, and the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP). The decision is based on the administrative record file for OU1 of the
Site. This document is issued by EPA Region 8, the lead agency, and the Colorado Department
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of Public Health and Environment (CDPHE), the support agency. EPA and CDPHE concur on
the selected interim remedy presented herein.
ASSESSMENT OF SITE
The IRAs selected in this IROD are necessary to protect the public health and welfare and the
environment from actual or threatened releases of hazardous substances into the environment.
DESCRIPTION OF SELECTED INTERIM REMEDY
The selected interim remedy will provide protection of human health and the environment in the
short term and is intended to provide adequate protection until subsequent remedies are selected.
The selected interim remedy addresses mine portal mining-influenced water (MIW) discharges,
mining-related source/storm water interactions, mine portal pond sediments, in-stream mine
wastes, and mining-impacted recreation staging areas. The selected interim remedy includes the
following five IRAs:
• The mine portal MIW discharges IRA involves construction of diversion and isolation
components to route mine portal MIW discharge around contaminated mine waste with
the potential for interaction and co-mingling at mining-related sources.
• The mining-related source/storm water interactions IRA involves construction of
diversion and isolation components to route stormwater around mine portals and/or
contaminated mine waste with the potential for interaction and co-mingling at mining-
related sources.
• The mine portal pond sediments IRA involves excavating existing sediment and repairing
berms within mine portal ponds to allow continued pond function.
• The in-stream mine wastes IRA involves excavating in-stream mine wastes at mining-
related sources that impede flow or are susceptible to erosion or leaching of
contaminants.
• The mining-impacted recreation staging areas IRA involves containment/isolation of
mine wastes within mining-impacted recreation staging areas (i.e., dispersed campsites),
using covers to reduce disturbances of mine wastes and migration of contaminants.
The selected interim remedy also includes common elements that would be required to
implement all five IRAs. Examples of these common elements include, but are not limited to,
pre-construction surveys, erosion and sediment control measures, dust suppression, access road
improvements (as necessary), generation of uncontaminated borrow for construction of remedial
components and access roads, and implementation of institutional controls.
STATUTORY DETERMINATIONS
The selected interim remedy meets the mandates of CERCLA § 121 and the NCP. The selected
interim remedy will provide protection of human health and the environment in the short term
until subsequent remedies are selected. It will comply with all federal and state requirements that
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are applicable or relevant and appropriate to the IRAs or invoke CERCLA applicable or relevant
and appropriate requirement (ARAR) waivers. The selected interim remedy is also cost effective.
Permanent solutions and alternative treatment technologies or resource recovery technologies are
not a component of the selected interim remedy. The selected interim remedy is only an interim
solution for OU1. Permanent solutions and alternative treatment technologies or resource
recovery technologies will be addressed as part of the final remedy for the Site.
Treatment was not chosen as a component of the selected interim remedy. Because this action
does not constitute the final remedy for OU1, the statutory preference for remedies that employ
treatment that reduce toxicity, mobility, or volume as a principal element will be addressed by the
final response action.
While the Site-wide RI and risk assessments are ongoing, it is assumed that the selected interim
remedy will not result in unlimited use and unrestricted exposure land use scenarios. Because
this remedy will result in hazardous substances, pollutants, or contaminants remaining on site
above levels that allow for unlimited use and unrestricted exposure, a statutory review will be
conducted no less often than each 5 years to ensure that the remedy is, or will be, protective of
human health and the environment.
RECORD OF DECISION DATA CERTIFICATION CHECKLIST
The following information is included in the decision summary section (Part 2) of this IROD:
• Chemicals of potential concern (COPCs) and their respective concentrations (Section 5.0
- Summary of Site Characteristics; Appendix A - Preliminary Remedial Investigation
Report);
• Current and reasonably anticipated future land use assumptions used in the risk
memoranda (Section 6.0 - Current or Reasonably Anticipated Future Land and Resource
Uses; Section 7.0 - Summary of Site Risks);
• Risks represented by the COPCs (Section 7.0 - Summary of Risks; Appendix B - Risk
Assessment Information);
• Cleanup levels established for the COPCs and the basis for the levels (Section 8.0 -
Remedial Action Objectives and Remedial Goals);
• How source materials constituting principal threats are addressed (Section 11.0 —
Principal Threat Wastes; Section 12.0 - Selected Interim Remedy);
• Potential land use that will be available at the Site as a result of the selected interim
remedy (Section 12.0 - Selected Interim Remedy);
• Estimated capital, annual operations and maintenance (O&M), and total present value
costs; discount rate; and the number of years over which the remedy cost estimates are
projected (Section 12.0 - Selected Interim Remedy); and
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• Key factors that led to selecting the remedy (Section 12.0 - Selected Interim Remedy;
Section 14.0 - Statutory Determinations).
Additional information can be found in the administrative record file for this Site (SEMS
#CON000802497), available on EPA's BPMD website.
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AUTHORIZING SIGNATURES
j '¦ . ; v.. _ 1
Bcis\ Sniidm^er, Director Date
Superfimd and Emergency Management Division
U.S. EPA Region 8
Jennifer Opila. Division Director Date
Hazardous Materials and Waste Management Division
Colorado Department of Public ! (ealth and Environment
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DECISION SUMMARY
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TABLE OF CONTENTS
1.0 INTRODUCTION 1
1.1 BASIS 01 INTERIM ACTIONS 1
1.2 SITE DESCRIPTION 2
1.3 INTERIM RECORD OF DECISION FORMAT 3
2.0 SITE HISTORY AND RESPONSE ACTIVITIES 5
2.1 SITE BACKGROUND AM) HISTORY 5
2.1.1 S ite Mining History 5
2.2 RESPONSE ACTIVITIES 5
2.2.1 Listing on the National Priorities List 5
2.2.2 Summary of Previous Cleanup Actions 5
2.2.2.1 Mine Portal MIW Discharges 6
2.2.2.2 Mine Portal Pond Sediments 6
2.2.3 Summary of Site Investigations 7
2.2.3.1 1996-2000 USGS Sampling and Analysis 7
2.2.3.2 1997-1999 CDMG Sampling 7
2.2.3.3 2015 EPA/ESAT Sampling 8
2.2.3.4 2016 EPA/ESAT Sampling 8
3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION 10
3.1 INTERVIEWS AND COMMUNITY INVOLVEMENT PLAN 10
3.2 INFORMATION REPOSITORIES 10
3.3 SUPPORT FOR COMMUNITY GROUPS 10
3.4 FACT SHEETS 11
3.5 PUBLISHED ADVERTISEMENTS 11
3.6 PUBLIC MEETINGS AND AVAILABILITY SESSISONS 11
3.7 PROPOSED PLAN, PUBLIC MEETING, AND PUBLIC COMMENT PERIOD
11
3.8 IROI) RESPONSIVENESS SUMMARY 12
3.9 ADDITIONAL COMMUNITY ENGAGEMENT 12
4.0 SCOPE AND ROLE OF RESPONSE ACTIONS 13
4.1 OVERALL STRATEGY AND RELATIONSHIP OF OPERABLE UNITS ... 13
4.2 APPROACH FOR INTERIM REMEDIAL ACTIONS 13
4.2.1 Mine Portal MIW Discharges 14
4.2.2 Mining-Related Source/Storm water Interactions 14
4.2.3 Mine Portal Pond Sediments 14
4.2.4 In-Stream Mine Wastes 15
4.2.5 Mining Impacted Recreation Staging Areas 15
4.2.6 Documentation Supporting IRAs 15
5.0 SUMMARY OF SITE CHARACTERISTICS 17
5.1 SITE OVERVIEW 17
5.1.1 S ite Location and Topography 17
5.1.2 Climate 17
5.1.3 Geology 18
5.1.4 Surface Water Hydrology 18
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5.1.5 Subsurface Hydrogeology 19
5.1.6 Conceptual Site Model 19
5.2 SAMPLING STRATEGY 20
5.3 TYPES OF CONTAMINATION AND KNOWN POTENTIAL ROUTES OF
MIGRATION 20
5.3.1 Media 20
5.3.1.1 Solid Media 20
5.3.1.2 Aqueous Media 21
5.3.2 Overview of Fate and Transport 21
5.3.3 Fate and Transport Pathways Related to IRA Implementation 23
5.3.3.1 Mine Portal MIW Discharges 23
5.3.3.2 Mining -Related S ource/ Storm water Interactions 23
5.3.3.3 Mine Portal Pond S ediments 23
5.3.3.4 In-Stream Mine Wastes 23
5.3.3.5 Mining-Impacted Recreation Staging Areas 23
5.4 SOURCE AND NATURE OF CONTAMINATION 24
5.4.1 Summary of Drainage Basins 25
5.4.1.1 Mineral Creek Drainage Basin 25
5.4.1.2 Cement Creek Drainage Basin 25
5.4.1.3 Upper Animas River Drainage Basin 25
5.4.2 Summary of Mining-Related Source by IRAs 26
5.4.2.1 Mine Portal MIW Discharge 26
5.4.2.2 Mining-Related Source/Stormwater Interactions 29
5.4.2.3 Mine Portal Pond Sediments 30
5.4.2.4 In-Stream Mine Wastes 32
5.4.2.5 Mining-Impacted Recreation Staging Areas 32
6.0 CURRENT AND REASONABLY ANTICIPATED FUTURE LAND AND
RESOURCE USES 34
6.1 LAND USE 34
6.1.1 Surrounding Land Use and Population 34
6.2 GROUNDWATER AND SURFACE WATER USE 34
7.0 SUMMARY OF RISKS 35
7.1 HUMAN HEALTH AND ECOLOGICAL RISK 35
7.1.1 Potential Receptors 35
7.1.2 Exposure Pathways 35
7.1.3 Summary of Human Health Risk 35
7.1.4 Summary of Ecological Risk 37
7.2 BASIS OF ACTION 38
7.2.1 Human Health Risk 38
7.2.2 Ecological Risk 38
8.0 REMEDIAL ACTION OBJECTIVES AND CLEANUP LEVELS 39
8.1 REMEDIAL ACTION OBJECTIVES 39
8.1.1 Mine Portal MIW Discharges 39
8.1.2 Mining -Related S ource/ Storm water Interactions 39
8.1.3 MinePortalPondS ediments 39
8.1.4 In-Stream Mine Wastes 40
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8.1.5 Mining-Impacted Recreation Staging Areas 40
8.2 CLEANUP CRITERIA 40
8.2.1 Human Health Cleanup Levels 40
8.2.2 Ecological Remedial Clearance Criteria 40
9.0 DESCRIPTION OF ALTERNATIVES 42
9.1 SUMMARY OF GENERAL RESPONSE ACTIONS, REMEDIAL
TECHNOLOGIES, AND PROCESS OPTIONS CONSIDERED DURING
ALTERNATIVE DEVELOPMENT 42
9.2 DEVELOPMENT OF REMEDIAL ALTERNATIVES 44
9.3 COMMON ELEMENTS BETWEEN REMEDIAL ALTERNATIVES 45
9.3.1 Pre-Construction Common Elements 45
9.3.2 Construction Common Elements 45
9.3.3 Post-Construction Common Elements 45
9.3.4 Annual or Periodic Monitoring Common Elements 46
9.4 DESCRIPTION OF REMEDIAL ALTERNATIVES FOR MINE PORTAL MIW
DISCHARGES 46
9.4.1 Alternative A1: No Action 46
9.4.2 Alternative A2: Diversion/Isolation 47
9.5 DESCRIPTION OF REMEDIAL ALTERNATIVES FOR MINING-RELATED
SOURCE/STORMWATER INTERACTIONS 49
9.5.1 Alternative B1: No Action 49
9.5.2 Alternative B2: Stormwater Diversion/Isolation 50
9.6 DESCRIPTION OF REMEDIAL ALTERNATIVES FOR MINE PORTAL
POND SEDIMENTS 52
9.6.1 Alternative CI: No Action 52
9.6.2 Alternative C2: Excavation and Interim Local Waste Management 53
9.7 DESCRIPTION OF REMEDIAL ALTERNATIVES FOR IN-STREAM MINE
WASTES 55
9.7.1 Alternative D1: No Action 55
9.7.2 Alternative D2: Excavation and Interim Local Waste Management 56
9.8 DESCRIPTION OF REMEDIAL ALTERNATIVES FOR MINING-IMPACTED
RECREATION STAGING AREAS 58
9.8.1 Alternative El: No Action 58
9.8.2 Alternative E2: Containment/Isolation 59
10.0 COMPARATIVE ANALYSIS OF ALTERNATIVES 62
10.1 COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES FOR MINE
PORTAL MIW DISCHARGES (ALTERNATIVES A1 AND A2) 62
10.1.1 Overall Protection of Human Health and the Environment 62
10.1.2 Compliance with ARARs 63
10.1.3 Long-Term Effectiveness and Permanence 65
10.1.4 Reduction of Toxicity, Mobility, or Volume through Treatment 66
10.1.5 Short-Term Effectiveness 66
10.1.6 Implementability 67
10.1.7 Cost 67
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10.2 COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES FOR
MINING-RELATED SOURCE/STORMWATER INTERACTIONS
(ALTERNATIVES B1 AND B2) 67
10.2.1 Overall Protection of Human Health and the Environment 67
10.2.2 Compliance with ARARs 68
10.2.3 Long-Term Effectiveness and Permanence 70
10.2.4 Reduction of Toxicity, Mobility, or Volume through Treatment 70
10.2.5 Short-Term Effectiveness 71
10.2.6 Implementability 71
10.2.7 Cost 71
10.3 COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES FOR MINE
PORTAL POND SEDIMENTS (ALTERNATIVES CI AND C2) 72
10.3.1 Overall Protection of Human Health and the Environment 72
10.3.2 Compliance with ARARs 72
10.3.3 Long-Term Effectiveness and Permanence 75
10.3.4 Reduction of Toxicity, Mobility, or Volume through Treatment 75
10.3.5 Short-Term Effectiveness 76
10.3.6 Implementability 76
10.3.7 Cost 77
10.4 COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES FOR IN-
STREAM MINE WASTES (ALTERNATIVES 1)1 AND D2) 77
10.4.1 Overall Protection of Human Health and the Environment 77
10.4.2 Compliance with ARARs 78
10.4.3 Long-Term Effectiveness and Permanence 80
10.4.4 Reduction of Toxicity, Mobility, or Volume through Treatment 81
10.4.5 Short-Term Effectiveness 81
10.4.6 Implementability 81
10.4.7 Cost 82
10.5 COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES FOR
MINING-IMPACTED RECREATION STAGING AREAS (ALTERNATIVES
El ANDE2) 82
10.5.1 Overall Protection of Human Health and the Environment 82
10.5.2 Compliance with ARARs 83
10.5.3 Long-Term Effectiveness and Permanence 85
10.5.4 Reduction of Toxicity, Mobility, or Volume through Treatment 85
10.5.5 Short-Term Effectiveness 85
10.5.6 Implementability 86
10.5.7 Cost 86
10.6 MODIFYING CRITERIA 88
10.6.1 State Acceptance 88
10.6.2 Community Acceptance 88
10.6.3 Modifications Made as a Result of Comments 88
11.0 PRINCIPAL THREAT WASTES 89
12.0 SELECTED INTERIM REMEDY 90
12.1 MINE PORTAL VIIW DISCHARGES 90
12.1.1 Short Description of the Selected Interim Remedy 90
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12.1.2 Rationale for the Selected Interim Remedy 91
12.1.3 Detailed Description of the Selected Interim Remedy 91
12.1.4 Estimated Cost of the Selected Interim Remedy 93
12.1.5 Expected Outcomes of the Selected Interim Remedy 93
12.2 MINING-RELATED SOURCE/STORMWATER INTERACTIONS 94
12.2.1 Short Description of the Selected Interim Remedy 94
12.2.2 Rationale for the Selected Interim Remedy 94
12.2.3 Detailed Description of the Selected Interim Remedy 94
12.2.4 Estimated Cost of the Selected Interim Remedy 96
12.2.5 Expected Outcomes of the Selected Interim Remedy 96
12.3 MINE PORTAL POND SEDIMENTS 97
12.3.1 Short Description of the Selected Interim Remedy 97
12.3.2 Rationale for the Selected Interim Remedy 97
12.3.3 Detailed Description of the Selected Interim Remedy 97
12.3.4 Estimated Cost of the Selected Interim Remedy 99
12.3.5 Expected Outcomes of the Selected Interim Remedy 99
12.4 IN-STREAM MINE WASTES 100
12.4.1 Short Description of the Selected Interim Remedy 100
12.4.2 Rationale for the Selected Interim Remedy 100
12.4.3 Detailed Description of the Selected Interim Remedy 100
12.4.4 Estimated Cost of the Selected Interim Remedy 102
12.4.5 Expected Outcomes of the Selected Interim Remedy 102
12.5 MINING-IMPACTED RECREATION STAGING AREAS 103
12.5.1 Short Description of the Selected Interim Remedy 103
12.5.2 Rationale for the Selected Interim Remedy 103
12.5.3 Detailed Description of the Selected Interim Remedy 103
12.5.4 Estimated Cost of the Selected Interim Remedy 104
12.5.5 Expected Outcomes of the Selected Interim Remedy 105
13.0 INSTITUTIONAL AND LAND USE CONTROLS 106
13.1 INSTITUTIONAL AND LAND USE CONTROLS AT MINING-IMPACTED
RECREATION STAGING AREAS 106
13 .2 INSTITUTIONAL AND LAND USE CONTROLS FOR ENGINEERED
REMEDIAL FEATURES LIKELY TO BE PERMANENT 106
13.3 LAND USE RESTRICTIONS 107
14.0 STATUTORY DETERMINATIONS 108
14.1 MINE PORTAL VIIW DISCHARGES 108
14.1.1 Protection of Human Health and the Environment 108
14.1.2 Compliance with ARARs 108
14.1.2.1 Chemical-Specific ARARs 108
14.1.2.2 Location- and Action-Specific ARARs 109
14.1.2.3 ARARWaivers Ill
14.1.3 Cost Effectiveness Ill
14.1.3.1 Utilization of Permanent Solutions and Alternative Treatment (or
Resource Recovery) Technologies to the Maximum Extent
Practicable 112
14.1.3.2 Preference for Treatment as a Principal Element 112
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14.1.4 Five-Year Site Reviews 112
14.2 MINING-RELATED SOURCE/STORMWATER INTERACTIONS 113
14.2.1 Protection of Human Health and the Environment 113
14.2.2 Compliance with ARARs 113
14.2.2.1 Chemical-Specific ARARs 113
14.2.2.2 Location- and Action-Specific ARARs 113
14.2.2.3 ARAR Waivers 115
14.2.3 Cost Effectiveness 115
14.2.4 Utilization of Permanent Solutions and Alternative Treatment (or Resource
Recovery) Technologies to the Maximum Extent Practicable 116
14.2.5 Preference for Treatment as a Principal Element 116
14.2.6 Five-Year Site Reviews 117
14.3 MINE PORTAL POND SEDIMENTS 117
14.3.1 Protection of Human Health and the Environment 117
14.3.2 Compliance with ARARs 117
14.3.2.1 Chemical-Specific ARARs 117
14.3.2.2 Location- and Action-Specific ARARs 117
14.3.2.3 ARAR Waivers 120
14.3.3 Cost Effectiveness 120
14.3.4 Utilization of Permanent Solutions and Alternative Treatment (or Resource
Recovery) Technologies to the Maximum Extent Practicable 121
14.3.5 Preference for Treatment as a Principal Element 121
14.3.6 Five-Year Site Reviews 121
14.4 IN-STREAM MINE WASTES 122
14.4.1 Protection of Human Health and the Environment 122
14.4.2 Compliance with ARARs 122
14.4.2.1 Chemical-Specific ARARs 122
14.4.2.2 Location- and Action-Specific ARARs 122
14.4.2.3 ARAR Waivers 124
14.4.3 Cost Effectiveness 125
14.4.4 Utilization of Permanent Solutions and Alternative Treatment (or Resource
Recovery) Technologies to the Maximum Extent Practicable 126
14.4.5 Preference for Treatment as a Principal Element 126
14.4.6 Five-Year Site Reviews 126
14.5 MINING-IMPACTED RECREATION STAGING AREAS 126
14.5.1 Protection of Human Health and the Environment 127
14.5.2 Compliance with ARARs 127
14.5.2.1 Chemical-Specific ARARs 127
14.5.2.2 Location- and Action-Specific ARARs 127
14.5.2.3 ARAR Waivers 129
14.5.3 Cost Effectiveness 130
14.5.4 Utilization of Permanent Solutions and Alternative Treatment (or Resource
Recovery) Technologies to the Maximum Extent Practicable 130
14.5.5 Preference for Treatment as a Principal Element 130
14.5.6 Five-Year Site Reviews 131
15.0 DOCUMENTATION OF SIGNIFICANT CHANGES 132
16.0 REFERENCES 133
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LIST OF APPENDICES
Appendix A Preliminary Remedial Investigation Report
Part 1 Response to Public Comments - Preliminary Remedial Investigation
Report for the Bonita Peak Mining District
Part 2 Preliminary Remedial Investigation Report
Appendix B Risk Assessment Information
Part 1.1 A Risk Estimates for Trespass Camping Scenarios at Dispersed Campsites
Part 1.1B Interim Chronic Lead Risk Evaluation
Part 1.2 Human Health Acute Arsenic Screening Levels
Part 2 Ecological Risk Technical Memorandum
Appendix C Summary of Federal and State ARARs
LIST OF EXHIBITS
Exhibit 5-1 ARD and AMD Generation and Migration 22
Exhibit 5-2 Mining-Related Sources within Mineral Creek Drainage Basin 25
Exhibit 5-3 Mining-Related Sources within Cement Creek Drainage Basin 25
Exhibit 5-4 Mining-Related Sources within Upper Animas River Drainage Basin 26
Exhibit 5-5 Summary of Mining-Related Sources for the Mine Portal MIW Discharge IRA
26
Exhibit 5-6 Summary of Mining-Related Sources for the Mining-Related Source/
Stormwater Interactions IRA 29
Exhibit 5-7 Summary of Mining-Related Sources for the Mine Portal Pond Sediments IRA
31
Exhibit 5-8 Summary of Mining-Related Source for the In-Stream Mine Wastes IRA 32
Exhibit 5-9 Summary of Mining-Related Sources for the Mining-Impacted Recreation
Staging Areas IRA 33
Exhibit 9-1 Identified Remedial Technologies and Process Options for the Development of
Remedial Alternatives 43
Exhibit 9-2 Summary of Major Remedial Components and Associated Quantities for
Alternative A2 48
Exhibit 9-3 Summary of Major Remedial Components and Associated Quantities for
Alternative B2 51
Exhibit 9-4 Summary of Major Remedial Components and Associated Quantities for
Alternative C2 54
Exhibit 9-5 Summary of Major Remedial Components and Associated Quantities for
Alternative D2 57
Exhibit 9-6 Summary of Major Remedial Components and Associated Quantities for
Alternative E2 60
Exhibit 10-1 Summary of Comparative Analysis for Remedial Alternatives 87
Exhibit 12-1 Summary of Major Remedial Components and Associated Quantities for the
Mine Portal MIW Discharges Selected Interim Remedy 93
Exhibit 12-2 Summary of Major Remedial Components and Associated Quantities for the
Mining-Related Source/Storm water Interactions Selected Interim Remedy 96
Exhibit 12-3 Summary of Major Remedial Components and Associated Quantities for the
Mine Portal Pond Sediments Selected Interim Remedy 99
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Exhibit 12-4 Summary of Major Remedial Components and Associated Quantities for the In-
Stream Mine Wastes Selected Interim Remedy 101
Exhibit 12-5 Summary of Major Remedial Components and Associated Quantities for the
Mining-Impacted Recreation Staging Areas Selected Interim Remedy 104
LIST OF TABLES
Table 9-1A Matrix of Process Options for Mine Portal MIW Discharges Alternative
Development
Table 9-1B Matrix of Process Options for Mining-Related Source/Storm water Interactions
Alternative Development
Table 9-1C Matrix of Process Options for Mine Portal Pond Sediments Alternative
Development
Table 9-1D Matrix of Process Options for In-Stream Mine Wastes Alternative Development
Table 9-1E Matrix of Process Options for Mining-Impacted Recreation Staging Areas
Alternative Development
Table 12-1A Cost Estimate Summary for Mine Portal MIW Discharges IRA for the Selected
Interim Remedy
Table 12-1B Cost Estimate Summary for Mine Portal MIW Discharges IRA for the Selected
Interim Remedy - Brooklyn Mine
Table 12-2A Cost Estimate Summary for Mining-Related Source/Storm water Interactions IRA
for the Selected Interim Remedy
Table 12-2B Cost Estimate Summary for Mining-Related Source/Storm water Interactions IRA
for the Selected Interim Remedy - Brooklyn Mine
Table 12-3 A Cost Estimate Summary for Mine Portal Pond Sediments IRA for the Selected
Interim Remedy
Table 12-3B Cost Estimate Summary for Mine Portal Pond Sediments IRA for the Selected
Interim Remedy - Brooklyn Mine
Table 12-4 Cost Estimate Summary for In-Stream Mine Wastes IRA for the Selected Interim
Remedy
Table 12-5 Cost Estimate Summary for Mining-Impacted Recreation Staging Areas IRA for
the Selected Interim Remedy
LIST OF FIGURES
Figure 1-1 Site Vicinity Map
Figure 1-2 Mining-Related Sources - Mineral Creek Drainage Basin
Figure 1-3 Mining-Related Sources - Cement Creek Drainage Basin
Figure 1-4 Mining-Related Sources - Upper Animas Area Drainage Basin
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LIST OF ACRONYMS
AMD
acid-mine drainage
ARAR
applicable or relevant and appropriate requirement
ARD
acid-rock drainage
ATV
all-terrain vehicle
BLM
Bureau of Land Management
BMI
benthic macroinvertebrate
BMP
best management practice
BPMD
Bonita Peak Mining District
CAG
Community Advisory Group
CERCLA
Comprehensive Environmental Response, Compensation, and Liability Act
CCR
Colorado Code of Regulations
CDM Smith
CDM Federal Programs Corporation
CDMG
Colorado Division of Minerals and Geology
CDPHE
Colorado Department of Public Health and Environment
CDPS
Colorado Discharge Permit System
CFR
Code of Federal Regulations
cfs
cubic feet per second
CIP
community involvement plan
COPC
chemical of potential concern
C.R.S.
Colorado Revised Statutes
CSM
conceptual site model
EPA
U.S. Environmental Protection Agency
ESAT
Environmental Services Assistance Team
FEMA
Federal Emergency Management Agency
FFS
focused feasibility study
FRTR
Federal Remediation Technologies Roundtable
FS
feasibility study
GPS
Global Positioning System
HQ
hazard quotient
HUC
hydrologic unit code
IC
institutional control
IRA
interim remedial action
IROD
interim record of decision
LUC
land use control
MIW
mining-influenced water
MLRB
Mined Land Reclamation Board
NCP
National Oil and Hazardous Substances Pollution Contingency Plan
NGVD29
National Geodetic Vertical Datum of 1929
NO A A
National Oceanic and Atmospheric Administration
NPL
National Priorities List
O&M
operation and maintenance
OU
operable unit
PPE
personal protective equipment
RAO
remedial action objective
RCRA
Resource Conservation and Recovery Act
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RG
remediation goal
RI
remedial investigation
SEMS
Superfund Enterprise Management System
Site
Bonita Peak Mining District Superfund Site
TAG
technical assistance grant
TASC
Technical Assistance Services for Communities
TechLaw
TechLaw, Inc.
U.S.C.
United States Code
USFS
U.S. Forest Service
USFWS
U.S. Fish and Wildlife Service
USGS
U.S. Geological Survey
°F
degrees Fahrenheit
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1.0 INTRODUCTION
This interim record of decision (IROD) is for the Bonita Peak Mining District Superfund Site
(Site) (Superfund Enterprise Management System [SEMS] #CON000802497). The U.S.
Environmental Protection Agency (EPA) is the lead agency and the Colorado Department of
Public Health and Environment (CDPHE) is the support agency. Interim remedial actions (IRAs)
addressed in this IROD will be fund-financed. While the EPA will serve as the lead agency for
the IRAs, the U.S. Forest Service (USFS) will implement work at Brooklyn Mine, which is
located on lands managed by the U.S. Forest Service (USFS), as the lead agency for the purpose
of project management with funding from the U.S. Department of Agriculture. The Site is in
southwestern Colorado in San Juan County, where multiple mining-related contaminants have
been found in one or more media (surface water, sediment, soil, and waste rock) due to historic
mining activities.
This IROD is the decision document following a streamlined investigation and evaluation of
conditions at the Site. EPA's streamlined investigation and evaluation of conditions included
performing a preliminary remedial investigation (RI) and a focused feasibility study (FFS). The
preliminary RI report (included as Appendix A) includes a summary of the available data to
document the current understanding of the nature of mining-related contamination associated
with the 23 mining-related sources in the IROD. The FFS report presents the results of the
development and detailed evaluation of remedial alternatives.
The steps leading up to the IROD also included opportunities for public involvement, including
participating in a public meeting for and commenting on the proposed plan (issued June 14,
2018) during the 60-day public comment period following issuance.
This IROD documents EPA's selected interim remedy for contaminant migration issues
identified in the FFS. The next step in the Superfund process will be completing remedial
designs followed by implementing IRAs based on the selected interim remedy documented in
this IROD. Ultimately, a Site-wide RI, feasibility study (FS), and record of decision will be
completed in the future to provide a final remedial solution for the Site.
1.1 BASIS OF INTERIM ACTIONS
EPA is pursuing the use of an adaptive management approach for the Site. Adaptive
management is a formal and systematic site management approach that targets management and
resource decisions with the goal of incrementally reducing site uncertainties while supporting
continued site progress toward achieving protection of human health and the environment. At the
Site, this strategy allows for EPA to continue to address site uncertainties through an ongoing
Site-wide RI while using existing information to evaluate, select, and conduct response actions.
Data and observations from the ongoing Site-wide RI identified 26 mining-related sources
(including two dispersed campsites) with contaminant migration issues that could be initially
addressed through interim actions. As described in Section 12.0, due to minor modifications, the
selected interim remedy applies to 23 mining-related sources.
Interim actions are defined in A Guide to Preparing Superfund Proposed Plans, Records of
Decision, and Other Remedy Selection Decision Documents (EPA 1999) as those that are limited
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in scope and address contaminated areas or media that will also be addressed by a final remedial
action. Reasons for taking interim actions include the need to:
• Take quick action to protect human health and the environment from an imminent threat
in the short term while a final remedial solution is being developed; or
• Institute temporary measures to stabilize a site and/or prevent further migration of
contaminants or further environmental degradation.
As part of the adaptive management approach, the effectiveness of the IRAs will be assessed and
evaluated to inform the ongoing RI and future response actions.
1.2 SITE DESCRIPTION
The Site is centered in southwestern Colorado in San Juan County (Figure 1-1). Within the Site,
there are three main drainages (Mineral Creek, Cement Creek, and Upper Animas River), which
flow into the Animas River at Silverton as shown in Figures 1-2, 1-3, and 1-4. After the three
main drainages combine as the Animas River, it flows south from Silverton to Durango,
Colorado, crosses into New Mexico, and joins the San Juan River in Farmington, New Mexico.
The three main drainages within the Site contain over 400 abandoned or inactive mines, where
large- to small-scale mining operations occurred. The Site listing on the National Priorities List
(NPL) identifies 48 mining-related sources or potential sources for contaminated media affecting
the three main drainages (EPA 2016a). The contaminated media evaluated in this IROD include
solid media (i.e., mine waste, contaminated sediment, and contaminated soil) and aqueous media
(i.e., mining-influenced water [MIW] and surface water). The IROD addresses five different
contaminant migration issues:
• Mine portal MIW discharge
• Mining-related source/storm water interactions
• Mine portal pond sediments
• In-stream mine wastes
• Mining-impacted recreation staging areas
The Site is currently organized into three operable units (OUs):
• OU1: Site-wide - OU1 encompasses the entire Bonita Peak Mining District Superfund
Site.
• OU2: Mayflower - OU2 includes the Mayflower Tailing Ponds No. 1, No. 2, No. 3, and
No. 4 and the Mayflower Mill and Tailings Study Area.
• OU3: Bonita Peak Groundwater System - OU3 generally includes the saturated and
unsaturated workings of the Sunnyside Mine, associated drainage and haulage tunnels,
nearby mines not known to be connected to the Sunnyside Mine by workings (e.g. Red &
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Bonita Mine and Gold King Mine), and the surrounding geographic area that may be
hydraulically connected or influenced by current and/or historical releases from or
management of these mines.
Each of the 23 mining-related sources (including two dispersed campsites) identified are part of
OU1 and are the focus of this IROD.
1.3 INTERIM RECORD OF DECISION FORMAT
This IROD is organized in the following sections:
Part I: Declaration
Part II: Decision Summary
• Section 1.0- Introduction. Provides a brief introduction to the IROD.
• Section 2.0 - Site History and Response Activities. Provides a brief history of the Site
and EPA's activities at the Site.
• Section 3.0 - Highlights of Community Participation. Describes the range of community
outreach activities for the Site.
• Section 4.0 - Scope and Role of the Response Actions. Describes how the IRAs selected
for the Site fit into the overall scope of the Site and the OUs.
• Section 5.0 - Summary of Site Characteristics. Contains an overview of the Site and a
summary of the results of the preliminary RI.
• Section 6.0 - Current and Reasonably Anticipated Future Land and Resource Uses.
Describes land and resource uses.
• Section 7.0 - Summary of Risks. Discusses the human health and ecological risk
information.
• Section 8.0 - Remedial Action Objectives and Cleanup Levels. Discusses the remedial
action objectives and related cleanup levels developed by EPA to protect human health
and the environment at the Site.
• Section 9.0 - Description of Alternatives. Describes the remedial alternatives developed
and evaluated in the FFS for each contaminant migration issue, including a description of
remedy components, common elements, and expected outcomes.
• Section 10.0 - Comparative Analysis of Alternatives. Presents a summary of the remedial
alternatives for each contaminant migration issue that were retained for detailed analysis
in the FFS.
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• Section 11.0- Principal Threat Wastes. Discusses whether principal threat wastes were
identified for the IRAs and discusses how the selected interim remedy will prevent
exposure to such wastes.
• Section 12.0 - Selected Interim Remedy. Provides a detailed description of the selected
interim remedy consisting of IRAs for each contaminant migration issue, including its
components, cost, expected outcomes, performance standards, and compliance with
EPA's environmental justice mandate.
• Section 13.0 - Institutional and Land Use Controls. Describes the land use controls and
institutional controls that will be evaluated for the selected interim remedy.
• Section 14.0 - Statutory Determinations. Describes how the selected interim remedy is
protective of human health and the environment, complies with or appropriately waives
applicable or relevant and appropriate requirements (ARARs), is cost effective, and uses
permanent solutions and alternative treatment technologies or resource recovery
technologies to the maximum extent practicable.
• Section 15.0 - Documentation of Significant Changes. Confirms no significant changes
were made to the preferred alternatives outlined in the proposed plan prior to becoming
the selected interim remedy described in this IROD.
• Section 16.0 - References. Provides a list of references cited in the IROD.
Part III: Responsiveness Summary
• Section 1.0 - Summary of opportunities for public involvement surrounding the proposed
plan.
• Section 2.0 - Summary of quantitative information about the comments received—how
many stakeholders provided written comments, names of commenters serving in an
official capacity (e.g., state officials, Animas River Stakeholders Group), and what topics
raised the most comments, concerns, and questions. Topics where conflicting comments
were received are also noted.
• Section 3.0 - Summary of how EPA is responding or making changes to the proposed
plan on a general level.
• Section 4.0 - Summary (by topic) of significant comments received, both supportive and
non-supportive, and EPA's response. These are summarized by 16 primary categories of
comments.
• Section 5.0 - References. Provides a list of references cited in the IROD.
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2.0
SITE HISTORY AND RESPONSE ACTIVITIES
2.1 SITE BACKGROUND AND HISTORY
2.1.1 Site Mining History
The three main drainages within the Site contain over 400 abandoned or inactive mines, where
large- to small-scale mining operations occurred. San Juan County is comprised of 10 historic
mining districts (Colorado Geological Survey 2017). Historic mining districts within the Mineral
Creek, Cement Creek, and Upper Animas River drainages (referred to as "the mining districts")
include Animas, Animas Forks, Cement Creek, Eureka, Ice Lake Basin, and Mineral Point. A
map and descriptions of the historic mining districts are available on the Colorado Geological
Survey's website (http://coloradogeologicalsurvev.org/mineral-resources/historic-mining-
di stri cts/san-i uan-county/).
The following background information comes from an investigation document by TechLaw
(which supported the EPA/Environmental Services Assistance Team [ESAT]). Early mining
activities began in the 1870s with slow initial production of ore due to the high cost and difficult
access to the mines. In the late 1870s and early 1880s, the completion of roads, railroads, and
construction of a smelter in Durango encouraged mining operations. The discovery of silver in
the base-metal ores was the major factor in establishing Silverton as a permanent settlement
(TechLaw, Inc. [TechLaw] 2017).
Furthermore, improvements to methods of concentrating low-grade ore in both the 1890s and
late 1910s were implemented at the Sunnyside Mine to increase recovery of metals (Burbank and
Luedke 1969). Falling metal prices in the 1890s led to a decrease in mining, and numerous
smaller operations were forced to close. By 1900, there were 12 concentration mills in the valley
sending products to the Kendrick and Gelder Smelter near the mouth of Cement Creek. Mining
and milling operations slowed down circa 1905, and mines were consolidated into fewer and
larger operations with the facilities for milling large volumes of ore. After 1907, mining and
milling continued throughout the basin whenever prices were favorable (TechLaw 2017). The
major mining operations in the Eureka district included the Sunnyside and Gold King Mines
(Burbank and Luedke 1969). Sunnyside Mine shut down in 1930, reopened briefly in 1937-38,
and then remained inactive until new ownership resumed operation of the mine in 1959 (Burbank
and Luedke 1969; EPA 2016a). By the 1970s, only one year-round active mine (Sunnyside
Mine) remained in the county, which closed permanently in 1991 (TechLaw 2017; EPA 2016a).
2.2 RESPONSE ACTIVITIES
2.2.1 Listing on the National Priorities List
The Site was proposed for addition to the NPL in April 2016, and the listing became effective in
September 2016 (EPA 2016b).
2.2.2 Summary of Previous Cleanup Actions
EPA has been active at portions of the Site prior to the NPL listing. Response actions have
included efforts to control ongoing releases at the Gold King Mine and Red and Bonita Mine
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(EPA 2017 and EPA 2014, respectively). Past cleanup efforts at the mining-related sources
addressed in this IROD have been conducted by multiple parties (federal, state, and/or private).
The following subsections describe previous cleanup actions.
2.2.2.1 Mine Portal MIW Discharges
Past efforts to address mine portal MIW discharges at the Site have included the construction of
diversion channels and installation of piping to route MIW around mine waste. The following
mining-related sources have had past cleanup actions to address mine portal MIW discharges:
• Bandora Mine
• Brooklyn Mine
• Frisco/Bagley Tunnel
• Junction Mine
• Henrietta Mine
• Mammoth Tunnel
• Natalie/Occidental Mine
• Pride of the West Mine
• Silver Wing Mine
• Terry Tunnel
• Yukon Tunnel
While past cleanup efforts at these mining-related sources have included construction of
diversion channels and installation of piping, there is no indication that any follow-up
maintenance activities have been conducted.
2.2.2.2 Mine Portal Pond Sediments
Past cleanup efforts at numerous mining-related sources have included the construction of ponds
to aid in reducing chemicals of potential concern (COPCs) in MIW. The following mining-
related sources have had past cleanup actions related to mine portal pond sediments:
• Anglo Saxon Mine
• Brooklyn Mine
• Frisco/Bagley Mine
• Koehler Tunnel / Junction Mine
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• Mammoth Tunnel
• Silver Wing Mine
• Sunbank Group Mine
While past cleanup efforts at these mining-related sources have included construction of ponds,
there is no indication that any follow-up activities to remove accumulated sediments in the ponds
have been conducted.
2.2.3 Summary of Site Investigations
This section provides a summary and brief discussion of select previous sampling efforts and
Site investigations completed by ESAT, the U.S. Geological Survey (USGS), and the Colorado
Division of Minerals and Geology (CDMG), now known as the Colorado Division of
Reclamation, Mining and Safety (DRMS). Site investigations are ongoing; the data presented in
the preliminary RI (Appendix A) are not intended to provide a complete characterization of the
individual mining-related sources nor the complete nature and extent of contamination, but rather
provide information supporting IRAs for the mining-related sources addressed in this IROD.
2.2.3.1 1996-2000 USGS Sampling and Analysis
Investigations by USGS included field sampling of mine waste, mill tailings, and adit drainages
at mining-related sources in the Animas River, Cement Creek, and Mineral Creek basins, with
subsequent reporting (Church et al. 2007). A summary of the work is as follows:
• The purpose of the study was to describe the magnitude of contamination contributed by
mine-adit water, mine-waste dumps, and mill tailings on public land.
• Visits were conducted at more than 300 mines.
• Mine-waste dump and mill-tailings samples were collected from 97 mine waste dump
sites and 18 mill tailings sites, and 20 samples of unmined, altered rock were also
collected. These samples of mine-waste dump material, mill tailings, and altered rocks
were studied using a passive leach method.
• The size of mine-waste dumps at mines was estimated using length, width, and thickness.
• Surface water samples were collected at 108 mine portals and mine waste dumps.
• Annually, from 1997 to 2000, observations and sampling of mine adit locations was
conducted in late August or early September during low-flow conditions.
2.2.3.2 1997-1999 CDMG Sampling
Field sampling (and subsequent reporting) by CDMG of mines along the Animas River above
Eureka, and along the Animas River below Eureka and in the Cement Creek and Mineral Creek
basins, occurred between 1997 and 2000 (Herron et al. 1997, 1998, 1999, and 2000). A summary
of the work is as follows:
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Water samples were collected for metals, ions, and wet chemistry analyses for mines on
both public and private land.
• Flow measurements were collected concurrent with water samples.
• Baseline water quality samples were collected in October 1996, and February and June
1997, in Cement Creek.
• Waste rock and mill tailing samples were collected at a total of 138 mines in the Upper
Animas, Cement Creek, and Mineral Creek drainages.
• The mining wastes were investigated to provide information for prioritizing future mine
location reclamation activities to be performed by the Animas River Stakeholders Group.
2.2.3.3 2015 EPA/ESAT Sampling
Major 2015 EPA/ESAT field activities conducted at the Site (TechLaw 2016) and relevant to this
IROD include the following:
• June 9-10, 2015 - High-flow, real-time field water quality measurements, stream flow
data collection, surface water sampling, photographic documentation, and Global
Positioning System (GPS) coordinate collection.
• August 4-6, 2015 - Real-time field water quality measurements, surface water sampling,
soil/waste rock sampling, pore water sampling, sediment sampling, photographic
documentation, and GPS coordinate collection.
• September 22-26, 2015 - Low-flow, real-time field water quality measurements, stream
flow data collection, surface water sampling, pore water sampling, sediment sampling,
photographic documentation, and GPS coordinate collection.
2.2.3.4 2016 EPA/ESAT Sampling
With field support from stakeholders such as the Bureau of Land Management (BLM), DRMS,
and USFS, major 2016 EPA/ESAT field activities conducted at the Site (TechLaw 2017) and
relevant to this IROD include the following:
• June 6-9, 2016 - High-flow, low elevation, real-time field water quality measurements,
stream flow data collection, surface water sampling, photographic documentation, and
GPS coordinate collection.
• June 28-30, 2016 - High-flow, high elevation, real-time field water quality
measurements, stream flow data collection, surface water sampling, photographic
documentation, and GPS coordinate collection.
• July 25-29, 2016 - Waste rock, campground, and road soil sampling, photographic
documentation, and GPS coordinate collection.
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• September 27-30 and October 4-8, 2016 - Low-flow, real-time field water quality
measurements, stream flow data collection, surface water sampling, sediment sampling,
overbank soil sampling, pore-water sampling, photographic documentation, and GPS
coordinate collection.
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3.0
HIGHLIGHTS OF COMMUNITY PARTICIPATION
EPA is implementing a robust program of community participation at the Site that exceeds the
requirements of CERCLA. EPA began community involvement for the Site prior to the Site's
listing on the NPL in September 2016, and active community involvement related to the Site
continues today. A brief description of community involvement activities implemented at the
Site since 2015 is provided in the following subsection. All documents described are publicly
available on EPA's Bonita Peak Mining District (BPMD) website
(www.epa. gov/superfund/bonita-peak). along with updates on the Superfund process and coming
events, access to reports and plans, and Site contacts.
3.1 INTERVIEWS AND COMMUNITY INVOLVEMENT PLAN
In late 2016 and early 2017, EPA and CDPHE conducted community interviews with
stakeholders affected by the Site to obtain general information, identify community concerns and
issues, and determine how best to communicate with the public. Interviewees included local
officials and stakeholders from Silverton; San Juan County; Durango, Colorado; La Plata
County, and the Southern Ute Indian Tribe. Findings were supplemented with information
gathered during face-to-face interactions between EPA, CDPHE, and the communities.
Using the information from those interviews, a community involvement plan (CIP) was prepared
and distributed in August 2017 (CDM Federal Programs Corporation [CDM Smith] 2017). The
CIP is available on EPA's BPMD website.
3.2 INFORMATION REPOSITORIES
EPA Region 8 established two information repositories in Colorado and assisted EPA Regions 6
and 9 in establishing repositories in New Mexico and the Navajo Nation. The repositories contain
basic information for public review, documents about Site activities, technical documents, the
CIP, and general information about the Superfund program.
Information repositories are located at the:
• Silverton Public Library, 1117 Reese Street, Silverton, Colorado
• Durango Public Library, 1900 East Third Avenue, Durango, Colorado
• Farmington Public Library, 2101 Farmington Avenue, Farmington, New Mexico
• Dine College Shiprock Campus Library, 1228 Yucca Street, Shiprock, New Mexico
The administrative record is housed at the EPA Superfund Records Center in Denver, Colorado.
Information about the administrative record file and information repositories has been included
in Site fact sheets and on EPA's BPMD website.
3.3 SUPPORT FOR COMMUNITY GROUPS
EPA provided information about the availability of technical assistance to communities in
presentations and in writing. A community advisory group (CAG) was formed in January 2019
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to provide a forum for stakeholders and the Site team to share information and discuss issues
related to the Superfund decision-making process. There have been discussions in the
communities about forming an organization to apply for a technical assistance grant (TAG).
Community representatives have advised EPA that enough technical expertise is available within
the community to provide technical assistance as needed. EPA provided a technical advisor and a
technical expert to the Silverton/San Juan County Planning Group through the Technical
Assistance Services for Communities (TASC) program in 2016 and 2017.
The Silverton/San Juan County Planning Group is the entity comprised of local officials and
residents that provides Silverton and San Juan County the decision-making "seat at the table," as
requested by the Governor of Colorado, Silverton, and San Juan County in their letters to EPA
supporting the addition of the Site to the NPL. EPA coordinates with and involves the
Silverton/San Juan County Planning Group as much as possible in all phases of work and all
decisions concerning the Site.
3.4 FACT SHEETS
EPA prepares fact sheets for the Site that provide information to the community at key points. Fact
sheets are distributed electronically, via EPA's electronic mailing list and are available to the
public at EPA's BPMP website. Printed copies are distributed at public meetings. Examples of
fact sheets issued are Innovative Technologies, March 2018, and Interim Sludge Management
Questions and Answers, June 2018.
3.5 PUBLISHED ADVERTISEMENTS
EPA posts public notices in local newspapers about public comment opportunities, upcoming
events, and other Site-related information. These media outlets include the Silverton Standard,
the Durango Herald, the Durango Telegraph, and the Southern Ute Drum.
3.6 PUBLIC MEETINGS AND AVAILABILITY SESSISONS
EPA has prepared multiple presentations and handouts that provide specific information to the
public. As an example, EPA has hosted fall and spring public meetings in Colorado and New
Mexico, and at the Navajo Nation, to update community members about Site activities.
Presentations are available on EPA's BPMD website and include Virtual Tour of the Water
Treatment Plant at Gladstone, Colorado; BPMD Digging Deeper - Hydrology; BPMD Team
Biographies; BPMD Hydrology Path Forward; Summary of Superfund Resources Available to
Communities; and Introduction to Risk Assessment.
3.7 PROPOSED PLAN, PUBLIC MEETING, AND PUBLIC COMMENT PERIOD
EPA issued its Proposed Plan for Interim Remedial Actions on June 14, 2018. The proposed plan
was made available in electronic format at the four Site information repositories. An electronic
notice with links to relevant documents was posted on EPA's BPMD website throughout the
public comment period.
A public meeting for the proposed plan was held on June 21, 2018 in Silverton, Colorado. EPA
gave a brief presentation, and the public had an opportunity to provide oral and written comment.
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A stenographer provided transcription services for the meeting, and the transcript and a videotape
of the presentation were made available on EPA's BPMD website.
The 30-day public comment period for the proposed plan began on June 14, 2018, and was
extended for an additional 30 days (through August 15, 2018) at stakeholder request.
Announcement of the initial public comment period and public comment meeting were published
in the June Bonita Peak Mining District Update, which was sent to the Site's email list on June
14, 2018. A notice of the extension of the public comment period was sent to the Site's email list
July 16, 2018. Notices were also published in the Silverton Standard, the Durango Herald, the
Durango Telegraph, and the Southern Ute Drum.
3.8 IROD RESPONSIVENESS SUMMARY
This IROD includes the responsiveness summary for the proposed plan (Part 3 of this IROD).
3.9 ADDITIONAL COMMUNITY ENGAGEMENT
EPA has conducted other activities with the goal of engaging and informing the public. Those
activities include:
• Electronic Updates. EPA issues monthly updates of Site activities in the form of the
Bonita Peak Mining District Update. These two-page updates provide recent activities,
upcoming events, items new to the website, and more. Spanish-language versions are also
available. Past copies of the update are available to the public from the website.
• Early Release of Public Comment. In response to a media request, EPA released the
public comments received on its proposed plan prior to the issuance of this IROD. A fact
sheet documenting this release and the redacted comments are available on EPA's BPMD
website.
• Tours. EPA has conducted several tours specific to issues at the Site. These tours focused
on cultural resources, the Gladstone interim water treatment plant, and the mining-related
sources at the Site.
• BPMD Calendar. Beginning in May 2018, EPA posted a calendar of field activities on
EPA's BPMD website so local emergency managers and the public have easy access to
past, current, and planned activities.
• Emergency Alerts. EPA uses the 2017 Animas River Alert and Notification Plan to
communicate to participants events that affect the appearance of or water quality in the
Animas River. Plan participants include state and local emergency management agencies,
public health departments, downstream states and tribes, and local officials.
• Outreach Regarding Future Land Use. No formal process has been conducted to
solicit views from the public specifically regarding future land use; however, as noted in
Section 3.7, EPA has provided the public with opportunity to provide comments
regarding future land use during the public meeting and the public comment period.
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4.0
SCOPE AND ROLE OF RESPONSE ACTIONS
The following subsections describe the scope and role of the response actions within the overall
Site cleanup strategy and the relationship of the OUs.
4.1 OVERALL STRATEGY AND RELATIONSHIP OF OPERABLE UNITS
The Site is currently organized into three OUs as described in Section 1.2. Each of the 23
mining-related sources (including two dispersed campsites) identified within this IROD are part
of OU1. For purposes of this IROD and the overall strategy, an emphasis is placed on the three
main drainage basins that make up the Site (Mineral Creek drainage basin, Cement Creek
drainage basin, and Upper Animas River drainage basin), as discussed in detail in Section 5.4.
This IROD presents the selected interim remedy to address specific contaminant migration issues
at the mining-related sources identified in the initial characterization and could be addressed by
IRAs. These specific contaminant migration issues include:
• mine portal MIW discharges
• mining-related source/storm water interactions
• mine portal pond sediments
• in-stream mine wastes
• mining-impacted recreation staging areas
4.2 APPROACH FOR INTERIM REMEDIAL ACTIONS
The following subsections describe the relationship of contaminant migration issues that are
evaluated within this IROD. In addition, this subsection describes how the list of mining-related
sources were selected for this IROD.
The Site-wide RI and risk assessments are ongoing and will provide information to guide Site-
wide objectives. EPA is taking an adaptive management approach to the Site as described in
Section 1.1. Initial characterization identified 26 mining-related sources where IRAs may be
appropriate to reduce contributions from these mining-related sources that add to unacceptable
human health and ecological risks in the Animas River watershed at the Site in advance of
comprehensive remedial action. As described in Section 12.0, due to minor modifications, the
selected interim remedy applies to 23 mining-related sources. The actions evaluated in this IROD
are intended to address identified mining-related sources to reduce risk contaminant migration.
These actions have secondary benefit of reducing variability during the ongoing RI. Performance
data from the IRAs will be collected and evaluated to inform the ongoing Site-wide RI and future
response actions. The following subsections provide a description of each contaminant migration
issue addressed in this IROD and the rationale for inclusion.
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4.2.1 Mine Portal MIW Discharges
MIW is problematic when discharged from a mine portal or opening that is partially obstructed
by environmental media or debris. This issue also occurs where there is a clear interaction
between mine wastes that exceed ecological risk-based screening levels, as discussed in the
preliminary RI, and discharged mine portal MIW. Previously installed safety measures (e.g.,
grates) and engineered barriers (e.g., bulkheads) are not considered for this category.
The discharge of MIW onto adjacent mine wastes could increase the potential for erosion or
mass wasting of COPCs in particulate form and/or cause leaching of COPCs from the mine
wastes, which contribute to unacceptable ecological risks. Obstructions to MIW discharges from
mine portals also have the potential to impound MIW, sediments, and precipitates within
unstable mine workings. If discharge from the mine portal is partially obstructed, it has a
potential to create an unstable impoundment of MIW, sediments, and metal precipitates of
limited depth. While the minimal depth of that impoundment due to a partial obstruction would
not result in flooded mine workings and buildup of significant hydraulic head that results in
catastrophic releases, there could be enough MIW and sediment buildup after removing a partial
obstruction in a temporary surge of flow to surface water with COPCs further contributing to
unacceptable ecological risks.
The specific mining-related sources evaluated in this IROD for mine portal MIW discharges are
identified in Section 5.4.2.1.
4.2.2 Mining-Related Source/Stormwater Interactions
Upgradient stormwater generated from falling or stored precipitation (e.g., snowmelt) is
problematic when it interacts with mine waste that exceeds ecological risk-based screening levels
or interacts with (enters) a mine portal.
Co-mingling of stormwater and mining-related sources could lead to transport of COPCs to
surface water, which contribute to unacceptable ecological risks. This transport could occur due
to erosion or mass wasting of contaminants in particulate form, and/or infiltration of the
stormwater and generation of MIW.
The specific mining-related sources evaluated in this IROD for mining-related source/stormwater
interactions are identified in Section 5.4.2.2.
4.2.3 Mine Portal Pond Sediments
Sediments that exceed ecological risk-based screening levels, as discussed in the preliminary RI,
are problematic when the sediments have been deposited within the horizontal extent of mine
portal ponds. Sediment within mine portal ponds is partially formed when metals settle out of
mine portal MIW discharge through either the formation of iron oxy-hydroxides and subsequent
co-precipitation (as with arsenic), or through the physical settling of undissolved metals.
Mine portal ponds with significant sediment accumulation have reduced operational capacity
(e.g., storage space), which affects MIW detention time for settling of sediments and precipitates.
Reduced capacities in the mine portal ponds also increase the likelihood for "short circuiting,"
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where MIW bypasses the pond or passes to the next pond in the series without sufficient
retention time. The accumulated sediments in ponds also have the potential for uncontrolled
release of COPCs (both in particulate form and MIW) to surface water during storm events,
contributing to unacceptable ecological risks.
The specific mining-related sources evaluated in this IROD for mine portal pond sediments are
identified in Section 5.4.2.3.
4.2.4 In-Stream Mine Wastes
In-stream mine wastes are mine wastes entirely within a stream are problematic when the in-
stream mine wastes exceed ecological risk-based screening levels, as discussed in the
preliminary RI. In-stream mine wastes impede the flow of surface water in streams, increasing
the potential for erosion or mass wasting of contamination in particulate form and/or leaching of
COPCs from mine wastes to surface water, which contribute to unacceptable ecological risks.
The specific mining-related sources evaluated in this IROD for in-stream mine wastes are
identified in Section 5.4.2.4.
4.2.5 Mining Impacted Recreation Staging Areas
Mining-impacted recreation staging areas occur at mining-related sources used for camping related
to staging for recreational uses (e.g., established campgrounds or dispersed campsites) within 1,000
feet of U.S. Highway 550 (Mineral Creek), San Juan County Road 110 (Cement Creek), and San
Juan County Road 2 (Upper Animas River), and adjacent to a pond or stream. A "dispersed"
campsite is an area that is suitable for camping or where camping is known to occur but may not be a
formal campground. These mining-related sources have mine waste or contaminated soil that exceed
applicable human health risk-based levels for arsenic or lead presented in Appendix B, Part 1.
Recreation staging uses that are sedentary, such as camping, result in repeated surface disturbances
that result in potential exposures of recreational human receptors to arsenic or lead.
Camping at mining-impacted recreation staging areas causes repeated disturbances of mine
wastes and contaminated soils that could result in exposure to arsenic through incidental
ingestion or lead through inhalation and ingestion. Many of these areas are attractive to
recreational visitors because they are often flat and unvegetated, perhaps indicating to the visitor
that these barren areas are supposed to be used. Contributions to human health risks (from lead
under chronic exposure scenario or arsenic under acute exposure scenario) from mine wastes and
contaminated soils at recreation staging areas could occur due to camping or other sedentary
activities.
The specific mining-related sources evaluated in this IROD for mining-impacted recreation
staging areas are identified in Section 5.4.2.5.
4.2.6 Documentation Supporting IRAs
IRAs are addressed in two EPA guidance documents: A Guide to Preparing SuperfundProposed
Plans, Records of Decision, and Other Remedy Selection Decision Documents (EPA 1999) and
Role of the Baseline Risk Assessment in Superfund Remedy Selection Decisions (EPA 1991a).
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Interim actions do not require completed baseline risk assessments nor completed RI reports but
must have sufficient documentation to support the rationale for IRAs to fulfill the National Oil
and Hazardous Substances Pollution Contingency Plan's (NCP's) administrative record
requirements. Data sufficient to support IRA decisions in an IROD can be extracted from an
ongoing Site-wide RI and evaluated in an FFS that includes a short analysis of a limited number
of alternatives.
EPA prepared the FFS to evaluate a limited number of remedial alternatives for specific
contaminant migration issues. Because the contemplated alternatives are limited in scope, the
remedial technology/process option screening and alternative screening steps suggested for a
comprehensive FS are not needed. Information supporting the FFS included a preliminary RI and
human health/ecological risk information memoranda completed concurrently with the FFS,
which are included as Appendices A and B, respectively. This supporting information was used
to characterize conditions with respect to mining-related sources with identified contaminant
migration issues, determine the nature of contamination at the mining-related sources related to
these migration issues, and summarize unacceptable risks to human health and aquatic ecological
receptors posed by the migration of the contaminated media at these mining-related sources, to
the degree they have been identified.
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5.0
SUMMARY OF SITE CHARACTERISTICS
The summary of Site characteristics includes an overview of physical characteristics, and the
nature and extent of contamination. Additional details of the Site characteristics and the nature
and extent of contamination are presented in the preliminary RI (Appendix A).
5.1 SITE OVERVIEW
5.1.1 Site Location and Topography
The Site is centered in southwestern Colorado in San Juan County. The Site listing identifies 48
mining-related sources, which span across five different USGS 7.5-Minute Topographic
Quadrangles including Handies Peak, Howardsville, Ironton, Ophir, and Silverton (USGS 2016a
through 2016e). Within the Site, there are three main drainages (Mineral Creek, Cement Creek,
and Upper Animas River), which flow into the Animas River at Silverton as shown in Figures 1-2,
1-3, and 1-4. The 48 mining-related sources were identified as sources or potential sources for
contaminated media affecting the three main drainages (EPA 2016a). In addition, two dispersed
campsites have been identified that contain contaminated media.
Mineral Creek originates at the top of Red Mountain Pass and flows approximately 9.3 miles
before entering the Animas River southwest of Silverton. Cement Creek is approximately 8 miles
long, flowing from north to south before the confluence with the Animas River at Silverton
(Herron et al. 1998). The Upper Animas River begins approximately 14 miles northeast of
Silverton. After the three main drainages combine as the Animas River, it flows south from
Silverton to Durango, crosses into New Mexico, and joins the San Juan River in Farmington,
New Mexico.
Formed from Pleistocene glaciation and Holocene erosion, the terrain of the western San Juan
Mountains is steep and rugged (USGS 2007a). The elevation ranges from approximately 9,500
feet National Geodetic Vertical Datum of 1929 (NGVD29) at the Mayflower Tailings to 12,800
feet NGVD29 at the Mountain Queen Mine, the highest mining-related source at the Site.
5.1.2 Climate
The portions of the Site within San Juan County have a subalpine to alpine climate with snowy,
cold winters and cool summers. In the subalpine climate region, the minimum and maximum
mean temperatures for January and July are 2 degrees Fahrenheit (°F)/32°F and 40°F/74°F,
respectively (Chapman et al. 2006). In the alpine climate region, the minimum and maximum
mean temperatures for January and July are minus 8°F/24°F and 36°F/72°F, respectively
(Chapman et al. 2006).
Long-term climate data, including precipitation, for Silverton has been collected by a participating
National Weather Service Cooperative Observing Program weather station. The National Oceanic
and Atmospheric Administration (NOAA) has a record of climate data for the Silverton, Colorado
station dating back to 1905 (NOAA 2018). The weather station is currently located at a latitude of
37.809 North and a longitude of 107.663 West. In 2016, the Silverton station recorded annual
precipitation of approximately 19 inches (NOAA 2018). The greatest amount of snowfall is
between November and April, with an average snowfall of 12 feet per year (EPA 2016c).
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5.1.3 Geology
The geology of the Site within San Juan County is relevant to the assessment of the
hydrogeological framework and understanding of potential source materials present. Therefore,
this section focuses on the description of the bedrock geology. Section 1.1.5 of the preliminary RI
(included as Appendix A) provides additional details on the bedrock geology, ore mineralization,
and Site soils. Other aspects of the Site geology were described by Yager and Bove (USGS
2007a), Burbank and Luedke (1969), and Free et al. (1989).
The Site is centered in the western San Juan Mountains in the area of the Silverton and San Juan
calderas. The younger Silverton caldera is situated within the older San Juan caldera, forming
between approximately 28 and 27 million years ago (Ma) (USGS 2007a). During and after the
caldera formation period, volcanotectonic events occurred that introduced extensive Tertiary-aged
volcanic rock and extensive mineralization within fractured host rock (USGS 2007b). Volcanic
formations of the San Juan volcanic field cover land north and east of the Silverton caldera.
Comprised of pyroclastic rocks and lava flows, the San Juan volcanic field lies on the Paleozoic
and Mesozoic rock formation (Free et al. 1989).
5.1.4 Surface Water Hydrology
The Animas River watershed extends from the mountainous terrain in San Juan County,
Colorado, south into the San Juan River in Northern New Mexico (URS Operating Services
2012). The three major tributaries of the Animas River in San Juan County include Mineral
Creek (hydrologic unit code [HUC] 14081040103), Cement Creek (HUC 14081040102), and the
Upper Animas River (HUC 14081040101). Cement Creek enters the Upper Animas River on the
east side of Silverton. About 1 mile downstream from that confluence, Mineral Creek enters the
Upper Animas River south of town. Stream flow for the three major tributaries at USGS gaging
stations are summarized below, and the stream gaging station locations are shown on Figure 1-1.
• Mineral Creek Drainage Basin, USGS gaging station 09359010 (USGS 2018a)
o This USGS gaging station is located at Mineral Creek, immediately southwest of
Silverton. Mineral Creek confluences with the Animas River approximately 3/4 mile
downstream of this gaging station.
o The highest discharge occurs in June, with a monthly average flow of 389 cubic feet
per second (cfs).
o The lowest discharges occur throughout January and February, with monthly average
flows of 21 to 22 cfs, respectively.
• Cement Creek Drainage Basin, USGS gaging station 09358550 (USGS 2018b)
o This USGS gaging station is located at Cement Creek, immediately north of
Silverton. Mineral Creek confluences with the Animas River approximately XU mile
downstream of this gaging station.
o The highest discharge occurs in June, with a monthly average flow of 131 cfs.
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o The lowest discharges occur throughout January and February, with monthly average
flows of 13 cfs for both months.
• Upper Animas River Drainage Basin, USGS gaging station 09358000 (USGS 2018c)
o This USGS gaging station is located at the Animas River as it flows along the
southeastern edge of Silverton. Cement Creek's confluence with the Animas
River is approximately Vio mile downstream of this gaging station.
o The highest discharge occurs in June, with a monthly average flow of 503 cfs.
o The lowest discharges occur throughout January and February, with monthly average
flows of 24 to 26 cfs, respectively.
• Upper Animas River Drainage Basin, USGS gaging station 09359020 (USGS 2018d)
o This USGS gaging station is located at the Animas River south of Silverton. Mineral
Creek's confluence with the Animas River is approximately 1 mile upstream of this
gaging station.
o The highest discharge occurs in June, with a monthly average flow of 1,050 cfs.
o The lowest discharges occur throughout January and February, with monthly average
flows of 60 and 64 cfs, respectively.
5.1.5 Subsurface Hydrogeology
Years of mining and the installation of bulkheads has significantly influenced bedrock
groundwater elevations within the Site. Historically, groundwater flowed along fractures and
faults, with minimal leakage through bedrock, likely due to low primary permeability. With the
advent of underground mining, bedrock groundwater that once followed natural fractures instead
followed the new path of least resistance—the networks of tunnels in the underground mine
workings. Thus, drainage and haulage tunnels form preferential flow paths for bedrock
groundwater. Water emanating from adits originated from the bedrock groundwater systems at
the Site. Addressing sources of contamination within the bedrock groundwater systems or within
mine workings is outside the scope of this IROD.
The presence and/or extent of perched groundwater in overburden material or alluvial
groundwater is not currently known at the mining-related sources. Addressing sources of
contamination within the perched or alluvial groundwater is outside the scope of this IROD.
5.1.6 Conceptual Site Model
A conceptual site model (CSM) is a basic description of how contaminants enter the
environment, how they are transported, and what routes of exposure to organisms and humans
occur. It provides a framework for assessing risks from contaminants, developing remedial
strategies, and determining source control requirements and methods to address unacceptable
risks. A comprehensive CSM has not been developed for the Site, however, the CSM will be
developed and included as part of the future Site-wide RI. A description of the identified
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migration routes and exposure pathways relevant to the contaminant migration issues addressed
by IRAs covered in this IROD is provided in Section 5.3.
5.2 SAMPLING STRATEGY
Currently, EPA is collecting data to support evaluation of contributors of sources for
contaminant loading of waterways and identify areas where additional data is required to
evaluate the Site. Because site investigations are ongoing and there has been limited amount of
sampling conducted to date, the focus has been on the nature of contamination. The data
presented in the preliminary RI are not intended to provide a complete characterization of the
individual mining-related sources nor the complete extent of contamination.
As discussed in Section 2.2.3, field sampling conducted to date has included field activities by
USGS and CDMG between 1996 and 2000, and sampling by EPA/ESAT in 2015 and 2016. The
data collected include water quality data for surface water and adit discharges, stream sediment,
waste rock and soils, and mine waste leachability results. The contaminants discussed in the
preliminary RI (Appendix A) include aluminum, arsenic, cadmium, copper, iron, lead,
manganese, mercury, and zinc.
5.3 TYPES OF CONTAMINATION AND KNOWN POTENTIAL ROUTES OF
MIGRATION
5.3.1 Media
The following subsections provide definitions for the contaminated media present at the mining-
related sources discussed further in Section 5.4.
5.3.1.1 Solid Media
Solid media are defined as mining-related solid media that release contaminants to surface water
bodies and pose unacceptable risk to human and ecological receptors. Solid media have been
subdivided into three subcategories, which are discussed below.
Mine Waste
Mine waste is a mining-related solid waste with elevated contaminant concentrations, water
soluble contaminant loads, and/or acid-generating potential. It includes waste rock, ore, tailings,
and contaminated fills that have been generated and/or processed during mining operations.
Sediment
Sediment is a solid medium impacted by mine waste with elevated contaminant concentrations
that mainly consists of metal precipitates (i.e., sludge) from untreated MIW that have settled
from surface waters after discharge from mining-related sources (e.g., mine adits). Sediment
typically precipitates within Site stream banks, river bottoms, and adit portal detention ponds.
Sediment may also include natural material or mine waste that has been deposited within streams
or detention ponds due to erosion of adjacent natural (i.e., stream banks) or mining-related
source (i.e., waste rock) material. Sediment may also generate MIW when in contact with water.
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Contaminated Soil
Contaminated soil is native soil that has been impacted by or mixed with other contaminated
media (solid or aqueous). Native soil can be affected by either physical dispersion (e.g., erosion,
wind, traffic) or hydrogeochemical dispersion of contaminants. Hydrogeochemical dispersion is
a broad term that relates to leaching of metals and acidity from mine waste through MIW
generation, and sequestration of dissolved metals and acidity in soils as the MIW migrates over
or through them.
5.3.1.2 Aqueous Media
Aqueous media has been subdivided into three subcategories, which are described in the
following subsections.
Mining-Influenced Water
MIW is water that is contaminated or influenced by mining-related activities and is a contaminant
source medium where it discharges from a mine portal or contacts a solid source medium. It is a
broad term that does not specify the source of the contamination (other than a mining activity) or
the pH of the water. MIW can include both acid-mine drainage (AMD) and acid-rock drainage
(ARD), or water that is not acidic. AMD is metal-bearing, acidic water discharged from
underground mine workings through adits, tunnels, or shafts (collectively referred to as
"portals"). ARD is a similar discharge of metal-bearing acidic water resulting from water seeping
or flowing through and from acid-generating materials such as pyritic waste rock, tailings piles,
or mineralized rock formations. MIW forms when water and oxygen interact with sulfide-rich
mine wastes, host rocks, or vein rocks. Sulfuric acid forms and can dissolve additional metals into
the MIW. This MIW can discharge through adit portals and enter surface water. Both AMD and
ARD provide more information about the source and nature of the water than does the term MIW;
however, in this IROD, impacted water is referred to as "MIW."
Surface Water
Surface water includes water within streams or natural ponds. Impacted surface water may
episodically or periodically have elevated contaminant concentrations based on contact with or
migration of contaminants from solid media and/or MIW. For purposes of the IROD, surface
water within Mineral Creek, Cement Creek, and the Upper Animas River and tributaries was
considered the receiving water bodies at the Site.
Groundwater
As discussed in Section 5.1.5, groundwater at the Site may include perched groundwater, alluvial
groundwater, and bedrock groundwater systems. Groundwater will not be discussed further in this
IROD because addressing groundwater is not within the scope of the IRAs.
5.3.2 Overview of Fate and Transport
The sources of contaminants at specific mining-related sources at the Site are presented in the
preliminary RI. Site investigations are ongoing; the fate and transport discussion presented in this
section is not intended to be complete and final for the Site. The fate and transport discussion
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herein is focused on currently identified contaminant migration issues at the Site to be addressed
through implementation of the IRAs.
Contaminants at the mining-related sources within the Site, specifically metals and metalloids
(such as arsenic, which have properties of metals and non-metals), are present in solid phase
materials (mine waste rock, tailings, soil, and bedrock outcrops) and in MIW at the Site. Adverse
impacts are associated with transformation of solid phase metals and metalloids into forms that
are mobile and potentially harmful to humans and ecological receptors. The interaction of water
and oxygen with sulfide minerals, especially pyrite, can result in generation of MIW and partial
or complete dissolution of metals and/or metalloids from the solid phase, which provides a
mechanism for contaminant migration into surface water and potentially groundwater, where it
exists. These processes increase the mobility of contaminants in the environment and therefore
increase the potential for impacts to receptors.
Numerous mining-related sources within the Site contain acidic MIW in the form of AMD and
ARD. Exhibit 5-1 presents a summary of the process of AMD and ARD formation and a
description of the migration of these types of MIW in the environment.
Source Materials
Containing pyrite
Oxygen
Increased exposure to ^
oxygen from mining activity
Sulfide
oxidationoccurs
when the three
components of the triangle interact
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Water
Precipitation, groundwater,
andsurface water
ARD/APilD: Mobilizes contaminationandmoves it across and beyond the Site
Migration Routes: ARD runoff, surface water, andgroundv/ater
Exposure Pathways: Ingestion, dermal contact, inhalation
Potential Receptors: On-site workers and recreational visitors; off site
residents and recreational visitors; and wildlife
Exhibit 5-1 ARD and AMD Generation and Migration
At the Site, the surface waters in the main stems of Cement Creek, Mineral Creek, and the Upper
Animas River carry high loads of total and dissolved metals and high acidity into the Animas
River near Silverton even though substantial dilution with cleaner water occurs. Aquatic life in
the affected waterways is exposed to the elevated levels of metals.
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5.3.3 Fate and Transport Pathways Related to IRA Implementation
The following subsections describe the fate and transport mechanisms that are applicable to the
specific issues addressed through implementation of IRAs at the Site.
5.3.3.1 Mine Portal MIW Discharges
Several mining-related sources contain draining adits that discharge MIW onto or adjacent to
mine waste piles. These MIW discharges contacting mine waste are likely to lead to increased
leaching of metals from the mine waste into surface water, as well as increase erosion and
transport of mine waste or contaminated soil into receiving waters. Several other mining-related
sources have constructed diversions that route the MIW discharge away from mine waste but
require maintenance to prevent contact between the MIW and mine waste materials.
Many mining-related sources have mine waste that has been transported in front of a flowing
adit. This mine waste can result in increased potential for obstructed adit flow and subsequent
uncontrolled releases and erosion of mine waste materials into surface water.
5.3.3.2 Mining-Related Source/Stormwater Interactions
Stormwater run-on at mining-related sources can contact mine waste, which results in increased
leaching of metals from the mine waste to surface water.
5.3.3.3 Mine Portal Pond Sediments
Several mining-related sources addressed by the IRAs use settling ponds to reduce metals
concentrations from their adit MIW discharge. This allows metals to settle out of the adit discharge
water through either formation of iron oxy-hydroxides and subsequent co-precipitation (as with
arsenic), or through the physical settling of undissolved metals. This process produces residual
sludge in the settling ponds. If sufficient sludge and sediment accumulates in the ponds and
reduces the residence time of adit discharge in the ponds, or if accumulated sludge diverts the adit
discharge such that water does not flow through the settling ponds as intended, then the ability for
metals to settle out of the adit discharge water is diminished.
5.3.3.4 In-Stream Mine Wastes
Many mining-related sources have mine waste that has been transported into a stream channel.
This mine waste can result in increased potential for obstructed surface water flow and
subsequent uncontrolled releases and erosion of mine waste materials into surface water, as well
as additional metals leaching from the obstructive mine waste into nearby surface water bodies.
5.3.3.5 Mining-Impacted Recreation Staging Areas
Several mine-related sources addressed by the IRAs are used for recreational staging purposes or
camping, and these activities have the potential to physically disturb mine waste or contaminated
soil, potentially increasing the potential for human exposure to contaminants.
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5.4
SOURCE AND NATURE OF CONTAMINATION
The focus of this IROD is the mining-related sources identified in the initial characterization that
could be addressed by IRAs. This IROD uses two primary characteristics, definable by location,
to group mining-related sources for identification and evaluation: road accessibility and
ecoregions (as they relate to elevation). Road accessibility and ecoregions were chosen because
they have significant impacts on the IRAs in this IROD. Additional information on these two
characteristics include:
• Road accessibility: Most mining-related sources are accessible via U.S. Highway 550
(paved surfacing) or San Juan County roads (gravel surfacing). The level of maintenance
varies among these gravel county roads and is based on volume and speed of traffic,
weather conditions, erosion, and elevation (San Juan County 2018). The FFS considers
three main roads to be readily accessible (i.e., conventional access): U.S. Highway 550
(Mineral Creek), San Juan County Road 110 (Cement Creek), and San Juan County Road
2 (Upper Animas River). After conventional access ends on these named roads or a
secondary road starts from them, the county roads may become narrower and are
typically only accessible using a four-wheel drive vehicle (i.e., nonconventional access).
The assumption in this IROD is that San Juan County Road 110 has conventional access
from Silverton to the Gladstone area and that San Juan County Road 2 has conventional
access from Silverton to the Eureka area.
• Ecoregion: Designations are based on the ecoregions of Colorado, which are made up of
areas of general similarity in ecosystems and in the type, quality, and quantity of
environmental resources (Chapman et al. 2006). Environmental factors that help group
the ecoregions include geology, physiography, vegetation, climate, soils, land use,
wildlife, and hydrology. The two ecoregions covering the mining-related sources at the
Site are Volcanic Subalpine Forests and Alpine Zone. These will be referred to as
"subalpine" and "alpine," respectively, within this IROD, for simplicity. The elevation
range for subalpine mining-related sources is between 9,000 and 12,000 feet in elevation,
and the elevation range for alpine mining-related sources is from 10,000 to greater than
14,400 feet in elevation (Chapman et al. 2006). Additional references indicate a more
precise division between the subalpine and alpine ecoregions (referred to as "zones") at
an elevation of 11,500 feet (Agnew 2005, BLM 2018, National Park Service 2018). For
purpose of this IROD, the subalpine and alpine zones will be separated at an elevation of
11,500 feet.
Using the two characteristics previously discussed, mining-related sources included in this IROD
have been organized into four categories as follows:
• conventional access-alpine
• conventional access-subalpine
• nonconventional access-alpine
• nonconventional access-subalpine
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5.4.1 Summary of Drainage Basins
5.4.1.1 Mineral Creek Drainage Basin
The Mineral Creek drainage basin includes seven mining-related sources, five of which are
addressed by IRAs in this IROD. The locations within the Mineral Creek drainage basin of these
mining-related sources are shown on Figure 1-2. A summary of the mining-related sources within
the Mineral Creek drainage basin addressed by this IROD is presented in Exhibit 5-2.
Exhibit 5-2 Mining-Related Sources within Mineral Creek Drainage Basin
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X
X
X
Koehler Tunnel
CAS
X
X
X
Brooklyn Mine
NAS
X
X
X
Bandora Mine
NAS
X
X
Category: CAA - conventional access-alpine; CAS - conventional access-subalpine; NAA - nonconventional access-alpine;
NAS - nonconventional access-subalpine
5.4.1.2 Cement Creek Drainage Basin
The Cement Creek drainage basin includes 14 mining-related sources, six of which are addressed
by IRAs in this IROD. The mining-related sources specific to the IRAs are shown on Figure 1-3.
A summary of the mining-related sources within the Cement Creek drainage basin addressed by
this IROD is presented in Exhibit 5-3.
Exhibit 5-3 Mining-Related Sources within Cement Creek Drainage Basin
Mininii-Ui'liik'd Source
Ciilciion
Mine Porlsil
M IW
Disciplines
Mininii-
Kclsilcd
Source/
Siornmsilcr
1 nteriicl itins
Mine Porlsil
Pond
Sediments
ln-S(re;im
Mine
\\ .isles
Mininii-
Impsiclcd
Rcc resi lion
Sl;i«in« Aresis
C irand Mosuil Mine
\ . .
X
X
Nalalie/( )ccidental Mine
NAS
X
I IenrieUa Mine
NAS
X
Mammoth Tunnel
CAS
X
X
Anglo Saxon Mine
CAS
X
X
Yukon Tunnel
CAS
X
X
Category: CAA - conventional access-alpine; CAS - conventional access-subalpine; NAA - nonconventional access-alpine;
NAS -nonconventional access-subalpine
5.4.1.3 Upper Animas River Drainage Basin
The Upper Animas River drainage basin includes 27 mining-related sources, 12 of addressed by
IRAs in this IROD. The two dispersed campsites (identified as Campground 4 and Campground 7)
are also located within the Upper Animas River drainage basin and are also considered mining-
related sources addressed by IRAs in this IROD. The mining-related sources specific to the IRAs
are shown on Figure 1-4. A summary of the mining-related within the Upper Animas River
drainage basin addressed by this IROD is presented in Exhibit 5-4.
Interim Record of Decision - Final DS-25
OU1 Bonita Peak Mining District Superfund Site
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Exhibit 5-4 Mining-Related Sources within Upper Animas River Drainage Basin
Mininii-RchiU'd
Mine
Mininii-
Mine Porhil
Sou rce/
Port ;il
ImpucU'd
MIW
Slonm\;ilcr
Pond
In-SiiTiim
Kccrc;ilion
MiniiiiHii'liilcri Soiiito
( iiU'j;»r\
Disciplines
Inlcriiclions
Sediments
Mine Wiislcs
Si;i«in« Amis
Ben 1 Sutler Mine
NAA
Mountain Queen Mine
NAA
Vermillion Mine
NAA
X
X
Sunbank Group Mine
NAA
X
X
X
Frisco/Bagley Tunnel
NAS
X
X
Columbus Mine
NAS
X
X
Campground 7
NAS
X
Silver Wing Mine
NAS
X
X
X
Tom Moore Mine
NAS
X
Terry Tunnel
NAA
X
Pride of the West Mine
NAS
X
Campground 4
CAS
X
Category: CAA - conventional access-alpine; CAS - conventional access-subalpine; NAA - nonconventional access-alpine;
NAS - nonconventional access-subalpine
5.4.2 Summary of Mining-Related Source by IRAs
5.4.2.1 Mine Portal MIW Discharge
Eighteen mining-related sources have mine portal MIW discharges identified to be addressed in
this IROD. Exhibit 5-5 summarizes mining-related sources included for this IRA.
Exhibit 5-5 Summary of Mining-Related Sources for the
Mine Portal MIW Discharge IRA
Mine Porhil MIW
Mininii-Rchik'd Source
(;i lesion
Disciplines
Mineral Creek 1 )rainas>c 1 Jasin
Junction Mine
CAS
X
Koehler Tunnel
CAS
X
Brooklyn Mine
NAS
X
Bandora Mine
NAS
X
Cement Creek Drainage Basin
Natalie/Occidental Mine
NAS
X
Flenrietta Mine
NAS
X
Mammoth Tunnel
CAS
X
Anglo Saxon Mine
CAS
X
Yukon Tunnel
CAS
X
I Jpper Animas River Drainage Basin
Mountain Queen Mine
NAA
X
Vermillion Mine
NAA
X
Sunbank Group Mine
NAA
X
Frisco/Bagley Tunnel
NAS
X
Columbus Mine
NAS
X
Silver Wing Mine
NAS
X
Tom Moore Mine
NAS
X
Terry Tunnel
NAA
X
Pride of the West Mine
NAS
X
Category: CAA - conventional access-alpine; CAS - conventional access-subalpine; NAA - nonconventional access-alpine;
NAS - nonconventional access-subalpine
Interim Record of Decision - Final DS-26
OU1 Bonita Peak Mining District Superfund Site
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Detailed descriptions, figures identifying relevant features and sample locations, and sample
results for the mining-related sources evaluated in this IROD can be found in Section 4 of the
preliminary RI (included as Appendix A). Brief descriptions of the mining-related sources
identified for mine portal MIW discharges are as follows:
• The Junction Mine and Koehler Tunnel (along with Longfellow Mine) are co-located at
the headwaters of Mineral Creek. Mine portal MIW discharges from both the Junction
Mine's adit and Koehler Tunnel combine into a pond.
• The Brooklyn Mine is located on the east side of Mineral Creek within Brown's Gulch.
Existing mine portal MIW discharge is piped from the Level 2 adit to a constructed
channel lined with Burns Formation rock, which then discharges downgradient of the
mine waste.
• The Bandora Mine is located along South Fork Mineral Creek. There are two flowing
adits. Mine portal MIW discharge from the main flowing adit (which is collapsed) flows
into a diversion channel and then downslope east of the main mine waste dump.
However, breaks in the discharge channel allow MIW to flow over mine waste.
• The Natalie/Occidental Mine is approximately one mile southeast of Gladstone along the
South Fork of Cement Creek. Mine portal MIW discharge from the adit flows southwest
over soil and adjacent to waste rock before entering the creek.
• The Henrietta Mine is located on the south side of Prospect Gulch. There are portals into
at least six levels of this mine. Presently, the 700 Level adit flows only during high-flow
conditions and is diverted into a drainage channel that flows on the southeastern side of
the waste rock. Access to this adit is partially blocked by waste rock.
• The Mammoth Tunnel is located along Cement Creek near the mouth of Georgia Gulch.
Mine portal MIW discharges from a pipe protruding from the collapsed adit. The MIW
flow is channelized and flows down the mine waste in a lined channel into two settling
ponds.
• The Anglo Saxon Mine is located along Cement Creek approximately 3 miles upstream
from Silverton. This mine consists of two adits: a main adit close to the road, and the
Porcupine Gulch adit located 400 feet up Porcupine Gulch from the main adit. Mine
portal MIW discharge from the main adit flows across a moderately eroded waste pile,
and cascades down to a culvert underneath the road to a constructed settling pond before
continuing to Cement Creek.
• The Yukon Tunnel is located along Cement Creek approximately 2.5 miles upstream
from Silverton. Mine portal MIW discharge is directed within the adit into a pipe which
discharges to the north of a large waste rock pile in Illinois Gulch adjacent to the mine.
• The Mountain Queen Mine is located on the east side of Hurricane Peak at the
headwaters of California Gulch, with a shaft near the top of California Pass and a
draining adit east of the shaft. The adit opening is covered with a grate, and rock fall
Interim Record of Decision - Final
OU1 Bonita Peak Mining District Superfund Site
DS-27
-------
occurred recently above the grate. The mine portal MIW discharge from this adit flows
around both sides of the waste rock pile located at the adit and into California Gulch.
• The Vermillion Mine is located in a large gentle swale high on the north side of
California Gulch near the southwestern flank of Houghton Mountain. There is one
draining adit at the Vermillion Mine site. The adit discharge flows south over soil before
infiltrating into the waste rock pile. The drainage continues to flow approximately 2,000
feet south and southeast where it enters the West Fork Animas River.
• The Sunbank Group Mine is located within Placer Gulch. The main adit is sealed with a
concrete block; however, flow is coming out of the top of the concrete block and from
seeps upgradient of the adit block. Adit discharge is directed into a series of settling
ponds immediately adjacent to Placer Gulch. The ponds appear to no longer be functional
and adit drainage no longer flows sequentially through the ponds prior to discharging into
Placer Gulch.
• The Frisco/Bagley Tunnel is located approximately 0.5 miles west of Animas Forks on
the north side of California Gulch. A rock and mortar closure with a grate is installed at
the adit portal located on top of the waste rock pile on the north side of the road. The
mine portal MIW discharge is channelized southwest across a waste rock pile, and red
staining is highly visible throughout the channels, which flow into California Gulch. A
small settling pond is present within the channel. Additional adit flow ponds on top of the
waste rock pile during periods of high flow.
• The Columbus Mine is located across the stream in California Gulch from Animas Forks.
It has a single discharging adit from which mine portal MIW discharge infiltrates into the
waste rock file and then emerges at the base. There are a series of seeps below both levels
of waste rock that may be from the adit discharge.
• The Silver Wing Mine is located on the east side of the Upper Animas River, south of
Animas Forks. Adit flow is directed into a settling pond and was formerly directed through
bioreactor tanks prior to discharge to the Upper Animas River. The bioreactor tanks are not
functional, and flow currently bypasses the former tanks and is piped to the river.
• The Tom Moore Mine is located approximately 0.5 miles south of the Silver Wing Mine.
There is no maintained road access. There is one discharging adit from which mine portal
MIW discharge flows over the waste rock pile and into the Upper Animas River.
• Terry Tunnel is located approximately 0.25 miles southeast of the Ben Franklin Mine. It
is bulkheaded and buried, and most mine portal MIW discharge flows out of the
bulkheaded tunnel into a drainage ditch that directs water around the reclaimed waste
rock pile. MIW also seeps out below the bulkheaded tunnel and pools on the mine waste
below the tunnel.
• The Pride of the West Mine is located on the east side of Cunningham Gulch. The
primary adit has a metal frame cover and is chained and padlocked. The primary adit's
mine portal MIW discharges through a channel on top of a large waste rock pile, through
Interim Record of Decision - Final
OU1 Bonita Peak Mining District Superfund Site
DS-28
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a culvert, and down a gully on the waste rock pile into the stream. Two additional, non-
flowing, grated adits are located north of the flowing adit.
5.4.2.2 Mining-Related Source/Stormwater Interactions
Ten mining-related sources have mining-related source/stormwater interactions that have been
identified to be addressed in this IROD. Exhibit 5-6 summarizes mining-related sources included
for this IRA.
Exhibit 5-6 Summary of Mining-Related Sources for the Mining-Related Source/
Stormwater Interactions IRA
Mininii-RckiU'd Source
( iik'iion
Mining-Kcl;iU-(l Source/
Siormwiilcr 1 iitornct ions
Mineral Creek Drainage Basin
Brooklyn Mine
NAS
X
Bandora Mine
NAS
X
Cement Creek Drainage Basin
Grand Mogul Mine
NAA
X
Yukon Tunnel
CAS
X
Upper Animas River Drainage Basin
Ben Butler Mine
NAA
X
Mountain Queen Mine
NAA
X
Vermillion Mine
NAA
X
Sunbank Group Mine
NAA
X
Columbus Mine
NAS
X
Silver Wing Mine
NAS
X
Category: CAA - conventional access-alpine; CAS - conventional access-subalpine; NAA - nonconventional access-alpine;
NAS - nonconventional access-subalpine
Detailed descriptions, figures identifying relevant features and sample locations, and sample
results for the mining-related sources evaluated in this IROD can be found in Section 4 of the
preliminary RI (included as Appendix A). Brief descriptions of the mining-related sources
identified for mining-related sources/storm water interactions are as follows:
• The Brooklyn Mine is located on the east side of Mineral Creek within Brown's Gulch.
The topography of the area is such that stormwater from upgradient of the Brooklyn Mine
passes over mine waste.
• The Bandora Mine is located along South Fork Mineral Creek. There are two flowing
adits. Stormwater from upgradient of the Bandora Mine passes over mine waste due to
the local topography.
• The Grand Mogul Mine is in the Ross Basin about 0.5 miles east of the Mogul Mine.
Three piles of mine waste from the workings of the Grand Mogul Mine are located on the
north side of Cement Creek. The topography of the area is such that stormwater from
upgradient of the mine waste piles flows over them. Gullies are present on the waste rock
piles and the piles have a moderate degree of erosion.
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OU1 Bonita Peak Mining District Superfund Site
DS-29
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• The Yukon Tunnel is located along Cement Creek approximately 2.5 miles upstream
from Silverton. The topography of the area is such that stormwater from upgradient of
Yukon Tunnel passes over mine waste.
• The Ben Butler Mine is located on the north side of Burrows Creek on the south slope of
Denver Hill, approximately 1,200 feet north of the London Mine. There are no direct
roads to access the mining-related source. There are two shafts and three stopes at the
site, which are all filled with water. The topography of the area is such that stormwater
from upgradient of Ben Butler Mine passes over mine waste. A 200-yard-long vegetation
kill zone extends downslope from the waste dump towards Burrows Creek.
• The Mountain Queen Mine is located on the east side of Hurricane Peak at the
headwaters of California Gulch, with a shaft near the top of California Pass and a
draining adit east of the shaft. The topography of the area is such that stormwater from
upgradient of the adit flows over the mine waste located at the adit.
• The Vermillion Mine is located in a large gentle swale high on the north side of California
Gulch near the southwestern flank of Houghton Mountain. The topography of the area is
such that stormwater from upgradient of Vermillion Mine flows over mine waste.
• The Sunbank Group Mine is located within Placer Gulch. An existing stormwater
diversion is located upgradient of the main waste rock pile.
• The Columbus Mine is located across the stream in California Gulch from Animas Forks.
The topography of the area is such that stormwater from upgradient of the Columbus
Mine passes over mine waste.
• The Silver Wing Mine is located on the east side of the Upper Animas River, south of
Animas Forks. The topography of the area is such that stormwater from upgradient of
Silver Wing Mine passes over mine waste.
5.4.2.3 Mine Portal Pond Sediments
Eight mining-related sources have mine portal pond sediments that have been identified to be
addressed in this IROD. Exhibit 5-7 summarizes mining-related sources included for this IRA.
Interim Record of Decision - Final
OU1 Bonita Peak Mining District Superfund Site
DS-30
-------
Exhibit 5-7 Summary of Mining-Related Sources for the Mine Portal Pond
Sediments IRA
Miniiili-Rchilcd Source
(;i lotion
Mine I'orliil Poiul
Sod i mollis
Mineral Creek Drainage Basin
Junction Mine
CAS
X
Koehler Tunnel
CAS
X
Brooklyn Mine
NAS
X
Cement Creek Drainage Basin
Mammoth Tunnel
CAS
X
Anglo Saxon Mine
CAS
X
I Jpper Animas River Drainage Basin
Sunbank Group Mine
NAA
X
Frisco/Bagley Tunnel
NAS
X
Silver Wing Mine
NAS
X
Category: CAA - conventional access-alpine; CAS - conventional access-subalpine; NAA - nonconventional access-alpine;
NAS - nonconventional access-subalpine
Detailed descriptions, figures identifying relevant features and sample locations, and sample
results for the mining-related sources evaluated in this IROD can be found in Section 4 of the
preliminary RI (included as Appendix A). Brief descriptions of the mining-related sources
identified for mine portal pond sediments are as follows:
• The Junction Mine and Koehler Tunnel (along with Longfellow Mine) are co-located at
the headwaters of Mineral Creek. Mine portal MIW discharges from both the Junction
Mine's adit and Koehler Tunnel combine into a pond.
• The Brooklyn Mine is located on the east side of Mineral Creek within Brown's Gulch.
Two ponds are located east of the primary mine area.
• The Mammoth Tunnel is located along Cement Creek near the mouth of Georgia Gulch.
Mine portal MIW discharges from a pipe protruding from the collapsed adit. The MIW flow
is channelized and flows down the mine waste in a lined channel into two settling ponds.
• The Anglo Saxon Mine is located along Cement Creek approximately 3 miles upstream
from Silverton. Mine portal MIW discharge from the main adit flows across a moderately
eroded waste pile, and cascades down to a culvert underneath the road to a constructed
settling pond before continuing to Cement Creek.
• The Sunbank Group Mine is located within Placer Gulch. Adit discharge is directed into
a series of settling ponds immediately adjacent to Placer Gulch. The ponds appear to no
longer be functional and adit drainage no longer flows sequentially through the ponds
prior to discharging into Placer Gulch.
• The Frisco/Bagley Tunnel is located approximately 0.5 miles west of Animas Forks on the
north side of California Gulch. The mine portal MIW discharge is channelized southwest
across a waste rock pile, and red staining is highly visible throughout the channels, which
flow into California Gulch. A small settling pond is present within the channel.
Interim Record of Decision - Final
OU1 Bonita Peak Mining District Superfund Site
DS-31
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• The Silver Wing Mine is located on the east side of the Upper Animas River, south of
Animas Forks. Adit flow is directed into a settling pond and was formerly directed through
bioreactor tanks prior to discharge to the Upper Animas River. The bioreactor tanks are not
functional, and flow currently bypasses the former tanks and is piped to the river.
5.4.2.4 In-Stream Mine Wastes
One mining-related source has in-stream mine waste that has been identified to be addressed in
this IROD. Exhibit 5-8 summarizes mining-related source included for this IRA.
Exhibit 5-8 Summary of Mining-Related Source for the
In-Stream Mine Wastes IRA
Mininii-Ri'liilcd Sourer
( .lienor\
lu-Siiviini Mine \\;is(es
Mineral Creek I )rainage 1 iasin
None
Cement Creek Drainage Basin
C hand Mogul Mine
NAA
X
I Jpper Animas River Drainage Basin
None
Category: CAA - conventional access-alpine; CAS - conventional access-subalpine;
NAA - nonconventional access-alpine; NAS - nonconventional access-subalpine
Detailed descriptions, figures identifying relevant features and sample locations, and sample
results for the mining-related sources evaluated in this IROD can be found in Section 4 of the
preliminary RI (included as Appendix A). A brief description of the mining-related source
identified for in-stream mine waste is as follows:
• The Grand Mogul Mine is in the Ross Basin about 0.5 miles east of the Mogul Mine.
Three piles of mine waste from the workings of the Grand Mogul Mine are located on the
north side of Cement Creek. A perennial tributary cuts through the smallest (west) waste
rock pile.
5.4.2.5 Mining-Impacted Recreation Staging Areas
Five mining-related sources have mining-impacted recreation staging areas that have been
identified to be addressed in this IROD. Exhibit 5-9 summarizes mining-related sources included
for this IRA.
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OU1 Bonita Peak Mining District Superfund Site
DS-32
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Exhibit 5-9 Summary of Mining-Related Sources for the Mining-Impacted
Recreation Staging Areas IRA
Mininii-Rcliik-d Source
CsiU'Kttn
MiniiiiHmpiicU'ri
KcciViilion S(;i»in» Amis
Mineral Creek Drainage Basin
Longfellow Mine
CAS
X
Junction Mine
CAS
X
Koehler Tunnel
CAS
X
Cement Creek Drainage Basin
None
Upper Animas River Drainage Basin
Campground 7
NAS
X
Campground 4
CAS
X
Category: CAA - conventional access-alpine; CAS - conventional access-subalpine;
NAA - nonconventional access-alpine; NAS - nonconventional access-subalpine
Detailed descriptions, figures identifying relevant features and sample locations, and sample
results for the mining-related sources evaluated in this IROD can be found in Section 4 of the
preliminary RI (included as Appendix A). Brief descriptions of the mining-related sources
identified for mining-impacted recreation staging areas are as follows:
• The Longfellow Mine, Junction Mine, and Koehler Tunnel are all co-located at the
headwaters of Mineral Creek. Waste rock samples at these three locations exceeded the
human health risk-based level for arsenic. The area is used as a launch point for
recreational tours and is frequently visited with evidence of previous camping.
• Campground 7 is located approximately 1.1 miles south of Animas Forks, on the west
side of the Upper Animas River at the road fork below a bridge crossing the Upper
Animas River. Campground 7 is considered a dispersed campsite. It is near the former
location of the Eclipse Smelter according to USGS (Church et al. 2007). A sample of
soil/waste rock from this location exceeded the human health risk-based level for lead. It
is accessible to the public and used for recreational purposes.
• Campground 4 is located near the Animas River adjacent to a spur off County Road 2
below Howardsville, Colorado, approximately 900 feet below the Howardsville bridge
over the Upper Animas River. Campground 4 is considered a dispersed campsite. It was
identified as a mine tailings area by Colorado Division of Minerals and Geology,
described as Mill Tailings Site #20 in Herron et al. (2000). A sample of soil/waste rock
from this location exceeded the human health risk-based level for lead. It is accessible to
the public and used for recreational purposes.
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OU1 Bonita Peak Mining District Superfund Site
DS-33
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6.0 CURRENT AND REASONABLY ANTICIPATED FUTURE LAND AND
RESOURCE USES
The current and reasonably anticipated future land uses for the Site are an important
consideration for the development of remedial action objectives (RAOs) and remedial criteria
such as cleanup levels to ensure remedial alternatives are protective of human health and the
environment. The condition of the Site after remediation must be considered in evaluating future
land uses or activities and the related protection to human health and the environment that is
provided. Detailed information on current and future land uses within the Site are discussed in
this section.
6.1 LAND USE
The land within the Site includes several different ownership/management types: private mining
claims, private property, parcels managed by BLM, and areas managed by the USFS. Mining-
related sources evaluated in this IROD are located on private mining claims, except for the
Brooklyn Mine, which is a mixed ownership mining-related source (private-public lands) where
many surface features are on public land managed by the USFS.
The assumption in this IROD is that recreation will remain the predominant future land use for
both public property (i.e., USFS-managed lands) and private property that have mining-related
sources remediated as part of the IRAs.
6.1.1 Surrounding Land Use and Population
The Census 2010 population for San Juan County, Colorado was approximately 700 people (U.S.
Census Bureau 2010). Historically, mining was the main industry in the area; therefore, there are
many inactive and abandoned mines within the three watersheds. Tourism including skiing and
recreation, retail, and construction are now the most common industries (DATA USA 2015,
City-Data.com 2016).
6.2 GROUNDWATER AND SURFACE WATER USE
Like land use, surface water supports recreational uses such as rafting. In addition, surface water
from the three main drainage basins that are part of the Site (Cement Creek, Mineral Creek,
Upper Animas River) are potential drinking water sources. These surface waters also serve as the
habitat for a variety of aquatic organisms.
The assumption in this IROD is that recreation, potential drinking water, and ecological habitat
will remain the predominant surface water uses for the Site.
Many unknowns exist about the presence and quality of groundwater at the Site. No groundwater
analytical data are available for the mining-related sources addressed in this IROD. Until a
comprehensive investigation of the presence and quality of groundwater can be conducted at the
Site, a full determination of groundwater use at the Site cannot be completed.
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OU1 Bonita Peak Mining District Superfund Site
DS-34
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7.0 SUMMARY OF RISKS
While the Site-wide risk assessments are ongoing, human health and ecological risk memoranda
were developed to support the development of the FFS. The human health and ecological risk
memoranda (Appendix B) were developed specifically to document and summarize unacceptable
risks to human health and aquatic ecological receptors posed by the migration of the identified
contaminated media at mining-related sources. The following sections provide a brief overview of
the risk methodology, summarize the risk results, and present the overall risk conclusions for both
human health and ecological receptors.
7.1 HUMAN HEALTH AND ECOLOGICAL RISK
7.1.1 Potential Receptors
Potential human receptors as identified in Appendix B, Part 1 consist of campers. Potential
ecological receptors as identified in Appendix B, Part 2 consist of aquatic receptors (primarily fish
and benthic macroinvertebrate [BMI] communities) (CDM Smith 2018).
7.1.2 Exposure Pathways
Human exposure pathways for which interim risks were quantitatively evaluated in Appendix B,
Part 1 focused on the incidental ingestion and inhalation of soil and mine waste during camping.
Potential risks to recreational and occupational receptor populations from all exposure media and
pathways will be evaluated in the final human health risk assessment for the Site.
Ecological exposure pathways for which risks were quantitatively evaluated in Appendix B, Part 2
included ingestion and direct contact of aquatic receptors with surface water.
7.1.3 Summary of Human Health Risk
Human health risk, as discussed in this section, is the basis for understanding the risks associated
with the following contaminant migration issue:
• Mining-impacted recreation staging areas
Properties identified as mining-related recreation use areas used for camping are exclusively
evaluated for unacceptable human health risks. Appendix B, Part 1 presents the derivation and
application of risk-based thresholds for human health for lead and arsenic in soil/waste rock based
on a camping scenario within the mining districts. Lead and arsenic were selected for evaluation as
COPCs for the IRAs because concentrations are notably elevated at several locations within the
mining districts. Therefore, levels for lead and arsenic have been developed for consideration in the
identification of areas that may warrant IRA based on potential human health risks. These levels are
to be considered preliminary and subject to change pending finalization of the Site human health
risk assessment.
Appendix B, Part 1 includes two different human health evaluations: one based on lead exposures
(Part 1.1) and one based on arsenic exposures (Part 1.2) (CDM Smith 2018). Part 1.1 presents an
interim evaluation of risks from chronic lead exposure during camping and presents interim lead
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OU1 Bonita Peak Mining District Superfund Site
DS-35
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risk-based levels for the purposes of supporting IRA decisions in dispersed camping areas. Part 1.2
presents the derivation of acute screening levels for arsenic based on a camping scenario and
compares these screening levels to measured arsenic concentrations soil and waste rock samples
collected in the mining districts.
The camping scenario was selected for the human health evaluations because the camper is
anticipated to be the most sedentary of receptors (i.e., not moving about being exposed to a variety
of soil/mine waste sources, in contrast with hiker, hunter, fisherman, all-terrain vehicle [ATV]
rider/guide, and road worker receptors), which allows an evaluation of smaller exposure areas, such
as individual campgrounds. The camping scenario was also selected because the camper receptor
has the highest exposure to soil compared to the other recreational receptors (e.g., hiker, hunter,
recreational ATV rider) due primarily to incidental ingestion of soil. Focus was placed on exposure
to children, because they are often more vulnerable to pollutants than adults and soil ingestion is
higher due to increased frequency of contact through hand-to-mouth or object-to-mouth activity.
Exposure parameters for the IRA risk-based levels were based on child-specific camping soil
ingestion rates.
As presented in the interim human health risk evaluations included in Appendix B, Part 1, a
possibility exists that adverse health effects may occur from exposures to lead or arsenic in the
contaminated soils and waste rock within the mining districts. Based on the chronic evaluation of
lead exposures during camping (Part 1.1), there are two dispersed campsites with unacceptable
human health chronic exposures from lead in soil: Campground 4 and Campground 7 (see Figure 1-
4).
In response to comments on the 14 days per year exposure frequency assumption for the dispersed
camping scenario received during the public comment period for the proposed plan, an alternate
trespass camping scenario was also evaluated to determine whether heavy metals (lead in
particular) may pose an unacceptable risk under a shorter exposure frequency scenario. This
alternate scenario evaluated an exposure frequency of 2 days per year for campers in dispersed
campsites to determine if levels of lead pose a risk above a level of concern. This change would
account for a family camping with a child (under the age of 6 years) present that unknowingly uses
unmarked private property within the BPMD as a campsite before being discovered and asked to
leave by the property owner. This alternate exposure scenario evaluation indicates that, even if the
exposure frequency were assumed to be only 2 days per year, lead concentrations at both
Campground 4 and Campground 7 would still be well above risk-based recreational screening
levels based on an RBA of 0.6, which supports the conclusions of the FFS for inclusion in this
IROD. This additional risk evaluation is included in Appendix B, Part 1.1.
Based on the acute evaluation of arsenic exposures (Part 1.2), when identifying potential locations
where interim actions may be needed, the appropriate screening level (i.e., 14-day versus 2-day)
will depend upon the type and duration of exposure that may reasonably be anticipated to occur at
the location of interest. For example, the 14-day screening level should be used when evaluating
established campgrounds and areas where extended camping may occur (e.g., the dispersed
campsites), whereas the 2-day screening level should be used when evaluating other types of
potential recreational use areas. There are no dispersed campsites with measured arsenic
concentrations above the 14-day acute arsenic screening level. However, there are three locations
(the Longfellow Mine, Junction Mine, and Koehler Tunnel; see Figure 1-2) where waste rock
concentrations are higher than the 2-day acute arsenic screening level.
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7.1.4 Summary of Ecological Risk
Ecological risk, as discussed in this section, is the basis for understanding the risks associated
with the following contaminant migration issues:
• Mine portal MIW discharge
• Mining-related source/storm water interactions
• Mine portal pond sediments
• In-stream mine wastes
The targeted outcome of the IRAs will be to reduce contaminant loading to receiving surface
waters to reduce ecological risks, as discussed in Appendix B, Part 2. The ecological risk
evaluation focuses on aquatic ecological risk, primarily risks to fish. It has been noted that BMI
communities in most reaches are also currently at risk, and many of the factors limiting BMI
communities are like those limiting fish communities.
Fish have recently been documented in several other reaches of the Animas River and tributaries as
a part of qualitative habitat surveys conducted by the USGS in 2016. These locations include trout
in Cunningham Creek near its mouth, in the South Fork of Mineral Creek near its mouth, in
Mineral Creek between Mill Creek and the Middle Fork of Mineral Creek, and in Mineral Creek
below the South Fork of Mineral Creek (see Figure 2 in Appendix B, Part 2).
While aquatic life is unlikely to be directly exposed to MIW (i.e., mine portal discharges) prior to
entering the receiving stream, MIW can significantly increase in-stream metals concentrations,
subsequently contributing to risks to fish. An evaluation of the hazard quotients (HQs) is presented
in Table 1 and Figures 3 through 5 in Appendix B, Part 2. HQs were computed by comparing
surface water concentrations with Colorado's hardness-based chronic aquatic life water quality
criteria (concentration/criteria). The Colorado State Water Quality Criteria regulation (CDPHE
2018) is the primary source of surface water benchmarks was used in the evaluation, but chronic
toxicity thresholds summarized by Buchman (2008) were also used when Colorado State Water
Quality Criteria were not available. Table 1 in Appendix B, Part 2 reveals there are few locations
where maximum individual metal HQ values are less than one (COPCs evaluated include
aluminum, cadmium, copper, and zinc), with many locations in both adit drainages and downstream
surface waters demonstrating HQs greater than 100. If the value of an HQ is less than or equal to
one, risk of unacceptable adverse effects in exposed organisms is deemed acceptable. If the HQ
exceeds one, the risk of adverse effects in exposed organisms may be of concern, with the
probability and/or severity of adverse effect tending to increase as the value of the HQ increases.
HQ values should be interpreted as estimates rather than highly precise values because the values
are predictions and are subject to the uncertainties inherent in both the estimates of exposure and
the estimates of toxicity benchmarks. Recognizing this, surface water measurements are far
elevated above water quality criteria at many locations.
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7.2 BASIS OF ACTION
7.2.1 Human Health Risk
As discussed in Section 7.1.3, a possibility exists that adverse health effects may occur from
exposures to lead or arsenic in the contaminated soils and waste rock at the mining-related
sources evaluated in this IROD under a camping scenario. Based on the chronic evaluations of
lead exposures during camping, there are two dispersed campsites where interim actions are
recommended to address potentially unacceptable human health exposures from lead in soil:
Campground 4 and Campground 7. Based on the acute evaluation of arsenic exposures during
camping, there are three locations (the Longfellow Mine, Junction Mine, and Koehler Tunnel)
where interim actions are recommended to address potentially unacceptable human health acute
exposure of arsenic in waste rock. Thus, human health risk is the basis for addressing the
following contaminant migration issue:
• Mining-impacted recreation staging areas
7.2.2 Ecological Risk
As discussed in Section 7.1.4, the health of aquatic ecosystems within the Animas River and its
tributaries are currently impaired by high concentrations of toxic metals emanating from a wide
range of mining-related and natural sources distributed throughout the greater Animas River
watershed. In many locations, metals concentrations are currently so elevated that aquatic life
does not and likely cannot exist. In other locations, metals-tolerant organisms (e.g., brook trout)
are currently able to persist. Actions that result in sustained metal loading reduction function to
reduce toxic metals exposure to resident organisms (or potentially resident) within these streams.
If enough of these actions are taken, improved survival, abundance and diversity of aquatic life
can reasonably be expected where aquatic ecosystems are currently marginal. Further, expansion
of the spatial extent of aquatic communities may also be possible as instream water quality
improves. Thus, ecological risk is the basis for addressing the following contaminant migration
issues:
• Mine portal MIW discharge
• Mining-related source/storm water interactions
• Mine portal pond sediments
• In-stream mine wastes
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8.0 REMEDIAL ACTION OBJECTIVES AND CLEANUP LEVELS
8.1 REMEDIAL ACTION OBJECTIVES
RAOs are typically developed by evaluating several sources of information, including results of
the risk assessments and ARARs. These inputs are the basis for determining whether protection
of human health and the environment is achieved for a particular remedial alternative.
The scope of the RAOs in this IROD is intended to address human health or ecological risks only
for the five contaminant migration issues identified in Section 7.2. The RAOs are not intended to
address all potential human health and/or ecological risks because the information (i.e., RI and
human health/ecological risk information) supporting the IROD is preliminary and the actions to
be taken are interim. The final remedial decisions for these mining-related sources will address
all known unacceptable human health and ecological risks.
The following RAO was identified to address known aquatic ecological risks:
1. Reduce transport from mine waste, contaminated soil, and contaminated
sediment into surface water of COPCs that contribute to unacceptable ecological
risks.
The following RAOs were identified to address known human health risks:
2. Reduce human exposure through ingestion and inhalation to mine waste and
contaminated soils containing lead that result in greater than a 5 percent chance of
exceeding a blood lead level of 5 micrograms per deciliter during camping activities.
3. Reduce human exposure through ingestion of mine waste and contaminated soils
containing arsenic that exceeds risk-based levels for acute exposures during camping
activities.
The following subsections discuss the RAOs pertinent to each IRA for the five contaminant
migration issues.
8.1.1 Mine Portal MIW Discharges
RAO 1 applies to mine portal MIW discharges IRA, which addresses known aquatic ecological
risks. RAOs 2 and 3 are not pertinent.
8.1.2 Mining-Related Source/Stormwater Interactions
RAO 1 applies to mining-related source/stormwater interactions IRA, which addresses known
aquatic ecological risks. RAOs 2 and 3 are not pertinent.
8.1.3 Mine Portal Pond Sediments
RAO 1 applies to the mine portal pond sediments IRA, which addresses known aquatic
ecological risks. RAOs 2 and 3 are not pertinent.
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8.1.4 In-Stream Mine Wastes
RAO 1 applies to the in-stream mine wastes IRA, which addresses known aquatic ecological
risks. RAOs 2 and 3 are not pertinent.
8.1.5 Mining-Impacted Recreation Staging Areas
RAOs 2 and 3 apply to the mining-impacted recreation staging areas IRA, which addresses
known human health risks. RAO 1 is not pertinent.
8.2 CLEANUP CRITERIA
Remediation goals (RGs), or cleanup levels, are concentration-based goals for individual chemicals
for specific medium and land use combinations at CERCLA sites (EPA 1991b). They are typically
presented as chemical- and media-specific values that when met, achieve the RAOs. RGs are
discussed in theNCP (40 Code of Federal Regulations [CFR] 300.430(e)(2)(i)). Identification and
selection of the cleanup levels are typically based on RAOs, the current and reasonably anticipated
future land uses, and the ARARs.
The following subsections describe the development of cleanup levels, as appropriate, and remedial
clearance criteria to determine that the IRAs have achieved the RAOs through reductions of human
health risks and ecological risks, respectively.
8.2.1 Human Health Cleanup Levels
Human health cleanup levels for lead and arsenic in mine wastes and contaminated soil at
recreational staging areas are presented in Appendix B, Part 1. Achievement of the cleanup levels
through implementation of remedial alternatives would result in acceptable risks to human health
from camping.
In addition to the use of COPC analytical data to delineate the extent of remediation for mining-
impacted recreation use areas, physical information such as, but not limited to, topography and
soil types (i.e., relatively flat areas free of large boulders and cobbles) will be used to define the
relevant exposure area for camping and thus the horizontal extent of remediation. Once the extent
of remediation encompasses the horizontal extent of exposure areas for camping, the cleanup
levels will then be used after remediation to determine the resulting conditions in mine waste and
soil meet the RAOs for human health risk from lead and arsenic.
8.2.2 Ecological Remedial Clearance Criteria
As stated in Section 8.1, the ecological RAO includes reducing COPCs that contribute to
unacceptable aquatic ecological risks from contaminated media being addressed under the scope
of the IRAs. While it is possible to derive media-based cleanup levels for the contaminants
addressed as part of the IRAs, the derivation is complicated by the preliminary nature of the RI
and risk assessment information that focus on specific COPCs and specific receptors and
exposure pathways rather than a comprehensive list of contaminants, pathways, and receptors.
The ecological RAO is focused on source migration control that would contribute to, but not
necessarily result in, acceptable risks for aquatic ecological receptors. For these reasons, media-
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based cleanup levels have not been established for the IRAs addressing unacceptable ecological
risks. In lieu of cleanup levels, the IRAs are anticipated to be guided based on remedial clearance
criteria.
Remedial clearance criteria define the conditions that must be met for the remedial components or
approaches to be deemed complete for purposes of the IRAs addressing unacceptable aquatic
ecological risk. Because the focus of remedial alternatives addressing unacceptable aquatic
ecological risks is source isolation/separation and contaminant migration control, there are not
chemical-based criteria directly applied to contaminated source media (e.g., mine wastes and
mine portal pond sediment) to determine completion. Rather, clearance criteria for each IRA will
be established during remedy implementation to determine that the IRA components have been
constructed to achieve source isolation/separation and migration control. Examples of remedial
clearance criteria could include but are not limited to maximum allowable depths of accumulated
sludge in mine portal ponds, minimum separation distances between MIW mine portal discharges
and mine wastes, or lack of visual indications of mine waste remaining in streams. Actual
remedial clearance criteria to be used will be developed during remedial design of the IRAs in
conjunction with source-specific conditions.
Performance evaluation monitoring will also be conducted to measure the extent by which
ecological and human health risks associated with contributions from these mining-related
sources have been reduced by the IRAs. Performance evaluation monitoring demonstrating
stability of mining-related sources and reductions in contributions of COPCs migrating from
these contaminated source media would be used to confirm that the RAOs have been achieved.
Examples of performance evaluation monitoring include collection of surface water samples for
COPC analysis and measurements/observations of parameters that indicate stability with respect
to surface erosion or mass movement. Actual performance evaluation monitoring approaches to
be used will be developed during remedial design of the IRAs in conjunction with source-specific
conditions. These data will provide information about the effectiveness of the IRAs and are
intended to help inform future remedial decisions at the Site.
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9.0 DESCRIPTION OF ALTERNATIVES
This section describes the remedial alternatives as developed and evaluated in the FFS, including a
brief explanation of the alternatives developed to address the five contaminant migration issues
identified in Section 7.2. It includes common elements of alternatives, description of remedy
components, and expected outcomes for each alternative. The detailed evaluation and comparative
analysis of alternatives described in this section is summarized in Section 10.
9.1 SUMMARY OF GENERAL RESPONSE ACTIONS, REMEDIAL
TECHNOLOGIES, AND PROCESS OPTIONS CONSIDERED DURING
ALTERNATIVE DEVELOPMENT
The two-step screening process of general response actions, remedial technologies, and process
options indicated in the RI/FS guidance (EPA 1988), was excluded from the FFS due to the
streamlined approach to the FFS, as discussed in Section 1. The general response actions,
remedial technologies, and process options were identified based on their documented use to
remediate similar contaminant migration issues at other CERCLA mine sites.
The identification process consists of the following general steps:
• Identify general response actions for the five contaminant migration issues that will
satisfy the RAOs identified in Section 8.1.
• Compile remedial technologies and process options for each general response action that
are viable for remediation of these contaminant migration issues using the informational
sources discussed below.
The primary source of information used to identify remedial technologies and process options is
the Federal Remediation Technologies Roundtable (FRTR) Remediation Technologies Screening
Matrix and Reference Guide, Version 4.0 (FRTR 2007). Other sources of information used to
identify remedial technologies and process options include previous studies and work conducted
by federal and state agencies performing response action work at the Site, relevant EPA
guidance, published literature and vendor information, stakeholder input, and engineering
judgment based on other mine waste remediation projects with inorganic contamination.
The remedial technologies and process options presented in Exhibit 9-1 have substantial
potential and applicability as standalone remedies, or have remedial benefits if combined with
other remedial technologies, to achieve the RAOs identified in Section 8.1. Although other
remedial technologies and process options within the identified general response actions (e.g.,
off-site disposal) could also be successful and were considered, they were ultimately not
identified for the relatively simple scope of IRAs identified in this IROD.
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Exhibit 9-1 Identified Remedial Technologies and Process Options for the Development of
Remedial Alternatives
(. 01101:11
Response
Action
Kcmcrihil
Tcchnolo^
Process Option
Description of Option
No Action
None
None
No action would be taken. The contaminated media remain
in their existing condition.
Institutional
Controls (ICs)
Non-
Engineered
Controls
Governmental controls,
proprietary controls,
enforcement tools with
IC components, and/or
informational devices
ICs would be implemented as needed to maintain integrity of
the proposed remedies.
Containment
Surface Source
Controls
Grading
Contaminated solid media would be contoured to promote
drainage and facilitate other technologies and process
options.
Soil/rock exposure
barrier
Contaminated solid media would be covered with a layer of
uncontaminated soil or rock with sufficient thickness to
reduce erosion and eliminate surface exposure of
contaminated media.
Hydraulic
Isolation,
Diversion, and
Separation
Measures
French drain and/or
interception trench
Interceptor trenches or French drains would be constructed
to collect and route mine portal MIW discharge and/or
stormwater migrating as surface flow or interflow around
contaminated solid media to prevent co-mingling of
uncontaminated and contaminated solid/aqueous media.
Open channel
Open channels would be constructed to collect and route
mine portal MIW discharge and/or stormwater around
contaminated solid media to prevent co-mingling of
uncontaminated and contaminated solid/aqueous media.
Collection/diversion
piping or liner
Collection/diversion piping or liner would be used to divert
mine portal MIW discharge and/or stormwater around
contaminated solid media.
Berms
Berms would be constructed around contaminated solid
media to prevent co-mingling of solid and aqueous media
and minimize erosion and transport.
Removal,
Transport, and
Disposal
Removal
Mechanical removal
(excavation)
Contaminated media would be excavated using mechanical
methods. Dewatering (using gravity and/or amendments) at
the mining-related source may be required to implement this
process option.
Pneumatic removal
(vacuum excavation)
Contaminated media would be excavated using vacuum
hoses, vacuum trucks, or other pneumatic conveyance
systems. Dewatering (using gravity and/or amendments) at
the mining-related source may be required to implement this
process option.
Transport
Mechanical transport
(hauling/conveying)
Excavated contaminated media would be transported by
truck or other mechanical conveyance method to a
disposal/management location. Dewatering (using gravity
and/or amendments) at the mining-related source may be
required to implement this process option.
Pneumatic transport
(vacuum extraction)
Excavated contaminated media would be piped using a
vacuum system to a disposal/management location.
Dewatering (using gravity and/or amendments) at the
mining-related source may be required to implement this
process option.
Disposal
Interim local waste
management
Excavated contaminated media would be temporarily
managed locally until permanent disposal solutions are
selected.
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9.2 DEVELOPMENT OF REMEDIAL ALTERNATIVES
Table 9-1 (A through E) provides matrices that indicate how the remedial technologies and
representative process options were combined in consideration of the supplemental information
to create the limited number of remedial alternatives for each contaminant migration issue for
IRA in the FFS.
For alternative identification and evaluation, "representative" or "selected" process options were
selected for evaluation within the remedial technology category to simplify the analysis and
comparison of alternatives. An example of "representative" selection of process options is
associated with the general response action of removal. Although multiple types of removal
process options are identified and could be considered during remedial design, only mechanical
excavation is selected as being representative for purposes of remedial alternative identification
and description.
The remedial alternatives assembled for the five contaminant migration issues include:
Mine Portal MIW Discharges
• Alternative A1: No Action
• Alternative A2: Diversion/Isolation
Mining-Related Source/Stormwater Interactions
• Alternative B1: No Action
• Alternative B2: Stormwater Diversion/Isolation
Mine Portal Pond Sediments
• Alternative C1: No Action
• Alternative C2: Excavation and Interim Local Waste Management
In-Stream Mine Wastes
• Alternative D1: No Action
• Alternative D2: Excavation and Interim Local Waste Management
Mining-Impacted Recreation Staging Areas
• Alternative El: No Action
• Alternative E2: Containment/Isolation
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9.3 COMMON ELEMENTS BETWEEN REMEDIAL ALTERNATIVES
This subsection identifies the key common elements that would be required as part of all
remedial alternatives (other than No Action alternatives). Examples of common elements
include, but are not limited to, the following:
9.3.1 Pre-Construction Common Elements
• Pre-construction surveys including topographic surveys (i.e., property boundary surveys),
cultural resources surveys, habitat surveys, noxious weed surveys, wetland delineations,
and other surveys as identified in Appendix C of the FFS for compliance with ARARs,
would be conducted as necessary prior to implementing IRAs at mining-related sources.
• Erosion and sediment control measures would be implemented, as necessary, to protect
nearby areas.
9.3.2 Construction Common Elements
• It is assumed that a designated uncontaminated borrow source(s) (outside of mining-
related sources) for constructing remedial components and access roads would be
generated and transported from a public or private property at an on-site (i.e., within the
Site) location. It is assumed that the suitable borrow location(s) would have sufficient
volume to provide the required materials for each of the alternatives.
• Dust suppression would be maintained to eliminate contaminant migration during
alternatives implementation. Water-based dust suppression is assumed to be conducted in
most situations, but chemical-based dust suppression could be considered during
construction for some specific applications like haul road maintenance.
• Access road improvements would be implemented, as necessary, to provide access to
mining-related sources that are targeted for IRAs, using standard construction equipment.
It is assumed that improvements would primarily be made for access from county roads
and that these roads would be restored to their pre-construction condition following
completion of the IRAs; however, restoration of roads to pre-construction condition may
be deferred on a case-by-case basis for the selected remedy.
• Site rehabilitation/reclamation would be conducted following construction only to
physically stabilize areas disturbed during IRA activities from subsequent erosion and
sedimentation.
9.3.3 Post-Construction Common Elements
• ICs involve non-engineered measures, such as administrative and legal controls, that help
to minimize the potential for exposure to contamination and/or protect the integrity of a
response action. These include governmental controls, enforcement tools with IC
components, proprietary controls, and informational devices. These controls or
combinations of controls would be implemented as needed, at federally managed lands
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(e.g., portions of Brooklyn Mine on lands managed by USFS) and at private properties to
maintain integrity of the proposed remedial components.
9.3.4 Annual or Periodic Monitoring Common Elements
• Remedy performance monitoring would generally consist of visual inspection and/or
sample collection and analysis. The specifics of the remedy performance monitoring for
each alternative are detailed in the following subsections.
• Maintenance would be performed as necessary to maintain the integrity of the remedial
components. The specifics of maintenance for each alternative are detailed in the
following subsections.
• While the Site-wide risk assessment is ongoing, it is assumed that these proposed actions
would not result in unlimited use and unrestricted exposure land use scenarios. Therefore,
five-year reviews are assumed to be conducted for the mining-related sources included in
the IRAs in conjunction with sources addressed by other response actions as part of Site-
wide activities.
9.4 DESCRIPTION OF REMEDIAL ALTERNATIVES FOR MINE PORTAL MIW
DISCHARGES
9.4.1 Alternative Al: No Action
• Estimated capital cost: $ 0
• Estimated total operations and maintenance (O&M) costs (over 15 years): $ 0
• Estimated total periodic costs (over 15 years): $ 0
• Estimated total present value cost: $ 0
• Estimated construction timeframe: None
• Estimated time to achieve RAOs: will never comply with RAOs
Alternative Al (No Action) is required by the NCP to provide an environmental baseline against
which impacts of the other remedial alternatives can be compared. This alternative would leave
mine portal MIW discharges and partial obstructions to these discharges in their current state,
and no action would be initiated to remediate them or otherwise mitigate contaminant migration
and transport with the associated contributions to unacceptable risks to the environment.
Summary of Major Remedial Components and Associated Quantities for Alternative Al:
None (no action taken)
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Key ARARs:
Because no action is taken, no chemical-, location-, or action-specific ARARs would be triggered.
Expected Outcomes:
• While the Site-wide risk assessment is ongoing, it is assumed that the alternative would not
result in unlimited use and unrestricted exposure land use scenarios.
• Unaddressed obstructed MIW discharges have a potential to create an unstable
impoundment of MIW, sediments, and metal precipitates that could be released to surface
water in an uncontrolled manner.
• This alternative would not reduce generation and migration of MIW, and would not reduce
releases to surface water from interaction with mining-related sources.
• Mine portal MIW discharges would migrate to surface water and could continue to
contribute to unacceptable ecological risks.
9.4.2 Alternative A2: Diversion/Isolation
• Estimated capital cost: $ 1,082,000
• Estimated total O&M costs (over 15 years): $ 1,890,000
• Estimated total periodic costs (over 15 years): $ 301,000
• Estimated total present value cost: $ 2,411,000
• Estimated construction timeframe: one season for individual mining-related sources, up
to 5 years for all sources
• Estimated time to achieve RAOs: upon completion of construction of Alternative A2
remedy components
Alternative A2 would involve construction of diversion and isolation components to route mine
portal MIW discharge around contaminated mine waste with the potential for interaction and co-
mingling at mining-related sources. Alternative A2 would also include maintenance of previously
existing and newly constructed diversion and isolation components.
Diversion or isolation components implemented at each mining-related source would be chosen
on a location-by-location basis. Open channels typically would be constructed to collect mine
portal MIW discharge and divert it around the existing mine waste. The construction of berms
immediately upgradient of mine waste, collection/diversion piping or liners, or a combination of
multiple types of components are also viable for locations that are not conducive to open-channel
diversion. At mining-related sources with existing MIW diversion or isolation components,
repairs would be conducted to improve the conditions of those components.
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In addition to mine wastes excavated for open-channel diversion, mine wastes or other materials
at the entrance to a mine portal that are partially obstructing the free flow of mine portal MIW
discharge would be excavated. During the excavation process, the excavated wastes would be
placed at the mining-related source for gravity dewatering. Physical characterization such as
analysis of geotechnical parameters would be conducted, as needed, on excavated and dewatered
mine waste to evaluate physical stability. Excavated wastes would be managed locally at the
mining-related source on an interim basis. Interim local waste management would include best
management practices (BMPs) such as berming, as necessary, to address fugitive dust and
potential erosion and sedimentation issues. Final remedial approaches for managed wastes will be
addressed as part of future remedy decisions and response actions.
Monitoring and maintenance of the diversion/isolation components and interim local waste
management locations would be conducted as needed, primarily due to events that could
compromise the components (e.g., lack of adherence to ICs, storm events, wildland fires).
Monitoring would consist of non-intrusive (surface) visual inspection of diversion and isolation
components to assess maintenance requirements and remedy performance monitoring consisting
of surface water measurements and/or sample collection and analysis would be conducted to
monitor effectiveness of the implemented IRA. Maintenance would be then performed as
necessary to maintain the integrity of both newly constructed and previously existing diversion
and isolation components.
Alternative A2 would also include implementing the common elements required for all
alternatives (other than No Action alternatives), as described in Section 9.3.
Summary of Major Remedial Components and Associated Quantities for Alternative A2:
Exhibit 9-2 provides a summary of the major remedial components for Alternative A2 requiring
construction and the estimated quantities for these components.
Exhibit 9-2 Summary of Major Remedial Components and Associated Quantities for Alternative A2
Koiiiodiiil ( niiipoiu'iil
I nil
I'lsliniiili'd
Estimated number of mining-related sources with mine portal MIW discharges
EA
20
Estimated total length of diversion/isolation components to be constructed
LF
3,560
Estimated in-place volume of mine wastes/materials partially obstructing mine portal
MIW discharges
CY
30
Estimated weight of dewatering agent (assumed to be diatomaceous earth)
TON
4
Estimated in-place volume of borrow material for remedial component construction
CY
3,220
Notes:
Although detailed quantities have been provided, they should be considered approximate for evaluation purposes only.
This exhibit summarizes the quantities for Alternative A2 of the FFS. As described in Section 12.0, due to minor modifications,
the selected interim remedy has minor differences in quantities.
EA - each, LF - linear feet, CY - cubic yards, TON - tons
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Key ARARs:
• Colorado Basic Standards and Methodologies for Surface Water (5 Colorado Code of
Regulations [CCR] 1002-31, pursuant to Colorado Revised Statutes [C.R.S.] §§ 25-8-
101-703)
• Colorado Basic Standards for Groundwater, (5 CCR 1002-41, pursuant to C.R.S. §§ 25-
8-101-703)
• Colorado Solid Waste Disposal Sites and Facilities Regulations (6 CCR 1007-2, pursuant
to C.R.S. §§ 30-20-100.5 et seq. §§ 30-20-101-515)
• Colorado Mined Land Reclamation Act (C.R.S. §§ 34-32-101 et. seq. and regulations 2
CCR 407-1 Rules 1.1 and 3)
• Colorado Effluent Limitations (5 CCR 1002-62, pursuant to C.R.S. § 25-8-205)
Expected Outcomes:
• Alternative A2 would provide protection of human health and the environment in the
short term and is intended to provide adequate protection until a final remedy is selected.
• Alternative A2 would provide stabilization of the mining-related sources and prevent
further environmental degradation.
• The loading of COPCs is expected to decrease under this alternative because
diversion/isolation components addressing the interaction between mine portal MIW
discharges and mine wastes reduces the contact of the water with the waste, thereby
reducing leaching and formation of MIW. However, the water quality in the streams,
irrespective of the removed mine wastes and diversion/isolation components, would still
be impacted and contribute to unacceptable ecological risks.
• While the Site-wide risk assessment is ongoing, it is assumed that the alternative would
not result in unlimited use and unrestricted exposure land use scenarios.
9.5 DESCRIPTION OF REMEDIAL ALTERNATIVES FOR MINING-RELATED
SOURCE/STORMWATER INTERACTIONS
9.5.1 Alternative Bl: No Action
• Estimated capital cost: $ 0
• Estimated total O&M costs (over 15 years): $ 0
• Estimated total periodic costs (over 15 years): $ 0
• Estimated total present value cost: $ 0
• Estimated construction timeframe: None
• Estimated time to achieve RAOs: will never comply with RAOs
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Alternative B1 (No Action) is required by the NCP to provide an environmental baseline against
which impacts of the other remedial alternatives can be compared. This alternative would leave
stormwater discharges to mining-related sources in their current state, and no action would be
initiated to remediate them or otherwise mitigate contaminant migration and transport from them
with the associated contributions to unacceptable risks to the environment.
Summary of Major Remedial Components and Associated Quantities for Alternative Bl:
None (no action taken)
Key ARARs:
Because no action is taken, no chemical-, location-, or action-specific ARARs would be triggered.
Expected Outcomes:
• While the Site-wide risk assessment is ongoing, it is assumed that the alternative would
not result in unlimited use and unrestricted exposure land use scenarios.
• This alternative would not reduce generation and migration of MIW, and would not
reduce releases to surface water from interaction with mining-related sources.
• Left uncontrolled, stormwater discharges interacting with mining-related sources could
migrate to surface water and could continue to contribute to unacceptable ecological risks.
9.5.2 Alternative B2: Stormwater Diversion/Isolation
• Estimated capital cost: $ 1,035,000
• Estimated total O&M costs (over 15 years): $ 1,260,000
• Estimated total periodic costs (over 15 years): $ 147,000
• Estimated total present value cost: $ 1,889,000
• Estimated construction timeframe: one season for individual mining-related sources, up
to 5 years for all sources
• Estimated time to achieve RAOs: upon completion of construction of Alternative B2
remedy components
Alternative B2 would involve construction of diversion and isolation components to route
stormwater around mine portals and/or contaminated mine waste with the potential for
interaction and co-mingling at mining-related sources. Alternative B2 would also include
maintenance of previously existing and newly constructed diversion and isolation components.
Diversion or isolation components implemented at each mining-related source would be chosen
on a location-by-location basis. Open channels typically would be constructed to collect
stormwater and divert it around the existing mine portals or mine waste. The construction of
berms immediately upgradient of mine portals or mine waste, collection/diversion piping or
liners, or a combination of multiple types of components are also viable for locations that are not
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conducive to open-channel diversion. At mining-related sources with existing stormwater
diversion or isolation components, repairs would be conducted to improve the conditions of
those components.
Where amenable, this alternative could include subsurface components in conjunction with the
surface components previously described. Subsurface components such as interception trenches
or French drains could be constructed to intercept stormwater that has infiltrated into the shallow
subsurface and divert it around mine portals or mine waste.
Monitoring and maintenance of the diversion/isolation components would be conducted as
needed, primarily due to events that could compromise the components (e.g., lack of adherence
to ICs, storm events, wildland fires). Monitoring would consist of non-intrusive (surface) visual
inspection of diversion and isolation components to assess maintenance requirements and
remedy performance monitoring consisting of surface water measurements and/or sample
collection and analysis would be conducted to monitor effectiveness of the implemented IRA.
Maintenance would be then performed as necessary to maintain the integrity of both newly
constructed and previously existing diversion and isolation components.
Alternative B2 would also include implementing the common elements required for all
alternatives (other than No Action alternatives), as described in Section 9.3.
Summary of Major Remedial Components and Associated Quantities for Alternative B2:
Exhibit 9-3 provides a summary of the major remedial components for Alternative B2 requiring
construction and the estimated quantities for these components.
Exhibit 9-3 Summary of Major Remedial Components and Associated Quantities for Alternative B2
Koiiiodiiil ( niiipoiu'iil
I nil
I'lsliniiili'd
Estimated number of mining-related sources with mining-related source/stormwater
interactions
EA
11
Estimated total length of diversion/isolation components to be constructed
LF
4,270
Estimated in-place volume of borrow material for remedial component construction
CY
3,400
Notes:
Although detailed quantities have been provided, they should be considered approximate for evaluation purposes only.
This exhibit summarizes the quantities for Alternative B2 of the FFS. As described in Section 12.0, due to minor modifications,
the selected interim remedy has minor differences in quantities.
EA - each, LF - linear feet, CY - cubic yards
Key ARARs:
• Colorado Basic Standards and Methodologies for Surface Water (5 CCR 1002-31,
pursuant to C.R.S. §§ 25-8-101-703)
• Colorado Basic Standards for Groundwater, (5 CCR 1002-41, pursuant to C.R.S. §§ 25-
8-101-703)
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• Colorado Solid Waste Disposal Sites and Facilities Regulations (6 CCR 1007-2, pursuant
to C.R.S. §§ 30-20-100.5 et seq. §§ 30-20-101-515)
• Colorado Mined Land Reclamation Act (C.R.S. §§ 34-32-101et. seq. and regulations
2 CCR 407-1 Rules 1.1 and 3)
• Colorado Effluent Limitations (5 CCR 1002-62, pursuant to C.R.S. § 25-8-205)
Expected Outcomes:
• Alternative B2 would provide protection of human health and the environment in the
short term and is intended to provide adequate protection until a final remedy is selected.
• Alternative B2 would provide stabilization of the mining-related sources and prevent
further environmental degradation.
• Routing of storm water around mine portals and/or contaminated mine wastes with the
potential for interaction and co-mingling at mining-related sources would reduce the
potential for stormwater to generate additional MIW and release particulates containing
COPCs to surface water, which contribute to unacceptable ecological risks. However, the
water quality in the streams, irrespective of diverted/isolated stormwater, would still be
impacted.
• While the Site-wide risk assessment is ongoing, it is assumed that the alternative would
not result in unlimited use and unrestricted exposure land use scenarios.
9.6 DESCRIPTION OF REMEDIAL ALTERNATIVES FOR MINE PORTAL POND
SEDIMENTS
9.6.1 Alternative CI: No Action
• Estimated capital cost: $ 0
• Estimated total O&M costs (over 15 years): $ 0
• Estimated total periodic costs (over 15 years): $ 0
• Estimated total present value cost: $ 0
• Estimated construction timeframe: None
• Estimated time to achieve RAOs: will never comply with RAOs
Alternative CI (No Action) is required by the NCP to provide an environmental baseline against
which impacts of the other remedial alternatives can be compared. This alternative would leave
mine portal pond sediments in their current state, and no further action would be initiated to
remediate them or otherwise mitigate contaminant migration and transport from them with the
associated contributions to unacceptable risks to the environment.
Summary of Major Remedial Components and Associated Quantities for Alternative BM1:
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None (no action taken)
Key ARARs:
Because no action is taken, no chemical-, location-, or action-specific ARARs would be triggered.
Expected Outcomes:
• While the Site-wide risk assessment is ongoing, it is assumed that the alternative would
not result in unlimited use and unrestricted exposure land use scenarios.
• Unaddressed sediments would continue to reduce storage space of MIW in in mine portal
ponds and result in the potential for uncontrolled releases of particulates and/or MIW
containing COPCs to surface water, which contribute to unacceptable ecological risks.
• Unaddressed sediments in mine portal ponds have potential to remobilize COPCs in
sediments and/or MIW during storm events.
9.6.2 Alternative C2: Excavation and Interim Local Waste Management
• Estimated capital cost: $ 1,355,000
• Estimated total O&M costs (over 15 years): $ 1,110,000
• Estimated total periodic costs (over 15 years): $ 2,387,000
• Estimated total present value cost: $ 3,384,000
• Estimated construction timeframe: one season for individual mining-related sources, up
to 5 years for all sources
• Estimated time to achieve RAOs: upon completion of construction of Alternative C2
remedy components
Alternative C2 would involve excavating existing sediment and repair of berms within mine
portal ponds to allow continued pond function.
Prior to removing sediment, the mine portal ponds would be drained. MIW within ponds would
be managed locally solely to facilitate sediment excavation. Short-circuiting of ponds (MIW
passing through or around the pond without treatment), if those conditions currently exist, would
also be addressed through the construction or repair of pond berms.
Excavating sediment would be conducted at mine portal ponds to facilitate continued function of
the ponds. During the excavation process, the excavated wastes would be placed at the mining-
related source for gravity dewatering. The location for this activity is assumed to be amenable to
dewatering without the need for liners or other isolation measures. Additional dewatering could
be implemented for saturated sediment through ex situ amendment with a dewatering agent, as
necessary, for handling and geotechnical stability prior to interim management at the mining-
related source. Physical characterization, such as analysis of geotechnical parameters, would be
conducted as needed on excavated and dewatered sediment to evaluate physical stability.
Excavated wastes would be managed locally at the mining-related source on an interim basis.
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Interim local waste management would include BMPs such as berming, as necessary, to address
fugitive dust and potential erosion and sedimentation issues. Final remedial approaches for
managed wastes would be addressed as part of future remedy decisions and response actions.
Monitoring and maintenance of the pond berms and interim local waste management locations
would be conducted as needed, primarily due to events that could compromise the components
(e.g., lack of adherence to ICs, storm events, wildland fires). Monitoring would consist of non-
intrusive (surface) visual inspection of interim local waste management locations to assess
maintenance requirements and monitor sediment levels in ponds and remedy performance
monitoring consisting of surface water measurements and/or sample collection and analysis
would be conducted to monitor effectiveness of the implemented IRA. Maintenance would be
then performed as necessary to remove future accumulation of sediment in ponds and to maintain
the integrity of both newly constructed and previously existing pond berms and interim
management location components.
Alternative C2 would also include implementing the common elements required for all alternatives
(other than No Action alternatives), as described in Section 9.3. The assumptions for Alternative
C2 would be refined at the time of remedial design using location-specific information.
Summary of Major Remedial Components and Associated Quantities for Alternative C2:
Exhibit 9-4 provides a summary of the major remedial components for Alternative C2 requiring
construction and the estimated quantities for these components.
Exhibit 9-4 Summary of Major Remedial Components and Associated Quantities for Alternative C2
Koiiiodiiil ( niiipoiu'iil
I nil
I'.sliiiiiilcd
Qii;uilil>
Estimated number of mining-related sources with mine portal pond sediments
EA
8
Estimated number of ponds
EA
14
Estimated horizontal extent of ponds
SF
68,800
Estimated in-place volume of mine portal pond sediments
CY
10,200
Estimated weight of dewatering agent (assumed to be diatomaceous earth)
TON
190
Estimated in-place volume of borrow material for remedial component construction
CY
2,710
Notes:
Although detailed quantities have been provided, they should be considered approximate for evaluation purposes only.
EA - each, SF - square feet, CY - cubic yards, TON - tons
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Key ARARs:
• Colorado Basic Standards and Methodologies for Surface Water (5 CCR 1002-31,
pursuant to C.R.S. §§ 25-8-101-703)
• Colorado Basic Standards for Groundwater, (5 CCR 1002-41, pursuant to C.R.S. §§ 25-
8-101-703)
• Colorado Solid Waste Disposal Sites and Facilities Regulations (6 CCR 1007-2, pursuant
to C.R.S. §§ 30-20-100.5 et seq. §§ 30-20-101-515)
• Colorado Mined Land Reclamation Act (C.R.S. §§ 34-32-101et. seq. and regulations 2
CCR 407-1 Rules 1.1 and 3)
• Colorado Effluent Limitations (5 CCR 1002-62, pursuant to C.R.S. § 25-8-205)
Expected Outcomes:
• Alternative C2 would provide protection of human health and the environment in the
short term and is intended to provide adequate protection until a final remedy is selected.
• Alternative C2 would provide stabilization of the mining-related sources and prevent
further environmental degradation.
• Excavating pond sediments improves the effectiveness of the pond and reduces the
potential for an uncontrolled release of MIW. However, the water quality in the streams,
irrespective of the removed mine portal pond sediments, would still be impacted.
• Residual risks remain from untreated mine portal pond sediments managed locally at the
mining-related source on an interim basis. Long-term effectiveness of interim local
management locations would be dependent on BMPs, inspection, and repair, as
necessary, to maintain their integrity.
• While the Site-wide risk assessment is ongoing, it is assumed that the alternative would
not result in unlimited use and unrestricted exposure land use scenarios.
9.7 DESCRIPTION OF REMEDIAL ALTERNATIVES FOR IN-STREAM MINE
WASTES
9.7.1 Alternative Dl: No Action
• Estimated capital cost: $ 0
• Estimated total O&M costs (over 15 years): $ 0
• Estimated total periodic costs (over 15 years): $ 0
• Estimated total present value cost: $ 0
• Estimated construction timeframe: None
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• Estimated time to achieve RAOs: will never comply with RAOs
Alternative D1 (No Action) is required by the NCP to provide an environmental baseline against
which impacts of the other remedial alternatives can be compared. This alternative would leave
in-stream mine wastes in their current state, and no further action would be initiated to remediate
them or otherwise mitigate contaminant migration and transport from them with the associated
contributions to unacceptable risks to the environment.
Summary of Major Remedial Components and Associated Quantities for Alternative BM1:
None (no action taken)
Key ARARs:
Because no action is taken, no chemical-, location-, or action-specific ARARs would be triggered.
Expected Outcomes:
• While the Site-wide risk assessment is ongoing, it is assumed that the alternative would
not result in unlimited use and unrestricted exposure land use scenarios.
• Unaddressed in-stream mine wastes would continue to have the potential for erosion and
result in the potential for releases of particulates and/or MIW containing COPCs to
surface water, which contribute to unacceptable ecological risks.
• Unaddressed in-stream mine wastes have potential to remobilize COPCs in particulate
form and/orMIW during storm events.
9.7.2 Alternative D2: Excavation and Interim Local Waste Management
• Estimated capital cost: $ 340,000
• Estimated total O&M costs (over 15 years): $ 405,000
• Estimated total periodic costs (over 15 years): $ 63,000
• Estimated total present value cost: $ 624,000
• Estimated construction timeframe: one season for individual mining-related sources, up
to 5 years for all sources
• Estimated time to achieve RAOs: upon completion of construction of Alternative D2
remedy components
Alternative D2 would involve excavating in-stream mine wastes at mining-related sources to
remove wastes that impede flow and are susceptible to erosion or leaching of contaminants to
surface water, which contribute to unacceptable ecological risks.
During the excavation process, the excavated wastes would be placed outside of the stream
channel adjacent to the mining-related source for gravity dewatering. The location for this
activity is assumed to be amenable to dewatering without the need for liners or other isolation
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measures. Additional dewatering could be implemented for saturated mine wastes through ex
situ amendment with a dewatering agent, as necessary, for handling and geotechnical stability
prior to interim management at the mining-related source. Physical characterization such as
analysis of geotechnical parameters would be conducted, as needed, on excavated and dewatered
sediment to evaluate physical stability. Excavated wastes would be managed locally at the
mining-related source on an interim basis. Interim local waste management would include BMPs
such as berming, as necessary, to address fugitive dust and potential erosion and sedimentation
issues. Final remedial approaches for managed wastes, would be addressed as part of future
remedy decisions and response actions.
Monitoring and maintenance of the interim local waste management locations would be
conducted as needed, primarily due to events that could compromise the components (e.g., lack
of adherence to ICs, storm events, wildland fires). Monitoring would consist of non-intrusive
(surface) visual inspection of interim local waste management locations to assess maintenance
requirements and remedy performance monitoring consisting of surface water measurements
and/or sample collection and analysis would be conducted to monitor effectiveness of the
implemented IRA. Maintenance would be then performed as necessary to maintain the integrity
of interim management location components.
Alternative D2 would also include implementing the common elements required for all alternatives
(other than No Action alternatives), as described in Section 9.3. The assumptions for Alternative
D2 would be refined at the time of remedial design using location-specific information.
Summary of Major Remedial Components and Associated Quantities for Alternative D2:
Exhibit 9-5 provides a summary of the major remedial components for Alternative D2 requiring
construction and the estimated quantities for these components.
Exhibit 9-5 Summary of Major Remedial Components and Associated Quantities for Alternative D2
Koiiiodiiil ( niiipoiu'iil
I nil
I'.sliiiiiilcd
Qii;uilil>
Estimated number of mining-related sources with in-stream mine wastes
EA
2
Estimated horizontal extent of in-stream mine wastes
SF
8,900
Estimated in-place volume of in-stream mine wastes
CY
990
Estimated weight of dewatering agent (assumed to be diatomaceous earth)
TON
20
Estimated in-place volume of borrow material for remedial component construction
CY
180
Notes:
Although detailed quantities have been provided, they should be considered approximate for evaluation purposes only.
This exhibit summarizes the quantities for Alternative D2 of the FFS. As described in Section 12.0, due to minor modifications,
the selected interim remedy has minor differences in quantities.
EA - each, SF - square feet, CY - cubic yards, TON - tons
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Key ARARs:
• Colorado Basic Standards and Methodologies for Surface Water (5 CCR 1002-31,
pursuant to C.R.S. §§ 25-8-101-703)
• Colorado Basic Standards for Groundwater, (5 CCR 1002-41, pursuant to C.R.S. §§ 25-
8-101-703)
• Colorado Solid Waste Disposal Sites and Facilities Regulations (6 CCR 1007-2, pursuant
to C.R.S. §§ 30-20-100.5 et seq. §§ 30-20-101-515)
• Colorado Mined Land Reclamation Act (C.R.S. §§ 34-32-101et. seq. and regulations 2
CCR 407-1 Rules 1.1 and 3)
• Colorado Effluent Limitations (5 CCR 1002-62, pursuant to C.R.S. § 25-8-205)
Expected Outcomes:
• Alternative D2 would provide protection of human health and the environment in the
short term and is intended to provide adequate protection until a final remedy is selected.
• Alternative D2 would provide stabilization of the mining-related sources and prevent
further environmental degradation.
• Through removal of in-stream mine wastes, the loading of COPCs is expected to decrease
because it reduces the contact of the water with the waste, thereby reducing leaching and
formation of MIW. However, the water quality in the streams, irrespective of the
removed mine wastes, would still be impacted.
• Residual risks would remain from untreated wastes managed locally at the mining-related
source on an interim basis. Long-term effectiveness of interim local management
locations would be dependent on BMPs, inspection, and repair, as necessary, to maintain
their integrity.
• While the Site-wide risk assessment is ongoing, it is assumed that the alternative would
not result in unlimited use and unrestricted exposure land use scenarios.
9.8 DESCRIPTION OF REMEDIAL ALTERNATIVES FOR MINING-IMPACTED
RECREATION STAGING AREAS
9.8.1 Alternative El: No Action
• Estimated capital cost: $ 0
• Estimated total O&M costs (over 15 years): $ 0
• Estimated total periodic costs (over 15 years): $ 0
• Estimated total present value cost: $ 0
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• Estimated construction timeframe: None
• Estimated time to achieve RAOs: will never comply with RAOs
Alternative El (No Action) is required by the NCP to provide an environmental baseline against
which impacts of the other remedial alternatives can be compared. This alternative would leave
mining-impacted recreation staging areas in their current state, and no further action would be
initiated to remediate them or otherwise mitigate contaminant migration and transport from them
with the associated contributions to unacceptable risks to human health.
Summary of Major Remedial Components and Associated Quantities for Alternative BM1:
None (no action taken)
Key ARARs:
Because no action is taken, no chemical-, location-, or action-specific ARARs would be triggered.
Expected Outcomes:
• While the Site-wide risk assessment is ongoing, it is assumed that the alternative would
not result in unlimited use and unrestricted exposure land use scenarios.
• Repeated disturbances of unaddressed mining-impacted recreation staging areas could
result in potential adverse lead and arsenic exposures to campers, assuming current or
reasonably anticipated future recreational use.
9.8.2 Alternative E2: Containment/Isolation
• Estimated capital cost: $ 1,210,000
• Estimated total O&M costs (over 15 years): $ 135,000
• Estimated total periodic costs (over 15 years): $ 623,000
• Estimated total present value cost: $ 1,668,000
• Estimated construction timeframe: one season for individual mining-related sources, up
to 5 years for all sources
• Estimated time to achieve RAOs: upon completion of construction of Alternative E2
remedy components
Alternative E2 includes containment/isolation of mine wastes within mining-impacted recreation
staging areas using covers to reduce disturbances of mine wastes and migration of contaminants.
A combination of different types of covers would be constructed at mining-impacted recreation
staging areas. The covers would provide an exposure barrier and eliminate surface exposure to
mine waste or contaminated soil. The covers would be sloped to promote positive drainage in
order to minimize erosion and to reduce infiltration that could saturate the subsurface and
compromise the integrity of the covers. The prepared mine waste or contaminated soil surface
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would then be covered with an engineered layer of soil (which could be vegetated) or a surface
layer of rock. The specific types of covers would be determined based on specific uses of each
mining-related source and availability of sufficient quantities of suitable cover materials for that
use. Covers would be revegetated or otherwise reclaimed to match active land use of each
mining-impacted recreation staging area.
Monitoring and maintenance of the covers would be conducted as needed, primarily due to
events that could compromise the components (e.g., lack of adherence to ICs, storm events,
wildland fires). Monitoring would consist of non-intrusive (surface) visual inspection of cover
components to assess remedy performance and maintenance requirements; maintenance would
be then performed as necessary to maintain the integrity of cover components.
Alternative E2 would also include implementing the common elements required for all
alternatives (other than No Action alternatives), as described in Section 9.3.
Summary of Major Remedial Components and Associated Quantities for Alternative E2:
Exhibit 9-6 provides a summary of the major remedial components for Alternative E2 requiring
construction and the estimated quantities for these components.
Exhibit 9-6 Summary of Major Remedial Components and Associated Quantities for
Alternative E2
Koiiiodiiil ( niiipoiu'iil
I nil
I'lsliniiili'd
Estimated number of mining-related sources with mining-impacted recreation
staging areas
EA
5
Estimated horizontal extent of aggregate (rock) covers to be constructed
AC
2.0
Estimated horizontal extent of soil covers to be constructed
AC
6.9
Estimated in-place volume of borrow material for remedial component construction
CY
18,600
Notes:
Although detailed quantities have been provided, they should be considered approximate for evaluation purposes only.
AC - acres, EA - each, CY - cubic yards
Key ARARs:
• Colorado Basic Standards and Methodologies for Surface Water (5 CCR 1002-31,
pursuant to C.R.S. §§ 25-8-101-703)
• Colorado Basic Standards for Groundwater, (5 CCR 1002-41, pursuant to C.R.S. §§ 25-
8-101-703)
• Colorado Solid Waste Disposal Sites and Facilities Regulations (6 CCR 1007-2, pursuant
to C.R.S. §§ 30-20-100.5 et seq. §§ 30-20-101-515)
• Colorado Mined Land Reclamation Act (C.R.S. §§ 34-32-101et. seq. and regulations 2
CCR 407-1 Rules 1.1 and 3)
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• Colorado Effluent Limitations (5 CCR 1002-62, pursuant to C.R.S. § 25-8-205)
Expected Outcomes:
• Alternative E2 would provide protection of human health and the environment in the
short term and is intended to provide adequate protection until a final remedy is selected.
• Alternative E2 would provide stabilization of the mining-related sources and prevent
further environmental degradation.
• Exposures to mine wastes and contaminated soils containing lead or arsenic that exceed
risk-based levels are reduced through covers installed over recreation staging areas.
• ICs would be implemented to protect the integrity of the covers from inappropriate
human activities that could breach the covers and cause exposures to mine wastes and
contaminated soils.
• While the Site-wide risk assessment is ongoing, it is assumed that the alternative would
not result in unlimited use and unrestricted exposure land use scenarios.
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10.0 COMPARATIVE ANALYSIS OF ALTERNATIVES
The FFS evaluated two remedial alternatives (including No Action alternatives required by the
NCP) for each of the five contaminant migration issues, for a total of ten alternatives. These
remedial alternatives were individually evaluated against the two threshold criteria and five
balancing criteria. A comparative analysis of the remedial alternatives for each contaminant
migration issue using the threshold and balancing criteria has been put into narrative form in the
following subsections. The results of the individual detailed analysis for each remedial
alternative are presented on Exhibit 10-1; presentation of this information aids in understanding
a comparative analysis of the alternatives and identifying the key tradeoffs between them. Only
significant comparative differences between alternatives are presented; the full rationale for the
qualitative ratings determined as part of detailed analysis for the individual alternatives is
provided in Appendix E of the FFS (CDM Smith 2018).
10.1 COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES FOR MINE
PORTAL MIW DISCHARGES (ALTERNATIVES A1 AND A2)
10.1.1 Overall Protection of Human Health and the Environment
Of the two alternatives, the No Action alternative (i.e., Alternative Al) would fail to provide
adequate protection of human health and the environment in the short term until a final remedy is
selected and would not achieve RAO 1 (RAOs 2 and 3 are not pertinent to this IRA). This
alternative would not provide stabilization of the mining-related sources and prevent further
environmental degradation. Unaddressed mine portal MIW discharge would continue to release
particulates containing COPCs to surface water and generate additional MIW from interaction
with mining-related sources, which contribute to unacceptable ecological risks. Thus, this
alternative was given a rating of "not adequate."
Alternative A2 was given a rating of "adequate" because, it would provide protection of human
health and the environment in the short term and is intended to provide adequate protection until
a final remedy is selected. This alternative would provide stabilization of the mining-related
sources and prevent further environmental degradation. Alternative A2 addresses RAO 1 by
constructing and/or maintaining diversion and isolation components to route mine portal MIW
discharge around contaminated mine waste with the potential for interaction and co-mingling at
mining-related sources. This would reduce the potential for mine portal MIW discharges to
generate additional MIW and reduce transport of particulates containing COPCs to surface
water, which contribute to unacceptable ecological risks. Mine wastes or other materials at the
entrance to a mine portal that are partially obstructing free flow of MIW discharge would be
excavated to reduce the potential for uncontrolled releases of particulates and MIW containing
COPCs to surface water, which contribute to unacceptable ecological risks. Excavated wastes
would be managed locally at the mining-related source on an interim basis. Interim local waste
management would include BMPs such as berming, as necessary, to address fugitive dust and
potential erosion and sedimentation issues. Residual risks would remain from untreated mine
wastes managed locally at the mining-related sources. Long-term effectiveness of interim waste
management locations would depend on BMPs, inspection, and repair, as necessary, to maintain
their integrity. EPA would measure the extent by which ecological risks associated with
contributions from MIW discharges have been reduced by this alternative. This data would
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provide information about the effectiveness of the IRA and is intended to help inform future
remedial decisions at the Site. ICs would be implemented to prevent activities that would disturb
the integrity of local waste management locations and diversion/isolation components and
prevent uses inconsistent with current and reasonably anticipated future land uses.
10.1.2 Compliance with ARARs
Under Alternative Al, unaddressed mine portal MIW discharges would continue to release
particulates containing COPCs to surface water. Because no action is taken, no chemical-,
location, or action-specific ARARs are triggered. Thus, this alternative was given a rating of
"none."
Chemical-specific ARARs would be pertinent to Alternative A2. State water quality standards
for COPCs would likely not be met for the streams receiving mine portal MIW discharges after
the alternative is constructed due to other contributing mining-related sources, thus the interim
measures CERCLA ARAR waiver would be invoked for the Colorado Basic Standards and
Methodologies for Surface Water. The Colorado Basic Standards for Groundwater would also be
waived using an interim measures CERCLA ARAR waiver because the limited RI information
available does not indicate that groundwater meeting the regulatory definition exists beneath the
mining-related sources addressed by this alternative.
Location- and action-specific ARARs for Alternative A2 would be addressed during
implementation of the IRA as indicated in the following paragraphs.
Excavation: The excavation of mine wastes from waters of the U.S. is assumed to be performed
with neat excavation only involving incidental fallback. Thus, the substantive requirements of
Section 404 would not be triggered. If grading or excavation activities result in a discharge of
dredge material, the substantive requirements of Nationwide Permit 20 (Response Operations for
Oil or Hazardous Substances) would be met.
Dust Suppression: Dust suppression and emission-controlled equipment would be used during
construction activities for the alternative to achieve compliance with Colorado emission control
requirements.
Dewatering: If effluent discharge to surface water is necessary during dewatering activities,
activities would be conducted in a way to minimize infiltration into the ground surface that could
cause additional degradation of groundwater. Because the groundwater, as defined in 5 CCR
1002-41, is not known to be present below the mining-related sources, an interim measures
CERCLA ARAR waiver would be invoked. An interim measures CERCLA ARAR waiver
would also be invoked to waive the substantive provisions of Colorado Effluent Limitations and
Colorado Discharge Permit System (CDPS) regulations for groundwater.
If effluent discharge to surface water is necessary from dewatering activities, the discharge limit
requirements of Colorado effluent limitations would be met without treatment at the dewatering
locations; otherwise an interim measures CERCLA ARAR waiver would be invoked. Similarly,
the substantive provisions of the CDPS regulations would be met; otherwise an interim measures
CERCLA ARAR waiver would be invoked.
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Interim Local Waste Management: Mine wastes at the Site were derived directly or indirectly
from the extraction of ore and thus would be exempt from management as a Resource
Conservation and Recovery Act (RCRA) hazardous waste (i.e., the Bevill exemption), thus mine
wastes would be classified as a non-hazardous solid waste.
Pursuant to the Solid Wastes Disposal Sites and Facilities Act, C.R.S. § 30-20-102(4), mining
operations including reclamation activities with approved reclamation plans under a Colorado
Mined Land Reclamation Board (MLRB) permit may dispose of solid wastes generated by such
operations within the permitted area without obtaining a Certificate of Designation. The CDPHE
interprets this provision to exempt CERCLA response actions performed consistently with
MLRB regulation 2 CCR 407-1 Rule 3 (Reclamation Performance Standards) to be compliant
with Colorado's regulations pertaining to solid waste disposal.
All waste handling and disposal activities under this alternative would be performed in
accordance with substantive requirements of the relevant and appropriate subparts of MLRB
regulation 2 CCR 407-1 Rule 3 (Reclamation Performance Standards), which would allow the
alternative to be compliant with substantive requirements of the Colorado Solid Waste Disposal
Sites and Facilities Regulations.
Placement, grading, and backfilling of wastes for interim local management would be performed
to meet relevant and appropriate substantive requirements of 2 CCR 407-1 Rule 3.
Surface Reclamation: All surface reclamation activities under this alternative, including
placement, grading, and backfilling, would be performed to meet relevant and appropriate
substantive requirements of 2 CCR 407-1 Rule 3.
Construction Activities: Cultural resource surveys have not been completed for all mining-
related sources addressed by this alternative. If any cultural resources are found, surveys will be
necessary to determine if adverse effects would occur, and if so, how the effects may be
minimized or mitigated in accordance with the National Historic Preservation Act,
Archaeological and Historic Preservation Act, and Historic Sites Act.
If bald or golden eagles are observed during remedial design and IRA, activities must be
modified and conducted to conserve the species and their habitat to comply with the substantive
requirements of the Bald and Golden Eagle Protection Act.
If the IRA involves activities modifying streams or water bodies that affect wildlife and/or non-
game fish, federal agencies must comply with substantive requirements identified by the U.S.
Fish and Wildlife Service (USFWS) and the relevant state agency with jurisdiction over wildlife
resources in accordance with Fish and Wildlife Coordination Act and implementing regulations.
If threatened or endangered species are identified at these mining-related sources during remedial
design and IRA, activities must be modified and conducted to conserve the species and their
habitat in accordance with the Endangered Species Act.
If migratory birds are identified during remedial design and IRA, activities must be modified and
conducted to conserve the species and their habitat in accordance with the Migratory Bird Treaty
Act.
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The alternative would not be conducted within streams. However, if activities were to impact
streams, they would be carried out in a manner to avoid adversely affecting wildlife and/or non-
game fish within streams. Compliance would be achieved through coordination with the
Colorado Division of Parks Wildlife and in accordance with the Colorado Wildlife Enforcement
and Penalties Act and Colorado Non-game, Endangered, or Threatened Species Act.
It is not anticipated that nests or dens of wildlife exist at the mine locations. If they were to be
encountered, the alternative would be implemented to avoid disturbing or destroying nests or
dens. Compliance would be achieved through coordination with the Colorado Division of Parks
Wildlife and in accordance with substantive requirements of Colorado Wildlife Commission
regulations.
Activities conducted during the IRA on USFS-managed land, such as obtaining borrow material
and implementing the IRA at the Brooklyn Mine, would need to comply with the substantive
requirements of the San Juan National Forest and Tres Rios Field Office Land and Resource
Management Plan.
If the IRA involves activities that affect identified floodplains or wetlands, activities will be
carried out in a manner to avoid adversely affecting them and thus meet the substantive
requirements of the Clean Water Act, Section 404 regulations and Federal Emergency
Management Agency (FEMA) Floodplain Management Regulations. Activities under this
alternative would be carried out in a manner that will comply with Colorado Noise Abatement
Statue 25-12-103.
Since Alternative A2 could comply with substantive requirements of ARARs or invoke
CERCLA ARAR waivers, it was given rating of "will comply, but may require CERCLA ARAR
waiver(s)."
10.1.3 Long-Term Effectiveness and Permanence
Alternative A1 fails to provide long-term effectiveness and permanence since no action is taken.
Unaddressed obstructed MIW discharges have potential to create unstable impoundments of
MIW, sediments, and metal precipitates that could be released to surface water in an
uncontrolled manner. This alternative would not reduce generation and migration of MIW and
would not reduce releases of COPCs to surface water from interaction of MIW with mining-
related sources. Left uncontrolled, mine portal MIW discharges could migrate to surface water
and continue to contribute to unacceptable ecological risks. This alternative would not provide
stabilization of the mining-related sources and prevent further environmental degradation. Thus,
this alternative was given a rating of "none."
The loading of COPCs is expected to decrease under Alternative A2 because diversion/isolation
components addressing the interaction between mine portal MIW discharges and mine wastes
reduces leaching and formation of MIW. However, the water quality in the streams, irrespective
of the diversion/isolation components, would still be impacted and contribute to unacceptable
ecological risks. Residual risks would remain from untreated mine wastes excavated for
diversion/isolation components and managed locally at the mining-related sources on an interim
basis. Inspection and repair of the diversion/isolation components would be performed as
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necessary to maintain their integrity. Long-term effectiveness of diversion/isolation components
and interim local management locations would be dependent on BMPs, inspection, and repair, as
necessary, to maintain their integrity. Inspection and repair of the diversion/isolation components
and interim local waste management locations would be conducted as needed, primarily due to
events that could compromise the components (e.g., lack of adherence to ICs, storm events,
wildland fires). Periodic monitoring and maintenance of interim management locations would be
performed until final disposition of managed waste that would be addressed as part of a future
response action. ICs would be implemented to prevent activities that would disturb the integrity
of local waste management locations and diversion/isolation components and prevent uses
inconsistent with current and reasonably anticipated future land uses
This alternative was given a rating of "moderate," primarily due to considerations affecting long-
term effectiveness and permanence of monitoring and maintaining isolation/diversion
components at waste rock piles below mine portal MIW discharges and interim local waste
management locations, with monitoring and maintenance as needed.
10.1.4 Reduction of Toxicity, Mobility, or Volume through Treatment
Alternatives A1 and A2 fail to provide a reduction of toxicity, mobility, or volume through
treatment since treatment is not a component of these alternatives. Although gravity dewatering
may result in positive benefits to geotechnical stability, it is not considered treatment per this
NCP criterion because it does not result in permanent and irreversible reductions in toxicity,
mobility, or volume of contamination. Thus, these alternatives were given a rating of "none."
10.1.5 Short-Term Effectiveness
No action, would be undertaken under Alternative A1 to address mine portal MIW discharges
interacting with mining-related sources. Thus, there are no short-term risks posed to the
community, workers, or environment during implementation of this alternative. Thus, this
alternative was given a rating of "none."
Alternative A2 would pose short-term risks to the community and workers related to increased
traffic from transporting equipment and borrow material. Driving on access roads that have high
centers, rock outcroppings, steep slopes, and lack sufficient width for transporting construction
equipment could cause accidents. Safety measures such as signage and flaggers would be
implemented to protect workers and the community from increased traffic. Short-term risks to
workers could also occur due to work in alpine areas and at the entrance to mine portals, but
would be mitigated through safety measures such as personal protective equipment (PPE) (e.g.,
steel toe boots) and work zones, as well as other safety practices.
There would also be short-term impact to the environment. Short-term increases in contaminant
loading could result due to disturbing the mine wastes during excavation, resulting in temporary
increases in production of MIW. The excavation of mine wastes or other materials at the
entrance to mine portals could cause a release of retained sludge and precipitates just inside the
mine portals behind the blockages and temporary surges of higher flows of MIW until re-
equilibration. Transporting and placing borrow material has potential environmental impacts
from equipment emissions and disturbing borrow locations. Developing borrow areas could
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adversely impact the environment. Mitigation measures could include selecting easily accessible
borrow locations and reclaiming borrow areas after use.
Alternative A2 was given a rating of "moderate," primarily due to the moderate quantities of
borrow material required and the limited short-term impacts of constructing diversion/isolation
components in uncontaminated areas of the mining-related sources. Alternative A2 was given a
rating of "moderate," primarily due to short-term impacts associated with working at mine
portals and MIW discharges and the moderate quantities of borrow material required for berm
and access road construction that would be transported to mining-related sources for this
alternative.
10.1.6 Implementability
Alternative A1 has no further action taken. Since no remedial action is taken, this alternative was
given a rating of "none."
Alternative A2 includes constructing diversion/isolation components, excavation, dewatering,
and interim local management of mine wastes. These are conventional construction practices and
can be implemented using available equipment and labor resources. Maintenance and monitoring
of diversion/isolation components and interim local waste management areas could prove
difficult due to difficult access and constrained locations, especially at alpine and subalpine-
category locations with non-conventional access. Uncontaminated borrow material for
constructing remedial components and access roads would be generated and transported from
within the Site, however borrow location(s) of suitable quantity and quality have not yet been
identified Monitoring and maintenance of ICs is dependent on periodic reviews of the
administrative and/or legal instruments used. Maintenance of ICs may be more difficult due to
various types of ownership and land use and would require agency coordination.
Alternative A2 was given a rating of "moderate," primarily due to challenges associated with
working at mine portals and MIW discharges and the moderate quantities of borrow material
required for berm and access road construction.
10.1.7 Cost
Present value costs for both alternatives were evaluated over a 15-year period after the base year
(Years 0 through 15).
The present value cost for Alternative A1 is $0. The present value cost for Alternative A2 is
$2,411,000.
10.2 COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES FOR MINING-
RELATED SOURCE/STORMWATER INTERACTIONS (ALTERNATIVES B1
AND B2)
10.2.1 Overall Protection of Human Health and the Environment
Of the two alternatives, the No Action alternative (i.e., Alternative Bl) would fail to provide
adequate protection of human health and the environment in the short term until a final remedy is
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selected and would not achieve RAO 1 (RAOs 2 and 3 are not pertinent to this IRA). This
alternative would not provide stabilization of the mining-related sources and prevent further
environmental degradation. Unaddressed stormwater interacting with mining-related sources
would continue to generate MIW and release particulates containing COPCs to surface water,
which contribute to unacceptable ecological risks. Thus, this alternative was given a rating of
"not adequate."
Alternative B2 was given a rating of "adequate" because, it would provide protection of human
health and the environment in the short term and is intended to provide adequate protection until
a final remedy is selected. This alternative would provide stabilization of the mining-related
sources and prevent further environmental degradation. Alternative B2 addresses RAO 1 by
constructing and/or maintaining diversion and isolation components to route stormwater around
mine portals and/or mine wastes with the potential for interaction and co-mingling at mining-
related sources. This would reduce the potential for stormwater to generate additional MIW and
reduce transport of particulates containing COPCs to surface water, which contribute to
unacceptable ecological risks. Wastes generated from excavating stormwater diversion
components such as open channels are assumed to be uncontaminated and do not have handling
and management requirements beyond BMPs for erosion and sedimentation. Monitoring and
maintenance of the diversion/isolation components would be conducted as needed, primarily due
to events that could compromise the components (e.g., lack of adherence to ICs, storm events,
wildland fires). EPA would measure the extent by which ecological risks associated with
contributions from mining-related source/storm water interactions have been reduced by this
alternative. This data would provide information about the effectiveness of the IRA and is
intended to help inform future remedial decisions at the Site. ICs would be implemented to
prevent activities that would disturb the integrity of diversion/isolation components and prevent
uses inconsistent with current and reasonably anticipated future land uses.
10.2.2 Compliance with ARARs
Under Alternative Bl, unaddressed stormwater interacting with mining-related sources would
continue to release particulates containing COPCs to surface water. Because no action is taken, no
chemical-, location-, or action-specific ARARs are triggered. Thus, this alternative was given a
rating of "none."
Chemical-specific ARARs would be pertinent to Alternative B2. State water quality standards
would likely not be met for streams receiving stormwater discharges after the alternative is
constructed due to other contributing mining-related sources, thus the interim measures CERCLA
ARAR waiver would be invoked for the Colorado Basic Standards and Methodologies for Surface
Water. The Colorado Basic Standards for Groundwater would also be waived using an interim
measures CERCLA ARAR waiver because the limited RI information available does not indicate
that groundwater meeting the regulatory definition exists beneath the mining-related sources
addressed by this alternative.
Location- and action-specific ARARs for Alternative B2 would be addressed during
implementation of the IRA as indicated in the following paragraphs.
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Excavation: The excavation of mine wastes from waters of the U.S. is assumed to be performed
with neat excavation only involving incidental fallback. Thus, the substantive requirements of
Section 404 would not be triggered. If grading or excavation activities result in a discharge of
dredge material, the substantive requirements of Nationwide Permit 20 (Response Operations for
Oil or Hazardous Substances) would be met.
Dust Suppression: Dust suppression and emission-controlled equipment would be used during
construction activities for the alternative to achieve compliance with Colorado Emission Control
requirements.
Surface Reclamation: All surface reclamation activities under this alternative, including
placement, grading, and backfilling, would be performed to meet relevant and appropriate
substantive requirements of 2 CCR 407-1 Rule 3.
Construction Activities: Cultural resource surveys have not been completed for all mining-
related sources addressed by this alternative. If any cultural resources are found, surveys will be
necessary to determine if adverse effects would occur, and if so, how the effects may be
minimized or mitigated in accordance with the National Historic Preservation Act,
Archaeological and Historic Preservation Act, and Historic Sites Act.
If bald or golden eagles are observed during remedial design and IRA, activities must be modified
and conducted to conserve the species and their habitat to comply with the substantive
requirements of the Bald and Golden Eagle Protection Act.
If the IRA involves activities modifying streams or water bodies that affect wildlife and/or non-
game fish, federal agencies must comply with substantive requirements identified by USFWS and
the relevant state agency with jurisdiction over wildlife resources in accordance with Fish and
Wildlife Coordination Act and implementing regulations.
If threatened or endangered species are identified at these mining-related sources during remedial
design and IRA, activities must be modified and conducted to conserve the species and their
habitat in accordance with the Endangered Species Act.
If migratory birds are identified during remedial design and IRA, activities must be modified and
conducted to conserve the species and their habitat in accordance with the Migratory Bird Treaty
Act.
The alternative would not be conducted within streams. However, if activities were to impact
streams, they would be carried out in a manner to avoid adversely affecting wildlife and/or non-
game fish within streams. Compliance would be achieved through coordination with the Colorado
Division of Parks Wildlife and in accordance with the Colorado Wildlife Enforcement and
Penalties Act and Colorado Non-game, Endangered, or Threatened Species Act.
It is not anticipated that nests or dens of wildlife exist at the mine locations. If they were to be
encountered, the alternative would be implemented to avoid disturbing or destroying nests or
dens. Compliance would be achieved through coordination with the Colorado Division of Parks
Wildlife and in accordance with substantive requirements of Colorado Wildlife Commission
regulations.
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Activities conducted during the IRA on USFS-managed land, such as obtaining borrow material
and implementing the IRA at the Brooklyn Mine, would need to comply with the substantive
requirements of the San Juan National Forest and Tres Rios Field Office Land and Resource
Management Plan.
If the IRA involves activities that affect identified floodplains or wetlands, activities will be
carried out in a manner to avoid adversely affecting them and thus meet the substantive
requirements of the Clean Water Act, Section 404 regulations and FEMA Floodplain
Management Regulations. Activities under this alternative would be carried out in a manner that
will comply with Colorado Noise Abatement Statue 25-12-103.
Since Alternative B2 could comply with substantive requirements of ARARs or invoke
CERCLA ARAR waivers, it was given rating of "will comply, but may require CERCLA ARAR
waiver(s)."
10.2.3 Long-Term Effectiveness and Permanence
Alternative B1 fails to provide long-term effectiveness and permanence since no action is taken.
This alternative would not reduce generation and migration of MIW from interaction of
stormwater with mining-related sources and would not reduce releases of COPCs to surface
water that would continue to contribute to unacceptable ecological risks. This alternative would
not provide stabilization of the mining-related sources and prevent further environmental
degradation. Thus, this alternative was given a rating of "none."
The loading of COPCs is expected to decrease under Alternative B2 because diversion/isolation
components addressing the interaction between stormwater and mining-related sources reduces
leaching and formation of MIW. Routing stormwater around mine portals and/or contaminated
mine wastes with the potential for interaction and co-mingling at mining-related sources would
reduce the potential for stormwater to generate additional MIW and release particulates
containing COPCs to surface water, which contribute to unacceptable ecological risks. However,
the water quality in the streams, irrespective of diversion/isolation components for stormwater,
would still be impacted and contribute to unacceptable ecological risks. Long-term effectiveness
of diversion/isolation components would depend on their integrity. Inspection and repair of the
diversion/isolation components would be conducted, as needed, primarily due to events that could
compromise the components (e.g., lack of adherence to ICs, storm events, wildland fires). ICs
would be implemented to prevent activities that would disturb the integrity of diversion/isolation
components and prevent uses inconsistent with current and reasonably anticipated future land
uses. This alternative was given a rating of "moderate to high," primarily due to the long-term
effectiveness and permanence of isolation/diversion components in uncontaminated areas of
mining-related sources, with monitoring and maintenance as needed.
10.2.4 Reduction of Toxicity, Mobility, or Volume through Treatment
Alternatives B1 and B2 fail to provide a reduction of toxicity, mobility, or volume through
treatment since treatment is not a component of these alternatives. Thus, these alternatives were
both given a rating of "none."
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10.2.5 Short-Term Effectiveness
No action would be undertaken under Alternative B1 to address stormwater discharges
interacting with mining-related sources. Thus, there are no short-term risks posed to the
community, workers, or environment during implementation of this alternative. Thus, this
alternative was given a rating of "none."
Alternative B2 would pose short-term risks to the community and workers related to increased
traffic. Driving on access roads that have high centers, rock outcroppings, steep slopes, and lack
sufficient width for transporting construction equipment could cause accidents. Safety measures
such as signage and flaggers would be implemented to protect workers and the community from
increased traffic. Short-term risks to workers would be mitigated through safety measures such
as PPE (e.g., steel toe boots) and work zones, as well as other safety practices. There would also
be short-term impacts to the environment. Transporting and placing borrow material has
potential environmental impacts from equipment emissions and disturbing borrow locations.
Developing borrow areas could adversely impact the environment. Mitigation measures could
include selecting easily accessible borrow locations and reclaiming borrow areas after use.
Alternative B2 was given a rating of "moderate to high," primarily due to the limited quantities
of borrow material required and the limited short-term impacts of constructing
diversion/isolation components in uncontaminated areas of the mining-related sources.
10.2.6 Implementability
Alternative B1 has no further action taken. Since no remedial action is taken, this alternative was
given a rating of "none."
Alternative B2 includes constructing diversion/isolation components. These are conventional
construction practices and can be implemented using available equipment and labor resources.
Maintenance and monitoring of diversion/isolation components could provide difficulties due to
difficult access and constrained locations, especially at non-conventional access-alpine and
subalpine categories. Uncontaminated borrow material for constructing remedial components
and access roads would be generated and transported from within the Site, however borrow
location(s) of suitable quantity and quality have not yet been identified. Monitoring and
maintenance of ICs is dependent on periodic reviews of the administrative and/or legal
instruments used. Maintenance of ICs may be more difficult due to various types of ownership
and land use and would require agency coordination.
Alternative B2 was given a rating of "moderate to high," primarily due to the limited quantities
of borrow material required and the relatively simple scope of constructing diversion/isolation
components for stormwater in uncontaminated areas.
10.2.7 Cost
Present value costs for both alternatives were evaluated over a 15-year period after the base year
(Years 0 through 15).
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The present value cost for Alternative B1 is $0. The present value cost for Alternative B2 is
$1,889,000.
10.3 COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES FOR MINE
PORTAL POND SEDIMENTS (ALTERNATIVES CI AND C2)
10.3.1 Overall Protection of Human Health and the Environment
Of the two alternatives, the No Action alternative (i.e., Alternative CI) would fail to provide
adequate protection of human health and the environment in the short term until a final remedy is
selected and would not achieve RAO 1 (RAOs 2 and 3 are not pertinent to this IRA). This
alternative would not provide stabilization of the mining-related sources and prevent further
environmental degradation. Unaddressed mine portal pond sediments would continue to reduce
storage space and residence time for MIW in ponds increasing the likelihood for short circuiting
and uncontrolled release of MIW and particulates containing COPCs, which contribute to
unacceptable ecological risks. Thus, this alternative was given a rating of "not adequate."
Alternative C2 was given a rating of "adequate" because, it would provide protection of human
health and the environment in a short term and is intended to provide adequate protection until a
final remedy is selected. This alternative would provide stabilization of the source and prevent
further environmental degradation. Alternative C2 addresses RAO 1 through excavation and
interim local waste management of pond sediments that would reduce the potential for
uncontrolled releases of particulates containing COPCs to surface water, which contribute to
unacceptable ecological risks. Excavation of pond sediments and repair of pond berms would
increase storage space for MIW in ponds and minimize short-circuiting of MIW to increase
residence time. Excavated mine portal pond sediments would be managed locally at the mining-
related source on an interim basis, but residual risks would remain from untreated mine portal
pond sediments managed locally. Interim local waste management would include BMPs such as
berming, as necessary, to address fugitive dust and potential erosion and sedimentation issues.
Long-term effectiveness of interim waste management locations would depend on BMPs,
inspection, and repair as necessary to maintain their integrity. Monitoring and maintenance of the
interim local waste management locations would be conducted as needed, primarily due to events
that could compromise the components (e.g., lack of adherence to ICs, storm events, wildland
fires). EPA would measure the extent by which ecological risks associated with contributions
from mine portal pond sediments have been reduced by this alternative. This data would provide
information about the effectiveness of the IRA and is intended to help inform future remedial
decisions at the Site. ICs would be implemented to prevent activities that would disturb the
integrity of local waste management locations and prevent uses inconsistent with current and
reasonably anticipated future land uses.
10.3.2 Compliance with ARARs
Under Alternative CI unaddressed mine portal pond sediments would continue to release
particulates containing COPCs to surface water. Because no action is taken, no chemical-,
location-, or action-specific ARARs are triggered. Thus, this alternative was given a rating of
"none."
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Chemical-specific ARARs would be pertinent to Alternative C2. State water quality standards
would not be met for the streams after removal of mine pond portal sediments is complete due to
other contributing mining-related sources; thus, the interim measures CERCLA ARAR waiver
would be invoked for the Colorado Basic Standards and Methodologies for Surface Water. The
Colorado Basic Standards for Groundwater would also be waived using an interim measures
CERCLA ARAR waiver because the limited RI information available does not indicate that
groundwater meeting the regulatory definition exists beneath the mining-related sources
addressed by this alternative.
Location- and action-specific ARARs for Alternative C2 would be addressed during
implementation of the IRA, as indicated in the following paragraphs.
Excavation: The excavation of mine wastes from waters of the United States is assumed to be
performed with neat excavation only involving incidental fallback. Thus, the substantive
requirements of Section 404 would not be triggered. If grading or excavation activities result in a
discharge of dredge material, the substantive requirements of Nationwide Permit 20 (Response
Operations for Oil or Hazardous Substances) would be met.
Dust Suppression: Dust suppression and emission-controlled equipment would be used during
construction activities for the alternative to achieve compliance with Colorado emission control
requirements.
Dewatering: If effluent discharge to surface water is necessary during dewatering or pond
draining activities, activities would be conducted in a way to minimize infiltration into the ground
surface that could cause additional degradation of groundwater. Because the groundwater, as
defined in 5 CCR 1002-41, is not known to be present below the mining-related sources, an
interim measures CERCLA ARAR waiver would be invoked. An interim measures CERCLA
ARAR waiver would also be invoked to waive the substantive provisions of CDPS regulations for
groundwater.
If effluent discharge to surface water is necessary during dewatering or pond draining activities,
the discharge limit requirements of Colorado effluent limitations would be met without treatment
at the dewatering locations; otherwise an interim measures CERCLA ARAR waiver would be
invoked. Similarly, the substantive provisions of the CDPS regulations would be met; otherwise
an interim measures CERCLA ARAR waiver would be invoked.
Interim Local Waste Management: Mine wastes at the Site were derived directly or indirectly
from the extraction of ore and thus would be exempt from management as a RCRA hazardous
waste (i.e., the Bevill exemption), thus mine wastes would be classified as a non-hazardous solid
waste.
Pursuant to the Solid Wastes Disposal Sites and Facilities Act, C.R.S. § 30-20-102(4), mining
operations including reclamation activities with approved reclamation plans under an MLRB
permit may dispose of solid wastes generated by such operations within the permitted area
without obtaining a Certificate of Designation. CDPHE interprets this provision to exempt
CERCLA response actions performed consistently with MLRB regulation 2 CCR 407-1 Rule 3
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(Reclamation Performance Standards) to be compliant with Colorado's regulations pertaining to
solid waste disposal.
All waste handling and disposal activities under this alternative would be performed in
accordance with substantive requirements of the relevant and appropriate subparts of MLRB
regulation 2 CCR 407-1 Rule 3 (Reclamation Performance Standards), which would allow
alternative to be compliant with substantive requirements of the Colorado Solid Waste Disposal
Sites and Facilities Regulations.
Placement, grading, and backfilling of wastes for interim local management would be performed
to meet relevant and appropriate substantive requirements of 2 CCR 407-1 Rule 3.
Surface Reclamation: All surface reclamation activities under this alternative, including
placement, grading, and backfilling, would be performed to meet relevant and appropriate
substantive requirements of 2 CCR 407-1 Rule 3.
Construction Activities: Cultural resource surveys have not been completed for all mining-
related sources addressed by this alternative. If any cultural resources are found, surveys will be
necessary to determine if adverse effects would occur, and if so, how the effects may be
minimized or mitigated in accordance with the National Historic Preservation Act,
Archaeological and Historic Preservation Act, and Historic Sites Act.
If bald or golden eagles are observed during remedial design and IRA, activities must be modified
and conducted to conserve the species and their habitat to comply with the substantive
requirements of the Bald and Golden Eagle Protection Act.
If the IRA involves activities modifying streams or water bodies that affect wildlife and/or non-
game fish, federal agencies must comply with substantive requirements identified by USFWS and
the relevant state agency with jurisdiction over wildlife resources in accordance with Fish and
Wildlife Coordination Act and implementing regulations.
If threatened or endangered species are identified at these mining-related sources during remedial
design and IRA, activities must be modified and conducted to conserve the species and their
habitat in accordance with the Endangered Species Act.
If migratory birds are identified during remedial design and IRA, activities must be modified and
conducted to conserve the species and their habitat in accordance with the Migratory Bird Treaty
Act.
The alternative would not be conducted within streams. However, if activities were to impact
streams, they would be carried out in a manner to avoid adversely affecting wildlife and/or non-
game fish within streams. Compliance would be achieved through coordination with the Colorado
Division of Parks Wildlife and in accordance with the Colorado Wildlife Enforcement and
Penalties Act and Colorado Non-game, Endangered, or Threatened Species Act.
It is not anticipated that nests or dens of wildlife exist at the mine locations. If they were to be
encountered, the alternative would be implemented to avoid disturbing or destroying nests or
dens. Compliance would be achieved through coordination with the Colorado Division of Parks
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Wildlife and in accordance with substantive requirements of Colorado Wildlife Commission
regulations.
Activities conducted during the IRA on USFS-managed land, such as obtaining borrow material
and implementing the IRA at the Brooklyn Mine, would need to comply with the substantive
requirements of the San Juan National Forest and Tres Rios Field Office Land and Resource
Management Plan.
If the IRA involves activities that affect identified floodplains or wetlands, activities will be
carried out in a manner to avoid adversely affecting them and thus meet the substantive
requirements of the Clean Water Act, Section 404 regulations and FEMA Floodplain
Management Regulations. Activities under this alternative would be carried out in a manner that
will comply with Colorado Noise Abatement Statue 25-12-103.
Since Alternative C2 could comply with substantive requirements of ARARs or invoke
CERCLA ARAR waivers, it was given rating of "will comply, but may require CERCLA ARAR
waiver(s)."
10.3.3 Long-Term Effectiveness and Permanence
Alternative CI fails to provide long-term effectiveness and permanence since no action is taken.
Unaddressed sediments would continue to reduce storage space of MIW in mine portal ponds and
result in the potential for uncontrolled releases of particulates and/or MIW containing COPCs to
surface water, which contribute to unacceptable ecological risks. This alternative would not
provide stabilization of the mining-related sources and prevent further environmental degradation.
Thus, this alternative was given a rating of "none."
Excavating mine portal pond sediments and repairing pond berms under Alternative C2 improves
the effectiveness of the ponds and reduces the potential for an uncontrolled release of MIW.
However, the water quality in the streams, irrespective of the excavated mine portal pond
sediments, would still be impacted. Residual risks remain from untreated mine portal pond
sediments managed locally at the mining-related source on an interim basis. Long-term
effectiveness of interim local waste management locations would depend on BMPs, inspection,
and repair, as necessary, to maintain their integrity. ICs would be implemented to prevent
activities that would disturb the integrity of local waste management locations and prevent uses
inconsistent with current and reasonably anticipated future land uses.
This alternative was given a rating of "moderate," primarily due to considerations affecting long-
term effectiveness and permanence of monitoring and maintaining mine portal ponds below mine
portal MIW discharges and interim local waste management locations, with monitoring and
maintenance as needed.
10.3.4 Reduction of Toxicity, Mobility, or Volume through Treatment
Alternatives CI and C2 fail to provide a reduction of toxicity, mobility, or volume through
treatment since treatment is not a component of these alternatives. Although gravity dewatering
under Alternative C2 may result in positive benefits to geotechnical stability, it is not considered
treatment per this NCP criterion because it does not result in permanent and irreversible
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reductions in toxicity, mobility, or volume of contamination. Thus, these alternatives were given a
rating of "none."
10.3.5 Short-Term Effectiveness
No action would be undertaken under Alternative CI to mine portal pond sediments. Thus, there
are no short-term risks posed to the community, workers, or environment during implementation
of this alternative. Thus, this alternative was given a rating of "none."
Short-term risk posed to the community and workers under Alternative C2 relate to increased
traffic. Driving on access roads that have high centers, rock outcroppings, steep slopes, and lack
sufficient width for transporting construction equipment could cause accidents. Safety measures
such as signage and flaggers would be implemented to protect workers and community from
increased traffic. Short-term risks to workers would be mitigated through safety measures such as
PPE (e.g., steel toe boots) and work zones, as well as other safety practices. Short-term risks to
workers and the community, and the environment could be mitigated through measures such as
water-based dust suppression.
There would also be short-term impacts to the environment. Short-term increases in contaminant
loading could result due to disturbing the mine portal pond sediments during excavation, resulting
in temporary increases in production of MIW. Transporting and placing borrow material has
potential environmental impacts from equipment emissions and disturbing borrow locations.
Developing borrow areas could adversely impact the environment. Mitigation measures could
include selecting easily accessible borrow locations and reclaiming borrow areas after use.
Alternative C2 was given a rating of "moderate to high," primarily due to the limited quantities of
borrow material required and the limited short-term impacts from excavating mine portal pond
sediments.
10.3.6 Implementability
Alternative CI has no further action taken, this alternative was given a rating of "none."
Alternative C2 includes excavation, dewatering, and interim local waste management of mine
portal pond sediments. These are conventional construction practices and can be implemented
using available equipment and labor resources. Maintenance and monitoring of interim local
waste management areas could prove difficult due to access and constrained mining-related
categories, especially at alpine and subalpine-category locations with non-conventional access.
Uncontaminated borrow material for constructing pond and interim local waste management
location berms and access roads would be generated and transported from within the Site,
however borrow location(s) of suitable quantity and quality have not yet been identified.
Monitoring and maintenance of ICs is dependent on periodic reviews of the administrative
and/or legal instruments used. Maintenance of ICs may be more difficult due to various types of
ownership and land use and would require agency coordination.
Alternative C2 was given a rating of "moderate," primarily due to challenges associated with
working with MIW discharges to ponds and moderate quantities of borrow material required for
berms and access road construction.
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10.3.7 Cost
Present value costs for both alternatives were evaluated over a 15-year period after the base year
(Years 0 through 15).
The present value cost for Alternative CI is $0. The present value cost for Alternative C2 is
$3,384,000.
10.4 COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES FOR IN-
STREAM MINE WASTES (ALTERNATIVES D1 AND D2)
10.4.1 Overall Protection of Human Health and the Environment
Of the two alternatives, the No Action alternative (i.e., Alternative Dl) would fail to provide
adequate protection of human health and the environment in the short term until a final remedy is
selected and would not achieve RAO 1 (RAOs 2 and 3 are not pertinent to this IRA). This
alternative would not provide stabilization of the mining-related sources and prevent further
environmental degradation. Unaddressed in-stream mine wastes would continue to impede
stream flow, increasing the potential for erosion or mass movement of contamination in
particulate form and/or leaching of contaminants from mine wastes. Unaddressed in-stream mine
wastes could result in migration of particulates and/or MIW containing COPCs to surface water
especially during periods of precipitation and snowmelt, which contribute to unacceptable
ecological risks. Thus, this alternative was given a rating of "not adequate."
Alternative D2 was given a rating of "adequate" because, it would provide protection of human
health and the environment in a short term and is intended to provide adequate protection until a
final remedy is selected. This alternative would provide stabilization of the mining-related
sources and prevent further environmental degradation. Alternative D2 achieves RAO 1 by
excavating in-stream mine wastes that impede flow or are susceptible to erosion or leaching of
contaminants and formation of MIW and reduces transport of particulates containing COPCs to
surface water, which contribute to unacceptable ecological risks. Excavated in-stream mine
wastes would be managed locally at the mining-related sources on an interim basis. Interim local
waste management would include BMPs such as berming, as necessary, to address fugitive dust
and potential erosion and sedimentation issues but residual risks would remain from untreated in-
stream mine wastes managed locally. Monitoring and maintenance of the interim local waste
management locations would be conducted as needed, primarily due to events that could
compromise the components (e.g., lack of adherence to ICs, storm events, wildland fires).
Maintenance would be performed as necessary to maintain the integrity of interim management
location components. EPA would measure the extent by which ecological risks associated with
contributions from in-stream mine waste have been reduced by this alternative. This data would
provide information about the effectiveness of the IRA and is intended to help inform future
remedial decisions at the Site. ICs would be implemented to prevent activities that would disturb
the integrity of local waste management locations and prevent uses inconsistent with current and
reasonably anticipated future land uses.
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10.4.2 Compliance with ARARs
Unaddressed in-stream mine wastes under Alternative D1 would continue to release particulates
containing COPCs to surface water. Because no action is taken, no chemical-, location-, or action-
specific ARARs are triggered. Thus, this alternative was given a rating of "none."
Chemical-specific ARARs would be pertinent to Alternative D2. State water quality standards
would likely not be met for streams after removal of in-stream mine wastes due to other
contributing mining-related sources, thus the interim measures CERCLA ARAR waiver would be
invoked for the Colorado Basic Standards and Methodologies for Surface Water. The Colorado
Basic Standards for Groundwater would also be waived using an interim measures CERCLA
ARAR waiver because the limited RI information available does not indicate that groundwater
meeting the regulatory definition exists beneath the mining-related sources addressed by this
alternative.
Location- and action-specific ARARs for Alternative D2 would be addressed during
implementation of the IRA as indicated in the following paragraphs.
Excavation: The excavation of mine wastes from waters of the United States is assumed to be
performed with neat excavation only involving incidental fallback. Thus, the substantive
requirements of Section 404 would not be triggered. If grading or excavation activities result in a
discharge of dredge material, the substantive requirements of Nationwide Permit 20 (Response
Operations for Oil or Hazardous Substances) would be met.
Dust Suppression: Dust suppression and emission-controlled equipment would be used during
construction activities for the alternative to achieve compliance with Colorado Emission Control
requirements.
Dewatering: If effluent discharge to surface water is necessary during dewatering activities,
activities would be conducted in a way to minimize infiltration into the ground surface that could
cause additional degradation of groundwater. Because the groundwater, as defined in 5 CCR
1002-41, is not known to be present below the mining-related sources, an interim measures
CERCLA ARAR waiver would be invoked. An interim measures CERCLA ARAR waiver would
also be invoked to waive the substantive provisions of Colorado Effluent Limitations and CDPS
regulations for groundwater.
If effluent discharge to surface water is necessary during dewatering activities,, the discharge
limit requirements of Colorado Effluent Limitations would be met without treatment at the
dewatering locations; otherwise an interim measures CERCLA ARAR waiver would be invoked.
Similarly, the substantive provisions of the CDPS regulations would be met; otherwise an interim
measures CERCLA ARAR waiver would be invoked.
Interim Local Waste Management: Mine wastes at the Site were derived directly or indirectly
from the extraction of ore and thus would be exempt from management as a RCRA hazardous
waste (i.e., the Bevill exemption), thus mine wastes would be classified as a non-hazardous solid
waste.
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Pursuant to the Solid Wastes Disposal Sites and Facilities Act, C.R.S. § 30-20-102(4), mining
operations including reclamation activities with approved reclamation plans under an MLRB
permit may dispose of solid wastes generated by such operations within the permitted area
without obtaining a Certificate of Designation. CDPHE interprets this provision to exempt
CERCLA response actions performed consistently with MLRB regulation 2 CCR 407-1 Rule 3
(Reclamation Performance Standards) to be compliant with Colorado's regulations pertaining to
solid waste disposal.
All waste handling and disposal activities under this alternative would be performed in
accordance with substantive requirements of the relevant and appropriate subparts of MLRB
regulation 2 CCR 407-1 Rule 3 (Reclamation Performance Standards), which would allow the
alternative to be compliant with substantive requirements of the Colorado Solid Waste Disposal
Sites and Facilities Regulations.
Placement, grading, and backfilling of wastes for interim local management would be performed
to meet relevant and appropriate substantive requirements of 2 CCR 407-1 Rule 3.
Surface Reclamation: All surface reclamation activities under this alternative, including
placement, grading, and backfilling, would be performed to meet relevant and appropriate
substantive requirements of 2 CCR 407-1 Rule 3.
Construction Activities: Cultural resource surveys have not been completed for all mining-
related sources addressed by this alternative. If any cultural resources are found, surveys will be
necessary to determine if adverse effects would occur, and if so, how the effects may be
minimized or mitigated in accordance with the National Historic Preservation Act,
Archaeological and Historic Preservation Act, and Historic Sites Act.
If bald or golden eagles are observed during remedial design and IRA, activities must be modified
and conducted to conserve the species and their habitat to comply with the substantive
requirements of the Bald and Golden Eagle Protection Act.
If the IRA involves activities modifying streams or water bodies that affect wildlife and/or non-
game fish, federal agencies must comply with substantive requirements identified by USFWS and
the relevant state agency with jurisdiction over wildlife resources in accordance with Fish and
Wildlife Coordination Act and implementing regulations.
If threatened or endangered species are identified at these mining-related sources during remedial
design and IRA, activities must be modified and conducted to conserve the species and their
habitat in accordance with the Endangered Species Act.
If migratory birds are identified during remedial design and IRA, activities must be modified and
conducted to conserve the species and their habitat in accordance with the Migratory Bird Treaty
Act.
If activities were to impact streams, they would be carried out in a manner to avoid adversely
affecting wildlife and/or non-game fish within streams. Compliance would be achieved through
coordination with the Colorado Division of Parks Wildlife and in accordance with the Colorado
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Wildlife Enforcement and Penalties Act and Colorado Non-game, Endangered, or Threatened
Species Act.
It is not anticipated that nests or dens of wildlife exist at the mine locations. If they were to be
encountered, the alternative would be implemented to avoid disturbing or destroying nests or
dens. Compliance would be achieved through coordination with the Colorado Division of Parks
Wildlife and in accordance with substantive requirements of Colorado Wildlife Commission
regulations.
Activities conducted during the IRA on USFS-managed land, such as obtaining borrow material,
would need to comply with the substantive requirements of the San Juan National Forest and Tres
Rios Field Office Land and Resource Management Plan.
If the IRA involves activities that affect identified floodplains or wetlands, activities will be
carried out in a manner to avoid adversely affecting them and thus meet the substantive
requirements of the Clean Water Act, Section 404 regulations and FEMA Floodplain
Management Regulations. Activities under this alternative would be carried out in a manner that
will comply with Colorado Noise Abatement Statue 25-12-103.
Since Alternative D2 could comply with substantive requirements of ARARs or invoke CERCLA
ARAR waivers, it was given rating of "will comply, but may require CERCLA ARAR
waiver(s)."
10.4.3 Long-Term Effectiveness and Permanence
Alternative D1 fails to provide long-term effectiveness and permanence since no action is taken.
Unaddressed in-stream mine wastes would continue to have the potential for erosion and result in
the potential for releases of particulates and/or MIW containing COPCs to surface water, which
contribute to unacceptable ecological risks. This alternative would not provide stabilization of
the mining-related sources and prevent further environmental degradation. Thus, this alternative
was given a rating of "none."
The loading of COPCs is expected to decrease through removing in-stream mine wastes under
Alternative D2 because excavation and interim local waste management reduces the contact of
the water with the mine waste and thereby reduces leaching and formation of MIW and erosion
and transport of particulates containing COPCs to surface water, which contribute to
unacceptable ecological risks. However, the water quality in the streams, irrespective of the
excavated mine wastes, would still be impacted. Residual risks remain from untreated waste
managed locally at the mining-related source on an interim basis. Long-term effectiveness of
interim local management locations would depend on BMPs, inspection, and repair, as
necessary, to maintain their integrity. ICs would be implemented to prevent activities that would
disturb the integrity of local waste management locations and prevent uses inconsistent with
current and reasonably anticipated future land uses.
This alternative was given a rating of "moderate to high," primarily because excavated wastes
would no longer be present in streams and would be managed in interim local waste management
locations that could be monitored and maintained as needed.
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10.4.4 Reduction of Toxicity, Mobility, or Volume through Treatment
Alternatives D1 and D2 fail to provide a reduction of toxicity, mobility, or volume through
treatment since treatment is not a component of these alternatives. Although gravity dewatering
under Alternative D2 may result in positive benefits to geotechnical stability, it is not considered
treatment per this NCP criterion because it does not result in permanent and irreversible
reductions in toxicity, mobility, or volume of contamination. Thus, these alternatives were given
a rating of "none."
10.4.5 Short-Term Effectiveness
No action would be undertaken under Alternative D1 for in-stream mine wastes. Thus, there are
no short-term risks posed to the community, workers, or environment during implementation of
this alternative. Thus, this alternative was given a rating of "none."
Short-term risk posed to the community and workers under Alternative D2 relate to increased
traffic. Driving on access roads that have high centers, rock outcroppings, steep slopes, and lack
sufficient width for transporting construction equipment could cause accidents. Safety measures
such as signage and flaggers would be implemented to protect workers and community from
increased traffic. Short-term risks to workers would be mitigated through safety measures such
as PPE (e.g., steel toe boots) and work zones, as well as other safety practices.
There would also be short-term impacts to the environment. Short-term increases in contaminant
loading could result due to disturbing the in-stream mine wastes during excavation, resulting in
temporary increases in production of MIW. Transporting and placing borrow material would
have potential environmental impacts from equipment emissions and disturbing borrow
locations. Developing borrow areas could adversely impact the environment. Mitigation
measures could include selecting easily accessible borrow locations and reclaiming borrow areas
after use. Alternative D2 was given a rating of "moderate to high," primarily due to the limited
quantities of borrow material required and the limited short-term impacts of excavating in-stream
mine wastes.
10.4.6 Implementability
Alternative D1 has no further action taken. Since no remedial action is taken, this alternative was
given a rating of "none."
Alternative D2 includes excavation, dewatering, and interim local waste management of in-
stream mine waste. These are conventional construction practices and can be implemented using
available equipment and labor resources. Maintenance and monitoring of interim local waste
management areas could prove difficult due to access and constrained mining-related categories,
especially at alpine and subalpine-category locations with non-conventional access.
Uncontaminated borrow material for constructing remedial components and access roads would
be generated and transported from within the Site, however borrow location(s) of suitable
quantity and quality have not yet been identified. Monitoring and maintenance of ICs is
dependent on periodic reviews of the administrative and/or legal instruments used. Maintenance
of ICs may be more difficult due to various types of ownership and land use and would require
agency coordination.
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Alternative D2 was given a rating of "moderate," primarily due to the challenges of excavating
and dewatering in-stream mine wastes.
10.4.7 Cost
Present value costs for both alternatives were evaluated over a 15-year period after the base year
(Years 0 through 15).
The present value cost for Alternative D1 is $0. The present value cost for Alternative D2 is
$624,000.
10.5 COMPARATIVE ANALYSIS OF REMEDIAL ALTERNATIVES FOR MINING-
IMPACTED RECREATION STAGING AREAS (ALTERNATIVES El AND E2)
10.5.1 Overall Protection of Human Health and the Environment
Of the two alternatives, the No Action alternative (i.e., Alternative El) would fail to provide
protection of human health and the environment in the short term until a final remedy is selected.
This alternative would not provide stabilization of the mining-related sources and prevent further
environmental degradation. Unaddressed mining-impacted recreation staging areas would not
achieve RAOs 2 and 3 (RAO 1 is not pertinent to this IRA) since no action would be taken to
prevent human exposure through ingestion and inhalation to mine wastes and contaminated soils
containing lead and through ingestion to mine wastes and contaminated soils containing arsenic
that exceed risk-based levels during camping at recreation staging activities. Thus, this
alternative was given a rating of "not adequate."
Alternative E2 was given a rating of "adequate." Alternative E2 would provide protection of
human health and the environment in the short term until a final remedy is selected. This
alternative would provide stabilization of the mining-related sources at recreation staging areas,
prevent further environmental degradation, and achieve significant risk reduction quickly.
Alternative E2 addresses RAOs 2 and 3 by containing/isolating mine wastes and contaminated
soils within mining-impacted recreation staging areas. Combinations of aggregate and soil covers
would be implemented to reduce disturbances of mine wastes and contaminated soils, and
migration of contaminants. The covers would provide an exposure barrier and eliminate surface
exposure to mine waste and contaminated soils. The covers would be sloped to promote positive
drainage in order to minimize erosion and to reduce infiltration that could saturate the subsurface
and compromise the integrity of the covers. The covers used for containment/isolation of mine
wastes and contaminated soils could be breached if disturbed, resulting in potential COPC
exposures to campers. Long-term effectiveness of covers would depend on inspection and repair,
as necessary, to maintain their integrity. ICs would be implemented to prevent activities that
would disturb the integrity of the covers and prevent uses inconsistent with current and
reasonably anticipated future land uses. Monitoring and maintenance of the covers would be
conducted as needed, primarily due to events that could compromise the components (e.g., lack
of adherence to ICs, storm events, wildland fires). Maintenance would be performed as necessary
to maintain the integrity of covers.
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10.5.2 Compliance with ARARs
Under Alternative El, unaddressed mine wastes and contaminated soils at mining-impacted
recreation staging areas would continue to pose unacceptable risks to human health. Because no
action is taken, no chemical-, location-, or action-specific ARARs are triggered. Thus, this
alternative was given a rating of "none."
Chemical-specific ARARs would be pertinent to Alternative E2. State water quality standards
would likely not be met for streams after the capping of recreation use areas due to other
contributing mining-related sources, thus the interim measures CERCLA ARAR waiver would be
invoked for the Colorado Basic Standards and Methodologies for Surface Water. The Colorado
Basic Standards for Groundwater would also be waived using an interim measures CERCLA
ARAR waiver because the limited RI information available does not indicate that groundwater
meeting the regulatory definition exists beneath the mining-related sources addressed by this
alternative.
Location- and action-specific ARARs for Alternative E2 would be addressed during
implementation of the IRA as indicated in the following paragraphs.
Cover Placement: The placement and grading of covers is assumed to be performed without the
discharge of dredged or fill materials into the waters of the United States. Thus, the substantive
requirements of Section 404 would not be triggered. If grading activities result in a discharge of
dredge material, the substantive requirements of Nationwide Permit 20 (Response Operations for
Oil or Hazardous Substances) would be met. All cover placement activities would be conducted
in a way minimize infiltration, if present, into the ground surface that could cause additional
degradation of groundwater. Because the groundwater, as defined in 5 CCR 1002-41, is not
known to be present below the mining-related sources, an interim measures CERCLA ARAR
waiver would be invoked. An interim measures CERCLA ARAR waiver would also be invoked
to waive the substantive provisions of Colorado Effluent Limitations and CDPS regulations for
groundwater. For channelized stormwater discharges from covers, the substantive provisions of
the CDPS program would be met; otherwise an interim measures CERCLA ARAR waiver would
be invoked. During construction of the covers, the discharge limit requirements of Colorado
effluent limitations would be met without treatment; otherwise an interim measures CERCLA
ARAR waiver would be invoked.
Surface Reclamation: All surface reclamation activities under this alternative, including
placement, grading, and backfilling, would be performed to meet relevant and appropriate
substantive requirements of 2 CCR 407-1 Rule 3. During construction and seeding of covers,
compliance would be achieved through completion of noxious weed surveys and coordination
with the Colorado Division of Parks Wildlife and in accordance with Colorado Noxious Weed
Act and the San Juan County Noxious Weed regulations.
Dust Suppression: Dust suppression and emission-controlled equipment will be used during
construction activities for this alternative to achieve compliance with Colorado Emission Control
regulations.
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Construction Activities: Cultural resource surveys have not been completed for all mining-
related sources addressed by this alternative. If any cultural resources are found, surveys will be
necessary to determine if adverse effects would occur, and if so, how the effects may be
minimized or mitigated in accordance with the National Historic Preservation Act,
Archaeological and Historic Preservation Act, and Historic Sites Act.
If bald or golden eagles are observed during remedial design and IRA, activities must be modified
and conducted to conserve the species and their habitat to comply with the substantive
requirements of the Bald and Golden Eagle Protection Act.
If the IRA involves activities modifying streams or water bodies that affect wildlife and/or non-
game fish, federal agencies must comply with substantive requirements identified by USFWS and
the relevant state agency with jurisdiction over wildlife resources in accordance with Fish and
Wildlife Coordination Act and implementing regulations.
If threatened or endangered species are identified at these mining-related sources during remedial
design and IRA, activities must be modified and conducted to conserve the species and their
habitat in accordance with the Endangered Species Act.
If migratory birds are identified during remedial design and IRA, activities must be modified and
conducted to conserve the species and their habitat in accordance with the Migratory Bird Treaty
Act.
The alternative would not be conducted within streams. However, if activities were to impact
streams, they would be carried out in a manner to avoid adversely affecting wildlife and/or non-
game fish within streams. Compliance would be achieved through coordination with the Colorado
Division of Parks Wildlife and in accordance with the Colorado Wildlife Enforcement and
Penalties Act and Colorado Non-game, Endangered, or Threatened Species Act.
It is not anticipated that nests or dens of wildlife exist at the mine locations. If they were to be
encountered, the alternative would be implemented to avoid disturbing or destroying nests or
dens. Compliance would be achieved through coordination with the Colorado Division of Parks
Wildlife and in accordance with substantive requirements of Colorado Wildlife Commission
regulations.
Activities conducted during the IRA on USFS-managed land, such as obtaining borrow material,
would need to comply with the substantive requirements of the San Juan National Forest and Tres
Rios Field Office Land and Resource Management Plan.
If the alternative involves activities that affect identified floodplains or wetlands, activities will be
carried out in a manner to avoid adversely affecting them and thus meet the substantive
requirements of the Clean Water Act, Section 404 regulations and FEMA Floodplain
Management Regulations. Activities under this alternative would be carried out in a manner that
will comply with Colorado Noise Abatement Statue 25-12-103.
Since Alternative E2 could comply with substantive requirements of ARARs or invoke CERCLA
ARAR waivers, be waived, it was given rating of "will comply, but may require CERCLA ARAR
waiver(s)."
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10.5.3 Long-Term Effectiveness and Permanence
Alternative El fails to provide long-term effectiveness and permanence since no action is taken.
Unaddressed mine waste and contaminated soils at mining-impacted recreation staging areas
could result in potential adverse lead and arsenic exposures to humans during camping. This
alternative would not provide stabilization of the mining-related sources and prevent further
environmental degradation. Thus, this alternative was given a rating of "none."
Under Alternative E2, exposures to mine wastes and contaminated soils containing lead or arsenic
that exceed risk-based levels are reduced through covers installed over recreation staging areas.
However, the mine wastes and contaminated soils posing unacceptable human health risks would
be left in place under the covers. The covers used for containing/isolating mine wastes and
contaminated soils could be breached resulting in potential lead and arsenic exposures to campers
if disturbed. The covers would be sloped to promote positive drainage that minimizes erosion and
to reduces infiltration that could saturate the subsurface and compromise the integrity of the
covers. ICs would be implemented to prevent activities that would disturb the integrity of the
covers and prevent uses inconsistent with current and reasonably anticipated future land uses.
Long-term effectiveness of covers would depend on BMPs, inspection, and repair, as necessary,
to maintain their integrity. Thus, this alternative was given a rating of "moderate to high,"
primarily due to the long-term effectiveness and permanence of covers, with monitoring and
maintenance as needed.
10.5.4 Reduction of Toxicity, Mobility, or Volume through Treatment
Alternatives El and E2 fail to provide a reduction of toxicity, mobility, or volume through
treatment since treatment is not a component of these alternatives. Thus, both alternatives were
given a rating of "none."
10.5.5 Short-Term Effectiveness
No action, would be taken under Alternative El to mining-impacted recreation staging areas.
Thus, there are no short-term risks posed to the community, workers, or environment during
implementation of this alternative. Thus, this alternative was given a rating of "none."
Alternative E2 poses short-term risks to the community and workers related to increased traffic.
Driving on access roads that have high centers, rock outcroppings, steep slopes, and lack
sufficient width for transporting construction equipment could cause accidents. Safety measures
such as signage and flaggers would be implemented to protect workers and community from
increased traffic. Short-term risks to workers would be mitigated through safety measures such
as PPE (e.g., steel toe boots) and work zones, as well as other safety practices. Alternative E2
would involve disturbing mine wastes and contaminated soils, which could pose potential
adverse impacts through dispersion of dust. Short-term risks to workers, the community, and the
environment could be mitigated through measures such as water- or chemical- based suppression
for controlling dust during construction.
There would also be short-term impacts to the environment. Transporting and placing borrow
material has potential environmental impacts from equipment emissions and disturbing borrow
locations. Developing borrow areas could adversely impact the environment. Mitigation
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measures could include selecting easily accessible borrow locations and reclaiming borrow areas
after use.
Thus, Alternative E2 was given a rating of "moderate," primarily due to the significant quantities
of borrow material required and the short-term impacts associated with developing and
transporting borrow material for constructing covers.
10.5.6 Implementability
Alternative El has no further action taken. Since no remedial action is taken, this alternative was
given a rating of "none."
Alternative E2 involves cover placement. This is a conventional construction practice and can be
implemented using available equipment and labor resources. Uncontaminated borrow material
for constructing covers and access roads would be generated and transported from within the
Site, however borrow location(s) of suitable quantity and quality have not yet been identified.
Monitoring and maintenance of ICs is dependent on periodic reviews of the administrative
and/or legal instruments used. Maintenance of ICs may be more difficult due to various types of
ownership and land use and would require agency coordination.
Thus, Alternative E2 was given a rating of "moderate," primarily due to the significant quantities
of borrow material required for cover construction.
10.5.7 Cost
Present value costs for both alternatives were evaluated over a 15-year period after the base year
(Years 0 through 15).
The present value cost for Alternative El is $0. The present value cost for Alternative E2 is
$1,668,000.
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Exhibit 10-1 Summary of Comparative Analysis for Remedial Alternatives
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PlVSCIll \ ill III' Cosl
(Dolliirs)1
Mine Porhil \ll\\ Dischiirgcs Allcrn;ili\i*s
Alternative A1 - No Action2
Not Adequate
None
None
None
None
None
$0
Alternative A2 - Diversion/Isolation
Adequate
Will comply, but may
require CERCLA ARAR
waiver(s)
Moderate
None
Moderate
Moderate
$2,411,000
Mining-Kcliilcd Sourcc/Siornmsiicr lnlcr;iclions Allcrn;ili\cs
Alli-rnali\ i' lil \ij WI iuii
Not Adequate
None
None
None
None
None
$0
Alternative B2 - Stormwater Diversion/Isolation
Adequate
Will comply, but may
require CERCLA ARAR
waiver(s)
Moderate to High
None
Moderate to High
Moderate to High
$1,889,000
Mine I'oi'liil Pond Sodimoil(s \llcrn:ili\os
Alternative CI - No Action2
Not Adequate
None
None
None
None
None
$0
Alternative C2 - Excavation and Interim Local Waste Management
Adequate
Will comply, but may
require CERCLA ARAR
waiver(s)
Moderate
None
Moderate to High
Moderate
$3,384,000
1 ii-Siro:iin Mine \\;is(os Allorn:ili\os
Alternative Dl - No Action2
Not Adequate
None
None
None
None
None
$0
Alternative D2 - Excavation and Interim Local Waste Management
Adequate
Will comply, but may
require CERCLA ARAR
waiver(s)
Moderate to High
None
Moderate to High
Moderate
$624,000
Mining-lni|i;uicd Kccn-iilion Siii«in« \iv;is Allcrn;ili\cs
Allcriialivc LI \u Acikmi
Not Adequate
None
None
None
None
None
$0
Alternative E2 - Containment/Isolation
Adequate
Will comply, but may
require CERCLA ARAR
waiver(s)
Moderate to High
None
Moderate
Moderate
$1,668,000
Notes:
1. Present value costs and quantitative ratings are subject to change. Detailed cost spreadsheets (cost summaries, present value analyses, and cost worksheets) for each alternative are presented in Appendix F of the FFS (CDM Smith2018).
2. Alternatives A1, Bl, CI, Dl, and El represent the No Action alternatives required by theNCP.
Legend for Qualitative Ratings System:
Threshold Criteria
(Overall Protection of Human
Health and the Environment)
Not Adequate
Adequate
Threshold Criteria
(Compliance with ARARs)
None
Will comply
Will comply, but may require
CERCLA ARAR waiver(s)
Balancing Criteria
(Excluding Cost)
None
Low
Low to Moderate
Moderate
Moderate to High
High
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10.6 MODIFYING CRITERIA
10.6.1 State Acceptance
State (support agency) acceptance is a modifying criterion under the NCP. Assessment of the
state acceptance was completed after comments on the proposed plan were submitted to EPA
during the formal comment period. Thus, state acceptance was not considered in the detailed
analysis of alternatives presented in the FFS.
Part 3 of this IROD provides discussion of the input provided by the state during the formal
comment period.
10.6.2 Community Acceptance
Community acceptance is also a modifying criterion under the NCP. Community assessment was
completed after EPA received public comments on the proposed plan during the public
commenting period. Thus, community acceptance was not considered in the detailed analysis of
alternatives presented in the FFS.
Part 3 of this IROD provides discussion of the community acceptance, including responses to
comments provided by members of the community during the formal comment period.
10.6.3 Modifications Made as a Result of Comments
Comments from the CDPHE and the general public were addressed through clarification and
explanation. These can be found in Part 3 of this document, the responsiveness summary. Based
on these written and oral comments, EPA has not made any significant changes to the original
proposal but has provided clarifying information in this IROD based on the comments.
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11.0 PRINCIPAL THREAT WASTES
Principal threat wastes are source materials considered to be highly toxic or highly mobile that
generally cannot be reliably contained or would present significant risk to human health or the
environment should exposure occur. Low-level threat wastes are those source materials that
generally can be reliably contained and would present only a low risk in the event of release.
Source materials are materials that include or contain hazardous substances, pollutants, or
contaminants that act as a reservoir for migration of contamination to groundwater, surface
water, or air or act as a source for direct exposure.
Based on those definitions, solid media at the mining-related sources that contain contaminants
above their respective remedial criteria constitute source materials because they act as a reservoir
for migration of contamination to groundwater and surface water. Solid media, such as mine
waste, sediment, and contaminated soil, are source materials for MIW generation.
Solid media, including mine waste, sediment, and contaminated soil, at the mining-related
sources addressed by interim measures are not considered principal threat waste for the
following reasons:
• Contaminants in solid media are not highly toxic.
o The contaminants present are not in forms or at concentrations that would result in
designation of characteristic hazardous waste due to toxicity (i.e., through the toxicity
characteristic leaching procedure) if it were otherwise not exempt from regulation
under RCRA by the Bevill amendment.
• Contaminants in solid media are not highly mobile.
o The contaminants present at this Site are inorganics that are generally bound as part
of mineral assemblages within the solid media and are only mobile when in contact
with acidic water over time.
• Contaminants in solid media can be reliably contained.
o The contaminants present at this Site are inorganics generally bound as part of
mineral assemblages within the solid media. Solid mine materials are particularly
amenable to containment strategies that also isolate the contaminants with water,
resulting in leaching and migration.
Solid media at the mining-related sources addressed by this IROD are thus considered a low-
level threat waste. Additional discussion in Section 14.0 describes the NCP statutory preference
for treatment of principal threat waste and subsequent exclusion of treatment as a principal
element of the remedy.
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12.0 SELECTED INTERIM REMEDY
Based on consideration of the CERCLA requirements, the detailed analysis of remedial
alternatives, state comments, and all public comments (see Part 3, Responsiveness Summary),
EPA has determined that the preferred remedial alternatives for the IRAs presented in the
proposed plan for the Site-wide cleanup is the appropriate remedy for the Site. The selected
interim remedy consists of Alternative A2: Diversion/Isolation, Alternative B2: Stormwater
Diversion/Isolation, Alternative C2: Excavation and Interim Local Waste Management,
Alternative D2: Excavation and Interim Local Waste Management, Alternative E2:
Containment/Isolation, with minor modifications as described in this section.
Minor modifications to the information presented in the proposed plan, as described in this
section, were implemented based on comments provided during the formal comment period as
well as additional information gathered following the release of the proposed plan. These minor
modifications include:
• The number of mining-related sources identified for IRAs was reduced from 26 to 23 due
to the three other mining-related sources being completed under other authority in a
future action.
• ARARs pertaining to the selected interim remedy, including the use of the CERCLA
interim measures waiver for specific ARARs, were clarified. A summary of federal and
state ARARs for the selected interim remedy is attached as Appendix C.
• As described in Section 7.1.3, an alternate trespass camping scenario was evaluated in
response to comments received during the public comment period for the proposed plan.
As a result of these modifications, the quantities and costs associated with the preferred
alternatives presented in the proposed plan (and Section 9.0) have been updated in the following
subsections.
The selected interim remedy will target specific contaminant migration issues from mining-
related sources (including campgrounds) for interim remediation. The final remedial decisions
for these mining-related sources will be made in a final record of decision.
The following subsections provide the rationale, detailed description, estimated costs, and
expected outcome for each IRA of the selected interim remedy.
12.1 MINE PORTAL MIW DISCHARGES
12.1.1 Short Description of the Selected Interim Remedy
The mine portal MIW discharges selected interim remedy involves construction of diversion and
isolation components to route mine portal MIW discharge around contaminated mine waste with
the potential for interaction and co-mingling at mining-related sources. It would also include
maintenance of previously existing and newly constructed diversion and isolation components.
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12.1.2 Rationale for the Selected Interim Remedy
The mine portal MIW discharges selected interim remedy reduces the potential for uncontrolled
releases of particulates and MIW from sediment in mine portal ponds that contribute to
unacceptable ecological risks. The mine portal MIW discharges selected interim remedy will
achieve RAO 1 by routing mine portal MIW discharge around contaminated mine waste with the
potential for interaction and co-mingling at mining-related sources. RAOs 2 and 3 are not
pertinent to this IRA.
12.1.3 Detailed Description of the Selected Interim Remedy
Diversion or isolation components implemented at each mining-related source will be chosen on
a location-by-location basis. Open channels typically will be constructed to collect mine portal
MIW discharge and divert it around the existing mine waste. The construction of berms
immediately upgradient of mine waste, collection/diversion piping or liners, or a combination of
multiple types of components are also viable for locations that are not conducive to open-channel
diversion. Berms will be considered at locations with underlying rock surfaces, while
collection/diversion piping or liners will be considered at locations with steep slopes or other
features that pose challenges, such as roads directly adjacent to proposed diversion/isolation
components. These assumptions will be refined at the time of remedial design using location-
specific information. At mining-related sources with existing MIW diversion or isolation
components, repairs will be conducted to improve the conditions of those components.
In addition to mine wastes excavated for open-channel diversion, mine wastes or other materials
at the entrance to a mine portal that are partially obstructing the free flow of mine portal MIW
discharge will be excavated. During the excavation process, the excavated wastes will be placed
at the mining-related source for gravity dewatering as needed. The location for this activity is
assumed to be amenable to dewatering without the need for liners or other isolation measures.
Additional dewatering could be implemented for saturated materials through ex situ amendment
with a dewatering agent, as necessary, for handling and geotechnical stability prior to interim
management at the mining-related source. Physical characterization such as analysis of
geotechnical parameters will be conducted, as needed, on excavated and dewatered mine waste
to evaluate physical stability. All dewatering activities will be conducted in a way to minimize
infiltration into the ground surfaces. Excavated wastes will be managed locally at the mining-
related source on an interim basis. Interim local waste management will include BMPs such as
berming, as necessary, to address fugitive dust and potential erosion and sedimentation issues.
Final remedial approaches for managed wastes will be addressed as part of future remedy
decisions and response actions.
Monitoring to evaluate performance standards and achievement of RAO 1 will include non-
intrusive (surface) visual inspection to confirm remedy components prevent co-mingling of mine
portal MIW discharges and contaminated mine waste. Additional remedy performance
monitoring consisting of surface water measurements and/or sample collection and analysis will
be conducted to monitor effectiveness of the implemented IRA.
Maintenance of the diversion/isolation components and interim local waste management
locations will be conducted as needed, primarily due to events that could compromise the
components (e.g., storm events, wildland fires). Non-intrusive (surface) visual inspection of
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interim local management locations and diversion/isolation components will be conducted to
assess maintenance requirements. Maintenance will be then performed as necessary to maintain
the integrity of both newly constructed and previously existing components.
The mine portal MIW discharges selected interim remedy will also include common elements
that will be required as part of the selected interim remedy for all contaminant migration issues,
as described in Section 9.3. Examples of these common elements include, but are not limited to,
pre-construction surveys, erosion and sediment control measures, dust suppression, access road
improvements (as necessary), and generation of uncontaminated borrow for construction of
remedial components and access roads.
Mine portal MIW discharges will be addressed at the following mining-related sources:
• Junction Mine
• Koehler Tunnel
• Brooklyn Mine
• Bandora Mine
• Natalie/Occidental Mine
• Henrietta Mine
• Mammoth Tunnel
• Anglo Saxon Mine
• Yukon Tunnel
• Mountain Queen Mine
• Vermillion Mine
• Sunbank Group Mine
• Frisco/Bagley Tunnel
• Columbus Mine
• Silver Wing Mine
• Tom Moore Mine
• Terry Tunnel
• Pride of the West Mine
Exhibit 12-1 provides a summary of the major remedial components for the mine portal MIW
discharges selected interim remedy and the estimated quantities for these components.
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Exhibit 12-1 Summary of Major Remedial Components and Associated Quantities for
the Mine Portal MIW Discharges Selected Interim Remedy
Koiiiodiiil ( niiipoiu'iil
I nil
I'.sliiiiiilcd
Qii;uilil>
Estimated number of mining-related sources with mine portal MIW discharges
EA
18
Estimated total length of diversion/isolation components to be constructed
LF
3,320
Estimated in-place volume of mine wastes/materials partially obstructing mine portal
MIW discharges
CY
30
Estimated weight of dewatering agent (assumed to be diatomaceous earth)
TON
4
Estimated in-place volume of borrow material for remedial component construction
CY
3,160
Notes:
Although detailed quantities have been provided, they should be considered approximate for evaluation purposes only.
EA - each, LF - linear feet, CY - cubic yards, TON - tons
12.1.4 Estimated Cost of the Selected Interim Remedy
The present value cost of the mine portal MIW discharges selected interim remedy is
approximately $2,411,000. The estimated capital costs are $1,082,000, and O&M and periodic
costs (over 15 years) are $2,191,000. The construction timeframe is estimated to be one season
for individual mining-related sources, and up to 5 years for all sources addressed by this IRA for
mine portal MIW discharges. Table 12-1A presents the cost estimate summary for the mine
portal MIW discharges selected interim remedy, including the present value analysis on a year-
by-year basis, assuming a real discount rate of 7 percent. Table 12-1B presents the cost estimate
summary for the mine portal MIW discharges selected interim remedy at the Brooklyn Mine.
The information in Tables 12-1A and 12-1B is based on the best available information regarding
the anticipated scope of the mine portal MIW discharges selected interim remedy. Changes in the
cost elements may occur as a result of new information and data collected during the engineering
design of the selected interim remedy. This is an order-of-magnitude engineering cost estimate
that is expected to be within +50 to -30 percent of the actual project cost.
12.1.5 Expected Outcomes of the Selected Interim Remedy
The mine portal MIW discharges selected interim remedy will provide protection of human
health and the environment in the short term and is intended to provide adequate protection until
a final remedy is selected. While the Site-wide risk assessment is ongoing, it is assumed that the
alternative will not result in unlimited use and unrestricted exposure land use scenarios.
The loading of COPCs is expected to decrease under the mine portal MIW discharges selected
interim remedy because diversion/isolation components addressing the interaction between mine
portal MIW discharges and mine wastes reduces the contact of the water with the waste. This
will reduce the potential for mine portal MIW discharges to generate additional MIW and reduce
transport and deposition of particulates containing COPCs to surface water, which contribute to
unacceptable ecological risks. However, the water quality in the streams, irrespective of the
removed mine wastes and diversion/isolation components, will still be impacted and contribute
to unacceptable ecological risks. Short-term increases in contaminant loading could result due to
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disturbances of the mine wastes during excavation, resulting in temporary increases in
production of MIW.
Intrusive monitoring, consisting of surface water measurements and/or sample collection and
analysis, will be conducted to monitor effectiveness of the implemented remedy. This data will
provide information about the effectiveness of the IRA and is intended to help inform future
remedial decisions at the Site.
Residual risks remain from untreated mine wastes managed locally at the mining-related source
on an interim basis. Local management of excavated mine wastes will include BMPs such as
berming, as necessary, to address fugitive dust and potential erosion and sedimentation issues as
well as inspection and repair, as necessary, to maintain their integrity of interim waste
management locations.
The anticipated socioeconomic and community revitalization impacts and environmental and
ecological benefits of the mine portal MIW discharges selected interim remedy will be limited
given the interim nature and limited scope of these actions.
12.2 MINING-RELATED SOURCE/STORMWATER INTERACTIONS
12.2.1 Short Description of the Selected Interim Remedy
The mining-related source/storm water interactions selected interim remedy involves construction
of diversion and isolation components to route stormwater around mine portals and/or
contaminated mine waste with the potential for interaction and co-mingling at mining-related
sources. It would also include maintenance of previously existing and newly constructed
diversion and isolation components.
12.2.2 Rationale for the Selected Interim Remedy
The mining-related source/storm water interactions selected interim remedy reduces the potential
for uncontrolled releases of particulates and MIW from mine waste through a reduction of the
contact between waste and stormwater. The mining-related source/stormwater interactions
selected interim remedy will achieve RAO 1 by routing stormwater around mine portals and/or
contaminated mine waste with the potential for interaction and co-mingling at mining-related
sources. RAOs 2 and 3 are not pertinent to this IRA.
12.2.3 Detailed Description of the Selected Interim Remedy
Diversion or isolation components implemented at each mining-related source will be chosen on a
location-by-location basis. Open channels typically will be constructed to collect stormwater and
divert it around the existing mine portals or mine waste. The construction of berms immediately
upgradient of mine portals or mine waste, collection/diversion piping or liners, or a combination
of multiple types of components are also viable for locations that are not conducive to open-
channel diversion. Berms will be considered at locations with underlying rock surfaces, while
collection/diversion piping or liners will be considered at locations with steep slopes or other
features that will pose challenges, such as roads directly adjacent to proposed diversion/isolation
components. These assumptions will be refined at the time of remedial design using location-
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specific information. At mining-related sources with existing stormwater diversion or isolation
components, repairs will be conducted to improve the conditions of those components. Wastes
generated from excavation stormwater diversion components such as open channels are assumed
to be uncontaminated and do not have handling and management requirements beyond BMPs for
erosion and sedimentation.
Where amenable, the mining-related source/storm water interactions selected interim remedy
could include subsurface components in conjunction with the surface components previously
described. Subsurface components such as interception trenches or French drains could be
constructed to intercept stormwater that has infiltrated into the shallow subsurface and divert it
around mine portals or mine waste.
Monitoring to evaluate performance standards and achievement of RAO 1 will include non-
intrusive (surface) visual inspection to confirm diversion and isolations components prevent co-
mingling of stormwater and contaminated mine waste. Additional remedy performance
monitoring consisting of surface water measurements and/or sample collection and analysis will
be conducted to monitor effectiveness of the implemented IRA.
Maintenance of the diversion/isolation components will be conducted as needed, primarily due to
events that could compromise the components (e.g., storm events, wildland fires). Non-intrusive
(surface) visual inspection of diversion and isolation components will be conducted to assess
maintenance requirements. Maintenance will be then performed as necessary to maintain the
integrity of both newly constructed and previously existing diversion and isolation components.
The mining-related source/storm water interactions selected interim remedy will also include
common elements that will be required as part of the selected interim remedy for all contaminant
migration issues, as described in Section 9.3. Examples of these common elements include, but
are not limited to, pre-construction surveys, erosion and sediment control measures, dust
suppression, access road improvements (as necessary), and generation of uncontaminated borrow
for construction of remedial components and access roads.
Mining-related source/storm water interactions will be addressed at the following mining-related
sources:
• Brooklyn Mine
• Bandora Mine
• Grand Mogul Mine
• Yukon Tunnel
• Ben Butler Mine
• Mountain Queen Mine
• Vermillion Mine
• Sunbank Group Mine
• Columbus Mine
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• Silver Wing Mine
Exhibit 12-2 provides a summary of the major remedial components for the mining-related
source/storm water interactions selected interim remedy and the estimated quantities for these
components.
Exhibit 12-2 Summary of Major Remedial Components and Associated Quantities for
the Mining-Related Source/Stormwater Interactions Selected Interim Remedy
Ki'incriiiil ( omponi'iil
I nil
I'lsliniiili'd
Qiiiinlih
Estimated number of mining-related sources with mining-related source/stormwaler
interactions
EA
10
Estimated total length of diversion/isolation components to be constructed
LF
4,120
Estimated in-place volume of borrow material for remedial component construction
CY
3,400
Notes:
Although detailed quantities have been provided, they should be considered approximate for evaluation purposes only.
EA - each, LF - linear feet, CY - cubic yards
12.2.4 Estimated Cost of the Selected Interim Remedy
The present value cost of the mining-related source/stormwater interactions selected interim
remedy is approximately $1,889,000. The estimated capital costs are $1,035,000, and O&M and
periodic costs (over 15 years) are $1,407,000. The construction timeframe is estimated to be one
season for individual mining-related sources, and up to 5 years for all sources addressed by this
IRA for mining-related source/stormwater interactions. Table 12-2A presents the cost estimate
summary for the mining-related source/stormwater interactions selected interim remedy,
including the present value analysis on a year-by-year basis, assuming a real discount rate of 7
percent. Table 12-2B presents the cost estimate summary for the mining-related
source/stormwater interactions selected interim remedy at the Brooklyn Mine.
The information in Tables 12-2A and 12-2B is based on the best available information regarding
the anticipated scope of the mining-related source/stormwater interactions selected interim
remedy. Changes in the cost elements may occur as a result of new information and data
collected during the engineering design of the selected interim remedy. This is an order-of-
magnitude engineering cost estimate that is expected to be within +50 to -30 percent of the actual
project cost.
12.2.5 Expected Outcomes of the Selected Interim Remedy
The mining-related source/stormwater interactions selected interim remedy will provide
protection of human health and the environment in the short term and is intended to provide
adequate protection until a final remedy is selected. While the Site-wide risk assessment is
ongoing, it is assumed that the alternative will not result in unlimited use and unrestricted
exposure land use scenarios.
The loading of COPCs is expected to decrease under the mining-related source/stormwater
interactions selected interim remedy because routing of stormwater around mine portals and/or
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contaminated mine wastes with the potential for interaction and co-mingling at mining-related
sources This will reduce the potential for stormwater to generate additional MIW and release
particulates containing COPCs to surface water, which contribute to unacceptable ecological
risks. However, the water quality in the streams, irrespective of diverted/isolated stormwater,
will still be impacted.
Intrusive monitoring, consisting of surface water measurements and/or sample collection and
analysis, will be conducted to monitor effectiveness of the implemented remedy. This data will
provide information about the effectiveness of the IRA and is intended to help inform future
remedial decisions at the Site.
The anticipated socioeconomic and community revitalization impacts and environmental and
ecological benefits of the mining-related source/storm water interactions selected interim remedy
will be limited given the interim nature and limited scope of these actions.
12.3 MINE PORTAL POND SEDIMENTS
12.3.1 Short Description of the Selected Interim Remedy
The mine portal pond sediments selected interim remedy involves excavation of existing
sediment and repair of berms within mine portal ponds to allow continued pond function.
Excavated wastes will be managed locally at the mining-related source on an interim basis.
12.3.2 Rationale for the Selected Interim Remedy
The mine portal pond sediments selected interim remedy reduces the potential for uncontrolled
releases of particulates and MIW from sediment in mine portal ponds that contribute to
unacceptable ecological risks. The mine portal pond sediments selected interim remedy will
achieve RAO 1 by excavation of existing sediment and repair of berms within mine portal ponds
to allow continued pond function. RAOs 2 and 3 are not pertinent to this IRA.
12.3.3 Detailed Description of the Selected Interim Remedy
Prior to removing sediment, the mine portal ponds will be drained as needed. MIW within ponds
will be managed locally solely to facilitate sediment excavation without treatment or external
discharge to surface water. At mining-related sources where multiple ponds exist, MIW
management from mine portals will include diversion of the MIW from one pond into the other
ponds while mine portal pond sediment is being excavated. At mining-related sources where
only one pond exists, mine portal pond sediment could be removed in phases using temporary
berms in order to manage MIW within the pond. Short-circuiting of ponds (MIW passing
through or around the pond without treatment), if those conditions currently exist, will also be
addressed through the construction or repair of pond berms.
Excavating sediment will be conducted at mine portal ponds to facilitate continued function of
the ponds. During the excavation process, the excavated wastes will be placed at the mining-
related source for gravity dewatering as needed. The location for this activity is assumed to be
amenable to dewatering without the need for liners or other isolation measures. Additional
dewatering could be implemented for saturated sediment through ex situ amendment with a
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dewatering agent, as necessary, for handling and geotechnical stability prior to interim
management at the mining-related source. Physical characterization, such as analysis of
geotechnical parameters, will be conducted as needed on excavated and dewatered sediment to
evaluate physical stability. All dewatering activities will be conducted in a way to minimize
infiltration into the ground surfaces. Excavated wastes will be managed locally at the mining-
related source on an interim basis. It is assumed that placement will be at an already impacted
area; therefore, placement of mine portal pond sediment will not risk contaminating a previously
unimpacted area. Interim local waste management will include BMPs such as berming, as
necessary, to address fugitive dust and potential erosion and sedimentation issues. Final remedial
approaches for managed wastes will be addressed as part of future remedy decisions and
response actions.
Monitoring to evaluate performance standards and achievement of RAO 1 will include non-
intrusive (surface) visual inspection to monitor sediment levels in ponds and continued pond
function. Additional remedy performance monitoring consisting of surface water measurements
and/or sample collection and analysis will be conducted to monitor effectiveness of the
implemented IRA.
Maintenance of the pond berms and interim local waste management locations will be conducted
as needed, primarily due to events that could compromise the components (e.g., storm events,
wildland fires). Non-intrusive (surface) visual inspection of interim local waste management
locations will be conducted to assess maintenance requirements. Maintenance will be then
performed as necessary to remove future accumulation of sediment in ponds and to maintain the
integrity of both newly constructed and previously existing pond berms and interim management
location components.
The mine portal pond sediments selected interim remedy will also include common elements that
will be required as part of the selected interim remedy for all contaminant migration issues, as
described in Section 9.3. Examples of these common elements include, but are not limited to,
pre-construction surveys, erosion and sediment control measures, dust suppression, access road
improvements (as necessary), and generation of uncontaminated borrow for construction of
remedial components and access roads. The assumptions for the mine portal pond sediments
selected interim remedy will be refined at the time of remedial design using location-specific
information.
Mine portal pond sediments will be addressed at the following mining-related sources:
• Junction Mine
• Koehler Tunnel
• Brooklyn Mine
• Mammoth Tunnel
• Anglo Saxon Mine
• Sunbank Group Mine
• Frisco/Bagley Tunnel
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• Silver Wing Mine
Exhibit 12-3 provides a summary of the major remedial components for the mine portal pond
sediments selected interim remedy and the estimated quantities for these components.
Exhibit 12-3 Summary of Major Remedial Components and Associated Quantities for
the Mine Portal Pond Sediments Selected Interim Remedy
Ki'im-rihil ( ompoiienl
I nil
K Mi muled
Qu;m(i(\
Estimated number of mining-related sources with mine portal pond sediments
EA
8
Estimated number of ponds
EA
14
Estimated horizontal extent of ponds
SF
68,800
Estimated in-place volume of mine portal pond sediments
CY
10,200
Estimated weight of dewatering agent (assumed to be diatomaceous earth)
TON
190
Estimated in-place volume of borrow material for remedial component construction
CY
2,710
Notes:
Although detailed quantities have been provided, they should be considered approximate for evaluation purposes only.
EA - each, SF - square feet, CY - cubic yards, TON - tons
12.3.4 Estimated Cost of the Selected Interim Remedy
The present value cost of the mine portal pond sediments selected interim remedy is
approximately $3,384,000. The estimated capital costs are $1,355,000, and O&M and periodic
costs (over 15 years) are $3,497,000. The construction timeframe is estimated to be one season
for individual mining-related sources, up to 5 years for all sources addressed by this IRA for
mine portal pond sediments. Table 12-3 A presents the cost estimate summary for the mine portal
pond sediments selected interim remedy, including the present value analysis on a year-by-year
basis, assuming a real discount rate of 7 percent. Table 12-3B presents the cost estimate
summary for the mine portal pond sediments selected interim remedy at the Brooklyn Mine.
The information in Tables 12-3A and 12-3B is based on the best available information regarding
the anticipated scope of the mine portal pond sediments selected interim remedy. Changes in the
cost elements are likely to occur as a result of new information and data collected during the
engineering design of the selected interim remedy. This is an order-of-magnitude engineering
cost estimate that is expected to be within +50 to -30 percent of the actual project cost.
12.3.5 Expected Outcomes of the Selected Interim Remedy
The mine portal pond sediments selected interim remedy will provide protection of human health
and the environment in the short term and is intended to provide adequate protection until a final
remedy is selected. While the Site-wide risk assessment is ongoing, it is assumed that the
alternative will not result in unlimited use and unrestricted exposure land use scenarios.
The loading of COPCs is expected to decrease under the mine portal pond sediments selected
interim remedy because excavating pond sediments improves the effectiveness of the pond. This
will reduce the potential for uncontrolled releases, transport, and deposition of particulates and
MIW containing COPCs to surface water from mine portal ponds, which contribute to
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unacceptable ecological risks. However, the water quality in the streams, irrespective of the
removed mine portal pond sediments, will still be impacted. Short-term increases in contaminant
loading could result due to disturbance of the mine portal pond sediments during excavation,
resulting in temporary increases in production of MIW.
Intrusive monitoring, consisting of surface water measurements and/or sample collection and
analysis, will be conducted to monitor effectiveness of the implemented remedy. This data will
provide information about the effectiveness of the IRA and is intended to help inform future
remedial decisions at the Site.
Residual risks remain from untreated mine portal pond sediments managed locally at the mining-
related source on an interim basis. Local management of mine portal pond sediments will include
BMPs such as berming, as necessary, to address fugitive dust and potential erosion and
sedimentation issues as well as inspection and repair, as necessary, to maintain their integrity of
interim waste management locations.
The anticipated socioeconomic and community revitalization impacts and environmental and
ecological benefits of the mine portal pond sediments selected interim remedy will be limited
given the interim nature and limited scope of these actions.
12.4 IN-STREAM MINE WASTES
12.4.1 Short Description of the Selected Interim Remedy
The in-stream mine wastes selected interim remedy involves excavation of in-stream mine
wastes at mining-related sources to remove wastes that impede flow or are susceptible to erosion
or leaching of contaminants. Excavated wastes will be managed locally at the mining-related
source on an interim basis.
12.4.2 Rationale for the Selected Interim Remedy
The in-stream mine wastes selected interim remedy reduces the potential for uncontrolled
releases of particulates and MIW from in-stream mine wastes that contribute to unacceptable
ecological risks. The in-stream mine wastes selected interim remedy will achieve RAO 1 by
excavation of in-stream mine wastes at mining-related sources to remove wastes that impede
flow or are susceptible to erosion or leaching of contaminants. RAOs 2 and 3 are not pertinent to
this IRA.
12.4.3 Detailed Description of the Selected Interim Remedy
During the excavation process, the excavated wastes will be placed outside of the stream channel
adjacent to the mining-related source for gravity dewatering. The location for this activity is
assumed to be amenable to dewatering without the need for liners or other isolation measures.
Additional dewatering could be implemented for saturated mine wastes through ex situ
amendment with a dewatering agent, as necessary, for handling and geotechnical stability prior
to interim management at the mining-related source. Physical characterization such as analysis of
geotechnical parameters will be conducted, as needed, on excavated and dewatered sediment to
evaluate physical stability. All dewatering activities will be conducted in a way to minimize
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infiltration into the ground surfaces. Excavated wastes will be managed locally at the mining-
related source on an interim basis. It is assumed that placement will be at an already impacted
area; therefore, placement of in-stream mine wastes will not risk contaminating a previously
unimpacted area. Interim local waste management will include BMPs such as berming, as
necessary, to address fugitive dust and potential erosion and sedimentation issues. Final remedial
approaches for managed wastes, will be addressed as part of future remedy decisions and
response actions.
Monitoring to evaluate performance standards and achievement of RAO 1 will include non-
intrusive (surface) visual inspection to confirm removal of in-stream mine waste. Additional
remedy performance monitoring consisting of surface water measurements and/or sample
collection and analysis will be conducted to monitor effectiveness of the implemented IRA.
Maintenance of the interim local waste management locations will be conducted as needed,
primarily due to events that could compromise the components (e.g., storm events, wildland
fires). Non-intrusive (surface) visual inspection of interim local waste management locations will
be conducted to assess maintenance requirements. Maintenance will be then performed as
necessary to maintain the integrity of interim management location components.
The in-stream mine wastes selected interim remedy will also include common elements that will
be required as part of the selected interim remedy for all contaminant migration issues, as
described in Section 9.3. Examples of these common elements include, but are not limited to,
pre-construction surveys, erosion and sediment control measures, dust suppression, access road
improvements (as necessary), and generation of uncontaminated borrow for construction of
remedial components and access roads. The assumptions for the in-stream mine wastes selected
interim remedy will be refined at the time of remedial design using location-specific information.
In-stream mine wastes will be addressed at the following mining-related source:
• Grand Mogul Mine
Exhibit 12-4 provides a summary of the major remedial components for the in-stream mine
wastes selected interim remedy and the estimated quantities for these components.
Exhibit 12-4 Summary of Major Remedial Components and Associated Quantities for
the In-Stream Mine Wastes Selected Interim Remedy
Koiiiodiiil ( niiipoiu'iil
I nil
I'.sliiiiiilcd
Qii;uilil>
Estimated number of mining-related sources with in-stream mine wastes
EA
1
Estimated horizontal extent of in-stream mine wastes
SF
4,200
Estimated in-place volume of in-stream mine wastes
CY
470
Estimated weight of dewatering agent (assumed to be diatomaceous earth)
TON
10
Estimated in-place volume of borrow material for remedial component construction
CY
90
Notes:
Although detailed quantities have been provided, they should be considered approximate for evaluation purposes only.
EA - each, SF - square feet, CY - cubic yards, TON - tons
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12.4.4 Estimated Cost of the Selected Interim Remedy
The present value cost of the in-stream mine wastes selected interim remedy is approximately
$512,000. The estimated capital costs are $264,000, and O&M and periodic costs (over 15 years)
are $408,000. The construction timeframe is estimated to be one season. Table 12-4 presents the
cost estimate summary for the in-stream mine wastes selected interim remedy, including the
present value analysis on a year-by-year basis, assuming a real discount rate of 7 percent.
The information in Table 12-4 is based on the best available information regarding the
anticipated scope of the in-stream mine wastes selected interim remedy. Changes in the cost
elements are likely to occur as a result of new information and data collected during the
engineering design of the selected interim remedy. This is an order-of-magnitude engineering
cost estimate that is expected to be within +50 to -30 percent of the actual project cost.
12.4.5 Expected Outcomes of the Selected Interim Remedy
The in-stream mine wastes selected interim remedy will provide protection of human health and
the environment in the short term and is intended to provide adequate protection until a final
remedy is selected. While the Site-wide risk assessment is ongoing, it is assumed that the
alternative will not result in unlimited use and unrestricted exposure land use scenarios.
Through removal of in-stream mine wastes, the loading of COPCs is expected to decrease
because it reduces the contact of the water with the waste. This will reduce formation of MIW
and transport and deposition of particulates containing COPCs to surface water, which contribute
to unacceptable ecological risks. However, the water quality in the streams, irrespective of the
removed mine wastes, will still be impacted. Short-term increases in contaminants loading could
result due to disturbance of the mine wastes during excavation, resulting in temporary increase in
production of MIW.
Intrusive monitoring, consisting of surface water measurements and/or sample collection and
analysis, will be conducted to monitor effectiveness of the implemented remedy. This data will
provide information about the effectiveness of the alternative and is intended to help inform
future remedial decisions at the Site.
Residual risks will remain from untreated wastes managed locally at the mining-related source
on an interim basis. Local management of wastes will include BMPs such as berming, as
necessary, to address fugitive dust and potential erosion and sedimentation issues as well as
inspection and repair, as necessary, to maintain their integrity of interim waste management
locations.
The anticipated socioeconomic and community revitalization impacts and environmental and
ecological benefits of the in-stream mine wastes selected interim remedy will be limited given
the interim nature and limited scope of these actions.
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12.5 MINING-IMPACTED RECREATION STAGING AREAS
12.5.1 Short Description of the Selected Interim Remedy
The mining-impacted recreation staging areas selected interim remedy includes
containment/isolation of mine wastes within mining-impacted recreation staging areas using
covers to reduce disturbances of mine wastes and migration of contaminants. The covers will
provide an exposure barrier and eliminate surface exposure to mine waste or contaminated soil.
12.5.2 Rationale for the Selected Interim Remedy
The mining-impacted recreation staging areas selected interim remedy will break the pathway for
soil ingestion and reduce the potential for uncontrolled releases of particulates that contribute to
unacceptable ecological risk. The mining-impacted recreation staging areas selected interim
remedy will achieve RAOs 2 and 3 by containment/isolation of mine wastes within mining-
impacted recreation staging areas using covers to reduce disturbances of mine wastes and
migration of contaminants. RAO 1 is not pertinent to this IRA.
12.5.3 Detailed Description of the Selected Interim Remedy
A combination of different types of covers will be constructed at mining-impacted recreation
staging areas. The covers will be sloped to promote positive drainage in order to minimize
erosion and to reduce infiltration that could saturate the subsurface and compromise the integrity
of the covers. The prepared mine waste or contaminated soil surface will then be covered with an
engineered layer of soil (which could be vegetated) or a surface layer of rock. Vegetated layers
will be amended with organics, lime, and fertilizer, and then seeded. The specific types of covers
will be determined based on specific recreation staging uses of each mining-related source and
availability of sufficient quantities of suitable cover materials for that use. Aggregate covers are
assumed to be constructed over mine waste or contaminated soil at portions of staging areas
exposed to continuous vehicle traffic, such as parking areas adjacent to campsites and along
stream banks of campsites. Soil covers are assumed to be constructed over mine waste at areas
not exposed to continuous vehicle traffic, such as the campsites themselves. These assumptions
will be refined at the time of remedial design.
A pre-design investigation will be conducted to include sample collection and analysis at the
mining-impacted recreation staging areas. Results from the pre-design investigation will be used
to delineate the horizontal extent of remediation at the mining-impacted recreation staging areas,
based on a comparison to the human health cleanup levels detailed in Section 8.2.1. For purposes
of the IROD, physical information such as, but not limited to, topography and soil types (i.e.,
relatively flat areas free of large boulders and cobbles) was used to conservatively estimate the
horizontal extent of remediation.
Monitoring to evaluate performance standards and achievement of RAOs 2 and 3 will include
non-intrusive (surface) visual inspection to monitor integrity of the covers.
Maintenance of the interim local waste management locations will be conducted as needed,
primarily due to events that could compromise the components (e.g., storm events, wildland
fires). Non-intrusive (surface) visual inspection of cover components will be conducted to assess
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maintenance requirements. Maintenance will be then performed as necessary to maintain the
integrity of cover components.
The mining-impacted recreation staging areas selected interim remedy will also include common
elements that will be required as part of the selected interim remedy for all contaminant
migration issues, as described in Section 9.3. Examples of these common elements include, but
are not limited to, pre-construction surveys, erosion and sediment control measures, dust
suppression, access road improvements (as necessary), and generation of uncontaminated borrow
for construction of remedial components and access roads.
Mining-impacted recreation staging areas will be addressed at the following mining-related sources:
• Longfellow Mine
• Junction Mine
• Koehler Tunnel
• Campground 4
• Campground 7
Exhibit 12-5 provides a summary of the major remedial components for the mining-impacted
recreation staging areas selected interim remedy and the estimated quantities for these
components.
Exhibit 12-5 Summary of Major Remedial Components and Associated Quantities for
the Mining-Impacted Recreation Staging Areas Selected Interim Remedy
Ki'im-rihil ( ompoiienl
I nil
K Mi muled
Qu;m(i(\
Estimated number of mining-related sources with mining-impacted recreation
staging areas
EA
5
Estimated horizontal extent of aggregate (rock) covers to be constructed
AC
2.0
Estimated horizontal extent of soil covers to be constructed
AC
6.9
Estimated in-place volume of borrow material for remedial component construction
CY
18,600
Notes:
Although detailed quantities have been provided, they should be considered approximate for evaluation purposes only.
AC - acres, EA - each, CY - cubic yards
12.5.4 Estimated Cost of the Selected Interim Remedy
The present value cost of the mining-impacted recreation staging areas selected interim remedy
is approximately $1,668,000. The estimated capital costs are $1,210,000, and O&M and periodic
costs (over 15 years) are $758,000. The construction timeframe is estimated to be one season for
individual mining-related sources, up to 5 years for all mining-impacted recreation staging areas.
Table 12-5 presents the cost estimate summary for the mining-impacted recreation staging areas
selected interim remedy, including the present value analysis on a year-by-year basis, assuming a
real discount rate of 7 percent.
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The information in Table 12-5 is based on the best available information regarding the
anticipated scope of the mining-impacted recreation staging areas selected interim remedy.
Changes in the cost elements are likely to occur as a result of new information and data collected
during the engineering design of the selected interim remedy. This is an order-of-magnitude
engineering cost estimate that is expected to be within +50 to -30 percent of the actual project
cost.
12.5.5 Expected Outcomes of the Selected Interim Remedy
The mining-impacted recreation staging areas selected interim remedy will provide protection of
human health and the environment in the short term and is intended to provide adequate
protection until a final remedy is selected. While the Site-wide risk assessment is ongoing, it is
assumed that the alternative will not result in unlimited use and unrestricted exposure land use
scenarios.
Covers will be implemented to reduce disturbances of mine wastes and contaminated soils, and
exposure to mine wastes and contaminated soils containing lead or arsenic that exceed cleanup
levels will be reduced.
Performance monitoring, consisting of non-intrusive (surface) visual inspection of cover
components, will be conducted to monitor effectiveness of the implemented remedy.
The anticipated socioeconomic and community revitalization impacts and environmental and
ecological benefits of the mining-impacted recreation staging areas selected interim remedy will
be limited given the interim nature and limited scope of these actions.
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13.0 INSTITUTIONAL AND LAND USE CONTROLS
ICs are defined as "non-engineered instruments that help minimize the potential for exposure to
contamination and/or protect the integrity of a response action" in the Institutional Controls: A
Guide to Planning, Implementing, Maintaining, and Enforcing Institutional Controls at
Contaminated Sites (EPA 2012). ICs are a subset of land use controls (LUCs). LUCs include
engineering and physical barriers, such as fences and signs, as well as ICs.
Final ICs will be selected in the final record of decision; however, the NCP recommends that ICs
should be used to supplement engineering controls during all phases of cleanup. See NCP §
300.430(a)(l)(iii)(D). The need for and type of LUCs, including ICs, will be evaluated at each
source area during the design phase of these IRAs. Prior to the final record of decision, EPA and
the State of Colorado will work together to implement LUCs, including ICs, necessary to protect
the integrity of the IRAs taken in this IROD. ICs will include governmental or proprietary
controls on land use as provided by the Colorado Environmental Covenants Statute, C.R.S. §§
25-15-317 etseq. (EC Statute), enforcement tools that limit certain activities, and informational
devices to provide information or notification to local communities, recreational users and other
interested persons, as appropriate.
As discussed in subsections 13.1 and 13.2, the EC Statute has been identified as an applicable
requirement for the mining-impacted recreation staging areas and those components of the IRAs
determined to include engineered remedial features likely to be permanent. In the event San Juan
County does not enact an ordinance pursuant to C.R.S. § 25-15-320, EPA in coordination with
the State will evaluate the use of restrictive notices as well as the use of LUCs, including other
ICs, at all the source areas addressed in this IROD to provide notice or prevent access pending
the final remedial action.
13.1 INSTITUTIONAL AND LAND USE CONTROLS AT MINING-IMPACTED
RECREATION STAGING AREAS
As specified in Section 12.5, covers will be used at the mining-impacted recreation staging areas
to break human health exposure pathways associated with soil ingestion and reduce the potential
for uncontrolled releasees of particulates contributing to ecological risk. The IRA at these areas
will result in waste left in place above levels safe for unlimited use and unrestricted exposure and
may constitute the final remedy at these areas. In addition, the covers are engineered remedial
features likely to be permanent as described in subsection 13.2. Accordingly, the EC Statute has
been identified as an applicable requirement for these areas. EPA will work with the State of
Colorado to implement ICs pursuant to the EC Statute, and other appropriate LUCs.
13.2 INSTITUTIONAL AND LAND USE CONTROLS FOR ENGINEERED
REMEDIAL FEATURES LIKELY TO BE PERMANENT
As specified in Section 12, the selected interim remedy includes components that will
incorporate engineered remedial features likely to be permanent. The engineered remedial
features likely to be permanent of the selected remedy include: (1) diversion or isolation
components of Alternative A2 (Diversion/Isolation of Mine Portal MIW Discharges); (2)
diversion or isolation components to route stormwater around mine portals associated with
Alternative B2 (Stormwater Diversion/Isolation); (3) maintenance and repair of mine portal
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ponds associated with Alternative C2 (Excavation and Interim Local Waste Management of
Mine Portal Pond Sediments); and (4) containment and isolation of mine wastes within mining-
impacted recreation staging areas using covers as described in Alternative E2
(Containment/Isolation of In-Stream Mine Wastes). EPA has determined components of the
IRAs involving interim local waste management described in Alternative D2 do not constitute
engineered remedial features likely to be permanent. Accordingly, the EC Statute has been
identified as an applicable requirement for these features. EPA will work with the State of
Colorado to implement the EC Statute at properties where engineered remedial features likely to
be permanent are incorporated.
13.3 LAND USE RESTRICTIONS
The following land use restrictions will be included in any environmental covenant or notice of
environmental use restrictions recorded as an IC pursuant to this Record of Decision at mine-
impacted recreation staging areas and for engineered remedial features likely to be permanent:
No tilling, excavation, grading, construction, or any other activity that disturbs the ground
surface or subsurface or that would in any manner interfere with or adversely affect the
implementation, integrity, or protectiveness of the remedial features is permitted.
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14.0 STATUTORY DETERMINATIONS
Under CERCLA Section 121 and the NCP, EPA must select a remedy that is protective of
human health and the environment, complies with or appropriately waives ARARs, is cost
effective, and uses permanent solutions and alternative treatment technologies or resource
recovery technologies to the maximum extent practicable. In addition, CERCLA includes a
preference for remedies that include treatment that permanently and significantly reduces the
volume, toxicity, or mobility of hazardous wastes as a principal element. The following sections
discuss how the five IRAs comprising the selected interim remedy meets these statutory
requirements.
14.1 MINE PORTAL MIW DISCHARGES
The following subsections discuss the statutory determinations for the mine portal MIW
discharges IRA of the selected interim remedy.
14.1.1 Protection of Human Health and the Environment
The mine portal MIW discharges selected interim remedy will provide protection of human
health and the environment in the short term and is intended to provide adequate protection until
a final remedy is selected. It will provide stabilization of the mining-related sources and prevent
further environmental degradation. The mine portal MIW discharges selected interim remedy
addresses RAO 1 by constructing and/or maintaining diversion and isolation components to route
mine portal MIW discharge around contaminated mine waste with the potential for interaction
and co-mingling at mining-related sources. This will reduce the potential for mine portal MIW
discharges to generate additional MIW and reduce transport and deposition of particulates
containing COPCs to surface water, which contribute to unacceptable ecological risks. Mine
wastes or other materials at the entrance to a mine portal that are partially obstructing free flow
of MIW discharge will be excavated to reduce the potential for uncontrolled releases of
particulates and MIW containing COPCs to surface water, which contribute to unacceptable
ecological risks. EPA will measure the extent by which ecological risks associated with
contributions from MIW discharges have been reduced by this selected interim remedy.
14.1.2 Compliance with ARARs
14.1.2.1 Chemical-Specific ARARs
Chemical-specific ARARs will be pertinent to the mine portal MIW discharges selected interim
remedy. State water quality standards for COPCs will likely not be met for the streams receiving
mine portal MIW discharges after the selected interim remedy is constructed due to other
contributing mining-related sources, thus the interim measures CERCLA ARAR waiver will be
invoked for the Colorado Basic Standards and Methodologies for Surface Water. The Colorado
Basic Standards for Groundwater will also be waived using an interim measures CERCLA
ARAR waiver because the limited RI information available does not indicate that groundwater
meeting the regulatory definition exists beneath the mining-related sources addressed by the
selected interim remedy.
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14.1.2.2 Location- and Action-Specific ARARs
Location- and action-specific ARARs for the mine portal MIW discharges selected interim
remedy will be addressed during implementation of the IRA, as indicated in the following
paragraphs.
Excavation: The excavation of mine wastes from waters of the United States is assumed to be
performed with neat excavation only involving incidental fallback. Thus, the substantive
requirements of Section 404 will not be triggered. If grading or excavation activities result in a
discharge of dredge material, the substantive requirements of Nationwide Permit 20 (Response
Operations for Oil or Hazardous Substances) will be met.
Dust Suppression: Dust suppression and emission-controlled equipment will be used during
construction activities for the selected interim remedy to achieve compliance with Colorado
emission control requirements.
Dewatering: If effluent discharge to surface water is necessary during dewatering,, activities
would be conducted in a way to minimize infiltration into the ground surface that could cause
additional degradation of groundwater. Because the groundwater, as defined in 5 CCR 1002-41,
is not known to be present below the mining-related sources, an interim measures CERCLA
ARAR waiver will be invoked. An interim measures CERCLA ARAR waiver will also be
invoked to waive the substantive provisions of Colorado Effluent Limitations and CDPS
regulations for groundwater.
If effluent discharge to surface water is necessary during dewatering, the discharge limit
requirements of Colorado effluent limitations will be met without treatment at the dewatering
locations; otherwise an interim measures CERCLA ARAR waiver will be invoked. Similarly, the
substantive provisions of the CDPS regulations will be met; otherwise an interim measures
CERCLA ARAR waiver will be invoked.
Interim Local Waste Management: Mine wastes at the Site were derived directly or indirectly
from the extraction of ore and thus will be exempt from management as a RCRA hazardous
waste (i.e., the Bevill exemption), thus mine wastes will be classified as a non-hazardous solid
waste.
Pursuant to the Solid Wastes Disposal Sites and Facilities Act, C.R.S. § 30-20-102(4), mining
operations including reclamation activities with approved reclamation plans under an MLRB
permit may dispose of solid wastes generated by such operations within the permitted area
without obtaining a Certificate of Designation. The CDPHE interprets this provision to exempt
CERCLA response actions performed consistently with MLRB regulation 2 CCR 407-1 Rule 3
(Reclamation Performance Standards) to be compliant with Colorado's regulations pertaining to
solid waste disposal.
All waste handling and disposal activities under the selected interim remedy will be performed in
accordance with substantive requirements of the relevant and appropriate subparts of MLRB
regulation 2 CCR 407-1 Rule 3 (Reclamation Performance Standards), which will allow the
selected interim remedy to be compliant with substantive requirements of the Colorado Solid
Waste Disposal Sites and Facilities Regulations.
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Grading of wastes for interim local management will be performed to meet relevant and
appropriate substantive requirements of 2 CCR 407-1 Rule 3.
Surface Reclamation: Surface reclamation activities under the selected interim remedy,
including grading, will be performed to meet relevant and appropriate substantive requirements
of 2 CCR 407-1 Rule 3.
Construction Activities: Cultural resource surveys have not been completed for all mining-
related sources addressed by the selected interim remedy. If any cultural resources are found,
surveys will be necessary to determine if adverse effects will occur, and if so, how the effects
may be minimized or mitigated in accordance with the National Historic Preservation Act,
Archaeological and Historic Preservation Act, and Historic Sites Act.
If bald or golden eagles are observed during remedial design and IRA, activities must be
modified and conducted to conserve the species and their habitat to comply with the substantive
requirements of the Bald and Golden Eagle Protection Act.
If the IRA involves activities modifying streams or water bodies that affect wildlife and/or non-
game fish, federal agencies must comply with substantive requirements identified by the USFWS
and the relevant state agency with jurisdiction over wildlife resources in accordance with Fish
and Wildlife Coordination Act and implementing regulations.
If threatened or endangered species are identified at these mining-related sources during remedial
design and IRA, activities must be modified and conducted to conserve the species and their
habitat in accordance with the Endangered Species Act and relevant and appropriate substantive
requirements of 40 CFR 257.
If migratory birds are identified during remedial design and IRA, activities must be modified and
conducted to conserve the species and their habitat in accordance with the Migratory Bird Treaty
Act.
This selected interim remedy will not be conducted within streams. However, if activities were to
impact streams, they will be carried out in a manner to avoid adversely affecting wildlife and/or
non-game fish within streams. Compliance will be achieved through coordination with the
Colorado Division of Parks Wildlife and in accordance with the Colorado Wildlife Enforcement
and Penalties Act and Colorado Non-game, Endangered, or Threatened Species Act.
It is not anticipated that nests or dens of wildlife exist at the mine locations. If they were to be
encountered, the selected interim remedy will be implemented to avoid disturbing or destroying
nests or dens. Compliance will be achieved through coordination with the Colorado Division of
Parks and Wildlife and in accordance with substantive requirements of Colorado Wildlife
Commission regulations.
Planning for activities conducted during the IRA on USFS-managed land, such as obtaining
borrow material and implementing the IRA at the Brooklyn Mine, will consider pertinent
information provided within the San Juan National Forest and Tres Rios Field Office Land and
Resource Management Plan.
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If the IRA involves activities that affect identified floodplains or wetlands, activities will be
carried out in a manner to avoid adversely affecting them and thus meet the substantive
requirements of the Clean Water Act, Section 404 regulations, 40 CFR Part 6, Appendix A, and
relevant and appropriate substantive requirements of 40 CFR 257.
Activities under the selected interim remedy will be carried out in a manner that will comply
with Colorado Noise Abatement Statue 25-12-103.
14.1.2.3 ARAR Waivers
Compliance with certain ARARs may not be possible for components of the mine portal MIW
discharges selected interim remedy since they are interim in scope and do not address all
contaminated media posing unacceptable human health and ecological risks. Thus, the CERCLA
interim measures waiver is the most pertinent to the selected interim remedy and the only
CERCLA ARAR waiver identified in this IROD.
Blanket use of the CERCLA interim measures waiver will occur where the expectation is that,
regardless of the conditions (i.e., the particular IRA, activity within the IRA, and/or mining-
related source location), the ARAR will not be complied with and thus the waiver is invoked on
a blanket basis. The ARARs that will fall under blanket waiver use include:
• Federal
o Clean Water Act 33 U.S.C. §§ 1342, et seq., Point Source Discharges Requirements,
Section 402
• State of Colorado
o Colorado Basic Standards for Groundwater, 5 CCR 1002-41, pursuant to C.R.S. §§
25-8-101-703
o Colorado Surface Water Quality Classifications and Numeric Standards, 5 CCR
1002-34, pursuant to C.R.S.§§ 25-8-203 and 204
o CDPS Regulations, 5 CCR 1002-61, Regulation No. 61, pursuant to C.R.S.§ 25-8-
501 -509
o Colorado Effluent Limitations, 5 CCR 1002-62, pursuant to C.R.S.§ 25-8-205
14.1.3 Cost Effectiveness
The mine portal MIW discharges selected interim remedy is cost effective and represents a
reasonable value for the money to be spent. In making this determination, the following
definition was used: "A remedy shall be cost effective if its costs are proportional to its overall
effectiveness" [NCP §300.430(f)(l)(ii)(D)]. This is determined by evaluating the overall
effectiveness of the selected interim remedy and comparing that effectiveness to the overall
costs. Effectiveness is evaluated by examining how the remedy meets three criteria: long-term
effectiveness and permanence; reduction in toxicity, mobility, and volume through treatment;
and short-term effectiveness. Overall effectiveness of the remedial alternatives was compared to
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costs to determine cost effectiveness. The relationship of the overall effectiveness of the mine
portal MIW discharges selected interim remedy was determined to be proportional to its cost,
and hence this remedy represents a reasonable value for the cost to be incurred.
The cost of the mine portal MIW discharges selected interim remedy is expected to have a
present value cost of approximately $2,285,000. Compared to the other alternative considered
(No Action), the mine portal MIW discharges selected interim remedy has a higher cost, but it is
the only alternative expected to provide protection of human health and the environment as an
interim measure. EPA believes the mine portal MIW discharges selected interim remedy
achieves an appropriate balance between cost effectiveness and adequate protectiveness.
14.1.3.1 Utilization of Permanent Solutions and Alternative Treatment (or Resource
Recovery) Technologies to the Maximum Extent Practicable
This determination looks at whether the selected interim remedy provides the best balance of
tradeoffs among the alternatives with respect to the balancing criteria set forth in NCP
§300.430(f)(l)(i)(B) such that it represents the maximum extent to which permanence and
treatment can be practicably used at the Site. NCP §300.430(f)(l)(ii)(E) provides that the
balancing shall emphasize the factors of "long-term effectiveness" and "reduction of toxicity,
mobility, or volume through treatment," and shall consider the preference for treatment and bias
against off-site disposal. The modifying criteria were also considered in making this
determination.
The mine portal MIW discharges selected interim remedy is an interim solution only, and is not
intended to utilize permanent solutions and alternative treatment (or resource recovery)
technologies to the maximum extent practicable. Permanent solutions and alternative treatment
technologies or resource recovery technologies will be addressed as part of the final response
action.
14.1.3.2 Preference for Treatment as a Principal Element
This determination looks at whether the selected interim remedy provides treatment as a
principal element. The NCP establishes the expectation that treatment will be used to address
principal threat wastes whenever practicable (40 CFR 300.430[a][l][iii][A]). Principal threat
wastes are those source materials that are considered to be highly toxic or highly mobile that
generally cannot be contained in a reliable manner or will present a significant risk to human
health and the environment should exposure occur. As discussed in Section 11.0 of this IROD,
EPA has determined that media addressed by this IRA do not involve principal threat waste. In
addition, because this action does not constitute the final remedy, the statutory preference for
remedies that employ treatment that reduces toxicity, mobility, or volume as a principal element
will be considered and addressed by the final response action.
14.1.4 Five-Year Site Reviews
While the Site-wide risk assessment is ongoing, it is assumed that the mine portal MIW
discharges selected interim remedy will not result in unlimited use and unrestricted exposure
land use scenarios. Therefore, five-year reviews pursuant to CERCLA § 121(c) and NCP
§300.430(f)(5)(iii)(C) are assumed to be conducted for the mining-related sources included as
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part of this selected interim remedy in conjunction with sources addressed by other response
actions as part of Site-wide activities. EPA shall conduct a review of remedial actions no less
often than each 5 years after the initiation of such remedial action to ensure the remedy is, or will
be, protective of human health and the environment.
14.2 MINING-RELATED SOURCE/STORMWATER INTERACTIONS
The following subsections discuss the statutory determinations for the mining-related
source/storm water interactions IRA of the selected interim remedy.
14.2.1 Protection of Human Health and the Environment
The mining-related source/storm water interactions selected interim remedy will provide
protection of human health and the environment in the short term and is intended to provide
adequate protection until a final remedy is selected. It will provide stabilization of the mining-
related sources and prevent further environmental degradation. The mining-related
source/storm water interactions selected interim remedy addresses RAO 1 by constructing and/or
maintaining diversion and isolation components to route stormwater around mine portals and/or
mine wastes with the potential for interaction and co-mingling at mining-related sources. This
will reduce the potential for stormwater to generate additional MIW and reduce transport and
deposition of particulates containing COPCs to surface water, which contribute to unacceptable
aquatic ecological risks. EPA will measure the extent by which ecological risks associated with
contributions from mining-related source/storm water interactions have been reduced by the
selected interim remedy.
14.2.2 Compliance with ARARs
14.2.2.1 Chemical-Specific ARARs
Chemical-specific ARARs will be pertinent to the mining-related source/storm water interactions
selected interim remedy. State water quality standards will likely not be met for streams
receiving stormwater discharges after the selected interim remedy is constructed due to other
contributing mining-related sources, thus the interim measures CERCLA ARAR waiver will be
invoked for the Colorado Basic Standards and Methodologies for Surface Water. The Colorado
Basic Standards for Groundwater will also be waived using an interim measures CERCLA
ARAR waiver because the limited RI information available does not indicate that groundwater
meeting the regulatory definition exists beneath the mining-related sources addressed by the
selected interim remedy.
14.2.2.2 Location- and Action-Specific ARARs
Location- and action-specific ARARs for the mining-related source/storm water interactions
selected interim remedy will be addressed during implementation of the IRA as indicated in the
following paragraphs.
Excavation: The excavation of mine wastes from waters of the United States is assumed to be
performed with neat excavation only involving incidental fallback. Thus, the substantive
requirements of Section 404 will not be triggered. If grading or excavation activities result in a
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discharge of dredge material, the substantive requirements of Nationwide Permit 20 (Response
Operations for Oil or Hazardous Substances) will be met.
Dust Suppression: Dust suppression and emission-controlled equipment will be used during
construction activities for the selected interim remedy to achieve compliance with Colorado
Emission Control requirements.
Surface Reclamation: Surface reclamation activities under the selected interim remedy,
including grading, will be performed to meet relevant and appropriate substantive requirements
of 2 CCR 407-1 Rule 3.
Construction Activities: Cultural resource surveys have not been completed for all mining-
related sources addressed by the selected interim remedy. If any cultural resources are found,
surveys will be necessary to determine if adverse effects will occur, and if so, how the effects
may be minimized or mitigated in accordance with the National Historic Preservation Act,
Archaeological and Historic Preservation Act, and Historic Sites Act.
If bald or golden eagles are observed during remedial design and IRA, activities must be
modified and conducted to conserve the species and their habitat to comply with the substantive
requirements of the Bald and Golden Eagle Protection Act.
If the IRA involves activities modifying streams or water bodies that affect wildlife and/or non-
game fish, federal agencies must comply with substantive requirements identified by USFWS
and the relevant state agency with jurisdiction over wildlife resources in accordance with Fish
and Wildlife Coordination Act and implementing regulations.
If threatened or endangered species are identified at these mining-related sources during remedial
design and IRA, activities must be modified and conducted to conserve the species and their
habitat in accordance with the Endangered Species Act and relevant and appropriate substantive
requirements of 40 CFR 257.
If migratory birds are identified during remedial design and IRA, activities must be modified and
conducted to conserve the species and their habitat in accordance with the Migratory Bird Treaty
Act.
The mining-related source/storm water interactions selected interim remedy will not be conducted
within streams. However, if activities were to impact streams, they will be carried out in a
manner to avoid adversely affecting wildlife and/or non-game fish within streams. Compliance
will be achieved through coordination with the Colorado Division of Parks Wildlife and in
accordance with the Colorado Wildlife Enforcement and Penalties Act and Colorado Non-game,
Endangered, or Threatened Species Act.
It is not anticipated that nests or dens of wildlife exist at the mine locations. If they were to be
encountered, the selected interim remedy will be implemented to avoid disturbing or destroying
nests or dens. Compliance will be achieved through coordination with the Colorado Division of
Parks Wildlife and in accordance with substantive requirements of Colorado Wildlife
Commission regulations.
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Planning for activities conducted during the IRA on USFS-managed land, such as obtaining
borrow material and implementing the IRA at the Brooklyn Mine, will consider pertinent
information provided within the San Juan National Forest and Tres Rios Field Office Land and
Resource Management Plan.
If the IRA involves activities that affect identified floodplains or wetlands, activities will be
carried out in a manner to avoid adversely affecting them and thus meet the substantive
requirements of the Clean Water Act, Section 404 regulations, 40 CFR Part 6, Appendix A, and
relevant and appropriate substantive requirements of 40 CFR 257.
Activities under the selected interim remedy will be carried out in a manner that will comply
with Colorado Noise Abatement Statue 25-12-103.
14.2.2.3 ARAR Waivers
Compliance with certain ARARs may not be possible for components of the mine portal MIW
discharges selected interim remedy since they are interim in scope and do not address all
contaminated media posing unacceptable human health and ecological risks. Thus, the CERCLA
interim measures waiver is the most pertinent to the selected interim remedy and the only
CERCLA ARAR waiver identified in this IROD.
Blanket use of the CERCLA interim measures waiver will occur where the expectation is that
regardless of the conditions (i.e., the particular IRA, activity within the IRA, and/or mining-
related source location) that the ARAR will not be complied with and thus the waiver is invoked
on a blanket basis. The ARARs that will fall under blanket waiver use include:
• Federal
o Clean Water Act 33 U.S.C. §§ 1342, et seq., Point Source Discharges Requirements,
Section 402
• State of Colorado
o Colorado Basic Standards for Groundwater, 5 CCR 1002-41, pursuant to C.R.S. §§
25-8-101-703
o Colorado Surface Water Quality Classifications and Numeric Standards, 5 CCR
1002-34, pursuant to C.R.S.§§ 25-8-203 and 204
o CDPS Regulations, 5 CCR 1002-61, Regulation No. 61, pursuant to C.R.S.§ 25-8-
501 -509
o Colorado Effluent Limitations, 5 CCR 1002-62, pursuant to C.R.S.§ 25-8-205
14.2.3 Cost Effectiveness
The mining-related source/storm water interactions selected interim remedy is cost effective and
represents a reasonable value for the money to be spent. In making this determination, the
following definition was used: "A remedy shall be cost effective if its costs are proportional to its
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overall effectiveness" [NCP §300.430(f)(l)(ii)(D)]. This is determined by evaluating the overall
effectiveness of the selected interim remedy and comparing that effectiveness to the overall
costs. Effectiveness is evaluated by examining how the remedy meets three criteria: long-term
effectiveness and permanence; reduction in toxicity, mobility, and volume through treatment;
and short-term effectiveness. Overall effectiveness of the remedial alternatives was compared to
costs to determine cost effectiveness. The relationship of the overall effectiveness of the selected
interim remedy was determined to be proportional to its cost, and hence this remedy represents a
reasonable value for the cost to be incurred.
The cost of the mine-related source/storm water interactions selected interim remedy is expected
to have a present value cost of approximately $1,836,000. Compared to the other alternative
considered (No Action), the mining-related source/storm water interactions selected interim
remedy has a higher cost, but it is the only alternative expected to provide protection of human
health and the environment as an interim measure. EPA believes the mining-related
source/storm water interactions selected interim remedy achieves an appropriate balance between
cost effectiveness and adequate protectiveness.
14.2.4 Utilization of Permanent Solutions and Alternative Treatment (or Resource
Recovery) Technologies to the Maximum Extent Practicable
This determination looks at whether the selected interim remedy provides the best balance of
tradeoffs among the alternatives with respect to the balancing criteria set forth in NCP
§300.430(f)(l)(i)(B) such that it represents the maximum extent to which permanence and
treatment can be practicably used at the Site. NCP §300.430(f)(l)(ii)(E) provides that the
balancing shall emphasize the factors of "long-term effectiveness" and "reduction of toxicity,
mobility, or volume through treatment," and shall consider the preference for treatment and bias
against off-site disposal. The modifying criteria were also considered in making this
determination.
This mining-related source/storm water interactions selected interim remedy is an interim
solution only, and is not intended to use permanent solutions and alternative treatment (or
resource recovery) technologies to the maximum extent practicable. Permanent solutions and
alternative treatment technologies or resource recovery technologies will be addressed as part of
the final response action.
14.2.5 Preference for Treatment as a Principal Element
This determination looks at whether the selected interim remedy provides treatment as a
principal element. The NCP establishes the expectation that treatment will be used to address
principal threat wastes whenever practicable (40 CFR 300.430[a][l][iii][A]). Principal threat
wastes are those source materials that are considered to be highly toxic or highly mobile that
generally cannot be contained in a reliable manner or will present a significant risk to human
health and the environment should exposure occur. As discussed in Section 11.0 of this IROD,
EPA has determined that media addressed by this IRA do not involve principal threat waste. In
addition, because this action does not constitute the final remedy, the statutory preference for
remedies that employ treatment that reduces toxicity, mobility, or volume as a principal element
will be considered and addressed by the final response action.
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14.2.6 Five-Year Site Reviews
While the Site-wide risk assessment is ongoing, it is assumed that the mining-related
source/storm water interactions selected interim remedy will not result in unlimited use and
unrestricted exposure land use scenarios. Therefore, five-year reviews pursuant to CERCLA
§121 (c) and NCP §300.430(f)(5)(iii)(C) are assumed to be conducted for the mining-related
sources included as part of this selected interim remedy in conjunction with sources addressed by
other response actions as part of Site-wide activities. EPA shall conduct a review of remedial
actions no less often than each 5 years after the initiation of such remedial action to ensure the
remedy is, or will be, protective of human health and the environment.
14.3 MINE PORTAL POND SEDIMENTS
The following subsections discuss the statutory determinations for the mine portal pond
sediments IRA of the selected interim remedy.
14.3.1 Protection of Human Health and the Environment
The mine portal pond sediments selected interim remedy will provide protection of human health
and the environment in a short term and is intended to provide adequate protection until a final
remedy is selected. It will provide stabilization of the source and prevent further environmental
degradation. The mine portal pond sediments selected interim remedy addresses RAO 1 through
excavation and interim local waste management of pond sediments that will reduce the potential
for uncontrolled releases of particulates containing COPCs to surface water, which contribute to
unacceptable ecological risks. Excavation of pond sediments and repair of pond berms will
increase storage space for MIW in ponds and minimize short-circuiting of MIW to increase
residence time. EPA will measure the extent by which ecological risks associated with
contributions from mine portal pond sediments have been reduced by the mine portal pond
sediments selected interim remedy.
14.3.2 Compliance with ARARs
14.3.2.1 Chemical-Specific ARARs
Chemical-specific ARARs will be pertinent to the mine portal pond sediments selected interim
remedy. State water quality standards will not be met for the streams after removal of mine pond
portal sediments is complete due to other contributing mining-related sources; thus, the interim
measures CERCLA ARAR waiver will be invoked for the Colorado Basic Standards and
Methodologies for Surface Water. The Colorado Basic Standards for Groundwater will also be
waived using an interim measures CERCLA ARAR waiver because the limited RI information
available does not indicate that groundwater meeting the regulatory definition exists beneath the
mining-related sources addressed by the selected interim remedy.
14.3.2.2 Location- and Action-Specific ARARs
Location- and action-specific ARARs for the mine portal pond sediments selected interim
remedy will be addressed during implementation of the IRA, as indicated in the following
paragraphs.
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Excavation: The excavation of mine wastes from waters of the United States is assumed to be
performed with neat excavation only involving incidental fallback. Thus, the substantive
requirements of Section 404 will not be triggered. If grading or excavation activities result in a
discharge of dredge material, the substantive requirements of Nationwide Permit 20 (Response
Operations for Oil or Hazardous Substances) will be met.
Dust Suppression: Dust suppression and emission-controlled equipment will be used during
construction activities for the selected interim remedy to achieve compliance with Colorado
emission control requirements.
Dewatering: If effluent discharge to surface water is necessary during dewatering or pond
draining activities, activities would be conducted in a way to minimize infiltration into the
ground surface that could cause additional degradation of groundwater. Because the
groundwater, as defined in 5 CCR 1002-41, is not known to be present below the mining-related
sources, an interim measures CERCLA ARAR waiver will be invoked. An interim measures
CERCLA ARAR waiver will also be invoked to waive the substantive provisions of CDPS
regulations for groundwater.
If effluent discharge to surface water is necessary during dewatering, the discharge limit
requirements of Colorado effluent limitations will be met without treatment at the dewatering
locations; otherwise an interim measures CERCLA ARAR waiver will be invoked. Similarly, the
substantive provisions of the CDPS regulations will be met; otherwise an interim measures
CERCLA ARAR waiver will be invoked.
Interim Local Waste Management: Mine wastes at the Site were derived directly or indirectly
from the extraction of ore and thus will be exempt from management as a RCRA hazardous
waste (i.e., the Bevill exemption), thus mine wastes will be classified as a non-hazardous solid
waste.
Pursuant to the Solid Wastes Disposal Sites and Facilities Act, C.R.S. § 30-20-102(4), mining
operations including reclamation activities with approved reclamation plans under an MLRB
permit may dispose of solid wastes generated by such operations within the permitted area
without obtaining a Certificate of Designation. CDPHE interprets this provision to exempt
CERCLA response actions performed consistently with MLRB regulation 2 CCR 407-1 Rule 3
(Reclamation Performance Standards) to be compliant with Colorado's regulations pertaining to
solid waste disposal.
All waste handling and disposal activities under the selected interim remedy will be performed in
accordance with substantive requirements of the relevant and appropriate subparts of MLRB
regulation 2 CCR 407-1 Rule 3 (Reclamation Performance Standards), which will allow the
selected interim remedy to be compliant with substantive requirements of the Colorado Solid
Waste Disposal Sites and Facilities Regulations.
Grading of wastes for interim local management will be performed to meet relevant and
appropriate substantive requirements of 2 CCR 407-1 Rule 3.
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Surface Reclamation: Surface reclamation activities under the selected interim remedy,
including grading, will be performed to meet relevant and appropriate substantive requirements
of 2 CCR 407-1 Rule 3.
Construction Activities: Cultural resource surveys have not been completed for all mining-
related sources addressed by the selected interim remedy. If any cultural resources are found,
surveys will be necessary to determine if adverse effects will occur, and if so, how the effects
may be minimized or mitigated in accordance with the National Historic Preservation Act,
Archaeological and Historic Preservation Act, and Historic Sites Act.
If bald or golden eagles are observed during remedial design and IRA, activities must be
modified and conducted to conserve the species and their habitat to comply with the substantive
requirements of the Bald and Golden Eagle Protection Act.
If the IRA involves activities modifying streams or water bodies that affect wildlife and/or non-
game fish, federal agencies must comply with substantive requirements identified by USFWS
and the relevant state agency with jurisdiction over wildlife resources in accordance with Fish
and Wildlife Coordination Act and implementing regulations.
If threatened or endangered species are identified at these mining-related sources during remedial
design and IRA, activities must be modified and conducted to conserve the species and their
habitat in accordance with the Endangered Species Act and relevant and appropriate substantive
requirements of 40 CFR 257.
If migratory birds are identified during remedial design and IRA, activities must be modified and
conducted to conserve the species and their habitat in accordance with the Migratory Bird Treaty
Act.
The mine portal pond sediments selected interim remedy will not be conducted within streams.
However, if activities were to impact streams, they will be carried out in a manner to avoid
adversely affecting wildlife and/or non-game fish within streams. Compliance will be achieved
through coordination with the Colorado Division of Parks Wildlife and in accordance with the
Colorado Wildlife Enforcement and Penalties Act and Colorado Non-game, Endangered, or
Threatened Species Act.
It is not anticipated that nests or dens of wildlife exist at the mine locations. If they were to be
encountered, the selected interim remedy will be implemented to avoid disturbing or destroying
nests or dens. Compliance will be achieved through coordination with the Colorado Division of
Parks Wildlife and in accordance with substantive requirements of Colorado Wildlife
Commission regulations.
Planning for activities conducted during the IRA on USFS-managed land, such as obtaining
borrow material and implementing the IRA at the Brooklyn Mine, will consider pertinent
information provided within the San Juan National Forest and Tres Rios Field Office Land and
Resource Management Plan.
If the IRA involves activities that affect identified floodplains or wetlands, activities will be
carried out in a manner to avoid adversely affecting them and thus meet the substantive
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requirements of the Clean Water Act, Section 404 regulations, 40 CFR Part 6, Appendix A, and
relevant and appropriate substantive requirements of 40 CFR 257.
Activities under the selected interim remedy will be carried out in a manner that will comply
with Colorado Noise Abatement Statue 25-12-103.
14.3.2.3 ARAR Waivers
Compliance with certain ARARs may not be possible for components of the mine portal MIW
discharges selected interim remedy since they are interim in scope and do not address all
contaminated media posing unacceptable human health and ecological risks. Thus, the CERCLA
interim measures waiver is the most pertinent to the selected interim remedy and the only
CERCLA ARAR waiver identified in this IROD.
Blanket use of the CERCLA interim measures waiver will occur where the expectation is that
regardless of the conditions (i.e., the particular IRA, activity within the IRA, and/or mining-
related source location) that the ARAR will not be complied with and thus the waiver is invoked
on a blanket basis. The ARARs that will fall under blanket waiver use include:
• Federal
o Clean Water Act 33 U.S.C. §§ 1342, et seq., Point Source Discharges Requirements,
Section 402
• State of Colorado
o Colorado Basic Standards for Groundwater, 5 CCR 1002-41, pursuant to C.R.S. §§
25-8-101-703
o Colorado Surface Water Quality Classifications and Numeric Standards, 5 CCR
1002-34, pursuant to C.R.S.§§ 25-8-203 and 204
o CDPS Regulations, 5 CCR 1002-61, Regulation No. 61, pursuant to C.R.S.§ 25-8-
501 -509
o Colorado Effluent Limitations, 5 CCR 1002-62, pursuant to C.R.S.§ 25-8-205
14.3.3 Cost Effectiveness
The mine portal pond sediments selected interim remedy is cost effective and represents a
reasonable value for the money to be spent. In making this determination, the following
definition was used: "A remedy shall be cost effective if its costs are proportional to its overall
effectiveness" [NCP §300.430(f)(l)(ii)(D)]. This is determined by evaluating the overall
effectiveness of the selected interim remedy and comparing that effectiveness to the overall
costs. Effectiveness is evaluated by examining how the remedy meets three criteria: long-term
effectiveness and permanence; reduction in toxicity, mobility, and volume through treatment;
and short-term effectiveness. Overall effectiveness of the remedial alternatives was compared to
costs to determine cost effectiveness. The relationship of the overall effectiveness of the mine
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portal pond sediments selected interim remedy was determined to be proportional to its cost, and
hence this remedy represents a reasonable value for the cost to be incurred.
The cost of the mine portal pond sediments selected interim remedy is expected to have a present
value cost of approximately $3,384,000. Compared to the other alternative considered (No
Action), the mine portal pond sediments selected interim remedy has a higher cost, but it is the
only alternative expected to provide protection of human health and the environment as an
interim measure. EPA believes the mine portal pond sediments selected interim remedy achieves
an appropriate balance between cost effectiveness and adequate protectiveness.
14.3.4 Utilization of Permanent Solutions and Alternative Treatment (or Resource
Recovery) Technologies to the Maximum Extent Practicable
This determination looks at whether the selected interim remedy provides the best balance of
tradeoffs among the alternatives with respect to the balancing criteria set forth in NCP
§300.430(f)(l)(i)(B) such that it represents the maximum extent to which permanence and
treatment can be practicably used at the Site. NCP §300.430(f)(l)(ii)(E) provides that the
balancing shall emphasize the factors of "long-term effectiveness" and "reduction of toxicity,
mobility, or volume through treatment," and shall consider the preference for treatment and bias
against off-site disposal. The modifying criteria were also considered in making this
determination.
The mine portal pond sediments selected interim remedy is an interim solution only, and is not
intended to use permanent solutions and alternative treatment (or resource recovery) technologies
to the maximum extent practicable. Permanent solutions and alternative treatment technologies or
resource recovery technologies will be addressed as part of the final response action.
14.3.5 Preference for Treatment as a Principal Element
This determination looks at whether the selected interim remedy provides treatment as a
principal element. The NCP establishes the expectation that treatment will be used to address
principal threat wastes whenever practicable (40 CFR 300.430[a][l][iii][A]). Principal threat
wastes are those source materials that are considered to be highly toxic or highly mobile that
generally cannot be contained in a reliable manner or will present a significant risk to human
health and the environment should exposure occur. As discussed in Section 11.0 of this IROD,
EPA has determined that media addressed by this IRA do not involve principal threat waste. In
addition, because this action does not constitute the final remedy, the statutory preference for
remedies that employ treatment that reduces toxicity, mobility, or volume as a principal element
will be considered and addressed by the final response action.
14.3.6 Five-Year Site Reviews
While the Site-wide risk assessment is ongoing, it is assumed that the mine portal pond
sediments selected interim remedy will not result in unlimited use and unrestricted exposure land
use scenarios. Therefore, five-year reviews pursuant to CERCLA §121(c) and NCP
§300.430(f)(5)(iii)(C) are assumed to be conducted for the mining-related sources included as
part of this selected interim remedy in conjunction with sources addressed by other response
actions as part of Site-wide activities. EPA shall conduct a review of remedial actions no less
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often than each 5 years after the initiation of such remedial action to ensure the remedy is, or will
be, protective of human health and the environment.
14.4 IN-STREAM MINE WASTES
The following subsections discuss the statutory determinations for the in-stream mine wastes
IRA of the selected interim remedy.
14.4.1 Protection of Human Health and the Environment
The in-stream mine wastes selected interim remedy will provide protection of human health and
the environment in a short term and is intended to provide adequate protection until a final
remedy is selected. It will provide stabilization of the mining-related sources and prevent further
environmental degradation. The in-stream mine wastes selected interim remedy achieves RAO 1
by excavating in-stream mine wastes that impede flow or are susceptible to erosion or leaching
of contaminants and formation of MIW and reduces transport of particulates containing COPCs
to surface water, which contribute to unacceptable ecological risks. EPA will measure the extent
by which ecological risks associated with contributions from in-stream mine waste have been
reduced by the in-stream mine wastes selected interim remedy.
14.4.2 Compliance with ARARs
14.4.2.1 Chemical-Specific ARARs
Chemical-specific ARARs will be pertinent to the in-stream mine wastes selected interim
remedy. State water quality standards will likely not be met for streams after removal of in-
stream mine wastes due to other contributing mining-related sources, thus the interim measures
CERCLA ARAR waiver will be invoked for the Colorado Basic Standards and Methodologies
for Surface Water. The Colorado Basic Standards for Groundwater will also be waived using an
interim measures CERCLA ARAR waiver because the limited RI information available does not
indicate that groundwater meeting the regulatory definition exists beneath the mining-related
sources addressed by the selected interim remedy.
14.4.2.2 Location- and Action-Specific ARARs
Location- and action-specific ARARs for the selected interim remedy will be addressed during
implementation of the IRA as indicated in the following paragraphs.
Excavation: The excavation of mine wastes from waters of the United States is assumed to be
performed with neat excavation only involving incidental fallback. Thus, the substantive
requirements of Section 404 will not be triggered. If grading or excavation activities result in a
discharge of dredge material, the substantive requirements of Nationwide Permit 20 (Response
Operations for Oil or Hazardous Substances) will be met.
Dust Suppression: Dust suppression and emission-controlled equipment will be used during
construction activities for the selected interim remedy to achieve compliance with Colorado
Emission Control requirements.
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Dewatering: If effluent discharge to surface water is necessary during dewatering activities,,
activities would be conducted in a way to minimize infiltration into the ground surface that could
cause additional degradation of groundwater. Because the groundwater, as defined in 5 CCR
1002-41, is not known to be present below the mining-related sources, an interim measures
CERCLA ARAR waiver will be invoked. An interim measures CERCLA ARAR waiver will
also be invoked to waive the substantive provisions of Colorado Effluent Limitations and CDPS
regulations for groundwater.
If effluent discharge to surface water is necessary during dewatering, the discharge limit
requirements of Colorado Effluent Limitations will be met without treatment at the dewatering
locations; otherwise an interim measures CERCLA ARAR waiver will be invoked. Similarly, the
substantive provisions of the CDPS regulations will be met; otherwise an interim measures
CERCLA ARAR waiver will be invoked.
Interim Local Waste Management: Mine wastes at the Site were derived directly or indirectly
from the extraction of ore and thus will be exempt from management as a RCRA hazardous
waste (i.e., the Bevill exemption), thus mine wastes will be classified as a non-hazardous solid
waste.
Pursuant to the Solid Wastes Disposal Sites and Facilities Act, C.R.S. § 30-20-102(4), mining
operations including reclamation activities with approved reclamation plans under an MLRB
permit may dispose of solid wastes generated by such operations within the permitted area
without obtaining a Certificate of Designation. CDPHE interprets this provision to exempt
CERCLA response actions performed consistently with MLRB regulation 2 CCR 407-1 Rule 3
(Reclamation Performance Standards) to be compliant with Colorado's regulations pertaining to
solid waste disposal.
All waste handling and disposal activities under the selected interim remedy will be performed in
accordance with substantive requirements of the relevant and appropriate subparts of MLRB
regulation 2 CCR 407-1 Rule 3 (Reclamation Performance Standards), which will allow the
selected interim remedy to be compliant with substantive requirements of the Colorado Solid
Waste Disposal Sites and Facilities Regulations.
Grading of wastes for interim local management will be performed to meet relevant and
appropriate substantive requirements of 2 CCR 407-1 Rule 3.
Surface Reclamation: Surface reclamation activities under the selected interim remedy,
including grading, will be performed to meet relevant and appropriate substantive requirements
of 2 CCR 407-1 Rule 3.
Construction Activities: Cultural resource surveys have not been completed for all mining-
related sources addressed by the selected interim remedy. If any cultural resources are found,
surveys will be necessary to determine if adverse effects will occur, and if so, how the effects
may be minimized or mitigated in accordance with the National Historic Preservation Act,
Archaeological and Historic Preservation Act, and Historic Sites Act.
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If bald or golden eagles are observed during remedial design and IRA, activities must be
modified and conducted to conserve the species and their habitat to comply with the substantive
requirements of the Bald and Golden Eagle Protection Act.
If the IRA involves activities modifying streams or water bodies that affect wildlife and/or non-
game fish, federal agencies must comply with substantive requirements identified by USFWS
and the relevant state agency with jurisdiction over wildlife resources in accordance with Fish
and Wildlife Coordination Act and implementing regulations.
If threatened or endangered species are identified at these mining-related sources during remedial
design and IRA, activities must be modified and conducted to conserve the species and their
habitat in accordance with the Endangered Species Act and relevant and appropriate substantive
requirements of 40 CFR 257.
If migratory birds are identified during remedial design and IRA, activities must be modified and
conducted to conserve the species and their habitat in accordance with the Migratory Bird Treaty
Act.
If activities were to impact streams, they will be carried out in a manner to avoid adversely
affecting wildlife and/or non-game fish within streams. Compliance will be achieved through
coordination with the Colorado Division of Parks Wildlife and in accordance with the Colorado
Wildlife Enforcement and Penalties Act and Colorado Non-game, Endangered, or Threatened
Species Act.
It is not anticipated that nests or dens of wildlife exist at the mine locations. If they were to be
encountered, the selected interim remedy will be implemented to avoid disturbing or destroying
nests or dens. Compliance will be achieved through coordination with the Colorado Division of
Parks Wildlife and in accordance with substantive requirements of Colorado Wildlife
Commission regulations.
Planning for activities conducted during the IRA on USFS-managed land, such as obtaining
borrow material, will consider pertinent information provided within the San Juan National
Forest and Tres Rios Field Office Land and Resource Management Plan.
If the IRA involves activities that affect identified floodplains or wetlands, activities will be
carried out in a manner to avoid adversely affecting them and thus meet the substantive
requirements of the Clean Water Act, Section 404 regulations, 40 CFR Part 6, Appendix A, and
relevant and appropriate substantive requirements of 40 CFR 257.
Activities under the selected interim remedy will be carried out in a manner that will comply
with Colorado Noise Abatement Statue 25-12-103.
14.4.2.3 ARAR Waivers
Compliance with certain ARARs may not be possible for components of the mine portal MIW
discharges selected interim remedy since they are interim in scope and do not address all
contaminated media posing unacceptable human health and ecological risks. Thus, the CERCLA
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interim measures waiver is the most pertinent to the selected interim remedy and the only
CERCLA ARAR waiver identified in this IROD.
Blanket use of the CERCLA interim measures waiver will occur where the expectation is that
regardless of the conditions (i.e., the particular IRA, activity within the IRA, and/or mining-
related source location) that the ARAR will not be complied with and thus the waiver is invoked
on a blanket basis. The ARARs that will fall under blanket waiver use include:
• Federal
o Clean Water Act 33 U.S.C. §§ 1342, et seq., Point Source Discharges Requirements,
Section 402
• State of Colorado
o Colorado Basic Standards for Groundwater, 5 CCR 1002-41, pursuant to C.R.S. §§
25-8-101-703
o Colorado Surface Water Quality Classifications and Numeric Standards, 5 CCR
1002-34, pursuant to C.R.S.§§ 25-8-203 and 204
o CDPS Regulations, 5 CCR 1002-61, Regulation No. 61, pursuant to C.R.S.§ 25-8-
501 -509
o Colorado Effluent Limitations, 5 CCR 1002-62, pursuant to C.R.S.§ 25-8-205
14.4.3 Cost Effectiveness
The in-stream mine wastes selected interim remedy addressing in-stream mine wastes is cost
effective and represents a reasonable value for the money to be spent. In making this
determination, the following definition was used: "A remedy shall be cost effective if its costs
are proportional to its overall effectiveness" [NCP §300.430(f)(l)(ii)(D)]. This is determined by
evaluating the overall effectiveness of the selected interim remedy and comparing that
effectiveness to the overall costs. Effectiveness is evaluated by examining how the remedy meets
three criteria: long-term effectiveness and permanence; reduction in toxicity, mobility, and
volume through treatment; and short-term effectiveness. Overall effectiveness of the remedial
alternatives was compared to costs to determine cost effectiveness. The relationship of the
overall effectiveness of the selected interim remedy was determined to be proportional to its cost,
and hence this remedy represents a reasonable value for the cost to be incurred.
The cost of the in-stream mine wastes selected interim remedy is expected to have a present
value cost of approximately $512,000. Compared to the other alternative considered (No
Action), the in-stream mine wastes selected interim remedy has a higher cost, but it is the only
alternative expected to provide protection of human health and the environment as an interim
measure. EPA believes the in-stream mine wastes selected interim remedy achieves an
appropriate balance between cost effectiveness and adequate protectiveness.
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14.4.4 Utilization of Permanent Solutions and Alternative Treatment (or Resource
Recovery) Technologies to the Maximum Extent Practicable
This determination looks at whether the selected interim remedy provides the best balance of
tradeoffs among the alternatives with respect to the balancing criteria set forth in NCP
§300.430(f)(l)(i)(B) such that it represents the maximum extent to which permanence and
treatment can be practicably used at the Site. NCP §300.430(f)(l)(ii)(E) provides that the
balancing shall emphasize the factors of "long-term effectiveness" and "reduction of toxicity,
mobility, or volume through treatment," and shall consider the preference for treatment and bias
against off-site disposal. The modifying criteria were also considered in making this
determination.
This in-stream mine wastes selected interim remedy is an interim solution only, and is not
intended to use permanent solutions and alternative treatment (or resource recovery)
technologies to the maximum extent practicable. Permanent solutions and alternative treatment
technologies or resource recovery technologies will be addressed as part of the final response
action.
14.4.5 Preference for Treatment as a Principal Element
This determination looks at whether the selected interim remedy provides treatment as a
principal element. The NCP establishes the expectation that treatment will be used to address
principal threat wastes whenever practicable (40 CFR 300.430[a][l][iii][A]). Principal threat
wastes are those source materials that are considered to be highly toxic or highly mobile that
generally cannot be contained in a reliable manner or will present a significant risk to human
health and the environment should exposure occur. As discussed in Section 11.0 of this IROD,
EPA has determined that media addressed by this IRA do not involve principal threat waste. In
addition, because this action does not constitute the final remedy, the statutory preference for
remedies that employ treatment that reduces toxicity, mobility, or volume as a principal element
will be considered and addressed by the final response action.
14.4.6 Five-Year Site Reviews
While the Site-wide risk assessment is ongoing, it is assumed that the in-stream mine wastes
selected interim remedy will not result in unlimited use and unrestricted exposure land use
scenarios. Therefore, five-year reviews pursuant to CERCLA § 121(c) and NCP
§300.430(f)(5)(iii)(C) are assumed to be conducted for the mining-related sources included as
part of this selected interim remedy in conjunction with sources addressed by other response
actions as part of Site-wide activities. EPA shall conduct a review of remedial actions no less
often than each 5 years after the initiation of such remedial action to ensure the remedy is, or will
be, protective of human health and the environment.
14.5 MINING-IMPACTED RECREATION STAGING AREAS
The following subsections discuss the statutory determinations for the mining-impacted
recreation staging areas IRA of the selected interim remedy.
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14.5.1 Protection of Human Health and the Environment
The mining-impacted recreation staging areas selected interim remedy will provide protection of
human health and the environment in the short term until a final remedy is selected. It will
provide stabilization of the mining-related sources at recreation staging areas, prevent further
environmental degradation, and achieve significant risk reduction quickly. The mining-impacted
recreation staging areas selected interim remedy addresses RAOs 2 and 3 by containing/isolating
mine wastes and contaminated soils within mining-impacted recreation staging areas.
Combinations of aggregate and soil covers will be implemented to reduce disturbances of mine
wastes and contaminated soils, and migration of contaminants. The covers will provide an
exposure barrier and eliminate surface exposure to mine waste and contaminated soils. The
covers will be sloped to promote positive drainage in order to minimize erosion and to reduce
infiltration that could saturate the subsurface and compromise the integrity of the covers. The
covers used for containment/isolation of mine wastes and contaminated soils could be breached
if disturbed, resulting in potential COPC exposures to campers.
14.5.2 Compliance with ARARs
14.5.2.1 Chemical-Specific ARARs
Chemical-specific ARARs will be pertinent to the mining-impacted recreation staging areas
selected interim remedy. State water quality standards will likely not be met for streams after the
capping of recreation use areas due to other contributing mining-related sources, thus the interim
measures CERCLA ARAR waiver will be invoked for the Colorado Basic Standards and
Methodologies for Surface Water. The Colorado Basic Standards for Groundwater will also be
waived using an interim measures CERCLA ARAR waiver because the limited RI information
available does not indicate that groundwater meeting the regulatory definition exists beneath the
mining-related sources addressed by the selected interim remedy.
14.5.2.2 Location- and Action-Specific ARARs
Location- and action-specific ARARs for the mining-impacted recreation staging areas selected
interim remedy will be addressed during implementation of the IRA as indicated in the following
paragraphs.
Cover Placement: The placement and grading of covers is assumed to be performed without the
discharge of dredged or fill materials into the waters of the United States. Thus, the substantive
requirements of Section 404 will not be triggered. If grading activities result in a discharge of
dredge material, the substantive requirements of Nationwide Permit 20 (Response Operations for
Oil or Hazardous Substances) will be met. All cover placement activities will be conducted in a
way minimize infiltration, if present, into the ground surface that could cause additional
degradation of groundwater. Because the groundwater, as defined in 5 CCR 1002-41, is not
known to be present below the mining-related sources, an interim measures CERCLA ARAR
waiver will be invoked. An interim measures CERCLA ARAR waiver will also be invoked to
waive the substantive provisions of Colorado Effluent Limitations and CDPS regulations for
groundwater. For channelized stormwater discharges from covers, the substantive provisions of
the CDPS program will be met; otherwise an interim measures CERCLA ARAR waiver will be
invoked. During construction of the covers, the discharge limit requirements of Colorado effluent
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limitations will be met without treatment; otherwise an interim measures CERCLA ARAR
waiver will be invoked.
Surface Reclamation: Surface reclamation activities under the selected interim remedy,
including grading, will be performed to meet relevant and appropriate substantive requirements
of 2 CCR 407-1 Rule 3. During construction and seeding of covers, compliance will be achieved
through completion of noxious weed surveys and coordination with the Colorado Division of
Parks Wildlife and in accordance with Colorado Noxious Weed Act and the San Juan County
Noxious Weed regulations.
Dust Suppression: Dust suppression and emission-controlled equipment will be used during
construction activities for the selected interim remedy to achieve compliance with Colorado
Emission Control regulations.
Construction Activities: Cultural resource surveys have not been completed for all mining-
related sources addressed by the selected interim remedy. If any cultural resources are found,
surveys will be necessary to determine if adverse effects will occur, and if so, how the effects
may be minimized or mitigated in accordance with the National Historic Preservation Act,
Archaeological and Historic Preservation Act, and Historic Sites Act.
If bald or golden eagles are observed during remedial design and IRA, activities must be
modified and conducted to conserve the species and their habitat to comply with the substantive
requirements of the Bald and Golden Eagle Protection Act.
If the IRA involves activities modifying streams or water bodies that affect wildlife and/or non-
game fish, federal agencies must comply with substantive requirements identified by USFWS
and the relevant state agency with jurisdiction over wildlife resources in accordance with Fish
and Wildlife Coordination Act and implementing regulations.
If threatened or endangered species are identified at these mining-related sources during remedial
design and IRA, activities must be modified and conducted to conserve the species and their
habitat in accordance with the Endangered Species Act and relevant and appropriate substantive
requirements of 40 CFR 257.
If migratory birds are identified during remedial design and IRA, activities must be modified and
conducted to conserve the species and their habitat in accordance with the Migratory Bird Treaty
Act.
The mining-impacted recreation staging areas selected interim remedy will not be conducted
within streams. However, if activities were to impact streams, they will be carried out in a
manner to avoid adversely affecting wildlife and/or non-game fish within streams. Compliance
will be achieved through coordination with the Colorado Division of Parks Wildlife and in
accordance with the Colorado Wildlife Enforcement and Penalties Act and Colorado Non-game,
Endangered, or Threatened Species Act.
It is not anticipated that nests or dens of wildlife exist at the mine locations. If they were to be
encountered, the selected interim remedy will be implemented to avoid disturbing or destroying
nests or dens. Compliance will be achieved through coordination with the Colorado Division of
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Parks Wildlife and in accordance with substantive requirements of Colorado Wildlife
Commission regulations.
Planning for activities conducted during the IRA on USFS-managed land, such as obtaining
borrow material, will consider pertinent information provided within the San Juan National
Forest and Tres Rios Field Office Land and Resource Management Plan.
If the selected interim remedy involves activities that affect identified floodplains or wetlands,
activities will be carried out in a manner to avoid adversely affecting them and thus meet the
substantive requirements of the Clean Water Act, Section 404 regulations, 40 CFR Part 6,
Appendix A, and relevant and appropriate substantive requirements of 40 CFR 257.
Activities under the selected interim remedy will be carried out in a manner that will comply
with Colorado Noise Abatement Statue 25-12-103.
14.5.2.3 ARAR Waivers
Compliance with certain ARARs may not be possible for components of the mine portal MIW
discharges selected interim remedy since they are interim in scope and do not address all
contaminated media posing unacceptable human health and ecological risks. Thus, the CERCLA
interim measures waiver is the most pertinent to the selected interim remedy and the only
CERCLA ARAR waiver identified in this IROD.
Blanket use of the CERCLA interim measures waiver will occur where the expectation is that
regardless of the conditions (i.e., the particular IRA, activity within the IRA, and/or mining-
related source location) that the ARAR will not be complied with and thus the waiver is invoked
on a blanket basis. The ARARs that will fall under blanket waiver use include:
• Federal
o Clean Water Act 33 U.S.C. §§ 1342, et seq., Point Source Discharges Requirements,
Section 402
• State of Colorado
o Colorado Basic Standards for Groundwater, 5 CCR 1002-41, pursuant to C.R.S. §§
25-8-101-703
o Colorado Surface Water Quality Classifications and Numeric Standards, 5 CCR
1002-34, pursuant to C.R.S.§§ 25-8-203 and 204
o CDPS Regulations, 5 CCR 1002-61, Regulation No. 61, pursuant to C.R.S.§ 25-8-
501 -509
o Colorado Effluent Limitations, 5 CCR 1002-62, pursuant to C.R.S.§ 25-8-205
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14.5.3 Cost Effectiveness
The mining-impacted recreation staging areas selected interim remedy is cost effective and
represents a reasonable value for the money to be spent. In making this determination, the
following definition was used: "A remedy shall be cost effective if its costs are proportional to its
overall effectiveness" [NCP §300.430(f)(l)(ii)(D)]. This is determined by evaluating the overall
effectiveness of the selected interim remedy and comparing that effectiveness to the overall
costs. Effectiveness is evaluated by examining how the remedy meets three criteria: long-term
effectiveness and permanence; reduction in toxicity, mobility, and volume through treatment;
and short-term effectiveness. Overall effectiveness of the remedial alternatives was compared to
costs to determine cost effectiveness. The relationship of the overall effectiveness of the mining-
impacted recreation staging areas selected interim remedy was determined to be proportional to
its cost, and hence this remedy represents a reasonable value for the cost to be incurred.
The cost of the mining-impacted recreation staging areas portion of the mining-impacted
recreation staging areas selected interim remedy is expected to have a present value cost of
approximately $1,668,000. Compared to the other alternative considered (No Action), the
mining-impacted recreation staging areas selected interim remedy has a higher cost, but it is the
only alternative expected to provide protection of human health and the environment as an
interim measure. EPA believes the mining-impacted recreation staging areas selected interim
remedy achieves an appropriate balance between cost effectiveness and adequate protectiveness.
14.5.4 Utilization of Permanent Solutions and Alternative Treatment (or Resource
Recovery) Technologies to the Maximum Extent Practicable
This determination looks at whether the selected interim remedy provides the best balance of
tradeoffs among the alternatives with respect to the balancing criteria set forth in NCP
§300.430(f)(l)(i)(B) such that it represents the maximum extent to which permanence and
treatment can be practicably used at the Site. NCP §300.430(f)(l)(ii)(E) provides that the
balancing shall emphasize the factors of "long-term effectiveness" and "reduction of toxicity,
mobility, or volume through treatment," and shall consider the preference for treatment and bias
against off-site disposal. The modifying criteria were also considered in making this
determination.
The mining-impacted recreation staging areas selected interim remedy is an interim solution
only, and is not intended to use permanent solutions and alternative treatment (or resource
recovery) technologies to the maximum extent practicable. Permanent solutions and alternative
treatment technologies or resource recovery technologies will be addressed as part of the final
response action.
14.5.5 Preference for Treatment as a Principal Element
This determination looks at whether the selected interim remedy provides treatment as a
principal element. The NCP establishes the expectation that treatment will be used to address
principal threat wastes whenever practicable (40 CFR 300.430[a][l][iii][A]). Principal threat
wastes are those source materials that are considered to be highly toxic or highly mobile that
generally cannot be contained in a reliable manner or will present a significant risk to human
health and the environment should exposure occur. As discussed in Section 11.0 of this IROD,
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EPA has determined that media addressed by this IRA do not involve principal threat waste. In
addition, because this action does not constitute the final remedy, the statutory preference for
remedies that employ treatment that reduces toxicity, mobility, or volume as a principal element
will be considered and addressed by the final response action.
14.5.6 Five-Year Site Reviews
While the Site-wide risk assessment is ongoing, it is assumed that the mining-impacted
recreation staging areas selected interim remedy will not result in unlimited use and unrestricted
exposure land use scenarios. Therefore, five-year reviews pursuant to CERCLA §121(c) and
NCP §300.430(f)(5)(iii)(C) are assumed to be conducted for the mining-related sources included
as part of this selected interim remedy in conjunction with sources addressed by other response
actions as part of Site-wide activities. EPA shall conduct a review of remedial actions no less
often than each 5 years after the initiation of such remedial action to ensure the remedy is, or will
be, protective of human health and the environment.
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15.0 DOCUMENTATION OF SIGNIFICANT CHANGES
The proposed plan for IRAs for the Site was released for public comment in June 2018. It
identified Alternative A2 as the preferred alternative for mine portal MIW discharges,
Alternative B2 as the preferred alternative for mining-related source/storm water interactions,
Alternative C2 as the preferred alternative for mine portal pond sediments, Alternative D2 as the
preferred alternative for in-stream mine wastes, and Alternative E2 as the preferred alternative
for mining-impacted recreation staging areas. Those alternatives are described in Section 12.0 of
this IROD as the selected interim remedy.
The public comment period was extended from 30 to 60 days, and EPA reviewed all written and
verbal comments submitted during that comment period. It was determined that no significant
changes to the remedy, as originally identified in the proposed plan, were necessary. It should be
noted, however, that addenda to the preliminary RI and the risk assessment information are
included in Appendices A and B, respectively, of this IROD. In addition, final identification of
ARARs pertaining to the selected interim remedy have been made, as presented in Appendix C.
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EPA. 1999. A Guide to Preparing Superfund Proposed Plans, Records of Decision, and Other
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county-colo-superfund-list.html.
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Herron, J., Stover, B., Krabacher, P., Bucknam, D. 1991 .Mineral Creek Reclamation Feasibility
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Herron, J., Stover, B., Krabacher, P. 2000. Reclamation Feasibility Report Animas River Below
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Integrated Investigations of Environmental Effects of Historical Mining in the Animas River
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January 24, 2018, at
https://waterdata.usgs.gov/nwis/inventory?agency _code=USGS&site_no=09359020.
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TABLES
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Table 9-1A
Matrix of Process Options for Mine Portal MIW Discharges Alternative Development
Bonita Peak Mining District Superfund Site
General Kesponse
Action
Remedial
Technolo»\
Process Option
Allcrnali\e A1
Allcrnali\e A2
No Action
Diversion/Isolation
No Action
None
None
~
Institutional Controls
Non-Engineered
Controls
Governmental Controls.
Proprietary Controls,
Enforcement Tools with IC
Components, and
Informational Devices
¦/
Containment
Surface Source
Controls
Grading
•/
Soil/Rock Exposure Barrier
Hydraulic Isolation,
Diversion, and
Separation Measures
French Drain and/or
Interception Trench
¦/
Open Channel
¦/
Collection/Diversion Piping
or Liner
¦/
Berms
•/
Removal, Transport,
Disposal
Removal
Mechanical Excavation
(Excavation)
Pneumatic Excavation
(Vacuum Extraction)
Transport
Mechanical Transport
(Hauling/Conveying)
Pneumatic Transport
(Vacuum Extraction)
Disposal
Interim Local Waste
Management
Notes:
- Exhibit 9-1 summarizes all technology process options identified for all media. Check marks in the table above indicated process options that will be
implemented as necessary for each alternative for mine portal MIW discharges as defined in Section 9.
- For purposes of FS evaluation, representative process options are selected for evaluation within the remedial technology category to simplify the analysis
and comparison of alternatives, as described in Section 9.2.
-------
Table 9-1B
Matrix of Process Options for Mining-Related Source/Stormwater Interactions Alternative Development
Bonita Peak Mining District Superfund Site
General Kesponse
Aclion
Remedial
Technolo»\
Process Option
Allernali\c 151
Allcrnali\e 152
No Aclion
SluriiiwaUT
l)i\ersion/lsolalion
No Action
None
None
~
Institutional Controls
Non-Engineered
Controls
Governmental Controls.
Proprietary Controls,
Enforcement Tools with IC
Components, and
Informational Devices
¦/
Containment
Surface Source
Controls
Grading
•/
Soil/Rock Exposure Barrier
Hydraulic Isolation,
Diversion, and
Separation Measures
French Drain and/or
Interception Trench
¦/
Open Channel
¦/
Collection/Diversion Piping
or Liner
¦/
Berms
•/
Removal, Transport,
Disposal
Removal
Mechanical Excavation
(Excavation)
Pneumatic Excavation
(Vacuum Extraction)
Transport
Mechanical Transport
(Hauling/Conveying)
Pneumatic Transport
(Vacuum Extraction)
Disposal
Interim Local Waste
Management
Notes:
- Exhibit 9-1 summarizes all technology process options identified for all media. Check marks in the table above indicated process options that will be
implemented as necessary for each alternative for mining-related source/stormwater interactions as defined in Section 9.
- For purposes of FS evaluation, representative process options are selected for evaluation within the remedial technology category to simplify the analysis
and comparison of alternatives, as described in Section 9.2.
-------
Table 9-1C
Matrix of Process Options for Mine Portal Pond Sediments Alternative Development
Bonita Peak Mining District Superfund Site
General Kesponse
A cl ion
Remedial
Teihnolo»\
Process Option
.\llernali\e CI
.\llernali\e C2
No Aclion
r.\ca\alion and Inlerim
Local Wasle Manaucmenl
No Action
None
None
~
Institutional Controls
Non-Engineered
Controls
Governmental Controls.
Proprietary Controls,
Enforcement Tools with IC
Components, and
Informational Devices
¦/
Containment
Surface Source
Controls
Grading
•/
Soil/Rock Exposure Barrier
Hydraulic Isolation,
Diversion, and
Separation Measures
French Drain and/or
Interception Trench
Open Channel
Collection/Diversion Piping
or Liner
Berms
•/
Removal, Transport,
Disposal
Removal
Mechanical Excavation
(Excavation)
¦/
Pneumatic Excavation
(Vacuum Extraction)
¦/
Transport
Mechanical Transport
(Hauling/Conveying)
¦/
Pneumatic Transport
(Vacuum Extraction)
¦/
Disposal
Interim Local Waste
Management
¦/
Notes:
- Exhibit 9-1 summarizes all technology process options identified for all media. Check marks in the table above indicated process options that will be
implemented as necessary for each alternative for mine portal pond sediments as defined in Section 9.
- For purposes of FS evaluation, representative process options are selected for evaluation within the remedial technology category to simplify the analysis
and comparison of alternatives, as described in Section 9.2.
-------
Table 9-1D
Matrix of Process Options for In-Stream Mine Wastes Alternative Development
Bonita Peak Mining District Superfund Site
General Kesponse
Ailion
Remedial
Teihnolo»\
Process Option
Allcrnali\e 1)1
Allcrnali\e 1)2
No Aclion
r.\ca\alion and Ink-rim
Local Wasle Management
No Action
None
None
~
Institutional Controls
Non-Engineered
Controls
Governmental Controls.
Proprietary Controls,
Enforcement Tools with IC
Components, and
Informational Devices
¦/
Containment
Surface Source
Controls
Grading
•/
Soil/Rock Exposure Barrier
Hydraulic Isolation,
Diversion, and
Separation Measures
French Drain and/or
Interception Trench
Open Channel
Collection/Diversion Piping
or Liner
Berms
•/
Removal, Transport,
Disposal
Removal
Mechanical Excavation
(Excavation)
¦/
Pneumatic Excavation
(Vacuum Extraction)
¦/
Transport
Mechanical Transport
(Hauling/Conveying)
¦/
Pneumatic Transport
(Vacuum Extraction)
¦/
Disposal
Interim Local Waste
Management
¦/
Notes:
- Exhibit 9-1 summarizes all technology process options identified for all media. Check marks in the table above indicated process options that will be
implemented as necessary for each alternative for in-stream mine wastes as defined in Section 9.
- For purposes of FS evaluation, representative process options are selected for evaluation within the remedial technology category to simplify the analysis
and comparison of alternatives, as described in Section 9.2.
-------
Table 9-1E
Matrix of Process Options for Mining-Impacted Recreation Staging Areas Alternative Development
Bonita Peak Mining District Superfund Site
General Kesponse
Aclion
Remedial
Technolo»\
Process Option
Alleriiali\e 111
Alleriiali\e 112
No Aclion
(oiilainmeiil/lsolalioii
No Action
None
None
~
Institutional Controls
Non-Engineered
Controls
Governmental Controls.
Proprietary Controls,
Enforcement Tools with IC
Components, and
Informational Devices
¦/
Containment
Surface Source
Controls
Grading
¦/
Soil/Rock Exposure Barrier
~
Hydraulic Isolation,
Diversion, and
Separation Measures
French Drain and/or
Interception Trench
Open Channel
Collection/Diversion Piping
or Liner
Berms
Removal, Transport,
Disposal
Removal
Mechanical Excavation
(Excavation)
Pneumatic Excavation
(Vacuum Extraction)
Transport
Mechanical Transport
(Hauling/Conveying)
Pneumatic Transport
(Vacuum Extraction)
Disposal
Interim Local Waste
Management
Notes:
- Exhibit 9-1 summarizes all technology process options identified for all media. Check marks in the table above indicated process options that will be
implemented as necessary for each alternative for mining-impacted recreation staging areas as defined in Section 9.
- For purposes of FS evaluation, representative process options are selected for evaluation within the remedial technology category to simplify the analysis
and comparison of alternatives, as described in Section 9.2.
-------
Table 12-1A: Cost Estimate Summary for Mine Portal MIW Discharges ERA for the Selected Interim Remedy
CAPITAL COSTS: (Assumed to be Incurred During Year 0)
DESCRIPTION
Institutional Controls
Mobilization/Demobilization
Installation of Diversion/Isolation Components
Nonconventional Access-Alpine Locations
Nonconventional Access-Subalpine Locations
Conventional Access-Subalpine Locations
Repairs of Existing Diversion/Isolation Components
Excavation, Dewatering, and Management of Mine Waste at Local Interim Management Areas
Access Road Improvements
Development of Borrow Materials
Transportation of Borrow Materials
Dust Control
Erosion Control and Reclamation of Areas Disturbed during Construction
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
5,300
3,160
3,640
BCY
LCY
UNIT COST
$12,447
$35,936
$7,397
$32,575
$66
$46
$48,065
$15,641
$35,678
$12,447
$35,936
$7,397
$32,575
$1,994
$243,812
$88,010
$97,362
$48,065
$15,641
$627,516
$188,255
Project Management
Remedial Design
Construction Management
TOTAL
$48,946
$97,893
$65,262
TOTAL CAPITAL COST
ANNUAL O&M COSTS (Assumed to be Incurred Annually During Year 1 through 15)
DESCRIPTION
Inspection of Remedial Components
Surface Water Monitoring
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
UNIT COST
$91,916
$18,383
Project Management
TOTAL
TOTAL ANNUAL O&M COST
PERIODIC O&M COSTS (Assumed to be Incurred Once Every 2 Years During Year 1 through 15)
DESCRIPTION
Post-Construction Maintenance
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
Project Management
TOTAL
UNIT COST
$31,273
TOTAL
$31,273
$31,273
$6,255
$37,528
$3,753
TOTAL PERIODIC O&M COST
Summary of Present Value Analysis
Year
Capital Costs
Annual O&M Costs
Periodic O&M Costs
Total Annual Expenditure
Discount Factor (7.0%)
Present Value
0
$1,028,000
$0
$0
$1,028,000
1.0000
$1,028,000
1
$0
$119,000
$0
$119,000
0.9346
$111,217
2
$0
$119,000
$41,000
$160,000
0.8734
$139,744
3
$0
$119,000
$0
$119,000
0.8163
$97,140
4
$0
$119,000
$41,000
$160,000
0.7629
$122,064
5
$0
$119,000
$0
$119,000
0.713
$84,847
6
$0
$119,000
$41,000
$160,000
0.6663
$106,608
7
$0
$119,000
$0
$119,000
0.6227
$74,101
8
$0
$119,000
$41,000
$160,000
0.582
$93,120
9
$0
$119,000
$0
$119,000
0.5439
$64,724
10
$0
$119,000
$41,000
$160,000
0.5083
$81,328
11
$0
$119,000
$0
$119,000
0.4751
$56,537
12
$0
$119,000
$41,000
$160,000
0.444
$71,040
13
$0
$119,000
$0
$119,000
0.415
$49,385
14
$0
$119,000
$41,000
$160,000
0.3878
$62,048
15
$0
$119,000
$0
$119,000
0.3624
$43,126
TOTALS:
$1,028,000
$1,785,000
$287,000
$3,100,000
$2,285,029
TOTAL PRESENT VALUE OF SELECTED REMEDY 4
nare discounted by a factor for that year representing the 7 0% real disc
Inflation and depreciation are excluded from the present value cost
¦ an accuracy between -30% to +50% of actual costs, based on the see
ncal services costs are based on guidance from Section 5 0 of "A Guid
een -30% to +50% of actual costs, based on the scope presented The;
nended by "A Guide to Developing and Documenting Cost Estir
id Documenting Cost Estimate
reasibility Study", EPA 2000
design
-------
Table 12-IB: Cost Estimate Summary for Mine Portal MIW Discharges ERA for the Selected Interim Remedy - Brooklyn Mine
CAPITAL COSTS: (Assumed to be Incurred During Year 0)
DESCRIPTION
QTY
UNIT(S)
UNIT COST
TOTAL
Institutional Controls'
1
LS
$1,075
$1,075
Mobilization/Demobilization
1
LS
$10,860
$10,860
Installation of Diversion/Isolation Components
1
LS
$8,801
$8,801
Repairs of Existing Diversion/Isolation Components
1
LS
$9,938
$9,938
Excavation, Dewatering, and Management of Mine Waste at Local Interim Management Areas
27
BCY
$77
$2,081
Access Road Improvements
1
LS
$6,250
$6,250
Development of Borrow Materials
160
BCY
$47
$7,454
Transportation of Borrow Materials
200
LCY
$26
$5,166
Dust Control
1
LS
$8,931
$8,931
Erosion Control and Reclamation of Areas Disturbed during Construction
1
LS
$8,382
$8,382
SUBTOTAL
$68,938
Contingency (Scope and Bid)
30%
$20,681
SUBTOTAL
$89,619
Project Management2
10%
$8,962
Remedial Design2
20%
$17,924
Construction Management
15%
$13,443
TOTAL
$129,948
TOTAL CAPITAL COST
$130,000
ANNUAL O&M COSTS (Assumed to be Incurred Annually During Year 1 through 15)
DESCRIPTION
Inspection of Remedial Components
Surface Water Monitoring3
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
Project Management2
TOTAL
TOTAL ANNUAL O&M COST
UNIT COST
$2,668
TOTAL
$2,668
$2,668
$534
$3,202
$320
PERIODIC O&M COSTS (Assumed to be Incurred Once Every 2 Years During Year 1 through 15)
DESCRIPTION
Post-Construction Maintenance
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
Project Management2
TOTAL
TOTAL PERIODIC O&M COST
UNIT COST
Summary of Present Value Analysis
Year
Capital Costs
Annual O&M Costs
Periodic O&M Costs
Total Annual Expenditure
Discount Factor (7.0%)
Present Value
0
$130,000
$0
$0
$130,000
1.0000
$130,000
1
$0
$4,000
$0
$4,000
0.9346
$3,738
2
$0
$4,000
$11,000
$15,000
0.8734
$13,101
3
$0
$4,000
$0
$4,000
0.8163
$3,265
4
$0
$4,000
$11,000
$15,000
0.7629
$11,444
5
$0
$4,000
$0
$4,000
0.713
$2,852
6
$0
$4,000
$11,000
$15,000
0.6663
$9,995
7
$0
$4,000
$0
$4,000
0.6227
$2,491
8
$0
$4,000
$11,000
$15,000
0.582
$8,730
9
$0
$4,000
$0
$4,000
0.5439
$2,176
10
$0
$4,000
$11,000
$15,000
0.5083
$7,625
11
$0
$4,000
$0
$4,000
0.4751
$1,900
12
$0
$4,000
$11,000
$15,000
0.444
$6,660
13
$0
$4,000
$0
$4,000
0.415
$1,660
14
$0
$4,000
$11,000
$15,000
0.3878
$5,817
15
$0
$4,000
$0
$4,000
0.3624
$1,450
TOTALS:
$130,000
$60,000
$77,000
$267,000
$212,904
TOTAL PRESENT VALUE OF MINE PORTAL MIW DISCHARGES IRA FOR THE SELECTED REMEDY - BROOKLYN MINE '
btubonal controls could include governmental controls such as changes to The San Juan National Forest and Tres Rios Field Office Land and Resource Management Plan
centages for contingency and professional/technical services costs are based on guidance from Section 5 0 of "A Guide to Developing and Documenting Cost Estimates Dun
; assumed that surface water monitoring would be conducted at Brooklyn Mine as part of remedy performance monitoring However, It is assumed that surface water monitc
: period of analysis for the selected remedy is assumed to be 15 years post construction
il expend®
in-30% to+50% of ac
»e an accuracy between -30% to +50% of ac
le Feasibility Study", EPA 2000 T
-------
Table 12-2A: Cost Estimate Summary for Mining-Related Source/Stormwater Interactions ERA for the Selected Interim Remedy
CAPITAL COSTS: (Assumed to be Incurred During Year 0)
DESCRIPTION
Institutional Controls
Mobilization/Demobilization
Installation of Surface Stormwater Diversion/Isolation Components
Noneonventional Access-Alpine Locations
Nonconventional Access-Subalpine Locations
Conventional Access-Subalpine Locations
Installation of Subsurface Stormwater Diversion/Isolation Components
Nonconventional Access-Alpine Locations
Nonconventional Access-Subalpine Locations
Conventional Access-Subalpine Locations
Access Road Improvements
Development of Borrow Materials
Transportation of Borrow Materials
Dust Control
Erosion Control and Reclamation of Areas Disturbed during Construction
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
Project Management
Remedial Design
Construction Management
TOTAL
TOTAL CAPITAL COST
ANNUAL O&M COSTS (Assumed to be Incurred Annually During Year 1 through 15)
DESCRIPTION
Inspection of Remedial Components
Surface Water Monitoring
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
Project Management
TOTAL
TOTAL ANNUAL O&M COST
5,000
3,400
3,770
BCY
LCY
UNIT COST
$31,840
$30,599
$4,639
$48,390
$12,521
UNIT COST
$6,567
$26,937
SUBTOTAL
PERIODIC O&M COSTS (Assumed to be Incurred Once Every 2 Years During Year 1 through 15)
DESCRIPTION
Post-Construction Maintenance
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
Project Management
TOTAL
TOTAL PERIODIC O&M COST
UNIT COST
$15,273
Summary of Present Value Analysis
$31,840
$30,599
$4,639
$8,151
$5,772
$1,427
$239,369
$91,968
$115,376
$48,390
$12,521
$624,304
$187,291
$48,696
$97,391
$64,928
TOTAL
$6,567
$53,874
TOTAL
$15,273
$15,273
$3,055
$18,328
$1,833
Year
Capital Costs
Annual O&M Costs
Periodic O&M Costs
Total Annual Expenditure
Discount Factor (7.0%)
Present Value
0
$1,023,000
$0
$0
$1,023,000
1.0000
$1,023,000
1
$0
$80,000
$0
$80,000
0.9346
$74,768
2
$0
$80,000
$20,000
$100,000
0.8734
$87,340
3
$0
$80,000
$0
$80,000
0.8163
$65,304
4
$0
$80,000
$20,000
$100,000
0.7629
$76,290
5
$0
$80,000
$0
$80,000
0.713
$57,040
6
$0
$80,000
$20,000
$100,000
0.6663
$66,630
7
$0
$80,000
$0
$80,000
0.6227
$49,816
8
$0
$80,000
$20,000
$100,000
0.582
$58,200
9
$0
$80,000
$0
$80,000
0.5439
$43,512
10
$0
$80,000
$20,000
$100,000
0.5083
$50,830
11
$0
$80,000
$0
$80,000
0.4751
$38,008
12
$0
$80,000
$20,000
$100,000
0.444
$44,400
13
$0
$80,000
$0
$80,000
0.415
$33,200
14
$0
$80,000
$20,000
$100,000
0.3878
$38,780
15
$0
$80,000
$0
$80,000
0.3624
$28,992
TOTALS:
$1,023,000
$1,200,000
$140,000
$2,363,000
$1,836,110
TOTAL PRESENT VALUE OF SELECTED REMEDY 4
$1,836,000
Votes:
The period of analysis for the
umedtobe 15 years postconsa
Motion
Total annual expenditure is the
total cost per yearwi
th no discounting
e total annual enpen
ture discounted by a factor for
that year representing the 7 0% real discount rate
ecommendedby "A Gui
e to Develo
ing and Documenting Cost Estimates During the Feasibili
ty Study", EPA 2000
Total present value is rounded
othe nearest $1,000
Inflation and depreciation are e
Kcluded from the present value cost
osts presented for this alternate
e are expected to hav
e an accuracy between -30% t
+50% of actual costs, based on the scope presen
ed
ercentages used for contingenc
lrucal services costs are based
n guidance from Section 5 0 of "A Guide to Deve
ping and Documenting C
ost Eshmat
s During the Feasibility Study", EPA 2000
osts presented are expected to
ave an accuracy ben
veen -30% to +50% of actual c
sts, based on the scope presented They are prep
ired solely for remedy se
caon and n
ot for remedial design
Jmt costs represent total cost div
quantity for each item and are
ounded to the nearest whole number Due to the
unding in the unit costs, n
ulaplying t
e estimated quanaty by unit cost may not exactly equal th
total cost
-------
Table 12-2B: Cost Estimate Summary for Mining-Related Source/Stormwater Interactions ERA for the Selected Interim Remedy - Brooklyn Mine
CAPITAL COSTS: (Assumed to be Incurred During Year 0)
DESCRIPTION
QTY
UNIT(S)
UNIT COST
TOTAL
Institutional Controls'
1
LS
$1,075
$1,075
Mobilization/Demobilization
1
LS
$6,860
$6,860
Installation of Surface Stormwater Diversion/Isolation Components
1
LS
$6,279
$6,279
Installation of Subsurface Stormwater Diversion/Isolation Components
40
LF
$33
$1,321
Access Road Improvements
1
LS
$6,250
$6,250
Development of Borrow Materials
120
BCY
$57
$6,889
Transportation of Borrow Materials
120
LCY
$26
$3,099
Dust Control
1
LS
$325
$325
Erosion Control and Reclamation of Areas Disturbed during Construction
1
LS
$1,642
$1,642
SUBTOTAL
$33,740
Contingency (Scope and Bid)
30%
$10,122
SUBTOTAL
$43,862
Project Management2
10%
$4,386
Remedial Design2
20%
$8,772
Construction Management
15%
$6,579
TOTAL
$63,599
TOTAL CAPITAL COST
$64,000
ANNUAL O&M COSTS (Assumed to be Incurred Annually During Year 1 through 15)
DESCRIPTION
Inspection of Remedial Components
Surface Water Monitoring3
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
Project Management2
TOTAL
UNIT COST
$2,668
TOTAL ANNUAL O&M COST
TOTAL
$2,668
$2,668
$534
$3,202
$320
PERIODIC O&M COSTS (Assumed to be Incurred Once Every 2 Years During Year 1 through 15)
DESCRIPTION
Post-Construction Maintenance
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
Project Management2
TOTAL
TOTAL PERIODIC O&M COST
UNIT COST
$2,896
TOTAL
$2,896
$3,475
$348
Summary of Present Value Analysis
Year
Capital Costs
Annual O&M Costs
Periodic O&M Costs
Total Annual Expenditure
Discount Factor (7.0%)
Present Value
0
$100,000
$0
$0
$100,000
1.0000
$100,000
1
$0
$4,000
$0
$4,000
0.9346
$3,738
2
$0
$4,000
$4,000
$8,000
0.8734
$6,987
3
$0
$4,000
$0
$4,000
0.8163
$3,265
4
$0
$4,000
$4,000
$8,000
0.7629
$6,103
5
$0
$4,000
$0
$4,000
0.713
$2,852
6
$0
$4,000
$4,000
$8,000
0.6663
$5,330
7
$0
$4,000
$0
$4,000
0.6227
$2,491
8
$0
$4,000
$4,000
$8,000
0.582
$4,656
9
$0
$4,000
$0
$4,000
0.5439
$2,176
10
$0
$4,000
$4,000
$8,000
0.5083
$4,066
11
$0
$4,000
$0
$4,000
0.4751
$1,900
12
$0
$4,000
$4,000
$8,000
0.444
$3,552
13
$0
$4,000
$0
$4,000
0.415
$1,660
14
$0
$4,000
$4,000
$8,000
0.3878
$3,102
15
$0
$4,000
$0
$4,000
0.3624
$1,450
TOTALS:
$100,000
$60,000
$28,000
$188,000
$153,328
TOTAL PRESENT VALUE OF MINING-RELATED SOURCE/STORMWATER INTERACTIONS IRA FOR THE SELECTED REMEDY - BROOKLYN MINE '
•ols such as changes to The San Juan National Forest and Tres Rios Field Office Land and Resource Management Plan
al seraces costs are based on guidance from Section 5 0 of "A Guide to Developing and Documenting Cost Estimates During the Feasibility Study", EPA 2000 The percent;
sts associated with Brooklyn Mine only
conducted at Brooklyn Mine as part of remedy performance monitoring However, It is assumed that surface water monitoring would be conducted at a watershed level Th
nare discounted by a factor for that year representing the 7 0% real discount rate recommended by "A Guide to Developing and Documenting Cost Estimates During the Fea:
Inflation and depreciation are excluded from the present value cost
¦ an accuracy between -30% to +50% of actual costs, based on the scope presented
een -30% to +50% of actual costs, based on the scope presented They are prepared solely for remedy selection and not for remedial design
i period of analysis for tl
:al annual expenditure is
-------
Table^2-3Aj_CostJistimate_Suinmai2^or^Bne^ortal^ondJ>etonMits^^^or^he_Sdected^nteiTmRemed^_
CAPITAL COSTS: (Assumed to be Incurred During Year 0)
DESCRIPTION
Institutional Controls
Mobilization/Demobilization
Pond Draining and Repair of Pond Berms
Mine Portal Pond Sediment Excavation
Geoteehnieal Characterization - Sampling Dewatered Mine Portal Pond Sediment
Management and Dewatering of Mine Portal Pond Sediment at Interim Local Waste Management
Access Road Improvements
Development of Borrow Materials
Transportation of Borrow Materials
Dust Control
Erosion Control and Reclamation of Areas Disturbed during Construction
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
Project Management
Remedial Design
Construction Management
TOTAL
TOTAL CAPITAL COST
514,600
10,192
2,710
3,070
UNIT(S)
UNIT COST
TOTAL
LS
$8,599
$8,599
LS
$19,619
$19,619
GAL
$0.06
$32,885
BCY
$4
$43,070
EA
$403
$19,751
LCY
$22
$265,683
LF
$47
$224,184
BCY
$28
$75,195
LCY
$26
$79,621
LS
$47,091
$47,091
LS
$11,225
$11,225
$826,923
$64,500
$129,000
ANNUAL O&M COSTS (Assumed to be Incurred Annually During Year 1 through 15)
DESCRIPTION
Inspection of Remedial Components
Surface Water Monitoring
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
Project Management
TOTAL
TOTAL ANNUAL O&M COST
UNIT COST
$4,926
$25,453
TOTAL
$4,926
$50,906
$66,998
$6,700
PERIODIC O&M COSTS - INTERIM LOCAL MANAGEMENT AREA (Assumed to be Incurred Once Every 2 Years During Year 1 through 15)
DESCRIPTION QTY
Post-Construction Maintenance of Interim Local Management Areas 1
SUBTOTAL
Contingency (Scope and Bid) 20%
SUBTOTAL
Project Management 10%
TOTAL
UNIT COST
TOTAL PERIODIC O&M COST
$9,618
$962
PERIODIC O&M COSTS - POND CLEANOUT (Assumed to be Incurred Once Every 3 Years During Year 1 through 15)
DESCRIPTION QTY
Periodic Removal of Mine Portal Pond Sediment 1
SUBTOTAL
Contingency (Scope and Bid) 30%
SUBTOTAL
Project Management 8%
Remedial Design 15%
Construction Management 10%
TOTAL
TOTAL PERIODIC O&M COST
UNIT COST
$267,360
TOTAL
$267,360
$27,805
$52,135
$34,757
Summary of Present Value Analysis
Annual O&M Costs
Periodic O&M Costs
Total Annual Expenditure
Discount Factor (7.0%)
TOTAL PRESENT VALUE OF SELECTED REMEDY 4
nod of analysis for
nnual expenditure i:
: nearest $1,000 Inflation and depreciation are excluded from the present value cost
¦ expected to have an accuracy between -30% to +50% of actual costs, based on the scope prese
professional/technical services costs are based on guidance from Section 5 0 of "A Guide to Dev
an accuracy between -30% to +50% of actual costs, based on the scope presented They are pre
nendedby "A Guide to Dev
id Documenting Cost Estir
id Documenting Cost Estimates During the Feasibility Study", EPA 2000
Present Value
0
$1,355,000
$0
$0
$1,355,000
1.0000
$1,355,000
1
$0
$74,000
$0
$74,000
0.9346
$69,160
2
$0
$74,000
$11,000
$85,000
0.8734
$74,239
3
$0
$74,000
$462,000
$536,000
0.8163
$437,537
4
$0
$74,000
$11,000
$85,000
0.7629
$64,847
5
$0
$74,000
$0
$74,000
0.713
$52,762
6
$0
$74,000
$473,000
$547,000
0.6663
$364,466
7
$0
$74,000
$0
$74,000
0.6227
$46,080
8
$0
$74,000
$11,000
$85,000
0.582
$49,470
9
$0
$74,000
$462,000
$536,000
0.5439
$291,530
10
$0
$74,000
$11,000
$85,000
0.5083
$43,206
11
$0
$74,000
$0
$74,000
0.4751
$35,157
12
$0
$74,000
$473,000
$547,000
0.444
$242,868
13
$0
$74,000
$0
$74,000
0.415
$30,710
14
$0
$74,000
$11,000
$85,000
0.3878
$32,963
15
$0
$74,000
$462,000
$536,000
0.3624
$194,246
TOTALS:
$1,355,000
$1,110,000
$2,387,000
$4,852,000 |
$3,384,241
-------
Table^2-3Bj_CostJistimateJ>ummai2^or^line^ortal^ondJ>e
-------
Tj»ble_1^4^Cos£^stimateJ>ummai^JW_In-StreamMine_Waste^ffiAJW_theJ>elected^InterimIlemed^
CAPITAL COSTS: (Assumed to be Incurred During Year 0)
DESCRIPTION
Institutional Controls
Mobilization/Demobilization
In-Stream Mine Waste Excavation
Geoteehnieal Characterization - Sampling Dewatered In-Stream Mine Waste
Management and Dewatering of In-Stream Mine Waste at Interim Local Waste Management Areas
Access Road Improvements
Development of Borrow Materials
Transportation of Borrow Materials
Dust Control
Erosion Control and Reclamation of Areas Disturbed during Construction
SUBTOTAL
QTY
UNIT(S)
UNIT COST
TOTAL
1
LS
$8,599
$8,599
1
LS
$8,802
$8,802
467
BCY
$4
$2,045
3
EA
$394
$1,182
570
LCY
$26
$14,579
100
LF
$515
$51,481
90
BCY
$57
$5,165
170
LCY
$57
$9,624
1
LS
$42,220
$42,220
1
LS
$9,107
$9,107
$152,804
Contingency (Scope and Bid) 30%
SUBTOTAL $198,645
Project Management 8% $15,892
Remedial Design 15% $29,797
Construction Management 10% $19,865
TOTAL $264,199
TOTAL CAPITAL COST
| $264,000 |
ANNUAL O&M COSTS (Assumed to be Incurred Annually During Year 1 through 15)
DESCRIPTION
Inspection of Remedial Components
Surface Water Monitoring
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
Project Management
TOTAL
TOTAL ANNUAL O&M COST
PERIODIC O&M COSTS (Assumed to be Incurred Once Every 2 Years During Year 1 through 15)
UNIT COST TOTAL
$2,668 $2,668
$7,312 $14,623
SUBTOTAL $17,291
$3,458
SUBTOTAL $20,749
$2,075
TOTAL $22,824
| $23,000 |
DESCRIPTION
Post-Construction Maintenance
SUBTOTAL
Contingency (Scope and Bid)
SUBTOTAL
Project Management
TOTAL
TOTAL PERIODIC O&M COST
UNIT COST
$7,010
SUBTOTAL
TOTAL
$7,010
$7,010
$1,402
Summary of Present Value Analysis
Year
Capital Costs
Annual O&M Costs
Periodic O&M Costs
Total Annual Expenditure
Discount Factor (7.0%)
Present Value
0
$264,000
$0
$0
$264,000
1.0000
$264,000
1
$0
$23,000
$0
$23,000
0.9346
$21,496
2
$0
$23,000
$9,000
$32,000
0.8734
$27,949
3
$0
$23,000
$0
$23,000
0.8163
$18,775
4
$0
$23,000
$9,000
$32,000
0.7629
$24,413
5
$0
$23,000
$0
$23,000
0.713
$16,399
6
$0
$23,000
$9,000
$32,000
0.6663
$21,322
7
$0
$23,000
$0
$23,000
0.6227
$14,322
8
$0
$23,000
$9,000
$32,000
0.582
$18,624
9
$0
$23,000
$0
$23,000
0.5439
$12,510
10
$0
$23,000
$9,000
$32,000
0.5083
$16,266
11
$0
$23,000
$0
$23,000
0.4751
$10,927
12
$0
$23,000
$9,000
$32,000
0.444
$14,208
13
$0
$23,000
$0
$23,000
0.415
$9,545
14
$0
$23,000
$9,000
$32,000
0.3878
$12,410
15
$0
$23,000
$0
$23,000
0.3624
$8,335
TOTALS:
$264,000
$345,000
$63,000
$672,000
$511,501
TOTAL PRESENT VALUE OF SELECTED REMEDY4 | $512,000
-------
Table 12-5: Cost Estimate Summary for Mining-Impacted Recreation Staging Areas IRA for the Selected Interim Remedy
CAPITAL COSTS: (Assumed to be Incurred During Year 0)
DESCRIPTION
QTY UNIT(S)
UNIT COST
TOTAL
Institutional Controls
1 LS
S8,599
S8,599
Mobilization/Demobilization
1 LS
S12,562
S12,562
Placement of Gravel Cover
2.0 ACR
S13,494
S26,987
Placement of Soil Cover
6.9 ACR
S21,981
S151,669
Access Road Improvements
1 LS
S50,000
S50,000
Development of Borrow Materials
18,600 BCY
S7
S133,493
Transportation of Borrow Materials
21,900 LCY
S15
S333,371
Dust Control
1 LS
S75,670
S75,670
Erosion Control
1 LS
S8,210
S8,210
SUBTOTAL
S800,561
Contingency (Scope and Bid)
20%
S160,l 12
SUBTOTAL
S960,673
Project Management
6%
S57,640
Remedial Design
12%
SI 15,281
Construction Management
8%
S76,854
TOTAL
SI,210,448
TOTAL CAPITAL COST
L
SI,210,000 |
ANNUAL O&M COSTS (Assumed to be Incurred Annually During Year 1 through 15)
DESCRIPTION
QTY UNIT(S)
UNIT COST
TOTAL
Inspection of Remedial Components
1 LS
S6,567
S6,567
SUBTOTAL
S6,567
Contingency (Scope and Bid)
20%
SI,313
SUBTOTAL
S7,880
Project Management
10%
S788
TOTAL
S8,668
TOTAL ANNUAL O&M COST
L
$9,000 |
PERIODIC O&M COSTS (Assumed to be Incurred Once Every 2 Years During Year 1 through 15)
DESCRIPTION
QTY UNIT(S)
UNIT COST
TOTAL
Post-Construction Maintenance
1 LS
S67,385
S67,385
SUBTOTAL
S67,385
Contingency (Scope and Bid)
20%
S13,477
SUBTOTAL
S80,862
Project Management
10%
S8,086
TOTAL
S88,948
TOTAL PERIODIC O&M COST
L
$89,000 |
Summary of Present Value Analysis
Year1 Capital Costs
Annual O&M Costs
Periodic O&M Costs Total Annual Expenditure
Discount Factor (7.0%)
Present Value
0 $1,210,000
SO
SO SI,210,000
1.0000
SI,210,000
1
$0
S9,000
SO S9,000
0.9346
S8,411
2
SO
S9,000
S89,000 S98,000
0.8734
S85,593
3
so
S9,000
SO S9,000
0.8163
S7,347
4
so
S9,000
S89,000 S98,000
0.7629
S74,764
5
so
S9,000
SO S9,000
0.713
S6,417
6
so
S9,000
S89,000 S98,000
0.6663
S65,297
7
so
S9,000
SO S9,000
0.6227
S5,604
8
so
S9,000
S89,000 S98,000
0.582
S57,036
9
so
S9,000
SO S9,000
0.5439
S4,895
10
so
S9,000
S89,000 S98,000
0.5083
S49,813
11
so
S9,000
SO S9,000
0.4751
S4,276
12
so
S9,000
S89,000 S98,000
0.444
S43,512
13
so
S9,000
SO S9,000
0.415
S3,735
14
so
S9,000
S89,000 S98,000
0.3878
S38,004
15
so
S9,000
SO S9,000
0.3624
S3,262
TOTALS: $1,210,000
S135,000
S623,000 SI,968,000
SI,667,966
TOTAL PRESENT VALUE OF SELECTED REMEDY 4
1
$1,668,000 |
Notes:
The period of analysis for the selected remedy is assumed
o be 15 years post con
2 Total annual expenditure is the total cost per year with no discounting
Present value cost by year is the total annual expenditure discounted by a factor for that year representing the 7 0% real discount rate recommended by "A Guide to Developing and Documenting Cost Estimates During the Feasibility Study", EPA 2000
Total present value is rounded to the nearest $1,000 Inflation and depreciation are
excluded from the present value cost
Costs presented for this alternative are expected to have an
curacy between -30% t
+50% of actual costs, based on the scope presented
Percentages used for contingency and professional/technical
services costs are base
on guidance from Section 5 0 of "A Guide
o Developing and Documenting Cost Estimates During the Feasibility Study", EPA 2000
Costs presented are expected to have an accuracy between -30% to +50% of actual c
sts, based on the scope presented They are
prepared solely for remedy selection and not for remedial design
Unit costs represent total cost divided by the estimated quantity for each item and are
rounded to the nearest whole number Due
o the rounding in the unit costs, multiplying the estimated quantity by unit cost may
not exactly equal the total cost
Abbreviations:
ACR Acre
BCY Bank Cubic Yard
EA Each
LF Linear Feet
LCY Loose Cubic Yard
LS Lump Sum
-------
FIGURES
-------
United States
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Hanson Peak
Bald Mountain
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Mountain
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Silver/
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-------
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Interim Remedial Action
- Mining-Related Source - 2
~ Interim Remedial Actions
Mining-Related Source - 3
Interim Remedial Actions
A Mountain Peak
Forest Service
Road
Road
— US Highway
Streams
Figure 1-2
Mining-Related Sources-
Mineral Creek Drainage Basin
Bonita Peak Mining District Superfund Site | San Juan County, CO
0 0.25 0.5 0.75 1
1 I I I J
1 in = 0.75 miles Miies
Background Terrain Sources: Esri, USGS, NO A A
Source. Esri, DigitatGbbe, GeoEye, Earthstar
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IGN, and the GIS User Community
Road Source: US Census Tiger/hne
Waterways and Waterbodies Source: Nationai
Hydrography Dataset - USGS
-------
Red Mountain
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IGN, and the GIS User Community
Road Source: US Census Tiger/bne
Waterways and Waterbodies Source: National
Hydrography Dataset - USGS
Mining-Related Source -
Excluded from I ROD
Mining-Related Source - 1
Interim Remedial Action
Mining-Related Source - 2
Interim Remedial Actions
Mountain Peak
Road
Highway
Streams
Figure 1-3
Mining-Related Sources-
Cement Creek Drainage Basin
Bonita Peak Mining District Superfund Site | San Juan County, CO
-------
Background Terrain Sources: Esri, USGS, NO A A
Source. Esri, DigitalGlobe, GeoEye, Earthstar
Geographies, CNES/ArbusDS, USD A, USGS,AeroGRID,
IGN, and the GIS User Community
Road Source: US Census Tiger/hne
Waterways and Waterbodies Source: National
Hydrography Dataset - USGS
_ Mining-Related Source -1
Interim Remedial Action
m Mining-Related Source - 2
Interim Remedial Actions
Mining-Related Source - 3
Interim Remedial Actions
Mountain Peak
Forest Service
Road
Road
Highway
Streams
Figure 1-4
Mining-Related Sources -
Upper Animas Area Drainage Basin
Bonita Peak Mining District Superfund Site | San Juan County, CO
-------
APPENDIX A
PRELIMINARY REMEDIAL INVESTIGATION REPORT
-------
APPENDIX A - PART 1
RESPONSE TO PUBLIC COMMENTS
PRELIMINARY REMEDIAL INVESTIGATION REPORT FOR THE
BONITA PEAK MINING DISTRICT
-------
'smith
Memorandum
To: Rob Parker, Remedial Project Manager, U.S. Environmental Protection Agency Region 8
From: Tommy Cook and Neil Smith, CDM Federal Programs Corporation
Date: 10/19/2018
Subject: Response to Public Comments - Preliminary Remedial Investigation Report for the
Bonita Peak Mining District
This memorandum was drafted to summarize updates to the preliminaiy remedial investigation
(RI] report submitted as Appendix A to the focused feasibility study in May 2018 (CDM Federal
Programs Corporation 2018] as part of the interim remedial action proposed to take place within
the Bonita Peak Mining District Superfund Site (the Site] in San Juan County, Colorado. These
updates are in response to public comments on the documents received between June 14 and
August 15, 2018, which necessitate a change to the main text and tables of the preliminaiy RI
report.
Section 4.8.2.1 of the text and Table 4-1 present a flow measurement of 0.7 gallons per minute
(gpm] at sampling location DM6 at the London Mine. This measurement was conducted by the
Colorado Division of Reclamation, Mining, and Safety (DRMS] on September 16, 2016, 2 weeks
before the September 30, 2016 analytical sample was collected at this location. During sampling on
September 30, 2016, there was no flow reported at location DM6 (TechLaw, Inc. 2017], The
reported flow value from DRMS of 0.7 gpm was collected at location DM7, rather than DM6. Table
4-1 has been modified to indicate the flow of 0.7 gpm was measured at location DM7, and a column
has been added indicating dates flow measurements were collected by DRMS if different than the
date the analytical sample for surface water was collected by the U.S. Environmental Protection
Agency/Environmental Services Assistances Team. The revised Table 4-1 is presented as
Attachment A to this memorandum.
References
CDM Federal Programs Corporation. 2018. Final Focused Feasibility Study Report. Interim Remedial
Actions. Bonita Peak Mining District Superfund Site. San Juan County, Colorado. Prepared for the U.S.
Environmental Protection Agency, Region 8.
TechLaw, Inc. 2017. Draft Sampling Activities Report, 2016 Sampling Activities Report, Bonita Peak
Mining District, San Juan/La Plata Counties, Colorado. Prepared for U.S. Environmental Protection
Agency, Region 8.
Appendix A, Part 1 - Response to Public Comments - Preliminary RI Report BPMD_10192018
-------
Mr. Rob Parker
October 19, 2018
Page 2
Attachment:
Attachment A Revised Table 4-1, Preliminaiy Remedial Investigation Report.
Appendix A, Part 1 - Response to Public Comments - Preliminary Rl Report BPMD_10192018
-------
Table 4-1
Total and Dissolved Metals for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Metal Concentrations (ng/L)
Aluminum
Arsenic
Cadmium
Copper
Iron
Manganese
Lead
Zinc
T
D
T
D
T
D
T
D
T
D
T
D
T
D
T
D
Station
Mine Location
Name
Analytical
Sample Date
Flow
pH Measurement
Date*
Flow
(gpm)
Result Q
Result
Q
Result
Q
Result Q
Result Q
Result Q
Result
Q
Result
Q
Result
Q
Result Q
Result Q
Result Q
Result
Q
Result Q
Result Q
Result Q
Longfellow Mine
M02D
6/29/2016
6.61
15
286
33.4
J
3.85
J
2.64
0.5
U
0.1
U
8.91
7.2
650
179
J
80
51.9
1.45
0.213
10
U
10
U
M02D
10/7/2016
6.83
4.9
183
22.4
J
2.5
U
1.67
J
0.5
U
0.1
U
5.04
4.14
577
146
J
88.1
64.7
0.931
J
0.185
J
10
U
10
Junction Mine
M02B
6/29/2016
6.15
12
1720
227
143
57.2
7.17
7.46
261
182
16600
13500
348
365
131
5.26
1640
1770
M02B
10/7/2016
3.86
2.9
7110
6320
303
213
25.1
26.1
777
794
64000
56100
1780
1740
304
300
6590
6510
KoehlerTunnel
M02K1
6/29/2016
4.54
0.1
3870
3720
2.5
U
2.5
U
40.7
40.5
3170
3310
324
309
16600
16400
3.19
3.29
17700
18100
M02C
10/7/2016
6.12
4.5
12900
1950
3000
1020
86.2
89.4
3140
2100
177000
152000
37600
37300
152
1.51
41500
41400
M02E
6/29/2016
--
--
3500
2460
177
30.4
19.4
21.1
891
863
17600
13000
7220
7020
100
36.6
7870
7930
M02E
10/7/2016
3.60
9.0
8100
7590
234
67.4
47.2
42.8
1610
1410
40400
33800
20800
17200
59.8
73.4
22400
18700
M02
6/29/2016
5.76
150
2590
422
119
15.1
12.2
12.5
522
449
10000
6710
4120
4050
75.3
8.87
4590
4690
M02
10/7/2016
8.03
23
6770
6190
90.3
30.3
35.7
36.4
1290
1320
17100
15200
16200
15600
35.5
35.1
16800
16400
Brooklyn Mine
M12
6/7/2016
4.55
--
3460
290
7.59
J
0.5
U
0.726
J
0.719
15.6
6.08
7400
136
J
488
301
14.6
0.198
J
174
156
M12
6/29/2016
5.08
438
3370
3030
2.5
U
0.5
U
3.94
4.02
33.9
34.4
911
410
1320
1300
3.3
2.52
861
887
M12
9/29/2016
4.17
165
9130
8700
2.5
U
0.5
U
6.07
6.2
53.4
54.4
1210
1040
2280
2280
3.88
4.02
1300
1370
M12A
6/29/2016
4.51
--
3850
3120
2.5
U
0.5
U
1.05
1.11
22.9
22.3
1590
362
799
763
7.04
1.44
282
276
M12A
9/30/2016
4.45
151
10200
9630
2.5
U
0.5
U
1.28
1.49
31.7
32.2
1200
627
1440
1440
1.66
1.55
347
363
M12B
6/29/2016
4.76
223
3940
3510
2.5
U
0.5
U
0.5
U
0.266
11.1
11.2
966
419
545
535
1.11
0.65
61
54.6
M12B
9/30/2016
4.55
151
11900
11000
2.5
U
0.5
U
0.5
U
0.307
19.6
20.1
1770
1050
1190
1190
0.81
J
0.631
81
81.5
M12C
6/29/2016
3.63
7.3
1890
1010
20.7
0.5
U
14.9
15.6
236
177
26400
4070
5240
5100
25.1
1.69
4670
4600
M12C
9/29/2016
3.84
1.1
3620
2920
39.3
1.63
J
19.1
18.7
348
300
58800
16300
6440
6430
116
20.7
5780
6060
M12C
9/30/2016
3.84
1.1
3020
2450
20.6
2.7
19
18.8
319
302
33700
16600
6380
6390
25
18.2
5690
5950
M12D
9/30/2016
3.72
2.2
2770
2170
20.1
1.4
J
18.9
19
328
317
27600
10400
6300
6300
24.7
19.5
5810
6100
M12F
10/7/2016
7.79
--
83.1
48.1
J
2.5
U
0.908
J
0.5
U
0.1
U
2.5
U
0.945
J
105
J
100
U
193
4.09
J
0.5
U
0.1
U
10
U
10
M12G
10/7/2016
4.07
--
642
576
2.5
U
0.5
U
0.5
U
0.433
22.1
23.8
591
502
938
915
126
125
117
121
Bandora Mine
M23
9/27/2016
5.98
7351
2070
554
2.5
U
0.5
U
0.5
U
0.349
2.5
U
1.33
162
J
100
U
200
200
0.5
U
0.246
32.5
40
M24A
9/28/2016
6.96
--
957
36
J
12.8
0.5
U
67.8
35.8
1070
3.15
74900
195
J
6770
4870
977
0.147
J
13500
8750
M24B
9/28/2016
6.71
9/29/2016
24
210
37.8
J
2.5
U
0.507
J
49.3
48
233
19.3
16100
5300
5290
4940
201
3.69
11200
11200
M24C
9/28/2016
7.41
--
31.2
J
30.1
J
2.5
U
2.5
U
0.5
U
0.5
U
2.5
U
2.5
U
112
J
141
J
2100
2030
0.663
J
0.581
J
540
541
M24D
9/27/2016
6.87
--
200
20
U
2.5
U
0.5
U
42.4
35.2
189
2.23
11500
100
U
4780
4630
177
0.1
U
10700
9250
M25
6/29/2016
6.28
21553
696
49.7
J
2.5
U
0.5
U
0.5
U
0.336
2.5
U
1.28
100
U
100
U
90.7
89.8
0.5
U
0.1
U
58.4
64.1
M25
9/27/2016
6.12
9317
1840
266
2.5
U
0.5
U
0.54
J
0.622
2.5
U
1.2
159
J
100
U
207
202
0.5
U
0.1
U
104
111
Grand Mogul
Mine
CC01C
6/29/2016
3.59
--
2010
1850
2.5
U
1.56
J
18.7
17.6
470
462
2410
2210
1720
1660
39.7
38.2
3650
3660
CC01C
9/28/2016
4.10
3.6
10300
9720
37.1
39
95.4
97
2620
2620
57900
55100
6120
6050
27.9
26.4
24500
25100
CC01C1
6/29/2016
3.17
--
4570
4190
3.85
J
5.54
41.7
35.1
T
1440
1360
10000
12700
3760
3570
33.7
33
8850
8550
CC01C1
9/28/2016
3.96
9/20/2016
2.8
15000
14100
20.3
21.8
127
130
5080
5070
54600
52200
11400
11300
7.59
7.12
31300
31600
CC01C2
6/29/2016
3.42
73
2960
2750
2.5
U
0.617
J
23.1
21.5
733
708
3030
2850
2180
2090
28.1
26.9
4680
4660
CC01C2
9/28/2016
4.12
9.0
8090
7730
2.5
U
2.94
69.1
62.9
2220
2130
9380
8900
5730
5610
22.1
21.5
14900
14700
CC01F
6/29/2016
7.27
--
238
97.6
2.5
U
0.5
U
1.19
1.2
31.1
20.6
100
U
100
TT
82.5
78.2
8.04
3.8
267
261
CC01F
9/28/2016
7.16
--
372
114
2.5
U
0.5
U
2.7
2.77
59
29.7
100
U
100
u
126
123
2.93
0.843
475
454
CC01H
6/29/2016
6.12
2904
721
197
2.5
U
0.5
U
5.39
5.41
163
133
611
100
u
474
450
10
2.98
1120
1100
CC01H
9/27/2016
6.31
368
663
213
2.5
U
0.5
U
7.13
7.34
161
141
582
100
u
417
407
2.14
0.348
1600
1610
CC02I
6/28/2016
4.69
7.3
979
924
2.5
U
0.5
U
6.17
6.11
24
24.4
100
U
100
u
121
122
8.84
8.46
1750
1770
CC02I
9/27/2016
5.90
350
1880
1000
2.5
U
0.5
U
11.2
12
128
116
224
J
100
TT
2330
2280
2.93
1.8
2140
2110
CC01U
6/28/2016
6.16
5327
1120
197
2.5
U
0.5
u
4.18
4.3
69.2
51.5
299
100
TT
1890
1810
8.95
2.04
815
802
CC01U
9/27/2016
5.72
378
1860
926
2.5
U
0.5
u
12.1
12.1
131
117
244
J
100
TT
2310
2260
4.53
3.11
2200
2160
'smith
-------
Table 4-1
Total and Dissolved Metals for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Metal Concentrations (ng/L)
Aluminum
Arsenic
Cadmium
Copper
Iron
Manganese
Lead
Zinc
T
D
T
D
T
D
T
D
T
D
T
D
T
D
T
D
Station
Mine Location
Name
Analytical
Sample Date
Flow
pH Measurement
Date*
Flow
(gpm)
Result Q
Result
Q
Result
Q
Result Q
Result Q
Result Q
Result
Q
Result
Q
Result
Q
Result Q
Result Q
Result Q
Result
Q
Result Q
Result Q
Result Q
Natalie/Occident
al Mine
CC14
6/10/2015
6.09
--
1830
1150
4.46
J
1.88
J
5.25
4.68
86.9
67.6
19800
18000
1980
1940
7.3
0.339
843
884
CC14
9/29/2015
6.32
--
920
664
2.5
U
2.5
U
1.82
1.78
7.78
3.51
J
19600
18100
2630
2680
3.41
0.557
J
732
751
CC14
6/9/2016
6.13
--
2440
1900
2.5
U
5
U
5.59
5.9
90.8
75.9
27200
27200
2670
2680
9.84
1.63
J
1130
1150
CC14
9/29/2016
5.39
9/21/2016
407
955
791
2.53
J
2.94
J
1.87
1.87
7.17
3.16
J
18600
17600
2520
2480
3.17
0.536
J
704
673
CC15
6/9/2016
--
7277
643
91.6
2.5
U
0.5
U
0.5
U
0.271
8.71
4.97
796
100
U
84.3
81.2
0.579
J
0.1
U
61.6
64.6
CC15
9/29/2016
7.00
301
446
95.8
2.5
U
0.5
U
0.5
U
0.226
5.38
2.92
145
J
100
U
64.2
63.5
0.5
U
0.1
U
36
36.1
CC15A
6/9/2016
--
7206
751
177
2.5
U
0.5
U
0.787
J
0.831
15.8
10.2
2920
2530
325
331
1.28
0.1
U
165
171
CC15A
9/29/2016
6.80
1170
868
267
2.5
U
2.5
U
1.16
1.2
8.95
4.21
J
9330
8340
1410
1390
1.93
0.5
U
403
391
Henrietta Mine
CC24G
6/30/2016
4.61
--
1840
1790
2.72
J
3.5
0.5
U
0.293
36.9
35.8
20900
20400
72.9
75.6
3.3
3.17
116
123
CC22D
6/8/2016
5.76
--
488
84.4
2.5
U
0.5
U
1.65
1.61
46.1
37.1
944
127
J
92.1
73.4
31.4
8.1
406
432
CC22D
9/29/2016
5.79
73
1130
124
2.5
U
0.5
U
1.7
1.74
42.6
28.9
1440
211
J
307
289
59.9
18.3
435
400
CC22B
6/8/2016
4.73
--
811
622
2.5
U
0.5
U
1.11
1.22
34
33.8
663
312
110
109
23.9
18.1
302
333
CC22B
9/29/2016
4.33
131
3600
3120
2.5
U
0.5
U
1.43
1.61
33.6
33.3
533
347
584
567
43.8
40.3
376
372
CC24B
6/8/2016
4.37
--
904
666
2.5
U
0.848
J
1.08
1.29
58.9
57.9
1210
769
124
119
25.6
18.9
330
342
CC24B
9/29/2016
3.93
166
2790
2460
2.5
U
0.5
U
2.03
2.32
106
107
1740
1450
506
498
44.5
44.2
549
571
Anglo Saxon
Mine
CC37
6/7/2016
6.53
41
500
477
7.91
J
6.93
J
2.75
2.52
7.68
7.03
28200
28400
8940
9050
10.3
2.04
2930
3040
CC37
9/28/2016
6.53
41
458
433
7.17
J
6.78
J
2.26
2.36
5.21
4.09
J
28700
25700
8700
8580
8.44
0.964
J
2830
2850
CC38
6/7/2016
7.43
--
1160
86.5
2.6
J
0.5
U
0.5
U
0.363
11.9
6.54
2260
556
640
592
31.1
2.73
179
162
CC38
9/28/2016
7.25
37
438
61.4
2.96
J
2.5
U
2.11
1.97
18.8
2.58
J
11600
6300
7860
7770
8.73
0.5
U
1790
1640
CC38B
6/7/2016
6.15
59
885
790
6.39
J
3.32
J
2.06
2.08
58.8
65.9
20500
16300
11600
11600
9.54
0.542
J
2290
2450
CC38B
9/28/2016
6.67
36
638
211
5.93
J
3.36
J
1.95
1.81
24.4
7.69
21800
17300
12400
12100
3.89
0.5
U
2530
2480
CC38C
6/7/2016
7.07
--
1530
104
2.5
U
0.5
U
0.5
U
0.206
19.9
5.06
2160
100
U
105
18.2
110
2.85
103
49.5
CC38C
9/28/2016
7.32
15
266
95.8
2.5
U
0.5
U
2.2
2.46
20.2
10.9
107
J
100
U
91
89.9
24.4
9.58
533
555
CC39
6/7/2016
5.26
--
2140
643
4.72
J
0.5
U
2.26
2.19
70.1
53.9
6800
2100
932
869
50.9
5.29
669
658
CC39
9/27/2016
3.62
7970
6770
5930
6.93
J
2.6
J
5.72
5.78
108
99.7
14800
10000
4460
4400
44.7
20.5
2400
2330
CC39B
6/7/2016
5.10
--
2230
913
5.76
J
0.5
U
2.41
2.33
69.3
58.7
6790
2330
917
834
58.8
8.64
657
679
CC39B
9/28/2016
3.82
6993
6180
5760
4.78
J
2.5
U
5.43
5.49
55
59
13700
12500
4690
4700
13.7
13.5
2140
2170
Yukon Tunnel
CC41
6/7/2016
5.16
--
2410
907
4.12
J
0.5
U
2.98
2.91
99.4
72.6
8110
2460
1060
978
43.1
5.73
858
854
CC41
9/27/2016
3.55
6939
6220
5520
6.49
J
2.5
U
6.63
6.36
141
96.3
12500
7480
5110
4920
27.2
17.1
2610
2420
CC43C
6/7/2016
6.82
--
533
171
2.5
U
2.5
U
0.5
TT
0.5
U
11.6
3.98
T
2460
1190
793
768
2.76
0.5
TT
109
100
CC43C
9/27/2016
6.68
--
486
168
2.5
U
2.5
U
0.5
Ti"
0.5
TT
12.2
2.94
T
2440
1110
1130
1090
2.65
0.5
~u"
121
108
CC43D
6/7/2016
2.98
--
30900
28200
2.5
U
0.81
J
21.4
18.4
3610
2770
42900
39300
6530
6170
3.89
4.11
5810
5720
CC43E
6/7/2016
5.37
--
3020
891
5.63
J
0.5
u
3
3.19
104
82.3
10000
2250
1100
977
59.4
4.52
912
919
CC43E
9/27/2016
3.88
7069
5630
5240
3.6
J
2.5
u
5.06
5.01
84.9
81.9
10100
7080
4170
4150
15.2
13.9
2070
2050
Boston Mine
A07D
6/28/2016
4.23
--
5970
5550
2.5
U
0.5
u
7.55
7
38.9
34.6
242
J
149
T
2160
2100
11.6
9.47
1130
1140
A07D
10/5/2016
4.11
9.0
16000
15100
2.5
U
0.5
u
19.1
19.5
92.5
92.5
100
U
100
Ti"
4860
4810
7.22
7.47
2840
2830
A07D1
6/28/2016
4.26
55
19300
18000
2.5
U
0.5
u
33.2
32.4
55.5
51.3
100
U
100
Ti"
6080
5890
1.52
1.26
6020
5870
A07D2
6/28/2016
4.31
--
2340
2150
2.5
U
0.5
u
25.5
23.8
96.2
90
100
U
100
~u~
824
793
22.5
18.7
3740
3680
A07E
6/28/2016
4.18
--
4830
4570
2.5
U
0.5
u
5.02
4.93
35.4
33
234
J
141
T
1820
1780
11.6
9.77
715
718
A07E
10/5/2016
3.86
49
13800
13000
2.5
U
0.5
u
12.3
13.3
64.6
68.8
311
304
5090
4950
14
15.4
2150
2120
'smith
-------
Table 4-1
Total and Dissolved Metals for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Metal Concentrations (ng/L)
Aluminum
Arsenic
Cadmium
Copper
Iron
Manganese
Lead
Zinc
T
D
T
D
T
D
T
D
T
D
T
D
T
D
T
D
Station
Mine Location
Name
Analytical
Sample Date
Flow
pH Measurement
Date*
Flow
(gpm)
Result Q
Result
Q
Result
Q
Result Q
Result Q
Result Q
Result
Q
Result
Q
Result
Q
Result Q
Result Q
Result Q
Result
Q
Result Q
Result Q
Result Q
London Mine
DM6
6/28/2016
6.13
3.2
121
88.5
2.5
U
0.5
U
8.17
8.7
30.3
30
443
324
189
197
61.7
48.3
1540
1680
DM6
9/30/2016
3.21
--
1220
1100
2.5
U
1.36
J
84.4
71.4
260
218
6180
4870
1640
1550
226
202
17200
17200
DM7
6/8/2016
6.69
--
360
23.1
J
4.25
J
0.595
J
13.8
12.8
41.3
4.53
2150
100
U
277
234
13.3
0.1
J
2930
2870
DM7
6/28/2016
6.05
1.1
644
41.2
J
11.9
2.58
46.2
43.2
107
9.99
4700
255
1030
984
22.1
0.23
8130
8120
DM7
9/30/2016
6.41
9/16/2016
0.7
929
37.9
J
14.8
2.86
49.4
42
123
6.57
7400
312
1230
1230
27.9
0.1
U
8170
8280
A07B1
6/28/2016
4.28
1329
7230
6790
2.5
U
0.5
U
11.3
10.8
43.5
39.8
148
J
103
J
2540
2480
11.2
9.57
1810
1790
A07B
9/30/2015
4.30
21
14000
13400
2.5
U
0.5
U
21.7
23
49.8
51.5
166
J
102
J
5890
6110
8.87
9.44
3990
4340
A07B
6/28/2016
4.323
1206
6860
6440
2.5
U
0.5
U
10.4
10.7
42.2
38.9
134
J
108
J
2380
2340
10.8
9.34
1690
1720
A07B
9/30/2016
4.08
186
17100
17000
2.5
U
0.5
U
26.4
24.1
61.6
56.6
170
J
161
J
5980
5920
10.5
9.35
4260
4280
Ben Butler Mine
BB1
6/28/2016
3.97
--
546
502
2.5
U
0.5
U
10.7
10.6
192
189
373
303
92.8
89.6
830
819
2080
2050
Mountain Queen
Mine
A18
10/6/2016
7.30
--
520
87.5
2.5
U
2.5
U
2.53
2.53
46.4
27.9
123
J
100
U
498
476
0.996
J
0.5
U
374
360
A19A
9/30/2015
3.70
0.8
3310
3200
2.5
U
1.42
J
44.5
45.7
1270
1270
5110
5050
5750
5700
192
208
5630
6230
A19A
9/28/2016
--
2.7
3270
3180
2.5
U
1.32
J
43
37.9
1260
1150
5470
5100
4190
4030
139
137
5060
4920
Vermillion Mine
CG4
9/30/2015
5.01
247
16300
15500
2.5
U
0.5
U
18.2
18.7
47.2
72.6
140
J
127
J
36400
36600
0.567
J
0.552
6030
6270
CG4
6/28/2016
6.58
6127
3820
2790
2.5
U
0.5
U
5.49
5.81
18.5
16
108
J
100
U
9020
9210
1.16
0.452
1550
1660
CG4
10/6/2016
5.47
1006
14900
12100
2.5
U
0.5
U
13.8
14.2
36.6
34.8
495
183
J
27300
26600
1.36
0.644
4380
4240
CG5
6/28/2016
5.48
--
628
602
2.5
U
0.5
U
7.84
7.67
61.3
60.5
100
U
100
U
472
479
47.7
44.8
1730
1900
CG6
9/30/2015
5.17
189
13700
12000
2.5
U
0.5
U
15.9
16.4
41.2
35.9
151
J
106
J
31600
31500
1.41
0.597
5260
5310
CG6
6/28/2016
6.46
7803
3620
2540
2.5
U
0.5
U
5.74
5.65
18.3
15.8
111
J
100
U
8750
8630
2.16
1.21
1560
1620
CG6
9/30/2016
4.97
785
11900
10400
2.5
U
0.5
U
12.2
11.1
31.8
25.6
100
U
100
U
25600
25700
0.889
J
0.414
3510
3700
CG6A
6/29/2016
6.57
5679
4500
2390
2.5
U
0.5
U
5.57
5.58
23.4
14.9
1150
100
U
8350
8360
26.2
1.4
1580
1690
Sunbank Group
Mine
A21
9/29/2015
5.54
76
2290
815
2.5
U
0.5
U
3.85
3.93
14.2
12.6
1020
801
1880
1900
34.1
32.6
1700
1780
A21
6/29/2016
6.94
4916
1050
125
2.5
U
0.5
U
3.88
3.55
42.3
27.3
100
U
100
U
3120
2980
9.02
2.35
1410
1340
A21
9/30/2016
5.93
515
1490
304
2.5
U
0.5
U
4.03
3.65
18.1
12.4
289
248
J
1550
1480
103
7.61
1610
1560
A22
9/29/2015
5.97
61
340
29.7
J
2.5
U
0.5
U
1.84
1.99
8.15
4.71
100
U
100
U
346
348
4.52
2.01
1050
1150
A22
6/29/2016
6.99
3576
1090
148
2.5
U
0.5
U
3.65
3.62
43
31.1
100
U
100
U
3370
3250
6.09
T
1.05
1360
1360
A22
9/30/2016
6.46
531
1160
76.1
2.5
U
0.5
U
3.11
2.96
14.1
7.3
100
U
100
U
1250
1190
4.32
0.863
1430
1380
A21A
9/29/2015
4.79
16.4
13600
13500
2.5
U
1.4
J
12.1
12.1
2.5
TT
1.44
16400
16300
9460
9600
194
198
4590
4930
A21A
6/29/2016
5.51
--
14100
13200
2.5
U
1.29
J
11.9
10.9
2.5
Ti"
0.774
J
19200
16500
8980
8750
253
216
4300
4270
A21A
9/30/2016
3.78
--
15100
15000
2.5
U
1.76
J
13.3
13
2.5
Ti"
1.04
18000
17100
9160
8980
188
190
4710
4670
Frisco/Bagley
Tunnel
A12
6/9/2015
7.14
83
285
107
2.5
u
1.34
J
4.69
4.69
5.29
4.7
2390
2210
7950
8190
4.02
0.591
3500
3830
A12
10/1/2015
6.25
18
434
285
2.5
u
2.47
4.47
4.77
2.5
Ti"
2.36
4390
3550
16500
16600
1.39
T
0.482
5470
6080
A12
6/7/2016
6.48
18
642
550
2.5
u
2.14
7.76
8.51
7.36
6.95
4450
4170
16300
16300
1.61
0.355
6640
6980
A12
9/28/2016
--
58
356
325
2.5
u
1.86
J
5.43
4.94
2.93
T
2.62
2450
2210
13900
13700
0.5
TT
0.1
TT
5090
5060
A13
6/9/2015
6.20
25192
1120
305
2.5
u
0.5
U
2.39
2.26
22.9
11.5
239
J
100
U
1960
1980
28.9
2.82
757
802
A13
9/29/2015
5.31
521
7530
5590
2.5
u
0.5
u
9.78
10.2
31.4
28.3
292
203
J
18200
18900
8.85
7.83
3500
3920
A13
6/7/2016
6.57
--
2060
966
2.5
u
0.5
u
2.87
2.49
28.2
8.33
633
100
U
3510
3280
106
2.44
950
859
A13
9/30/2016
5.43
2053
6270
4680
2.5
u
0.5
u
7.17
6.88
22.7
17.2
152
J
117
J
13400
13400
4.2
2.56
2360
2360
CG9
6/9/2015
6.28
23919
1020
267
2.5
u
0.5
u
2
2.07
17.9
10.3
206
J
100
U
1910
1880
15.3
2.12
701
727
CG9
9/29/2015
5.48
610
7140
4020
2.5
u
0.5
u
9.53
10.3
31.8
26.8
479
297
18300
18000
8.7
6.16
3980
3880
CG9
6/7/2016
6.50
--
1810
551
2.5
u
0.5
u
2.77
2.2
38.9
8.83
556
100
U
2780
2530
152
2.87
881
777
CG9
9/30/2016
5.27
2182
5590
3680
2.5
u
0.5
u
6.92
6.41
23.1
16.5
196
J
167
J
12600
12600
4.05
2.59
2300
2430
'smith
-------
Table 4-1
Total and Dissolved Metals for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Metal Concentrations (ng/L)
Aluminum
Arsenic
Cadmium
Copper
Iron
Manganese
Lead
Zinc
T
D
T
D
T
D
T
D
T
D
T
D
T
D
T
D
Station
Mine Location
Name
Analytical
Sample Date
Flow
pH Measurement
Date*
Flow
(gpm)
Result Q
Result
Q
Result
Q
Result Q
Result Q
Result Q
Result
Q
Result
Q
Result
Q
Result Q
Result Q
Result Q
Result
Q
Result Q
Result Q
Result Q
Columbus Mine
A10
6/9/2015
6.18
--
991
247
2.5
U
0.5
U
2.62
3.02
23.1
16.2
199
J
100
U
2100
2080
14.4
2.81
967
969
A10
9/29/2015
5.43
634
6280
3800
2.5
U
0.5
U
11.1
11.6
41.2
39.4
401
306
17500
18000
8.13
7.22
4130
4560
A10
6/7/2016
--
16137
1480
774
2.5
U
0.5
U
2.54
2.72
20.5
12.9
195
J
100
U
3160
3100
37.3
3.67
934
932
A10
9/29/2016
5.13
2387
5480
3790
2.5
U
0.5
U
7.69
7.48
30.9
25.1
204
J
136
J
13000
12700
5.66
4.31
2670
2630
AHA
6/9/2015
3.05
37
3370
3160
8.65
J
6.38
194
193
2510
2510
11700
12200
1840
1900
1010
947
47000
51200
A11A
9/29/2015
2.89
0.1
31000
29500
12
12
1090
896
6800
6790
61100
61100
17600
17900
254
289
278000
302000
A11A
6/7/2016
4.16
27
3360
3450
5.91
J
5.43
180
173
2350
2310
11300
11600
1710
1720
911
913
40300
43100
A11A
9/30/2016
2.85
0.3
25600
24900
14
11
1030
938
6960
6300
54700
51600
12400
12100
302
254
229000
223000
CG11
6/9/2015
6.26
21799
1000
222
2.5
U
0.5
U
2.11
2.28
15.8
9.39
179
J
100
U
1910
1970
10.8
1.87
696
762
CG11
9/29/2015
5.34
572
6610
3830
2.5
U
0.5
U
9.54
10.2
31.5
27.9
440
324
17700
17600
7.29
5.96
3930
3930
CG11
6/7/2016
6.46
--
1480
587
2.5
U
0.5
U
2.29
2.17
24.9
8.96
306
100
U
2690
2550
89.9
2.74
765
759
J
CG11
9/30/2016
5.34
3305
5390
3510
2.5
U
0.5
U
6.89
6.28
22.4
17.1
173
J
163
J
12200
12100
4.15
3.23
2280
2380
Silver Wing Mine
A28
6/9/2015
7.57
--
137
43.5
J
2.5
U
0.5
U
2.04
1.78
7.23
6.88
100
U
100
U
736
721
1.81
0.763
452
480
A28
9/30/2015
7.03
1754
1400
39.5
J
2.5
U
0.5
U
4.69
4.43
12.2
3.56
100
U
100
U
3870
3800
3.85
0.442
1360
1330
A28
6/28/2016
7.62
--
848
52
2.5
U
0.5
U
2.25
2.46
11.3
4.73
100
U
100
U
1850
1780
3.48
0.613
587
569
A30
6/9/2015
7.52
--
454
44.7
J
2.5
U
0.5
U
2.07
1.85
23.5
13.4
115
J
100
u
745
715
7.76
0.918
507
496
A30
9/30/2015
5.82
2503
1390
42.9
J
2.5
U
0.5
U
4.79
4.44
83.2
19.3
180
J
100
u
3810
3750
4.82
0.313
1440
1410
A30
6/7/2016
7.54
--
747
54.6
2.5
U
0.5
U
1.9
1.92
18.6
7.99
204
J
100
u
1250
1190
14.6
0.672
505
504
A29
6/9/2015
6.42
--
1380
428
99.7
2.5
U
14
14.1
6190
2320
10900
2470
3100
3120
25.8
0.5
U
3950
4010
A29
9/30/2015
5.74
--
1860
958
132
4.4
16.6
15.1
10200
4200
16000
6130
3520
3480
25.5
0.1
U
4320
4500
A29
6/7/2016
6.49
7.3
1590
762
161
2.87
16.1
16.4
6280
2730
13700
3870
3300
3170
22.7
0.1
U
4220
4260
A29
9/28/2016
--
--
1590
603
110
3.1
14.8
14.6
6970
2770
11700
2790
3290
3250
19.1
0.159
J
4020
3870
A29A
6/9/2015
6.96
--
825
31.5
J
39.7
2.5
U
13.4
13.5
3820
712
5570
100
u
3030
3040
12.8
0.5
U
3790
3830
A29A
6/7/2016
7.08
--
1800
98.5
143
1.17
J
14.7
15.3
6660
509
15600
137
J
3070
3130
61.8
0.1
TT
3900
3960
Tom Moore Mine
A30A
6/8/2016
7.29
--
659
45.8
T
2.5
U
0.5
U
1.86
1.82
15.6
6.44
201
J
100
u
1200
1120
11.5
0.582
469
474
A30A
9/29/2016
6.94
--
1740
74.2
2.5
U
0.5
U
4.25
3.98
35.2
7.45
102
J
100
u
3760
3670
3.22
0.321
1130
1030
A30B
6/8/2016
7.45
--
602
47.3
T
2.5
U
0.5
U
1.68
1.71
14.5
5.98
204
J
100
u
1100
1010
12.1
0.532
433
433
A30B
9/29/2016
6.97
7096
1810
67.5
2.5
U
0.5
U
4.09
3.98
53.4
7.79
128
J
100
u
3670
3580
3.48
0.339
1120
1020
DM22
6/28/2016
7.31
--
29.6
J
23.3
T
2.5
U
0.5
U
1.14
1.18
2.5
U
0.515
J
100
U
100
u
409
411
0.826
J
0.284
627
673
DM22
9/28/2016
--
21
27.1
T
23.9
T
2.5
U
0.5
U
0.77
J
0.811
2.5
TT
0.598
T
100
U
100
u
165
156
0.5
TT
0.1
TT
572
619
Ben Franklin
Mine
ARD1
9/29/2015
3.10
--
7180
6370
2.5
U
0.558
J
57.5
55.6
1940
1970
3560
2390
22300
22300
840
861
19900
19500
ARD1
6/28/2016
2.76
--
3860
3630
2.5
U
0.5
u
43.8
41
1990
1880
5520
5190
12700
12300
745
720
12500
12300
ARD1
9/28/2016
3.12
--
9980
9650
2.5
U
2.5
u
79.7
72.9
2690
2420
4080
3940
26000
26100
747
686
23000
24300
EG3A
9/29/2015
7.25
35
63
31.7
T
2.5
U
0.5
u
0.551
T
0.588
11.4
9.78
100
U
100
u
116
107
4.18
2.45
217
215
EG3A
6/28/2016
6.24
4657
153
87.3
2.5
U
0.5
u
3.33
3.35
12.9
11.6
100
J
100
u
633
650
2.63
0.691
1120
1210
EG3A
9/29/2016
6.94
--
31.9
T
24.1
T
2.5
U
0.5
u
0.5
TT
0.228
2.79
T
1.79
100
U
100
u
18.3
16.2
0.5
TT
0.152
T
79.8
85.7
EG5
9/30/2015
7.14
--
31.8
T
25.6
T
2.5
U
0.5
u
0.5
TT
0.535
6.27
5.53
100
U
100
u
53.2
53.2
1.68
1.12
221
228
EG5
6/28/2016
7.01
--
132
91.2
2.5
u
0.5
u
3.11
3.33
14.8
12.2
100
u
100
u
636
655
2.56
1.74
1120
1200
EG5
9/28/2016
7.70
222
96.5
64.4
2.5
u
0.5
u
1.18
1.18
12.2
8.05
100
u
100
u
144
144
3.11
1.48
493
529
A39A
6/28/2016
7.59
--
133
99
2.5
u
0.5
u
3.25
3.19
16.2
13.8
100
u
100
u
607
593
3.06
2.14
1040
1030
'smith
-------
Table 4-1
Total and Dissolved Metals for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Metal Concentrations (ng/L)
Aluminum
Arsenic
Cadmium
Copper
Iron
Manganese
Lead
Zinc
T
D
T
D
T
D
T
D
T
D
T
D
T
D
T
D
Mine Location
Station
Name
Analytical
Sample Date
PH
Flow
Measurement
Date*
Flow
(gpm)
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
TerryTunnel
A38
6/28/2016
7.14
--
66.2
63.1
2.5
u
0.5
u
0.5
u
0.148
J
2.5
u
1.26
237
J
100
u
10600
10400
2.36
0.1
u
1180
1150
A38
9/28/2016
7.07
--
82.3
76.3
2.5
u
2.5
u
0.726
J
0.5
u
2.5
u
2.5
u
940
100
u
11000
10700
8.53
0.5
u
1340
1220
A39
9/30/2015
7.10
--
118
48.8
J-
2.5
u
0.5
u
1.2
1.08
22.8
14.6
100
u
100
u
256
250
5.01
2.23
385
393
A39
6/28/2016
7.55
--
133
88.6
2.5
u
0.5
u
3.06
3.06
15.6
13.7
100
u
100
u
589
568
3.13
2.12
1000
1010
A39
9/28/2016
7.51
--
180
109
2.5
u
0.5
u
1.73
1.61
29.7
17.9
100
u
100
u
310
305
7.6
2.09
618
630
EG6
6/10/2015
7.36
--
229
91
2.5
u
0.5
u
2.69
2.69
25.8
19.7
190
J
100
u
1340
1280
6.08
1.83
1110
1080
EG6
9/30/2015
7.22
98
20
u
20
Ti"
2.5
u
0.5
u
0.71
T
0.794
3.98
T
4.22
100
u
100
u
96.8
94.3
0.869
J
0.796
430
429
EG6
6/28/2016
7.44
7133
113
80.5
2.5
"u"
0.5
u
2.07
1.94
11.4
9.09
100
TT
100
u
417
415
2.19
1.05
671
716
EG6
9/28/2016
7.48
373
112
54.5
2.5
"u"
0.5
u
1.22
1.19
13.9
9.34
100
Ti"
100
u
251
248
3.85
0.76
430
456
Pride of the West
Mine
A50
6/7/2016
7.75
--
201
36.8
T
2.5
"u"
0.5
u
11.8
12.2
54.5
16.6
209
T
100
u
401
394
42.2
7.77
2190
2130
A50
9/28/2016
7.67
--
137
39.3
T
2.5
"u"
0.5
u
7.51
7.39
26.3
9.88
122
T
100
u
239
238
17.6
4.15
1360
1350
CU4
6/7/2016
7.39
--
1380
57
2.5
"u"
0.5
u
0.5
TT
0.1
TT
2.8
T
0.723
T
1420
100
u
152
4.21
T
27.5
0.298
13.2
J
10
CU4
9/28/2016
7.45
6610
23.3
T
20
TT
2.5
u
0.5
u
0.5
u
0.1
u
6.62
0.628
j
100
TT
100
u
4.47
J
3.63
j
1.9
0.149
T
10
u
10
u
CU4A
6/7/2016
7.36
--
658
60.7
2.5
u
0.5
u
0.5
u
0.1
u
3.88
T
0.93
j
770
100
u
174
4.84
j
46.4
0.488
35.1
10
u
CU4A
9/28/2016
7.23
6739
33.9
T
20
Ti"
2.5
u
0.5
u
0.5
u
0.152
j
2.5
u
0.882
j
100
TT
100
u
6
4.03
j
1.27
0.296
24.3
28.6
Notes:
Q- qualifier
- data not available
T - total recoverable
D - dissolved
- value exceeds WQCC acute standards - value exceeds WQCC chronicstandards
J - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample
U - Indicates compound was analyzed for, but not detected in sample. Value shown is quantitation limit of method
gpm - gallons per minute * - provided if flow measurement date is different from analytical sample date
l_ig/L - micrograms per liter
'smith
Page 5 of 5
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APPENDIX A - PART 2
PRELIMINARY REMEDIAL INVESTIGATION REPORT
-------
USACE Contract No: W912DQ-15-D-3013
Task Order No: DK04
Preliminary Remedial
Investigation Report
U.S. Army Corps of Engineers
Omaha District
Interim Remedial Actions
Bonita Peak Mining District Superfund Site
San Juan County, Colorado
May 2018
%
-------
Bonita Peak Mining District Superfund Site
Interim Remedial Actions
San Juan County, Colorado
Preliminary Remedial Investigation Report
Contract No. W912DQ-15-D-3013
Task Order No.: DK04
May 2018
Prepared for:
U.S. Environmental Protection Agency
Region 8
1595 Wynkoop Street
Denver, Colorado 80202
Prepared by:
CDM Federal Programs Corporation
555 17th Street, Suite 500
Denver, Colorado 80202
Under a contract with:
U.S. Army Corps of Engineers
Omaha District
1616 Capitol Avenue
Omaha, Nebraska 68102
-------
Table of Contents
Section 1 Introduction 1-1
1.1 Site Description and Background 1-1
1.1.1 Site Location and Setting 1-1
1.1.2 Site Mining History 1-2
1.1.3 NPL Listing 1-3
1.1.4 Climate 1-3
1.1.5 Geology 1-3
1.1.5.1 Stratigraphy 1-3
1.1.5.2 Ore Mineralization 1-4
1.1.5.3 Soils 1-4
1.1.6 Surface Water Hydrology 1-6
1.1.6.1 Mineral Creek Drainage Basin 1-6
1.1.6.2 Cement Creek Drainage Basin 1-6
1.1.6.3 Upper Animas River Drainage Basin 1-6
1.1.7 Subsurface Hydrogeology 1-7
1.2 Report Organization 1-7
Section 2 Previous Investigations and Data Presented 2-1
2.1 Sampling Summaries 2-1
2.1.1 1996-2000 USGS Sampling and Analysis 2-1
2.1.2 1997-1999 CDMG Sampling 2-2
2.1.3 2015 EPA/ESAT Sampling 2-2
2.1.4 2016 EPA/ESAT Sampling 2-3
Section 3 Contaminant Sources, Fate, and Transport 3-1
3.1 Contaminated Environmental Media 3-1
3.1.1 Solid Media 3-1
3.1.1.1 Mine Waste 3-1
3.1.1.2 Sediment 3-1
3.1.1.3 Contaminated Soil 3-1
3.1.2 Aqueous Media 3-1
3.1.2.1 Mining-Influenced Water 3-1
3.1.2.2 Surface Water 3-2
3.1.2.3 Groundwater 3-2
3.2 Fate and Transport of Contaminants 3-2
3.2.1 Overview of Fate and Transport 3-2
3.2.2 Fate and Transport Pathways Related to IRA Implementation 3-4
Section 4 Preliminary Evaluation of Environmental Data 4-1
4.1 Screening Criteria for Affected Media 4-1
4.2 Sampling Results at Mining-Related Sources - Mineral Creek Headwaters 4-3
4.2.1 Longfellow Mine 4-3
4.2.1.1 Longfellow Mine Surface Water 4-4
%Sih
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Table of Contents
4.2.1.2 Longfellow Mine CDMG and EPA/ESAT Waste Rock SPLP 4-4
4.2.1.3 Longfellow Mine Soils, Waste Rock, and Sediment 4-4
4.2.2 Junction Mine 4-4
4.2.2.1 Junction Mine Adit Discharge 4-5
4.2.2.2 Junction Mine CDMG and EPA/ESAT Waste Rock SPLP 4-5
4.2.2.3 Junction Mine Soils, Waste Rock, and Sediment 4-5
4.2.3 Koehler Tunnel 4-5
4.2.3.1 Koehler Tunnel Adit Discharge and Surface Water 4-6
4.2.3.2 Koehler Tunnel CDMG and EPA/ESAT Waste Rock SPLP 4-6
4.2.3.3 Koehler Tunnel Soils, Waste Rock, and Sediment 4-6
4.3 Sampling Results at Mining-Related Sources - Browns Gulch 4-7
4.3.1 Brooklyn Mine 4-7
4.3.1.1 Brooklyn Mine Adit Discharge and Surface Water 4-7
4.3.1.2 Brooklyn Mine CDMG and EPA/ESAT Waste Rock SPLP 4-8
4.3.1.3 Brooklyn Mine Soils, Waste Rock, and Sediment 4-8
4.4 Sampling Results at Mining-Related Sources - South Fork Mineral Creek 4-8
4.4.1 Bandora Mine 4-8
4.4.1.1 Bandora Mine Adit Discharge and Surface Water 4-9
4.4.1.2 Bandora Mine CDMG and EPA/ESAT Waste Rock SPLP 4-9
4.4.1.3 Bandora Mine Soils, Waste Rock, and Sediment 4-9
4.5 Sampling Results at Mining-Related Sources - Upper Cement Creek 4-10
4.5.1 Grand Mogul Mine 4-10
4.5.1.1 Grand Mogul Mine Adit Discharge and Surface Water 4-10
4.5.1.2 Grand Mogul Mine CDMG and EPA/ESAT Waste Rock SPLP 4-11
4.5.1.3 Grand Mogul Mine Soils, Waste Rock, and Sediment 4-11
4.6 Sampling Results at Mining-Related Sources - Gladstone Area 4-12
4.6.1 Natalie/Occidental Mine 4-12
4.6.1.1 Natalie/Occidental Mine Adit Discharge and Surface Water 4-12
4.6.1.2 Natalie/Occidental Mine CDMG and EPA/ESAT Waste Rock SPLP 4-13
4.6.1.3 Natalie/Occidental Mine Soils, Waste Rock, and Sediment 4-13
4.7 Sampling Results at Mining-Related Sources - Lower Cement Creek 4-13
4.7.1 Henrietta Mine 4-13
4.7.1.1 Henrietta Mine Adit Discharge and Surface Water 4-13
4.7.1.2 Henrietta Mine CDMG and EPA/ESAT Waste Rock SPLP 4-14
4.7.1.3 Henrietta Mine Soils, Waste Rock, and Sediment 4-14
4.7.2 Mammoth Tunnel 4-14
4.7.3 Anglo Saxon Mine 4-15
4.7.3.1 Anglo Saxon Mine Adit Discharge and Surface Water 4-15
4.7.3.2 Anglo Saxon Mine CDMG and EPA/ESAT Waste Rock SPLP 4-16
4.7.3.3 Anglo Saxon Mine Soils, Waste Rock, and Sediment 4-16
4.7.4 Yukon Tunnel 4-16
4.7.4.1 Yukon Tunnel Adit Discharge and Surface Water 4-17
4.7.4.2 Yukon Tunnel CDMG and EPA/ESAT Waste Rock SPLP 4-17
4.7.4.3 Yukon Tunnel Soils, Waste Rock, and Sediment 4-17
4.8 Sampling Results at Mining-Related Sources - Burrows Creek 4-18
4.8.1 Boston Mine 4-18
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Table of Contents
4.8.1.1 Boston Mine Surface Water 4-18
4.8.1.2 Boston Mine Leachate 4-18
4.8.1.3 Boston Mine Soils, Waste Rock, and Sediment 4-19
4.8.2 London Mine 4-19
4.8.2.1 London Mine Surface Water 4-19
4.8.2.2 London Mine Leachate 4-20
4.8.2.3 London Mine Soils, Waste Rock, and Sediment 4-20
4.8.3 Ben Butler Mine 4-20
4.8.3.1 Ben Butler Mine Adit Discharge and Surface Water 4-20
4.8.3.2 Ben Butler Mine CDMG and EPA/ESAT Waste Rock SPLP 4-20
4.8.3.3 Ben Butler Mine Soils, Waste Rock, and Sediment 4-21
4.9 Sampling Results at Mining-Related Sources - Animas River Headwaters 4-21
4.9.1 Mountain Queen Mine 4-21
4.9.1.1 Mountain Queen Mine Adit Discharge and Surface Water 4-21
4.9.1.2 Mountain Queen Mine CDMG and EPA/ESAT Waste Rock SPLP 4-22
4.9.1.3 Mountain Queen Mine Soils, Waste Rock, and Sediment 4-22
4.9.2 Vermillion Mine 4-22
4.9.2.1 Vermillion Mine Adit Discharge and Surface Water 4-22
4.9.2.2 Vermillion Mine CDMG and EPA/ESAT Waste Rock SPLP 4-23
4.9.2.3 Vermillion Mine Soils, Waste Rock, and Sediment 4-23
4.9.3 Sunbank Group Mine 4-23
4.9.3.1 Sunbank Group Mine Surface Water 4-23
4.9.3.2 Sunbank Group Mine Leachate 4-24
4.9.3.3 Sunbank Group Mine Soils, Waste Rock, and Sediment 4-24
4.9.4 Frisco/Bagley Tunnel 4-24
4.9.4.1 Frisco/Bagley Tunnel Adit Discharge and Surface Water 4-25
4.9.4.2 Frisco/Bagley Tunnel CDMG and EPA/ESAT Waste Rock SPLP 4-25
4.9.4.3 Frisco/Bagley Tunnel Soils, Waste Rock, and Sediment 4-26
4.9.5 Columbus Mine 4-26
4.9.5.1 Columbus Mine Adit Discharge and Surface Water 4-26
4.9.5.2 Columbus Mine CDMG and EPA/ESAT Waste Rock SPLP 4-27
4.9.5.3 Columbus Mine Soils, Waste Rock, and Sediment 4-27
4.10 Sampling Results at Mining-Related Sources - Animas Forks to Eureka 4-27
4.10.1 Campground 7 4-27
4.10.1.1 Campground 7 Waste Rock 4-28
4.10.2 Silver Wing Mine 4-28
4.10.2.1 Silver Wing Mine Surface Water 4-28
4.10.2.2 Silver Wing Mine Leachate 4-29
4.10.2.3 Silver Wing Mine Soils, Waste Rock, and Sediment 4-29
4.10.3 Tom Moore Mine 4-29
4.10.3.1 Tom Moore Mine Adit Discharge and Surface Water 4-29
4.10.3.2 Tom Moore Mine CDMG and EPA/ESAT Waste Rock SPLP 4-30
4.10.3.3 Tom Moore Mine Soils, Waste Rock, and Sediment 4-30
4.11 Sampling Results at Mining-Related Sources - Eureka Gulch 4-30
4.11.1 Ben Franklin Mine 4-30
4.11.1.1 Ben Franklin Mine Adit Discharge and Surface Water 4-31
cStfm
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Table of Contents
4.11.1.2 Ben Franklin Mine CDMG and EPA/ESAT Waste Rock SPLP 4-31
4.11.1.3 Ben Franklin Mine Soils, Waste Rock, and Sediment 4-31
4.11.2 Terry Tunnel 4-32
4.11.2.1 Terry Tunnel Adit Discharge and Surface Water 4-32
4.11.2.2 Terry Tunnel CDMG and EPA/ESAT Waste Rock SPLP 4-32
4.11.2.3 Terry Tunnel Soils, Waste Rock, and Sediment 4-32
4.12 Sampling Results at Mining-Related Sources - Cunningham Gulch 4-33
4.12.1 Pride of the West Mine 4-33
4.12.1.1 Pride of the West Mine Adit Discharge and Surface Water 4-33
4.12.1.2 Pride of the West Mine CDMG and EPA/ESAT Waste Rock SPLP 4-33
4.12.1.3 Pride of the West Mine Soils, Waste Rock, and Sediment 4-33
4.13 Sampling Results at Mining-Related Sources - Howardsville to Silverton 4-34
4.13.1 Campground 4 4-34
4.13.1.1 Campground 4 CDMG Waste Rock SPLP 4-34
4.13.1.2 Campground 4 Waste Rock 4-34
Section 5 References 5-1
List of Exhibits
Exhibit 1-1 Soil Map Units within Mining-Related Sources 1-5
Exhibit 3-1 ARD and AMD Generation and Migration 3-4
Exhibit 4-1 Soils and Waste Rock Metals Human Health Risk-Based Levels 4-3
Exhibit 4-2 Sediments Metals Screening Levels 4-3
List of Figures
Figure 1-1 Site Location Map
Figure 1-2 Mining-Related Sources - Mineral Creek Drainage Basin
Figure 1-3 Mining-Related Sources - Cement Creek Drainage Basin
Figure 1-4 Mining-Related Sources - Upper Animas Area Drainage Basin
Figure 4-1 Longfellow Mine, Junction Mine, and Koehler Tunnel
Figure 4-2 Brooklyn Mine
Figure 4-3 Bandora Mine
Figure 4-4 Grand Mogul Mine
Figure 4-5 Natalie/Occidental Mine
Figure 4-6 Henrietta Mine
Figure 4-7 Mammoth Tunnel
Figure 4-8 Anglo Saxon Mine
Figure 4-9 Yukon Tunnel
Figure 4-10 Boston Mine
Figure 4-11 London Mine
Figure 4-12 Ben Butler Mine
Figure 4-13 Mountain Queen Mine
iv
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Table of Contents
Figure 4-14 Vermillion Mine
Figure 4-15 Sunbank Group Mine
Figure 4-16 Frisco/Bagley Tunnel
Figure 4-17 Columbus Mine
Figure 4-18 Campground 7
Figure 4-19 Silver Wing Mine
Figure 4-20 Tom Moore Mine
Figure 4-21 Ben Franklin Mine
Figure 4-22 Terry Tunnel
Figure 4-23 Pride of the West Mine
Figure 4-24 Campground 4
List of Tables
Table 2-1 Evaluation Summary of Existing Data Reports
Table 4-1 Total and Dissolved Metals for 2015 and 2016 EPA/ESAT Surface Water Samples
Table 4-2 CDMG Waste Rock Volume and Leachability Metals
Table 4-3 Total Metals Concentrations for 2016 and 2016 EPA/ESAT SPLP Samples
Table 4-4 Total Recoverable Metals Concentrations for 2015 and 2016 EPA/ESAT Waste Rock
and Soil Samples
Table 4-5 Metals Concentrations for 2016 EPA/ESAT Sediment Samples
Attachments
Attachment A Total and Dissolved Metals, Anions, Alkalinity, and Hardness Data for 2015 and 2016
EPA/ESAT Surface Water Samples
Attachment B Total Recoverable Metals Concentrations for 2015 and 2016 EPA/ESAT Waste Rock
and Soil Samples
%
-------
Table of Contents
Acronyms and Abbreviations
A1 aluminum
AMD acid-mine drainage
ARD acid-rock drainage
As arsenic
Au gold
BPMD Bonita Peak Mining District
Cd cadmium
CDM Smith CDM Federal Programs Corporation
CDMG Colorado Division of Minerals and Geology
CDPHE Colorado Department of Public Health and the Environment
CERCLAComprehensive Environmental Response, Compensation, and Liability Act
Cfs
CGS
Cu
cy
DRMS
IRA
EPA
ESAT
Fe
FFS
gpm
GPS
Hg
HRS
mg/kg
mg/L
MIW
ml
Mn
NGVD29
NOAA
NPL
NRCS
Pb
RI
Site
SPLP
su
TechLaw
TVS
USACE
USGS
WQCC
Zn
mI/l
cubic feet per second
Colorado Geological Survey
copper
cubic yard
Colorado Division Reclamation, Mining and Safety
interim remedial action
U.S. Environmental Protection Agency
Environmental Services Assistance Team
iron
focused feasibility study
gallons per minute
global positioning system
mercury
Hazard Ranking System
milligrams per kilogram
milligrams per liter
mining-influenced water
milliliter
manganese
National Geodetic Vertical Datum of 1929
National Oceanic and Atmospheric Administration
National Priorities List
U.S. Department of Agriculture Natural Resource Conservation Service
lead
remedial investigation
BPMD Superfund Site
synthetic precipitation leaching procedure
standard units
TechLaw, Inc.
table value standard
U.S. Army Corps of Engineers
U.S. Geological Survey
Water Quality Control Commission
zinc
ftopM'phfrtfer
VI
smitfi
-------
Section 1
Introduction
This preliminary remedial investigation (RI) report for the Bonita Peak Mining District (BPMD)
Superfund Site (Site) in San Juan County, Colorado was prepared by CDM Federal Programs
Corporation (CDM Smith) for the U.S. Army Corps of Engineers (USACE) Omaha District on behalf
of the U.S. Environmental Protection Agency (EPA) Region 8. This preliminary RI was prepared as
part of Task Order No. DK04 under USACE Contract No. W912DQ-15-D-3013 and was generally
developed in accordance with the National Oil and Hazardous Substances Pollution Contingency
Plan (40 Code of Federal Regulations 300.430(e)) and EPA's Guidance for Conducting Remedial
Investigations and Feasibility Studies under CERCLA (EPA 1988). This preliminary RI is intended to
meet the requirements of a preliminary site characterization summary detailed in EPA 1988 and
includes a summary of site data collected under the initial field sampling program.
The Hazard Ranking System documentation record for the Site (EPA 2016a) indicated there are
48 mining-related sources where ongoing characterization and risk evaluation is needed to
determine whether and what additional actions under the Comprehensive Environmental
Response, Compensation, and Liability Act (CERCLA) may be appropriate. The Site-wide RI and
risk assessments are ongoing and will provide information to guide Site-wide objectives. EPA is
taking an adaptive management approach to the Site, and data and observations from the initial
characterization identified 26 mining-related sources (including two dispersed campground
areas) with contaminant migration issues that could be initially addressed through interim
remedial actions (IRAs) while the Site-wide RI is ongoing.
The purpose of this preliminary RI report is to summarize the available data and document the
current understanding of the nature of mining-related contamination associated with 26 of the
mining-related sources under consideration for IRAs, in support of the focused feasibility study
(FFS).
1.1 Site Description and Background
This section presents an overview of the general Site location, climate, and history. Figure 1-1
shows the general location of the Site.
1.1.1 Site Location and Setting
The Site is centered in southwestern Colorado in San Juan County. It spans across five different
U.S. Geological Survey (USGS) 7.5-Minute Topographic Quadrangles including Handies Peak,
Howardsville, Ironton, Ophir, and Silverton (USGS 2016a through 2016e). Within the Site, there
are three main drainages (Mineral Creek, Cement Creek, and Upper Animas River) that flow into
the Animas River at Silverton, Colorado as shown in Figures 1-2,1-3, and 1-4, respectively.
Mineral Creek originates at the top of Red Mountain Pass and flows approximately 9.3 miles
before entering the Animas River southwest of Silverton. Cement Creek is approximately 8 miles
long, flowing from north to south before the confluence with the Animas River at Silverton
(Herron et al. 1998). The Upper Animas River begins approximately 14 miles northeast of
1-1
-------
Section 1 • Introduction
Silverton. After the three main drainages combine as the Animas River, it flows south from
Silverton to Durango, Colorado, crosses into New Mexico, and joins the San Juan River in
Farmington, New Mexico.
Formed from Pleistocene glaciation and Holocene erosion, the terrain of the western San Juan
Mountains is steep and rugged (USGS 2007a). The elevation ranges from approximately 9,500
feet National Geodetic Vertical Datum of 1929 (NGVD29) at the Mayflower Tailings to 12,800 feet
NGVD29 at the Mountain Queen Mine, the highest mining-related source at the Site.
1.1.2 Site Mining History
The three main drainages within the Site contain some 400 abandoned or inactive mines where
large- to small-scale mining operations occurred. San Juan County is comprised of 10 historic
mining districts (Colorado Geological Survey [CGS] 2017a). Historic mining districts within the
Mineral Creek, Cement Creek, and Upper Animas River drainages (referred to as "the mining
districts") include Animas, Animas Forks, Cement Creek, Eureka, Ice Lake Basin, and Mineral
Point The discovery of gold and silver brought miners to the Silverton area and the Animas
Mining District in the early 1870s. In the late 1870s and early 1880s, the completion of roads,
railroads, and construction of a smelter in Durango encouraged mining operations. The discovery
of silver in the base-metal ores was the major factor in establishing Silverton as a permanent
settlement (TechLaw, Inc. [TechLaw] 2017). Between 1870 and 1890, the richer ore deposits
were discovered and mined to the extent possible. Not until 1890 was any serious attempt made
to mine and concentrate the larger low-grade ore bodies in the area. By 1900, there were 12
concentration mills in the valley sending products to the Kendrick and Gelder Smelter near the
mouth of Cement Creek. Mining and milling operations slowed down circa 1905, and mines were
consolidated into fewer and larger operations with the facilities for milling large volumes of ore.
After 1907, mining and milling continued throughout the basin whenever prices were favorable
(TechLaw 2017).
Gladstone, located about eight miles upstream of Silverton on Cement Creek, is the site of a
historic mining town developed in the 1880s commensurate with the onset of mining in the
surrounding area. The town was the central location and railroad terminus for the milling and
shipping of mine ores from the surrounding 3-square-mile valley. The town declined in the 1920s
and no remnants of the town remain.
Eureka is located approximately 8 miles northeast of Silverton at the confluence of Upper Animas
River and Eureka Gulch. Some of the mines located up Eureka Gulch include Sunnyside Mine,
Clipper Mine, Ben Franklin Mine, Bavarian Mine, Midway Mine, Moonbeam Mine, and Ransom
Mine (Herron etal. 2000). The Sunnyside Flotation Mill in Eureka was built in 1917 with a 600-
ton-per-day capacity. Two settling ponds were built in the Animas River valley but after the mill
was abandoned in 1949, the tailings dams were partially washed out and tailings were washed
down the Animas River (Church et al. 2007). By the 1970s, only one year-round active mine
(Sunnyside Mine) remained in the county (CGS 2017b). This mine ceased production in 1991.
Animas Forks, named for the three forks of the Animas River, is located 12 miles northeast of
Silverton in San Juan County, CO and was first established in 1874. There were numerous mines
located upstream of Animas Forks. The town started to decline in 1910 when the Gold Prince Mill
ceased operation and became a ghost town in the 1920s.
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Section 1 • Introduction
1.1.3 NPL Listing
The Site was proposed for addition to the National Priorities List in April 2016 and the listing
became effective in September 2016 (EPA 2016c).
1.1.4 Climate
The portions of the Site within San Juan County have a subalpine to alpine climate with snowy,
cold winters and cool summers. In the subalpine climate region, the minimum and maximum mean
temperatures for January and July are 2 degrees Fahrenheit (°F)/32°F and 40°F/74°F, respectively
(Chapman et al. 2006). In the alpine climate region, the minimum and maximum mean
temperatures for January and July are minus 8°F/24°F and 36°F/72°F, respectively (Chapman et
al. 2006).
Long-term climate data, including precipitation, for Silverton, Colorado has been collected by a
participating National Weather Service Cooperative Observing Program weather station. The
National Oceanic and Atmospheric Administration (NOAA) has a record of climate data for the
Silverton, Colorado station dating back to 1905 (NOAA 2018). The weather station is currently
located at a latitude of 37.809 North and a longitude of 107.663 West In 2016, the Silverton
station recorded annual precipitation of approximately 19 inches (NOAA 2018). The greatest
amount of snowfall is between November and April, with an average snowfall of 12 feet per year
(EPA 2016b).
1.1.5 Geology
The geology of the Site within San Juan County is relevant to the assessment of the
hydro geological framework and understanding of potential source materials present. Therefore,
this section focuses on the description of the bedrock geology and ore mineralization. Other
aspects of the Site geology were described by Yager and Bove (USGS 2007a), Burbank and Luedke
(1969), and Free et al. (1989).
1.1.5.1 Stratigraphy
The Site is centered in the western San Juan Mountains in the area of the Silverton and San Juan
calderas. The younger Silverton caldera is situated within the older San Juan caldera, forming
between approximately 28 and 27 million years ago (USGS 2007a). During and after the caldera
formation period, volcanotectonic events occurred that introduced extensive Tertiary-aged volcanic
rock and extensive mineralization within fractured host rock (USGS 2007b). Volcanic formations of
the San Juan volcanic field cover land north and east of the Silverton caldera. Comprised of
pyroclastic rocks and lava flows, the San Juan volcanic field lies on the Paleozoic and Mesozoic rock
formation (Free etal. 1989).
The general stratigraphy in the region consists of Precambrian crystalline basement, Paleozoic to
Tertiary sedimentary rocks, Tertiary volcanic rocks, and Quaternary deposits (USGS 2007a).
¦ Precambrian rocks underlie the Site but are only exposed at the surface south of Silverton
along the Animas River and Cunningham Creek (USGS 2007b). These generally consist of
amphibolite, schist, and gneiss. Mineral phases in these rocks have high acid-neutralizing
capacity and influence water-rock interactions (USGS 2007a).
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Section 1 • Introduction
¦ Paleozoic, Mesozoic, and Tertiary sedimentary rocks are primarily exposed south of
Silverton along the Animas River and west in the basins draining South Fork Mineral Creek
(USGS 2007a). These units are of varying thicknesses and compositions including
conglomerates, sandstones, siltstones, shales, limestones, and other types of sedimentary
rocks as discussed in Yager and Bove (USGS 2007a).
¦ Tertiary volcanic rocks comprise the bulk of the exposed rocks in the region. Tertiary
volcanism began approximately 35 Ma with deposition of the San Juan Formation via lava
flows, eruptions forming the San Juan and Silverton calderas and subsequent collapse, and
additional lava flows depositing the Silverton Volcanics Group (USGS 2007a). An extensive
system of faults and veins characterize the San Juan and Silverton calderas.
• Most of the Site is located in the collapsed Silverton caldera within the Silverton
Volcanic Group (Free et al. 1989, Herron et al. 2000). Three main volcanic units
compose the caldera fill (Free etal. 1989):
o The Eureka Tuff is the lowest formation in the Silverton Volcanic Group and is a
lithic rhyolitic ashflow tuff.
o The Burns Formation is fairly uniform and most commonly composed of rhyodacite,
ridged quartz-latic flows, and flow breccias and tuffs (Burbank and Luedke 1969,
Free etal. 1989).
o The Henson Formation is the uppermost formation in the Silverton Volcanic Group,
primarily andestitic pyroclastites. An irregular fracture system formed in this
member, characterized by layers of volcanic breccias, lapillite, and tuffite.
¦ Quaternary surficial deposits are the result of glaciation and weathering of bedrock in the
headwaters of subbasins. The surficial deposits are either acid generating or acid
neutralizing depending on their bedrock source (USGS 2007a).
1.1.5.2 Ore Mineralization
Research conducted by Free et al. is the main source of mineralization information. Their
research shows that mineralization occurred in two main phases 23 and 11 Ma (Free et al. 1989).
Base metal mineralization occurred first, during recurring volcanic activity near a quartz -
monzonite stock in the southern caldera region. Gold (Au) was mineralized epithermally from
heat generated by movement of the Red Mountain porphyry stock, which is located in the north-
central caldera region. It is hypothesized that meteoric hydrothermal solutions from the Red
Mountain Stock funneled through the open fracture system, causing several Au-concentrating
alterations. At the Site, Au was concentrated in lodes, which are ore veins in fissures and between
layers of rock.
1.1.5.3 Soils
Soil map units were reviewed for mining-related sources using soil survey areas from the U.S.
Department of Agriculture Natural Resource Conservation Service (NRCS) (NRCS 2016).
These soil map units are based on landscape-scale similarities observed in parent material,
general soil characteristics, elevation, precipitation, position within the landscape, and vegetation.
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Section 1 • Introduction
Soil surveys are generated at a 1:24,000 scale and any enlargement of maps beyond the scale of
mapping could result in a decrease in accuracy of soil line placement Due to the size of the
mining-related sources and the methodology used to map soil units, some variations could be
expected.
Based on the soil survey areas, the soil map units listed in Exhibit 1-1 were identified within the
mining-related sources evaluated in this preliminary RI.
Exhibit 1-1 Soil Map Units within Mining-Related Sources
Mineral Creek Drainage Basin
Longfellow Mine
250 - Snowdon-Rock outcrop complex, 30 to 65 percent slopes
Junction Mine
250 - Snowdon-Rock outcrop complex, 30 to 65 percent slopes
Koehler Tunnel
250 - Snowdon-Rock outcrop complex, 30 to 65 percent slopes
Brooklyn Mine
250 - Snowdon-Rock outcrop complex, 30 to 65 percent slopes
Bandora Mine
162 - Quazar-Varden complex, 15 to 65 percent slopes
Cement Creek Drainage Basin
Grand Mogul Mine
337 - Whitecross-Rock outcrop complex, 45 to 75 percent slopes
Natalie/Occidental Mine
339 - Henson very gravelly loam, 30 to 60 percent slopes
Henrietta Mine
337 - Whitecross-Rock outcrop complex, 45 to 75 percent slopes
Mammoth Tunnel
54 - Quazar very cobbly loam, 5 to 25 percent slopes; 250 - Snowdon-Rock outcrop
complex, 30 to 65 percent slopes
Anglo Saxon Mine
331 - Needleton stony loam, 30 to 65 percent slopes
Yukon Tunnel
331 - Needleton stony loam, 30 to 65 percent slopes
Upper Animas River Drainage Basin
Boston Mine
337 - Whitecross-Rock outcrop complex, 45 to 75 percent slopes
London Mine
56 - Typic Cryaquents-Cryaquolls-Cryofibrists complex, 0 to 5 percent slopes; 342 -
Telluride-Rock outcrop complex, 15 to 45 percent slopes; 337 - Whitecross-Rock outcrop
complex, 45 to 75 percent slopes
Ben Butler Mine
342 - Telluride-Rock outcrop complex, 15 to 45 percent slopes
Mountain Queen Mine
339 - Henson very gravelly loam, 30 to 60 percent slopes
Vermillion Mine
337 - Whitecross-Rock outcrop complex, 45 to 75 percent slopes
Sunbank Group Mine
339 - Henson very gravelly loam, 30 to 60 percent slopes
Frisco/Bagley Tunnel
337 - Whitecross-Rock outcrop complex, 45 to 75 percent slopes; 56 - Typic Cryaquents-
Cryaquolls-Cryofibrists complex, 0 to 5 percent slopes
Columbus Mine
337 - Whitecross-Rock outcrop complex, 45 to 75 percent slopes; 54 - Quazar very cobbly
loam, 5 to 25 percent slopes
Campground 7
162 - Quazar-Varden complex, 15 to 65 percent slopes
Silver Wing Mine
162 - Quazar-Varden complex, 15 to 65 percent slopes
Tom Moore Mine
162 - Quazar-Varden complex, 15 to 65 percent slopes
Ben Franklin Mine
340 - Moran very gravelly loam, 10 to 30 percent slopes
Terry Tunnel
343 - Telluride-Rock outcrop complex, 45 to 75 percent slopes
Pride of the West Mine
251 - Rock outcrop-Snowdon complex, 45 to 75 percent slopes
Campground 4
57 - Howardsville gravelly loam, 1 to 6 percent slopes
iOnly significant soil map units have been indicated; other soil map units may be present but have minimal extents
within the mining-related sources.
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Section 1 • Introduction
1.1.6 Surface Water Hydrology
The Animas River watershed extends from the mountainous terrain in San Juan County, Colorado,
south into the San Juan River in Northern New Mexico (URS Operating Services 2012). The three
major tributaries of the Animas River in San Juan County include Mineral Creek, Cement Creek,
and the Upper Animas River. Cement Creek enters the Upper Animas River on the east side of
Silverton, Colorado. About 1 mile downstream from that confluence, Mineral Creek enters the
Upper Animas River south of town. The three major tributaries are briefly described in this
section.
1.1.6.1 Mineral Creek Drainage Basin
The Mineral Creek gaging station (Station 09359010) is located at Silverton, Colorado at elevation
9,246 feetNGVD29 (USGS 2018a). The drainage area is 52.3 square miles (33,472 acres) (USGS
2018a). The stream gage location is shown on Figure 1-1. Daily stream discharge values have
been recorded and averaged since 1991. The highest discharge occurs in June, with a monthly
average flow of 389 cubic feet per second (cfs). The lowest discharges occur throughout January
and February, with monthly average flows of 21 to 22 cfs, respectively (USGS 2018a).
1.1.6.2 Cement Creek Drainage Basin
The Cement Creek watershed area is 20.1 square miles (12,864 acres) (USGS 2018b). Cement
Creek occurs within the northern portion of the Animas River watershed. The Cement Creek USGS
stream gage at Silverton, Colorado (Station 09358550) is located near the confluence of Cement
Creek and the Animas River, at elevation 9,380 feetNGVD29 (USGS 2018b). The stream gage
location is shown on Figure 1-1. Daily stream discharge values have been recorded and averaged
since 1991. The highest discharge occurs in June, with a monthly average flow of 131 cfs. The
lowest discharges occur throughout January and February, with monthly average flows of 13 cfs
for both months (USGS 2018b).
1.1.6.3 Upper Animas River Drainage Basin
USGS gaging station 09358000 is located approximately 700 feet upstream from the confluence of
Cement Creek and the Animas River, at elevation 9,290 feetNGVD29 (USGS 2018c). The
watershed area of the Animas River at Silverton measured from this station is 70.6 square miles
(45,184 acres) (USGS 2018c). The stream gage location is shown on Figure 1-1. Daily stream
discharge values have been recorded and averaged since 1991. The highest discharge occurs in
June, with a monthly average flow of 503 cfs. The lowest discharges occur throughout January
and February, with monthly average flows of 24 to 26 cfs, respectively (USGS 2018c).
USGS gaging station 09359020 is located about 0.7 miles downstream from the confluence of
Mineral Creek and the Upper Animas River, at elevation 9,199 feetNAVD88 (USGS 2018d). The
watershed area of the Animas River below Silverton measured from this station is 146 square
miles (93,440 acres) (USGS 2018d). The stream gage location is shown on Figure 1-1. Daily
stream discharge values have been recorded and averaged since 1991. The highest discharge
occurs in June, with a monthly average flow of 1,050 cfs. The lowest discharges occur throughout
January and February, with monthly average flows of 60 and 64 cfs, respectively (USGS 2018d).
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Section 1 • Introduction
1.1.7 Subsurface Hydrogeology
Years of mining and the installation of bulkheads has significantly influenced bedrock
groundwater elevations within the Site. Historically, groundwater flowed along fractures and
faults, with minimal leakage through bedrock, likely due to low primary permeability. With the
advent of underground mining, bedrock groundwater that once followed natural fractures
instead followed the new path of least resistance—the networks of tunnels in the underground
mine workings. Thus, drainage and haulage tunnels form preferential flow paths for bedrock
groundwater.
Permeability in the bedrock generally decreases with depth, as the overburden pressure
increases, forming a near-surface aquifer within interconnected fractures and joints (Stover
2007). Additionally, permeability is greater within the welded tuffs such as the layer dividing the
upper and lower members of the Burns Formation (Simon Hydro-Search 1993). Major fractures
(secondary permeability) serve as one of the main conduits for groundwater flow through the
bedrock system and between mine workings. It is understood that water emanating from adits
originated from the bedrock groundwater systems at the Site, but the IRAs contemplated would
not address sources of contamination within the bedrock groundwater systems or within mine
workings. Thus, bedrock groundwater will not be discussed further in this report.
The presence and/or extent of perched groundwater in overburden material or alluvial
groundwater is not currently known at the mining-related sources described in the FFS and no
groundwater analytical data are available for these mining-related sources. Thus, it is unknown
whether perched overburden groundwater or alluvial groundwater is present at the mining-
related sources.
1.2 Report Organization
The preliminary RI report is organized in a manner that generally conforms to EPA guidance
(EPA 1988) and includes five sections as follows:
¦ Section 1 - Introduction. Provides the purpose and organization of the report, a brief
description of the Site location and layout, and a summary of mining and regulatory
activities conducted to date at the Site.
¦ Section 2 - Previous Investigations and Data Presented. Provides a summary of Site
investigations and data presented in this report
¦ Section 3 - Contaminant Sources, Fate and Transport Provides definitions of the
contaminated environmental media presented in this report and provides a discussion of
the processes that transform solid phase metals and metalloids into mobile forms, and the
transport pathways that create potential for harm to humans and aquatic life.
¦ Section 4 - Preliminary Evaluation of Environmental Data. Provides a discussion of the
environmental data presented for each of the 26 mining-related sources discussed in this
report.
¦ Section 5 - References. References and documents referred to in this report.
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Section 2
Previous Investigations and Data Presented
This section provides a summary and brief discussion of select previous sampling efforts and Site
investigations completed by EPA/Environmental Services Assistance Team (ESAT), the Colorado
Division of Minerals and Geology (CDMG), and U.S. Geological Survey (USGS), which are presented
in this report It should be noted that Site investigations are ongoing; the data presented in this
report are not intended to provide a complete characterization of the individual mining-related
sources nor the complete nature and extent of contamination.
References to previous reports are included where appropriate to provide Site background
information and summarize historical conditions. Readily available data sets judged to be valid
and usable were compiled and summarized in this report, with a focus on the data collected by
EPA/ESAT in 2015 and 2016 (TechLaw 2016, 2017). The EPA/ESAT data are expected to be most
representative of recent conditions at the mining-related sources discussed in this report. Data
collected previously on waste rock leachability and estimated waste rock volumes collected by
CDMG and USGS are also presented, as these data are expected to still be representative of
current Site conditions. Table 2-1 presents a summary of the data sources used in this report and
includes an evaluation of the usability of these secondary data sources.
2.1 Sampling Summaries
The following summarizes field activities completed by EPA/ESAT, CDMG, and USGS.
2.1.11996-2000 USGS Sampling and Analysis
Field sampling by USGS of mine waste, mill tailings, and adit drainages at mining-related sources
in the Animas River, Cement Creek, and Mineral Creek basins with subsequent reporting (Church
et al. 2007) will be partly discussed in Section 4 of this preliminary RI report, specifically the
estimated sizes of mine waste materials at each of the mining-related sources. A summary of the
work is as follows:
¦ The purpose of the study was to describe the magnitude of contamination contributed by
mine-adit water, mine-waste dumps, and mill tailings on public land.
¦ Visits were conducted at more than 300 mines.
¦ Mine-waste dump and mill-tailings samples were collected from 97 mine waste dump sites
and 18 mill tailings sites, and 20 samples of unmined, altered rock were also collected.
These samples of mine-waste dump material, mill tailings, and altered rocks were studied
using a passive leach method.
¦ The size of mine-waste dumps at mines was estimated using length, width, and thickness.
¦ Surface water samples were collected at 108 mine portals and mine waste dumps.
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Section 2 • Previous Investigations and Data Presented
¦ Annually, from 1997 to 2000, observations and sampling of mine adit locations was
conducted in late August or early September during low-flow conditions.
2.1.2 1997-1999 CDMG Sampling
Field sampling by CDMG of mines in the Animas River above Eureka, Animas River below Eureka,
Cement Creek, and Mineral Creek basins with subsequent reporting occurred between 1997 and
2000 (Herron et al. 1997,1998,1999, and 2000). This data will be discussed in Section 3 of this
preliminary RI report A summary of the work is as follows:
¦ Water samples were collected for metals, ions, and wet chemistry analyses for mines on
both public and private land.
¦ Flow measurements were collected concurrent with water samples.
¦ Baseline water quality samples were collected in October 1996, and February and June
1997 in Cement Creek.
¦ Waste rock and mill tailing samples were collected at a total of 138 mines in the Upper
Animas, Cement Creek, and Mineral Creek drainages. The samples were collected from the
top 2 inches of soil material at a minimum of 10 and maximum of 20 locations at each mine
location. The samples were composited in 1-gallon plastic bags and mixed in the field, after
which 150 milliliters (ml) of sample was removed and mixed with 300 ml of deionized
water in a 1-liter plastic beaker. After 90 minutes of settling, the liquid was filtered using 2-
micron soil filters and measured for pH, total acidity, and specific conductance. The
remaining liquid was acidified with nitric acid and shipped for laboratory analysis of metals
and cations.
¦ The mining wastes were investigated to provide information for prioritizing future mine
location reclamation activities to be performed by the Animas River Stakeholders Group.
2.1.3 2015 EPA/ESAT Sampling
Major 2015 EPA/ESAT field activities conducted at the Site and relevantto this report include the
following:
¦ June 9-10, 2015 - High-flow real-time field water quality measurements, stream flow data
collection, surface water sampling, photo documentation, and global positioning system
(GPS) coordinate collection.
¦ August 4-6, 2015 - Real-time field water quality measurements, surface water sampling,
soil/waste rock sampling, pore water sampling, sediment sampling, photo documentation,
and GPS coordinate collection.
¦ September 22-26, 2015 - Low-flow real-time field water quality measurements, stream
flow data collection, surface water sampling, pore water sampling, sediment sampling,
photo documentation, and GPS coordinate collection.
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Section 2 • Previous Investigations and Data Presented
2.1.4 2016 EPA/ESAT Sampling
With field support from stakeholders such as the U.S. Bureau of Land Management; Colorado
Division of Reclamation, Mining, and Safety (DRMS); and the U.S. Forest Service, major 2016
EPA/ESAT field activities conducted at the Site and relevant to this report include the following:
¦ June 6-9, 2016 - High-flow, low elevation, real-time field water quality measurements,
stream flow data collection, surface water sampling, photo documentation, and GPS
coordinate collection.
¦ June 28-30, 2016 - High-flow, high elevation, real-time field water quality measurements,
stream flow data collection, surface water sampling, photo documentation, and GPS
coordinate collection.
¦ July 25-29, 2016 - Waste rock, campground, and road soil sampling, photo documentation,
and GPS coordinate collection.
¦ September 27-30 and October 4-8, 2016 - Low-flow, real-time field water quality
measurements, stream flow data collection, surface water sampling, sediment sampling,
overbank soil sampling, pore-water sampling, photo documentation, and GPS coordinate
collection.
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Section 3
Contaminant Sources, Fate, and Transport
3.1 Contaminated Environmental Media
The following subsections provide definitions for the contaminated media present at the mining-
related sources discussed in detail in Section 4.
3.1.1 Solid Media
Solid media are defined as mining-related solid media that release contaminants to surface water
bodies and pose unacceptable risk to ecological receptors. Solid media have been subdivided into
three subcategories, which are discussed in the following subsections.
3.1.1.1 Mine Waste
Mine waste is a mining-related solid waste with elevated contaminant concentrations, water
soluble contaminant loads, and/or acid-generating potential. It includes waste rock, ore, tailings,
and contaminated fills that have been generated and/or processed during mining operations.
3.1.1.2 Sediment
Sediment is a mining-related solid waste material with elevated contaminant concentrations that
mainly consists of metal precipitates (i.e., sludge) from untreated mining-influenced water (MIW)
that have settled from surface waters after discharge from mining-related sources (e.g., mine
adits). Naturally occurring sources of sediment, which include iron fens (a location where metal
precipitates form on the surface at groundwater gaining reaches of drainage basins), are present
at the Site but would not be addressed as part of anticipated remedial actions. Sediment typically
precipitates within Site stream banks, river bottoms, and adit portal detention ponds. Sediment
may also include natural material or mine waste that has been deposited within streams or
detention ponds due to erosion of adjacent natural (i.e., stream banks) or mining-related source
(i.e., waste rock) material. Sediment may also generate MIW when in contact with water.
3.1.1.3 Contaminated Soil
Contaminated soil is native soil that has been impacted by or mixed with other contaminated media
(solid or aqueous). Native soil can be affected by either physical dispersion (e.g., erosion, wind,
traffic) or hydrogeochemical dispersion of contaminants. Hydrogeochemical dispersion is a broad
term that relates to leaching of metals and acidity from mine waste through MIW generation, and
sequestration of dissolved metals and acidity in soils as the MIW migrates over or through them.
3.1.2 Aqueous Media
Aqueous media has been subdivided into three subcategories, which are described in the
following subsections.
3.1.2.1 Mining-Influenced Water
MIW is water that is contaminated or influenced by mining-related activities and is a contaminant
source medium where it discharges from a mine portal or contacts a solid source medium. It is a
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Section 3 • Contaminant Sources, Fate, and Transport
broad term that does not specify the source of the contamination (other than a mining activity) or
the pH of the water. MIW can include both acid-mine drainage (AMD) and acid-rock drainage
(ARD), or water that is not acidic. AMD is metal-bearing, acidic water discharged from
underground mine workings through adits, tunnels, or shafts (collectively referred to as
"portals"). ARD is a similar discharge of metal-bearing acidic water resulting from water seeping
or flowing through and from acid-generating materials such as pyritic waste rock, tailings piles,
or mineralized rock formations. MIW forms when water and oxygen interact with sulfide-rich
mine wastes, host rocks, or vein rocks. Sulfuric acid forms and can dissolve additional metals into
the MIW. This MIW can discharge through adit portals and enter surface water. Both AMD and
ARD provide more information about the source and nature of the water than does the term MIW;
however, in this preliminary RI report, impacted water is referred to as "MIW."
3.1.2.2 Surface Water
Surface water includes water within streams or natural ponds. Impacted surface water may
episodically or periodically have elevated contaminant concentrations based on contact with or
migration of contaminants from solid media and/or MIW. For purposes of this preliminary RI
report, surface water within Mineral Creek, Cement Creek, and the Upper Animas River and
tributaries will be considered the receiving water bodies at the Site.
3.1.2.3 Groundwater
As discussed in Section 1.1.7, groundwater at the Site may include perched groundwater, alluvial
groundwater, and bedrock groundwater systems.
The presence and/or extent of perched groundwater in overburden material or alluvial
groundwater is not currently known at the mining-related sources described in this preliminary
RI and no groundwater analytical data are available for these mining-related sources. Thus it is
unknown whether perched overburden groundwater or alluvial groundwater is present at the
mining-related sources and whether any perched overburden groundwater or alluvial
groundwater has been previously or currently impacted by mining-related sources. It is
understood that water emanating from adits originated from the bedrock groundwater systems
at the Site, but the IRAs contemplated would not address sources of contamination within the
bedrock groundwater system or within mine workings. Thus, bedrock groundwater will not be
discussed further in this preliminary RI report.
3.2 Fate and Transport of Contaminants
The sources of contaminants at specific mining-related sources at the Site are presented in
Section 4.2. It should be noted that Site investigations are ongoing; the fate and transport
discussion presented in this report is not intended to be complete and final for the Site. The fate
and transport discussion herein is focused on currently identified issues at the Site to be
addressed through implementation of the IRAs.
3.2.1 Overview of Fate and Transport
Contaminants at the mining-related sources within the Site, specifically metals and metalloids
(which have properties of metals and non-metals, such as arsenic [As]), are present in solid phase
materials at the Site (mine waste rock, tailings, soil, and bedrock outcrops) and in MIW. Adverse
impacts are associated with transformation of solid phase metals and metalloids into forms that
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Section itaminant Sources, Fate, and Transport
are mobile and potentially harmful to humans and ecological receptors. Crushing and grinding
during mining and mineral processing may cause metals to mobilize in the form of very fine-
grained particulates that can be physically transported by wind or water. Interaction with water
and oxygen with sulfide minerals, especially pyrite, can result in generation of MIW and partial or
complete dissolution of metals and/or metalloids from the solid phase, which provides a
mechanism for contaminant migration into surface water and potentially groundwater, where it
exists. These processes increase the mobility of contaminants in the environment and, therefore,
increase the potential for impacts to receptors.
The releases from mining-related sources result in contamination of media, such as surface soil,
surface water, sediment, and groundwater, which go on to release contaminants in many ways,
including:
¦ Release of contaminants in surface water to sediments (through precipitation, deposition,
and adsorption), biota (through uptake), and groundwater (through infiltration)
¦ Release of contaminated soils to surface water via erosion or to groundwater via
infiltration and leaching
¦ Release of contaminants in soil to biota (through uptake) or air (wind-generated dust)
¦ Release of contaminants in groundwater to surface water
¦ Release of contaminants in sediment to surface water (through adsorption/desorption)
and biota (through uptake)
Cycling of contaminants among Site media will also occur. For example, metals may partition
between surface water and sediments and migrate between surface water and groundwater in
gaining and losing stream reaches.
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Section 3 Contaminant Sources, Fate, and Transport
Numerous mining-related sources within the Site contain acidic MIW in the form of AMD and
ARD. Exhibit 3-1 presents a summary of the process of AMD and ARD formation and a
description of the migration of these types of MIW in the environment.
Source Materials
Containing pyrite
Sulfide
oxidation occurs
when the three
components of the triangle interact
and are catalyzed by microorganisms
Oxygen \ Water
Increased exposure to precipitation, gruunctr/ater,
oxygen from mining activity and surface water
ARDj'AM D: Mobilizes contamination and moves it across and beyond the Site
Migration Routes: ARD runoff, surfacewater, and groundwater
Exposure Pathways: Ingestion, dermal contact, inhalation
contact,
Potential Receptors: On-site workers and recreational visitors: oft site
residents and recreational visitors; andwildlife
Exhibit 3-1 ARD and AMD Generation and Migration
At the Site, the surface waters in the main stems of Cement Creek, Mineral Creek, and the Upper
Animas River carry high loads of total and dissolved metals and high acidity into the Animas River
near Silverton even though substantial dilution with cleaner water occurs. Aquatic life in the
affected waterways is exposed to the elevated levels of metals.
3.2.2 Fate and Transport Pathways Related to IRA Implementation
The following fate and transport mechanisms are applicable to the specific issues planned to be
addressed through implementation of IRAs at the Site:
¦ The Junction Mine, Koehler Tunnel, Mammoth Tunnel, Anglo Saxon Mine, Sunbank Group,
Frisco/Bagley, and Silver Wing Mine utilize settling ponds to reduce metals concentrations
from their adit MIW discharge. This allows metals to settle out of the adit discharge water
through either formation of iron (Fe) oxy-hydroxides and subsequent co-precipitation
(such as the case with As), or through the physical settling of undissolved metals. This
process produces residual sludge in the settling ponds. If sufficient sludge and sediment
accumulates in the ponds and reduces the residence time of adit discharge in the ponds, or
if accumulated sludge diverts the adit discharge such that water does not flow through the
settling ponds as intended, then the ability for metals to settle out of the adit discharge
water is diminished.
3-4
Igfto,
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Section itaminant Sources, Fate, and Transport
¦ Several mining-related sources contain draining adits that discharge MIW onto or adjacent
to mine waste piles. These MIW discharges contacting mine waste are likely to lead to
increased leaching of metals from the mine waste into surface water, as well as increase
erosion and transport of mine waste or contaminated soil into receiving waters. Several
other mining-related sources have constructed diversions that route the MIW discharge
away from mine waste but require maintenance to prevent contact between the MIW and
mine waste materials.
¦ Stormwater run-on at mining-related sources can contact mine waste, which results in
increased leaching of metals from the mine waste to surface water.
¦ Many mining-related sources have mine waste that has been transported in front of a
flowing adit or into a stream channel. This mine waste can result in increased potential for
obstructed surface water flow and subsequent uncontrolled releases and erosion of mine
waste materials into surface water, as well as additional metals leaching from the
obstructive mine waste into nearby surface water bodies.
¦ Several mine-related sources at the Site are used for recreational staging purposes or
camping, and these activities have the potential to physically disturb mine waste or
contaminated soil, potentially increasing the potential for human exposure to
contaminants.
¦ Mine waste is capable of generating MIW when in contact with water (e.g., stormwater,
mine portal MIW discharge). In addition, some mine waste can impede the unrestricted
flow of surface water in streams and/or MIW from mine portals (e.g., adits). Mine waste
obstructing free flow increases the potential for mass wasting of contamination in
particulate form and/or leaching of contaminants from the mine waste as MIW.
3-5
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Section 3 • Contaminant Sources, Fate, and Transport
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3-6
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Section 4
Preliminary Evaluation of Environmental Data
Currently, EPA is collecting data to support evaluation of contributors of sources for contaminant
loading of waterways and identify areas where additional data is required to evaluate the Site.
The following section presents a summary of results from sampling and other field activities
relevant to actions at the 26 mining-related sources discussed in this preliminary RI report. The
summarized data include available recent water quality data for surface water and adit
discharges, stream sediment, waste rock and soils, and mine waste leachability results. The
contaminants discussed in this report include aluminum (Al), As, cadmium (Cd), copper (Cu), Fe,
lead (Pb), manganese (Mn), mercury (Hg), and zinc (Zn).
4.1 Screening Criteria for Affected Media
MIW, surface water, and synthetic precipitation leachate procedure (SPLP) soil and waste rock
results from CDMG and EPA/ESAT are discussed in the following sections and are compared to
Colorado Department of Public Health and Environment (CDPHE) Water Quality Control
Commission (WQCC) Regulation 34, Classifications and Numeric Standards for San Juan River and
Dolores River Basins (CDPHE 2016). From this regulation, the following acute and chronic table
value standards (TVSs) for metals were used for comparison to surface water analytical results
from the Site. It is important to note that the TVSs described below are being used as screening
levels for evaluation of existing environmental data, and that preliminary remedial goals have not
yet been developed for the Site; therefore, these TVSs are currently not being used as cleanup
criteria.
Al (total recoverable):
Acute = g(l-3695 * Ln[hardness] + 1.8308)
Chronic = gC1-3695 * Ln[hardness] - 0.1158) Qr gy^ wfiicfiever less (ptf < 7 0)
Chronic = e^13695 * Ln[hardness] - 0.1158) (pH > j
As:Acute = 340
Chronic = 100 (total recoverable)
Cd:
Acute = (1.136672 — Ln[hardness\ * o.041838)e(-0,9151*Ln['iardne's's'-3,1485->
Chronic = (1.101672 — Ln[hardness] * 0.041838)e^0,7998 * Lnihardness] -4.4451)
Cu:
Acute = g(°-9422 * Ln[hardness]-1.7408)
4-1
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Section 4 • Preliminary Evaluation of Environmental Data
Chronic = g(0-8545 *Ln[hardness]—1.7428)
Fe (total recoverable):
Acute = Not Applicable
Chronic = 1000
Pb:
Acute = (1.46203 — Ln[hardness] * 0.145712)e(-1,273 *Lnlhardness]~1A6)
Chronic = (1.46203 — Ln[hardness] * 0.145712)e^1,273*Lnlhardness]~4-705)
Mn:
Acute = g(°-333l * Ln[hardness] + 6.4676)
Chronic = g(°-333l * Ln[hardness] + 5.8743)
Zn:
Acute = 0 978 * e(°-9094 * Ln[hardness] + 0.9095)
Chronic = 0 986 * e(°-9094 * Ln[hardness] + 0.6235)
Hardness (maximum of 400 milligrams per liter (mg/L), except for Al, for which hardness shall
not exceed 220 mg/L):
[CaC03] = 2.5 * [Ca2+] + 4.1 * [Mg2+]
Concentrations of metals calculated using TVSs are in micrograms per liter ([ig/L), and hardness
is in milligrams per liter (mg/L) as calcium carbonate. These criteria were chosen to evaluate the
surface water and SPLP data using hardness-based aquatic life criteria developed by CDPHE
(CDPHE 2016) and to provide a consistent basis for evaluation of concentrations of relevant
metals in surface water. At some sampling locations, the calculated TVS standard is higher than
the typical federal water quality criteria, but because CDPHE WQCC Regulation 34 states that
"The imposition of effluent limits required under the Federal Act for point sources and cost-
effective and reasonable best-management practices for nonpoint sources are not likely to lead to
the establishment of aquatic life in these segments", these more stringent standards were not
used to analyze the surface water and SPLP samples discussed in this preliminary RI report.
A summary of relevant MIW and surface water data collected in 2015 and 2016 by ESAT and
comparison to applicable WQCC standards is provided in Table 4-1, while a summary of all 2015
and 2016 analytical data for MIW and surface water is presented in Attachment A. Additionally,
the leaching test and SPLP results from CDMG and ESAT in Table 4-2 and Table 4-3 are also
discussed relative to these water quality standards. Acute WQCC standards are always higher
than the chronic standards, and if the discussion in Section 4.2 states an exceedance of a WQCC
acute standard, the chronic standard was also exceeded but will not be stated.
4-2
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Section 4 Preliminary Evaluation of Environmental Data
Total metals results from soil and waste rock samples are also discussed in Section 4.2 and are
presented in Table 4-4, while a summary of all 2015 and 2016 analytical soil and waste rock data
is presented in Attachment B. Metals results from soil and waste rock at mining-impacted
recreation staging areas (e.g., established campgrounds or dispersed campsites) were compared
to applicable human health risk-based levels presented in Appendix B of the FFS. These
screening levels (in units of milligrams per kilograms [mg/kg]) are presented in Exhibit 4-1.
Exhibit 4-1 Soils and Waste Rock Metals Human Health Risk-Based Levels
Soil and Waste Rock Risk Based Levels (mg/kg)
Analyte
As
Pb
Campground Soil
122
2,081
Waste Rock
1,419
NA
Additionally, total metals results from sediment samples are discussed in Section 4.2 and are
presented in Table 4-5. The analytical results from these sediment samples were compared to
ecological risk-based screening levels based on Macdonald et al. (2000) and Ingersoll et al.
(1996). These screening levels are provided in Exhibit 4-2.
Exhibit 4-2 Sediments Metals Screening Levels
Sediment Concentration Screening Levels (mg/kg)
Al
As
Cd
Cu
Fe
Pb
Mn
Hg
Zn
26,000
9.79
0.99
31.6
188,400
35.8
631
0.18
121
The following discusses historical sampling results conducted at each of the 26 mining-related
sources. To present information about the mining-related sources in a manner that accounts for
the locations of the mining-related sources within the watersheds, Section 4.2 groups mining-
related sources into subareas for discussion. These subareas are generally shown on Figures 1-1
through 1-4.
4.2 Sampling Results at Mining-Related Sources - Mineral
Creek Headwaters
4.2.1 Longfellow Mine
The Longfellow Mine is located at the headwaters of Mineral Creek at an elevation of
approximately 11,160 feet National Geodetic Vertical Datum of 1929 (NGVD29) near the top of
Red Mountain Pass just east of U.S. Highway 550 and is readily accessible to the public. This
mining-related source is adjacent to the Junction Mine and Koehler Tunnel. Water flows from
upgradient areas into a diversion channel around an onsite waste rock pile, and into the Mineral
Creek Headwaters. A wooden shaft house and shaft are present at the waste rock pile. Figure 4-1
shows sample locations and other features of this mining-related source.
According to CDMG (Herron et al. 1997), approximately 32,000 cubic yards (cy) of mine waste
from the Longfellow Mine, Junction Mine, and Koehler Tunnel was removed by Sunnyside Gold
4-3
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Section 4 • Preliminary Evaluation of Environmental Data
Corporation in 1996 and 1997 to the Mayflower tailings repository near Silverton. Most of the
remaining waste rock at the Longfellow Mine has been capped.
The following sections describe results of analyses conducted for Longfellow Mine surface water,
SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.2.1.1 Longfellow Mine Surface Water
In 2016, one water quality sampling location was sampled for the Longfellow Mine (Table 4-1) at
a surface water location north of the shaft house (M02D) (Figure 4-1). The measured flow rate
was higher during high-flow conditions in June, at 15 gallons per minute (gpm), than in October
during low-flow (4.9 gpm). The pH was only marginally lower in the June sample compared to
October sample (6.61 standard units [su] versus 6.83 su).
The June 2016 sample exceeded the acute aquatic life standards (acute standards) for Cu, and
chronic aquatic life standards (chronic standards) for Al. The October 2016 sample exceeded the
chronic standards for Al and Cu.
4.2.1.2 Longfellow Mine CDMG and EPA/ESAT Waste Rock SPLP
No waste rock samples were collected at the Longfellow Mine during the CDMG investigation, and
USGS estimates that there was 5,500 cy of waste rock material onsite (Table 4-2). However, an
SPLP test was conducted on waste rock collected in July 2016 at the Longfellow Mine (WR-M02B)
(Table 4-3) and the results exceeded the chronic standard for Pb.
4.2.1.3 Longfellow Mine Soils, Waste Rock, and Sediment
As shown in Table 4-4, a waste rock sample collected from WR-M02B in July 2016 exceeded the
waste rock human health risk-based level for As.
No sediment samples (Table 4-5) were collected from the Longfellow mine in 2015 or 2016.
4.2.2 Junction Mine
The Junction Mine is located at the headwaters of Mineral Creek at an elevation of approximately
11,160 feet NGVD29 near the top of Red Mountain Pass just east of U.S. Highway 550, and thus is
readily accessible to the public. This mining-related source is adjacent to the Koehler Tunnel and
Longfellow Mine. A draining adit is present, and water from the adit flows into an onsite pond
that combines with flow from the discharging adit at the Koehler Mine. There is visible precipitate
formation in the pond, and soil around the adit flow exhibits staining, indicating seasonally higher
flows of MIW. Figure 4-1 shows sample locations and other features of this mining-related
source.
According to CDMG (Herron et al. 1997), approximately 32,000 cy of mine waste from the
Longfellow Mine, Junction Mine, and Koehler Tunnel was removed by Sunnyside Gold
Corporation in 1996 and 1997 to the tailings repository near Silverton.
The following sections describe results of analyses conducted for Junction Mine surface water,
SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
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Section 4 • Preliminary Evaluation of Environmental Data
4.2.2.1 Junction Mine Adit Discharge
In 2016, one water quality sampling location was sampled for the Junction Mine (Table 4-1) at
the adit (M02B) (Figure 4-1). The measured flow rate was higher during high-flow conditions in
June at 12 gpm, than in October during low-flow (2.9 gpm). The adit water quality data indicate
dilution with higher flows, because concentrations were higher in the October sample than the
June sample, and the pH was significantly lower (3.86 su in October versus 6.15 su in June).
The June and October 2016 adit samples exceeded acute aquatic life standards (acute standards)
for Cd, Cu, and Zn, and chronic aquatic life standards (chronic standards) for Al, As, and Fe. The
chronic and acute standards for Pb were also exceeded for the June and October adit samples,
respectively.
4.2.2.2 Junction Mine CDMG and EPA/ESAT Waste Rock SPLP
No waste rock samples were collected at the Junction Mine during the CDMG investigation.
However, one SPLP test was conducted on waste rock collected in July 2016 at the Junction Mine
(WR-M02D) (Table 4-3). The SPLP results exceeded the acute standards for Cd, Cu, Pb, and Zn,
and the chronic standard for Al. This indicates that despite the removal of the majority of waste
rock at this mining-related source, impacted solid media remains that generates leachate
exceeding surface water quality standards.
4.2.2.3 Junction Mine Soils, Waste Rock, and Sediment
As shown in Table 4-4, a waste rock sample collected from WR-M02D in July 2016 exceeded the
human health risk-based level for As.
Per Table 4-5, a sediment sample (M02E) collected from the settling pond collected in October
2016 exceeded sediment ecological screening levels (sediment screening levels) for As, Cd, Cu, Pb,
Hg, and Zn. Concentrations of As, Cd, Cu, and Zn in this pond sediment sample were the highest
among Mineral Creek mining-related sources.
4.2.3 Koehler Tunnel
The Koehler Tunnel is located in upper Mineral Creak at an elevation of 11,160 feetNGVD29 near
the top of Red Mountain Pass, adjacent to the Junction and Longfellow Mines. This mining-related
source is accessible to the public.
The Koehler Tunnel was bulkheaded in 2003 with additional grouting around the bulkhead in
2011 (Colorado Division of Reclamation, Mining and Safety [DRMS] 2011); however, some water
still discharges from the adit and orange precipitates are present in drainage. The adit discharges
down a talus slope and flows into the same pond as the Junction Mine adit discharge. According to
CDMG (Herron et al. 1997), mine waste from the Junction Mine, Koehler Tunnel, and Longfellow
Mine was removed by Sunnyside Gold Corporation to the tailings repository near Silverton, and
most structures were removed. Figure 4-1 shows sample locations and features of this mining-
related source.
Per CDMG (Herron etal. 1997), the adit and waste rock at the Koehler mining-related source
produced 52 to 56 percent of the Fe loading and over 90 percent of the Zn loading to Mineral
4-5
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Section 4 • Preliminary Evaluation of Environmental Data
Creek prior to installation of the bulkhead. The bulkhead has been effective at improving water
quality in the upper Mineral Creek watershed (DRMS 2011).
The following sections describe results of analyses conducted for Koehler Tunnel surface water,
SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.2.3.1 Koehler Tunnel Adit Discharge and Surface Water
In 2016, four water quality sampling locations were collected at the Koehler Mine (Table 4-1).
Samples were collected from a flowing pipe below the adit (M0K21), from the adit discharge
(M02C), from the outlet of the pond (M02E), and from downstream of Koehler Tunnel in Mineral
Creek (M02) (Figure 4-1). It is unknown if the pipe water sample can be compared to the adit
discharge sample.
Flow from the adit (M02C) was 4.5 gpm in October 2016, and the June sample collected from the
M02K1 pipe had a flow rate of only 0.1 gpm. The Koehler Tunnel adit sample had a pH of 6.12 su
in October, and exceeded the acute standards for Al, As, Cd, Cu, Mn, and Zn and the chronic
standard for Fe. The pipe water sample had a pH of 4.54 su in June, and exceeded the acute
standards for Cd, Cu, Mn, and Zn, and the chronic standard for Al. The settling pond outlet
(M02E), which contains water from both the Koehler Tunnel and the Junction Mine adit, was
sampled in June and October 2016 and metals concentrations in both samples exceeded acute
standards for Cd, Cu, Mn, and Zn, and chronic standards for Al, As, Fe, and Pb. The flow rate was
measured in October at 9 gpm, with a pH of 3.6 su. Concentrations in the pond were generally
lower than the concentrations from the adit and the pond pH was several units lower than the
adit in October. Downstream in Mineral Creek (M02), in June and October, flows were 150 and 23
gpm, respectively, pH was 5.76 and 8.03 su, respectively, and acute standards for Cd, Cu, Mn, and
Zn, and chronic standards for Al, Fe, and Pb, were exceeded during both sampling events.
4.2.3.2 Koehler Tunnel CDMG and EPA/ESAT Waste Rock SPLP
No waste rock samples were collected at the Koehler Mine during the CDMG investigation.
However, two SPLP tests were conducted on one soil/waste rock sample collected in July 2016 at
the Koehler Mine (WR-M02C) (Table 4-3). These SPLP tests were performed on waste rock
passing a 10-sieve, which has a 0.0787-inch opening, and 60-sieve, which has a 0.0098-inch
opening. For the 10- and 60-sieve samples, the SPLP results exceeded the acute standard for As,
and the chronic standards for Al, Fe, and Pb. The 60-sieve sample fraction exceeded the chronic
standard for Cu as well. These results indicate that despite the removal of most of the waste rock
at this mining-related source, impacted solid media remains that generates leachate exceeding
surface water quality standards.
4.2.3.3 Koehler Tunnel Soils, Waste Rock, and Sediment
Table 4-4 shows results for waste rock and soil samples collected at the Koehler Tunnel. Samples
were collected from waste rock/soil (WR-M02C), the onsite pond (M02E), and from downstream
in Mineral Creek (M02). From the waste rock/soil at WR-M02C, concentrations of As were 13,700
mg/kg in the 10-sieve fraction and 22,200 mg/kg in the 60-sieve fraction, which were the highest
among waste rock samples collected at the Site. The results from the 10-sieve and 60-sieve
fractions at WR-M02C exceeded the human health risk-based level for As.
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Section 4 • Preliminary Evaluation of Environmental Data
Per Table 4-5, as discussed for the Junction Mine above, a sediment sample from the settling
pond collected in October 2016 (M02E) had the highest As, Cd, Cu, and Zn concentrations found
in sediments at Mineral Creek mining-related sources. This sample exceeded sediment screening
levels for As, Cd, Cu, Pb, Hg, and Zn.
4.3 Sampling Results at Mining-Related Sources - Browns
Gulch
4.3.1 Brooklyn Mine
The Brooklyn Mine adit is located on the east side of Mineral Creek along a steep walled portion
of Brown's Gulch at an elevation of approximately 11,400 feetNGVD29. Forest Service Road 825
passes through the site, making it accessible to the public. The Mine has a flowing adit with a
metal grate, and flow is piped away from the adit to a constructed channel lined with Burns
Formation rock, which has become armored and stained with orange precipitate. There are visual
impacts to surface soils from surface water flow after discharge from the constructed channel.
There is a possible collapsed adit located above the draining adit. There are three structures on
the site, and there are two constructed ponds along Forest Service Road 825 located east of the
Brooklyn Mine. A large volume of waste rock is present and a large vegetation kill zone with
orange staining is seen at the base of the slope where water discharges from the channel. Figure
4-2 shows sample locations and features of this mining-related source.
The following sections describe results of analyses conducted for the Brooklyn Mine surface
water, SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.3.1.1 Brooklyn Mine Adit Discharge and Surface Water
In 2016, five total water quality sampling locations were collected for the Brooklyn Mine
(Table 4-1). Samples were collected from the adit (M12C), an adit diversion channel (M12D),
upstream of the Brooklyn Mine in Browns Gulch (M12B), downstream of the diversion channel in
Emporium Creek (which flows through Browns Gulch) (M12A), downstream of the Brooklyn
Mine in Browns Gulch (before the confluence with Mineral Creek) (M12), and the two ponds
along Forest Service Road 825 (M12F and M12G) (Figure 4-2).
In 2016, adit flow (M12C) was higher in June (7.3 gpm) than in September (1.1 gpm), while pH
ranged from 3.63 to 3.84 su. It should be noted that maintenance was completed on the adit
diversion piping in October 2016 to improve flow through the diversion. In September, the adit-
diversion channel (M12D) pH was 3.72 su, which is similar to the adit. Upstream in Browns Gulch
(M12B), June and September flows were 223 and 151 gpm, respectively, and pH ranged from 4.55
to 4.76 su. Downstream of the Brooklyn Mine, in Browns Gulch, before the confluence with
Mineral Creek (M12), June and September flows were 438 and 165 gpm, respectively, and pH
ranged from 4.17 to 5.08 su. In 2016, Emporium Creek, downstream of the adit diversion channel
(M12A), had a flow of 151 gpm in September; pH was 4.51 su in June and 4.45 su in September. In
October 2016, the northern pond sample (M12F) had apH of 7.79 su, while the southern pond
sample (M12G) had a pH of 4.07 su.
The June and September 2016 adit samples exceeded acute standards for Cd, Cu, Mn, and Zn, and
chronic standards for Al, Pb, and Fe. The adit water quality data appear to indicate metals dilution
%
4-7
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Section 4 • Preliminary Evaluation of Environmental Data
with higher flows because concentrations were higher in the two September adit samples than
the June sample. In the adit diversion channel in September, metals concentrations were similar
to the adit Between upstream and downstream of the Brooklyn Mine in Browns Gulch, Cd and Zn
concentrations increased such that they exceeded chronic and acute standards, respectively. The
sample collected from one pond (location M12F) in October 2016 did not exceed any acute or
chronic water quality standards, while the sample from pond location M12G in October 2016
exceeded acute standards for Cu, Pb, and Zn, and chronic standards for A1 and Cd.
4.3.1.2 Brooklyn Mine CDMG and EPA/ESAT Waste Rock SPLP
Three leachate samples were collected by CDMG from waste rock at the Brooklyn Mine. These
waste rock samples all exceeded the acute standards for Al, Cd, Cu, Mn, Pb, and Zn, and the
chronic standards for Fe. USGS estimated 15,000 cy of waste rock material onsite.
Per Table 4-3, three SPLP samples were analyzed from waste rock samples collected in July 2016
at the Brooklyn Mine (WR-M12, WR1-M12, and WR2-M12). For the WR-M12 sample near the
adit, SPLP results exceeded the acute standards for Cu, Pb, and Zn, and the chronic standards for
Al, Fe, and Pb. For the WR1-M12 sample collected from waste rock below the adit, the acute
standards were exceeded for Cd, Cu, Mn, Pb, and Zn, and chronic standards for Al and Fe, while
the WR2-M12 sample also exceeded the acute standard for Al. The WR1-M12 waste rock sample
had the highest Al, Fe, and Mn concentrations of any SPLP sample collected for the Mineral Creek
mining-related sources.
4.3.1.3 Brooklyn Mine Soils, Waste Rock, and Sediment
Per Table 4-4, samples were collected from the Brooklyn Mine at three waste rock pile locations
(WR-M12, WR1-M12, and WR2-M12), onsite adit soil (M12C), two adit channel locations
(M12D,and M12E), upstream of the mine in Browns Gulch (M12B), in Emporium Creek after the
diversion channel (M12A), and downstream of the mine in Browns Gulch (M12).
Per Table 4-5, sediment samples were collected ateight locations in 2016 atthe Brooklyn Mine.
The two adit discharge sample exceeded sediment screening levels for As, Cu, Pb, Hg, and Zn. The
Brown's Gulch upstream sample exceeded sediment screening levels for As, Cu, Pb, Mn, and Zn,
while the Brown's Gulch downstream sample only exceeded sediment screening levels for As and
Pb. Within the adit drainage channel, the first sampling location M12E exceeded sediment
screening levels for As, Cu, Fe, Pb, and Zn, the second sampling location M12D exceeded sediment
screening levels for Al, As, Cd, Cu, Fe, Pb, Mn, and Zn, while the third sampling location M12A only
exceeded sediment screening levels for As and Pb. Two samples collected at the two ponds
present east of the Brooklyn Mine (M12F and M12G) exceeded sediment screening levels for As,
Cd, Cu, Pb, and Zn.
4.4 Sampling Results at Mining-Related Sources - South Fork
Mineral Creek
4.4.1 Bandora Mine
The Bandora Mine is located west of Mineral Creek along the South Fork at an elevation range
between 10,690 feet to 11,000 feetNGVD29. The mine is situated on a uniform, southeast-facing,
steep mountain slope in a forested subalpine terrain just below timberline. The mine is visible
4-8
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Section 4 • Preliminary Evaluation of Environmental Data
from County Road 585 and is accessible to the public. The mine has two flowing adits. The main
adit is collapsed and discharge from both adits flow in a diversion channel to the northeast and
then downslope and across the road into the South Fork of Mineral Creek. Large amounts of
orange precipitates are visible in flow channels and on rocks. There are two dilapidated
structures onsite. Figure 4-3 shows sample locations and features of this mining-related source.
The following sections describe results of analyses conducted for the Bandora Mine surface
water, SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.4.1.1 Bandora Mine Adit Discharge and Surface Water
In 2016, six total water quality sampling locations were collected for the Bandora Mine (Table 4-1).
Samples were collected from two adit locations (M24B and M24C), two samples from the adit
drainage channel (M24A and M24D), upstream of Bandora Mine in the South Fork of Mineral Creek
(M23), and downstream of Bandora Mine in the South Fork of Mineral Creek (M25) (Figure 4-3).
In September 2016, Bandora Mine adit flow at M24B was measured to be 24 gpm and had a pH of
6.71 su. In September 2016 from the lower adit location M24C, pH was 6.96 and 7.41 su,
respectively. In the adit flow channel samples M24A and M24D, pH was measured at 6.96 and
6.87 su, respectively, in September. Upstream of Bandora Mine (M23), flow was 7,351 gpm in
September 2016, with a pH of 5.98. In June and September 2016, downstream flow (M25) was
21,553 and 9,317 gpm, respectively, and pH was 6.28 and 6.12 su, respectively. These results
indicate that there was not a noticeable change in pH within South Fork Mineral Creek across the
Bandora Mine site.
The September 2016 M24B adit sample exceeded acute standards for Cd, Mn, and Zn, and chronic
standards for Al, Cu, and Fe. The M24C adit sample only exceeded the acute standard for Zn. The
adit flow channel samples M24A and M24D exceeded acute standards for Cd, Mn, and Zn, and
chronic standards for Al and Fe. In September, both upstream and downstream samples M23 and
M25 exceeded chronic standards for Al and Cd, while downstream sample M25 also exceeded the
chronic standard for Zn.
4.4.1.2 Bandora Mine CDMG and EPA/ESAT Waste Rock SPLP
One leachate sample was collected by CDMG from waste rock at the Bandora Mine (Table 4-2).
The waste rock sample exceeded the acute standards for Cd, Cu, Pb, and Zn. CDMG and USGS
estimated 5,500 cy of waste rock material onsite.
Per Table 4-3, four SPLP samples were analyzed from waste rock samples collected in July 2016
at the Bandora Mine (WR1-M24, WR2-M24, WR3-M24, and WR4-M24). All samples exceeded the
acute standards for Mn, Pb, and Zn. The WR1-M24, WR2-M24, and WR3-M24 samples also
exceeded acute standards for Cd and Cu, and chronic standard for Fe. The WR1-M24 and WR3-
M24 samples also exceeded chronic Al standards. The WR1-M24, WR2-M24, and WR3-M24 SPLP
samples had the highest Cd, Cu, Pb, and Zn levels among waste rock samples collected at the
Mineral Creek mining-related sources.
4.4.1.3 Bandora Mine Soils, Waste Rock, and Sediment
Per Table 4-4, samples were collected from the Bandora Mine at four waste rock pile locations
(WR1-M24, WR2-M24, WR3-M24, and WR4-M24), the adit drainage channel above the South
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Section 4 • Preliminary Evaluation of Environmental Data
Fork of Mineral Creek (M24D), an upstream location (M23), and a downstream location (M25).
Waste rock samples collected at Bandora had the highest Cu concentrations in all of Mineral
Creek and some of the highest Pb and Zn concentrations in all of the Site. Concentrations typically
increased between the upstream and downstream points.
Per Table 4-5, sediment samples were collected in 2016 at locations upstream and downstream
from the Bandora Mine. Metals concentrations typically increased between the upstream and
downstream samples, and the downstream sample exceeded sediment screening levels for Cd, Cu,
Pb, and Zn.
4.5 Sampling Results at Mining-Related Sources - Upper
Cement Creek
4.5.1 Grand Mogul Mine
The Grand Mogul Mine is located in Ross Basin, about 0.5 miles east of the Mogul Mine main adit
near the base of the north basin wall at an elevation of 11,800 feetNGVD29. The Grand Mogul
Mine is difficult to access via a jeep trail. The main and most eastern adit is collapsed. Flow from
beneath the Grand Mogul Mine waste rock travels westward over soil for approximately 650 feet
before entering upper Cement Creek. The overland flow path is heavily stained with orange
precipitates. Three piles of mine waste from the workings of the Grand Mogul Mine are located on
the north side of Cement Creek. Flow from the collapsed eastern adit is likely seeping out of the
toe of the easternmost waste rock pile. Gullies are present on the waste rock piles and the piles
have a moderate degree of erosion. A large shaft or stope covered with metal grate is located at
the second waste rock pile. There are no other structures onsite. Figure 4-4 shows sample
locations and features of this mining-related source.
The following sections describe results of analyses conducted for the Grand Mogul Mine surface
water, SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.5.1.1 Grand Mogul Mine Adit Discharge and Surface Water
In 2016, seven total water quality sampling locations were collected for the Grand Mogul Mine
(Table 4-1). Samples were collected from two eastern waste rock seep locations (CC01C and
CC01C1), an adit and waste rock discharge channel before confluence with Cement Creek (CC01C2),
upstream of Grand Mogul Mine in Cement Creek (CC01F), Cement Creek after confluence with the
adit and waste rock drainage channel (CC01H) (before confluence with Queen Anne Mine
tributary), in the western waste rock drainage channel (CC02I), and downstream in Cement Creek
after confluence with the western rock pile drainage and all Grand Mogul mining-related sources
(CC01U) (Figure 4-4).
In September 2016, Grand Mogul Mine seep flows were measured at CC01C and CC01C1 at 3.6 and
2.8 gpm, respectively, with pH values of 4.1 and 3.96 su, respectively. Flows were not measured at
CC01C and CC01C1 during June 2016. In the seep flow channel in June and September, CC01C2 had
flows of 73 and 9 gpm, respectively, andpH values of 3.42 and 4.12 su, respectively. Flow at
Cement Creek upstream location CC01F was not measured; pH in June and September was 7.27
and 7.16 su, respectively. In Cement Creek at CC02H in June and September 2016, flow was 2,904
and 368 gpm, respectively, while pH values were 6.12 and 6.31 su, respectively. In the western
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Section 4 • Preliminary Evaluation of Environmental Data
waste rock pile drainage channel at CC02I, flow was 7.3 in June 2016, and pH was 4.69 su.
Downstream of Grand Mogul Mine in Cement Creek at CC01U in June and September 2016, flow
was 5,327 and 378 gpm, respectively, while pH was 6.16 and 5.72 su, respectively. These results
indicate that the Grand Mogul Mine adversely affected pH values in Cement Creek.
In 2016, June and September adit and waste rock channel water samples CC01C, CC01C1, and
CC01C2 all exceeded acute standards for Al, Cd, Cu, and Zn, and exceeded chronic standards for
Fe. These three sampling points also had exceedances of acute and chronic Mn and Pb during June
and September 2016, and Mn concentrations were some of the highest in Cement Creek. The
Grand Mogul Mine upstream location in June and September exceeded acute standards for Cu and
Zn, and chronic standards for Al and Cd. Cement Creek after confluence with the adit and waste
rock drainage channel (CC01H) sample exceeded acute standards for Cd, Cu, and Zn, and the
chronic standard for Al. The drainage channel for the western waste rock pile (CC02I) and the
Grand Mogul Mine downstream (CC01U) samples exceeded acute standards for Cd, Cu, and Zn,
and the chronic standard for Al, and the downstream sample also exceeded the chronic standard
for Mn. Results presented in Table 4-1 show that water flowing from the Grand Mogul Mine
meaningfully increased concentrations of Al, Cd, Cu, Fe, Mn, and Zn in Cement Creek.
4.5.1.2 Grand Mogul Mine CDMG and EPA/ESAT Waste Rock SPLP
Two leachate samples were collected by CDMG from waste rock at the Grand Mogul Mine (Table
4-2). These waste rock samples all exceeded the acute standards for Al, Cd, Cu, Pb, and Zn, and the
chronic standards for Fe. CDMG estimated 8,000 and 9,000 cy of waste rock at the west and east
waste rock piles, respectively, while USGS estimated 9,000 cy total of waste rock material onsite.
Per Table 4-3, three SPLP samples were analyzed from waste rock samples collected in July 2016
at the Grand Mogul Mine (WR-CC01C, WR-CC01C2, and WR-CC02A). These samples exceeded the
acute standards for Cd, Cu, Pb, and Zn, and chronic standards for Al. The WR-CC01C2 and
WR-CC02A samples also exceeded the chronic Fe standard. The Grand Mogul Mine WR-CC01C
and WR-CC01C2 SPLP samples had the highest Cd, Cu, Pb, and Zn concentrations among waste
rock samples collected at Cement Creek mining-related sources.
4.5.1.3 Grand Mogul Mine Soils, Waste Rock, and Sediment
Per Table 4-4, samples were collected from the Grand Mogul Mine at three waste rock pile
locations (WR-CC01C, WR-CC01C2, and WR-CC02A), two seep locations below the eastern waste
rock piles (CC01C and CC01C1), the adit and waste rock drainage channel before confluence with
Cement Creek (CC01C2), upstream of the mine in Cement Creek (CC01F), in Cement Creek after
confluence with the eastern adit and waste rock discharge channel (CC01H), in a drainage channel
for the western waste rock (CC02I), and downstream of all Grand Mogul mining-related sources in
Cement Creek (CC01U). The WR-CC01C and WR-CC01C2 waste rock samples had the highest Pb
and Zn concentrations among Cement Creek mining-related sources, and the CC01C2 drainage
channel location had the highest Al, Cd, and Mn concentrations of any sample collected among the
Cement Creek mining-related sources.
Per Table 4-5, sediment samples were collected in 2016 at seven locations at the Grand Mogul
Mine. All samples exceeded sediment screening levels for As, Cu, Pb, Mn, and Zn, and all samples
except for CC01C also exceeded sediment screening levels for Cd.
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Section 4 • Preliminary Evaluation of Environmental Data
4.6 Sampling Results at Mining-Related Sources - Gladstone
Area
4.6.1 Natalie/Occidental Mine
The Natalie/Occidental mine is located one mile southeast of Gladstone on the north side of the
South Fork of Cement Creek, directly across from the Big Colorado Mine. The discharging adit
elevation is at 11,000 feetNGVD29. The Natalie/Occidental Mine is accessible via a county road
and is accessible to the public. The primary discharging adit is covered with a grate, and a
possible collapsed adit and exploration pit are upslope of the primary adit The adit discharge
flows southwest over soil and adjacent to waste rock for approximately 240 feet before entering
the South Fork of Cement Creek. Heavy orange precipitate is observed throughout this adit flow
channel. Precipitate buildup behind the adit grate has raised the level with which water flows out
of the adit. Staining on the grate indicates that higher flows have been present historically.
Discharged adit water flows over waste rock at the site, and the onsite waste rock is being
undercut by the South Fork of Cement Creek with a high degree of erosion. Figure 4-5 shows
sample locations and features of this mining-related source.
The following sections describe results of analyses conducted for the Natalie/Occidental Mine
surface water, SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.6.1.1 Natalie/Occidental Mine Adit Discharge and Surface Water
In 2015 and 2016, three total water quality sampling locations were collected for the
Natalie/Occidental Mine (Table 4-1). Samples were collected from an adit location (CC14),
upstream of Natalie/Occidental Mine in the South Fork of Cement Creek (CC15), and downstream
of Natalie Occidental Mine in the South Fork of Cement Creek (CC15A) (Figure 4-5).
In September 2016, the adit flow rate was measured at CC14 at 407 gpm, with a pH value of 5.39
su. The remaining 2015 and 2016 aditpH values ranged from 6.09 to 6.32 su. Upstream of
Natalie/Occidental in the South Fork of Cement Creek at CC15, flows were measured at 7,277 and
301 gpm in June and September 2016, respectively, with no pH measurement in June and a pH
value of 7 su in September. Downstream of the Natalie/Occidental Mine in the South Fork of
Cement Creek at CC15A, flows were measured as 7,206 and 1,170 gpm in June and September
2016, respectively, with a pH value of 6.8 su in September and no pH measurement in June. These
results indicate that the Natalie/Occidental Mine significantly contributes to flow to the South
Fork of Cement Creek during September low-flow conditions.
In 2015 and 2016, the Natalie/Occidental Mine adit discharge exceeded acute standards for Zn,
and chronic standards for Al, Cd, and Fe. Additionally, the June 2015 and 2016 samples exceeded
acute standards for Cu. Upstream samples from 2016 only exceeded the chronic standards for Al.
Downstream of the Natalie/Occidental Mine, the June 2016 sample exceeded the acute standard
for Zn and chronic standards for Al, Cd, Cu, and Fe, while the September 2016 sample exceeded the
chronic standards for Al, Cd, Fe, and Zn. These water quality results indicate that the Natalie/
Occidental Mine increases concentrations of Fe, Mn, and Zn in the South Fork of Cement Creek.
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Section 4 • Preliminary Evaluation of Environmental Data
4.6.1.2 Natalie/Occidental Mine CDMG and EPA/ESAT Waste Rock SPLP
One leachate sample was collected by CDMG from waste rock atthe Natalie/Occidental Mine
(Table 4-2). This waste rock sample exceeded the acute standard for Al, Cd, Cu, Pb, and Zn, and
the chronic standard for Fe. CDMG and USGS estimated 6,800 cy of waste rock material onsite.
Per Table 4-3, two SPLP samples were analyzed from waste rock samples collected in July 2016
at the Natalie/Occidental Mine (WR-CC14A and WR-CC14B). These samples exceeded the acute
standards for Al and Pb, and chronic standards for Fe. The WR-CC14B sample also exceeded the
acute Zn standard.
4.6.1.3 Natalie/Occidental Mine Soils, Waste Rock, and Sediment
Per Table 4-4, samples were collected from the Natalie/Occidental Mine at two waste rock pile
locations (WR-CC14A and WR-CC14B), upstream of the mine in the South Fork of Cement Creek
(CC15), and downstream of the mine in the South Fork of Cement Creek (CC15A).
Per Table 4-5, sediment samples were collected in 2016 at two locations (upstream and
downstream in South Fork of Cement Creek) atthe Natalie/Occidental Mine. Metals concentrations
were typically higher downstream of the mine and exceeded sediment screening levels for As, Cu,
and Pb in all samples.
4.7 Sampling Results at Mining-Related Sources - Lower
Cement Creek
4.7.1 Henrietta Mine
The Henrietta Mine is located on the south side of Prospect Gulch and is accessible by 4-wheel
drive vehicle from County Road 35, with at least six levels into the mine. The 700 Level entrance
to the mine is at an elevation of 11,360 feetNGVD29. The 800 Level is collapsed and
topographically below and north of the 700 Level portal, close to Prospect Gulch. CDMG reported
a large compound waste dump located at the adit portals of the 700 and 800 levels, which is
divided by Prospect Gulch and is mostly located on the south side of Prospect Gulch below the
700 Level. CDMG estimated from a survey that 30,000 cy of waste are onsite from the 700 and
800 levels, while USGS estimated approximately 36,000 cy. This 700- and 800-level waste rock
pile has since been reclaimed. Presently, the 700 Level adit flows only during high-flow
conditions and is diverted into a drainage channel that flows on the southeastern side of the
waste rock. There is a small cabin located near the 700 Level adit. A grate is in place on the 700
Level portal and the surrounding slope is eroding. Additional orange precipitate is present in
Prospect Gulch downstream of a wooden dam near the 800 Level adit. Figure 4-6 shows relevant
features of this mining-related source.
The following sections describe results of analyses conducted for the Henrietta Mine surface
water, SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.7.1.1 Henrietta Mine Adit Discharge and Surface Water
In 2016, three total water quality sampling locations were collected for the Henrietta Mine
(Table 4-1). Samples were collected from the 700 Level adit location (CC24G), upstream of
%
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Section 4 • Preliminary Evaluation of Environmental Data
Henrietta Mine in Prospect Gulch (CC22D), a midpoint in Prospect Gulch (CC22B), and
downstream of Henrietta Mine in Prospect Gulch (CC24B) (Figure 4-6).
Flows were measured from the Prospect Gulch upstream (CC22D), midpoint (CC22B), and
downstream (CC24B) locations in September 2016 as 73,131, and 166 gpm, respectively, with
pH values of 5.79, 4.33, and 3.93 su, respectively. pH values were similar between June and
September at the upstream location but dropped at the midpoint and downstream location
between high- and low-flow conditions. These flow and pH results indicate that the northern and
southern waste rock seeps and 800 Level adit are impacting Prospect Gulch flow and pH during
both high- and low-flow conditions. At the 700-level adit (CC24G), flows were not measured in
2016, and pH was 4.61 in June 2016.
The June 2016 Henrietta Mine 700-level adit water sample exceeded acute standards for Al, Cu,
and Zn, and chronic standards for Cd, Fe, and Pb. The 2016 upstream and midpoint samples
exceeded the acute standards for Al, Cd, Cu, Pb, and Zn. The downstream June sample exceeded
acute standards for Cu and Zn and chronic standards for Al, Cd, Fe, and Pb, while the downstream
September sample exceeded acute standards for Al, Cd, Cu, Pb, and Zn and the chronic standard
for Fe. Concentrations of Al and Pb increased between the upstream and midpoint samples during
both high- and low-flow samples, and concentrations typically increased between the upstream
and downstream sampling points.
4.7.1.2 Henrietta Mine CDMG and EPA/ESAT Waste Rock SPLP
Three leachate samples were collected by CDMG from waste rock at the Henrietta Mine (Table 4-2).
These samples exceeded the acute standards for Al, Cd, Cu, Pb, and Zn, and the chronic standard for
Fe. CDMG and USGS estimated 30,000 cy of waste rock material onsite.
Per Table 4-3, one SPLP test was conducted on a waste rock sample collected in July 2016 atthe
toe of the Henrietta Mine waste rock pile (WR-CC22). This sample exceeded the acute standard
for Pb and chronic standards for Al and Fe.
4.7.1.3 Henrietta Mine Soils, Waste Rock, and Sediment
Per Table 4-4, samples were collected from the Henrietta Mine in July 2016 at one waste rock
location (WR-CC22), and in September 2016 atone upstream soil location in Prospect Gulch
(CC22D), one midpoint location in Prospect Gulch (CC22B), and one downstream soil location in
Prospect Gulch (CC24B).
Per Table 4-5, sediment samples were collected in September 2016 at three locations atthe
Henrietta Mine. Metals concentrations exceeded sediment screening levels for As, Cd, Cu, Pb, and
Zn. Except for Al, metals concentrations typically decreased in Prospect Gulch between the
upstream and downstream samples.
4.7.2 Mammoth Tunnel
The Mammoth Tunnel is located on the west side of Cement Creek near the mouth of Georgia Gulch
at an elevation of 10,400 feet NGVD29. This mining-related source is located on a county road and
is accessible to the public. The USGS estimated the waste rock pile at 100 cy. The adit is collapsed
and a pipe protrudes from the side of the hill to allow discharge. The adit flow is channelized and
flows down the side of the waste rock in a lined channel into two constructed settling ponds. Some
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Section 4 • Preliminary Evaluation of Environmental Data
of the discharged flow bypasses the first pond into the second pond. Adit discharge does not flow
out of second pond, but instead seeps into the ground. Algae and Fe staining and metal precipitates
are found throughout the discharge channel and ponds. Figure 4-7 shows relevant features of this
mining-related source.
Due to property access limitations, analytical samples were not collected by EPA/ESAT for any
media during their 2015/2016 sampling events. Thus, limited historic information from the USGS
and CDMG are provided. According to the leachability test performed by CDMG on waste rock
from the Mammoth Tunnel, the leachate exceeded the water quality screening criteria for acute
Al, Cd, Cu, and Zn (Table 4-2).
4.7.3 Anglo Saxon Mine
The Anglo Saxon Mine is adjacent to County Road 110 on the west side of Cement Creek,
approximately 3 miles upstream from Silverton. The site is accessible to the public. This mine
consists of an adit located close to County Road 110. The adit is at an elevation of 10,080 feet
NGVD29 and the adit discharge flows from a collapsed wooden structure. The main adit discharges
across a moderately eroded waste pile, and cascades down to a culvert underneath the road to a
constructed settling pond before continuing to Cement Creek. Orange precipitate staining is
observed on the flow channels draining from this primary adit. A wooden shack and a crib wall are
present at the site. Figure 4-8 shows sample locations and features of this mining-related source.
The following sections describe results of analyses conducted for the Anglo Saxon Mine surface
water, SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.7.3.1 Anglo Saxon Mine Adit Discharge and Surface Water
In 2016, six total water quality sampling locations were collected for the Anglo Saxon Mine and
Porcupine adit area (Table 4-1). Samples were collected from the lower (main) adit location
(CC37), upstream of Anglo Saxon Mine in Cement Creek (CC39B), downstream of Anglo Saxon
Mine in Cement Creek (CC39), Porcupine Gulch adit (upper adit) (CC38B), upstream of upper adit
in Porcupine Gulch (CC38C), and downstream of the upper adit before confluence with Cement
Creek (CC38) (Figure 4-8).
Flows were measured from the lower main adit (CC37) in June and September 2016 to be 41 gpm
during both events, with a pH of 6.53 su during both events. At the upper adit (CC38B) in June
and September, flows were 59 and 36 gpm, respectively, with pH values of 6.15 and 6.67 su,
respectively. Upstream (CC38C) and downstream (CC38) of the upper adit in September, flows in
Porcupine Gulch were 15 and 37 gpm, respectively, and pH was 7.32 and 7.25 su, respectively.
Upstream of the Anglo Saxon Mine in Cement Creek (CC39B), flow was 6,993 gpm in September
(no flow measured in June), and pH in June and September was 5.1 and 3.82 su, respectively.
Downstream of Anglo Saxon Mine in Cement Creek (CC39), flow was 7,970 gpm in September (no
flow measured in June), and pH in June and September was 5.26 and 3.62 su, respectively. These
results indicate that the Porcupine Gulch adit contributes significantly to flow in Porcupine Gulch
during low-flow, and the effect of seasonal flows reduces Cement Creek pH at this point by
approximately 1.5 su between June and September, though the pH is relatively unchanged across
the site.
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Section 4 • Preliminary Evaluation of Environmental Data
The 2016 Anglo Saxon Mine main adit and Porcupine Gulch adit water samples all exceeded acute
standards for Mn and Zn, and chronic standards for Al, Cd, and Fe. The June 2016 sample from the
Porcupine Gulch adit also exceeded the acute standard for Cu. These metals concentrations do not
appear to change meaningfully between June to September. Upstream and downstream locations
in Cement Creek both exceeded acute standards for Cu and Zn, and chronic standards for Al, Cd,
Fe, and Pb.
4.7.3.2 Anglo Saxon Mine CDMG and EPA/ESAT Waste Rock SPLP
One leachate sample was collected by CDMG from waste rock at the Anglo Saxon Mine (Table 4-2).
This sample exceeded the acute standards for Al, Cd, Cu, Pb, and Zn, and the chronic standard for
Fe. CDMG and USGS estimated there was 2,200 cy of waste rock material onsite.
Per Table 4-3, four SPLP tests were conducted on two waste rock samples collected in July 2016
at the Anglo Saxon Mine and the Porcupine Gulch adit (WR-CC37 and WR-CC38B). These SPLP
tests were performed on waste rock passing a 10- and 60-sieve. The WR-CC37 10-sieve sample
exceeded acute standards for Pb and Zn, and chronic standard for Mn, while the 60-sieve portion
also exceeded the acute standards for Al, Cu, and Mn, and chronic standard for Fe. The 60-sieve
portion of this sample contained the highest Fe and Mn concentrations among the Cement Creek
mining-related sources. For the WR-CC38B 10- and 60-sieve samples, acute standards were
exceeded for Al, Cd, Cu, Pb, and Zn, and chronic standard for Fe.
4.7.3.3 Anglo Saxon Mine Soils, Waste Rock, and Sediment
Per Table 4-4, samples were collected from the Anglo Saxon Mine and Porcupine Gulch adit in
2016 attwo waste rock pile locations (WR-CC37 and WR-CC38B), three locations in Porcupine
Gulch before confluence with Cement Creek (CC38, CC38C, and CC38D), upstream of the mine in
Cement Creek (CC39B), and downstream of the mine in Cement Creek (CC39).
Per Table 4-5, sediment samples were collected in 2016 at five locations at the Anglo Saxon Mine.
The upstream CC39B location exceeded sediment screening levels for As, Cd, Cu, Pb, Mn, and Zn,
while the downstream location only exceeded sediment screening levels for As, Cu, Pb, and Zn.
The three sampling locations in Porcupine Gulch all exceeded sediment screening levels for As,
Cd, Cu, Pb, Mn, and Zn, and the CC38 location also exceeded the sediment screening level for Fe.
Metals concentrations did not typically increase in Cement Creek between the mine upstream and
downstream samples.
4.7.4 Yukon Tunnel
The Yukon Tunnel lies on the east side of Cement Creek along County Road 110 about 2.5 miles
upstream from Silverton. Access is via an old bridge across Cement Creek at an elevation of
10,080 feet NGVD29. The site access road is gated but still accessible by walking. The adit has a
metal door and the closure is in generally poor condition. Adit discharge is directed within the
adit into a pipe, which discharges to the north of a large waste rock pile into Illinois Gulch
adjacent to the mine. There is a moderate amount of erosion on the waste rock pile, and four
structures are onsite. Figure 4-9 shows sample locations and features of this mining-related
source.
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Section 4 • Preliminary Evaluation of Environmental Data
The following sections describe results of analyses conducted for the Yukon Tunnel surface
water, SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.7.4.1 Yukon Tunnel Adit Discharge and Surface Water
In 2016, four total water quality sampling locations were collected for the Yukon Tunnel
(Table 4-1). Samples were collected from the adit discharge pipe (CC43C), upstream in Cement
Creek (CC41), downstream in Cement Creek (CC43E), and from an onsite pond where previous
reclamation activities had occurred (CC43D) (Figure 4-9).
In September 2016, flows were measured at the upstream (CC41) and downstream (CC43E)
points in Cement Creek as 6,939 and 7,069 gpm, respectively, with pH values of 3.55 and 3.88 su,
respectively. In June, the upstream and downstream locations in Cement Creek had pH values of
5.16 and 5.37 su, respectively. These results indicate pH effects from seasonal flows in Cement
Creek. The pond location (CC43D) pH was 2.98 su in June. The pH at the pipe outlet from the
Yukon Tunnel adit (CC43C) in June and September 2016 was 6.82 and 6.68 su, respectively, and
flow was not measured.
In 2016, the adit discharge pipe (CC43C) exceeded chronic standards A1 and Fe, while the onsite
reclaimed pond sample in June 2016 (CC43D) exceeded acute standards for Al, Cd, Cu, Mn, and Zn,
and chronic standards for Fe. The metals concentrations in the reclaimed pond were typically
orders of magnitude above those from the adit location. In Cement Creek upstream (CC41) and
downstream (CC43E) of Yukon Tunnel in June, acute standards were exceeded for Cd, Cu, and Zn,
and chronic standards for Al, Fe, and Pb. In September, the upstream and downstream locations
exceeded acute standards for Cu and Zn, and chronic standards for Al, Cd, Fe, and Pb. From Table
4-1, these results indicate that in June 2016, metals concentrations increased across the Yukon
Tunnel site, while in September 2016 metals concentrations decreased across the site.
4.7.4.2 Yukon Tunnel CDMG and EPA/ESAT Waste Rock SPLP
One leachate sample was collected by CDMG from waste rock at the Yukon Tunnel (Table 4-2).
This sample exceeded the acute standards for Al, Cd, Cu, Pb, and Zn. CDMG and USGS estimated
18,000 cy of waste rock material onsite.
Per Table 4-3, one SPLP sample was analyzed from waste rock samples collected in July 2016 at
the Yukon Tunnel (WR-CC43). This sample exceeded the acute standards for Al, Cd, Cu, Pb, and
Zn, and chronic standard for Fe. This sample had the highest waste rock SPLP Al concentration of
any sample among the Cement Creek mining-related sources.
4.7.4.3 Yukon Tunnel Soils, Waste Rock, and Sediment
Per Table 4-4, samples were collected from the Yukon Tunnel in 2016 atone waste rock pile
location (WR-CC43), an onsite pond location (CC43D), in Illinois Gulch before confluence with
Cement Creek (CC42), upstream of the mine in Cement Creek (CC41), and downstream of the
mine in Cement Creek (CC43E).
Per Table 4-5, sediment samples were collected in 2016 at four locations at the Yukon Tunnel. At
the Cement Creek upstream and downstream locations, metals concentrations exceeded sediment
screening levels for As, Pb, and Zn, while the downstream location also exceeded sediment
screening levels for Cd and Cu. The two samples collected from Illinois Gulch exceeded sediment
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Section 4 • Preliminary Evaluation of Environmental Data
screening levels for As, Cu, Pb, Mn, and Zn, and the CC42 sample also exceeded sediment
screening levels for Cd. Additionally, Mn sediment concentrations were elevated at the mouth of
Illinois Gulch compared to Cement Creek.
4.8 Sampling Results at Mining-Related Sources - Burrows
Creek
4.8.1 Boston Mine
The Boston Mine is located on the north side of Burrows Creek (a tributary to the upper Animas
River), along the northwest side of Houghton Mountain above the trans-basin diversion ditch at
an elevation of 12,088 feetNGVD29. This mining-related source is between the Red Cloud and
Dewitt Mines, and is accessible to the public off County Road 18. This location consists of a 900-cy
waste rock pile and tunnel. There is no visible flow from the tunnel. A polyvinyl chloride pipe
coming out of the concrete cover was not discharging during the site visit in fall 2016. Burrows
Creek flows adjacent to the waste rock in a channel, and there is evidence of waste rock and soil
eroding and sloughing off into the channel. There are no structures onsite. Figure 4-10 shows
sample locations and features of this mining-related source.
The following sections describe results of analyses conducted for Boston Mine surface water,
SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.8.1.1 Boston Mine Surface Water
In 2016, three total water quality sampling locations were collected from the Boston Mine (Table
4-1). Samples were collected at an upstream location above the mine (A07E), the trans-basin
diversion ditch above the confluence with Burrows Creek (A07D1), the trans-basin diversion
ditch below Burrows Creek (A07D2), and a downstream location in Burrows Creek just before the
Dewitt Mine (A07D). No locations represent an adit discharge but demonstrate the change in
water quality from water flowing through the Boston Mine site (Figure 4-10).
In October 2016, the flow atthe upstream (A07E) and downstream (A07D) points was reported
to be 49 and 9 gpm, respectively. In the trans-basin ditch upstream of the site (A07D1), flow was
55 gpm in June. No other flow rate measurements were available. The upstream June and October
samples had pH values of 4.18 and 3.86 su, respectively, and the downstream June and October
samples had pH values of 4.23 and 4.11 su, respectively. At all sampling locations, the June and
October samples exceeded the acute standards for Al, Cd, Cu, Mn, and Zn, and the chronic
standard for Pb. In the trans-basin diversion sample upstream of the site, the pH was 4.26 su and
the sample had the highest Al, Cd, Mn, and Zn at the Boston Mine. At the upstream and
downstream locations in Burrows Gulch, concentrations were typically higher in October than in
June and concentrations increased between upstream and downstream points.
4.8.1.2 Boston Mine Leachate
One leachate sample was collected by CDMG from waste rock atthe Boston Mine from the lower
shaft (Table 4-2). This sample exceeded the acute standard for Cd, Cu, Pb, and Zn, and the chronic
standard for Al. CDMG and USGS estimated 900 cy of waste rock material onsite. Per Table 4-3,
one SPLP sample was analyzed from waste rock samples collected in July 2016 atthe Boston Mine
(WR-BSN). This sample exceeded the acute standards for Cd, Pb, and Zn.
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Section 4 • Preliminary Evaluation of Environmental Data
4.8.1.3 Boston Mine Soils, Waste Rock, and Sediment
Table 4-4 presents 2016 waste rock sample results for the Boston Mine. Samples were collected
at a waste rock location (WR-BSN), upstream of the Mine in Burrow Gulch (A07E), and
downstream of the mine (A07D).
Per Table 4-5, sediment samples were collected in 2016 at two locations atthe Boston Mine in
Burrows Creek. With the exception of Al, metals concentrations increased upstream to
downstream. Metals concentrations exceeded sediment screening levels for As, Cd, Cu, Pb, Mn,
and Zn in both samples.
4.8.2 London Mine
The London Mine is located on the north side of Burrows Creek along the north side of Houghton
Mountain at an elevation of 11,976 feetNGVD29. This mining-related source is directly off County
Road 18 and is easily accessible to the public. There are two adits: one has a 3-foot by 3-foot grate
and the other is collapsed. Flow is observed from each adit and seeps are present around the base
of two large waste rock piles. CDMG and USGS estimated 3,300 cy of waste rock at this location.
Orange precipitates are present in adit flow, and vegetation is stressed. Figure 4-11 shows
sample locations and other features of this mining-related source.
The following sections describe results of analyses conducted for London Mine surface water,
SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.8.2.1 London Mine Surface Water
In 2015 and 2016, four total water quality sampling locations were collected from the London
Mine (Table 4-1). Samples were collected atthe west adit (DM6), the east adit (DM7), an
upstream location in Burrows Creek (A07B1), and a downstream location in Burrows Creek
(A07B) (Figure 4-11). Location A07B was the only location sampled in 2015 in September.
Flow rates were measured at the two adit locations in June 2016. The west adit (DM6) had a
higher flow rate of 3.2 gpm compared to the east adit (DM7) at 1.1 gpm. Discharge atthe west
adit dropped to 0.7 gpm during the September 2016 event; the east adit flow rate was not
measured. The westaditpH dropped from 6.13 to 3.21 su in 2016, and the eastaditpH was 6.69
and 6.41 su in June and September 2016, respectively. In June 2016, the upstream location in
Burrows Creek (A07B1) had a flow rate of 1329 gpm and a pH of 4.28 su, and the downstream
location (A07B) had a flow rate of 1206 gpm and a pH of 4.32 su. During low-flow conditions in
September 2015, the downstream location in Burrows Creek had a flow rate of 21 gpm and a pH
of 4.3, and in September 2016 had a flow rate of 186 gpm and a pH of 4.08 su.
In June 2016, the west adit sample exceeded acute standards for Cd, Cu, Pb, and Zn, and the chronic
standard for Al. Metals concentrations in the west adit September 2016 sample had a nearly 10-fold
increase over the June 2016 sample. The east adit samples exceeded acute standards for Cd and Zn,
and chronic standards for Al and Fe. Upstream and downstream samples in Burrows Creek
exceeded acute standards for Al, Cd, Cu, Mn, and Zn, and chronic standards for Pb.
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Section 4 • Preliminary Evaluation of Environmental Data
4.8.2.2 London Mine Leachate
One leachate sample was collected by CDMG from waste rock at the London Mine (Table 4-2).
This sample exceeded the acute standards for Cd, Cu, Pb, and Zn, and the chronic standard for Al.
CDMG and USGS estimated 3,300 cy of waste rock material onsite.
Per Table 4-3, three SPLP samples were analyzed from waste rock samples collected in August
2015 and July 2016 at the London Mine (WR1-LND, WR2-LND, and AE18). The samples all
exceeded the acute standards for Cd, Cu, Pb, and Zn. The WR1-LND and AE18 samples also
exceeded the chronic standards for Al.
4.8.2.3 London Mine Soils, Waste Rock, and Sediment
Table 4-4 presents 2015 and 2016 waste rock sample results from the London Mine. Samples
were collected from three waste rock locations (WR1-LND, WR2-LND, and AE18), and soil
downstream of the mine in Burrows Creek (A07B). The sample collected downstream of London
Mine had the highest Al concentration in waste rock and soil samples collected at the Site.
Per Table 4-5, a total of three sediment samples were collected in 2015 and 2016 at location
A07B, downstream of the London Mine in Burrows Creek. Metals concentrations exceeded
sediment screening levels for As, Cd, Cu, Pb, Mn, and Zn in all samples.
4.8.3 Ben Butler Mine
Ben Butler Mine is located on the north side of Burrows Creek on the south slope of Denver Hill at
an elevation of 12,200 feetNGVD29, approximately 1,200 feet north of the London Mine. The
mine is off County Road 18, but there are no direct roads to the site and it is not readily accessible
to the public. There are two shafts and three stopes at the site, which are all filled with water.
CDMG estimates 500 cy of waste rock at this location. There are scattered metal and wood debris
onsite, but no structures. A 200-yard-long vegetation kill zone extends downslope from the waste
dump towards Burrows Creek. Figure 4-12 shows sample locations and other features of this
mining-related source.
The following sections describe results of analyses conducted for Ben Butler Mine surface water,
SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.8.3.1 Ben Butler Mine Adit Discharge and Surface Water
In June 2016, one water quality sample was collected for the Ben Butler Mine (Table 4-1) atthe
shaft location (BB1) (Figure 4-12). Flow was not measured, pH was 3.97 su, and acute standards
were exceeded for Al, Cd, Cu, Pb, and Zn.
4.8.3.2 Ben Butler Mine CDMG and EPA/ESAT Waste Rock SPLP
One leachate sample was collected by CDMG from waste rock atthe Ben Butler Mine (Table 4-2).
This sample exceeded the acute standards for Al, Cd, Cu, Pb, and Zn, and the chronic standard for
Fe. CDMG and USGS estimated 500 cy of waste rock material onsite. Of the CDMG samples, the
waste rock at Ben Butler had the highest concentrations of Al, Cd, Fe, and Zn samples among the
Animas River mining-related sources.
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Section 4 • Preliminary Evaluation of Environmental Data
Per Table 4-3, one SPLP sample was analyzed from waste rock samples collected in July 2016 at
the Ben Butler Mine (WR-BB). This sample exceeded the acute standards for Cd, Cu, Pb, and Zn,
and chronic standard for Fe. The concentrations of Pb and Zn in this waste rock SPLP sample
were among the highest for Animas River mining-related sources.
4.8.3.3 Ben Butler Mine Soils, Waste Rock, and Sediment
Table 4-4 presents 2016 waste rock sample results from the Ben Butler Mine. Samples were
collected from a waste rock location (WR-BB), and soil downstream of the mine in a drainage
channel (BB2).
Per Table 4-5, a sediment sample was collected in 2016 atlocation BB2 atthe Ben Butler Mine
below the waste rock pile. Metals concentrations exceeded sediment screening levels for As, Cd,
Cu, Pb, Mn, and Zn in the sample.
4.9 Sampling Results at Mining-Related Sources - Animas
River Headwaters
4.9.1 Mountain Queen Mine
The Mountain Queen Mine is located on the east side of Hurricane Peak at the headwaters of
California Gulch, with a shaft near the top of California Pass at an elevation of 12,790 feet NGVD29
and a draining adit east of the shaft at an elevation of 12,375 feet NGVD29. There are three shafts:
a collapsed shaft, a shaft/vent, and an upper shaft drill pad with a drill rod sticking out of ground.
The waste rock pile at the upper shaft is situated adjacent to the 4-wheel drive road over
California Pass and CDMG estimates 1,900 cy of material at this location. CDMG estimates the
waste rock pile located at the lower adit has approximately 3,200 cy of material, and snow
commonly drifts around the rock pile. There are moderate degrees of erosion on both waste rock
piles. The mine is directly off the road and is accessible to the public. The lower adit opening is
covered with a grate and rock fall occurred recently above the grate. The adit discharge flows
around both sides of the waste rock pile and into California Gulch. Figure 4-13 shows sample
locations and other features of this mining-related source.
The following sections describe results of analyses conducted for Mountain Queen Mine surface
water, SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.9.1.1 Mountain Queen Mine Adit Discharge and Surface Water
In 2015 and 2016, two total water quality sampling locations were collected for the Mountain
Queen Mine (Table 4-1). Samples were collected from the lower adit location (A19A), and
downstream of the mine in California Gulch (A18) (Figure 4-13).
In September 2015 and September 2016, flows were measured atthe adit (A19A) to be 0.8 and
2.7 gpm, respectively. pH at the adit was 3.70 su in September 2015, and pH was not reported in
September 2016. In October 2016, downstream flow at A18 was not measured, andpH was 7.30
su.
Atthe adit location in September 2015 and September 2016, acute standards were exceeded for
Al, Cd, Cu, Mn, Pb, and Zn, and chronic standards were exceeded for Fe. Downstream, the chronic
standards were exceeded for Al, Cd, and Cu.
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Section 4 • Preliminary Evaluation of Environmental Data
4.9.1.2 Mountain Queen Mine CDMG and EPA/ESAT Waste Rock SPLP
Two leachate samples were collected by CDMG from waste rock at the Mountain Queen Mine at
the upper shaft and lower adit locations (Table 4-2). These samples exceeded the acute
standards for Cd, Cu, Pb, and Zn, and the chronic standard for Al. The upper shaft also exceeded
the chronic standard for Fe. CDMG and USGS estimated 5,100 and 1,900 cy of waste rock material
onsite, respectively, for the upper and lower locations.
Per Table 4-3, two SPLP samples were analyzed from waste rock samples collected in August
2015 at the Mountain Queen Mine (AE1 and AE2). These samples both exceeded the acute
standards for Cu, Pb, and Zn, and chronic standard for Al. The AE1 sample also exceeded the acute
standard for Cd. The AE1 upper-shaft waste rock SPLP location had the highest Pb concentration
among Animas River mining-related sources.
4.9.1.3 Mountain Queen Mine Soils, Waste Rock, and Sediment
Table 4-4 presents 2015 waste rock sample results from the Mountain Queen Mine. Samples
were collected from an upper shaft location (AE1) and adit downstream (AE2).
Per Table 4-5, sediment samples were collected in 2015 at two locations atthe Mountain Queen
Mine in upper California Gulch. Metals concentrations exceeded sediment screening levels for As,
Cu, Pb, Mn, and Zn in both samples, and Cd in the downstream sample.
4.9.2 Vermillion Mine
The Vermillion Mine is located in a large gentle swale high on the north side of California Gulch
near the southwestern flank of Houghton Mountain at an elevation of 12,440 feet NGVD29. The
site requires hiking to access and has limited accessibility to the public. There is one draining adit
at the Vermillion Mine site. The adit discharge flows south over soil before infiltrating into the
waste rock pile. The drainage continues to flow approximately 2,000 feet south and southeast
where it enters the West Fork Animas River. CDMG and USGS estimated 5,100 cy of waste rock at
this location. Figure 4-14 shows sample locations and other features of this mining-related source.
The following sections describe results of analyses conducted for Vermillion Mine surface water,
SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.9.2.1 Vermillion Mine Adit Discharge and Surface Water
In 2015 and 2016, four total water quality sampling locations were collected for the Vermillion
Mine (Table 4-1). Samples were collected from a drainage channel downstream of the upper adit
(CG5), upstream of the mine in California Gulch (CG4), downstream of the mine in California
Gulch (CG6), and further downstream in California Gulch (CG6A) (Figure 4-14).
In 2016, the adit drainage channel (CG5) flow was not measured; pH was 5.48 su. Upstream of the
mine (CG4), the flow rate was 247 gpm in September 2015, 6,127 gpm in June 2016, and 1,006
gpm in October 2016. The pH at this pointranged from 5.01 to 6.58 atthese times, with lower pH
values observed during low-flow in September and October. Downstream of the mine at CG6, the
flow rate was 189 gpm in September 2015, 7,803 gpm in June 2016, and 785 gpm in September
2016. The pH ranged from 4.97 to 6.46 su atthese times, and as with the upstream location, lower
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Section 4 • Preliminary Evaluation of Environmental Data
flows had lower pH values. The farther downstream sampling location (CG6A) had a flow of 5,679
gpm and a pH of 6.57 su in June 2016.
At all sampling locations, acute standards were exceeded for Al, Cd, Cu, and Zn. Acute standards
for Mn were also exceeded during most events. Metals concentrations were typically lower
between the upstream and downstream locations.
4.9.2.2 Vermillion Mine CDMG and EPA/ESAT Waste Rock SPLP
One leachate sample was collected by CDMG from waste rock at the Vermillion Mine (Table 4-2).
This sample exceeded the acute standards for Al, Cd, Cu, Pb, and Zn, and the chronic standards for
Fe and Mn. CDMG and USGS estimated 5,100 cy of waste rock material onsite.
Per Table 4-3, one SPLP sample was analyzed from waste rock samples collected in July 2016 at
the Vermillion Mine near the adit (AE9A). This sample exceeded the acute standards for Cu, Pb,
and Zn, and chronic standards for Al and Fe.
4.9.2.3 Vermillion Mine Soils, Waste Rock, and Sediment
Table 4-4 presents 2016 waste rock sample results from the Vermillion Mine. Samples were
collected from a waste rock location (AE9A) and downstream of the mine in California Gulch
(CG6).
Per Table 4-5, sediment samples were collected in 2015 and 2016 at two locations atthe
Vermillion Mine. Metals concentrations exceeded sediment screening levels for As, Cu, Pb, Mn,
and Zn in all samples, and exceeded sediment screening levels for Cd in all samples except for
September 2016.
4.9.3 Sunbank Group Mine
The Sunbank Group Mine is located directly east of the road in Placer Gulch and is accessible to
the public. The adit is sealed with a concrete block; however, flow is coming out of the top of the
concrete block and from seeps upgradient of the adit block. Adit discharge is directed into a series
of settling ponds immediately adjacent to Placer Gulch. The ponds appear to no longer be
functional and adit drainage no longer flows sequentially through the ponds prior to discharging
into Placer Gulch. Fe precipitate is present in the drainage. Waste rock has been regraded along
the slope and partially vegetated, but the volume was not estimated. There are no onsite
structures. Figure 4-15 shows sample locations and features of this mining-related source.
The following sections describe results of analyses conducted for Sunbank Group Mine surface
water, SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.9.3.1 Sunbank Group Mine Surface Water
In 2015 and 2016, three total water quality sampling locations were collected for the Sunbank
Mine Group (Table 4-1). Samples were collected from the adit discharge location (A21A),
upstream of the mine in Placer Gulch (A22), and downstream of the mine (A21) (Figure 4-15).
Atthe adit location (A21A), flow was measured in September 2015 at 16.4 gpm and the pH was
4.79 su. No flows were recorded with the 2016 adit samples; pH was 5.51 and 3.78 in June and
September 2016, respectively. Upstream of the mine (A22), the flow was 3,576 gpm in June 2016,
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Section 4 • Preliminary Evaluation of Environmental Data
and 61 and 531 gpm in September 2015 and 2016, respectively. pH values at these times ranged
from 5.97 to 6.99 su with lower pH values occurring during low-flow conditions. Downstream of
the mine in Placer Gulch (A21), the flow was 4,916 gpm in June 2016, and 76 and 515 gpm in
September 2015 and 2016, respectively. pH values atthese times ranged from 5.54 to 6.94 su, with
lower pH values occurring during low-flow conditions. A pH decrease across the Sunbank Group
Mine was observed during fall low-flow conditions, but that effect is not apparent during spring
high-flow conditions.
At the adit in 2015 and 2016, all water samples exceeded the acute standards for Al, Cd, Mn, Pb,
and Zn, and the chronic standard for Fe. The June 2016 upstream sample also exceeded acute
standards for Cd, Cu, and Mn, and the upstream September 2015 and 2016 samples also exceeded
the chronic standard for Cd. 2015 and 2016 downstream samples exceeded the acute standards
for Cd and Zn and the chronic standards for Al and Pb. The June 2016 downstream sample also
exceeded the acute standards for Cu and Mn, and the downstream September samples also had
exceedances of the chronic standards for Cu, Fe, and Mn. Comparing metals results between
upstream and downstream locations suggests that there is an increase in Fe, Pb, and Zn
concentrations in Placer Gulch due to the Sunbank Mine Group.
4.9.3.2 Sunbank Group Mine Leachate
No waste rock samples were collected at the Sunbank Group Mine during the CDMG investigation.
However, three SPLP samples were analyzed from waste rock samples collected in August 2015
at locations AE44, AE45, and AE46 (Table 4-3). Leachate concentrations exceeded the acute
standards for Cd, Cu, Pb, and Zn at all three locations. Additionally, at AE45 and AE46, the acute
standards were exceeded for Al and Mn. At the AE45 location, waste rock SPLP concentrations of
Al and Mn were among the highest of waste rock samples for the Animas River mining-related
sources.
4.9.3.3 Sunbank Group Mine Soils, Waste Rock, and Sediment
Table 4-4 presents 2015 and 2016 soil and waste rock sample results for the Sunbank Group
Mine. Samples were collected from three adit locations (AE44, AE45, and AE46), an upstream
location in Placer Gulch (A22), and downstream location in Placer Gulch (A21).
Per Table 4-5, sediment samples were collected in 2015 and 2016 at two locations atthe
Sunbank Mine Group in Placer Gulch. Metals concentrations exceeded sediment screening levels
for As, Cd, Cu, Pb, Mn, Hg, and Zn in all samples. Concentrations of Hg were significantly higher
than sediments from all other mining-related sources, and concentrations of Pb and Zn noticeably
increased between the upstream and downstream locations.
4.9.4 Frisco/Bagley Tunnel
The Frisco/Bagley Tunnel is located approximately 0.5 miles west of Animas Forks on the north
side of California Gulch. The site is located at an elevation of 11,440 feet NGVD29. A 4-wheel drive
access road (County Road 9) passes through the mine area and splits a large waste rock pile in
two, making it accessible to the public. CDMG and USGS estimated these two waste rock piles at
41,000 cy and 20,500 cy, respectively. A rock and mortar closure with a grate is installed at the
adit portal located on top of the waste rock pile on the north side of the road. The adit discharge is
channelized southwest across a waste rock pile and red staining is highly visible throughout the
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Section 4 • Preliminary Evaluation of Environmental Data
channels, which flow into California Gulch. Vegetation kill is apparent at the site and within the
adit flow channel. Additional adit flow ponds on top of the waste rock pile. Water seeps out base
of waste rock pile, and the waste rock pile is being undercut by California Gulch. There is a mill
structure onsite. Figure 4-16 shows sample locations and features of this mining-related source.
The following sections describe results of analyses conducted for the Frisco/Bagley Tunnel
surface water, SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.9.4.1 Frisco/Bagley Tunnel Adit Discharge and Surface Water
In 2015 and 2016, three total water quality sampling locations were collected for the Frisco/
Bagley Tunnel (Table 4-1). Samples were collected from an adit discharge channel (A12),
upstream of the mine in California Gulch (A13), and downstream of the mine (CG9) (Figure 4-16).
In the adit discharge channel (A12), flows ranged from 18 to 83 gpm during high-flow conditions
in June 2015 and 2016, and from 18 to 58 gpm during low-flow conditions in September 2015
and October 2016. pH atthe adit ranged from 6.25 to 7.14 su in 2015 and 2016. Upstream of the
Frisco/Bagley Tunnel at A13, flow was 25,192 gpm in June 2015, and flow ranged from 521 to
2,053 gpm in September 2015 and 2016, respectively. Downstream flows atCG9 were similar.
Upstream (A13) pH in June 2015 and 2016 ranged from 6.20 to 6.57 su, which decreased and
ranged from 5.31 to 5.43 su in September 2015 and 2016, indicating that seasonal changes in pH
are occurring in this area. Downstream of the mine at CG9, June 2015 and 2016 samples had a pH
range of 6.28 to 6.50 su, and a range of 5.27 to 5.48 su in September.
The Frisco/Bagley Tunnel adit channel samples all exceeded acute standards for Mn and Zn, and
chronic standards for Al, Cd, and Fe. The upstream samples all exceeded acute standards for Al,
Cd, Cu, and Zn. Also, except the June 2015 sample, all upstream samples exceeded the acute
standard for Mn, and except the September 2016 sample, all upstream samples exceeded the
chronic standard for Pb. The downstream samples all exceeded acute standards for Cd and Zn.
Also, except the September 2015 sample, all downstream samples exceeded the acute standard
for Al, except the September 2016 sample, all downstream samples exceeded the acute standard
for Cu and the chronic standard for Pb, and except the June 2015 sample, all downstream samples
exceeded the acute standard for Mn. The data from Table 4-1 indicate that metals concentrations
in California Gulch at this point were higher during fall low-flow conditions when compared to
June high-flow conditions.
4.9.4.2 Frisco/Bagley Tunnel CDMG and EPA/ESAT Waste Rock SPLP
Two leachate samples were collected by CDMG from waste rock and tailings at the Frisco/Bagley
Tunnel (Table 4-2). These samples exceeded the acute standards for Cd, Cu, Pb, and Zn, and the
tailings sample exceeded the chronic standard for Al. CDMG and USGS estimated 41,000 and
20,500 cy of waste rock material onsite, respectively.
Per Table 4-3, two SPLP samples were analyzed from waste rock samples collected in August
2015 atthe Frisco/Bagley Tunnel (AE10 and AE10A). The AE10 sample exceeded the acute
standards for Cd and Zn, and chronic standards for Mn and Pb. The AE10A sample exceeded the
chronic standards for Cd, Mn, and Pb, and had the lowest waste rock SPLP concentrations for Zn
waste rock samples among the Animas River mining-related sources.
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Section 4 • Preliminary Evaluation of Environmental Data
4.9.4.3 Frisco/Bagley Tunnel Soils, Waste Rock, and Sediment
Table 4-4 presents 2015 and 2016 soil and waste rock sample results for the Frisco/Bagley
Tunnel. Samples were collected from two waste rock locations (AE10 and AE10A), a location
north of the mine (GC-OPP), an upstream location in California Gulch (A13), and a downstream
location in California Gulch (CG9). The downstream sample had the highest Mn and Zn
concentrations of any sample collected in the Upper Animas River.
Per Table 4-5, sediment samples were collected in 2015 and 2016 at three locations at the
Frisco/Bagley Tunnel. Metals concentrations exceeded sediment screening levels for As, Cd, Cu,
Pb, Mn, and Zn at all locations, and Fe exceeded sediment screening levels at the adit drainage in
September 2016. Sediment concentrations of Fe and Zn at the adit drainage were the highest
measured among Animas River mining-related sources, and metals concentrations typically
increased between the upstream and downstream sample.
4.9.5 Columbus Mine
The Columbus Mine adit is located across the stream in California Gulch from Animas Forks at an
elevation of 11,240 feet NGVD29. The site is adjacent to County Road 9 and is accessible to the
public. CDMG and USGS both estimated 24,000 cy of waste rock onsite. The site has a single
discharging adit that infiltrates into the waste rock pile, which flows south for approximately 300
feet before emerging at the base of the waste rock and enters California Gulch. There are a series
of seeps below both levels of the waste rock pile that may be from the adit discharge. The waste
rock pile is both moderately eroded and being undercut at the creek. At the adit, a 3-foot by 3-foot
grate is installed. There are four dilapidated buildings onsite. Figure 4-17 shows sample
locations and features of this mining-related source.
The following sections describe results of analyses conducted for the Columbus Mine surface
water, SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.9.5.1 Columbus Mine Adit Discharge and Surface Water
In 2015 and 2016, three total water quality sampling locations were collected for the Columbus
Mine (Table 4-1). Samples were collected from an adit discharge (All A), upstream of the mine in
California Gulch (CG11), and downstream of the mine before confluence with the Upper Animas
River (A10) (Figure 4-17).
At the adit discharge (AllA) in June 2015 and 2016, flow ranged from 27 to 37 gpm and pH
ranged from 3.05 to 4.16 su. In October 2015 and 2016, flow at the adit ranged from 0.1 to 0.3
gpm and pH ranged from 2.85 to 2.89 su, indicating a notable seasonal change in adit discharge.
Upstream of Columbus at CG11, flow was 21,799 gpm in June 2015 and pH ranged from 6.26 to
6.46 su in June 2015 and 2016, while flow ranged from 572 to 3,305 gpm and pH was 5.34 su in
September 2015 and 2016. Downstream from the Columbus Mine at A10, pH was 6.18 su in June
2015 and flow was 16,137 gpm in June 2016, and flow ranged from 634 to 2387 gpm and pH
ranged from 5.13 to 5.43 su in September 2015 and 2016.
The Columbus Mine adit samples all exceeded acute standards for Al, Cd, Cu, Mn, Pb, and Zn, and
chronic standards for Fe. Adit samples from the Columbus Mine contained the highest
concentrations of Cd and Zn measured in the Upper Animas basin. All upstream and downstream
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Section 4 • Preliminary Evaluation of Environmental Data
samples exceeded acute standards for Cd, Cu, and Zn, and chronic standards for Pb. Except for the
September 2015 and 2016 upstream samples, all samples also exceeded the acute standard for Al,
and except for the June 2015 upstream sample, all samples exceeded the acute standard for Mn.
The data from Table 4-1 indicate that adit metals concentrations were typically orders of
magnitude higher than upstream and downstream concentrations in the West Fork Animas River,
and that metals concentrations in the West Fork Animas River at the Columbus Mine were higher
during September low-flow conditions than during June high-flow conditions.
4.9.5.2 Columbus Mine CDMG and EPA/ESAT Waste Rock SPLP
One leachate sample was collected by CDMG from waste rock at the Columbus Mine (Table 4-2).
This sample exceeded the acute standards for Cd, Cu, Pb, and Zn, and the chronic standard for Al.
CDMG and USGS estimated there was 24,000 cy of waste rock material onsite.
Per Table 4-3, one SPLP sample was analyzed from waste rock samples collected in August 2015
at the Columbus Mine near the adit (AE13). This sample exceeded the acute standards for Cd, Cu,
and Zn, and chronic standards for Mn and Pb.
4.9.5.3 Columbus Mine Soils, Waste Rock, and Sediment
Table 4-4 presents 2015 and 2016 waste rock sample results for the Columbus Mine. Samples
were collected from the waste rock (AE13), an upstream location in California Gulch (CG11), and
downstream location in California Gulch (A10).
Per Table 4-5, sediment samples were collected in 2015 and 2016 at two locations atthe
Columbus Mine. Metals concentrations exceeded sediment screening levels for As, Cd, Cu, Pb, Mn,
and Zn at all locations, and Al and Hg exceeded sediment screening levels in the downstream
sample in September 2015. The sediment concentration of Al in the downstream sample in
September 2015 was the highest measured among Animas River mining-related sources.
4.10 Sampling Results at Mining-Related Sources - Animas
Forks to Eureka
4.10.1 Campground 7
Campground 7 is located approximately 1.1 miles south of Animas Forks, on the west side of the
Upper Animas River at the road fork below a bridge crossing the Upper Animas River.
Campground 7 is considered a dispersed campsite, an area that is suitable for camping or where
camping is known to occur but may not be a formal campground. Campground 7 is near the
former location of the Eclipse Smelter according to USGS (Church et al. 2007), at an elevation of
approximately 10,800 feet. The site is accessible to the public and is used for recreational
purposes. Figure 4-18 shows relevant features of this mining-related source.
The following section describes results of analyses conducted for the Campground 7 location for
soil/waste rock concentrations, as provided in Table 4-4. No surface water, leachability, or
sediment samples are associated specifically with this location.
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Section 4 • Preliminary Evaluation of Environmental Data
4.10.1.1 Campground 7 Waste Rock
Per Table 4-4, a sample of soil/waste rock was collected in July 2016 from the Campground 7
location (CMP7). The sample exceeded the human health risk-based level for Pb.
4.10.2 Silver Wing Mine
The Silver Wing Mine is located on the east side of the Upper Animas River, south of Animas
Forks, at an elevation of 10,500 feetNGVD29. This mining-related source is generally not
accessible to the public. CDMG and USGS estimated 10,000 cy of waste material onsite. Adit flow
is directed into a settling pond, which was formerly directed though bioreactor tanks prior to
discharge to the Upper Animas River. The bioreactor tanks are not functional, and flow currently
bypasses the former tanks and is piped to the river. Figure 4-19 shows relevant features of this
mining-related source.
The following sections describe results of analyses conducted for Silver Wing Mine surface water,
SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.10.2.1 Silver Wing Mine Surface Water
In 2015 and 2016, four total water quality sampling locations were collected for the Silver Wing
Mine (Table 4-1). Samples were collected from the adit discharge location (A29), a discharging
pipe into the Animas River (A29A), upstream of the mine in the Upper Animas River (A28), and
downstream of the mine in the Upper Animas River (A30) (Figure 4-19).
The flow rate was measured only once atthe adit (A29) in June 2016 at 7.3 gpm. Flow atthe
discharge point into the Upper Animas River (A29A) was not measured in 2015 or 2016 so it is
unknown if flow is lost between the adit and the pipe discharge point. Flow was measured in
September 2015 atthe upstream (A28) and downstream (A30) points to be 1,754 and 2,503 gpm,
respectively. Flow was not reported at the upstream and downstream locations in the Upper
Animas River in 2016. Atthe adit, pH ranged from 6.42 to 6.49 su in June 2015 and June 2016,
respectively, and was 5.74 su in September 2015. pH was not reported at the adit in September
2016. Atthe discharging pipe, pH ranged from 6.96 to 7.08 su in June 2015 and 2016. In June
2015 and 2016, upstream pH ranged from 7.57 to 7.62 su, and downstream pH ranged from 7.52
to 7.54 su. In September 2015, a change in pH between upstream and downstream was observed
(7.03 and 5.82 su, respectively).
At the adit and adit discharging pipe, water quality samples exceeded acute standards for Cd, Cu,
and Zn, and exceeded the chronic standard for Al, Fe, and Mn. Except for the June 2015 sample,
adit samples exceeded the chronic standard for As. There does not appear to be a significant
increase in metals concentrations between high- and low-flow conditions atthe adit
Upstream of the Silver Wing Mine in the Upper Animas River, water samples exceeded acute
standards for Cd and Zn, and the chronic standards for Al. At this location, acute standards were
also exceeded for Cu and Mn during June and September 2015, respectively.
Downstream of the mine, acute standards were exceeded for Cd and Zn, and chronic standards for
Al. The June 2015 and 2016 downstream samples also exceeded the acute standards for Cu and
the chronic standard for Pb. The September 2015 sample also exceeded the acute standard for Mn
4-28
-------
Section 4 • Preliminary Evaluation of Environmental Data
and the chronic standard for Cu. Between high-flow and low-flow conditions at both the upstream
and downstream points, there is an increase in metals concentrations in the Upper Animas River.
4.10.2.2 Silver Wing Mine Leachate
One leachate sample was collected by CDMG from waste rock at the Silver Wing Mine (Table 4-2).
This sample exceeded the acute standards for Al, Cd, Cu, Mn, Pb, and Zn, and the chronic standard
for Fe. CDMG and USGS estimated 10,000 cy of waste rock material onsite.
Per Table 4-3, two SPLP samples were analyzed from waste rock samples collected in August
2015 atthe Silver Wing Mine near the adit (AE32A and AE32b). At AE32A, leachate concentrations
exceeded acute standards for Cd, Cu, Pb, and Zn, and chronic standards for Al and Fe. At AE32b,
leachate concentrations exceed acute standards for Al, Cd, Cu, Pb, and Zn, and chronic standards
for Fe and Mn. Atthe AE32B location, the waste rock SPLP concentration of Cu was orders of
magnitude higher than those typically found in the other Animas River mining-related sources.
4.10.2.3 Silver Wing Mine Soils, Waste Rock, and Sediment
Per Table 4-4, two waste rock samples were collected in August 2015 from the Silver Wing Mine
site (AE32Aand AE32b).
Per Table 4-5, sediment samples were collected in August and September 2015 attwo locations
at the Silver Wing Mine. Metals concentrations exceeded sediment screening levels for As, Cd, Cu,
Pb, Mn, and Zn at both locations. Concentrations of Al. Cu, and Mn typically increased between the
upstream and downstream sample locations.
4.10.3 Tom Moore Mine
The Tom Moore Mine aditis located approximately 1.25 miles north of Eureka on County Road 2
at an elevation of 10,360 feet NGVD29. The mine is located across the Upper Animas River from
the road and has very limited accessibility to the public. CDMG and USGS both estimated 4,000 cy
of waste rock onsite. The waste rock pile is located immediately adjacent to the Upper Animas
River, and erosion and undercutting of the waste rock is observed. A concrete foundation is
present onsite. Figure 4-20 shows relevant features of this mining-related source.
The following sections describe results of analyses conducted for Tom Moore Mine surface water,
SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.10.3.1 Tom Moore Mine Adit Discharge and Surface Water
In 2016, three total water quality sampling locations were collected for the Tom Moore Mine
(Table 4-1). Samples were collected from the adit discharge location (DM22), upstream of the
mine (A3 OA), and downstream of the mine (A3 0B) (Figure 4-20).
Flow was measured atthe adit location (DM22) in September 2016 to be 21 gpm, and pH at this
location was 7.31 su in June 2016. Downstream of the mine at A30B, flow was 7,096 gpm in
September 2016. Upstream pH ranged from 6.94 to 7.29 su at A30A, and downstream pH ranged
from 6.97 to 7.45 su, where the lower pH values corresponded to fall low-flow conditions.
Atthe Tom Moore Mine adit, acute standards were only exceeded for Zn, and chronic standards
for Cd. Upstream and downstream metals concentrations exceeded acute standards for Cd and Zn,
4-29
-------
Section 4 • Preliminary Evaluation of Environmental Data
and chronic standards for Al. At this point in the Upper Animas River, acute Cu standards were
exceeded during June 2015 and 2016 high-flow conditions and acute Mn standards were
exceeded during September low-flow conditions. Metals concentrations in the Upper Animas
River were also generally higher during low-flow conditions.
4.10.3.2 Tom Moore Mine CDMG and EPA/ESAT Waste Rock SPLP
One leachate sample was collected by CDMG from soil/waste rock at the Tom Moore Mine
(Table 4-2). This sample exceeded the acute standards for Al, Cd, Cu, Mn, Pb, and Zn, and the
chronic standard for Fe. CDMG and USGS estimated 4,000 cy of waste rock material onsite.
Per Table 4-3, one SPLP sample was analyzed from waste rock samples collected in July 2016 at
the Tom Moore Mine (WR-TM). This sample exceeded the acute standards for Cd, Cu, Mn, Pb, and
Zn, and chronic standards for Al and Fe. Waste rock SPLP concentrations of Al, Cd, Mn, and Zn in
this waste rock sample were significantly higher than those typically found in the Animas River
mining-related sources.
4.10.3.3 Tom Moore Mine Soils, Waste Rock, and Sediment
Per Table 4-4, one waste rock sample was collected in August 2016 from the Tom Moore Mine at
an onsite waste rock location (WR-TM).
Per Table 4-5, sediment samples were collected in 2016 at two locations atthe Tom Moore Mine.
Metals concentrations exceeded screening levels for As, Cd, Cu, Pb, Mn, and Zn at both locations.
Metals concentrations in sediments did not typically increase between the upstream and
downstream sample.
4.11 Sampling Results at Mining-Related Sources - Eureka
Gulch
4.11.1 Ben Franklin Mine
This Ben Franklin Mine is located immediately below the confluence of the headwaters of Eureka
Gulch at an elevation of 11,920 feetNGVD29. The site is adjacent to County Road 25 and is
accessible to the public. A barbed wire fence is present surrounding a stope atthe site. Currently,
stream flow has been diverted through a culvert across the road to the main channel of Eureka
Gulch to avoid flowing through the stope. The mine adit shows signs of seasonal discharge. The
waste rock pile is located adjacent to Eureka Gulch and there is a moderate degree of erosion of
this waste rock. USGS estimated 500 cy of waste rock onsite. A portion of the waste rock has been
used to create a levee for the stream channel. Waste rock at the adit discharge smells of sulfur.
Eureka Gulch flows on the north side of waste rock. There is stressed vegetation below the waste
rock. There are no structures onsite. Figure 4-21 shows relevant features of this mining-related
source.
The following sections describe results of analyses conducted for Ben Franklin Mine surface
water, SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4-30
-------
Section 4 • Preliminary Evaluation of Environmental Data
4.11.1.1 Ben Franklin Mine Adit Discharge and Surface Water
In 2015 and 2016, four total water quality sampling locations were collected for the Ben Franklin
Mine (Table 4-1). Samples were collected from the drainage of the waste rock pile (ARD1),
upstream of the mine before culvert under road (EG3A), near the midpoint of the Ben Franklin
Mine waste rock in Eureka Gulch (EG5), and downstream of the mine (A39A) (Figure 4-21).
Upstream of the mine atEG3A, flow was 35 gpm September 2015 and 4,657gpm in June 2016,
while flow was 222 gpm in September 2016 atthe mine midpoint location (EG5). At the upstream
location, pH ranged from 6.24 to 7.25 su, with the lower pH occurring during spring high-flow
conditions in 2016. Atthe mine midpoint location, pH ranged from 7.01 to 7.14 su, while pH was
7.59 su in June 2016 atthe downstream location. Atthe waste rock pile drainage location (ARD1),
pH ranged from 2.76 to 3.10 su.
Atthe waste rock pile drainage location, acute standards were exceeded for Al, Cd, Cu, Mn, Pb,
and Zn, and chronic standards for Fe. These metals concentrations from the waste rock pile were
orders of magnitude above those found upstream and downstream of the mine in Eureka Gulch.
Upstream of the Ben Franklin Mine, June 2016 acute standards were exceeded for Cd, Cu, and Zn,
while September 2015 exceeded the acute standard for Zn, and chronic standards for Cd, Cu, and
Pb. Downstream in June 2016, acute standards were exceeded for Cd, Cu, and Zn, and chronic
standards for Al, and Pb. In June 2016, the midpoint waste rock sample exceeded acute standards
for Cd, Cu, and Zn, and chronic standards for Al and Pb. Metals concentrations were generally
higher during spring high-flow conditions when compared to fall low-flow conditions atthe
upstream and midpoint sample locations.
4.11.1.2 Ben Franklin Mine CDMG and EPA/ESAT Waste Rock SPLP
Two leachate samples were collected by CDMG from waste rock atthe Ben Franklin Mine
(Table 4-2). The prospect sample exceeded the acute standards for Cd, Cu, Mn, Pb, and Zn, and
the mine sample exceeded the acute standards for Al, Cd, Cu, Mn, Pb, and Zn, and the chronic
standard for Fe. CDMG and USGS estimated 500 cy of waste rock material onsite.
Per Table 4-3, one SPLP sample was analyzed from waste rock samples collected in August 2015
atthe Ben Franklin Mine (BE4). This sample exceeded the acute standards for Cd, Cu, Mn, Pb, and
Zn, and chronic standards for Al and Fe.
4.11.1.3 Ben Franklin Mine Soils, Waste Rock, and Sediment
Per Table 4-4, waste rock and soil samples were collected in 2015 and 2016 from the Ben
Franklin Mine at a waste rock location (BE4), an upstream location in Eureka Gulch (EG3A), and a
location downstream from the onsite stope (EG5).
Per Table 4-5, sediment samples were collected in 2015 and 2016 at three locations atthe Ben
Franklin Mine. Metals concentrations exceeded sediment screening levels for As, Cd, Cu, Pb, Mn,
and Zn at all locations. Hg was elevated above sediment screening levels in the upstream
September 2015 sample, and the September 2016 downstream sample had the highest Pb and
Mn concentrations of the Animas River mining-related sources. Metals concentrations in
sediments typically increased between the upstream and downstream samples.
%
4-31
-------
Section 4 • Preliminary Evaluation of Environmental Data
4.11.2 Terry Tunnel
The Terry Tunnel is located just south of County Road 25 at an elevation of 11,560 feetNGVD29.
There is a road onto the waste rock pile which is accessible to the public. The Terry Tunnel is
bulkheaded and buried, and water flows out of the bulkheaded tunnel into a drainage ditch that
directs water around the reclaimed waste rock pile. The waste rock pile has been covered by
native rock material; Eureka Gulch flows below the toe of the waste rock pile. There are no
structures onsite. Figure 4-22 shows relevant features of this mining-related source.
The following sections describe results of analyses conducted for Terry Tunnel surface water,
SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.11.2.1 Terry Tunnel Adit Discharge and Surface Water
In 2015 and 2016, three total water quality sampling locations were collected for the Terry
Tunnel (Table 4-1). Samples were collected from the tunnel drainage (A38), upstream of the
reclaimed waste rock pile (A39), and downstream of Terry Tunnel in Eureka Gulch (EG6)
(Figure 4-22).
At the Terry Tunnel drainage (A3 8), flow was not measured in June or September 2016; pH
ranged from 7.07 su to 7.16 su. Upstream at A39 and downstream of Terry Tunnel at EG6, pH
ranged from 7.10 to 7.55 su in 2015 and 2016. Flow downstream of the Terry Tunnel was 7,133
gpm in June 2016 and was 98 and 373 gpm in September 2015 and September 2016, respectively.
At the tunnel drainage, metals concentrations in 2016 exceeded acute standards for Mn and Zn.
Upstream of the reclaimed waste rock, metals concentrations in June 2016 exceeded acute
standards for Cd, Cu, and Zn, and chronic standards for A1 and Pb. The September 2015 and 2016
upstream samples exceeded acute standards for Cu and Zn, and chronic standards for A1 and Cd.
Downstream of Terry Tunnel in June 2015 and 2016, acute standards were exceeded for Cd, Cu,
and Zn, and the chronic standard for Al. Downstream of Terry Tunnel in September 2015 and
2016, metals concentrations were lower than in June of those years and acute standards were
exceeded only for Zn. These results indicate that the Terry Tunnel did not meaningfully
contribute to metals concentrations in Eureka Gulch at these points in time.
4.11.2.2 Terry Tunnel CDMG and EPA/ESAT Waste Rock SPLP
No waste rock leachability samples were collected at the Terry Tunnel during the CDMG or recent
ESAT investigations.
4.11.2.3 Terry Tunnel Soils, Waste Rock, and Sediment
Per Table 4-4, soil samples were collected in 2016 from the Terry Tunnel at an upstream location
in Eureka Gulch (A39) and a downstream location (EG6).
Per Table 4-5, sediment samples were collected in 2015 and 2016 at two locations atthe Terry
Tunnel. Metals concentrations exceeded sediment screening levels for As, Cd, Cu, Pb, Mn, and Zn
at all locations.
4-32
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Section 4 • Preliminary Evaluation of Environmental Data
4.12 Sampling Results at Mining-Related Sources -
Cunningham Gulch
4.12.1 Pride of the West Mine
The Pride of the West Mine is located on the east side of Cunningham Creek off of County Road 4
at an elevation of 10,280 feet NGVD29. The site is gated but is still accessible to the public by
walking. The primary adit has a metal frame cover and is chained and padlocked. The primary
adit discharges water through a channel on top of a large waste rock pile, through a culvert, and
down a gully on the waste rock pile into the stream. Two additional, nonflowing, grated adits are
located north of the flowing adit The waste rock pile is of unknown size but is large and spans
along the canyon wall. In 1997, approximately 84,000 cy of tailings were removed. The degree of
erosion of the waste rock is moderate, and the pile is being undercut by the stream. There are six
structures onsite in various stages of repair. There is an onsite bunkhouse, which is advertised as
a vacation rental. Figure 4-23 shows relevant features of this mining-related source.
The following sections describe results of analyses conducted for the Pride of the West Mine
surface water, SPLP, soils, waste rock, and sediments, as provided in Tables 4-1 through 4-5.
4.12.1.1 Pride of the West Mine Adit Discharge and Surface Water
In 2016, three total water quality sampling locations were collected for the Pride of the West Mine
(Table 4-1). Samples were collected from an upstream location in Cunningham Creek (CU4), a
downstream location in Cunningham Creek (CU4A), and an adit location (A50) (Figure 4-23).
In September 2016, upstream (CU4) and downstream (CU4A) flows were 6,610 and 6,739 gpm,
respectively. Adit flow at A50 was not reported. 2016 upstream pH ranged from 7.39 to 7.45,
downstream pH ranged from 7.23 to 7.36 su, and aditpH ranged from 7.67 to 7.75 su.
Upstream and downstream sampling points both exceeded acute standards for A1 in June 2016.
Fe was also elevated during June 2016 high-flow conditions relative to the fall. At the adit, all
samples in 2016 exceeded acute standards for Cd and Zn and chronic standards for Al, while June
2016 samples also had exceedances of chronic standards for Cu and Pb.
4.12.1.2 Pride of the West Mine CDMG and EPA/ESAT Waste Rock SPLP
No waste rock samples were collected at the Pride of the West Mine during the CDMG
investigation. However, two SPLP locations were analyzed from waste rock samples collected in
July 2016 (WR-PWN and WR-PWS) (Table 4-3). The WR-PWN sample exceeded the acute
standard for Cd, and the chronic standards for Al, Pb and Zn. The 10- and 60-sieve portions of the
WR-PWS sample both exceeded acute standards for Cd, Cu, Pb, and Zn, and the chronic standard
for Al.
4.12.1.3 Pride of the West Mine Soils, Waste Rock, and Sediment
Per Table 4-4, waste rock and soil samples were collected in 2016 from the Pride of the West
Mine at north and south waste rock locations (WR-PWN and WR-PWS), an upstream location in
Cunningham Creek (CU4), and a downstream location (CU4A).
%
4-33
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Section 4 • Preliminary Evaluation of Environmental Data
Per Table 4-5, sediment samples were collected in 2016 at three locations at the Pride ofthe
West Mine. At the adit, metals concentrations exceeded sediment screening levels for As, Cd, Cu,
Pb, Mn, and Zn. Upstream of the mine in Cunningham Creek, metals concentrations exceeded
sediment screening levels for Pb, Mn, and Zn. Downstream of the mine, sediments exceeded
sediment screening levels for Cd, Pb, Mn, and Zn. Metals concentrations in sediments typically
increased between the upstream and downstream sample.
4.13 Sampling Results at Mining-Related Sources -
Howardsville to Silverton
4.13.1 Campground 4
Campground 4 is located near the Animas River adjacent to a spur road off of County Road 2
below Howardsville, approximately 900 feet below the Howardsville bridge over the Upper
Animas River. The Campground 4 location sits at an elevation of approximately 9,600 feet
Campground 4 is considered a dispersed campsite, an area that is suitable for camping or where
camping is known to occur but may not be a formal campground. The Campground 4 area was
identified as a mine tailings area by CDMG, described as Mill Tailings Site #20 in Herron et al.
(2000). The site is adjacent to the spur road and is accessible to the public and used for
recreational purposes. Figure 4-24 shows relevant features of this mining-related source.
The following sections describe results of analyses conducted for the Campground 4 location for
leachability and soil/waste rock concentrations, as provided in Tables 4-2 and 4-4. No surface
water or sediment samples are associated specifically with this location.
4.13.1.1 Campground 4 CDMG Waste Rock SPLP
One leachate sample was collected by CDMG from the tailings and waste rock at the Campground
4 area/mill tailings site #20 (Table 4-2). The leachability results exceeded the acute standards
for Cd, Cu, Mn, Pb, and Zn, and the chronic standard for Al. CDMG estimated 1,200 cy of
tailings/waste rock material onsite.
4.13.1.2 Campground 4 Waste Rock
Per Table 4-4, a sample of soil/waste rock was collected in 2016 from the Campground 4
location (CMP4). The sample exceeded the human health risk-based level for Pb. In addition to
elevated Cu and Zn, this sample had the highest Pb and Hg in waste rock and soils measured in
the Upper Animas River.
4-34
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Section 5
References
Burbank, W.S. and R.G. Luedke. 1969. Geology and Ore Deposits of the Eureka and Adjoining
Districts San Juan Mountains¦, Colorado. U.S. Geological Survey Professional Paper 535.
Church, S.E., von Guerard, Paul, and Finger, S.E., eds. 2007. Integrated investigations of
environmental effects of historical mining in the Animas River watershed, San Juan County
Colorado. U.S. Geological Survey Professional Paper 1651.
CDPHE. 2016. Classifications and Numeric Standards for San Juan River and Dolores River Basins.
Regulation Number 34.
CGS. 2017a. Map of San Juan County, accessed June 20, 2017,
?eologicalsurvey.or£
CGS. 2017b. Map of Eureka, accessed June 20, 2017,
http://coloradogeologicalsurvey.org/mmeral-resources/historic-mmmg-districts/san-iuan-
countv/eureka
Chapman, S.S., G.E. Griffith, J.M. Ornemik, A.B. Price, J. Freeouf, and D.L. Schrupp. 2006. Ecoregions
of Colorado. Reston, Virginia. (U.S. Geological Survey map).
DRMS. 2011. Koehler Two Drilling and Grouting, Animas River Stakeholders Group, Non-Point
Source 319 Project. 4 pages.
EPA. 1988. Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA.
U.S. Environmental Protection Agency. EPA/540/G-89/004. Interim Final.
EPA. 2016a. Hazard Ranking System Documentation Record. U.S. Environmental Protection
Agency.
EPA. 2016b. Documentation of an Emergency Removal Action at the Gold King Mine Release Site,
San Juan CountyColorado, initiated pursuant to the On-Scene Coordinator's delegated authority
under CERCLA Section 104 and a Request for Approval and Funding to Continue the Emergency
Removal Action including Exemptions from the 12-Month and $2 Million Statutory Limits in
Removal Actions. U.S. Environmental Protection Agency.
EPA. 2016c. EPA adds Bonita Peak Mining District Site in San Juan County, Colo, to Superfund List.
Accessed June 20, 2017, https://www.epa.gov/newsreleases/epa-adds-bonita-peak-mining-
district-site-san-juan-county-colo-superfund-list
Free, B., RW. Hutchinson, and B.C. Koch. 1989. Gold Deposition at Gold King, Silverton Caldera,
Colorado. Naturwissenschaftlicher Verein, Gratz, Styria, Austria. Available at
http://www.zobodat.at/pdf/MittNatVerSt 120 0135-0143.pdf
%
5-1
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Section 5 • References
Herron, J., Stover, B., Krabacher, P., Bucknam, D. 1997. "Mineral Creek Reclamation Feasibility
Report." Colorado Division of Minerals and Geology. Unpublished.
Herron, J., Stover, B., Krabacher, P. 1998. "Cement Creek Reclamation Feasibility Report."
Colorado Division of Minerals and Geology. Unpublished.
Herron, J., Stover, B., Krabacher, P. 1999. "Reclamation Feasibility Report Animas River Above
Eureka." Colorado Division of Minerals and Geology. Unpublished.
Herron, J., Stover, B., Krabacher, P. 2000. "Reclamation Feasibility Report Animas River Below
Eureka." Colorado Division of Minerals and Geology. Unpublished.
Ingersoll et al. 1996. "Calculation and Evaluation of Sediment Effect Concentrations for the
Amphipod Hyalella azteca and the Midge Chironomus riparius." Journal of Great Lakes Research
22, no. 3: pp 22:602-623.
MacDonald et al. 2000. "Development and Evaluation of Consensus-Based Sediment Quality
Guidelines for Freshwater Ecosystems". Environmental Contamination and Toxicology. Volume
39, Issue 1 (July): pp 20-31.
NOAA. 2018. Global Summary of the Year Station Details (2016), accessed March 14, 2018, at
https://www.ncdc.noaa.gov/cdo-web/datasets/GSOY/stations/ GHCND:USC00057656/detail.
NRCS. 2016. Web Soil Survey. Natural Resources Conservation Service, United States Department
of Agriculture. Survey Area Data: September 23, 2016, accessed February 14, 2017, at
http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm
Simon Hydro-Search. 1993. Evaluation of Hydraulic and Hydrochemical Aspects of Proposed
Bulkheads¦, Sunnyside Mine, San Juan CountyColorado. Report prepared for Sunnyside Gold
Corporation.
Stover, B.K. 2007. Report of Structural Geologic Investigation, Red & Bonita Mine, San Juan County
Colorado. Colorado Division of Reclamation, Mining, and Safety.
TechLaw. 2016. Sampling Activities Report, 2015 Sampling Events, Bonita Peak Mining District, San
Juan/La Plata Counties; Colorado. Prepared for U.S. Environmental Protection Agency.
TechLaw. 2017. Draft Sampling Activities Report, 2016 Sampling Events, Bonita Peak Mining
District, San Juan/La Plata Counties, Colorado. Prepared for U.S. Environmental Protection Agency.
URS Operating Services. 2012. START3 - Cement Creek Wetland and Sensitive Habitat Findings
Report, San Juan County, Colorado. Available at https://semspub.epa.gov/work/08/1771048.pdf.
USGS. 2007a. Geologic Framework. Chapter El of Integrated Investigations of Environmental
Effects of Historical Mining in the Animas River Watershed, San Juan County, Colorado. U.S.
Geological Survey Professional Paper 1651.
5-2
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Section 5
USGS. 2007b. The Animas River Watershed, San Juan County, Colorado. Chapter B of Integrated
Investigations of Environmental Effects of Historical Mining in the Animas River Watershed, San
Juan County, Colorado. U.S. Geological Survey Professional Paper 1651.
USGS. 2018a. Station 09359010, Mineral Creek at Silverton, Colorado, accessed on January 24,
2018, at https://waterdata.usgs.gov/nwis/inventory7agency code=USGS&site no=09359010.
USGS. 2018b. Station 09358550, Cement Creek at Silverton, Colorado, accessed on January 24,
2018, at https://waterdata.usgs.gov/nwis/inventory/7site no=09358550&agencv cd=USGS.
USGS. 2018c. Station 09358000, Animas River at Silverton, Colorado, accessed on January 24,
2018, at https://waterdata.usgs.gov/nwis/inventory7agency code=USGS&site no=09358000.
USGS. 2018d. Station 09359020, Animas River below Silverton, Colorado, accessed on January 24,
2018, at https://waterdata.usgs.gov/nwis/inventory7agency code=USGS&site no=09359020.
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Section 5 • References
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5-4
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Tables
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Tables
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Table 2-1
Evaluation Summary of Existing Data Reports
Preliminary Remedial Investigation Report, Bonita Peak Mining District
Data Source
(originating
organization,
report title, and
date)
Report Description
(data types,
generation, and
collection dates)
Data generated
under an
approved quality
plan or sampling
document?
Measurement
performance
criteria met?
Reporting limits
low enough to
meet the
performance
criteria?
Data
comparable
to other
accepted
data sets?
Data
relevant to
existing site
conditions?
How will the data
be used?
Limitations on
Data Use
USGS
Professional Paper
1651
(2007)
Mine waste material
volumes data
collected 1996-2000
Unknown
NA
NA
NA
Yes
Approximation of
mine waste
material volumes
Volumes
reported are
estimated
CDMG
Reclamation
Feasibility
Reports (Herron et
al. 1997,1998,
1999, and 2000)
Mine waste
leachability test data
collected 1997-1999
Unknown
Unknown
Unknown
Unknown
Yes
Screening-level
comparison to
water quality
standards to
evaluate metals
leachability
Use for
background
informatio
n only
EPA/ESAT,
Sampling and
Analysis Report
(ESAT 2016)
Surface water,
sediment, soil/waste
rock, and leachability
test data collected
2015
Yes
Yes
Yes
Yes
Yes
Comparison to
water quality
standards and
risk-based
screening levels
None
EPA/ESAT,
Sampling and
Analysis Report
(ESAT 2017)
2016 surface water,
sediment, soil/waste
rock, and leachability
test data collected
2016
Yes
Yes
Yes
Yes
Yes
Comparison to
water quality
standards and
risk-based
screening levels
None
Notes:
USGS - U.S. Geological Survey
CDMG - Colorado Division of Minerals and Geology
NA - not applicable
EPA - U.S. Environmental Protection Agency
ESAT- Environmental Services Assistance Team
-------
Table 4-1
Total and Dissolved Metals for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Arsenic
Cadmium
Copper
Iron
Manganese
Lead
Zinc
D
T
D
T
D
T
D
T
D
T
D
T
D
T
D
Mine Location
Station
Name
Sample Date
PH
Flow
(gpm)
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Longfellow Mine
M02D
6/29/2016
6.61
15
286
33.4
J
3.85
J
2.64
0.5
U
0.1
u
8.91
7.2
650
179
J
80
51.9
1.45
0.213
10
U
10
u
M02D
10/7/2016
6.83
4.9
183
22.4
J
2.5
U
1.67
J
0.5
u
0.1
u
5.04
4.14
577
146
J
88.1
64.7
0.931
J
0.185
J
10
u
10
u
Junction Mine
M02B
6/29/2016
6.15
12
1720
227
143
57.2
7.17
7.46
261
182
16600
13500
348
365
131
5.26
1640
1770
M02B
10/7/2016
3.86
2.9
7110
6320
303
213
25.1
26.1
111
794
64000
56100
1780
1740
304
300
6590
6510
Koehler Tunnel
M02K1
6/29/2016
4.54
0.1
3870
3720
2.5
u
2.5
u
40.7
40.5
3170
3310
324
309
16600
16400
3.19
3.29
17700
18100
M02C
10/7/2016
6.12
4.5
12900
1950
3000
1020
86.2
89.4
3140
2100
177000
152000
37600
37300
152
1.51
41500
41400
M02E
6/29/2016
-
-
3500
2460
177
30.4
19.4
21.1
891
863
17600
13000
7220
7020
100
36.6
7870
7930
M02E
10/7/2016
3.60
9.0
8100
7590
234
67.4
47.2
42.8
1610
1410
40400
33800
20800
17200
59.8
73.4
22400
18700
M02
6/29/2016
5.76
150
2590
422
119
15.1
12.2
12.5
522
449
10000
6710
4120
4050
75.3
8.87
4590
4690
M02
10/7/2016
8.03
23
6770
6190
90.3
30.3
35.7
36.4
1290
1320
17100
15200
16200
15600
35.5
35.1
16800
16400
Brooklyn Mine
M12
6/7/2016
4.55
-
3460
290
7.59
J
0.5
u
0.726
J
0.719
15.6
6.08
7400
136
J
488
301
14.6
0.198
J
174
156
M12
6/29/2016
5.08
438
3370
3030
2.5
u
0.5
u
3.94
4.02
33.9
34.4
911
410
1320
1300
3.3
2.52
861
887
M12
9/29/2016
4.17
165
9130
8700
2.5
u
0.5
u
6.07
6.2
53.4
54.4
1210
1040
2280
2280
3.88
4.02
1300
1370
M12A
6/29/2016
4.51
-
3850
3120
2.5
u
0.5
u
1.05
1.11
22.9
22.3
1590
362
799
763
7.04
1.44
282
276
M12A
9/30/2016
4.45
151
10200
9630
2.5
u
0.5
u
1.28
1.49
31.7
32.2
1200
627
1440
1440
1.66
1.55
347
363
M12B
6/29/2016
4.76
223
3940
3510
2.5
u
0.5
u
0.5
u
0.266
11.1
11.2
966
419
545
535
1.11
0.65
61
54.6
M12B
9/30/2016
4.55
151
11900
11000
2.5
u
0.5
u
0.5
u
0.307
19.6
20.1
1770
1050
1190
1190
0.81
J
0.631
81
81.5
M12C
6/29/2016
3.63
7.3
1890
1010
20.7
0.5
u
14.9
15.6
236
177
26400
4070
5240
5100
25.1
1.69
4670
4600
M12C
9/29/2016
3.84
1.1
3620
2920
39.3
1.63
J
19.1
18.7
348
300
58800
16300
6440
6430
116
20.7
5780
6060
M12C
9/30/2016
3.84
1.1
3020
2450
20.6
2.7
19
18.8
319
302
33700
16600
6380
6390
25
18.2
5690
5950
M12D
9/30/2016
3.72
2.2
2770
2170
20.1
1.4
J
18.9
19
328
317
27600
10400
6300
6300
24.7
19.5
5810
6100
M12F
10/7/2016
7.79
-
83.1
48.1
J
2.5
u
0.908
J
0.5
u
0.1
u
2.5
U
0.945
J
105
J
100
u
193
4.09
J
0.5
U
0.1
u
10
u
10
~u~
M12G
10/7/2016
4.07
-
642
576
2.5
u
0.5
u
0.5
u
0.433
22.1
23.8
591
502
938
915
126
125
117
121
Bandora Mine
M23
9/27/2016
5.98
7351
2070
554
2.5
u
0.5
u
0.5
u
0.349
2.5
u
1.33
162
J
100
u
200
200
0.5
u
0.246
32.5
40
M24A
9/28/2016
6.96
-
957
36
J
12.8
0.5
u
67.8
35.8
1070
3.15
74900
195
J
6770
4870
977
0.147
J
13500
8750
M24B
9/28/2016
6.71
24
210
37.8
J
2.5
u
0.507
J
49.3
48
233
19.3
16100
5300
5290
4940
201
3.69
11200
11200
M24C
9/28/2016
7.41
-
31.2
J
30.1
J
2.5
u
2.5
u
0.5
u
0.5
u
2.5
u
2.5
u
112
J
141
J
2100
2030
0.663
J
0.581
J
540
541
M24D
9/27/2016
6.87
-
200
20
u
2.5
u
0.5
u
42.4
35.2
189
2.23
11500
100
u
4780
4630
177
0.1
u
10700
9250
M2B
6/29/2016
6.28
21553
696
49.7
J
2.5
u
0.5
u
0.5
u
0.336
2.5
u
1.28
100
U
100
u
90.7
89.8
0.5
u
0.1
u
58.4
64.1
M2B
9/27/2016
6.12
9317
1840
266
2.5
u
0.5
u
0.54
J
0.622
2.5
u
1.2
159
J
100
u
207
202
0.5
u
0.1
u
104
111
Grand Mogul
Mine
CC01C
6/29/2016
3.59
-
2010
1850
2.5
u
1.56
J
18.7
17.6
470
462
2410
2210
1720
1660
39.7
38.2
3650
3660
CC01C
9/28/2016
4.10
3.6
10300
9720
37.1
39
95.4
97
2620
2620
57900
55100
6120
6050
27.9
26.4
24500
25100
CC01C1
6/29/2016
3.17
-
4570
4190
3.85
J
5.54
41.7
35.1
J
1440
1360
10000
12700
3760
3570
33.7
33
8850
8550
CC01C1
9/28/2016
3.96
2.8
15000
14100
20.3
21.8
127
130
5080
5070
54600
52200
11400
11300
7.59
7.12
31300
31600
CC01C2
6/29/2016
3.42
73
2960
2750
2.5
u
0.617
J
23.1
21.5
733
708
3030
2850
2180
2090
28.1
26.9
4680
4660
CC01C2
9/28/2016
4.12
9.0
8090
7730
2.5
u
2.94
69.1
62.9
2220
2130
9380
8900
5730
5610
22.1
21.5
14900
14700
CC01F
6/29/2016
7.27
-
238
97.6
2.5
u
0.5
u
1.19
1.2
31.1
20.6
100
u
100
~u"
82.5
78.2
8.04
3.8
267
261
CC01F
9/28/2016
7.16
-
372
114
2.5
u
0.5
u
2.7
2.77
59
29.7
100
u
100
u
126
123
2.93
0.843
475
454
CC01H
6/29/2016
6.12
2904
721
197
2.5
u
0.5
u
5.39
5.41
163
133
611
100
u
474
450
10
2.98
1120
1100
CC01H
9/27/2016
6.31
368
663
213
2.5
u
0.5
u
7.13
7.34
161
141
582
100
u
417
407
2.14
0.348
1600
1610
CC02I
6/28/2016
4.69
7.3
979
924
2.5
u
0.5
u
6.17
6.11
24
24.4
100
u
100
u
121
122
8.84
8.46
1750
1770
CC02I
9/27/2016
5.90
350
1880
1000
2.5
u
0.5
u
11.2
12
128
116
224
J
100
u
2330
2280
2.93
1.8
2140
2110
CC01U
6/28/2016
6.16
5327
1120
197
2.5
u
0.5
u
4.18
4.3
69.2
51.5
299
100
u
1890
1810
8.95
2.04
815
802
CC01U
9/27/2016
5.72
378
1860
926
2.5
u
0.5
u
12.1
12.1
131
117
244
J
100
u
2310
2260
4.53
3.11
2200
2160
-------
Table 4-1
Total and Dissolved Metals for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Arsenic
Cadmium
Copper
Iron
Manganese
Lead
Zinc
D
T
D
T
D
T
D
T
D
T
D
T
D
T
D
Mine Location
Station
Name
Sample Date
PH
Flow
(gpm)
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Natalie/Occident
al Mine
CC14
6/10/201B
6.09
-
1830
11B0
4.46
J
1.88
J
B.2B
4.68
86.9
67.6
19800
18000
1980
1940
7.3
0.339
843
884
CC14
9/29/20IB
6.32
-
920
664
2.B
U
2.B
u
1.82
1.78
7.78
3.B1
J
19600
18100
2630
2680
3.41
0.BB7
J
732
7B1
CC14
6/9/2016
6.13
-
2440
1900
2.B
u
B
u
B.B9
B.9
90.8
7B.9
27200
27200
2670
2680
9.84
1.63
J
1130
11B0
CC14
9/29/2016
B.39
407
9BB
791
2.B3
J
2.94
J
1.87
1.87
7.17
3.16
J
18600
17600
2B20
2480
3.17
0.B36
J
704
673
CC1B
6/9/2016
-
7277
643
91.6
2.B
u
0.B
u
O.B
U
0.271
8.71
4.97
796
100
u
84.3
81.2
0.B79
J
0.1
u
61.6
64.6
CC1B
9/29/2016
7.00
301
446
9B.8
2.B
u
0.B
u
O.B
u
0.226
B.38
2.92
14B
J
100
u
64.2
63.B
O.B
U
0.1
u
36
36.1
CC1BA
6/9/2016
-
7206
7B1
177
2.B
u
0.B
u
0.787
J
0.831
1B.8
10.2
2920
2B30
32B
331
1.28
0.1
u
16B
171
CC1BA
9/29/2016
6.80
1170
868
267
2.B
u
2.B
u
1.16
1.2
8.9B
4.21
J
9330
8340
1410
1390
1.93
O.B
u
403
391
Henrietta Mine
CC24G
6/30/2016
4.61
-
1840
1790
2.72
J
3.B
O.B
u
0.293
36.9
3B.8
20900
20400
72.9
7B.6
3.3
3.17
116
123
CC22D
6/8/2016
B.76
-
488
84.4
2.B
u
0.B
u
1.6B
1.61
46.1
37.1
944
127
J
92.1
73.4
31.4
8.1
406
432
CC22D
9/29/2016
B.79
73
1130
124
2.B
u
0.B
u
1.7
1.74
42.6
28.9
1440
211
J
307
289
B9.9
18.3
43B
400
CC22B
6/8/2016
4.73
-
811
622
2.B
u
0.B
u
1.11
1.22
34
33.8
663
312
110
109
23.9
18.1
302
333
CC22B
9/29/2016
4.33
131
3600
3120
2.B
u
0.B
u
1.43
1.61
33.6
33.3
B33
347
B84
B67
43.8
40.3
376
372
CC24B
6/8/2016
4.37
-
904
666
2.B
u
0.848
J
1.08
1.29
B8.9
B7.9
1210
769
124
119
2B.6
18.9
330
342
CC24B
9/29/2016
3.93
166
2790
2460
2.B
u
0.B
u
2.03
2.32
106
107
1740
14B0
B06
498
44.B
44.2
B49
B71
Anglo Saxon
Mine
CC37
6/7/2016
6.B3
41
BOO
477
7.91
J
6.93
J
2.7B
2.B2
7.68
7.03
28200
28400
8940
90B0
10.3
2.04
2930
3040
CC37
9/28/2016
6.B3
41
4B8
433
7.17
J
6.78
J
2.26
2.36
B.21
4.09
J
28700
2B700
8700
8B80
8.44
0.964
J
2830
28B0
CC38
6/7/2016
7.43
-
1160
86.B
2.6
J
0.B
u
O.B
u
0.363
11.9
6.B4
2260
BB6
640
B92
31.1
2.73
179
162
CC38
9/28/2016
7.2B
37
438
61.4
2.96
J
2.B
u
2.11
1.97
18.8
2.B8
J
11600
6300
7860
7770
8.73
O.B
u
1790
1640
CC38B
6/7/2016
6.IB
B9
88B
790
6.39
J
3.32
J
2.06
2.08
B8.8
6B.9
20B00
16300
11600
11600
9.B4
0.B42
J
2290
24B0
CC38B
9/28/2016
6.67
36
638
211
B.93
J
3.36
J
1.9B
1.81
24.4
7.69
21800
17300
12400
12100
3.89
O.B
u
2B30
2480
CC38C
6/7/2016
7.07
-
1B30
104
2.B
u
0.B
u
O.B
u
0.206
19.9
B.06
2160
100
u
10B
18.2
110
2.8B
103
49.B
CC38C
9/28/2016
7.32
IB
266
9B.8
2.B
u
0.B
u
2.2
2.46
20.2
10.9
107
J
100
u
91
89.9
24.4
9.B8
B33
BBB
CC39
6/7/2016
B.26
-
2140
643
4.72
J
0.B
u
2.26
2.19
70.1
B3.9
6800
2100
932
869
B0.9
B.29
669
6B8
CC39
9/27/2016
3.62
7970
6770
B930
6.93
J
2.6
J
B.72
B.78
108
99.7
14800
10000
4460
4400
44.7
20.B
2400
2330
CC39B
6/7/2016
B.10
-
2230
913
B.76
J
0.B
u
2.41
2.33
69.3
B8.7
6790
2330
917
834
B8.8
8.64
6B7
679
CC39B
9/28/2016
3.82
6993
6180
B760
4.78
J
2.B
u
B.43
B.49
BB
B9
13700
12B00
4690
4700
13.7
13.B
2140
2170
Yukon Tunnel
CC41
6/7/2016
B.16
-
2410
907
4.12
J
0.B
u
2.98
2.91
99.4
72.6
8110
2460
1060
978
43.1
B.73
8B8
8B4
CC41
9/27/2016
3.BB
6939
6220
BB20
6.49
J
2.B
u
6.63
6.36
141
96.3
12B00
7480
B110
4920
27.2
17.1
2610
2420
CC43C
6/7/2016
6.82
-
B33
171
2.B
u
2.B
u
O.B
u
O.B
u
11.6
3.98
J
2460
1190
793
768
2.76
O.B
u
109
100
CC43C
9/27/2016
6.68
-
486
168
2.B
u
2.B
u
O.B
u
O.B
u
12.2
2.94
J
2440
1110
1130
1090
2.6B
O.B
u
121
108
CC43D
6/7/2016
2.98
-
30900
28200
2.B
u
0.81
J
21.4
18.4
3610
2770
42900
39300
6B30
6170
3.89
4.11
B810
B720
CC43E
6/7/2016
B.37
-
3020
891
B.63
J
0.B
u
3
3.19
104
82.3
10000
22B0
1100
977
B9.4
4.B2
912
919
CC43E
9/27/2016
3.88
7069
B630
B240
3.6
J
2.B
u
B.06
B.01
84.9
81.9
10100
7080
4170
41B0
IB.2
13.9
2070
20B0
Boston Mine
A07D
6/28/2016
4.23
-
B970
BBB0
2.B
u
0.B
u
7.BB
7
38.9
34.6
242
J
149
T
2160
2100
11.6
9.47
1130
1140
A07D
10/B/2016
4.11
9.0
16000
IB 100
2.B
u
0.B
u
19.1
19.B
92.B
92.B
100
U
100
u
4860
4810
7.22
7.47
2840
2830
A07D1
6/28/2016
4.26
BB
19300
18000
2.B
u
O.B
u
33.2
32.4
BB.B
B1.3
100
u
100
u
6080
B890
1.B2
1.26
6020
B870
A07D2
6/28/2016
4.31
-
2340
21B0
2.B
u
O.B
u
2B.B
23.8
96.2
90
100
u
100
u
824
793
22.B
18.7
3740
3680
A07E
6/28/2016
4.18
-
4830
4B70
2.B
u
O.B
u
B.02
4.93
3B.4
33
234
J
141
J
1820
1780
11.6
9.77
7 IB
718
A07E
10/B/2016
3.86
49
13800
13000
2.B
u
O.B
u
12.3
13.3
64.6
68.8
311
304
B090
49B0
14
1B.4
21B0
2120
CDIVI .
Smith
-------
Table 4-1
Total and Dissolved Metals for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Arsenic
Cadmium
Copper
Iron
Manganese
Lead
Zinc
D
T
D
T
D
T
D
T
D
T
D
T
D
T
D
Mine Location
Station
Name
Sample Date
PH
Flow
(gpm)
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
London Mine
DM6
6/28/2016
6.13
3.2
121
88.5
2.5
U
0.5
u
8.17
8.7
30.3
30
443
324
189
197
61.7
48.3
1540
1680
DM6
9/30/2016
3.21
0.7
1220
1100
2.5
u
1.36
J
84.4
71.4
260
218
6180
4870
1640
1550
226
202
17200
17200
DM7
6/8/2016
6.69
-
360
23.1
J
4.25
J
0.595
J
13.8
12.8
41.3
4.53
2150
100
u
277
234
13.3
0.1
J
2930
2870
DM7
6/28/2016
6.05
1.1
644
41.2
J
11.9
2.58
46.2
43.2
107
9.99
4700
255
1030
984
22.1
0.23
8130
8120
DM7
9/30/2016
6.41
-
929
37.9
J
14.8
2.86
49.4
42
123
6.57
7400
312
1230
1230
27.9
0.1
u
8170
8280
A07B1
6/28/2016
4.28
1329
7230
6790
2.5
u
0.5
u
11.3
10.8
43.5
39.8
148
J
103
J
2540
2480
11.2
9.57
1810
1790
A07B
9/30/2015
4.30
21
14000
13400
2.5
u
0.5
u
21.7
23
49.8
51.5
166
J
102
J
5890
6110
8.87
9.44
3990
4340
A07B
6/28/2016
4.323
1206
6860
6440
2.5
u
0.5
u
10.4
10.7
42.2
38.9
134
J
108
J
2380
2340
10.8
9.34
1690
1720
A07B
9/30/2016
4.08
186
17100
17000
2.5
u
0.5
u
26.4
24.1
61.6
56.6
170
J
161
J
5980
5920
10.5
9.35
4260
4280
Ben Butler Mine
BB1
6/28/2016
3.97
-
546
502
2.5
u
0.5
u
10.7
10.6
192
189
373
303
92.8
89.6
830
819
2080
2050
Mountain Queen
Mine
A18
10/6/2016
7.30
-
520
87.5
2.5
u
2.5
u
2.53
2.53
46.4
27.9
123
J
100
u
498
476
0.996
J
0.5
u
374
360
A19 A
9/30/2015
3.70
0.8
3310
3200
2.5
u
1.42
J
44.5
45.7
1270
1270
5110
5050
5750
5700
192
208
5630
6230
A19 A
9/28/2016
-
2.7
3270
3180
2.5
u
1.32
J
43
37.9
1260
1150
5470
5100
4190
4030
139
137
5060
4920
Vermillion Mine
CG4
9/30/2015
5.01
247
16300
15500
2.5
u
0.5
u
18.2
18.7
47.2
72.6
140
J
127
J
36400
36600
0.567
J
0.552
6030
6270
CG4
6/28/2016
6.58
6127
3820
2790
2.5
u
0.5
u
5.49
5.81
18.5
16
108
J
100
u
9020
9210
1.16
0.452
1550
1660
CG4
10/6/2016
5.47
1006
14900
12100
2.5
u
0.5
u
13.8
14.2
36.6
34.8
495
183
J
27300
26600
1.36
0.644
4380
4240
CGB
6/28/2016
5.48
-
628
602
2.5
u
0.5
u
7.84
7.67
61.3
60.5
100
U
100
u
472
479
47.7
44.8
1730
1900
CG6
9/30/2015
5.17
189
13700
12000
2.5
u
0.5
u
15.9
16.4
41.2
35.9
151
J
106
J
31600
31500
1.41
0.597
5260
5310
CG6
6/28/2016
6.46
7803
3620
2540
2.5
u
0.5
u
5.74
5.65
18.3
15.8
111
J
100
u
8750
8630
2.16
1.21
1560
1620
CG6
9/30/2016
4.97
785
11900
10400
2.5
u
0.5
u
12.2
11.1
31.8
25.6
100
u
100
u
25600
25700
0.889
J
0.414
3510
3700
CG6A
6/29/2016
6.57
5679
4500
2390
2.5
u
0.5
u
5.57
5.58
23.4
14.9
1150
100
u
8350
8360
26.2
1.4
1580
1690
Sunbank Group
Mine
A21
9/29/2015
5.54
76
2290
815
2.5
u
0.5
u
3.85
3.93
14.2
12.6
1020
801
1880
1900
34.1
32.6
1700
1780
A21
6/29/2016
6.94
4916
1050
125
2.5
u
0.5
u
3.88
3.55
42.3
27.3
100
u
100
u
3120
2980
9.02
2.35
1410
1340
A21
9/30/2016
5.93
515
1490
304
2.5
u
0.5
u
4.03
3.65
18.1
12.4
289
248
J
1550
1480
103
7.61
1610
1560
A22
9/29/2015
5.97
61
340
29.7
J
2.5
u
0.5
u
1.84
1.99
8.15
4.71
100
u
100
u
346
348
4.52
2.01
1050
1150
A22
6/29/2016
6.99
3576
1090
148
2.5
u
0.5
u
3.65
3.62
43
31.1
100
u
100
u
3370
3250
6.09
J
1.05
1360
1360
A22
9/30/2016
6.46
531
1160
76.1
2.5
u
0.5
u
3.11
2.96
14.1
7.3
100
u
100
u
1250
1190
4.32
0.863
1430
1380
A21A
9/29/2015
4.79
16.4
13600
13500
2.5
u
1.4
J
12.1
12.1
2.5
U
1.44
16400
16300
9460
9600
194
198
4590
4930
A21A
6/29/2016
5.51
-
14100
13200
2.5
u
1.29
J
11.9
10.9
2.5
u
0.774
J
19200
16500
8980
8750
253
216
4300
4270
A21A
9/30/2016
3.78
-
15100
15000
2.5
u
1.76
J
13.3
13
2.5
u
1.04
18000
17100
9160
8980
188
190
4710
4670
Frisco/Bagley
Tunnel
A12
6/9/2015
7.14
83
285
107
2.5
u
1.34
J
4.69
4.69
5.29
4.7
2390
2210
7950
8190
4.02
0.591
3500
3830
A12
10/1/2015
6.25
18
434
285
2.5
u
2.47
4.47
4.77
2.5
u
2.36
4390
3550
16500
16600
1.39
J
0.482
5470
6080
A12
6/7/2016
6.48
18
642
550
2.5
u
2.14
7.76
8.51
7.36
6.95
4450
4170
16300
16300
1.61
0.355
6640
6980
A12
9/28/2016
-
58
356
325
2.5
u
1.86
J
5.43
4.94
2.93
J
2.62
2450
2210
13900
13700
0.5
U
0.1
u
5090
5060
A13
6/9/2015
6.20
25192
1120
305
2.5
u
0.5
u
2.39
2.26
22.9
11.5
239
J
100
u
1960
1980
28.9
2.82
757
802
A13
9/29/2015
5.31
521
7530
5590
2.5
u
0.5
u
9.78
10.2
31.4
28.3
292
203
J
18200
18900
8.85
7.83
3500
3920
A13
6/7/2016
6.57
-
2060
966
2.5
u
0.5
u
2.87
2.49
28.2
8.33
633
100
u
3510
3280
106
2.44
950
859
A13
9/30/2016
5.43
2053
6270
4680
2.5
u
0.5
u
7.17
6.88
22.7
17.2
152
J
117
J
13400
13400
4.2
2.56
2360
2360
CG9
6/9/2015
6.28
23919
1020
267
2.5
u
0.5
u
2
2.07
17.9
10.3
206
J
100
u
1910
1880
15.3
2.12
701
727
CG9
9/29/2015
5.48
610
7140
4020
2.5
u
0.5
u
9.53
10.3
31.8
26.8
479
297
18300
18000
8.7
6.16
3980
3880
CG9
6/7/2016
6.50
-
1810
551
2.5
u
0.5
u
2.77
2.2
38.9
8.83
556
100
u
2780
2530
152
2.87
881
111
CG9
9/30/2016
5.27
2182
5590
3680
2.5
u
0.5
u
6.92
6.41
23.1
16.5
196
J
167
J
12600
12600
4.05
2.59
2300
2430
-------
Table 4-1
Total and Dissolved Metals for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Arsenic
Cadmium
Copper
Iron
Manganese
Lead
Zinc
D
T
D
T
D
T
D
T
D
T
D
T
D
T
D
Mine Location
Station
Name
Sample Date
PH
Flow
(gpm)
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Columbus Mine
A10
6/9/20IB
6.18
-
991
247
2.B
U
0.B
u
2.62
3.02
23.1
16.2
199
J
100
u
2100
2080
14.4
2.81
967
969
A10
9/29/20IB
B.43
634
6280
3800
2.B
u
0.B
u
11.1
11.6
41.2
39.4
401
306
17S00
18000
8.13
7.22
4130
4560
A10
6/7/2016
-
16137
1480
774
2.B
u
0.B
u
2.B4
2.72
20.B
12.9
19 B
J
100
u
3160
3100
37.3
3.67
934
932
A10
9/29/2016
B.13
2387
B480
3790
2.B
u
0.B
u
7.69
7.48
30.9
2B.1
204
J
136
J
13000
12700
B.66
4.31
2670
2630
AHA
6/9/20IB
3.0B
37
3370
3160
8.6B
J
6.38
194
193
2B10
2B10
11700
12200
1840
1900
1010
947
47000
51200
A11A
9/29/20IB
2.89
0.1
31000
29B00
12
12
1090
896
6800
6790
61100
61100
17600
17900
2S4
289
278000
302000
A11A
6/7/2016
4.16
27
3360
34B0
B.91
J
B.43
180
173
23B0
2310
11300
11600
1710
1720
911
913
40300
43100
A11A
9/30/2016
2.8B
0.3
2B600
24900
14
11
1030
938
6960
6300
B4700
S1600
12400
12100
302
254
229000
223000
CG11
6/9/20IB
6.26
21799
1000
222
2.B
u
0.B
u
2.11
2.28
1B.8
9.39
179
J
100
u
1910
1970
10.8
1.87
696
762
CG11
9/29/20IB
B.34
B72
6610
3830
2.B
u
0.B
u
9.B4
10.2
31.B
27.9
440
324
17700
17600
7.29
5.96
3930
3930
CG11
6/7/2016
6.46
-
1480
B87
2.B
u
0.B
u
2.29
2.17
24.9
8.96
306
100
u
2690
2BS0
89.9
2.74
765
759
J
CG11
9/30/2016
B.34
330B
B390
3B10
2.B
u
0.B
u
6.89
6.28
22.4
17.1
173
J
163
J
12200
12100
4.IB
3.23
2280
2380
Silver Wing Mine
A28
6/9/20IB
7.B7
-
137
43.B
J
2.B
u
0.B
u
2.04
1.78
7.23
6.88
100
U
100
u
736
721
1.81
0.763
452
480
A28
9/30/20IB
7.03
17B4
1400
39.B
J
2.B
u
0.B
u
4.69
4.43
12.2
3.B6
100
u
100
u
3870
3800
3.8S
0.442
1360
1330
A28
6/28/2016
7.62
-
848
B2
2.B
u
0.B
u
2.2B
2.46
11.3
4.73
100
u
100
u
18B0
1780
3.48
0.613
587
569
A30
6/9/20IB
7.B2
-
4B4
44.7
J
2.B
u
0.B
u
2.07
1.8B
23.B
13.4
11B
J
100
u
74S
7 IB
7.76
0.918
507
496
A30
9/30/20IB
B.82
2B03
1390
42.9
J
2.B
u
0.B
u
4.79
4.44
83.2
19.3
180
J
100
u
3810
37S0
4.82
0.313
1440
1410
A30
6/7/2016
7.B4
-
747
B4.6
2.B
u
0.B
u
1.9
1.92
18.6
7.99
204
J
100
u
12B0
1190
14.6
0.672
505
504
A29
6/9/20IB
6.42
-
1380
428
99.7
2.B
u
14
14.1
6190
2320
10900
2470
3100
3120
2B.8
0.5
u
3950
4010
A29
9/30/20IB
B.74
-
1860
9B8
132
4.4
16.6
1B.1
10200
4200
16000
6130
3S20
3480
2S.B
0.1
u
4320
4500
A29
6/7/2016
6.49
7.3
1B90
762
161
2.87
16.1
16.4
6280
2730
13700
3870
3300
3170
22.7
0.1
u
4220
4260
A29
9/28/2016
-
-
1B90
603
110
3.1
14.8
14.6
6970
2770
11700
2790
3290
32B0
19.1
0.159
J
4020
3870
A29A
6/9/20IB
6.96
-
82B
31.B
J
39.7
2.B
u
13.4
13.B
3820
712
SB70
100
u
3030
3040
12.8
0.5
u
3790
3830
A29A
6/7/2016
7.08
-
1800
98.B
143
1.17
J
14.7
IB.3
6660
B09
1S600
137
J
3070
3130
61.8
0.1
u
3900
3960
Tom Moore Mine
A30A
6/8/2016
7.29
-
6B9
4B.8
J
2.B
u
0.B
u
1.86
1.82
IB.6
6.44
201
J
100
u
1200
1120
11.5
0.582
469
474
A30A
9/29/2016
6.94
-
1740
74.2
2.B
u
0.B
u
4.2B
3.98
3B.2
7.4B
102
J
100
u
3760
3670
3.22
0.321
1130
1030
A30B
6/8/2016
7.4B
-
602
47.3
J
2.B
u
0.B
u
1.68
1.71
14.B
B.98
204
J
100
u
1100
1010
12.1
0.532
433
433
A30B
9/29/2016
6.97
7096
1810
67.B
2.B
u
0.B
u
4.09
3.98
B3.4
7.79
128
J
100
u
3670
3S80
3.48
0.339
1120
1020
DM22
6/28/2016
7.31
-
29.6
J
23.3
J
2.B
u
0.B
u
1.14
1.18
2.B
U
0.B1B
J
100
u
100
u
409
411
0.826
J
0.284
627
673
DM22
9/28/2016
-
21
27.1
J
23.9
J
2.B
u
0.B
u
0.77
J
0.811
2.B
u
0.B98
J
100
u
100
u
16B
1B6
0.5
U
0.1
u
572
619
Ben Franklin
Mine
ARD1
9/29/20IB
3.10
-
7180
6370
2.B
u
0.BB8
J
B7.B
BB.6
1940
1970
3B60
2390
22300
22300
840
861
19900
19500
ARD1
6/28/2016
2.76
-
3860
3630
2.B
u
0.B
u
43.8
41
1990
1880
SB20
B190
12700
12300
745
720
12500
12300
ARD1
9/28/2016
3.12
-
9980
96B0
2.B
u
2.B
u
79.7
72.9
2690
2420
4080
3940
26000
26100
747
686
23000
24300
EG3A
9/29/20IB
7.2B
3B
63
31.7
T
2.B
u
O.B
u
0.BB1
T
0.B88
11.4
9.78
100
u
100
u
116
107
4.18
2.45
217
215
EG3A
6/28/2016
6.24
46B7
1B3
87.3
2.B
u
O.B
u
3.33
3.3B
12.9
11.6
100
J
100
u
633
6S0
2.63
0.691
1120
1210
EG3A
9/29/2016
6.94
-
31.9
T
24.1
T
2.B
u
O.B
u
O.B
~u"
0.228
2.79
T
1.79
100
u
100
u
18.3
16.2
0.5
~u"
0.152
J
79.8
85.7
EGB
9/30/20IB
7.14
-
31.8
j
2B.6
j
2.B
u
O.B
u
O.B
u
0.B3B
6.27
B.B3
100
u
100
u
S3.2
S3.2
1.68
1.12
221
228
EGB
6/28/2016
7.01
-
132
91.2
2.B
u
O.B
u
3.11
3.33
14.8
12.2
100
u
100
u
636
6SB
2.56
1.74
1120
1200
EGB
9/28/2016
7.70
222
96.B
64.4
2.B
u
O.B
u
1.18
1.18
12.2
8.0B
100
u
100
u
144
144
3.11
1.48
493
529
A39A
6/28/2016
7.B9
--
133
99
2.B
u
O.B
u
3.2B
3.19
16.2
13.8
100
u
100
u
607
S93
3.06
2.14
1040
1030
-------
Table 4-1
Total and Dissolved Metals for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Mine Location
Station
Name
Sample Date
PH
Flow
(gpm)
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Terry Tunnel
A38
6/28/2016
7.14
-
66.2
63.1
2.B
u
0.B
u
0.B
u
0.148
J
2.B
u
1.26
237
J
100
u
10600
10400
2.36
0.1
u
1180
11B0
A38
9/28/2016
7.07
-
82.3
76.3
2.B
u
2.B
u
0.726
J
0.B
u
2.B
u
2.B
u
940
100
u
11000
10700
8.B3
O.B
u
1340
1220
A39
9/30/20IB
7.10
-
118
48.8
J-
2.B
u
0.B
u
1.2
1.08
22.8
14.6
100
u
100
u
2B6
2B0
B.01
2.23
38B
393
A39
6/28/2016
7.BB
-
133
88.6
2.B
u
0.B
u
3.06
3.06
IB.6
13.7
100
u
100
u
B89
B68
3.13
2.12
1000
1010
A39
9/28/2016
7.B1
-
180
109
2.B
u
0.B
u
1.73
1.61
29.7
17.9
100
u
100
u
310
30B
7.6
2.09
618
630
EG6
6/10/201B
7.36
-
229
91
2.B
u
0.B
u
2.69
2.69
2B.8
19.7
190
J
100
u
1340
1280
6.08
1.83
1110
1080
EG6
9/30/20IB
7.22
98
20
u
20
~u"
2.B
u
0.B
u
0.71
T
0.794
3.98
T
4.22
100
u
100
u
96.8
94.3
0.869
J
0.796
430
429
EG6
6/28/2016
7.44
7133
113
80.B
2.B
u
0.B
u
2.07
1.94
11.4
9.09
100
u
100
u
417
41B
2.19
1.0B
671
716
EG6
9/28/2016
7.48
373
112
B4.B
2.B
u
0.B
u
1.22
1.19
13.9
9.34
100
u
100
u
2B1
248
3.8B
0.76
430
4B6
Pride of the West
Mine
ABO
6/7/2016
7.7B
-
201
36.8
T
2.B
u
0.B
u
11.8
12.2
B4.B
16.6
209
J
100
u
401
394
42.2
7.77
2190
2130
ABO
9/28/2016
7.67
-
137
39.3
j
2.B
u
0.B
u
7.B1
7.39
26.3
9.88
122
J
100
u
239
238
17.6
4.IB
1360
13B0
CU4
6/7/2016
7.39
-
1380
B7
2.B
u
0.B
u
0.B
~u"
0.1
TT
2.8
T
0.723
T
1420
100
u
1B2
4.21
J
27.B
0.298
13.2
J
10
u
CU4
9/28/2016
7.4B
6610
23.3
T
20
~u"
2.B
u
0.B
u
0.B
u
0.1
u
6.62
0.628
j
100
~u~
100
u
4.47
J
3.63
J
1.9
0.149
T
10
u
10
u
CU4A
6/7/2016
7.36
-
6B8
60.7
2.B
u
0.B
u
0.B
u
0.1
u
3.88
T
0.93
j
770
100
u
174
4.84
J
46.4
0.488
3B.1
10
u
CU4A
9/28/2016
7.23
6739
33.9
T
20
~u"
2.B
u
0.B
u
0.B
u
0.1B2
j
2.B
u
0.882
j
100
"u"
100
u
6
4.03
J
1.27
0.296
24.3
28.6
Notes:
Q- qualifier
" - data not available
T - total recoverable
D - dissolved
- value exceeds WQCC acute standards - value exceeds WQCC chronic standards
J - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample
U - Indicates compound was analyzed for, but not detected in sample. Value shown is quantitation limit of method
gpm - gallons per minute
|ig/L - micrograms per liter
-------
Table 4-2
CDMG Waste Rock Volume and Leachability Metals
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Mine Site
Location
CDMG Volume of
USGS Volume of
Aluminum
Cadmium
Copper
Iron
Manganese
Lead
Zinc
Hg/L
Hg/L
Hg/L
Hg/L
Hg/L
Hg/L
Hg/L
Mineral Creek
Longfellow Mine
Longfellow Mine
10,000
5,500
-
-
-
-
-
-
-
Junction Mine
Junction Mine
NA
NA
NA
NA
NA
NA
NA
NA
NA
Koehler Tunnel
Koehler Tunnel Waste Rock: Removed
-
-
-
-
-
-
-
-
-
Brooklyn Recent
-
34,452
455
4,534
592,762
69,771
2,748
70,610
Brooklyn Mine
Brooklyn Upper
-
15,000
37,895
177
2,186
568,294
10,068
226
9,327
Brooklyn Lower
-
18,895
110
1,478
115,585
20,941
190
18,129
Bandora Mine
Bandora Mine
5,500
5,500
BDL
54
10
14
842
124
7,920
Cement Creek
Grand Mogul Mine
Grand Mogul - West (of stope)
8,000
9,000
13,600
60
5,560
59,900
4
1,760
12,700
Grand Mogul - East
9,000
13,000
557
8,120
207,000
5
2,570
107,000
Natalie/Occidental Mine
Natalie/Occidental Mine
6,800
6,800
11,100
9
372
44,000
0
490
1,260
Henrietta 7 Mine North Pile (8 level)
30,000
5,600
1,030
8
198
3,470
0
617
1,730
Henrietta Mine
Henrietta 7 Mine South Pile
30,000
12,500
104
3,070
209,000
1
2,490
19,700
Henrietta 3 Mine
-
2,000
37,200
127
18,300
853,000
3
2,230
19,400
Mammoth Tunnel
Mammoth Tunnel
-
100
900
3
56
300
1
BDL
410
Anglo Saxon Mine
Anglo Saxon Mine
2,200
2,200
32,000
107
5,350
524,000
5
545
17,600
Yukon Tunnel
Yukon Tunnel
18,000
18,000
2,390
8
120
510
4
5
1,170
Animas River
Boston Mine
Boston (Lower Burrows Gulch Shaft)
900
900
88
4
32
230
120
100
710
London Mine
London Mine
3,300
3,300
230
10
140
830
270
4,000
1,700
Ben Butler Mine
Ben Butler Mine
500
500
12,000
350
3,500
97,000
530
3,000
71,000
Mountain Queen Mine
Mountain Queen Shaft
5,100
1,900
220
20
280
2,300
64
6,500
3,300
Mountain Queen Adit
280
28
390
230
460
2,000
5,100
Vermillion Mine
Vermillion Mine
5,100
5,100
2,300
84
590
7,200
1,400
2,500
18,000
Sunbank Group Mine
Sunbank Group Mine
NA
NA
NA
NA
NA
NA
NA
NA
NA
Frisco/Bagley T unnel
Bagley Tunnel
41,000
20,500
76
8
38
81
1,000
380
2,100
Bagley Mill Tailings
130
9
180
160
190
13,000
1,800
Columbus Mine
Columbus Adit
24,000
24,000
440
54
660
190
2
1,000
10,000
Silver Wing Mine
Silver Wing Mine
10,000
10,000
12,000
120
15,000
48,000
21,000
2,500
16,000
Tom Moore Mine
Tom Moore Mine
4,000
4,000
12,000
270
760
6,000
34,000
1,000
58,000
Ben Franklin Mine
Ben Franklin Prospect
NA
NA
80
2
32
258
106
10,676
432
Ben Franklin Mine
500
500
32,293
154
5,106
243,286
39,544
1,804
37,768
Terry Tunnel
Terry Tunnel
NA
NA
NA
NA
NA
NA
NA
NA
NA
Pride of the West
Pride of the West
NA
NA
NA
NA
NA
NA
NA
NA
NA
Campground 4
Campground 4
1,200
NA
264
38
169
272
5,608
222
7,702
Notes:
All results shown are from the CDMG leaching tests; USGS test data is not provided
CDMG - Colorado Division of Minerals and Geology
USGS - United States Geologic Survey
NA - mine site not identified within CDMG/USGS dataset
" - mine site identified but has no data within CDMG or USGS dataset
- sample exceeds WQCC acute criteria
- sample exceeds WQCC chronic criteria
*Although the metals results shown in this table are for total metals, the standards for dissolved metals are discussed
**Since data is not available, hardness is calculated assuming (conservatively) calcium and magnesium concentrations
CY - cubic yards
|ig/L - micrograms per liter
BDL- Below Detection Limit
T - total recoverable metals
in this report as a guideline for analysis and consistency to
of 5000 |ig/L, which are the basis for the WQCC standards
the surface water discussions
calculations
-------
Table 4-3
Total Metals Concentrations for 2015 and 2016 EPA/ESAT SPLP Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Sample Location
Mine Location
Sample
Aluminum
(Hg/L)
Arsenic
(Hg/L)
Cadmium
(Hg/L)
Copper
(Hg/L)
Manganese
(Hg/L)
Mercury
(jig/L)
Mineral Creek |
WR-M02B
Longfellow Mine
7/28/2016
200
U
13.3
5
U
25
U
411
52.4
88.9
0.2
U
60
U
WR-M02D
Junction Mine
7/28/2016
235
14.1
6.4
186
701
351
1410
0.2
U
943
WR-M02C (10 sieve)
KoehlerTunnel
7/28/2016
317
541
5
U
25
U
5140
74.2
142
0.2
U
60
U
WR-M02C (60 sieve)
7/28/2016
347
560
5
U
34.1
6950
118
122
0.2
U
118
WR-M12
Brooklyn Mine
7/28/2016
528
10
u
5
U
57
1010
644
186
0.2
U
419
WR1-M12
7/28/2016
5280
10
u
15.7
411
18100
4800
1940
0.25
J+
2800
WR2-M12
7/28/2016
1810
10
u
11.6
158
2960
3210
271
0.061
J+
2270
WR1-M24
Bandora Mine
7/28/2016
531
10
u
136
43.6
1940
1240
453
0.1
J+
16300
WR2-M24
7/28/2016
200
U
10
u
24.8
709
2170
404
7780
0.057
J+
3510
WR3-M24
7/28/2016
205
10
u
112
63.7
1270
510
817
0.046
J+
8380
WR4-M24
7/28/2016
200
U
10
u
4
J
25
U
355
23
50.7
0.16
J+
1140
Cement Creek |
WR-CC01C
Grand Mogul Mine
7/27/2016
492
10
u
22.9
686
549
405
9720
0.24
J+
4990
WR-CC01C2
7/27/2016
397
10
u
19.2
342
1560
393
7970
0.24
J+
4140
WR-CC02A
7/27/2016
429
4.8
J
5
U
76.8
1060
307
303
0.2
U
678
WR-CC14A
Natalie/Occidental
Mine
7/27/2016
766
10
u
5
U
25
U
1720
50.8
84.3
0.2
U
60
U
WR-CC14B
7/27/2016
1710
16.5
5
U
25
U
5500
206
313
0.2
U
153
WR-CC22
Henrietta Mine
7/27/2016
235
10
u
5
U
25
U
1120
79.3
300
0.2
U
60
U
WR-CC29
Mammoth Tunnel
-
-
--
--
-
--
-
--
-
-
WR-CC37 (10 sieve)
Anglo Saxon Mine
7/27/2016
200
U
10
u
5
U
25
U
473
1380
52.6
0.2
U
153
WR-CC37 (60 sieve)
7/27/2016
3870
6.8
J
5
U
37
33100
2340
365
0.2
U
280
WR-CC38B (10 sieve)
7/27/2016
3090
10
u
5.7
341
6950
164
1590
0.2
U
1300
WR-CC38B (60 sieve)
7/27/2016
3470
4
J
6.8
410
7690
180
2030
0.52
1660
WR-CC43
Yukon Tunnel
7/27/2016
8030
4.6
J
6.2
501
14200
991
1630
0.2
U
1200
Animas River |
WR-BSN
Boston Mine
7/26/2016
200
U
10
u
6.4
25
U
644
40.1
110
0.081
J+
876
WR1-LND
London Mine
7/26/2016
373
10
u
4.9
J
106
1270
50.7
284
0.15
J+
409
WR2-LND
7/26/2016
200
U
10
u
7.9
29.7
100
U
511
395
0.1
J+
1510
AE18
8/5/2015
39.3
J
10
u
12
62.2
54.7
J
103
3870
J-
0.19
J-
2370
WR-BB
Ben Butler Mine
7/26/2016
200
U
10
u
43.2
104
1230
140
7930
0.11
J+
7450
AE1
Mountain Queen Mine
8/5/2015
89.9
J
10
u
12.4
173
503
34.6
10200
J-
0.2
UJ
2050
AE2
8/5/2015
60
J
10
u
5
U
12
J
47
J
222
24.5
J-
0.2
UJ
81.8
AE9A
Vermillion Mine
7/27/2016
443
18.9
0.13
J
26.1
2480
15
U
1120
2
J+
85.1
AE44
Sunbank Group Mine
8/6/2015
200
U
10
u
0.5
J
5
J
100
U
609
26
J-
0.2
U
49.1
J
AE45
8/6/2015
2550
10
u
9.2
217
133
4980
235
J-
0.2
UJ
1480
AE46
8/6/2015
985
10
u
7.2
210
51
J
4210
49
J-
0.2
UJ
1340
AE10
Frisco/Bagley Tunnel
8/5/2015
200
U
10
u
12.9
1.9
J
100
UJ
1300
9
J-
0.2
u
2850
J
AE10A
8/5/2015
200
U
10
u
0.9
J
3.6
J
100
U
1490
8
J-
0.2
u
12.3
J
AE13
Columbus Mine
8/4/2015
200
U
10
u
11.4
6.1
J
100
U
1110
J-
4.7
J
0.36
1680
J-
AE32A
Silver Wing Mine
8/4/2015
1630
7.6
J
11.6
1920
7750
736
4660
0.2
u
2490
AE32B
8/4/2015
965
4.2
J
9.7
10000
J
1310
1140
J-
296
J
0.13
J
1830
J-
WR-TM
Tom Moore Mine
7/27/2016
1890
95.7
87.5
163
2790
3810
566
J
0.14
J+
17200
BE4
Ben Franklin Mine
8/4/2015
505
10
u
7.7
251
1170
2680
1300
0.2
u
2250
-
TerryTunnel
-
-
--
--
-
--
-
--
-
-
WR-PWN
Pride of the West Mine
7/27/2016
91
J
10
u
10.7
6.8
J
251
314
169
J
0.16
J+
303
WR-PWS (10 Sieve)
7/27/2016
100
J
10
u
7.5
17.2
J
340
295
276
J
0.11
J+
330
WR-PWS (60 Sieve)
7/27/2016
384
10
u
10.9
21.5
J
849
474
339
J
0.16
J+
576
Notes:
J - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample
J- - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample, likely to have a low bias
J+ - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample, likely to have a high bias
U - Indicates compound was analyzed for, but not detected in sample. Value listed is quantitation limit of method
UJ - The analyte was analyzed for, but was not detected. The reported value is approximate and may be inaccurate or imprecise
"U" samples are shown as their respective method reporting limit
Hg/L - micrograms per liter NA - not applicable
T - total recoverable "10-sieve" - soil sample was passed through a number 10 sieve
- no data available "60-sieve" - soil sample was passed through a number 60 sieve
SPLP - synthetic precipitation leachate procedure
'Although the metals results shown in this table are for total metals, the provided standards for dissolved metals are discussed in this report
as a guideline for analysis and consistency to the surface water discussions
- sample exceeds WQCC acute criteria
- sample exceeds WQCC chronic criteria
(Sm!th
-------
Table 4-4
Total Recoverable Metals Concentrations for 2015 and 2016 EPA/ESAT Waste Rock and Soil Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Sample
Location
Mine Location
Waste Rock/Soil Sample Location
Sample
Date
Aluminum
(mg/kg)
Arsenic
(mg/kg)
Cadmium
(mg/kg)
Copper
(mg/kg)
Iron
(mg/kg)
Manganese
(mg/kg)
Mercury
(mg/kg)
Zinc
(mg/kg)
Human Health Risk-Based Levels - Campground Soils A
122
2,081
Human Health Risk-Based Levels - Waste RockA
1,419
Mineral Creek
WR-M02B
Longfellow Mine
Longfellow Mine Waste Rock
7/28/2016
5920
J
3160
4.8
J-
669
45700
J
3680
528
J
0.56
1340
WR-M02D
Junction Mine
Junction Mine Waste Rock
7/28/2016
8630
J
1720
5.4
J-
487
75900
J
10200
388
J
7.6
1980
WR-M02C
KoehlerTunnel Waste Rock (10 sieve)
7/28/2016
6300
J
13700
3.3
J-
539
160000
J
3740
1700
J
3
910
WR-M02C
KoehlerTunnel
KoehlerTunnel Waste Rock (60 sieve)
7/28/2016
7250
J
22200
5
UJ
470
203000
J
2930
1330
J
1.8
911
M02E
Junction Mine / KoehlerTunnel Pond
10/7/2016
11700
125
2.5
175
28200
217
668
0.11
405
M02
Junction Mine / KoehlerTunnel Downstream
10/7/2016
20400
14.6
0.056
U
30.2
33900
53.7
981
0.092
J
135
WR-M12
Brooklyn Mine Adit Waste Rock
7/28/2016
7610
J
86.4
0.18
J-
47.4
47200
J
1920
571
J
0.14
145
WR1-M12
Brooklyn Mine Waste Rock #1
7/28/2016
6060
72.5
1.8
J
123
51400
2950
J
422
0.2
903
WR2-M12
Brooklyn Mine Waste Rock #2
7/28/2016
11600
137
0.51
J
117
65100
1310
J
847
0.0034
U
311
M12C
Brooklyn Adit
9/30/2016
10400
103
J
0.052
U
99.2
J
56200
3370
456
1.2
J+
763
J
M12D
Brooklyn Mine
Brooklyn Drainage Channel
9/30/2016
6960
39.6
J
1.1
28.8
J
48500
405
1750
0.067
J+
314
J
M12E
Brooklyn Drainage Channel
10/7/2016
22600
7.2
0.048
U
23
41900
100
1900
0.011
J
186
M12A
Brooklyn Drainage Channel Downstream
9/30/2016
9880
J
36.8
J
0.057
U
24.5
32300
J
62.5
764
0.035
J
88.3
J
M12B
Brooklyn Mine Upstream in Browns Gulch
9/30/2016
8260
J
34.5
J
0.049
UJ
15.9
27400
J
48.1
251
0.05
J
55.6
J
M12
Brooklyn Mine Downstream in Browns Gulch
9/29/2016
15700
J
16.4
J
1.9
J-
56.3
40900
J
241
3520
0.075
J
446
J
WR1-M24
Bandora Mine Waste Rock #1
7/28/2016
6580
85
86.3
J
1410
50200
14700
J
15700
0.37
12800
WR2-M24
Bandora Mine Waste Rock #2
7/28/2016
8160
108
10.7
J
1710
64700
24400
J
1040
0.49
11100
WR3-M24
Bandora Mine Waste Rock #3
7/28/2016
4640
150
147
J
1610
23500
23200
J
15100
0.71
66800
WR4-M24
Bandora Mine
Bandora Mine Waste Rock #4
7/28/2016
12700
33.9
160
J
2790
126000
2450
J
72100
0.0049
U
16600
M24D
Bandora Mine Drainage into South Fork
9/27/2016
21300
8.9
21.1
197
31300
J
349
6020
J
0.039
J
4120
M23
Bandora Mine Upstream
9/27/2016
14600
4
0.21
J
13.9
23700
J
19
380
J
0.026
J
88.7
M25
Bandora Mine Downstream
9/27/2016
18200
27.9
1.1
12
17300
J
55.3
709
J
0.039
J
174
Cement Creek
WR-CC01C
Grand Mogul Mine Waste Rock 1
7/27/2016
4970
106
15.2
J
2050
40800
19900
J
977
1.4
17900
WR-CC01C2
Grand Mogul Mine Waste Rock 2
7/27/2016
3550
81
20.1
J
758
30800
12800
J
670
1.5
14700
WR-CC02A
Grand Mogul Mine Western Waste Rock
7/27/2016
4390
J
72.9
4.7
J-
225
24300
J
5140
382
J
0.45
3510
CC01F
Grand Mogul Mine Upstream
9/28/2016
12300
23
J
0.054
U
59.5
J
27200
462
J
1670
0.062
J+
173
J
CC01C
Grand Mogul Mine
Grand Mogul Mine below Waste Rock 1
9/28/2016
10400
41.4
J
0.91
191
J
32700
1150
J
1560
0.31
J+
280
J
CC01C1
Grand Mogul Mine below Waste Rock 2
9/28/2016
11400
36.6
J
3.9
192
J
26000
1080
J
2460
0.1
J+
737
J
CC01C2
Grand Mogul Mine before Confluence with CC
9/28/2016
25300
36.3
J
54.5
995
J
33600
1650
J
35900
0.041
J+
5560
J
CC01H
Grand Mogul Mine after Confluence with CC
9/27/2016
16800
41.3
J
6.5
549
J
34000
896
J
6960
0.059
J+
629
J
CC02I
Grand Mogul Western Waste Rock Channel
9/27/2016
15000
J
28.4
3.2
J
131
36100
J
930
3910
0.055
J
567
CC01U
Grand Mogul Mine Downstream in CC
9/27/2016
13000
J
50.5
2.5
J
241
39400
J
711
4130
0.038
J
642
WR-CC14A
Natalie/Occidental Mine Waste Rock 1
7/27/2016
11200
J
28.9
0.15
J-
48.3
38300
J
484
614
J
0.0033
U
310
WR-CC14B
Natalie/Occidental
Natalie/Occidental Mine Waste Rock 2
7/27/2016
7390
J
35.9
0.29
J-
71.4
59800
J
845
712
J
0.18
223
CC15
Mine
Natalie/Occidental Mine Upstream
9/29/2016
9570
J
14.8
J-
0.049
U
25.2
J
41900
J
78.6
J
453
J
0.012
J
53.7
J
CC15A
Natalie/Occidental Mine Downstream
9/29/2016
8220
J
20.5
J-
0.049
U
29.9
J
37700
J
259
J
359
J
0.027
J
146
J
TrRilh
-------
Table 4-4
Total Recoverable Metals Concentrations for 2015 and 2016 EPA/ESAT Waste Rock and Soil Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Sample
Location
Mine Location
Waste Rock/Soil Sample Location
Sample
Date
Aluminum
(mg/kg)
Arsenic
(mg/kg]
Cadmium
(mg/kg)
Copper
(mg/kg)
Iron
(mg/kg
(r
Manganese
g) (mg/kg)
Mercury
(mg/kg)
Zinc
(mg/kg)
Human Health Risk-Based Levels - Campground Soils A
122
2,081
Human Health Risk-Based Levels - Waste RockA
1,419
WR-CC22
Henrietta Mine
Henrietta Mine Waste Rock
7/27/2016
7330
J
109
5.2
J-
264
27200
J
6700
366
J
0.31
4320
CC22D
Henrietta Mine Upstream
9/29/2016
6880
J
63.3
J
3.5
J
61.4
J
42100
J
568
J
289
J
0.096
J
898
J
CC22B
Henrietta Mine Midpoint
9/29/2016
8670
J
77.5
J
0.84
46.7
J
46500
J
617
204
J
0.12
352
CC24B
Henrietta Mine Downstream
9/29/2016
5430
J
59.8
J
0.053
U
28
J
26900
J
165
J
190
J
0.028
J
35
J
WR-CC29
Mammoth Tunnel
Mammoth Tunnel Waste Rock
--
--
--
--
--
--
--
--
--
--
WR-CC37
Anglo Saxon Mine
Anglo Saxon Mine Lower Waste Rock (10 sieve)
7/27/2016
10400
J
41.8
0.42
J-
71.4
87200
J
785
3780
J
0.0035
U
283
WR-CC37
Anglo Saxon Mine Lower Waste Rock (60 sieve)
7/27/2016
11200
J
45
0.53
J-
96.1
122000
J
959
3810
J
0.12
414
WR-CC38B
Anglo Saxon Mine Upper Waste Rock (10 sieve)
7/27/2016
4230
J
143
4.3
J-
283
61000
J
3340
300
J
0.42
1650
WR-CC38B
Anglo Saxon Mine Upper Waste Rock (60 sieve)
7/27/2016
4850
J
232
2.3
J-
485
77400
J
4650
177
J
0.56
2240
CC39B
Anglo Saxon Mine Upstream
9/28/2016
9290
J
42.8
J
2.7
122
J
70500
J
626
764
J
0.042
J
904
J
CC38C
Anglo Saxon Mine In Porcupine Gulch
9/28/2016
11200
J
73.5
J
1.7
93.9
J
40500
J
1480
1150
J
0.031
J
546
J
CC38D
Anglo Saxon Mine In Porcupine Gulch
9/28/2016
9870
J
48.8
J
3.7
76.5
J
42700
J
890
926
J
0.073
J
638
J
CC38
Anglo Saxon Mine In Porcupine Gulch
9/28/2016
11000
J
46.3
J
0.66
54.3
J
40300
J
540
585
J
0.047
J
285
J
CC39
Anglo Saxon Mine Downstream
9/27/2016
9170
J
36.4
J
1
61.7
J
57400
J
414
650
J
0.02
J
577
J
WR-CC43
Yukon Tunnel
Yukon Tunnel Waste Rock
7/27/2016
9750
J
51.8
3.5
J-
2580
69800
J
3160
711
J
0.26
844
CC41
Yukon Tunnel Upstream
9/27/2016
9410
J
45.2
J
2.1
77.9
J
56600
J
621
575
J
0.041
J
502
J
CC43E
Yukon Tunnel Downstream
9/27/2016
8380
J
57.2
J
0.82
48.9
J
53100
J
343
583
J
0.032
J
765
J
CC42
Yukon Tunnel in Illinois Gulch
9/27/2016
8230
J
7.3
J
0.47
J
58.2
J
27200
J
422
385
J
0.29
101
J
CC43D
Yukon Tunnel Pond
9/27/2016
14800
J
31.8
J
0.29
J
93.3
J
65700
J
205
960
J
0.028
J
177
J
Animas River
A07E
Boston Mine
Boston Mine Upstream
10/5/2016
13600
J
114
3.3
175
J
106000
J
505
J
7540
J
0.054
J
434
J
WR-BSN
Boston Mine Waste Rock
7/26/2016
3270
245
15.8
J
81.8
25900
4660
J
122
1.7
4450
A07D
Boston Mine Downstream
10/5/2016
21700
J
59.2
3.2
59.2
J
23000
J
487
J
2710
J
0.051
J
818
J
WR1-LND
London Mine
London Mine Waste Rock 1
7/26/2016
3240
94
17.8
J
166
28900
3300
J
161
0.6
2250
WR2-LND
London Mine Waste Rock 2
7/26/2016
4980
169
33.3
J
143
25000
5490
J
713
0.53
7690
AE18
London Mine Waste Rock 3
8/5/2015
1130
J
119
J
34.7
J
197
J
14600
J
5660
J
107
J
0.66
9680
J
A07B
London Mine Downstream
9/30/2016
48300
34.7
7
208
36800
561
10700
0.056
J
546
J
WR-BB
Ben Butler Mine
Ben Butler Mine Waste Rock
7/26/2016
6720
207
29.3
J
435
35500
24000
J
194
0.77
20200
BB2
Ben Butler Mine Downstream
10/5/2016
14700
J
60.1
0.99
21.9
J
22900
J
473
J
910
J
0.028
J
328
J
AE1
Mountain Queen Mine
Mountain Queen Upper Shaft
8/5/2015
1920
J
227
J
95.8
J
664
J
32000
J
35700
J
54.3
J
1.5
12400
J
AE2
Mountain Queen Adit
8/5/2015
1010
J
106
J
2.5
J
117
J
15700
J
1950
J
258
J
1.8
621
J
AE9A
Vermillion Mine
Vermillion Mine Waste Rock
7/27/2016
2610
147
23.8
J
213
25800
10400
J
60.4
1.1
8520
CG6
Vermillion Mine Downstream
9/30/2016
25400
29.9
J
1.6
J
156
J-
40100
J
162
7020
J
0.038
J
813
AE44
Sunbank Group Mine
Sunbank Group Mine Upper Adit
8/6/2015
5310
J
148
J
1.1
J
422
J
47500
J
2040
J
3080
J
0.2
496
J
AE45
Sunbank Group Mine
8/6/2015
6350
J
109
J
2.7
J
270
J
55100
J
2210
J
8240
J
0.24
640
J
AE46
Sunbank Group Mine Waste Rock
8/6/2015
7580
J
170
J
0.68
J
246
J
102000
J
631
J
12800
J
0.26
295
J
A22
Sunbank Group Mine Upstream
9/30/2016
21200
44.8
J
9.8
J
318
J-
24000
J
1500
19600
J
0.16
1600
A21
Sunbank Group Mine Downstream
9/30/2016
17000
79.3
5.7
518
37000
3390
4270
0.86
1460
J
SPrKilh
-------
Table 4-4
Total Recoverable Metals Concentrations for 2015 and 2016 EPA/ESAT Waste Rock and Soil Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Sample
Location
Mine Location
Waste Rock/Soil Sample Location
Sample
Date
Aluminum
(mg/kg)
Arsenic
(mg/kg]
Cadmium
(mg/kg)
Copper
(mg/kg)
Iron
(mg/kg
(r
Manganese
g) (mg/kg)
Mercury
(mg/kg)
Zinc
(mg/kg)
Human Health Risk-Based Levels - Campground Soils A
122
2,081
Human Health Risk-Based Levels - Waste RockA
1,419
AE10
Frisco/Bagley Tunnel
Bagley Tunnel Waste Rock - North
8/5/2015
2910
J
174
J
10
J
337
J
33800
J
7040
J
4040
J
1.2
1980
J
AE10A
Bagley Tunnel Waste Rock - South
8/5/2015
3810
J
150
J
14.9
J
143
J
37600
J
3400
J
2640
J
0.82
3200
J
A13
Bagley Tunnel Upstream
9/30/2016
15800
41.2
J
15.9
J
466
J-
28900
J
6000
14800
J
2.6
2100
CG9
Bagley Tunnel Downstream
9/30/2016
16900
176
J
216
J
2890
J-
69700
J
1730
55900
J
0.2
J
30200
GC-OPP
Bagley Tunnel - North of Mine
7/27/2016
17800
30.4
J-
0.98
26.9
23700
J
151
1700
0.0036
U
327
AE13
Columbus Mine
Columbus Mine Waste Rock
8/4/2015
6000
J
91.9
J
6.4
J
512
J
41700
J
6060
J
1160
J
0.74
1750
J
CG11
Columbus Mine Upstream
9/30/2016
15500
41.7
J
5.9
J
182
J-
29300
J
1300
6080
J
1.2
857
A10
Columbus Mine Downstream
9/29/2016
12800
J
60.2
J
1.3
141
J4
40500
J
1870
J
2350
J
0.64
404
J
CMP7
Campground 7
Campground 7
7/26/2016
13300
86.9
J-
10.6
339
23500
J
11800
1560
0.29
5290
AE32A
Silver Wing Mine
Silver Wing Mine
8/4/2015
1480
J
702
J
10.5
J
3830
J
43400
J
7010
J
357
J
0.17
1340
J
AE32b
Silver Wing Mine
8/4/2015
1310
J
729
J
8.6
J
2530
J
38600
J
4710
J
289
J
0.51
1970
J
WR-TM
Tom Moore Mine
Tom Moore Mine
7/27/2016
4690
361
7.6
J
106
J
42400
8180
837
J
0.14
3080
BE4
Ben Franklin Mine
Ben Franklin Mine
8/4/2015
3610
J
57.3
J
6.4
J
475
J
49100
J
6770
J
1130
J
0.47
2870
J
EG3A
Ben Franklin Mine Upstream
9/29/2016
17300
J
17.4
J
0.71
96.9
J4
55600
J
605
J
1620
J
0.23
282
J
EG5
Ben Franklin Mine Downstream
9/28/2016
18100
42.4
4.9
J
192
J
65400
730
J
5830
J
0.046
J
1050
A3 9
Terry Tunnel
Terry Tunnel Upstream
9/28/2016
17700
18.6
12.2
J
456
J
60100
1010
J
9450
J
0.055
J
3640
EG6
Terry Tunnel Downstream
9/28/2016
16000
31.7
11
J
439
J
67000
1770
J
15100
J
0.11
J
3450
WR-PWN
Pride of the West
Mine
Pride of the West Mine North
7/27/2016
7420
27.8
39.7
906
J
25200
13900
5450
J
0.0033
U
9920
WR-PWS
Pride of the West Mine South (10 sieve)
7/27/2016
9090
85.7
46.8
1640
J
42700
16300
5860
J
0.27
12100
WR-PWS
Pride of the West Mine South (60 sieve)
7/27/2016
10300
113
54.9
1540
J
50600
26700
6580
J
0.55
13100
CU4
Pride of the West Upstream
9/28/2016
10500
J
23.4
2.2
105
J
21800
J
1760
2210
J
0.015
J
665
J
CU4A
Pride of the West Downstream
9/28/2016
13000
J
9.2
2
47.2
J
30200
J
820
1260
J
0.012
J
458
J
CMP4
Campground 4
Campground 4
7/26/2016
8550
62.9
J-
94.3
2510
37400
J
44200
910
6
17300
Notes:
Waste rock samples are indicated by a "WR" in the sample location name mg/kg - milligrams per kilogram
CC - Cement Creek - no data available
U - Indicates compound was analyzed for, but not detected in sample "U" samples are reported as the method detection limit
UJ - The analyte was analyzed for, but was not detected. The reported value is approximate and may be inaccurate or imprecise
J - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample
J- - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample, likely to have a low bias
A - human health risk-based levels are presented and discussed in Appendix B of the Focused Feasibility Study.
- level exceeds the lead human health risk-based value of 2,081 mg/kg for campgrounds. See Appendix B of the Focused Feasibility Study.
- level exceeds the arsenic human health risk-based value of 122 mg/kg for campgrounds. See Appendix B of the Focused Feasibility Study.
- level exceeds the arsenic human health risk-based value of 1,419 mg/kg for waste rock. See Appendix B of the Focused Feasibility Study.
SPrKilh
-------
Table 4-5
Metals Concentrations for 2016 EPA/ESAT Sediment Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Sample
Location
Mine Location
Sample Location
Sample
Date
Aluminum
(mg/kg)
Arsenic
(mg/kg)
Cadmium
(mg/kg)
Copper
(mg/kg)
Iron
(mg/kg)
Lead
(mg/kg)
Manganese
(mg/kg)
Mercury
(mg/kg)
Zinc
(mg/kg)
Sediments Ecological Risk-Based Screening Levels
26000
9.79
0.99
31.6
188400
35.8
631
0.18
121
Mineral Creek |
M02E
Junction Mine
Junction Mine / Koehler Tunnel Pond
10/7/2016
8150
3080
12.4
972
184000
458
257
0.35
1700
M12C
Brooklyn Mine
Brooklyn Mine Adit Discharge
9/30/2016
6850
62.6
0.059
U
52.8
38500
2950
299
0.66
228
M12B
Brooklyn Mine Upstream in Browns Gulch
9/30/2016
12100
60.1
0.7
40.7
40000
126
662
0.033
J
184
M12
Brooklyn Mine Downstream in Browns Gulch
9/29/2016
12900
25.6
0.32
J
27.5
39700
115
535
0.039
J
102
M12E
Brooklyn Mine Discharge Channel 1
10/7/2016
2020
279
0.039
U
102
390000
101
320
0.018
J
139
M12D
Brooklyn Mine Discharge Channel 2
9/30/2016
37200
113
1.7
140
109000
1340
5390
0.0085
U
892
M12A
Brooklyn Mine Discharge Channel 3
9/30/2016
9870
49.5
0.13
J
31
41100
51.4
474
0.043
J
71.9
M23
Bandora Mine
Bandora Mine Upstream
9/27/2016
8490
5.1
0.23
J
18.1
18500
9.4
631
0.0043
u
109
M25
Bandora Mine Downstream
9/27/2016
12900
5.8
2.1
46.5
19700
36.1
559
0.0045
u
402
Cement Creek |
CC01C
Grand Mogul Mine
Grand Mogul Mine at toe of Waste Rock
9/28/2016
4310
458
0.99
168
198000
612
2750
0.11
J
333
CC01C1
Grand Mogul Mine at toe of Waste Rock
9/28/2016
4210
455
1.3
202
59600
959
10700
0.079
J
348
CC01C2
Grand Mogul Mine upstream of Cement Creek
9/28/2016
18700
386
49.8
1230
79600
2070
42300
0.043
J
3770
CC01F
Upstream of Grand Mogul Mine
9/28/2016
13400
27.1
10.9
1200
32000
1400
5770
0.026
J
2550
CC01H
Cement Creek after Confluence with Grand Mogul East Drainage Channel
9/27/2016
13000
39.6
5
710
34800
1240
5150
0.041
J
1150
CC02I
Grand Mogul Western Waste Rock Drainage Channel
9/27/2016
11000
51
1.3
J
132
26100
384
2710
0.0053
J
419
CC01U
Downstream of Grand Mogul and Queen Anne in Cement Creek
9/27/2016
9910
39.1
1.5
J
131
25000
326
3610
0.013
J
471
CC15
Natalie/Occidental Mine
Upstream of Natalie/Occidental Mine
9/29/2016
10400
11.8
0.056
u
34.2
52300
44.3
424
0.016
J
86.3
CC15A
Downstream of Natalie/Occidental Mine
9/29/2016
8730
11.8
0.059
u
48.4
98300
93.6
444
0.011
J
111
CC22D
Henrietta Mine
Upstream of Henrietta Mine
9/29/2016
9110
46.6
1.4
155
31800
664
353
J
0.089
J
613
CC22B
Midpoint of Henrietta Mine
9/29/2016
12900
58.2
1.6
166
37800
807
365
0.16
J
511
CC24B
Downstream of Henrietta Mine
9/29/2016
6400
52.2
1
47.2
40500
466
221
0.12
J
299
CC38
Anglo Saxon Mine
Porcupine Gulch Immediately Before Cement Creek Confluence
9/28/2016
16400
156
5.5
J
482
926000
687
3870
0.044
J
6180
CC38C
Porcupine Gulch Upstream of Anglo Saxon Mine
9/28/2016
18600
55.8
3.5
182
58800
2080
2500
0.059
J
2040
CC38D
Porcupine Gulch Between Upper and Lower Anglo Saxon Adit
9/28/2016
9170
118
5.4
431
178000
897
2870
0.021
J
1760
CC39
Cement Creek below Anglo Saxon Mine
9/27/2016
9010
41.6
0.98
46.1
93700
307
620
0.0044
u
299
CC39B
Cement Creek above Anglo Saxon Mine
9/28/2016
8800
36.3
2.6
141
J
86700
359
668
0.0081
J
799
CC41
Yukon Tunnel
Cement Creek above Yukon Tunnel
9/27/2016
7700
56.4
0.86
26.1
52000
493
345
0.043
J
312
CC42
Illinois Gulch at mouth to Cement Creek
9/27/2016
16800
64.9
4.8
416
83800
134
18600
0.01
J
1310
CC42F
Illinois Gulch Above Yukon Tunnel Discharge Pipe
9/27/2016
11100
11.5
0.35
J
52.1
31400
119
811
0.0044
u
142
CC43E
Cement Creek Below Yukon Tunnel
9/27/2016
8500
75.1
1.2
38.3
70300
390
426
0.063
J
402
Animas River |
A07E
Boston Mine
Upstream of Boston Mine
10/5/2016
20500
J_
73.2
2.2
94.3
28600
J_
734
6920
0.056
J_
359
A07D
Downstream of Boston Mine
10/5/2016
18000
J_
95.5
5.9
126
43900
J_
884
16600
0.047
J_
681
A07B
London Mine
London Mine Downstream
9/30/2016
25200
28.1
9
126
27500
372
10100
0.029
553
A07B
London Mine Downstream
9/30/2015
27500
59.3
10.8
301
58800
889
J_
16900
0.024
889
A07B
London Mine Downstream
8/5/2015
16100
~T_
43.8
12.9
235
39400
~T
760
J_
14200
0.038
~T
716
BB2
Ben Butler Mine
Below Ben Butler Waste Rock
10/5/2016
14500
88.7
11.2
397
26100
1130
5750
0.042
2640
A19
Mountain Queen Mine
Mountain Queen Mine Upstream
8/5/2015
7460
j_
62.6
~T_
0.88
~T
114
~T
36100
1130
~T
1960
~T
0.034
j_
163
~T_
A18
Mountain Queen Mine Downstream
8/5/2015
14900
j
26.3
j
2.1
j
327
j
44400
j
195
j
1910
j
0.083
j
376
j
1
-------
Table 4-5
Metals Concentrations for 2016 EPA/ESAT Sediment Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Sample
Location
Mine Location
Sample Location
Sample
Date
Aluminum
(mg/kg)
Arsenic
(mg/kg
Cadmium
(mg/kg)
Copper
(mg/kg
Iron
(mg/kg
Lead
(mg/kg
Manganese
(mg/kg)
Mercury
(mg/kg
Zinc
(mg/kg
Sediments Ecological Risk-Based Screening Levels
26000
9.79
0.99
31.6
188400
35.8
631
0.18
121
CG4
Vermillion Mine
Vermillion Mine Upstream
10/6/2016
17800
17
1.3
123
32900
77.5
5010
0.0042
U
390
CG4
Vermillion Mine Upstream
8/5/2015
15900
J
17.2
J
1.3
J
152
J
30900
J
74.9
J
4460
J
0.016
J
338
CG6
Vermillion Mine Downstream
9/30/2016
19600
15.3
0.89
J-
106
34200
92.9
3690
0.019
J
436
CG6
Vermillion Mine Downstream
8/5/2015
18500
J
23.3
J
2.1
J
177
J
34100
J
92.8
J
8300
J
0.014
J
424
~T_
A22
Sunbank Group Mine
Sunbank Group Mine Upstream
9/30/2016
9580
82.3
21.7
446
24100
4060
21000
0.51
2690
A22
Sunbank Group Mine Upstream
9/29/2015
7690
J-
46.6
25.4
111
24000
5120
19000
0.639
6250
A22
Sunbank Group Mine Upstream
8/6/2015
5440
J
39.8
J
41.8
J
896
J
17800
J
5420
J
20500
J
1.1
8970
~T_
A21
Sunbank Group Mine Downstream
9/30/2016
14400
73.2
17
644
29200
4310
7050
12.8
5720
A21
Sunbank Group Mine Downstream
9/29/2015
26800
J-
44
51.5
1560
32600
9180
J
31600
0.701
11900
A21
Sunbank Group Mine Downstream
8/6/2015
6940
J
40.1
J
30.9
J
911
J
18900
J
6470
J
21600
J
1.2
9450
~T_
A13
Frisco/Bagley Tunnel
Bagley Tunnel Upstream
9/30/2016
15200
32.9
7.4
238
24700
2100
18500
0.12
1150
A13
Bagley Tunnel Upstream
9/29/2015
20400
29
4.58
239
33200
911
J
9860
0.033
1120
A12
Bagley Tunnel Adit Drainage
9/28/2016
23700
61.6
J-
28.4
171
209000
J-
271
J-
45600
J
0.106
J-
12500
CG9
Bagley Tunnel Downstream
9/30/2016
15700
69.3
10.4
473
36100
2600
11300
0.082
J
2980
CG11
Columbus Mine
Columbus Mine Upstream
9/30/2016
11400
35.9
8
162
21900
1170
10300
0.078
J
1830
A10
Columbus Mine Downstream
9/29/2016
8170
18.3
1.2
57.2
18700
455
1660
J
0.11
359
A10
Columbus Mine Downstream
9/29/2015
44600
41.7
7.46
477
28400
2190
J
9230
0.234
2240
A10
Columbus Mine Downstream
8/4/2015
10200
J
30.9
J
7
J
295
J
23300
J
1220
J
15600
J
0.11
J
821
~T_
A28
Silver Wing Mine
Silver Wing Mine Upstream
9/30/2015
10100
J-
63
12.2
280
30900
1130
J
7640
0.049
2790
A28
Silver Wing Mine Upstream
8/4/2015
8590
J
36.2
J
5.7
J
195
J
19700
J
304
J
6380
J
0.013
u
959
~T_
A30
Silver Wing Mine Downstream
9/30/2015
13900
J-
37.8
10.9
355
21200
766
J
10500
0.019
J
2740
A30
Silver Wing Mine Downstream
8/4/2015
9750
J
50.3
J
14.2
J
324
J
26700
J
629
J
7300
J
0.014
u
1520
~T_
A30A
Tom Moore Mine
Tom Moore Mine Upstream
9/29/2016
8750
68.1
5.2
312
26000
848
20300
0.016
J
1510
A30B
Tom Moore Mine Downstream
9/29/2016
9780
38.5
7.1
158
24500
454
4740
0.0039
u
1150
EG3A
Ben Franklin Mine
Ben Franklin Mine Upstream
9/29/2016
18000
18.3
5.4
146
43300
266
4770
0.023
J
1500
EG3A
Ben Franklin Mine Upstream
9/29/2015
12300
17.8
J
5.18
242
44100
948
J-
4280
0.336
1610
EG3A
Ben Franklin Mine Upstream
8/4/2015
16400
J
16.7
J
7.3
J
179
J
40600
J
304
J
5020
J
0.025
J
1090
~T_
EG5
Ben Franklin Mine Downstream
9/28/2016
14100
69.3
10.9
472
55500
12100
47300
0.037
J
11400
EG5
Ben Franklin Mine Downstream
9/30/2015
21800
19.7
J_
19.2
318
76700
2070
J-
7060
0.075
6460
EG5
Ben Franklin Mine Downstream
8/4/2015
14600
~T_
21.6
J_
34.4
~T
637
~T_
47800
~T
1070
J
9890
~T
0.046
J
2360
~T_
A39
Terry Tunnel
Terry Tunnel Upstream
9/28/2016
14800
32.1
11.5
432
61200
1940
7080
0.055
J
3640
EG6
Terry Tunnel Downstream
9/28/2016
16200
28.7
16.3
419
46800
1090
9120
0.046
J
3660
EG6
Terry Tunnel Downstream
9/30/2015
12900
18.1
~T_
14.4
334
38600
1040
J-
10800
0.035
4360
EG6
Terry Tunnel Downstream
8/4/2015
14000
~T_
23.9
17.3
~T
535
~T_
42500
~T
1090
J
12000
~T
0.092
J
3290
~T_
CU4
Pride of the West Mine
Pride of the West Mine Upstream
9/28/2016
13900
4
0.63
10.5
33100
98.5
1830
0.004
u
161
CU4A
Pride of the West Mine Downstream
9/28/2016
13400
6.8
2
20.2
29500
378
1350
0.0045
u
502
A50
Pride of the West Mine Adit
9/28/2016
6790
31.4
28.9
837
21400
8910
9510
0.055
J
11300
Notes:
J - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample
U - Indicates compound was analyzed for, but not detected in sample
J- - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample, likely to have a low bias
mg/kg - milligrams per kilogram
" - no data available
"U" samples are reported as the method detection limit
- level exceeds the ecological risk-based screening levels for sediments
2
-------
Figures
-------
Figures
This page intentionally left blank.
-------
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Bonita Peak Mining District Superfund Site | San Juan County, CO
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0
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Excludedfrom Preliminary Rl
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-------
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Mining-Related Sources-
Forest service Mineral Creek Drainage Basin
Road
Bonita Peak Mining District Superfund Site |San Juan County, CO
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Streams
-------
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Bonita Peak Mining District Superfund Site [ San Juan County, CO
Preliminary Remedial Investigation
-------
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' SOUTH F ORK?
MINERAL CREEK
M
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Longfellow Mine, Junction Mine, and Koehler Tunnel
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
-------
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Figure 4-2
Brooklyn Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
-------
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Figure 4-3
Bandora Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
-------
mm
Potential
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CEMENT
CREEK
A
N
0 25 50 100
1 I I I I I I I I
Feet
Background Terrain Sources: Esri1' USGS,
NOAA
Road and Railroad Source: US Census
Tiaer/Une
Waterways and Waterbodies Source:
National Hydrography Data set- USGS
Legend
Samples
® Surface Water
~ Sediment
A Waste Rock and Soil Sample
Figure 4-4
Grand Mogul Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
-------
Mine Waste
CC15A
WR-CC14 A **
WR-CC14B
MIW'Discfiarge
Mi he'" Waste'
% V v:V;iy.
r Mine
Location
CEMENT
CREEK
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imagerst tO/U/2015.
Road and Railroad Source: US Census
Tiger/Line
Waterways and Waterbodies Source:
National Hydrography Data set- USGS
Legend
Samples
^ Surface Water
~ Sediment
A Waste Rock and Soil Sample
Note:
MIW = mining-influenced water
Figure 4-5
Natalie/Occidental Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
-------
CC22B
CC24B
CC22D
s
Mine Waste
CC24G
MIWjDischarge:
Legend
Samples
Figure 4-6
Henrietta Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
Mine
Location
Surface Water
Sediment
Waste Rock and Soil Sample
CEMENT
CREEK
Background Terrain Sources: Esri, USGS,
NOAA
Road and Railroad Source: US Census
Tiger/line
Waterways and Waterbodies Source:
National Hydrography Data set- USGS
Note:
MIW = mining-influenced water
-------
CC29B
Mine Waste
MlW Discharge
MlW Discharge
Sediment Pond
Sediment Pond
CC28C
CC29D
Legend
Samples
^ Surface Water
~ Sediment
A Waste Rock and Soil Sample
Figure 4-7
Mammoth Tunnel
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
Mine
Location
CEMENT
CREEK
Feet
Background Terrain: Google Earth Pro
megem 10/12/2015
Road and Railroad Source: US Census
Tiger/Line
Waterways and Waterbodies Source:
National Hydrography Data set- USGS
Note:
MIW = mining-influenced water
-------
CC39B \V
MIW Discharge
Sediment Pond
Mine Waste
MlWjbischarge]
glo;
SAXON LIMINE
¦ I'Ad'it t*S
CC38B
WR-CC38B
[CC38D
CC38C:
Legend
Samples
^ Surface Water
~ Sediment
A Waste Rock and Soil Sample
Figure 4-8
Anglo Saxon Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
CEMENT I Mine
CRE El- Location
Background Terrain: Google Earth Pro
imagery 10/11/2015
Road and Railroad Source: US Census
Tiger Aim
Waterways and Waterbodies Source:
National Hydrography Data set- USGS
Note:
MIW = mining-influenced water
-------
CC42F
MIW Discharge
Potential |H
StormwaterJ
Interactional
WR-CC43
YUKON TUNNEL
CC43D
Mine Waste
CC43E
Legend
Samples
^ Surface Water
~ Sediment
A Waste Rock and Soil Sample
Figure 4-9
Yukon Tunnel
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
CEMENT
CREEK
Background Terrain Esri, HERE, Garmin, ffl
Open$ tree (Map contributors
Sources: Esri, USGS, NOAA
Source: Esri, DigitaiGiobe, GsoEye, Earths tar
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-------
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BOSTON MINE
^TWR^BSNf ¦ j , ,
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Location
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Samples
Figure 4-10
Boston Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
Surface Water
Sediment
Waste Rock and Soil
AftiMAS
Wl/Efl
Background Terrain Sources: fori, USGS,
fiOAA
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National hydrography Dataset - USGS
Ir^ Km. . -
-------
MlW Discharge
' 'jl
MinewVaste
MIW Discharge
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Mine
Location
Legend
Samples
Figure 4-11
London Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
Surface Water
Sediment
Waste Rock and Soil Sample
MIMAS
mven
Background Terrain: Google Earth Pro
Imagery, 10/12/2015
Road and Railroad Source: US Census
Tiger/line
Waterways and Waterbodies Source:
National Hydrography Data set- USGS
Note:
MIW = mining-influenced water
yi , - <.
-------
' Mine
^Location
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men
A
N
120
0 30 60
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10/12/2015
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T>ger/Line
Waterways and Waterbodies Source:
National Hydrography Data set- USGS
Legend
Samples
$ Surface Water
~ Sediment
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Figure 4-12
Ben Butler Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
-------
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Legend
Samples
Q Surface Water
~ Sediment
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Note:
MIW = mining-influenced water
Figure 4-13
Mountain Queen Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
-------
¦potential
Stormwater
Interaction
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Figure 4-14
Vermillion Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
-------
-—
SUNBANK
GROUP MINE
A AE45
Potential
Storm water
Enter act iorii
SedimentPond
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Sedi me'lit RondIM
ii'-? :
MIW Discharge
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MIW
Discharge
mm
' — *&-, _
Legend
Samples
O Surface Water
~ Sediment
A Waste Rock and Soil Sample
Figure 4-15
Sunbank Group Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
Mine
Location
ANIMAS
RIVER
Background Terrain: Google Earth Pro
Imagery, 10/12/2015
ftoad and Railroad Source: US Census
Tiger/Line
Waterways and Water bodies Source:
National hydrography Data set- USGS
Note:
MIW = mining-influenced water
©3MBED
-------
-------
>-fPotenti alj
Stormwater
flnteTaSiorv
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- Stormwater
Interaction
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MIW Discharge,
Mine-Waste
-s -w
Legend
Samples
Figure 4-17
Columbus Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
r Mine
Location
Surface Water
Sediment
Waste Rock and Soil
MIMAS
PiVEg
Background Terrain: Google Earth Pro
Imagery, 10/12/2015
ftoad and Railroad Source: US Census
Tiger/tine
Waterways and Waterbodies Source:
National Hydrography Data set- USGS
Note:
MIW = mining-influenced water
"ffi®
-------
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Tiger/tine
Waterways and Waterbodies Source:
National Hydrography Data set- USGS
Legend
Samples
A Waste Rock and Soil
Figure 4-18
Campground 7
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
-------
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Silver Wing Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
Note:
MIW = mining-influenced water
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Waste
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Samples
Figure 4-21
Ben Franklin Mine
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
Surface Water
Mine ^
Location a
Sediment
Waste Rock and Soil
A MM AS
Background Terrain Sources: Esri, USGS,
NOAA
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Note:
MIW = mining-influenced water
-------
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Figure 4-22
Terry Tunnel
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
-------
-------
MinelWaste
¦ MMS
H RIVER
Mine
Location
Figure 4-24
Campground 4
Bonita Peak Mining District Superfund Site | San Juan County, CO
Preliminary Remedial Investigation
A
N
0 30 60 120
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Background Terrain Sources: EsriUSGS,
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AeroGftID, IGN, and the GiS User Community
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Legend
Samples
A Waste Rock and Soil
-------
Attachment A
Total and Dissolved Metals, Anions, Alkalinity, and
Hardness Data for 2015 and 2016 EPA/ESAT
Surface Water Samples
-------
Attachment A • Total and Dissolved Metals, Anions, Alkalinity, and Hardness Data for 2015 and 2018 EPA/ESAT
Surface Water Samples
This page intentionally left blank.
-------
Attachment A
Total and Dissolved Metals, Anions, Alkalinity, and Hardness Data for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Mine Site
Station
Name
Sample Date
pH
Flow
(gpm)
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Longfellow Mine
M02D
6/29/2016
6.61
15
286
33.4
J
2.5
U
0.5
U
3.85
J
2.64
2
U
2
U
0.5
U
0.1
U
10100
870
5
U
1
U
8.91
7.2
650
179
J
2590
2420
M02D
10/7/2016
6.83
4.9
183
22.4
J
2.5
u
0.5
U
2.5
U
1.67
J
2
u
2
U
0.5
u
0.1
U
12400
11700
5
u
1
U
5.04
4.14
577
146
J
29 0
2770
Junction Mine
M02B
6/29/2016
6.15
12
1720
227
2.5
u
0.864
J
143
57.2
2
u
2
u
7.17
7.46
29500
28300
5
u
1
u
261
182
16600
13500
8400
7900
M02B
10/7/2016
3.86
2.9
7110
6320
2.5
u
0.536
J
303
213
2
u
2
u
25.1
26.1
56300
52900
5
u
1.28
J
777
794
64000
56100
12300
11300
Koehler Tunnel
M02K1
6/29/2016
4.54
0.1
3870
3720
2.5
u
2.5
u
2.5
U
2.5
U
2.02
J
2.07
J
40.7
40.5
170000
164000
5
u
5
u
3170
3310
324
309
26000
24900
M02C
10/7/2016
6.12
4.5
12900
1950
2.5
u
2.5
u
3000
1020
3.41
J
2
u
86.2
89.4
391000
370000
5.72
J
5
u
3140
2100
177000
152000
54600
51500
M02E
6/29/2016
~
-
3500
2460
2.5
u
0.5
u
177
30.4
2
u
2
u
19.4
21.1
103000
600
5
u
1
u
891
863
17600
13000
15600
14700
M02E
10/7/2016
3.6
.0
8100
7590
2.5
u
2.5
u
234
67.4
2
u
2
u
47.2
42.8
231000
198000
5
u
5
u
1610
1410
40400
33800
33500
29600
M02
6/29/2016
5.76
150
2590
422
2.5
u
0.5
u
119
15.1
2
u
2
u
12.2
12.5
74800
73300
5
u
1
u
522
449
10000
6710
11600
11200
M02
10/7/2016
8.03
23
6770
6190
2.5
u
2.5
u
0.3
30.3
2
u
2
u
35.7
36.4
195000
179000
5
u
5
u
1290
1320
17100
15200
28100
26200
Brooklyn Mine
M12
6/7/2016
4.55
-
3460
290
2.5
u
0.5
u
7.59
J
0.5
u
2
u
2
u
0.726
J
0.719
11800
11400
5
u
1
u
15.6
6.08
7400
136
J
2190
1830
M12
6/29/2016
5.08
438
3370
3030
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
3.94
4.02
30000
29300
5
u
1
u
33.9
34.4
11
410
5320
5080
M12
/29/2016
4.17
165
130
8700
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
6.07
6.2
50300
48800
5
u
1
u
53.4
54.4
1210
1040
020
8800
M12A
6/29/2016
4.51
-
3850
3120
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.05
1.11
24500
23500
5
u
1
u
22.9
22.3
1590
362
4490
4090
M12A
/30/2016
4.45
151
10200
630
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.28
1.49
42400
41400
5
u
1
u
31.7
32.2
1200
627
7500
7350
M12B
6/29/2016
4.76
223
3940
3510
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
u
0.266
20500
19500
5
u
1
u
11.1
11.2
66
419
3830
3630
M12B
/30/2016
4.55
151
11900
11000
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
u
0.307
37300
36300
5
u
1
u
19.6
20.1
1770
1050
7210
6840
M12C
6/29/2016
3.63
7.3
1890
1010
2.5
u
0.5
u
20.7
0.5
u
2
u
2
u
14.9
15.6
89800
86800
5
u
1
u
236
177
26400
4070
17400
16700
M12C
/29/2016
3.84
1.1
3620
2920
2.5
u
0.5
u
39.3
1.63
J
2
u
2
u
19.1
18.7
4700
3700
5
u
1.18
J
348
300
58800
16300
17700
17500
M12C
/30/2016
3.84
1.1
3020
2450
2.5
u
0.5
u
20.6
2.7
2
u
2
u
19
18.8
3600
0600
5
u
1.07
J
319
302
33700
16600
17100
16400
M12D
/30/2016
3.72
2.2
2770
2170
2.5
u
0.5
u
20.1
1.4
J
2
u
2
u
18.9
19
3200
1700
5
u
1
u
328
317
27600
10400
17100
16500
M12F
10/7/2016
7.79
-
83.1
48.1
J
2.5
u
0.5
u
2.5
u
0.908
J
2
u
2
u
0.5
u
0.1
u
800
4900
5
u
1
u
2.5
U
0.945
J
105
J
100
u
6470
6140
M12G
10/7/2016
4.07
-
642
576
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
u
0.433
13300
12500
5
u
1
u
22.1
23.8
591
502
1960
1860
Bandora Mine
M23
/27/2016
5.98
7351
2070
554
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
u
0.349
24200
22900
5
u
1
u
2.5
U
1.33
162
J
100
u
4070
3940
M24A
/28/2016
6.96
-
57
36
J
3.05
J
0.5
u
12.8
0.5
u
3.01
J
2
u
67.8
35.8
0300
84700
5
u
1
u
1070
3.15
74900
195
J
6730
6470
M24B
/28/2016
6.71
24
210
37.8
J
2.5
u
0.5
u
2.5
u
0.507
J
2
u
2
u
49.3
48
0300
84200
5
u
1
u
233
19.3
16100
5300
6570
6320
M24C
/28/2016
7.41
-
31.2
J
30.1
J
2.5
u
2.5
u
2.5
u
2.5
u
2
u
2
u
0.5
u
0.5
u
138000
127000
5
u
5
u
2.5
U
2.5
U
112
J
141
J
7280
7030
M24D
/27/2016
6.87
-
200
20
U
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
42.4
35.2
0500
84000
5
u
1
u
189
2.23
11500
100
u
6580
6330
M25
6/29/2016
6.28
21553
696
49.7
J
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
u
0.336
16200
15800
5
u
1
u
2.5
U
1.28
100
U
100
u
2960
2840
M25
/27/2016
6.12
317
1840
266
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.54
J
0.622
25900
24400
5
u
1
u
2.5
u
1.2
159
J
100
u
39 0
3760
Grand Mogul
Mine
CC01C
6/29/2016
3.59
-
2010
1850
2.5
u
0.5
u
2.5
u
1.56
J
2
u
2
u
18.7
17.6
12700
12000
5
u
1
u
470
462
2410
2210
2240
2080
CC01C
/28/2016
4.1
3.6
10300
720
2.5
u
2.5
u
37.1
39
2
u
2
u
5.4
7
21900
20900
5
u
5
u
2620
2620
57900
55100
040
8660
CC01C1
6/29/2016
3.17
-
4570
4190
2.5
u
0.5
UJ
3.85
J
5.54
2
u
2
u
41.7
35.1
J
14000
13200
5
u
1
u
1440
1360
10000
12700
4250
3920
CC01C1
/28/2016
3.96
2.8
15000
14100
2.5
u
2.5
u
20.3
21.8
2
u
2
u
127
130
23100
21800
5.56
J
5
u
5080
5070
54600
52200
12000
11600
CC01C2
6/29/2016
3.42
73
2960
2750
2.5
u
0.5
u
2.5
u
0.617
J
2
u
2
u
23.1
21.5
13200
12300
5
u
1
u
733
708
3030
2850
2690
2520
CC01C2
/28/2016
4.12
.0
8090
7730
2.5
u
0.5
u
2.5
u
2.94
2
u
2
u
69.1
62.9
17700
16600
5
u
1.13
J
2220
2130
380
8900
6610
6340
CC01F
6/29/2016
7.27
-
238
7.6
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.19
1.2
30900
29100
5
u
1
u
31.1
20.6
100
U
100
u
2850
2660
CC01F
/28/2016
7.16
-
372
114
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
2.7
2.77
52800
49700
5
u
1
u
59
29.7
100
U
100
u
4600
4380
CC01H
6/29/2016
6.12
2904
721
197
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
5.39
5.41
27000
25300
5
u
1
u
163
133
611
100
u
2780
2610
CC01H
/27/2016
6.31
368
663
213
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
7.13
7.34
45700
43700
5
u
1
u
161
141
582
100
u
4420
4300
CC02I
6/28/2016
4.69
7.3
79
24
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
6.17
6.11
34700
33100
5
u
1
u
24
24.4
100
U
100
u
4620
4370
CC02I
/27/2016
5.90
350
1880
1000
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
11.2
12
55900
53100
5
u
1
u
128
116
224
J
100
u
7170
6980
CC01U
6/28/2016
6.16
5327
1120
197
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
4.18
4.3
32600
30800
5
u
1
u
69.2
51.5
29
100
u
4220
3920
CC01U
/27/2016
5.72
378
1860
26
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
12.1
12.1
57200
54000
5
u
1
u
131
117
244
J
100
u
7280
7140
Natalie/Occident
al Mine
CC14
6/10/2015
6.09
-
1830
1150
2.5
u
0.5
u
4.46
J
1.88
J
2
u
2
u
5.25
4.68
159000
158000
5
u
1
u
86.9
67.6
19800
18000
7790
7490
CC14
/29/2015
6.32
-
20
664
2.5
u
2.5
u
2.5
u
2.5
u
2
u
2
u
1.82
1.78
206000
185000
5
u
5
u
7.78
3.51
J
19600
18100
110
8600
CC14
6/9/2016
6.13
-
2440
1900
2.5
u
5
u
2.5
u
5
u
2
u
2
u
5.59
5.9
184000
189000
5
u
10
u
0.8
75.9
27200
27200
830
40
CC14
/29/2016
5.39
407
55
791
2.5
u
2.5
u
2.53
J
2.94
J
2
u
2
u
1.87
1.87
209000
198000
5
u
5
u
7.17
3.16
J
18600
17600
040
8770
CC15
6/9/2016
-
7277
643
1.6
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
u
0.271
18700
19500
5
u
1
u
8.71
4.97
796
100
u
1490
1530
CC15
/29/2016
7
301
446
5.8
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
u
0.226
36600
34200
5
u
1
u
5.38
2.92
145
J
100
u
2090
2020
CC15A
6/9/2016
-
7206
751
177
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.787
J
0.831
35600
36200
5
u
1
u
15.8
10.2
2920
2530
2310
2350
CC15A
/29/2016
6.8
1170
868
267
2.5
u
2.5
u
2.5
u
2.5
u
2
u
2
u
1.16
1.2
128000
121000
5
u
5
u
8.95
4.21
J
330
8340
5860
5700
Henrietta Mine
CC24G
6/30/2016
4.61
-
1840
1790
2.5
u
0.5
u
2.72
J
3.5
2
u
2
u
0.5
u
0.293
3010
3170
5
u
1
u
36.9
35.8
20900
20400
1080
1060
CC22D
6/8/2016
5.76
-
488
84.4
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.65
1.61
20
10100
5
u
1
u
46.1
37.1
44
127
J
1310
1340
CC22D
/29/2016
5.79
73
1130
124
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.7
1.74
41600
38300
5
u
1
u
42.6
28.9
1440
211
J
4880
4670
CC22B
6/8/2016
4.73
-
811
622
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.11
1.22
510
570
5
u
1
u
34
33.8
663
312
1370
1370
CC22B
/29/2016
4.33
131
3600
3120
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.43
1.61
37400
35600
5
u
1
u
33.6
33.3
533
347
5520
5270
CC24B
6/8/2016
4.37
-
04
666
2.5
u
0.5
u
2.5
u
0.848
J
2
u
2
u
1.08
1.29
10300
10400
5
u
1
u
58.9
57.9
1210
769
1440
1520
CC24B
/29/2016
3.93
166
2790
2460
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
2.03
2.32
39700
38700
5
u
1
u
106
107
1740
1450
5440
5260
Anglo Saxon
Mine
CC37
6/7/2016
-
41
500
477
2.5
u
2.5
u
7.91
J
6.93
J
2.03
J
2
u
2.75
2.52
297000
304000
5
u
5
u
7.68
7.03
28200
28400
18300
19000
CC37
/28/2016
6.53
41
458
433
2.5
u
2.5
u
7.17
J
6.78
J
2
u
2
u
2.26
2.36
306000
29 000
5
u
5
u
5.21
4.09
T
28700
25700
18500
18300
CC38
6/7/2016
7.43
-
1160
86.5
2.5
u
0.5
u
2.6
J
0.5
u
2
u
2
u
0.5
~u~
0.363
15800
15800
5
u
1
u
11.9
6.54
2260
556
1720
1670
CC38B
6/7/2016
6.15
59
885
790
2.5
u
2.5
u
6.39
J
3.32
J
2
u
2
u
2.06
2.08
218000
216000
5
u
5
u
58.8
65.9
20500
16300
13400
13800
CC38B
/28/2016
6.67
36
638
211
2.5
u
2.5
u
5.93
J
3.36
J
2
u
2
u
1.95
1.81
279000
273000
5
u
5
u
24.4
7.69
21800
17300
16900
16600
CC38C
6/7/2016
7.07
-
1530
104
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
~u~
0.206
5720
5540
5
u
1
u
19.9
5.06
2160
100
~u~
1120
1030
CC38C
/28/2016
7.32
15
266
5.8
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
2.2
2.46
24900
24200
5
u
1
u
20.2
10.9
107
T
100
u
5110
4940
CC39
6/7/2016
5.26
-
2140
643
2.5
u
0.5
u
4.72
J
0.5
u
2
u
2
u
2.26
2.19
29000
29100
5
u
1
u
70.1
53.9
6800
2100
2690
2470
CC39
/27/2016
3.62
7970
6770
5930
2.5
u
2.5
u
6.93
J
2.6
J
2
u
2
u
5.72
5.78
164000
158000
5
u
5
u
108
.7
14800
10000
30
560
CC39B
6/7/2016
5.1
-
2230
13
2.5
u
0.5
u
5.76
J
0.5
u
2
u
2
u
2.41
2.33
30700
29800
5
u
1
u
69.3
58.7
6790
2330
2830
2480
CC39B
/28/2016
3.82
69 3
6180
5760
2.5
u
2.5
u
4.78
J
2.5
u
2
u
2
u
5.43
5.49
162000
158000
5
u
5
u
55
59
13700
12500
870
520
(Sm!th
-------
Attachment A
Total and Dissolved Metals, Anions, Alkalinity, and Hardness Data for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Mine Site
Station
Name
Sample Date
pH
Flow
(gpm)
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Yukon Tunnel
CC41
6/7/2016
5.16
-
2410
07
2.5
U
0.5
U
4.12
J
0.5
U
2
U
2
U
2.98
2.91
33000
33000
5
u
1
U
.4
72.6
8110
2460
2960
2720
CC41
/27/2016
3.55
6939
6220
5520
2.5
u
2.5
U
6.49
J
2.5
U
2
u
2
U
6.63
6.36
172000
162000
5
u
5
U
141
6.3
12500
7480
10200
660
CC43C
6/7/2016
6.82
-
533
171
2.5
u
2.5
u
2.5
U
2.5
u
2
u
2
u
0.5
U
0.5
U
228000
233000
5
u
5
u
11.6
3.98
J
2460
1190
6810
7120
CC43C
/27/2016
6.68
-
486
168
2.5
u
2.5
u
2.5
U
2.5
u
2
u
2
u
0.5
U
0.5
U
223000
215000
5
u
5
u
12.2
2.94
J
2440
1110
6770
6500
CC43D
6/7/2016
2.98
-
30900
28200
2.5
u
0.5
u
2.5
u
0.81
J
3.11
J
2.41
J
21.4
18.4
3500
1700
5
u
3.82
3610
2770
42900
39300
23400
21900
CC43E
6/7/2016
5.37
-
3020
891
2.5
u
0.5
u
5.63
J
0.5
u
2
u
2
u
3
3.19
34900
34700
5
u
1
u
104
82.3
10000
2250
3280
2760
CC43E
/27/2016
3.88
7069
5630
5240
2.5
u
2.5
u
3.6
J
2.5
u
2
u
2
u
5.06
5.01
167000
160000
5
u
5
u
84.9
81.9
10100
7080
420
210
Boston Mine
A07D
6/28/2016
4.23
-
5970
5550
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
7.55
7
7830
7130
5
u
1
u
38.9
34.6
242
J
149
J
1130
1060
A07D
10/5/2016
4.11
.0
16000
15100
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
19.1
19.5
15500
14700
5
u
1
u
2.5
2.5
100
U
100
U
2950
2790
A07D1
6/28/2016
4.26
55
19300
18000
2.5
u
0.5
u
2.5
u
0.5
u
3.41
J
3.31
J
33.2
32.4
14200
13100
5
u
1
u
55.5
51.3
100
U
100
U
2340
2170
A07D2
6/28/2016
4.31
-
2340
2150
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
25.5
23.8
3300
3090
5
u
1
u
6.2
0
100
U
100
u
334
310
A07E
6/28/2016
4.18
-
4830
4570
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
5.02
4.93
7080
6700
5
u
1
u
35.4
33
234
J
141
J
1030
86
A07E
10/5/2016
3.86
49
13800
13000
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
12.3
13.3
14900
14300
5
u
1
u
64.6
68.8
311
304
2770
2620
London Mine
DM6
6/28/2016
6.13
3.2
121
88.5
2.5
u
1.67
2.5
u
0.5
u
2
u
2
u
8.17
8.7
170
8920
5
u
1
u
30.3
30
443
324
529
527
DM6
/30/2016
3.21
0.7
1220
1100
2.5
u
0.911
J
2.5
u
1.36
J
2
u
2
u
84.4
71.4
26200
24900
5
u
1
u
260
218
6180
4870
1680
1580
DM7
6/8/2016
6.69
-
360
23.1
J
3.18
J
1.64
4.25
J
0.595
J
2
u
2
u
13.8
12.8
22400
22800
5
u
1
u
41.3
4.53
2150
100
u
1520
1490
DM7
6/28/2016
6.05
1.1
644
41.2
J
4.77
J
2.89
11.9
2.58
2
u
2
u
46.2
43.2
54500
52000
5
u
1
u
107
.9
4700
255
3480
3390
DM7
/30/2016
6.41
-
29
37.9
J
4.06
J
2.25
14.8
2.86
2
u
2
u
49.4
42
57800
56800
5
u
1
u
123
6.57
7400
312
3880
3780
A07B1
6/28/2016
4.28
1329
7230
6790
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
11.3
10.8
140
8610
5
u
1
u
43.5
39.8
148
J
103
J
1340
1250
A07B
/30/2015
4.3
21
14000
13400
2.5
u
0.5
u
2.5
u
0.5
u
5.81
5.98
21.7
23
32600
31400
5
u
1
u
49.8
51.5
166
J
102
J
4760
4530
A07B
6/28/2016
4.323
1206
6860
6440
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
10.4
10.7
030
8550
5
u
1
u
42.2
38.9
134
J
108
J
1310
1240
A07B
/30/2016
4.08
186
17100
17000
2.5
u
0.5
u
2.5
u
0.5
u
4.92
J
4.86
J
26.4
24.1
25300
24500
5
u
1
u
61.6
56.6
170
J
161
J
3950
3830
Ben Butler Mine
BB1
6/28/2016
3.97
-
546
502
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
10.7
10.6
5230
5000
5
u
1
u
192
189
373
303
451
428
Mountain Queen
Mine
A18
10/6/2016
7.3
-
520
87.5
2.5
u
2.5
u
2.5
u
2.5
u
2
u
2
u
2.53
2.53
114000
108000
5
u
5
u
46.4
27.9
123
J
100
u
15700
14900
A19A
/30/2015
3.7
0.8
3310
3200
2.5
u
0.5
u
2.5
u
1.42
J
2
u
2
u
44.5
45.7
15800
15000
5
u
1
u
1270
1270
5110
5050
2010
2000
A19A
/28/2016
-
2.7
3270
3180
2.5
u
0.5
u
2.5
u
1.32
J
2
u
2
u
43
37.9
15200
14100
5
u
1
u
1260
1150
5470
5100
1790
1720
Vermillion Mine
CG4
/30/2015
5.01
247
16300
15500
2.5
u
0.5
u
2.5
u
0.5
u
21.7
22
18.2
18.7
64700
60200
5
u
1
u
47.2
72.6
140
J
127
J
13900
13600
CG4
6/28/2016
6.58
6127
3820
2790
2.5
u
0.5
u
2.5
u
0.5
u
5.41
4.6
J
5.49
5.81
31800
31100
5
u
1
u
18.5
16
108
J
100
u
5610
5470
CG4
10/6/2016
5.47
1006
14900
12100
2.5
u
0.5
u
2.5
u
0.5
u
19.5
16.8
13.8
14.2
49800
45900
5
u
1
u
36.6
34.8
495
183
J
11100
10200
CG5
6/28/2016
5.48
-
628
602
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
7.84
7.67
3730
3680
5
u
1
u
61.3
60.5
100
U
100
u
446
436
CG6
/30/2015
5.17
189
13700
12000
2.5
u
0.5
u
2.5
u
0.5
u
18.3
17
15.9
16.4
67200
63500
5
u
1
u
41.2
35.9
151
J
106
J
12500
12500
CG6
6/28/2016
6.46
7803
3620
2540
2.5
u
0.5
u
2.5
u
0.5
u
5.31
4.24
J
5.74
5.65
31600
30600
5
u
1
u
18.3
15.8
111
J
100
u
5400
5210
CG6
/30/2016
4.97
785
11900
10400
2.5
u
0.5
u
2.5
u
0.5
u
18.6
17.5
12.2
11.1
49300
48000
5
u
1
u
31.8
25.6
100
U
100
u
660
370
CG6A
6/29/2016
6.57
5679
4500
2390
2.5
u
0.5
u
2.5
u
0.5
u
5.15
3.89
J
5.57
5.58
31000
29600
5
u
1
u
23.4
14.9
1150
100
u
5530
5150
Sunbank Group
Mine
A21
/29/2015
5.54
76
2290
815
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
3.85
3.93
46500
44300
5
u
1
u
14.2
12.6
1020
801
4620
4570
A21
6/29/2016
6.94
4916
1050
125
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
3.88
3.55
25300
22900
5
u
1
u
42.3
27.3
100
U
100
u
29 0
2820
A21
/30/2016
5.93
515
1490
304
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
4.03
3.65
38900
36400
5
u
1
u
18.1
12.4
289
248
J
3870
3780
A22
/29/2015
5.97
61
340
29.7
J
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.84
1.9
52900
50300
5
u
1
u
8.15
4.71
100
U
100
u
4570
4490
A22
6/29/2016
6.9
3576
1090
148
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
3.65
3.62
25000
23300
5
u
1
u
43
31.1
100
U
100
u
3030
2880
A22
/30/2016
6.46
531
1160
76.1
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
3.11
2.96
40000
37600
5
u
1
u
14.1
7.3
100
u
100
u
3780
3680
A21A
/29/2015
4.79
16
13600
13500
2.5
u
0.5
u
2.5
u
1.4
J
2.41
J
2.49
J
12.1
12.1
15800
15400
5
u
1
u
2.5
U
1.44
16400
16300
5040
5080
A21A
6/29/2016
5.51
-
14100
13200
2.5
u
0.5
u
2.5
u
1.29
J
2.38
J
2.42
J
11.9
10.9
17000
15900
5
u
1
u
2.5
U
0.774
J
19200
16500
5150
4870
A21A
/30/2016
3.78
-
15100
15000
2.5
u
0.5
u
2.5
u
1.76
J
2.83
J
2.75
J
13.3
13
15800
15000
5
u
1
u
2.5
u
1.04
18000
17100
5320
5210
Frisco/Bagley
Tunnel
A12
6/9/2015
7.14
83
285
107
2.5
u
0.5
u
2.5
u
1.34
J
2
u
2
u
4.69
4.69
70500
78800
5
u
1
u
5.29
4.7
2390
2210
4970
4550
A12
10/1/2015
6.25
18
434
285
2.5
u
0.5
u
2.5
u
2.47
2
u
2
u
4.47
4.77
148000
147000
5
u
1.69
J
2.5
~u~
2.36
4390
3550
490
480
A12
6/7/2016
6.48
18
642
550
2.5
u
0.5
u
2.5
u
2.14
4.9
J
2.01
J
7.76
8.51
141000
141000
5
u
2.4
7.36
6.95
4450
4170
230
370
A12
/28/2016
-
58
356
325
2.5
u
0.5
u
2.5
u
1.86
T
2
u
2
u
5.43
4.94
149000
142000
5
u
2.12
2.93
T
2.62
2450
2210
320
280
A13
6/9/2015
6.2
25192
1120
305
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
2.39
2.26
8660
10000
5
u
1
~u~
22.9
11.5
239
T
100
~u~
1360
1260
A13
/29/2015
5.31
521
7530
5590
2.5
u
0.5
u
2.5
u
0.5
u
10.3
.29
.78
10.2
54600
53400
5
u
1
u
31.4
28.3
292
203
J
8590
8440
A13
6/7/2016
6.57
-
2060
66
2.5
u
0.5
u
2.5
u
0.5
u
2
~u~
2
~u~
2.87
2.49
590
660
5
u
1
u
28.2
8.33
633
100
u
1700
1610
A13
/30/2016
5.43
2053
6270
4680
2.5
u
0.5
u
2.5
u
0.5
u
.51
8.12
7.17
6.88
39700
38200
5
u
1
u
22.7
17.2
152
T
117
J
6220
6140
CG9
6/9/2015
6.28
23919
1020
267
2.5
u
0.5
u
2.5
u
0.5
u
2
~u~
2
~u~
2
2.07
490
830
5
u
1
u
17.9
10.3
206
j
100
u
1390
1360
CG9
/29/2015
5.48
610
7140
4020
2.5
u
0.5
u
2.5
u
0.5
u
.58
7.09
.53
10.3
67200
62200
5
u
1
u
31.8
26.8
479
297
8870
8640
CG9
6/7/2016
6.5
-
1810
551
2.5
u
0.5
u
2.5
u
0.5
u
2
~u~
2
~u~
2.77
2.2
660
660
5
u
1
u
38.9
8.83
556
100
~u~
1510
1480
CG9
/30/2016
5.27
2182
5590
3680
2.5
u
0.5
u
2.5
u
0.5
u
8.07
6.64
6.92
6.41
41900
40700
5
u
1
u
23.1
16.5
196
T
167
J
6180
5880
(Sm!th
-------
Attachment A
Total and Dissolved Metals, Anions, Alkalinity, and Hardness Data for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Mine Site
Station
Name
Sample Date
pH
Flow
(gpm)
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Columbus Mine
A10
6/9/2015
6.18
-
1
247
2.5
U
0.5
u
2.5
U
0.5
u
2
U
2
U
2.62
3.02
10400
10400
5
u
1
U
23.1
16.2
19
J
100
u
1460
1460
A10
/29/2015
5.43
634
6280
3800
2.5
u
0.5
u
2.5
U
0.5
u
8.46
6.56
11.1
11.6
65300
62500
5
u
1
U
41.2
39.4
401
306
8820
8480
A10
6/7/2016
-
16137
1480
774
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
U
2.54
2.72
11800
11900
5
u
1
u
20.5
12.9
195
J
100
u
1810
1830
A10
/29/2016
5.13
2387
5480
3790
2.5
u
0.5
u
2.5
u
0.5
u
8.57
7.01
7.69
7.48
43200
41100
5
u
1
u
30.9
25.1
204
J
136
J
6130
5980
AHA
6/9/2015
3.05
37
3370
3160
2.5
u
0.5
u
8.65
J
6.38
2
u
2
u
194
193
4340
4830
5
u
1
u
2510
2510
11700
12200
1460
1390
AHA
/29/2015
2.89
0.1
31000
29500
2.5
u
0.5
u
12
12
8.11
8.33
1090
896
38200
36400
5
u
3.93
6800
6790
61100
61100
12600
11900
A11A
6/7/2016
4.16
27
3360
3450
2.5
u
0.5
u
5.91
J
5.43
2
u
2
u
180
173
4230
4390
5
u
1
u
2350
2310
11300
11600
1460
1510
A11A
/30/2016
2.85
0.3
25600
24900
2.5
u
2.5
u
14
11
6.22
6.13
1030
38
30100
28400
6.12
J
5
u
6960
6300
54700
51600
650
400
CG11
6/9/2015
6.26
2179
1000
222
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
2.11
2.28
10100
80
5
u
1
u
15.8
.39
179
J
100
u
1450
1410
CG11
/29/2015
5.34
572
6610
3830
2.5
u
0.5
u
2.5
u
0.5
u
8.81
6.5
.54
10.2
66600
62200
5
u
1
u
31.5
27.9
440
324
8780
8550
CG11
6/7/2016
6.46
-
1480
587
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
2.29
2.17
10300
10500
5
u
1
u
24.9
8.96
306
100
u
1560
1570
CG11
/30/2016
5.34
3305
5390
3510
2.5
u
0.5
u
2.5
u
0.5
u
7.68
6.25
6.89
6.28
40800
40300
5
u
1
u
22.4
17.1
173
J
163
J
5970
5790
Silver Wing Mine
A28
6/9/2015
7.57
-
137
43.5
J
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
2.04
1.78
12100
12900
5
u
1
u
7.23
6.88
100
U
100
u
1290
1220
A28
/30/2015
7.03
1754
1400
39.5
J
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
4.69
4.43
56000
51600
5
u
1
u
12.2
3.56
100
U
100
u
5470
5180
A28
6/28/2016
7.62
-
848
52
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
2.25
2.46
18500
18000
5
u
1
u
11.3
4.73
100
U
100
u
2140
2060
A30
6/9/2015
7.52
-
454
44.7
J
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
2.07
1.85
11800
13100
5
u
1
u
23.5
13.4
115
J
100
u
1250
1210
A30
/30/2015
5.82
2503
1390
42.9
J
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
4.79
4.44
57000
52900
5
u
1
u
83.2
19.3
180
J
100
u
5550
5200
A30
6/7/2016
7.54
-
747
54.6
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.9
1.92
12800
13400
5
u
1
u
18.6
7.9
204
J
100
u
1410
1460
A29
6/9/2015
6.42
-
1380
428
2.5
u
2.5
u
.7
2.5
u
2
u
2
u
14
14.1
117000
129000
5
u
5
u
6190
2320
10900
2470
4890
4800
A29
/30/2015
5.74
-
1860
58
3.43
J
1.16
132
4.4
2
u
2
u
16.6
15.1
134000
123000
5
u
1
u
10200
4200
16000
6130
5440
5130
A29
6/7/2016
6.49
7.3
1590
762
4.15
J
1.16
161
2.87
2
u
2
u
16.1
16.4
131000
141000
5
u
1.32
J
6280
2730
13700
3870
5390
5580
A29
/28/2016
-
-
1590
603
2.5
u
0.748
J
110
3.1
2
u
2
u
14.8
14.6
138000
131000
5
u
1
u
6970
2770
11700
2790
5360
5240
A29A
6/9/2015
6.96
-
825
31.5
J
2.5
u
2.5
u
39.7
2.5
u
2
u
2
u
13.4
13.5
117000
126000
5
u
5
u
3820
712
5570
100
u
4940
4870
A29A
6/7/2016
7.08
-
1800
8.5
5.38
0.944
J
143
1.17
J
2
u
2
u
14.7
15.3
127000
132000
5
u
1
u
6660
509
15600
137
J
5150
5400
Tom Moore Mine
A3 OA
6/8/2016
7.29
-
659
45.8
J
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.86
1.82
12500
12800
5
u
1
u
15.6
6.44
201
J
100
u
1410
1360
A3 OA
/29/2016
6.94
-
1740
74.2
2.5
u
0.5
u
2.5
u
0.5
u
2.27
J
2
u
4.25
3.98
44900
42500
5
u
1
u
35.2
7.45
102
J
100
u
4430
4330
A30B
6/8/2016
7.45
-
602
47.3
J
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.68
1.71
13900
14100
5
u
1
u
14.5
5.98
204
J
100
u
1530
1530
A30B
/29/2016
6.97
7096
1810
67.5
2.5
u
0.5
u
2.5
u
0.5
u
2.37
J
2
u
4.09
3.98
45600
42700
5
u
1
u
53.4
7.79
128
J
100
u
4410
4290
DM22
6/28/2016
7.31
-
29.6
J
23.3
J
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.14
1.18
71200
68800
5
u
2.92
2.5
U
0.515
J
100
U
100
u
1970
1910
DM22
/28/2016
-
21
27.1
J
23.9
J
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.77
J
0.811
78400
75900
5
u
1.53
J
2.5
U
0.598
J
100
U
100
u
2250
2150
Ben Franklin
Mine
ARD1
/29/2015
3.1
-
7180
6370
2.5
u
0.5
u
2.5
u
0.558
J
2
u
2
u
57.5
55.6
37900
33700
5
u
1
u
1940
1970
3560
2390
10300
470
ARD1
6/28/2016
2.76
-
3860
3630
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
43.8
41
25800
24200
5
u
1
u
19 0
1880
5520
5190
5080
4820
ARD1
/28/2016
3.12
-
80
650
2.5
u
2.5
u
2.5
u
2.5
u
2
u
2
u
79.7
72.9
38300
37300
5
u
5
u
2690
2420
4080
3940
11300
11000
EG3A
/29/2015
7.25
35
63
31.7
J
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.551
J
0.588
33700
33200
5
u
1
u
11.4
.78
100
U
100
u
2650
2610
EG3A
6/28/2016
6.24
4657
153
87.3
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
3.33
3.35
23600
22900
5
u
1
u
12.9
11.6
100
J
100
u
1890
1810
EG3A
/29/2016
6.94
-
31.9
J
24.1
J
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
U
0.228
39200
37800
5
u
1
u
2.79
J
1.79
100
U
100
u
3960
3610
EG5
/30/2015
7.14
-
31.8
J
25.6
J
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
u
0.535
34000
33700
5
u
1
u
6.27
5.53
100
u
100
u
2610
2590
EG5
6/28/2016
7.01
-
132
1.2
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
3.11
3.33
23100
22800
5
u
1
u
14.8
12.2
100
u
100
u
1820
1810
EG5
/28/2016
7.7
222
6.5
64.4
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.18
1.18
37600
37200
5
u
1
u
12.2
8.05
100
u
100
u
3470
3380
A39A
6/28/2016
7.59
-
133
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
3.25
3.19
23400
21900
5
u
1
u
16.2
13.8
100
u
100
u
1820
1710
Terry Tunnel
A38
6/28/2016
7.14
-
66.2
63.1
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
u
0.148
J
207000
196000
5
u
3.17
2.5
U
1.26
237
J
100
u
11200
10700
A38
/28/2016
7.07
-
82.3
76.3
~
2.5
u
2.5
u
2.5
u
2.5
u
2
u
2
u
0.726
J
0.5
u
215000
213000
5
u
5
u
2.5
u
2.5
U
40
100
u
11700
11900
A39
/30/2015
7.1
-
118
48.8
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.2
1.08
32700
32100
5
u
1
u
22.8
14.6
100
u"
100
u
2740
2650
A39
6/28/2016
7.55
-
133
88.6
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
3.06
3.06
22700
21600
5
u
1
u
15.6
13.7
100
u
100
u
1790
1690
A39
/28/2016
7.51
-
180
109
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.73
1.61
36600
35300
5
u
1
u
29.7
17.9
100
u
100
u
3400
3340
EG6
6/10/2015
7.36
-
229
1
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
2.69
2.69
17200
17000
5
u
1
u
25.8
19.7
190
J
100
u
1440
1410
EG6
/30/2015
7.22
8
20
~U~
20
~u~
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.71
T
0.794
44200
43700
5
u
1
u
3.98
T
4.22
100
u
100
u
2950
2910
EG6
6/28/2016
7.44
7133
113
80.5
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
2.07
1.94
20300
20100
5
u
1
u
11.4
.09
100
u
100
u
1680
1610
EG6
/28/2016
7.48
373
112
54.5
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
1.22
1.19
31900
31100
5
u
1
u
13.9
.34
100
u
100
u
2810
2730
Pride of the West
Mine
A50
6/7/2016
7.75
-
201
36.8
T
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
11.8
12.2
67200
68700
5
u
1.9
J
54.5
16.6
209
J
100
u
4710
4860
A50
/28/2016
7.67
-
137
39.3
j
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
7.51
7.39
76700
76000
5
u
1.98
J
26.3
.88
122
J
100
u
5230
5280
CU4
6/7/2016
7.39
-
1380
57
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
~u~
0.1
~u~
10100
350
5
u
1
u
2.8
T
0.723
T
1420
100
u
1340
67
CU4
/28/2016
7.45
6610
23.3
T
20
~u~
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
u
0.1
u
22500
22100
5
u
1
u
6.62
0.628
j
100
u"
100
u
19 0
1920
CU4A
6/7/2016
7.36
-
658
60.7
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
u
0.1
u
10600
690
5
u
1
u
3.88
T
0.93
j
770
100
u
1160
60
CU4A
/28/2016
7.23
6739
33.9
T
20
~u~
2.5
u
0.5
u
2.5
u
0.5
u
2
u
2
u
0.5
u
0.152
J
24200
24000
5
u
1
u
2.5
u
0.882
j
100
u"
100
u
2030
19 0
Notes:
Q-qualifier J9 IndicatesSin estimated value. The associated numerical value is9he approximate concentration of the analyte in the sample
" - data not available U - IndicatesSfcompound wasSnalyzed for,
-------
Attachment A
Total and Dissolved Metals, Anions, Alkalinity, and Hardness Data for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Lead
Nickel
Metal Concentrations {pg/L
Selenium
Silver
Strontium
Thallium
Zinc
Chloride
(mg/L)
Fluoride
(mg/L)
Sulfate as
S04 (mg/L)
Total Alkalinity {mg
CaC03 /L)
Nitrate/Nitrite as N
(mg/L)
Hardness
(mg/L)
D
T
D
T
D
T
D
T
D
T
D
T
D
T
D
T
T
T
T
T
D
Mine Site
Station
Name
Sample Date
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Longfellow Mine
M02D
6/29/2016
80
51.9
1.45
0.213
2.5
U
0.5
U
5
U
1
U
2.5
U
0.5
U
273
259
5
U
1
U
10
U
10
U
0.7
J
0.1
U
16.6
20.2
0.1
u
35
M02D
10/7/2016
88.1
64.7
0.931
J
0.185
J
2.5
U
0.5
u
5
U
1
u
2.5
U
0.5
u
361
344
J
5
U
1
u
10
U
10
U
0.4
J
0.1
u
19.9
23.3
0.1
u
41
Junction Mine
M02B
6/29/2016
348
365
131
5.26
3.75
J
4.03
5
u
1
u
2.5
u
0.5
u
1240
1180
5
u
1
u
1640
1770
0.8
0.4
120
5
u
0.1
u
103
M02B
10/7/2016
1780
1740
304
300
16.6
17
5
u
1
u
2.5
u
0.5
u
3180
3000
J
5
u
1
u
6590
6510
4
U
1.7
J
336
5
u
1
u
179
Koehler Tunnel
M02K1
6/29/2016
16600
16400
3.19
3.29
71.9
77.8
5
u
5
u
2.5
u
2.5
u
6330
5980
5
u
5
u
17700
18100
2.8
J
2
642
5
u
0.4
u
513
M02C
10/7/2016
37600
37300
152
1.51
182
185
5
u
5
u
2.5
u
2.5
u
13100
12400
J
5.79
J
6.27
J
41500
41400
4
u
3.6
1630
5
u
1
u
1140
M02E
6/29/2016
7220
7020
100
36.6
32.3
32.4
5
u
1
u
2.5
u
0.5
u
3160
2950
5
u
1
u
7870
7930
3.1
J
0.8
385
5
u
0.4
u
309
M02E
10/7/2016
20800
17200
59.8
73.4
2.5
80.5
5
u
5
u
2.5
u
2.5
u
7320
6360
J
5
u
5
u
22400
18700
4
u
2.3
45
5
u
1
u
617
M02
6/29/2016
4120
4050
75.3
8.87
17.6
18.8
5
u
1
u
2.5
u
0.5
u
2430
2340
5
u
1
u
4590
4690
1.6
0.4
272
5
u
0.2
u
229
M02
10/7/2016
16200
15600
35.5
35.1
70.5
72.5
5
u
5
u
2.5
u
2.5
u
5910
5600
J
5
u
5
u
16800
16400
4
u
1.4
J
735
5
u
1
u
555
Brooklyn Mine
M12
6/7/2016
488
301
14.6
0.198
J
2.5
u
1.44
5
u
1
u
2.5
u
0.5
u
154
139
5
u
1
u
174
156
0.7
J
0.1
J
34.7
5
u
0.1
u
36
M12
6/29/2016
1320
1300
3.3
2.52
6.04
6.55
5
u
1
u
2.5
u
0.5
u
384
366
5
u
1
u
861
887
0.8
0.3
118
5
u
0.1
u
4
M12
/29/2016
2280
2280
3.88
4.02
12.1
11.4
5
u
1
u
2.5
u
0.5
u
59
579
5
u
1
u
1300
1370
0.8
u
0.6
231
5
u
0.2
u
158
M12A
6/29/2016
79
763
7.04
1.44
4.17
J
4.28
5
u
1
u
2.5
u
0.5
u
397
368
5
u
1
u
282
276
0.8
0.3
6.3
5
u
0.1
u
76
M12A
/30/2016
1440
1440
1.66
1.55
8.86
8.4
5
u
1
u
2.5
u
0.5
u
612
598
5
u
1
u
347
363
0.8
J
0.6
205
5
u
0.2
u
134
M12B
6/29/2016
545
535
1.11
0.65
2.97
J
3.37
5
u
1
u
2.5
u
0.5
u
334
315
5
u
1
u
61
54.6
0.8
0.3
84.7
5
u
0.1
u
64
M12B
/30/2016
1190
1190
0.81
J
0.631
7.84
7.48
5
u
1
u
2.5
u
0.5
u
570
546
5
u
1
u
81
81.5
0.9
J
0.6
197
5
u
0.2
u
119
M12C
6/29/2016
5240
5100
25.1
1.69
7.88
.21
5
u
1
u
2.5
u
0.5
u
2570
2420
5
u
1
u
4670
4600
3.9
1.4
591
5
u
0.4
u
286
M12C
/29/2016
6440
6430
116
20.7
12.9
11.8
5
u
1
u
2.5
u
0.5
u
2440
2410
5
u
1
u
5780
6060
0.8
u
1
392
-
-
306
M12C
/30/2016
6380
6390
25
18.2
12.9
12.1
5
u
1
u
2.5
u
0.5
u
2340
2270
5
u
1
u
5690
5950
1.6
u
0.9
402
5
u
0.4
u
293
M12D
/30/2016
6300
6300
24.7
19.5
11.7
11.2
5
u
1
u
2.5
u
0.5
u
2410
2320
5
u
1
u
5810
6100
1.6
u
0.9
380
5
u
0.4
u
297
M12F
10/7/2016
193
4.09
J
0.5
U
0.1
U
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
2630
2470
J
5
u
1
u
10
u
10
u
0.8
u
0.4
229
58.9
0.2
u
262
M12G
10/7/2016
38
15
126
125
2.71
J
3.79
5
u
1
u
2.5
u
0.5
u
188
176
J
5
u
1
u
117
121
0.4
u
0.2
51.7
5
u
0.1
u
39
Bandora Mine
M23
/27/2016
200
200
0.5
U
0.246
4.96
J
4.97
5
u
1
u
2.5
u
0.5
u
149
138
5
u
1
u
32.5
40
0.4
J
0.2
79.9
5
u
0.1
J
73
M24A
/28/2016
6770
4870
77
0.147
J
10.5
7.7
5
u
1
u
2.5
u
0.5
u
603
549
5
u
1
u
13500
8750
0.8
u
0.9
259
32.6
0.2
u
238
M24B
/28/2016
5290
4940
201
3.69
8.79
8.14
5
u
1
u
2.5
u
0.5
u
588
543
5
u
1
u
11200
11200
-
-
-
-
-
236
M24C
/28/2016
2100
2030
0.663
J
0.581
J
2.5
u
2.5
u
5
u
5
u
2.5
u
2.5
u
816
750
5
u
5
u
540
541
1.6
u
0.7
J
275
104
0.4
u
346
M24D
/27/2016
4780
4630
177
0.1
u
8.83
8.14
5
u
1
u
2.5
u
0.5
u
588
542
5
u
1
u
10700
250
0.8
u
0.8
257
29.3
0.2
u
236
M25
6/29/2016
0.7
89.8
0.5
u
0.1
u
2.82
J
3.12
5
u
1
u
2.5
u
0.5
u
112
106
5
u
1
u
58.4
64.1
0.9
0.2
50.5
5
u
0.1
J
51
M25
/27/2016
207
202
0.5
u
0.1
u
4.72
J
4.75
5
u
1
u
2.5
u
0.5
u
167
152
5
u
1
u
104
111
0.4
J
0.2
83.1
5
u
0.1
J
76
Grand Mogul
Mine
CC01C
6/29/2016
1720
1660
39.7
38.2
2.65
J
2.86
5
u
1
u
2.5
u
0.5
u
33.7
31.1
5
u
1
u
3650
3660
0.8
0.6
67.9
5
u
0.1
J
39
CC01C
/28/2016
6120
6050
27.9
26.4
14.2
13.3
5
u
5
u
2.5
u
2.5
u
68
63.4
5
u
5
u
24500
25100
1.6
u
2.6
401
5
u
0.4
u
88
CC01C1
6/29/2016
3760
3570
33.7
33
5.51
5.43
5
u
1
u
2.5
u
0.5
UJ
34.4
32.3
5
u
1
u
8850
8550
0.8
0.9
157
5
u
0.1
J
49
CC01C1
/28/2016
11400
11300
7.59
7.12
15.7
15.3
5
u
5
u
2.5
u
2.5
u
48.5
45.8
5
u
5
u
31300
31600
1.6
u
2.9
478
5
u
0.4
u
102
CC01C2
6/29/2016
2180
2090
28.1
26.9
3.14
J
3.36
5
u
1
u
2.5
u
0.5
u
48.9
45.8
5
u
1
u
4680
4660
0.8
0.6
88
5
u
0.2
41
CC01C2
/28/2016
5730
5610
22.1
21.5
.01
8.86
5
u
1.32
J
2.5
u
0.5
u
70.7
67.2
5
u
1
u
14900
14700
0.8
u
1.7
200
5
u
0.2
u
68
CC01F
6/29/2016
82.5
78.2
8.04
3.8
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
284
269
5
u
1
u
267
261
0.7
J
0.2
71.8
16.2
0.2
84
CC01F
/28/2016
126
123
2.93
0.843
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
528
497
5
u
1
u
475
454
0.4
u
0.3
134
21
0.1
J
142
CC01H
6/29/2016
474
450
10
2.98
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
236
223
5
u
1
u
1120
1100
0.7
J
0.2
74.7
6.81
J
0.2
74
CC01H
/27/2016
417
407
2.14
0.348
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
413
391
5
u
1
u
1600
1610
0.4
u
0.4
131
8.31
J
0.1
J
127
CC02I
6/28/2016
121
122
8.84
8.46
4.95
J
5.2
5
u
1
u
2.5
u
0.5
u
166
157
5
u
1
u
1750
1770
CC02I
/27/2016
2330
2280
2.93
1.8
8.34
4.08
5
u
1
u
2.5
u
0.5
u
362
341
5
u
1
u
2140
2110
CC01U
6/28/2016
1890
1810
8.95
2.04
2.5
u
1.53
5
u
1
u
2.5
u
0.5
u
225
214
5
u
1
u
815
802
0.7
J
0.4
101
5.05
J
0.2
3
CC01U
/27/2016
2310
2260
4.53
3.11
8.34
4.21
5
u
1
u
2.5
u
0.5
u
361
349
5
u
1
u
2200
2160
0.4
u
0.9
182
5
u
0.1
J
164
Natalie/Occident
al Mine
CC14
6/10/2015
1980
1940
7.3
0.339
5.47
5.38
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
843
884
-
-
-
-
-
424
CC14
/29/2015
2630
2680
3.41
0.557
J
2.5
u
3.65
J
5
u
5
u
2.5
u
2.5
u
-
-
2.5
u
2.5
u
732
751
8
u
3.2
J
684
J
.27
J
2
u
498
CC14
6/9/2016
2670
2680
.84
1.63
J
4.63
J
5.15
J
5
u
10
u
2.5
u
5
u
2260
2190
5
u
10
u
1130
1150
6.4
J
3.3
501
6.42
J
1
u
512
CC14
/29/2016
2520
2480
3.17
0.536
J
3.01
J
2.5
u
5
u
5
u
2.5
u
2.5
u
2380
2300
5
u
5
u
704
673
-
-
-
-
-
531
CC15
6/9/2016
84.3
81.2
0.579
J
0.1
u
2.5
u
1.06
5
u
1
u
2.5
u
0.5
u
143
144
5
u
1
u
61.6
64.6
0.7
J
0.3
48.8
5.03
J
0.2
55
CC15
/29/2016
64.2
63.5
0.5
u
0.1
u
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
333
317
5
u
1
u
36
36.1
0.4
u
0.5
1.9
.79
J
0.1
J
4
CC15A
6/9/2016
325
331
1.28
0.1
u
2.5
u
1.33
5
u
1
u
2.5
u
0.5
u
343
342
7.34
J
1
u
165
171
0.7
J
0.5
7.5
5.09
J
0.2
100
CC15A
/29/2016
1410
1390
1.93
0.5
u
2.5
u
2.5
u
5
u
5
u
2.5
u
2.5
u
1440
1380
5
u
5
u
403
391
0.8
u
1.7
344
.05
J
0.2
u
326
Henrietta Mine
CC24G
6/30/2016
72.9
75.6
3.3
3.17
8.66
8.39
5
u
1.42
J
2.5
u
0.5
u
17.1
16.4
5
u
1
u
116
123
0.9
0.1
u
119
5
u
0.1
J
12
CC22D
6/8/2016
2.1
73.4
31.4
8.1
2.5
u
1.03
5
u
1
u
2.5
u
0.5
u
244
240
5
u
1
u
406
432
0.7
J
0.1
u
28.4
5
u
0.1
u
31
CC22D
/29/2016
307
289
59.9
18.3
2.63
J
2.39
5
u
1
u
2.5
u
0.5
u
1050
1040
5
u
1
u
435
400
0.4
J
0.2
128
5
u
0.1
u
115
CC22B
6/8/2016
110
109
23.9
18.1
2.5
u
1.63
5
u
1
u
2.5
u
0.5
u
207
202
5
u
1
u
302
333
0.7
J
0.1
J
31.3
5
u
0.1
u
30
CC22B
/29/2016
584
567
43.8
40.3
5.65
5.5
5
u
1
u
2.5
u
0.5
u
819
824
5
u
1
u
376
372
0.4
u
0.3
144
5
u
0.1
u
111
CC24B
6/8/2016
124
119
25.6
18.9
2.5
u
1.77
5
u
1
u
2.5
u
0.5
u
214
208
5
u
1
u
330
342
0.7
J
0.1
J
35.2
5
u
0.1
u
32
CC24B
/29/2016
506
498
44.5
44.2
4.9
J
4.76
5
u
1
u
2.5
u
0.5
u
887
857
5
u
1
u
549
571
0.4
J
0.3
147
5
u
0.1
u
118
Anglo Saxon
Mine
CC37
6/7/2016
8940
050
10.3
2.04
3.95
J
2.5
u
5
u
5
u
2.5
u
2.5
u
4690
4670
8.95
J
5
u
2930
3040
-
-
-
-
-
837
CC37
/28/2016
8700
8580
8.44
0.964
T~
3.63
J
2.5
u
5
u
5
u
2.5
u
2.5
u
4790
4640
5
u
5
u
2830
2850
-
-
-
-
-
822
CC38
6/7/2016
640
592
31.1
2.73
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
251
239
10.1
1
u
179
162
0.7
T
0.2
38.6
7.65
J
0.1
u
46
CC38B
6/7/2016
11600
11600
.54
0.542
T~
4.09
J
10.7
5
u
5
u
2.5
u
2.5
u
3260
3200
5
~u~
5
u
2290
2450
-
-
-
-
-
595
CC38B
/28/2016
12400
12100
3.89
0.5
u
2.8
J
2.5
~u~
5
u
5
u
2.5
u
2.5
u
4330
4170
5
u
5
u
2530
2480
-
-
-
-
-
749
CC38C
6/7/2016
105
18.2
110
2.85
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
7.9
88.1
5
u
1
u
103
49.5
0.8
0.1
77
11.6
8.34
J
0.1
u
18
CC38C
/28/2016
1
89.9
24.4
.58
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
453
431
5
u
1
u
533
555
0.4
T
0.1
j
73
13.6
0.1
u
81
CC39
6/7/2016
32
869
50.9
5.29
2.9
J
1.74
5
u
1
u
2.5
u
0.5
u
324
316
5
u
1
u
669
658
0.9
0.4
1
5
u
0.1
u
83
CC39
/27/2016
4460
4400
44.7
20.5
10.9
10.2
5
u
5
u
2.5
u
2.5
u
1820
1720
10.8
5
u
2400
2330
1.6
77
1.8
542
5
u
0.4
u
433
CC39B
6/7/2016
17
834
58.8
8.64
3.19
T
2.24
5
u
1
u
2.5
u
0.5
u
324
300
5
~u~
1
u
657
679
2.6
0.4
5
5
u
0.1
J
85
CC39B
/28/2016
4690
4700
13.7
13.5
10.2
10.4
5
u
5
u
2.5
u
2.5
u
1890
1800
11.6
5
u
2140
2170
1.6
77
1.8
554
5
u
0.4
u
435
(Sm!th
-------
Attachment A
Total and Dissolved Metals, Anions, Alkalinity, and Hardness Data for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Lead
Nickel
Metal Concentrations {pg/L
Selenium
Silver
Strontium
Thallium
Zinc
Chloride
(mg/L)
Fluoride
(mg/L)
Sulfate as
S04 (mg/L)
Total Alkalinity {mg
CaC03 /L)
Nitrate/Nitrite as N
(mg/L)
Hardness
(mg/L)
D
T
D
T
D
T
D
T
D
T
D
T
D
T
D
T
T
T
T
T
D
Mine Site
Station
Name
Sample Date
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Yukon Tunnel
CC41
6/7/2016
1060
78
43.1
5.73
2.85
J
2.12
5
U
1
u
2.5
U
0.5
u
332
323
5
U
1
u
858
854
0.8
0.4
105
5
u
0.1
J
3
CC41
/27/2016
5110
4920
27.2
17.1
10.6
.09
5
U
5
u
2.5
U
2.5
u
1970
1860
5
U
5
u
2610
2420
1.6
U
1.8
554
5
u
0.4
U
444
CC43C
6/7/2016
793
768
2.76
0.5
U
2.5
U
2.5
U
5
u
5
u
2.5
u
2.5
u
4910
4780
5
u
5
u
109
100
-
-
-
-
-
611
CC43C
/27/2016
1130
1090
2.65
0.5
U
2.5
U
2.5
U
5
u
5
u
2.5
u
2.5
u
4710
4610
5
u
5
u
121
108
-
-
-
-
-
564
CC43D
6/7/2016
6530
6170
3.89
4.11
39
30.7
5
u
1.43
J
2.5
u
0.5
u
1300
1240
5
u
1
u
5810
5720
6.4
J
4.4
563
5
u
1
U
319
CC43E
6/7/2016
1100
77
59.4
4.52
2.89
J
2.17
5
u
1
u
2.5
u
0.5
u
387
362
5
u
1
u
12
19
0.8
0.4
106
5
u
0.1
J
8
CC43E
/27/2016
4170
4150
15.2
13.9
.19
7.68
5
u
5
u
2.5
u
2.5
u
2080
2050
5
u
5
u
2070
2050
1.6
U
1.7
535
5
u
0.4
u
437
Boston Mine
A07D
6/28/2016
2160
2100
11.6
.47
4.73
J
4.45
5
u
1
u
2.5
u
0.5
u
13.5
12.3
5
u
1
u
1130
1140
0.7
J
0.2
58.8
5
u
0.1
u
22
A07D
10/5/2016
4860
4810
7.22
7.47
10.7
10.6
5
u
1
u
2.5
u
0.5
u
21
19.9
7.76
J
1
u
2840
2830
0.4
u
0.6
155
5
u
0.1
J
48
A07D1
6/28/2016
6080
5890
1.52
1.26
15.6
14.4
5
u
1
u
2.5
u
0.5
u
19.1
17.5
5
u
1
u
6020
5870
0.9
0.7
168
5
u
0.1
u
42
A07D2
6/28/2016
824
793
22.5
18.7
2.5
u
1.95
5
u
1
u
2.5
u
0.5
u
13.6
12.5
5
u
1
u
3740
3680
0.8
0.1
J
28
5
u
0.2
A07E
6/28/2016
1820
1780
11.6
.77
3.9
J
3.5
5
u
1
u
2.5
u
0.5
u
12.9
12
5
u
1
u
715
718
0.7
J
0.2
51.2
5
u
0.1
u
21
A07E
10/5/2016
5090
4950
14
15.4
8.9
.06
5
u
1
u
2.5
u
0.5
u
19.2
18.2
8.15
J
1
u
2150
2120
0.4
u
0.6
143
5
u
0.2
46
London Mine
DM6
6/28/2016
189
197
61.7
48.3
2.5
u
0.5
U
5
u
1
u
2.5
u
0.5
u
50.6
48.4
J
5
u
1
u
1540
1680
1
0.1
U
25.1
5
u
0.1
u
24
DM6
/30/2016
1640
1550
226
202
5.27
3.9
5
u
1
u
2.5
u
0.5
u
257
225
5
u
1
u
17200
17200
0.8
u
0.4
135
5
u
0.2
u
69
DM7
6/8/2016
277
234
13.3
0.1
J
2.5
u
0.5
U
5
u
1
u
2.5
u
0.5
u
290
292
5
u
1
u
2930
2870
1
0.4
51
16
0.1
u
63
DM7
6/28/2016
1030
84
22.1
0.23
2.5
u
0.57
J
5
u
1
u
2.5
u
0.5
u
765
730
J
5
u
1
u
8130
8120
1.7
0.8
137
33.7
0.1
u
144
DM7
/30/2016
1230
1230
27.9
0.1
u
2.5
u
0.739
J
5
u
1
u
2.5
u
0.5
u
845
784
5
u
1
u
8170
8280
1.4
J
1.1
153
34.9
0.2
u
157
A07B1
6/28/2016
2540
2480
11.2
.57
5.82
5.51
5
u
1
u
2.5
u
0.5
u
19.6
18.1
13.5
1
u
1810
1790
0.7
J
0.4
72
5
u
0.1
u
27
A07B
/30/2015
5890
6110
8.87
.44
13.5
13.9
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
39 0
4340
1.6
u
1.9
217
J
5
u
0.4
u
7
A07B
6/28/2016
2380
2340
10.8
.34
6.65
5.23
5
u
1
u
2.5
u
0.5
u
22.7
20.9
12.3
1
u
1690
1720
0.8
0.4
68.2
5
u
0.1
u
26
A07B
/30/2016
5980
5920
10.5
.35
14.4
13.7
5
u
1
u
2.5
u
0.5
u
66
64.8
5
u
1
u
4260
4280
0.4
u
1.8
191
5
u
0.1
J
77
Ben Butler Mine
BB1
6/28/2016
2.8
89.6
830
819
2.5
u
0.627
J
5
u
1
u
6.01
6.2
25.5
24
5
u
1
u
2080
2050
1.2
0.1
U
30.3
5
u
0.5
14
Mountain Queen
Mine
A18
10/6/2016
498
476
0.9 6
J
0.5
u
2.5
u
2.5
u
5
u
5
u
2.5
u
2.5
u
1020
70
5
u
5
u
374
360
0.8
u
0.8
328
27.4
0.2
J
332
A19A
/30/2015
5750
5700
192
208
4.91
J
4.74
5
u
1
u
2.5
u
0.889
J
-
-
2.5
u
0.5
u
5630
6230
0.8
u
1.4
128
J
5
u
0.2
u
46
A19A
/28/2016
4190
4030
139
137
4.69
J
4.29
5
u
1
u
2.5
u
0.679
J
55.4
53.5
10
1
u
5060
4920
-
-
-
-
-
42
Vermillion Mine
CG4
/30/2015
36400
36600
0.567
J
0.552
19.2
19.9
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
6030
6270
4
u
12.3
487
J
5
u
1
u
207
CG4
6/28/2016
020
210
1.16
0.452
4.32
J
4.39
5
u
1
u
2.5
u
0.5
u
198
190
5
u
1
u
1550
1660
0.7
J
2.2
128
5
u
0.1
J
100
CG4
10/6/2016
27300
26600
1.36
0.644
14.7
14.5
5
u
1
u
2.5
u
0.5
u
209
197
5
u
1
u
4380
4240
0.8
u
.2
277
5
u
0.2
u
157
CG5
6/28/2016
472
479
47.7
44.8
2.5
u
1.16
5
u
1
u
2.5
u
0.5
u
11.1
10.7
5
u
1
u
1730
1900
0.7
J
0.1
U
19.3
5
u
0.1
u
11
CG6
/30/2015
31600
31500
1.41
0.597
17.4
16.4
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
5260
5310
4
u
11.3
447
J
5
u
1
u
210
CG6
6/28/2016
8750
8630
2.16
1.21
4.5
J
4.18
5
u
1
u
2.5
u
0.5
u
201
193
12.7
1
u
1560
1620
0.7
J
2.3
124
5
u
0.1
J
8
CG6
/30/2016
25600
25700
0.889
J
0.414
13.6
11.5
5
u
1
u
2.5
u
0.5
u
255
242
5
u
1
u
3510
3700
0.4
u
.1
251
5
u
0.1
u
158
CG6A
6/29/2016
8350
8360
26.2
1.4
4.58
J
4.29
5
u
1
u
2.5
u
0.5
u
194
182
5
u
1
u
1580
1690
0.7
J
2.1
121
5
u
0.1
J
5
Sunbank Group
Mine
A21
/29/2015
1880
1900
34.1
32.6
2.5
u
1.51
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
1700
1780
0.8
u
0.7
167
J
5
u
0.2
u
129
A21
6/29/2016
3120
2980
.02
2.35
4.67
J
4.1
5
u
1
u
2.5
u
0.5
u
181
168
5
u
1
u
1410
1340
0.7
J
0.5
75
5
u
0.1
J
69
A21
/30/2016
1550
1480
103
7.61
3.76
J
3.45
5
u
1
u
2.5
u
0.5
u
266
256
5
u
1
u
1610
1560
0.4
u
0.7
114
5
u
0.1
J
106
A22
/29/2015
346
348
4.52
2.01
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
1050
1150
0.8
u
0.6
159
J
13.8
0.2
u
144
A22
6/29/2016
3370
3250
6.09
J
1.05
4.61
J
4.33
5
u
1
u
2.5
u
0.5
u
196
186
5
u
1
u
1360
1360
0.7
J
0.5
76.4
5.49
J
0.1
J
70
A22
/30/2016
1250
1190
4.32
0.863
4.02
J
3.46
5
u
1
u
2.5
u
0.5
u
292
281
5
u
1
u
1430
1380
0.4
u
0.9
112
6.94
J
0.1
J
109
A21A
/29/2015
460
600
194
198
10.4
.95
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
1.72
4590
4930
4
u
1
U
255
J
5
u
1
u
59
A21A
6/29/2016
8980
8750
253
216
11
.3
5
u
1
u
2.5
u
0.5
u
55.4
51.5
5
u
1.54
J
4300
4270
0.8
1
195
5
u
0.1
u
60
A21A
/30/2016
160
8980
188
190
11.4
10.1
5
u
1
u
2.5
u
0.5
u
48
46.3
5
u
1.61
J
4710
4670
0.4
u
1.2
206
5
u
0.1
u
59
Frisco/Bagley
Tunnel
A12
6/9/2015
7950
8190
4.02
0.591
2.5
u
2.64
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
3500
3830
-
-
-
-
-
215
A12
10/1/2015
16500
16600
1.39
J
0.482
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
5470
6080
4
u
1.1
J
466
J
63
1
u
406
A12
6/7/2016
16300
16300
1.61
0.355
2.5
u
1.62
5
u
1
u
2.5
u
0.5
u
724
711
5
u
1
u
6640
6980
1.5
J
1.2
414
37.4
0.2
u
391
A12
/28/2016
13900
13700
0.5
~U~
0.1
~u~
2.5
u
0.898
T
5
u
1
u
2.5
u
0.5
u
841
816
5
u
1
u
5090
5060
-
-
-
-
-
394
A13
6/9/2015
1960
1980
28.9
2.82
2.5
u
1.58
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
757
802
-
-
-
-
-
30
A13
/29/2015
18200
18900
8.85
7.83
8.88
.47
5
u
1
u
2.5
u
0.5
u
-
-
12.8
0.5
u
3500
3920
1.6
"u
6
263
T
5
u
0.4
u
168
A13
6/7/2016
3510
3280
106
2.44
2.5
~u~
1.75
5
u
1
u
2.5
u
0.5
u
41.2
40.3
5
~u~
1
u
50
859
0.7
j
0.9
36.3
5
u
0.1
u
31
A13
/30/2016
13400
13400
4.2
2.56
8.36
7.31
5
u
1
u
2.5
u
0.5
u
225
221
5
u
1
u
2360
2360
0.4
j
4.5
168
5
u
0.1
u
121
CG9
6/9/2015
1910
1880
15.3
2.12
2.5
~u~
1.67
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
701
727
-
-
-
-
-
30
CG9
/29/2015
18300
18000
8.7
6.16
8.93
.73
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
3980
3880
1.6
77
6.2
306
T
5
u
0.4
u
191
CG9
6/7/2016
2780
2530
152
2.87
2.5
~u~
1.49
5
u
1
u
2.5
u
0.5
u
42.6
42.2
5
u
1
u
881
777
0.7
j
0.6
33.3
5
u
0.1
u
30
CG9
/30/2016
12600
12600
4.05
2.59
6.76
5.84
5
u
1
u
2.5
u
0.5
u
246
229
5
u
1
u
2300
2430
0.4
j
4.1
170
5
u
0.1
u
126
(Sm!th
-------
Attachment A
Total and Dissolved Metals, Anions, Alkalinity, and Hardness Data for 2015 and 2016 EPA/ESAT Surface Water Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Lead
Nickel
Metal Concentrations {pg/L
Selenium
Silver
Strontium
Thallium
Zinc
Chloride
(mg/L)
Fluoride
(mg/L)
Sulfate as
S04 (mg/L)
Total Alkalinity {mg
CaC03 /L)
Nitrate/Nitrite as N
(mg/L)
Hardness
(mg/L)
D
T
D
T
D
T
D
T
D
T
D
T
D
T
D
T
T
T
T
T
D
Mine Site
Station
Name
Sample Date
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Result
Q
Columbus9>/line
A10
6/9/2015
2100
2080
14.4
2.81
2.5
U
1.83
5
U
1
u
2.5
U
0.5
u
-
-
2.5
U
0.5
u
67
69
-
-
-
-
-
32
A10
/29/2015
17500
18000
8.13
7.22
7.9
8.38
5
u
1
u
2.5
U
0.5
u
-
-
2.5
u
0.5
u
4130
4560
1.6
U
5.4
279
J
5
U
0.4
U
191
A10
6/7/2016
3160
3100
37.3
3.67
2.5
U
1.87
5
u
1
u
2.5
u
0.5
u
52.7
52.6
5
u
1
u
34
32
0.7
J
0.8
41.8
5
U
0.1
U
37
A10
/29/2016
13000
12700
5.66
4.31
7.42
6.68
5
u
1
u
2.5
u
0.5
u
237
232
5
u
1
u
2670
2630
0.4
U
4.2
170
5
u
0.1
U
127
AHA
6/9/2015
1840
1900
1010
47
7.64
8.34
5
u
3.71
2.5
u
0.5
u
-
-
2.5
u
0.5
u
47000
51200
-
-
-
-
-
18
AHA
/29/2015
17600
17900
254
289
66.5
65.8
17.4
15.8
2.5
u
0.5
u
-
-
2.5
u
0.676
J
278000
302000
8
u
2
U
1440
J
5
u
2
U
140
AHA
6/7/2016
1710
1720
11
13
7.65
7.7
5
u
1.17
J
2.5
u
0.5
u
15.9
16.2
5
u
1
u
40300
43100
1.3
J
0.2
J
178
5
u
0.3
J
17
AHA
/30/2016
12400
12100
302
254
58.5
52.6
19.1
12.5
2.5
u
2.5
u
5
0.4
5
u
5
u
229000
223000
4
u
1.1
J
50
5
u
1
u
110
CG11
6/9/2015
1910
1970
10.8
1.87
2.5
u
1.72
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
696
762
-
-
-
-
-
31
CG11
/29/2015
17700
17600
7.29
5.96
8.98
8.94
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
3930
3930
1.6
u
6
303
J
5
u
0.4
u
191
CG11
6/7/2016
2690
2550
89.9
2.74
2.5
u
1.68
5
u
1
u
2.5
u
0.5
u
45.7
45.8
5
u
1
u
765
759
J
0.7
J
0.7
35.9
5
u
0.1
u
33
CG11
/30/2016
12200
12100
4.15
3.23
6.68
5.52
5
u
1
u
2.5
u
0.5
u
239
226
5
u
1
u
2280
2380
0.4
J
4
165
5
u
0.1
u
124
Silver Wing Mine
A28
6/9/2015
736
721
1.81
0.763
2.5
u
0.826
J
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
452
480
-
-
-
-
-
37
A28
/30/2015
3870
3800
3.85
0.442
2.5
u
0.525
J
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
1360
1330
0.8
u
1.2
160
J
23.5
0.2
u
150
A28
6/28/2016
1850
1780
3.48
0.613
2.5
u
0.921
J
5
u
1
u
2.5
u
0.5
u
116
112
11
1
u
587
569
0.7
J
0.4
48.1
11.1
0.1
J
53
A30
6/9/2015
745
715
7.76
0.918
2.5
u
0.778
J
5
u
1
u
2.5
u
0.5
u
-
-
12
0.5
u
507
496
-
-
-
-
-
38
A30
/30/2015
3810
3750
4.82
0.313
2.73
J
0.5
u
5
u
1
u
2.5
u
0.5
u
-
-
15.5
J+
0.5
u
1440
1410
0.8
u
1.2
163
J
23.2
0.2
u
154
A30
6/7/2016
1250
1190
14.6
0.672
2.5
u
0.595
J
5
u
1
u
2.5
u
0.5
u
65.8
64.5
5
u
1
u
505
504
0.7
J
0.4
29.8
.78
J
0.1
J
39
A29
6/9/2015
3100
3120
25.8
0.5
U
2.5
u
2.5
u
5
u
5
u
2.5
u
2.5
u
-
-
2.5
u
2.5
u
3950
4010
-
-
-
-
-
341
A29
/30/2015
3520
3480
25.5
0.1
U
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
-
-
15
J+
0.5
u
4320
4500
4
u
3.6
407
J
25.1
1
u
329
A29
6/7/2016
3300
3170
22.7
0.1
u
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
1620
1710
5
u
1
u
4220
4260
1.4
J
3.4
350
31.2
0.2
u
375
A29
/28/2016
3290
3250
19.1
0.159
J
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
1730
1670
5
u
1
u
4020
3870
-
-
-
-
-
349
A29A
6/9/2015
3030
3040
12.8
0.5
u
2.5
u
2.5
u
5
u
5
u
2.5
u
2.5
u
-
-
12
2.5
u
3790
3830
-
-
-
-
-
335
A29A
6/7/2016
3070
3130
61.8
0.1
u
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
1580
1610
5
u
1
u
3900
3960
0.7
J
1.7
171
27.6
0.1
u
352
Tom Moore Mine
A3 OA
6/8/2016
1200
1120
11.5
0.582
2.5
u
0.557
J
5
u
1
u
2.5
u
0.5
u
64.9
65.9
5
u
1
u
469
474
0.7
J
0.4
29.3
10
0.1
J
38
A3 OA
/29/2016
3760
3670
3.22
0.321
2.5
u
1.43
5
u
1
u
2.5
u
0.5
u
264
257
5
u
1
u
1130
1030
0.4
u
1.3
120
16.8
0.2
124
A30B
6/8/2016
1100
1010
12.1
0.532
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
75.1
74.3
5
u
1
u
433
433
0.7
J
0.3
31.3
11.4
0.1
J
42
A30B
/29/2016
3670
3580
3.48
0.339
2.5
u
1.25
5
u
1
u
2.5
u
0.5
u
267
259
5
u
1
u
1120
1020
0.4
u
1.3
120
16.7
0.2
124
DM22
6/28/2016
409
411
0.826
J
0.284
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
694
662
J
5
u
1
u
627
673
0.8
1
85.3
100
0.1
u
180
DM22
/28/2016
165
156
0.5
U
0.1
u
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
774
719
5
u
1
u
572
619
-
-
-
-
-
198
Ben Franklin
Mine
ARD1
/29/2015
22300
22300
840
861
12.8
11.8
5
u
1.12
J
2.5
u
1.71
-
-
2.5
u
0.5
u
19 00
19500
4
u
1.1
J
351
J
5
u
1
u
123
ARD1
6/28/2016
12700
12300
745
720
8.89
7.98
5
u
1
u
2.5
u
2.32
166
157
5
u
1
u
12500
12300
-
-
-
-
-
80
ARD1
/28/2016
26000
26100
747
686
15.4
13.6
5
u
5
u
2.5
u
2.5
u
242
231
5
u
5
u
23000
24300
2
u
1.8
338
5
u
0.5
u
138
EG3A
/29/2015
116
107
4.18
2.45
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
217
215
0.8
u
0.2
U
69.7
J
31
0.2
u
4
EG3A
6/28/2016
633
650
2.63
0.691
2.5
u
0.803
J
5
u
1
u
2.5
u
0.5
u
186
179
J
5
u
1
u
1120
1210
-
-
-
-
-
65
EG3A
/29/2016
18.3
16.2
0.5
U
0.152
J
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
346
312
5
u
1
u
79.8
85.7
0.4
u
0.1
J
89.6
25.2
0.1
J
109
EG5
/30/2015
53.2
53.2
1.68
1.12
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
221
228
0.8
u
0.2
U
67.1
J
34.3
0.2
u
5
EG5
6/28/2016
636
655
2.56
1.74
2.5
u
0.73
J
5
u
1
u
2.5
u
0.5
u
182
184
J
10.6
1
u
1120
1200
-
-
-
-
-
64
EG5
/28/2016
144
144
3.11
1.48
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
359
329
5
u
1
u
493
529
0.4
u
0.3
89.8
23.9
0.1
u
107
A39A
6/28/2016
607
593
3.06
2.14
2.5
u
0.6
J
5
u
1
u
2.5
u
0.5
u
192
182
5
u
1
u
1040
1030
0.7
J
0.2
49.2
17.4
0.1
J
62
Terry Tunnel
A38
6/28/2016
10600
10400
2.36
0.1
u
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
4040
3860
12
1
u
1180
1150
1.6
1.1
490
100
0.2
J
534
A38
/28/2016
11000
10700
8.53
0.5
u
2.5
u
2.5
u
5
u
5
u
2.5
u
2.5
u
4170
4180
5
u
5
u
1340
1220
4
u
1.4
J
504
103
1
u
580
A39
/30/2015
256
250
5.01
2.23
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
385
393
0.8
u
0.2
U
70.8
J
31
0.2
u
1
A39
6/28/2016
589
568
3.13
2.12
2.5
u
0.594
J
5
u
1
u
2.5
u
0.5
u
192
180
5
u
1
u
1000
1010
0.7
J
0.2
48.2
17.2
0.1
J
61
A39
/28/2016
310
305
7.6
2.09
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
339
331
5
u
1
u
618
630
0.4
u
0.3
86.9
23
0.1
u
102
EG6
6/10/2015
1340
1280
6.08
1.83
2.5
u
1.13
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
1110
1080
-
-
-
-
-
48
EG6
/30/2015
6.8
4.3
0.869
T
0.796
2.5
u
0.5
~u~
5
u
1
u
2.5
u
0.5
u
-
-
2.5
u
0.5
u
430
429
0.8
77
0.2
u
105
T
25.9
0.2
u
121
EG6
6/28/2016
417
415
2.19
1.05
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
170
176
T
11.5
1
u
671
716
0.7
j
0.2
42.6
16.3
0.1
u
57
EG6
/28/2016
251
248
3.85
0.76
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
335
305
5
~u~
1
u
430
456
0.4
u
0.2
73.2
22
0.1
u
89
Pride of the West
Mine
A50
6/7/2016
401
394
42.2
7.77
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
541
540
5
u
1
u
2190
2130
0.8
0.2
112
83
0.2
191
A50
/28/2016
239
238
17.6
4.15
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
667
630
5
u
1
u
1360
1350
0.4
77
0.2
128
0.8
0.1
J
211
CU4
6/7/2016
152
4.21
J
27.5
0.298
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
114
106
5
u
1
u
13.2
J
10
~u~
0.7
j
0.1
u
5.9
24.6
0.1
u
27
CU4
/28/2016
4.47
J
3.63
J
1.9
0.149
T~
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
284
265
5
u
1
u
10
U
10
u
0.4
j
0.1
u
19.9
45.8
0.1
u
63
CU4A
6/7/2016
174
4.84
J
46.4
0.488
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
117
108
5
u
1
u
35.1
10
u
0.7
j
0.1
u
6.2
25.2
0.1
u
28
CU4A
/28/2016
6
4.03
J
1.27
0.296
2.5
u
0.5
u
5
u
1
u
2.5
u
0.5
u
292
279
5
u
1
u
24.3
28.6
0.4
j
0.1
u
23.2
47.8
0.1
u
68
Notes:
Q - qualifier J - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample
" - data not available U - Indicates compound was analyzed for, but not detected in sample. Value shown isSjuantitation limit of method
T - total recoverable gpm - gallons per minute
D - dissolved pg/L- micrograms per liter
C
-------
Attachment B
Total Recoverable Metals Concentrations for 2015
and 2016 EPA/ESAT Waste Rock and Soil Samples
-------
Attachment B • Total Recoverable Metals Concentrations for 2015 and 2018 EPA/ESAI Waste Rock and
Soil Samples
This page intentionally left blank.
-------
Sample
Location
WR-M02B
Longfellow Mine Waste Rock
7/28/2016
5920
J
49.2
J-
3160
133
0.3
U
4.8
J-
10500
J
3.8
4.9
669
WR-M02D
Junction Mine Waste Rock
7/28/2016
8630
J
30.1
J-
1720
145
0.55
J
5.4
J-
1410
J
16.5
5
487
WR-M02C
KoehlerTunnel Waste Rock (10 sieve)
7/28/2016
6300
J
18.5
J-
13700
101
1.8
U
3.3
J-
28500
J
6.2
8.9
539
WR-M02C
KoehlerTunnel Waste Rock (60 sieve)
7/28/2016
7250
J
21.3
J-
22200
135
0.29
5
UJ
65300
J
10.9
9
J
470
M02E
Junction Mine / Koehler Tunnel Pond
10/7/2016
11700
2.5
J
125
100
0.044
u
2.5
20800
3.4
7.1
175
M02
Junction Mine / Koehler Tunnel Downstream
10/7/2016
20400
0.04
UJ
14.6
166
0.053
u
0.056
u
4250
6.5
10.5
30.2
WR-M12
7/28/2016
7610
J
2.7
J-
86.4
92.4
0.12
J
0.18
J-
3
UJ
9.9
2.2
47.4
WR1-M12
7/28/2016
6060
12.7
72.5
91.5
0.14
1.8
J
1440
3.1
4.4
123
WR2-M12
7/28/2016
11600
5.5
137
103
0.22
0.51
J
1930
5.3
4.8
117
M12C
9/30/2016
10400
3.5
J
103
J
64.8
J
0.05
u
0.052
u
1280
J
2.9
3.3
99.2
J
M12D
9/30/2016
6960
1.6
J
39.6
J
127
J
0.047
u
1.1
679
J
10.5
15.6
28.8
J
M12E
10/7/2016
22600
0.034
UJ
7.2
106
0.046
u
0.048
u
2700
4.6
9.3
23
M12A
9/30/2016
9880
J
0.041
UJ
36.8
J
161
J-
0.054
u
0.057
u
3360
J
3.4
14.3
J
24.5
M12B
9/30/2016
8260
J
0.035
UJ
34.5
J
103
J-
0.047
u
0.049
UJ
3.3
UJ
1.1
J
4.8
J
15.9
M12
9/29/2016
15700
J
0.037
UJ
16.4
J
170
J-
0.049
u
1.9
J-
3240
J
10.5
19.1
J
56.3
WR1-M24
7/28/2016
6580
59.3
85
149
1.6
86.3
J
2970
3.9
20.4
1410
WR2-M24
7/28/2016
8160
176
108
1110
0.47
10.7
J
18700
5.1
3.7
1710
WR3-M24
7/28/2016
4640
118
J
150
58.1
J
0.58
147
J
9250
2.1
4.2
J
1610
WR4-M24
7/28/2016
12700
4.5
33.9
184
4
160
J
1400
7.1
117
2790
M24D
9/27/2016
21300
0.85
J
8.9
93.8
J
0.79
21.1
5220
J
5.4
11.1
J
197
M23
9/27/2016
14600
0.13
J
4
76.7
J
0.3
J
0.21
J
4920
J
5.9
5.8
J
13.9
M25
andora Mine Downstream
9/27/2016
18200
0.31
J
27.9
141
J
0.47
J
1.1
12800
J
6.7
5.8
J
12
Attachment B
Total Recoverable Metals Concentrations for 2015 and 2016 EPA/ESAT Waste Rock and Soil Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Waste Rock/Soil Sample Location
Antimony
Mineral Cre k
Cement Cre k
WR-CC01C
Grand Mogul Mine Waste Rock 1
7/27/2016 4970
65.8
106
64.9
0.17
15.2
596
3.8
2050
Grand Mogul Mine Waste Rock 2
7/27/2016
3550
WR-CC02A
Grand Mogul Mine Western Waste Rock
7/27/2016
4390
28.4
72.9
132
0.21
1.6
0.47
225
CC01F
Grand Mogul Mine Upstream
9/28/2016
12300
0.039
23
0.052
0.054
1260
5.8
10.2
59.5
Grand Mogul Mine below Waste Rock 1
9/28/2016
CC01C1
Grand Mogul Mine below Waste Rock 2
9/28/2016
11400
0.048
36.6
99.5
0.064
3.9
1720
5.3
192
Grand Mogul Mine before Confluence with CC
9/28/2016
CC01H
Grand Mogul Mine after Confluence with CC
9/27/2016
16800
0.044
41.3
62.8
0.83
Grand Mogul Western Waste Rock Channel
9/27/2016
CC01U
Grand Mogul Mine Downstream in CC
9/27/2016
13000
7.2
50.5
126
0.9
2.5
1660
5.6
10.8
241
Natalie/Occidental Mine Waste Rock 1
7/27/2016
WR-CC14B
Natalie/Occidental Mine Waste Rock 2
7/27/2016
7390
2.5
35.9
67.5
0.28
0.29
656
3.7
6.7
Natalie/Occidental Mine Upstream
9/29/2016
CC15A
Natalie/Occidental Mine Downstream
9/29/2016
8220
0.035
20.5
51.2
0.046
0.049
1040
2.6
3.9
29.9
Henrietta Mine Waste Rock
7/27/2016
0.21
5.2
86000
3.1
2.7
264
CC22D
Henrietta Mine Upstream
9/29/2016
6880
2.1
63.3
35.2
0.17
3.5
1010
1.9
2.1
61.4
Henrietta Mine Midpoint
9/29/2016
CC24B
Henrietta Mine Downstream
9/29/2016
5430
59.8
224
0.12
0.053
3.5
3.8
2.4
28
Anglo Saxon Mine Lower Waste Rock (10 sieve)
7/27/2016
WR-CC37
Anglo Saxon Mine Lower Waste Rock (60 sieve)
7/27/2016
11200
3.4
118
0.49
0.53
3.9
23.7
96.1
Anglo Saxon Mine Upper Waste Rock (10 sieve)
7/27/2016
WR-CC38B
Anglo Saxon Mine Upper Waste Rock (60 sieve)
7/27/2016
4850
110
232
103
0.13
2.3
1.3
485
Anglo Saxon Mine Upstream
9/28/2016
CC38C
Anglo Saxon Mine In Porcupine Gulch
9/28/2016
11200
2.7
73.5
95.3
0.3
1470
8.1
93.9
Anglo Saxon Mine In Porcupine Gulch
9/28/2016
CC38
Anglo Saxon Mine In Porcupine Gulch
9/28/2016
11000
0.82
46.3
106
0.27
0.66
1260
2.7
3.4
54.3
Anglo Saxon Mine Downstream
9/27/2016
WR-CC43
Yukon Tunnel Waste Rock
7/27/2016
9750
13
51.8
52.3
0.083
3.5
4160
3.4
4.2
2580
Yukon Tunnel Upstream
9/27/2016
CC43E
Yukon Tunnel Downstream
9/27/2016
8380
3.7
57.2
63
0.16
0.82
635
3.5
48.9
CC42
Yukon Tunnel in Illinois Gulch
9/27/2016
8230
7.3
CC43D
Yukon Tunnel Pond
9/27/2016
14800
31.8
109
0.29
0.29
2570
9.2
93.3
Notes:
Waste rock samples are indicated by a "WR" in the sample location name
CC - Cement Creek
U - Indicates compound was analyzed for, but not detected in sample
UJ - The analyte was analyzed for, but was not detected. The reported value is approximate and may be inaccurate or imprecise
J - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample
J- - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample, likely to have a low bia:
mg/kg - milligrams per kilogram
- no data available
11U" samples are reported as the method detection limit
CsDrRith
1 of 4
-------
Sample
Location
Attachment B
Total Recoverable Metals Concentrations for 2015 and 2016 EPA/ESAT Waste Rock and Soil Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Waste Rock/Soil Sample Location
Antimony
Animas River
A07E
oston Mine Upstream
10/5/2016
13600
85
1.2
3.3
431
6.6
36.2
oston Mine Waste Rock
7/26/2016
A07D
oston Mine Downstream
10/5/2016
21700
0.045
59.2
3.2
1050
59.2
London Mine Waste Rock 1
7/26/2016
WR2-LND
London Mine Waste Rock 2
7/26/2016
4980
87.9
169
52.5
0.19
33.3
719
2.1
143
London Mine Waste Rock 3
8/5/2015
A07B
London Mine Downstream
9/30/2016
48300
3.2
34.7
41.9
2.9
7.6
25
208
utler Mine Waste Rock
7/26/2016
utler Mine Downstream
10/5/2016
14700
0.038
60.1
0.46
0.99
1600
4.9
21.9
Mountain Queen Upper Shaft
8/5/2015
AE2
Mountain Queen Adit
8/5/2015
1010
27.5
106
150
0.004
2.5
132
0.61
0.27
Vermillion Mine Waste Rock
7/27/2016
CG6
Vermillion Mine Downstream
9/30/2016
25400
0.047
29.9
39.9
6.1
1.6
2930
15.2
156
Sunbank Group Mine Upper Adit
8/6/2015
Sunbank Group Mine
8/6/2015
6350
50
109
93.4
0.49
2.7
242
21.5
270
Sunbank Group Mine Waste Rock
8/6/2015
All
Sunbank Group Mine Upstream
9/30/2016
21200
3.1
44.8
169
9.8
3.7
6.7
13.4
318
Sunbank Group Mine Downstream
9/30/2016
AE10
aglev Tunnel Waste Rock - North
8/5/2015
2910
13.8
86.2
0.73
10
918
6.6
337
aglevTunnel Waste Rock - South
8/5/2015
A13
aglev Tunnel Upstream
9/30/2016
15800
12
41.2
113
15.9
2530
6.5
466
aglev Tunnel Downstream
9/30/2016
GC-OPP
aglev Tunnel - North of Mine
7/27/2016
17800
0.57
30.4
105
0.97
0.98
4120
8.3
26.9
Columbus Mine Waste Rock
8/4/2015
CG11
Columbus Mine Upstream
9/30/2016
15500
59.3
5.9
2410
5.2
182
Columbus Mine Downstream
9/29/2016
CMP7
Campground 7
7/26/2016
13300
42.5
86.9
180
0.8
10.6
3620
8.1
5.9
339
Silver Wing Mine
8/4/2015
AE32B
Silver Wing Mine
8/4/2015
1310
273
729
86.3
0.004
8.6
214
0.97
0.84
2530
Tom Moore Mine
7/27/2016
_E±_
en Franklin Mine
8/4/2015
3610
12.6
57.3
40.4
0.1
6.4
957
2.9
3.8
en Franklin Mine Upstream
9/29/2016
EG5
en Franklin Mine Downstream
9/28/2016
18100
1.2
42.4
108
0.84
4.9
2790
192
Terry Tunnel Upstream
9/28/2016
EG 6
Terry Tunnel Downstream
9/28/2016
16000
2.4
31.7
85.3
0.86
2760
6.3
17.3
439
Pride of the West Mine North
7/27/2016
WR-PWS
Pride of the West Mine South (10 sieve)
7/27/2016
9090
33.7
85.7
61.8
0.86
46.8
14600
10.6
1640
Pride of the West Mine South (60 sieve)
7/27/2016
CU4
Pride of the West Upstream
9/28/2016
10500
0.035
23.4
28.9
0.047
2.2
2490
2.4
105
CU4A
Pride of the West Downstream
9/28/2016
13000
3.8
9.2
CMP4
Campground 4
7/26/2016
8550
46.8
62.9
75.7
0.32
94.3
2310
4.3
2510
Notes:
Waste rock samples are indicated by a "WR" in the sample location name
CC - Cement Creek
U - Indicates compound was analyzed for, but not detected in sample
UJ - The analyte was analyzed for, but was not detected. The reported value is approximate and may be inaccurate or imprecise
J - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample
J- - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample, likely to have a low bia:
mg/kg - milligrams per kilogram
- no data available
11U" samples are reported as the method detection limit
CsDrRith
2 of 4
-------
Attachment B
Total Recoverable Metals Concentrations for 2015 and 2016 EPA/ESAT Waste Rock and Soil Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Sample
Location
Waste Rock/Soil Sample Location
Magnesium
Molybdenum
WR-M02B
Longfellow Mine Waste Rock
7/28/2016
45700
J
3680
1760
J
528
J
0.56
5.2
4.7
1.9
J
27.2
J-
0.54
11
1340
WR-M02D
Junction Mine Waste Rock
7/28/2016
75900
J
10200
2820
J
388
J
7.6
1.7
J
10.3
6
J
35.9
J-
0.89
27.3
1980
WR-M02C
KoehlerTunnel Waste Rock (10 sieve)
7/28/2016
160000
J
3740
2910
J
1700
J
3
4.6
J
2.1
U
3
J
14.6
J-
3.4
70.3
910
WR-M02C
KoehlerTunnel Waste Rock (60 sieve)
7/28/2016
203000
J
2930
4180
J
1330
J
1.8
6.7
J
5.4
U
2.8
J
10.4
J-
7.3
107
911
M02E
Junction Mine / Koehler Tunnel Pond
10/7/2016
28200
217
3170
668
0.11
0.95
J
4.3
1.3
J
0.98
0.042
U
17.7
405
M02
Junction Mine / Koehler Tunnel Downstream
10/7/2016
33900
53.7
5690
981
0.092
J
0.68
J
5.5
1.2
J
0.036
U
0.051
U
24.7
135
WR-M12
7/28/2016
47200
J
1920
4020
J
571
J
0.14
6.5
4.3
1.9
J
14.3
J-
0.32
19
145
WR1-M12
7/28/2016
51400
2950
J
2070
422
0.2
5.4
2.9
2
27
J
0.4
13.6
903
WR2-M12
7/28/2016
65100
1310
J
5720
847
0.0034
U
2.3
4.8
1.2
6.2
J
0.28
22.4
311
M12C
9/30/2016
56200
3370
3730
456
1.2
J+
3.8
2.6
2
J
18.2
0.047
U
18.6
763
J
M12D
9/30/2016
48500
405
3260
1750
0.067
J+
1.6
J
8.9
1.8
J
2.8
0.044
U
27.1
314
J
M12E
10/7/2016
41900
100
9480
1900
0.011
J
0.79
J
5.3
1
J
0.031
U
0.044
U
20.8
186
M12A
9/30/2016
32300
J
62.5
2210
764
0.035
J
1.2
J
7.7
J
1.6
J
1
J-
0.051
U
22.8
88.3
J
M12B
9/30/2016
27400
J
48.1
1030
251
0.05
J
0.7
J
1.8
J
1
J
0.032
u
0.044
U
10.1
55.6
J
M12
9/29/2016
40900
J
241
6170
3520
0.075
J
2.9
12.3
J
2.1
J
0.033
UJ
0.047
U
25.9
446
J
WR1-M24
7/28/2016
50200
14700
J
2110
15700
0.37
38.8
11.8
3
92.4
J
0.16
11.8
12800
WR2-M24
7/28/2016
64700
24400
J
967
1040
0.49
36.9
1.6
7.7
40.4
J
0.18
19.7
11100
WR3-M24
7/28/2016
23500
23200
J
1990
15100
0.71
48.8
J
8.2
J
3.3
48.4
J
0.2
8.3
66800
WR4-M24
7/28/2016
126000
2450
J
2360
72100
0.0049
u
25
34.6
3
5.9
J
0.33
20.6
16600
M24D
9/27/2016
31300
J
349
6480
6020
J
0.039
J
2.5
10.2
J
1.5
J
1.6
0.042
U
22.5
J
4120
M23
9/27/2016
23700
J
19
5620
380
J
0.026
J
2.2
J
7.1
J
1.2
J
0.035
u
0.049
U
26.1
J
88.7
M25
andora Mine Downstream
9/27/2016
17300
J
55.3
4060
709
J
0.039
J
1
J
5.5
J
0.96
J
0.036
u
0.051
U
23.1
J
174
Mineral Cre k
Cement Cre k
WR-CC01C
Grand Mogul Mine Waste Rock 1
7/27/2016
40800
19900
2410
977
6.3
32.1
0.44
19.8
17900
Grand Mogul Mine Waste Rock 2
7/27/2016
WR-CC02A
Grand Mogul Mine Western Waste Rock
7/27/2016
24300
5140
847
382
0.45
25
0.49
3.8
19.7
0.39
9.9
3510
CC01F
Grand Mogul Mine Upstream
9/28/2016
27200
462
5070
1670
0.062
4.9
1.2
0.049
16.9
173
Grand Mogul Mine below Waste Rock 1
9/28/2016
CC01C1
Grand Mogul Mine below Waste Rock 2
9/28/2016
26000
1080
3050
2460
0.1
1.8
2.9
0.06
12.6
737
Grand Mogul Mine before Confluence with CC
9/28/2016
3.2
19
3.3
3.4
19.8
5560
Grand Mogul Mine after Confluence with CC
9/27/2016
CC02I
Grand Mogul Western Waste Rock Channel
9/27/2016
36100
930
4050
3910
0.055
6.2
1.3
1.6
0.053
27.7
567
CC01U
Grand Mogul Mine Downstream in CC
9/27/2016
39400
6850
4130
0.038
7.9
2.4
4.2
0.048
21.4
642
Natalie/Occidental Mine Waste Rock 1
7/27/2016
WR-CC14B
Natalie/Occidental Mine Waste Rock 2
7/27/2016
59800
845
3040
712
0.18
37.9
1.8
5.3
12.5
0.24
24.9
223
Natalie/Occidental Mine Upstream
9/29/2016
0.032
0.045
18.8
53.7
CC15A
Natalie/Occidental Mine Downstream
9/29/2016
37700
259
3080
359
0.027
6.7
1.9
2.4
0.044
146
Henrietta Mine Waste Rock
7/27/2016
CC22D
Henrietta Mine Upstream
9/29/2016
42100
568
1970
289
0.096
0.91
1.3
1.6
1.3
0.041
12.1
Henrietta Mine Midpoint
9/29/2016
CC24B
Henrietta Mine Downstream
9/29/2016
26900
165
1470
190
0.028
1.8
2.4
0.9
0.048
20.4
35
Anglo Saxon Mine Lower Waste Rock (10 sieve)
7/27/2016
WR-CC37
Anglo Saxon Mine Lower Waste Rock (60 sieve)
7/27/2016
122000
959
3660
3810
0.12
12.3
5.8
3.8
0.24
26.7
Anglo Saxon Mine Upper Waste Rock (10 sieve)
7/27/2016
WR-CC38B
Anglo Saxon Mine Upper Waste Rock (60 sieve)
7/27/2016
77400
4650
1040
0.56
36.5
13.1
22.*
0.66
25
2240
Anglo Saxon Mine Upstream
9/28/2016
CC38C
Anglo Saxon Mine In Porcupine Gulch
9/28/2016
40500
1480
4850
1150
0.031
1.8
1.9
2.6
3.5
0.048
16.7
546
Anglo Saxon Mine In Porcupine Gulch
9/28/2016
CC38
Anglo Saxon Mine In Porcupine Gulch
9/28/2016
40300
540
3930
585
0.047
1.8
2.3
1.3
0.083
17.3
285
Anglo Saxon Mine Downstream
9/27/2016
WR-CC43
Yukon Tunnel Waste Rock
7/27/2016
69800
3160
2700
0.26
45.8
3.5
13.4
16.3
0.38
23.8
844
Yukon Tunnel Upstream
9/27/2016
CC43E
Yukon Tunnel Downstream
9/27/2016
53100
343
4030
583
0.032
2.7
2.3
0.043
27.8
765
CC42
Yukon Tunnel in Illinois Gulch
9/27/2016
CC43D
Yukon Tunnel Pond
9/27/2016
65700
205
7660
960
0.028
6.5
2.1
0.99
0.044
20.9
Notes:
Waste rock samples are indicated by a "WR" in the sample location name
CC - Cement Creek
U - Indicates compound was analyzed for, but not detected in sample
UJ - The analyte was analyzed for, but was not detected. The reported value is appr
J - Indicates an estimated value. The associated numerical value is the approximate <
J- - Indicates an estimated value. The associated numerical value is the approximate
mg/kg - milligrams per kilogram
- no data available
11U" samples are reported as the method detection limit
CsDrRith
3 of 4
-------
Attachment B
Total Recoverable Metals Concentrations for 2015 and 2016 EPA/ESAT Waste Rock and Soil Samples
Bonita Peak Mining District, San Juan County, Colorado
Preliminary Remedial Investigation Report
Sample
Location
Waste Rock/Soil Sample Location
Sample
Date
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
Thallium
Vanadium
Zinc
Animas River |
A07E
10/5/2016
106000
J
505
J
1340
J
7540
J
0.054
J
29.1
3.4
J
2.5
J
4.1
3.3
12.4
434
_J_
WR-BSN
7/26/2016
25900
4660
J
2.2
U
122
1.7
118
J
0.68
J
0.99
22.4
J
2.3
4.5
4450
A07D
10/5/2016
23000
J
487
J
3800
J
2710
J
0.051
J
3.7
5.2
J
1.9
J
2
0.057
U
16.7
818
7
WR1-LND
London Mine Waste Rock 1
7/26/2016
28900
3300
J
2.2
U
161
0.6
16.2
1
2.9
16.9
J
0.63
5.7
2250
WR2-LND
London Mine Waste Rock 2
7/26/2016
25000
5490
J
1570
713
0.53
48.9
1.3
1.4
35.4
J
2
12
7690
AE18
London Mine Waste Rock 3
8/5/2015
14600
J
5660
J
277
J
107
J
0.66
-
-
1.2
J
2.2
J
47.4
J
2
J
4.5
J
9680
7
A07B
London Mine Downstream
9/30/2016
36800
561
1640
J
10700
0.056
J
7.4
3.8
2.4
J
1.9
0.1
U
4.6
J
546
_J_
WR-
pn utler Mine Waste Rock
7/26/2016
35500
24000
J
995
194
0.77
49.8
J
0.97
J
1.2
93.7
J
2.3
10
20200
pn utler Mine Downstream
10/5/2016
22900
J
473
J
3030
J
910
J
0.028
J
2.2
J
4
J
0.92
J
1.2
0.048
u
19.5
328
7
AE1
Mountain Queen Upper Shaft
8/5/2015
32000
J
35700
J
30.2
J
54.3
J
1.5
-
-
0.35
J
32.3
J
16
J
0.003
UJ
5.4
J
12400
AE2
Mountain Queen Adit
8/5/2015
15700
J
1950
J
157
J
258
J
1.8
-
-
0.31
J
2.3
J
49.6
J
0.003
UJ
3.1
J
621
AE9A
Vermillion Mine Waste Rock
7/27/2016
25800
10400
J
2.1
U
60.4
1.1
41.2
0.42
2.9
45.1
J
1
5.1
8520
CG6
Vermillion Mine Downstream
9/30/2016
40100
J
162
9250
J
7020
J
0.038
J
4.7
7.4
J
2.5
J
0.042
U
0.06
u
32.5
813
AE44
Sunbank Group Mine Upper Adit
8/6/2015
47500
J
2040
J
847
J
3080
J
0.2
-
-
3.1
J
0.092
UJ
20.1
J
2.8
J
17.7
J
496
7
AE45
Sunbank Group Mine
8/6/2015
55100
J
2210
J
1310
J
8240
J
0.24
-
-
2.8
J
0.2
UJ
20.3
J
4.6
J
14.9
J
640
AE46
Sunbank Group Mine Waste Rock
8/6/2015
102000
J
631
J
1750
J
12800
J
0.26
-
-
2.6
J
0.12
UJ
8.7
J
6
J
24.7
J
295
A22
Sunbank Group Mine Upstream
9/30/2016
24000
J
1500
3270
J
19600
J
0.16
4.7
6.5
J
2.6
J
4.2
0.78
21.4
1600
A21
Sunbank Group Mine Downstream
9/30/2016
37000
3390
3200
J
4270
0.86
7.8
3.6
3.4
J
10.4
0.11
u
13.8
1460
7
AE10
8/5/2015
33800
J
7040
J
1050
J
4040
J
1.2
-
-
2.4
J
0.17
UJ
27.1
J
1.4
J
8.1
J
1980
AE10A
8/5/2015
37600
J
3400
J
1760
J
2640
J
0.82
-
-
1.2
J
0.083
UJ
17.3
J
1.1
J
7.4
J
3200
j_
A13
9/30/2016
28900
J
6000
4490
J
14800
J
2.6
12.9
4.6
J
2.1
J
21.8
0.063
u
14.9
2100
CG9
9/30/2016
69700
J
1730
1550
J
55900
J
0.2
J
81.8
53.1
J
5.9
J
5.9
0.11
u
8.6
30200
GC-OPP
7/27/2016
23700
J
151
4710
1700
0.0036
U
5.4
5.3
0.92
0.84
0.2
23.1
327
AE13
Columbus Mine Waste Rock
8/4/2015
41700
J
6060
J
3570
J
1160
J
0.74
-
-
3.8
J
0.17
UJ
17.7
J
0.81
J
20.1
J
1750
7
CG11
Columbus Mine Upstream
9/30/2016
29300
J
1300
6190
J
6080
J
1.2
6.3
4.6
J
1.8
J
5.2
0.047
u
19.5
857
A10
Columbus Mine Downstream
9/29/2016
40500
J
1870
J
6420
J
2350
J
0.64
16.3
3.6
J
1.2
J
5.9
0.041
u
20.3
404
7
CMP7
Campground 7
7/26/2016
23500
J
11800
4200
1560
0.29
6.4
5.1
2.9
26.7
0.43
24.4
5290
AE32A
Silver Wing Mine
8/4/2015
43400
J
7010
J
886
J
357
J
0.17
-
-
1.9
J
4.3
J
16
J
0.003
UJ
12.4
J
1340
7
AE32B
Silver Wing Mine
8/4/2015
38600
J
4710
J
516
J
289
J
0.51
-
-
0.73
J
3
J
17.6
J
0.003
UJ
10.7
J
1970
_j_
WR-TM
Tom Moore Mine
7/27/2016
42400
8180
852
J
837
J
0.14
159
J
0.67
J
1.1
10.4
J
1.9
11.4
3080
F4
8/4/2015
49100
J
6770
J
2300
J
1130
J
0.47
-
-
2.6
J
1.7
J
34.8
J
0.37
J
15.6
J
2870
7
EG3A
pn Franklin Mine Unstream
9/29/2016
55600
_J_
605
_J_
9260
_J_
1620
_J_
0.23
2.1
10
J
2.2
J
4.9
0.041
u
39.2
282
_j_
EG5
pn Franklin Mine Downstream
9/28/2016
65400
730
_J_
8550
_J_
5830
_J_
0.046
~T
6.1
00
00
J
2.8
4.9
J
0.04
u
32.7
1050
A39
Terry Tunnel Upstream
9/28/2016
60100
1010
_J_
10100
_J_
9450
_J_
0.055
j
9.5
11.5
J
3
7.6
J
0.042
u
25.9
3640
EG 6
Terry Tunnel Downstream
9/28/2016
67000
1770
_J_
8530
_J_
15100
_J_
0.11
j
5.2
9.2
J
2.3
T
5.8
J
0.044
u
27.8
3450
WR-PWN
Pride of the West Mine North
7/27/2016
25200
13900
5290
_J_
5450
_J_
0.0033
U
101
4.5
3
12.9
0.23
9
9920
WR-PWS
Pride of the West Mine South (10 sieve)
7/27/2016
42700
16300
5830
_J_
5860
_J_
0.27
82.4
5.5
1.2
50.4
0.29
14
12100
WR-PWS
Pride of the West Mine South (60 sieve)
7/27/2016
50600
26700
5260
_J_
6580
_J_
0.55
91.7
7
2
49.3
0.38
16.6
13100
CU4
Pride of the West Upstream
9/28/2016
21800
7
1760
4570
_J_
2210
_J_
0.015
~T
7.1
2.3
T
1
T
2
0.045
77
9.3
665
7
CU4A
Pride of the West Downstream
9/28/2016
30200
_j_
820
5120
_J_
1260
_J_
0.012
j
4.4
3.9
j
1.9
j
2.4
0.046
u
32.1
458
_j_
CMP4
Campground 4
7/26/2016
37400
j
44200
3150
910
6
118
T
2.8
7.1
96.9
0.3
15.4
17300
Notes:
Waste rock samples are indicated by a "WR" in the sample location name
CC - Cement Creek
U - Indicates compound was analyzed for, but not detected in sample
UJ - The analyte was analyzed for, but was not detected. The reported value is approximate and may be inaccurate or imprecise
J - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample
J- - Indicates an estimated value. The associated numerical value is the approximate concentration of the analyte in the sample, likely to have a low bias
mg/kg - milligrams per kilogram
" - no data available
11U" samples are reported as the method detection limit
CsDrRith
4 of 4
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APPENDIX B
RISK ASSESSMENT INFORMATION
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APPENDIX B - PART 1.1A
RISK ESTIMATES FOR TRESPASS CAMPING SCENARIOS AT
DISPERSED CAMPSITES
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 8
1595 Wynkoop Street
DENVER, CO 80202-1129
Phone 800-227-8917
http://vwvw.epa.gov/region08
October 4, 2018
MEMORANDUM
SUBJECT: Final Risk Estimates for Trespass Camping Scenarios at Dispersed Campsites within
the Bonita Peak Mining District (BPMD) Superfund Site
The purpose of this memorandum is to provide a discussion of the human health risks associated with
limited-duration trespass camping scenarios on dispersed campsites within the Bonita Peak Mining
District (BPMD) located in southwestern Colorado. Landownership within the BPMD includes
government owned land as well as some parcels that are private property. This memorandum is in
response to public comments that question the validity of including private lands or inholdings within
the BPMD that have documented seasonal use as dispersed campsites in the risk evaluations
developed for the BPMD Final Focused Feasibility Study (FFS) for Interim Remedial Actions (CDM
Smith 2018). The risk evaluation presented in Appendix B of the FFS includes a dispersed camping
scenario consisting of an exposure frequency of 14 days per year. In response to the public comments
on this exposure frequency assumption, an alternate trespass camping scenario was evaluated to
determine whether heavy metals (lead in particular) may pose an unacceptable risk under a shorter
exposure frequency scenario. This alternate scenario evaluated an exposure frequency of 2 days per
year for campers in dispersed campsites to determine if levels of lead pose a risk above a level of
concern. This change would account for a family camping with a child (under the age of 6 years)
present that unknowingly uses unmarked private property within the BPMD as a campsite before
being discovered and asked to leave by the property owner.
Previous investigations have concluded that historic mining activities in the BPMD have impacted
soil, sediment, surface water, and groundwater in the area with elevated concentrations of heavy
metals, such as lead and arsenic, that exceed human health screening levels for residents and
industrial workers (EPA 2018). For the 13 dispersed campsites identified and sampled within the
BPMD, lead concentrations in soil range from less than 100 mg/kg to greater than 50,000 mg/kg, with
an average of approximately 6,400 mg/kg. The highest value observed was in "dispersed campsite 4",
which is the commenter's private property.
FROM: Steven B. Merritt
Industrial Hygienist/Risk Assessor
TO:
Rob Parker
Remedial Project Manager
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Concern over health effects from elevated blood lead levels is greatest for young children or the fetus
of pregnant women. There are several reasons for this focus on young children or the fetus, including
the following: children are often more vulnerable to pollutants than adults due to differences in
behavior and biology that can lead to greater exposure and/or unique windows of susceptibility
during development, soil ingestion rates for young children are higher than adults due to increased
frequency of contact through hand-to-mouth or object-to-mouth activity, and lead is particularly
harmful to the developing brain and nervous system of fetuses and young children.
EPA recommends the use of toxicokinetic models to correlate blood lead concentrations with
exposure and adverse health effects. EPA recommends the use of the Integrated Exposure Uptake
Biokinetic (IEUBK) model to evaluate exposures from lead-contaminated media in children in a
residential setting (EPA 1994) and the Adult Lead Methodology (ALM) to evaluate potential risks
from lead exposure in adults (females of childbearing age) (EPA 2016). Both the IEUBK model and
the ALM can be used to predict blood lead concentrations in exposed individuals and estimate the
probability of a blood lead concentration exceeding a level of concern. Unfortunately, for a trespass
camping scenario, the IEUBK and ALM are not valid with exposure durations of less than 14 days, so
a different approach was needed to estimate acute risks from lead exposures. Because acute
recreational screening levels are not readily available for use to evaluate potential risks to campers in
dispersed campsites, this memorandum will outline the process for developing these levels for lead.
EPA has recommended the use of the All Ages Lead Model (AALM) for evaluating short-term
exposure scenarios. The AALM is still in development, however, a beta version (FORTRAN 1.0) of
this model is available (upon EPA request) and was used in researching effects of lead exposures at
various life stages to support the development of the acute screening levels. The version of the model
used to derive acute lead screening values in this appendix was provided by EPA on March 13, 2018.
The AALM was used to evaluate a "pulse" exposure occurring for 2 days by a child due to incidental
ingestion of soil/waste rock encountered at a specific location (e.g., dispersed campsite). The model
output includes predicted lead concentrations for specified time step intervals (e.g., daily) with
interpolated changes between steps in various body compartments including the blood, plasma,
kidney, liver, bone, etc. This output can be used to determine peak blood lead (PbB) concentrations
following a pulse exposure.
Table 1 presents the general input parameters used to derive acute screening levels for lead,
recognizing that several of the assumptions may differ from those typically used in an evaluation of
chronic exposure to lead.
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Table 1. General Parameters Used to Calculate the Acute Lead Screening Levels
Parameter
Value
Source
Target PbB level (ng/dL)
19.5
EPA 2016
Maternal PbB level (ng/dL)
0.8
EPA 2017a
Default drinking water concentration (ng/L)
0.9
EPA 2017a
Background soil lead concentration (mg/kg)
66
Scribe database
RBA
0.6
EPA 2003
Receptor gender
Female
AALM model
mg/kg - milligrams per kilogram
PbB - blood lead
RBA - relative bioavailability
Mg/dL - micrograms per deciliter
Mg/L - micrograms per liter
The rationale for the selection of each input provided in Table 1 is presented below:
¦ Target PbB level - An acute blood lead threshold of 20 micrograms per deciliter (|ig/dL) was
identified in Office of Land and Emergency Management (OLEM) Directive 9285.6-54,
Recommendations for Assessing Short-term Exposure Involving Lead at Superfund Sites (EPA
2016). Per EPA (2016), a PbB level of 20 |ig/dL could be considered as a short-term elevation
in PbB that would trigger a response action. This is based on the interpretation of the Center for
Disease Control (CDC) recommendation that PbB levels in the range of 20 to 44 |ig/dL would
result in a home visit by a public health agency within 24 hours of a referral from a physician
(CDC 2012). For the purposes of this evaluation, 19.5 |ig/dL was selected as target PbB for
establishing an acute screening level, to account for rounding to two significant digits.
¦ Maternal PbB level - A maternal PbB level of 0.8 |ig/dL was selected based the
recommendation provided in OLEM Directive 9285.6-56 (EPA 2017b).
¦ Default drinking water concentration - A default lead drinking water concentration of 0.9
micrograms per liter (|ig/L) was selected based the recommendation provided in the
Headquarters Lead Consultation Intake Form for the Colorado Smelter Superfund Site (EPA
2017a).
¦ Background soil lead concentration - A background soil lead concentration of 66 milligrams
per kilogram (mg/kg) was selected based on the mean soil lead concentration measured in
upland reference soil collected within the BPMD.
¦ Relative bioavailability (RBA) - The default RBA of 60% recommended by EPA (2003) was
selected. The implications of this assumption are discussed further below.
¦ Receptor gender - A female receptor was selected because female children have a lower body
weight than male children (per default inputs in the AALM). A receptor with a lower body
weight is more sensitive to exposure compared to a receptor with a higher body weight.
3
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Table 2 presents the scenario-specific input parameters used to derive the acute screening level for
lead.
Table 2. Scenario-Specific Parameters Used to Calculate the Acute Lead Screening Levels
Scenario 1 Scenario 2 Scenario 3
Parameter CTE Resident CTE Camping RME Camping Source
Soil intake rate during pulse
exposure (g soil/day)
0.094
0.367
1.592
EPA 2017a, EPA 2008
(Table 5-6)
Soil intake rate prior to pulse
exposure (g soil/day)
0.086
0.094
0.094
EPA 2017a
Water intake rate (L water/day)
0.43
0.51
0.51
EPA 2017a
Diet intake rate (|jg Pb/day)
5.03
5.21
5.21
EPA 2017a
Receptor age at first pulse exposure
1 year old
(365 days)
2 years old
(730 days)
2 years old
(730 days)
EPA 2008 (Table 5-6)
CTE - central tendency exposure
g-grams
L-liter
Pb - lead
RME - reasonable maximum exposure
Mg- micrograms
The rationale for the selection of each input provided in Table 2 is presented below:
¦ Soil intake rate during pulse exposure - Multiple soil intake rates were selected for use in the
model to present a range of acute screening levels. In each case, the most conservative soil
intake rate available for each scenario was selected so that the most sensitive receptor was used
in the model.
• Scenario 1 - The soil intake rate selected for a CTE resident was 0.094 grams per day
(g/day). This value was selected because it is the highest intake rate provided in the
Headquarters Lead Consultation Intake Form for the Colorado Smelter Superfund Site
(EPA 2017a) for children under the age of 6 years. This value corresponds to a 1-year-old
to 2-year-old receptor.
• Scenario 2 - The soil intake rate selected for a CTE child while camping was 0.367 g/day
because this is the highest geometric mean intake rate provided in the Child-Specific
Exposure Factors Handbook (EPA 2008, Table 5-6). This value corresponds to a 2-year-old
to 3-year-old girl. The study upon which this value is based evaluated soil intake using a
tracer element methodology for 78 children aged 1 to 5 years old at campgrounds (Van
W'ijnen et al. 1990).
• Scenario 3 - The soil intake rate selected for a RME child while camping was 1.592 g/day
because this is the 95th percentile (computed using the reported geomean and geometric
standard deviation) for the intake rates provided for the 2-year-old to 3-year-old girl (EPA
2008, Table 5-6).
4
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¦ Soil intake rate prior to pulse exposure - The soil intake rate prior to the pulse selected for use
in the model was the soil intake rate provided in the Headquarters Lead Consultation Intake
Form for the Colorado Smelter Superfund Site (EPA 2017a) for the age group prior to the
pulse. For Scenario 1, where the pulse occurs on day 365, the soil intake rate prior to the pulse
was 0.086 g/day (soil intake rate for a 0-year old to 1-year old). Likewise, for Scenarios 2 and
3, where the pulse occurs on day 730, the soil intake rate prior to pulse was 0.094 g/day (soil
intake rate for a 1-year old to 2-year old).
¦ Water intake rate - The drinking water intake rate selected for use in the model was 0.43 to
0.51 liters per day (L/day), depending on the scenario, based the recommended values provided
in the Headquarters Lead Consultation Intake Form for the Colorado Smelter Superfund Site
(EPA 2017a). The 0.43 L/day intake rate was applied to the 1-year old (Scenario 1), whereas
the 0.51 L/day intake rate was applied to the 2-year old to 3-year old (Scenarios 2 and 3).
¦ Dietary intake rate - The dietary lead intake rate selected for use in the model was 5.03 to 5.21
micrograms per day (|ig/day), depending on the scenario, based the recommended values
provided in the Headquarters Lead Consultation Intake Form for the Colorado Smelter
Superfund Site (EPA 2017a). The 5.03 |i g/day intake rate was applied to the 1-year old
(Scenario 1), whereas the 5.21 |ig/day intake rate was applied to the 2-year old to 3-year old
(Scenarios 2 and 3).
¦ Receptor age at first pulse exposure - The age at first pulse exposure was 365 days (1 year old)
for Scenario 1 and 730 days (2 years old) for Scenarios 2 and 3.
Table 3 presents the acute screening levels for lead that were derived based on the inputs and
scenarios that have been described above. The acute screening levels were derived by determining
(through iterative model runs) the soil/waste rock concentration that would result in a predicted peak
PbB concentration of 19.5 |ig/dL.
Table 3. Acute Lead Screening Levels (mg/kg)
Scenario
Screening Level
(RBA = 0.6)
Scenario 1
8,036
Scenario 2
3,196
Scenario 3
737
mg/kg - milligrams per kilogram
For demonstration purposes, Figure 1 presents a graphical display of the predicted PbB
concentrations based on the acute screening levels developed for a 2-day exposure for Scenario 2. As
seen, the predicted PbB concentrations rise sharply for the 2-day exposure to soils containing 3,196
mg/kg to reach the threshold of 19.5 |ig/dL.
5
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Age (Days)
Hg/dL - micrograms per deciliter
Cblood - concentration of lead in blood
Table 4 presents a comparison of the acute lead screening levels based on a 2-day exposure for
Scenario 3 with varying RBA values (0.60 versus 0.20) to demonstrate the potential difference in
screening levels if a lower RBA value were used. As seen, the change in screening level is inversely
proportional to the change in RBA; decreasing the RBA by a factor of 3 increases the screening level
by a factor of 3.
Table 4. Effect of Using a Different RBA Value on Acute Lead Screening Levels (mg/kg)
Scenario
Screening Level
(RBA = 0.2)
Scenario 1
24,108
Scenario 2
9,588
Scenario 3
2,210
mg/kg - milligrams per kilogram
RBA - relative bioavailability
The concentration of lead at dispersed campsite 4 (51,714 ppm) is greater than the acute screening
levels for all scenarios described above (regardless of the assumed ingestion rate). In addition, even if
RBA values were at the lower end of the range possible (0.2), lead concentrations at dispersed
campsite 4 are higher than screening levels.
6
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This alternate exposure scenario evaluation indicates that, even if the exposure frequency were
assumed to be only 2 days per year, lead concentrations at dispersed campsite 4 would still be well
above risk-based recreational screening levels, which supports the conclusions of the FFS for this
location.
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REFERENCES
CDC. 2012. CDC Recommendations for Children's Blood Lead Levels (BLLs). Atlanta, Georgia:
Centers for Disease Control and Prevention: Atlanta, GA.
CDM Federal Programs Corporation (CDM Smith). 2018. Final Focused Feasibility Study Report.
Interim Remedial Actions. Bonita Peak Mining District Superfund Site. San Juan County, Colorado.
May.
EPA. 1994. Guidance Manual for the Integrated Exposure Uptake Biokinetic Model for Lead in
Children. U.S. Environmental Protection Agency, Office of Emergency and Remedial Response.
EPA/540/R-93/081.
EPA. 2003. Recommendations of the Technical Review Workgroup for Lead for an Approach to
Assessing Risks Associated with Adult Exposures to Lead in Soil. Final. EPA-540-R-03-001.
January.
EPA. 2008. Child-Specific Exposure Factors Handbook. U.S. Environmental Protection Agency.
EPA/600/R-06/096F. https://cfpub.epa.gov/ncea/risk/recordisplav.cfm?deid=199243.
EPA. 2016. Recommendations for Assessing Short-term Exposure Involving Lead at Superfund Sites.
U.S. Environmental Protection Agency, Office of Land and Emergency Management. OLEM
Directive 9285.6-54.
EPA. 2017a. Headquarters Lead Consultation Intake Form for the Colorado Smelter Superfund Site.
Submitted 4/11/17. https://semspub.epa.gov/work/08/1884173.pdf
EPA. 2017b. Update to the Adult Lead Methodology's Default Baseline Blood Lead Concentration
and Geometric Standard Deviation Parameters and the Integrated Exposure Uptake Biokinetic
Model's Default Maternal Blood Lead Concentration at Birth Variable.
EPA. 2018. Regional Screening Level (RSL) Summary Table. May.
8
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APPENDIX B - PART 1.1B
INTERIM CHRONIC LEAD RISK EVALUATION
-------
Appendix B - Part 1.1
Interim Chronic Lead Risk Evaluation
1.0 Introduction
This appendix describes an interim evaluation of potential lead risks from exposures to lead in
soil/waste rock at the Bonita Peak Mining District Superfund Site (Site) located in southwestern
Colorado. The Site consists of 48 historic mines or mining-related sources where ongoing releases
of metal-laden water and sediments are occurring within the Mineral Creek, Cement Creek, and
Upper Animas River drainages in San Juan County, Colorado. Drainages within the Site contain
over 400 abandoned or inactive mines where large- to small-scale mining operations occurred.
San Juan County is comprised of 10 historic mining districts (Colorado Geological Survey 2017).
Historic mining districts within the Mineral Creek, Cement Creek, and Upper Animas River
drainages (referred to as "the mining districts" in this appendix) include Animas, Animas Forks,
Cement Creek, Eureka, Ice Lake Basin, and Mineral Point
This interim lead risk evaluation was developed to support the identification of areas that may
warrant interim remedial action in 2018. This evaluation is to be considered preliminary and
subject to change pending completion of the Bonita Peak Mining District human health risk
assessment (HHRA).
Lead was selected for evaluation because soil concentrations are notably elevated at several
locations within the mining districts and lead is often an important human health risk driver for
mining-related contamination. The camping scenario was selected for this evaluation because the
camper receptor likely has the highest exposure to soil, due primarily to incidental ingestion of
soil, compared to the other recreational receptors (e.g., hiker, hunter, recreational ATV rider)
being considered in the HHRA. The camping scenario was also selected because this receptor
includes exposures both as a young child and as an older child/adult Children are often more
vulnerable to pollutants than adults, particularly for lead exposures, because of differences in
behavior and biology that can result in greater exposure and/or unique windows of susceptibility
during development Additionally, soil ingestion rates for young children are higher than adults
due to increased frequency of contact through hand-to-mouth or object-to-mouth activity.
Potential risks to a variety of recreational and occupational receptor populations from all
contaminants of interest (lead and nonlead) and all exposure media and pathways will be
evaluated as part of the Bonita Peak Mining District HHRA
2.0 Overview
Risks from lead are evaluated using a somewhat different approach than for most other
chemicals. Because lead is widespread in the environment, exposure can occur from many
sources. Thus, lead risks are usually based on consideration of total exposure (all sources) rather
than just site-related sources. Additionally, because studies of lead exposures and resultant
health effects in humans traditionally have been described in terms of blood lead level, lead
exposures and risks typically are assessed by describing the levels of lead that may occur in the
B-l
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Appendix B, Part 1.1, Interim Chronic Lead Risk Evaluation •
blood of exposed populations and comparing these to blood lead levels of potential health
concern. For convenience, the concentration of lead in blood is usually abbreviated PbB, and is
expressed in units of micrograms of lead per deciliter of blood ([ig/dL).
Concern over health effects from elevated blood lead levels is greatest for young children or the
fetuses of pregnant women. There are several reasons for this focus on young children or the
fetus, including the following: (1) young children typically have higher exposures to lead-
contaminated media per unit body weight than adults, (2) young children typically have higher
lead absorption rates than adults, and (3) young children and fetuses are more susceptible to
effects of lead than are adults. EPA has identified 10 |J.g/dL as the concentration level at which
effects begin to occur that warrant avoidance and has set as a goal that there should be no more
than a 5% chance that a child will have a blood lead value above 10 |J.g/dL (EPA 1994). The
Centers for Disease Control (CDC) has identified 5 |J.g/dL as a "reference level" for blood lead in
children1 (CDC 2012). This concentration corresponds to the 97.5th percentile of blood lead levels
in children in the U.S. The EPA is in the process of evaluating the CDC recommendations and
implications for Superfund risk assessments. Until this assessment is complete, EPA recommends
that lead risk assessments consider current scientific conclusions, which have shown adverse
health effects at levels less than 10 |J.g/dL (EPA 2016). On this basis, this interim lead risk
evaluation will employ a PbB threshold of 5 |J.g/dL. For convenience, the probability of a blood
lead value exceeding 5 |J.g/dL is referred to as P5.
Although the PbB threshold is based on studies in young children, it is generally assumed that the
same value is applicable to a fetus in utero. Available data suggest that the ratio of the blood lead
level in a fetus to that of the mother is approximately 0.9 (Goyer 1990). Thus, the concentration of
lead in blood in a pregnant female that would correspond to a PbB of 5 |J.g/dL in the fetus is:
PbB(mother) = 5 |J.g/dL / 0.9 = 5.6 |J.g/dL
3.0 Lead Exposure Models and Parameters
EPA recommends the use of toxicokinetic models to correlate blood lead concentrations with
exposure and adverse health effects. EPA recommends the use of the Integrated Exposure Uptake
Biokinetic (IEUBK) model to evaluate exposures from lead-contaminated media in children in a
residential setting (EPA 1994) and the Adult Lead Methodology (ALM) to evaluate potential risks
from lead exposure in adults (females of childbearing age) (EPA 2003a). Both the IEUBK model
and the ALM can be used to predict blood lead concentrations in exposed individuals and
estimate the probability of a blood lead concentration exceeding a level of concern as described
below.
3.1 IEUBK Model
The IEUBK model developed by EPA predicts the likely range of blood lead levels in a population
of young children (aged 0 to 84 months) exposed to a specified set of environmental lead levels
(EPA 1994). This model requires as input data on the levels of lead in soil, dust, water, air, and
diet at a location and on the amount of these media ingested or inhaled by a child living at that
1 http: //www.cdc. go v/nceMead/AC'CLPP/blood lead levels.htm
B-2
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Appendix B, Part 1.1, Interim Chronic Lead Risk Evaluation •
location. For the purposes of this interim lead risk evaluation, soil is the site-specific source
medium of primary interest for interim actions.
All inputs to the IEUBK model are central tendency point estimates. These point estimates are
used to calculate an estimate of the central tendency (the geometric mean) of the distribution of
blood lead values that might occur in a population of children exposed to the specified conditions.
Assuming the distribution is lognormal, and given (as input) an estimate of the variability
between different children (this is specified by the geometric standard deviation [GSD]), the
model calculates the expected distribution of blood lead values and estimates the probability that
any random child might have a blood lead value over the set target blood lead level (i.e., 5 [ig/dL).
3.2 ALM
The ALM (EPA 2003a, 2009), based on the work of Bowers etal. (1994), predicts the blood lead
level in a person with a site-related lead exposure by summing the baseline blood lead level
(PbBO) (that which would occur in the absence of any site-related exposures) with the increment
in blood lead that is expected as a result of increased exposure due to contact with a lead-
contaminated exposure medium. The latter is estimated by multiplying the average daily
absorbed dose of lead from site-related exposures by a biokinetic slope factor (BKSF). Thus, the
basic equation for exposure to lead in soil is:
PbB = PbBO + BKSF • CSOii,adj • IRsoii • AFSOii
where:
PbB = Geometric mean blood lead concentration ([ig/dL) in women of child-bearing age
who are exposed to the site
PbBO = Baseline geometric mean blood lead concentration ([ig/dL) in women of child-
bearing age in the absence of exposures to the site
BKSF = Biokinetic slope factor ([ig/dL blood lead increase per microgram per day lead
absorbed)
CSOii,adj = Average lead concentration in soil expressed in units of micrograms per gram
([ig/g), adjusted for the site-specific exposure frequency as described below in Section
3.3.2.
IRsoii = Intake rate of soil expressed in units of grams per day (g/day)
AFSoii = Absorption fraction of lead from soil (dimensionless)
As noted above, for the purposes of this interim lead risk evaluation, soil is the site-specific source
medium of primary interest for interim actions; however, risks from all exposure media (soil,
sediment, diet, water) will be evaluated as part of the Bonita Peak Mining District HHRA.
Once the geometric mean (GM) blood lead value in adult women who are exposed at the site is
calculated, the full distribution of likely blood lead values in the population of exposed individuals
can then be estimated by assuming the distribution is lognormal with a specified individual
B-3
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Appendix B, Part 1.1, Interim Chronic Lead Risk Evaluation •
geometric standard deviation (GSDi). The 95 th percentile of the predicted distribution is given by
the following equation (Aitchison and Brown 1957):
95th = GM • GSDii^s
3.3 Evaluation of Intermittent Exposures
Both the IEUBK model and the ALM are designed to evaluate exposures that are approximately
continuous (365 days per year). However, camper exposures are intermittent, occurring less than
365 days per year. When exposure is intermittent rather than continuous, the IEUBK model and
ALM can still be used by adjusting the site-related exposure concentration that occurs during the
exposure interval to a continuous exposure rate that yields the same total yearly exposure.
However, this adjustment is reasonable only in cases where exposure occurs with a relatively
constant frequency over a time interval long enough to establish an approximately steady-state
response (EPA 2003b). Short-term exposures are not suitable for approximations as continuous
exposures. To prevent applications of the lead models to exposure scenarios where an
adjustment from intermittent to continuous exposure is not appropriate, EPA (2003b)
recommends that these models only be applied to exposures that satisfy two criteria:
¦ The exposure frequency during the exposure interval is at least 1 day per week.
¦ The duration of the exposure interval is at least 3 consecutive months.
For the dispersed camper, the exposure frequency is based on the Guidelines for the San Juan
National Forest (U.S. Forest Service [USFS] 2017). As stated in these guidelines, campers are
permitted to camp in a National Forest for 14 days per month for 2 months. After they have been
in the forest for 28 days, campers are to leave the National Forest. Thus, the maximum allowable
camping time is 28 days per year. Lead risk assessments typically rely on central tendency
exposure2 (CTE) estimates. For the purposes of this interim lead risk evaluation, the exposure
frequency was assumed to be one-half the maximum allowable time (14 days per year), with
exposures occurring during consecutive summer months, for both the child camper and the older
child/adult camper. Thus, this exposure frequency meets the minimum criteria specified in EPA
(2003b).
Continuous exposures were determined such that they accounted for contributions from both
impacted soil while on-site and unimpacted (background) media while off-site as described
below.
3.3.1 IEUBK Model
For the IEUBK model, the average site soil lead concentration was adjusted by simulating a
continuous exposure as follows:
CtWA — [Csite EFsite + Cbkg ' (365-EFsite)]/365
2 CTE exposure estimates are intended to represent mean or median exposures for the population of interest (i.e.,
near the central portion of the range).
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Appendix B, Part 1.1, Interim Chronic Lead Risk Evaluation •
where:
Ctwa = Time-weigh ted average soil lead concentration (milligrams of lead per kilogram of
soil [mg/kg])
CSite = Average soil lead concentration across the dispersed campsites (mg/kg)
EFSite = Exposure frequency at dispersed campsites (days/year)
Cbkg = Background soil lead concentration in uncontaminated medium (mg/kg)
3.3.2 ALM
The same general approach followed for the IEUBK model is followed for the ALM, excluding the
contribution from background. This is because the PbBO term used in the ALM is intended to
represent background exposure to lead. Thus, the average site soil lead concentration was
adjusted as follows:
Cadj — Csite (EFsite/365)
where:
Cadj = Adjusted average soil lead concentration (|J.g/g)
CSite = Average soil lead concentration across the dispersed campsites (|J.g/g)
EFSite = Exposure frequency at dispersed campsites (days/year)
3.4 IEUBK Model Inputs
Table B-l presents the IEUBK input parameters used in this assessment. All model runs were
performed using IEUBK Version 1.1, Build 11. All input parameters are set equal to EPA IEUBK
defaults (EPA 1994), except as described below.
Soil Exposure Point Concentration
See Section 3.6 for a description of the exposure point concentration (EPC) for soil used in the
IEUBK model.
Relative Bioavailability
The default value of relative bioavailability (RBA) for lead in soil and dust assumed by the IEUBK
model is 0.60 (EPA 2007). Studies of lead RBA at a variety of mine sites suggests this is a typical
value, but values at some sites maybe higher or lower (EPA 2007). EPA measured the
bioavailability of lead in several roadway and waste rock samples collected within the mining
districts. The average site-specific RBA was 0.22, but RBA values were variable, ranging from 0 to
0.51, depending upon the sampling location (TechLaw, Inc. 2017). However, there are no
measured RBA data for soils collected from camping areas within the mining districts. Therefore,
the EPA default lead RBA value of 0.60 was assumed for this interim lead risk evaluation. This
assumption is likely to be conservative as site-specific RBA measurements suggest that lead is in a
form that is less readily absorbed. Based on a default absolute absorption fraction of 0.50 for lead
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Appendix B, Part 1.1, Interim Chronic Lead Risk Evaluation
in water and diet, this RBA corresponds to an absolute bioavailability of 0.30 (30%) to be used for
soil and dust in the IEUBK model.
Target Blood Lead Level Threshold
As discussed previously in Section 2, this interim lead risk evaluation will employ a PbB threshold
of 5 |J.g/dL. The goal is there should be no more than a 5% chance that a child will have a blood
lead value above 5 |J.g/dL, which is referred to as P5.
Maternal Blood Lead
As recommended by EPA (2017a), the IEUBK default maternal blood lead concentration 1.0
|ig/dL was changed to 0.8 |ig/dL.
Intake Rates
The residential water intake rates, inhalation rates, dietary intake rates, and soil/dust intake
rates were adjusted to be consistent with the values identified in the EPA Technical Review
Workgroup (TRW) Lead Consultation for the Colorado Smelter Superfund Site (EPA 2017b).
Because soil contact and intake during camping is higher than during typical residential
exposures, camping-specific average soil intake rates were obtained from the Exposure Factors
Handbook (EPA 2017c; Table 5-20). For the purposes of estimating exposures, a time-weighted
soil intake rate, which included both the residential and camping-specific values, was calculated
as follows:
IRtWA = [IRcamp ' EFsite + IRres • (365-EFsite)]/365
where:
IRtwa = Time-weighted soil/dust intake rate
IRcamp = Camping-specific soil/dust intake rate3
EFSite = Exposure frequency at dispersed campsites (days/year)
IRbkgres = Residential-specific soil/dust intake rate
Lead Drinking Water Concentration
As documented in the EPA TRW Lead Consultation for the Colorado Smelter Superfund Site (EPA
2017b), the default lead drinking water concentration was adjusted from 4 to 0.9 |ig/L, based on
the TRW re-analysis of the national drinking water system data reported to EPA.
Age Range
As recommended in EPA's Recommendations for Default Age Range in the IEUBK Model (EPA
2017d), the IEUBK default setting was adjusted to use an age range of 12 to 72 months rather
than 0 to 84 months.
3 Based on the average intake rate (as calculated from the geometric mean and standard deviation) across boys and
girls. See also Table B-l footnotes.
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Appendix B, Part 1.1, Interim Chronic Lead Risk Evaluation •
3.5 ALM Inputs
Lead risks for adult receptors (women of child-bearing age) were calculated using the ALM. Table
B-2 summarizes the ALM-specific input values used in this evaluation. Except for the absorption
fraction, all values are EPA-recommended defaults. The EPA TRW recommendations for ALM
(EPA 2003a) identify a default absorption fraction (AF) for soluble lead in soil of 0.20 but do not
specify AF values for other media. As described above for the IEUBK model, the lead RBA for soil
was assumed to be equal to the EPA default of 0.60. Based on this RBA, the AF for soil is:
AF(soil) = AF (soluble lead) • RBA = 0.20 • 0.60 = 0.12
See Section 3.6 for a description of the EPC for soil used in the ALM.
3.6 Concentration of Lead in Site Media
Camping area soil samples were collected using either a 30- or 5-point composite, depending on
size of the area, from a depth of 0 to 2 inches with plastic scoops after breaking up the soil with a
shovel. Samples were collected from 13 "dispersed" campsites4 in designated backcountry areas
located throughout the mining districts. Table B-3 presents a summary of the lead soil
concentrations for each dispersed campsite.
In accordance with EPA guidance (EPA 2000), when evaluating exposures from lead in soil, the
soil size fraction of interest is the fine (250 micrometers [[im] or less) size fraction. However,
most soil samples were not sieved prior to analysis; thus, sample results represent the bulk size
fraction (2 millimeters [mm] or less). There were only three soil samples from camping areas that
were sieved. These three samples indicate lead concentrations in the fine size fraction may be
about 1.17 times higher than the bulk size fraction. Therefore, lead concentrations for the fine
fraction were estimated based on measured bulk fraction concentrations using a camping area-
specific fines enrichment factor of 1.17 as follows:
Csoil,250[im — 1.17 • Csoil, 2 mm
where:
Csoii, 250 nm = Estimated lead concentration in soil for the fine (250 [im) fraction
(mg/kg)
CSoii, 2 mm = Measured lead concentration in soil for the bulk (2 mm) fraction
(mg/kg)
For the purposes of this lead evaluation, two exposure area scenarios were evaluated. The first
scenario evaluated exposures based on the average concentration across all the dispersed
campsites, which assumes a camper would frequent multiple dispersed campsites within the
mining districts over the camping exposure time. Inspection of Table B-3 shows there is
considerable variability in soil lead concentrations across the 13 campsites, with fine fraction
concentrations ranging from 86 to more than 51,000 mg/kg. Thus, the second scenario evaluated
4 A "dispersed" campsite is an area that is suitable for camping or where camping is known to occur but may not be a formal
campground. Soil from the USFS South Mineral Campground (CMP14) was not included in this evaluation because it will be
evaluated as a different type of camping exposure area in the Bonita Peak Mining District HHRA.
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Appendix B, Part 1.1, Interim Chronic Lead Risk Evaluation •
exposures on a campsite-by-campsite basis, which assumes a camper spends all their camping
exposure time at a single campsite location.
The basic time-weighted equations presented in Section 3.3 apply regardless of the scenario. For
illustration, the time-weighted soil concentration (for the fine size fraction) used in the IEUBK
model based on the mean concentration across all dispersed campsites is presented in Table B-l
and was calculated as follows:
Ctwa = [6,399 mg/kg • 14 days/year + 100 mg/kg • 351 days/year] / 365 days/year = 342 mg/kg
Likewise, the adjusted soil concentration used in the ALM based on the mean concentration
across all dispersed campsites is presented in Table B-2 and was calculated as:
Cadj = [6,399 mg/kg • 14 days/year] / 365 days/year = 245 mg/kg
Upland reference areas, located upgradient of the contamination sources in the mining districts,
were sampled using composite sampling (as 15-point composites). Only natural, undeveloped
areas not likely to be impacted by roads and other anthropogenic features that could be sources
of contamination were selected. A range of different upland vegetation communities, consisting of
sub-alpine forests and meadows and alpine meadows, were sampled. In total, 17 samples were
collected from four unique upland areas (two areas within the Upper Animas River watershed5
and two areas within the Mineral Creek watershed6) (TechLaw, Inc. 2018). The background soil
concentration of lead used in this evaluation was 100 mg/kg, which is approximately the 95%
upper confidence limit on the mean concentration across all the upland reference soil samples.
As noted previously, the focus of this interim lead risk evaluation is on exposures from soil. The
contribution of lead exposures from other media (e.g., diet, sediment, surface water) at the
dispersed campsites is likely to be much lower than from soil. Risks from all exposure media will
be evaluated as part of the Bonita Peak Mining District HHRA
4.0 Results
4.1 Risk Estimates
Potential risks from lead exposures for campers in the dispersed camping areas in the mining
districts are shown in Table B-4 (Panel A) (for young children) and Table B-5 (for fetuses of
pregnant women).
There is a 20% probability that PbB levels in young children will exceed 5 |J.g/dL (see Table B-4,
Panel A) based on the average across all dispersed campsites, which is above the selected health-
based goal (P5 < 5%). The campsite-specific evaluation shows there are four campsites where P5
is greater than 5%, including Campgrounds 2, 3, 4, and 7.
There is only 3% probability that PbB levels in fetuses will exceed 5 |J.g/dL (see Table B-5) based
on the average across all dispersed campsites, which is below the health-based goal. However, the
5 Collected near Clipper Mine and near Frisco/Bagley Tunnel
6 Collected near Koehler Tunnel and near Bandora Mine
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Appendix B, Part 1.1, Interim Chronic Lead Risk Evaluation •
campsite-specific evaluation shows two campsites, Campgrounds 4 and 7, as having P5 greater
than 5%.
4.2 Derivation of Interim Risk-Based Level
The primary risk driver for lead exposures is the child camper exposure scenario (as evidenced
by the fact the predicted P5 values are higher based on IEUBK than ALM). Thus, an interim risk-
based human health preliminary remediation goal (PRG) was calculated to ensure that post-
remedial exposure conditions would result in a P5 < 5% as determined based on IEUBK.
Recall the EPC used in the IEUBK model is a time-weighted soil lead concentration (Ctwa) that
accounts for both site and background exposure. Using the IEUBK input parameters specified in
Section 3.4, the Ctwa PRG must be 176 mg/kg or lower to achieve the target PbB of 5 |J.g/dL. The
corresponding Csite concentration is calculated by re-arranging the equation shown in Section
3.3.1 to solve for CSite while setting CTwa equal to 176 mg/kg and Cbkg equal to 100 mg/kg:
Csite = [(Ctwa * 365) - (Cbkg * (365 - EFsite))] / EFsite
where:
CSite = Average lead PRG across the dispersed campsites (mg/kg)
Ctwa = Time-weigh ted average soil lead PRG (176 mg/kg)
Cbkg = Background soil lead concentration (100 mg/kg)
EFsite = Exposure frequency at dispersed campsites (14 days/year)
Based on this calculation, to achieve the target PbB of 5 |J.g/dL, Csite must be 2,081 mg/kg or lower.
As illustrated in Panel B of Table B-4, if Csite is 2,081 mg/kg, the time-weighted EPC (Ctwa) is 176
mg/kg and the resulting P5 is 5%. Therefore, the interim human health risk-based level for lead
in soil at the dispersed campsites is 2,081 mg/kg. This risk-based level is based on the fine
fraction (250 [im); the corresponding soil lead risk-based level based on the bulk fraction (2 mm)
is 1,779 mg/kg. Inspection of Table B-l shows Campgrounds 2, 3, 4, and 7 have soil lead
concentrations above this interim risk-based level.
However, this risk-based level is based on an assumed default lead RBA of 0.6. As discussed
above, even though there are no data on site-specific RBA levels in the camping areas, EPA has
measured the bioavailability of lead in several roadway and waste rock samples. The average
site-specific RBA was 0.22, which suggests that lead in the mining districts is in a form that is less
readily absorbed. As illustrated in Panel B of Table B-4, if the actual RBA in the camping areas is
closer to 0.2, the risk-based level would be 11,598 mg/kg based on the fine fraction (250 [im).
Inspection of Table B-l shows only Campgrounds 4 and 7 have soil lead concentrations above
the risk-based level based on an RBA of 0.2.
Note these risk-based levels apply to the average soil lead concentration across an entire
campsite exposure area; it is not to be applied to individual samples within the campsite as a not-
to-exceed value.
%
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Appendix B, Part 1.1, Interim Chronic Lead Risk Evaluation •
5.0 Conclusion
Potential risks from lead exposures for campers in the dispersed camping areas in the mining
districts are above the selected health-based goal (P5 < 5%). Unacceptable lead exposures are
primarily attributable to elevated soil lead concentrations at four dispersed campsites —
Campgrounds 2, 3, 4, and 7.
For Campgrounds 2 and 3, the need for remedial action depends upon the site-specific RBA of
lead in soil. If the lead RBA is near the default (0.6), remedial action would be needed; if the lead
RBA is closer to the levels measured in roadway/waste rock samples (0.2), remedial action would
not be needed. On this basis, it is recommended that any decisions regarding actions at these two
campsites be delayed until site-specific measurements of RBA at the campsites can be completed.
For Campgrounds 4 and 7, the soil lead levels exceed the health-based goals for both children and
fetuses. In addition, P5 is expected to be greater than 5% at these two campsites, even if RBA
were assumed to be similar to levels measured in roadway/waste rock samples (0.2). On this
basis, it is recommended these two campsites be included for interim actions in 2018.
The interim risk-based levels for lead presented in this appendix is to be considered preliminary
for consideration in risk management decision-making in support of interim remedial actions
within the mining districts in 2018. The need for additional remediation will be determined after
the completion of the Bonita Peak Mining District HHRA.
6.0 References
Aitchison, J. andJ.AC. Brown. 1957. The Lognormal Distribution. University of Cambridge
Department of Applied Economics Monograph. Cambridge University Press.
Bowers, T.S., B.D. Beck, and H.S. Karam. 1994. Assessing the Relationship Between Environmental
Lead Concentrations and Adult Blood Lead Levels. Risk Analysis 14:183-189.
CDC (Centers for Disease Control and Prevention). 2012. CDC Recommendations for Children's
Blood Lead Levels (BLLs). Atlanta, Georgia: Centers for Disease Control and Prevention: Atlanta,
GA.
Colorado Geological Survey. 2017. San Juan County. Accessed at:
http://coloradogeologicalsurvey.org/mineral-resources/historic-mining-districts/san-juan-
county/ on Tune 20, 2017.
EPA. 2017a. Update to the Adult Lead Methodology's Default Baseline Blood Lead Concentration
and Geometric Standard Deviation Parameters and the Integrated Exposure Uptake Biokinetic
Model's Default Maternal Blood Lead Concentration at Birth Variable. U.S. Environmental
Protection Agency, Office of Land and Emergency Management. OLEM Directive 9285.6-56. May
17.
EPA. 2017b. Headquarters Lead Consultation Intake Form for the Colorado Smelter Superfund
Site. Submitted 4/11/17. https://semspub.epa.gov/work/08/1884173.pdf
B-10
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Appendix B, Part 1.1, Interim Chronic Lead Risk Evaluation •
EPA. 2017c. Update for Chapter 5 of the Exposure Factors Handbook, Soil and Dust Ingestion. U.S.
Environmental Protection Agency, Office of Research and Development EPA/600/R-17/384F.
September.
EPA. 2017d. Recommendations for Default Age Range in the IEUBK Model. U.S. Environmental
Protection Agency, Office of Land and Emergency Management. OLEM Directive 9200.2-177.
November 15.
EPA. 2016. Updated Scientific Considerations for Lead in Soil Cleanups. U.S. Environmental
Protection Agency, Office of Land and Emergency Management. OLEM Directive 9200.2-167.
December 22.
EPA. 2009. Update of the Adult Lead Methodology's Default Baseline Blood Lead Concentration and
Geometric Standard Deviation Parameters. U.S. Environmental Protection Agency, Office of
Superfund Remediation and Technology Innovation. OSWER 9200.2-82. June.
EPA. 2008. Child-Specific Exposure Factors Handbook. U.S. Environmental Protection Agency,
Office of Research and Development, National Center for Environmental Assessment. EPA/600/R-
06/096F. September.
EPA. 2007. Estimation of Relative Bioavailability of Lead in Soil and Soil-Like Material Using In Vivo
and In Vitro Methods. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency
Response. OSWER 9285.7-77. June.
EPA. 2003a. Recommendations of the Technical Review Workgroup for Lead for an Approach to
Assessing Risks Associated with Adult Exposures to Lead in Soil. Final. EPA-540-R-03-001. January.
EPA. 2003b. Assessing Intermittent or Variable Exposures at Lead Sites. U.S. Environmental
Protection Agency, Office of Solid Waste and Emergency Response. EPA-540-R-03-008. OSWER
#9285.7-76.
EPA. 2000. Short Sheet: TRW Recommendations for Sampling and Analysis of Soil at Lead (Pb) Sites.
EPA 540-F-00-010. April.
EPA. 1994. Guidance Manual for the Integrated Exposure Uptake Biokinetic Model for Lead in
Children. U.S. Environmental Protection Agency, Office of Emergency and Remedial Response.
EPA/540/R-93/081.
Goyer, R.A. 1990. Transplacental Transport of Lead. Environ. Health Perspect. 89:101-105.
TechLaw, Inc. 2017. Sampling Activities Report, 2016 Sampling Events; Bonita Peak Mining District
Site, San Juan/La Plata Counties, Colorado. Prepared by the Environmental Services Assistance
Team, TechLaw, Inc. for U.S. Environmental Protection Agency, Region 8. May.
TechLaw, Inc. 2018. Sampling Activities Report, 2017 Sampling Events, Bonita Peak Mining District
Site, San Juan/La Plata Counties, Colorado. Prepared by the Environmental Services Assistance
Team, TechLaw, Inc. for U.S. Environmental Protection Agency, Region 8.
B-ll
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Appendix B, Part 1.1, Interim Chronic Lead Risk Evaluation •
USFS (U.S. Forest Service). 2017. Guidelines for the San Juan National Forest. Available at:
https://www.fs.usda. gov/activity/saniuan/recreation/camping-cabins/?recid=42 72 8&actid=34
B-12
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TABLE B-l
IEUBK INPUT PARAMETERS
Focused Feasibility Study, Bonita Peak Mining District
Panel A. Age-Independent Values
Parameter Value Basis
Soil concentration
(mg/kg)
site
6,399
Mean across all dispersed campsites (see Table B-l)
background
100
Assumed based on site-specific upland reference3
time-weighted
342
Time-weight adjustedb
Drinking water concentration (ng/L)
0.9
EPA (2017d)
Indoor dust concentration
249.4
Cdust = (0.7 x Csoil) + (100 x Cair,out) (IEUBK default; EPA
1994)
Outdoor air concentration (^g/m3)
0.1
IEUBK default (OSWER 9285.7-22; EPA 1994)
Indoor air concentration (^g/m3)
30% of outdoor
IEUBK default (OSWER 9285.7-22; EPA 1994)
Exposure frequency [EF] (days/year)
14
USFS (2017); one-half maximum allowable time
Absorption fraction [AF] (water)
0.50
IEUBK default (OSWER 9285.7-22; EPA 1994)
Absorption fraction [AF] (diet)
0.50
IEUBK default (OSWER 9285.7-22; EPA 1994)
Relative bioavailability [RBA] (soil)
0.60
EPA default (OSWER 9285.7-80; EPA 2007)
Absorption fraction [AF] (soil,dust)
0.30
AF(soil) = AF(water) x RBA(soil)
Absorption fraction [AF] (air)
0.32
IEUBK default (OSWER 9285.7-22; EPA 1994)
Fraction of soil + dust that is soil
0.45
IEUBK default (OSWER 9285.7-22; EPA 1994)
Geometric standard deviation [GSD]
1.6
IEUBK default (OSWER 9285.7-22; EPA 1994)
Maternal PbB concentration (^g/dL)
0.8
EPA default (OLEM 9285.6-56; EPA 2017a)
Target PbB concentration (^g/dL)
5.0
CDC (2012); professional judgment
Panel B. Age-Dependent Values
Airc
Diet'
Water'
Soil and Dust
Age
Time Outdoors
(hours)
Ventilation Rate
(m3/day)
Dietary Intake
(Hg lead/day)
Water Intake
(L/day)
Residential Intake
Rate (g/day)c
Campground
Intake Rated
(g/day)
Time-weighted
Intake Rate6
(g/day)
0-12 mo (0-1 yrs)
1.0
3.22
2.66
0.40
0.086
0.38 f
0.097
12-24 mos (1-2 yrs)
2.0
4.97
5.03
0.43
0.094
0.38
0.105
24-36 mos (2-3 yrs)
3.0
6.09
5.21
0.51
0.067
0.43
0.081
36-48 mos (3-4 yrs)
4.0
6.95
5.58
0.54
0.063
0.16
0.067
48-60 mos (4-5 yrs)
4.0
7.68
5.64
0.57
0.067
0.16
0.071
60-72 mos (5-6 yrs)
4.0
8.32
6.04
0.6
0.052
0.20 g
0.058
72-84 mo (6-7 yrs)
4.0
8.89
5.95
0.63
0.055
0.20 g
0.061
Notes:
[a] Based on 95% upper confidence limit on the mean concentration for the site-specific upland reference dataset.
[b] C(adjusted) = C(site) • (EF/365) + C(background) ¦ ((365-EF)/365)
[c] Values are based on Colorado Smelter Lead Consultation letter (EPA 2017b)
[d] Values are based on campground-specific soil intake rates from Exposure Factors Handbook (EPA 2017c), Table 5-20 (averaged across girls and boys). Arithmetic
mean calculated from geometric mean (GM) and geometric standard deviation (GSD) as: GM * EXP(0.5 * LN(GSD)A2).
[e] IR(adjusted) = IR(campground) ¦ (EF/365) + IR(residential) ¦ ((365-EF)/365)
[f] No values for 0-1 years provided; assumed to be equal to 1-2 years intake rate.
[g] No values for >5 years provided; assumed to be equal to intake rate across all age groups.
|ig lead/day = micrograms of lead per day
|ig/dL= micrograms of lead per deciliter of blood
|ig/L= micrograms per liter of water
|ig/m3 = micrograms per cubic meter of air
CDC = Centers for Disease Control
Cdust = dust concentration
Csoil = soil concentration
EPA= U.S. Environmental Protection Agency
g/day = grams of soil per day
IEUBK = Integrated Exposure Uptake Biokinetic
L/day = liters of water per day
m3/day = cubic meters of air per day
mg/kg = milligrams of lead per kilogram of soil (or dust)
OSWER = Office of Solid Waste and Emergency Response
PbB = blood lead
USFS = U.S. Forest Service
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TABLE B-2
ADULT LEAD MODEL INPUT PARAMETERS
Focused Feasibility Study, Bonita Peak Mining District
Parameter
Units
Value
Source
Notes
Baseline geomean PbB [PbBO]
Hg/dL
0.6
NHANES 2009-2014
Biokinetic slope factor [BKSF]
Hg/dL per ng/day
0.4
EPA (2003a)
EPA ALM default
Ratio
--
0.9
EPA (2003a)
EPA ALM default
Target PbB (fetus)
Hg/dL
5.0
CDC (2012)
Professional judgement
Target PbB (mother)
Hg/dL
5.6
Calculated
Target PbB (fetus) / Ratio
Geometric std. deviation [GSD]
-
1.8
NHANES 2009-2014
Exposure Frequency [EF]
days/year
14
USFS (2017)
One-half maximum allowable time
Soil Concentration:
site
adjusted
Hg/g
Hg/g
6,399
245
Site-specific (see Table B-l)
Exposure frequency adjusted
Mean across all dispersed campsites
Csite * EF / 365 days/year
Soil Ingestion Rate [IRsoil]
g/day
0.1
Professional judgment
CTE exposure parameter
Soil relative bioavailability [RBAsoil]
--
0.60
EPA (2007)
EPA ALM default
Soil absorption fraction [AFsoil]
--
0.12
Calculated; EPA (2003a)
0.2 (default) * 0.6 (RBAsoil)
Basic Equations:
PbB(mother) = PbBO + BKSF * Csoil,adj * IRsoil *AFsoil
PbB(fetus) = PbB(mother) * Ratio
IJg/d = micrograms of lead per day
l_ig/dL = micrograms of lead per deciliter of blood
Hg/g = micrograms of lead per gram of soil
ALM = Adult Lead Methodology
C = concentration
CDC = Centers for Disease Control
CTE = central tendency exposure
days/year = days per year
EPA = U.S. Environmental Protection Agency
g/day = grams of soil per day
NHANES = National Health and Nutrition Examination Survey
PbB = blood lead
USFS = U.S. Forest Service
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TABLE B-3
SOIL LEAD CONCENTRATIONS IN DISPERSED CAMPSITES
Focused Feasibility Study, Bonita Peak Mining District
Dispersed
Campsite
ID
Sample ID
Sample Date
Soil Lead Cone, (mg/kg)
2 mm
250 nm
CMP2
MH1E13
7/26/2016
2,880
3,370
_[a]_
CMP3
A8M5-4732
9/27/2017
7,260
8,494
_[a]_
CMP4
MH1E14
7/26/2016
44,200
51,714
_[a]_
CMP5
MH1E15
7/26/2016
200
234
_[a]_
CMP7
MH1E16
7/26/2016
11,800
13,806
_[a]_
CMP8
A8M5-4733
9/27/2017
1,320
1,544
_[a]_
CMP9
MH1E17
7/27/2016
1,330
1,556
_[a]_
CMP10
MH1E18
7/27/2016
74
86
_[a]_
CMP11
MH1E19
7/28/2016
431
480
M
CMP12
MH1E21
7/27/2016
257
276
J5I
CMP13
MH1E23
7/28/2016
100
117
_[a]_
CMP15
MH1E26
7/28/2016
530
620
_[a]_
CMP15A
MH1L12
9/28/2016
761
890
[a]
mean: 6,399
[a] Estimated based on camping area-specific fines enrichment factor of
1.17:
^soil, 250-|im — ^-7 " ^soil, 2-mm
[b] Measured
Hm = micrometers
Cone. = concentration
ID = identification
mg/kg = milligrams per kilogram soil
mm = millimeters
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TABLE B-4
EVALUATION OF RISK FROM LEAD USING THE IEUBK MODEL
Focused Feasibility Study, Bonita Peak Mining District
Panel A. Exposure at Dispersed Campsites
Exposure Location
Soil Lead Concentration (mg/kg)
Time-
Site Bkg weighted
EPCa
P5 (% Above
Target Blood
Lead of 5 |ig/dL)
Dispersed Campsites - all
6,399
100
342
20%
CMP2
3,370
100
225
9%
CMP3
8,494
100
422
29%
CMP4
51,714
100
2,080
97%
CMP5
234
100
105
2%
CMP7
13,806
100
626
52%
CMP8
1,544
100
155
4%
CMP9
1,556
100
156
4%
CMP10
86
100
99
1%
CMP11
480
100
115
2%
CMP12
276
100
107
2%
CMP13
117
100
101
1%
CMP15
620
100
120
2%
CMP15A
890
100
130
3%
Panel B. Derivation of Risk-based Cleanup Level
greater than 5%
Soil Lead Concentration (mg/kg)
P5 (% Above
Target Blood
Lead of 5 |ig/dL)
Exposure Location
(RBA)
Site
Bkg
Time-
weighted
EPCa
Camping Area (RBA=0.6)
2,081
100
176
5.0%
Camping Area (RBA=0.2)
11,598
100
541
5.0%
risk-based level for site
Notes:
[a] C(adjusted) = C(site) ¦ (EF/365) + C(bkg) ¦ ((365-EF)/365)
% = percent
Hg/dL = micrograms per deciliter
C(bkg) = soil lead concentration for background
C(site) = soil lead concentration for the site
EF = exposure frequency (days per year)
EPC = exposure point concentration
IEUBK = Integrated Exposure Uptake Biokinetic
mg/kg = milligrams lead per kilogram soil
RBA = relative bioavailability
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TABLE B-5
ADULT LEAD MODEL OUTPUT
Focused Feasibility Study, Bonita Peak Mining District
Exposure Location
Csoil, site
Absorbed
dose from
soil
GM PbB
(mother)
mu [ln(GM
PbB mother)]
sigma
[In(GSD)]
P5 (fetus)
Hg/g
Hg/day
Hg/dL
%
Dispersed Campsites - all
6,399
2.95
1.8
0.58
0.59
3%
CMP2
3,370
1.55
1.2
0.20
0.59
<0.01%
CMP3
8,494
3.91
2.2
0.77
0.59
5%
CMP4
51,714
23.80
10.1
2.31
0.59
85%
CMP5
234
0.11
0.6
-0.44
0.59
<0.01%
CMP7
13,806
6.35
3.1
1.14
0.59
17%
CMP8
1,544
0.71
0.9
-0.12
0.59
<0.01%
CMP9
1,556
0.72
0.9
-0.12
0.59
<0.01%
CMP10
86
0.04
0.6
-0.48
0.59
<0.01%
CMP11
480
0.22
0.7
-0.37
0.59
<0.01%
CMP12
276
0.13
0.7
-0.43
0.59
<0.01%
CMP13
117
0.05
0.6
-0.48
0.59
<0.01%
CMP15
620
0.29
0.7
-0.34
0.59
<0.01%
CMP15A
890
0.41
0.8
-0.27
0.59
<0.01%
greater than 5%
% = percent
Hg/day = micrograms of lead per day
Hg/dL= micrograms of lead per deciliter of blood
Hg/g = micrograms of lead per gram of soil
Csoil, site = soil lead concentration for the site
GM = geometric mean
GSD = geometric standard deviation
PbB = blood lead
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APPENDIX B - PART 1.2
HUMAN HEALTH ACUTE ARSENIC SCREENING LEVELS
-------
Appendix B - Part 1.2
Human Health Acute Arsenic Screening Levels
1.0 Introduction
This appendix describes an interim evaluation of potential arsenic risks from exposures to
arsenic in soil/waste rock at the Bonita Peak Mining District Superfund Site (Site) located in
southwestern Colorado. The Site consists of 48 historic mines or mining-related sources where
ongoing releases of metal-laden water and sediments are occurring within the Mineral Creek,
Cement Creek, and Upper Animas River drainages in San Juan County, Colorado. Drainages within
the Site contain over 400 abandoned or inactive mines where large- to small-scale mining
operations occurred. San Juan County is comprised of 10 historic mining districts (Colorado
Geological Survey 2017). Historic mining districts within the Mineral Creek, Cement Creek, and
Upper Animas River drainages (referred to as "the mining districts" in this appendix) include
Animas, Animas Forks, Cement Creek, Eureka, Ice Lake Basin, and Mineral Point
Acute screening levels have been developed for consideration in the identification of areas that
may warrant interim remedial actions in 2018. These levels are to be considered preliminary and
subject to change pending completion of the Bonita Peak Mining District human health risk
assessment (HHRA).
Arsenic was selected for evaluation because soil concentrations are notably elevated at several
locations within the mining districts and arsenic is often an important human health risk driver
for mining-related contamination. The camping scenario was selected for the derivation of acute
screening levels because the camper is anticipated to be the most sedentary of receptors (i.e., not
moving about being exposed to a variety of soil/mine waste sources, in contrast with hiker,
hunter, fisherman, all-terrain vehicle rider/guide, and road worker receptors). Derivation of
screening levels for a sedentary receptor allows for the application of these screening levels to
smaller exposure areas, such as individual campgrounds.
In addition, focus was placed on exposures to children because children are often more
vulnerable to pollutants than adults due to differences in behavior and biology that can lead to
greater exposure and/or unique windows of susceptibility during development Additionally, soil
ingestion rates for young children are higher than adults due to increased frequency of contact
through hand-to-mouth or object-to-mouth activity. Thus, exposure parameters used in the
derivation of the acute screening levels were tailored for children 1 to 3 years old depending on
the exposure scenario. Three exposure scenarios for a child that may camp within the mining
districts were evaluated:
¦ Scenario 1: Child, based on central tendency exposure (CTE) residential soil intake rates
identified in the EPA Technical Review Workgroup (TRW) Lead Consultation for the
Colorado Smelter Superfund Site (EPA 2017a)
¦ Scenario 2: Child, based on CTE soil intake rates specific to a camping exposure scenario
(EPA 2017b)
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Appendix B, Part 1.2, Human Health Acute Arsenic Screening Levels •
¦ Scenario 3: Child, based on reasonable maximum exposure (RME) soil intake rates specific
to a camping exposure scenario (EPA 2017b)
Potential risks to a variety of recreational and occupational receptor populations from all
contaminants of interest and all exposure media and pathways will be evaluated as part of the
Bonita Peak Mining District HHRA.
2.0 Derivation of Acute Screening Levels
As noted above, acute screening levels have been developed for multiple exposure scenarios
resulting in a range of acute screening levels for consideration in risk management decision-
making. The sections below present the approach and assumptions used in the derivation of the
acute screening levels for arsenic for application to soil/waste rock.
Acute screening levels were developed based on exposure durations of 2 days and 14 days. An
exposure duration of 2 days represents a camping duration of a weekend, while 14 days
represents the maximum allowable time that may be spent camping in one location in the
National Forest (U.S. Forest Service [USFS] 2017).
2.1 Toxicity Data
Acute toxicity information is generally lacking for arsenic, and acute arsenic screening levels
specific to the type of receptors present within the mining districts (i.e., recreational visitors) are
not available. A review of Toxicological Profile for Arsenic developed by the Agency for Toxic
Substances and Disease Registry (ATSDR) reveals oral doses as low as 0.02 to 0.06 milligrams of
arsenic per kilogram body weight per day (mg/kg BW/day) have been reported to cause toxic
effects in some individuals (ATSDR 1989). Severe exposures can result in acute encephalopathy,
congestive heart failure, stupor, convulsions, paralysis, coma, and death. The acute lethal dose to
humans has been estimated to be about 0.6 mg/kg BW/day (ATSDR 1989).
Washington State Department of Health (WSDOH) provides a synopsis of published scientific
information related to soil exposure and acute toxicity in Hazards of Short-term Exposure to
Arsenic Contaminated Soil (WSDOH 1999). The most sensitive reported indicators of acute
toxicity appear to be edema, conjunctivitis, liver enlargement, irritation of the mucous
membranes, and gastrointestinal problems, such as vomiting, diarrhea, cramps, and pain.
Transient adverse health effects commonly occur when doses between 0.035 and 0.071
milligrams of arsenic per kilogram of body weight (mg/kg BW) are ingested. The best estimate of
an acute threshold for transient effects is 0.05 mg/kg BW.
Using the acute transient effect dose information, acute arsenic screening levels can be derived
for each of the three exposure scenarios. The equation used to derive the acute screening levels is
as follows:
ASLas = (ATE / SF) / (IR / CFm / BW • ED • RBA)
where:
ASLas = Acute screening level for arsenic (mg/kg soil)
B-2
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Appendix B, Part 1.2, Human Health Acute Arsenic Screening Levels •
ATE = Acute transient effect (mg/kg BW)
SF = Toxicity safety factor (unitless)
IR = Soil intake rate (g soil/day)
CFir = Conversion factor for intake rate, convert g to kg
BW = Body weight (kg BW)
ED = Exposure duration (days)
RBA = Relative bioavailability
2.2 Exposure Data
Table B-l presents the general input parameters used to derive the acute screening levels for
arsenic, recognizing that several of the assumptions may differ from those typically used in an
evaluation of chronic exposures.
Table B-l. General Parameters Used to Calculate the Acute Arsenic Screening Levels
Parameter
Value
Source
Receptor gender
Female
EPA 2008 (Table 8-10)
Acute transient effect dose
0.05
WSDOH 1999
(mg arsenic/kg body weight)
Toxicity safety factor
(unitless)
10
WSDOH 1999
RBA
0.1
TechLaw (2017)
mg- milligrams
kg - kilograms
RBA - relative bioavailability
The rationale for the selection of each input provided in Table B-l is presented below:
¦ Receptor gender - A female receptor was selected because female children have a lower
body weight than male children (EPA 2008). A receptor with a lower body weight is more
sensitive to exposure compared to a receptor with a higher body weight
¦ Acute transient effect dose - The best estimate acute transient effect dose was selected to
represent the dose at which edema, conjunctivitis, liver enlargement, irritation of the
mucous membranes, and/or gastrointestinal problems (vomiting diarrhea, cramps, and
pain) may occur (WSDOH 1999).
¦ Toxicity safety factor - A no-effect level is typically estimated by dividing the dose observed
to cause health effects by a safety factor. There is little scientific information available to
guide the selection of a safety factor for short-term exposure to arsenic in soil. The
selection must be based on judgement of the margin of safety desired for protection from
the potential adverse consequences of this type of event. For the three scenarios, a safety
factor of 10, to derive a no-effect level from an acute effect level, was considered adequate
to calculate soil arsenic concentrations protective of human health. This choice was based
B-3
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Appendix B, Part 1.2, Human Health Acute Arsenic Screening Levels >
on consideration of documented variability in human sensitivity to the toxic effects of
arsenic as well as consideration of likelihood of occurrence of the various scenarios
(WSDOH 1999).
¦ RBA - Arsenic RBA was determined by measuring in vitro bioaccessability for roadway and
waste rock samples collected within the mining districts. The mean estimate of RBA for
arsenic was 0.06, with values ranging from 0.03 to 0.11 (TechLaw, Inc. 2017). There was
little difference in mean RBA between these two media types (0.08 for roadway samples
and 0.05 for waste rock samples). To simplify this evaluation and to be conservative, an
RBA of 0.1 was selected for use in the calculations. The implications of this simplifying
assumption are discussed further below.
Table B-2 presents the scenario-specific input parameters used to derive the acute screening
level for arsenic.
Table B-2. Scenario-Specific Parameters Used to Calculate the Acute Arsenic Screening Levels
Parameter
Scenario 1
CTE Resident
Scenario 2
CTE Camping
Scenario 3
RME Camping
Source
Soil intake rate during
exposure (g soil/day)
0.094
0.367
1.592
Scenario 1: EPA 2017a
Scenario 2 & 3: EPA 2017b (Table 5-20)
Receptor age at exposure
1 year old
2 years old
2 years old
EPA 2017b (Table 5-20)
Receptor body weight (kg)
11.0
12.5
12.5
EPA 2008 (Table 8-10)
CTE - central tendency exposure
g-grams
kg - kilograms
RME - reasonable maximum exposure
The rationale for the selection of each input provided in Table B-2 is presented below:
¦ Soil intake rate during exposure - Multiple soil intake rates were selected for use to present
a range of acute screening levels. In each case, the most conservative soil intake rate
available for each scenario was selected so that the most sensitive receptor was used in the
model.
• Scenario 1 - The soil intake rate selected for a CTE resident was 0.094 grams per day
(g/day). This value was selected because it is the highest mean intake rate provided in
the EPA TRW Lead Consultation for the Colorado Smelter Superfund Site (EPA 2017a)
for children under the age of 6 years. This value corresponds to a 1-year-old to 2-year-
old receptor.
• Scenario 2 - The soil intake rate selected for a CTE child while camping was 0.367
g/day because this is the highest geometric mean intake rate provided in the Exposure
Factors Handbook (EPA 2017b, Table 5-20). This value corresponds to a 2-year-old to 3-
year-old girl. The study upon which this value is based evaluated soil intake using a
tracer element methodology for 78 children aged 1 to 5 years old at campgrounds (Van
W'ijnen et al. 1990).
B-4
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Appendix B, Part 1.2, Human Health Acute Arsenic Screening Levels •
• Scenario 3 - The soil intake rate selected for an RME child while camping was 1.592
g/day because this is the 95th percentile (computed using the reported geomean and
geometric standard deviation) for the intake rates provided for the 2-year-old to 3-
year-old girl (EPA 2017, Table 5-20).
¦ Receptor age at exposure - The age at exposure was a 1 year old for Scenario 1, and 2 years
old for Scenarios 2 and 3.
¦ Receptor body weight - The receptor body weight was selected to correlate to the age and
gender of the receptor. The mean female body weights for a 1-year old and 2-year old were
selected (EPA 2008, Table 8-10).
2.3 Screening Levels
Table B-3 presents the acute screening levels for arsenic based on a 2-day and 14-day exposure
to soil/waste rock that were derived based on the inputs provided in the tables above and for the
scenarios that have been described.
Table B-3. Acute Arsenic Screening Levels (mg/kg)
Scenario
2-Day Exposure
14-Day Exposure
Scenario 1
2,926
418
Scenario 2
851
122
Scenario 3
196
28
mg/kg - milligrams per kilogram
Table B-4 presents a comparison of the acute arsenic screening levels with varying RBA values
(0.1 versus 0.06) to demonstrate the change in the screening level if a lower RBA value were
used. As seen, the change in screening level is inversely proportional to the change in RBA;
decreasing the RBA by a factor of 1.7 increases the screening level by 1.7.
Table B-4. Effect of Using a Different RBA Value on Acute Arsenic Screening Levels (mg/kg)
2-Day Exposure
14-Day Exposure
Scenario
RBA = 0.1
RBA = 0.06
RBA = 0.1
RBA = 0.06
Scenario 1
2,926
4,876
418
697
Scenario 2
851
1,419
122
203
Scenario 3
196
327
28
47
mg/kg - milligrams per kilogram
RBA - relative bioavailability
3.0 Conclusions
A range of screening levels have been provided based on the understanding there may be
differences in the applicable exposure scenario depending upon the type of location being
evaluated. When identifying potential locations where interim actions may be needed, the
appropriate screening level (i.e., 14-day versus 2-day) will depend upon the type and duration of
exposure that may reasonably be anticipated to occur at the location of interest. For example, the
14-day screening level should be used when evaluating established campgrounds and areas
where extended camping may occur (e.g., the dispersed campsites), whereas the 2-day screening
B-5
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Appendix B, Part 1.2, Human Health Acute Arsenic Screening Levels >
level should be used when evaluating other types of potential recreational use areas. When
evaluating locations, such as the camping areas, where site-specific RBA data are not available,
assuming a higher RBA of 0.1 is most appropriate; however, when evaluating locations where
site-specific RBA data are applicable, such as the waste rock areas, use of the average RBA of 0.06
is most appropriate.
Figure B-l illustrates a comparison of measured soil/waste rock arsenic concentrations to the
acute screening levels for Scenarios 1, 2, and 3. For reference, measured concentrations from
upland reference locations are also shown. The site-specific upland reference soil dataset
includes 17 samples collected from natural, undeveloped areas within the mining districts not
likely to be impacted by roads and other anthropogenic features that could be sources of
contamination.
Figure B-l. Comparison of Soil/Waste Rock Arsenic Concentrations to Acute Screening Levels
• Arsenic Result
Scenario 1
Scenario 2
Scenario3
• •
• •
Camping Areas Waste Rock Upland Reference Soil
[14-day, RBA=0.1) [2-day, RBA=0.06]
Screening Levels:
Scenario 1 = Residential CTE soil intake rates
Scenario 2 = Camping-specific CTE soil intake rates
Scenario 3 = Camping-specific RME soil intake rates
CTE = central tendency exposure
mg/kg = milligrams per kilogram
RBA = relative bioavailability
RME = reasonable maximum exposure
Scenarios 2 and 3 employ camping-specific intake rates, which are likely to be more applicable to
the recreational scenarios of interest within the mining districts. Thus, these scenarios were
selected in preference to Scenario 1. For the purposes of this evaluation, Scenario 2 (based on
CTE intake rates) was selected in preference to Scenario 3 (based on RME intake rates). This is
B-6
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Appendix B, Part 1.2, Human Health Acute Arsenic Screening Levels •
because this focused evaluation is seeking to address those areas where exposures may be
greatest, even for those individuals with "typical" intake rates. In addition, it appears the 14-day
screening levels for Scenario 3 may be overly conservative in consideration of local background
levels of arsenic. Inspection of the site-specific upland reference soil dataset shows background
arsenic soil concentrations ranges from about 2 to 26 mg/kg (mean of 11 mg/kg) (TechLaw, Inc.
2018), whereas the 14-day Scenario 3 screening level is 28 mg/kg. It is not expected that
naturally occurring levels of arsenic would approach an acutely toxic threshold based on a short-
term exposure scenario. On this basis, it is recommended interim action determinations be based
on the Scenario 2 screening levels.
When soil/waste rock arsenic concentrations are compared to Scenario 2 screening levels (see
grey line series in Figure B-l), there are no camping area samples that are above the 14-day level
(122 mg/kg at RBA of 0.1), butthere are several samples from waste rock areas above the 2-day
level (1,419 mg/kg at RBA of 0.06). Indeed, there are three locations - Koehler Tunnel, Junction
Mine, and Longfellow Mine - where arsenic concentrations in waste rock are higher than 1,000
mg/kg.
The acute screening levels for arsenic presented in this appendix are to be considered
preliminary for consideration in risk management decision-making in support of interim
remedial actions within the mining districts in 2018. The need for additional remediation will be
determined after the completion of the Bonita Peak Mining District HHRA.
4.0 References
ATSDR (Agency for Toxic Substances and Disease Registry). 1999. Toxicological Profile for Arsenic.
Atlanta, Georgia: Agency for Toxic Substances and Disease Registry, U.S. Public Health Service.
ATSDR/TP-88/02.
Colorado Geological Survey. 2017. San Juan County. Accessed at:
http://coloradogeologicalsurvey.org/mineral-resources/historic-mining-districts/san-iuan-
county/ on Tune 20, 2017.
EPA (U.S. Environmental Protection Agency). 2008. Child-Specific Exposure Factors Handbook. U.S.
Environmental Protection Agency. EPA/600/R-06/096F.
https://cfpub.epa. gov/ncea/risk/recordisplay.cfm?deid=199243.
EPA. 2017a. Headquarters Lead Consultation Intake Form for the Colorado Smelter Superfund
Site. Submitted 4/11/17. https://semspub.epa.gov/work/08/1884173.pdf
EPA. 2017b. Update for Chapter 5 of the Exposure Factors Handbookf, Soil and Dust Ingestion. U.S.
Environmental Protection Agency, Office of Research and Development EPA/600/R-17/384F.
September.
TechLaw, Inc. 2017. Sampling Activities Report, 2016 Sampling Events, Bonita Peak Mining District
Site, San Juan/La Plata Counties, Colorado. Prepared by the Environmental Services Assistance
Team, TechLaw, Inc. for U.S. Environmental Protection Agency, Region 8. May.
%
B-7
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Appendix B, Part 1.2, Human Health Acute Arsenic Screening Levels •
TechLaw, Inc. 2018. Sampling Activities Report, 2017 Sampling Events, Bonita Peak Mining District
Site, San Juan/La Plata Counties, Colorado. Prepared by the Environmental Services Assistance
Team, TechLaw, Inc. for U.S. Environmental Protection Agency, Region 8.
USFS (U.S. Forest Service). 2017. San Juan National Forest Guidelines for Dispersed Camping,
accessed December 18, 2017, at https://www.fs. usda.gov/activity/saniuan/recreation/camping-
cabins/?recid=42 72 8&actid=3 4.
Van W'ijnen, J.H.; P. Clausing, and B. Brunekreff. 1990. Estimated soil ingestion by children.
Environmental Research 51:147162.
WSDOH (Washington State Department of Health). 1999. Hazards of Short-Term Exposure to
Arsenic Contaminated Soil. Washington State Department of Health, accessed February 13, 2018,
at: https://www.doh.wa.gOv/Portals/l/Documents/Pubs/334-284.pdf
B-8
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APPENDIX B - PART 2
ECOLOGICAL RISK TECHNICAL MEMORANDUM
-------
05/11/18
To: Rebecca Thomas, Remedial Project Manager, USEPA Region 8
From: Andrew Todd, PhD, Aquatic Toxicologist, USEPA Region 8
Subject: Ecological Risk Technical Memorandum- Proposed Interim Remedial Actions in the
Bonita Peak Mining District
Rebecca,
Per your request, this technical memorandum was drafted to summarize the potential for
reduction of ecological risk associated with the Interim Remedial Action proposed to take place
within the Bonita Peak Mining District ("Site") Superfund Site in San Juan County, Colorado. In
the following analysis, I have considered these proposed actions through the lens of their role in
contributing to ecological risk within the Site. Of note, because the terrestrial ecological risk
assessment for the Site is currently in the early stages of development, this memorandum will
focus on the potential for reduction of aquatic ecological risk through the proposed Interim
Remedial Action.
Background
The Animas River and many of its tributaries have high concentrations of inorganic
contamination in the surface water and sediment originating both from legacy mining-related
sources as well as from natural sources not directly attributable to mining. Elevated metals
concentrations in surface waters and sediments can pose significant risk to potentially resident
aquatic organisms through a variety of mechanisms, including through both acute and chronic
toxicity.
Past efforts to assess existing risk to aquatic ecosystems within the Animas River watershed are
documented in the Draft Baseline Ecological Risk Assessment ("Draft BERA") for the Upper
Animas Mining District (USEPA 2015). The spatial scope of that investigation considered the
mainstems of the Animas River, Cement Creek, and Mineral Creek near their respective
confluences in the town of Silverton, as well as the Animas River from Silverton downstream to
Baker's Bridge north of Durango.
The Draft BERA evaluated several lines of evidence in quantifying ecological risk to the Animas
River, including:
• Comparison of metal concentrations measured in site environmental media (surface
water, sediment, pore water) to known toxicity thresholds
• Toxicity testing exposing aquatic organisms within a controlled laboratory environment
to site environmental media
• Assessment of aquatic community characteristics in the field [e.g. quantifying fish and
benthic macroinvertebrate (BMI) populations and locations]
1
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The Draft BERA reached several conclusions regarding mining-related risk to the aquatic
ecosystems in the Animas River watershed. Initially, all lines of evidence indicated that benthic
macroinvertebrate communities are currently impaired in most of the reaches of the Animas
River that were evaluated. Similarly, the Draft BERA concluded that fish communities in the
evaluated reaches of the Animas River, Cement Creek, and Mineral Creek are either non-existent
or highly stressed due to high metals concentrations.
For the sake of simplification, in considering how the proposed Interim Remedial Action will
affect aquatic ecological risk within the Animas River and tributaries, this memorandum will
focus primarily on fish. As noted above, BMI communities in most reaches of the Animas are
currently at risk as well. However, because many of the factors limiting these BMI communities
are similar to those limiting fish communities (e.g. acute and chronic toxicity of metals), it is
expected that the instream BMI communities would respond in a similar fashion as fish to
reductions in metal loading.
Known Fisheries in the upper Animas River and Tributaries
Routine fish sampling has been conducted by Colorado Parks and Wildlife ("CPW") within the
Animas River below its confluence with Mineral Creek and downstream to the city of Durango.
In the reach immediately below Silverton, CPW has three sampling locations (A-72, Elk Park,
and Teft Spur), collectively referred to as Animas River #3. CPW has an additional long-term
fishery sampling site on the Animas River at Howardsville (Animas River #4). Figure 1
illustrates inter-annual trends of the brook trout fishery in the Animas River at Howardsville and
the three sites immediately below Silverton.
At CPW's Howardsville site, densities of brook trout at this location have fluctuated over the
years, but have remained relatively stable over the past two decades (1998, 2005, 2010, 2014,
and 2015 sampling events) (Figure 1). The water quality at this site reflects metal loading from
upper Animas sources, including proposed Interim Remedial Action locations in the Burrows
Gulch, Animas Forks, and Eureka areas.
CPW's A-72 site is the closest to Silverton, and has been documented to be essentially devoid of
fish (5 brook trout per mile were found in 2005) (Figure 1). The water quality at this site (and all
sites within CPW's Animas River #3 section) reflects metal loading from the Animas River,
Cement Creek, and Mineral Creek drainages, including all of the proposed Interim Remedial
Action locations.
CPW's Elk Park Site is located approximately 5 miles downstream of A-72, and just upstream of
Elk Creek. As opposed to A-72, this site sustained a brook trout fishery of between 70 - 90 fish
per mile through sampling in 2005. After that point, brook trout populations have been
significantly reduced (although 2 brook trout were captured in 2015) (Figure 1).
At CPW's Teft Spur site, fisheries surveys have revealed significant reductions in the density of
the relatively metals-tolerant brook trout, as well as the elimination of populations of metals-
sensitive salmonid species such as the cutthroat, rainbow and brown trout. For example, while
brook trout densities at the Teft Spur site remained between 300 - 350 fish per mile in three
2
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surveys before 2006 (1992, 1998, and 2005), more recent surveys have documented brook trout
densities near 100 fish per mile in the last three surveys (2010, 2014, 2015) (Figure 1). These
dramatic fisheries impacts coincided with a period of increasing metals concentrations within
this reach of the Animas River (i.e. between 2005 and 2010) (CPW 2010), in part attributable to
the termination of operation of a key water treatment plant in the Cement Creek drainage in mid-
2004.
Finally, fish have recently been documented in several other reaches of the Animas River and
tributaries as a part of qualitative habitat surveys conducted by the USGS in 2016 as seen in
Figure 2. These locations include trout populations in Cunningham Creek near its mouth, in the
South Fork of Mineral Creek near its mouth, in Mineral Creek between Mill Creek and the
Middle Fork of Mineral Creek, and in Mineral Creek below the South Fork of Mineral Creek.
Potential Risk Reduction Benefits from Proposed Interim Remedial Action
Each of the proposed Interim Remedial Action has as a potential benefit to the reduction of
metals concentrations in surface waters downgradient of them by addressing potential mining
related sources and/or the reduction of stormwater or mining-related discharges comingling with
these sources. Importantly, many of the metals originating from the Interim Remedial Action
mining-related sources are known to be toxic to aquatic life at elevated levels. Table 1 presents
hazard quotients (HQs) for samples collected from adit drainages and surface water found
immediately downstream of proposed Interim Remedial Action mining-related sources until the
next potential influence on the surface water body was encountered (e.g., another creek or
mining-related source) in the Animas River, Cement Creek and Mineral Creek drainages. HQs
were computed by comparing surface water concentrations with Colorado's hardness-based
chronic aquatic life water quality criteria (concentration / criteria) for aluminum, cadmium,
copper, and zinc for samples collected in 2015 to present. HQs greater than one indicate there is
a potential unacceptable risk to aquatic life under CERCLA. Figure 3 to Figure 5 present the
maximum individual HQs across the four metals for each sampling location to provide an overall
impression of the magnitude of HQ at Interim Remedial Action locations. As seen, there are few
locations where maximum individual metal HQ values are less than one, with many locations in
both adit drainages and downstream surface waters demonstrating HQs greater than 100.
While aquatic life is unlikely to be directly exposed to mine-related surface water drainages (i.e.,
mine portal discharges), where they enter the receiving stream, they can significantly increase
instream metals concentrations. Many toxic metals are conservatively transported in surface
waters, and can remain in solution well downstream of where they were loaded. As such, actions
that reduce toxic metal loading to surface waters containing aquatic ecosystems (or to surface
waters that are tributary to waters containing aquatic ecosystems) are likely to reduce the metal-
related ecological risk to resident or potentially-resident aquatic communities in the immediate
receiving waters as well as hydrologically-connected downstream reaches.
3
-------
Cement Creek
While Cement Creek has long been characterized as being unable to support aquatic life, the
Animas River below Cement Creek contains fisheries that are sensitive to changes in instream
metals concentration (Figure 1). Just as worsening of instream water quality between 2005 and
2010 surveys resulted in the reduction of brook trout density and overall fish species diversity at
CPW's Teft Spur site, it is reasonable to predict that a sustained reduction of metal loading to
this stream reach from Cement Creek is likely to reduce risk to resident or potentially-resident
aquatic life. Further, improvements resulting from the reduction of dissolved metal-related risk
would be expected in reaches of the Animas downstream of Teft Spur as well (e.g. Animas River
in Durango).
Mineral Creek
Reduction of metal loading would be expected to reduce risk to the trout population that has been
documented in the South Fork of Mineral Creek to its mouth. An Interim Remedial Action may
improve conditions in the mainstem of Mineral Creek and beyond into the Animas River as
described above.
Upper Animas River
Sustained reduction of metal loading through Interim Remedial Action (excluding the proposed
action at the Pride of the West Mine) would be expected to reduce risk to the trout population
present in the Animas River between Maggie Gulch and Cunningham Creek (Figure 1). The
proposed Interim Remedial Action at the Pride of the West Mine would be expected to reduce
risk to the trout population that has been documented in Cunningham Creek below the influence
of the mine. All of these actions would be expected to improve water quality in the Animas River
below Howardsville, including reaches of the Animas below Silverton described above.
Conclusions
The health of aquatic ecosystems within the Animas River and its tributaries are currently limited
by high concentrations of toxic metals emanating from a wide range of mining-related and
natural sources distributed throughout the greater Animas River watershed. In many locations,
metals concentrations are currently so elevated that aquatic life is precluded. In other locations,
metals-tolerant organisms (e.g. brook trout) are currently able to persist. Actions that result in
sustained metal loading reduction function to reduce toxic metals exposure to resident organisms
(or potentially resident) within these streams. If enough of these actions are taken, improved
survival, abundance and diversity of aquatic life can reasonably be expected where aquatic
ecosystems are currently marginal. Further, expansion of the spatial extent of aquatic
communities may also be possible as instream water quality improves.
4
-------
References
CPW. 2010. 2010 Animas River Report. San Juan Basin. Report written by Jim White, Aquatic
Biologist, CDOW.
USEPA. 2015. Final Draft Baseline Ecological Risk Assessment Upper Animas Mining District,
San Juan County, Colorado. Prepared by: TechLaw, Inc. ESAT Region 8. Prepared for: U.S.
Environmental Protection Agency, Region 8. April.
5
-------
Brook Trout Density in Animas River- Howardsville to TeftSpur
1200
1992 1998 2005 2010 2014 2015
Year
¦ Howardsville hA-72 ¦ Elk Park ¦ TeftSpur
Figure 1. Fish densities in the Animas River at four sites. The Flowardsville Site (CPW Animas Site #4)
is located just above Cunningham Creek on the Animas. The remaining sites (A-72, Elk Park, Tcft Spur)
are in progressive order on the Animas River below Silverton. Data were collected and reported by
Colorado Parks and Wildlife (CPW 2010; CPW 2014; CPW 2015).
6
-------
ELECTROFISHING RESULTS
0 Fish Absent
@ Fish Present
^pources Esri, $i?RE, DeLorme, TomTom, Intermap. incremeri! P Corp , GEBCO, U.SGS. FAO, NPS, NRCAN
'.JbeoBase IGN. Kadaster NL, Ordnance|Survey. Esri Japan. METI. Esri China (Hong Kong), swisstopo
Figure 2. U.S. Geological Survey Electrofishing Results (2016)
Bonita Peak Mining District
San Juan County, CO
-------
.
Brooklyn M tie
OURAY !
COUNTY '
Bandora Mine
Background Terrain Sources: Esri, USGS,
NOAA
Source: Esri, DigitalGiobe, GeoEye, Earthstor
Geographies, CNES/Airbus DS, USDA, USGS,
AeroGRID, tGN, and the GIS User Community
Road and Railroad Source: US Census
Legend
, j Proposed Interim Remedial
Action Location
— Road
Hazard Quotient (HQ)
• HQs 1
O HQ >1 and s 25
C HQ >25 and s 100
• HQ >100
Figure 3
Maximum Hazard Quotients in Mine Discharges and Surface
Water for Aluminum, Cadmium, Cooper, and Zinc at Locations Downstream of
Proposed Interim Remedial Action Locations - Mineral Creek
Bonita Peak Mining District | San Juan Count/, CO
CDM
lafcj
Smith
-------
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Mogul Mine
[Mammoth
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m Smith
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SAN MIGUEL ;
COUNTY
Legend
OURAY i
COUNTY \
Miles
Background Terrain Sources: Esri, USGS,
NOAA
Source: Esri, DigitolGbbe, GeoEye, Earthstar
Geographies, CNES/Airbus OS, US DA, USGS,
AeroGRiD, IGN, ond theGtS User Community
Road and Railroad Source: US Census
I , Proposed Interim Remedial
Action Location
Hazard Quotient (HQ)
• HQ< 1
O HQ >1 and <25
® HQ >25 and < 100
• HQ >100
- Road
fT. gP ;
4 *
; i
Z* n
Figure 4
Maximum Hazard Quotients in Mine Discharges and Surface
Water for Aluminum, Cadmium, Cooper, and Zinc at Locations Downstream of
Proposed Interim Remedial Action Locations - Cement Creek
Bonita Peak Mining District | San Juan County, CO
-------
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Background Terrain Sources: Esri, USGS>
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Source: Esri, DigitolGlobe, GeoEye, Earths tar
GeographiesCNES/Airbus DS, USDA, USGS,
AeroGRID, IGN, and the CIS User Community
Road and Railroad Source: US Census
' 1 /V
(• .
Legend
,V1 Proposed Interim Remedial
Action Location
Hazard Quotient (HQ)
• HQS 1
O HQ > 1 and s 25
© HQ >25 and < 100
• HQ >100
Road
Figure 5
Maximum Hazard Quotients in Mine Discharges and Surface
Waterfor Aluminum, Cadmium, Cooper, and Zinc at Locations Downstream of
Proposed Interim Remedial Action Locations - Upper Animas Area
Bonita Peak Mining District | San Juan County, CO
fo% CDM
WJ Smith
-------
TABLE 1
Hazard Quotients in Mine Discharges and Surface Water for Aluminum, Cadmium, Cooper, and Zinc at Locations Downstream
of Proposed Interim Remedial Action Locations
Bonita Peak Mining District
Sample
Date
Hazard Quotient (HQ)
Maximum
HQ
Drainage
Su b-Drainage
Location
Aluminum
Cadmium
Copper
Zinc
M24A
9/28
2016
11
44
0.2
33
44
M24B
9/28
2016
2
59
1
42
59
South Fork Mineral Creek
M24D
9/27
2016
2
43
0.1
35
43
M25
6/29
2016
8
1
0.3
1
21
9/27
2016
21
2
0.2
1
M02
6/29
2016
30
16
25
18
78
10/7
2016
78
30
45
38
M02B
6/29
2016
20
17
20
14
82
10/7
2016
82
40
54
32
M02C
10/7
2016
148
74
72
97
148
M02E
6/29
2016
40
21
37
23
93
10/7
2016
93
36
48
44
M02K
6/29
2016
77
45
73
50
77
M02K1
6/29
2016
44
34
113
42
113
6/30
2016
22
5
18
5
M03
6/30
2016
20
5
17
5
22
Mineral Creek
10/8
2016
1
8
21
8
M04
10/8
2016
1
7
5
11
11
located in the main stem of
M05
10/8
2016
0.9
7
5
11
11
Mineral Creek
6/7
2016
40
4
2
3
M12
6/29
2016
39
10
4
8
105
9/29
2016
105
10
4
7
M12A
6/29
2016
44
3
3
3
117
9/30
2016
117
3
3
2
M12B
6/29
2016
45
0.9
2
0.7
137
9/30
2016
137
0.6
2
0.6
6/29
2016
22
17
8
15
M12C
9/30
2016
35
20
13
18
42
9/29
2016
42
19
13
18
M12D
9/30
2016
32
20
14
19
32
M12E
10/7
2016
28
17
11
17
28
M12F
10/7
2016
0.06
0.1
0.05
0.02
0.1
M12G
10/7
2016
7
2
6
2
7
CC42
6/7
2016
0.3
0.1
0.1
0.1
6
9/27
2016
6
0.2
0.04
0.2
CC43C
6/7
2016
6
0.2
0.1
0.2
6
Illinois Gulch
9/27
2016
6
0.2
0.1
0.3
CC43D
6/7
2016
355
18
115
16
355
Cement Creek
CC43E
6/7
2016
35
8
9
8
65
9/27
2016
65
4
3
5
CC24
6/8
2016
12
10
25
10
40
Prospect Gulch
9/29
2016
40
7
16
6
CC24B
6/8
2016
10
7
17
8
32
9/29
2016
32
5
10
4
6/10
2015
21
4
2
2
9/29
2015
11
1
0.1
2
CC14
7/15
2015
18
0.5
0.1
2
28
6/9
2016
28
5
3
3
South Fork Cement Creek
9/29
2016
11
2
0.1
2
CC15A
6/9
2016
9
2
1
1
10
9/29
2016
10
1
0.2
1
CC16B
6/9
2016
12
2
2
1
23
9/29
2016
23
1
0.5
1
7/15
2015
20
61
58
57
CC01C
6/29
2016
23
84
115
71
326
9/28
2016
118
252
326
233
Cement Creek
CC01C1
6/29
2016
53
142
279
135
557
9/28
2016
172
302
557
256
CC01C2
6/29
2016
34
99
169
87
331
9/28
2016
93
198
331
172
located in the main stem of
Cement Creek
CC01H
6/29
2016
8
16
19
12
19
9/27
2016
8
14
13
11
CC01S
6/29
2016
32
14
6
8
48
9/27
2016
48
25
5
12
CC01T
6/29
2016
20
12
6
7
22
9/27
2016
22
20
9
11
CC01U
6/28
2016
13
11
6
7
21
9/27
2016
21
20
9
11
CC02I
6/28
2016
11
14
3
14
22
9/27
2016
22
20
9
11
Page 1 of 3
-------
TABLE 1
Hazard Quotients in Mine Discharges and Surface Water for Aluminum, Cadmium, Cooper, and Zinc at Locations Downstream of
Proposed Early Interim Remedial Action Locations
Bonita Peak Mining District
Sample
Date
Hazard Quotient (HQ)
Maximum
HQ
Drainage
Su b-Drainage
Location
Aluminum
Cadmium
Copper
Zinc
CC38
6/7/2016
7
2
1
3
7
Cement Creek
located in the main stem of
9/28/2016
0.3
2
0.1
4
Cement Creek
CC39
6/7/2016
25
6
7
6
78
9/27/2016
78
5
3
5
A50
6/7/2016
0.2
18
1
10
18
Cunningham Creek
9/28/2016
0.1
10
0.6
6
CU4A
6/7/2016
7
0.3
0.3
0.1
7
9/28/2016
0.1
0.5
0.1
0.3
9/30/2015
129
51
9
30
A07
6/8/2016
49
46
9
35
137
9/30/2016
137
56
8
34
9/30/2015
161
55
10
32
A07A
6/28/2016
75
67
16
40
171
9/30/2016
171
63
9
38
9/30/2015
161
55
6
37
A07B
6/28/2016
81
70
14
48
197
9/30/2016
197
69
8
45
A07B1
6/28/2016
83
68
14
49
83
A07B2
6/28/2016
4
0.5
0.1
0.6
4
North Fork Animas River
A07B3
6/28/2016
167
122
16
67
167
9/30/2015
179
61
9
52
A07C
6/28/2016
89
64
14
47
182
10/5/2016
182
73
10
54
6/28/2016
85
52
14
37
A07D
6/28/2016
86
49
13
34
184
10/5/2016
184
80
19
46
A07D1
6/28/2016
222
147
12
107
222
A07D2
6/28/2016
118
346
79
271
346
A07E
6/28/2016
79
38
14
24
159
10/5/2016
159
56
15
35
BB1
6/28/2016
15
110
113
101
113
A38
6/28/2016
0.05
0.1
0.04
3
3
9/28/2016
0.1
0.2
0.04
3
9/30/2015
0.3
3
2
4
A39
6/28/2016
0.5
10
2
13
13
9/28/2016
0.3
4
2
5
Animas River
A39A
6/28/2016
0.5
11
2
13
13
9/29/2015
83
112
184
133
ARD1
6/28/2016
44
114
254
124
254
9/28/2016
115
135
205
150
9/29/2015
39
73
168
70
South Fork Animas River
DM32
6/28/2016
31
122
245
132
245
9/29/2016
0.7
0.6
0.2
0.2
9/29/2015
0.1
1
1
2
EG3A
6/28/2016
2
11
2
15
15
9/29/2016
0.4
0.5
0.2
0.7
9/30/2015
0.1
1
0.6
2
EG 5
6/28/2016
0.5
11
2
15
15
9/28/2016
0.2
3
0.8
4
6/10/2015
1
11
4
17
EG 6
9/30/2015
0.02
2
0.4
3
17
6/28/2016
0.5
7
2
10
9/28/2016
0.3
3
1
4
6/9/2015
11
17
5
23
A10
9/29/2015
72
17
3
21
72
6/7/2016
17
14
3
19
9/29/2016
63
15
2
17
6/9/2015
14
13
3
19
All
9/29/2015
76
15
2
19
76
6/7/2016
19
11
2
17
9/30/2016
63
13
2
16
West Fork Animas River
6/9/2015
79
1662
1213
2009
AHA
9/29/2015
356
1639
569
1835
2057
6/7/2016
81
1555
1172
1782
9/30/2016
294
2057
648
1687
6/9/2015
0.2
6
0.3
16
10/1/2015
5
4
0.1
14
A12
6/7/2016
7
7
0.2
17
17
9/28/2016
4
4
0.1
12
9/28/2016
4
4
0.1
12
Page 2 of 3
-------
TABLE 1
Hazard Quotients in Mine Discharges and Surface Water for Aluminum, Cadmium, Cooper, and Zinc at Locations Downstream of
Proposed Early Interim Remedial Action Locations
Bonita Peak Mining District
Sample
Date
Hazard Quotient (HQ)
Maximum
HQ
Drainage
Su b-Drainage
Location
Aluminum
Cadmium
Copper
Zinc
6/10/2015
36
18
3
24
A15
9/29/2015
138
21
2
22
138
6/8/2016
34
16
2
21
9/30/2016
126
18
2
19
9/30/2015
0.1
2
0.06
3
A16
6/28/2016
0.1
2
0.04
3
3
9/28/2016
0.8
2
0.1
3
A18
10/6/2016
0.4
2
1
1
2
A18B
6/28/2016
47
9
2
8
213
10/6/2016
213
20
3
17
A19A
9/30/2015
38
194
275
104
275
9/28/2016
38
172
269
89
6/10/2015
6
10
5
16
A20
9/29/2015
14
8
2
13
16
6/29/2016
10
9
3
14
9/30/2016
11
7
1
11
9/29/2015
26
8
1
12
A21
6/29/2016
12
11
4
15
26
West Fork Animas River
9/30/2016
17
8
1
12
9/29/2015
156
42
0.3
66
A21A
6/29/2016
162
38
0.1
56
174
9/30/2016
174
46
0.2
62
6/9/2015
11
13
3
18
CG11
9/29/2015
76
15
2
18
76
6/7/2016
17
12
3
17
Animas River
9/30/2016
62
13
2
16
CG5
6/28/2016
26
96
45
117
117
6/28/2016
26
97
44
116
CG5A
6/29/2016
26
95
44
120
120
9/30/2015
157
22
2
22
CG6
6/28/2016
42
14
2
14
157
9/30/2016
137
19
2
20
CG6A
6/29/2016
52
14
2
14
52
6/29/2016
52
14
2
15
6/9/2015
12
12
3
18
CG9
9/29/2015
82
15
2
18
82
6/7/2016
21
13
3
19
9/30/2016
64
13
2
16
6/9/2015
16
13
91
11
A29
9/30/2015
21
15
170
13
170
6/7/2016
18
14
99
11
9/28/2016
18
13
106
10
A29A
6/9/2015
9
13
28
11
28
located in the main stem of
the Animas River
6/7/2016
1
14
19
10
6/9/2015
4
9
3
10
A30
9/30/2015
16
8
1
8
16
6/7/2016
6
9
2
10
A30B
6/8/2016
4
8
1
8
21
9/29/2016
21
8
0.7
7
DM22
6/28/2016
0.03
2
0.03
3
3
9/28/2016
0.3
1
0.04
3
Maximum Hazard Quotient color legend:
|] HQ< 1
HQ> land <25
HQ> 25 and < 100
I HQ >100
Page 3 of 3
-------
APPENDIX C
SUMMARY OF FEDERAL AND STATE ARARS
-------
Summary of Applicable or Relevant and Appropriate Requirements (ARARs)
Bonita Peak Mining District Superfund Site
Interim Remedial Actions (IRAs)
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1
National Historic
Preservation Act
(NHPA) and
Implementing
Regulations
16 United States
Code (U.S.C.) 470
36 Code of Federal
Regulations (C.F.R.)
Part 800
Applicable
This statute and implementing regulations require
federal agencies to take into account the effect of this
response action upon any district, site, building,
structure, or object that is included in or eligible for the
National Register of Historic Places (generally,
50 years old or older).
Only the substantive requirements of the NHPA are
applicable to the IRAs.
Cultural resource surveys have not been completed for
all mining-related sources addressed by the IRAs. If
cultural resources on or eligible for the national register
are present, it will be necessary during remedial design
and remedial action to determine if there will be an
adverse effect and if so how the effect may be
minimized or mitigated.
2
Archaeological and
Historic Preservation
Act and Implementing
Regulations
16 U.S.C. §469
43 C.F.R. § 7
Applicable
This statute and implementing regulations establish
requirements for the evaluation and preservation of
historical and archaeological data, which may be
destroyed through alteration of terrain as a result of a
federal construction project or a federally licensed
activity or program. Archaeological investigations
conducted at a site pursuant to the Act must be
conducted by a professional archaeologist.
Cultural resource surveys have not been completed for
all mining-related sources addressed by the IRAs. To
date, no such resources have been found at the Site. If
any are found, the EPA will analyze mitigation
measures, and if appropriate, those measures will be
incorporated into remedial design and remedial action.
3
Historic Sites Act 16
U.S.C. § 461, etseq.
Applicable
The statute requires federal agencies to consider the
existence and location of potential and existing
National Natural Landmarks to avoid undesirable
impacts on such landmarks.
Cultural resource surveys have not been completed for
all mining-related sources addressed by the IRA. To
date, no National Natural Landmarks have been
identified at the Site.
4
Fish and Wildlife
Coordination Act and
Implementing
Regulations
16 U.S.C. § 662, et
seq.,
50 C.F.R. § 83
33 C.F.R. § 320-330
Applicable
This statute and implementing regulations require
coordination with federal and state agencies for
federally funded projects to ensure that any
modification of any stream or other water body
affected by any action authorized or funded by the
federal agency provides for adequate protection of fish
and wildlife resources.
If the IRA involves activities modifying streams or
water bodies that affect wildlife and/or non-game fish,
federal agencies must comply with substantive
requirements identified by the U.S. Fish and Wildlife
Service and the relevant state agency with jurisdiction
over wildlife resources.
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Bald and Golden Eagle
Protection Act
16 U.S.C. § 668 etseq.
Applicable
This requirement makes it unlaw lid lor anyone to lake,
possess, import, export, transport, sell, purchase, barter,
or offer for sale, purchase, or barter, any bald or golden
eagle, or the parts, nests, or eggs of such a bird except
under the terms of a valid permit issued pursuant to
Federal regulations. In addition to immediate impacts,
this requirement also covers impacts that result from
human-induced alterations initiated around a
previously used nest site during a time when eagles are
not present, if, upon the eagle's return, such alterations
agitate or bother an eagle to a degree that interferes
with or interrupts normal breeding, feeding, or
sheltering habits, and causes injury, death or nest
abandonment.
If bald or golden eagles are identified at these mining-
related sources during remedial design and remedial
action, activities must be modified and conducted to
conserve the species and their habitat.
6
Endangered Species
Act, 16 U.S.C. § 1531
et seq.
and Implementing
Regulations,
50 C.F.R. §§ 17 and
402
Applicable
This statute and implementing regulations provide that
federal activities not jeopardize the continued existence
of any threatened or endangered species.
16U.S.C. § 1536(a) of the Endangered Species Act
requires consultation with the U.S. Fish and Wildlife
Service to identify the possible presence of protected
species and mitigate potential impacts on such species.
Substantive compliance with the ESA means that the
lead agency must identify whether a threatened or
endangered species, or its critical habitat, will be
affected by a proposed response action. If so, the
agency must avoid the action or take appropriate
mitigation measures so that the action does not affect
the species or its critical habitat. If, at any point, the
conclusion is reached that endangered species are not
present or will not be affected, no further action is
required.
Canada Lynx (federally threatened mammal) and
southwestern willow flycatcher (federally endangered
bird) have been identified in San Juan County, but not
necessarily found at the Site. Surveys to identify
threatened and endangered species at the mining-
related sources addressed by this IRA have not been
completed.
If threatened or endangered species are identified at
these mining-related sources during remedial design
and remedial action, activities must be modified and
conducted to conserve the species and their habitat.
7
Migratory Bird Treaty
Act 16 U.S.C. §703
50C.F.R. § 10.12
Applicable
This statute and implementing regulations makes it
unlawful for anyone to take, possess, import, export,
transport, sell, purchase, barter, or offer for sale,
purchase, or barter, any migratory bird, or the parts,
nests, or eggs of such a bird except under the terms of a
valid permit issued pursuant to these regulations.
If migratory birds are identified at these mining-related
sources during remedial design and remedial action,
activities must be modified and conducted to conserve
the species and their habitat.
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Criteria for
Classification of Solid
Waste Disposal
Facilities and
Practices
40 C.F.R. §§ 257
257.2,257.3-1,257.3-
2(a), 257.3-2(c),
Relev ant and
Appropriate
This regulation establishes standards with which solid
waste disposal must comply to avoid possible adverse
effects on health or the environment. These criteria
apply to both solid waste disposal facilities and
practices that are not otherwise excepted in the
regulation. Part 257.3-1 states that that facilities or
practices in floodplains not restrict floods or result in
washout of solid waste. Part 257.3-2 provides for the
protection of threatened or endangered species.
If threatened or endangered species are identified
within areas designated for solid waste disposal,
disposal activities must protect them.
If floodplains are delineated within areas designated for
solid waste disposal, disposal activities within them
will be carried out in a manner to avoid restricting
floods or resulting in washout of solid wastes.
RCRA Subtitle D specifically regulates nonhazardous
solid waste. Because the State of Colorado has been
delegated the authority to implement the solid waste
program regulated under RCRA Subtitle D, the
substantive requirements will be enforced through the
Colorado Solid Waste Regulations.
10
Clean Water Act 33
U.S.C. § 1342, etseq.,
Point Source
Discharges
Requirements, Section
402
Relevant and
Appropriate
Section 402 of the Clean Water Act, 33 U.S.C. § 1342,
et seq., authorizes the issuance of permits for the
discharge of any pollutant. This includes storm water
discharges associated with industrial activity. See, 40
C.F.R § 122.26(a)(l)(iii). Industrial activity includes
inactive mining operations that discharge storm water
contaminated by contact with or that has come into
contact with any overburden, raw material,
intermediate products, finished products, byproducts or
waste products located on the site of such operations,
see, 40 CFR 122.26(b)(14)(iii); landfills, land
application sites, and open dumps that receive or have
received any industrial wastes including those subject
to regulation under RCRA subtitle D, see, 40 CFR
122.26(b)(14)(v); and construction activity including
clearing, grading, and excavation activities, see, 40
CFR 122.26(b)(14)(x).
Because the State of Colorado has been delegated the
authority to implement the Clean Water Act,
substantive requirements will be enforced through the
Colorado Pollutant Discharge Elimination System
(CPDES). Blanket use of the CERCLA interim
measures waiver will occur for this ARAR, as
described in Section 14 of Part 2 of the IROD.
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Clean Water Act 404,
33 U.S.C. § 1344, et.
seq.,
Dredge and Fill
Provisions
Section 404 (b)(1)
40 C.F.R. § 230
Applicable
Section 404 regulates the discharge of dredged or lill
materials into waters of the United States including
return flow from such activity. This program is
implemented through regulations set forth in the 404
(b)(1) guidelines, 40 C.F.R. § 230. The guidelines
specify: the restriction on discharge (40 C.F.R. §
230.10); the factual determinations that need to be
made on short-and long-term effects of proposed
discharge of dredge or fill material on the physical,
chemical, and biological components of the aquatic
environment (40 C.F.R. § 230.11) in light of Subpart C
through F of the guidelines; and the findings of
compliance on the restrictions (40 C.F.R. § 230.12).
Subpart J of the guidelines provide the standards and
criteria for the use of all types of compensatory
mitigation when the response action will result in
unavoidable impacts to the aquatic environment.
If the remediation of mining-related sources during the
IRA involves the discharge of dredged or fill materials
into waters of the United States identified at the Site,
activities would be implemented in compliance with
substantive requirements of these regulations. The in-
stream mine waste IRA is expected to the only IRA
that could result in the discharge of dredged or fill
materials into waters of the United States.
12
National Forest
Management Act
(NFMA)
To be
Considered
The National Forest Management Act (NFMA) is the
primary statute governing the administration of
National Forest System (NFS) land. It was passed in
1976 as an amendment to the Forest and Rangeland
Renewable Resources Planning Act of 1974, which
called for the management of renewable resources on
NFS land. The NFMA requires the Secretary of
Agriculture to assess forest lands, develop a
management program based on multiple-use, sustained-
yield principles, and implement a resource
management plan for each unit of the NFS. The NFMA
is at 16 U.S.C. §§ 1601-1614.
This statute required the development of the San Juan
National Forest and Tres Rios Field Office Land and
Resource Management Plan to govern activities
performed on NFS land. Activities conducted during
the IRA on NFS-managed land would consider
pertinent information within the Plan developed as a
result of this Act.
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The San Juan National
Forest and Tres Rios
Field Office Land and
Resource Management
Plan
To be
Considered
The purpose of this Land and Resource Management
Plan (LRMP) is to provide strategic guidance for future
management of all National Forest System (NFS) lands
managed by the San Juan National Forest (SJNF) and
lands within the Tres Rios Field Office (TRFO)
administered by the Bureau of Land Management
(BLM), except for those lands included in the BLM's
Canyons of the Ancients National Monument. This
LRMP guides the restoration or maintenance of the
health of these lands to promote a sustainable flow of
uses, benefits, products, services, and visitor
opportunities. It provides a framework for informed
decision making, while guiding resource management
programs, practices, uses, and projects. It does not
include specific project and activity decisions. Those
decisions are made later, after more detailed analysis
and further public involvement.
The San Juan National Forest and Tres Rios Field
Office Land and Resource Management Plan is
available at:
https://www.fs.usda.gov/detail/sanjuan/landmanageme
nt/planning/?cid=stelprdb5432707
The Plan contains standards and management direction
for all actions to be taken on NFS land within the San
Juan National Forest boundaries. Any remedial and
removal action decisions made under CERCLA would
be expected to consider pertinent standards and
management direction (collectively, "plan
components") set forth in the Plan.
Standard and Guidelines from the Plan that may be
applicable are: Abandoned Mine Lands and Hazardous
Materials 2.21.1 through 2.21.9, Acid-Mine Runoff,
2.3.56, 2.5.26, Riparian Area and Wetland Ecosystems,
2.4.20, Aquatic Ecosystems and Fisheries, 2.5.18,
2.5.19, 2.5.25, Water Resources, 2.6.29, 2.6.30, 2.6.34,
2.6.39, Bats, 2.3.37,2.3.38, 2.3.51-54, Fens, 2.4.7,
Roads, 2.13.22,2.13.23, 2.13.24.
14
Statement of
Procedures on
Floodplain
Management and
Wetlands Protection
40 CFRPart6,
Appendix A
Relevant and
Appropriate
40 CFR Part 6, Appendix A contains EPA's statement
of procedures for carrying out the provisions of
Executive Order 11988 (Floodplain Management) and
11990 (Protection of Wetlands).
If the IRA involves activities that affect floodplains or
wetlands, activities will be carried out in a manner to
avoid adversely affecting them or mitigate impacts.
15
Floodplain
Management
Regulations
Executive Order No.
11988
To be
Considered
This Executive Order requires federal agencies avoid,
to the extent possible, adverse effects associated with
direct or indirect development of a floodplain, or to
minimize adverse impacts if no practicable alternative
exists.
If floodplains are identified within areas designated for
the IRA, activities actions will be carried out in a
manner to avoid adversely affecting them or mitigate
impacts.
16
Protection of Wetlands
Regulations Executive
Order No. 11990
To be
Considered
This Executive Orders requires federal agencies to
avoid, to the extent possible, the adverse impacts
associated with the destruction or loss of wetlands and
to avoid support of new construction in wetlands if a
practicable alternative exists.
If jurisdictional wetlands are identified within areas
designated for the IRA, activities will be carried out in
a manner to avoid adversely affecting them or mitigate
impacts.
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RESPONSIVENESS SUMMARY
1.0 OVERVIEW AND BACKGROUND ON COMMUNITY INVOLVEMENT
Community involvement is an important aspect of the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) process. The U.S. Environmental Protection
Agency (EPA) is implementing a robust program of community participation at the Bonita Peak
Mining District (BPMD) Superfund Site (Site) that exceeds the requirements of CERCLA. EPA
began community involvement for the Site prior to the Site's listing on the National Priorities
List (NPL) in September 2016, and active community involvement related to the Site continues
today.
The following section describes some of the community involvement activities implemented at
the Site since 2015. All documents described are publicly available on EPA's BPMD website
(www.epa. gov/supeifund/bonita-peak). along with updates on the Superfund process and coming
events, access to reports and plans, and Site contacts.
EPA Region 8 established two information repositories in Colorado and assisted EPA Regions 6
and 9 in establishing repositories in New Mexico and the Navajo Nation, respectively. The
repositories contain basic information for public review, documents about Site activities,
technical documents, the community involvement plan (CIP), and general information about the
Superfund program.
Information repositories are located at the:
• Silverton Public Library, 1117 Reese Street, Silverton, Colorado
• Durango Public Library, 1900 East Third Avenue, Durango, Colorado
• Farmington Public Library, 2101 Farmington Avenue, Farmington, New Mexico
• Dine College Shiprock Campus Library, 1228 Yucca Street, Shiprock, New Mexico
The administrative record is housed at the EPA Superfund Records Center in Denver, Colorado.
Information about the administrative record file and information repositories has been included
in Site fact sheets and on EPA's BPMD website.
In late 2016 and early 2017, EPA and the Colorado Department of Public Health and
Environment (CDPHE) conducted community interviews with stakeholders affected by the Site
to obtain general information, identify community concerns and issues, and determine how best
to communicate with the public. Interviewees included local officials and stakeholders from
Silverton; San Juan County, Colorado; Durango, Colorado; La Plata County, Colorado; and the
Southern Ute Indian Tribe. Findings were supplemented with information gathered during face-
to-face interactions between EPA, CDPHE, and the communities.
Using the information from those interviews, a CIP was prepared and distributed in August 2017.
The CIP is available on EPA's BPMD website.
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EPA provided information about the availability of technical assistance to communities in
presentations and in writing. A community advisory group (CAG) was formed in January 2019
to provide a forum for stakeholders and the Site team to share information and discuss issues
related to the Superfund decision-making process.
There have been discussions in the communities about forming an organization to apply for a
technical assistance grant (TAG). However, community representatives have expressed the
opinion that enough technical expertise is available within the community to provide technical
assistance as needed. EPA provided a technical advisor and a technical expert to the
Silverton/San Juan County Planning Group through the Technical Assistance Services for
Communities (TASC) program in 2016 and 2017.
EPA recognizes and acknowledges that the Silverton/San Juan County Planning Group is the
entity comprised of local officials and residents that provides Silverton and San Juan County the
decision-making "seat at the table," as requested by the Governor of Colorado, Silverton, and San
Juan County in their letters to EPA supporting the addition of the Site to the NPL. EPA
coordinates with and involves the Silverton/San Juan County Planning Group as much as possible
in all phases of work and all decisions concerning the Site.
EPA prepares fact sheets for the Site that provide information to the community at key points. Fact
sheets are distributed electronically via EPA's electronic mailing list, and are available to the public
at EPA's BPMD website. Printed copies are distributed at public meetings. Examples of fact sheets
issued are Innovative Technologies, March 2018, and Interim Sludge Management Questions and
Answers, June 2018.
EPA posts public notices in local newspapers about public comment opportunities, upcoming
events, and other Site-related information. These media outlets include the Silverton Standard,
the Durango Herald, the Durango Telegraph, and the Southern Ute Drum.
EPA has prepared multiple presentations and handouts that provide specific information to the
public. As an example, EPA has hosted fall and spring public meetings in Colorado and New
Mexico, and at the Navajo Nation, to update community members about Site activities.
Presentations are available on EPA's BPMD website and include Virtual Tour of the Water
Treatment Plant at Gladstone, Colorado; BPMD Digging Deeper - Hydrology; BPMD Team
Biographies; BPMD Hydrology Path Forward; Summary of Superfund Resources Available to
Communities; and Introduction to Risk Assessment.
EPA issued its Proposed Plan for Interim Remedial Actions on June 14, 2018. The proposed plan
was made available in electronic format at the four Site information repositories. An electronic
notice with links to relevant documents was posted on EPA's BPMD website throughout the
public comment period.
A public meeting for the proposed plan was held on June 21, 2018, in Silverton, Colorado. EPA
gave a brief presentation, and the public had an opportunity to provide oral and written comment.
A stenographer provided transcription services for the meeting, and the transcript and a videotape
of the presentation were made available on EPA's BPMD website.
The 30-day public comment period for the proposed plan began on June 14, 2018, and was
extended for an additional 30 days (through August 15, 2018) at stakeholder request.
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Announcement of the initial public comment period and public comment meeting were published
in the June Bonita Peak Mining District Update, which was sent to the Site's email list on
June 14, 2018. A notice of the extension of the public comment period was sent to the Site's
email list July 16, 2018. Notices were also published in the Silverton Standard, the Durango
Herald, the Durango Telegraph, and the Southern Ute Drum.
EPA issues monthly updates of Site activities in the form of the Bonita Peak Mining District
Update. These two-page updates provide recent activities, upcoming events, items new to the
website, and more. Spanish-language versions are also available. Past copies of the update are
available to the public from the website.
EPA has conducted several tours specific to issues at the Site. These tours focused on cultural
resources, the Gladstone interim water treatment plant (IWTP), and the mining-related sources at
the Site.
Beginning in May 2018, EPA posted a calendar of field activities on EPA's BPMD website so
local emergency managers and the public have easy access to past, current, and planned
activities.
EPA uses the 2017 Animas River Alert and Notification Plan to communicate to participants
events that affect the appearance of or water quality in the Animas River. Plan participants
include state and local emergency management agencies, public health departments, downstream
states and tribes, and local officials.
Continued community involvement will be vital as future response actions are planned. For more
information on community involvement throughout the CERCLA process, see Section 3 of Part 2
of this interim record of decision (IROD).
2.0 PUBLIC AND STAKEHOLDER COMMENTS ON THE SELECTED INTERIM
REMEDY
A total of 299 comments were received from 24 commenters on the proposed plan. Comments
were received by mail (letters), email, and submission of oral comments at public meetings
(stenographer's transcript). Submissions that covered many different topics, such as letters, were
split up by EPA into individual comments by topic, using best judgement. Each submission was
given a sequential individual comment identification (ID) number. Some commenters submitted
comments more than once during the comment period using one or more methods (letter, email).
For each ID number assigned, basic information (date received, commenter name, comment
method, title) was tracked and organized in a master spreadsheet.
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A summary of the number of comments made by individuals, businesses, organizations, and
government entities are:
• 6 citizens - 16 comments
• Animas Rivers Stakeholder Group (2 commenters) - 61 comments
• Borrego Consulting Services, LLC - 11 comments
• CDPHE - 10 comments
• Environmental Video - 5 comments
• Geosyntec Consultants (a consultant for Eureka Gulch Properties LLC, Houghton
Mountain Mines LLC, Houghton Land Preservation LLC, and Planetary Properties LLC)
- 14 comments
• Navajo Nation - 23 comments
• New Mexico Environment Department - 6 comments
• New Mexico Wildlife Federation - 1 comment
• San Juan Citizens Alliance - 21 comments
• Silverton LP Gas LLC - 1 comment
• Silverton Photographies - 4 comments
• Southwestern Water Conservation District - 2 comments
• Sunnyside Gold Corporation - 50 comments
• Trout Unlimited - 22 comments
• Utah Department of Environmental Quality - 12 comments
• U.S. Forest Service - 2 comments
• Yost Brothers, LLC - 38 comments
EPA received one set of comments after the close of the comment period. The comments were
labeled as "late comments" and added to the administrative record file. EPA reviewed the late
comments. Consistent with 40 Code of Federal Regulations (CFR) § 300.825(c), the comments
are included in the administrative record file as late comments, as opposed to being incorporated
into the responsiveness summary, because none of the comments or other information submitted
with the comments substantially support the need to significantly alter EPA's selected interim
remedy.
Many comments received by EPA were not directly related to the proposed interim remedial
actions (IRAs) but rather focused on other activities occurring at the Site, such as treating water
at the IWTP and disposing of the sludge generated at the IWTP. Of those comments related to
the IRAs, the five most commonly received comments were:
• Selection of mining-related sources (42 comments) - Includes comments on sitewide
cleanup strategy, selection criteria, and contaminant migration.
• Effectiveness of IRAs (32 comments) - Includes comments on lack of quantitative
information, uncertainty of effectiveness, and performance monitoring.
• Adequacy of the focused feasibility study (FFS)/proposed plan (25 comments) -
Includes comments on plan details, alternative components, and the proposed plan.
• Risk assessment (19 comments) - Includes comments on background, ecological risk,
data evaluation, trespasser-related risk, and cleanup levels.
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• Cost effectiveness (19 comments) - Includes comments on whether the IRAs are the
best use of the dollars being spent.
A list of the primary comment categories is presented below. A summary of the content of these
comments is provided in Section 3.
Primary Comment Categories
1.
Selection of Mining-Related Sources
2.
Effectiveness of IRAs
3.
Adequacy of the FFS/Proposed Plan
4.
Risk Assessment
5.
Cost Effectiveness
6.
General Support/Opposition
7.
Proposed Technical/Contracting Approach
8.
Stakeholder Involvement
9.
Statutory Requirements
10.
Preliminary RI
11.
Cost
12.
Short-Term Risk
13.
Waste Management
14.
Limited Number of Alternatives
15.
Editorial
16.
Comments Not Specific to IRAs
Conflicting comments between different stakeholders were generally limited to two categories:
General Support/Opposition and Stakeholder Involvement. In the General Support/Opposition
category, multiple stakeholders indicated support for the IRAs discussed in the proposed plan,
while other stakeholders opposed the IRAs. Within the Stakeholder Involvement category, some
commenters indicated EPA provided ample engagement opportunities for stakeholders, while
other commenters indicated stakeholder engagement was lacking.
3.0 RESPONSE TO COMMENTS NARRATIVE
3.1 Responsiveness Summary Narrative for Selection of Mining-Related Sources and
IRAs
Selection Criteria: Several commenters indicated that it was not clear how the 26 mining-
related sources were selected for inclusion in the FFS and proposed plan for IRAs. In addition,
the commenters raised concerns that American Tunnel, Gold King Mine, Red and Bonita Mine,
and Mogul Mine were not included in the list of mining-related sources for IRAs.
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EPA completed an initial characterization of mining-related sources where IRAs to address
specific contaminant migration issues might be beneficial based on technical work and data
already collected by EPA, other stakeholder agencies, and advocacy groups such as the Animas
River Stakeholders Group (ARSG). This included collaborative discussions with partner
agencies on various approaches to performing early interim actions, such as those indicated in
the proposed plan. The IRAs identified in the FFS are not meant to be inclusive of all actions
required at the Site but will reduce risks and contaminant migration. The effectiveness of the
IRAs will be assessed and evaluated to inform the ongoing remedial investigation (RI) and future
response actions.
Concurrent with the work selected in this IROD, EPA is continuing cleanup work both under
CERCLA removal and remedial authorities for the mentioned mining-related sources. EPA
continues to complete response actions in the Cement Creek drainage, which include continued
operation of the IWTP and efforts to control ongoing releases at the Gold King Mine, Red and
Bonita Mine, and American Tunnel. EPA is also conducting ongoing RI, which includes
collection of data to support evaluation of contributors of sources for contaminant loading of
receiving waterways, and identifying areas where additional data is required to evaluate the Site.
EPA is also evaluating various locations within the Site to be used as repositories for mine waste
and IWTP sludge.
As some commenters have pointed out, past cleanup efforts at some of the mining-related
sources addressed in this IROD have been conducted by multiple parties (federal, state, and/or
private) and their opinion is that these mining-related sources should not be included in this
IROD. While past efforts at these mining-related sources have included actions like those
identified in the IRAs, there is no indication that the remedial action objectives and goals
identified in this IROD would be fully achieved solely by the previous actions. In addition,
follow-up maintenance activities have not been conducted at the mining-related sources to
maintain the effectiveness of these previous actions to meet the requirements of the IROD.
Contaminant Migration Issues: The State of Colorado (represented by CDPHE) indicated the
FFS was missing contaminant migration issues for certain mining-related sources. CDPHE
indicated in-stream mine waste would likely need to be addressed at Natalie/Occidental Mine
and Sunbank Group Mine.
As discussed in the Selection Criteria subcategory in Section 3.1, the EPA identified mining-
related sources where IRAs might be beneficial through a collaborative effort with partner
agencies based on technical work and data already collected. The IRAs identified in the FFS are
not meant to be inclusive of all mining-related sources and potential actions required at the Site.
EPA has discussed with CDPHE the proposed mining-related sources and potential actions and
has determined that the actions proposed by CDPHE in the comments will be looked at during
evaluation of future response actions at the Site.
Site-wide Strategy: Several commenters indicated the actions included in the FFS and proposed
plan are not presented as part of a long-term plan. In particular, commenters asked how these fit
into the overall Site-wide strategy and how work was being prioritized.
EPA is pursuing the use of an adaptive management approach for the Site. Adaptive
management is a formal and systematic site management approach that targets management and
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resource decisions with the goal of incrementally reducing site uncertainties while supporting
continued site progress toward achieving protection of human health and the environment. At the
Site, this strategy allows for EPA to continue to address site uncertainties through an ongoing
Site-wide RI while using existing information to evaluate, select, and conduct response actions.
The IRAs identified in the FFS are early efforts to implement this adaptive management
approach. These IRAs identified in the FFS are not meant to be inclusive of all actions required
at the Site but will reduce risks and contaminant migration. The effectiveness of the IRAs will be
assessed and evaluated to inform the ongoing RI and future response actions.
Concurrently with the work selected in the IROD, EPA is continuing work both under Removal
and Remedial authorities, as discussed in the Selection Criteria subcategory in Section 3.1. The
IRAs are not being prioritized over these other Site-wide actions but will be completed
concurrently as part of the comprehensive Site-wide strategy. The IRAs are one effort in EPA's
overall plan to address contamination at the Site.
3.2 Responsiveness Summary Narrative for Effectiveness of IRAs
Lack of Quantitative Information: Several commenters expressed concern that the FFS and
proposed plan lacked quantitative information about the effectiveness of the proposed IRAs. In
particular, several commenters noted that EPA did not estimate baseline conditions of metals
loading in streams nor the expected reductions in metals loading that would result from the
proposed IRAs.
EPA is conducting an ongoing RI that includes data collection to support evaluation of
contributors of sources for contaminant loading of receiving waterways and identifying areas
where additional data is required to evaluate the Site. The purpose of the IRAs is to target
specific contaminant migration issues for IRA while the RI is ongoing. Because a full evaluation
of the contributors of natural and mining-related sources for contaminant loading has not been
completed, the evaluations of baseline contaminant loading and loading reductions in the FFS are
qualitative. Once that RI is complete, EPA will be able to provide a more detailed evaluation of
metal loading at individual mining-related sources, which could include quantitative estimates of
loading, as appropriate, given the data collected.
In addition to the ongoing RI, as noted in the Remedial Goals and Remedy Performance
Monitoring subcategory in Section 3.2, remedy performance monitoring would be implemented
to monitor the effectiveness of the IRAs. Remedy performance monitoring would involve
surface water measurements and sample collection both upstream and downstream of mining-
related sources included in the selected interim remedy to estimate the loading reduction of
contaminants from the IRAs.
As discussed in the FFS, the loading of chemicals of potential concern (COPCs) is expected to
decrease under the proposed IRAs because the remedial components would reduce the contact of
the water with the waste, thereby reducing leaching and formation of mining-influenced water
(MIW). The proposed IRAs would also provide stabilization of the mining-related sources and
prevent further environmental degradation. Appendix D of the FFS provides a qualitative
discussion of the protectiveness and effectiveness considerations for the alternatives addressing
the five contaminant migration issues, and how the alternatives would be expected to meet
remedial action objectives (RAOs).
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Uncertain Effectiveness: Several commenters questioned the effectiveness of the proposed
IRAs. In particular, some commenters indicated the effectiveness of the proposed IRAs is either
unclear or speculative, and some commenters indicated the IRAs would not provide any
demonstratable beneficial improvement to the conditions at the Site and may result in additional
adverse impacts over existing conditions.
The IRAs described in this IROD are the first step in the remedial approach for the Site. The
IRAs are not intended to fully address all potential risks at the Site, as the Site has not been fully
characterized at this time. As discussed in Section 1.2.2 of the FFS, the following are the reasons
for taking interim actions:
• Take quick action to protect human health and the environment from an imminent threat
in the short term, while a final remedial solution is being developed; or
• Institute temporary measures to stabilize a site and/or prevent further migration of
contaminants or further environmental degradation.
The IRAs described in the selected interim remedy of this IROD have been employed at similar
watershed mine sites. These technologies are known to be effective at addressing the five
contaminant migration issues identified for IRAs. An essential part of the IRAs is the
performance remedy monitoring, which will provide EPA data about the effectiveness of the
implemented measures. The effectiveness of the IRAs will be assessed and evaluated to inform
the ongoing RI and future response actions.
As noted in the Lack of Quantitative Information subcategory in Section 3.2, the loading of
COPCs is expected to decrease under the proposed IRAs because the remedial components
would reduce the contact of the water with the waste, thereby reducing erosion and reducing
leaching and formation of MIW. The proposed IRAs would also provide stabilization of the
mining-related sources and prevent further environmental degradation. Appendix D of the FFS
provides a qualitative discussion of the protectiveness and effectiveness considerations for the
alternatives addressing the five contaminant migration issues and how the alternatives would be
expected to meet RAOs.
Some response activities undertaken by the agencies, such as removing waste rock from creeks
or streams, may cause localized, temporary discoloration of these streams. Although EPA would
employ best management practices (BMPs) to minimize these temporary impacts, impacts
cannot be entirely eliminated. In order to notify stakeholders of impact events in the most
efficient and prompt way, EPA is using the 2017 Animas River Alert and Notification Plan for
its communications to stakeholders related to any events that affect the appearance or water
quality in the Animas River, as noted in the Short-Term Risk category in Section 3.12.
Remedial Goals and Remedy Performance Monitoring: Multiple commenters indicated it is
not clear what the remedial goals of the IRAs are or how those goals would be met. Additionally,
several commenters indicated that not enough information was included on how EPA planned to
evaluate the effectiveness of the selected interim remedy.
As discussed in Section 3.5 of the FFS, the RAOs are the following:
1. Reduce transport from mine waste, contaminated soil, and contaminated sediment into
surface water of COPCs that contribute to unacceptable ecological risks.
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2. Reduce human exposure through ingestion and inhalation to mine waste and
contaminated soils containing lead that result in greater than a 5 percent chance of
exceeding a blood lead level of 5 micrograms per deciliter (ng/dL) during camping
activities.
3. Reduce human exposure through ingestion of mine waste and contaminated soils
containing arsenic that exceed risk-based levels for acute exposures during camping
activities.
The selected interim remedy, consisting of IRAs to address five contaminant migration issues,
would provide stabilization of the mining-related sources and prevent further environmental
degradation while meeting the RAOs. As noted in Comment the Lack of Quantitative
Information subcategory in Section 3.2, the loading of COPCs is expected to decrease under the
proposed IRAs because the remedial components would reduce the contact of the water with the
waste, thereby reducing leaching and formation of MIW. Appendix D of the FFS provides a
qualitative discussion of the protectiveness and effectiveness considerations for the alternatives
addressing the five contaminant migration issues and how the alternatives would be expected to
meet RAOs. Thus, the selected interim remedy would provide protection of human health and
environment in the short term and is intended to provide adequate protection until a final remedy
is selected.
Remedy performance monitoring would generally consist of sample collection and analysis. The
specifics of the remedy performance monitoring would be determined during remedial design.
However, it is anticipated that remedy performance monitoring for the four IRAs addressing
ecological risks at mine portal MIW discharges, mining-related sources/storm water interactions,
mine portal pond sediments, and in-stream mine wastes would involve surface water
measurements and sample collection both upstream and downstream of each mining-related
source addressed by IRAs to calculate the loading reduction from the actions. In addition,
remedy performance monitoring for the IRA addressing human health risks at mining-impacted
recreation staging areas would include a pre-design investigation prior to the construction of
covers to delineate the extent of contamination, followed by non-intrusive monitoring (i.e.,
inspections) after the construction of covers to confirm protectiveness of the covers.
3.3 Responsiveness Summary Narrative for Adequacy of the FFS/Proposed Plan
Alternative Components: Two commenters, including the State of Colorado (represented by
CDPHE), provided recommendations for inclusion of certain components such as environmental
covenants, signs, and fencing as part of the alternatives, and requested consultation with
Colorado Division of Parks and Wildlife as part of pre-construction activities. The State of
Colorado (represented by CDPHE) also requested that selective capping with signage and
fencing be considered for mining-impacted recreation staging areas in lieu of complete capping
considered for Alternative E2.
EPA has determined the identified remedy components provide the best approach for risk
reduction under the IRAs contemplated. The assumptions presented in the FFS associated with
cover material, thickness of covers, types of cap layers, and/or horizontal extent of covers, were
assumptions for the purposes of evaluating alternatives according to the National Oil and
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Hazardous Substances Pollution Contingency Plan (NCP) criteria and developing cost estimates
for the remedial alternatives. These assumptions will be finalized during the remedial design.
EPA will implement institutional controls (IC) to ensure the interim remedies remain protective
pending final remediation.
Detailed Plans: Several commenters indicated that detailed remediation plans should be
provided on a mining-related, source-specific level. In addition, other asked specific questions
about how certain remedial components of the IRAs, including covers, erosion controls, and
stabilization features for channels, would be constructed.
The proposed plan and this IROD describe the selected interim remedy for five IRAs and the
underlying information that supports the decision for selecting the remedy. Specific details of
how each selected interim remedy will be implemented at specific mining-related sources
identified within the IROD for the five IRAs will be developed during the remedial design phase,
which begins after the IROD is finalized. EPA will develop source-specific remediation plans
during the remedial design phase. Additionally, details of the five IRAs for remedy components,
such as covers, erosion controls, and stabilization features for channels, will be determined
during remedial design, which is the appropriate time for those types of evaluations. Contact
information for community members to communicate concerns to EPA during remedial action
construction will be provided.
Proposed Plan: One commenter indicated that the proposed plan was too general and did not
provide enough detail about the alternatives considered for the five IRAs, the concentrations of
COPCs at the Site, how the alternatives would satisfy preliminary remedial action objectives
(PRAOs), and how the alternatives are evaluated against CERCLA evaluation criteria.
In accordance with EPA guidance, as described in A Guide to Preparing SuperfundProposed
Plans, Records of Decision, and Other Remedy Selection Documents (EPA 1999), the purpose of
the proposed plan is to briefly summarize the alternatives studied in the detailed analysis phase
of the RI/FS, highlighting key factors that led to identifying the preferred alternative. The
proposed plan does not provide the same level of detail as other documents (e.g., FFS) in the
administrative record for the Site. The FFS, however, provides a greater level of detail, which
should be sufficient to address this comment. The FFS and corresponding appendices, including
the preliminary RI and risk assessment information, contain detailed descriptions of the
alternatives for the five contaminant migration issues to be addressed by the IRAs, contain
information on COPCs, discuss how the alternatives would satisfy PRAOs, and discuss how the
alternatives are evaluated against the CERCLA evaluation criteria. Additional details of how the
selected interim remedy will be implemented will be developed during the remedial design,
which begins after the IROD is finalized (as detailed in the Detailed Plans subcategory in Section
3.3).
3.4 Responsiveness Summary Narrative for Risk Assessment
Background: Multiple commenters raised concern regarding the lack of discussion of the natural
background conditions and how background was considered as part of the risk evaluations.
Risk assessments are still in development for the Site and will present an evaluation of Site-
related risk relative to background conditions or multiple lines of evidence for evaluating
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background risk, if applicable. These interim risk evaluations were developed solely to support
the identification of mining-related sources that may warrant an IRA due to five specific
contaminant migration issues. EPA's Role of the Baseline Risk Assessment in Superfund Remedy
Selection Decisions guidance (EPA 1991) supports the use of preliminary investigation and risk
assessment information to support an FFS and does not require the RI or risk assessments to have
been completed.
Qualitative risk information may be presented if quantitative risk information is not yet available.
The interim risk evaluations support the IRAs, which have been identified to reduce
contributions from mining-related sources that add unacceptable human health and ecological
risks in the Animas River watershed at the Site while a comprehensive remedial action is
developed. The role of natural background conditions in determining nature and extent of
contamination and associated unacceptable risks to human health and the environment from
mining-related sources are ongoing as part of the RI and risk assessments for the Site.
Cleanup Levels: One commenter indicated there was no information in the proposed plan on
how the cleanup levels were derived. That commenter also questioned why one cleanup level
was set for lead in soil and another cleanup level was set for arsenic in waste rock piles.
In accordance with EPA guidance, as described in A Guide to Preparing Superfund Proposed
Plans, Records of Decision, and Other Remedy Selection Documents (EPA 1999), the purpose of
the proposed plan is to briefly summarize the alternatives studied in the detailed analysis phase
of the RI/FS, highlighting key factors that led to identifying the preferred alternative. The
proposed plan does not provide the same level of detail as other Site documents. However, the
FFS, which is part of the administrative record file for the Site, provides a greater level of detail,
as requested by the commenter. Appendix B of the FFS (Risk Assessment Information) contains
the memoranda that outline the derivation of the screening levels for lead and arsenic outlined in
the proposed plan and the rationale for doing so. In brief, the screening levels were developed to
be representative of recreational exposure at the Site. Recreational screening levels pertinent to
the type of exposure being evaluated at the Site are not readily available. The camping scenario
was selected because the camper is anticipated to be the most sedentary of receptors (i.e., not
moving about being exposed to a variety of soil/mine waste sources, in contrast with a hiker,
hunter, fisherman, all-terrain vehicle rider/guide, and road worker). Derivation of screening
levels for a sedentary receptor allows for application of the screening levels to smaller areas,
such as individual campsites. The screening values mentioned in the comment were developed
for different media and/or different receptors than those that were developed for the Site. The
screening value of 20,000 milligrams per kilogram (mg/kg) was developed for sediment
exposure, whereas the screening value of 500 mg/kg was developed for a specific site in Texas.
For the purposes of the interim evaluation of arsenic risks, two screening levels were developed
according to the type and duration of an activity that may reasonably be anticipated to occur at a
location of interest. The 14-day screening level (for soil) was used for dispersed campsites where
extended camping may occur, whereas the 2-day screening level (for waste rock) should be used
when evaluating other types of potential recreation use areas (e.g., recreational launch points
nearby where camping may occur), where a 2-day exposure is reasonable to assume. Arsenic was
selected for evaluation because soil concentrations are notably elevated at several locations
compared to other locations where sample were collected. The 14-day and 2-day screening levels
for arsenic are presented in Appendix B of the FFS.
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A 14-day screening level for lead was developed for dispersed campsites where extended
camping may occur. Lead was selected for evaluation because inspection of the available
campsite data revealed select locations had lead concentrations at orders of magnitude greater
than the other locations. Other metals had generally similar concentrations across the campsite
locations. The 14-day screening level for lead is presented in Appendix B of the FFS.
As described in the Trespasser-Related Risks comment subcategory in Section 3.4, 2-day
screening levels for lead were developed in response to public comments received. Based on
these comments, an alternate trespass camping scenario was evaluated to determine whether lead
may pose an unacceptable risk under a shorter exposure frequency scenario. This alternate
scenario evaluated an exposure frequency of 2 days per year for campers in dispersed campsites
to determine if levels of lead pose a risk above a level of concern. This scenario allows
evaluation of potential risk to a family camping with a child (under the age of 6 years) that
unknowingly uses unmarked private property within the Site as a campsite before being
discovered and asked to leave by the property owner. This information has been attached as an
appendix to this IROD.
Data Evaluation: One commenter indicated that several sample locations were omitted from the
ecological risk evaluations and other data points were mischaracterized.
The comprehensive RI and baseline ecological risk assessment are still in development for the
Site. EPA will take these comments into consideration during development of the RI and the
baseline ecological risk assessment for the Site. These interim risk evaluations were developed
solely to support the identification of mining-related sources that may warrant an IRA. EPA's
Role of the Baseline Risk Assessment in Superfund Remedy Selection Decisions guidance
supports the use of preliminary investigation and risk assessment information to support an FFS
and does not require a completed RI or risk assessments.
Qualitative risk information may be presented if quantitative risk information is not yet available.
The interim risk evaluations support the IRAs, which have been identified to reduce
contributions from mining-related sources that add unacceptable human health and ecological
risks in the Animas River watershed at the Site while a comprehensive remedial action is
developed.
It is recognized that stream flow and concentration of metals from mining-related source areas is
an important consideration for identifying locations warranting remediation at the Site. This level
of evaluation will be presented in the RI report and baseline ecological risk assessment for the
Site. However, the purpose of the hazard quotient (HQ) evaluation presented in Appendix B, Part
2 of the FFS was to demonstrate that concentrations of metals in the main drainages at the Site
(Upper Animas River, Cement Creek, and Mineral Creek), downstream of mining-related
sources considered for IRAs, are highly elevated relative to screening values and thus warrant
action to address the five contaminant migration issues identified in the FFS. HQs were derived
using samples collected within the main drainages at the Site (Upper Animas River, Cement
Creek, and Mineral Creek) and not from individual mine drainages or lower-order streams with
varying flow rates and concentrations.
Ecological Risk: One commenter raised concerns that lead, manganese, arsenic, and mercury
were not considered when presenting HQs for ecological risks, including terrestrial ecological
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receptors. Another commenter questioned whether high HQs justified remediation if the flow
and metal loading was very small.
It is recognized that stream flow and concentration of metals from mining-related source areas is
an important consideration for identifying locations warranting remediation at the Site. This level
of evaluation will be presented in the baseline ecological risk assessment for the Site. The
purpose of the HQ evaluation presented in Appendix B, Part 2 of the FFS was to demonstrate
that concentrations of metals in the main drainages at the Site (Upper Animas River, Cement
Creek, and Mineral Creek), downstream of locations selected for IRAs, are highly elevated
relative to screening values. HQs were derived using samples collected within the main
drainages at the Site, not from individual mine drainages or lower-order streams with varying
flow rates and concentrations.
Based on this rationale, the interim ecological evaluation in the risk memorandum of the FFS
was developed to solely support the identification of mining-related sources that may warrant an
IRA for the five contaminant migration issues identified in the FFS. The terrestrial ecological
risk assessment is currently in the early stages of development and interim ecological evaluation
is only intended to provide an evaluation related to aquatic ecological risk, primarily risks to fish.
The goal of the HQ evaluation was accomplished by presenting HQs for select metals that are
typical risk drivers for aquatic receptors at mining-impacted sites. It was not necessary to
develop and present HQ values for all metals at the Site.
Trespasser-Related Risks: One commenter indicated she is a property owner of one of the
mining-related sources considered for IRA and disagreed with prioritizing the proposed action
for her property. The commenter also noted that her property was private, access to the property
was blocked to the public, and it was not a campground; therefore, her property should not be
evaluated as a campground for IRA.
As described in Appendix B, Part 1.1 of the FFS, an interim evaluation of potential lead risks
from exposures to lead in soil/waste rock at the Site was completed. This interim lead risk
evaluation was developed to support the identification of mining-related sources that may
warrant IRAs. Campground 4 was considered in the FFS and the associated human health risk
memorandum as a mining-related source that could pose unacceptable human health risks from
use as a recreation staging area, which could include camping. The human health risk evaluation
supporting the FFS reviewed a 14-day camping scenario with a focus on exposure to children
based on residential and camping soil ingestion rates. Campsite soil samples were collected from
multiple surficial locations and composited prior to analysis. This interim evaluation of potential
lead risks was based on samples collected by EPA, and identified two dispersed campsites
(Campground 4 and Campground 7) with levels of lead that exceed all screening levels
developed for consideration in the FFS.
Based on these comments provided by the property owner, an alternate trespass camping
scenario was evaluated to determine whether heavy metals (lead in particular) may pose an
unacceptable risk under a shorter exposure frequency scenario (i.e., less than 14 days), as
documented in Appendix B, Part 1.1 of this IROD. This alternate scenario evaluated an exposure
frequency of 2 days per year for campers in dispersed campsites to determine if levels of lead
pose a risk above a level of concern. This scenario allows evaluation of potential risk to a family
camping with a child (under the age of 6 years) that unknowingly uses unmarked private
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property within the BPMD as a campsite before being discovered and asked to leave by the
property owner. The screening levels developed for the 2-day exposure are based on a target
blood lead level recommendations from the Center for Disease Control, as described in
Appendix B, Part 1.1 of this IROD. This alternate exposure scenario evaluation indicates that
even if the exposure frequency were assumed to be only 2 days per year, lead concentrations at
Campground 4 would still be well above risk-based recreational screening levels, which supports
the conclusions of the FFS. This information has been attached as an appendix to this IROD.
As identified by the commenter (Campground 4), while signs are posted at the property
indicating that the land is private property, EPA and CDPHE have witnessed campers at the
property on multiple occasions and observed signs of camping (i.e., fire rings), which supports
the inclusion of Campground 4 as a recreation staging area requiring an IRA.
3.5 Responsiveness Summary Narrative for Cost Effectiveness
Several commenters raised concerns about the cost effectiveness of the proposed IRAs. In
particular, the commenters thought that the money for the proposed IRAs could be spent for
other actions at the Site that would be more beneficial/effective than the proposed IRAs. In
addition, multiple commenters indicated there is no cost/benefit analysis to understand the metals
reduction that will be achieved compared to the money spent on these actions.
A cost-effectiveness determination is required as part of the two-step remedy selection process
indicated at 40 CFR §300.430(f). Specifically, 40 CFR §300.430(f)(l)(ii)(D)) describes how
cost-effectiveness is determined as:
Cost-effectiveness is determined by evaluating the following three of the five balancing
criteria to determine overall effectiveness: long-term effectiveness and permanence,
reduction of toxicity, mobility, or volume through treatment, and short-term effectiveness.
Overall effectiveness is then compared to cost to ensure that the remedy is cost-effective.
A remedy shall be cost-effective if its costs are proportional to its overall effectiveness.
Section 14.0 in Part 2 of the IROD provides EPA's analysis and determination of cost-
effectiveness, as provided by the NCP. Per the NCP [40 CFR 300.430(e)(9)], the FFS included a
qualitative and comparative analysis of the individual balancing criteria of long-term
effectiveness and permanence, reduction of toxicity, mobility, or volume through treatment,
short-term effectiveness, implementability, and cost. Further, as discussed above, the IROD
includes the agency's determination of how the selected interim remedy is cost-effective as the
NCP requires (see Section 14.0 of Part 2 of the IROD).
The proposed IRAs address five contaminant migration issues at total of 23 different mining-
related sources. Thus, the proposed IRAs target almost half of the 48 mining-related sources that
were identified in the Site's listing on the NPL. The total costs presented in the remedial
alternative cost estimates include both the initial construction costs and the costs for 15 years of
post-construction operations and maintenance (O&M) for 23 different mining-related sources.
Depending on the timing and determination of the final remedy for the Site, O&M may not be
required for the full 15 years.
As noted in the Lack of Quantitative Information subcategory in Section 3.2, the loading of
COPCs is expected to decrease under the proposed IRAs because the remedial components
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would reduce the contact of the water with the waste, thereby reducing erosion and reducing
leaching and formation of MIW. Appendix D of the FFS provides a qualitative discussion of the
protectiveness and effectiveness considerations for the alternatives addressing the five
contaminant migration issues and how the alternatives would be expected to meet RAOs.
Multiple commenters noted that money would be better at other areas of the Site, specifically at
the Gladstone IWTP. The scope of the IRAs and the cost-effectiveness determination for the
selected interim remedy in the IROD is specific to the contaminant migration issues identified in
the FFS (including mine portal MIW discharges, mining-related source/storm water interactions,
mine portal pond sediments, in-stream mine wastes, and mining-impacted recreation staging
areas) and not other contamination-related issues existing at the Site. While the comments on the
Gladstone IWTP and other areas outside of the IRAs do not directly impact the scope of this
IROD, they will be considered when EPA plans future efforts and response actions for the Site.
Additionally, as noted in the Site-wide Strategy subcategory in Section 3.1, these IRAs are part
of a Site-wide strategy, with future response actions to address other areas of the Site.
3.6 Responsiveness Summary Narrative for General Support/Opposition
Several commenters provided commenters indicating their general support or opposition to the
proposed IRAs. In addition, multiple commenters indicated support for the comments submitted
by Peter Butler (ARSG) and asked for careful consideration of those comments.
EPA sought, in its proposed plan and selected interim remedy, to develop protective and cost-
effective alternatives that balance several important factors, including the ability to take quick
action to protect human health and the environment in the short term while a final remedial
solution is being developed, and stabilizing mining-related sources to prevent further migration
of contaminants.
While ongoing characterization is needed for the Site-wide RI, a review of initial data has
identified multiple types of contaminant migration issues that could be mitigated by IRAs. This
initial characterization identified 26 mining-related sources (reduced to 23 mining-related
sources in the IROD) where IRAs would be appropriate to reduce contributions from these
mining-related sources that add to unacceptable human health and ecological risks in the Animas
River watershed at the Site in advance of comprehensive remedial action. As stated in Section 12
of Part 2 of the IROD, the selected interim remedy, consisting of IRAs for five contaminant
migration issues at various mining-related sources, will protect human health and the
environment in the short term and is intended to provide adequate protection until a final remedy
is selected.
The selected interim remedy is interim in nature, and while it targets five specific contaminant
migration issues, it does not address the full extent of remedial activities that will be conducted
at the Site. Once a Site-wide RI is completed, the final remedial decisions for the entire Site will
be made in a final record of decision.
3.7 Responsiveness Summary Narrative for Proposed Technical/Contracting Approach
Technical Approach: A few commenters recommended looking at treatment approaches for the
IRAs. One commenter indicated his proposed technical approaches for IRAs (including
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treatment technologies) would allow EPA to meet the requirements of the EPA Technology
Policy and would provide greater protection and effectiveness than the proposed IRAs.
As discussed in the Hazardous Determination subcategory in Section 3.13, the scope of the IRAs
do not necessitate treatment because EPA has determined that the contaminated media addressed
by these IRAs do not involve principal threat waste and these IRAs do not constitute the final
remedy. The IRAs exclude treatment of MIW discharged from mine portals. Untreated wastes
for IRAs will be managed locally at the mining-related source on an interim basis for the IRAs
until a final remedy is selected. Treatment media that bind contaminants in solid sources would
make it more difficult to remove and relocate wastes later. Local management of wastes on an
interim basis for the IRAs will consider design features and BMPs to minimize contaminant
migration without the need to specifically treat wastes. Although gravity dewatering may result
in positive benefits to geotechnical stability for excavated mine wastes, it is not considered
treatment per the NCP, as it does not result in permanent or irreversible reductions in toxicity,
mobility, or volume of contamination. Additional dewatering could be implemented for saturated
mine wastes through ex situ amendment with a dewatering agent, as necessary, for handling and
geotechnical stability prior to interim management at the mining-related source. Permanent
solutions and alternative treatment technologies or resource recovery technologies will be
addressed as part of the final response action rather than these IRAs.
EPA agrees with the commenters that treatment approaches should be evaluated at the Site.
Evaluating and implementing treatment approaches is part of EPA's adaptive management
strategy, as funding allows. EPA is currently evaluating treatment options at select mining-
related sources. When a remedial approach has been developed, EPA will present the option to
the public as part of future FSs. EPA encourages the public to continue sharing ideas related to
treatment approaches or actions at the Site which could be evaluated as part of future FSs.
Procurement/Contracting Approach: One commenter provided recommendations regarding
procurement and contracting of the IRAs for EPA's consideration. The suggestions focused on
expanding the procurement subcontracting opportunities based on performance, competition, and
best value to the government.
EPA is required to follow the specifications set forth in Federal Acquisition Regulation (FAR).
The FAR is the principal set of rules in the FAR System regarding government procurement in
the United States and is codified in Chapter 1 of Title 48 of the CFR (48 CFR 1).
3.8 Responsiveness Summary Narrative for Stakeholder Involvement
Comments received regarding stakeholders were mixed. Some comments (e.g., from the San
Juan Citizens Alliance) were encouraged by the community and stakeholder outreach associated
with this proposed plan, whereas other comments (e.g., from Sunnyside Gold Corporation)
suggested that EPA failed to consider stakeholder input. Other commenters requested that EPA
engage additional governmental agencies regarding future action.
EPA completed an initial characterization of mining-related sources where IRAs to address
specific contaminant migration issues might be beneficial based on technical work and data
already collected by EPA, other stakeholder agencies, and advocacy groups such as the ARSG.
This included collaborative discussions with partner agencies on various approaches to
performing early interim actions such as those indicated in the proposed plan. The partner
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agencies included the Bureau of Land Management (BLM), CDPHE, U.S. Forest Service
(USFS), and Colorado Division of Reclamation, Mining and Safety. During this initial
characterization, there were several mining-related sources located on BLM land identified as
having the potential to receive some benefit from response actions. BLM proposed to implement
response actions for these mining-related sources using their own CERCLA authority. BLM has
continued to remain involved in the process of developing and reviewing the IRAs for the
mining-related sources identified in the FFS and selected in this IROD.
EPA has implemented a robust program of community participation at the Site that meets and
exceeds the requirements of CERCLA. EPA began community involvement for the Site prior to
the Site's listing on the NPL in September 2016, and active community involvement related to
the Site continues today. A summary of these activities is discussed in Section 1.0 of this
responsiveness summary. During development of the FFS, EPA communicated progress towards
development of the IRAs and mining-related sources identified for IRAs to the group of local
officials and residents known as the Silverton/San Juan County Planning Group. In addition,
EPA is working with private property owners on IRAs at certain mining-related sources, which
is one of the reasons the number of mining-related sources identified for IRAs was reduced from
26 to 23 in the IROD. EPA looks forward to continued collaboration with stakeholders and the
community at the Site.
EPA sought public comment on the proposed plan from June 14, 2018 to August 15, 2018. The
agency received comments during a June 21, 2018 public meeting and in writing. In response to
commenters and a media request, EPA took an additional outreach step and released the public
comments received on EPA's Proposed Plan for Interim Remedial Action in advance of the
publication of the IROD. EPA released the public comments on September 10, 2018. Due to
heightened interest, EPA made these comments available before completing its analysis of them
and prior to inclusion of the comments as part of the responsiveness summary in a published
IROD. This release aligned with the agency's goal for transparency. Personally identifiable
information was redacted from the comments to protect the commenter's privacy.
All stakeholder comments are important and valuable to EPA. EPA has not made any significant
changes to the original proposal but has provided clarifying information based on the comments
in the IROD. The comments will be further considered during the remedial design and remedial
action phase, as appropriate.
3.9 Responsiveness Summary Narrative for Statutory Requirements
ARARs: Several commenters highlighted concerns related to the applicable or relevant and
appropriate requirements (ARARs) presented in the FFS and proposed plan. One commenter
requested clarity about the use of environmental covenants on private and federal land and how
waivers will be applied as part of the planned actions. Another commenter was concerned about
the regulations protecting historic features at the Site.
EPA will implement ICs to ensure the interim remedies remain protective pending final
remedies. EPA will seek environmental covenants or restrictive notices where waste is left in
place above levels allowing for unrestricted use or where remediation features are located as part
of an IC plan.
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As noted in the FFS, the type of ARAR waiver that is anticipated to be implemented as part of
the IRAs is the CERCLA interim measures waiver. By definition, that type of waiver can only
apply to interim measures and does not apply to final response actions. Therefore, when the final
response actions for the Site are determined in a future decision documents, the CERCLA
interim measures waiver will not be available to waive ARARs. At that time, identified final
ARARs will be complied with or waived using a different CERCLA ARAR waiver.
Appendix C of the FFS cited numerous rules and regulations related to protection of historic and
cultural resources including the National Historic Preservation Act and Implementing
Regulations, the Archaeological and Historic Preservation Act and Implementing Regulations,
and the Historic Sites Act. As noted in Section 5.4.1 of the FFS, pre-construction activities will
include cultural resources surveys. If cultural resources are found, EPA will determine if there
will be adverse effects on the cultural resources from the IRA as designed for the specific
mining-related source in question and will either avoid the cultural resource or take mitigative
steps to comply with pertinent ARARs.
Lack of Treatment or Permanent Solutions: Two commenters questioned whether the
alternatives satisfied the statutory requirements of CERCLA § 121, including the preference for
treatment as a principal element to permanently reduce the volume, toxicity, or mobility of the
hazardous substances, pollutants, and contaminants. In addition, one commenter questioned
whether the alternatives provided permanent solutions.
These comments address two statutory and regulatory requirements considered when selecting a
remedy under CERCLA:
• Preference for Treatment as a Principal Element
• Utilization of Permanent Solutions and Alternative Treatment (or Resource Recovery)
Technologies to the Maximum Extent Practicable
The preference for treatment determination looks at whether the selected interim remedy
provides treatment as a principal element. The NCP establishes the expectation that treatment
will be used to address principal threat wastes whenever practicable (40 CFR
300.430[a][l][iii][A]). Principal threat wastes are those source materials that are considered to be
highly toxic or highly mobile that generally cannot be contained in a reliable manner or will
present a significant risk to human health and the environment should exposure occur. As
discussed in Section 11.0 of Part 2 of this IROD, EPA has determined that contaminated media
addressed by these IRAs do not involve principal threat waste. In addition, because these IRAs
do not constitute the final remedy, the statutory preference for remedies that employ treatment
that reduces toxicity, mobility, or volume as a principal element will be considered and
addressed by the final response action rather than these IRAs.
The utilization of permanent solutions and alternative treatment technologies determination looks
at whether the selected interim remedy provides the best balance of tradeoffs among the
alternatives with respect to the balancing criteria set forth in NCP §300.430(f)(l)(i)(B) such that
it represents the maximum extent to which permanence and treatment can be practicably used at
the Site. NCP §300.430(f)(l)(ii)(E) provides that the balancing shall emphasize the factors of
"long-term effectiveness" and "reduction of toxicity, mobility, or volume through treatment,"
and shall consider the preference for treatment and bias against off-site disposal. The modifying
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criteria were also considered in making this determination. These IRAs are interim solutions only
and are not intended to utilize permanent solutions and alternative treatment (or resource
recovery) technologies to the maximum extent practicable. Permanent solutions and alternative
treatment technologies or resource recovery technologies will be addressed as part of the final
response action rather than these IRAs.
Justification for Actions: One commenter indicated there is not justification for the actions
outlined in the proposed plan because the IRAs do not meet the threshold of representing
immediate threats or actions that will result in significant risk reductions.
As noted in the EPA's Role of the Baseline Risk Assessment in Superfund Remedy Selection
Decisions guidance, "Early and interim action RODs do not require a completed baseline risk
assessment, although enough information must be available to demonstrate the potential for risk
and the need to take action." Appendix B of the FFS demonstrated the potential unacceptable
risks to human health or ecological receptors from the contamination migration issues posed by
the mining-related sources included in the FFS.
As noted in Section 14.0 of Part 2 of this IROD, the selected interim remedy will provide
stabilization of the mining-related sources and prevent further environmental degradation, thus
meeting the criteria for taking an interim action.
3.10 Responsiveness Summary Narrative for Preliminary RI
Data Evaluation: Several commenters questioned the use of historic data from others (e.g.,
ARSG) or the variability of historic data when compared to data collected as part of initial RI
characterization. In addition, one commenter questioned the evaluation of data at several mining-
related sources.
The preliminary RI was limited in scope, and its purpose was solely to support the development
of the FFS for remedial alternatives to address five contaminant migration issues. The
preliminary RI was not meant to be a comprehensive evaluation of the entire Site nor the
universe of characterization data that exist for the Site. The preliminary RI met the requirements
of a preliminary site characterization summary, as described in Guidance for Conducting
Remedial Investigations and Feasibility Studies under CERCLA (EPA 1988). The
comprehensive RI of the Site is ongoing, and additional data collection activities are needed to
fully determine the nature and extent of impacts and characterize fate and transport pathways at
the mining-related sources within the Site. That RI will include evaluation of available historical
data for the mining-related sources, including data collected by the Colorado Division of
Minerals and Geology and ARSG as part of previous investigative efforts.
Regarding the specific comments related to the Boston Mine, London Mine, and Sunbank Group
Mine, the additional detailed interpretation of Site data will be included in the comprehensive RI
report, as investigations at the Site are ongoing. However, some portions of the specific
comments related to flow measurement information in the preliminary RI report were helpful
and considered for incorporation into the IROD. An addendum to the preliminary RI report was
prepared to address a discrepancy in flow measurement date and location at the London Mine,
and to clarify dates of flow measurements collected at several locations presented in the
preliminary RI report.
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3.11 Responsiveness Summary Narrative for Cost
Multiple commenters had concerns about the costs that were presented in the FFS and proposed
plan. Three commenters indicated that they thought the costs were too high, while other
commenters indicated that they thought costs were double counted or that costs should be
presented on a mining-related, source-specific basis rather than on a contaminant migration
issue-specific basis. The State of Colorado (represented by CDPHE) recommended adding
additional text delineating O&M cost responsibilities.
EPA documented the assumptions used in developing the remedial alternative cost estimates
within Appendix F of the FFS. Cost estimates were developed consistent with EPA's guidance
for FS cost estimates A Guide to Developing and Documenting Cost Estimates During the
Feasibility Study, and include the level of detail and cost estimating backup (i.e., calculation
sheets and supporting unit cost data) necessary to meet the accuracy requirements for FS cost
estimates. EPA cost estimating guidance states that the purpose for FS cost estimates is to
compare remedial alternatives during the remedy selection process, not for establishing
construction project budgets nor for negotiating Superfund settlements with potentially
responsible parties to pay for cleanups. The total costs presented in the remedial alternative cost
estimates include both the initial construction costs and the costs for 15 years of post-
construction O&M. Depending on the timing and determination of the final remedy for the Site,
O&M may not be required for the full 15 years.
The cost estimates in the FFS are sufficient for comparing remedial alternatives and selecting a
remedy, but are not intended to be highly accurate because the level of detail for the scope of the
alternatives in a FS is much lower than later, during design and construction of a remedy, when
more data are available and there is a better understanding of the construction timelines and
funding. This is particularly true of projects such as the BPMD IRAs cleanup, where a large
number of mining-related sources are being considered for IRAs addressing five different
contaminant migration issues, so the sequencing of construction work is complex. The cost
estimates are developed to reflect the understanding of the alternatives as described in the FFS
given the uncertainties that exist and will continue to exist even after a decision on a remedy
approach is made, prior to remedial design and construction.
Multiple commenters raised concern about whether some costs were double counted. As noted in
Section 6.1.7 of the FFS, the alternative-specific costs exclude consideration of other remedial
alternatives that address other contaminant migration issues at the same mining-related sources
and locations due to uncertainties such as phasing and funding of the IRAs over the period of
implementation. Thus, some common cost elements, such as those discussed in Section 5.4.1 of
the FFS (e.g., road improvements for accessing mining-related sources), may be duplicative
between alternatives and may result in conservative estimates when considering concurrent
implementation of alternatives during remedial action. While this may be perceived as double
counting, this approach allows remedial alternatives to be more representative if they were to be
implemented individually, and this approach still meets the expected accuracy of remedial
alternatives cost estimates for comparative purposes.
Two commenters stated that costs should be presented on a mining-related, source-specific basis
rather than on a contaminant migration issue-specific basis. Based on EPA's guidance for FS
cost estimates, costs in a FS should be presented on an alternative-specific basis. Given that the
remedial alternatives in the FFS were assembled to address the five individual contaminant
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migration issues rather than alternatives for each mining-related source, it is appropriate that
costs were presented based on the contaminant migration issues as opposed to a source-by-
source basis. Additionally, as described previously, FS cost estimates are not developed for the
purposes of establishing project budgets nor for allocating costs on a source-by-source basis, so
that level of precision is not warranted at this phase of the CERCLA process. Detailed
construction cost estimates will be developed on a source-specific basis during remedial design.
The State of Colorado (represented by CDPHE) also commented that O&M activities and related
costs should identify the party or parties responsible for them. The FFS and IROD should not
identify parties and their cost responsibilities. As previously stated, the remedial alternative cost
estimates are meant for comparative purposes to select IRAs for the five contaminant issues, not
for budgeting or cost allocation.
3.12 Responsiveness Summary Narrative for Short-Term Risk
Multiple commenters indicated concern over short-term risks associated with the implementation
of the IRAs, such as potential unplanned discharges of MIW, fugitive dust emissions, and
infiltration of MIW. The comments requested that the EPA detail what actions would be taken to
reduce those short-term risks.
The proposed plan and FFS, as well as this IROD, describe the selected interim remedy for five
IRAs and the underlying information that supports the decision. Use of BMPs for minimizing
impacts from IRAs was identified in the description of remedial alternatives addressing the five
contaminant migration issues. Specific details of how the selected interim remedy will be
implemented (such as use of BMPs) at specific mining-related sources identified within the
IROD for the five IRAs are typically not included in the proposed plan, FFS, and IROD, but are
developed in the remedial design phase. Additionally, details of the five IRAs for BMPs and
fugitive dust will be determined during remedial design, which is the appropriate time for those
types of evaluations. Contact information for community members to communicate concerns to
EPA during remedial action construction will be provided.
Regarding concerns of the potential for sudden, uncontrolled fluid mine waste releases occurring
during implementation of IRAs, EPA will develop hazard consultation packages for CERCLA
activities at abandoned hard rock mining and mineral processing sites. These consultation
packages will document the review and implementation of BMPs and approaches considered for
mining-related source remediation activities that could result in an uncontrolled release of MIW.
The consultation packages would be developed during the remedial design for pertinent mining-
related sources with the potential for uncontrolled releases.
Some response activities undertaken by the agencies, such as removing waste rock from creeks
or streams, may cause localized, temporary discoloration of these streams. Although EPA would
employ BMPs to minimize these temporary impacts, the impacts cannot be entirely eliminated.
In addition, natural events such as large thunderstorms or incidents not related to remedial
activities at the Site may also impact streams. In order to notify stakeholders of these events in
the most efficient and prompt way, EPA is using 2017 Animas River Alert and Notification Plan
for its communications to stakeholders related to any events that affect the appearance or water
quality in the Animas River. EPA will use the plan, which will be updated in 2019, for proactive
notifications regarding planned activities at the Site and to alert stakeholders about any impacts
to streams from IRA work being conducted at the Site. In addition, field crews will use the plan
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if they observe any situations not related to IRA activities that impact streams. The 2017 Animas
River Alert and Notification Plan participants include state and local emergency management
agencies, public health departments, downstream states and tribes, and local officials.
3.13 Responsiveness Summary Narrative for Waste Management
Hazardous Determination: Two commenters provided comments relating to whether materials
encountered during IRAs would be considered contaminated and/or hazardous. One commenter
noted that while materials exempted under the Resource Conservation and Recovery Act's
(RCRA's) Bevill amendments would not be classified as hazardous waste, those materials would
still be considered hazardous substances and recommended being diligent about how the word
"hazardous" is used. Another commenter questioned why it was assumed that materials
excavated for the stormwater diversions' construction are uncontaminated.
Diligence must be used with respect to the word "hazardous." As noted in the FFS, mine wastes
at the Site were derived directly or indirectly from the extraction of ore and thus would be
exempt from management as a RCRA hazardous waste (i.e., the Bevill exemption); mine wastes
would be classified as non-hazardous waste. However, these mine wastes do contain substances
regulated by CERCLA, which pose contaminant migration issues and thus provide the rationale
for IRAs to address them.
Materials excavated for the stormwater diversions' construction would be uncontaminated
because the stormwater diversion components would be constructed uphill/upgradient from the
mine workings and existing mine waste designated as mining-related sources. As such, it is
expected that the native soil/rock that would be excavated would be unimpacted by the mining
activity that is the cause of the CERCLA release or threatened release of hazardous substances,
and represent otherwise natural conditions.
Local Management of Wastes: One commenter asked whether there would be sufficient
capacity for local management of waste for all alternatives involving local waste management
and whether ponds have sufficient capacity to manage MIW during pond sediment removals. In
addition, the commenter asked why waste would be left in place and if there was a plan to
remove the waste in the future.
There is sufficient capacity for local management of excavated wastes for the proposed IRAs.
Local management does not necessarily specify that the excavated wastes will be managed at the
mining-related source location from which it was generated. It is possible that in areas with
multiple mining-related sources with proposed IRAs, the excavated wastes would be
consolidated within the area of contamination into one local management area. Specifics of the
local management areas will be detailed further in the remedial design using location-specific
information.
Similarly, there are sufficient means to manage MIW within mine portal ponds without treatment
or discharge to local waters. As described in the FFS, at mining-related sources where multiple
ponds exist, MIW management from mine portals would include diversion of the MIW from one
pond into the other ponds while mine portal pond sediment is being excavated. At mining-related
sources where only one pond exists, mine portal pond sediment could be removed in phases
using temporary berms to manage MIW within the pond. However, the exact method of MIW
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management and need for discharge of MIW outside of ponds, if any, would be determined on a
source-specific basis during remedial design. If discharge of MIW outside of ponds were to be
required at a specific mining-related source, BMPs as described in the description of the selected
alternative for mine pond portal sediments would be employed to minimize any impacts to
receiving surface water bodies.
The human health risk information presented in Appendix B of the FFS indicated that mining-
impacted recreation staging areas represented potential human health risks for a camping
scenario. Based on the determinations made within the IROD, containment/isolation (covering)
of mining-impacted recreation staging areas would be a protective and cost-effective measure for
addressing the potential human health risks represented by the camping scenario. As indicated
for all contaminant migration issues addressed in the FFS, final remedial approaches for
managed wastes would be re-evaluated as part of future remedy decisions and response actions.
3.14 Responsiveness Summary Narrative for Limited Number of Alternatives
A couple commenters indicated concern with the number of alternatives considered for each
contaminant migration issue and indicated that more than two alternatives should have been
evaluated.
Interim actions are meant to protect human health and the environment in the short term, while a
final remedial solution is being developed. In accordance with EPA guidance, as described in A
Guide to Preparing Superfund Proposed Plans, Records of Decision, and Other Remedy
Selection Documents (EPA 1999), interim actions are limited in nature and consider a limited
number of alternatives (generally three or fewer). EPA determined during development of the
FFS that the nature of five contaminant migration issues addressed by proposed IRAs did not
warrant the development of multiple alternatives.
3.15 Responsiveness Summary Narrative for Editorial
One commenter noted there was an editorial error in Section 8.1.2 of the FFS document.
The specific text identified by the commenter has been corrected in the IROD.
3.16 Responsiveness Summary Narrative for Comments Not Specific to IRAs
Community Involvement: Several commenters provided comments regarding different topics
involving community involvement. Multiple commenters indicated it was difficult for the public
to understand what documents are publicly available and how to find those documents. Several
commenters inquired about when public comments were due and if an extension of the public
comment period was possible. One commenter indicated that the EPA has failed to give the
public ample opportunity to communicate their concerns with the proposed IRAs. Lastly,
multiple commenters indicated that EPA should provide an updated emergency notification plan
to ensure that the community will be informed in the event of a future release.
EPA announced a 30-day public comment period and extended the comment period for an
additional 30 days. This provided additional time for citizens to review and comment on the
preferred alternatives for the five proposed IRAs along with supporting documentation. During
the comment period, EPA accepted comments on all aspects of the interim action remedy.
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Comments were accepted on the proposed plan and all supporting documents, including the
preliminary RI report, FFS report, and risk assessment information. As noted in the proposed
plan, Site documents are available on the EPA website at https://www.epa.gov/superfund/bonita-
peak or by calling the EPA Superfund Records Center at 800-227-8917 ext. 312-7273. They are
also available at the following information repositories:
• Silverton Public Library, 1117 Reese Street, Silverton, Colorado
• Durango Public Library, 1900 East Third Avenue, Durango, Colorado
• Farmington Public Library, 2101 Farmington Avenue, Farmington, New Mexico
• Dine College Shiprock Campus Library, 1228 Yucca Street, Shiprock, New Mexico
As discussed in the Detailed Plans subcategory in Section 3.3, specific details of how the
selected interim remedy will be implemented are developed in the remedial design, which begins
after the IROD is signed. To facilitate the IRAs, EPA intends to survey the mining claims
associated with the mining-related sources and areas where construction may likely occur. EPA
is doing this to ensure boundaries are understood before proceeding with the work and will be
working with property owners during this process.
As noted in the Short-Term Risk category in Section 3.12, EPA is using the 2017 Animas River
Alert and Notification Plan for its communications to stakeholders related to any events that
affect the appearance or water quality in the Animas River. EPA will use the plan, which will be
updated in 2019, for proactive notifications regarding planned activities at the Site and to alert
stakeholders about any impacts to the river from work being conducted at the Site. The 2017
Animas River Alert and Notification Plan participants include state and local emergency
management agencies, public health departments, downstream states, and tribes and local
officials.
General Comment: Numerous commenters provided general comments and questions that were
unrelated to the content of the proposed plan and corresponding documents. Some of the topics
included a clarification of that commenter's own public comments, and a comment thanking
EPA for the opportunity to demonstrate their technology.
These comments are on topics not related to the proposed plan. Thus, these comments are not
addressed further in the responsiveness summary. However, these comments are still important
and valuable to EPA. They will be considered and addressed by EPA based on the substance of
the comment.
Personal Health Concerns: One commenter mentioned personal health concerns.
Public health issues at the Site are being investigated through a Public Health Assessment being
conducted by the Agency for Toxic Substances and Disease Registry. The aim of this evaluation
is to find out if people are being exposed to hazardous substances and, if so, whether that
exposure is harmful and should be stopped or reduced.
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Interim Water Treatment Plant: Several commenters provided comments about the operation
of the Gladstone IWTP. Multiple commenters requested that EPA operate the IWTP at full
capacity, so that discharges from additional mining-related sources can be treated there.
The expansion of the IWTP at Gladstone to treat additional sources of water was not included in
the Proposed Plan for Interim Remedial Actions at the Bonita Peak Mining District.
EPA's current approach for improving water quality in the mining district, as reflected in the
IRAs, is the remediation of sources of contamination. While the agency continues remediation
work, it will also explore the option of treating more sources of mine-impacted water at the
IWTP at Gladstone. The agency will consider the significant technical hurdles, including
procuring and maintaining adequate facilities for impounding the large amounts of waste
generated by lime treatment, and any more cost-effective alternatives to long-term treatment of
large volumes of water. The Superfund process is thorough, deliberate, and designed to secure
cleanup actions that are supported by sound science. When completed, detailed risk assessment
documents and the full investigation of the Bonita Peak Groundwater System will inform
decisions about the appropriate long-term remedial actions and technologies to be used at the
site.
Interim Sludge Management Location at Kittimac: Several commenters provided comments
about the management of sludge generated at the IWTP. Multiple commenters mentioned EPA
did not provide a public comment period regarding the decision to move sludge generated at the
IWTP to Kittimac. In addition, the multiple commenters stated there are environmental impacts
to storing sludges at Kittimac and opposed the decision.
The establishment of the interim sludge management location at Kittimac was not included in the
Proposed Plan for Interim Remedial Actions at the Bonita Peak Mining District.
An engineering evaluation and cost analysis (EE/CA) for the Gladstone IWTP, which included a
discussion of short-term maintenance of sludge at an interim sludge management location, was
prepared in advance of constructing the facility. Public comments received on the EE/CA were
considered as EPA approved the Action Memorandum authorizing the operation of the IWTP.
The administrative record for the Action Memorandum, including the EE/CA and other
supporting documents, can be found at EPA's BPMD website.
Natural Resource Damage Assessment and Restoration (NRDA): Three commenters
requested that EPA incorporate NRDA regulations into the IRAs. The commenters requested that
EPA coordinate with the applicable natural resources trustees as part of the NRDA regulations to
ensure an effective restoration.
By providing a proposed plan for public comment for the proposed IRAs, EPA is, in essence,
coordinating with the states' NRDA programs. EPA welcomes coordination with NRDA
programs to facilitate future restoration efforts by other parties.
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4.0 MODIFICATIONS TO THE PROPOSED PLAN MADE AS A RESULT OF
COMMENTS
Written and oral comments provided on the proposed plan were addressed through clarification
and explanation in this responsiveness summary. Based on the comments, EPA has not made any
significant changes to the selected interim remedy described in the proposed plan. However,
EPA has provided clarifying information in this IROD, including in addenda to the preliminary
RI and the risk assessment information, which are included in Appendices A and B, respectively.
It was determined that no significant changes to the remedy, as originally identified in the
proposed plan, were necessary. In addition, final identification of ARAR requirements pertaining
to the selected interim remedy have been made, as presented in Appendix C.
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5.0 REFERENCES
EPA. 1988. Guidance for Conducting Remedial Investigations and Feasibility Studies under
CERCLA. U.S. Environmental Protection Agency. OSWER Directive 9355.0-01.
EPA. 1991. Role of the Baseline Risk Assessment in Superfund Remedy Selection Decisions. U.S.
Environmental Protection Agency. OSWER Directive 9355.0-30.
EPA. 1999. A Guide to Preparing Superfund Proposed Plans, Records of Decision, and Other
Remedy Selection Decision Documents. U.S. Environmental Protection Agency.
EPA 540-R-98-031.
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